JP2001227399A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress torque fluctuations in changeover of a combustion mode of a cylinder injection engine. SOLUTION: To suppress torque fluctuations generated by changes in control parameters (throttle opening, EGR quantity, etc.), adjusted for holding the stable combustion state before/after the changeover of the combustion mode, a request illustration torque is corrected by the torque efficiency (air-fuel ration efficiency and ignition timing efficiency) in the homogenous combustion mode so that a target air quantity set according to the request illustration torque is corrected. In the stratified charge combustion mode, the request illustration torque is corrected by the torque efficiency (air-fuel ratio efficiency) so that a target air quantity set according to the request illustration torque is corrected. In the stratified charge combustion mode, the torque fluctuation may be suppressed by the correction of the ignition timing besides the correction of the target quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for an internal combustion engine for controlling the operation of an internal combustion engine having a function of suppressing a torque fluctuation contrary to a driver's intention.

[0002]

2. Description of the Related Art In recent years, the demand for an in-cylinder injection type engine (direct injection type engine) having features of low fuel consumption, low exhaust emission, and high output has been rapidly increasing. At the time of low load, this in-cylinder injection engine improves fuel efficiency by directly injecting a small amount of fuel into the cylinder in a compression stroke to form a stratified mixture and perform stratified combustion. The engine output is increased by increasing the injection amount and injecting directly into the cylinder during the intake stroke to form a homogeneous mixture and perform homogeneous combustion. In this in-cylinder injection engine, the throttle opening and the exhaust ring flow rate (EGR amount) are adjusted before and after switching the combustion mode to maintain a stable combustion state. However, if the throttle opening and the EGR valve opening are adjusted when switching the combustion mode, the air-fuel ratio in the cylinder and the pumping loss torque change due to the effect.
The shaft torque of the engine fluctuates, causing a step (torque shock) in the shaft torque.

Therefore, in Japanese Patent Application Laid-Open No. 11-22517, when switching from the stratified combustion mode (compression stroke injection mode) to the homogeneous combustion mode (intake stroke injection mode), the air-fuel ratio is corrected to change the combustion mode. The step of the shaft torque is reduced.

[0004]

However, in order to switch the combustion mode while maintaining the combustion in a stable state at the time of switching the combustion mode, it is necessary to switch while always maintaining the air-fuel ratio at an appropriate value. Therefore, as described in the above publication, if the air-fuel ratio is corrected to suppress the torque fluctuation when switching the combustion mode, the air-fuel ratio may deviate from an appropriate value, and the combustion state may become unstable.

Further, in the lean burn engine, since the lean operation is performed in a low load region and the air-fuel ratio is switched to stoichiometric or rich in a high load region, the torque fluctuation is caused even when switching between lean operation and stoichiometric rich operation. Occurs. Further, in a lean burn engine equipped with a NOx storage reduction type lean NOx catalyst, NO
It is necessary to intermittently switch to the stoichiometric rich operation during the lean operation in order to occlude x and reduce and purify the NOx occluded during the stoichiometric rich operation. In this case also, torque fluctuation occurs. Further, even in a normal intake port injection type engine, for example, when switching between catalyst warm-up control (ignition retard control) and normal control, torque fluctuation occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and therefore has as its object to suppress torque fluctuation while maintaining combustion stability even when a control parameter causing torque fluctuation is adjusted. It is an object of the present invention to provide a control device for an internal combustion engine that can improve drivability.

[0007]

According to a first aspect of the present invention, there is provided a control apparatus for an internal combustion engine, wherein a control parameter causing a torque fluctuation is adjusted based on an operation state of the internal combustion engine. Sometimes, the torque fluctuation suppressing means converts the amount of torque fluctuation due to the adjustment amount of the control parameter into the amount of change of the control parameter not involved in the adjustment, and changes the control parameter by the amount of the change, thereby changing the torque fluctuation. Is suppressed. For example, when the throttle opening and the exhaust gas flow rate (EGR amount) are adjusted in order to maintain a stable combustion state, the amount of torque variation due to the opening adjustment amount is not controlled by a control parameter (for example, (Amount of fuel, ignition timing, etc.), and the control parameter is changed by the amount of change to suppress torque fluctuation. In this way, even when the control parameter that causes the torque fluctuation is adjusted,
Torque fluctuation can be suppressed while maintaining combustion stability, and drivability can be improved.

The present invention is applicable to any of a lean burn engine, an intake port injection engine, and a direct injection engine. When the present invention is applied to a direct injection engine, a torque fluctuation caused by a change in a control parameter adjusted to maintain a stable combustion state before and after the combustion mode switching is stratified. In the combustion mode, suppression is performed by correcting the fuel amount, and in the homogeneous combustion mode, suppression is performed by correcting the air amount and / or the ignition timing. That is, in the stratified combustion mode, since the engine output is controlled by the fuel amount, the torque fluctuation that occurs immediately after switching to the stratified combustion mode or immediately before switching to the homogeneous combustion mode can be effectively suppressed by correcting the fuel amount. it can. In addition, in the homogeneous combustion mode, as in the case of the intake port injection engine, the engine output is controlled by the amount of air, so that the torque fluctuation that occurs immediately after switching to the homogeneous combustion mode or immediately before switching to the stratified combustion mode is caused by the variation of the air amount. It can be suppressed by correction. Furthermore, in the homogeneous combustion mode, since the range of ignition timing at which stable combustion can be performed is relatively wide,
The torque fluctuation can also be suppressed by correcting the ignition timing. Since the correction of the ignition timing has a better response of the torque correction than the correction of the air amount, in the correction of the air amount, if the torque correction is not in time, if the correction of the ignition timing is performed,
Torque fluctuation can be suppressed with good responsiveness.

In this case, in the stratified combustion mode, the fuel amount is corrected by correcting the required torque when the required torque is converted into the fuel amount, and in the homogeneous combustion mode, the required torque is converted to the air. The air amount may be corrected by correcting the required torque when converting the air amount. Even in this case, the same effect as that of the second aspect can be obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a direct injection engine will be described below with reference to the drawings. First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner (not shown) is provided at the most upstream portion of the intake pipe 12 of the direct injection engine 11 which is a direct injection internal combustion engine, and an air for detecting an intake air amount is provided downstream of the air cleaner. A flow meter 13 is provided. A throttle valve 15 whose opening is adjusted by a motor 14 such as a DC motor is provided downstream of the air flow meter 13. This motor 1
4 is driven based on an output signal from an engine electronic control circuit (hereinafter referred to as “ECU”) 16,
The opening of the throttle valve 15 (throttle opening) is controlled, and the amount of intake air to each cylinder (in-cylinder air amount) is adjusted according to the throttle opening.

A surge tank 17 is provided downstream of the throttle valve 15.
An intake pressure sensor 18 for detecting the intake pressure Pm is attached. An intake manifold 19 for introducing air into each cylinder of the engine 11 is connected to the surge tank 17. A swirl control valve 20 for controlling a swirl flow in the cylinder of the engine 11 is provided in the intake manifold 19 of each cylinder. Is provided.

A fuel injection valve 21 for directly injecting fuel into the cylinder is mounted on an upper portion of each cylinder of the engine 11, and the fuel in a fuel tank 22 is pressurized to a high pressure by a fuel pump 23 to thereby increase the fuel in each cylinder. The fuel is supplied to the injection valve 21 and the fuel pressure (fuel pressure) is detected by the fuel pressure sensor 24. An ignition plug 25 is attached to a cylinder head of the engine 11 for each cylinder, and the mixture in the cylinder is ignited by spark discharge of each ignition plug 25.

An intake valve 26 and an exhaust valve 27 of the engine 11 are driven by camshafts 28 and 29, respectively, and a camshaft 28 on the intake side is provided with a hydraulic type for changing the opening / closing timing of the intake valve 26 in accordance with the operation state. The variable valve timing mechanism 30 is provided. The hydraulic pressure for driving the variable valve timing mechanism 30 is controlled by the hydraulic control valve 3
1 is controlled. The reciprocating motion of the piston 32 of each cylinder of the engine 11 drives the crankshaft 33 to rotate, and the torque of the crankshaft 33 drives the external load 34 (compressor, alternator, pump for power steering, etc.) and the vehicle drive system. Is done.
A water temperature sensor 35 for detecting a cooling water temperature is attached to a cylinder block of the engine 11.

On the other hand, a catalyst 37 such as a three-way catalyst for purifying exhaust gas is provided in an exhaust pipe 36 of the engine 11, and an air-fuel ratio sensor 38 for detecting an air-fuel ratio of exhaust gas is provided upstream of the catalyst 37. ing. An EGR pipe 39 for recirculating a part of the exhaust gas to the intake side is provided between the upstream side of the air-fuel ratio sensor 38 of the exhaust pipe 36 and the surge tank 17.
An EGR valve 40 for controlling the exhaust gas flow rate (EGR amount) is provided in the middle of the EGR pipe 39.

ECU 16 for controlling the operating state of the engine
Is mainly composed of a microcomputer, and executes a torque demand control program stored in a ROM (storage medium) of the microcomputer, whereby a required illustrated torque calculating means 51, a combustion mode switching means 52, a homogeneous combustion mode The functions of the control means 53, the stratified combustion mode control means 54, and the target air-fuel ratio setting means 55 are realized. Hereinafter, each of these functions will be specifically described.

The required indicated torque calculating means 51 calculates the required indicated torque based on the output of an accelerator sensor 41 (see FIG. 1) for detecting the opening of the accelerator pedal (accelerator opening). Here, the required indicated torque is a required value (target value) of the indicated torque, and the indicated torque is the engine 11
, Ie, torque including internal loss torque of the engine 11 and external load torque (load of accessories). Therefore, the torque obtained by subtracting the internal loss torque and the external load torque from the indicated torque becomes the shaft torque (net torque) extracted from the crankshaft 33, and the vehicle drive system is driven by the shaft torque.

The required indicated torque calculating means 51 calculates a required shaft torque based on the output (accelerator opening) of the accelerator sensor 41, the engine rotation speed Ne, the vehicle speed, and the like. , And the idle speed control (I
The required indicated torque is obtained by correcting the increase or decrease of the torque by the SC control). Here, the internal loss torque to be added to the required shaft torque is a mechanical friction loss and a pumping loss. The mechanical friction loss is calculated by a map or a mathematical formula based on the engine rotation speed Ne and the cooling water temperature THW. Is calculated by a map or a mathematical expression based on the engine rotation speed Ne and the intake pressure Pm. The external load torque to be added to the required shaft torque is a load torque of accessories (an air conditioner compressor, an alternator, a power steering pump, etc.) driven by the power of the engine 11, and includes an air conditioner signal and an alternator field current. It is set according to the like.

Further, the required indicated torque calculating means 51 obtains the required indicated torque by correcting the required shaft torque obtained by adding the internal loss torque and the external load torque by a torque increase / decrease by idle speed control (ISC control). . Correction torque by ISC control (torque increase / decrease)
Is calculated by a map or a mathematical expression based on the target idle rotation speed Netarget and the current engine rotation speed Ne.

On the other hand, the target air-fuel ratio setting means 55 sets a target air-fuel ratio (target A / F) using a map or the like based on the required indicated torque calculated by the required indicated torque calculating means 51 and the engine speed Ne. The target air-fuel ratio is determined by the homogeneous combustion mode control means 53 and the stratified combustion mode control means 54.
Used in both.

The combustion mode switching means 52 switches the combustion mode by selecting either the homogeneous combustion mode control means 53 or the stratified combustion mode control means 54 from a map or the like according to the engine speed Ne and the required indicated torque. For example, in the low rotation region and the low torque region, the stratified combustion mode control means 54 is selected, and the operation is performed in the stratified combustion mode.
During the stratified combustion mode operation, a small amount of fuel is directly injected into the cylinder in the compression stroke to form a stratified mixture and perform stratified combustion, thereby improving fuel efficiency. In the middle / high rotation range and the middle / high torque range, the homogeneous combustion mode control means 5
3 is selected and operated in the homogeneous combustion mode. During the homogeneous combustion mode operation, the engine output and the shaft torque are increased by increasing the fuel injection amount and injecting directly into the cylinder during the intake stroke to form a homogeneous mixture and perform homogeneous combustion.

Next, each function of the homogeneous combustion mode control means 53 will be described with reference to FIG. The homogeneous combustion mode control means 53 includes a torque efficiency correction means 56 (corresponding to a torque fluctuation suppression means) for suppressing torque fluctuation at the time of switching the combustion mode, and sets the required indicated torque corrected by the torque efficiency correction means 56 to a target torque. The air demand type torque demand control which sets the throttle opening degree by converting into the air amount is performed. The torque efficiency correction means 56 takes into account that torque fluctuations may occur due to changes in control parameters (ignition timing and in-cylinder air-fuel ratio) that are adjusted to maintain a stable combustion state before and after the combustion mode switching, and a request diagram. The torque is corrected by the following equation using ignition timing efficiency (SA efficiency) and air-fuel ratio efficiency (A / F efficiency). Required indicated torque after correction = Required indicated torque / (ignition timing efficiency × air-fuel ratio efficiency)

Here, the ignition timing efficiency is a dimensionless parameter for evaluating the effect of the ignition retard amount on the indicated torque, and is set by a map according to the ignition retard amount as shown in FIG. When the ignition retard amount is 0, the indicated torque becomes maximum. Therefore, when the ignition retard amount is 0, the ignition timing efficiency is set to 1. In other words, the ignition timing efficiency represents the magnitude of the indicated torque corresponding to the ignition retard amount relative to the magnitude of the indicated torque when the ignition retard amount is 0 as “1”. Things.

The air-fuel ratio efficiency is a dimensionless parameter for evaluating the effect of the in-cylinder air-fuel ratio on the indicated torque. As shown in FIG. 5, the air-fuel ratio efficiency is set by a map according to the target air-fuel ratio described above. You. In other words, the air-fuel ratio efficiency represents the magnitude of the indicated torque corresponding to the target air-fuel ratio with reference to the magnitude of the indicated torque at the reference air-fuel ratio being “1”. The map of the ignition timing efficiency and the map of the air-fuel ratio efficiency are set in advance by experiments or simulations and stored in the ROM of the ECU 16.

The homogeneous combustion mode control means 53 calculates a target air amount from a map or the like based on the required indicated torque corrected by the torque efficiency correction means 56 and the engine rotation speed Ne, and calculates the target air amount and the engine rotation speed Ne, Target EG
A throttle opening command value is calculated using an air system reverse model based on the R amount, the internal EGR amount (the advance amount of the variable valve timing mechanism 30), and the like. Here, the air system inverse model is a model obtained by reversing the input / output relationship of the air system model simulating the flow of air from the throttle valve 15 to the intake port. A control signal corresponding to the throttle opening command value calculated by the air system inverse model is output to the motor 14 of the electronic throttle system, and the throttle valve 15 is driven to control the throttle opening.

The homogeneous combustion mode control means 53 calculates a target fuel amount by dividing the estimated in-cylinder air amount (or actual air amount) by the target air-fuel ratio, and various correction coefficients (water temperature) are added to the target fuel amount. Correction coefficient, feedback correction coefficient, learning correction coefficient, etc.) to obtain a final fuel injection amount, and an injection pulse having a pulse width corresponding to the fuel injection amount is supplied to the fuel injection valve 21 in the intake stroke of each cylinder. Output and execute fuel injection. As a result, during the homogeneous combustion mode operation, the fuel is directly injected into the cylinder during the intake stroke to form a homogeneous mixture and perform homogeneous combustion.

Further, the homogeneous combustion mode control means 53 calculates a target EGR amount from a map or the like in accordance with the operation state,
The EGR valve 40 is driven according to the calculation result to
The R amount is controlled to the target EGR amount. In addition, the homogeneous combustion mode control means 53 calculates the ignition timing of each cylinder according to the operating state using a map or the like, and stores the ignition timing in the ignition plug 25.
, A high voltage is applied to generate spark discharge. The ignition timing efficiency described above is calculated from the retard amount of the ignition timing by using the map of FIG.

Next, each function of the stratified combustion mode control means 54 will be described with reference to FIG. The stratified combustion mode control means 54 includes a torque efficiency correction means 57 (corresponding to a torque fluctuation suppression means) for suppressing a torque fluctuation at the time of switching the combustion mode, and sets the required indicated torque corrected by the torque efficiency correction means 57 to a target. The target fuel amount is converted to a fuel amount, the target air amount is multiplied by the target air-fuel ratio, the target air amount is obtained, and a fuel priority type torque demand control for setting the throttle opening is performed. The torque efficiency correction means 57 considers that a torque fluctuation occurs due to a change in a control parameter (air-fuel ratio in a cylinder) adjusted to maintain a stable combustion state before and after the combustion mode switching, and reduces the required indicated torque to an empty state. The required indicated torque is corrected by dividing by the fuel ratio efficiency. Required indicated torque after correction = Required indicated torque / Air-fuel ratio efficiency

Here, the method of calculating the air-fuel ratio efficiency is calculated by the map shown in FIG. 5 according to the above-mentioned target air-fuel ratio as in the case of the homogeneous combustion mode control means 53. Note that, in the stratified combustion mode, the range of the ignition timing at which stable combustion can be performed is extremely narrow, and the ignition timing is not corrected so as to cause torque fluctuation.
It is not necessary to consider ignition timing efficiency.

The stratified combustion mode control means 54 calculates a target fuel amount by a map or the like based on the required indicated torque corrected by the torque efficiency correction means 57 and the engine speed Ne, and various correction coefficients are added to the target fuel amount. (A water temperature correction coefficient, a feedback correction coefficient, a learning correction coefficient, etc.) to obtain a final fuel injection quantity, and an injection pulse having a pulse width corresponding to the fuel injection quantity is supplied to the fuel injection valve in the compression stroke of each cylinder. 21 to execute fuel injection. This allows
During the stratified charge combustion mode operation, the fuel is directly injected into the cylinder in the compression stroke to form a stratified mixture and perform stratified charge combustion.

Further, the stratified combustion mode control means 54 calculates the ignition timing according to the target fuel amount and the engine speed Ne by using a map or the like, and applies a high voltage to the ignition plug 25 at the ignition timing to generate the spark discharge. generate.

The stratified combustion mode control means 54 calculates a target air amount by multiplying the target fuel amount by the target air-fuel ratio.
The target air amount, the engine speed Ne, and the target EGR
The throttle opening command value is calculated using an air system reverse model based on the amount, the internal EGR amount (the advance amount of the variable valve timing mechanism 30), and the like, and a control signal corresponding to the throttle opening command value is calculated. Motor 14 for electronic throttle system
And the throttle valve 15 is driven to control the throttle opening. Further, the EGR valve 40 is driven according to the target EGR amount to control the EGR amount to the target EGR amount.

The torque demand control of the in-cylinder injection type engine 11 described above is executed by the ECU 16 in a procedure as shown in FIGS. First, step 10
In step 1, the required shaft torque is calculated based on the output of the accelerator sensor 41 (accelerator opening), the engine rotation speed Ne, the vehicle speed, and the like. In the next step 102, the required shaft torque is added to the internal loss torque (mechanical friction loss and The pumping loss) and the external load torque are added, and the required indicated torque is obtained by correcting the torque consumed by the ISC control from the torque. Thereafter, the routine proceeds to step 103, where one of the homogeneous combustion mode and the stratified combustion mode is selected from a map or the like according to the required indicated torque and the engine rotation speed Ne.

When operating in the homogeneous combustion mode, the process proceeds from step 104 to step 105, and
The target air-fuel ratio is set on a map or the like based on the required indicated torque and the engine rotation speed Ne obtained in step 2, and the target EGR amount is set on a map or the like according to the driving state. Thereafter, the process proceeds to Step 106, and Step 10 is performed.
The required indicated torque obtained in step 2 is corrected by the following equation based on the ignition timing efficiency and the air-fuel ratio efficiency. Required indicated torque after correction = Required indicated torque / (ignition timing efficiency × air-fuel ratio efficiency)

Thereafter, the routine proceeds to step 107, where a target air amount is calculated by a map or the like based on the corrected required indicated torque and the engine rotation speed Ne, and the target air amount, the engine rotation speed Ne, the EGR rate and the like are calculated. Then, a command value of the throttle opening is calculated using an air system inverse model (step 108). Thereafter, a control signal corresponding to the command value of the throttle opening is transmitted to the motor 14 of the electronic throttle system.
To control the throttle opening by driving the throttle valve 15 (step 109).

During the operation in the homogeneous combustion mode, in step 110, the ignition timing is calculated from a map or the like according to the operation state, and an igniter (not shown) is driven in accordance with the ignition timing to execute ignition. (Step 111). In step 112, the target opening of the EGR valve 40 is calculated according to the target EGR amount, and the EGR rate is estimated (step 113), and this EGR rate is reflected in the calculation of the throttle opening (step 108). . Then, in step 114, the EGR valve 40 is driven to the target opening to control the EGR amount to the target EGR amount.

During the operation in the homogeneous combustion mode, the output of the air flow meter 13 (the amount of air passing through the throttle) and the output of the intake pressure sensor 18 (the intake pressure Pm) are read in steps 115 and 116 to obtain the air passing through the throttle. The amount and the intake pressure Pm are detected. The intake pressure Pm is used to calculate a pumping loss when calculating the required indicated torque in step 102. The pumping loss is calculated by a map or a mathematical expression based on the intake pressure Pm and the engine speed Ne.

After the detection of the amount of air passing through the throttle and the intake pressure Pm, the routine proceeds to step 117, where the estimated in-cylinder air amount is calculated from the amount of air passing through the throttle, the intake pressure Pm, and the engine speed Ne using the in-cylinder air amount estimation model. I do. Thereafter, the target fuel amount is calculated by dividing the estimated in-cylinder air amount by the target air-fuel ratio (step 118), and various correction coefficients (water temperature correction coefficient, feedback correction coefficient, learning correction coefficient, etc.) are added to the target fuel amount. Is multiplied to obtain a final fuel injection amount (step 119). Thereafter, an injection pulse having a pulse width corresponding to the fuel injection amount is supplied to the fuel injection valve 2 during the intake stroke of each cylinder.
1 to execute fuel injection (step 120).
As a result, during the homogeneous combustion mode operation, fuel is directly injected into the cylinder during the intake stroke to form a homogeneous mixture and perform homogeneous combustion.

On the other hand, when operating in the stratified combustion mode,
Proceeding from step 104 to step 121 in FIG. 7, the target air-fuel ratio is set on a map or the like based on the required indicated torque and the engine rotation speed Ne obtained in step 102, and the target EGR amount is mapped on the map according to the driving state. Set by. Thereafter, the routine proceeds to step 122, where the required indicated torque obtained in step 102 is corrected by the following equation using the air-fuel ratio efficiency. Required indicated torque after correction = Required indicated torque / Air-fuel ratio efficiency

Thereafter, the routine proceeds to step 123, where a target fuel amount is calculated by a map or the like based on the required torque indicated after the correction and the engine speed Ne, and various correction coefficients (water temperature correction coefficient, (A feedback correction coefficient, a learning correction coefficient, etc.) to obtain a final fuel injection amount (step 124), and an injection pulse having a pulse width corresponding to the fuel injection amount is supplied to the fuel injection valve 2 in the compression stroke of each cylinder.
1 to execute fuel injection (step 125).
Thus, during the stratified charge combustion mode operation, the fuel is directly injected into the cylinder during the compression stroke to form a stratified mixture and perform stratified charge combustion.

Further, during the operation in the stratified combustion mode, the target air amount is determined by multiplying the target air-fuel ratio and the target fuel amount (step 126), and the target air amount and the engine speed Ne are determined.
A command value for the throttle opening is calculated using an air system inverse model based on the above-mentioned parameters (step 127), and a control signal corresponding to the command value for the throttle opening is output to the motor 14 of the electronic throttle system, and the throttle valve is controlled. 15 to drive the throttle opening (step 128). Further, in step 129, the target opening of the EGR valve 40 is calculated according to the target EGR amount, and the EGR rate is estimated (step 130), and this EGR rate is reflected in the calculation of the throttle opening (step 127). . Then, in step 131, the EGR valve 40 is driven to the target opening to control the EGR amount to the target EGR amount. Further, in step 132, the ignition timing is calculated from a map or the like according to the operation state, and an igniter (not shown) is driven to perform ignition in accordance with the ignition timing (step 133).

According to the control method of the direct injection engine 11 of the present embodiment described above, the control parameters (at least the throttle opening and the EGR amount) adjusted to maintain a stable combustion state before and after the combustion mode switching is performed. ), The target fuel amount is corrected in the stratified combustion mode (steps 122 and 123), and the target air amount is corrected in the homogeneous combustion mode (steps 106 and 107). Torque fluctuation can be suppressed while maintaining combustion stability, and drivability can be improved.

In general, in the homogeneous combustion mode, since the range of ignition timing at which stable combustion can be performed is relatively wide, torque fluctuation can be suppressed even by correcting the ignition timing. Since the correction of the ignition timing has better responsiveness of the torque correction than the correction of the air amount, when the correction of the air amount is not in time, if the correction of the ignition timing is performed, the responsiveness of the torque fluctuation can be reduced. Can be suppressed well.

In this embodiment, steps 106, 1
In step 22, the required indicated torque is corrected by the torque efficiency (air-fuel ratio efficiency, ignition timing efficiency) to correct the target air amount and the target fuel amount. However, the required indicated torque is not corrected by the torque efficiency. After calculating the target air amount and the target fuel amount, the target air amount and the target fuel amount may be corrected at a rate corresponding to the torque efficiency.

The present invention is not limited to the direct injection engine, but is also applicable to a lean burn engine or an intake port injection engine. For example, if the present invention is applied to a lean burn engine, it is possible to suppress a torque fluctuation occurring when switching between lean operation and stoichiometric rich operation. Further, if the present invention is applied to an intake port injection engine, torque fluctuations that occur when switching between ignition timing retard control such as catalyst warm-up control and normal ignition control can be suppressed. In short, the present invention is applicable to a case where a control parameter causing a torque variation is adjusted based on an operating state regardless of the type of an engine, and the amount of torque variation due to the adjustment amount is changed by a control parameter that is not involved in the adjustment. The control parameter may be changed by an amount corresponding to the change amount to suppress the torque fluctuation.

When calculating the required indicated torque, FIG.
In order to simplify the calculation, add a loss / load other than the internal loss and external load shown in FIG. 2 and, on the contrary, ignore some loss / load from the internal loss and external load shown in FIG. You may do it.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire in-cylinder injection type engine control system showing an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an outline of torque demand control of the direct injection engine;

FIG. 3A is a block diagram illustrating a function of a homogeneous combustion mode control unit, and FIG. 3B is a block diagram illustrating a function of a stratified combustion mode control unit;

FIG. 4 is a diagram showing an example of a map of ignition timing efficiency using an ignition retard amount as a parameter;

FIG. 5 is a diagram showing an example of an air-fuel ratio efficiency map using a target air-fuel ratio as a parameter;

FIG. 6 is a flowchart illustrating an outline of torque demand control of a direct injection engine (part 1);

FIG. 7 is a flowchart for explaining the outline of torque demand control of the direct injection engine (part 2);

[Explanation of symbols]

11. In-cylinder injection engine (in-cylinder injection internal combustion engine), 1
2 ... intake pipe, 13 ... air flow meter, 15 ... throttle valve, 16 ... ECU (torque fluctuation suppressing means) 18 ...
Intake pressure sensor, 21: fuel injection valve, 25: spark plug,
33 ... crankshaft, 34 ... external load, 36 ... exhaust pipe, 4
0: EGR valve, 41: accelerator sensor, 51: required indicated torque calculating means, 52: combustion mode switching means, 53
... homogenous combustion mode control means, 54 ... stratified combustion mode control means, 55 ... target air-fuel ratio setting means, 56, 57 ... torque efficiency correction means (torque fluctuation suppression means).

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 3G022 AA07 AA09 AA10 DA02 EA07 FA06 GA05 GA06 GA07 GA08 GA17 GA19 3G084 AA04 BA05 BA06 BA09 BA13 BA17 BA20 DA11 DA12 EB09 FA05 FA07 FA10 FA11 FA18 FA19 FA26 FA33 3G301 HA01 HA04 HA18 JA04 LA00 LA01 MA11 NC04 NE01 NE06 NE12 PA01Z PA07Z PA11Z PD02Z PE01Z PF01Z PF03Z PF11Z PF12Z PF13Z PF14Z

Claims (3)

[Claims] An internal combustion engine control device that determines a required torque required by a driver and controls the operation of the internal combustion engine based on the required torque. When the control parameter is adjusted, the amount of torque fluctuation due to the adjustment amount is converted into the amount of change in the control parameter that has not been involved in the adjustment, and the torque fluctuation is suppressed by changing the control parameter by the amount of change. A control device for an internal combustion engine, comprising a torque fluctuation suppressing means. 2. A stratified combustion mode in which fuel is injected into a cylinder in a compression stroke to perform stratified combustion, and a homogeneous combustion mode in which fuel is injected into a cylinder in an intake stroke to perform homogeneous combustion is switched according to an operation state. The torque fluctuation suppression means is applied to a direct injection type internal combustion engine, wherein the torque fluctuation caused by a change in a control parameter adjusted to maintain a stable combustion state before and after the combustion mode switching is changed in the stratified combustion mode. The control device for an internal combustion engine according to claim 1, wherein the control is performed by correcting the fuel amount, and in the homogeneous combustion mode, the control is performed by correcting the air amount and / or the ignition timing. 3. In the stratified combustion mode, the torque fluctuation suppressing means corrects the fuel amount by correcting the required torque when converting the required torque into a fuel amount, and converts the required torque into an air amount in the homogeneous combustion mode. 3. The control device for an internal combustion engine according to claim 2, wherein the air amount is corrected by correcting the required torque when converting the torque into the control value.