JP2002021613A - Fuel control device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a torque shortage at the time of acceleration operation of diesel engine. SOLUTION: An ignition timing of fuel fed to a combustion chamber is controlled corresponding to an operation state of engine and a target value of suction air amount is set corresponding to the operation state of the engine to control a suction of air to the control chamber based on the target value. A fuel injection timing is advance-corrected based on a deviation of an actual fresh air amount and a target fresh air amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device for an automobile diesel engine or the like.

[0002]

2. Description of the Related Art A fuel injection timing of a diesel engine or an ignition timing of a gasoline engine is appropriately advanced in accordance with a change in operating conditions of the engine, so that the ignition timing of fuel is advanced to increase the torque generated by the engine. I have. For example, Japanese Patent Application Laid-Open No. H10-238377 discloses that in a diesel engine in which the fuel injection timing is controlled in accordance with the engine speed and the engine load, the speed and the engine speed after the speed change are changed. Is described, a target injection timing after the shift is determined based on the predicted value, and the command value of the injection timing is advanced from the target injection timing after the shift before the shift is completed. This is to reduce the response delay of the injection timing control at the time of shifting, to improve the acceleration and the exhaust performance.

Further, the above publication describes that the injection timing is feedback-controlled based on the deviation between the target injection timing and the actual injection timing, and that the control gain is corrected in accordance with the presence or absence of rapid acceleration, rapid deceleration, and shift. Have been.

[0004]

In an engine, the amount of fuel supplied to a combustion chamber, the amount of intake air, and the ignition timing of fuel are controlled in accordance with the operating state of the engine. Unlike this, the intake air amount has a large delay until it actually reaches the target value. That is, when the target value of the intake air amount is changed due to a change in the engine operating conditions such as during acceleration, even if the operation amount of the actuator for adjusting the intake air amount is changed accordingly, the air drawn into the combustion chamber is changed. It takes time for the amount to actually reach the target value. For this purpose, the intake air amount is controlled so that the operation amount of the actuator changes earlier in response to changes in the engine operating conditions, but it cannot respond sufficiently, and the engine torque is excessive during the transition period. Shortage tends to occur, and the exhaust performance also deteriorates.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention corrects and controls the ignition timing of fuel in accordance with a deviation of an actual intake air amount from a target value.

That is, according to the present invention, in a combustion control apparatus for an engine in which the ignition timing of fuel supplied to a combustion chamber is controlled in accordance with the operation state of the engine, the target value of the intake air amount is set to Intake air amount control means for controlling intake of air into the combustion chamber based on the target value, and correcting the ignition timing according to a deviation of the intake air amount from the target value. And an ignition timing correction means.

Therefore, when the actual intake air amount lags behind the change in the target value in the transition period when the operating state of the engine changes, the delay is corrected by correcting the ignition timing so that, for example, excessive or insufficient engine torque is not caused. Or the exhaust performance can be compensated so as not to deteriorate.

Further, the present invention provides a combustion control apparatus for an engine as described above, wherein target torque setting means for setting a target torque of the engine in accordance with an operation state of the engine;
An ignition timing setting means for setting a target value of the ignition timing according to a target torque set by the target torque setting means for controlling the ignition timing; and Intake air amount setting means for setting the target value of the intake air amount according to the target torque set by the torque setting means, wherein the ignition timing correction means adjusts the ignition timing set by the ignition timing setting means. And correcting the engine torque to approach the target torque in accordance with the deviation of the intake air amount from the target value.

Therefore, even when the actual intake air amount lags behind the change in the target value, the ignition timing is corrected according to the deviation of the intake air amount from the target value, so that the engine torque approaches the target torque. be able to.

In this case, the ignition timing correction means corrects the ignition timing when the intake air amount is smaller than the target value, and increases as the deviation of the intake air amount from the target value increases. The advance angle may be increased.
Thus, when the intake air amount lags behind the change in the target value during engine acceleration, shortage of engine torque can be avoided.

Further, fuel supply amount setting means for setting a target value of the amount of fuel to be supplied to the combustion chamber according to the target torque set by the target torque setting means, and a fuel supply amount setting means for setting the target value. Calculating means for obtaining an engine torque obtained when the amount of fuel burned at the ignition timing corrected by the ignition timing correction means, and an engine torque obtained by the torque calculation means and the target torque setting means. It is preferable to provide a fuel supply amount correcting means for correcting the fuel supply amount based on a deviation from the set target torque so that the engine torque approaches the target torque.

That is, there is a limit to the amount of engine torque that can be increased by accelerating the ignition timing of fuel from the viewpoint of improving exhaust performance. For example, in a gasoline engine, if the ignition timing is advanced, the maximum combustion temperature increases, the amount of NOx in the exhaust gas increases, and the amount of HC (hydrocarbon) also increases. In a diesel engine, if the fuel injection timing is advanced, the ignition delay period becomes longer, the premixed combustion becomes sharper, and the temperature of the combustion chamber rises sharply, so that the NOx amount increases.

Therefore, when the engine torque obtained by the correction of the ignition timing by the ignition timing correction means is lower than the target torque, the fuel supply amount set by the fuel supply amount setting means is increased and corrected. This is advantageous in avoiding engine torque shortage during acceleration, and it is not necessary to excessively advance the ignition timing, which is advantageous in improving exhaust performance.

In the case where feedback control for determining the operation amount of the intake air amount adjusting means based on a control deviation between the intake air amount and the target value is employed for controlling the intake of air into the combustion chamber, It is preferable that the ignition timing correction means determines the correction amount of the ignition timing based on a smoothed value obtained by performing a smoothing process in which the previous operation amount is reflected in the operation amount at a predetermined ratio.

Since the operation amount of the feedback control corresponds to the control deviation between the intake air amount and the target value, if the ignition timing is corrected based on this operation amount, the deviation of the intake air amount from the target value Correction according to the degree of However, if this operation amount is directly reflected in the correction value, for example, when the engine is suddenly accelerated, the operation amount increases sharply, and the advance angle increases suddenly. , NOx amount also increases rapidly. Therefore, a sharp advance angle is avoided by determining a correction amount of the ignition timing based on a value obtained by modifying the operation amount.

In this case, when the engine load is equal to or less than the predetermined value or when the engine speed is equal to or less than the predetermined value, it is preferable to make the reflection ratio of the last operation amount larger than other engine operation regions. Thus, it is possible to prevent the advance angle of the ignition timing from suddenly increasing when the engine is rapidly accelerated.

The above-described invention is particularly effective when applied to a diesel engine whose ignition timing is controlled by adjusting the fuel injection timing for injecting fuel directly into the combustion chamber. In this case, the ignition timing setting means serves as a fuel injection timing setting means, and the ignition timing correction means serves as a fuel injection timing correction means.

That is, in the case of a gasoline engine, when there is a delay in the change of the intake air amount, even if the shortage of the engine torque caused by the change is compensated by increasing the fuel supply amount, the exhaust performance does not greatly deteriorate. However, in the case of a diesel engine, if the amount of fuel injection is increased while the amount of intake air is insufficient, smoke (soot) increases.
On the other hand, if the shortage of torque is compensated for by advancing the fuel injection timing, the advancing angle acts in a direction to reduce smoke. Therefore, even when the fuel injection amount is increased, it is possible to prevent the smoke amount from excessively increasing.

[0019]

As described above, according to the present invention, the ignition timing of the fuel supplied to the combustion chamber is controlled according to the operating state of the engine, and the target value of the intake air amount is changed to the operating state of the engine. The ignition timing is corrected according to a deviation of the intake air amount from the target value in a combustion control device for an engine which is set in accordance with the target value and controls the intake of air into the combustion chamber based on the target value. Therefore, when the actual intake air amount is delayed with respect to the change in the target value in the transition period when the operation state of the engine changes, the delay is corrected by correcting the ignition timing so that, for example, excessive or insufficient engine torque does not occur. Or so that the exhaust performance is not deteriorated.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an overall configuration of a combustion control apparatus A for a diesel engine according to an embodiment of the present invention, and 1 is an engine body of a multi-cylinder diesel engine mounted on a vehicle. The engine body 1 has a plurality of cylinders 2 (only one is shown), and a piston 3 is reciprocally fitted into each of the cylinders 2. The combustion chamber 4 is formed. In addition, an injector (fuel injection valve) 5 is disposed substantially at the center of the upper surface of the combustion chamber 4 with the injection hole at the tip end facing the combustion chamber 4.
The injection holes are opened and closed at a predetermined injection timing for each cylinder so that fuel is directly injected into the combustion chamber 4.

Each of the injectors 5 is connected to a common common rail (accumulator) 6 for storing high-pressure fuel.
A high-pressure supply pump 8 driven by a crankshaft 7 is connected to the common rail 6. The high-pressure supply pump 8 operates so that the fuel pressure in the common rail 6 detected by the pressure sensor 6a is maintained at a predetermined value or more. A crank angle sensor 9 for detecting a rotation angle of the crank shaft 7 is provided.
Is composed of a plate to be detected (not shown) provided at the end of the crankshaft 7 and an electromagnetic pickup arranged to face the outer periphery of the plate, and the electromagnetic pickup is provided around the entire periphery of the plate to be detected. A pulse signal is output in response to the passage of the projections formed at predetermined angles.

Reference numeral 10 denotes an intake passage for supplying intake air (air) filtered by an air cleaner (not shown) to the combustion chamber 4 of the engine body 1. At a downstream end of the intake passage 10, a surge tank (not shown) is provided. Each passage branched from the surge tank is connected to each cylinder 2 by an intake port.
Are connected to the combustion chamber 4. The surge tank is provided with an intake pressure sensor 10a for detecting a supercharging pressure supplied to each cylinder 2. The intake passage 10 includes, in order from the upstream side to the downstream side, a hot film type air flow sensor 11 for detecting a flow rate of intake air taken into the engine body 1, and a blower 12 driven by a turbine 21 to compress intake air. An intercooler 13 for cooling the intake air compressed by the blower 12 and an intake throttle valve (intake air amount adjusting means) 14 for reducing the cross-sectional area of the intake passage 10 are provided. The intake throttle valve 14 is a butterfly valve provided with a notch so that intake air can flow even in a fully closed state. Like the EGR valve 24 described later, the magnitude of the negative pressure acting on the diaphragm 15 is negative pressure. The opening degree of the valve is controlled by being adjusted by the control electromagnetic valve 16. Further, the intake throttle valve 1
4 is provided with a sensor (not shown) for detecting the opening.

An exhaust passage 20 for exhausting exhaust gas from the combustion chamber 4 of each cylinder 2 is connected to the combustion chamber 4 of each cylinder 2 via an exhaust manifold. The exhaust passage 20 includes, in order from the upstream side to the downstream side, a linear O2 sensor 17 for detecting the oxygen concentration in the exhaust gas, a turbine 21 rotated by the exhaust flow, and HC and CO in the exhaust gas.
And a catalytic converter 22 capable of purifying NOx.

An exhaust gas recirculation passage (hereinafter, referred to as an EGR passage) 23 for recirculating a part of the exhaust gas to the intake side branches from a portion of the exhaust passage 20 upstream of the turbine 21, and a portion downstream of the EGR passage 23. The end is connected to the intake passage 10 downstream of the intake throttle valve 14. Near the downstream end in the middle of the EGR passage 23, an exhaust gas recirculation amount adjusting valve (intake air amount adjusting means: hereinafter referred to as an EGR valve) whose opening degree can be adjusted.
A part of the exhaust gas is recirculated to the intake passage 10 while adjusting the flow rate of the exhaust gas in the exhaust passage 20 by the EGR valve 24.

Therefore, fresh air (air) passing through the intake throttle valve 14 and exhaust gas passing through the EGR valve 24 are sucked into the combustion chamber 4, and the intake air is adjusted by adjusting the exhaust gas recirculation amount by the EGR valve 24. The amount can be adjusted.

The EGR valve 24 is of a negative pressure responsive type, and a negative pressure passage 27 is connected to a negative pressure chamber of the valve box. The negative pressure passage 27 is connected to a vacuum pump (negative pressure source) 29 via a negative pressure control electromagnetic valve 28. The negative pressure passage 27 is controlled by a control signal (current) from an ECU 35 described later. By opening and closing 27, the negative pressure for driving the EGR valve in the negative pressure chamber is adjusted, whereby the opening of the EGR passage 23 is linearly adjusted.

The turbocharger 25 is a VGT (Variable Geometry Turbo), to which a diaphragm 30 is attached, and a solenoid valve 3 for negative pressure control.
By adjusting the negative pressure acting on the diaphragm 30 by 1, the cross-sectional area of the exhaust gas passage is adjusted.

Each of the injectors 5, high pressure supply pump 8, intake throttle valve 14, EGR valve 24, turbocharger 25
And the like are configured to be operated by a control signal from a control unit (Engine Control Unit: hereinafter referred to as ECU) 35. On the other hand, the ECU 35 receives an output signal from the pressure sensor 6a, an output signal from the crank angle sensor 9, an output signal from the pressure sensor 10a, an output signal from the air flow sensor 11, and an output signal from the O2 sensor 17. An output signal, an output signal from the temperature sensor 18, an output signal from the lift sensor 26 of the EGR valve 24, and an accelerator opening sensor for detecting an operation amount (accelerator opening) of an accelerator pedal (not shown) by a driver of the vehicle. 3
2 are input at least.

The fuel injection amount (fuel supply amount) and the fuel injection timing (ignition timing) of the injector 5 are controlled according to the operating state of the engine body 1, and the common rail pressure by the operation of the high-pressure supply pump 8, ie, the common rail pressure, The fuel injection pressure is controlled, and in addition, the EGR valve 24 is controlled.
And the operation control of the turbocharger 25 (VGT control) is performed.

FIG. 2 shows the fuel injection amount, fuel injection timing, EGR
FIG. 4 is a block diagram related to control of a valve and a turbocharger (VGT) 25. In the figure, reference numeral 41 denotes a target torque setting section for setting a target torque (output torque) Tref of the engine, and an optimum value of the target torque Tref with respect to changes in the accelerator opening (engine load) Acc and the engine speed Ne. Is experimentally determined and recorded, and with reference to this, the accelerator opening Acc detected by the accelerator opening sensor 32 and the engine speed Ne detected by the crank angle sensor 9 are referred to. Set the target torque Tref. The fuel injection amount control 42 is a basic injection amount setting section for setting a target basic injection amount Qbase of the fuel, and includes an engine speed Ne, a target torque Tref, and a fresh air amount (intake air amount, not including fuel). The same applies hereinafter.), The basic injection amount Q
A three-dimensional map in which the optimum value of base is experimentally determined and recorded is provided, and the air flow sensor 11
Air Volume (Actual Air) Detected by Target and Target Torque Tre
basic injection quantity Qbase based on f and engine speed Ne
Set. A correction amount Qc set by an injection amount correction setting section described later is added to the basic injection amount Qbase to obtain a target injection amount QT, which is used for controlling the fuel injection valve 5. Intake air amount (exhaust gas recirculation) control In the target fresh air amount setting unit 43, the target fresh air amount Airref is set using the target torque Tref and the engine speed Ne. That is, the target fresh air amount setting unit 43 includes a two-dimensional map in which the optimum value of the target air-fuel ratio A / Fref is experimentally determined and recorded with respect to changes in the target torque Tref and the engine speed Ne. The target air-fuel ratio A / Fref is determined with reference to the map, and the target air-fuel ratio A / Fref and the basic injection amount setting unit 4 are determined.
A target fresh air amount Airref = Qbase × A / Fref is obtained using the basic injection amount Qbase obtained in step 2.

The target air-fuel ratio A / Fref is a control target value for determining the exhaust gas recirculation amount so as to achieve both reduction of NOx and reduction of smoke. That is, when the air-fuel ratio increases, the NOx amount tends to increase.
If the air-fuel ratio is lowered by increasing the exhaust gas recirculation amount, the generation of NOx can be reduced. However, as shown in FIG. 3 exemplifying the relationship between the air-fuel ratio of the diesel engine and the amount of smoke, when the air-fuel ratio becomes equal to or less than the air-fuel ratio that has changed to the rich side, the amount of smoke increases rapidly. That is, there is a limit even if the exhaust gas recirculation amount is increased to reduce the NOx amount. Therefore, in order to achieve both reduction of the NOx amount and suppression of the increase in the smoke amount, the target air-fuel ratio A / Fref is set to a value on the rich side as much as possible before the smoke amount starts to increase rapidly.

The new air amount is controlled with the target new air amount Airref as a target. This control does not directly adjust the fresh air amount itself, but changes the fresh air amount by adjusting the recirculation amount of the exhaust gas. That is, feedback control is used to adjust the exhaust gas recirculation amount.
In the target EGR valve opening degree setting unit 44, the target fresh air amount Airr
EGR based on the control deviation ΔAir between ef and the actual fresh air volume Air
A feedback value (operating amount) AirF / B is obtained from the PID, and the target opening EG of the EGR valve 24 is determined based on the AirF / B.
Rref is set, and based on this, the EGR valve 24 is operated. VGT control In the target boost pressure setting section 45, the target boost pressure Boostref is set using the target torque Tref and the engine speed Ne. That is, the target boost pressure setting unit 45 includes a two-dimensional map in which the optimum value of the target boost pressure Boostref is experimentally determined and recorded with respect to the change in the target torque Tref and the engine speed Ne. See target boost pressure Boos
Set tref. Then, the turbocharger 25 is feedback-controlled with the target boost pressure Boostref as a target. That is, in the target VGT opening setting section 46, V is set based on the control deviation ΔBoost between the intake pressure Boost detected by the intake pressure sensor 10a and the target boost pressure Boostref.
GT feedback value (manipulated variable) BoostF / B is calculated,
The target VGT opening degree VGTref is set based on this BoostF / B, and the turbocharger 25 is operated based on this. Fuel Injection Timing Control In the basic injection timing setting unit 47, a target basic injection timing Ibase of fuel is set using the target torque Tref and the engine speed Ne. That is, the basic injection timing setting unit 47 includes a two-dimensional map in which the optimum value of the basic injection timing Ibase is experimentally determined and electronically recorded with respect to changes in the target torque Tref and the engine speed Ne. The basic injection timing Ibase is set with reference to the map. Then, the basic injection timing Ibase is calculated by the injection timing correction value calculation unit 4.
The guard value is corrected by the addition of the correction value Ic calculated in step 8, the guard processing section 49 performs a predetermined guard process on the corrected injection timing IT, and provides the control for the fuel injection valve 4.

The injection timing correction value calculator 48 calculates the target fresh air amount.
An injection timing correction value Ic is obtained based on a control deviation ΔAir between Airref and the actual fresh air amount Air and a control deviation ΔBoost between the intake pressure Boost and the target boost pressure Boostref.
The correction of the injection timing corrects the response delay of the change in the fresh air amount to the control of the R valve 24 and the excess or deficiency of the torque due to the response delay of the change in the intake pressure to the VGT control.

That is, an averaging process is performed in the averaging processor 50 to the EGR feedback value AirF / B obtained based on the control deviation ΔAir of the fresh air amount, and the EGR feedback value AirF / B ′ becomes insufficient based on the obtained averaging value AirF / B ′. The torque setting unit 51 obtains an insufficient torque ΔTAir corresponding to the control deviation ΔAir of the fresh air amount. This insufficient torque ΔTAir is set to have a relationship proportional to the smoothing value AirF / B ′. This insufficient torque ΔTAir can be corrected according to the intake air temperature. That is, the correction is such that the insufficient torque ΔTAir increases as the intake air temperature increases during the acceleration operation of the engine. This is because the higher the intake air temperature, the lower the efficiency of charging the combustion chamber with the intake air, and the lower the engine torque.

The EGR feedback value AirF / B is calculated by giving a relatively large gain in order to enhance the responsiveness of EGR control.
If this is reflected in c, the change in the injection timing will be abrupt, which may cause a torque shock. Therefore, the above-described annealing process is performed. This smoothing process reflects the previous value at a predetermined ratio (1-α) to the current value of AirF / B as shown in the following equation.

AirF / B '= α × Current value of AirF / B + (1-
α) × Fast value of AirF / B where 0 <α <1. In the engine operating region where the accelerator opening (engine load) Acc is equal to or less than a predetermined value or the engine speed Ne is equal to or less than a predetermined value, α is set smaller than in other operating regions. This is to prevent the advance angle of the ignition timing from suddenly increasing when the engine is suddenly accelerated.

A smoothing process is performed in the smoothing unit 52 on the VGT feedback value BoostF / B obtained based on the control deviation ΔBoost of the supercharging pressure, and the VGT feedback value BoostF / B ′ is determined based on the obtained smoothed value BoostF / B ′. Insufficient torque ΔTBoost corresponding to the control deviation ΔBoost of the supercharging pressure in the torque setting unit 53
Is required. This insufficient torque ΔTBoost is also the average value Boo
The relationship is set so as to be proportional to stF / B ′, and can be corrected according to the intake air temperature similarly to the insufficient torque ΔAir.

The smoothing process in this case is also performed in order to avoid a sudden change in the injection timing for the same reason as above, and the present value of BoostF / B is added to the previous value as shown in the following equation. Is reflected at a predetermined ratio (1−β).

BoostF / B ′ = α × Current value of BoostF / B + (1
−β) × BoostF / B, the previous value where 0 <β <1. Further, in an engine operation region where the accelerator opening (engine load) Acc is equal to or less than a predetermined value or the engine speed Ne is equal to or less than a predetermined value, β is set smaller than in other operation regions. This is to prevent the advance angle of the ignition timing from suddenly increasing when the engine suddenly accelerates.

Thus, the injection timing correction value calculating section 48
In the above, the sum ΔT (= ΔTAir + Δ
TBoost), and a correction value Ic of the injection timing is referred to with reference to a preset map based on the total insufficient torque ΔT.
Is required. This map shows a correction value I of the injection timing necessary to compensate for the insufficient torque in relation to the total insufficient torque ΔT.
c is obtained experimentally in advance and electronically recorded.

The insufficient torques ΔTAir and ΔTBoost may become negative values corresponding to the control deviations ΔAir and ΔBoost. In this case, it means that the torque is excessive.

The total shortage torque ΔT and the injection timing correction value Ic are basically in a proportional relationship as schematically shown in FIG. 4, but the maximum allowable when ΔT is plus (torque shortage). The absolute value of the maximum retard amount that is allowed when minus (excessive torque) is smaller than the advance amount is smaller. This is because if the retard of the injection timing is excessive, smoke increases. As shown by the broken line in FIG. 4, the degree of change in the amount of retardation when ΔT increases negatively may be made smaller than the degree of change in the amount of advance angle when ΔT increases positively.

The guard process for the injection timing IT limits the advance and retard. Limit advance angle is N
For example, 30 ° CA before the top dead center of the compression stroke is set from the viewpoint of preventing excessive increase of Ox, and the limit retard angle is set, for example, 10 ° CA after the top dead center of the compression stroke from the viewpoint of prevention of smoke. Correction of fuel injection amount In the predicted torque setting section 54, the engine torque Tc expected to be obtained when the basic injection amount Qbase is injected at the injection timing IT subjected to the above-described corrected guard processing.
Is obtained with reference to a preset map. This map is a three-dimensional map in which the relationship between the injection timing IT, the basic injection amount Qbase, and the engine torque Tc is obtained in advance through experiments and electronically recorded. FIG. 5 shows the injection timing IT and the injection timing IT at a specific fuel injection amount. As shown in the relationship with the engine torque Tc, the engine torque Tc is set to increase as the injection timing IT shifts to the advance side. And then
The difference ΔTref between the expected torque Tc and the target torque Tref
Is obtained by the torque difference calculation unit 55, and the torque difference ΔTre
The injection amount correction value Qc corresponding to the injection amount correction value setting unit 5
6 is obtained and added to the basic injection amount Qbase (subtracted when the predicted torque Tc is larger than the target torque Tref).

(Flow of Fuel Injection Control) The flow of fuel injection control will be specifically described based on the control flow shown in FIG. This control is executed at every predetermined crank angle.

In step A1 after the start, a crank angle signal, an air flow sensor output, an accelerator opening, and the like are read. In the following step A2, the accelerator opening A
A target torque Tref is set by referring to a map based on cc and the engine speed Ne. In step A3,
The basic injection amount Qbase is set by referring to a map based on the engine speed Ne, the target torque Tref, and the actual Air.
In step A4, the basic injection timing I is determined by referring to a map based on the engine speed Ne and the target torque Tref.
Set base.

In the subsequent step A5, the EGR feedback value AirF / B obtained by the intake air amount control system is subjected to a smoothing process to obtain a smoothed value AirF / B '. In step A6, the insufficient torque ΔTAir is obtained by referring to the map based on the smoothing value AirF / B '. Subsequent step A7
, A smoothing process is performed on the VGT feedback value BoostF / B obtained by the supercharging pressure control system to obtain the smoothed value BoostF.
/ B '. In step A8, the average value BoostF
/ B 'and refer to the map to find the insufficient torque ΔTBoost
Ask for.

In the following step A9, the insufficient torque Δ
The total shortage torque ΔT is obtained based on TAir and ΔTBoost. In step A10, a correction value Ic of the injection timing is set with reference to a map based on the total insufficient torque ΔT.
In step A11, the correction value Ic is added to the previously set basic injection timing Ibase to obtain an injection timing IT, and in step A12, this is subjected to guard processing.

In the following step A13, an expected torque Tc is set by referring to a map based on the injection timing IT after the guard processing and the basic injection amount Qbase. Step A1
In step 4, the difference ΔTref between the previously set target torque Tref and the expected torque Tc is determined, and this torque difference ΔTref
In step A15, an injection amount correction value Qc is set with reference to a map based on the above.

Then, in step A16, the correction value Qc is added to the basic injection amount Qbase to obtain the final injection amount QT, and when the injection timing IT is reached, fuel injection is executed (steps A17 and A18).

(Flow of intake air amount (EGR) control) FIG. 7
The flow of the intake air amount control will be specifically described based on the control flow shown in FIG. This control is executed at every predetermined crank angle.

In step B1 after the start, a crank angle signal, an air flow sensor output, an accelerator opening, and the like are read. In the following step B2, the target torque Tre
A target air-fuel ratio A / Fref is obtained by referring to a map based on f and the engine speed Ne, and a target fresh air amount Airref is set based on the target air-fuel ratio A / Fref and the basic injection amount Qbase. In step B3, a control deviation ΔAir between the target fresh air amount Airref and the actual fresh air amount Air is determined. This control deviation ΔAi
and EGR by PID in step B4 based on
Find feedback value AirF / B.

In the following step B5, a primary advance compensation process of the EGR feedback value AirF / B is performed in order to increase the response of the control to the change in the control deviation. 0 <adv
<1. Then, in step B6, the EGR
The target value EGRref of the EGR valve opening is set based on the feedback value AirF / B, and in step B7, the target value EGRr
When ef exceeds a predetermined limit value, a guard process is performed with this value as the limit value, and EGR is performed based on the obtained EGRref.
The valve 24 is driven (Step B8).

(Flow of Supercharging Pressure (VGT) Control) The flow of the supercharging pressure control will be specifically described based on the control flow shown in FIG. This control is executed at every predetermined crank angle.

In step C1 after the start, the crank angle signal, the output of the intake pressure sensor, the accelerator opening and the like are read. In the following step C2, the target torque Tref
A target boost pressure Boostref is determined by referring to a map based on the engine speed Ne and the engine speed Ne. In step C3, a control deviation ΔBo between the target boost pressure Boostref and the actual boost pressure Boost is determined.
Find ost. Based on this control deviation ΔBoost, in step C4, the VGT feedback value Boos
Find tF / B.

In the following step C5, a target value of the VGT opening is set based on the VGT feedback value BoostF / B. In step C6, if the target value exceeds a predetermined limit value, the guard is set to this limit value. The processing is performed, and the VGT 25 is driven based on the obtained target VGT opening (step C7).

As described above, if the change in the actual fresh air amount is delayed with respect to the change in the target fresh air amount, for example, when the actual fresh air amount becomes insufficient during acceleration of the engine, the fuel injection timing is advanced. Since the correction is corrected, the engine is prevented from running out of torque. On the other hand, if the actual fresh air amount becomes excessive during the deceleration of the engine, the fuel injection timing is corrected to be retarded. Can be avoided. Also, if the change in the actual supercharging pressure is delayed with respect to the change in the target supercharging pressure, for example, when the actual supercharging pressure becomes insufficient with respect to the target supercharging pressure during acceleration of the engine, the fuel injection timing becomes Since the advance angle is corrected, the engine torque shortage can be avoided.On the other hand, if the actual supercharging pressure becomes excessive during the deceleration of the engine, the fuel injection timing is retarded and the torque may be excessively increased. can avoid.

In determining the correction value of the injection timing, the EGR feedback value AirF / B and the VGT feedback value BoostF / B are used in a smooth manner, so that the intake air amount (exhaust gas recirculation amount) control, the supercharging pressure , The sudden change of the injection timing can be prevented and the torque shock can be avoided. Further, since the smoothing gains α and β become smaller when the accelerator opening is equal to or less than a predetermined value or the engine speed is equal to or less than a predetermined value, it is possible to prevent a sudden change in the injection timing when shifting from idling operation to acceleration operation, for example. Torque shock can be avoided.

In addition, during the acceleration operation of the engine, the shortage torque ΔT increases as the intake air temperature increases.
This is advantageous for eliminating torque shortage.

Further, when there is a difference between the engine torque obtained by the above-described correction of the injection timing and the target torque Tref, the increase / decrease correction of the fuel injection amount is performed, so that it is easy to secure the target torque. Further, since this increase / decrease correction can be performed, it is not necessary to excessively advance or retard the injection timing, which is advantageous in preventing the exhaust performance from being deteriorated. Although the above embodiment relates to a diesel engine, the present invention can also be applied to a gasoline engine. In that case, the ignition timing is corrected instead of the fuel injection timing.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a combustion control device for a diesel engine according to the present invention.

FIG. 2 is a control block diagram of the combustion control device.

FIG. 3 is a graph showing a relationship between an air-fuel ratio and a smoke amount of a diesel engine.

FIG. 4 is a graph showing a relationship between insufficient torque ΔT and an injection timing correction value Ic.

FIG. 5: Injection timing IT and engine torque (expected torque)
FIG. 4 is a graph showing a relationship with Tc.

FIG. 6 is a flowchart showing the flow of fuel injection control.

FIG. 7 is a flowchart showing a flow of intake air amount (EGR) control.

FIG. 8 is a flowchart showing a flow of supercharging pressure control.

[Explanation of symbols]

 A Combustion control device for diesel engine 1 Engine body 2 Cylinder 4 Combustion chamber 5 Injector (fuel injection valve) 9 Crank angle sensor (Engine speed sensor) 10 Intake passage 10 a Intake pressure sensor 11 Air flow sensor 11 20 Exhaust passage 22 Catalytic converter 23 Exhaust gas recirculation passage (EGR passage) 24 Exhaust gas recirculation amount control valve (EGR valve) 25 Turbocharger 32 Accelerator opening sensor 35 ECU (control unit) 41 Target torque setting unit 42 Basic injection amount setting unit 43 Target new air amount setting Part 44 target EGR valve opening setting part 45 target supercharging pressure setting part 46 target VGT opening setting part 47 basic injection timing setting part 48 injection timing correction value calculation part 49 guard processing part 50 smoothing processing part 51 insufficient torque setting part 52 Annealing section 53 Insufficient torque setting section 54 Expected torque Setting unit 55 torque difference calculation section

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 43/00 301 F02D 43/00 301J 301W 45/00 364 45/00 364A F02P 5/15 F02P 5/15 JF term (for reference) 3G022 AA05 AA10 CA04 DA01 DA02 EA01 EA07 FA03 FA06 GA01 GA05 GA06 GA07 GA08 GA09 3G084 AA01 BA08 BA13 BA15 BA20 CA04 DA01 DA10 EA11 EB08 EB12 EB25 EC02 EC03 FA08 FA10 FA11 FA12 FA18 FA33 HA11 HA13 JA01 JA24 KA12 LA03 LC02 MA11 MA18 NA01 NA08 NC02 ND02 NE11 NE12 NE17 NE19 PA01A PA04Z PA07Z PA11Z PA16A PA16Z PA17Z PB08Z PD04A PD15A PE01Z PE03Z PE06A PE06Z PE08Z PF03Z

Claims (7)

[Claims] 1. An engine combustion control device in which the ignition timing of fuel supplied to a combustion chamber is controlled in accordance with an operation state of an engine, wherein a target value of an intake air amount is set in accordance with the operation state of the engine. Intake air amount control means for controlling intake of air into the combustion chamber based on the target value; and ignition timing correction means for correcting the ignition timing in accordance with a deviation of the intake air amount from the target value. A combustion control device for an engine, comprising: 2. The combustion control device for an engine according to claim 1, wherein target torque setting means for setting a target torque of the engine in accordance with an operation state of the engine; An ignition timing setting means for setting the target value of the ignition timing according to a target torque set by the torque setting means; and an ignition timing setting means for controlling the intake air amount according to a target torque set by the target torque setting means. Means for setting the target value of the intake air amount, the ignition timing correction means determines the ignition timing set by the ignition timing setting means from the target value of the intake air amount. An engine combustion control device, wherein an engine torque is corrected in accordance with a deviation so as to approach the target torque. 3. The combustion control device for an engine according to claim 2, wherein the ignition timing correction means performs an advance correction of the ignition timing when the intake air amount is smaller than a target value, and further comprises: A combustion control device for an engine, wherein the advance angle is increased as the deviation of the amount from the target value increases. 4. The fuel supply device according to claim 2, wherein a target value of an amount of fuel supplied to the combustion chamber is set according to a target torque set by the target torque setting means. Setting means; torque calculating means for obtaining an engine torque obtained when the amount of fuel set by the fuel supply amount setting means is burned at the ignition timing corrected by the ignition timing correcting means; Fuel supply amount correcting means for correcting the fuel supply amount such that the engine torque approaches the target torque based on a deviation between the engine torque obtained by the above and the target torque set by the target torque setting means. A combustion control device for an engine, comprising: 5. The combustion control device for an engine according to claim 2, wherein the control of the intake of air into the combustion chamber is performed by an intake air amount adjusting means based on a control deviation between the intake air amount and the target value. Feedback control for determining an operation amount, wherein the ignition timing correction means adjusts the ignition timing correction amount based on a smoothed value obtained by performing a smoothing process of reflecting a previous operation amount to the operation amount at a predetermined rate. A combustion control device for an engine, which is to be determined. 6. The engine combustion control device according to claim 5, wherein when the engine load is equal to or less than a predetermined value or when the engine speed is equal to or less than the predetermined value, the previous operation amount is set smaller than other engine operation ranges. An engine combustion control device characterized by increasing the reflection ratio of the engine. 7. The combustion control device for an engine according to claim 1, wherein the ignition timing of the engine is controlled by adjusting a fuel injection timing for directly injecting fuel into a combustion chamber. An ignition control device for an engine, wherein the ignition timing correction means is a fuel injection timing correction means.