JP4378665B2 - Control device and control method for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device and a control method for an internal combustion engine that controls operation of the internal combustion engine by determining a required torque requested by a driver.
[0002]
[Prior art]
In recent automobile engine control that has been electronically controlled, in order to realize responsive drivability that responds quickly to the driver's accelerator operation, the driver determines the driver's accelerator opening, engine speed, etc. In other cases, so-called torque demand control is performed in which the acceleration force (torque) required by the vehicle is determined and the throttle opening, fuel injection amount, ignition timing, and the like are controlled according to the torque required by the driver. In the conventional torque demand control, the throttle opening is controlled based on the target air-fuel ratio determined from the required torque in order to satisfy the required torque to the engine and the target air-fuel ratio at the same time, while determined from the intake air amount and the target air-fuel ratio. The fuel injection amount is controlled based on the target fuel amount (see Japanese Patent Laid-Open No. 9-287513).
[0003]
[Problems to be solved by the invention]
However, in the conventional torque demand control, in a transient state in which the load changes suddenly, the time between the timing at which the in-cylinder charged air amount is determined and the timing at which the fuel injection amount is determined based on the target air-fuel ratio and the intake air amount. An error due to the deviation occurs, and the ratio (air-fuel ratio) between the actual cylinder air charge amount and the cylinder inflow fuel amount deviates from the target air-fuel ratio, and the control accuracy of the air-fuel ratio at the time of transition deteriorates. There was a drawback.
[0004]
That is, since the cylinder charge air amount is not determined until the intake valve closing timing, the cylinder charge air amount determination timing is considerably delayed from the fuel injection amount determination timing (immediately before the intake valve opening timing). Moreover, there is a response delay of the throttle valve and a flow delay of the intake air from when the command value of the throttle opening is output to the electronic throttle until the throttle opening actually changes and the in-cylinder charged air amount changes. . On the other hand, the in-cylinder inflow fuel amount is affected by fuel transportation delay due to air system wall surface attached fuel (wet) or the like. Since the influence of the fuel transport delay and the throttle valve response delay becomes large during the transition, the ratio (air-fuel ratio) between the in-cylinder charged air amount and the in-cylinder inflow fuel amount deviates from the target air-fuel ratio during the transition.
[0005]
The present invention has been made in consideration of such circumstances, and therefore, the object of the present invention is to provide a control device and control method for an internal combustion engine that can perform accurate air-fuel ratio control even in a transient state in a torque demand control system. Is to provide.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the first and third aspects of the present invention, a fuel injection valve for injecting fuel is attached in the vicinity of the intake port of each cylinder of the internal combustion engine, and based on the required torque by the reference model calculation means. A reference model of the target in-cylinder charged air amount is calculated, the target in-cylinder inflow fuel amount calculation means calculates the target in-cylinder inflow fuel amount based on the reference model and the target air-fuel ratio, and the fuel injection control means calculates the air system. In consideration of fuel transportation delay due to fuel adhering to the wall, etc., the fuel injection amount to be injected from the fuel injection valve is determined so that the actual in-cylinder inflow fuel amount matches the target in-cylinder inflow fuel amount, and the throttle opening command value The calculation means calculates a command value for the throttle opening based on at least the reference model of the target cylinder charge air amount and the internal combustion engine rotational speed. Further, as shown in FIG. 4 (a), the throttle control means performs a delay time (Z ^−L ) from the fuel injection amount determination timing to the intake valve closing timing at which the cylinder charge air amount and the cylinder inflow fuel amount are determined. slow-is time (Z ^-L) throttle valve response delay time is shorter than the (Z ^-m) and the time shift amount ^(Z - ^(Lm)) only the fuel phase of the command value of the throttle opening The target in-cylinder obtained by delaying the phase by the delay time (Z ^-L ) from the reference model to the intake valve closing timing by driving the throttle valve with a delay from the injection amount determination timing The throttle opening is controlled so as to match the amount of charge air. In this way, in the torque demand control system, taking into account the time delay from the determination of the air system dynamic characteristics, the fuel transport system dynamic characteristics, and the fuel injection amount determination to the cylinder charge air amount determination (intake valve closing timing). The control of the in-cylinder charged air amount and the in-cylinder inflow fuel amount can be synchronized, and the ratio between the actual in-cylinder charged air amount and the in-cylinder inflow fuel amount (air-fuel ratio) is always matched with the target air-fuel ratio. Can do. Thus, accurate air-fuel ratio control can be performed even during a transition, acceleration response can be improved, and exhaust emission can be reduced.
[0007]
In this case, it is preferable to set a reference model of the target cylinder air charge amount based on a value obtained by smoothing the required torque (first-order lag process). In this way, the reference model of the target cylinder air charge amount can be set by a simple calculation process.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 which is an internal combustion engine, and an air flow meter 14 for detecting the intake air amount is provided downstream of the air cleaner 13. On the downstream side of the air flow meter 14, a throttle valve 15 driven by a motor (not shown) and the like, and a throttle opening sensor 16 for detecting the throttle opening are provided.
[0009]
Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17. The surge tank 17 is provided with an intake manifold 19 for introducing intake air to each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. ing.
[0010]
On the other hand, a catalyst 22 such as a three-way catalyst for purifying CO, HC, NOx, etc. in the exhaust gas is installed in the middle of the exhaust pipe 21 of the engine 11. An air-fuel ratio sensor 23 (or oxygen sensor) that detects the air-fuel ratio of the exhaust gas is provided on the upstream side of the catalyst 22. A cooling water temperature sensor 24 for detecting the cooling water temperature and a crank angle sensor 25 for detecting the engine rotation speed are attached to the cylinder block of the engine 11. Further, an accelerator sensor 26 for detecting the opening degree of the accelerator pedal (accelerator opening degree) is provided.
[0011]
Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 27. The ECU 27 is mainly composed of a microcomputer, and controls the fuel injection amount and the throttle opening by executing the torque demand control program of FIG. 2 stored in a built-in ROM (storage medium).
[0012]
In the intake port injection engine 11, as shown in FIG. 3, the fuel injection amount is determined immediately before the intake valve opening timing to perform injection setting, and the fuel injection valve 20 is driven immediately before or after the intake valve opening timing. To perform fuel injection. In the fuel transportation system until the injected fuel actually flows into the cylinder, there is a fuel transportation delay due to air system wall-attached fuel (wet), etc., so the in-cylinder inflow fuel amount changes with a delay from the fuel injection timing. To do. Further, since the in-cylinder charged air amount is not determined until the intake valve closing timing, the in-cylinder charged air amount determining timing is considerably delayed from the fuel injection amount determining timing (immediately before the intake valve opening timing). Moreover, there is a response delay of the throttle valve and a flow delay of the intake air from when the command value of the throttle opening is output to the electronic throttle until the throttle opening actually changes and the in-cylinder charged air amount changes. .
[0013]
The effects of the time delay from the determination of the air system dynamic characteristics, the fuel transport system dynamic characteristics, and the determination of the fuel injection amount to the determination of the in-cylinder charged air amount (intake valve closing timing) increase during transients. If this is not taken into consideration, the ratio (air-fuel ratio) between the in-cylinder charged air amount and the in-cylinder inflow fuel amount will deviate from the target air-fuel ratio at the time of transition.
[0014]
Therefore, in the present embodiment, as shown in FIG. 4A, a reference model of the target cylinder charge air amount is calculated based on the required torque, and the target cylinder inflow fuel is calculated based on the reference model and the target air-fuel ratio. The fuel injection amount to be injected from the fuel injection valve 20 is calculated so that the actual in-cylinder inflow fuel amount coincides with the target in-cylinder inflow fuel amount in consideration of the fuel transportation delay due to the fuel attached to the air system wall and the like. Further, the throttle opening command value is calculated based on the reference model of the target cylinder charge air amount, the engine speed, and the like. Then, the fuel injection amount determining timing delay time until the intake valve closing timing (Z ^-L) and the time shift amount of the response delay time of the throttle valve ^{15 (Z -m) (Z -} (Lm)) only the throttle opening When the throttle valve 15 is driven by delaying the phase of the command value of the degree from the fuel injection amount determination timing, the actual cylinder air charge amount becomes equal to the delay time (Z ^−L ), The throttle opening is controlled so as to coincide with the target in-cylinder charged air amount obtained by delaying the phase.
[0015]
The processing contents of the torque demand control program shown in FIG. 2 for executing this control will be described below. First, in step 101, the accelerator opening is detected from the output of the accelerator sensor 26, and in the next step 102, the required torque is calculated based on the accelerator opening. At this time, the required torque may be calculated in consideration of the engine rotation speed, the vehicle speed, and the like in addition to the accelerator opening.
[0016]
Then, after the required torque is smoothed (first-order lag processing) in step 103, the value obtained by smoothing the required torque is multiplied by a predetermined gain in step 104, and the target in-cylinder charged air amount is determined. Calculate the model. The processing of these steps 103 and 104 plays a role corresponding to the normative model calculation means in the claims.
[0017]
After the calculation of the reference model, the routine proceeds to step 105, where the timing synchronization delay time (Z- ^(Lm) ) for synchronizing the in-cylinder inflow fuel amount and the in-cylinder charged air amount is determined according to the engine speed, the intake air amount, etc. Set by map. Here, the timing synchronization delay time (Z- ^(Lm) ) is the delay time (Z ^-L ) from the fuel injection amount determination timing to the intake valve closing timing and the response delay time (Z ^-m ) of the throttle valve 15. It corresponds to the time difference. The response delay time (Z ^−m ) of the throttle valve 15 is a delay time from when the throttle opening command value is output to the electronic throttle until the throttle opening actually changes.
[0018]
Thereafter, in step 106, a throttle opening command value is calculated based on the reference model of the target cylinder charge air amount, the engine speed, etc., and in the next step 107, a control signal corresponding to the throttle opening command value is calculated. ^Is delayed from the fuel injection amount determination timing by the timing synchronization delay time (Z- ^(Lm) ) and output to the motor of the electronic throttle, and the throttle valve 15 is driven to control the throttle opening. The process of step 106 plays a role corresponding to the throttle opening command value calculation means in the claims, and the processes of steps 105 and 107 play a role corresponding to the throttle control means in the claims.
[0019]
On the other hand, in the control of the fuel injection amount, in step 108, the target air-fuel ratio is set by a map or the like based on the required torque and the engine speed, and in the next step 109, the target in-cylinder charged air amount is divided by the target air-fuel ratio. Thus, the target in-cylinder inflow fuel amount is obtained. The processing of this step 109 plays a role corresponding to the target in-cylinder inflow fuel amount calculation means in the claims.
[0020]
Thereafter, in step 110, a fuel transport delay correction coefficient for taking into account the fuel transport delay due to the air system wall surface attached fuel or the like is calculated. In step 111, the actual air-fuel ratio is detected from the output of the air-fuel ratio sensor 23, and in the next step 112, an air-fuel ratio feedback correction coefficient is calculated according to the deviation between the actual air-fuel ratio and the target air-fuel ratio.
[0021]
Thereafter, in step 113, a final fuel injection amount is obtained by multiplying the target in-cylinder inflow fuel amount by a fuel transport delay correction coefficient, an air-fuel ratio feedback correction coefficient, a water temperature correction coefficient, and the like. In the next step 114, an injection pulse having a pulse width corresponding to the fuel injection amount is output to the fuel injection valve 20 to inject fuel. The processing of these steps 110 to 114 plays a role corresponding to the fuel injection control means in the claims.
[0022]
In the present embodiment described above, as shown in FIG. 4A, a reference model of the target cylinder charge air amount is calculated based on the required torque, and the target cylinder inflow is calculated based on the reference model and the target air-fuel ratio. while calculating a fuel amount to determine the fuel injection amount so that the actual cylinder inflow fuel amount in consideration of the fuel transport delay due to the air system fuel deposited on the wall or the like coincides with the target cylinder inflow fuel amount, further, the target The intake valve closing timing at which the throttle opening command value is calculated based on the reference model of the in-cylinder charged air amount and the engine speed, and the in-cylinder charged air amount and in-cylinder inflow fuel amount are determined from the fuel injection amount determination timing delay time until (Z ^-L) and the time shift amount of the response delay time of the throttle valve ^{15 (Z -m) (Z -} (Lm)) only the phase of the throttle opening command value the fuel injection amount determining timing Slow to delay Since the torque valve 15 is driven, the cylinder is considered in consideration of the time delay from the determination of the air system dynamic characteristics, the fuel transport system dynamic characteristics, and the fuel injection amount determination to the cylinder charge air amount determination (intake valve closing timing). The control of the in-cylinder air amount and the in-cylinder inflow fuel amount can be synchronized, and the ratio (air-fuel ratio) between the actual in-cylinder in-cylinder air amount and the in-cylinder inflow fuel amount can always be matched with the target air-fuel ratio. . Thus, accurate air-fuel ratio control can be performed even during a transition, acceleration response can be improved, and exhaust emission can be reduced.
[0023]
On the other hand, in the comparative example shown in FIG. 4B, the time between the delay time (Z ^−L ) from the fuel injection amount determination timing to the intake valve closing timing and the response delay time (Z ^−m ) of the throttle valve 15. Since the amount of deviation is not taken into account and the phase of the fuel injection amount and the throttle opening command value is synchronized, the ratio (air-fuel ratio) between the in-cylinder charged air amount and the in-cylinder inflow fuel amount at the time of transition is Due to the timing difference between the two, the air-fuel ratio deviates from the target air-fuel ratio, and the control accuracy of the air-fuel ratio at the time of transition deteriorates.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment of the present invention. FIG. 2 is a flowchart explaining an outline of torque demand control. FIG. 3 is an engine cycle, in-cylinder inflow fuel amount, and in-cylinder filling. FIG. 4A is a diagram illustrating a control method according to an embodiment of the present invention, and FIG. 4B is a diagram illustrating a control method according to a comparative example.
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter, 15 ... Throttle valve, 18 ... Intake pipe pressure sensor, 20 ... Fuel injection valve, 25 ... Crank angle sensor, 26 ... Accelerator sensor, 27 ... ECU (Standard model calculation means, target cylinder inflow fuel amount calculation means, combustion injection control means, throttle control means).

Claims (3)

Control of an internal combustion engine in which a fuel injection valve for injecting fuel is installed in the vicinity of an intake port of each cylinder of the internal combustion engine, and a required torque requested by a driver is determined and operation of the internal combustion engine is controlled based on the required torque In the device
A norm model calculation means for setting a norm model of the target cylinder charge air amount based on the required torque;
Target in-cylinder inflow fuel amount calculation means for calculating a target in-cylinder inflow fuel amount based on the reference model of the target in-cylinder charged air amount and the target air-fuel ratio;
Fuel injection control for determining the fuel injection amount to be injected from the fuel injection valve so that the actual in-cylinder inflow fuel amount matches the target in-cylinder inflow fuel amount in consideration of fuel transportation delay due to fuel adhering to the intake system wall surface, etc. Means,
Throttle opening command value calculation means for calculating a command value of the throttle opening based on at least a reference model of the target cylinder charge air amount and the internal combustion engine rotation speed;
It said fuel injection control means by the fuel injection amount determined in-cylinder charged air amount from timing and cylinder inflow fuel amount is delayed until the intake valve closing timing to determine the time (Z ^-L) and slow-is time (Z ^-L) than a short time the throttle valve response delay time (Z ^-m) and the time shift amount - the ^{(Z (Lm))} only the throttle valve delays the phase of the command value of the throttle opening from said fuel injection amount determining timing By driving, the actual in-cylinder charged air amount matches the target in-cylinder charged air amount obtained by delaying the phase of the reference model by the delay time (Z- ^L ) until the intake valve closing timing. A control device for an internal combustion engine, comprising: throttle control means for controlling a throttle opening.   2. The control device for an internal combustion engine according to claim 1, wherein the reference model calculation unit sets a reference model of the target cylinder charge air amount based on a value obtained by performing the smoothing process on the required torque. Control of an internal combustion engine in which a fuel injection valve for injecting fuel is installed in the vicinity of an intake port of each cylinder of the internal combustion engine, and a required torque requested by a driver is determined and operation of the internal combustion engine is controlled based on the required torque In the method
Based on the required torque, the reference model of the target cylinder charge air amount is calculated, the target cylinder inflow fuel amount is calculated based on the reference model and the target air-fuel ratio, and the fuel transportation delay due to the fuel adhering to the intake system wall surface, etc. The fuel injection amount to be injected from the fuel injection valve is determined so that the actual in-cylinder inflow fuel amount coincides with the target in-cylinder inflow fuel amount, and at least the norm of the target in-cylinder charged air amount A command value of the throttle opening is calculated based on the model and the internal combustion engine rotational speed, and a delay time (Z ⁻⁾ from the fuel injection amount determination timing to the intake valve closing timing at which the cylinder charge air amount and the cylinder inflow fuel amount are determined. ^L) and slow-is time (Z ^-L) response delay time of the throttle valve is shorter than the (Z ^-m) and the time shift amount of ^(Z - ^(Lm)) by a phase command value of the throttle opening The fuel injection amount decision The target in-cylinder obtained by delaying the phase of the reference model by the delay time (Z ^-L ) from the reference model to the intake valve closing timing by driving the throttle valve with a delay from a fixed timing A control method for an internal combustion engine, wherein the throttle opening is controlled so as to coincide with the amount of charged air.

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