JP4941280B2 - Engine residual gas amount estimation device and residual gas amount estimation method - Google Patents

Description

  The present invention relates to a residual gas amount estimation device and a residual gas amount estimation method for an engine (internal combustion engine).

Means for calculating the temperature in the combustion chamber when the exhaust valve is closed, means for calculating the pressure in the combustion chamber when the exhaust valve is closed, means for calculating the gas constant of the exhaust composition according to the combustion air-fuel ratio, and Means for calculating the amount of gas in the combustion chamber when the exhaust valve is closed based on the temperature, pressure in the combustion chamber, and gas constant; and means for calculating the amount of blowback gas during the overlap between the exhaust valve opening period and the intake valve opening period And a means for calculating an amount of residual gas in the combustion chamber based on the amount of gas in the combustion chamber and the amount of blown back gas during the overlap (see Patent Document 1).
JP 2004-108262 A

  Incidentally, since the residual gas amount in the combustion chamber affects the ignition timing and the air-fuel ratio, it is desirable to estimate the residual gas amount in the combustion chamber and correct the ignition timing, the air-fuel ratio, and the like with the estimated residual gas amount in the combustion chamber.

  On the other hand, there is an increasing demand to provide an exhaust valve opening / closing timing variable mechanism that can change the exhaust valve opening / closing timing and an intake valve opening / closing timing variable mechanism that can change the opening / closing timing of the intake valve. For example, if the exhaust valve opening / closing timing variable mechanism is operated and the exhaust valve opening timing is made earlier than in the non-operating state, the exhaust temperature becomes high, and warming up of the catalyst provided in the exhaust passage can be promoted. Further, if the overlap between the intake valve opening period and the exhaust valve opening period is increased by making the exhaust valve opening timing earlier than in the non-operating state, the amount of residual gas in the combustion chamber increases and the pumping loss can be reduced. Further, if the overlap between the opening period of the intake valve and the opening period of the exhaust valve is made larger than that in the non-operating state at a high rotational speed, the inertia force of the intake can be increased. For these various purposes, an exhaust valve opening / closing timing variable mechanism and an intake valve opening / closing timing variable mechanism are provided, and the exhaust valve opening / closing timing variable mechanism and the intake valve opening / closing timing variable mechanism are switched from a non-operating state to an operating state. As a result, the exhaust gas pressure and the combustion chamber pressure are different from the values in the non-operating state, and as a result, the residual gas amount in the combustion chamber after the valve overlap between the exhaust valve opening period and the intake valve opening period is also in the non-operating state. It will change greatly from the time value.

  Therefore, even when the exhaust valve opening / closing timing variable mechanism and the intake valve opening / closing timing variable mechanism are switched from the non-operating state to the operating state, the residual gas amount in the combustion chamber after the valve overlap between the exhaust valve opening period and the intake valve opening period ends. In order to find a method for calculating the air flow accurately, various experiments and simulations were conducted. As a result, there were three types of waveforms in the gas flow around the exhaust valve during valve overlap during the exhaust valve open period and the intake valve open period. It was newly discovered. The three types of waveforms are waveforms when there is both gas blowback from the exhaust port into the combustion chamber and gas blowout from the combustion chamber into the exhaust port, and only gas blowback from the exhaust port into the combustion chamber exists. There are three waveforms: a waveform in the case where no gas is discharged, and a waveform in the case where only gas is blown out from the combustion chamber to the exhaust port.

  Among these, the waveform when there is only the gas blowout from the combustion chamber to the exhaust port is because the pressure in the combustion chamber is compressed in the exhaust stroke, and the cause is blown out from the combustion chamber to the exhaust port. It was found that the gas flow was in a choked state.

  In view of this, the present invention provides the amount of residual gas in the combustion chamber and the exhaust valve after the valve overlap between the exhaust valve open period and the intake valve open period, even when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked. An object of the present invention is to provide a residual gas amount estimation device and a residual gas amount estimation method capable of accurately estimating the residual gas amount in the combustion chamber when there is no valve overlap between the open period and the intake valve open period.

  The present invention determines whether or not the pressure in the combustion chamber is compressed in the exhaust stroke based on the amount of change in the volume in the combustion chamber accompanying the movement of the piston and the amount of gas that can pass through the exhaust valve. When the pressure in the combustion chamber is compressed by the exhaust stroke, the flow of the gas blown out from the combustion chamber to the exhaust port is choked so that the change in volume in the combustion chamber is equal to the amount of gas that can pass through the exhaust valve. Calculated as the starting crank angle (CACOMP), and the combustion chamber at the intake valve opening timing when the flow of gas blown from the combustion chamber to the exhaust port is choked based on the calculated choke state starting crank angle (CACOMP) The pressure (PIVO ′) is calculated, and the intake air flow when the flow of gas blown out from the calculated combustion chamber to the exhaust port becomes choked. The amount of blown gas (M23) from the combustion chamber to the exhaust port is calculated on the basis of the pressure in the combustion chamber (PIVO ') at the opening time of the valve, and the amount of combustion chamber gas (MR1) at the intake valve opening timing and this amount of blown gas (M23) is configured to estimate the amount of residual gas in the combustion chamber after the overlap between the exhaust valve opening period and the intake valve opening period.

  Further, the present invention determines whether or not the pressure in the combustion chamber is compressed in the exhaust stroke based on the volume change in the combustion chamber accompanying the movement of the piston and the amount of gas that can pass through the exhaust valve. When the pressure in the combustion chamber is compressed in the exhaust stroke based on the determination result, the flow of gas that blows out from the combustion chamber to the exhaust port at the crank angle at which the volume change in the combustion chamber is equal to the amount of gas that can pass through the exhaust valve is choked. Is calculated as a crank angle (CACOMP) for starting the state, and the pressure in the combustion chamber (PEVC ′) at the exhaust valve closing timing is calculated based on the calculated crank state starting crank angle (CACOMP). Exhaust valve when the flow of gas blown out from the combustion chamber to the exhaust port is choked based on the combustion chamber pressure (PEVC ') at the time The amount of gas in the combustion chamber (MR1 ′) at the time is calculated, and the amount of gas in the combustion chamber (MR1 ′) at the closing time of the exhaust valve is left in the combustion chamber when there is no overlap between the exhaust valve opening period and the intake valve opening period It is configured to estimate the amount of gas.

  The combustion chamber pressure (PIVO) at the intake valve opening timing is greatly influenced by the exhaust valve opening area at the intake valve opening timing (IVO). When the exhaust valve is sufficiently open at the intake valve opening timing (IVO) (that is, when the flow of gas blown from the combustion chamber to the exhaust port does not enter the choke state), the pressure Pcyl in the combustion chamber is shown in the left of FIG. Becomes equal to the exhaust pressure Pex.

  On the other hand, when the exhaust valve is almost closed at the intake valve opening timing (IVO) (that is, when the flow of gas blown from the combustion chamber to the exhaust port is choked), as shown in FIG. As the combustion chamber volume changes, the combustion chamber pressure Pcyl changes (increases away from the exhaust pressure Pex), and the deviation from the exhaust pressure Pex increases. For this reason, even when the flow of gas blown from the combustion chamber to the exhaust port becomes choked, it is assumed that the combustion chamber pressure (PIVO) at the intake valve opening timing is equal to the exhaust pressure, and the exhaust valve opening period and the intake valve If the residual gas amount in the combustion chamber after the overlap in the open period is estimated, an error corresponding to the pressure difference from the exhaust pressure Pex of the pressure in the combustion chamber at the intake valve opening timing occurs.

  In contrast, according to the present invention, whether or not the pressure in the combustion chamber is compressed in the exhaust stroke based on the volume change in the combustion chamber accompanying the movement of the piston and the amount of gas that can pass through the exhaust valve. When the pressure in the combustion chamber is compressed during the exhaust stroke according to the determination result, the crank angle at which the change in volume in the combustion chamber is equal to the amount of gas that can pass through the exhaust valve is equal to the amount of gas blown out from the combustion chamber to the exhaust port. The flow is calculated as a crank angle (CACOMP) for starting the choke state, and the intake valve opening when the flow of gas blown from the combustion chamber to the exhaust port based on the calculated choke state start crank angle (CACOMP) is in the choke state is calculated. The combustion chamber pressure (PIVO ') at the time is calculated, and the flow of the gas blown out from the calculated combustion chamber to the exhaust port is choked. Based on the combustion chamber pressure (PIVO ') when the intake valve is open, the amount of gas blown from the combustion chamber to the exhaust port (M23) is calculated, and the combustion chamber gas amount (MR1) when the intake valve is opened and this Since the amount of residual gas in the combustion chamber after the overlap between the exhaust valve opening period and the intake valve opening period is estimated from the amount of blown-out gas (M23), the flow of gas blown out from the combustion chamber to the exhaust port in the exhaust stroke becomes choked. In this case, the residual gas amount in the combustion chamber after the overlap between the exhaust valve opening period and the intake valve opening period can be accurately estimated.

  Next, assuming that the combustion chamber pressure (PIVO) at the intake valve opening timing is equal to the exhaust pressure, the combustion chamber gas amount (MR1) at the intake valve opening timing is calculated by a state equation (see equation (1)). When there is no overlap between the intake valve opening period and the exhaust valve opening period, it is conceivable that the combustion chamber gas amount (MR1) at the intake valve opening timing is directly used as the residual gas amount in the combustion chamber.

  However, as shown in FIG. 42, even when there is no overlap between the intake valve open period and the exhaust valve open period, the flow of gas blown out from the combustion chamber to the exhaust port in the exhaust stroke becomes a choke state, and the pressure in the combustion chamber It has been found that Pcyl may rise away from the exhaust pressure Pex. Therefore, even in such a case, if the combustion chamber gas amount (MR1) at the intake valve opening timing is calculated on the assumption that the combustion chamber pressure (PIVO) at the intake valve opening timing is equal to the exhaust pressure, the combustion chamber pressure Pcyl is calculated. An error corresponding to the pressure difference from the exhaust pressure Pex occurs in the estimation of the residual gas amount in the combustion chamber when there is no overlap between the intake valve open period and the exhaust valve open period.

  According to the present invention, it is determined whether or not the pressure in the combustion chamber is compressed in the exhaust stroke based on the amount of change in the volume in the combustion chamber accompanying the movement of the piston and the amount of gas that can pass through the exhaust valve. When the chamber pressure is compressed in the exhaust stroke, the crank angle at which the amount of change in the combustion chamber volume is equal to the amount of gas that can pass through the exhaust valve (CACOMP), and based on the calculated choke state start crank angle (CACOMP), the pressure in the combustion chamber (PEVC ′) when the exhaust valve closes when the flow of gas blown from the combustion chamber to the exhaust port is in the choke state. ) And the combustion chamber when the exhaust valve closes when the flow of gas blown from the calculated combustion chamber to the exhaust port becomes choked The combustion chamber gas amount (MR1 ′) at the exhaust valve closing timing is calculated based on the pressure (PEVC ′), and the combustion chamber gas amount (MR1 ′) at the exhaust valve closing timing is calculated based on the exhaust valve opening period and the intake valve opening time. Since it is estimated as the amount of residual gas in the combustion chamber when there is no overlap in the period, the flow of gas blown from the combustion chamber to the exhaust port in the exhaust stroke when there is no overlap between the intake valve open period and the exhaust valve open period is choked Even in this case, it is possible to accurately estimate the residual gas amount in the combustion chamber when there is no overlap between the exhaust valve opening period and the intake valve opening period.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of an engine control device having an engine residual gas amount estimation device.

  The air is stored in the intake collector 2 and then introduced into the combustion chamber 5 of each cylinder via the intake manifold 4. Fuel is injected and supplied from a fuel injector 21 disposed in the intake port 4 of each cylinder. The fuel injected into the air is vaporized and mixed with the air to form a gas (air mixture) and flows into the combustion chamber 5. This air-fuel mixture is confined in the combustion chamber 5 when the intake valve 15 is closed, and is compressed by the rise of the piston 6.

  When a spark is blown by the spark plug 14 slightly before the compression top dead center and the compressed air-fuel mixture is ignited, the flame spreads and then explosively burns, and the gas pressure by this combustion works to push down the piston 6. This work is taken out as the rotational force of the crankshaft 7. The combusted gas (exhaust gas) is discharged into the exhaust passage 8 when the exhaust valve 16 is opened.

A three-way catalyst 9 is provided in the exhaust passage 8. When the air-fuel ratio of the exhaust gas is in a narrow range (window) centered on the stoichiometric air-fuel ratio, the three-way catalyst 9 can efficiently remove harmful three components such as HC, CO, and NOx contained in the exhaust gas simultaneously. Since the air-fuel ratio is the ratio between the intake air amount and the fuel amount, the intake air amount introduced into the combustion chamber 5 per one cycle of the engine (crank angle 720 deg section in a four-cycle engine) and the fuel from the fuel injector 21 The engine controller 31 injects fuel from the fuel injector 21 based on the intake air flow rate signal from the air flow sensor 32 and the signal from the crank angle sensors (33, 34) so that the ratio to the injection amount becomes the stoichiometric air-fuel ratio. The amount is determined and the air-fuel ratio is feedback controlled based on a signal from an O ₂ sensor 35 provided upstream of the three-way catalyst 9.

  A cam sprocket and a crank sprocket are respectively attached to the front portions of the intake valve camshaft 25, the exhaust valve camshaft 26, and the crankshaft 7, and a camshaft is provided by timing timing chains (not shown) around these sprockets. 25 and 26 are driven by the crankshaft 7 of the engine, and are interposed between the cam sprocket and the intake valve camshaft 25 to continuously adjust the phase of the intake valve cam with a constant operating angle. A variable intake valve timing control mechanism (hereinafter referred to as “VTC mechanism for intake valve”) 27 that can be controlled, and a cam sprocket and an exhaust valve camshaft 26 are interposed between the camshaft 26 and the exhaust valve camshaft 26 so that the operating angle remains constant. Variable exhaust valve timing capable of continuously controlling cam phase Control mechanism (hereinafter, referred to as. "VTC mechanism for exhaust valves") and a 28. When the opening / closing timing of the intake valve 15 and the opening / closing timing of the exhaust valve 16 are changed, the amount of inert gas remaining in the combustion chamber 5 (the amount of residual gas in the combustion chamber) changes. As the amount of residual gas in the combustion chamber increases, the pumping loss decreases and the fuel efficiency improves. The engine controller 31 determines the target intake valve closing timing and the target exhaust valve closing timing from the operating conditions (engine load and rotational speed) at that time, and the intake valve VTC mechanism 27, exhaust gas so as to obtain these target values. The intake valve closing timing and the exhaust valve closing timing are controlled via each actuator of the valve VTC mechanism 28.

  In the engine controller 31 to which the atmospheric pressure signal from the atmospheric pressure sensor 36 and the intake pressure signal from the intake pressure sensor 44 are input, these signals and commands given to the intake valve VTC mechanism 27 and the exhaust valve VTC mechanism 28 are given. The residual gas amount in the combustion chamber is estimated based on the value, and the target intake valve closing timing and the target exhaust valve closing timing are feedback controlled based on the estimated residual gas amount in the combustion chamber.

  Next, a method for calculating the amount of residual gas in the combustion chamber after the overlap between the exhaust valve opening period and the intake valve opening period will be described.

  Here, the present invention is an invention closely related to the prior application device (see Japanese Patent Application No. 2007-191243), and the constituent elements of the present invention partially overlap the constituent elements of the prior application device. Therefore, in the following, the prior application apparatus will be described first, and then the present invention will be referred to. Since the prior application device has described the first to fifth embodiments, the embodiment related to the present invention is the sixth embodiment.

  The prior application device is particularly intended for the case where an exhaust valve VTC mechanism is provided. In order not to complicate the story, the intake valve VTC mechanism 27 is assumed to be in an inoperative state below, that is, the intake valve opening timing IVO is a constant value. It explains as being. Note that the present invention does not exclude the one provided with the intake valve VTC mechanism 27. When the intake valve VTC mechanism 27 is also provided, the intake valve opening timing IVO need only be considered as a variable value. In this embodiment, the exhaust valve VTC mechanism is described. However, the variable exhaust valve lift amount control mechanism (exhaust valve VEL mechanism) capable of continuously controlling the operating angle is provided, or the exhaust valve VTC is provided. The present invention can also be applied to a case where both a mechanism and an exhaust valve VEL mechanism are provided.

  As shown in FIG. 2, the intake valve opening timing (“IVO” in the figure), the intake valve opening period and the exhaust valve opening period overlap (“O / L” in the figure), the exhaust valve closing timing ( In the figure, “during EVC”), the residual gas amount in the combustion chamber is considered in four stages of the intake stroke.

  First, the amount of gas in the combustion chamber at the intake valve opening timing IVO is MR1 [kg]. During the overlap of the intake valve open period and the exhaust valve open period, the amount of gas flowing out from the combustion chamber 5 to the intake port 4 is M1 [kg], and the amount of gas flowing from the exhaust port 11 into the combustion chamber 5 is If M2 [kg], the amount of gas in the combustion chamber at the exhaust valve closing timing EVC is MR1-M1 + M2. In the intake stroke, the burnt gas M1 [kg] flowing out to the intake port 4 flows into the combustion chamber 5 again, so that the final residual amount in the combustion chamber when the exhaust valve is closed, that is, the intake valve The residual gas amount in the combustion chamber after the overlap between the open period and the exhaust valve open period (exactly immediately after the overlap) is MR1 + M2. Therefore, the prior application apparatus calculates the combustion chamber gas amount MR1 at the intake valve opening timing IVO and the blowback gas amount M2 from the exhaust port during the overlap between the opening period of the intake valve and the opening period of the exhaust valve. The sum is calculated as the amount of residual gas in the combustion chamber after the overlap between the intake valve open period and the exhaust valve open period. That is, the residual gas amount in the combustion chamber after the overlap between the intake valve open period and the exhaust valve open period is calculated by the following equation.

Residual gas amount in combustion chamber = MR1 + M2 (Supplement 1)
In the following, the calculation principle of the combustion chamber gas amount MR1 at the intake valve opening timing IVO in the first term on the right side of the (Auxiliary 1) equation will be described first, and then the intake valve opening period in the second term on the right side of the (Auxiliary 1) equation. The calculation principle of the blowback gas amount M2 during the overlap of the exhaust valve opening period will be described.
1. Calculation Principle of Combustion Chamber Gas Amount MR1 at Intake Valve Open Timing The combustion chamber gas amount MR1 at the intake valve opening timing is calculated based on the following equation of state.

MR1 = PIVO · VIVO / (REX · TIVO) (1)
However, PIVO: combustion chamber pressure [kPa] at intake valve opening timing IVO,
VIVO: combustion chamber volume at intake valve opening timing IVO [m ^ 3],
TIVO: Combustion chamber temperature [K] at intake valve opening timing IVO,
REX: exhaust gas constant [kJ / kg / K],
Hereinafter, the calculation methods of the exhaust gas constant REX, the combustion chamber volume VIVO at the intake valve opening timing, the combustion chamber pressure PIVO at the intake valve opening timing, and the combustion chamber temperature TIVO at the intake valve opening timing in the equation (1) will be described. This will be described in this order.
<1> Method for calculating the exhaust gas constant REX The number of moles of combustion chamber gas EGR when the intake valve opens mol is given by:

EGR mol = (mass gas in combustion chamber when intake valve is open) / (exhaust molecular weight)
= {RESTR / (1-RESTR)}
× (mass of air fuel mixture) / (exhaust molecular weight)
= {RESTR / (1-RESTR)}
× {(12 × n + m)
+ (N + m / 4) / TFBYA × (32 + 0.79 / 0.21 × 28)}
/ (44 × A + 18 × B + 28 × C + 32 × D + 28 × E) × SUM
... (2)
Where RESTR: residual gas rate,
TFBYA: target equivalent ratio,
n: number of carbon atoms in the fuel, the average composition of the gasoline _{C n H m = C 8 H} 18
Use
m: the number of hydrogen atoms in the fuel, the average composition of the gasoline _{C n H m = C 8 H} 18
Use
A: Number of moles of CO ₂
B: number of moles of H ₂ O,
C: number of moles of N ₂ ,
D: Number of moles of O ₂ (provided that D = 0 when φ> 1),
E: Number of moles of CO (provided that E = 0 when φ ≦ 1),
SUM: Total number of moles of exhaust,
44: molecular weight of CO ₂ [kg / kmol],
18: H ₂ O molecular weight [kg / kmol],
28: N ₂ molecular weight [kg / kmol],
32: Molecular weight of O ₂ [kg / kmol],
28: Molecular weight of CO [kg / kmol],
Here, RESTR / (1-RESTR) on the right side of the equation (2) is a ratio of the mass of the combustion chamber gas to the mass of the air fuel mixture at the intake valve opening timing, and this ratio is multiplied by the mass of the air fuel mixture. Thus, the gas mass in the combustion chamber when the intake valve is opened can be obtained. (2) 12 × n + m on the right side of the equation is the mass of fuel (C _n H _m ), (n + m / 4) / TFBYA × (32 + 0.79 / 0.21 × 28) is the mass of air, and the sum of these is air The fuel mixture mass.

  The residual gas rate RESTR is a value defined by the following equation, and in practice, a suitable value by simulation is used.

RESTR = burnt gas amount / total gas amount
= (Combustion chamber residual gas amount + external EGR amount)
/ (Intake air amount + fuel amount + combustion chamber residual gas amount)
... (Supplement 2)
The target equivalent ratio TFBYA on the right side of the equation (2) is a map (adapted value) based on the engine load and the rotational speed Ne as shown in FIG. The number of moles A to B on the right side of the formula (2) is shown in FIG. In FIG. 4, φ is the target equivalent ratio.

  Therefore, the chemical reaction formula is as follows.

C _n H _m + (n + m / 4) / TFBYA × (O ₂ + 0.79 / 0.21 × N ₂ )
+ RESTR / (1-RESTR) × {(12 × n + m) + (n + m / 4)
/TFBYA×(32+0.79/0.21×28)}
/ (44 × A + 18 × B + 28 × C + 32 × D + 28 × E) × SUM
× (A · CO ₂ + B · H ₂ O + C · N ₂ + D · O ₂ + E · CO) / SUM
→ A · CO ₂ + B · H ₂ O + C · N ₂ + D · O ₂ + E · CO
... (3)
From the law of conservation of mass
44 x A + 18 x B + 28 x C + 32 x D + 28 x E
= 1 / (1-RESTR) * ((12 * n + m) + (n + m / 4) / TFBYA
× (32 + 0.79 / 0.21 × 28) (4)
Therefore, the following equation is obtained by substituting equation (4) into equation (3).

C _n H _m + (n + m / 4) / TFBYA × (0 ₂ + 0.79 / 0.21 × N ₂ )
+ RESTR × (A · CO ₂ + B · H ₂ O + C · N ₂ + D · O ₂ + E · CO)
→ A · CO ₂ + B · H ₂ O + C · N ₂ + D · O ₂ + E · CO
... (5)
From equation (5), the exhaust gas constant REX is
REX = R0 / Mex (6)
However, R0: General gas constant (= 834.3J / kgK),
Mex: exhaust molecular weight [kg / kmol],
It is calculated by the following formula. The exhaust molecular weight Mex on the right side of the equation (6) is calculated by the following equation.

Mex = (44 × A + 18 × B + 28 × C + 32 × D + 28 × E) × SUM
... (Supplement 3)
However, AB: the number of moles of each molecule, see formula (2).

SUM: Total number of moles of exhaust, see equation (2).
<2> Method of calculating combustion chamber volume VIVO at intake valve opening timing The combustion chamber volume VIVO at the intake valve opening timing is calculated by the following equation.

VIVO = π × D ^ 2 × H / 4 + Vc (7)
Where D: bore diameter [m],
H: Displacement amount from TDC [m],
Vc: gap volume [m ^ 3],
The displacement amount H from the TDC on the right side of the equation (7) is calculated by the following equation.

H = ((CND + ST / 2) ^ 2- (CR off-PIS off ^ 2) ^ (1/2)
− (ST / 2 × cos (IVO + θoff) + (CND ^ 2-X ^ 2) ^ (1/2))
(8)
Where CND: connecting rod length [m],
CR off: Crank pin offset [m],
PIN off: Piston offset [m],
ST: Stroke [m],
IVO: Exhaust valve closing timing [degATDC]
θoff: angle [deg] from crank vertical position to TDC,
X: distance [m] from the large end of the connecting rod to the center of the piston pin,
Here, the intake valve opening timing IVO on the right side of the equation (8) is known from the command value given to the intake valve VTC mechanism 27. The unit of the intake valve opening timing IVO may be a crank angle measured on the retard side with an appropriate crank angle position (for example, compression top dead center) as a reference.

  X and θoff on the right side of equation (8) and the gap volume Vc on the right side of equation (7) are calculated by the following equation.

X = ST / 2 × sin (EVC−θoff) −CR off + PIN off
... (9)
θoff = arcsin ((CR evc-PIS off / CND + ST / 2)
(10)
Vc = (π / 4) × D ^ 2 × ST / (ε−1) (11)
However, ε: compression ratio, constant determined for each engine <3> Method of calculating combustion chamber pressure PIVO at intake valve opening timing Combustion chamber pressure PIVO [kPa] at intake valve opening timing has a sufficiently large exhaust valve opening Therefore, it is assumed that it is equal to the exhaust pressure. A difference value (pressure pulsation around the exhaust valve at each crank angle) between the combustion chamber pressure at each crank angle and the average exhaust pressure when the average exhaust pressure PEX [kPa] is used as a reference is stored as a map. Then, a difference value PCTRM [kPa] between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing is obtained with reference to the stored map, and the combustion chamber pressure and the average exhaust gas at the intake valve opening timing obtained are obtained. The sum of the difference value PCTRM and the average exhaust pressure PEX is used as the combustion chamber pressure PIVO at the intake valve opening timing, that is, the combustion chamber pressure PIVO at the intake valve opening timing is calculated by the following equation.

PIVO = PEX + PCTRM (12)
Here, the reason why the difference value PCTRM between the pressure in the combustion chamber and the average exhaust pressure when the intake valve is opened as shown in the equation (12) is as follows. That is, if the exhaust flow rate is known, the average exhaust pressure can be found from PV = nRT. However, since the actual pressure in the combustion chamber and the exhaust pressure change every moment with respect to the crank angle due to the influence of pulsation as shown in FIG. 14, the average value of the exhaust pressure is changed to PEX as shown in FIG. And the difference between the pressure in the combustion chamber at the intake valve opening timing and the average exhaust pressure (that is, the pressure pulsation around the exhaust valve at the intake valve opening timing) is represented by PCTRM.

  However, in terms of control, since it is not desired to represent the difference value between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing as a negative value, the average exhaust pressure PEX is set to the difference value as shown at the right end of FIG. The difference value PCTRM between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing is expressed with the lower end of the difference value being zero. Accordingly, in the following, the average exhaust pressure PEX, the difference value PCTRM between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing (and the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle) are shown in FIG. The value shown at the right end.

  Next, a method for calculating the difference value PCTRM between the pressure in the combustion chamber and the average exhaust pressure when the intake valve is opened will be described.

  The difference value PCTRM between the pressure in the combustion chamber at the intake valve opening timing and the average exhaust pressure can be regarded as proportional to the charging efficiency when the exhaust valve opening timing EVO and the rotational speed Ne are constant from FIG. Therefore, the difference between the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is minimum, the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is maximum, Are stored in each map. FIG. 6 shows the map contents of the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is minimum or the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is maximum. Show. In FIG. 6, the abscissa represents the crank angle and the ordinate represents the rotational speed Ne, and small, medium and large pressure values (both positive values) are entered in each of the 25 small sections divided by the grid. ing. For this reason, in each of the rotation speed ranges 1 to 5 divided into five, the characteristic of the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle is shown on the right side, and the rotation range is Once determined, the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle corresponding to the rotation region is determined. Therefore, since the intake valve opening timing IVO is known from the engine specifications, the crank chamber angle corresponding to the intake valve opening timing IVO and the rotational speed Ne at that time are compared with the combustion chamber pressure and average at each crank angle shown in FIG. By referring to the map of the difference value with the exhaust pressure, the difference value PCTRM (= Pmin described later) between the pressure in the combustion chamber and the average exhaust pressure when the intake valve is open when the charging efficiency is minimum, or the intake air when the charging efficiency is maximum A difference value PCTRM (= Pmax described later) between the pressure in the combustion chamber and the average exhaust pressure at the valve opening timing can be obtained. FIG. 6 is an example, and the value stored in each small section is different between the minimum filling efficiency and the maximum filling efficiency. Find the difference value between the combustion chamber pressure and average exhaust pressure at each crank angle when the charging efficiency is minimum, and the difference value between the combustion chamber pressure and average exhaust pressure at each crank angle when the charging efficiency is maximum. Each of the two crank angles is stored as a map of the difference value between the combustion chamber pressure and the average exhaust pressure.

  Since the actual charging efficiency during engine operation is between the minimum charging efficiency value and the maximum charging efficiency value, the map of the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is minimum, and the charging It is obtained by interpolation calculation using the map of the difference value between the combustion chamber pressure and the average exhaust pressure at each of the two crank angles in the map of the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle at the maximum efficiency. That's fine. That is, the difference value between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing when the charging efficiency is minimum is Pmin, and the difference value between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing when the charging efficiency is maximum. Pmax, where a is the difference between the minimum charging efficiency and the actual charging efficiency, and b is the difference between the maximum charging efficiency and the actual charging efficiency, the combustion chamber pressure at the opening timing of the intake valve at the actual charging efficiency A difference value PCTRM from the average exhaust pressure can be obtained by the following interpolation calculation formula.

PCTRM = Pmin + (Pmax−Pmin) × a / (a + b)
... (13)
a = ITAC-ITACMN (Supplement 4)
b = ITACMX-ITAC (Supplement 5)
Where Pmin: difference value [kPa] between the pressure in the combustion chamber and the average exhaust pressure when the intake valve is opened when the charging efficiency is maximum,
Pmax: difference value [kPa] between the pressure in the combustion chamber and the average exhaust pressure when the intake valve is opened when the charging efficiency is minimum,
ITAC: Actual filling efficiency [%], the calculation method will be explained later
ITACMN: minimum filling efficiency [%]
ITACMX: Maximum filling efficiency [%]
Here, the filling efficiency minimum value ITACMN on the right side of (Supplement 4) and the charging efficiency maximum value ITACMX on the right side of (Supplement 5) are obtained in advance using the engine load and the rotational speed Ne as parameters.

  Now, when the exhaust valve VTC mechanism 28 is provided, when the exhaust valve VTC mechanism 28 is switched from the non-operating state to the operating state, the exhaust valve opening timing EVO and the exhaust valve closing timing EVC are not adjusted to the exhaust valve VTC mechanism 28. Moving from the most retarded position in the operating state to the advanced angle side, the displacement of the exhaust valve pressure pulsation is caused by the movement of the exhaust valve opening / closing timing. Therefore, when the exhaust valve VTC mechanism 28 is not operated (that is, when the exhaust valve VTC mechanism is not provided), the map of the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle shown in FIG. 6 is applied. When the exhaust valve VTC mechanism 28 is operating, the combustion chamber pressure and the average exhaust pressure at each crank angle shown in FIG. 6 are adapted to when the exhaust valve VTC mechanism is not operating. If the difference value PCTRM between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing is obtained using the difference value map as it is, the difference in exhaust gas pressure pulsation due to the operation of the exhaust valve VTC mechanism 28 is obtained. An error occurs in the calculation of the difference value PCTRM between the combustion chamber pressure and the average exhaust pressure when the intake valve is open, and the combustion chamber pressure PIVO (combustion chamber residual gas amount) when the intake valve is open Calculation error occurs. Accordingly, when the exhaust valve VTC mechanism 28 is operated, it is necessary to newly calculate a difference value PCTRM between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing when the exhaust valve VTC mechanism is operated.

  Therefore, the following is a discussion of this. First, when the exhaust valve VTC mechanism 28 is in an inoperative state under the condition that the exhaust temperature is at the reference exhaust temperature, that is, the exhaust valve opening timing EVO is at the maximum of the initial position. The pressure pulsation waveform of the pressure in the combustion chamber at the retarded position (indicated by “EVO delay” in the figure) and the operation of the exhaust valve VTC mechanism 28 under the condition that the exhaust temperature is at the reference exhaust temperature, FIG. 7 shows the pressure pulsation waveform (indicated by “EVO early” in the figure) of the pressure in the combustion chamber when EVO is advanced by a predetermined value ADV. According to FIG. 7, when the exhaust valve opening timing EVO is advanced by, for example, a crank angle of 10 degrees (the unit of the crank angle is expressed as [degCA] hereinafter), the reference pressure pulsation waveform is shifted to the left side by the same 10 degCA ( This means that if they move parallel to the advance angle side, they overlap exactly, that is, the wavelength of the pressure pulsation waveform of the pressure in the combustion chamber does not change. Here, the reference pressure pulsation waveform is a pressure pulsation waveform of the combustion chamber pressure when the exhaust valve VTC mechanism 28 is in an inoperative state under the condition of the reference exhaust temperature. The lowest exhaust temperature is set as the reference exhaust temperature.

  Accordingly, in this case, the difference value PCTRM between the pressure in the combustion chamber and the average exhaust pressure when the exhaust valve VTC mechanism is operated when the exhaust valve VTC mechanism is operated can be calculated as follows. That is, when the model waveform is shown in FIG. 16, FIG. 16 shows only the pulsation component extracted from the pressure pulsation waveform of the exhaust pressure. Assuming that the waveform of the pulsation when the exhaust valve VTC mechanism 28 is not operated is a solid line, when the exhaust valve opening timing EVO is advanced by a predetermined value ADV due to the operation of the exhaust valve VTC mechanism 28, the waveform of the pulsation is from the solid line. It will translate to the left side of the dashed line. If there is an intake valve opening timing IVO at the illustrated position, the difference value PCTRM between the pressure in the combustion chamber and the average exhaust pressure at the intake valve opening timing when the exhaust valve VTC mechanism is not in operation is the value at the position marked with ●. However, the difference value PCTRM between the combustion chamber pressure and the average exhaust pressure when the intake valve opening timing when the intake / exhaust valve VTC mechanism is desired is shifted to the value indicated by the circle mark. The value at this circle mark position is the same as the value on the solid line at the crank angle (IVO + ADV) delayed from the intake valve opening timing IVO by a predetermined value ADV, that is, the value at the mark position Δ. That is, in order to obtain the difference value PCTRM between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing when the exhaust valve opening timing is advanced by the predetermined value ADV by the operation of the exhaust valve VTC mechanism 28, In place of the intake valve opening timing IVO, a value obtained by adding a predetermined value ADV to the intake valve opening timing IVO is used for the characteristics of the solid line, that is, at each crank angle shown in FIG. 6 that is adapted when the exhaust valve VTC mechanism is not operated. This means that a difference value map between the combustion chamber pressure and the average exhaust pressure may be referred to. In other words, when the exhaust valve VTC mechanism 28 is in a non-operating state, a map of the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is minimum at the reference exhaust temperature, and when the charging efficiency is maximum. If the two difference value maps, the difference value map between the combustion chamber pressure and the average exhaust pressure at each crank angle, are adapted, the exhaust valve opening timing EVO is determined by the operation of the exhaust valve VTC mechanism 28. The difference between the combustion chamber pressure at each of these two crank angles and the average exhaust pressure from the crank angle obtained by adding the predetermined value ADV to the intake valve opening timing IVO and the rotational speed Ne at that time when the valve is advanced by the value ADV Referring to the map of values, the difference between the combustion chamber pressure at the intake valve opening timing when the charging efficiency is minimum and the average exhaust pressure, and the combustion chamber at the intake valve opening timing when the charging efficiency is maximum By obtaining the difference between the force and the average exhaust pressure, the intake valve at the time when the charging efficiency is minimum is obtained even when the exhaust valve opening timing EVO is advanced by the predetermined value ADV by the operation of the exhaust valve VTC mechanism 28. The difference value PCTRM (Pmin) between the combustion chamber pressure and the average exhaust pressure at the opening timing and the difference value PCTRM (Pmax) between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing at the maximum charging efficiency are accurately obtained. It can be done.

  FIGS. 7 and 16 show the case where the exhaust temperature is at the reference exhaust temperature, that is, the exhaust temperature does not change between when the exhaust valve VTC mechanism 28 is inactive and when it is in operation. Consider a case where the temperature is higher than the exhaust temperature. That is, the pulsation waveform of the pressure in the combustion chamber when the exhaust valve VTC mechanism 28 is in a non-operating state under the condition that the exhaust temperature is at the reference exhaust temperature (indicated by “IVO delay” in the figure), and the exhaust temperature is the reference exhaust. The pulsation waveform of the pressure in the combustion chamber when the exhaust valve opening timing EVO is advanced by a predetermined value ADV by the operation of the exhaust valve VTC mechanism 28 under a condition higher than the temperature (indicated by “IVO early” in the figure). 8 is shown in a superimposed manner in FIG. According to FIG. 8, when the exhaust valve opening timing EVO advances, for example, by 10 deg CA, the reference pressure pulsation waveform moves to the left (advance angle side) by the same 10 deg CA, and unlike in FIG. This shows that the wavelength of the pressure pulsation waveform is shortened.

  Accordingly, in this case, the difference value PCTRM between the pressure in the combustion chamber and the average exhaust pressure when the exhaust valve VTC mechanism is operated when the exhaust valve VTC mechanism is operated can be calculated as follows. That is, when the model waveform is shown in FIG. 17, FIG. 17 also shows only the pulsation portion extracted from the pulsation waveform of the exhaust pressure as in FIG. Under the condition that the exhaust temperature is at the reference exhaust temperature, assuming that the waveform of the pulsation is a solid line when the exhaust valve VTC mechanism 28 is not operating, the exhaust temperature is higher than the reference exhaust temperature even when the exhaust valve VTC mechanism 28 is not operating. If the conditions on the side are satisfied, the wavelength of the pulsation component waveform becomes shorter, so the waveform of the pulsation component changes from a solid line to a broken line. In other words, when the exhaust gas temperature is higher than the reference exhaust gas temperature, the pulsation waveform is equivalent to the pulsation wavelength being shorter than when the exhaust gas temperature is at the reference exhaust gas temperature, based on the exhaust valve opening timing. Also move to the left.

  Thus, even when the exhaust valve VTC mechanism is not in operation, the wavelength of the pulsation waveform is shortened by the exhaust temperature deviating from the reference exhaust temperature to a higher temperature side (when the exhaust temperature deviates from the reference exhaust temperature to the lower temperature side, the pulsation component When the waveform is longer), the exhaust valve VTC mechanism is inactive when the exhaust temperature deviates from the reference exhaust temperature by correcting the reference pulsation waveform based on the exhaust speed. A new pulsation waveform is calculated. Here, the reference pulsation waveform is a pulsation waveform under the condition that the exhaust temperature is at the reference exhaust temperature. For example, the reference pulsation component waveform is stored with the crank angle as a parameter for each of the five rotation regions in accordance with FIG. Then, with reference to the newly calculated pulsation waveform for each of the five rotation ranges in accordance with FIG. 6, the exhaust valve VTC mechanism is not operated under the condition that the exhaust temperature deviates from the reference exhaust temperature. A map of the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle at the time is created. That is, FIG. 6 is a map of the difference value between the pressure in the combustion chamber and the average exhaust pressure at each crank angle, which is prepared in advance by adapting when the exhaust valve is not operating under the condition where the exhaust temperature is at the reference exhaust temperature. Whenever the exhaust gas temperature deviates to a higher temperature than the reference exhaust gas temperature, the combustion chamber pressure at each crank angle that meets the exhaust valve non-operating condition with the exhaust gas temperature deviating from the reference exhaust gas temperature. And a new map of the difference value between the average exhaust pressure and the average exhaust pressure.

  Next, when the exhaust valve opening timing EVO is advanced by a predetermined value ADV due to the operation of the exhaust valve VTC mechanism 28 under the condition where the exhaust temperature is higher than the reference exhaust temperature, the pulsation waveform is superimposed on FIG. As shown in the figure, the line moves further to the left from the broken line to the one-dot chain line.

  Now, assuming that the intake valve opening timing IVO is at the position shown in the figure, the pressure in the combustion chamber at the intake valve opening timing when the exhaust valve VTC mechanism is not operated under the condition that the exhaust temperature deviates to a higher temperature side than the reference exhaust temperature. The difference value PCTRM between the average exhaust pressure and the average exhaust pressure is the value at the position marked with ◎, but the intake valve opening timing to be obtained when the exhaust valve VTC mechanism is operated under the condition that the exhaust temperature deviates from the reference exhaust temperature. The difference value PCTRM between the pressure in the combustion chamber and the average exhaust pressure at is shifted to the value at the position marked with a circle. The value at this circle mark position is the same as the value on the broken line at the crank angle (IVO + ADV) delayed by the predetermined value ADV from the intake valve opening timing IVO, that is, the value at the mark position Δ. This means that the pressure in the combustion chamber at the intake valve opening timing when the exhaust valve opening timing is advanced by a predetermined value ADV by the operation of the exhaust valve VTC mechanism 28 under the condition that the exhaust temperature deviates from the reference exhaust temperature. In order to obtain the difference value PCTRM between the intake valve opening timing IVO and the intake valve opening timing IVO, a value obtained by adding a predetermined value ADV is used instead of the intake valve opening timing IVO. It is only necessary to refer to the map of the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle newly created so as to be adapted when the exhaust valve VTC mechanism is not operated under a condition deviating to a higher temperature side. Means that. In other words, the pulsation waveform (that is, the reference pulsation waveform) when the exhaust valve VTC mechanism is not operated under the condition that the exhaust temperature is at the reference exhaust temperature when the charging efficiency is minimum and when the charging efficiency is maximum is shown in FIG. The crank angle is stored in the map as a parameter for each rotation range, and when the exhaust temperature deviates to a higher temperature side than the reference exhaust temperature, the exhaust speed (exhaust pressure) is compared with the reference pulsation waveform. 6 for the pulsation when the exhaust valve VTC mechanism is not operated under the condition that the exhaust temperature deviates from the reference exhaust temperature to the higher temperature side. Combustion at each crank angle when the exhaust valve VTC mechanism is not operating and when the charging efficiency is minimum, under the condition that the exhaust temperature deviates to a higher temperature than the reference exhaust temperature based on the pulsation waveform for each rotation range A map of the difference between the internal pressure and the average exhaust pressure, and combustion at each crank angle when the exhaust valve VTC mechanism is not operating and the charging efficiency is maximum under the condition that the exhaust temperature deviates from the reference exhaust temperature. A map of the difference value between the combustion chamber pressure and the average exhaust pressure at each of the two crank angles of the map of the difference value between the chamber pressure and the average exhaust pressure is newly created in the same manner as in FIG. When the exhaust valve opening timing EVO is advanced by a predetermined value ADV by the operation of the exhaust valve VTC mechanism 28 under the condition that the exhaust temperature deviates to a higher temperature side than the reference exhaust temperature, the predetermined value ADV is set to the intake valve opening timing IVO. Referring to the map of the difference value between the combustion chamber pressure and the average exhaust pressure at each of the two newly created crank angles from the added crank angle and the rotational speed Ne at that time, the exhaust temperature is the reference exhaust temperature. The difference value PCTRM (= Pmin) between the pressure in the combustion chamber and the average exhaust pressure when the exhaust valve VTC mechanism is operated and the charging efficiency is minimum when the exhaust temperature is higher and the exhaust temperature is the reference The difference value PC between the combustion chamber pressure and the average exhaust pressure when the exhaust valve VTC mechanism is operated under conditions deviating from the exhaust temperature and the intake valve is open when the charging efficiency is maximum By obtaining RM (= Pmax), the exhaust valve opening timing EVO is advanced by a predetermined value ADV by the operation of the exhaust valve VTC mechanism 28 under the condition that the exhaust temperature deviates from the reference exhaust temperature. The difference value PCTRM (= Pmin) between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing when the charging efficiency is minimum and the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing when the charging efficiency is maximum The difference value PCTRM (= Pmax) can be obtained with high accuracy.

  In FIGS. 8 and 17, the case where the exhaust temperature deviates from the reference exhaust temperature to the higher temperature side has been described. Here, since the lowest exhaust temperature is set as the reference exhaust temperature, the case where the exhaust temperature deviates from the reference exhaust temperature due to the difference in operating conditions was considered, but as described later, the highest reference exhaust temperature is assumed. When the exhaust temperature is set, it must be considered that the exhaust temperature deviates from the reference exhaust temperature due to the difference in operating conditions. In this case, even when the exhaust valve VTC mechanism 28 is not in operation, if the exhaust gas temperature is lower than the reference exhaust gas temperature, the wavelength of the pulsation waveform becomes longer. Since the pulsation component waveform moves to the right side with respect to the exhaust valve opening timing as compared with when the exhaust gas temperature is at the reference exhaust gas temperature, it can be considered in the same manner as in the present embodiment.

  The exhaust velocity c [m / s] is calculated using the sonic velocity formula as follows.

c = (κ × PIVO / ρ) (14)
Where κ is the specific heat ratio of the exhaust, and the calculation method will be explained later
PIVO: Combustion chamber pressure [kPa] at intake valve opening timing,
ρ: exhaust density,
The following equation is used to calculate the exhaust density ρ on the right side of equation (14).

ρ = REX × TEX / PIVO (15)
However, REX: exhaust gas constant [kJ / kg / K], calculated with equation (6)
TEX: average exhaust temperature [K], the calculation method will be described later
PIVO: Combustion chamber pressure [kPa] at intake valve opening timing,
From the equations (14) and (15), the exhaust velocity c can be calculated by the following equation with the exhaust gas density ρ eliminated.

c = (κ × REX × TEX) ^ (1/2) (16)
However, REX: exhaust gas constant [kJ / kg / K], calculated with equation (6)
TEX: Average exhaust gas temperature [K], the calculation method will be described later Since the distance L from the combustion chamber to the catalyst 9 is known, the pulsation waveform when the exhaust gas temperature is higher than the reference exhaust gas temperature by the following equation The wavelength λ [m] is calculated.

λ = L / c (17)
Where L: distance from combustion chamber to catalyst 9 [m]
Here, since the wavelength λ0 of the reference pulsation waveform is predetermined, the correction term is λ / λ0. Therefore, the pulsation waveform when the exhaust temperature deviates to a higher temperature than the reference exhaust temperature can be obtained as follows.

Pulsation waveform when deviating from reference exhaust temperature to high temperature side = Reference pulsation waveform x (λ / λ0) (Appendix 6)
The calculation method of the specific heat ratio κ on the right side of the above equation (16) will be described. The constant pressure specific heat Cp of the exhaust gas is considered by the following simplified reaction formula.

Cp = (Cp_CO ₂ (TEX) × A + Cp_H ₂ O (TEX) × B
+ Cp_N ₂ (TEX) × C + Cp_O ₂ (TEX) × D
+ Cp_CO (TEX) × E)
/ (44 × A + 18 × B + 28 × C + 32 × D + 28 × E)
... (18)
However, Cp_CO ₂ (TEX): constant pressure specific heat at the average exhaust temperature of CO ₂
[J / kmolK],
Cp_H ₂ O (TEX): constant pressure specific heat at an average exhaust temperature of H ₂ O
[J / kmolK],
Cp_N ₂ (TEX): constant pressure specific heat at the average exhaust temperature of N ₂
[J / kmolK],
Cp_O ₂ (TEX): constant pressure specific heat at O ₂ average exhaust temperature
[J / kmolK],
Cp_CO (TEX): constant pressure specific heat at the average exhaust temperature of CO
[J / kmolK],
Each constant pressure specific heat on the right side of the equation (18) is calculated by the following equation as a function of the average exhaust temperature TEX. In (Supplement 7-1) to (Supplement 7-5), TEX ^ 4 is generally used, but TEX ^ 5 and TEX ^ 6 are added in the prior application apparatus.

Cp_CO ₂ (TEX) = 5.0 × 10 ^ (− 20) × TEX ^ 6
+ 1.0 × 10 ^ (− 16) × TEX ^ 5
−5.0 × 10 ^ (− 12) × TEX ^ 4
+ 2.0 × 10 ^ (− 08) × TEX ^ 3
−6.0 × 10 ^ (− 05) × TEX ^ 2
+ 0.0727 × TEX + 20.075
... (Supplement 7-1)
Cp_H ₂ O (TEX) = 7.0 × 10 ^ (− 21) × TEX ^ 6
−4.0 × 10 ^ (− 16) × TEX ^ 5
+ 4.0 × 10 ^ (− 12) × TEX ^ 4
−2.0 × 10 ^ (− 08) × TEX ^ 3
+ 3.0 × 10 ^ (− 05) × TEX ^ 2
-0.0057 × TEX + 33.393
... (Supplement 7-2)
Cp_N ₂ (TEX) = 4.0 × 10 ^ (− 19) × TEX ^ 6
−4.0 × 10 ^ (− 15) × TEX ^ 5
+ 2.0 × 10 ^ (− 11) × TEX ^ 4
−4.0 × 10 ^ (− 08) × TEX ^ 3
+ 5.0 × 10 ^ (− 05) × TEX ^ 2
-0.0207 × TEX + 31.894
... (Supplement 7-3)
Cp_O ₂ (TEX) = 5.0 × 10 ^ (− 19) × TEX ^ 6
−5.0 × 10 ^ (− 15) × TEX ^ 5
+ 2.0 × 10 ^ (− 11) × TEX ^ 4
−4.0 × 10 ^ (− 08) × TEX ^ 3
+ 3.0 × 10 ^ (− 05) × TEX ^ 2
-0.0014 × TEX + 27.941
... (Supplement 7-4)
Cp_CO (TEX) = 3.0 × 10 ^ (− 19) × TEX ^ 6
−4.0 × 10 ^ (− 15) × TEX ^ 5
+ 2.0 × 10 ^ (− 11) × TEX ^ 4
−4.0 × 10 ^ (− 08) × TEX ^ 3
+ 5.0 × 10 ^ (− 05) × TEX ^ 2
−0.0173 × TEX + 31.175
... (Supplement 7-5)
The specific heat ratio κ of the exhaust gas is calculated by the following equation from the constant pressure specific heat CP of the exhaust gas determined by the equation (18).

κ = Cp / (Cp−REX) (19)
The method of calculating the filling efficiency ITAC on the right side of the above (complement 4) and the right side of the (complement 5) will be described. The actual filling efficiency ITAC is calculated by the following equation.

ITAC = MA / MAMX (Supplement 8)
MA: Intake air amount [kg / s]
MAMX: intake air amount [kg / s] at maximum charging efficiency,
Here, the intake air amount MA is detected by the air flow sensor 32. The intake air amount MAMX at the maximum filling efficiency is a value measured by an actual machine.

  Next, a method for calculating the average exhaust pressure PEX in the first term on the right side of the equation (12) will be described.

  The average exhaust pressure PEX is calculated by the following equation.

PEX = ((KTBF × MFEXG ^ 2 + KLMF × MFEXG) × REX
× TEX / 1000000 + PPAMB ^ 2) ^ (1/2)
... (20)
However, MFEXG: exhaust flow rate [kg / s],
PPAMB: atmospheric pressure [kPa],
KTBF: Turbulence coefficient, experimentally adapted value
KLMF: Laminar flow coefficient, experimentally adapted value
REX: Exhaust gas constant, calculated with equation (6)
TEX: Average exhaust temperature, and a calculation method will be described later. Equation (20) calculates the average exhaust pressure PEX from the pressure loss of each part (catalyst) in the exhaust pipe and the atmospheric pressure PPAMB. The exhaust pipe pressure loss occurs at the catalyst 9 inlet (turbulent flow) and the catalyst 9 (laminar flow). The turbulence coefficient and laminar flow coefficient are compatible terms determined by each model (exhaust manifold and catalyst system). The atmospheric pressure PPAMB is detected by the atmospheric pressure sensor 36. The reason for dividing by 1000000 is to convert the gas flow rate [kg / s] to the pressure [kPa].

  The exhaust flow rate MFEXG on the right side of the equation (20) is calculated by the following equation.

MFEXG = MA × (1 + TFBYA / 14.7) (21)
However, MA: intake air amount [kg / s],
TFBYA: target equivalent ratio,
Here, the intake air amount MA is detected by the air flow sensor 32. The target equivalent ratio TFBYA is obtained by referring to a map (see FIG. 3) using the engine load and the rotational speed as parameters.
<4> Method of calculating combustion chamber temperature TIVO at intake valve opening timing Combustion chamber temperature TIVO at intake valve opening timing is calculated from the state represented by average exhaust temperature TEX and average exhaust pressure PEX to intake valve opening timing IVO. Assuming that the state change is an adiabatic change, it is calculated by the following equation.

TIVO = TEX. (PIVO / PEX) ^ ((κ-1) / κ)
... (22)
However, PIVO: Combustion chamber pressure [kPa] at intake valve opening timing, calculated by equation (12)
PEX: Average exhaust pressure [kPa], calculated with equation (20)
[kappa]: Specific heat ratio of exhaust, calculated by equation (19) A method for calculating the average exhaust temperature TEX on the right side of equations (20) and (22) will be described.

  The following empirical formula obtained from the characteristics of FIG. 9, where the average exhaust temperature TEX [K] is the waste heat ratio (the value obtained by dividing the waste heat at that time by the maximum waste heat) on the horizontal axis and the exhaust temperature on the vertical axis. Calculate from

TEX = TEXMX− (TEXMX−TEXMN) × exp (−KTEX × Q ′)
... (23)
However, Q ′: Waste heat quantity [kW],
TEXMX: Exhaust equilibrium temperature [K] when waste heat is maximum, experimental value
TEXMN: Equilibrium exhaust temperature [K] when waste heat is zero, experimental value
KTEX: Sensitivity of waste heat quantity to exhaust temperature (arbitrary constant),
The amount of waste heat Q ′ on the right side of the equation (23) is calculated by subtracting the shaft work from the supply heat amount, and is calculated by the following equation.

Q ′ = MA × TFBYA / 14.7 × (HL−HV) × NCYL / 2
-2π × TENG × Ne / 60 (24)
However, MA: intake air amount, see formula (21)
TFBYA: target equivalent ratio, see formula (21)
HL: Low calorific value [kW], fit value by simulation
HV: latent heat of vaporization [kw], fit value by simulation
NCYL: Total number of cylinders,
TENG: Estimated actual torque value [Nm],
Ne: Engine rotation speed [rpm],
In the equation (24), the shaft work is calculated as the shaft work per engine revolution by multiplying the actual torque estimated value TENG by 2π. The actual torque estimated value TENG is obtained by referring to a map as shown in FIG. 10 using the charging efficiency ITAC and the engine speed Ne as parameters. The engine speed Ne is detected by a crank angle sensor (33, 34).
2. Calculation Method of Blowback Gas M2 The overlap between the intake valve open period and the exhaust valve open period includes a minus overlap and a plus overlap as shown in FIG.
<1> In the case of minus overlap In the minus overlap shown in the upper part of FIG. 11, the amount of residual gas in the combustion chamber at the intake valve opening timing is equal to the amount of residual gas in the combustion chamber at the exhaust valve closing timing EVC. Although the combustion chamber gas blows back to the intake port side at the intake valve opening timing IVO, it is re-inflowed in the intake stroke. Become. That is, in the case of minus overlap, the blown back gas amount M2 = 0.
<2> In the case of plus overlap In the case of plus overlap shown in the lower part of FIG. 11, as described above, the blowback gas amount M2 during the overlap of the intake valve open period and the exhaust valve open period is taken into consideration. There is a need to.

  FIG. 12 shows that in the case of plus overlap, the pressure in the combustion chamber (Pcyl), the exhaust pressure (Pex), the intake pressure (Ain), the gas flow around the exhaust valve, the intake valve, and the opening area of the exhaust valve The model shows how the valve changes during the overlap between the opening period and the opening period of the exhaust valve, that is, in the crank angle section from the intake valve opening timing IVO to the exhaust valve closing timing EVC.

  The amount of blowback gas blown back from the exhaust port 11 into the combustion chamber during the overlap is integrated from the intake valve opening timing IVO to the exhaust valve closing timing EVC with respect to the crank valve angle of the gas flow around the exhaust valve in FIG. To calculate). However, in consideration of on-board calculation, it is not practical to calculate the gas flow rate around the exhaust valve that changes every moment with respect to the crank angle. Therefore, as shown in FIG. 13, the waveform of the gas flow rate around the exhaust valve is approximated by two straight lines, a straight line 1 (first straight line) rising to the right and a straight line 2 (second straight line) falling to the right. The area of the two triangles composed of the straight line of the intake valve opening timing IVO (vertical line passing through IVO in FIG. 13) and the horizontal line of zero gas flow around the exhaust valve is obtained. The blowback gas amount M2 during the overlap between the period and the open period of the exhaust valve is estimated. That is, in FIG. 13, the gas flow around the exhaust valve is negative from point a to point b, that is, the gas from the exhaust port 11 blows back to the intake port 4, and the gas flow around the exhaust valve is positive after point b, that is, the intake port 4. Since the gas blown back into the combustion chamber flows into the combustion chamber, the blown back gas amount M2 [kg] is calculated by the following equation.

M2 = | IVO−θ0 | × (dm / dθ) ivo / 2
+ | EVC-θ0 | × (dm / dθ) c / 2 (25)
However, IVO: intake valve opening timing [degCA],
(Dm / dθ) ivo: Gas flow around the exhaust valve when the intake valve opens
[Kg / degCA],
θ0: crank angle [degCA] at point b where the gas flow around the exhaust valve becomes zero,
θ1: crank angle at the intersection c of the straight line 1 and the straight line 2
[DegCA],
(Dm / dθ) c: Gas flow around the exhaust valve at the intersection c
[Kg / degCA],
Since the gas flow rate around the exhaust valve is positive in the direction flowing from the combustion chamber to the exhaust port 11, the first term on the right side of the equation (25) is a negative value, the second term on the right side is a positive value, and the equation (25) The entire right side is considered to be a negative value as judged from FIG. 13. At that time, when substituting the value of the right side of equation (25) into the above (complement 1), the absolute value of M2 is taken and added. As the crank angle θ in the equation (25), a crank angle measured on the retard side from an appropriate crank angle position (for example, compression top dead center) is used.

  In an engine that does not include the exhaust valve VTC mechanism 28, the exhaust valve closing timing EVC is fixed (here, the intake valve opening timing IVO is also fixed), so both of the two straight lines shown in FIG. ) In the right side of the equation, the intake valve opening timing IVO, the exhaust valve closing timing EVC, the exhaust valve surrounding gas flow rate (dm / dθ) ivo at the intake valve opening timing, the crank angle θ0 at the point b at which the exhaust valve surrounding gas flow rate becomes zero, If the gas flow rate around the exhaust valve (dm / dθ) c at the intersection point c is adapted in advance, the blow back gas amount M2 can be calculated by the equation (25).

  However, when the exhaust valve VTC mechanism 28 is provided as in the present embodiment, it is assumed that the exhaust valve closing timing EVC is at the position shown in FIG. 13 when the exhaust valve VTC mechanism 28 is not in operation. When the exhaust valve closing timing EVC is advanced from the most retarded position which is the initial position when the exhaust valve VTC mechanism is not operated by the operation of the VTC mechanism 28, the straight line 2 shown in FIG. 1 does not change), the crank angle θ1 of the intersection c of the straight line 1 and the straight line 2 and, therefore, the gas flow around the exhaust valve (dm / dθ) c at the intersection c becomes small. The amount of gas flowing into (the triangular area on the right side of FIG. 13) decreases. That is, when the exhaust valve VTC mechanism 28 is provided, the exhaust valve closing timing is advanced by the operation of the exhaust valve VTC mechanism 28 from the initial position when the exhaust valve VTC mechanism is not operated. If the blowback gas amount M2 is calculated using a value that is pre-adapted when the valve VTC mechanism is not operated, an error corresponding to the movement of the straight line 2 in the calculation of the blowback gas amount M2 (that is, the gas blown back to the intake port 4). This means that an error corresponding to a decrease in the amount of gas flowing into the combustion chamber occurs. Accordingly, when the exhaust valve VTC mechanism 28 is operated, the straight line 2 is determined each time in accordance with the exhaust valve closing timing EVC when the exhaust valve VTC mechanism is operated, and the amount of blown back gas is determined based on the determined straight line 2. It is necessary to calculate M2.

Hereinafter, the calculation method of the straight line 1 and the straight line 2 will be described.
[1] Calculation method of straight line 1 (a) Calculation method of exhaust gas flow around exhaust valve (dm / dθ) ivo at intake valve opening timing Since intake valve opening gas flow rate is 0 at intake valve opening timing IVO, intake valve At the opening time IVO,
Mass change in combustion chamber = Gas flow around exhaust valve (26)
Calculate as. Differentiating both sides of the equation of state (M = P × V / R / T) yields:

dM / dt = d (P × V / R / T) / dt
= V / R / T x dP / dt + 10 P / R / T x dV / dt
−V × P / T / R ^ 2 × dR / dt
−V × P / T ^ 2 / R × dT / dt
... (27)
M: Mass of gas in combustion chamber [kg]
P: combustion chamber pressure [kPa], PIVO when intake valve is open
V: combustion chamber volume [m ^ 3], set to VIVO when the intake valve opens
T: Combustion chamber gas temperature [K], TIVO at intake valve opening timing
R: Gas constant [kg / mol · K], REX at intake valve opening timing Each change in combustion chamber gas temperature and gas constant at intake valve opening timing is minute.
dR / dt = 0, dT / dt = 0 (Supplement 9)
Assume that Assuming that the rate of change in the pressure in the combustion chamber during the overlap between the opening period of the intake valve and the opening period of the exhaust valve is constant, and that the pressure in the combustion chamber becomes equal to the average manifold pressure when the exhaust valve is closed, the following equation holds.

dP / dt = Cpa (28)
Cpa = (PEVC-PIVO) / ((EVC-IVO) / 360 × Ne / 60)
... (Supplement 10)
Where Cpa: time derivative of combustion chamber pressure,
PIVO: Combustion chamber pressure [kPa] at intake valve opening timing, calculated by <3> above
PEVC: Combustion chamber pressure [kPa] at exhaust valve closing timing, equal to average intake pressure
Ne: Engine rotation speed [rpm],
Here, the unit of [/ degCA] is converted into the unit of [/ sec] by dividing PEVC-PIVO by 360 × Ne / 60. The average intake pressure is detected by the intake pressure sensor 44. The engine speed Ne is detected by a crank angle sensor (33, 34).

further,
dθ / dt = 360 × Ne / 60 = 6 × Ne (29)
However, since θ is detected by the crank angle and crank angle sensors (33, 34), when the equations (29) and (28) are substituted into the equation (26), the equation (26) becomes as follows. .

dM / dθ = V / R / T × Cpa / 6 / Ne + P / R / T × dV / dθ
... (30)
On the other hand, since the rate of change of the combustion chamber volume changes linearly near the intake top dead center, it is approximated by the following equation.

dV / dθ = Cva · θ + Cvb (31)
However, Cva: slope of the straight line when the horizontal axis represents the crank angle and the vertical axis represents the rate of change in the combustion chamber volume near the intake top dead center [m ^ 3 / deg ^ 2]
Cvb: intercept of the straight line when the crank angle is plotted on the horizontal axis and the volumetric change rate in the combustion chamber is plotted on the vertical axis near the intake top dead center [m ^ 3]
Substituting equation (31) into equation (30), equation (30) becomes as follows.

dM / dθ = V / 6 / Ne / R / T × Cpa + P / R / T × (Cva · θ + Cvb)
... (32)
Here, from the equations (26) and (32), the gas flow around the exhaust valve (dm / dθ) ivo [kg / degCA] at the intake valve opening timing is given by the following equation.

(Dm / dθ) ivo = VIVO × Cpa / 6 / Ne / REX / TIVO
+ PIVO / REX / TIVO × (Cva × IVO + Cvb)
... (33)
However, VIVO: combustion chamber volume at the time of intake valve opening [m ^ 3], calculated
TIVO: Combustion chamber temperature [K] at intake valve opening timing, calculated
PIVO: Combustion chamber pressure [kPa] at intake valve opening timing, calculated
IVO: intake valve opening timing [degCA], calculated
REX: exhaust gas constant [kJ / mol / K], calculated
Ne: Engine rotation speed [rpm]
(A) Method for calculating crank angle θ0 at point b Since the gas flow rate around the exhaust valve at point b is 0, the gas flow rate around the intake valve is equal to the change in mass in the combustion chamber, as in equation (26).
And From the equation of state, the mass change in the combustion chamber is

dM / dt = d (P × V / R / T) / dt
= V / R / T * dP / dt + P / R / T * dV / dt
−V × P / T / R ^ 2 × dR / dt
-V * P / T ^ 2 / R * dT / dt (35)
M: Mass of gas in combustion chamber [kg]
P: Combustion chamber pressure [kPa], exhaust gas flow around exhaust valve = 0, equal to exhaust pressure, exhaust pressure = (PEX + PIVO) / 2
V: Combustion chamber volume [m ^ 3], gas flow around exhaust valve = 0 near intake top dead center, and change in combustion chamber volume is negligible, so combustion chamber at intake top dead center Use volume = gap volume Vc (calculated)
T: TEX when gas temperature in combustion chamber [K] and gas flow around exhaust valve = 0
R: Gas constant [kg / mol · K], R EX when the gas flow rate around the exhaust valve = 0 When the gas flow rate around the exhaust valve = 0, it is near the intake top dead center. Because changes in combustion chamber gas temperature and gas constant are minute,
dR / dt = 0, dT / dt = 0 (Supplement 11)
Assume that Next, the intake valve passage gas amount (dm / dt) in can be expressed by the following equation.

(Dm / dt) in = Ain × Pex / (REX × TEX) × κ ^ (1/2)
× (2 / (κ + 1)) ^ (κ + 1)
/ (2 / (κ-1)) × RMF1 (36)
However, Ain: intake valve opening area, a calculation method will be described later
TEX: Average exhaust temperature, calculated
Pex: Exhaust pressure, here (PEX + PIVO) / 2
REX: exhaust gas constant, calculated
κ: Specific heat ratio of exhaust, calculated
RMF1: flow rate ratio,
The flow rate ratio RMF1 on the right side of the equation (36) is used to calculate the ratio of the intake valve passage gas flow rate at the sonic speed and the normal intake valve passage gas flow rate (the crank angle when the exhaust valve surrounding gas flow rate = 0). Flow rate ratio) and can be expressed by the following equation.

RMF1 = (Pin / Pex) ^ (1 / κ) × (2 × κ / (κ−1))
× (1- (Pin / Pex) ^ ((κ-1) / κ)) ^ (1/2)
/ Κ ^ (1/2) / (2 / (κ + 1)) ^ ((κ + 1) / 2 / (κ-1))
... (37)
However, Pin: average intake pressure, adapted value by experiment
Pex: Exhaust pressure, here (PEX + PIVO) / 2 Here, the exhaust pressure Pex in equation (37) is (PEX + PIVO) / 2 because the gas flow around the exhaust valve is in the first half of the overlap This is because the pulsation in the combustion chamber is large.

Also,
β = Pex / (REX × TEX) × κ ^ (1/2)
× (2 / (κ + 1)) ^ (κ + 1) / (2 / (κ-1)) × RMF1 (38)
Then, the equation (36) becomes the following equation.

(Dm / dt) in = Ain × β (Supplement 12)
Since the gas flow rate around the exhaust valve is zero, dM / dt = (dm / dt) in. Further, when the valve profile (map value) immediately after the intake valve opening timing is approximated by a quadratic function, the intake valve opening area Ain [m ^ 2] is expressed by the following equation.

Ain = Cai × (θ−IVO) ^ 2 (Supplement 13)
Where Cai: coefficient,
IVO: intake valve opening timing [degCA],
Therefore, equation (35) becomes the following equation.

V / R / T × dP / dt + P / R / T × dV / dt
= Cai * ([theta] -IVO) ^ 2 * [beta] (39)
VTDC / REX / TEX × 6 × Ne = X (Supplement 14) by using the above equations (27), (28), and (30) described for point a.
PEX / REX / TEX × 6 × Ne = α (Supplement 15)
Where VTDC: combustion chamber volume at top dead center [m ^ 3],
Then, the equation (39) becomes the following equation.

βCaiθ ^ 2-θ × (2 × β × Cai × IVO + α × Cva)
−β × Cai × IVO ^ 2-α × Cva-X × Cpa = 0
... (Supplement 16)
Since (Equation 16) is a quadratic equation for the crank angle θ, when the crank angle θ is solved, the solution is obtained by the following equation.

θ = 2 × β × Cai × IVO + α × Cva
± ((2 × β × Cai × IVO + α × Cva) ^ 2−4 × β × Cai
× (−β × Cai × IVO ^ 2-α × Cva-X × Cpa))
^ (1/2) / 2 / β / Cai (Supplement 17)
If the crank angle θ0 when the gas flow rate around the exhaust valve is zero is the positive value of the two solutions, θ0 is expressed by the following equation.

θ0 = 2 × β × Cai × IVO + α × Cva
− ((2 × β × Cai × IVO + α × Cva) ^ 2−4 × β × Cai
× (−β × Cai × IVO ^ 2-α × Cva-X × Cpa))
^ (1/2) / 2 / β / Cai (Supplement 18)
Therefore, if the straight line 1 passing through the points a and b is set as a function y1, the function y1 is the crank angle θ0, the intake valve opening timing IVO, the intake air when the gas flow around the exhaust valve thus obtained becomes zero. Using the gas flow around the exhaust valve (dm / dθ) ivo at the valve opening timing, the following equation is given.

y1 = − (dm / dθ) ivo / (θ0−IVO) × θ
+ (Dm / dθ) ivo / (θ0−IVO) × θ0
... (Supplement 19)
However, (dm / dθ) ivo: Gas flow around the exhaust valve when the intake valve is open
[Kg / degCA]
θ0: Crank angle [degCA °] when the gas flow around the exhaust valve becomes zero
[2] Calculation Method for Line 2 The amount of blown back gas in the second half of the overlap between the opening period of the intake valve and the opening period of the exhaust valve (after the crank angle θ1 of the intersection c) is approximated by the line 2 passing through the points d and e. Basically, the crank angle θ2 at the point d may be anywhere after the crank angle θ1 at the intersection c and before the exhaust bubble closing timing EVC, but here the crank angle is between the intake valve opening period and the exhaust valve opening period. The crank angle position at the point where 3/4 of the overlap period has elapsed (the crank angle position on the retard side from the crank angle position when the two straight lines intersect). That is, the crank angle θ2 of the point d is given by the following equation.

θ2 = EVC− (EVC−IVO) / 4 (Supplement 20)
However, EVC: exhaust valve closing timing [degCA],
IVO: intake valve opening timing “degCA”,
Here, since the intake valve opening timing IVO is considered to be fixed, it is a constant value. Further, the exhaust valve closing timing EVC can be known from a command value given to the exhaust valve VTC mechanism 28.

  It is assumed that the intake valve 16 is sufficiently open at the crank angle θ2 and the pressure in the combustion chamber is substantially equal to the intake pressure. The gas flow around the exhaust valve at point d (dm / dθ) d [kg / degCA] is calculated by the following equation.

(Dm / dθ) d = Aex × PEX / (REX × TEX) ^ (1/2)
× κ ^ (1/2) × (2 / (κ + 1)) ^ ((κ + 1)
/ (2 × (κ−1))) × RMF2 / 6 / Ne
... (40)
However, the exhaust valve opening area at Aex: θ2, and a calculation method will be described later
PEX: Average exhaust pressure, calculated
REX: exhaust gas constant, calculated
TEX: exhaust temperature, calculated
κ: Specific heat ratio of exhaust, calculated
RMF2: flow ratio,
The flow rate ratio RMF2 on the right side of the equation (40) is a flow rate ratio used when calculating the gas flow rate around the exhaust valve at the crank angle position at which 3/4 of the overlap period has elapsed, and can be expressed by the following equation.

RMF2 = (Pin / PEX) ^ (1 / κ) × (2 × κ / (κ−1))
× (1- (Pin / PEX) ^ ((κ-1) / κ)) ^ (1/2)
/ Κ ^ (1/2) / (2 / (κ + 1)) ^ ((κ + 1) / 2 / (κ-1))
... (Supplement 21)
However, Pin: average intake pressure, adapted value by experiment
Here, the average exhaust pressure PEX is used in (Supplement 21) because the point where 3/4 of the overlap period has passed is in the latter half of the overlap. This is because pulsation is reduced.

  The exhaust valve opening area Aex with respect to the crank angle θ2 at the point d on the right side of the equation (40) is calculated as follows. In FIG. 18, assuming that the waveform of the exhaust valve opening area when the exhaust valve VTC mechanism is not operating is a solid line, when the exhaust valve closing timing EVC is advanced by a predetermined value ADV by the operation of the exhaust valve VTC mechanism 28, the exhaust valve opening is The waveform of the area translates from the solid line to the one-dot chain line to the left. If the crank angle θ2 at the point d is at the position shown in the figure, the exhaust valve opening area Aex with respect to the crank angle θ2 at the point d is the value at the position marked with ● when the exhaust valve VTC mechanism is not operating. The exhaust valve opening area Aex when the VTC mechanism for the intake / exhaust valve to be calculated is moved to the side where it becomes smaller to the value of the mark O. The smaller value of the circle mark position is the same as the value on the solid line at the crank angle (θ2 + ADV) delayed by a predetermined value ADV from the crank angle θ2 at the point d, that is, the value of the mark Δ position. . That is, when the exhaust valve closing timing EVC is advanced by a predetermined value ADV by the operation of the exhaust valve VTC mechanism 28, the exhaust valve opening area Aex at the crank angle θ2 at the point d is obtained at the point d. Instead of the crank angle θ2, the value obtained by adding the predetermined value ADV to the crank angle θ2 at the point d is used to obtain the characteristic of the solid line, that is, the characteristic of the exhaust valve opening area that is suitable when the exhaust valve VTC mechanism is not operated. It means that it only has to be referred. In other words, the exhaust valve opening area characteristics (solid line characteristics shown in FIG. 18) that are suitable when the exhaust valve VTC mechanism is not in operation are stored as an exhaust valve area table with the crank angle as a parameter. When the exhaust valve closing timing EVC is advanced by a predetermined value ADV by the operation of the VTC mechanism 28, the exhaust valve area table is referred to from the crank angle obtained by adding the predetermined value ADV to the crank angle θ2 at the point d. Even when the exhaust valve closing timing EVC is advanced by the predetermined value ADV by the operation of the exhaust valve VTC mechanism 28, the exhaust valve opening area Aex with respect to the crank angle θ2 at the point d can be obtained with high accuracy.

  At point e, the exhaust valve 16 is closed, so the gas flow rate around the exhaust valve becomes zero. Therefore, if the straight line 2 passing through the points d and e is set as a function y2, the function y2 is calculated based on the exhaust gas flow rate around the exhaust valve (dm / dθ) d and the exhaust valve VTC mechanism operation. The exhaust valve closing timing EVC at the time (when the exhaust valve VTC mechanism is not operated, the exhaust valve closing timing EVC when the exhaust valve VTC mechanism is not operated) is given by the following equation.

y2 = -4 * (dm / d [theta]) d / (EVC-IVO) * ([theta] -EVC)
... (41)
When the equation (41) and the above (complement 19) are solved simultaneously, the crank angle θ as the solution is calculated as the crank angle θ1 of the point c.

  Further, the gas flow around the exhaust valve (dm / dθ) c at the point c is obtained by substituting the crank angle θ1 at the point c into the crank angle θ in the equation (41).

  The three values of the gas flow around the exhaust valve (dm / dθ) ivo, the crank angle θ0 at the point b, and the gas flow around the exhaust valve (dm / dθ) c at the point c are calculated as described above. Substituting into the above equation (25), the blowback gas amount M2 during the overlap between the intake valve open period and the exhaust valve open period is calculated.

  This concludes the description of the calculation of the combustion chamber residual gas when the exhaust valve VTC mechanism 28 is provided.

  Next, FIG. 19 is a block diagram of a combustion chamber residual gas amount estimation device performed in the engine controller 31. The device is an intake valve opening timing combustion chamber volume calculation unit 51, an exhaust gas constant calculation unit 52, an average exhaust temperature calculation. 53, average exhaust pressure calculation unit 54, specific heat ratio calculation unit 55, charging efficiency calculation unit 56, intake valve opening timing combustion chamber pressure calculation unit 57, intake valve opening timing combustion chamber temperature calculation unit 58, intake valve opening timing combustion chamber A gas amount calculation unit 59, an overlapped blow-back gas amount calculation unit 60, and a residual gas amount calculation unit 61 are included.

  First, the intake valve opening timing combustion chamber volume calculation unit 51 calculates the combustion chamber volume VIVO at the intake valve opening timing using the intake valve opening timing IVO and the above equations (7) to (11). Here, the exhaust valve closing timing EVC is known from the command value given to the exhaust valve VTC mechanism 28.

  The exhaust gas constant calculation unit 52 calculates the exhaust gas constant REX using the target equivalent ratio TFBYA and the above-described equations (6) and (complement 3). The target equivalent ratio is a value corresponding to the engine load and the rotational speed Ne as shown in FIG.

  In the average exhaust temperature calculation unit 53, the average torque estimated value TENG, the intake air amount MA detected by the airflow sensor 32, the target equivalence ratio TFBYA, and the engine speed Ne are averaged using the above formulas (23) and (24). An exhaust temperature TEX is calculated.

  In the average exhaust pressure calculation unit 54, the intake air amount MA detected by the air flow sensor 32, the target equivalence ratio TFBYA, the engine speed Ne, the exhaust gas constant REX, the atmospheric pressure PPAMB detected by the atmospheric pressure sensor 36, and the above ( The average exhaust pressure PEX is calculated using the equations (20) and (21).

  The specific heat ratio calculation unit 55 uses the average exhaust temperature TEX, the exhaust gas constant REX, and the specific heat of the exhaust using the above equations (18), (Supplement 7-1) to (Supplement 7-5), and Equation (19). The ratio κ is calculated.

  The charging efficiency calculation unit 56 calculates the actual charging efficiency ITAC using the intake air amount MA detected by the airflow sensor 32 and the above (Supplement 8) equation.

  In the intake valve opening timing combustion chamber pressure calculating section 57, the average exhaust temperature TEX, the engine speed Ne, the intake valve opening timing IVO, the exhaust valve closing timing EVC, the average exhaust pressure PEX, the actual charging efficiency ITAC, and the specific heat ratio κ of the exhaust gas. Then, the combustion chamber pressure PIVO at the intake valve opening timing is calculated using the above equations (12), (13), (16), (17), and (Supplement 6).

  In the intake valve opening timing combustion chamber temperature calculation unit 58, the combustion chamber pressure PIVO, the average exhaust pressure PEX, the average exhaust temperature TEX at the intake valve opening timing, and the above formulas (22), (23), and (24) Is used to calculate the combustion chamber temperature TIVO at the intake valve opening timing.

  In the intake valve opening timing combustion chamber gas amount calculation unit 59, the combustion chamber volume VIVO at the intake valve opening timing, the exhaust gas constant EX, the combustion chamber pressure PIVO at the intake valve opening timing, and the combustion chamber temperature TIVO at the intake valve opening timing And the combustion chamber gas amount MR1 at the intake valve opening timing is calculated using the above equation (1).

  In the overlapped blowback gas amount calculation unit 60, the combustion chamber temperature TIVO at the intake valve opening timing, the combustion chamber pressure PIVO at the intake valve opening timing, the intake valve opening timing IVO, the exhaust valve closing timing EVC, the average exhaust pressure PEX, The specific heat ratio κ of the exhaust gas, the engine rotational speed Ne, the intake pressure detected by the intake pressure sensor 44, the exhaust gas constant REX, the combustion chamber volume VIVO at the intake valve opening timing, the above formulas (25), (33), Blow-back gas during overlap of the open period of the intake valve and the open period of the exhaust valve using the formulas (A.18), (A.19), (A20), (40), (41), etc. The amount M2 is calculated.

  The combustion chamber residual gas amount calculation unit 61 adds the blow-back gas amount M2 during the overlap between the intake valve opening period and the exhaust valve opening period, and the combustion chamber gas amount MR1 at the intake valve opening timing, thereby adding the intake valve opening period. And the amount of residual gas in the combustion chamber after the overlap of the exhaust valve open period is calculated.

  Here, the effect of 1st Embodiment of a prior application apparatus is demonstrated.

  When the exhaust valve VTC mechanism 28 is switched from a non-operating state (first state) to an operating state (second state), exhaust at the exhaust valve opening timing when the exhaust valve VTC mechanism is operated. Since the pressure and the pressure in the combustion chamber are different from the exhaust pressure and the pressure in the combustion chamber when the exhaust valve VTC mechanism is not operated, the intake valve open period and the exhaust valve The amount of residual gas in the combustion chamber after the overlap of the period is also greatly changed from the value when the exhaust valve VTC mechanism is not operated.

  In this case, according to the first embodiment of the prior application apparatus, as shown in FIG. 19, the intake valve opening timing combustion chamber pressure calculating section 57 based on the exhaust valve closing timing EVC when the exhaust valve VTC mechanism is operated. Calculates the combustion chamber pressure PIVO at the intake valve opening timing when the exhaust valve VTC mechanism is operated, and the intake valve opening timing combustion chamber temperature calculation section 58 performs exhaust based on the combustion chamber pressure PIVO at the intake valve opening timing. The combustion chamber temperature TIVO at the intake valve opening timing when the valve VTC mechanism is operated is calculated, and the intake valve opening is calculated based on the combustion chamber pressure PIVO at the intake valve opening timing and the combustion chamber temperature TIVO at the intake valve opening timing. The timing combustion chamber gas amount calculation unit 59 calculates the combustion chamber gas amount MR1 when the exhaust valve VTC mechanism is activated, and the exhaust valve VTC machine. Based on the exhaust valve closing timing at the time of operation, the overlapped blowback gas amount calculation unit 60 calculates the amount of blowback gas M2 during the overlap between the intake valve open period and the exhaust valve open period when the exhaust valve VTC mechanism is operated. Based on the combustion chamber gas amount MR1 when the exhaust valve VTC mechanism is activated and the blowback gas amount M2 during the overlap, the combustion chamber residual gas amount calculation unit 61 determines the exhaust valve VTC mechanism. The residual gas amount in the combustion chamber after the overlap between the intake valve open period and the exhaust valve open period during operation is calculated. That is, when the exhaust valve VTC mechanism 28 is switched from the non-operating state to the operating state, the combustion chamber pressure PIVO at the intake valve opening timing when the exhaust valve VTC mechanism operates and the intake air when the exhaust valve VTC mechanism operates The combustion chamber temperature TIVO at the valve opening timing is calculated again, and the combustion chamber gas amount MR1 at the intake valve opening timing when the exhaust valve VTC mechanism is operated is calculated based on the calculated value, and the exhaust valve VTC is calculated. When the exhaust valve VTC mechanism 28 is switched from the non-operating state to the operating state because the blow-back gas amount M2 during overlap is calculated when the exhaust valve VTC mechanism is operating based on the intake valve closing timing when the mechanism is operating. In addition, the amount of residual gas in the combustion chamber after the overlap between the intake valve open period and the exhaust valve open period can be accurately estimated. That.

  When the exhaust valve VTC mechanism 28 is switched from the non-operating state to the operating state at the reference exhaust temperature, the combustion chamber pressure at the reference exhaust temperature and the intake valve opening timing when the exhaust valve VTC mechanism is operated is This is different from the pressure in the combustion chamber at the intake valve opening timing at the exhaust temperature and when the exhaust valve VTC mechanism is not operated.

  In this case, according to the first embodiment of the prior application device, the average exhaust pressure PEX is calculated (see the above formulas (20) and (21)), and the exhaust valve is opened when the exhaust valve VTC mechanism is operated. Based on the timing and the difference between the pressure in the combustion chamber at each crank angle and the average exhaust pressure at the reference exhaust temperature and when the exhaust valve VTC mechanism is not operating (pressure pulsation around the exhaust valve at each crank angle) Then, a difference value PCTRM between the combustion chamber pressure and the average exhaust pressure at the reference exhaust temperature and at the intake valve opening timing when the exhaust valve VTC mechanism is operated is calculated (see the description with reference to FIG. 16). Based on the difference value PCTRM and the average exhaust pressure PEX between the combustion chamber pressure and the average exhaust pressure at the calculated reference exhaust temperature and when the exhaust valve VTC mechanism is operated, the exhaust valve VTC mechanism is operated. The combustion chamber pressure PIVO at the intake valve opening timing when the valve VTC mechanism is operated is calculated (see the above equation (12)), so that the exhaust valve VTC mechanism 28 is switched from the non-operating state to the operating state at the reference exhaust temperature. Even in such a case, it is possible to accurately estimate the combustion chamber pressure PIVO at the reference exhaust temperature and the intake valve opening timing when the exhaust valve VTC mechanism is operated.

  As a method of realizing a differential value between the pressure in the combustion chamber at the intake valve opening timing and the average exhaust pressure when the exhaust valve VTC mechanism is operated (pressure pulsation around the exhaust valve at the intake valve opening timing), the exhaust valve VTC is used. It is considered that a map of the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle when the exhaust valve VTC mechanism is operated is created and stored for each different exhaust valve opening timing during the mechanism operation. However, this method requires enormous storage capacity.

  On the other hand, according to the first embodiment of the prior application apparatus, it is necessary to memorize the pressure in the combustion chamber at each crank angle when the exhaust valve VTC mechanism is not operated, as shown in FIG. And only the difference between the average exhaust pressure and the storage capacity can be greatly reduced.

  When switching from the reference exhaust temperature to the exhaust temperature higher than the reference exhaust temperature due to a change in the operating state when the exhaust valve VTC mechanism is not operated, the exhaust speed c at the exhaust temperature higher than the reference exhaust temperature c The (exhaust pressure propagation speed) becomes larger than that at the reference exhaust temperature, and the wavelength λ for the exhaust pressure pulsation becomes shorter than the wavelength λ0 at the reference exhaust temperature. Therefore, the pressure in the combustion chamber when the exhaust temperature is higher than the reference exhaust temperature and the intake valve opening timing when the exhaust valve VTC mechanism is not operating is the same as the intake valve opening when the exhaust valve VTC mechanism is not operating. It will be different from the pressure in the combustion chamber at the time. Further, when the exhaust valve VTC mechanism 28 is switched from the non-operating state to the operating state when the exhaust temperature is higher than the reference exhaust temperature, the exhaust valve VTC mechanism 28 is operated when the exhaust temperature is higher than the reference exhaust temperature and when the exhaust valve VTC mechanism is operated. The pressure in the combustion chamber when the intake valve is open is different from the pressure in the combustion chamber when the exhaust temperature is higher than the reference exhaust temperature and when the exhaust valve VTC mechanism is not operating.

  In this case, according to the first embodiment of the prior application apparatus, the average exhaust pressure PEX is calculated (see the above formulas (20) and (21)), and the exhaust temperature deviated to a higher temperature side than the reference exhaust temperature. Exhaust speed c (exhaust pressure propagation speed) is calculated (see the above equation (16)), the calculated exhaust speed c, and the exhaust valve opening timing when the exhaust valve VTC mechanism is operated, Based on the difference between the pressure in the combustion chamber at each crank angle and the average exhaust pressure at the reference exhaust temperature and when the exhaust valve VTC mechanism is not in operation (the pressure pulsation around the exhaust valve at the intake valve opening timing), The difference value PCTRM between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing when the exhaust temperature deviates from the reference exhaust temperature and when the exhaust valve VTC mechanism is operated. Pressure pulsation) ( 17), the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing when the exhaust temperature deviates higher than the calculated reference exhaust temperature and when the exhaust valve VTC mechanism is operated. Is calculated based on the difference value PCTRM and the average exhaust pressure PEX, at the exhaust temperature deviating to a higher temperature than the reference exhaust temperature and at the intake valve opening timing when the exhaust valve VTC mechanism is operated (above) (Refer to equation (12)). It is possible to accurately estimate the pressure PIVO in the combustion chamber when the exhaust temperature deviates to a higher temperature than the reference exhaust temperature and when the intake valve is opened when the exhaust valve VTC mechanism is operated. Kill.

  For example, the exhaust valve closing timing EVC when the exhaust valve VTC mechanism is activated is advanced by a predetermined value ADV from the non-operating state of the exhaust valve VTC mechanism. If it moves, the blow-back gas in the overlap between the intake valve open period and the exhaust valve open period when the exhaust valve VTC mechanism is operated is reduced by the amount of the gas blown back to the intake port 4 flowing into the combustion chamber. The amount M2 becomes larger than that when the exhaust valve VTC mechanism is not operated, corresponding to the advance angle of the exhaust valve closing timing. For this reason, even when the exhaust valve closing timing is shifted to the advance side by a predetermined value ADV from the time when the exhaust valve VTC mechanism is not operated when the exhaust valve VTC mechanism is operated, the blow-back remains as it is when the exhaust valve VTC mechanism is not operated. When calculating the amount of gas, an error corresponding to the advance angle of the exhaust valve closing timing (that is, an error corresponding to a decrease in the amount of gas flowing back into the intake port 4 into the combustion chamber) ) Occurs.

  On the other hand, according to the first embodiment of the prior application apparatus, the gas flow rate around the exhaust valve (dm / dθ) from the intake valve opening timing to the exhaust valve closing timing when the exhaust valve VTC mechanism is operated (each crank angle). The exhaust valve VTC is calculated based on the exhaust valve surrounding gas flow (dm / dθ) from the intake valve opening timing to the exhaust valve closing timing when the exhaust valve VTC mechanism is operated. Since the blow-back gas amount M2 during the overlap between the intake valve opening period and the exhaust valve opening period when the mechanism is operating is calculated, the exhaust valve VTC mechanism 28 can be used even when the exhaust valve VTC mechanism 28 is switched from non-operating to operating. It is possible to accurately estimate the blown back gas amount M2 during the overlap between the intake valve opening period and the exhaust valve opening period when the VTC mechanism is operated.

  According to the first embodiment of the prior application device, as shown in FIG. 13, the gas flow rate around the exhaust valve ((dm / m) from the intake valve opening timing IVO to the exhaust valve closing timing EVC when the exhaust valve VTC mechanism is operated. dθ) The waveform of the gas flow around the exhaust valve at each crank angle) is approximated by two straight lines, a straight line 1 (first straight line) and a straight line 2 (second straight line), and the two straight lines; By obtaining the area of two triangles composed of a straight line of the intake valve opening timing IVO and a horizontal line of zero gas flow around the exhaust valve (see the above equation (25)), intake air when the exhaust valve VTC mechanism is operated Since the blowback gas amount M2 during the overlap between the valve open period and the exhaust valve open period is calculated, the blowback gas amount M2 during the overlap between the intake valve open period and the exhaust valve open period when the exhaust valve VTC mechanism operates. Calculation becomes easy.

  The exhaust valve opening area at each crank angle when the exhaust valve VTC mechanism is not operated and the exhaust valve opening area at each crank angle when the exhaust valve VTC mechanism is operated are separately stored as table values. 3/4 of the overlap period of the intake valve opening period and the exhaust valve opening period when the exhaust valve VTC mechanism is not in operation has elapsed with reference to one table from the exhaust valve closing timing when the valve VTC mechanism is not operating The exhaust valve opening area at the point d1 (the crank angle position retarded from the crank angle position when the two straight lines intersect) is obtained, and the exhaust valve surrounding gas at the point d1 is obtained based on the obtained exhaust valve opening area. Calculate the flow rate and refer to the other table from the exhaust valve closing timing when the exhaust valve VTC mechanism is activated, and open the intake valve when the exhaust valve VTC mechanism is activated. And the exhaust valve opening area at a point d2 (a crank angle position that is retarded from the crank angle position when the two straight lines intersect) at which 3/4 of the overlap period of the exhaust valve opening period has elapsed, Calculation of the gas flow rate around the exhaust valve at the point d2 based on the obtained exhaust valve opening area requires twice the storage capacity of the table.

  In contrast, according to the first embodiment of the prior application device, the exhaust valve opening area at each crank angle when the exhaust valve VTC mechanism is not operated is stored as a table value, and the exhaust valve VTC mechanism is operated. Based on the exhaust valve closing timing at this time and this table value, a point d (two straight lines) at which 3/4 of the overlap period of the intake valve open period and the exhaust valve open period when the exhaust valve VTC mechanism is operated has elapsed. A gas flow rate (dm / dθ) d around the exhaust valve at a crank angle position that is retarded from the crank angle position at the time of crossing is calculated. That is, according to the first embodiment of the prior application apparatus, it is only necessary to memorize the exhaust valve opening area at each crank angle when the exhaust valve VTC mechanism is not operated, so that the storage capacity is reduced. Can be done.

  When the exhaust valve VTC mechanism is activated (or when the exhaust valve VTC mechanism is not activated), the overlap period of the intake valve open period and the exhaust valve open period (hereinafter simply referred to as “overlap period”) is short. Even if the crank angle θ2 at the point d is set to a constant value (crank angle position at which 3/4 of the overlap period has elapsed), the intake valve opening period and exhaust gas when the exhaust valve VTC mechanism is operated The blown back gas amount M2 during the overlap of the valve opening period can be calculated with high accuracy. The waveform of the gas flow rate dm / dθ around the exhaust valve during the overlap between the intake valve opening period and the exhaust valve opening period, which is formed by a curve, is approximated by two oblique straight lines. For example, as shown in FIG. 20A, if the overlap period is shorter than a predetermined value, the exhaust valve surrounding gas at the crank angle θ0 when the exhaust valve surrounding gas flow rate dm / dθ becomes zero during the overlap. Since the gradient of the flow rate is small and the amount of blown back gas M2 during the overlap between the intake valve open period and the exhaust valve open period is small, the crank angle θ2 at the point d, which is the crank angle position determined by the overlap period, is not the optimum value. However, the calculation accuracy of the blowback gas amount M2 during the overlap between the intake valve open period and the exhaust valve open period does not deteriorate so much.

  However, depending on the specifications of the engine and the exhaust valve VTC mechanism, the overlap period may be longer than a predetermined value. In such an engine, when the overlap period is smaller than a predetermined value when the exhaust valve VTC mechanism is operated, the crank angle θ2 at the point d is set to a constant value, and the overlap period when the exhaust valve VTC mechanism is operated. Even when the amount of blown back gas M2 can be calculated accurately, if the overlap period when the exhaust valve VTC mechanism is activated is longer than a predetermined value, the gas flow rate dm / dθ around the exhaust valve becomes zero during the overlap. The gradient of the gas flow rate around the exhaust valve at the crank angle θ0 at the time becomes larger, and the gas flow rate around the exhaust valve dm / at each crank angle from the intake valve opening timing to the exhaust valve closing timing when the exhaust valve VTC mechanism operates. Since the waveform of dθ has many parts composed of curves, the overlap period when the exhaust valve VTC mechanism is operated is a predetermined value. Even when the exhaust valve VTC mechanism is longer, if the overlap angle when the exhaust valve VTC mechanism is operated is less than a predetermined value, the crank angle θ2 at the point d is used as it is, the exhaust valve VTC mechanism operates. The calculation error of the blowback gas amount M2 during the overlap between the intake valve open period and the exhaust valve open period at that time becomes large. That is, as the overlap period during the operation of the exhaust valve VTC mechanism becomes longer, as shown in FIG. 20B, the exhaust valve surrounding gas flow rate at the crank angle θ0 when the exhaust valve surrounding gas flow rate becomes zero is shown. Since the slope is large and the number of curved parts increases and the deviation between the two slanted straight lines 1 and 2 and the waveform of the gas flow rate dm / dθ around the exhaust valve increases, the crank angle position determined by the overlap period If the crank angle θ2 at a certain point d is not set to an optimal position, it is composed of two diagonal straight lines, a straight line of the intake valve opening timing IVO, and a horizontal line where the gas flow rate dm / dθ around the exhaust valve is zero. The estimation accuracy of the blowback gas amount M2 during the overlap between the intake valve open period and the exhaust valve open period, which is calculated as the area of the two triangles, is deteriorated. It is. In FIGS. 20A and 20B, the intake valve opening timing IVO is shown to be coincident, but it is not necessarily coincident. As the overlap period becomes longer, the differential pressure between the intake port pressure and the exhaust port pressure becomes smaller and the flow velocity of the gas blown through becomes constant without increasing any more. The differential pressure of the exhaust port pressure is small and the gas flow rate is constant.

  Therefore, in the second embodiment of the prior application device, the exhaust valve closing timing EVC is moved from the most advanced angle position, which is the initial position when the exhaust valve VTC mechanism is not operated, to the retard side by the operation of the exhaust valve VTC mechanism 28. Handle the case where the valve overlap period becomes longer due to movement. That is, in the second embodiment of the prior application device, when the overlap period is longer than a predetermined value when the exhaust valve VTC mechanism is operated, the crank angle θ2 at the point d (the first straight line and the second straight line) The crank angle position on the retarded side from the crank angle position when the straight line intersects with the exhaust valve VTC mechanism, and when the exhaust valve open period and the exhaust valve open period overlap, the gas flow around the exhaust valve dm / dθ Is calculated based on the gradient of the gas flow rate around the exhaust valve at the crank angle θ0 when becomes zero.

  The object of the second embodiment of the prior application device is not limited to the case where the valve overlap period becomes longer due to the operation of the exhaust valve VTC mechanism 28 while the intake valve opening timing IVO remains constant. For example, in the first embodiment of the above-mentioned prior application apparatus, the intake valve VTC mechanism 27 has been described as being in an inoperative state. However, when the intake valve VTC mechanism 27 is operated, the exhaust valve closing timing EVC changes. However, there is a case where the intake valve opening timing IVO moves to the advance side and the valve overlap period becomes longer. In this case as well, the second embodiment of the prior application device can be applied. The second embodiment of the prior application apparatus can also be applied when both the intake valve VTC mechanism 27 and the exhaust valve VTC mechanism 28 are operated to increase the valve overlap period. In short, the second embodiment of the prior application apparatus can be applied when the valve overlap period becomes longer due to the combination of operation and non-operation of the intake valve VTC mechanism 27 and the exhaust valve VTC mechanism 28.

  Next, a method of setting the crank angle θ2 at the point d when the overlap period becomes longer than a predetermined value due to the operation of the exhaust valve VTC mechanism will be specifically described with reference to FIG.

  As shown in FIG. 21, it is assumed that the waveform of the gas flow around the exhaust valve when the overlap period is longer than a predetermined value when the exhaust valve VTC mechanism is operated is obtained by actual measurement or simulation. In this case, θ21, θ22,..., Θ2n-1, θ2n (n is a positive number) are taken for each constant crank angle toward the left side from the point e, and the points on the curve at these crank angles are In this order, d1, d2,..., Dn-1, dn. As the number of n increases, the calculation accuracy of the blow-back gas amount M2 during the overlap between the intake valve opening period and the exhaust valve opening period improves, but on the other hand, the calculation time increases. Determine the number of n.

  First, the amount of blown back gas during the overlap of the intake valve open period and the exhaust valve open period when the straight line connecting the point e and the first d1 point is a temporary straight line 2 (see FIG. 21) is the above [2]. Calculate according to the above. That is, the gas flow around the exhaust valve (dm / dθ) d1 at the point d1 is calculated from the crank angle θ21 at the point d1 using the above equation (40), and the gas flow around the exhaust valve (dm / d) at this point d1. The function y2 is determined by substituting dθ) d1 into the equation (41), and the function y2 and the equation (complement 7) are combined to calculate the crank angle θ1 at the point c. Further, the gas flow around the exhaust valve (dm / dθ) c at the point c is obtained by substituting the crank angle θ1 at the point c into the crank angle θ in the equation (41). On the other hand, the gas flow around the exhaust valve (dm / dθ) ivo at the intake valve opening timing and the crank angle θ0 at point b are calculated from FIG. The three values of the gas flow around the exhaust valve (dm / dθ) ivo, the crank angle θ0 at the point b, and the gas flow around the exhaust valve (dm / dθ) c at the point c are calculated as described above. Substituting into the above equation (25), the amount of blow-back gas during the overlap between the intake valve opening period and the exhaust valve opening period when the straight line connecting the points e and d1 is defined as the temporary line 2 is calculated. The calculated value is M2theo1. Naturally from FIG. 21, when the straight line connecting the point e and the first d1 point is a temporary straight line 2, the blowback gas amount calculation value M2theo1 during the overlap of the intake valve open period and the exhaust valve open period is It is smaller than the actual amount of blown-back gas during the overlap between the intake valve open period and the exhaust valve open period.

  Next, when the straight line connecting the point e and the second point d2 is a temporary straight line 2, the amount of blown back gas during the overlap between the intake valve open period and the exhaust valve open period is described above in [2]. And the calculated value is M2theo2. As shown in FIG. 21, when the straight line connecting the point e and the second d2 point is defined as a temporary straight line 2, the blowback gas amount calculation value M2theo2 during the overlap of the intake valve open period and the exhaust valve open period is also the intake valve open period. And less than the actual amount of blown-back gas during the overlap of the exhaust valve opening period.

  In the same manner, the blowback gas amount calculation value M2theo3 during the overlap between the intake valve opening period and the exhaust valve opening period when the straight line connecting the point e and the points d3,. ..., dM2theon is obtained one after another according to the above-mentioned in [2]. In this way, when the total n blown back gas amount calculated values M2theo1,..., DM2theon are obtained, these n calculated values include actual values during the overlap of the intake valve open period and the exhaust valve open period. It is considered that a value close to the amount of blown-back gas is included.

  On the other hand, the actual blown-back gas amount M2real during the overlap between the intake valve opening period and the exhaust valve opening period is obtained from the waveform diagram of FIG. 21 by calculation on the diagram, or by actual measurement or simulation.

  Next, the calculated actual blown gas amount M2real is compared with the n blown gas amount calculated values M2theo1,..., M2theon, and one calculated blown gas amount closest to the actual blown gas amount M2real is selected. To do. For example, if the blown-back gas amount calculation value M2theo10 is a value closest to the actual blown-back gas amount M2real, a line connecting the point e and the tenth point d10 with respect to the waveform of FIG. ) Is a straight line 2, it is a straight line that best approximates the actual blown-back gas amount M2real, so the crank angle θ 210 at the point d 10 is determined as the crank angle θ 2 at the point d.

  Next, the inclination (dm2 / d2θ) 0 of the exhaust gas flow around the exhaust valve at the crank angle θ0 when the exhaust gas flow around the exhaust valve dm / dθ becomes zero is calculated from the waveform diagram of FIG. And the gradient of the gas flow around the exhaust valve (dm2 / d2θ) 0 at the crank angle θ0 when the gas flow around the exhaust valve becomes zero, the actual blown gas amount M2real, and the n blown gas amounts One data ((dm 2 / d 2 θ) 0, θ 2) obtained by coupling the crank angle θ 2 at the point d obtained by comparison with the calculated value is obtained. This completes the operation of collecting one couple data to be performed on the waveform diagram of FIG.

  If the overlap period is different from that in FIG. 21, the waveform of the gas flow around the exhaust valve during the overlap between the intake valve open period and the exhaust valve open period also differs from the waveform in FIG. Therefore, when the overlap period becomes longer, the overlap period when the calculation error of the blowback gas amount M2 during the overlap between the intake valve opening period and the exhaust valve opening period starts to become a problem is set to the predetermined value A, and the maximum overlap is achieved. Assuming that the period is the maximum value B, the characteristics of the gas flow rate around k exhaust valves (k is a positive number) with different overlap periods between the predetermined value A and the maximum value B including the predetermined value A and the maximum value B. Can be obtained by actual measurement or simulation in the same manner as in FIG. As the number of k increases, the calculation accuracy of the blow-back gas amount M2 during the overlap between the intake valve opening period and the exhaust valve opening period improves, but on the other hand, the actual measurement and simulation man-hours increase. Determine the number of k in consideration of balance. If k is 32, for example, one of them is shown in FIG. 21. Therefore, the above operation is repeated for each of the remaining 31 exhaust valve surrounding gas flow rates with different overlap periods. A straight line 2 that best approximates the blown back gas amount M2real is determined. In this way, for each waveform of the gas flow rate around 32 exhaust valves with different overlap periods, the straight line 2 that best approximates the actual blown gas amount M2real, that is, the crank angle θ2 at the point d that determines the straight line 2 is determined. Are obtained respectively.

  On the other hand, from the respective waveforms of the 32 exhaust valve surrounding gas flows having different overlap periods, the gradient (dm2 / d2θ) 0 of the exhaust valve surrounding gas flow at the crank angle θ0 when the exhaust valve surrounding gas flow rate becomes zero is obtained. When calculating sequentially from the waveform diagram or by actual measurement or simulation, the slope of the gas flow around the exhaust valve (dm2 / d2θ) 0 at the crank angle θ0 when the gas flow around the exhaust valve becomes zero is , 32 couple data with the crank angle θ2 at the point d as a couple are obtained. This completes all the couple data collection.

Next, the horizontal axis is the slope (dm ² / d ² θ) 0 of the exhaust gas flow around the exhaust valve at the crank angle θ0 when the gas flow around the exhaust valve becomes zero, and the vertical axis is (EVC−θ2) / ( When the 32 collected data collected above are plotted on the graph EVC-IVO), as shown in FIG. 22, the inclination of the gas flow rate around the exhaust valve at the crank angle θ0 when the gas flow rate around the exhaust valve becomes zero, as shown in FIG. It has been found for the first time that there is a strong correlation between (dm ² / d ² θ) 0 and (EVC−θ2) / (EVC-IVO), that is, there is a proportional relationship (see straight line) between the two. Here, the value of (EVC-θ2) / (EVC-IVO) on the vertical axis in FIG. 22 represents the ratio of EVC-θ2 to the overlap period (EVC-IVO). The vertical axis in FIG. 22 is not the crank angle θ2 itself at the point d, but (EVC-θ2) / (EVC-IVO) is more general in terms of the ratio of EVC-θ2 to the overlap period. This is because differences in engine displacement and differences in the size of the exhaust valve VTC mechanism can be eliminated.

  As shown in FIG. 22, the slope of the straight line indicating the correlation and the y-intercept can be obtained as matching values (where the origin and the y-axis are placed is determined appropriately). When the predetermined value ROLM1 and the obtained y-intercept are set to the predetermined value ROLA1, the following equation is established.

(EVC-θ2) / (EVC-IVO) = ROLM1 × (dm ² / d ² θ) 0
+ ROLA1
... (42)
When this equation (42) is arranged with respect to the crank angle θ2 at the point d, the following equation is obtained.

θ2 = EVC− (EVC−IVO)
× ((dm ² / d ² θ) 0 × ROLM1 + ROLA1)
... (43)
However, EVC: exhaust valve closing timing [degCA],
IVO: intake valve opening timing [degCA],
(Dm ² / d ² m) 0: When the gas flow around the exhaust valve is zero
Gradient of gas flow around the exhaust valve,
ROLM1: predetermined value (conforming value),
ROLA1: predetermined value (conforming value),
This equation (43) is an equation that gives the crank angle θ2 at the point d when the overlap period is longer than a predetermined value. Here, the slope (dm ² / d ² θ) 0 of the exhaust gas flow around the exhaust valve at the crank angle θ 0 when the gas flow around the exhaust valve becomes zero on the right side of the equation (43) is the above (complement 19) Is obtained by substituting the crank angle θ0 when the gas flow rate around the exhaust valve becomes zero, which is obtained by the above (Appendix 18) equation, into d (y1) / dθ. it can.

The slope of the exhaust gas flow around the exhaust valve at the crank angle θ0 when the gas flow around the exhaust valve becomes zero (dm ² / d ² θ) 0 and the slope of the straight line 1 are not so different (see FIG. 20B). ), The slope of the straight line 1 is used as the slope (dm ² / d ² θ) 0 of the exhaust gas flow around the exhaust valve at the crank angle θ 0 when the gas flow around the exhaust valve becomes zero on the right side of the equation (43). That is, the crank angle θ2 at the point d can be calculated by the following equation (third embodiment of the prior application device).

θ2 = EVC− (EVC−IVO)
× ((dy1 / dθ) × ROLM1 + ROLA1)
... (44)
However, EVC: exhaust valve closing timing [degCA],
IVO: intake valve opening timing [degCA],
: Slope of straight line 1,
ROLM1: predetermined value (conforming value),
ROLA1: predetermined value (conforming value),
Here, the slope (dy1 / dθ) of the straight line 1 on the right side of the equation (44) is given by the following equation from the above (complement 19).

dy1 / dθ = − (dm / dθ)) ivo / (θ0−IVO) (45)
Compared with the above (complement 20) equation that gives the crank angle θ2 at the point d in the first embodiment of the prior application device, the portion of (dm ² / d ² θ) 0 × ROLM1 + ROLA1 on the right side of the equation (43) It can be seen that the first embodiment of the prior application apparatus is set to ¼ as a constant. On the other hand, in the second and third embodiments of the prior application apparatus, the constants in the first embodiment of the prior application apparatus are given as variables. In other words, in the first embodiment of the prior application device, the crank angle θ2 at the point d is set as a constant, whereas in the second and third embodiments of the prior application device, the overlap period is greater than a predetermined value. If it is long, the crank angle θ2 at the point d instead of the constant is set to the gradient (dm ² / d ² θ) 0 of the exhaust gas flow around the exhaust valve at the crank angle θ0 when the gas flow around the exhaust valve becomes zero. It is given as a function of the slope of the straight line 1 (dy1 / dθ).

As described above, the second and third embodiments of the prior application apparatus mainly deal with the case where the overlap period is longer than the predetermined value, but the same idea is extended to the case where the overlap period is less than the predetermined value. Even when the overlap period is less than the predetermined value, the crank angle θ2 at the point d is calculated by the above equation (43), the above equations (44), and (45) (that is, the gas flow rate dm around the exhaust valve). The gradient of the gas flow around the exhaust valve at the crank angle θ0 when / dθ becomes zero (given as a function of the slope (dm ² / d ² θ) 0 or the slope of the straight line 1 (dy1 / dθ)).

  However, the second and third embodiments of the prior application device are not limited to this case. For example, the method of setting the crank angle θ2 at the point d may be different between the case where the overlap period is less than a predetermined value and the case where the overlap period is longer than the predetermined value. In this case, it is necessary to determine whether or not the overlap period is longer than a predetermined value. As the predetermined value, the predetermined value A may be applied. That is, if the engine specification and the specification of the exhaust valve VTC mechanism are determined, it is determined in which range the overlap period when the exhaust valve VTC mechanism is operated, so whether or not the overlap period is longer than a predetermined value. A predetermined value for determining can be determined by adaptation.

Next, as an inclination (dm ² / d ² θ) 0 of the exhaust gas flow around the exhaust valve at the crank angle θ 0 when the exhaust gas flow around the exhaust valve becomes zero during the overlap between the intake valve open period and the exhaust valve open period. As can be seen from the approximation of the slope (dy1 / dθ) of the straight line 1 in the third embodiment of the prior application device, the gas flow rate around the exhaust valve at the crank angle θ0 when the gas flow rate around the exhaust valve becomes zero is shown. The slope (dm ² / d ² θ) 0 is a value related to the value of the first half of the gas flow rate around the exhaust valve during the overlap between the intake valve open period and the exhaust valve open period. Therefore, when the exhaust gas flow rate around the exhaust valve becomes zero, it is examined whether there is a value that can be substituted in addition to the gradient (dm ² / d ² θ) 0 of the exhaust gas flow rate around the exhaust valve at the crank angle θ0. The gas flow around the exhaust valve (dm / dθ) rand at any crank angle θ between the intake valve opening timing IVO and the crank angle θ0 when the gas flow around the exhaust valve becomes zero. It has been found that the gas flow rate around the exhaust valve (dm / dθ) ivo may be sufficient. That is, on the horizontal axis of FIG. 22, the exhaust valve surrounding gas flow rate (dm / dθ) at an arbitrary crank angle θ between the intake valve opening timing IVO and the crank angle θ0 when the exhaust valve surrounding gas flow rate becomes zero. There is also a strong correlation between the two values on the horizontal axis and the vertical axis when rand and the exhaust gas flow around the exhaust valve (dm / dθ) ivo when the intake valve is open, that is, there is a proportional relationship between the two. Found that there is. In summary, including the cases of the second and third embodiments of the prior application device, the following four values can be the horizontal axis in FIG.
<< 1 >> Slope of the gas flow around the exhaust valve at the crank angle θ0 when the gas flow around the exhaust valve becomes zero (dm ² / d ² m) 0
<< 2 >> The slope of the straight line 1 (dy1 / dθ)
<< 3 >> Gas flow around the exhaust valve (dm / dθ) ra nd at any crank angle between the intake valve opening timing IVO and the crank angle θ0 when the gas flow around the exhaust valve becomes zero
<< 4 >> Gas flow around the exhaust valve (dm / dθ) ivo when the intake valve is open
Since the formula for calculating the crank angle θ2 at the point d in the case of << 1 >> and << 2 >> is shown in the above formulas (43) and (44), the crank angle at the point d in the case of << 3 >> above. A formula for calculating θ2 is shown below (fourth embodiment of the prior application device).

θ2 = EVC− (EVC−IVO)
× ((dm / dθ) rand × ROLM2 + ROLA2)
... (46)
However, EVC: exhaust valve closing timing [degCA],
IVO: intake valve opening timing [degCA],
(Dm / dθ) rand: The gas flow rate around the exhaust valve at any crank angle θ between the intake valve opening timing IVO and the crank angle θ0 at which the gas flow rate around the exhaust valve becomes zero.
[Kg / degCA],
ROLM2: predetermined value (conforming value),
ROLA2: predetermined value (conforming value),
Here, the exhaust gas flow around the exhaust valve (dm / dθ) at an arbitrary crank angle between the intake valve opening timing IVO and the crank angle θ0 when the exhaust gas flow around the exhaust valve becomes zero on the right side of the equation (46). rand is obtained from line 1. In other words, the value of the function y1 obtained by substituting the predetermined crank angle into the above (Supplement 19) from the intake valve opening timing IVO to the crank angle θ0 when the gas flow around the exhaust valve becomes zero. The exhaust valve surrounding gas flow rate (dm / dθ) rand at any crank angle between the intake valve opening timing IVO and the crank angle θ0 when the exhaust valve surrounding gas flow rate becomes zero may be set.

  Similarly, the calculation formula of the crank angle θ2 at the point d in the case of << 4 >> is shown below (fifth embodiment of the prior application device).

θ2 = EVC− (EVC−IVO)
× ((dm / dθ) ivo × ROLM3 + ROLA3)
... (47)
However, EVC: exhaust valve closing timing [degCA],
IVO: intake valve opening timing [degCA],
(Dm / dθ) ivo: Gas flow around the exhaust valve when the intake valve opens
[Kg / degCA],
ROLM3: predetermined value (conforming value),
ROLA3: predetermined value (conforming value),
Here, the exhaust valve surrounding gas flow rate (dm / dθ) ivo at the intake valve opening timing on the right side of the equation (47) has been calculated by the equation (33).

  Next, how the engine controller 31 calculates the crank angle θ2 at the point d and how the blowback gas amount M2 is obtained using the calculated crank angle θ2 at the point d will be described. Here, to be described representatively in the case of the third embodiment of the prior application device, FIG. 23 is a block diagram of the overlapped blow-back gas amount calculation unit 60 (see FIG. 19) of the third embodiment of the prior application device. is there.

  First, in the intake valve opening timing gas flow rate calculation unit 71, the combustion chamber temperature TIVO at the intake valve opening timing, the combustion chamber pressure PIVO at the intake valve opening timing, the combustion chamber volume VIVO at the intake valve opening timing, and the intake valve opening timing From the IVO, the exhaust gas constant REX, and the engine rotational speed Ne, the exhaust gas flow around the exhaust valve (dm / dθ) ivo at the intake valve opening timing is calculated using the above equation (33).

  In the crank angle calculation unit 72 when the gas flow rate is zero, the exhaust pressure Pex (= (PEX + PIVO) / 2), the exhaust gas constant REX, the average exhaust temperature TEX, the exhaust specific heat ratio κ, the flow rate ratio RMF1, and the intake valve opening timing IVO are described above. The crank angle θ0 when the gas flow rate around the exhaust valve becomes zero is calculated using Equations (38) and (Supplement 18).

  In the straight line 1 setting unit 73, the above (complementary) is determined from the exhaust valve surrounding gas flow rate (dm / dθ) ivo at the intake valve opening timing, the crank angle θ0 when the exhaust valve surrounding gas flow rate becomes zero, and the intake valve opening timing IVO. 19) The function y1 is set using the equation. In the straight line 1 slope calculation unit 74, the exhaust valve surrounding gas flow rate (dm / dθ) ivo at the intake valve open timing calculated by the intake valve open timing gas flow rate calculation unit 71, similarly, the crank angle calculation unit at zero gas flow rate The slope (dy1 / dθ) of the straight line 1 is calculated from the crank angle θ0 and the intake valve opening timing IVO when the gas flow rate around the exhaust valve calculated in 72 is zero and the above equation (45).

  In the crank angle calculation unit 75 at the point d, the slope of the straight line 1 (dy1 / dθ), the exhaust valve closing timing EVC, the intake valve opening timing IVO, and the predetermined values ROLM1 and ROLA1 are used at the point d using the above equation (44). The crank angle θ2 is calculated. Thus, in the third embodiment of the prior application device, the crank angle θ2 at the point d is calculated based on the slope of the straight line 1 (dy1 / dθ).

  The exhaust valve opening area calculation unit 76 calculates the exhaust valve opening area Aex with respect to the crank angle θ2 at this point d in accordance with the above-described case in FIG.

  In the gas flow rate calculation unit 77 at the point d, the exhaust valve opening area Aex, the exhaust pressure Pex (= (PEX + PIVO) / 2), the exhaust gas constant REX, the exhaust temperature TEX, and the specific heat ratio of the exhaust with respect to the crank angle θ2 at the point d. The gas flow rate around the exhaust valve (dm / dθ) d at point d is calculated from κ and the flow rate ratio RMF2 using the above equation (40).

  In the straight line 2 setting unit 78, the function y2 is set using the above equation (41) from the gas flow around the exhaust valve (dm / dθ) d, the exhaust valve closing timing EVC, and the intake valve opening timing IVO at this point d.

  The crank angle calculation unit 79 at the point c calculates the crank angle θ1 at the intersection c by simultaneously solving the two functions y1 and y2 set as described above.

  The gas flow rate calculation unit 80 at the point c calculates the gas flow rate around the exhaust valve (dm / dθ) c at the point c by substituting the crank angle θ1 at the point c into the function y1.

  In the blowback gas amount calculation unit 81, the exhaust valve surrounding gas flow rate (dm / dθ) ivo at the intake valve opening timing obtained in this way, the crank angle θ0 when the exhaust valve surrounding gas flow rate becomes zero, and the point c The blowback gas amount M2 is calculated from the crank angle θ1, the gas flow around the exhaust valve at the point c (dm / dθ) c, and the intake valve opening timing IVO using the above equation (25).

  Here, the effects of the second, third, fourth, and fifth embodiments of the prior application device will be described.

When the overlap period during operation of the exhaust valve VTC mechanism is less than a predetermined value, the crank angle position (θ2) on the retard side from the crank angle position (θ1) when the two straight lines 1 and 2 intersect Is set to a constant value (crank angle position at which 3/4 of the overlap period has elapsed), and the blow-back gas during the overlap of the intake valve open period and the exhaust valve open period when the exhaust valve VTC mechanism is operated Even if the amount M2 is calculated with high accuracy, if the overlap period when the exhaust valve VTC mechanism is activated is longer than a predetermined value, the intake valve opening timing IVO to the exhaust valve closing timing EVC when the exhaust valve VTC mechanism is activated Since the waveform of the gas flow rate around the exhaust valve at each crank angle of the crankshaft is composed of a curved portion, the overlap period when the exhaust valve VTC mechanism is operated If the crank angle position θ2 at the point d, which is set when the overlap period when the exhaust valve VTC mechanism is operated, is less than the predetermined value, is used as it is, The calculation error of the blow-back gas amount M2 during the overlap between the intake valve opening period and the exhaust valve opening period when the valve VTC mechanism is operating becomes large. However, when the exhaust valve VTC mechanism is operating (during the second state) ) In the case where the overlap period is longer than a predetermined value, the crank angle θ2 at the point d (the crank angle position on the retard side from the crank angle position when the two straight lines of the first straight line and the second straight line intersect) ) According to the second embodiment of the prior application device, when the exhaust valve VTC mechanism is in operation and the exhaust valve open period and the exhaust valve open period overlap the gas flow around the exhaust valve becomes zero. Based on the gradient (dm ² / d ² θ) 0 of the gas flow around the exhaust valve at the rank angle θ0 (see the above equation (43)), according to the third embodiment of the prior application apparatus, the straight line 1 (first On the basis of the slope (dy1 / dθ) of the straight line (see the above formulas (45) and (44)), according to the fourth embodiment of the prior application device, the exhaust valve is determined from the crank angle at the intake valve opening timing IVO. The gas flow rate around the exhaust valve (dm) at any crank angle up to the crank angle θ0 when the gas flow rate around the exhaust valve during the overlap between the intake valve open period and the exhaust valve open period when the VTC mechanism is operating becomes zero. / Dθ) based on rand (see equation (46) above), according to the fifth embodiment of the prior application device, based on the exhaust valve surrounding gas flow rate (dm / dθ) ivo at the intake valve opening timing IVO (above (See equation (47)) , Overlap period even if is longer than a predetermined value, thereof longer, the gas amount M2 blowback in the overlap of the exhaust valve opening period and the intake valve open period can be accurately calculated.

  This completes the description of the prior application device.

According to subsequent experiments and simulations, the waveform of the gas flow rate around the exhaust valve during the overlap of the intake valve open period and the exhaust valve open period is different in operating conditions, particularly the exhaust valve opening / closing timing, as shown in FIG. As shown in the left, middle, and right, it has been found that there are three types of waveforms. Each waveform is explained as follows.
(Ii) Waveforms when both gas blowout from the combustion chamber to the exhaust port and gas blowback from the exhaust port to the combustion chamber exist (in the case of the left in FIG. 24) (b) Gas from the combustion chamber to the exhaust port Waveform when only gas is blown out (in the case of FIG. 24) (ha) Waveform when only gas is blown back from the exhaust port into the combustion chamber (in the case of the right side of FIG. 24) The direction flowing from the port 11 into the combustion chamber 5 is positive, and the direction flowing from the combustion chamber 5 to the exhaust port 11 is negative. Since this is convenient, the flow direction from the exhaust port 11 into the combustion chamber 5 may be negative, and the flow direction from the combustion chamber 5 to the exhaust port 11 may be positive.

  In this way, when the exhaust valve opening / closing timing differs due to the difference in operating conditions and three different waveforms appear in the gas flow rate around the exhaust valve during the overlap between the intake valve open period and the exhaust valve open period, Therefore, it is necessary to determine (estimate) whether the waveform of the gas flow rate around the exhaust valve during the overlap between the intake valve open period and the exhaust valve open period belongs to the left, middle, or right waveform in FIG.

  A method for determining which of the three different waveforms belongs to will be described below as a sixth embodiment of the present invention. Since the prior application apparatus describes up to the fifth embodiment, the sixth embodiment is the first embodiment of the present invention. However, the first embodiment has been described as the first embodiment of the present invention. Will be confused and will be described as a sixth embodiment of the present invention.

  In the sixth embodiment of the present invention, the waveform of the gas flow rate around the exhaust valve during the overlap of the intake valve open period and the exhaust valve open period by any of the following two operations a and b is left, middle or right in FIG. It is determined whether the waveform is in the case of.

  Operation a: The crank angle θ0 when the gas flow rate around the exhaust valve becomes zero is calculated by the following equation in the same manner as in the prior application device.

θ0 = 2 × β × Cai × IVO + α × Cva
− ((2 × β × Cai × IVO + α × Cva) ^ 2−4 × β × Cai
× (−β × Cai × IVO ^ 2-α × Cva-X × Cpa))
^ (1/2) / 2 / β / Cai (50)
However, IVO: intake valve opening timing [degCA]
Cpa: Time differential value of the pressure in the combustion chamber, calculated by (complement 10)
Cai: coefficient
Cva: slope of a straight line when the horizontal axis represents the crank angle and the vertical axis represents the rate of change in the combustion chamber volume near the intake top dead center [m ^ 3 / deg ^ 2]
α: = PEX / REX / TEX × 6 × Ne
X: = VTDC / REX / TEX × 6 × Ne
Β on the right side of equation (50) is calculated by the following equation.

β = Pex / (REX × TEX) × κ ^ (1/2)
× (2 / (κ + 1)) ^ (κ + 1) / (2 / (κ-1)) × RMF1 (51)
Where Pex: exhaust pressure, here (PEX + PIVO) / 2
REX: exhaust gas constant, calculated by equation (20) above
TEX: Average exhaust temperature, calculated by the above equation (23)
κ: Specific heat ratio of exhaust, calculated by equation (19) above
RMF1: Flow rate ratio, calculated from the above equation (37) These equations (50) and (51) are the same as the equations (complement 18) and (38) described in the first embodiment of the prior application device. It is.

  If the crank angle θ0 when the gas flow rate around the exhaust valve is zero calculated during the overlap between the intake valve open period and the exhaust valve open period is the waveform in the case of the left in FIG. On the other hand, if the crank angle θ0 when the gas flow around the exhaust valve becomes zero is not during the overlap of the intake valve open period and the exhaust valve open period, it is one of the waveforms in the right case in FIG. Is determined. Since it can be determined that the waveform is in the case of the left side of FIG. 24, the next operation b is to determine whether the waveform is in the case of the right side in FIG.

  Operation b: In FIG. 24, the difference in the waveform on the right side of FIG. 24 is in the direction of gas flow at the intake valve opening timing IVO, whether gas is blown out from the combustion chamber 5 to the exhaust port 11, or It may be based on whether the gas is blowing back from the exhaust port 11 into the combustion chamber 5. In consideration of the pressure, when the gas is blown out from the combustion chamber 5 to the exhaust port 11, the pressure in the combustion chamber becomes higher than the exhaust pressure, and conversely, the gas blows back from the exhaust port 11 into the combustion chamber 5. When the combustion chamber pressure is lower than the exhaust pressure, the combustion chamber pressure is higher than the exhaust pressure. In this case, the case in FIG. It can be determined that there is.

  Therefore, when the pressure in the combustion chamber and the exhaust pressure during the overlap between the intake valve open period and the exhaust valve open period were measured, an unexpected result was obtained as shown in FIG. That is, FIG. 25 shows the gas flow waveform around the exhaust valve in the left, middle, and right states of FIG. 24, the intake pressure Pint, the exhaust pressure Pex, the pressure history of the combustion chamber pressure Pcyl, The intake valve opening area Ain and the exhaust valve opening area Aex) are shown, but what is unique in FIG. 25 is that in FIG. 25, that is, the combustion chamber pressure Pcyl is exhausted in the vicinity of the intake valve opening timing IVO. The point is that the pressure Pex is increased. When this point is analyzed, the reason why the pressure Pcyl in the combustion chamber rises beyond the exhaust pressure Pex as shown in FIG. 25 is that the gas flow between the combustion chamber 5 and the exhaust port 11 near the intake valve opening timing IVO. It turned out to be in a choke state. In other words, the reason why the gas flow from the combustion chamber 5 to the exhaust port 11 is choked is that the exhaust valve opening area in the vicinity of the intake valve opening timing IVO is very small. When the amount of gas that can pass through the exhaust valve becomes smaller than the amount of change, the gas in the combustion chamber 5 that could not pass through the exhaust valve 16 is compressed in the exhaust stroke in which the piston 6 rises. This is because it rises higher than the pressure.

  This will be further described with reference to FIG. 26. As shown in the enlarged view on the right side of FIG. 26, the amount of change in the combustion chamber volume accompanying the movement of the piston 6 (shown as “in-cylinder volume change amount” in the figure). Is a simple straight line going up to the right near the exhaust top dead center (TDC) (approximate), whereas the amount of gas that can pass through the exhaust valve decreases rapidly and converges to zero. For this reason, in a region where the curve exceeds a straight line (indicated by hatching), gas cannot be discharged from the combustion chamber 5 to the exhaust port 11 (that is, in a choked state), and the piston 6 rising in the exhaust stroke causes the combustion chamber 5 to rise. It will be compressed inside. The curve intersects the straight line at two points, but the crank angle when the curve intersects the straight line earlier in time is the choke state start crank angle (the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 starts the choke state). Crank angle) The timing at which the choke state is finished at CACOMP is the crank angle when the quadratic curve is late in time and intersects the straight line (simply, the intake valve opening timing IVO).

  Therefore, in the sixth embodiment of the present invention, it is determined whether or not the flow of the gas blown out from the combustion chamber 5 to the exhaust port 11 enters the choke state based on the choke state start crank angle CACOMP. Actually, the choke state start crank angle CACOMP is compared with the intake valve opening timing IVO, and the choke state start crank angle CACOMP is coincident with the intake valve opening timing IVO or when it is more advanced than the intake valve opening timing IVO. When the flow of the gas blown out from the combustion chamber 5 to the exhaust port 11 becomes a choke state (the waveform of the gas flow around the exhaust valve shown in FIG. 24), the choke state start crank angle CACOMP becomes the intake valve opening timing IVO. When it is on the more retarded side, it is determined that the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 is not in a choked state (the waveform of the gas flow around the exhaust valve shown on the right in FIG. 24). Here, the counterpart to be compared with the choke state start crank angle CACOMP is the intake valve open timing IVO. When the choke state occurs, the intake valve open timing IVO is surely on the retard side with respect to the choke state start crank angle CACOMP. It is because it is considered.

  Next, calculation of the choke state start crank angle CACOMP will be considered.

From the equation of state of the ideal gas, the time derivative is
dm / dt = (P / RT) · dV / dt (52)
It is. However, since the changes in the pressure P, the gas constant R of the exhaust gas, and the temperature T are small, their time derivatives are ignored.

  Here, the derivative at time t is changed to the derivative at crank angle θ. Since dm / dθ · dθ / dt = (P / RT) · dV / dθ · dθ / dt, the following equation is obtained as a differential equation at the crank angle θ from the equation (52).

dm / dθ = (P / RT) · dV / dθ (53)
The orifice flow rate equation in the choke state is given by the equation of time differentiation as follows.

dm / dt = _{[C D · Aex2 · PEX / {} (REX · TEX) ^ (1/2)} ]
・ {Κ ^ (1/2)}
・ [(2 / (κ + 1)) ^ {(κ + 1) / 2 (κ-1)}]
... (54A)
Therefore, the equation (54A) is also transformed into a differential equation at the crank angle θ. That is,
dm / dt = (dm / dθ) · dθ / dt
= (Dm / dθ) · 6Ne
Therefore, using this equation, the equation representing the orifice flow rate equation (the equation (54A)) in the choke state as a differential equation with respect to the crank angle θ is as follows.

dm / dθ = [C _D · Aex2 · PEX
/ {6Ne (REX · TEX) ^ (1/2)}]
・ {Κ ^ (1/2)}
・ [(2 / (κ + 1)) ^ {(κ + 1) / 2 (κ-1)}]
... (54B)
Here, equation (53) represents the straight line shown on the right side of FIG. 26, and equation (54B) represents the curve shown on the right side of FIG. Therefore, the choke state start crank angle CACOMP, which is the crank angle when the amount of change in the combustion chamber volume near the exhaust top dead center due to the movement of the piston 6 and the amount of gas that can pass through the exhaust valve, coincides with the equation (53): If the equations (54B) are solved simultaneously, the solution is obtained as the choke state start crank angle CACOMP. That is, the following equation is obtained by solving the equations (53) and (54B) simultaneously.

[6Ne / {(REX · TEX) ^ (1/2)}] (dV / dθ)
-C _D · Aex 2 · {κ ^ (1/2)}
[{(2 / (κ + 1)} ^ (κ + 1) / {2 (κ-1)}] = 0
... (55)
However, dV / dθ: the amount of change in the combustion chamber volume near the exhaust top dead center due to the movement of the piston 6
Ne: Engine rotation speed [rpm]
Aex2: Exhaust valve opening area [m ^ 2]
REX: exhaust gas constant [kJ / mol / K]
TEX: Average exhaust temperature [K]
κ: Specific heat ratio [−]
C _D : Air resistance coefficient [−]
In equation (55), the combustion chamber volume change dV / dθ in the vicinity of the exhaust top dead center due to the movement of the piston 6 is right in the vicinity of the exhaust top dead center (TDC), as shown on the right side of FIG. It can be approximated by a straight line that rises. That is, the combustion chamber volume change dV / dθ can be expressed by a linear function of the crank angle θ. In this case, the inclination of the straight line is determined depending on the engine specifications and the engine speed Ne.

  Next, the exhaust valve opening area Aex2 of the expression (55) depends on the command value given to the exhaust valve VTC mechanism 28 when the exhaust valve VTC mechanism 28 is provided and the opening / closing timing of the exhaust valve 16 changes. Determined. For example, it is assumed that A1 in FIG. 27 is a characteristic of the exhaust valve opening area Aex2 when the exhaust valve VTC mechanism 28 is in the non-operating state (the most advanced angle position) (the exhaust valve closing timing at this time is the initial position EVC0). It is assumed that a predetermined command value is given to the exhaust valve VTC mechanism 28 in order to operate the exhaust valve VTC mechanism 28. If this command value is referred to as “exhaust VTC conversion angle”, the exhaust VTC conversion angle represents an amount by which the exhaust valve closing timing EVC is retarded from the initial position EVC0. For example, when 5 deg CA (crank angle is 5 degrees) is given as the exhaust VTC conversion angle, the characteristics of the exhaust valve opening area Aex2 shift from A1 to the right (retard side) by 5 deg CA and shift to A2, and the exhaust The valve closing timing EVC is EVC1 (= EVC0 + 5). If the exhaust VTC conversion angle is even larger, for example, 10 deg CA, the characteristic of the exhaust valve opening area Aex2 is further translated from A1 by 10 deg CA in the right direction and then shifted to A3, and the exhaust valve closing timing EVC becomes EVC2 (= EVC0 + 10). As described above, when the exhaust valve VTC mechanism 28 is in the operating state, the exhaust valve opening area Aex2 in the exhaust valve VTC mechanism inactive is translated by the exhaust VTC conversion angle. That is, the exhaust valve opening area Aex2 is determined depending on the exhaust VTC conversion angle. The reason why “2” is added after Aex is to distinguish it from “exhaust valve opening area Aex at crank angle θ2” appearing in the above-mentioned equation (40) of the prior application device.

Next, the specific heat ratio κ of the equation (55) can be obtained by referring to the map of FIG. 28 from the target equivalent ratio and the average exhaust temperature TEX, for example. The air resistance coefficient _CD is given in advance as a conforming value. The engine speed Ne is determined by operating conditions. The exhaust gas constant REX and the average exhaust temperature TEX are obtained by the above equations (6) and (23).

In summary, when the exhaust valve VTC mechanism 28 is not provided, the left side of the equation (55) is a function of the crank angle θ and the engine rotation speed Ne, and therefore the equation of the equation (55) is determined if the engine rotation speed Ne is determined. Can be obtained as a choke state start crank angle CACOMP. Further, when the exhaust valve VTC mechanism 28 is provided, C _D · Aex2 in the equation (55) changes according to the exhaust VTC conversion angle, so that the equation of the equation (55) is changed to the crank angle θ for each exhaust VTC conversion angle. It is necessary to calculate the choke state start crank angle CACOMP by solving for. In this case, since the equation (55) is not a simple equation such as a quadratic equation, the calculation load increases in order for the engine controller 31 to solve the equation in real time. Therefore, in the sixth embodiment of the present invention, the choke state start crank angle CACOMP data obtained by solving the equation (55) by making the engine speed Ne and the exhaust VTC conversion angle different from each other is used as the engine speed Ne. 34, and a map as shown in FIG. 34 is stored in advance in the ROM, and the map is referred to from the current engine speed Ne and the exhaust VTC conversion angle. The choke state start crank angle CACOMP is calculated.

  As shown in FIG. 34, the choke state start crank angle CACOMP becomes a retarded value as the exhaust VTC conversion angle increases under the condition where the engine rotational speed Ne is constant, and the engine under the condition where the exhaust VTC conversion angle is constant. The greater the rotational speed Ne, the slower the value.

The calculation method of the choke state start crank angle CACOMP is not limited to this. Basically, the exhaust valve opening area Aex2 (the upper concept is “exhaust valve opening / closing timing”) and the engine operating state (the piston 6 Calculated based on the change in combustion chamber volume dV / dθ in the vicinity of exhaust top dead center due to movement, engine rotational speed Ne, exhaust gas constant REX, average exhaust temperature TEX, specific heat ratio κ, and air resistance coefficient C _D ) Is something that can be done.

  By comparing the choke state start crank angle CACOMP calculated in this way with the intake valve opening timing IVO as described above, whether or not the flow of the gas blown out from the combustion chamber 5 to the exhaust port 11 enters the choke state. Can be determined. In this case, both the choke state start crank angle CACOMP and the intake valve opening timing IVO are values [degCA] measured on the retard side from the compression top dead center.

  This completes the description of the operation b.

  This control performed by the engine controller 31 will be described with reference to the flowchart of FIG.

  FIG. 29 is for setting the waveform determination flag according to the sixth embodiment of the present invention, and performs calculation every certain time (for example, every 10 ms).

  In step 101, it is determined whether or not there is an overlap between the intake valve open period and the exhaust valve open period. This can be understood from command values given to the intake valve VTC mechanism 27 and the exhaust valve VTC mechanism 28. If there is no overlap between the intake valve open period and the exhaust valve open period, the current process is terminated.

  When there is an overlap between the intake valve open period and the exhaust valve open period, the routine proceeds to step 102 where the exhaust pressure Pex [kPa] (= (PEX + PIVO) / 2) and the average exhaust pressure PEX [kPa] (calculated by the above equation (20)). Completed), combustion chamber volume VTDC [m ^ 3] (constant) at top dead center, exhaust gas constant REX [kJ / mol / K] (calculated by the above equation (6)), average exhaust temperature TEX [K] (Calculated with the above equation (23)), exhaust specific heat ratio κ [−] (calculated with the above equation (19) or from FIG. 28), flow rate ratio RMF1 [−] (calculated with the above equation (37)) The engine rotation speed Ne [rpm], the exhaust VTC conversion angle [degCA], the intake valve opening timing IVO [degCA], and the exhaust valve closing timing EVC [degCA] are read. The values of the exhaust VTC conversion angle, the intake valve opening timing IVO, and the exhaust valve closing timing EVC are known from command values given to the intake valve VTC mechanism 27 and the exhaust valve VTC mechanism 28.

In steps 103 and 104, the gas flow rate around the exhaust valve is zero before the exhaust valve 16 is closed in the same manner as described in the crank angle calculation unit 72 at zero gas flow rate in FIG. 23 of the third embodiment of the prior application device. Is calculated. That is, first in step 103, the exhaust pressure Pex, the exhaust gas constant REX, the average exhaust temperature TEX, the exhaust specific heat ratio κ, and the flow rate ratio RMF1 are used to calculate β according to the above equation (51), and the exhaust gas constant REX, the average exhaust temperature. Using TEX and engine speed Ne, α and X
α = PEX / REX / TEX × 6 × Ne
X = VTDC / REX / TEX × 6 × Ne
When the β, α, X and intake valve opening timing IVO are used in step 104, and the gas flow rate around the exhaust valve becomes zero before the exhaust valve 16 is closed according to the above equation (50). The crank angle θ0 [degCA] is calculated.

  In step 105, whether or not the crank angle θ0 calculated in this way so that the gas flow rate around the exhaust valve becomes zero before the exhaust valve 16 is closed is in the overlap between the intake valve open period and the exhaust valve open period, that is, The crank angle θ0 when the gas flow rate around the exhaust valve becomes zero is on the more retarded side than the intake valve opening timing IVO [degCA] and on the more advanced side than the exhaust valve closing timing EVC [degCA] (IVO <θ0). <EVC) is checked. If IVO <θ0 <EVC, it is determined that the crank angle θ0 when the gas flow around the exhaust valve becomes zero before the exhaust valve 16 is closed is in the overlap between the intake valve open period and the exhaust valve open period. Proceeding to step 106, the waveform determination flag (initially set to zero when the engine is started) = 1.

  In step 105, IVO <θ0 <EVC, that is, the crank angle θ0 when the gas flow rate around the exhaust valve becomes zero before the exhaust valve 16 is closed is equal to the intake valve opening timing IVO or more than the intake valve opening timing IVO. The crank angle θ0 when the gas flow rate around the exhaust valve becomes zero before the exhaust valve 16 is closed is equal to the exhaust valve closing timing EVC or on the retard side from the exhaust valve closing timing EVC when it is on the advance side. Sometimes, the routine proceeds to step 107, and the choke state start crank angle CACOMP [degCA] is calculated by referring to the map having the contents shown in FIG. 34 from the engine speed Ne and the exhaust VTC conversion angle.

  In step 108, the choke state start crank angle CACOMP thus obtained is compared with the intake valve opening timing IVO [degCA]. If the starting crank angle CACOMP of the choke state coincides with the intake valve opening timing IVO or is on the more advanced side than the intake valve opening timing IVO, the gas flow around the exhaust valve during the overlap between the intake valve opening period and the exhaust valve opening period Is determined to be a waveform when the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 is in a choke state, and the routine proceeds to step 109 where the waveform determination flag = 2. On the other hand, if the choke state start crank angle CACOMP is on the retard side of the intake valve opening timing IVO, the waveform of the gas flow around the exhaust valve during the overlap between the intake valve open period and the exhaust valve open period is the combustion chamber 5. It is determined that the waveform of the gas blown from the inside to the exhaust port 11 is a waveform when the choke state is not established, and the process proceeds from step 108 to step 110 to set the waveform determination flag = 3.

  As a result, the waveform determination flag = 1 indicates that the waveform of the gas flow rate around the exhaust valve during the overlap between the intake valve open period and the exhaust valve open period is as shown in the left of FIG. FIG. 24 shows that the waveform of the gas flow rate around the exhaust valve during the overlap between the period and the exhaust valve open period is as shown in FIG. 24. The waveform determination flag = 3 is the exhaust during the overlap between the intake valve open period and the exhaust valve open period. This represents that the waveform of the gas flow around the valve is as shown on the right side of FIG.

  Thus, after determining whether the waveform of the gas flow rate around the exhaust valve during the overlap between the intake valve open period and the exhaust valve open period is the waveform of the left, middle, or right in FIG. For each waveform, the area is calculated by approximating the waveform of the gas flow rate around the exhaust valve during the overlap of the intake valve open period and the exhaust valve open period with a straight line.

  This will be described with reference to FIG. 30. FIG. 30 collectively shows a method of linearly approximating each of the waveforms (i) to (ha) and the area to be calculated. When the above waveform (i) is obtained, as shown in the lower left part of FIG. 30, the area of the left triangle is used as the amount of blown gas M21 during the overlap between the intake valve open period and the exhaust valve open period, and the right triangle. Is the blow-back gas amount M22 during the overlap between the intake valve open period and the exhaust valve open period, and when the above waveform (b) is obtained, as shown in the lower part of FIG. As the blowout gas amount M23 during the overlap between the valve open period and the exhaust valve open period, when the above waveform is (), the sum of the trapezoidal area and the triangular area as shown in the lower part of FIG. Are calculated as the blowback gas amount M24 during the overlap between the intake valve open period and the exhaust valve open period.

  Hereinafter, an area calculation method for each of the waveforms (ii) to (ha) will be described.

<1> Method for Calculating the Area when the Waveform (i) is Above As shown on the left side of FIG. 30, a horizontal line with zero gas flow around the exhaust valve and a straight line of the intake valve opening timing IVO (vertical passing through IVO in FIG. 30) The area of the triangle surrounded by the straight line 1 and the straight line 1 is surrounded by the horizontal line, the straight line 1 and the straight line 2 with the gas flow around the exhaust valve being zero, as the blowout gas amount M21 during the overlap between the intake valve open period and the exhaust valve open period. The area of the triangle is defined as the blown back gas amount M22 during the overlap between the intake valve open period and the exhaust valve open period, that is, the blowout gas amount M21 during the overlap between the intake valve open period and the exhaust valve open period, the intake valve open period, and the exhaust. The blow-back gas amount M22 during the overlap of the valve opening period is calculated by the following equation.

M21 = | (dm / dθ) ivo | × (θ0−IVO) / 2 (56)
M22 = (dm / dθ) c × (EVC−θ0) / 2 (57)
However, (dm / dθ) ivo: Gas flow around the exhaust valve when the intake valve is open
[Kg / degCA]
(Dm / dθ) c: Gas flow around the exhaust valve at point c
[Kg / degCA]
θ0: Crank angle when the gas flow around the exhaust valve becomes zero before the exhaust valve is closed [degCA]
IVO: intake valve opening timing [degCA]
EVC: Exhaust valve closing timing [degCA]
In the first embodiment of the prior application apparatus, as shown in (25) above, the amount of gas blown from the combustion chamber 5 to the exhaust port 11 is also included in the amount of blown back gas from the exhaust port 11 to the combustion chamber 5. However, in the sixth embodiment of the present invention, the amount of gas blown out from the combustion chamber 5 to the exhaust port 11 (M21) and the amount of blowback gas from the exhaust port 11 into the combustion chamber 5 (M22) are calculated. They are handled separately.

<2> Method for calculating the area when the above waveform (b) is obtained As shown in FIG. 30, a horizontal line with zero gas flow around the exhaust valve and a straight line of the intake valve opening timing IVO (passes IVO in FIG. 30) The area of the triangle surrounded by the vertical line) and the straight line 1 is calculated as the amount of blown gas M23 during the overlap between the intake valve open period and the exhaust valve open period. However, it is not necessary to actually calculate the straight line 1 here. That is, in FIG. 30, the coordinates of the point a are (IVO, (dm / dθ) ivo) and the coordinates of the point e are (EVC, 0), so that the intake valve opening period and the exhaust valve opening period are overlapping. The amount of gas blown out M23 [kg]
M23 = | (dm / dθ) ivo | × (EVC-IVO) / 2 (58)
However, (dm / dθ) ivo: Gas flow around the exhaust valve when the intake valve is open
[Kg / degCA]
EVC: Exhaust valve closing timing [degCA]
IVO: intake valve opening timing [degCA]
It can be calculated from the following formula.

<3> Method for calculating area when waveform of (ha) above As shown in the right of FIG. 30, a horizontal line of zero exhaust gas flow around the exhaust valve and a straight line of the intake valve opening timing IVO (IVO passes on the right in FIG. 30) The area surrounded by the vertical line), the straight line 1 and the straight line 2 (the total area of the trapezoidal area and the triangular area) is calculated as the blow-back gas amount M24 during the overlap between the intake valve open period and the exhaust valve open period. Hereinafter, the calculation method of the straight line 1, the calculation method of the straight line 2, and the calculation method of the blown-back gas amount M24 will be described in this order.
[1] Calculation Method of Line 1 The same as the first embodiment of the prior application device. That is, the straight line 1 is calculated as a straight line connecting the point a and the point f. Here, the point f is a point where the gas flow rate around the exhaust valve becomes zero before the exhaust valve 16 is closed. The crank angle at which the gas flow around the exhaust valve becomes zero before the exhaust valve 16 is closed when the choke state does not occur, that is, the crank angle at the point f exists near the exhaust top dead center (TDC). It is approximated that the crank angle of f is at the exhaust top dead center θTDC. At this time, since the coordinates of the point a are (IVO, (dm / dθ) ivo) and the coordinates of the point f are (θTDC, 0), the function y1 that gives the straight line 1 is
y1 = (dm / dθ) ivo / (IVO−θTDC) × θ
− (Dm / dθ) ivo × θTDC / (IVO−θTDC)
... (59)
However, (dm / dθ) ivo: Gas flow around the exhaust valve when the intake valve is open
[Kg / degCA]
IVO: intake valve opening timing [degCA]
θTDC: Exhaust top dead center [degCA]
It can be obtained from the following formula.

Here, it is approximated that the point f is at the exhaust top dead center θTDC. However, since the point f actually deviates slightly (moves slightly) from the exhaust top dead center θTDC, a slight deviation from the exhaust top dead center is considered. When the engine speed Ne and the engine load are used as parameters, the crank angle (crank angle at the point f) at which the gas flow around the exhaust valve becomes zero before the exhaust valve 16 is closed can be obtained and given as a map. That's fine.
[2] Calculation Method of Line 2 The same as the first embodiment of the prior application device. That is, using the above equation (41) as it is, that is, the function y2 that gives the straight line 2 is
y2 = -4 * (dm / d [theta]) d / (EVC-IVO) * ([theta] -EVC)
... (60)
Where (dm / dθ) d: gas flow around the exhaust valve at point d
[Kg / degCA]
IVO: intake valve opening timing [degCA]
EVC: Exhaust valve closing timing [degCA]
It is calculated by the following formula.

  Here, the above equation (40) may be used to calculate the gas flow around the exhaust valve (dm / dθ) d at point d in equation (60).

By solving the equations (59) and (60) as simultaneous equations, the crank angle θ1 at the point c is obtained on the right side of FIG. 30, and the gas flow around the exhaust valve (dm / dθ) c at the crank angle θ1 at the point c is obtained. Is obtained by substituting the crank angle θ1 of the point c into the straight line 1 (formula (59)) or the straight line 2 (formula (60)).
[3] Calculation Method of Blowing Gas M24 When the coordinates of point a, point c, and point d are obtained in this way, the intake valve open period and exhaust valve open period corresponding to the trapezoidal area on the right side of FIG. Blowing gas amount M25 [kg] in the lap
M25 = {(dm / dθ) c + (dm / dθ) ivo)} × (θ1-IVO) / 2
... (61)
In the right side of FIG. 30, the blowback gas amount M26 [kg] during the overlap between the intake valve opening period and the exhaust valve opening period corresponding to the area of the triangle is
M26 = (dm / dθ) c × (EVC−θ1) / 2 (62)
The sum of these two blowback gas amounts M25 and M26 is used as the blowback gas amount M24 during the overlap between the intake valve open period and the exhaust valve open period, that is, the intake valve open period and the exhaust valve open according to the following formula: Calculate the blown back gas amount M24 [kg] during the overlap of the period M24 = M25 + M26 (63)
This concludes the description of the method of calculating the area for each waveform of (i) to (ha).

  This control performed by the engine controller 31 will be described with reference to the flowcharts of FIGS. 31, 32, and 33.

  31, FIG. 32, and FIG. 33 are for calculating the residual gas amount in the combustion chamber after the overlap between the exhaust valve opening period and the intake valve opening period of the sixth embodiment of the present invention (more precisely, immediately after the overlap ends). This is executed at regular intervals (for example, every 10 ms) following FIG.

  In step 111, the waveform determination flag (set according to FIG. 29) is observed. When the waveform determination flag = 1, the routine proceeds to step 112 and thereafter, and the amount of residual gas in the combustion chamber after the end of the overlap between the exhaust valve open period and the intake valve open period when the above waveform (i) is obtained is calculated. In this case, the method for calculating the amount of residual gas in the combustion chamber is the same as that of the prior application device. That is, the prior application device only considered when the waveform of (i) was obtained. Again, the explanation is as follows.

  In step 112, the combustion chamber temperature TIVO [K] at the intake valve opening timing (calculated by the above equation (22)), the combustion chamber pressure PIVO [kPa] at the intake valve opening timing (calculated by the above equation (12)). ), Combustion chamber volume VIVO [m ^ 3] at the intake valve opening timing (calculated from the above equation (7)), exhaust gas constant REX [kJ / mol / K] (calculated from the above equation (6)), Exhaust valve opening area Aex [m ^ 2] (calculated in accordance with the explanation in FIG. 18) at the engine rotation speed Ne [rpm] and crank angle θ2, and average exhaust pressure PEX [kPa] (calculated by the above equation (20)) Exhaust) temperature TEX [K] (calculated by the above equation (23)), flow rate ratio RMF2 [−] (calculated by the above (complement 21) equation), specific heat ratio κ [−] (the above equation (19) Also by Is calculated from FIG. 28), intake valve opening timing IVO [degCA], exhaust valve closing timing EVC [degCA], crank angle θ0 [degCA] when the gas flow around the exhaust valve becomes zero (calculated from FIG. 29) Then, the combustion chamber gas amount MR1 [kg] (calculated by the above formula (1)) at the intake valve opening timing IVO is read.

In step 113, the intake air is taken in using the combustion chamber temperature TIVO at the intake valve opening timing, the combustion chamber pressure PIVO at the intake valve opening timing, the combustion chamber volume VIVO at the intake valve opening timing, the exhaust gas constant REX, and the engine speed Ne. The gas flow rate (dm / dθ) ivo [kg / degCA] around the exhaust valve at the valve opening timing,
(Dm / dθ) ivo = VIVO × Cpa / 6 / Ne / REX / TIVO
+ PIVO / REX / TIVO × (Cva × IVO + Cvb)
... (64)
However, Cpa: time differential value of the pressure in the combustion chamber, already calculated by (complement 10)
Cva: slope of a straight line when the horizontal axis represents the crank angle and the vertical axis represents the rate of change in the combustion chamber volume near the intake top dead center [m ^ 3 / deg ^ 2]
Cvb: intercept of the straight line when the crank angle is plotted on the horizontal axis and the volumetric change rate in the combustion chamber is plotted on the vertical axis near the intake top dead center [m ^ 3]
In step 114, the exhaust gas flow around the exhaust valve (dm / dθ) ivo at the opening timing of the intake valve ivo, the crank angle θ0 when the exhaust gas flow around the exhaust valve becomes zero before the exhaust valve is closed, the intake air Using the valve opening timing IVO, a function y1 that gives a straight line 1 is
y1 = − (dm / dθ) ivo / (θ0−IVO) × θ
+ (Dm / dθ) ivo / (θ0−IVO) × θ0
... (65)
It is calculated by the following formula.

In step 115, the exhaust valve opening area Aex at the crank angle θ 2, the average exhaust pressure PEX, the exhaust gas constant REX, the exhaust temperature TEX, the flow rate ratio RMF 2, the specific heat ratio κ, and the engine rotational speed Ne are used to set the exhaust valve at point d. Ambient gas flow rate (dm / dθ) d [kg / degCA]
(Dm / dθ) d = Aex × PEX / (REX × TEX) ^ (1/2)
× κ ^ (1/2) × (2 / (κ + 1)) ^ ((κ + 1)
/ (2 × (κ−1))) × RMF2 / 6 / Ne
... (66)
In step 116, a function y2 that gives a straight line 2 using the exhaust gas flow around the exhaust valve (dm / dθ) d at this point d, the exhaust valve closing timing EVC, and the intake valve opening timing IVO is calculated as follows:
y2 = -4 * (dm / d [theta]) d / (EVC-IVO) * ([theta] -EVC)
... (67)
It is calculated by the following formula.

  In step 117, the equation (67) and the above equation (66) are solved simultaneously, and the crank angle θ which is the solution is calculated as the crank angle θ1 [degCA] at the point c.

  In step 118, by substituting the crank angle θ1 at the point c into the crank angle θ in the equation (67) or (66), the gas flow rate around the exhaust valve (dm / dθ) c [kg / degCA] at the point c is obtained. calculate.

  In steps 119 and 120, the exhaust gas flow rate around the exhaust valve (dm / dθ) ivo at the intake valve opening timing thus obtained, the crank angle θ0 at point b, and the exhaust gas flow rate around the exhaust valve at point c (dm / dθ). c, using the intake valve opening timing IVO and the exhaust valve closing timing EVC, the exhaust port 11 from the combustion chamber 5 during the overlap of the intake valve open period and the exhaust valve open period by the above formulas (56) and (57) The amount of gas blown into the combustion chamber 5 and the amount of blown back gas M22 [kg] from the exhaust port 11 during the overlap between the intake valve open period and the exhaust valve open period are calculated.

  In step 121, the amount of gas M21 blown from the combustion chamber 5 during the overlap between the intake valve open period and the exhaust valve open period to the exhaust port 11 and the exhaust port during the overlap between the intake valve open period and the exhaust valve open period. The exhaust valve opening period and the intake valve opening when the value obtained by adding the blowback gas amount M22 from 11 to the combustion chamber 5 to the combustion chamber gas amount MR1 at the intake valve opening timing IVO has the waveform (ii) above. The amount of residual gas in the combustion chamber after the overlap between the exhaust valve opening period and the intake valve opening period when the waveform in (i) above is obtained as kg].

Residual gas amount in combustion chamber = MR1 + M21 + M22 (68)
Here, the above equations (56), (57), and (68) are substantially the same as the equations (25) and (complement 1) given by the prior application device. Further, the above equations (64), (65), (66), and (67) are the equations (33), (complement 19), (40), and (41) given by the prior application device. Is the same formula.

  On the other hand, when the waveform determination flag is not 1 in step 111 in FIG. 31, the process proceeds to step 123 in FIG. 32 to check whether or not the waveform determination flag = 2. When the waveform determination flag = 2, the routine proceeds to step 124 and subsequent steps, and the amount of residual gas in the combustion chamber after the overlap of the exhaust valve open period and the intake valve open period when the above waveform is obtained is calculated.

  First, in step 124, as in steps 112 and 113 in FIG. 31, the combustion chamber temperature TIVO [K] at the intake valve opening timing (calculated by the above equation (22)), the combustion chamber pressure at the intake valve opening timing. PIVO [kPa] (calculated by the above equation (12)), combustion chamber volume VIVO [m ^ 3] at the intake valve opening timing (calculated by the above equation (7)), exhaust gas constant REX [kJ / mol / K] (calculated by the above equation (6)), engine rotational speed Ne [rpm], intake valve opening timing IVO [degCA], exhaust valve closing timing EVC [degCA], and intake valve opening timing IVO MR1 [kg] (calculated by the above equation (1)) is read, and in step 125, the combustion chamber at the intake valve opening timing is the same as in step 113 of FIG. The exhaust gas flow around the exhaust valve at the intake valve opening timing (dm /) using the temperature TIVO, the combustion chamber pressure PIVO at the intake valve opening timing, the combustion chamber volume VIVO at the intake valve opening timing, the exhaust gas constant REX, and the engine speed Ne. dθ) ivo [kg / degCA] is calculated by the above equation (64).

  In step 126, the intake valve opening period and the exhaust gas according to the above equation (58) using the exhaust gas flow around the exhaust valve (dm / dθ) ivo, the exhaust valve closing timing EVC, and the intake valve opening timing IVO at the intake valve opening timing. The amount of blown gas M23 [kg] during the overlap of the valve opening period is calculated, and in step 127, the amount of blown gas M23 during the overlap of the intake valve opening period and the exhaust valve opening period is burned at the intake valve opening timing IVO. The value added to the indoor gas amount MR1 is the residual gas amount in the combustion chamber after the overlap between the exhaust valve open period and the intake valve open period when the waveform of the above (B) is obtained. The residual gas amount [kg] in the combustion chamber after the overlap between the exhaust valve opening period and the intake valve opening period is calculated.

Residual gas amount in combustion chamber = MR1 + M23 (69)
On the other hand, when the waveform determination flag is not 2 in step 123 of FIG. 32, the process proceeds to step 128 of FIG. 33 to check whether or not the waveform determination flag is 3. When the waveform determination flag = 3, the routine proceeds to step 129 and subsequent steps, and the amount of residual gas in the combustion chamber after the end of the overlap between the exhaust valve open period and the intake valve open period is calculated.

  First, in steps 129 and 130, similarly to steps 112 and 113 in FIG. 31, the combustion chamber temperature TIVO [K] at the intake valve opening timing (calculated by the above equation (22)), the combustion at the intake valve opening timing. Indoor pressure PIVO [kPa] (calculated by the above equation (12)), combustion chamber volume VIVO [m ^ 3] at the intake valve opening timing (calculated by the above equation (7)), exhaust gas constant REX [kJ / mol / K] (calculated according to the above equation (6)), engine rotational speed Ne [rpm], exhaust valve opening area Aex [m ^ 2] at the crank angle θ2 (calculated according to the description in FIG. 18), Average exhaust pressure PEX [kPa] (calculated by the above equation (20)), exhaust temperature TEX [K] (calculated by the above equation (23)), flow rate ratio RMF2 [−] (above (supplement 21)) ), The specific heat ratio κ [−] (calculated from the above equation (19) or from FIG. 28), the intake valve opening timing IVO [degCA], the exhaust valve closing timing EVC [degCA], and the intake valve opening timing IVO. Of combustion chamber gas amount MR1 [kg], combustion chamber temperature TIVO at intake valve opening timing, combustion chamber pressure PIVO at intake valve opening timing, combustion chamber volume VIVO at intake valve opening timing, exhaust gas constant REX, Using the engine speed Ne, the exhaust gas flow around the exhaust valve (dm / dθ) ivo [kg / degCA] at the intake valve opening timing is calculated by the above equation (64).

  In step 131, a function y1 that gives a straight line 1 using the gas flow around the exhaust valve (dm / dθ) ivo at the intake valve opening timing, the intake valve opening timing IVO, and the exhaust top dead center θTDC is expressed by the above equation (59). calculate.

  In step 132, the exhaust valve opening point Aex at the crank angle θ2, the average exhaust pressure PEX, the exhaust gas constant REX, the exhaust temperature TEX, the flow rate ratio RMF2, the specific heat ratio κ, and the engine rotational speed Ne are used to set the exhaust valve at the point d. The surrounding gas flow rate (dm / dθ) d [kg / degCA] is calculated by the above equation (66), and in step 133, the exhaust valve surrounding gas flow rate (dm / dθ) d at this point d, the exhaust valve closing timing EVC, the intake air Using the valve opening timing IVO, a function y2 that gives a straight line 2 is calculated by the above equation (67).

  In step 134, the equation (67) and the above equation (66) are solved simultaneously, and the crank angle θ as the solution is calculated as the crank angle θ1 [degCA] at the point c.

  In step 135, by substituting the crank angle θ1 at the point c into the crank angle θ in the above equation (67) or (65), the gas flow around the exhaust valve at the point c (dm / dθ) c [kg / degCA]. ] Is calculated.

  In steps 136 and 137, the exhaust valve surrounding gas flow rate (dm / dθ) ivo at the intake valve opening timing determined in this way, the exhaust valve surrounding gas flow rate (dm / dθ) c at point c, and the crank angle at point c Using θ1, the intake valve opening timing IVO, and the exhaust valve closing timing EVC, from the exhaust port 11 during the overlap between the intake valve opening period and the exhaust valve opening period, the above equation (61) and (62) The blowback gas amounts M25 [kg] and M26 [kg] are calculated, and in step 138, the blowback gas amounts M25 and M26 in the two overlaps are added to the combustion chamber gas amount MR1 at the intake valve opening timing IVO. As the amount of residual gas in the combustion chamber after the overlap between the exhaust valve opening period and the intake valve opening period when the value becomes the waveform of the above (ha), that is, by the following equation The amount of residual gas [kg] in the combustion chamber after the end of the overlap between the exhaust valve opening period and the intake valve opening period when the above waveform (ha) is obtained is calculated.

Residual gas amount in combustion chamber = MR1 + M25 + M26 (70)
Here, the function and effect of the sixth embodiment of the present invention will be described.

  The waveform of the gas flow around the exhaust valve during the overlap between the exhaust valve opening period and the intake valve opening period includes the return of gas from the exhaust port 11 into the combustion chamber 5 and the gas flow from the combustion chamber 5 to the exhaust port 11. In addition to the waveform when both of the blowouts exist, only the waveform when there is only gas blowback from the exhaust port 11 into the combustion chamber 5 and only the gas blowout from the combustion chamber 5 to the exhaust port 11 are provided. We have newly discovered that there is a waveform when it does not exist. When this newly discovered phenomenon is analyzed, the waveform when only the gas blowout from the combustion chamber 5 to the exhaust port 11 is present is because the pressure in the combustion chamber is compressed in the exhaust stroke. It has been found that the fact that there is only a waveform when there is only gas blowback from the exhaust port 11 into the combustion chamber 5 is because the pressure in the combustion chamber is not compressed in the exhaust stroke.

  The sixth embodiment of the present invention has been made based on these newly found matters. According to the sixth embodiment of the present invention, the amount of change in the combustion chamber volume associated with the movement of the piston 6 and the exhaust valve can be passed. On the basis of the amount of gas, it is determined whether the pressure in the combustion chamber is compressed in the exhaust stroke or not (see Steps 108 to 110 in FIG. 29). When compressed in the stroke, the amount M23 of gas blown out from the combustion chamber 5 to the exhaust port 11 is calculated (see steps 123 and 126 in FIG. 32), and the combustion chamber gas amount MR1 at the intake valve opening timing IVO and this The amount of residual gas in the combustion chamber after the overlap between the exhaust valve open period and the intake valve open period is estimated from the blown-out gas amount M23 (see step 127 in FIG. 32). When the pressure in the combustion chamber is not compressed in the exhaust stroke according to the fixed result, the amount of blown back gas (M25, M26) from the exhaust port 11 into the combustion chamber 5 is calculated (see steps 128, 136, and 137 in FIG. 33), and the intake air From the combustion chamber gas amount MR1 at the valve opening timing IVO and the blowback gas amounts (M25, M26), the residual gas amount in the combustion chamber after the overlap between the exhaust valve opening period and the intake valve opening period is estimated (FIG. 33). (See step 138). Therefore, when only a gas blowout from the combustion chamber 5 to the exhaust port 11 is present (when the pressure in the combustion chamber is compressed in the exhaust stroke), or when combustion occurs from the exhaust port 11 Even when only the gas is blown back into the chamber 5 (when the pressure in the combustion chamber is not compressed in the exhaust stroke), the exhaust The combustion chamber residual gas amount of overlap after the end of the probe opening period and an intake valve open period can be accurately estimated.

According to the sixth embodiment of the present invention, the intake valve VTC mechanism 27 (intake valve opening / closing timing variable mechanism that can change the opening / closing timing of the intake valve) and the exhaust valve VTC mechanism 28 (changes the opening / closing timing of the exhaust valve). And a determination means for determining whether the pressure in the combustion chamber is compressed in the exhaust stroke or not compressed is a predetermined crank angle range including an exhaust top dead center. Exhaust valve opening area Aex2 (exhaust valve opening / closing timing) and engine operating state (amount of change in combustion chamber volume dV / dθ near exhaust top dead center due to movement of piston 6, engine rotational speed Ne, exhaust gas constant) On the basis of REX, average exhaust temperature TEX, specific heat ratio κ, air resistance coefficient C _D ), the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 becomes choked. Determination means (see Steps 107, 108 and FIG. 34 in FIG. 29), and when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in a choke state, the pressure in the combustion chamber is exhausted. In the case of compression in the stroke (see steps 108 and 109 in FIG. 29), the pressure in the combustion chamber is compressed in the exhaust stroke when the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 is not choked. Since it is determined that this is not the case (see steps 108 and 110 in FIG. 29), it is possible to accurately determine whether the pressure in the combustion chamber is compressed in the exhaust stroke or not.

  According to the sixth embodiment of the present invention, the exhaust valve opening / closing timing variable mechanism 28 is provided, and the determination means for determining whether the pressure in the combustion chamber is compressed or not in the exhaust stroke is the exhaust gas. Determination for determining whether or not the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in a choked state based on the exhaust VTC conversion angle that is a command value given to the valve opening / closing timing variable mechanism and the engine speed Ne. Means (see steps 107 and 108 in FIG. 29, FIG. 34), and the pressure in the combustion chamber is compressed in the exhaust stroke when the flow of gas blown out from the combustion chamber to the exhaust port becomes choked ( 29 (see steps 108 and 109 in FIG. 29), the pressure in the combustion chamber is discharged when the flow of gas blown from the combustion chamber to the exhaust port is not choked. Since it is determined that the compression is not performed in the stroke (see steps 108 and 110 in FIG. 29), it is determined whether the pressure in the combustion chamber is compressed in the exhaust stroke without increasing the calculation load on the engine controller 31. It is possible to easily determine whether this is the case.

  According to the sixth embodiment of the present invention, the determination means for determining whether or not the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 is in a choke state allows the volume change in the combustion chamber to pass through the exhaust valve. A crank angle equal to the amount of gas is calculated as a crank angle CACOMP at which the gas flow blown from the combustion chamber 5 to the exhaust port 11 starts a choke state (see step 107 in FIG. 29), and the calculated choke state start crank is calculated. This is means for determining whether or not the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is choked based on the angle CACOMP (see step 108 in FIG. 29), so that the actual gas in the combustion chamber 5 It can be determined whether or not the pressure in the combustion chamber is compressed in the exhaust stroke according to the state.

  According to the sixth embodiment of the present invention, when the choke state start crank angle CACOMP is equal to the intake valve opening timing IVO or on the advance side of the intake valve opening timing IVO, the gas blown out from the combustion chamber 5 to the exhaust port 11 is discharged. When the flow becomes choked, and when the choke state start crank angle CACOMP is on the retard side from the intake valve opening timing IVO, it is determined that the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 is not in the choke state ( 29 (see steps 108 to 110 in FIG. 29), it can be accurately determined whether or not the choke state is reached.

  According to the sixth embodiment of the present invention, when the pressure in the combustion chamber is not compressed in the exhaust stroke, the crank angle (for example, exhaust top dead center) when the gas flow around the exhaust valve becomes zero before the exhaust valve 16 is closed. And a straight line 1 (see y1 of step 131 in FIG. 33), an exhaust valve closing timing EVC and a predetermined crank angle θ2 set by the exhaust valve surrounding gas flow rate ((dm / dθ) ivo) at the intake valve opening timing IVO. A straight line 2 (see y2 of step 133 in FIG. 33) set by the gas flow around the exhaust valve ((dm / dθ) d) in FIG. 33 is calculated, and the amount of blowback gas from the exhaust port 11 into the combustion chamber 5 ( M25 and M26) are calculated using at least the straight line 1 and the straight line 2 (see steps 134 to 137 in FIG. 33), so that the blowback from the exhaust port 11 into the combustion chamber 5 is performed. When only a waveform is present, the amount of blown back gas (M25, M26) from the exhaust port 11 into the combustion chamber 5 can be accurately calculated.

  When the pressure in the combustion chamber is not compressed in the exhaust stroke, the crank angle θ0 when the gas flow rate around the exhaust valve becomes zero before the exhaust valve 16 is closed slightly deviates from the exhaust top dead center due to the difference in operating conditions (subtle However, according to the sixth embodiment of the present invention, the crank angle θ0 when the gas flow rate around the exhaust valve becomes zero before the exhaust valve 16 is closed depends on the engine load and the rotational speed. Therefore, even if the crank angle θ0 when the gas flow around the exhaust valve becomes zero before the exhaust valve 16 is closed may slightly deviate (move slightly) from the exhaust top dead center due to the difference in operating conditions, When the pressure in the combustion chamber is not compressed in the exhaust stroke, the waveform of the gas flow around the exhaust valve can be accurately approximated.

  When the pressure in the combustion chamber is not compressed in the exhaust stroke, the crank angle θ0 when the gas flow rate around the exhaust valve becomes zero before the exhaust valve 16 is closed exists near the exhaust top dead center in the entire operation region. According to the sixth embodiment of the present invention, the crank angle θ0 when the gas flow rate around the exhaust valve becomes zero before the exhaust valve 16 is closed is set to the exhaust top dead center, so the exhaust valve is closed before the exhaust valve is closed. The memory capacity can be reduced as compared with the case where the crank angle θ0 when the surrounding gas flow rate becomes zero is set according to the engine load and the rotational speed.

  According to the sixth embodiment of the present invention, when the pressure in the combustion chamber is compressed in the exhaust stroke, the gas flow around the exhaust valve ((dm / dθ) ivo) at the intake valve opening timing and the exhaust valve closing timing EVC Since the amount M23 of gas blown from the combustion chamber 5 to the exhaust port 11 is calculated using the intake valve closing timing IVO (see steps 125 and 126 in FIG. 32), the gas blown from the combustion chamber 5 to the exhaust port 11 is calculated. The amount M23 can be calculated with high accuracy.

  The combustion chamber pressure PIVO at the intake valve opening timing is greatly influenced by the exhaust valve opening area at the intake valve opening timing IVO. When the exhaust valve 16 is sufficiently open at the intake valve opening timing IVO (that is, when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is not choked), the pressure in the combustion chamber is as shown on the left in FIG. Pcyl becomes equal to the exhaust pressure Pex. Therefore, in the prior application apparatus, it is assumed that the combustion chamber pressure PIVO at the intake valve opening timing is equal to the exhaust pressure because the exhaust valve opening is sufficiently large.

  On the other hand, when the exhaust valve 16 is almost closed at the intake valve opening timing IVO (that is, when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is choked), combustion occurs as shown in FIG. The combustion chamber pressure Pcyl changes in accordance with the change in the indoor volume, and the deviation from the exhaust pressure Pex increases. Therefore, even when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in a choke state, the residual gas amount in the combustion chamber is estimated on the assumption that the combustion chamber pressure PIVO at the intake valve opening timing is equal to the exhaust pressure. Therefore, an error corresponding to the pressure difference from the exhaust pressure Pex of the pressure in the combustion chamber at the intake valve opening timing IVO occurs.

  Therefore, in the seventh embodiment of the present invention, a method for calculating the pressure in the combustion chamber at the intake valve opening timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in the choke state is used. This is different from the calculation method of the pressure in the combustion chamber at the intake valve opening timing IVO when the flow of the gas blown into the cylinder does not enter the choke state.

  Next, a method for calculating the pressure in the combustion chamber at the intake valve opening timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in the choke state will be described.

  Below, the pressure in the combustion chamber PIVO at the intake valve opening timing IVO calculated by the prior application device is the same as that at the intake valve opening timing IVO when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 does not enter the choke state. In order to treat it as the pressure in the combustion chamber and to distinguish it from PIVO of the prior application device, the pressure in the combustion chamber at the opening timing of the intake valve when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in the choked state ".

  When the gas equation of state is differentiated by the crank angle, the following equation is obtained.

dm / dθ = (∂m / ∂P) · dP / dθ + (∂m / ∂V) · dV / dθ
+ (∂m / ∂T) · dT / dθ + (∂m / ∂R) · dR / dθ
... (71)
Where m: In-cylinder gas amount [kg]
P: Combustion chamber pressure [kPa]
V: combustion chamber volume [m ^ 3]
T: Combustion chamber temperature [K]
R: exhaust gas constant [kJ / kg / K]
θ: Crank angle [degCA]
Further, the gas flow rate around the exhaust valve when choked by the exhaust valve 16 is expressed by the following equation from the orifice flow rate equation.

dm / d [theta] = _{[C D A T P / {6Ne} (RT) ^ (1/2)} ] · {κ ^ (1/2)}
・ [(2 / (κ + 1)) ^ {(κ + 1) / 2 (κ-1)}]
... (72)
Where C _D : Air resistance coefficient [−]
A _T : Opening area around the exhaust valve [m ^ 2]
Ne: Engine rotation speed [rpm]
κ: Specific heat ratio [−]
Equation (72) is basically the same as the equation (54B) described above in the sixth embodiment of the present invention. Since the gas flow rate around the exhaust valve in (71) exceeds the exhaust gas flow rate around the exhaust valve of (72), the choke state is started and the compression starts in the exhaust stroke. Therefore, the equations (71) and (72) The choke state start crank angle CACOMP can be calculated by solving the following equation with the crank angle θ equal to:

(∂m / ∂P) · dP / dθ + (∂m / ∂V) · dV / dθ
+ (∂m / ∂T) · dT / dθ + (∂m / ∂R) · dR / dθ
= _{[C D A T P / {6Ne} (RT) ^ (1/2)} ] · {κ ^ (1/2)}
・ [(2 / (κ + 1)) ^ {(κ + 1) / 2 (κ-1)}]
... (73)
Think further. Assuming that the change in temperature and gas constant is small near the crank angle where the choke starts, the right side of equation (71) is (∂m / ∂P) · dP / dθ and (∂m / ∂V) · dV / dθ. Therefore, equation (73) is rewritten as follows.

(∂m / ∂P) · dP / dθ + (∂m / ∂V) · dV / dθ
= _{[C D A T P / {6Ne} (RT) ^ (1/2)} ] · {κ ^ (1/2)}
・ [(2 / (κ + 1)) ^ {(κ + 1) / 2 (κ-1)}]
... (74)
Here, since m = ＰＶP = V / RT and ∂m / ∂V = P / RT from m = PV / RT which is the state equation of gas, substituting these into the left side of equation (74), The formula is obtained.

(V / RT) · dP / dθ + (P / RT) · dV / dθ
= _{[C D A T P / {6Ne} (RT) ^ (1/2)} ] · {κ ^ (1/2)}
・ [(2 / (κ + 1)) ^ {(κ + 1) / 2 (κ-1)}]
... (75)
When both sides of equation (75) are multiplied by RTdθ and both sides are divided by PV, the following equation is obtained.

dP / P = -dV / V
+ [{C _D A _T (RT) ^ (1/2)} / (6 NeV)] · {κ ^ (1/2)}
· [(2 / (κ + 1)) ^ {(κ + 1) / 2 (κ-1)}] · dθ
... (76)
When the equation (76) is integrated, the following equation is obtained.

lnP = lnP0 + lnV0−lnV
+ [{(RT) ^ (1/2)} / (6Ne)] · {κ ^ (1/2)}
・ [(2 / (κ + 1)) ^ {(κ + 1) / 2 (κ-1)}]
・ ∫ (C _D A _T / V) dθ
... (77)
However, P0: combustion chamber pressure at choke state start crank angle CACOMP
[KPa]
V0: Combustion chamber pressure at choke state start crank angle CACOMP
[M ^ 3]
Taking the index of the formula (77), the left side of the formula (77) becomes exp (lnP) = P, so the following formula is obtained.

P = exp (lnP0 + lnV0−lnV
+ [{(RT) ^ (1/2)} / (6Ne)] · {κ ^ (1/2)}
・ [(2 / (κ + 1)) ^ {(κ + 1) / 2 (κ-1)}]
・ ∫ (C _D A _T / V) dθ)
... (78)
Here, in order to coincide with the symbols used in the prior application device and the sixth embodiment of the present invention, P → PIVO, V → VIVO, R → REX, T → TEX, A → By replacing Aex2, the intake valve when the pressure in the combustion chamber at the opening timing of the intake valve when the waveform of the above (b) is reached, that is, the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in a choke state. The combustion chamber pressure PIVO ′ at the opening timing can be obtained by the following equation.

PIVO '= exp (lnP0 + lnV0-lnVIVO
+ [{(REX · TEX) ^ (1/2)} / (6Ne)] · {κ ^ (1/2)}
・ [(2 / (κ + 1)) ^ {(κ + 1) / 2 (κ-1)}]
・ ∫ (C _D Aex2 / V) dθ)
... (79)
However, P0: combustion chamber pressure at choke state start crank angle CACOMP
[KPa]
V0: Combustion chamber pressure at choke state start crank angle CACOMP
[M ^ 3]
VIVO: combustion chamber volume at opening timing of intake valve [m ^ 3]
REX: exhaust gas constant [kJ / kg / K]
TEX: Average exhaust temperature [K]
κ: Specific heat ratio [−]
Ne: Engine rotation speed [rpm]
C _D : Air resistance coefficient [−]
Aex2: Exhaust valve opening area [m ^ 2]
V: combustion chamber volume [m ^ 3]
FIG. 35 shows the correspondence between the value of equation (79) and the waveform of the pressure in the combustion chamber. That is, FIG. 35 shows the changes in the pressure history of the intake pressure Pint, the exhaust pressure Pex, the pressure in the combustion chamber Pcyl, and the opening areas of the intake and exhaust valves, and corresponds to FIG. As shown in FIG. 35, when the combustion chamber pressure Pcyl rises away from the exhaust pressure Pex at the choke state start crank angle CACOMP, and the intake valve 15 is opened at the subsequent intake valve opening timing IVO, the combustion chamber starts from that timing. The pressure Pcyl decreases toward the intake pressure Pint. The pressure in the combustion chamber at the choke state start crank angle CACOMP is P0, and the pressure in the combustion chamber at the intake valve opening timing IVO is PIVO ′.

The above equation (79) is expressed by the combustion chamber pressure P0 at the choke state start crank angle on the right side, the combustion chamber volume V0 at the choke state start crank angle, the combustion chamber volume VIVO at the intake valve opening timing, the exhaust gas constant REX, If the average exhaust temperature TEX, the specific heat ratio κ, and the integral value ∫ (C _D Aex2 / V) dθ are known, combustion at the intake valve opening timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked. This indicates that the indoor pressure PIVO ′ can be obtained. Here, the combustion chamber volume VIVO, the exhaust gas constant REX, the average exhaust gas temperature TEX, and the specific heat ratio κ at the intake valve opening timing have already been obtained by the prior application device. Therefore, there are only three remaining unknowns: the combustion chamber pressure P0 at the choke state start crank angle, the combustion chamber volume V0 at the choke state start crank angle, and the integral value ∫ (C _D Aex2 / V) dθ. Therefore, each of these three unknowns will be considered below.

  First, as shown in FIG. 35, the combustion chamber pressure P0 at the choke state start crank angle is a value when the combustion chamber pressure Pcyl leaves the exhaust pressure Pex. By using the calculation method of the combustion chamber pressure PIVO, the combustion chamber pressure P0 at the choke state start crank angle can be obtained. That is, in the prior application device, when the exhaust valve VTC mechanism 28 is not provided, the pressure in the combustion chamber and the average exhaust pressure at the intake valve opening timing at the actual charging efficiency from the intake valve opening timing IVO and the engine rotational speed Ne. Is calculated by adding the average exhaust pressure PEX to the combustion chamber pressure PIVO at the intake valve opening timing, and when the exhaust valve VTC mechanism 28 is provided, the exhaust temperature is the reference exhaust temperature. In this condition, instead of the intake valve opening timing IVO, a value obtained by shifting the IVO by the amount by which the exhaust valve opening timing and the exhaust valve closing timing are shifted to the advance side by the operation of the exhaust valve VTC mechanism 28 is obtained. By using this, the difference value PCTRM between the combustion chamber pressure at the intake valve opening timing and the average exhaust pressure at the actual charging efficiency is calculated, and the average exhaust By adding the force PEX calculates the combustion chamber pressure PIVO of the intake valve opening timing. Therefore, by using the choke state start crank angle CACOMP instead of the intake valve opening timing IVO of the prior application device, either the case where the exhaust valve VTC mechanism 28 is not provided or the case where the exhaust valve VTC mechanism 28 is provided is used. In addition, the combustion chamber pressure P0 at the choke state start crank angle CACOMP can be calculated.

  The prior application device describes a method of calculating the difference value PCTRM even when the exhaust valve VTC mechanism 28 is provided and the exhaust temperature is deviated to a higher temperature than the reference exhaust temperature. However, this case is excluded. It is not the purpose. In this case as well, it will be complicated to describe, so it is simply omitted.

Next, the combustion chamber volume V0 at the choke state starting crank angle is obtained by using the choke state starting crank angle CACOMP instead of the intake valve opening timing IVO in the method of calculating the combustion chamber volume VIVO at the intake valve opening timing. Can do. That is, in the prior application device, the combustion chamber volume VIVO at the intake valve opening timing is obtained from the intake valve opening timing IVO using the above equations (7) to (11), so that the intake valve opening timing IVO is substituted. The combustion chamber volume V0 at the choke state start crank angle can be similarly determined from the choke state start crank angle CACOMP. That is, from the choke state start crank angle CAcomp [degATDC], the displacement amount H ′ [m] from the TDC is
H '= ((CND + ST / 2) ^ 2- (CR off-PIS off ^ 2) ^ (1/2)
− (ST / 2 × cos (CACOMP + θoff) + (CND ^ 2-X ^ 2)
^ (1/2))
... (Supplement 22)
Where CND: connecting rod length [m],
CR off: Crank pin offset [m],
PIN off: Piston offset [m],
ST: Stroke [m],
θoff: angle [deg] from crank vertical position to TDC,
X: distance [m] from the large end of the connecting rod to the center of the piston pin,
Using the calculated displacement amount H ′ from the TDC,
V0 = π × D ^ 2 × H ′ / 4 + Vc (Supplement 23)
Where D: bore diameter [m],
Vc: gap volume [m ^ 3],
The combustion chamber volume V0 [m ^ 3] at the choke state start crank angle is calculated by the following equation. Here, the distance X of the right side of the (complement 22) equation, the angle θoff, and the gap area Vc of the (complement 23) equation are calculated by the above equations (9) to (11).

Next, for the integral value ∫ (C _D Aex2 / V) dθ, the air resistance coefficient C _D , the exhaust valve opening area Aex2, and the combustion chamber volume V are all functions of the crank angle θ, and the choke state start crank angle CACOMP It is known that it depends on the choke state start crank angle CACOMP and the intake valve opening timing IVO, since it is an integral value in the integration range from to the intake valve opening timing IVO. Accordingly, when the exhaust valve VTC mechanism 28 is not provided, the integral value ∫ (C _D Aex2 / V) dθ is calculated in advance on the desk in advance, and the choke state start crank angle CACOMP and the intake valve opening timing IVO Is stored as a parameter.

When the exhaust valve VTC mechanism 28 is provided, an exhaust VTC conversion angle at a certain interval is determined as a reference exhaust VTC conversion angle, and an integral value ∫ (C _D Aex2 //) is determined for each determined reference exhaust VTC conversion angle. V) A map is created by calculating the value of dθ. For example, FIG. 36 shows the contents of each map when the minimum value (0 deg CA), intermediate value (for example, 15 deg CA), and maximum value (for example, 30 deg CA) are used as the reference exhaust VTC conversion angle. If the current exhaust VTC conversion angle coincides with the reference exhaust VTC conversion angle, a map at the coincident reference exhaust VTC conversion angle is obtained by comparing the choke state start crank angle CACOMP and intake valve opening timing IVO at that time. , The value of the integral value ∫ (C _D Aex2 / V) dθ is calculated. When the current exhaust VTC conversion angle does not coincide with the reference exhaust VTC conversion angle, two reference exhaust VTC conversion angles closest to the current exhaust VTC conversion angle are selected, and a map with the selected reference exhaust VTC conversion angle is displayed. by reference, the integral value ∫ (C _D Aex2 / V) the values of dθ is calculated respectively, and the two integration values by interpolation calculation, the integral value for the current of the exhaust VTC conversion angle ∫ (C _D Aex2 / V ) Calculate the value of dθ. Since the interpolation calculation method in this case is well known, its description is omitted.

  This control performed by the engine controller 31 will be described with reference to the flowcharts of FIGS.

  37 and 38 are for calculating the combustion chamber pressure PIVO ′ at the intake valve opening timing according to the seventh embodiment of the present invention. For example, every 10 ms). That is, FIG. 29 is also a seventh embodiment of the present invention.

  In the seventh embodiment of the present invention, the case where the exhaust temperature is at the reference exhaust temperature will be described for simplicity. However, it is not intended to exclude the case where the exhaust temperature deviates to a higher temperature side than the reference exhaust temperature, but can be applied to the case where the exhaust temperature deviates to a higher temperature side than the reference exhaust temperature.

  In the prior application, the exhaust valve opening timing EVO and the exhaust valve closing timing EVC are in the most retarded position when the exhaust valve VTC mechanism 28 is not in operation, and when the exhaust valve VTC mechanism 28 is in operation, the exhaust valve opening timing EVO is open. Although the case where the timing EVO and the exhaust valve closing timing EVC move to the advance side has been described, in the seventh embodiment of the present invention, as in the sixth embodiment of the present invention, the exhaust valve VTC mechanism 28 is not operated. In this state, the exhaust valve opening timing EVO and the exhaust valve closing timing EVC are at the most advanced angle position, and when the exhaust valve VTC mechanism 28 is activated, the exhaust valve opening timing EVO and the exhaust valve closing timing EVC are retarded by the exhaust VTC conversion angle. The case of moving to the side will be described.

  In step 141, the average exhaust pressure PEX [kPa] (calculated from the above equation (20)), the exhaust gas constant REX [kJ / mol / K] (calculated from the above equation (6)), the average exhaust temperature TEX [K ] (Calculated from the above equation (23)), exhaust specific heat ratio κ [−] (calculated from the above equation (19) or from FIG. 28), actual charging efficiency ITAC [%] (above (complement 8) equation) ), The intake valve opening timing IVO [degCA], the combustion chamber volume VIVO [m ^ 3] at the intake valve opening timing, the engine rotational speed Ne [rpm], and the exhaust VTC conversion angle [degCA] are read. The values of the exhaust VTC conversion angle, the intake valve opening timing IVO, and the combustion chamber volume VIVO at the intake valve opening timing are known from the command values given to the intake valve VTC mechanism 27 and the exhaust valve VTC mechanism 28.

  In step 142, it is checked whether or not the waveform determination flag (set according to FIG. 29) = 0. When the waveform determination flag = 0, since the waveform determination has not been made yet, the current process is terminated as it is.

  When the waveform determination flag is not 0, the process proceeds to step 143 to check whether the waveform determination flag is 1, 2, or 3. When the waveform determination flag is 1 or 3, when the waveform (ii) is obtained or when the waveform (ha) is obtained, that is, when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is not choked. When it is determined that there is a waveform, the process proceeds to steps 144 to 149. On the other hand, when the waveform determination flag = 2, the waveform of (b) is obtained, that is, the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is choked. It is determined that it is time to proceed to step 150 and after in FIG.

  Steps 141 to 149 are portions for calculating the pressure in the combustion chamber at the intake valve opening timing when the flow of the gas blown from the combustion chamber 5 to the exhaust port 11 does not enter the choke state, and the gas blown from the combustion chamber 5 to the exhaust port 11 The calculation method of the pressure in the combustion chamber at the intake valve opening timing when the flow of the engine does not enter the choke state is the same as that of the prior application device.

  First, in step 144, the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is minimum is calculated from the crank angle obtained by subtracting the exhaust VTC conversion angle from the intake valve opening timing IVO and the engine rotational speed Ne. By referring to the map (see FIG. 6), a difference value Pmin between the pressure in the combustion chamber and the average exhaust pressure at the intake valve opening timing when the charging efficiency is minimum is obtained. In step 145, the map of the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is maximum, from the crank angle obtained by subtracting the exhaust VTC conversion angle from the intake valve opening timing IVO and the engine rotational speed Ne. By referring to (see FIG. 6), a difference value Pmax between the pressure in the combustion chamber and the average exhaust pressure at the intake valve opening timing when the charging efficiency is maximum is obtained.

  Here, the crank angle obtained by subtracting the exhaust VTC conversion angle from the intake valve opening timing IVO is used for the following reason. That is, in the prior application device, the exhaust valve opening timing EVO and the exhaust valve closing timing EVC are at the most retarded position when the exhaust valve VTC mechanism 28 is not in operation, and when the exhaust valve VTC mechanism 28 is in operation, the exhaust valve opening timing EVO Since the timing EVO and the exhaust valve closing timing EVC are moved to the advance side, when the exhaust valve VTC mechanism 28 is operated, instead of the intake valve opening timing IVO, the amount of movement to the advance side is set to IVO. The added value is used (see FIG. 16). However, in the seventh embodiment of the present invention, the exhaust valve opening timing EVO and the exhaust valve closing timing EVC are at the most advanced position when the exhaust valve VTC mechanism 28 is in an inoperative state, and the exhaust valve VTC mechanism 28 is in an operating state. Then, since the exhaust valve opening timing EVO and the exhaust valve closing timing EVC are moved to the retard side by the exhaust VTC conversion angle, when the exhaust valve VTC mechanism 28 is operated, instead of the intake valve opening timing IVO, This is because it is necessary to use a value obtained by subtracting the exhaust VTC conversion angle from IVO.

In steps 146 and 147, from the actual filling efficiency ITAC [%], the filling efficiency minimum value ITACMN [%], and the filling efficiency maximum value ITACMX [%],
a = ITAC-ITACMN (80)
b = ITACMX-ITAC (81)
The a and b [%] are calculated by the following equation, and the pressure in the combustion chamber and the average exhaust pressure at the intake valve opening timing when the actual charging efficiency is obtained in step 148 using these a and b and the above-described difference values Pmax and Pmin. The difference value PCTRM [kPa] from
PCTRM = Pmin + (Pmax−Pmin) × a / (a + b)
... (82)
In step 149 using the difference value PCTRM and the average exhaust pressure PEX,
PIVO = PEX + PCTRM (83)
The combustion chamber pressure PIVO [kPa] at the intake valve opening timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 does not enter the choke state is calculated by the following equation.

  Here, the above formulas (80), (81), (82), and (83) are the above (complement 4), (complement 5), (13), and (12) of the prior application device, respectively. ) Is the same formula.

  Next, step 150 and subsequent steps will be described. In step 150, the choke state start crank angle CACOMP [degCA] (calculated from FIG. 29) is read. As in step 107 of FIG. 29, the choke state start crank angle CACOMP may be calculated by referring to a map having the contents shown in FIG. 34 from the engine speed and the exhaust VTC conversion angle.

  Steps 151 to 159 are parts for calculating the combustion chamber pressure PIVO 'at the intake valve opening timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in the choke state. Among these, the operation itself in steps 151-156 is the same as the operation in steps 144-149 of FIG. That is, in steps 144 to 149 in FIG. 37, a difference value PCTRM at the intake valve opening timing IVO is obtained, and a value obtained by adding the difference value PCTRM and the average exhaust pressure PEX is used as the combustion chamber pressure PIVO at the intake valve opening timing. In Steps 151 to 156 of FIG. 38, a difference value PCTRM ′ at the choke state start crank angle CACOMP is obtained, and a value obtained by adding the difference value PCTRM ′ and the average exhaust pressure PEX is obtained at the choke state start crank angle. Calculated as the combustion chamber pressure P0. Note that “′” is added to the difference values Pmin, Pmax, and PCTRM in order to distinguish from the case where the flow of gas blown from the combustion chamber 5 to the exhaust port 11 does not enter the choke state.

  More specifically, in step 151, the combustion chamber pressure and the average exhaust pressure at each crank angle at the minimum charging efficiency are calculated from the crank angle obtained by subtracting the exhaust VTC conversion angle from the choke state start crank angle CACOMP and the engine rotational speed Ne. By referring to the difference value map (see FIG. 6), the difference value Pmin ′ between the combustion chamber pressure and the average exhaust pressure at the intake valve opening timing when the charging efficiency is minimum is obtained. In step 152, the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle at the maximum charging efficiency is calculated from the crank angle obtained by subtracting the exhaust VTC conversion angle from the choke state start crank angle CACOMP and the engine speed Ne. By referring to the map (see FIG. 6), a difference value Pmax ′ between the pressure in the combustion chamber and the average exhaust pressure at the intake valve opening timing when the charging efficiency is maximum is obtained.

In steps 153 and 154, from the actual filling efficiency ITAC [%], the filling efficiency minimum value ITACMN [%], and the filling efficiency maximum value ITACMX [%],
a = ITAC-ITACMN (84)
b = ITACMX-ITAC (85)
The a and b [%] are calculated by the following equation, and the pressure in the combustion chamber at the choke state start crank angle at the actual charging efficiency is determined in step 155 using the difference values Pmax ′ and Pmin ′. The difference value PCTRM ′ [kPa] from the average exhaust pressure is
PCTRM ′ = Pmin ′ + (Pmax′−Pmin ′) × a / (a + b)
... (86)
In step 156, using this difference value PCTRM 'and the average exhaust pressure PEX,
P0 = PEX + PCTRM '(87)
The combustion chamber pressure P0 [kPa] at the choke state start crank angle is calculated by the following equation.

  In step 157, the combustion chamber volume V0 [m ^ 3] at the choke state start crank angle is calculated from the choke state start crank angle CACOMP using the above (complement 22) and (complement 23) equations.

In step 158, the value of the integral value _D (C _D Aex2 / V) dθ is calculated by referring to a map having the contents shown in FIG. 36 from the intake valve opening timing IVO and the exhaust VTC conversion angle (with interpolation calculation).

In step 159, the combustion chamber pressure P0 at the choke state start crank angle, the combustion chamber volume V0 at the choke state start crank angle, and the integral value ∫ (C _D Aex2 / V) dθ described above are used. The combustion chamber pressure PIVO ′ at the opening timing of the intake valve when the flow of the gas blown from the combustion chamber 5 to the exhaust port 11 is in the choked state is calculated by the equation (79).

  39 to 41 are for calculating the residual gas amount in the combustion chamber after the end of the overlap between the exhaust valve opening period and the intake valve opening period of the seventh embodiment of the present invention (more precisely, immediately after the end of the overlap). 37 and 38 are executed at regular time intervals (for example, every 10 ms). The same step numbers are assigned to the same parts as those in FIGS. 31 to 33 of the sixth embodiment of the present invention.

39 to 41, the sixth embodiment of the present invention is different from the sixth embodiment of the present invention in that PIVO is present in steps 124 and 125 of FIG. 32 in the sixth embodiment of the present invention. Forty steps 161 and 162 are replaced with PIVO '. That is, in the seventh embodiment of the present invention, when the waveform determination flag = 2 in FIG. 40, the routine proceeds to step 161 where the intake valve is opened when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked. The combustion chamber pressure PIVO ′ at the time is read, and the intake valve is opened at step 162 using the combustion chamber pressure PIVO ′ at the opening timing of the intake valve when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked. The gas flow around the exhaust valve at the time (dm / dθ) ivo [kg / degCA],
(Dm / dθ) ivo = VIVO × Cpa / 6 / Ne / REX / TIVO
+ PIVO '/ REX / TIVO × (Cva × IVO + Cvb)
... (88)
However, Cpa: time differential value of the pressure in the combustion chamber, already calculated by (complement 10)
Cva: slope of a straight line when the horizontal axis represents the crank angle and the vertical axis represents the rate of change in the combustion chamber volume near the intake top dead center [m ^ 3 / deg ^ 2]
Cvb: intercept of the straight line when the crank angle is plotted on the horizontal axis and the volumetric change rate in the combustion chamber is plotted on the vertical axis near the intake top dead center [m ^ 3]
It is calculated by the following formula.

In step 126, the gas flow rate around the exhaust valve at the intake valve opening timing calculated using the combustion chamber pressure PIVO 'at the intake valve opening timing when the flow of the gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked. Using (dm / dθ) ivo,
M23 = | (dm / dθ) ivo | × (EVC-IVO) / 2 (89)
However, (dm / dθ) ivo: Gas flow around the exhaust valve when the intake valve is open
[Kg / degCA]
EVC: Exhaust valve closing timing [degCA]
IVO: intake valve opening timing [degCA]
The amount of blown-out gas M23 [kg] during the overlap between the intake valve open period and the exhaust valve open period is calculated by the following equation. In step 127, the amount of blown-out gas M23 during overlap between the intake valve open period and the exhaust valve open period is calculated. Is an overlap between the exhaust valve opening period and the intake valve opening period when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is choked. The amount of residual gas in the combustion chamber after the completion, that is, the combustion chamber after the overlap between the exhaust valve opening period and the intake valve opening period when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is choked by the following equation Residual gas amount [kg] is calculated.

Residual gas amount in combustion chamber = MR1 + M23 (90)
Here, the function and effect of the seventh embodiment of the present invention will be described.

  The combustion chamber pressure PIVO at the intake valve opening timing is greatly influenced by the exhaust valve opening area at the intake valve opening timing IVO. When the exhaust valve 16 is sufficiently open at the intake valve opening timing IVO (that is, when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is not choked), the pressure in the combustion chamber is as shown on the left in FIG. Pcyl becomes equal to the exhaust pressure Pex. Therefore, in the prior application device, it was assumed that the pressure in the combustion chamber PIVO when the intake valve was opened was equal to the exhaust pressure because the exhaust valve opening was sufficiently large.

  On the other hand, when the exhaust valve 16 is almost closed at the intake valve opening timing IVO (that is, when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is choked), it is shown in FIG. Thus, the combustion chamber pressure Pcyl changes with the change in the combustion chamber volume (increases away from the exhaust pressure Pex), and the deviation from the exhaust pressure Pex increases. Therefore, even when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in a choke state, it is assumed that the combustion chamber pressure PIVO at the intake valve opening timing is equal to the exhaust pressure, and the exhaust valve opening period and the intake valve If the residual gas amount in the combustion chamber after the overlap in the open period is estimated, an error corresponding to the pressure difference from the exhaust pressure Pex of the combustion chamber pressure at the intake valve opening timing IVO occurs.

  On the other hand, according to the seventh embodiment of the present invention (the invention described in claims 1 and 9), based on the amount of change in the combustion chamber volume accompanying the movement of the piston and the amount of gas that can pass through the exhaust valve. It is determined whether or not the pressure in the combustion chamber is compressed in the exhaust stroke (see steps 108 to 110 in FIG. 29), and when the pressure in the combustion chamber is compressed in the exhaust stroke based on this determination result, the volume in the combustion chamber is determined. The crank angle at which the amount of change is equal to the amount of gas that can pass through the exhaust valve is calculated as the crank angle CACOMP at which the gas flow blown from the combustion chamber 5 to the exhaust port 11 starts the choke state (step 143 in FIG. 37, FIG. 38), the flow of the gas blown out from the combustion chamber 5 to the exhaust port 11 is changed to the choke state based on the calculated choke state start crank angle CACOMP. The combustion chamber pressure PIVO ′ at the opening timing of the intake valve is calculated (see step 159 in FIG. 38), and the intake valve when the flow of gas blown from the calculated combustion chamber 5 to the exhaust port 11 is in the choke state is calculated. Based on the combustion chamber pressure PIVO ′ at the opening timing, the amount M23 of blown gas from the combustion chamber 5 to the exhaust port 11 is calculated (see step 111 in FIG. 39 and steps 123 and 126 in FIG. 40), and the intake valve opening timing is calculated. The amount of residual gas in the combustion chamber after the overlap between the exhaust valve opening period and the intake valve opening period is estimated from the combustion chamber gas amount MR1 and the blowout gas amount M23 (see step 127 in FIG. 40). The exhaust valve open period and the intake valve open period also when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked. The combustion chamber residual gas amount after Barappu completion can be accurately estimated.

  When the exhaust VTC conversion angle (command value given to the exhaust valve opening / closing timing variable mechanism) given to the exhaust valve VTC mechanism 28 changes, for example, the exhaust valve VTC mechanism 28 is switched from the non-operating state to the operating state, and the exhaust valve closing timing is changed. If the EVC changes to the retard side, the exhaust valve opening area at the intake valve opening timing IVO changes and the choke state start crank angle CACOMP changes to the retard side (see FIG. 34). According to the seventh embodiment (the invention described in claim 2), the choke state start crank angle CACOMP is calculated based on the engine rotational speed Ne and the exhaust VTC conversion angle (step 143 in FIG. 37, step 38 in FIG. 38). Even if the exhaust VTC conversion angle changes, the choke state start crank angle CACOMP can be calculated accurately.

  If the calculation of the choke state start crank angle CACOMP is theoretically performed, the above equation (73) is handled and a complicated calculation is required. In the seventh embodiment of the present invention (the invention according to claim 2), the value of the choke state start crank angle CACOMP itself is approximated to be substantially determined by the engine speed Ne and the exhaust valve opening area, and the engine speed Ne. Since the choke state start crank angle CACOMP is calculated using the exhaust VTC conversion angle that can know the exhaust valve opening area as a parameter (see FIG. 34), it is possible to avoid a complicated calculation that handles the above equation (73). ing.

  The pressure in the combustion chamber PIVO 'at the opening timing of the intake valve when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in the choked state is affected by the exhaust valve opening area. For example, when the exhaust valve VTC mechanism 28 is activated, the exhaust valve closing timing EVC changes in accordance with the exhaust VTC conversion angle, and the intake valve when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked. The combustion chamber pressure PIVO ′ at the opening timing changes from the value when the exhaust valve VTC mechanism 28 is in an inoperative state. Accordingly, the combustion chamber pressure PIVO ′ at the opening timing of the intake valve when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in a choked state when the exhaust valve VTC mechanism 28 is in an inoperative state can be accurately calculated. In addition, a map (see FIG. 6) of a difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is minimum, and a difference between the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is maximum. When matching the value map (see FIG. 6), when the exhaust valve VTC mechanism 28 is operated, if the same map is used without considering the exhaust VTC conversion angle, the operation of the exhaust valve VTC mechanism 28 is performed. Sometimes, an error corresponding to the exhaust VTC conversion angle causes combustion at the intake valve opening timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked. This occurs in the calculation of the internal pressure PIVO '. According to the seventh embodiment of the present invention (the invention described in claim 3), when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in a choked state. Since the combustion chamber pressure PIVO ′ at the intake valve opening timing is also calculated based on the exhaust VTC conversion angle (see steps 151 to 156 and 159 in FIG. 38), the combustion is performed even when the exhaust valve VTC mechanism 28 is operated. The combustion chamber pressure PIVO ′ at the opening timing of the intake valve when the flow of gas blown out from the chamber 5 to the exhaust port 11 becomes choked can be calculated with high accuracy.

According to the seventh embodiment of the present invention (the invention described in claim 4), the pressure in the combustion chamber is set to the exhaust stroke based on the change in the volume of the combustion chamber accompanying the movement of the piston 6 and the amount of gas that can pass through the exhaust valve. The determination means for determining whether or not the engine is compressed at the exhaust valve opening area Aex2 (exhaust valve opening / closing timing) in a predetermined crank angle range including the exhaust top dead center and the operating state of the engine (movement of the piston 6). Combustion chamber 5 based on the volume change dV / dθ of the combustion chamber near the exhaust top dead center, the engine speed Ne, the exhaust gas constant REX, the average exhaust temperature TEX, the specific heat ratio κ, and the air resistance coefficient C _D ). It is a judging means (see Steps 107, 108 and FIG. 34 in FIG. 29) for judging whether or not the flow of gas blown out from the inside to the exhaust port 11 is in a choke state. When it is determined that the pressure in the combustion chamber is compressed in the exhaust stroke when the flow of gas to be discharged is in the choke state (see steps 108 and 109 in FIG. 29), the pressure in the combustion chamber is compressed in the exhaust stroke. It is possible to accurately determine whether or not.

  In the sixth and seventh embodiments of the present invention, on the premise that there is an overlap between the intake valve open period and the exhaust valve open period, the exhaust port 11 from the combustion chamber 5 in the exhaust stroke in which the piston 6 ascends. As described above, there is a phenomenon in which the flow of the gas blown out into the choke state and the combustion chamber pressure Pcyl increases away from the exhaust pressure Pex, but as shown in FIG. 42, the intake valve open period and the exhaust valve open period Even when there is no overlap, it has also been found that there is a phenomenon in which the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 in the exhaust stroke becomes choked and the pressure Pcyl in the combustion chamber rises away from the exhaust pressure Pex. Yes.

  In FIG. 35, the combustion chamber pressure Pcyl rises away from the exhaust pressure Pex from the choke state start crank angle CACOMP, and the intake valve 15 is opened at the intake valve opening timing IVO in the middle of the increase. While the indoor pressure Pcyl suddenly decreases toward the intake pressure Pint, in FIG. 42, the intake valve opening timing IVO comes to a crank angle position delayed from the exhaust valve closing timing EVC, so the combustion chamber pressure Pcyl is There is a difference that after reaching the peak, it slowly decreases toward the intake pressure Pint.

  Here, in the prior application device, assuming that the combustion chamber pressure PIVO at the intake valve opening timing is equal to the exhaust pressure, the combustion chamber gas amount MR1 at the intake valve opening timing is expressed by the above equation (1), which is a state state equation. When there is no overlap between the intake valve opening period and the exhaust valve opening period, the combustion chamber gas amount MR1 at the intake valve opening timing is directly used as the combustion chamber residual gas amount. That is, in FIG. 19, when there is no overlap between the intake valve open period and the exhaust valve open period, M2 = 0, and MR1 is the amount of residual gas in the combustion chamber when there is no overlap between the intake valve open period and the exhaust valve open period. Become.

  However, even if there is no overlap between the intake valve open period and the exhaust valve open period as shown in FIG. 42, the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 in the exhaust stroke becomes a choke state, and the pressure in the combustion chamber Even when a phenomenon in which Pcyl increases away from the exhaust pressure Pex occurs, the combustion chamber gas amount MR1 at the intake valve opening timing is calculated on the assumption that the combustion chamber pressure PIVO at the intake valve opening timing is equal to the exhaust pressure. In (estimating the residual gas amount in the combustion chamber), an error corresponding to the pressure difference from the exhaust pressure Pex of the combustion chamber pressure Pcyl occurs.

  Therefore, in the eighth embodiment of the present invention, the combustion chamber pressure at the exhaust valve closing timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is choked is calculated. The amount of gas in the combustion chamber at the closing timing of the exhaust valve is calculated based on the pressure of the combustion chamber at the closing timing of the exhaust valve when the flow of gas blown into the choke state, and the amount of gas in the combustion chamber at the closing timing of the exhaust valve is calculated. The residual gas amount in the combustion chamber when there is no overlap between the intake valve open period and the exhaust valve open period is used as it is.

  In the following, in order to distinguish from the combustion chamber pressure PEVC at the exhaust valve closing timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 does not become choked (see the above (Supplement 10) formula), The pressure in the combustion chamber at the closing timing of the exhaust valve when the flow of the gas blown out to the exhaust port 11 is in the choke state is expressed as “PEVC ′”. Further, the amount of gas in the combustion chamber when the exhaust valve is closed is denoted by “MR1 ′”.

  First, the combustion chamber pressure PEVC ′ at the exhaust valve closing timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in the choked state is the same as that of the gas blown from the combustion chamber 5 to the exhaust port 11. It is calculated by the following equation using the above equation (79), which is a calculation equation of the combustion chamber pressure PIVO ′ at the exhaust valve closing timing.

PEVC ′ = exp (lnP0 + lnV0−lnVEVC
+ [{(REX · TEX) ^ (1/2)} / (6Ne)] · {κ ^ (1/2)}
・ [(2 / (κ + 1)) ^ {(κ + 1) / 2 (κ-1)}]
・ ∫ (C _D Aex2 / V) dθ)
... (91)
However, P0: combustion chamber pressure at choke state start crank angle CACOMP
[KPa]
V0: Combustion chamber pressure at choke state start crank angle CACOMP
[M ^ 3]
VEVC: combustion chamber volume at exhaust valve closing timing [m ^ 3]
REX: exhaust gas constant [kJ / kg / K]
TEX: Average exhaust temperature [K]
κ: Specific heat ratio [−]
Ne: Engine rotation speed [rpm]
C _D : Air resistance coefficient [−]
Aex2: Exhaust valve opening area [m ^ 2]
V: combustion chamber volume [m ^ 3]
The difference between the equation (91) and the equation (79) is that the combustion chamber volume VEVC at the exhaust valve closing timing is used instead of the combustion chamber volume VIVO at the intake valve opening timing, and the integral value. ∫ (C _D Aex2 / V) dθ is an integral value in the range from the choke state start crank angle CACOMP to the intake valve opening timing IVO in the equation (79), whereas ∫ (C _{D in the} equation (91) Aex2 / V) dθ is only an integral value having an integration range from the choke state start crank angle CACOMP to the exhaust valve closing timing EVC. However, the calculation method of the combustion chamber volume VEVC and the integral value ∫ (C _D Aex2 / V) dθ at the exhaust valve closing timing in the equation (91) is the same as the combustion chamber volume at the intake valve opening timing in the above equation (79). This is the same as the method of calculating VIVO and integral value ∫ (C _D Aex2 / V) dθ.

  Then, instead of the combustion chamber gas amount MR1 at the intake valve opening timing in the prior application device, the combustion chamber gas amount MR1 ′ at the exhaust valve closing timing is calculated by the following state equation using the above equation (1). The combustion chamber gas amount MR1 ′ at the exhaust valve closing timing is used as the residual gas amount in the combustion chamber when there is no overlap between the intake valve open period and the exhaust valve open period.

MR1 ′ = PEVC ′ · VEVC / (REX · TEVC) (92)
However, PEVC ': pressure in the combustion chamber at the exhaust valve closing timing EVC when the flow of gas blown from the combustion chamber to the exhaust port becomes choked
[KPa],
VEVC: combustion chamber volume at exhaust valve closing timing EVC when the flow of gas blown from the combustion chamber to the exhaust port becomes choked [m ^ 3],
TEVC: Combustion chamber temperature [K] at the exhaust valve closing timing EVC when the flow of gas blown out from the combustion chamber to the exhaust port becomes choked.
REX: exhaust gas constant [kJ / kg / K],
The combustion chamber temperature TEVC at the exhaust valve closing timing when the flow of gas blown from the combustion chamber 5 on the right side of the equation (92) into the exhaust port 11 is choked is calculated by the following equation using the above equation (22). do it.

TEVC = TEX · (PEVC ′ / PEX) ^ ((κ−1) / κ)
... (93)
PEVC ': Combustion chamber pressure when the exhaust valve closes when the gas flow from the combustion chamber to the exhaust port becomes choked
[KPa],
PEX: Average exhaust pressure [kPa], calculated with equation (20)
κ: specific heat ratio of exhaust gas, calculated by equation (19) This control performed by the engine controller 31 will be described with reference to the flowcharts of FIGS.

  FIG. 43 is for calculating the pressure in the combustion chamber PEVC ′ at the exhaust valve closing timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 in the eighth embodiment of the present invention becomes choked. Calculation is performed every time (for example, every 10 ms).

  However, for the sake of simplicity in the eighth embodiment of the present invention, it is assumed that the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 is choked when there is no overlap between the intake valve open period and the exhaust valve open period. And It is determined whether or not there is no overlap between the intake valve open period and the exhaust valve open period from the command values given to the intake valve VTC mechanism 27 and the exhaust valve VTC mechanism 28, and the intake valve open period and the exhaust valve When there is no overlap in the valve opening period, it is determined whether or not the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is choked, and the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is choked. The combustion chamber pressure PEVC ′ at the closing timing of the exhaust valve when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in the choked state may be calculated only when it is determined that Here, the determination as to whether or not the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in a choked state may be as follows. That is, as shown in FIG. 42, since the choke state is reached before the exhaust valve closing timing EVC, the choke state start crank angle CACOMP is compared with the exhaust valve closing timing EVC, and the choke state start crank angle CACOMP is determined as the exhaust valve closing timing EVC. When the flow of the gas blown out to the exhaust port 11 becomes the choke state when it is the same as the EVC or at the advance side of the exhaust valve closing timing EVC, the choke state start crank angle CACOMP is retarded from the exhaust valve closing timing EVC In this case, it may be determined that the flow of the gas blown out to the exhaust port 11 is not in the choked state.

  The exhaust temperature and the configuration of the exhaust valve VTC mechanism 28 are the same as those of the seventh embodiment of the present invention. That is, it is assumed that the exhaust temperature is at the reference exhaust temperature. The exhaust valve opening timing EVO and the exhaust valve closing timing EVC are at the most advanced position when the exhaust valve VTC mechanism 28 is not in operation, and when the exhaust valve VTC mechanism 28 is in operation, the exhaust valve opening timing EVO and the exhaust valve It is assumed that the closing timing EVC moves to the retard side by the exhaust VTC conversion angle.

  In step 171, the average exhaust pressure PEX [kPa] (calculated from the above equation (20)), the exhaust gas constant REX [kJ / mol / K] (calculated from the above equation (6)), the average exhaust temperature TEX [K ] (Calculated from the above equation (23)), exhaust specific heat ratio κ [−] (calculated from the above equation (19) or from FIG. 28), actual charging efficiency ITAC [%] (above (complement 8) equation) The exhaust valve closing timing EVC [degCA], the combustion chamber volume VEVC [m ^ 3], the engine rotational speed Ne [rpm], and the exhaust VTC conversion angle [degCA] at the exhaust valve closing timing are read. The values of the exhaust VTC conversion angle, the exhaust valve closing timing EVC, and the combustion chamber volume VEVC at the exhaust valve closing timing are known from the command values given to the intake valve VTC mechanism 27 and the exhaust valve VTC mechanism 28.

  In step 172, the choke state start crank angle CACOMP [degCA] is calculated by referring to the map having the contents shown in FIG. 34 from the engine speed Ne and the exhaust VTC conversion angle.

  The operations in steps 173 to 178 are the same as the operations in steps 144 to 149 in FIG. That is, in steps 144 to 149 in FIG. 37, a difference value PCTRM at the intake valve opening timing IVO is obtained, and a value obtained by adding the difference value PCTRM and the average exhaust pressure PEX is used as the combustion chamber pressure PIVO at the intake valve opening timing. In Steps 173 to 178 in FIG. 43, a difference value PCTRM ″ at the choke state start crank angle CACOMP is obtained, and a value obtained by adding the difference value PCTRM ″ and the average exhaust pressure PEX is obtained at the choke state start crank angle. Calculated as the combustion chamber pressure P0. In order to distinguish from the case where the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is not choked, “” is added to the difference values Pmin, Pmax, and PCTRM.

  More specifically, in step 173, from the crank angle obtained by subtracting the exhaust VTC conversion angle from the choke state start crank angle CACOMP and the engine rotational speed Ne, the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is minimum are calculated. By referring to the difference value map (see FIG. 6), a difference value Pmin "between the pressure in the combustion chamber and the average exhaust pressure at the intake valve opening timing when the charging efficiency is the minimum is obtained. Refer to the map (see Fig. 6) of the difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is maximum, from the crank angle obtained by subtracting the exhaust VTC conversion angle from the crank angle CACOMP and the engine speed Ne. By doing so, the difference value Pmax between the pressure in the combustion chamber and the average exhaust pressure when the intake valve is opened at the maximum charging efficiency Mel.

In steps 175 and 176, from the actual filling efficiency ITAC [%], the filling efficiency minimum value ITACMN [%], and the filling efficiency maximum value ITACMX [%],
a = ITAC-ITACMN (94)
b = ITACMX-ITAC (95)
A, b [%] is calculated by the following equation, and the pressure in the combustion chamber at the choke state start crank angle at the actual charging efficiency is determined in step 177 using the difference values Pmax ″ and Pmin ″. The difference value PCTRM "[kPa] from the average exhaust pressure is
PCTRM ″ = Pmin ″ + (Pmax ″ −Pmin ″) × a / (a + b)
... (96)
In step 178, using this difference value PCTRM "and the average exhaust pressure PEX,
P0 = PEX + PCTR ”” (97)
The combustion chamber pressure P0 [kPa] at the choke state start crank angle is calculated by the following equation.

  In step 179, the combustion chamber volume V0 [m ^ 3] at the choke state start crank angle is calculated from the choke state start crank angle CACOMP using the above (complement 22) and (complement 23) equations.

In step 180, the value of the integral value ∫ (C _D Aex2 / V) dθ is calculated by referring to a map having the contents shown in FIG. 45 from the exhaust valve closing timing EVC and the exhaust VTC conversion angle (with interpolation calculation). As shown in FIG. 45, the characteristic of the integral value ∫ (C _D Aex2 / V) dθ is the same as that of FIG.

In step 181, the combustion chamber pressure P0 at the choke state start crank angle, the combustion chamber volume V0 at the choke state start crank angle, and the integral value ∫ (C _D Aex2 / V) dθ are used as described above. The combustion chamber pressure PEVC ′ at the exhaust valve closing timing when the flow of the gas blown from the combustion chamber 5 to the exhaust port 11 is in the choked state is calculated by the equation (91).

  FIG. 44 is for calculating the residual gas amount in the combustion chamber when there is no overlap between the intake valve open period and the exhaust valve open period according to the eighth embodiment of the present invention. Every 10 ms).

  In step 191, similarly to step 171 in FIG. 43, the exhaust gas constant REX [kJ / mol / K] (calculated by the above equation (6)) and the average exhaust temperature TEX [K] (calculated by the above equation (23)). Exhaust) specific heat ratio κ [−] (calculated from the above equation (19) or from FIG. 28), the combustion chamber volume VEVC [m ^ 3] when the exhaust valve is closed, and the combustion chamber 5 to the exhaust port 11 The pressure in the combustion chamber PEVC ′ [kPa] (calculated from FIG. 43) at the exhaust valve closing timing when the flow of gas to be blown is in the choked state is read.

  In step 192, the average exhaust temperature TEX, the combustion chamber pressure PEVC 'at the exhaust valve closing timing when the flow of the gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked, the exhaust gas constant REX, and the specific heat ratio κ of the exhaust are determined. The combustion chamber temperature TEVC [K] at the exhaust valve closing timing when the flow of the gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked is calculated by the above equation (92). Combustion chamber temperature TEVC at the valve closing timing, combustion chamber pressure PEVC 'at the exhaust valve closing timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked, and the combustion chamber volume at the exhaust valve closing timing Using the VEVC and the exhaust gas constant REX, the combustion chamber gas amount MR1 ′ [kg] at the exhaust valve closing timing is calculated by the above equation (93). And, a combustion chamber residual gas quantity when there is no overlap as the intake valve open period and an exhaust valve open period of the combustion chamber gas amount MR1 'at the exhaust valve closing timing in step 194.

  Here, the function and effect of the eighth embodiment of the present invention will be described.

  In the prior application device, assuming that the combustion chamber pressure PIVO at the intake valve opening timing is equal to the exhaust pressure, the combustion chamber gas amount MR1 at the intake valve opening timing is calculated by the above equation (1), and the intake valve opening period and When there is no overlap in the exhaust valve opening period, the combustion chamber gas amount MR1 at the intake valve opening timing is directly used as the residual gas amount in the combustion chamber (see FIG. 19).

  However, as shown in FIG. 42, even when there is no overlap between the intake valve open period and the exhaust valve open period, the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 in the exhaust stroke becomes choked. It has been found that the combustion chamber pressure Pcyl may rise away from the exhaust pressure Pex. Therefore, even in such a case, if the combustion chamber gas amount MR1 at the intake valve opening timing is calculated on the assumption that the combustion chamber pressure PIVO at the intake valve opening timing is equal to the exhaust pressure, the exhaust pressure Pex of the combustion chamber pressure Pcyl is calculated. An error corresponding to the pressure difference from the above occurs in the estimation of the residual gas amount in the combustion chamber when there is no overlap between the intake valve open period and the exhaust valve open period.

  According to the eighth embodiment of the present invention (inventions according to claims 5 and 10), the pressure in the combustion chamber is set based on the volume change in the combustion chamber accompanying the movement of the piston 6 and the amount of gas that can pass through the exhaust valve. It is determined whether or not it is compressed in the exhaust stroke, and when the pressure in the combustion chamber is compressed in the exhaust stroke, the crank angle at which the volume change in the combustion chamber is equal to the amount of gas that can pass through the exhaust valve is combusted. The flow of the gas blown out from the chamber 5 to the exhaust port 11 is calculated as a crank angle CACOMP that starts the choke state (see step 172 in FIG. 43), and the exhaust gas is exhausted from the combustion chamber 5 based on the calculated choke state start crank angle CACOMP. The combustion chamber pressure PEVC ′ at the closing timing of the exhaust valve when the flow of gas blown out to the port 11 becomes choked is calculated (steps 173 to 18 in FIG. 43). Reference), and the combustion chamber gas amount MR1 at the exhaust valve closing timing based on the combustion chamber pressure PEVC 'at the exhaust valve closing timing when the flow of the gas blown out from the combustion chamber 5 to the exhaust port 11 becomes the choke state. Is calculated (see steps 191 to 193 in FIG. 44), and the combustion chamber gas amount MR1 ′ at the exhaust valve closing timing is determined as the residual gas amount in the combustion chamber when there is no overlap between the exhaust valve opening period and the intake valve opening period. (See step 194 in FIG. 44), the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 in the exhaust stroke becomes choked when there is no overlap between the intake valve open period and the exhaust valve open period. Sometimes, accurately estimate the amount of residual gas in the combustion chamber when there is no overlap between the exhaust valve opening period and the intake valve opening period. It can be.

  The pressure in the combustion chamber PEVC 'at the exhaust valve closing timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is choked is affected by the exhaust valve opening area. For example, when the exhaust valve VTC mechanism 28 is activated, the exhaust valve closing timing EVC changes in accordance with the exhaust VTC conversion angle, and the exhaust valve when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked. The pressure PEVC ′ in the combustion chamber at the closing timing changes from the value when the exhaust valve VTC mechanism 28 is not in operation. Therefore, the combustion chamber pressure PEVC ′ at the exhaust valve closing timing when the flow of the gas blown from the combustion chamber 5 to the exhaust port 11 is in the choked state when the exhaust valve VTC mechanism 28 is not operated is calculated with high accuracy. In addition, a map (see FIG. 6) of a difference value between the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is minimum, and a difference between the combustion chamber pressure and the average exhaust pressure at each crank angle when the charging efficiency is maximum. When matching the value map (see FIG. 6), when the exhaust valve VTC mechanism 28 is operated, if the same map is used without considering the exhaust VTC conversion angle, the operation of the exhaust valve VTC mechanism 28 is performed. Sometimes, an error corresponding to the exhaust VTC conversion angle causes combustion at the exhaust valve closing timing when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 becomes choked. This occurs in the calculation of the internal pressure PEVC '. According to the eighth embodiment of the present invention (the invention described in claim 6), when the flow of gas blown from the combustion chamber 5 to the exhaust port 11 is in a choke state. Since the combustion chamber pressure PEVC ′ at the exhaust valve closing timing is also calculated based on the exhaust VTC conversion angle (see steps 173 to 178 and 181 in FIG. 43), the combustion is performed even when the exhaust valve VTC mechanism 28 is operated. The combustion chamber pressure PEVC ′ at the exhaust valve closing timing when the flow of gas blown from the chamber 5 to the exhaust port 11 is in the choked state can be calculated with high accuracy.

  In the sixth, seventh, and eighth embodiments of the present invention, the command value given to the exhaust valve VTC mechanism 28 is the exhaust VTC conversion angle, and the exhaust valve closing timing EVC and the opening timing ( Although the case where the valve opening / closing timing is determined has been described, the present invention is not limited to this. For example, the opening / closing timing of the exhaust valve is also determined by the exhaust valve center angle. Therefore, if the command value given to the exhaust valve VTC mechanism 28 indicates the exhaust valve center angle, the exhaust valve center angle is converted into the exhaust VTC conversion. It can be used instead of the corner.

In the sixth embodiment of the present invention, the determination means for determining whether the pressure in the combustion chamber is compressed in the exhaust stroke or not is the exhaust valve opening area Aex (exhaust valve opening / closing timing), the engine Of the combustion chamber volume change dV / dθ near the exhaust top dead center due to the movement of the piston 6, engine rotational speed Ne, exhaust gas constant REX, average exhaust temperature TEX, specific heat ratio κ, air resistance coefficient C _D ), the determination means for determining whether or not the flow of the gas blown out from the combustion chamber 5 to the exhaust port 11 is in the choke state is not limited to this. 27 (an intake valve opening / closing timing variable mechanism capable of changing the opening / closing timing of the intake valve) and an exhaust valve VTC mechanism 28 (when the exhaust valve opening / closing can change the opening / closing timing of the exhaust valve) At least one of the intake valve opening timing and the exhaust valve opening timing And determining means for determining whether or not the flow of gas blown out from the combustion chamber 5 to the exhaust port 11 is choked based on the operating state of the engine.

  In the sixth, seventh, and eighth embodiments of the present invention, when the exhaust valve VTC mechanism 28 is not in operation, the exhaust valve opening / closing timing is at the most advanced angle position as the initial position. However, the present invention is not limited to this case. For example, when the exhaust valve VTC mechanism 28 is not operated, the exhaust valve opening / closing timing is at the most retarded position as the initial position, and when the exhaust valve opening / closing timing is activated, the exhaust valve opening / closing timing may be changed from the initial position to the advance side. Needless to say, the present invention is applicable.

  In the first aspect of the present invention, the function of the judging means is the steps 108 to 110 in FIG. 29, and the function of the estimating means is the step 143 in FIG. 37, the steps 150 and 159 in FIG. 38, the 111 in FIG. This is accomplished by steps 123, 126, and 127, respectively.

  In the fifth aspect of the present invention, the function of the determining means is performed by the engine controller 31, and the function of the estimating means is performed by steps 172 and 181 in FIG. 43 and steps 193 and 194 in FIG.

  In the invention according to claim 9, the determination processing procedure is based on steps 108 to 110 in FIG. 29, and the estimation processing procedure is step 143 in FIG. 37, steps 150 and 159 in FIG. 38, 111 in FIG. 39, and step 123 in FIG. , 126, 127, respectively.

  In the invention described in claim 10, the determination processing procedure is executed by the engine controller 31, and the estimation processing procedure is executed by steps 172 and 181 in FIG. 43 and steps 193 and 194 in FIG.

The schematic block diagram of the residual gas amount estimation apparatus of the engine of 1st Embodiment of a prior application apparatus. FIG. 3 is a stroke diagram for explaining a method of calculating the amount of residual gas in the combustion chamber when the intake valve is open. The map characteristic figure of a target equivalence ratio. The table | surface which put together the number of moles of the production | generation molecule | numerator after reaction. The characteristic view which shows the relationship between the difference value in charging efficiency, rotational speed, and intake valve opening timing. The map characteristic figure of the difference value of the combustion chamber pressure and average exhaust pressure at the time of the filling efficiency minimum or the filling efficiency maximum. FIG. 6 is a waveform diagram showing a shift in the pressure pulsation waveform of the pressure in the combustion chamber when the exhaust valve opening timing is advanced by a predetermined value from the most retarded position under the condition that the exhaust temperature is at the reference exhaust temperature. FIG. 6 is a waveform diagram showing a shift in the pressure pulsation waveform of the pressure in the combustion chamber when the exhaust temperature changes to a condition higher than the reference exhaust temperature and the exhaust valve opening timing is advanced by a predetermined value from the most retarded position. The characteristic view showing the relationship between exhaust temperature and waste heat quantity ratio. The map characteristic figure of an actual torque estimated value. A stroke diagram showing the difference between minus overlap and plus overlap. The combustion chamber pressure, the exhaust pressure, the gas flow rate around the exhaust valve, and the change waveform diagram of each opening area of the intake valve and the exhaust valve during the overlap between the exhaust valve open period and the intake valve open period. The figure for demonstrating calculation of the blow-back gas amount by 2 straight lines. The waveform diagram which shows the relationship between the pressure in a combustion chamber, the exhaust pressure, and the intake pressure in the crank angle section from the exhaust valve opening timing to the intake valve closing timing. The wave form diagram showing the pulsation of the pressure in a combustion chamber. FIG. 6 is a waveform diagram showing a pulsation shift when the exhaust valve VTC mechanism is operated under the condition that the exhaust temperature is at the reference exhaust temperature. This represents the pulsation deviation when the exhaust temperature changes to a condition higher than the reference exhaust temperature, and the pulsation deviation when the exhaust valve opening timing is further advanced from the most retarded position by a predetermined value in this state. Waveform diagram. The wave form diagram showing the deviation | shift of the exhaust valve opening area in crank angle (theta) 2 when operating the VTC mechanism for exhaust valves. The block diagram for calculation of the residual gas amount in a combustion chamber after the end of the overlap of the exhaust valve opening period and the intake valve opening period, which is executed by the engine controller. FIG. 5 is a waveform diagram showing changes in the gas flow rate around the exhaust valve during the overlap between the intake valve open period and the exhaust valve open period when the overlap period is less than a predetermined value and when the overlap period is longer than the predetermined value. FIG. 12 is a waveform diagram showing a change in the gas flow rate around the exhaust valve during the overlap between the intake valve open period and the exhaust valve open period when the overlap period of the second embodiment of the prior application device is longer than a predetermined value. The inclinations (dm ² / d ² θ) 0 and (EVC−θ 2) / () of the exhaust gas flow around the exhaust valve at the crank angle θ 0 when the gas flow around the exhaust valve becomes zero in the second embodiment of the prior application device. The characteristic view which shows the relationship with EVC-IVO). The block diagram of the blowback gas amount calculation part during overlap of the exhaust valve opening period and intake valve opening period of 3rd Embodiment of a prior application apparatus. The wave form diagram of the gas flow volume around the exhaust valve during the overlap of the exhaust valve open period and the intake valve open period of the sixth embodiment of the present invention. FIG. 24 is a waveform diagram in which the intake valve, exhaust pressure, pressure history of the pressure in the combustion chamber, and each opening area of the intake and exhaust valves are added to the exhaust gas flow waveform around the exhaust valve in the left, middle, and right states. The characteristic view for explaining the reason why the pressure in the combustion chamber is compressed in the exhaust stroke. FIG. 6 is a characteristic diagram of an exhaust valve opening area. The characteristic diagram of specific heat ratio. The flowchart for demonstrating the setting of the waveform determination flag of the 6th, 7th embodiment of this invention. FIG. 6 is a characteristic diagram showing a method for linearly approximating the exhaust gas flow waveform around the exhaust valve during the overlap between the exhaust valve open period and the intake valve open period, and the area to be calculated. The flowchart for demonstrating calculation of the residual gas amount in a combustion chamber after completion | finish of the overlap of the exhaust valve open period and intake valve open period of 6th Embodiment of this invention. The flowchart for demonstrating calculation of the residual gas amount in a combustion chamber after completion | finish of the overlap of the exhaust valve open period and intake valve open period of 6th Embodiment of this invention. The flowchart for demonstrating calculation of the residual gas amount in a combustion chamber after completion | finish of the overlap of the exhaust valve open period and intake valve open period of 6th Embodiment of this invention. The characteristic view of the choke state start crank angle of the sixth embodiment of the present invention. The timing chart which shows each change of the intake pressure of the 7th embodiment of the present invention, exhaust pressure, pressure in a combustion chamber, exhaust valve opening area, and intake valve opening area. FIG. 16 is a characteristic diagram of an integral value ∫ (C _D Aex2 / V) dθ at three reference exhaust VTC conversion angles according to the seventh embodiment of the present invention. The flowchart for demonstrating calculation of the pressure in a combustion chamber in the intake valve opening timing when the flow of the gas which blows off from a combustion chamber to an exhaust port of 7th Embodiment of this invention will be in a choke state. The flowchart for demonstrating calculation of the pressure in a combustion chamber in the intake valve opening timing when the flow of the gas which blows off from a combustion chamber to an exhaust port of 7th Embodiment of this invention will be in a choke state. The flowchart for demonstrating calculation of the combustion chamber residual gas amount after completion | finish of the overlap of the exhaust valve open period and intake valve open period of 7th Embodiment of this invention. The flowchart for demonstrating calculation of the combustion chamber residual gas amount after completion | finish of the overlap of the exhaust valve open period and intake valve open period of 7th Embodiment of this invention. The flowchart for demonstrating calculation of the combustion chamber residual gas amount after completion | finish of the overlap of the exhaust valve open period and intake valve open period of 7th Embodiment of this invention. The timing chart which shows each change of the intake pressure of the 8th Embodiment of this invention, an exhaust pressure, a combustion chamber pressure, an exhaust valve opening area, and an intake valve opening area. The flowchart for demonstrating calculation of the pressure in a combustion chamber in the exhaust valve closing time when the flow of the gas which blows off from a combustion chamber to an exhaust port of 8th Embodiment of this invention will be in a choke state. The flowchart for demonstrating calculation of the amount of residual gas in a combustion chamber when there is no overlap of the intake valve open period and exhaust valve open period of 8th Embodiment of this invention. Each characteristic diagram of integral value ∫ (C _D Aex2 / V) dθ at three reference exhaust VTC conversion angles according to the eighth embodiment of the present invention.

Explanation of symbols

1 Engine 5 Combustion chamber 15 Intake valve 16 Exhaust valve 28 Exhaust valve VTC mechanism (Exhaust valve opening / closing timing variable mechanism)
31 Engine controller

Claims (10)

Determining means for determining whether or not the pressure in the combustion chamber is compressed in the exhaust stroke based on the amount of change in the volume in the combustion chamber accompanying the movement of the piston and the amount of gas that can pass through the exhaust valve;
When the pressure in the combustion chamber is compressed in the exhaust stroke according to this determination result,
The crank angle at which the volume change in the combustion chamber is equal to the amount of gas that can pass through the exhaust valve is calculated as the crank angle at which the flow of gas blown from the combustion chamber to the exhaust port starts a choke state,
Based on the calculated choke state start crank angle, calculate the pressure in the combustion chamber at the intake valve opening timing when the flow of gas blown out from the combustion chamber to the exhaust port becomes the choke state,
Calculate the amount of gas blown from the combustion chamber to the exhaust port based on the pressure in the combustion chamber at the intake valve opening timing when the flow of gas blown out from the combustion chamber to the exhaust port is in the choke state,
And an estimation means for estimating the amount of residual gas in the combustion chamber after the overlap of the exhaust valve opening period and the intake valve opening period from the amount of gas in the combustion chamber when the intake valve is open and the amount of blown gas. Engine residual gas amount estimation device. Equipped with at least an exhaust valve opening / closing timing variable mechanism that can change the opening / closing timing of the exhaust valve,
2. The engine residual gas amount estimating device according to claim 1, wherein the choke state start crank angle is calculated based on an engine rotational speed and a command value given to the exhaust valve opening / closing timing variable mechanism. Equipped with at least an exhaust valve opening / closing timing variable mechanism that can change the opening / closing timing of the exhaust valve,
2. The engine residual gas amount estimating device according to claim 1, wherein the pressure in the combustion chamber at the time of opening the intake valve is also calculated based on a command value given to the exhaust valve opening / closing timing variable mechanism. Equipped with at least an exhaust valve opening / closing timing variable mechanism that can change the opening / closing timing of the exhaust valve,
The determination means is a determination means for determining whether the flow of gas blown from the combustion chamber to the exhaust port is in a choked state based on the exhaust valve opening / closing timing and the operating state of the engine,
The residual gas of the engine according to claim 1, wherein when the flow of gas blown from the combustion chamber to the exhaust port is in a choke state, it is determined that the pressure in the combustion chamber is compressed in an exhaust stroke. Quantity estimation device. Determining means for determining whether or not the pressure in the combustion chamber is compressed in the exhaust stroke based on the amount of change in the volume in the combustion chamber accompanying the movement of the piston and the amount of gas that can pass through the exhaust valve;
When the pressure in the combustion chamber is compressed in the exhaust stroke according to this determination result,
The crank angle at which the volume change in the combustion chamber is equal to the amount of gas that can pass through the exhaust valve is calculated as the crank angle at which the flow of gas blown from the combustion chamber to the exhaust port starts a choke state,
Based on this calculated choke state start crank angle, the combustion chamber pressure at the exhaust valve closing timing is calculated,
Based on the calculated pressure in the combustion chamber at the exhaust valve closing timing, the amount of gas in the combustion chamber at the exhaust valve closing timing when the flow of gas blown from the combustion chamber to the exhaust port is in a choked state is calculated,
And an estimation means for estimating the amount of gas in the combustion chamber when the exhaust valve is closed as the amount of residual gas in the combustion chamber when there is no overlap between the exhaust valve opening period and the intake valve opening period. Quantity estimation device. Equipped with at least an exhaust valve opening / closing timing variable mechanism that can change the opening / closing timing of the exhaust valve,
The combustion chamber pressure at the closing timing of the exhaust valve when the flow of gas blown from the combustion chamber to the exhaust port is in a choke state is also calculated based on a command value given to the exhaust valve opening / closing timing variable mechanism. The residual gas amount estimation device for an engine according to claim 5. Equipped with at least an exhaust valve opening / closing timing variable mechanism that can change the opening / closing timing of the exhaust valve,
6. The engine residual gas amount estimating device according to claim 5, wherein the choke state start crank angle is calculated based on an engine rotational speed and a command value given to the exhaust valve opening / closing timing variable mechanism. Equipped with at least an exhaust valve opening / closing timing variable mechanism that can change the opening / closing timing of the exhaust valve,
The determination means is a determination means for determining whether the flow of gas blown from the combustion chamber to the exhaust port is in a choked state based on the exhaust valve opening / closing timing and the operating state of the engine,
6. The engine residual gas according to claim 5, wherein when the flow of gas blown from the combustion chamber to the exhaust port is in a choked state, it is determined that the pressure in the combustion chamber is compressed in an exhaust stroke. Quantity estimation device. A determination processing procedure for determining whether or not the pressure in the combustion chamber is compressed in the exhaust stroke based on the amount of change in the combustion chamber volume accompanying the movement of the piston and the amount of gas that can pass through the exhaust valve;
When the pressure in the combustion chamber is compressed in the exhaust stroke according to this determination result,
The crank angle at which the volume change in the combustion chamber is equal to the amount of gas that can pass through the exhaust valve is calculated as the crank angle at which the flow of gas blown from the combustion chamber to the exhaust port starts a choke state,
Based on the calculated choke state start crank angle, calculate the pressure in the combustion chamber at the intake valve opening timing when the flow of gas blown out from the combustion chamber to the exhaust port becomes the choke state,
Calculate the amount of gas blown from the combustion chamber to the exhaust port based on the pressure in the combustion chamber at the intake valve opening timing when the flow of gas blown out from the combustion chamber to the exhaust port is in the choke state,
And an estimation processing procedure for estimating the amount of residual gas in the combustion chamber after the overlap of the exhaust valve opening period and the intake valve opening period from the amount of gas in the combustion chamber at the time of intake valve opening and this amount of blown gas. Engine residual gas amount estimation method. A determination processing procedure for determining whether or not the pressure in the combustion chamber is compressed in the exhaust stroke based on the amount of change in the combustion chamber volume accompanying the movement of the piston and the amount of gas that can pass through the exhaust valve;
When the pressure in the combustion chamber is compressed in the exhaust stroke according to this determination result,
The crank angle at which the volume change in the combustion chamber is equal to the amount of gas that can pass through the exhaust valve is calculated as the crank angle at which the flow of gas blown from the combustion chamber to the exhaust port starts a choke state,
Based on this calculated choke state start crank angle, the combustion chamber pressure at the exhaust valve closing timing is calculated,
Based on the calculated pressure in the combustion chamber at the exhaust valve closing timing, the amount of gas in the combustion chamber at the exhaust valve closing timing when the flow of gas blown from the combustion chamber to the exhaust port is in a choked state is calculated,
An estimation process procedure for estimating the amount of gas in the combustion chamber at the time when the exhaust valve is closed as the amount of residual gas in the combustion chamber when there is no overlap between the exhaust valve opening period and the intake valve opening period. Gas amount estimation method.