JP4158747B2 - Ignition timing control device for internal combustion engine - Google Patents

Description

  The present invention relates to an ignition timing control device for an internal combustion engine that controls ignition timing so as not to cause knocking.

  The ignition timing of the engine affects fuel consumption and output, and if the ignition timing is deviated, there is a risk of knocking or misfiring, so that control is very important. Normally, the ignition timing is controlled so that the cylinder pressure becomes the maximum at 10 to 15 degATDC. However, the maximum torque minimum advance ignition timing (Minimum Spark Advance for Best Torque; hereinafter abbreviated as “MBT”), which is the basis for setting the ignition timing, varies from moment to moment depending on engine speed, load, air-fuel ratio, EGR rate, etc. To do. Therefore, conventionally, a basic ignition timing map set according to the engine speed and load and a correction value map assuming various operating conditions are provided, and control is performed by referring to these maps according to the operating conditions. . However, in such a method, in order to improve accuracy, the number of grids of the map and the map itself must be increased, and enormous preliminary experiments are required to create the map.

Conventionally, when a knock is detected by a sensor, it is fed back to delay the ignition timing. However, this method cannot avoid a control delay because feedback control is performed after a knock that has actually occurred is detected. Therefore, in Patent Document 1, an in-cylinder pressure with respect to a crank angle and an in-cylinder gas temperature at a calculation start crank angle are input, and on the basis of them, the in-cylinder gas temperature is assumed to be adiabatically compressed. Is calculated, and the knock generation time is predicted assuming that the time when the in-cylinder gas temperature reaches 1200 K or more is the knock generation time.
JP-A-7-332149 (pages 3-5, FIGS. 1, 2, 5 etc.)

By the way, what calculates | requires self-ignition time from a 1 / τ map is known. According to this, the auto-ignition timing can be determined more accurately by tracing and knowing the pressure temperature of the unburned gas in the combustion chamber from the start of compression to combustion. However, in Patent Document 1, the in-cylinder pressure is directly detected using a pressure sensor. As described above, in the method using the sensor, it is necessary to adapt each time when the operating condition changes, so that the number of adaptation man-hours is large. Further, since the combustion state such as the heat generation amount and the combustion speed changes depending on the fuel property, the self-ignition timing also changes when the fuel property changes. Therefore, adapt without regard to fuel property poor accuracy, is adapted by considering the fuel property becomes enormous that man-hour for adaptation.

  The present invention has been made paying attention to such conventional problems, and does not require a large number of man-hours, and more accurate ignition timing control is also taken into account by taking fuel properties into consideration. An object of the present invention is to provide an ignition timing control device for an internal combustion engine.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

The present invention includes a fuel property estimation / detection means (500) for estimating or detecting a property of fuel consumed in an internal combustion engine, an operation state detection means (51) for detecting an operation state of the internal combustion engine, the fuel property and based on operating conditions, the cylinder temperature and pressure calculation means for calculating the temperature inside the cylinder pressure and the cylinder (531), unburned gas property value calculation for calculating the specific heat ratio of the unburned gas, based on the in-cylinder temperature Means (53221), unburned gas temperature calculating means (53222) for calculating an unburned gas temperature based on the unburned gas specific heat ratio and the in-cylinder pressure, the unburned gas temperature , the in-cylinder pressure, and the Ignition delay calculation means (5323) for calculating the ignition delay of the in-cylinder gas based on the fuel properties, knock generation index calculation means for calculating the knock generation index by time integration of the ignition delay (5324), and the occurrence of the knock based to index And calculates the ignition timing limit which does not generate knock Te knock limit ignition timing calculation means (54-55), characterized by having a.

  Since the combustion state such as the heat generation amount and the combustion speed changes depending on the fuel property, the ignition delay time also changes depending on the fuel property. There is a strong correlation between the ignition delay time and the ease of occurrence of knocking. Therefore, in the present invention, the temperature and pressure in the cylinder are calculated based on the fuel properties and the operating state, and the ignition delay of the cylinder gas is calculated based on the in-cylinder temperature pressure and fuel properties, so that no knock is generated. Since the limit ignition timing is calculated, more accurate knock limit ignition timing can be calculated.

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

  FIG. 1 is a schematic diagram for explaining the system of the present invention.

  The air is stored in the intake collector 2 and then introduced into the combustion chamber 5 of each cylinder via the intake manifold 3. 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.

  In order to ignite this compressed air-fuel mixture with a high-pressure spark, an ignition device 11 of an electronic power distribution system is provided in which an ignition coil with a built-in power transistor is arranged in each cylinder. That is, the ignition device 11 includes an ignition coil 13 that stores electrical energy from the battery, a power transistor that energizes and shuts off the primary side of the ignition coil 13, and a primary current of the ignition coil 13 that is provided on the ceiling of the combustion chamber 5. It includes a spark plug 14 that receives a high voltage generated on the secondary side of the ignition coil 13 due to interruption of the spark coil 13 and performs spark discharge.

  When a spark is blown off by the spark plug 14 slightly before the compression top dead center and the compressed 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 of 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 ° section in a four-cycle engine) and the fuel injector 21 The engine controller 50 controls the fuel from the fuel injector 21 based on the intake air flow rate signal from the air flow meter 32 and the signal from the crank angle sensor (33, 34) so that the ratio to the fuel injection amount becomes the stoichiometric air-fuel ratio. The injection 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 so-called electronically controlled throttle 22 in which a throttle valve 23 is driven by a throttle motor 24 is provided upstream of the intake collector 2. Since the torque requested by the driver appears in the amount of depression of the accelerator pedal 41 (accelerator opening), the engine controller 50 determines a target torque based on a signal from the accelerator sensor 42, and a target air for realizing this target torque. The amount is determined, and the opening degree of the throttle valve 23 is controlled via the throttle motor 24 so as to obtain this target air amount.

  Cam sprockets and crank sprockets are attached to the front portions of the intake valve camshaft 25, the exhaust valve camshaft 26, and the crankshaft 7, respectively, and a timing chain (not shown) is hung around these sprockets so that the camshaft 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. An exhaust valve cam control phase (hereinafter referred to as an “intake VTC mechanism”) 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 cam. Valve timing control mechanism (hereinafter referred to as “exhaust VTC mechanism”) Say.) 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 the inert gas remaining in the combustion chamber 5 changes. As the amount of the inert gas in the combustion chamber 5 increases, the pumping loss decreases and the fuel consumption improves. Therefore, the target intake valve closing timing and the target exhaust gas indicate how much inert gas should remain in the combustion chamber 5 depending on the operating conditions. The valve closing timing is determined in advance, and the engine controller 50 determines the target intake valve closing timing and the target exhaust valve closing timing based on the operating conditions (engine load and rotational speed) at that time, so that these target values can be obtained. The intake valve closing timing and the exhaust valve closing timing are controlled via the actuators of the intake VTC mechanism 27 and the exhaust VTC mechanism 28.

  An intake air temperature signal from the intake air temperature sensor 43, an intake air pressure signal from the intake air pressure sensor 44, an exhaust gas temperature signal from the exhaust air temperature sensor 45, and an exhaust gas pressure signal from the exhaust air pressure sensor 46 are output from the water temperature sensor 37. The engine controller 50 that is input together with the coolant temperature signal controls the ignition timing, which is the primary current cutoff timing of the spark plug 14, via the power transistor 13.

  Next, the basic concept of control that is a feature of the present invention will be described.

  2 and 3 are diagrams for explaining a knock generation mechanism.

  When the mixed gas is ignited and combustion is started, the heat generation rate rapidly increases (FIG. 2A). Then, the in-cylinder temperature (FIG. 2B) and the in-cylinder pressure (FIG. 2C) also increase. Then, if the unburned gas self-ignites and causes rapid combustion before the ignited fire is transmitted, knocking occurs (FIG. 2C). The reciprocal (1 / τ) of the self-ignition time τ represents the ignition delay. Knock occurs at a crank angle at which the time integral value of 1 / τ becomes 1 (FIG. 2D). That is, ∫1 / τ · dt is a knock occurrence index.

  This will be described in more detail with reference to FIG. FIG. 3A is a 1 / τ map with the in-cylinder temperature on the horizontal axis and the in-cylinder pressure on the vertical axis. If the in-cylinder temperature and in-cylinder pressure are known, the value of 1 / τ can be obtained from this map. 1 / τ is obtained along the history of in-cylinder pressure and in-cylinder temperature, and time integration is performed to obtain ∫1 / τ · dt. It can be estimated that knocking occurs at a crank angle where ∫1 / τ · dt = 1.

  The result of the estimation is shown in FIG. The actual value of the knocking crank angle is taken on the horizontal axis of FIG. 3B, while the estimated value of the knocking crank angle calculated as described above is taken on the vertical axis. Then, as is clear from FIG. 3B, the estimated value substantially coincided with the actually measured value, and it was proved that the above estimation was correct.

  The present inventor introduced ∫1 / τ · dt as a knock occurrence index. As a result, the knock generation index can be reduced to the in-cylinder pressure and the in-cylinder temperature. Since the in-cylinder pressure and the in-cylinder temperature are the most basic state quantities of the in-cylinder gas, it is possible to have substantially the same characteristics regardless of the engine model, and to the engine warm-up state and environmental conditions. Regardless, it is now possible to accurately estimate the knock occurrence time (time or crank angle at which the knock occurs) in real time.

  FIG. 4 is a control block diagram showing the overall control of the ignition timing control apparatus according to the present invention.

  The engine controller 50 sequentially calculates the combustion speed 521, the combustion period 522, and the basic ignition timing 523 based on the operating state 51, and calculates the knock generation index 53 to obtain the advance angle correction / limit (retard width) 54. From these, the knock limit ignition timing 55 is calculated.

  Next, each component block will be described in more detail. In addition, since the specific content of the basic ignition timing calculation part 52 is demonstrated in detail in Unexamined-Japanese-Patent No. 2003-148236, description is abbreviate | omitted in this case.

  FIG. 5 is a diagram illustrating the knock occurrence index block 53 in detail.

  In the knock generation index block 53, the basic ignition timing MBTCAL and the calculated crank angle interval delta_theta are input, and the calculated crank angle CA_calc (i) is sequentially calculated for each calculation counter (i) based on the knock generation index calculation start request JOB_REQ. . Then, the knock generation index 530 is calculated based on the calculated crank angle CA_calc (i), and the knock generation index idx_kocr (i) and the mass combustion ratio X_burn (i) are sequentially calculated for each calculation counter (i). The interrupt calculation is requested until the mass combustion ratio X_burn (i) exceeds the combustion ratio X_burn_end at the end of combustion.

  The knock generation index calculation block 530 will be described with reference to FIG. The knock generation index calculation block 530 includes an in-cylinder average temperature / pressure calculation block 531 and a knock generation index calculation block 532. In the cylinder average temperature / pressure calculation block 531, the crank angle CA, the engine speed NE, the basic ignition timing MBTCAL, the injection pulse width TP, the cylinder volume initial value V_cyl_ini, the cylinder temperature initial value T_cyl_ini, the cylinder pressure initial value P_cyl_ini, The in-cylinder temperature T_cyl, the in-cylinder pressure P_cyl, and the mass combustion ratio X_burn are calculated based on the ignition dead time IGNDEAD, the combustion period BURN, the reference combustion ratio X_ref, and the remaining gas ratio MRESFR. In knock generation index calculation block 532, knock generation index idx_kocr is calculated based on crank angle CA, engine speed NE, basic ignition timing MBTCAL, in-cylinder temperature T_cyl, and in-cylinder pressure P_cyl. The in-cylinder average temperature / pressure calculation block 531 will be described in detail with reference to FIG. 7, and the knock occurrence index calculation block 532 will be described in detail with reference to FIG.

  First, the in-cylinder average temperature / pressure calculation block 531 will be described with reference to FIG.

  The in-cylinder average temperature / pressure calculation block 531 includes a cylinder volume calculation block 5311, a heat generation amount calculation block 5312, a cooling loss calculation block 5313, and an in-cylinder temperature / pressure calculation block 5314.

  In the cylinder volume calculation block 5311, the cylinder volume V_cyl and the piston displacement x_pis are calculated based on the crank angle CA. In the calorific value calculation block 5312, based on the crank angle CA, the injection pulse width TP, the basic ignition timing MBTCAL, the ignition dead time IGNDEAD, the combustion period BURN, the reference combustion rate X_ref, the residual gas rate MRESFR, the heat generation rate Q_burn, the physical property calculation The mass combustion ratio X_burn_r and the mass combustion ratio X_burn are calculated. In the cooling loss calculation block 5313, the cylinder volume V_cyl, piston displacement x_pis, residual gas ratio MRESFR, cylinder temperature initial value T_cyl_ini, cylinder volume initial value V_cyl_ini, cylinder pressure initial value P_cyl_ini, engine speed NE, cylinder pressure previous value P_cyl_z The cooling loss Q_loss is calculated based on the previous in-cylinder temperature value T_cyl_z. In the in-cylinder temperature / pressure calculation block 5314, based on the injection pulse width TP, the cylinder volume V_cyl, the heat generation rate Q_burn, the physical property calculation mass combustion ratio X_burn_r, the cooling loss Q_loss, the in-cylinder pressure previous value P_cyl_z, and the in-cylinder temperature previous value T_cyl_z. Thus, the in-cylinder pressure P_cyl and the in-cylinder temperature T_cyl are calculated.

  Subsequently, each block constituting the in-cylinder average temperature / pressure calculation block 531 shown in FIG. 7 will be described in more detail.

  First, details of the cylinder volume calculation block 5311 will be described with reference to FIG. The cylinder volume calculation block 5311 includes a piston displacement calculation block 53111 and a cylinder volume calculation block 53112. In the piston displacement calculation block 53111, the piston displacement x_pis is calculated from the crank angle CA. In the cylinder volume calculation block 53112, the cylinder volume V_cyl is calculated.

  Next, details of the heat generation amount calculation block 5312 will be described with reference to FIG.

  The calorific value calculation block 5312 includes a Wiebe function constant setting block 53121, a heat generation rate calculation block 53122, a mass combustion ratio calculation block 53123, a calorific value / 1 cylinder / 1 cycle calculation block 53124, and a calorific value / 1 cylinder / And a calculation interval calculation block 53125.

Here, the Wiebe function will be described. In general, X = 1−exp [−a · [(θ−θ _S ) / θ _B ] ^{n +} as a function of the crank angle θ (deg) as a function of the heat release rate ¹ ]… (1)
θ _S : Actual combustion start crank angle (deg)
θ _B : Actual combustion period (deg)
a, n: can be described as constants. The above a and n are determined by the engine model such as the shape of the combustion chamber, the position of the spark plug, and the gas flow characteristics in the combustion chamber. This can be determined in advance by experiments or the like. This equation (1) is the Wiebe function.

Differentiating the above equation (1) by θ gives a function representing the heat generation rate,
dX / dθ
= A (n + 1) / θ _B · [(θ-θ _S ) / θ _B ] ⁿ · exp [-a · [(θ-θ _S ) / θ _B ] ^{n + 1} ] (2)
Solving equation (1) for the actual combustion period θ _B
θ _B = θ / [-log (1-X) / a] ^{1 / (n + 1)} (3)
It becomes.

Based on the above, the Wiebe function constant setting block 53121 will be described with reference to FIG. FIG. 10 is a control block diagram describing the above equation (3). That is, in the equation (3), the actual combustion period θ _B (BURN_r) can be calculated by substituting θ = BURN and X = X_ref. The Wiebe function constant setting block 53121 calculates the heat generation start timing BURN_ini based on the basic ignition timing MBTCAL and the ignition dead time IGNDEAD, and calculates the actual combustion duration BURN_r based on the combustion duration BURN and the reference combustion ratio X_ref. .

The heat generation rate calculation block 53122 will be described with reference to FIG. FIG. 11 is a control block diagram describing the above equation (2). That is, in equation (2), if θ = CA, θ _S = BURN_ini, and θ _B = BURN_r are substituted, the heat generation rate dX / dθ can be calculated. The heat generation rate calculation block 53122 calculates the heat generation rate based on the crank angle CA, the heat generation start timing BURN_ini, and the actual combustion period BURN_r.

The mass combustion ratio calculation block 53123 will be described with reference to FIG. FIG. 12 is a control block diagram describing the above equation (1). In other words, the mass combustion ratio X (X_burn) can be calculated by substituting θ = CA, θ _S = BURN_ini, and θ _B = BURN_r in equation (1). The mass combustion ratio calculation block 53123 calculates a mass combustion ratio X_burn and a physical property calculation mass combustion ratio X_burn_r based on the crank angle CA, the heat generation start timing BURN_ini, the actual combustion period BURN_r, and the residual gas ratio MRESFR.

  The calorific value / 1 cylinder / 1 cycle calculation block 53124 will be described with reference to FIG. FIG. 13 is a control block diagram showing that the amount of heat generated per cylinder per cycle is expressed by the following equation.

Heat generation per cylinder / cycle = [TP / (KCONST ・ ABYF)] ・ Heat_Lower
TP: Injection pulse width
KCONST: Constant
ABYF: Air-fuel ratio
Heat_Lower: Low calorific value Therefore, calorific value / 1 cylinder / cycle calculation block 53124 is based on injection pulse width TP, constant KCONST, air-fuel ratio ABYF, low calorific value Heat_Lower, and calorific value per cylinder per cycle. Is calculated.

  The low heat generation amount calculation block 531241 will be described with reference to FIG. FIG. 14 is a control block diagram showing that the low calorific value Heat_Lower is expressed by the following equation.

Heat_Lower = x ・ Halk + (1-x) ・ Hgas
x: alcohol concentration [%]
Halk: Low calorific value of alcohol (specific value) [J / kg]
Hgas: Low gasoline calorific value (Eigenvalue) [J / kg]
That is, this expression calculates the low heat value Heat_Lower by correcting the low heat value of gasoline and alcohol according to the alcohol concentration x. As a method for detecting / estimating the alcohol concentration x, a conventionally known method may be used. For example, an alcohol concentration sensor is disposed in the fuel tank and directly detected or calculated based on the exhaust air / fuel ratio. A correlation between the air-fuel ratio correction coefficient and the alcohol concentration may be obtained in advance, and the alcohol concentration may be estimated based on the detection value of the oxygen concentration sensor in the exhaust passage (for example, Japanese Patent Application No. 2003-34444).

  The heating value / 1 cylinder / calculation interval calculation block 53125 will be described with reference to FIG. The heat generation amount / 1 cylinder / calculation interval calculation block 53125 calculates a heat generation amount Q_burn based on the heat generation rate and the heat generation amount for each cylinder per cycle.

  The above is the description of the heat generation amount calculation block 5312. Next, details of the cooling loss calculation block 5313 of FIG. 7 will be described with reference to FIG.

  The cooling loss calculation block 5313 includes a combustion chamber surface area calculation block 53131, an average piston speed calculation block 53132, a motoring-gas property value calculation block 53133, a motoring-cylinder pressure calculation block 53134, and a motoring-cylinder temperature. It has a calculation block 53135, a heat transfer coefficient calculation block 53136, and a cooling loss calculation block 53137.

  The combustion chamber surface area calculation block 53131 calculates the combustion chamber surface area based on the piston displacement x_pis. The average piston speed calculation block 53132 calculates an average piston speed based on the engine speed.

  The motoring-gas property value calculation block 53133 calculates the specific heat ratio κ based on the mass combustion ratio obtained from the residual gas rate MRESFR and the in-cylinder temperature. Since the specific calculation method is the same as that of the gas property value calculation block 53141 (FIG. 20), the description is omitted here.

  The motoring-cylinder pressure calculation block 53134 calculates a cylinder pressure P_cyl based on the cylinder pressure previous value, the cylinder volume previous value, the cylinder volume current value, and the specific heat ratio κ. In this calculation, it is calculated as an adiabatic change. The motoring-in-cylinder temperature calculation block 53135 calculates the in-cylinder temperature T_cyl based on the previous in-cylinder temperature value, the previous cylinder volume value, the current cylinder volume value, and the specific heat ratio κ. In this calculation, it is calculated as an adiabatic change.

  Next, before describing the heat transfer coefficient calculation block 53136, the equation of the cooling loss Woschni will be described.

The cooling loss Q _L is calculated by:
Q _L = ∫ _t1 ^t2 h ・ A ・ (T-T _W ) ・ dt… (4)
h = 110 ・ d ^-0.2・ P ^0.8・ T ^-0.53・ [C ₁・ c _m + C ₂・ (V _S・ T _I ) / (P _I・ V _I ) ・ (P-P _M )] ^0.8 … (Five)
h: Heat transfer coefficient [kcal / (m ²・ h ・ K)]
d: Cylinder bore diameter [m]
V _S : Cylinder volume [m ³ ]
c _m : Average piston speed [m / s]
P _I : In-cylinder pressure when the intake valve is closed [kgf / cm ² ]
V _I : In-cylinder volume when intake valve is closed [m ³ ]
T _I : In-cylinder temperature when intake valve is closed [K]
P _M : Motoring cylinder pressure [kgf / cm ² ]
P: In-cylinder pressure [kgf / cm ² ]
T: In-cylinder temperature [K]
C ₁ : 6.18 (exhaust), 2.28 (compression and expansion) [-]
C ₂ : 3.24 × 10 ^-3 [m / (s · K)]
In the above, C ₁ and C ₂ are commonly used constants.

  FIG. 17 illustrates equation (5) as a control block. As shown in FIG. 17, the heat transfer coefficient calculation block 53136 is based on the cylinder pressure, the cylinder temperature, the average piston speed, the motoring cylinder pressure, the cylinder temperature initial value, the cylinder volume initial value, and the cylinder pressure initial value. Calculate the heat transfer coefficient.

  FIG. 18 illustrates the equation (4) as a control block. As shown in FIG. 18, the cooling loss calculation block 53137 calculates the cooling loss Q_loss based on the in-cylinder temperature, the combustion chamber wall temperature, the combustion chamber surface area, the heat transfer coefficient, the calculation interval, and the engine speed.

  The above is the description of the cooling loss calculation block 5313. Next, the in-cylinder temperature / pressure calculation block 5314 in FIG. 7 will be described with reference to FIG.

  The in-cylinder temperature / pressure calculation block 5314 includes a gas property value calculation block 53141, a total gas amount calculation block 53142, an adiabatic change in-cylinder pressure calculation block 53143, an adiabatic change in-cylinder temperature calculation block 53144, and an in-cylinder temperature calculation block. 53145 and an in-cylinder pressure calculation block 53146.

The gas property value calculation block 53141 calculates a gas property value (specific heat ratio, constant volume specific heat) based on the mass combustion ratio and the in-cylinder temperature. Here, when calculating gas properties based on the ratio of burnt gas (applying “mass combustion ratio for physical property calculation”),
(Gas property value) = (Burn gas property value) * (Burn gas ratio) + (Burn gas property value) * (1-Burned gas ratio)… (6)
Therefore, it is shown in the block diagram of FIG. As shown in FIG. 20, the gas property value calculation block 53141 obtains the constant volume specific heat and specific heat ratio of the burned portion based on the in-cylinder temperature T_cyl (initial value is T_cyl_ini), and also the in-cylinder temperature T_cyl (initial value). Based on T_cyl_ini), calculate the constant volume specific heat and specific heat ratio of the unburned portion, and multiply the ratio of burned portion and unburned portion to calculate the physical properties of the cylinder gas (specific heat ratio, constant volume specific heat) To do.

  As shown in FIG. 21, the total gas amount calculation block 53142 calculates the total gas amount based on the injection pulse width TP, KCONST, and the air-fuel ratio ABYF.

  The adiabatic change in-cylinder pressure calculation block 53143 calculates the adiabatic change in-cylinder pressure based on the previous cylinder pressure value, the previous cylinder volume value, the current cylinder volume value, and the specific heat ratio κ. The adiabatic change in-cylinder temperature calculation block 53144 calculates the adiabatic change in-cylinder temperature based on the previous cylinder temperature value, the previous cylinder volume value, the current cylinder volume value, and the specific heat ratio κ. The in-cylinder temperature calculation block 53145 calculates the in-cylinder temperature T_cyl based on the adiabatic change in-cylinder temperature, the heat generation amount, the cooling loss, the total gas amount, and the constant volume specific heat. The in-cylinder pressure calculation block 53146 calculates the in-cylinder pressure P_cyl based on the adiabatic change in-cylinder pressure, the in-cylinder temperature, and the adiabatic change in-cylinder temperature.

  The above is the description of the in-cylinder temperature / pressure calculation block 5314, and all of the in-cylinder average temperature / pressure calculation block 531 in FIG. 6 has been described. Next, the knock occurrence index calculation block 532 of FIG. 6 will be described in detail with reference to FIG.

  Knock generation index calculation block 532 includes a reset flag calculation block 5321, an unburned gas temperature calculation block 5322, an instantaneous ignition delay reciprocal calculation block 5323, and a knock generation index calculation block 5324.

  Details of the reset flag calculation block 5321 are shown in FIG. The reset flag calculation block 5321 sets a reset flag when the crank angle CA exceeds the basic ignition timing MBTCAL. The unburned gas temperature calculation block 5322 includes an unburned gas property value calculation block 53221 and an unburned gas temperature calculation block 53222 as shown in FIG. Since the unburned gas property value calculation block 53221 is the same as the gas property value calculation block 53141 (FIG. 20), the description thereof is omitted. The physical property value of only unburned gas is calculated by inputting zero as the mass combustion ratio. The unburned gas temperature calculation block 53222 calculates the unburned gas temperature T_ub based on the unburned gas temperature previous value, the in-cylinder pressure current value, the in-cylinder pressure previous value, and the specific heat ratio κ.

  The instantaneous ignition delay reciprocal calculation block 5323 will be described with reference to FIG. FIG. 25 is a control block diagram showing that the instantaneous ignition delay inverse tauinv is expressed by the following equation.

tauinv = x ・ (tauinv_85-tauinv_0) + tauinv_0
x: alcohol concentration [%]
tauinv_0: Reciprocal of instantaneous ignition delay when alcohol concentration is 0%
tauinv_85: Reciprocal of instantaneous ignition delay when alcohol concentration is 85% In other words, this formula is used for linear interpolation according to alcohol concentration by using tauinv_0 and reciprocal of instantaneous ignition delay when alcohol concentration is 85% and tauinv_85. By doing so, the reciprocal tauinv of instantaneous ignition delay is calculated.

  The instantaneous ignition delay reciprocal tauinv_0 when the alcohol concentration is 0% and the instantaneous ignition delay reciprocal tauinv_85 when the alcohol concentration is 85% are the unburned gas temperature T_ub and the in-cylinder pressure P_cyl, respectively, when the alcohol concentration is 0% in FIG. The 1 / τ map is obtained by applying to the 1 / τ map when the alcohol concentration is 85% in FIG. These maps are obtained in advance by experiments.

  As shown in FIG. 27, knock occurrence index calculation block 5324 calculates time from engine speed NE, and integrates instantaneous ignition delay inverse tauinv according to the time to calculate knock occurrence index idx_kocr. If the reset flag is set, the initial value zero is set as the knock occurrence index idx_kocr.

  The above is the description of the knock occurrence index calculation block 532 in FIG. 6, and all of the knock occurrence indices 53 in FIG. 4 have been described. Next, the retard width calculation block 54 of FIG. 4 will be described in detail with reference to FIG. FIG. 28 is a diagram showing a detailed control block of the retard width calculation block 54.

  The retard width calculation block 54 includes a crank angle calculation block 541, a mass combustion ratio calculation block 542, a knock strength calculation block 543, and a retard width calculation block 544.

  The crank angle calculation block 541 calculates the knock generation crank angle CA_knk from the knock generation index idx_kocr (i) and the calculated crank angle CA_calc (i) based on a diagram previously obtained through experiments.

  The mass combustion ratio calculation block 542 calculates a knock generation mass combustion ratio X_bknk from the calculated crank angle CA_calc (i), the mass combustion ratio X_burn (i), and the knock generation crank angle CA_knk based on a diagram obtained in advance by experiments. Ask.

  Knock strength calculation block 543 determines knock strength I_knk from knock generation crank angle CA_knk and knock generation mass combustion ratio X_bknk based on a diagram previously obtained through experiments. In the diagram in the figure, the arrow direction (downward) is the retard side.

  The retard width calculation block 544 calculates a retard width (advance correction limit) CA_rtd from the knock intensity I_knk based on a diagram previously obtained through experiments.

  Next, the knock limit ignition timing calculation block 55 of FIG. 4 will be described in detail with reference to FIG. FIG. 29 is a diagram showing a detailed control block of the knock limit ignition timing calculation block 55. The ignition timing ADV is obtained by retarding the retard width CA_rtd from the basic ignition timing MBTCAL.

  The control of the engine controller 50 shown in FIG. 4 has been described above.

  As described above in detail, in the present invention, the knock limit ignition timing is calculated based on the ignition delay. Since the combustion state such as the heat generation amount and the combustion speed changes depending on the fuel property, the ignition delay time also changes depending on the fuel property. There is a strong correlation between the ignition delay time and the ease of occurrence of knocking. Therefore, in the present invention, the more accurate knock limit ignition timing can be calculated by considering that the combustion state differs from the heat generation amount and the combustion speed depending on the fuel properties.

  Further, a heat generation pattern is obtained based on the fuel properties and the operation state, and the temperature and pressure in the cylinder are calculated based on the heat generation pattern. Since it did in this way, even if a combustion rate changes with a change in fuel properties and a heat generation pattern changes, a knock limit ignition timing can be calculated appropriately.

  Further, as the fuel properties, particularly the alcohol concentration is detected, and the in-cylinder temperature pressure corresponding to the alcohol concentration is calculated. Since it did in this way, exact knock limit ignition timing can be calculated corresponding to the change of alcohol concentration.

  Furthermore, the ignition delay is uniquely determined by the temperature and pressure if the fuel properties are determined. Accordingly, an appropriate ignition timing can be calculated by calculating a knock generation index using the ignition delay calculated based on the fuel properties and calculating the knock limit ignition timing based on the knock generation index.

  Moreover, the required retard amount increases as the mass combustion ratio immediately before the occurrence of knocking decreases. Therefore, since the knock intensity is calculated based on the mass combustion ratio immediately before the occurrence of knock and the knock limit ignition timing is obtained, an appropriate ignition timing can be calculated.

  Furthermore, since the in-cylinder temperature and the in-cylinder pressure are calculated and the ignition delay is calculated based on the calculated values, the ignition delay calculation means can have substantially the same characteristics regardless of the engine model, and the engine This makes it possible to calculate accurately in real time regardless of the warm-up condition and environmental conditions.

  Furthermore, whether or not knocking actually occurs can be appropriately estimated from the knocking timing (time or crank angle at which knocking occurs) and the mass combustion ratio immediately before the knocking. The knock limit ignition timing can be calculated appropriately.

  When knocking is predicted, it is possible to avoid actual knocking by performing retard correction of the ignition timing. The basic ignition timing can always be set with the aim of MBT, and the adaptation man-hours can be reduced and the fuel consumption can be improved. By appropriately setting the retard amount, it is possible to prevent the fuel consumption and the drivability from being deteriorated due to the retard being more than necessary.

  Furthermore, since the heat generation pattern is referred to, the mass combustion ratio can be calculated more easily and appropriately.

  Further, by taking into account changes in the in-cylinder temperature and the in-cylinder pressure from time to time, the knock occurrence index can be calculated more appropriately by integrating the reciprocal of the instantaneous ignition delay from time to time. As the number of calculation points at each calculation crank angle increases, the calculation accuracy of the knock index improves.

  Further, the integral value of the reciprocal of the instantaneous ignition delay is an index representing “ease of knock generation”, and the knock generation crank angle can be obtained by comparing this with a predetermined threshold value.

  And since it was set as the structure which calculates | requires an ignition delay and calculates a knock generation | occurrence | production timing and a knock limit ignition timing based on it, adaptation to an actual machine can be reduced significantly regardless of a model.

  Further, the knock limit ignition timing can be calculated by performing all the calculations without using the in-cylinder pressure sensor, so that the cost can be suppressed at a low cost.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

It is the schematic for demonstrating the system of this invention. It is a figure explaining a knock generation mechanism. It is a figure explaining a knock generation mechanism. It is a control block diagram which shows the whole control of the ignition timing control apparatus by this invention. It is a figure explaining the knock generation index block 53 in detail. It is a figure which shows the knock generation parameter | index calculation block 530. FIG. 11 is a diagram showing an in-cylinder average temperature / pressure calculation block 531. It is a figure which shows the cylinder volume calculation block 5311. It is a figure which shows the emitted-heat amount calculation block 5312. FIG. It is a figure which shows the Wiebe function constant setting block 53121. It is a figure which shows the heat release rate calculation block 53122. It is a figure which shows the mass combustion ratio calculation block 53123. It is a figure showing calorific value / 1 cylinder / 1 cycle calculation block 53124. It is a figure which shows the low calorific value calculation block 531241. It is a figure showing calorific value / 1 cylinder / calculation interval calculation block 53125. FIG. 11 is a diagram showing details of a cooling loss calculation block 5313. It is a figure which shows the heat transfer coefficient calculation block 53136. It is a figure which shows the cooling loss calculation block 53137. FIG. 10 is a diagram showing an in-cylinder temperature / pressure calculation block 5314. It is a figure which shows the motoring-gas physical property value calculation block 53133. It is a figure which shows the total gas amount calculation block 53142. FIG. It is a figure which shows the knock generation parameter | index calculation block 532. FIG. 12 is a diagram showing a reset flag calculation block 5321. It is a figure which shows the unburned gas temperature calculation block 5322. FIG. It is a figure which shows the instantaneous ignition delay reciprocal calculation block 5323. It is a figure which shows the 1 / τ map at the time of alcohol concentration 0% and 85%. It is a figure which shows the knock generation index calculation block 5324. It is a figure which shows the detailed control block of the retard width calculation block. FIG. 6 is a diagram showing a knock limit ignition timing calculation block 55.

Explanation of symbols

1 Engine 50 Engine controller 500 Alcohol concentration estimation / detector (fuel property estimation / detection means)
51 Operation state detection block (operation state detection means)
52 Basic ignition timing calculation block 53 Knock generation index block 531 In-cylinder average temperature / pressure calculation block (in-cylinder temperature / pressure calculation means)
5312 Calorific value calculation block (heat generation pattern calculation means)
5313 Cooling loss calculation block 5314 In-cylinder temperature / pressure calculation block (in-cylinder temperature / pressure calculation means)
532 Knock generation index calculation block 5322 Unburned gas temperature calculation block 5323 Instantaneous ignition delay reciprocal calculation block (ignition delay calculation means)
5324 Knock occurrence index calculation block (knock occurrence index calculation means)
54 retard width calculation block (knock limit ignition timing calculation means)
541 Crank angle calculation block (knock occurrence timing calculation means)
542 Mass combustion ratio calculation block (mass combustion ratio calculation means)
543 Knock strength calculation block (knock strength calculation means)
544 retard width calculation block 55 knock limit ignition timing calculation block (knock limit ignition timing calculation means)

Claims (4)

Fuel property estimation / detection means for estimating or detecting the property of fuel consumed in the internal combustion engine;
An operating state detecting means for detecting an operating state of the internal combustion engine;
In-cylinder temperature and pressure calculating means for calculating the in-cylinder temperature and the in-cylinder pressure based on the fuel property and the operating state;
And unburned gas property value calculating means for calculating the specific heat ratio of the unburned gas, based on the in-cylinder temperature,
Unburned gas temperature calculating means for calculating an unburned gas temperature based on the unburned gas specific heat ratio and the in-cylinder pressure;
And ignition delay calculating means for calculating the ignition delay of the cylinder interior gas on the basis of the fuel property and the unburned gas temperature and the cylinder pressure,
Knock occurrence index calculating means for calculating a knock occurrence index by time-integrating the ignition delay ;
Knock limit ignition timing calculation means for calculating a limit ignition timing that does not generate knock based on the knock occurrence index ;
An ignition timing control device for an internal combustion engine. The fuel property estimation / detection means is a means for estimating or detecting the alcohol concentration of the fuel as the fuel property.
The ignition timing control device for an internal combustion engine according to claim 1, comprising: The ignition delay calculation means is supplemented according to the alcohol concentration estimated or detected by the fuel property estimation / detection means based on the ignition delay map when the alcohol concentration is low and the ignition delay map when the alcohol concentration is high. To calculate the ignition delay,
The ignition timing control device for an internal combustion engine according to claim 2, wherein the ignition timing control device is an internal combustion engine. The knock limit ignition timing calculating means includes
A knock occurrence time calculating means for calculating a knock occurrence time based on the knock occurrence index;
A mass combustion ratio calculating means for calculating a mass combustion ratio of the in-cylinder gas immediately before the occurrence of the knock based on the knock generation time;
Knock strength calculating means for calculating knock strength based on the mass combustion ratio immediately before the occurrence of knock;
With
Based on the knock intensity, a limit ignition timing that does not cause knock is calculated,
The ignition timing control device for an internal combustion engine according to any one of claims 1 to 3, characterized in that:

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