JP2007278083A - Intake control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To implement highly-responsive torque control by a throttle control. <P>SOLUTION: Cylinder effective capacity corresponding to an intake stroke is calculated, virtual intake pressure as an estimation value of current intake pressure is calculated, virtual cylinder intake pressure as an estimation value of a current cylinder intake amount is calculated based on the cylinder effective capacity and virtual intake pressure, a target intake pressure is calculated from the target cylinder intake amount and a cylinder effective capacity, a target intake pressure change amount is calculated from deviation between the target intake pressure and the virtual intake pressure, a target intake amount change amount is calculated, a target intake amount is calculated by adding the target intake amount change amount to the virtual cylinder intake amount, a target opening area and target opening of the throttle value are calculated so as to acquire the target intake amount, and thereby the throttle valve is controlled. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an intake control device for an engine (internal combustion engine), and more particularly to a technique for improving responsiveness in throttle control.

Conventionally, in general internal combustion engines (gasoline engines), the intake air amount is controlled by a throttle valve. However, in order to eliminate the throttle loss caused by the throttle valve and improve fuel efficiency, the operating characteristics of the intake valve (valve timing, lift) Some control the intake air amount by variably controlling the amount.
However, if the intake negative pressure is required to suck the brake negative pressure source, purge gas, blow-by gas into the intake system in a passenger car etc., it is necessary to provide a throttle valve to generate the intake negative pressure under predetermined conditions, In the low load range, since it is difficult to control the air amount by the intake valve, there is a switch to control by the throttle valve.

However, the air amount control by the throttle valve control has a large response delay compared to the air amount control by the intake valve due to the manifold volume and the transport delay to the cylinder, and high response torque control cannot be performed.
In view of the above, Patent Document 1 discloses that an intake system model in which the throttle opening is input and the engine torque is output is constructed, and the target throttle opening for obtaining the target torque is expressed as the value of each coefficient in the transfer function of the intake system model. Has been disclosed, and a technique for achieving torque control with high response is disclosed.
JP 2002-309990 A

  Patent Document 1 applies a technique called MRACS to an engine, and identifies a target engine torque or a target cylinder filling air amount corresponding to the engine torque, and a coefficient of a general transfer function that does not consider physical phenomena. However, when applied to an engine, it is practically difficult to identify the coefficient following the change in the operating state, and this compensates for accuracy variations in such feedforward control. It was also necessary to use feedback control together, and the control was extremely complicated and lacked in practicality.

  The present invention has been made by paying attention to such a conventional problem. By controlling intermediate parameters in a throttle control transfer function model in consideration of physical phenomena, an intake air of an internal combustion engine that can realize high-response torque control. An object is to provide a control device.

For this reason, the present invention
Cylinder effective volume calculation means for calculating a cylinder effective volume corresponding to the intake stroke based on the engine operating state;
Virtual cylinder intake air amount calculating means for calculating a virtual cylinder intake air amount as a current cylinder intake air amount estimated value based on the cylinder effective volume;
Throttle control means for controlling a throttle valve based on the virtual cylinder intake air amount;
Constructed including.

The cylinder effective volume is calculated, and the throttle opening is controlled based on the virtual cylinder intake amount while estimating and calculating the virtual cylinder intake amount at the current throttle opening based on the cylinder effective volume.
Therefore, based on the virtual cylinder intake amount, highly responsive torque control is realized while calculating back the target throttle opening so as to compensate for the delay due to the manifold volume and obtain the target cylinder intake amount with a desired response. be able to.

In addition, a variable valve mechanism that controls the intake air amount by changing the operating angle, lift amount, or operating angle center phase of the intake valves other than the throttle valve is desired regardless of whether the variable valve mechanism is operated or not. Torque control can be realized with this response. However, even in an internal combustion engine that does not include such a variable valve mechanism, the present invention can be applied by calculating the cylinder effective volume.
Furthermore, a desired torque response characteristic can be obtained regardless of the operating state.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram of an engine (internal combustion engine).
The combustion chamber 52 defined by the piston 51 of each cylinder of the engine 1 is provided with an intake valve 54 and an exhaust valve 55 so as to surround the spark plug 53. The intake air passes through the intake passage 56 and is sucked into the combustion chamber 52 from the intake valve 54, and a manifold portion (intake manifold) 57 is disposed in the intake passage 56. Exhaust gas in the combustion chamber 52 is discharged from the exhaust valve 55 through the exhaust passage 58.

  The intake valve 54 is controlled by a variable valve mechanism 100 having variable valve operating characteristics. As will be described later, the variable valve mechanism includes an operating angle changing mechanism 10 that continuously changes an intake operating angle and a valve lift amount that are the operating angles of the intake valve 54, and an intake center phase that is a central phase of the intake operating angle. And a phase angle changing mechanism 20 that continuously changes. As for the exhaust valve 55, the valve characteristic is fixed in the present embodiment, but the valve characteristic may be variable by a variable valve mechanism as in the intake valve.

In the intake passage 56, an electric throttle valve 59 is provided upstream of the manifold portion 57. The intake passage 56 is also provided with an electromagnetic fuel injection valve 60 at the intake port portion of each cylinder.
Here, the operation of the ignition plug 53, the variable valve operating device 100 (the operating angle changing mechanism 10, the phase angle changing mechanism 20), the electric throttle valve 59 and the fuel injection valve 60 is controlled by a control unit (ECU) 61. .

  The ECU 61 outputs a crank angle signal in synchronization with the engine rotation, thereby detecting a crank angle sensor 62 that can detect the engine rotation speed Ne together with the crank angle position θ, and an accelerator for detecting an accelerator opening (accelerator pedal depression amount). Pedal sensor 63, hot-wire air flow meter 64 for measuring the flow rate of air flowing into the manifold portion 57 upstream of the throttle valve 59 in the intake passage 56, an intake air temperature sensor 65 for detecting the temperature (intake air temperature) in the manifold portion 57, etc. The signal from is input.

The fuel injection timing and the fuel injection amount of the fuel injection valve 60 are controlled based on engine operating conditions, and the fuel injection amount is set to a desired air-fuel ratio with respect to a cylinder intake air amount controlled as described later. Control.
The ignition timing by the spark plug 53 is controlled to MBT (optimum ignition timing on torque) or a knock limit based on engine operating conditions.

FIG. 2 shows the operating angle changing mechanism. Each cylinder is provided with a pair of intake valves 54. Above these intake valves 54, a hollow intake drive shaft 3 extends in the cylinder row direction. A swing cam 4 that contacts the valve lifter 54a of the intake valve 54 and opens and closes the intake valve 54 is fitted on the intake drive shaft 3 so as to be relatively rotatable.
Between the intake drive shaft 3 and the swing cam 4, an electric operating angle changing mechanism 10 that continuously changes an intake operating angle that is an operating angle of the intake valve 2 and a valve lift amount is provided. At one end of the intake drive shaft 3, an electrically driven phase that continuously changes the intake center phase, which is the center phase of the intake operation angle, by changing the phase of the intake drive shaft 3 with respect to a crankshaft (not shown). A change mechanism 20 is provided.

  As shown in FIGS. 2 and 3, the operating angle changing mechanism 10 includes a circular drive cam 11 that is eccentrically fixed to the intake drive shaft 3 and a ring shape that is externally fitted to the drive cam 11 so as to be relatively rotatable. A link 12, a control shaft 13 extending substantially parallel to the intake drive shaft 3 in the cylinder row direction, a circular control cam 14 that is fixedly provided eccentrically with respect to the control shaft 13, and a relative rotation with the control cam 14 And a rocker arm 15 having one end connected to the tip of the ring-shaped link 12, and a rod-shaped link 16 connected to the other end of the rocker arm 15 and the swing cam 4. The control shaft 13 is driven to rotate within a predetermined control range via the gear train 18 by the electric actuator 17.

With the above configuration, when the intake drive shaft 3 rotates in conjunction with the crankshaft, the ring-shaped link 12 moves substantially in translation through the drive cam 11 and the rocker arm 15 swings around the axis of the control cam 14. Then, the swing cam 4 swings via the rod-shaped link 16 and the intake valve 2 is driven to open and close.
Further, by changing the rotation angle of the control shaft 13, the axial center position of the control cam 14 that becomes the swing center of the rocker arm 15 is changed, and the posture of the swing cam 4 is changed. As a result, the intake operation angle and the valve lift amount continuously change while the intake center phase remains substantially constant.

  In such an operating angle changing mechanism 10, since the connecting portions of the members such as the bearing portion of the drive cam 11 and the bearing portion of the control cam 14 are in surface contact, lubrication is easy and durability and reliability are improved. Are better. In addition, since the swing cam 4 that drives the intake valve 2 is arranged coaxially with the intake drive shaft 3, for example, the swing cam is supported by another support shaft different from the intake drive shaft 3. In comparison, the control accuracy is excellent, the device itself is compact, and the engine is easy to mount. In particular, the present invention can be applied to a direct-acting valve system without adding a large layout change. Further, since the biasing means such as a return spring is not required, the friction of the valve operating system is suppressed to a low level.

  FIG. 4 shows an electric phase change mechanism 20. The phase changing mechanism 20 is fixed to a cam sprocket 25 that rotates in synchronization with the crankshaft, and is fixed to one end of the intake drive shaft 3 by a first rotating body 21 that rotates integrally with the cam sprocket 25 and a bolt 22a. A second rotating body 22 that rotates integrally with the intake drive shaft 3, and a cylindrical intermediate that meshes with the inner peripheral surface of the first rotating body 21 and the outer peripheral surface of the second rotating body 22 by a helical spline 26. And a gear 23.

  A drum 27 is connected to the intermediate gear 23 via a triple screw 28, and a torsion spring 29 is interposed between the drum 27 and the intermediate gear 23. The intermediate gear 23 is urged in the retarding direction (left direction in FIG. 3) by a torsion spring 29. When a voltage is applied to the electromagnetic retarder 24 to generate a magnetic force, the intermediate gear 23 passes through the drum 27 and the triple thread screw 28. It is moved in the advance direction (right direction in FIG. 3). Depending on the position of the intermediate gear 23 in the axial direction, the relative phase of the rotating bodies 21 and 22 changes, and the phase of the intake drive shaft 3 with respect to the crankshaft changes.

The electromagnetic retarder 24 is driven and controlled in accordance with the engine operating state by a control signal from the ECU 61 described below.
FIG. 5 shows a main block diagram of intake air amount control by the throttle valve 59 performed in the ECU 61.
The cylinder effective volume calculation unit calculates the cylinder effective volume corresponding to the intake stroke of the cylinder according to the operating state of the engine 1 and the operating characteristics of the intake valve 54 (particularly, valve timing).

The virtual intake pressure calculation unit calculates a virtual intake pressure that is an estimated value of the current intake pressure (manifold internal pressure) using an internal model of the intake system based on the target opening area of the throttle valve.
The virtual cylinder intake amount calculation unit calculates a virtual cylinder intake amount that is an estimated value of the current cylinder intake amount based on the cylinder effective volume and the virtual intake pressure.
On the other hand, the target cylinder air amount calculation unit calculates a target cylinder air amount corresponding to the target torque based on the accelerator opening APO, the engine speed Ne, and the like.

The target intake pressure calculation unit calculates a target intake pressure for realizing a target cylinder intake amount in the current cylinder effective volume.
The time constant calculation unit calculates a reference response time constant τ _pm for realizing the target intake pressure with a target response according to the drivability and other requirements.
The target intake pressure change amount calculation unit calculates the target intake pressure change amount based on the deviation between the target intake pressure and the virtual intake pressure and the reference response time constant τ _pm .

The target intake air amount change amount calculation unit converts the target intake air pressure change amount into a target intake air amount change amount (mass change amount).
The target intake air amount per time passing through the throttle valve is calculated by adding the target intake air amount change amount to the virtual cylinder intake air amount (converted into an amount per hour).
The target opening area calculation unit calculates the target opening area of the throttle valve 59 based on the target intake air amount.

The target opening calculation unit converts the target opening area into the target opening of the throttle valve 59.
The throttle valve control unit controls the throttle valve 59 based on the target opening.
Next, the detail of each said calculation part is demonstrated.
First, details of the cylinder effective volume calculation unit will be described based on the block diagram shown in FIG.
Statically, the stroke volume is a value obtained by subtracting the cylinder volume at the top dead center TDC from the cylinder volume at the intake valve closing timing IVC, but actually, the intake stroke start timing and end timing are respectively the top dead center. Deviation occurs at the point TDC and the intake valve closing timing IVC.

FIG. 7 shows changes in valve characteristics, in-cylinder pressure, and intake valve passage air flow rate during the intake stroke. Note that the intake valve closing timing IVC is controlled after bottom dead center.
As shown in the figure, before the intake valve closing timing IVC, the cylinder internal pressure reaches the intake pressure and the adiabatic compression change starts, that is, the intake stroke ends. The advance amount of the timing at which the actual intake stroke ends with respect to the intake valve closing timing IVC increases as the engine rotational speed Ne increases and as the valve lift amount decreases, the influence of inertia increases.

Therefore, in FIG. 6, first, the valve lift amount (maximum lift amount) Iv is calculated from the valve characteristics of the intake valve determined by the intake valve opening timing IVO and the intake valve closing timing IVC.
Next, a map using the advance amount as the IVC offset amount and the engine speed Ne and the valve lift amount as parameters is set, the IVC offset amount IVCOFS is obtained with reference to the map, and the IVC offset amount from the intake valve closing timing IVC is obtained. The crank angle position obtained by subtracting IVCOFS is calculated as the effective IVC at which the intake stroke ends.

  On the other hand, the deviation from the intake top dead center TDC at the time when the intake pressure due to the adiabatic expansion starts when the cylinder internal pressure coincides with the intake pressure is caused by exhaust blowback due to valve overlap. That is, as shown in FIG. 7, after the intake valve opens in the valve overlap state, the cylinder internal pressure gradually decreases from the exhaust pressure and becomes equal to the intake pressure PMAN after the intake top dead center TDC. The intake stroke by expansion is started. Since the opening area is small in the vicinity of the start of the intake valve opening, the decrease in the cylinder internal pressure is small, and the substantial decrease starts from the vicinity of the overlap center angle O / LCA at which the exhaust blowback flow rate becomes maximum. The amount of delay from when the cylinder internal pressure begins to drop to when the actual intake stroke starts (effective TDC) increases as the engine speed Ne increases and as the valve overlap amount (overlap opening area) decreases. As the influence of the pressure increases, the decrease in the cylinder internal pressure increases.

  Therefore, as shown in FIG. 6, first, the intake valve opening timing IVO and the intake valve closing timing IVC are input, and the overlap center angle O / LCA is calculated. Specifically, based on the valve characteristic IV of the intake valve determined by the intake valve opening timing IVO and the intake valve closing timing IVC, and the known exhaust valve valve characteristic EV, the lift amount of both characteristics matches (intersection point) ) Is calculated as the overlap center angle O / LCA.

Next, an overlap opening area O / LA (= intake valve opening area = exhaust valve opening area) with respect to the overlap center angle O / LCA is calculated with reference to a preset map. The overlap opening area O / LA has a larger characteristic as the overlap center angle O / LCA is smaller (when it is on the advance side).
Next, using the engine speed Ne and the overlap opening area O / LA as parameters, a map is set in which the delay amount from the overlap center angle O / LCA to the effective TDC is set as the TDC offset amount. Thus, the TDC offset amount TDCOFS is obtained, and the crank angle position obtained by adding the TDC offset amount TDCOFS to the overlap center angle O / LCA is calculated as the effective TDC.

In FIG. 6, the intake valve opening timing IVO, the intake valve closing timing IVC, and the effective TDC are inputted, and the cylinder volume VETDC at the effective TDC is calculated from the valve characteristics of the intake valve with reference to the map. The IVC and effective IVC are input, and the cylinder volume VEIVC at the effective IVC is calculated with reference to the map.
By subtracting the cylinder volume VETDC from the cylinder volume VEIVC, a cylinder effective volume VE (= VEIVC-VETDC) is calculated.

Next, details of the virtual intake pressure calculation unit will be described with reference to FIG.
In the upper right part of FIG. 8, the manifold internal pressure P in the actual opening area Atvo is obtained by applying the operation delay correction process {transfer function e ^−Ls / (T ₁ +1)} of the throttle valve 59 to the target opening area tAtvo. A model of a manifold plant for calculating _M is shown, and a virtual value as a predicted value when the target value is controlled is calculated using the model of the manifold plant. Hereinafter, the virtual value will be described with “′” added to the actual value.

A first order delay correction process {transfer function: 1 / (T ₁ s + 1)} is applied to the target opening area tAtvo of the throttle valve 59 calculated by the target opening area calculation unit in order to compensate for the delay from the throttle valve to the cylinder. TAtvo _H , the virtual intake air amount Q _A ′ is calculated by the following equation (transfer function K1).

P _A : Atmospheric pressure P _M : Manifold internal pressure = Intake pressure tA _TVOH : Target opening area after first-order lag correction R: Gas constant T _A : Atmospheric temperature = Intake temperature κ: Specific heat ratio Calculated based on the target opening area Deviation between the intake flow rate Q _A ′ per time flowing through the throttle valve and flowing into the manifold, and the outflow amount from the manifold calculated as described later, that is, the inflow amount Q _E ′ per time into the cylinder (= Q _A '-Q _E ') is calculated.

Next, the intake air amount deviation is converted into an intake pressure change amount (ΔP _M / Δt) ′ (transfer function: K2).
(ΔP _M / Δt) ′ = RT _A / V _M · (Q _A ′ −Q _E ′) (2)
V _M : Manifold volume The intake air pressure change amount (ΔP _M / Δt) ′ is integrated to calculate a virtual intake pressure P _M ′ (transfer function: 1 / s).

Next, the virtual cylinder intake air amount calculation unit will be described.
Based on the virtual intake pressure P _M ′ and the cylinder effective volume VE, a virtual cylinder intake amount Q _C ′ per cylinder is calculated by the following equation (transfer function: K3).
_{Q C '= P M' ·} VE / (RT A) ··· (3)
Next, the virtual cylinder intake air quantity Q _C, is converted into the flow rate Q _E per time by the following equation (transfer function: K4).

Q _E '= Q _C ' · n _cyl / 2 · Ne / 60 (4)
n _cyl : Total number of cylinders of the engine The virtual cylinder intake amount Q _E ′ per time is used for calculating the deviation from the next calculated intake flow rate Q _A ′ as described above, and the target as described later. used for calculating the intake air amount tQ _a.

Next, the target intake pressure calculation unit will be described.
The target cylinder intake air quantity tQ _C of the target torque equivalent calculated by the target cylinder intake air quantity calculation section as described above, the target intake pressure tP _M for realizing the current effective cylinder volume VE, calculated by the following equation.
_{tP M = tQ C · RT A} / VE ··· (5)
Next, the target intake pressure change amount calculation unit will be described.

Based on the deviation _{ΔP M (= tP M -P M} ) between the target intake pressure tP _M and virtual intake pressure _{P M,} so that the target intake pressure tP _M are realized nominal response time constant tau _pm, the target intake pressure A change amount t (ΔP _M / Δt) is calculated (transfer function: G = 1 / τ _pm ).
Next, the target intake air amount change amount calculation unit will be described.
Based on the intake air temperature T _A , the manifold volume V _M , and the gas constant R, the target intake air pressure change amount is converted into a target intake air amount change amount (mass change amount) t (ΔM _M / Δt) by the following equation (transmission) Function: 1 / K2).

t (ΔM _M / Δt) = t (ΔP _M / Δt) · V _M / (RT _A ) (6)
Next, the target intake air amount calculation unit will be described.
As shown in the following equation, the target intake air amount tQ _A per time passing through the throttle valve is calculated by adding the target intake air amount change amount t (ΔQ _A / Δt) to the virtual cylinder intake air amount Q _E.

tQ _A = Q _E + t (ΔQ _A / Δt) (7)
Next, the target opening area calculation unit will be described.
Based on the target intake air amount tQ _A , a target opening area tA _TVO of the throttle valve 59 is calculated by the following equation (transfer function: 1 / K).

The target opening calculation unit converts the target opening area tA _TVO into the target opening tTVO of the throttle valve 59 using a map or an arithmetic expression.
The throttle controller controls the throttle valve 59 by driving a throttle actuator based on the target opening degree tTVO.
As described above, in the present embodiment, the cylinder effective volume VE is calculated based on the engine operating state and the valve operating characteristics of the intake valve, and is an estimated value in which the current manifold internal pressure is set to the intake pressure according to the model of the manifold plant. calculating a virtual intake pressure P _M, based on the virtual cylinder intake air amount calculated by multiplying the virtual intake pressure P _M and these effective cylinder volume VE, the target cylinder in response (nominal response time constant tau _PM) to the target Since the throttle control is performed so as to obtain the intake air amount, the delay due to the volume of the manifold portion is compensated, and the torque control with high response equivalent to the torque control with the variable valve mechanism can be realized.

In addition, a desired torque response can be realized, such as a variable response according to the operating state, and the same response can be realized regardless of whether or not the variable valve mechanism is activated.
Further, complicated control such as identification of a transfer function coefficient and feedback control as in Patent Document 1 is not required, and control of intermediate parameters (manifold internal pressure) in a throttle control transfer function model considering physical phenomena is performed. By performing torque control, simple and highly accurate control can be realized.

  In addition, in patent document 1, although it is the structure which detects actual intake pressure and performs feedback control, the influence of intake pressure fluctuation (noise) comes out in that case, or it detects atmospheric pressure fall by high altitude driving | running | working Before the accelerator opening becomes fully open, the output becomes fully open and the drivability may be adversely affected, but the virtual intake pressure estimated in the present invention is not affected by intake pressure fluctuations or atmospheric pressure changes. Good drivability can be maintained.

1 is a diagram showing a configuration of an internal combustion engine (engine) according to an embodiment of the present invention. It is a perspective view which shows the operating angle change mechanism with which an engine same as the above is equipped. It is a partially expanded side view of an operating angle change mechanism same as the above. It is a figure which shows the phase change mechanism with which an engine same as the above is equipped. It is a main block diagram of intake air amount control of an embodiment same as the above. It is a block diagram Q of the cylinder effective volume calculation part of embodiment same as the above. It is a time chart which shows the mode of a change of the valve characteristic at the time of an intake stroke of the embodiment same as the above, a cylinder pressure, and an intake valve passage air flow rate. It is a block diagram which shows the detail of each calculation part of embodiment same as the above.

Explanation of symbols

1 engine (internal combustion engine)
DESCRIPTION OF SYMBOLS 10 Operation | movement change mechanism 20 Phase change mechanism 54 Intake valve 57 Manifold part 59 Electric throttle valve 61 ECU
62 Crank angle sensor 63 Accelerator pedal sensor 64 Air flow meter 65 Intake air temperature sensor

Claims (6)

Cylinder effective volume calculation means for calculating a cylinder effective volume corresponding to the intake stroke based on the engine operating state;
Virtual cylinder intake air amount calculating means for calculating a virtual cylinder intake air amount as a current cylinder intake air amount estimated value based on the cylinder effective volume;
Throttle control means for controlling a throttle valve based on the virtual cylinder intake air amount;
An intake control device for an internal combustion engine, comprising:   The internal combustion engine according to claim 1, further comprising means for calculating a target cylinder intake air amount, wherein the throttle control means controls the throttle valve so that the target cylinder intake air amount is obtained with a target response. Intake control device.   3. The internal combustion engine according to claim 1, wherein the effective stroke volume calculating unit calculates the cylinder effective volume based on a valve characteristic of an intake valve that is variably controlled and an engine operating state. 4. Intake control device.   Virtual cylinder intake pressure estimating means for calculating a virtual cylinder intake pressure as a current cylinder intake pressure estimated value is provided, and the virtual cylinder intake amount is calculated based on the virtual cylinder intake pressure and the cylinder effective volume. An intake control device for an internal combustion engine according to any one of claims 1 to 3.   Means for calculating a reference response time constant; means for calculating a target intake pressure; and means for calculating a target throttle opening based on the virtual intake pressure, target intake pressure, reference response time constant, and virtual cylinder intake amount. The intake control device for an internal combustion engine according to claim 4, comprising:   6. The apparatus according to claim 5, further comprising means for calculating a target cylinder intake air amount, wherein the means for calculating the target intake air pressure calculates a target intake air pressure based on a target cylinder intake air amount and a cylinder effective volume. An intake control device for an internal combustion engine.

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