JPH09217637A - Combustion control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of a combustion state even when there are change of fuel injection quantity for each cylinder, change of a state of an intake system, etc., on a combustion control device of an internal combustion engine free to carry out stratified combustion. SOLUTION: A fuel injection valve 11 is arranged in an inwall surface peripheral part of a cylinder head 4 in the neighbourhood of a first intake valve 6a and a second intake valve 6b, and fuel from the fuel injection valve 11 is injected is directly injected into a cylinder 1a. An electronic control device (ECU) 30 computes crank angle time, etc., in accordance with a detection result of a crank angle sensor 28, discriminates size of torque variation and discriminates whether it is torque variation on the rich side or torque variation on the lean side. Thereafter, final injection timing is properly corrected in accordance with its discrimination result. Consequently, even in the case when torque variation is different for each of the cylinders 1a, fuel injection timing suitable for ignition of each of the individual cylinders 1a is secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control apparatus for an internal combustion engine, and more particularly, to a combustion control apparatus for a direct injection type internal combustion engine.
The present invention relates to a combustion control device for an internal combustion engine capable of performing stratified combustion.

[0002]

2. Description of the Related Art In a conventionally used engine, fuel from a fuel injection valve is injected into an intake port, and a homogeneous mixture of fuel and air is supplied to a combustion chamber in advance. In such an engine, an intake passage is opened and closed by a throttle valve linked to an accelerator operation, and by this opening and closing, the amount of intake air supplied to a combustion chamber of the engine (consequently, a gas mixture in which fuel and air are homogeneously mixed). ) Is adjusted, thereby controlling the engine output.

[0003] However, in the technique based on the so-called homogeneous combustion described above, a large intake negative pressure is generated in accordance with the throttle operation of the throttle valve, and the pumping loss increases to lower the efficiency. On the other hand, by reducing the throttle valve throttle and supplying fuel directly to the combustion chamber, a combustible mixture is made to exist in the vicinity of the spark plug, and the air-fuel ratio of that part is increased to improve ignitability. So-called "stratified combustion"
That technology is known.

For example, in the technique disclosed in Japanese Patent Laid-Open No. 5-113146, fuel is directly injected into the combustion chamber (in-cylinder injection type). Further, in this technique, the fuel injection timing in the compression stroke is determined based on the fuel injection amount and the ignition timing in the compression stroke. With such a structure, it is possible to form an air-fuel mixture having good ignitability in the vicinity of the ignition plug at the time of ignition.

[0005]

However, in the above-mentioned prior art, although the injection fuel is evaporated to some extent and the optimum ignition timing is set from the end of injection, There was a problem to be noted. That is, the evaporation time of the fuel in each cylinder may differ due to changes in the fuel injection amount and changes in the intake system state (eg, EGR amount, swirl intensity, etc.). Therefore, the truly required interval from the end of injection to ignition is different for each cylinder, and the combustion state may be different for each cylinder.

Further, if the fuel injection direction is different for each cylinder, there is a possibility that the time until the fuel reaches the spark plug will be different. Even in such a case, the combustion state may be different for each cylinder.

As a result, there are cases where it is not possible to ensure suitable combustion, and there is a risk that engine rotation fluctuations and misfires may occur. The present invention has been made in view of the above-mentioned circumstances, and an object thereof is, in a combustion control device of an internal combustion engine capable of stratified combustion, a change in the fuel injection amount for each cylinder and a change in the state of the intake system. It is an object of the present invention to provide a combustion control device for an internal combustion engine that can prevent the deterioration of the combustion state due to that, even if the fuel injection direction differs for each cylinder.

[0008]

In order to achieve the above object, in the present invention, as shown in FIG. 1, a fuel injection means M2 for injecting fuel into a cylinder of an internal combustion engine M1 in order to perform stratified combustion. A fuel injection amount and an injection timing to be injected into the cylinder from the fuel injection means M2 based on the operating state detecting means M4 for detecting the operating state of the internal combustion engine M1 and the detection result of the operating state detecting means M4. In the combustion control device for the internal combustion engine, which includes the injection control means M5 that controls the fuel injection means M2 based on the calculated fuel injection amount and injection timing, the detection result of the operating state detection means M4 is used. Based on the combustion fluctuation detection means M6 for detecting combustion fluctuations of the internal combustion engine M1 and the combustion fluctuations detected by the combustion fluctuation detection means M6, it is possible to determine whether there is too much fuel or too little fuel. And determining means M7 for determining the variation, according to the determination result of said determining means M7, the injection to correct the fuel injection timing by the injection control means M5 timing correction means M
The point is that 8 and 8 are provided.

Further, in the invention as set forth in claim 2, as shown in FIG. 2, the fuel in the cylinder and the fuel injecting means M12 for injecting the fuel into the cylinder of the internal combustion engine M11 in order to perform the stratified combustion. Ignition means M13 for igniting and the internal combustion engine M
Based on the detection result of the operating state detecting means M14 for detecting the operating state of No. 1 and the operating state detecting means M14, the fuel injection amount and ignition timing injected from the fuel injecting means M12 into the cylinder are calculated, A combustion control device for an internal combustion engine, comprising: an injection / ignition control means M15 for controlling the fuel injection means M12 and the ignition means M13 based on the calculated fuel injection amount and ignition timing. Based on the detection result, the internal combustion engine M
Combustion fluctuation detecting means M16 for detecting combustion fluctuation of No. 11,
Based on the combustion fluctuation detected by the combustion fluctuation detecting means M16, a judging means M17 for judging fluctuation due to excessive fuel or insufficient fuel, and an ignition timing by the injection / ignition control means M15 according to the judgment result of the judging means M17. The gist is that an ignition timing correction means M18 for correcting the above is provided.

Further, in the invention according to claim 3, in the combustion control device for the internal combustion engine according to claim 1 or 2,
The gist of the judgment of the fluctuation due to the excessive fuel amount or the insufficient fuel amount by the judging means is to perform it based on the fluctuation of the output torque.

In addition, in the invention according to claim 4, in the combustion control device for the internal combustion engine according to claim 3, the fluctuation of the output torque is detected based on the crank angle time after ignition of each cylinder. That is the gist.

(Operation) According to the invention described in claim 1, as shown in FIG. 1, the fuel is injected into the cylinder of the internal combustion engine M1 by the fuel injection means M2, and the fuel in the cylinder is burned. Due to the explosion, the internal combustion engine M1 obtains a driving force. Further, the stratified charge combustion can be performed by the fuel in the cylinder of the internal combustion engine M1.

Further, the operating state detecting means M4 detects the operating state of the internal combustion engine M1, and based on the detection result, the injection control means M5 injects the fuel from the fuel injecting means M2 into the cylinder and the injection amount. The time is calculated.
Then, based on the calculated fuel injection amount and injection timing, the injection control means M5 causes the fuel injection means M2.
Is controlled.

Now, if the fuel evaporation time in each cylinder may differ due to a change in the fuel injection amount or a change in the state of the intake system (eg, EGR amount, swirl intensity, etc.), it is true for each cylinder. The required interval from the end of injection to ignition (combustion / explosion) may be different. Further, when the fuel injection direction is different for each cylinder, the time until the fuel reaches the spark plug may be different. In such a case, the combustion state may be different for each cylinder. However, in the present invention, based on the detection result of the operating state detecting means M4, the combustion fluctuation detecting means M6 detects the internal combustion engine M
The combustion fluctuation of No. 1 is detected, and the discrimination means M7 discriminates the fluctuation due to excessive fuel or insufficient fuel based on the combustion fluctuation. Further, according to the determination result of the determination means M7, the injection timing correction means M8 corrects the fuel injection timing by the injection control means M5.

Therefore, even in the above case,
Since the injection timing is appropriately corrected, an appropriate fuel injection timing can be secured for combustion / explosion (ignition) in each cylinder. Therefore, the optimum combustion state can be secured for each cylinder.

According to the second aspect of the invention, as shown in FIG. 2, the fuel is injected into the cylinder of the internal combustion engine M11 by the fuel injection means M12, and the fuel in the cylinder is injected by the ignition means M13. Is ignited, burns and explodes. As a result, the internal combustion engine M11 obtains a driving force. Further, stratified charge combustion can be performed by the fuel in the cylinder of the internal combustion engine M11.

Further, by the operating state detecting means M14,
The operating state of the internal combustion engine M11 is detected, and based on the detection result, the injection / ignition control means M15 calculates the fuel injection amount and the ignition timing injected from the fuel injection means M12 into the cylinder. Further, the fuel injection means M12 and the ignition means M13 are controlled by the injection / ignition control means M15 based on the calculated fuel injection amount and ignition timing.

With respect to the problem described in the operation of the invention described in claim 1, the operating condition detecting means M is used in the present invention.
Based on the detection result of 14, the combustion fluctuation detecting means M16 detects the combustion fluctuation of the internal combustion engine M11. And
Based on the detected combustion variation, the determination means M17 determines the variation due to excessive fuel or insufficient fuel. Further, according to the determination result of the determination means M17, the ignition timing correction means M18 corrects the ignition timing by the injection / ignition control means M15.

Therefore, even in the above case,
Since the ignition timing is appropriately corrected, an appropriate ignition timing according to each cylinder can be secured. Therefore, the optimum combustion state can be secured for each cylinder.

Further, according to the third aspect of the present invention,
In addition to the operation of the invention described in claim 1 or 2, the determination of the variation due to the excessive fuel amount or the insufficient fuel amount by the determination means is performed based on the variation of the output torque. here,
It has been found that the output torque variation characteristic due to excessive fuel is different from the output torque variation characteristic due to insufficient fuel, and from this fact, it is possible to accurately determine the variation due to excessive fuel or insufficient fuel. I can say.
Therefore, it becomes possible to make the above-mentioned operation more reliable.

In addition, according to the invention described in claim 4,
In addition to the action of the invention described in claim 3, the detection of the fluctuation of the output torque is performed based on the crank angle time after ignition of each cylinder. Here, it has been found that the fluctuation of the output torque corresponds to the fluctuation of the crank angle time of each cylinder, and from this fact, it is easy to detect the fluctuation of the output torque by detecting the crank angle time. And, it is possible to surely perform.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, a first embodiment of a combustion control apparatus for an internal combustion engine according to the present invention will be described in detail with reference to the drawings.

FIG. 3 is a schematic configuration diagram showing a fuel injection control device for a direct injection engine mounted on a vehicle in the present embodiment. The engine 1 as an internal combustion engine has, for example, four cylinders 1a, and the combustion chamber structure of each of the cylinders 1a is shown in FIG. As shown in these figures,
The engine 1 has a piston in a cylinder block 2, and the piston reciprocates in the cylinder block 2. A cylinder head 4 is provided above the cylinder block 2.
Is provided, and a combustion chamber 5 is formed between the piston and the cylinder head 4. Further, in the present embodiment, four valves are arranged per cylinder 1a, and in the figure, the first intake valve 6a, the second intake valve 6b, the first intake port 7a, and the first intake port 7b in the figure. Two intake ports, a pair of exhaust valves as 8, and a pair of exhaust ports as 9 are shown.

As shown in FIG. 4, the first intake port 7a
Is composed of a helical intake port, and the second intake port 7
b consists of a straight port that extends almost straight.
In addition, an ignition plug 10 as an ignition means is disposed at the center of the inner wall surface of the cylinder head 4. further,
A fuel injection valve 11 as a fuel injection means is disposed around the inner wall surface of the cylinder head 4 near the first intake valve 6a and the second intake valve 6b. That is, in the present embodiment, the fuel from the fuel injection valve 11 is directly supplied to the cylinder 1a.
It is designed to be injected inside.

As shown in FIG. 3, the first intake port 7a and the second intake port 7b of each cylinder 1a are provided with a first intake passage 15a and a second intake passage 15b formed in each intake manifold 15, respectively. Connected to the surge tank 16. A swirl control valve 17 is arranged in each second intake passage 15b. These swirl control valves 17 are connected to, for example, a step motor 19 via a common shaft 18. The step motor 19 is controlled based on an output signal from an electronic control unit (hereinafter simply referred to as “ECU”) 30 described later. Instead of the step motor 19, a motor controlled according to the negative pressure of the intake ports 7a and 7b of the engine 1 may be used.

The surge tank 16 includes an intake duct 20
Is connected to the air cleaner 21 via the
Inside, a throttle valve 23 that is opened and closed by a step motor 22 that is an actuator is arranged. That is, the throttle valve 23 of the present embodiment is of a so-called electronic control type. Basically, the throttle valve 23 is controlled to open and close by the step motor 22 being driven based on the output signal from the ECU 30. Is done. The intake duct 2 is opened and closed by opening and closing the throttle valve 23.
The amount of intake air that passes through 0 and is introduced into the combustion chamber 5 is adjusted. In the present embodiment, an intake passage is constituted by the intake duct 20, the surge tank 16, the first intake passage 15a, the second intake passage 15b, and the like. A throttle sensor 25 for detecting the opening (throttle opening TA) is provided near the throttle valve 23. An exhaust manifold 14 is connected to the exhaust port 9 of each cylinder. And
The exhaust gas after combustion is discharged to an exhaust duct (not shown) via the exhaust manifold 14.

Further, in the present embodiment, a known exhaust gas circulation (EGR) device 51 is provided. This EG
The R device 51 includes an EGR passage 5 as an exhaust gas circulation passage.
2 and an EGR valve 53 as an exhaust gas circulation valve provided midway in the passage 52. EGR passage 5
2 is an intake duct 20 on the downstream side of the throttle valve 23,
It is provided so as to communicate with the exhaust duct. The EGR valve 53 has a built-in valve seat, valve body, and step motor (all not shown). The opening degree of the EGR valve 53 fluctuates when the stepping motor intermittently displaces the valve body with respect to the valve seat. And EG
When the R valve 53 opens, a part of the exhaust gas discharged to the exhaust duct flows to the EGR passage 52. The exhaust gas flows to the intake duct 20 via the EGR valve 53. That is, a part of the exhaust gas is recirculated into the intake air-fuel mixture by the EGR device 51. At this time, the recirculation amount of the exhaust gas is adjusted by adjusting the opening degree of the EGR valve 53.

The above-described ECU 30 is formed of a digital computer, and is connected to a RAM (random access memory) 3 via a bidirectional bus 31.
2, a ROM (Read Only Memory) 33, a CPU (Central Processing Unit) 34 composed of a microprocessor, an input port 35 and an output port 36. In the present embodiment, the ECU 30 constitutes a combustion fluctuation detection means, a discrimination means, an injection control means, and an injection timing correction means.

An accelerator sensor 26A for generating an output voltage proportional to the amount of depression of the accelerator pedal 24 is connected to the accelerator pedal 24.
Accelerator opening ACCP is detected by 6A. The output voltage of the accelerator sensor 26A is input to the input port 35 via the AD converter 37. Similarly, the accelerator pedal 24 has a fully-closed switch 26B for detecting that the depression amount of the accelerator pedal 24 is "0".
Is provided. That is, the fully closed switch 26B
Generates a signal of "1" as the fully closed signal XL2SW when the depression amount of the accelerator pedal 24 is "0", and otherwise generates a signal of "0". The output voltage of the fully closed switch 26B is also input to the input port 35.

The top dead center sensor 27 generates an output pulse when the first cylinder 1a reaches the intake top dead center, for example.
This output pulse is input to the input port 35. The crank angle sensor 28 has a crankshaft of 30 ° CA, for example.
An output pulse is generated each time the motor rotates, and the output pulse is input to the input port. In the CPU 34, the top dead center sensor 2
The engine speed NE is calculated (read) from the output pulse of 7 and the output pulse of the crank angle sensor 28.

Further, the rotation angle of the shaft 18 is detected by a swirl control valve sensor 29,
Thereby, the opening of the swirl control valve 17 is measured. The output of the swirl control valve sensor 29 is supplied to an input port 35 via an A / D converter 37.
Is input to

At the same time, the throttle sensor 25 detects the throttle opening degree TA. The output of the throttle sensor 25 is input to an input port 35 via an A / D converter 37.

In addition, in the present embodiment, an intake pressure sensor 61 for detecting the pressure (intake pressure PiM) in the surge tank 16 is provided. Further, a water temperature sensor 62 that detects the temperature of the cooling water of the engine 1 (cooling water temperature THW) is provided. The outputs of both sensors 61 and 62 are also A /
It is adapted to be input to the input port 35 via the D converter 37.

In the present embodiment, the throttle sensor 25, the accelerator sensor 26A,
B, a top dead center sensor 27, a crank angle sensor 28, a swirl control valve sensor 29, an intake pressure sensor 61, a water temperature sensor 62, and the like constitute an operating state detecting means.

On the other hand, the output port 36 is connected to each fuel injection valve 11 and each step motor 1 via the corresponding drive circuit 38.
9, 22, the igniter 12 and the EGR valve 53 (step motor). Then, based on signals from the sensors 25 to 29, 61, and 62, the ECU 30 operates according to a control program stored in the ROM 33,
The fuel injection valve 11, the step motors 19 and 22, the igniter 12, the EGR valve 53 and the like are suitably controlled.

Next, a program relating to various controls according to the present embodiment in the engine combustion control device having the above-mentioned configuration will be described with reference to a flowchart. FIG. 5 is a flowchart showing an "injection timing control routine" for controlling the injector 11 and the like in the present embodiment to execute the fuel injection timing control, which is executed by interruption every 30 ° CA, for example.

When the processing shifts to this routine, the ECU
First, in step 101, the 30 reads various signals such as the cylinder discrimination signal from the various sensors 25 to 29, 61, 62, and also reads various flags set by a separate routine.

Next, at step 102, the corresponding cylinder 1a at the present time is discriminated, and the cylinder discriminator (i) is set (recognizing and setting what the cylinder number is).

Subsequently, in step 103, it is determined whether or not the torque fluctuation determination flag XSHK which is set by the "flag setting routine" described later and is read this time is "1". This torque fluctuation determination flag XSHK is
Generally, it is set to "1" when the torque fluctuation is large, and is set to "0" otherwise. When the torque fluctuation determination flag XSHK is "1", it is determined that the torque fluctuation is large and the combustion fluctuation occurs, and it is necessary to correct the injection timing, and the process proceeds to step 104.

In step 104, it is determined whether or not the lean rich determination flag XRLFLAG which is set by the "flag setting routine" described later and is read this time is "1". This lean rich determination flag XLRFL
AG is generally set to "1" when the fuel is lean for combustion and is set to "0" when the fuel is rich for combustion. . Then, the lean rich determination flag XLRFL
If AG is "1", it is regarded as lean and the injection timing correction term dAinj corresponding to the cylinder discriminator (i) is determined in step 105 to retard the injection timing.
Set (i). That is, a predetermined injection timing correction amount CAin from the injection timing correction term dAinj (i) until then.
The value obtained by subtracting j is used as a new injection timing correction term dAinj.
Set as (i).

On the other hand, the lean rich judgment flag XL
If RFLAG is "0", it is determined that the injection timing is rich, and the injection timing correction term dAin corresponding to the cylinder discriminator (i) is advanced in step 106 to advance the injection timing.
Set j (i). That is, the predetermined injection timing correction amount CAi is added to the injection timing correction term dAinj (i) up to that point.
The value obtained by adding nj is used as a new injection timing correction term dAinj.
Set as (i).

Then, proceeding from step 105 or 106, in step 107, the injection timing correction term dAinj (i) currently set is added to the basic injection timing Ainjb (i) calculated in a separate routine. The set value is set as the final injection timing Ainj (i), and the subsequent processing is once ended.

On the other hand, when it is determined in step 103 that the torque fluctuation determination flag XSHK is "0", the torque fluctuation is small and combustion has not fluctuated,
Since it is not necessary to correct the injection timing, the process jumps to step 107. Then, after executing the processing of step 107, the subsequent processing is temporarily terminated.

As described above, in the "injection timing control routine", it is determined whether or not the injection timing should be corrected according to the torque fluctuation determination flag XSHK at that time. When it is determined that the injection timing needs to be corrected, the lean rich determination flag XLRFLA is set.
Depending on G, the injection timing correction term dAinj (i) is increased or decreased. Also, the basic injection timing Ainjb
In contrast to (i), the injection timing is corrected by the amount that the injection timing correction term dAinj (i) is taken into consideration.

Next, the torque fluctuation determination flag XSHK
The processing operation for setting the lean rich determination flag XLRFLAG will be described. That is, the flowchart shown in FIG. 6 shows a “flag setting routine” executed by the ECU 30, and is executed by a regular interruption every predetermined time.

When the processing shifts to this routine, the ECU
First, in step 201, 30 calculates the crank angle time TCRANK (i) for each cylinder 1a (for each cylinder discriminator (i)). That is, the time required for the expansion stroke (every 180 ° CA for four cylinders) corresponding to each cylinder discriminator (i) is calculated.

Further, in the following step 202, the average crank angle time dTCRANK (i) corresponding to the cylinder discriminator (i) is calculated based on the crank angle time TCRANK (i) and the past data.

Further, in step 203, the crank angle time TCRANK (i) and past data,
Also, based on the average crank angle time dTCRANK (i) and the like, the average crank angle fluctuation amount mdTCRANK (i)
Is calculated. This average crank angle fluctuation amount mdTCRAN
K (i) is the crank angle time TCRANK (i) up to the past and present, and the average crank angle time dTCRA.
It is the average value of the deviation from NK (i).

Then, in step 204, the average crank angle fluctuation amount mdTCRANK calculated this time.
It is determined whether (i) is smaller than a predetermined reference value C2. Then, the average crank angle fluctuation amount mdTC
When RANK (i) is smaller than the reference value C2,
On the average, the fluctuation amount of the crank angle time is not so large, and the routine proceeds to step 205.

At step 205, the average crank angle time dTCR is calculated from the crank angle time TCRANK (i).
It is determined whether the absolute value of the value obtained by subtracting ANK (i) is smaller than a predetermined reference value C3. If the absolute value is smaller than the reference value C3, it is determined that the crank angle time fluctuation is small and the torque fluctuation is small, and the routine proceeds to step 206.

In step 206, the torque fluctuation determination flag X used in the above "injection timing control routine".
SHK is set to "0", and the subsequent processing is temporarily terminated.

In step 205, if the absolute value of the value obtained by subtracting the average crank angle time dTCRANK (i) from the crank angle time TCRANK (i) is not smaller than the reference value C3, on average, The amount of change in the crank angle time is not so large, but occasionally the crank angle time TCRANK (i) is equal to the average crank angle time dTCR.
It is recognized that there is a case where it is far from ANK (i).

Here, as shown in FIGS. 9 and 10, even when torque fluctuation occurs, there are torque fluctuations on the lean side (excess fuel amount) and torque fluctuations on the rich side (excess fuel amount). . That is, on the lean side, a torque fluctuation of a level larger than the permissible level always occurs (FIG. 9), and on the rich side, only a torque fluctuation of a level smaller than the permissible level occurs for most of the time. It has been found that even a large level of torque fluctuation occurs (Fig. 10). Therefore, as in the case where a negative determination is made in step 205, the average crank angle time fluctuation amount is not so large, but occasionally the crank angle time TCRANK (i) is equal to the average crank angle time dT.
It can be considered that the case in which it is determined that there is a case where CRANK (i) is separated from the CRANK (i) corresponds to the behavior illustrated in FIG. 10. That is, in this case, it can be considered that the torque fluctuation is occurring on the rich side. Therefore, in such a case, the process proceeds to step 207, the torque fluctuation determination flag XSHK is set to "1", and the lean rich determination flag XLRFLAG is set.
Is set to "0" (rich), and the subsequent processing is once ended.

On the other hand, when a negative determination is made in step 204, that is, the average crank angle fluctuation amount mdTC
When RANK (i) is not smaller than the reference value C2, it is determined that the variation amount of the crank angle time is large even on average, and the process proceeds to step 208. That is, in such a case, it is possible to determine that the torque fluctuation is always higher than the allowable level, and the behavior on the lean side as shown in FIG. 9 is applicable. Therefore, in step 208, the torque fluctuation determination flag XSHK is set to "1" and the lean rich determination flag XLRFLAG is set to "1" (lean), and the subsequent processing is temporarily terminated.

As described above, the above "flag setting routine"
In the above, the crank angle time TCRANK (i), the average crank angle time dTCRANK (i), and the average crank angle variation amount mdTCRANK (i) are calculated, and the current combustion state is determined according to these values. . That is, when it is determined that the variation of the crank angle time TCRANK (i) is small, it is determined that the torque variation is also small, and the torque variation determination flag XSHK is set to "0". On the other hand, on average, the amount of fluctuation of the crank angle time is not so large, but occasionally the crank angle time TCRANK (i) changes to the average crank angle time dTCRA.
When there is a case where it is separated from NK (i), the torque variation determination flag XSHK is set to "1" and the lean variation determination flag XLRFLAG is set as the torque variation corresponding to the torque variation on the rich side. "0"
Is set to Also, the average crank angle fluctuation amount mdTCR
When ANK (i) is not smaller than the reference value C2, the fluctuation amount of the crank angle time is large even on average, and the torque fluctuation is always higher than the allowable level. It is assumed that the flag XSHK is set to "1" and that the torque fluctuation corresponds to the torque fluctuation on the lean side.
RFLAG is set to "1".

Next, the operation and effect of this embodiment will be described. (A) If the fuel evaporation time in each cylinder 1a may differ due to a change in the fuel injection amount or a change in the intake system state (eg, EGR amount, swirl intensity, etc.), each cylinder 1a
In each case, the truly required interval from the end of injection to ignition may be different. Further, when the fuel injection direction is different for each cylinder 1a, the time until the fuel reaches the spark plug 10 may be different. In such a case, the combustion state may be different for each cylinder 1a.

For example, the injected fuel is the spark plug 10
The route as shown in FIG. 7 is followed before reaching. here,
Of the injected fuel, the torque fluctuation is small when the portion indicated by a in the figure reaches the spark plug 10, and the torque fluctuation is small, and the torque fluctuation can be suppressed below the allowable level shown in FIG. . As a result, a stable combustion state can be secured. That is, if the fuel injection is started on the retard side from the optimum timing due to the above factors, the fuel density becomes large and the torque fluctuation on the rich side occurs. Further, if the fuel injection is to be started on the advance side of this timing, the fuel density will be reduced and torque fluctuations on the lean side will occur.

In the present embodiment, the crank angle time TCRANK (i) and the average crank angle time dTCRAN are calculated.
K (i) and average crank angle fluctuation amount mdTCRANK
By calculating (i) and considering them, it is determined whether or not the current torque fluctuation is large. Further, along with this, when the torque fluctuation is large, it is determined whether it is the torque fluctuation on the rich side or the torque fluctuation on the lean side. Then, the torque fluctuation determination flag XSH
K and the lean rich determination flag XLRFLAG are set respectively.

Further, these flags XSHK, XLRFL
The final injection timing Ainj (i) is appropriately corrected based on AG. Therefore, even when torque fluctuations occur in each cylinder 1a as described above and the respective torque fluctuation states are different, the injection timing is appropriately corrected for each cylinder 1a, so that the individual cylinders 1a have different injection timings. For ignition, an appropriate fuel injection timing can be secured and an optimal combustion state can be secured. As a result, the rotation fluctuation of the engine 1
It is possible to prevent a misfire.

(B) Further, in the present embodiment, the torque fluctuation due to combustion on the rich side and the torque fluctuation due to combustion on the lean side are discriminated by the fluctuation characteristics of the output torque. As described above, the fact that the output torque variation characteristic at fuel rich (FIG. 10) is different from the output torque variation characteristic at fuel lean (FIG. 9) has been found. The change due to lean can be accurately discriminated. Therefore, the above-described effects can be made more reliable.

(C) In particular, in the present embodiment, the fluctuation of the output torque in (b) above is detected based on the crank angle time TCRANK (i) after ignition of each cylinder 1a. As described above, it is known that the fluctuation of the output torque corresponds to the crank angle time TCRANK (i) of each cylinder 1a, and from such a fact, the crank angle time TCRANK (i) and its fluctuation are calculated. By detecting it, it is easy to detect fluctuations in output torque, and
It can be done reliably.

(Second Embodiment) Next, a second embodiment of the present invention will be described. However, since the configuration and the like of this embodiment are the same as those of the above-described first embodiment, the same members and the like are denoted by the same reference numerals and description thereof is omitted. And, below, the first
The following description focuses on differences from the first embodiment.

That is, in the first embodiment, the stability of the combustion state is ensured by correcting the fuel injection timing. On the other hand, in the present embodiment, the torque fluctuation determination flag XSHK and the lean rich determination flag XL set by the "flag setting routine" are set.
The difference is that the stability of the combustion state is ensured by correcting the ignition timing based on RFLAG. Therefore, the content of the ignition timing correction control will be described below. In the present embodiment, the ECU 3
0 constitutes a combustion fluctuation detection means, a discrimination means, an injection / ignition control means, and an ignition timing correction means.

The flowchart shown in FIG. 11 is executed by the ECU 3
It shows an "ignition timing control routine" executed by 0, and is executed by interruption every 30 ° CA, for example. When the processing shifts to this routine, the ECU 30
First, in step 201, various sensors 25-2
Various signals such as a cylinder discrimination signal are read from 9, 61 and 62, and various flags XSHK and XLRFLAG set by the "flag setting routine" are read.

Next, at step 202, the corresponding cylinder 1a at the present time is discriminated and the cylinder discriminator (i) is set. Subsequently, in step 203, it is determined whether or not the torque fluctuation determination flag XSHK set by the "flag setting routine" and read this time is "1". Then, the torque fluctuation determination flag X
If SHK is "1", it is determined that the torque fluctuation is large and the combustion fluctuation occurs, and it is necessary to correct the ignition timing, and the routine proceeds to step 204.

In step 204, it is judged whether or not the lean rich judgment flag XLRFLAG set by the "flag setting routine" and read this time is "1". Then, the lean rich determination flag XLRFL
If AG is "1", it is regarded as lean, and in step 205, the ignition timing correction term dSA (i) corresponding to the cylinder discriminator (i) is advanced to advance the ignition timing.
Set. That is, the ignition timing correction term dS up to that point
A value obtained by adding a predetermined ignition timing correction amount CSA to A (i) is set as a new ignition timing correction term dSA (i).

On the other hand, the lean rich judgment flag XL
If RFLAG is "0", it is determined that the ignition timing is rich, and in step 206, the ignition timing correction term dSA corresponding to the cylinder discriminator (i) is retarded in order to retard the ignition timing.
Set (i). That is, a value obtained by subtracting the predetermined ignition timing correction amount CSA from the ignition timing correction term dSA (i) up to that point is set as a new ignition timing correction term dSA (i).

Then, proceeding from step 205 or 206, in step 207, the ignition timing correction term dSA (i) set this time is added to the basic ignition timing SAb (i) calculated in a separate routine. The set value is set as the final ignition timing SA (i), and the subsequent processing is once ended.

On the other hand, in step 203, when the torque fluctuation determination flag XSHK is judged to be "0", the torque fluctuation is small and combustion has not fluctuated,
Since it is not necessary to correct the ignition timing, the process jumps to step 207. Then, after executing the processing of step 207, the subsequent processing is once ended.

As described above, in the "ignition timing control routine", it is determined whether or not the ignition timing is to be corrected according to the torque fluctuation determination flag XSHK at that time. When it is determined that the ignition timing needs to be corrected, the lean rich determination flag XLRFLA is set.
Depending on G, the ignition timing correction term dSA (i) is increased or decreased. Then, with respect to the basic ignition timing SAb (i), the ignition timing is corrected by the amount that the ignition timing correction term dSA (i) is taken into consideration.

As described above, according to the present embodiment, the ignition timing is corrected instead of the fuel injection timing of the first embodiment. Therefore, the same operational effect as that of the first embodiment is obtained.

The present invention is not limited to the above embodiment, but may be configured as follows, for example. (1) In each of the above embodiments, the crank angle time TCRANK is based on the detection result of the crank angle sensor 28.
(I), average crank angle time dTCRANK (i) and average crank angle variation amount mdTCRANK (i) are calculated, and by considering them, the magnitude of the torque variation is determined, and whether the torque variation is on the lean side or not. The torque fluctuation on the rich side is discriminated. On the other hand, a combustion pressure sensor (not shown) is provided on the combustion chamber side of the cylinder head corresponding to each cylinder 1a so as to detect the combustion pressure, and determine the misfire level based on the combustion pressure (torque fluctuation). Determination of whether the torque fluctuation is on the lean side or the torque fluctuation is on the rich side).

Even with such a structure, the same operational effects as those of the above-described embodiment can be obtained. (2) In each of the above embodiments, the cylinder injection engine 1 is used.
Although the present invention has been embodied in, the invention may be embodied in any type as long as it is an internal combustion engine of a type that performs so-called stratified charge combustion or weakly stratified charge combustion. For example, a type in which the fuel is injected toward the back side of the head of the intake valves 6a and 6b of the intake ports 7a and 7b is also included. In addition, the intake valve 6a,
Although the fuel injection valve is provided on the side of 6b, the type of direct injection into the cylinder bore (combustion chamber 5) is also included. Furthermore, it can be embodied in a so-called direct injection diesel engine that does not have a spark plug. (3) In addition, in the above-described embodiment, the configuration has the helical intake port and is capable of generating so-called swirl, but it is not absolutely necessary to generate swirl. Therefore, for example, the swirl control valve 17, the step motor 19, and the like in the above embodiment can be omitted.

The technical idea which is not described in the claims and can be grasped from the above-described embodiment will be described below together with the effect thereof. (A) In the combustion control device for an internal combustion engine according to any one of claims 1 to 4, the determination of the fluctuation due to the excessive fuel amount or the excessive fuel amount by the determination means is based on the detection result of the combustion pressure detecting means in the cylinder. It is characterized by performing.

Even with such a structure, it is possible to secure the same operational effect as that of the third aspect.

[0076]

As described in detail above, according to the present invention,
In a combustion control device for an internal combustion engine capable of stratified combustion, even if there is a change in the fuel injection amount for each cylinder, a change in the state of the intake system, or the fuel injection direction may differ for each cylinder, As a result, it is possible to prevent the deterioration of the combustion state, which in turn can prevent the occurrence of problems such as fluctuations in rotation and misfire.

[Brief description of drawings]

FIG. 1 is a basic conceptual configuration diagram of the invention described in claim 1;

FIG. 2 is a basic conceptual configuration diagram of the invention described in claim 2;

FIG. 3 is a schematic configuration diagram showing a combustion control device for an engine according to the first embodiment.

FIG. 4 is an enlarged sectional view showing a cylinder portion of the engine.

FIG. 5 is a flowchart showing an “injection timing control routine” executed by the ECU.

FIG. 6 is a flowchart showing a “flag setting routine” executed by the ECU.

FIG. 7 is a schematic diagram showing an outline of a combustion chamber and behavior of injected fuel.

FIG. 8 is a graph showing the relationship between torque fluctuations that differ depending on the injection start timing.

FIG. 9 is a graph showing a characteristic of torque fluctuation with time on the lean side.

FIG. 10 is a graph showing characteristics of torque fluctuations over time on the rich side.

FIG. 11 is a flowchart showing an “ignition timing control routine” executed by an ECU in the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as internal combustion engine, 10 ... Spark plug, 1
DESCRIPTION OF SYMBOLS 1 ... Fuel injection valve, 12 ... Igniter, 25 ... Throttle sensor which comprises operating state detecting means, 26A ... Accelerator sensor which constitutes operating state detecting means, 26B ... Full closing switch which constitutes operating state detecting means, 27 ... Operation Top dead center sensor constituting state detecting means 28. Crank angle sensor constituting operating state detecting means 29. Swirl control valve sensor constituting operating state detecting means 30.
An ECU that constitutes combustion fluctuation detection means, determination means, injection control means, injection timing correction means, injection / ignition control means, ignition timing correction means.

Claims (4)

[Claims] 1. A fuel injection means for injecting fuel into a cylinder of an internal combustion engine to perform stratified combustion, an operating state detecting means for detecting an operating state of the internal combustion engine, and a detection result of the operating state detecting means. And an injection control unit that controls the fuel injection unit based on the calculated fuel injection amount and injection timing based on the calculated fuel injection amount and injection timing. In a combustion control device for an internal combustion engine, based on the detection result of the operating state detection means, combustion fluctuation detection means for detecting combustion fluctuation of the internal combustion engine; and combustion fluctuation detected by the combustion fluctuation detection means Alternatively, a discriminating unit for discriminating a fluctuation due to insufficient fuel, and an injection timing correcting unit for correcting the fuel injection timing by the injection control unit according to the discrimination result of the discriminating unit. Combustion control device for an internal combustion engine, wherein a provided. 2. A fuel injection means for injecting fuel into a cylinder of an internal combustion engine to perform stratified combustion, an ignition means for igniting fuel in the cylinder, and an operating state detection for detecting an operating state of the internal combustion engine. And a fuel injection amount and ignition timing injected from the fuel injection means into the cylinder based on the detection result of the operating state detection means, and based on the calculated fuel injection amount and ignition timing, A combustion control device for an internal combustion engine, comprising: a fuel injection means and an injection / ignition control means for controlling the ignition means; a combustion fluctuation detection for detecting a combustion fluctuation of the internal combustion engine based on a detection result of the operating state detection means. Means, a discrimination means for discriminating a fluctuation due to excessive fuel or an insufficient fuel by the combustion fluctuation detected by the combustion fluctuation detecting means, and according to a judgment result of the judging means, A combustion control device for an internal combustion engine, comprising: an ignition timing correction means for correcting the ignition timing by the injection / ignition control means. 3. The combustion control device for an internal combustion engine according to claim 1, wherein the determination of the variation due to the excessive fuel amount or the insufficient fuel amount by the determination means is performed based on the variation of the output torque. 4. The combustion control device for an internal combustion engine according to claim 3, wherein the fluctuation of the output torque is detected based on a crank angle time after ignition of each cylinder.