JP2002030969A - Air-fuel ratio control device for cylinder fuel injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform feedback control of an air-fuel ratio without the occurrence of a fluctuation of torque during stratified combustion operation of a cylinder fuel injection type engine. SOLUTION: During stratified combustion operation of the cylinder fuel injection type engine, an air-fuel ratio feedback execution condition is established and air-fuel ratio feedback control is started, feedback correction is effected on a throttle opening (an air amount) so that a real air-fuel ratio (a real A/F) is adjusted to a target air-fuel ratio (a target A/F). Since this constitution enables feedback control of an air-fuel ratio by correction of a throttle opening (an air amount), feedback control of an air-fuel ratio is stably executed without the occurrence of a fluctuation of torque through correction of a fuel injection amount during stratified combustion operation and control of an air-fuel ratio during stratified combustion operation and drivability are compatible with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control apparatus for a direct injection internal combustion engine which performs air-fuel ratio feedback control during stratified charge combustion operation.

[0002]

2. Description of the Related Art In recent years, the demand for an in-cylinder injection engine having features of low fuel consumption, low exhaust emission and high output has been rapidly increasing. At low load, this in-cylinder injection engine improves fuel efficiency by injecting a small amount of fuel in the compression stroke and stratifying a lean stratified air-fuel mixture, while increasing fuel injection amount at medium and high loads. The engine output is increased by increasing the amount and injecting it in the intake stroke to perform homogeneous combustion.

[0003] In the direct injection engine, during the homogeneous combustion operation, the air-fuel ratio feedback is increased in the same manner as in the conventional intake pipe injection engine in order to increase the exhaust gas purification rate of the three-way catalyst provided in the exhaust pipe. The control is performed, and the fuel injection amount is feedback-controlled so that the air-fuel ratio detected by the air-fuel ratio sensor provided in the exhaust pipe matches the target air-fuel ratio. However, during the stratified charge combustion operation in which the lean stratified mixture is stratifiedly burned, the output torque of the engine is controlled by controlling the fuel injection amount according to the driver's accelerator operation or the like. Has not been implemented.

[0004]

However, recently,
During the stratified charge combustion operation, it is required to control the air-fuel ratio within the lean combustion limit or to execute the air-fuel ratio feedback control in order to learn the concentration of fuel evaporative gas purged from the canister to the intake system. It is becoming.

However, as described above, during the stratified charge combustion operation, the fuel injection amount is controlled in accordance with the driver's accelerator operation or the like to control the output torque of the engine. As in the case of the pipe injection engine, when the air-fuel ratio is feedback-controlled by correcting the fuel injection amount, as shown in FIGS. 24 (a) and 24 (b), the air-fuel ratio feedback is obtained even during steady running without the driver operating the accelerator. The output torque of the engine changes due to the correction of the fuel injection amount by the control. For this reason, even during steady driving,
It is necessary to perform an accelerator operation to cancel the change in output torque due to the air-fuel ratio feedback control, which results in poor drivability.

Therefore, the air-fuel ratio control technology of an intake pipe injection type engine described in Japanese Patent Application Laid-Open No. 10-176591 is applied to a direct injection type engine to detect fluctuations in engine torque during stratified charge combustion operation. Feedback control of the air-fuel ratio can be considered. However, in this case, since the air-fuel ratio is corrected after the torque fluctuation occurs, the torque fluctuation cannot be completely prevented, and the situation that the drivability deteriorates remains unchanged. In addition, the detection of torque fluctuation is susceptible to vibration due to unevenness of the road surface, and has the disadvantage of low detection accuracy.

[0007] The present invention has been made in view of such circumstances, and accordingly, an object thereof is to perform air-fuel ratio feedback control during stratified combustion operation while preventing torque fluctuation. It is an object of the present invention to provide an air-fuel ratio control apparatus for a direct injection internal combustion engine that can achieve both air-fuel ratio control and drivability.

[0008]

Since the air-fuel ratio is the ratio between the amount of air and the amount of fuel injected, the air-fuel ratio can be changed by changing the amount of air without changing the amount of fuel injected. Can be.

Focusing on this point, the air-fuel ratio control apparatus for a direct injection internal combustion engine according to the first aspect of the present invention is configured such that the air-fuel ratio sensor detects the target air-fuel ratio by the air-fuel ratio feedback control means during stratified charge combustion operation. The air-fuel ratio is feedback-controlled by correcting the air amount so as to match the fuel ratio. With this configuration, the air-fuel ratio can be controlled to the target air-fuel ratio by correcting the air amount without correcting the fuel injection amount during the stratified charge combustion operation. As a result, the air-fuel ratio feedback control can be stably performed without causing torque fluctuation due to the correction of the fuel injection amount during the stratified combustion operation, and the air-fuel ratio control and the drivability during the stratified combustion operation can be compatible. Can be.

In this case, the amount of air (the amount of gas containing oxygen) flowing into the cylinder changes depending on the amount of intake air and the amount of exhaust gas, and therefore, one or both of the amount of intake air and the amount of exhaust gas are controlled. Although the air-fuel ratio may be controlled by controlling the air-fuel ratio, the amount of intake air is usually larger than the amount of exhaust gas, and the amount of intake air contains much more oxygen required for combustion. The method is more suitable for controlling the air-fuel ratio than the exhaust ring flow rate. Further, during the stratified charge combustion operation, the exhaust ring flow rate (EG
If the (R rate) is largely changed, the amount of generated NOx may increase or the flammability may be adversely affected.

The amount of intake air varies depending on the throttle opening, a variable valve timing mechanism, and a swirl control valve arranged in the intake system, and also varies depending on the EGR rate. This is the most important control parameter for controlling the amount of air. If the valve timing, the opening of the swirl control valve, and the like are significantly changed during the stratified charge combustion operation, the flammability may be adversely affected.

In consideration of these points, it is preferable that the correction of the air amount by the air-fuel ratio feedback control during the stratified charge combustion operation is performed by the correction of the throttle opening. In this way, when the air amount is corrected by the air-fuel ratio feedback control, the air amount can be accurately corrected without adversely affecting the EGR effect and the combustibility.

When the amount of air (throttle opening) changes, the pumping loss of the engine also changes.
When the correction amount of the air amount increases, the amount of change in the pumping loss increases, and there is a possibility that torque fluctuation that adversely affects drivability occurs.

As a countermeasure, when the correction amount of the air amount by the air-fuel ratio feedback control during the stratified charge combustion operation is out of a predetermined range, the fuel injection amount is changed according to the correction amount of the air amount. The correction may be made. In this way, even if the air amount correction amount increases and the pumping loss change amount increases, the fuel injection amount can be corrected by the amount that cancels the accompanying torque fluctuation. Even if the amount increases, it is possible to prevent the occurrence of torque fluctuation that adversely affects drivability.

In this case, when the correction amount of the air amount by the air-fuel ratio feedback control during the stratified charge combustion operation becomes equal to or more than a predetermined value on the increasing side, the fuel injection amount is reduced and corrected. It is preferable that the fuel injection amount is increased when the value becomes equal to or less than a predetermined value (minus value) on the decreasing side. That is, when the correction amount of the air amount becomes equal to or more than the predetermined value on the increasing side, the pumping loss decreases and the output torque increases, and accordingly, if the fuel injection amount is reduced and corrected, the output torque can be kept substantially constant. Can be. On the other hand, when the air amount correction amount becomes equal to or less than the predetermined amount on the decreasing side, the pumping loss increases and the output torque decreases.Therefore, if the fuel injection amount is increased and corrected accordingly, the output torque can be kept almost constant. it can.

In this case, the air amount correction amount used for determining whether or not the air amount correction amount is out of the predetermined range (that is, whether or not to perform the fuel injection amount correction for preventing torque fluctuation) is:
Although a target air amount correction amount or the like calculated by the air-fuel ratio feedback control may be used, in the system including the intake pipe pressure detecting means for detecting the intake pipe pressure as in claim 5, the air amount correction is performed. The determination as to whether the amount is outside the predetermined range may be made based on the amount of change in the intake pipe pressure detected by the intake pipe pressure detection means. That is, since the intake pipe pressure is the most suitable parameter for evaluating the pumping loss, it is determined whether or not to perform the fuel injection amount correction to prevent a torque fluctuation due to a change in the pumping loss. , It is possible to accurately prevent torque fluctuation due to a change in pumping loss. It should be noted that whether or not the fuel injection amount correction is to be performed may be determined based on a change amount of the actual intake air amount or a change amount of the actual throttle opening other than the change amount of the actual intake pipe pressure.

On the other hand, in a system having an exhaust gas recirculation control means for recirculating a part of the exhaust gas to the intake system, the correction amount of the throttle opening is controlled by the air-fuel ratio feedback control during the stratified combustion operation. Is outside the predetermined range, the correction amount of the throttle opening may be limited within the predetermined range, and instead, the air-fuel ratio may be feedback-controlled by correcting the exhaust gas recirculation amount. That is,
By limiting the correction amount of the throttle opening within a predetermined range, it is possible to reduce the change in pumping loss and prevent torque fluctuation that adversely affects drivability. And
By correcting the excess or deficiency of the intake air amount caused by the limitation of the correction amount of the throttle opening by increasing or decreasing the exhaust gas recirculation amount (EGR rate), it is possible to prevent the torque fluctuation due to the change of the pumping loss and to set the air-fuel ratio. The air-fuel ratio can be controlled (see FIG. 18).

Further, during the stratified charge combustion operation, fuel is injected during the compression stroke and ignited at the timing when the injected fuel flows to the vicinity of the spark plug to perform stratified charge combustion. When the amount of change in the amount of air charged in the cylinder increases, the gas flow in the cylinder changes and the behavior of the injected fuel changes, and as a result, the time required for the injected fuel to flow to the vicinity of the spark plug changes. Then, the position of the injected fuel at the time of ignition deviates from an appropriate position (near the spark plug), and the combustion state may be deteriorated.

As a countermeasure, when the air amount correction amount is out of a predetermined range by the air-fuel ratio feedback control during the stratified charge combustion operation, the fuel injection timing is adjusted according to the air amount correction amount. The correction may be made. That is, when the correction amount of the air amount increases, the behavior of the injected fuel in the cylinder changes, and the time required for the injected fuel to flow to the vicinity of the spark plug changes. If the relationship with the amount of correction is determined by experiments, simulations, etc., and the fuel injection timing is corrected in accordance with the amount of correction of air, even if the amount of correction of air becomes large, the injected fuel can be adjusted to the ignition timing. It can be made to flow near the spark plug, and the combustion state can be stabilized.

In this case, the fuel injection timing is advanced when the air amount correction amount is equal to or greater than the predetermined value on the increasing side, and when the air amount correction amount is equal to or less than the predetermined value on the decreasing side. It is preferable to retard the fuel injection timing. That is,
When the air amount correction amount becomes equal to or more than the predetermined value on the increasing side, the time required for the injected fuel to flow to the vicinity of the ignition plug becomes longer, and accordingly, the fuel injection timing is advanced and the fuel injection timing is adjusted from fuel injection to ignition. If the time is extended, the injected fuel can be made to reach the vicinity of the ignition plug in accordance with the ignition timing. On the other hand, when the air amount correction amount becomes equal to or less than the predetermined amount on the decreasing side, the time until the injected fuel flows to the vicinity of the ignition plug is shortened. If the time until ignition is shortened, the injected fuel can reach the vicinity of the spark plug in accordance with the ignition timing.

Further, when the air-fuel ratio is feedback-controlled by correcting the fuel injection amount during the homogeneous combustion operation, the air-fuel ratio feedback correction amount relating to the fuel injection amount during the homogeneous combustion operation is determined during the stratified combustion operation. May be reflected in the control of the fuel injection amount. In other words, the air-fuel ratio feedback correction amount relating to the fuel injection amount during the homogeneous combustion operation mainly corrects the system error of the fuel system due to individual differences of fuel injection valves or aging deterioration. If the air-fuel ratio feedback correction amount related to the injection amount is reflected in the control of the fuel injection amount during the stratified combustion operation, the fuel injection control can be performed with the system error of the fuel system corrected even during the stratified combustion operation. The accuracy of fuel injection control during combustion operation can be improved.

In this case, it is preferable that the air-fuel ratio feedback control based on the amount of air is performed during the stratified combustion operation after the air-fuel ratio feedback control based on the fuel injection amount is performed during the homogeneous combustion operation. In this way, the air-fuel ratio feedback correction amount relating to the fuel injection amount during the homogeneous combustion operation can be reflected in the control of the fuel injection amount during the stratified combustion operation.

During the stratified charge combustion operation, the air-fuel ratio is controlled in the ultra-lean range, so that the amount of air during the stratified charge combustion operation is much larger than the amount of air during the homogeneous charge combustion operation. The control range of the air amount (throttle opening) differs greatly from that during operation. For this reason, if the air-fuel ratio feedback correction amount relating to the air amount during the stratified charge combustion operation is reflected in the control of the air amount during the homogeneous combustion operation, a lean deviation or a rich deviation of the air-fuel ratio may occur.

Therefore, it is preferable that the air-fuel ratio feedback correction amount relating to the air amount during the stratified combustion operation is not reflected in the control of the air amount during the homogeneous combustion operation. In this way, it is possible to prevent a lean deviation or a rich deviation of the air-fuel ratio during the homogeneous combustion operation.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS << Embodiment (1) >> Hereinafter, an embodiment (1) of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of an intake pipe 12 of a direct injection type engine 11 which is a direct injection internal combustion engine, and an opening thereof is adjusted by a step motor 14 on the downstream side of the air cleaner 13. A throttle valve 15 is provided. This step 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 is adjusted according to the throttle opening. A throttle sensor 17 for detecting a throttle opening is provided near the throttle valve 15.

A surge tank 19 is provided downstream of the throttle valve 15. An intake pipe pressure sensor 18 (intake pipe pressure detecting means) for detecting an intake pipe pressure is attached to the surge tank 19. An intake manifold 20 for introducing air into each cylinder of the engine 11 is connected to the surge tank 19. A first intake passage 21 and a second intake passage 2 are provided in the intake manifold 20 of each cylinder.
The first intake passage 21 and the second intake passage 22 are respectively connected to two intake ports 23 formed in each cylinder of the engine 11.

An airflow control valve 24 for controlling the swirl flow intensity and the tumble flow intensity in the cylinder is disposed in the second intake passage 22 of each cylinder. Air flow control valve 24 for each cylinder
Are connected to a step motor 26 via a common shaft 25. This step motor 26 is
The opening degree of the airflow control valve 24 is controlled by driving based on the output signal from the controller, and the airflow intensity in each cylinder is adjusted according to the opening degree. An airflow control valve sensor 27 that detects the opening of the airflow control valve 24 is attached to the step motor 26.

A fuel injection valve 28 for directly injecting fuel into the cylinder is mounted on an upper part of each cylinder of the engine 11. Fuel sent from a fuel tank (not shown) to the fuel delivery pipe 30 through the fuel pipe 29 is directly injected into the cylinder from the fuel injection valve 28 of each cylinder, and mixed with the intake air introduced from the intake port 23. As a result, an air-fuel mixture is formed.

Further, an ignition plug (not shown) is attached to the cylinder head of the engine 11 for each cylinder, and the mixture in the cylinder is ignited by spark discharge of each ignition plug. The cylinder discrimination sensor 32 generates an output pulse when a specific cylinder (for example, the first cylinder) reaches the intake top dead center.
Has a constant crank angle (for example, 30 ° C.).
A) An output pulse is generated each time the motor rotates. From these output pulses, the crank angle and the engine rotation speed are detected, and cylinder discrimination is performed.

On the other hand, exhaust gas discharged from each exhaust port 35 of the engine 11 joins one exhaust pipe 37 via an exhaust manifold 36. The exhaust pipe 37 has a three-way catalyst 38 for purifying exhaust gas near the stoichiometric air-fuel ratio and a NO.
An x-storage lean NOx catalyst 39 is arranged in series. The lean NOx catalyst 39 adsorbs NOx in the exhaust gas during lean operation in which the oxygen concentration in the exhaust gas is high, and adsorbs when the air-fuel ratio is switched to rich and the oxygen concentration in the exhaust gas decreases. NOx is reduced and purified and released. On the upstream side of the three-way catalyst 38, an air-fuel ratio sensor 42 capable of detecting the air-fuel ratio (A / F) of the exhaust gas to an extremely lean region.
Is provided.

The air-fuel ratio sensor 4 in the exhaust pipe 37
An EGR pipe 40 for recirculating a part of the exhaust gas to the intake system is connected between the upstream side of the fuel tank 2 and the surge tank 19,
An EGR valve 41 is provided in the EGR pipe 40. The EGR pipe 40, the EGR valve 41, and the like constitute an exhaust gas recirculation control unit. The opening of the EGR valve 41 is controlled based on an output signal from the ECU 16, and the EGR amount (exhaust gas recirculation amount) is adjusted according to the opening. Further, the accelerator pedal 43 is provided with an accelerator sensor 44 for detecting an accelerator opening.

The output signals of the various sensors described above are supplied to the ECU
16 is input. The ECU 16 mainly includes a microcomputer, and controls the operation of the engine 11 by executing various control programs stored in a built-in ROM (storage medium).

During operation of the engine, the ECU 16 calculates a required torque based on the accelerator opening detected by the accelerator sensor 44, the engine speed Ne, and the like, as shown in FIG. 2, and calculates the required torque and the engine speed Ne. , One of the homogeneous combustion mode and the stratified combustion mode is selected from the combustion mode switching map shown in FIG. The combustion mode switching map in FIG. 3 is set so that the stratified combustion mode is selected in the low rotation and low torque regions, and the homogeneous combustion mode is selected in the middle and high rotation and medium and high torque regions. In the stratified combustion mode, a small amount of fuel is directly injected into the cylinder during the compression stroke to form a stratified mixture near the spark plug and perform stratified combustion, thereby improving fuel efficiency. Further, in the homogeneous combustion mode, the engine output is 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.

Thereafter, the ECU 16 determines the target A / F (target air-fuel ratio), fuel injection amount, injection timing, ignition timing, intake air amount (throttle opening), E according to the selected combustion mode.
Various basic control parameters such as the GR amount, the in-cylinder airflow intensity, the fuel pressure, and the valve timing are calculated.

Further, the ECU 16 selects the air-fuel ratio feedback control of a control method according to the combustion mode (hereinafter, "feedback" is abbreviated as "F / B"). In the homogeneous combustion mode, the fuel control type air-fuel ratio F / B control is selected, and the fuel injection amount is set so that the detected A / F (actual A / F of exhaust gas) of the air-fuel ratio sensor 42 becomes the target A / F. F / B
Calculate the correction amount. On the other hand, in the stratified combustion mode, the air-fuel ratio air-fuel ratio F / B control is selected and the air-fuel ratio sensor 42 is selected.
The F / B correction amount of the air amount (for example, the F / B correction amount of the throttle opening) is calculated so that the detected A / F (actual A / F of the exhaust gas) becomes the target A / F.

Thereafter, the ECU 16 applies various corrections to the basic control parameters as needed to obtain final control parameters, and based on the control parameters, the fuel injection valve 28, the spark plug, the throttle valve, and the like. 1
5. Drive the EGR valve 41, the airflow control valve 24, the fuel pump, the variable valve timing mechanism, and the like. Hereinafter, the ECU 16
The specific processing contents of each routine executed by the program will be described.

[Air-fuel ratio F / B control] The air-fuel ratio F / B shown in FIG.
The control routine is executed every predetermined time or every predetermined crank angle, and plays a role corresponding to an air-fuel ratio feedback control means described in claims. When this routine is started, first, in step 101, it is determined whether or not the F / B execution condition is satisfied, based on whether or not the F / B execution condition satisfaction flag F = 1. The F / B execution condition satisfaction flag F is set to "1" meaning the satisfaction of the F / B execution condition or "0" meaning the failure in the F / B execution condition satisfaction determination routine of FIG. . If the F / B execution condition is not satisfied (F / B execution condition satisfaction flag F = 0), this routine ends without performing the subsequent processing.

On the other hand, if it is determined that the F / B execution condition is satisfied (F / B execution condition satisfaction flag F = 1), the routine proceeds to step 102, where it is determined whether or not the current combustion mode is the stratified combustion mode. If the mode is the homogeneous combustion mode, the routine proceeds to step 103, where the air-fuel ratio F /
By executing the B control routine, the fuel control air-fuel ratio F
/ B control is performed and the actual A / F of the exhaust gas becomes the target A / F.
The fuel injection amount is feedback-corrected so that

The F / B of the fuel injection amount during the homogeneous combustion operation
The correction amount is also used for correcting the fuel injection amount during the stratified combustion operation. The F / B correction amount of the fuel injection amount is mainly for correcting a system error of the fuel injection amount due to individual differences of the fuel injection valves 28, aging, and the like. If the B correction amount is used to correct the fuel injection amount during the stratified charge combustion operation, a system error in the fuel injection amount during the stratified charge combustion operation can be corrected.

On the other hand, if it is determined in step 102 that the stratified combustion mode has been set, the process proceeds to step 104,
By executing an air-fuel ratio F / B control routine for stratified combustion operation shown in FIG. 6 described later, air-fuel ratio F / B control of the air control type is performed, and the actual A / F of exhaust gas is set to the target A / F. Feedback correction of the air amount (for example, throttle opening) is performed so as to be as follows.

The F / B correction amount of the air amount (throttle opening) during the stratified combustion operation is not used for controlling the air amount during the homogeneous combustion operation. During the stratified charge combustion operation, the air-fuel ratio is controlled to the ultra-lean region, so the amount of air during the stratified charge combustion operation is much larger than the amount of air during the homogeneous charge combustion operation. The control areas of the quantities are very different. Therefore, when the F / B correction amount of the air amount (throttle opening) during the stratified combustion operation is used for controlling the air amount (throttle opening) during the homogeneous combustion operation, a lean deviation or a rich deviation of the air-fuel ratio occurs. There is a possibility that. As a measure against this,
By prohibiting the use of the F / B correction amount of the air amount during the stratified combustion operation for controlling the air amount during the homogeneous combustion operation, a lean or rich deviation of the air-fuel ratio during the homogeneous combustion operation is prevented.

[F / B Execution Condition Satisfaction Determination] F / B in FIG.
The execution condition satisfaction determination routine is executed every predetermined time or every predetermined crank angle. When this routine is started, first, in steps 201 to 206, it is determined whether the following F / B execution conditions are satisfied. The cooling water temperature is equal to or higher than a predetermined temperature (step 20).
1) There is no request for rich air-fuel ratio (step 202) The air-fuel ratio sensor 42 is active (step 2)
03) The fuel injection valve 28 and the air-fuel ratio sensor 42 are normal (Step 204) If the current combustion mode is the stratified combustion mode, the fuel control air-fuel ratio F / B control is already executed in the homogeneous combustion mode. Being done (steps 205 and 206)

Here, the condition (1) is an F / B execution condition common to both the stratified combustion mode and the homogeneous combustion mode, and the condition (2) is an additional condition when the current combustion mode is the stratified combustion mode. This is an F / B execution condition. Therefore,
If the current combustion mode is the stratified combustion mode,
It is determined whether the F / B execution condition is satisfied based on all the conditions. If the current combustion mode is the homogeneous combustion mode, whether the F / B execution condition is satisfied only under the common condition Determine whether or not.

If the fuel control type air-fuel ratio F / B control during the homogeneous combustion operation has already been executed, the fuel injection during the stratified combustion operation is determined by the F / B correction amount of the fuel injection amount during the homogeneous combustion operation. The system error of the volume can be corrected,
If the air-controlled air-fuel ratio F / B control during the stratified combustion operation is performed after the fuel-controlled air-fuel ratio F / B control during the homogeneous combustion operation, the accuracy of the fuel injection control during the stratified combustion operation can be improved. improves. Therefore, in the present embodiment (1), when the current combustion mode is the stratified combustion mode, it is additional F / B that after the execution of the fuel control air-fuel ratio F / B control during the homogeneous combustion operation. Execution conditions.

When the current combustion mode is the homogeneous combustion mode, the F / B execution condition at the time of the homogeneous combustion operation is satisfied if all of the above conditions are satisfied, and when the current combustion mode is the stratified combustion mode, If all of the conditions are satisfied, the F / B execution condition at the time of stratified combustion operation is satisfied. If the F / B execution condition is satisfied, the process proceeds to step 207, and the F / B execution condition satisfaction flag F is set to "1". On the other hand, F /
If the B execution condition is not satisfied, the process proceeds to step 208, and the F / B execution condition satisfaction flag F is reset to “0”.

[Air-fuel ratio F / B control for stratified combustion operation] The air-fuel ratio F / B control routine for stratified combustion operation shown in FIG. 6 is a subroutine executed in step 104 in FIG.
When this routine is started, first, in step 301,
The actual A / F of the exhaust gas detected by the air-fuel ratio sensor 42 is read, and in the next step 301, it is determined whether or not the absolute value of the deviation between the target A / F and the actual A / F is equal to or more than a predetermined value ΔK. I do.

If the absolute value of the deviation between the target A / F and the actual A / F is equal to or larger than the predetermined value ΔK, the process proceeds to step 303, and the process proceeds to step 303 according to the deviation between the target A / F and the actual A / F. 7, a correction amount α for the air amount correction amount A (throttle opening degree correction amount A) in the previous calculation is calculated. In the map of the correction amount α, in a region where the deviation between the target A / F and the actual A / F is on the plus side (a region where the target A / F> the actual A / F), the correction amount α is a plus value (air amount increase). Side), and in a region where the deviation between the target A / F and the actual A / F is on the minus side (region where target A / F <actual A / F), the correction amount α is a negative value (air amount). (The weight loss side).

On the other hand, in step 302, the target A / F
When it is determined that the absolute value of the difference between the actual A / F and the actual A / F is smaller than the predetermined value ΔK, the actual A / F is controlled near the target A / F, and thus the air amount correction amount at the time of the previous calculation is calculated. It is determined that there is no need to correct A, and the flow advances to step 304 to set the correction amount α to 0.

As described above, after setting the correction amount α in step 303 or step 304,
To calculate the current air amount correction amount A (i) by adding the current correction amount α to the air amount correction amount A (i-1) at the previous calculation. A (i) = A (i-1) + α In the present embodiment (1), the air amount correction amount A is calculated as a value converted to a throttle opening correction amount.

[Calculation of Target Throttle Opening] The target throttle opening calculating routine shown in FIG. 8 is executed every predetermined time or every predetermined crank angle. When this routine is started, first, at step 401, a map of the basic target throttle opening degree θB using the engine speed Ne and the required torque as parameters is searched, and a search is made according to the current engine speed Ne and the required torque. Calculate the basic target throttle opening θB. As the map of the basic target throttle opening θB, a map for the stratified combustion mode and a map for the homogeneous combustion mode are set, and one of the maps is selected according to the current combustion mode.

Thereafter, the routine proceeds to step 402, where the air amount correction amount A (i) calculated in step 305 of FIG. 6 is added to the basic target throttle opening θB to correct the final target throttle opening. Calculate θF. θF = θB + A (i)

FIGS. 9A and 9B show the behavior of the air-fuel ratio F / B control during the stratified combustion operation of the embodiment (1) described above.
This will be described with reference to the time chart of FIG. FIG. 9A shows the behavior of the air-fuel ratio F / B control during steady running when the actual A / F is shifted to the lean side from the target A / F during the stratified charge combustion operation. The example of ()) shows the actual A / F during the stratified combustion operation.
Shows the behavior of the air-fuel ratio F / B control at the time of steady running in the case where is shifted to the rich side from the target A / F. In any case, during the stratified charge combustion operation, at time t1, when the F / B execution condition is satisfied and the air-control air-fuel ratio F / B control is started, the actual A / F becomes equal to the target A / F. The throttle opening (air amount) is feedback-corrected so as to be as follows. Thereby, during the stratified charge combustion operation, even if the fuel injection amount is not corrected,
Since the air-fuel ratio can be feedback-controlled by correcting the throttle opening (air amount), the air-fuel ratio feedback control can be performed stably without causing torque fluctuation during stratified combustion operation. Air-fuel ratio control and drivability can be compatible.

In this embodiment (1), the fuel injection amount during the stratified charge combustion operation is corrected using the F / B correction amount of the fuel injection amount during the homogeneous charge combustion operation. The system error of the fuel injection amount can be corrected, and the control accuracy of the fuel injection amount during the stratified combustion operation can be improved.

Further, in the embodiment (1), after the fuel control type air-fuel ratio F / B control is performed during the homogeneous combustion operation,
Since the air-fuel ratio F / B control is executed during the stratified charge combustion operation, the F / B correction amount of the fuel injection amount during the homogeneous charge combustion operation must be used for controlling the fuel injection amount during the stratified charge combustion operation. As a result, the control accuracy of the fuel injection amount is increased, and the control accuracy of the air-fuel ratio during stratified charge combustion operation can be improved.

Further, in the present embodiment (1), the air amount (throttle opening) is different between the stratified combustion operation and the homogeneous combustion operation.
In consideration of the large difference in the control range of the air-fuel ratio during the homogeneous combustion operation, the F / B correction amount of the air amount during the stratified combustion operation is not reflected in the control of the air amount during the homogeneous combustion operation. Can be prevented from being lean or rich.

<< Embodiment (2) >> By the way, as shown in FIG. 13, when the throttle opening (intake air amount) or the intake pipe pressure changes, the pumping loss of the engine 11 also changes. During the stratified charge combustion operation, if the air amount correction amount A (throttle opening correction amount) by the air control air-fuel ratio F / B control is not so large, the change in the pumping loss is also small, which adversely affects drivability. Such torque fluctuation does not occur, but if the air amount correction amount A becomes too large, the amount of change in pumping loss increases, and there is a possibility that torque fluctuation that adversely affects drivability may occur.

As a countermeasure against this, the embodiment (2) of the present invention
Then, by executing the air-fuel ratio F / B control routine for the stratified combustion operation in FIG. 10 and the fuel injection time calculation routine in FIG. 12, the air amount correction amount A is out of the predetermined range during the stratified combustion operation. In addition, the fuel injection amount (fuel injection time) is corrected in accordance with the air amount correction amount A to prevent the occurrence of torque fluctuation.

[Air-Fuel Ratio F / B Control for Stratified Combustion Operation] In the air-fuel ratio F / B control routine for stratified combustion operation shown in FIG. 10, first, Steps 501 to 505 are described in the first embodiment. The correction amount α is calculated in accordance with the deviation between the target A / F and the actual A / F in the same manner as in steps 301 to 305 in FIG. 6, and the current air amount correction amount A (i) = A (i− 1) +
Find α.

Thereafter, the routine proceeds to step 506, where it is determined whether or not the air amount correction amount A is equal to or larger than a predetermined amount A1 on the increasing side. If the air amount correction amount A is equal to or more than the predetermined amount A1 on the increasing side, a decrease in pumping loss cannot be ignored, and a torque increase that adversely affects drivability occurs. It is determined that the amount needs to be reduced, and the process proceeds to step 507.
The map shown in FIG. 11 is searched, and the correction amount β with respect to the fuel injection amount correction amount B in the previous calculation is calculated according to the air amount correction amount A. The map of the correction amount β is set such that the correction amount β becomes a positive value and the fuel injection amount is reduced and corrected in a region where the air amount correction amount A is equal to or larger than the predetermined value A1 on the increasing side. Is smaller than the predetermined value (-A2) on the decrease side, the correction amount β is set to a negative value so that the fuel injection amount is increased. In step 507, the correction amount β of the fuel injection amount correction amount B is set to a plus value (a decrease in the fuel injection amount) in order to cancel the increase in torque due to the decrease in the pumping loss.

On the other hand, at step 506, the air amount correction amount A
Is smaller than the increasing side predetermined value A1,
Proceeding to step 508, it is determined whether or not the air amount correction amount A is equal to or less than a predetermined value (-A2) on the decrease side. If the air amount correction amount A is equal to or smaller than the predetermined amount on the decrease side (-A2), an increase in pumping loss cannot be ignored and a torque decrease that adversely affects drivability occurs. It is determined that the fuel injection amount needs to be increased and corrected, and the routine proceeds to step 509, where the correction amount β of the fuel injection amount correction amount B is calculated from the map shown in FIG. In this case, the correction amount β of the fuel injection amount correction amount B is a negative value (increase in the fuel injection amount) in order to compensate for the torque decrease due to the increase in the pumping loss.
Is set to

It is to be noted that the increase-side predetermined value A1> the air amount correction amount A>
If it is determined to be the predetermined value on the decreasing side (-A2), the change in the pumping loss is small and the torque fluctuation that adversely affects the drivability does not occur. Therefore, it is not necessary to correct the fuel injection amount correction amount B. Judge, step 51
The process proceeds to 0, and the correction amount β is set to 0.

As described above, after the correction amount β is set in step 507, step 509, or step 510, the process proceeds to step 511, where the correction amount B (i-1) of the fuel injection amount used in the previous calculation is corrected this time. By adding the amount β, the current fuel injection amount correction amount B (i) is obtained. B (i) = B (i-1) + β

[Calculation of Fuel Injection Time] The fuel injection time calculation routine of FIG. 12 is executed at predetermined time intervals or at predetermined crank angles during the stratified charge combustion operation. The fuel injection time TAU during the stratified charge combustion operation is as follows. Is calculated. First, in step 601, a fuel pressure correction coefficient calculation routine (not shown) is executed to calculate a fuel pressure correction coefficient P corresponding to the current fuel pressure. In the next step 602, the fuel injection amount F / F during the homogeneous combustion operation is calculated. The B correction amount QFB is read.

Thereafter, in step 603, the fuel injection time TAU during the stratified charge combustion operation is calculated by the following equation. TAU = fuel injection amount Q × INJ characteristic coefficient TIIN × fuel pressure correction coefficient P × (1−F / B correction amount QFB during homogeneous combustion operation)
× (1—fuel injection amount correction amount B (i) during stratified charge combustion operation) Here, the fuel injection amount Q is a fuel injection amount calculated based on an accelerator opening and the like (required torque), and an INJ characteristic coefficient T
INJ is a coefficient for converting the fuel injection amount into the fuel injection time.

The behavior of the air-fuel ratio F / B control during the stratified charge combustion operation of the embodiment (2) described above will be described with reference to FIG. FIGS. 14A and 14B show that the air-fuel ratio air-fuel ratio F / B control is performed when the actual A / F greatly deviates from the target A / F toward the lean side during the stratified charge combustion operation. Therefore, the behavior when the throttle opening correction amount (air amount correction amount A) exceeds a predetermined value (-A2) on the decrease side is shown.

In the comparative example shown in FIG. 14B, during the stratified charge combustion operation, the air-fuel ratio F / B control is performed only by correcting the throttle opening (intake air amount).
For this reason, when the throttle opening correction amount (air amount correction amount A) exceeds the predetermined value (-A2) on the decreasing side, the increase in pumping loss cannot be ignored, the output torque decreases, and drivability may deteriorate. is there.

On the other hand, in this embodiment (2), as shown in FIG. 14A, when the throttle opening correction amount (air amount correction amount A) exceeds a predetermined value (-A2) on the decrease side. The fuel injection amount is increased and corrected according to the air amount correction amount A.
As a result, the decrease in torque due to the increase in the pumping loss can be canceled by the increase in torque due to the increase in the fuel injection amount, so that the throttle opening correction amount A (air amount correction amount A) is reduced to a predetermined value on the decrease side (− Even when A2) is exceeded, the output torque can be kept substantially constant during steady running, and drivability can be improved.

In this embodiment (2), it is determined whether or not to correct the fuel injection amount based on the air amount correction amount A (throttle opening correction amount) calculated by the ECU 16. In the case of the system including the pipe pressure sensor 18, it may be determined whether or not to correct the fuel injection amount based on the actual amount of change in the intake pipe pressure detected by the intake pipe pressure sensor 18. Since the intake pipe pressure is the most suitable parameter for evaluating the pumping loss, it is determined whether or not to perform the fuel injection amount correction to prevent torque fluctuation due to the change in the pumping loss. If the determination is made based on the amount, torque fluctuation due to a change in pumping loss can be accurately prevented. It should be noted that whether or not the fuel injection amount correction is to be performed may be determined based on a change amount of the actual intake air amount or a change amount of the actual throttle opening other than the change amount of the actual intake pipe pressure.

<< Embodiment (3) >> Next, an embodiment (3) of the present invention will be described with reference to FIGS. In the embodiment (2), when the air amount correction amount A falls outside the predetermined range during the stratified charge combustion operation, the fuel injection amount (fuel injection time) is corrected according to the air amount correction amount A, Although the occurrence of torque fluctuation is prevented, in the present embodiment (3), as shown in FIG.
Rate), the amount of oxygen in the cylinder gas (lean component)
Focusing on the fact that the air-fuel ratio can be changed by changing the air-fuel ratio, the stratified combustion operation air-fuel ratio F / B control routine shown in FIG. 15 and the target EGR opening calculation routine shown in FIG. 17 are executed. When the air amount correction amount A is out of the predetermined range during the combustion operation, the air amount correction amount A is limited to within the predetermined range to prevent torque fluctuation that adversely affects drivability and to reduce the air amount. The excess or deficiency of the intake air amount caused by the limitation of the amount correction amount A is corrected by increasing or decreasing the EGR amount to control the actual A / F to the target A / F.

[Air-Fuel Ratio F / B Control for Stratified Combustion Operation] In the air-fuel ratio F / B control routine for stratified combustion operation shown in FIG. 15, first, Steps 701 to 705 are described in the first embodiment. The correction amount α is calculated in accordance with the deviation between the target A / F and the actual A / F in the same manner as in steps 301 to 305 in FIG. 6, and the current air amount correction amount A (i) = A (i− 1) +
Find α.

Thereafter, the routine proceeds to step 706, where it is determined whether or not the air amount correction amount A is equal to or larger than a predetermined value A1 on the increasing side. If the air amount correction amount A is equal to or greater than the increase side predetermined value A1, the routine proceeds to step 707, where a map shown in FIG.
Is calculated according to the air amount correction amount A.

If the air amount correction amount A is equal to or larger than the predetermined amount A1 on the increasing side, the air amount correction amount A is limited to the predetermined value A1 on the increasing side by the guard processing in step 708, which will be described later. The lean component (oxygen or the like) of the in-cylinder gas becomes insufficient. On the other hand, if the air amount correction amount A is equal to or smaller than the predetermined amount on the decrease side (-A2), the air amount correction amount A is reduced to a predetermined value (-A
2), the lean component of the in-cylinder gas becomes excessive with respect to the target A / F.

Therefore, the map of the correction amount γ in FIG. 16 shows that the correction amount γ is set to a negative value in the region where the air amount correction amount A is equal to or larger than A1 (the region where the lean component is insufficient due to the guard processing). (EGR rate) is set so as to increase the ratio of fresh air (intake air) sucked into the cylinder by adjusting the amount of fresh air (intake air) to match the actual A / F with the target A / F.
In a region where the air amount correction amount A is equal to or less than -A2 (a region where the lean component becomes excessive due to the guard processing), the correction amount β is set to a plus value to increase and correct the EGR amount (EGR rate), thereby reducing the in-cylinder amount. The actual A / F is set to match the target A / F by reducing the proportion of fresh air (intake air) to be sucked into the A / F. In step 707, since the air amount correction amount A is equal to or larger than the increasing side predetermined value A1, the correction amount γ of the EGR correction amount C
Is set to a negative value (a decrease in the EGR amount). Thereafter, the routine proceeds to step 708, where the air amount correction amount A is subjected to guard processing with the predetermined value A1 on the increasing side (A = A1).

On the other hand, at step 706, the air amount correction amount A
Is smaller than the increasing side predetermined value A1,
Proceeding to step 709, it is determined whether or not the air amount correction amount A is equal to or less than a predetermined value (-A2) on the decrease side. If the air amount correction amount A is equal to or smaller than the predetermined amount on the decrease side (-A2), the process proceeds to step 710, and the correction amount γ of the EGR correction amount C is calculated from the map shown in FIG. I do. In this case, the correction amount γ of the EGR correction amount C is a plus value (EGR
It is set to increase the amount). Thereafter, the process proceeds to step 711, where the air amount correction amount A is subjected to guard processing with a predetermined value (-A2) on the decreasing side (A = -A2).

It should be noted that the increase-side predetermined value A1> the air amount correction amount A>
If it is determined that the predetermined value is on the decrease side (-A2), the actual A / F can be controlled to the target A / F only by the air amount correction amount A.
It is determined that there is no need to correct the EGR correction amount C, and the process proceeds to step 712, where the correction amount γ is set to 0.

Thereafter, step 708 or step 71
From step 1 or step 712, the process proceeds to step 713 to obtain the current EGR correction amount C (i) by adding the current correction amount γ to the EGR correction amount C (i-1) in the previous calculation. C (i) = C (i-1) + γ

[Calculation of target EGR opening] The target EG shown in FIG.
The R opening degree calculation routine is executed every predetermined time or every predetermined crank angle. When this routine is started, first, in step 801, a basic target EGR opening CB is calculated by searching a map of the basic target EGR opening CB using the engine speed Ne and the required torque as parameters. As the map of the basic target EGR opening CB, a map for the stratified combustion mode and a map for the homogeneous combustion mode are set, and one of the maps is selected according to the current combustion mode.

Thereafter, the routine proceeds to step 802, where the basic target EGR opening CB is calculated by the value E calculated at step 713 in FIG.
The final target EGR opening CF is calculated by adding and correcting the GR correction amount C (i). CF = CB + C (i)

The behavior of the air-fuel ratio F / B control during the stratified charge combustion operation of the embodiment (3) described above will be described with reference to the time chart of FIG. During the stratified charge combustion operation, when the actual A / F greatly deviates from the target A / F to the lean side, the air-fuel ratio air-fuel ratio F / B control is performed and the air amount correction amount A (throttle opening correction) Amount) is the predetermined value on the decrease side (-A2)
If it becomes less than the predetermined value, the air amount correction amount A is reduced to a predetermined value (-A2
) To prevent torque reduction due to an increase in pumping loss. At this time, if the EGR amount (EGR rate) is constant before and after the guard processing of the air amount correction amount A, the lean component of the in-cylinder gas becomes excessive, so that the EGR amount (EGR rate) is increased and corrected. Thus, the ratio of fresh air (intake air) sucked into the cylinder is reduced, the lean component of the gas in the cylinder is reduced, and the actual A / F is corrected to the rich side to achieve the target A.
/ F. Thus, the actual A / F can be controlled to the target A / F while the output torque is kept substantially constant, and the drivability can be improved.

<< Embodiment (4) >> During the stratified charge combustion operation, fuel is injected in the compression stroke and ignited at the timing when the injected fuel flows to the vicinity of the ignition plug to perform stratified charge combustion. When it becomes large (that is, when the amount of change in the amount of charged air in the cylinder becomes large), the gas flow in the cylinder changes and the behavior of the injected fuel changes, and as a result, the injected fuel flows to the vicinity of the spark plug. Time changes and the position of the injected fuel at the time of ignition is in the proper position (near the spark plug)
And the combustion state may be degraded.

As a countermeasure, the embodiment (4) of the present invention
Then, by executing the air-fuel ratio F / B control routine for the stratified combustion operation in FIG. 20 and the fuel injection timing calculation routine in FIG. 22, the air amount correction amount A is out of the predetermined range during the stratified combustion operation. Then, the fuel injection timing is corrected in accordance with the air amount correction amount A to stabilize the combustion state. That is, the relationship between the time until the injected fuel flows to the vicinity of the spark plug and the air amount correction amount A is obtained in advance by experiments, simulations, and the like, and the fuel injection timing is corrected according to the air amount correction amount A. Then, even if the air amount correction amount A increases, the injected fuel can flow to the vicinity of the ignition plug in accordance with the ignition timing, and the combustion state can be stabilized.

[Air-Fuel Ratio F / B Control for Stratified Combustion Operation] In the air-fuel ratio F / B control routine for stratified combustion operation shown in FIG. 20, first, in steps 901 to 905, the same method as in the embodiment (1) is used. After calculating the air amount correction amount A (i), the routine proceeds to step 906, where it is determined whether or not the air amount correction amount A is equal to or greater than a predetermined value E1 on the increasing side. If the air amount correction amount A is equal to or greater than the predetermined amount E1 on the increasing side, the time required for the injected fuel to reach the vicinity of the spark plug becomes longer, and it is determined that the fuel injection timing needs to be advanced. In step 907, the map shown in FIG. 21 is searched, and the correction amount δ for the fuel injection timing correction amount D in the previous calculation is calculated according to the air amount correction amount A. The map of the correction amount δ of the fuel injection timing correction amount D is set such that the correction amount δ is advanced on the advance side in the region where the air amount correction amount A is equal to or larger than the increasing side predetermined value E1. Is the predetermined value on the weight reduction side (-E2)
In the following regions, the correction amount δ is set to be on the retard side. In step 907, since the air amount correction amount A is equal to or greater than the increasing side predetermined value E1, the correction amount δ of the fuel injection timing correction amount D is set to the advanced side, and the time from fuel injection to ignition becomes longer.

On the other hand, in step 906, the air amount correction amount A
Is smaller than the increasing side predetermined value E1,
Proceeding to step 908, it is determined whether or not the air amount correction amount A is equal to or less than a predetermined amount on the decrease side (-E2). If the air amount correction amount A is equal to or less than the predetermined amount (-E2) on the decreasing side, the time required for the injected fuel to reach the vicinity of the spark plug becomes short, and it is necessary to retard the fuel injection timing. Then, the process proceeds to step 909, and the correction amount δ of the fuel injection timing correction amount D is determined from the map shown in FIG.
Is calculated. In this case, the correction amount δ of the fuel injection timing correction amount D is set on the retard side, and the time from fuel injection to ignition becomes shorter.

It should be noted that the increase-side predetermined value E1> the air amount correction amount A>
When it is determined to be the predetermined value on the decrease side (-E2), it is determined that it is not necessary to correct the fuel injection timing correction amount D, and the routine proceeds to step 910, where the correction amount δ is set to 0.

After the correction amount δ is set in step 907, step 909, or step 910 as described above, the process proceeds to step 911, where the correction amount D (i-1) of the fuel injection timing used in the previous calculation is corrected. By adding the amount δ, the current fuel injection amount correction amount D (i) is obtained. D (i) = D (i-1) + δ

[Calculation of Fuel Injection Timing] The fuel injection timing calculation routine shown in FIG. 22 is executed every predetermined time or every predetermined crank angle. When this routine is started, first, at step 1001, a map of the basic fuel injection timing DB using the engine speed Ne and the required torque as parameters is searched to calculate the basic fuel injection timing DB. As the map of the basic fuel injection timing DB, a map for the stratified combustion mode and a map for the homogeneous combustion mode are set, and one of the maps is selected according to the current combustion mode.

Thereafter, the routine proceeds to step 1002, in which the basic fuel injection timing DB is added with the fuel injection timing correction amount D (i) calculated in step 911 in FIG. Is calculated. DF = DB + D (i)

The behavior of the air-fuel ratio F / B control during the stratified charge combustion operation of the embodiment (4) described above will be described with reference to the time chart of FIG. During the stratified charge combustion operation, when the actual A / F greatly deviates from the target A / F to the rich side, the air control type air-fuel ratio F / B control is performed, and the air amount correction amount A (throttle opening degree) When the correction amount is equal to or greater than the predetermined amount E1 on the increasing side, the time required for the injected fuel to reach the vicinity of the ignition plug becomes longer, so that the fuel injection timing is advanced in accordance with the air amount correction amount A. As a result, even if the air amount correction amount A greatly changes, the injected fuel can reach the vicinity of the ignition plug in accordance with the ignition timing, and the combustion state can be stabilized. The correction of the fuel injection timing according to the air amount correction amount A may be performed in combination with the above-described embodiments (2) and (3).

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment (1) of the present invention.

FIG. 2 is a functional block diagram for explaining an outline of engine control;

FIG. 3 is a diagram conceptually showing an example of a combustion mode switching map.

FIG. 4 is a flowchart showing a flow of processing of an air-fuel ratio F / B control routine;

FIG. 5 is a flowchart showing the flow of processing of an F / B execution condition determination routine;

FIG. 6 shows an air-fuel ratio F / for a stratified combustion operation according to the embodiment (1).
Flow chart showing the flow of processing of the B control routine

FIG. 7 is a diagram conceptually showing an example of a map of a correction amount with respect to an air amount correction amount in a previous calculation.

FIG. 8 is a flowchart showing a processing flow of a target throttle opening calculation routine;

FIG. 9A shows the behavior of the air-fuel ratio F / B control during steady-state running when the actual A / F is shifted to the lean side from the target A / F during the stratified charge combustion operation in the embodiment (1). FIG. 9B is a time chart showing air-fuel ratio F / B control during steady-state running when the actual A / F is shifted to a richer side than the target A / F during the stratified charge combustion operation in the embodiment (1). Time chart showing behavior

FIG. 10 is an air-fuel ratio F for a stratified combustion operation according to the embodiment (2).
Flowchart showing the flow of the processing of the / B control routine

FIG. 11 is a diagram conceptually showing an example of a map of a correction amount with respect to a fuel injection amount correction amount in a previous calculation.

FIG. 12 is a flowchart showing the flow of processing of a fuel injection time calculation routine.

FIG. 13 is a diagram showing characteristics of pumping loss;

14A is a time chart showing the behavior of the air-fuel ratio F / B control during the stratified charge combustion operation according to the embodiment (2), and FIG.
Is a time chart showing the behavior of the air-fuel ratio F / B control during the stratified combustion operation of the comparative example.

FIG. 15 shows an air-fuel ratio F for a stratified combustion operation according to the embodiment (3).
Flowchart showing the flow of the processing of the / B control routine

FIG. 16 is a diagram conceptually showing an example of a map of a correction amount with respect to an EGR correction amount in a previous calculation.

FIG. 17 is a flowchart showing the flow of a process of a target EGR opening calculation routine;

FIG. 18 is a diagram showing a relationship between an air-fuel ratio and an EGR rate.

FIG. 19 is an air-fuel ratio F during a stratified combustion operation according to the embodiment (3).
Chart showing the behavior of / B control

FIG. 20 is an air-fuel ratio F for a stratified combustion operation according to the embodiment (4).
Flowchart showing the flow of the processing of the / B control routine

FIG. 21 is a diagram conceptually showing an example of a map of a correction amount with respect to a fuel injection timing correction amount in a previous calculation.

FIG. 22 is a flowchart showing the flow of a fuel injection timing calculation routine;

FIG. 23 is an air-fuel ratio F during a stratified combustion operation according to the embodiment (4).
Chart showing the behavior of / B control

24A is a time chart showing the behavior of the conventional air-fuel ratio F / B control when the actual A / F is shifted to the lean side from the target A / F, and FIG. Is a time chart showing the behavior of the conventional air-fuel ratio F / B control when the target A / F is shifted to a richer side than the target A / F is.

[Explanation of symbols]

11. In-cylinder injection engine (in-cylinder injection internal combustion engine), 1
5: throttle valve, 16: ECU (air-fuel ratio feedback control means), 18: intake pipe pressure sensor (intake pipe pressure detection means), 28: fuel injection valve, 37: exhaust pipe, 38: three-way catalyst, 39: lean NOx catalyst, 40 ... EGR pipe (exhaust gas recirculation control means), 41 ... EGR valve (exhaust gas recirculation control means), 42 ... Air-fuel ratio sensor.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 11/10 F02D 11/10 F 21/08 21/08 L 301 301A 301C 41/02 301 41/02 301A 310 310E 310F 335 335 43/00 301 43/00 301H 301J 301K 301N 45/00 324 45/00 324 F02M 25/07 550 F02M 25/07 550G 550M 550R 570 570A F-term (reference) 3G062 AA03 BA07BA04 DA01 DA02 EA10 ED01 ED04 ED10 FA02 FA05 FA06 FA12 GA02 GA04 GA06 GA17 3G065 AA04 AA06 AA07 CA12 CA13 DA06 DA15 EA09 EA12 FA12 GA00 GA01 GA10 GA41 GA46 HA02 HA21 HA22 JA04 JA09 JA11 KA02 3G084 AA04 BA05 BA09 BA09 BA09 EB12 FA07 FA10 FA11 FA19 FA20 FA 29 FA33 FA38 FA39 3G092 AA01 AA06 AA09 AA10 AA13 AA17 BA01 BA05 BA06 BB03 BB06 DC03 DC06 DC09 DE03S DG07 DG08 EA01 EA02 EA07 EA11 EB05 EC01 EC10 FA04 FA15 GA05 GA17 HA05Z HA06X HD04XHE01Z04 HA04 HA04 HA04 HA04 HA04 HA04 LA05 MA01 MA11 MA18 NC04 ND02 NE01 NE06 NE11 NE12 NE14 NE15 NE17 NE19 PA00Z PA01Z PA07Z PA11Z PD02Z PE01Z PE03Z PE04Z PE05Z PE08Z PF03Z

Claims (11)

[Claims] In an in-cylinder injection type internal combustion engine that injects fuel into a cylinder, an air-fuel ratio sensor that detects an air-fuel ratio of exhaust gas of the internal combustion engine and a target air-fuel ratio are set according to an operation state of the internal combustion engine. Target air-fuel ratio setting means; and air-fuel ratio feedback control means for performing air-fuel ratio feedback control so that the air-fuel ratio detected by the air-fuel ratio sensor matches the target air-fuel ratio. An air-fuel ratio control apparatus for an in-cylinder injection internal combustion engine, which performs feedback control of an air-fuel ratio by correcting an air amount during a stratified combustion operation in which fuel is injected by a fuel injection device. 2. The air-fuel ratio feedback control means,
2. The air-fuel ratio control device for a direct injection internal combustion engine according to claim 1, wherein the correction of the air amount by the air-fuel ratio feedback control during the stratified combustion operation is performed by correcting the throttle opening. 3. The air-fuel ratio feedback control means,
The fuel injection amount is corrected according to the air amount correction amount when the air amount correction amount by the air-fuel ratio feedback control during the stratified combustion operation is out of a predetermined range. An air-fuel ratio control device for a direct injection internal combustion engine. 4. The air-fuel ratio feedback control means,
The fuel injection amount is reduced when the air amount correction amount by the air-fuel ratio feedback control during the stratified combustion operation becomes equal to or more than a predetermined value on the increasing side, and the fuel injection is performed when the air amount correction amount becomes equal to or less than a predetermined value on the decreasing side. The air-fuel ratio control device for a direct injection internal combustion engine according to claim 3, wherein the amount is corrected to increase. 5. An intake pipe pressure detecting means for detecting an intake pipe pressure, wherein the air-fuel ratio feedback control means determines whether or not the air amount correction amount is outside a predetermined range by the intake pipe pressure detecting means. The air-fuel ratio control device for a direct injection internal combustion engine according to claim 3 or 4, wherein the control is performed based on a change amount of the intake pipe pressure detected in (1). 6. An exhaust gas recirculation control means for recirculating a part of exhaust gas to an intake system, wherein the air-fuel ratio feedback control means sets a predetermined correction amount of the throttle opening by air-fuel ratio feedback control during stratified combustion operation. When the value is out of the range, the correction amount of the throttle opening is limited to a predetermined range, and instead, the air-fuel ratio is feedback-controlled by correcting the exhaust gas recirculation amount by the exhaust gas recirculation control means. The air-fuel ratio control device for a direct injection internal combustion engine according to claim 2, wherein: 7. The air-fuel ratio feedback control means,
7. The fuel injection timing according to claim 1, wherein when the air amount correction amount is out of a predetermined range by the air-fuel ratio feedback control during the stratified combustion operation, the fuel injection timing is corrected according to the air amount correction amount. An air-fuel ratio control device for an in-cylinder injection internal combustion engine according to any one of claims 1 to 3. 8. The air-fuel ratio feedback control means,
When the air amount correction amount by the air-fuel ratio feedback control during the stratified charge combustion operation is equal to or more than the predetermined amount on the increasing side, the fuel injection timing is advanced and the amount of correction is reduced when the air amount correction amount is equal to or less than the predetermined value on the decreasing side. 8. The air-fuel ratio control apparatus for a direct injection internal combustion engine according to claim 7, wherein the fuel injection timing is retarded. 9. The air-fuel ratio feedback control means,
The air-fuel ratio is feedback-controlled by correcting the fuel injection amount during homogeneous combustion operation in which fuel is injected during the intake stroke, and the air-fuel ratio feedback correction amount related to the fuel injection amount during homogeneous combustion operation is used to control the fuel injection amount during stratified combustion operation. The air-fuel ratio control apparatus for a direct injection internal combustion engine according to any one of claims 1 to 8, wherein the control is reflected. 10. The air-fuel ratio feedback control means performs air-fuel ratio feedback control based on a fuel injection amount during a homogeneous combustion operation, and then performs air-fuel ratio feedback control based on an air amount during a stratified combustion operation. Item 10. An air-fuel ratio control device for a direct injection internal combustion engine according to item 9. 11. The air-fuel ratio feedback control means according to claim 9, wherein the air-fuel ratio feedback correction amount relating to the air amount during the stratified combustion operation is not reflected in the control of the air amount during the homogeneous combustion operation. An air-fuel ratio control device for an in-cylinder injection internal combustion engine according to claim 1.