JP4339599B2 - In-cylinder injection internal combustion engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an in-cylinder injection internal combustion engine in which fuel is injected into a cylinder in a compression stroke and stratified combustion is performed.
[0002]
[Prior art]
In recent years, the demand for in-cylinder injection engines that combine the features of low fuel consumption, low exhaust emissions, and high output has increased rapidly. This in-cylinder injection engine injects a small amount of fuel directly into the cylinder during the compression stroke at low load to stratify the mixture, and increases the fuel injection amount during high load to enter the cylinder during the intake stroke. Direct injection is performed so that the air-fuel mixture is combusted uniformly.
[0003]
In this in-cylinder injection engine, as shown in Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-221091), during the stratified combustion mode operation, the required torque is calculated based on the accelerator opening, etc. Based on this fuel injection amount, various control parameters such as fuel injection timing, ignition timing, intake air amount (throttle opening), EGR amount (EGR valve opening) are calculated. There is something that was made.
[0004]
Further, as shown in Patent Document 2 (Japanese Patent Laid-Open No. 2000-38953), during the stratified combustion mode operation, in order to suppress a torque shock that occurs during a shift of the automatic transmission and the like, For example, torque correction is performed by temporarily correcting the fuel injection amount.
[0005]
[Patent Document 1]
JP 2001-221091 A (pages 3 to 5 etc.)
[Patent Document 2]
JP 2000-38953 A (pages 4 to 5 etc.)
[0006]
[Problems to be solved by the invention]
As described above, in the stratified combustion mode operation, in the system that calculates various control parameters (fuel injection timing, ignition timing, intake air amount, EGR amount, etc.) based on the fuel injection amount calculated based on the required torque, For example, as shown in FIG. 5, when a torque down request is generated at the time of a shift of an automatic transmission and the like, the fuel injection amount is temporarily reduced to correct the torque and the torque correction is performed. Thus, various control parameters such as fuel injection timing, ignition timing, intake air amount (throttle opening), EGR amount (EGR valve opening), and the like also change.
[0007]
At that time, the fuel injection timing and the ignition timing can be changed almost instantaneously with almost no response delay, and can be changed in response to changes in the required torque, but the intake air amount, EGR amount, etc. In the air system, since it takes a certain amount of time for the actual intake air amount and the actual EGR amount to change to their target values in accordance with the change in the required torque, the intake air amount and the EGR amount are different from the change in the required torque. It changes with a response delay. For this reason, when the torque correction (correction of fuel injection amount) is temporarily performed for a short time during the stratified combustion mode operation, the control parameters of the air system having a large response delay such as the intake air amount and the EGR amount are changed. Then, the change timing may deviate from the change timing of the required torque, and the air-fuel ratio and torque may be disturbed, and exhaust emission and torque correction accuracy may be deteriorated.
[0008]
The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to stabilize the behavior of the air-fuel ratio when the torque correction is temporarily performed during the stratified combustion mode operation. Another object of the present invention is to provide a control device for a direct injection internal combustion engine that can improve the accuracy of torque correction.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a control apparatus for a direct injection internal combustion engine according to claim 1 of the present invention calculates a plurality of control parameters based on a required torque during stratified combustion mode operation by a control parameter calculation means. a system for temporarily correcting the required torque when the predetermined torque correction condition is satisfied by the torque correcting means, when the required torque is temporarily corrected in the stratified combustion mode operation, the request after it has been corrected Control parameters of fuel injection amount, fuel injection timing, and ignition timing are calculated based on torque, and intake air amount, exhaust gas recirculation amount, valve timing, fuel pressure are calculated based on the required torque before being temporarily corrected. At least one other control parameter is calculated. Then, when the required torque is temporarily corrected during the stratified combustion mode operation, control is performed based on the control parameter and other control parameters.
[0010]
In this way, when performing torque correction by temporarily correcting the required torque during the stratified combustion mode operation, a control parameter with good responsiveness is calculated based on the corrected required torque. Control parameters can be changed with good response in response to changes in torque. On the other hand, control parameters with poor responsiveness and large delays are calculated based on the required torque before correction so that they do not change much. Can do. As a result, when performing torque correction temporarily during stratified combustion mode operation, the behavior of the air-fuel ratio is stabilized and torque fluctuation is reduced compared to the conventional system (see FIG. 5) that changes all control parameters. Therefore, exhaust emission and torque correction accuracy can be improved.
[0014]
In this case, as in claim 2 , the control parameter calculated based on the corrected fuel injection amount is at least one of the fuel injection timing and the ignition timing, and the control parameter is calculated based on the fuel injection amount before correction. parameter, the intake air amount, exhaust gas recirculation amount, Ru least 1 Tsutosu of the valve timing, the fuel pressure. In this way, at the time of torque correction, the fuel injection timing and ignition timing with good responsiveness can be changed with good response in response to changes in the required torque (fuel injection amount), resulting in poor responsiveness and delay. The intake air amount, exhaust gas recirculation amount, valve timing, and fuel pressure that are large can be kept from changing so much.
[0015]
In addition, during stratified combustion mode operation, fuel is injected into the cylinder to form a stratified mixture, and the stratified mixture is ignited at the timing when it flows to the vicinity of the spark plug for stratified combustion, so good stratified combustion In order to ensure this, it is necessary to appropriately maintain the relationship between the in-cylinder airflow strength (swirl flow strength and tumble flow strength), fuel injection timing, and ignition timing.
[0017]
According to a third aspect of the present invention, it is preferable that the torque correction condition is satisfied in at least one operating state among a shift of the automatic transmission, a return from fuel cut, and an acceleration. In this way, the control for torque correction according to the present invention can be performed at the time of shifting, fuel cut recovery, and acceleration of an automatic transmission that needs to suppress torque shock. It is possible to prevent disturbance of the air-fuel ratio while effectively suppressing the time shock and the acceleration shock.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
<< 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 the intake pipe 12 of the cylinder injection engine 11 which is a cylinder injection internal combustion engine, and an air flow meter 14 for detecting the intake air amount is provided downstream of the air cleaner 13. It has been. A throttle valve 16 driven by a motor 15 such as a DC motor is provided on the downstream side of the air flow meter 14, and an opening degree (throttle opening degree) of the throttle valve 16 is detected by a throttle opening degree sensor 17.
[0019]
A surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 that introduces air into each cylinder of the engine 11, and controls the in-cylinder airflow strength (swirl flow strength and tumble flow strength) in the intake manifold 20 of each cylinder. An airflow control valve 31 is provided.
[0020]
A fuel injection valve 21 that directly injects fuel into the cylinder is attached to an upper portion of each cylinder of the engine 11. A spark plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 22. In addition, the intake valve 37 and the exhaust valve 38 of the engine 11 are provided with variable valve timing mechanisms 39 and 40 for varying the valve timing, respectively.
[0021]
A knock sensor 32 for detecting knocking and a cooling water temperature sensor 23 for detecting cooling water temperature are attached to the cylinder block of the engine 11. A crank angle sensor 24 that outputs a crank angle signal at every predetermined crank angle is attached to the outer peripheral side of the crankshaft (not shown). Based on the output signal of the crank angle sensor 24, the crank angle and the engine speed are detected.
[0022]
On the other hand, the exhaust pipe 25 of the engine 11 is provided with an upstream catalyst 26 and a downstream catalyst 27 for purifying the exhaust gas, and the air-fuel ratio or rich / lean of the exhaust gas is detected on the upstream side of the upstream catalyst 26. An exhaust gas sensor 28 (air-fuel ratio sensor, oxygen sensor, etc.) is provided. In the present embodiment, a three-way catalyst for purifying CO, HC, NOx, etc. in the exhaust gas near the stoichiometric air-fuel ratio is provided as the upstream side catalyst 26, and a NOx occlusion reduction type catalyst is provided as the downstream side catalyst 27. . This NOx occlusion reduction type catalyst occludes NOx in the exhaust gas when the air-fuel ratio of the exhaust gas is lean, and reduces and purifies the occluded NOx when the air-fuel ratio becomes near the stoichiometric air-fuel ratio or becomes rich. Has characteristics.
[0023]
Further, a part of the exhaust gas is recirculated to the intake side between the downstream side of the upstream catalyst 26 in the exhaust pipe 25 and the surge tank 18 on the downstream side of the throttle valve 16 in the intake pipe 12. An EGR pipe 33 is connected, and an EGR valve 34 for controlling the exhaust gas recirculation amount (EGR amount) is provided in the middle of the EGR pipe 33. Further, the accelerator sensor 36 detects the amount of depression of the accelerator pedal 35 (accelerator opening).
[0024]
Outputs of the various sensors described above are input to an engine control circuit (hereinafter referred to as “ECU”) 30. The ECU 30 is mainly composed of a microcomputer, and executes various control programs stored in a built-in ROM (storage medium), so that the fuel injection amount of the fuel injection valve 21 and the fuel are controlled according to the engine operating state. The injection timing, the ignition timing of the spark plug 22 and the like are controlled.
[0025]
The ECU 30 switches between the stratified combustion mode and the homogeneous combustion mode in accordance with the engine operating state (required torque, engine speed, etc.). In the stratified charge combustion mode, a small amount of fuel is directly injected into the cylinder in the compression stroke, and a stratified mixture is formed in the vicinity of the spark plug 22 for stratified charge combustion, thereby improving fuel efficiency. On the other hand, in the homogeneous combustion mode, the engine output is increased by increasing the fuel injection amount and directly injecting it into the cylinder during the intake stroke to form a homogeneous mixture and performing homogeneous combustion.
[0026]
As shown in FIG. 2, the ECU 30 calculates a required shaft torque based on the accelerator opening, the engine rotational speed Ne, the vehicle speed, and the like during the stratified combustion mode operation, and the internal loss torque and the external load torque are added to the required shaft torque. Then, the required indicated torque is obtained by adding a correction torque or the like by idle speed control (ISC).
[0027]
Here, the internal loss torque to be added to the required shaft torque is a mechanical friction loss and a pumping loss, and the mechanical friction loss is calculated by a map or the like based on the engine rotational speed Ne and the cooling water temperature. A map or the like is calculated based on the rotational speed Ne and the intake pipe pressure. The external load torque to be added to the required shaft torque is the load torque of auxiliary equipment (air conditioner compressor, alternator, power steering pump, etc.) driven by the power of the engine 11, and the air conditioner signal and alternator load current. It is set according to etc. Further, the ISC correction torque to be added to the required shaft torque is calculated by a map or the like based on the target idle speed and the current engine speed Ne.
[0028]
During normal operation during the stratified charge combustion mode operation (when no torque down request is generated), the ECU 30 maps the fuel injection amount, the fuel injection timing, the ignition based on the requested indicated torque and the engine speed Ne based on the requested indicated torque, respectively. By calculating various control parameters such as timing, in-cylinder airflow strength (airflow control valve opening), EGR amount (EGR valve opening), valve timing, fuel pressure, intake air amount (throttle opening), etc. In the range of the control parameter calculation means, and based on these control parameters, the fuel injection valve 21, the spark plug 22, the airflow control valve 31, the EGR valve 34, the variable valve timing mechanisms 39 and 40, the fuel pump ( (Not shown), the throttle valve 16 and the like are driven.
[0029]
In addition, during the stratified charge combustion mode operation, the ECU 30 performs torque reduction when a torque down request is generated in an operation state in which a torque shock is generated, for example, at the time of shifting of the automatic transmission, at the time of fuel cut return, or at the time of acceleration. By calculating the torque down amount necessary to suppress the shock, and subtracting this torque down amount from the required indicated torque to temporarily correct the indicated indicated torque, Play a role.
[0030]
When the torque reduction request is generated and the required indicated torque is temporarily corrected during the stratified combustion mode operation, the ECU 30 determines the fuel injection amount and the fuel injection timing based on the corrected indicated indicated torque and the engine rotational speed Ne. , Ignition timing, in-cylinder airflow strength (airflow control valve opening) is calculated from a map or the like, and EGR amount (EGR valve opening), valve timing, fuel pressure based on the required indicated torque before correction and engine speed Ne The intake air amount (throttle opening) is calculated using a map or the like.
[0031]
Here, the fuel injection amount, the fuel injection timing, and the ignition timing calculated based on the required indicated torque after correction are control parameters with good responsiveness, and the EGR amount (EGR) calculated based on the required indicated torque before correction. Valve opening), valve timing, fuel pressure, and intake air amount (throttle opening) are control parameters with poor response and large delay.
[0032]
An execution example of this embodiment (1) described above will be described with reference to the time chart of FIG. During normal operation in the stratified combustion mode operation (when no torque down request is generated), the required indicated torque is calculated based on the accelerator opening, etc., and the fuel injection amount and the fuel injection timing are calculated based on this required indicated torque. Various control parameters such as ignition timing, in-cylinder airflow strength (airflow control valve opening), EGR amount (EGR valve opening), intake air amount (throttle opening), valve timing, fuel pressure, and the like are calculated.
[0033]
Thereafter, when a torque down request is generated during a shift of the automatic transmission or the like, the requested indicated torque is temporarily reduced to correct the torque. During this torque correction, control parameters with good responsiveness (fuel injection amount, fuel injection timing, ignition timing, in-cylinder airflow strength) are calculated based on the corrected required indicated torque, thereby changing the indicated indicated torque. The response is changed according to the response. On the other hand, the control parameters (EGR amount, intake air amount, valve timing, fuel pressure) with poor response and large delay are calculated based on the requested indicated torque before correction so as not to change much. .
[0034]
This stabilizes the behavior of the air-fuel ratio and reduces torque fluctuations compared to the conventional system (see FIG. 5) in which all control parameters are changed when temporarily correcting torque during stratified combustion mode operation. Thus, exhaust emission and torque correction accuracy can be improved.
[0035]
Further, during the stratified charge combustion mode operation, fuel is injected into the cylinder to form a stratified mixture, and the stratified mixture is ignited at the timing when the stratified mixture flows to the vicinity of the spark plug 22 and stratified combustion is performed. In order to ensure combustion, it is necessary to appropriately maintain the relationship between the in-cylinder airflow intensity, the fuel injection timing, and the ignition timing.
[0036]
In this respect, in the present embodiment (1), the in-cylinder airflow strength is calculated based on the required indicated torque after correction in addition to the fuel injection timing and ignition timing at the time of torque correction. In-cylinder airflow strength can be changed at the same time according to changes in fuel injection timing and ignition timing, and the relationship between in-cylinder airflow strength, fuel injection timing, and ignition timing can be maintained appropriately, and good stratified combustion can be ensured. Can do.
[0037]
<< Embodiment (2) >>
Next, Embodiment (2) of this invention is demonstrated using FIG.
In the present embodiment (2), during normal operation during stratified combustion mode operation (when no torque down request is generated), the ECU 30 uses a map or the like based on the requested indicated torque and the engine rotational speed Ne to map the fuel injection amount. Based on this fuel injection amount, fuel injection timing, ignition timing, in-cylinder airflow strength (airflow control valve opening), EGR amount (EGR valve opening), valve timing, fuel pressure, intake air amount (throttle) Opening) etc. are calculated with a map or the like.
[0038]
When a torque reduction request is generated and the required indicated torque is temporarily corrected during the stratified combustion mode operation, the corrected fuel injection amount is calculated based on the corrected indicated indicated torque and the engine rotational speed Ne. Then, based on the corrected fuel injection amount and the engine rotational speed Ne, the fuel injection timing, ignition timing, and in-cylinder airflow strength (airflow control valve opening) are calculated using a map or the like. Further, a fuel injection amount before correction is calculated based on the requested indicated torque before correction and the engine rotational speed Ne, and an EGR amount (EGR valve opening) is calculated based on the fuel injection amount before correction and the engine rotational speed Ne. The valve timing, fuel pressure, and intake air amount (throttle opening) are calculated using a map or the like.
[0039]
In the embodiment (2) described above, as in the embodiment (1), the control parameter with good responsiveness follows the response with good response according to the change in the requested indicated torque torque (fuel injection amount) at the time of torque correction. Control parameters that have poor responsiveness and a large delay can be kept from changing so much that the air-fuel ratio behavior can be stabilized to reduce torque fluctuations, exhaust emissions, and torque correction. Accuracy can be improved.
[0040]
In each of the above embodiments (1) and (2), the present invention is applied to control at the time of torque correction for preventing torque fluctuation at the time of shifting of the automatic transmission, at the time of fuel cut return, and acceleration. However, the present invention is not limited to this, and the present invention may be applied to control at the time of torque correction when preventing torque fluctuation in other operating states such as when the anti-lock brake system is operated or when the traction control system is operated. .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire engine control system according to an embodiment (1) of the present invention. FIG. 2 is a functional block diagram for explaining a control parameter calculation method during stratified combustion mode operation according to an embodiment (1). FIG. 3 is a time chart showing an example of control at the time of torque correction during the stratified charge combustion mode operation of the embodiment (1). FIG. 4 explains a calculation method of control parameters during the stratified charge combustion mode operation of the embodiment (2). Functional block diagram for the purpose [FIG. 5] Time chart showing a control example at the time of torque correction during the conventional stratified combustion mode operation
DESCRIPTION OF SYMBOLS 11 ... Cylinder injection type engine (Cylinder injection type internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Cooling water temperature sensor, 24 ... Crank angle sensor, 25 ... Exhaust pipe, 30 ... ECU (control parameter calculation means, torque correction means), 31 ... Airflow control valve, 34 ... EGR valve, 36 ... Accelerator sensor, 37 ... Intake valve, 38 ... Exhaust valve, 39,40 ... Variable valve Timing mechanism.

Claims (3)

In a control apparatus for a direct injection internal combustion engine that operates in a stratified combustion mode in which fuel is injected into a cylinder in a compression stroke and stratified combustion is performed,
Control parameter calculating means for calculating a plurality of control parameters based on the required torque during the stratified combustion mode operation;
Torque correction means for temporarily correcting the required torque when a predetermined torque correction condition is satisfied,
Said control parameter calculating means, the when the required torque by the torque correcting means during stratified charge combustion mode operation Ru is temporarily corrected fuel injection amount based on the required torque after being corrected, the fuel injection timing, and calculates the control parameters of the ignition timing, intake air amount based on the required torque before being temporarily corrected exhaust gas recirculation amount is calculated at least one other control parameters of the valve timing, fuel pressure And
When the required torque is temporarily corrected by the torque correction means during the stratified combustion mode operation, the control is performed based on the control parameter calculated by the control parameter calculation means and the other control parameters. A control apparatus for a cylinder injection internal combustion engine. In a control apparatus for a direct injection internal combustion engine that operates in a stratified combustion mode in which fuel is injected into a cylinder in a compression stroke and stratified combustion is performed,
Control parameter calculating means for calculating a plurality of control parameters based on the fuel injection amount calculated based on the required torque during the stratified combustion mode operation;
Torque correction means for temporarily correcting the fuel injection amount when a predetermined torque correction condition is satisfied,
Said control parameter calculating means, the stratified by combustion mode the torque correction means during operation when the amount the fuel injection Ru is temporarily corrected, based on the fuel injection amount after correction fuel injection timing or ignition timing in which the calculated control parameters, the intake air amount based on the fuel injection amount before being temporarily corrected exhaust gas recirculation amount is calculated at least one other control parameters of the valve timing, fuel pressure There,
When the fuel injection amount is temporarily corrected by the torque correction unit during the stratified combustion mode operation, the control is performed based on the control parameter calculated by the control parameter calculation unit and the other control parameter. A control apparatus for a direct injection internal combustion engine. 3. The in-cylinder injection type according to claim 1, wherein the torque correction condition is satisfied in at least one operating state among a shift of the automatic transmission, a return from fuel cut, and an acceleration. Control device for internal combustion engine.

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