JP2625862B2 - Fuel injection amount control device for multi-cylinder internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection amount control device between multi-cylinder internal combustion engines.

[Conventional technology and issues]

Conventionally, there has been known an apparatus that calculates a combustion fluctuation from a combustion pressure in a combustion chamber and controls a fuel injection amount so that the combustion fluctuation does not exceed a predetermined value (Japanese Patent Laid-Open No. 60-150446). However, in this fuel injection amount control device, in the case of a multi-cylinder internal combustion engine, since the fuel state is different for each cylinder, the combustion pressure of all cylinders cannot be represented only by the combustion pressure of some cylinders. It is necessary to provide a combustion pressure sensor every time. For this reason, the conventional fuel injection amount control device has a problem that the whole device is expensive and the control becomes complicated, so that the calculation speed is relatively delayed as the engine speed increases, and the controllability is not good. .

An object of the present invention is to provide an inexpensive device that simplifies the control of the fuel injection amount and can control the fuel injection amount with high accuracy regardless of the engine speed.

Incidentally, JP-A-58-27837 and JP-A-58-38354
Japanese Patent Application Laid-Open Publication No. H11-163,867 discloses a configuration in which the fuel injection amount is controlled such that the combustion fluctuation approaches the misfire limit. However, as in the present invention, the fuel injection amount is controlled by an output signal of a combustion pressure sensor provided in one cylinder. It does not suggest a configuration that changes in accordance with.

[Means for solving the problem]

The fuel injection amount control device according to the present invention includes a combustion pressure sensor 35 provided for one cylinder, a means A for detecting an output torque difference between the cylinders by a crank angle sensor, and an output torque difference substantially eliminated. In this way, there is provided a means B for adjusting the output torque of each cylinder, and a means C for increasing or decreasing the fuel injection amount of all cylinders in accordance with the magnitude of the fluctuation of the combustion pressure of the one cylinder.

〔Example〕

 Hereinafter, the present invention will be described with reference to illustrated embodiments.

FIG. 2 shows a four-cylinder engine to which one embodiment of the present invention is applied. Four ignition plugs 21, 22, 23, and 24 are attached to the engine body 11 corresponding to the first to fourth cylinders, and the intake manifold 12 and the exhaust manifold 13 are connected. Each branch pipe of the intake manifold 12 is provided with a fuel injection valve 31, 32, 33, 34. That is, these fuel injection valves are provided for each cylinder and are controlled independently of each other.
A combustion pressure sensor 35 is provided in the first cylinder. A throttle valve 15 is provided in an intake passage 14 connected to an upstream side of the intake manifold 12, and a throttle sensor 16 is connected to a valve shaft of the throttle valve 15. Throttle sensor
Reference numeral 16 outputs an ON signal when the throttle valve 15 is substantially fully closed. The distributor 17 is driven to rotate by a camshaft (not shown), and each of the spark plugs 21, 22, 23, 24
Supply high voltage to The reference position sensor 18 is attached to the distributor 17 and outputs a reference position signal every 720 ° C. (crank angle). The crank angle sensor 19 is attached to the distributor 17 and outputs a signal every 30 ° C. (crank angle).

FIG. 3 shows the structure of the first cylinder. The combustion chamber 25 has a bore 27 formed with a cylinder block 26, and a cylinder head 28.
And a piston 29, and a combustion pressure sensor 35
Is mounted on the cylinder head 28 and projects into the combustion chamber 25.

The control circuit 41 includes a microcomputer, and detects a torque difference between the cylinders based on signals from the sensors 16, 18, and 19, and calculates a fuel injection amount for each cylinder, as described later. The control circuit 41 has a central processing unit (CPU) 42, a memory 43, an input port 44, and an output port 45, which are connected by a bus 46, as shown in FIG. Each sensor 16, 18, 19 is connected to an input port 44, and the combustion injectors 31, 32, 33, 34 are connected to an output port 45.

FIG. 4 shows a routine for detecting an output torque difference between the cylinders by the control circuit 41. This routine is interrupted and executed at every fixed crank angle.

In step 101, the current cylinder is set to the compression top dead center (TD
C) is determined. This determination is performed based on output signals from the reference position sensor 18 and the crank angle sensor 19, as is well known in the art. That is, the reference position signal is output at, for example, the compression TDC of the first cylinder, and 180 ° C. A, 360 ° C.,
After 540 ° C, the 3rd, 4th and 2nd cylinders are compressed TDC
It is in. If the predetermined cylinder is not currently in the compression TDC, the execution of step 101 terminates this routine immediately.
If the predetermined cylinder is in the compression TDC, step 102 is executed.

In step 102, 180 ° C. A after the compression TDC of the cylinder,
That is, the required time T180i in the explosion stroke is calculated based on the output signal of the crank angle sensor 19 and the timer. The required time T180i is proportional to the reciprocal of the output torque of the cylinder. In step 103, the cylinder counter i is incremented by one, and in step 104, it is determined whether or not the calculation of the required time T180i in step 102 has been completed for all cylinders. If the execution of step 102 has not been completed for all cylinders, the process proceeds to step 105, but if not completed, this routine ends immediately. In this embodiment, since the engine has four cylinders, step 104
Then, it may be determined whether or not the cylinder counter i has exceeded four. Note that 1, 2, 3, and 4 of the cylinder counter i indicate the ignition order, and correspond to the first, third, fourth, and second cylinders, respectively.

In step 105, the average required time T180AV at 180 ° C. of the explosion stroke of all cylinders is calculated. And step 10
In step 6, for each cylinder, the ratio Ki between the required time of the cylinder at 180 ° C. and the required time of all cylinders at 180 ° C. is determined. That is, the ratio Ki indicates the ratio between the torque of the cylinder and the average value of the torque of all cylinders.

In step 107, it is determined whether the fuel supply is currently cut off (fuel cut). Throttle sensor 16
When it is detected that the throttle valve 15 is substantially fully closed and the engine speed is higher than a predetermined value, it is determined that the fuel is currently being cut off.
Steps 121 and subsequent steps are executed, but when the throttle valve 15 is not fully closed, it is determined that the fuel is being cut, and then steps 111 and subsequent steps are executed.

In step 121, the ratio Ki is integrated for each cylinder to obtain an integrated value SKFCi, and the cycle counter Jf is set to 1
Is only incremented. That is, the integrated value SKFCi is
This is the sum of the ratio Ki between the required explosion stroke time of each cylinder and the average of the required explosion stroke times of all cylinders during fuel cut. The magnitude relation of the integrated value SFCFi of each cylinder during the fuel cut means an error in the angle detection of the crank angle sensor because each cylinder is not in the combustion body.

In step 122, it is determined whether or not the cycle counter Jf has reached 50, that is, in step 121, whether or not the ratio Ki has been integrated for 50 cycles. If the integration for 50 cycles has not been completed, the routine proceeds to step 117, where the cylinder counter i is set to 1, and this routine ends. Thereafter, the ratios Ki (step 106) are obtained again for all the cylinders. In step 122, the cycle counter Jf becomes 50
If so, in step 123, the integrated value SKFCi
Is replaced with the integrated value SKFi, and the integrated value SFCFi and the cycle counter EJf are cleared to zero.

In step 111, the ratio Ki of each cylinder during fuel supply
Are integrated to obtain an integrated value SKi, and the cycle counter J is incremented by one. Integrated value of each cylinder
SKi corresponds to the output torque of each cylinder,
Includes an error in the angle detection of the crank angle sensor. Before the counter J reaches 50, the process proceeds from step 112 to step 117, in which the cylinder counter i is set to 1 and this routine ends, but if the counter J has reached 50, the process proceeds to step 117.
113 is executed. That is, for two cylinders having continuous explosion strokes, the difference between the integrated values SKi and SKi _i-1 during fuel supply and the difference between the integrated values SKFi and SKFi _i-1 during fuel cut are determined, and further, the difference between these values is calculated. (SKi-SKi _i-1 ) and the difference (SKFi
−SKFi _i−1 ) is calculated. This change amount DSK
i represents the amount of decrease in torque in the cylinder, and an error in angle detection of the crank angle sensor has been removed.

In step 114, it is determined whether or not the amount of change DSKi is equal to or greater than a determination value. If the change amount DSKi is equal to or greater than the judgment value,
In step 115, the fuel injection correction coefficient KTAUi is increased by γ, and if the change amount DSKi is smaller than the determination value, step
Step 115 is not executed, and the current fuel injection correction coefficient KTAUi is maintained. Steps 114 and 115 are executed for all the cylinders, whereby the fuel injection amount is increased and corrected for the cylinders whose output torque is smaller than those of the other cylinders. Note that the fuel injection amount TAUi is obtained by TAUi = FAF × KTAUi × αi × TP. Where FAF is the feedback coefficient,
αi is a correction coefficient, TP is a basic injection amount, and the feedback coefficient FAF is corrected by an air-fuel ratio correction routine described later.

In step 116, the integrated value SKi and the cycle counter J are set to 0.
Is cleared, and in step 117, the cylinder counter i is set to 1.

Therefore, in this embodiment, first, one cycle (720 ° C.)
For each cylinder, the explosion stroke of each cylinder is 180 ° C and the average of all cylinders is 180
The ratio Ki to the ℃ A period is obtained, and the integrated values SKi, SKFi for 50 cycles during fuel supply or fuel cut
Is required. This integrated value is updated every 50 cycles. Then for two cylinders explosion stroke is continuously integrated value SKi, SKi _i-1 of the difference _{SKi-SK i-1} and the integrated value SKFi, SKF _i-1 of the difference _{(SKFi-SKF i-1)} and is calculated, If the change amount DSKi of these differences is equal to or greater than the determination value, it is determined that the output torque of the cylinder corresponding to the cylinder counter is too small, and the fuel injection amount is increased.

As described above, the magnitude relationship of the integrated value SKFi of each cylinder during the fuel cut indicates an error in the angle detection of the crank angle sensor because each cylinder is not in a combustion state. Therefore, if the torque generated during the explosion stroke is uniform in each cylinder, the magnitude relationship of the integrated value SKi of each cylinder during fuel supply is substantially the same as the magnitude relationship of the integrated value SKFi of each cylinder during fuel cut. . That is, the change amount DSKi is
This indicates whether the output torque of the cylinder is too small with respect to the output torque of the other cylinders. In this embodiment, in steps 114 and 115, the fuel injection correction coefficient KTAUi is increased for the cylinder whose output torque is too small to increase the fuel injection amount. As a result, the output torque difference is substantially eliminated for all cylinders, and the output torque of all cylinders is adjusted to be uniform.

FIG. 5 shows a routine for uniformly correcting the air heat ratio for all cylinders. This routine is executed after an interruption process every 720 ° C.

In step 201, the average effective pressure Pi stored in the memory 43 in advance is read. In the present embodiment, the average effective pressure Pi is the work amount ΔPi = P × ΔV between 5 ° C. every 5 ° C. in the compression stroke and the explosion stroke of the first cylinder (P is the combustion pressure, ΔV is 5 ° C. (The amount of change in the cylinder volume for each cylinder) is calculated and integrated, and the integrated value is divided by the stroke capacity Vh. In step 202, the counter L is incremented by 1 with an average effective pressure Pi of 16 cycles are stored in A ₁ to A _16, respectively. This counter L is 16
Is reached, a negative determination is made in step 203, and this routine ends as it is. However, if the counter L has reached 16, the process proceeds from step 203 to step 204.

In step 204, each average effective pressure P in 16 cycles
i varies ie variance S ² of (stored in step 202) is calculated. The variance S ² is the square of the standard deviation, Required by Next, at step 205, the counter L is cleared by 0. Then, in step 206, the variance S ²
There is discriminated whether or not larger than the set value, the feedback coefficient at 208 when the feedback coefficient FAF is made to increase by alpha, also distributed S ² is equal to or less than the set value in step 207 when the variance S ² is greater than the set value FAF is β
Only reduced.

Then, after the output torque of each cylinder is adjusted to be uniform by the output fluctuation detection routine, the air-fuel ratio correction routine adjusts the combustion pressure P of one cylinder according to the magnitude of the fluctuation (variance S ² ) of all cylinders. Is increased or decreased, ie, the fuel injection amount is increased or decreased. That is, after the output torques of all the cylinders are made uniform, the fuel injection amount is reduced and the air-fuel ratio is further made lean as long as the combustion fluctuation is within the allowable range.

If the output torques of all cylinders are not uniform, the lean limit (lean air-fuel ratio limit) is determined by the cylinder with the worst combustion state. The air-fuel ratio was controlled to be However, according to this embodiment, since the output torque of each cylinder is uniform as described above, the lean limit is expanded, and the air-fuel ratio can be made as lean as possible.
Accordingly, fuel efficiency is improved, it is possible to reduce the NO _X components in the exhaust gas. In this embodiment, the output signal of one combustion pressure sensor 35 is used to control the air-fuel ratio of all cylinders. Therefore, the air-fuel ratio control is simple, and the controllability does not decrease even when the engine speed increases. Further, since only one combustion pressure sensor 35 is required, the configuration is simple, and the whole apparatus is inexpensive.

In order to adjust the output torque of each cylinder to be uniform, it is not always necessary to control the fuel injection amount as in the above embodiment, and the ignition timing may be controlled for each cylinder.

〔The invention's effect〕

According to the fuel injection amount control device for a multi-cylinder internal combustion engine according to the present invention, the output torque of each cylinder is adjusted so that the output torque difference of each cylinder detected by each crank sensor is substantially eliminated, and one The fuel injection amount of all cylinders is increased or decreased according to the magnitude of the fluctuation of the combustion pressure detected by the combustion pressure sensor provided in the cylinder. The output torque value of each cylinder based on the crank angular velocity detected by the crank angle sensor is not accurate because it changes due to the vehicle running resistance or the like, but the output torque difference between the cylinders is offset by the vehicle running resistance or the like. Therefore, if the output torque of each cylinder is adjusted so that this output torque difference is substantially eliminated, the output torque of each cylinder can be made to exactly match. On the other hand, the fluctuation value of the combustion pressure detected by the combustion pressure sensor is accurate, and the combustion pressure of this cylinder is detected by the combustion pressure sensor provided in one cylinder, and the combustion pressure is determined according to the magnitude of the fluctuation of the combustion pressure. By increasing or decreasing the fuel injection amount of all cylinders, it becomes possible to control the fuel injection amount of all cylinders with high accuracy, in combination with the elimination of the output torque difference by each crank sensor. As described above, the fuel injection control device for a multi-cylinder internal combustion engine according to the present invention does not need to provide an expensive combustion pressure sensor for each cylinder, and furthermore, since the control of the fuel injection amount is relatively simple, the engine rotation Even if the number is high, it has sufficient followability.

[Brief description of the drawings]

1 is a configuration diagram of the invention, FIG. 2 is a diagram showing an engine to which one embodiment of the present invention is applied, FIG. 3 is a cross-sectional view showing a first cylinder, FIG. FIG. 5 is a flowchart of the air-fuel ratio correction routine. 21,22,23,24 …… Spark plug, 31,32,33,34 …… Fuel injection valve, 35 …… Combustion pressure sensor.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-27837 (JP, A) JP-A-58-38354 (JP, A) JP-A-61-55337 (JP, A)

Claims (1)

(57) [Claims] 1. A fuel injection amount control device for a multi-cylinder internal combustion engine, comprising: a combustion pressure sensor provided in one cylinder; a means for detecting an output torque difference between cylinders by a crank angle sensor; Means for adjusting the output torque of each cylinder so that the difference is substantially eliminated, and means for increasing or decreasing the fuel injection amount of all cylinders according to the magnitude of the combustion pressure fluctuation of the one cylinder A fuel injection amount control apparatus for a multi-cylinder internal combustion engine, comprising: