JPH01290946A - Control device for multi cylinder internal combustion engine - Google Patents

Abstract

PURPOSE:To provide possibility of deciding the air fuel ratio of a multi-cylinder internal-combustion engine, which performs simultaneous injection or group injection, further to a leaner side by increasing or decreasing the fuel amount so that the amount of change in the output torque made uniform becomes the set value. CONSTITUTION:In an internal-combustion engine with the ignition sequence set from No.1 to No.3, 4, and 2, a driver circuit 46 is connected with the fuel injection valves 28 for No.1, 4 cylinders while another driver circuit 47 with fuel injection valves 28 for No.2, 3 cylinders, and thus group injection takes place. A control device 40 calculates the torque change amount of each cylinder from the sensing value given by a pressure sensor 24. The ignition timing with an ignition plug 22 furnished on a cylinder with larger torque change is angle advanced to make the torque change even. Then the valve opening timings for the fuel injection valves 28 are controlled so that the torque change made even becomes the set value, and the fuel amount is increased or decreased. Thus the fuel injection amount is controlled for the group of cylinders with their torque changes made even, so that the air fuel ratio can be decided to the lean side.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control device for a multi-cylinder internal combustion engine configured to simultaneously inject fuel into two or more cylinders.

[Conventional technology]

Japanese Patent Laid-Open No. 57-28834 discloses a fuel injection system in which fuel is simultaneously injected into two cylinders in synchronization with each intake stroke of two cylinders having a stroke difference of 360' crank angle, that is, two cylinders whose intake strokes are performed alternately. The method is disclosed. In this case, in each cylinder, fuel injection is performed twice per combustion cycle, during the intake stroke of one cylinder and during the intake stroke of the other cylinder (in the explosion stroke when the intake valve is closed in the one cylinder). be exposed.

This fuel injection method promotes atomization of the fuel injected during the explosion stroke when the intake valve is closed, and the fuel injected during the intake stroke is stratified in the upper layer of the combustion chamber, resulting in good combustion. can be achieved.

Japanese Patent Laid-Open No. 60-150446 discloses that a pressure sensor is attached to each combustion chamber of an engine, the pressure in the combustion chamber is sampled at every predetermined crank angle, and the cumulative value of the sampling value of the pressure in the combustion chamber for 14 J cycles is sampled. The average effective pressure (corresponding to torque) is obtained by dividing by a number, the average effective pressure for each cycle thus obtained is sampled for multiple cycles, and the amount of torque fluctuation is calculated by calculating the mathematical variance (S!). Discloses that it will be calculated. Also, JP-A-58-27837 and JP-A-58
Japanese Patent No. 38354 discloses a configuration in which the fuel injection amount is controlled so that the combustion fluctuation approaches the point of misfire.

[Problem to be solved by the invention]

As described in Japanese Patent Application Laid-Open No. 57-28834 mentioned above, in a fuel injection device that simultaneously injects fuel into two cylinders in synchronization with each intake stroke of two cylinders whose intake strokes are performed alternately, one Two fuel injections are performed, one during the intake stroke of one cylinder and the other during the intake stroke of the other cylinder, but the amount of fuel injected during each injection is the same. Therefore, for example, if there are variations in the characteristics of the fuel injection valves, there will be variations in the fuel injection amount between cylinders, resulting in some cylinders having large torque fluctuations. However, since the drive circuit for the fuel injection valves installed in each cylinder is common, the fuel injection amount is restricted by the cylinder with large torque fluctuations, and the actual air-fuel ratio has to be slightly richer than the lean burn limit. .

The present invention equalizes torque fluctuations between cylinders in a multi-cylinder internal combustion engine that performs simultaneous injection or group injection,
It is an object of the present invention to provide a control device that can set the air-fuel ratio to a leaner side.

[Means to solve the problem]

As shown in the block diagram of the invention shown in FIG. means A for detecting torque fluctuations; ignition timing control means B for advancing the ignition timing of the ignition plugs 22 provided in cylinders with large output torque fluctuations to equalize the output torque fluctuations of the cylinders; The present invention is characterized by comprising means C for controlling the amount of fuel to be increased or decreased so that the amount of variation in the output torque thus determined becomes a set value.

[Example〕 The present invention will be explained below based on illustrated embodiments.

Referring to FIG. 2, the internal combustion engine main body 10 has a four-cylinder combustion chamber 12. An intake boat 14 and an exhaust boat 16 are formed in each cylinder.

An intake valve 18 and an exhaust valve 20, which are driven in synchronization with the engine crankshaft, are arranged in the intake boat 14 and the exhaust boat 16, respectively. Further, an ignition plug 22 is attached to the combustion chamber 12. Furthermore, a pressure sensor 24 is attached to the combustion chamber 12. Note that the intake boat 14 is formed in a helical shape so that the intake air generates a swirl within the combustion chamber 12.

The intake boat 14 is connected to each branch pipe of an intake manifold 26, and a fuel injection valve 28 is arranged in each branch pipe. A throttle valve 30 and an air flow meter 32 are arranged in the intake pipe upstream of the intake manifold 26. Exhaust boat 16 is connected to exhaust manifold 34. A rotation speed sensor 38 for detecting the engine rotation speed is attached to the distributor 36, and an igniter 39 is connected thereto.

Fuel injection valve 28 and igniter 39 are controlled by control circuit 40. The control circuit 40 is configured as a microcomputer, and includes a central processing unit (CP [7)].
41, a memory 42, an input port 43, and an output port 44, which are connected by a bus 45.

Drive circuits 46 and 47 are provided to control the fuel injection valve 28, and drive circuit 48 is provided to control the igniter 39. The control circuit 40 receives detection signals from the pressure sensor 24, air flow meter 32, rotation speed sensor 38, etc., and controls the fuel injection valve 2 via drive circuits 46 and 47.
8 and also sends a control signal to the igniter 39 via the drive circuit 4.

The first drive circuit 46 is connected to the fuel injection valve 28 of the first cylinder and the fuel injection valve 28 of the fourth cylinder, and can open these two fuel injection valves 28 at the same time for the same amount of time. The second drive circuit 47 is similarly connected to the fuel injection valve 28 of the second cylinder and the fuel injection valve 28 of the third cylinder. Here, the 6 ignition order is the order of 1st, 3rd, 4th and 2nd cylinders,
The intake stroke of the 1st and 4th cylinders is 360 in crank angle.
It is done every time. Similarly, the intake strokes of the second and third cylinders are alternately performed every 360 degrees of crank angle.

FIG. 3 shows the intake stroke and fuel injection timing for a four-cylinder engine. The intake stroke is indicated by hatching I, and the fuel injection timing is indicated by dotted J.

During the intake stroke of the first cylinder, fuel is injected into the first cylinder and the fourth cylinder simultaneously, and further, during the intake stroke of the fourth cylinder, fuel is injected into the first cylinder and the fourth cylinder simultaneously. The fuel injection valves 28 of the first and fourth cylinders are connected to the first drive circuit 4G.
The fuel injection time, that is, the fuel injection amount is the same. The same applies to the second and third cylinders.

In this embodiment, in a device that performs so-called group injection in which the first and fourth cylinders are made into one group and the second and third cylinders are made into another group, the output torque fluctuations between each group are equalized. This is to control output torque fluctuations between cylinders in the same group to a set value.

FIG. 4 shows a routine for controlling the output torque by the control circuit 40. This routine is executed by interrupt processing at every fixed crank angle.

In step 101, the torque fluctuation amount ΔT1 for each cylinder is calculated. In order to detect this torque fluctuation, the detected value of the pressure sensor 24 attached to each cylinder is used. The torque fluctuation amount ΔTri can be calculated using, for example, Japanese Patent Application Laid-Open No. 1504-1986.
It can be carried out according to the procedure described in Publication No. 46. In other words, 1. Sample the pressure in the combustion chamber at every predetermined crank angle, and divide the cumulative value of the sampled values of the pressure in the combustion chamber for one cycle by the number of samples to calculate the average effective pressure (
(corresponding to the torque), and sample the average effective pressure for each cycle obtained in this way for multiple cycles.
The amount of torque variation is calculated by calculating the mathematical variance (S2). Alternatively, the amount of torque fluctuation can be calculated by sampling the maximum pressure during combustion and calculating the variance of this maximum pressure. Or Jitsukai Showa 6
As described in No. 2-35877, calculate the engine load, the variation in engine rotational speed within a predetermined period of the explosion stroke, and the ratio between the engine load and the variation in engine rotational speed, and calculate this ratio. The amount of torque fluctuation can be detected from.

In this way, the torque fluctuation amount ΔTrl~ΔT for each cylinder,
, 4 is obtained, then in step 102, the first
and the average value Δ'r1 of the torque fluctuation of the fourth cylinder, that is, the first injection group. A V I is determined by, and in step 103, the average value of torque fluctuations of the second and third cylinders, that is, the second injection group ΔT rAv□
is required by. In step 104, the engine speed N, the engine load Q/N (where Q is the intake air amount)
, from a map with parameters such as engine water temperature Tw, etc.
A control target value for the amount of torque fluctuation is calculated.

In steps 111 to 114, the fuel injection amount of the first injection group is controlled based on the magnitude of the torque fluctuation of this injection group.

In step 111, it is determined whether the average torque fluctuation value ΔT r A V l of the first injection group is equal to the target value or not. If they are equal, steps 112 to 114 are skipped and the process proceeds to step 115, but if not, step 115 is performed. knob 1
At step 12, it is determined whether the average value Avl is larger than the target value. If the average value ΔT0□ is larger than the target (direct), it means that the average output torque fluctuation amount of the first and fourth cylinders is too large7. In this case, step 113 is executed and the fuel of the first injection group is The injection amount is increased.On the other hand, if the average value ΔT rAVl is smaller than the target value, the average output torque fluctuation amount of the first and fourth cylinders is small and there is still room to reduce the output torque, so step At step 114, the fuel injection amount of the first injection group is reduced.The fuel injection amount of the first injection group is thus controlled so that the average value ΔTFAvI approaches the target value.

The fuel injection amount of the second injection group is similarly controlled. That is, in step 115, if the average value ΔTrAvt of the torque variation ωJ of this injection group is equal to the target value, steps 116 to 118 are skipped, but if the average value ΔT r A V 2 is 4J equal to the target value, step 116 is skipped. executed. If the average value ΔT rAvx is larger than the target value, the second
The amount of fuel injection oil in the injection group is increased, and the average value ΔT,
If AV□ is smaller than the target value, the fuel injection amount of the second injection group is reduced in step 118.

In steps 121 to 126, the ignition advance angle is controlled so that the output torque fluctuation of the first cylinder and in steps 131 to 136 the output torque fluctuation of the fourth cylinder are both within the FiJi constant range. , This equalizes the magnitude of Truia fluctuations in each cylinder.

In step 121, the first cylinder's)・lux fluctuation amount ΔTr+
It is determined whether or not is equal to the average 4171ΔT r A V l. The torque fluctuation amount Δ1゛ of the first cylinder is the T average value Δ
If T r A V I is equal, steps 122-1
24 is skipped, but if the torque fluctuation amount Δ1゛r1 is not equal to the average value Δ'I'rA%H, in step 122 the torque fluctuation amount Δ]゛ is changed to the average value Δ'I', AVI
It is determined whether or not it is larger than . Torque fluctuation amount Δi'
If I' l is larger than the average value ΔT r A V +, in step 123, the advance angle correction amount ΔSAi of the ignition timing of the first cylinder is set (ll\a "CA" is changed to the 11 advance side. , T□ becomes the average value ΔT
rav+, in step 124, the ignition timing advance amount jE, MΔSAI of the first cylinder is changed to the retard side by the set value a"CA. Note that the set value a"C
The magnitude of A may take different values on the advance side and the retard side.

Next, in steps 125 and 126, a guard is applied to prevent the ignition advance angle from exceeding the maximum value. Zunawaji, in step 125, the advance angle correction amount ΔSAI is the maximum correction amount b''CA
If the lead angle correction amount ΔSAI is larger than the maximum correction amount b′CA, it is fixed at the maximum correction amount b′CA in step 126, but the lead angle correction amount Δ
If SAI is less than the maximum correction amount b''CACA, step 126
is blown away.

In steps 131-136, steps 121-126
The ignition advance amount of the fourth cylinder is controlled in exactly the same manner.

Note that steps 131 to 136 are respectively steps 12
1 to 126, and the explanation thereof will be omitted.

In each step 121 to 126, and 131 to 136, each torque fluctuation amount ΔT□ of the first and fourth cylinders.

, to T, , 4 are made equal to each other, and the torque fluctuations are equalized.

In the step after step 136, the ignition timing is controlled so that the torque fluctuation amount Δ"I' r Z + ΔTri of the second and third cylinders becomes equal to each other, in exactly the same way as the case of the first and fourth cylinders. be done.

FIG. 5 shows the relationship between ignition timing and torque fluctuation in a lean air-fuel ratio region. The amount of torque fluctuation is based on the ignition timing.
M B T (n+inimum advance f
It increases on the retard side and decreases on the advance side compared to the best torque, but when the amount of advance increases to a certain extent, it increases rapidly. Therefore, in this embodiment, the ignition timing in the cylinder with large torque fluctuation is changed to the advanced side with respect to the average torque fluctuation of the cylinders in the same injection group, and the amount of advance is Predetermined limits are in place to prevent the situation from worsening.

On the other hand, the ignition timing in cylinders with small torque fluctuations is changed to the retarded side. This equalizes torque fluctuations in each cylinder of the same injection group.

FIG. 6 shows changes in torque fluctuation amount and NOx emissions with respect to ignition timing when the air-fuel ratio becomes rich and lean. The amount of torque fluctuation becomes smaller overall when the air-fuel ratio becomes rich, and conversely becomes larger overall when the air-fuel ratio becomes lean. As described above, in this embodiment, the ignition timing is changed to be retarded from the standard value in cylinders where the amount of torque fluctuation is small, and the ignition timing is changed to the side more advanced than the standard value in cylinders where the amount of torque fluctuation is large. As a result, the amount of torque fluctuation is equalized for each cylinder. The amount of NOx emissions decreases as the air-fuel ratio becomes leaner, and decreases as the ignition timing changes to the retarded side. In this embodiment, the ignition timing is changed to the retarded side in cylinders where the amount of torque fluctuation is small, thereby reducing NOx emissions, and the ignition timing is changed to the advanced side in the cylinders where the amount of torque fluctuation is large. NOx emissions are increased. As a result, the amount of NOx emissions is almost the same as when the air-fuel ratio is the standard size, but in order to equalize the amount of torque fluctuation in all cylinders, it is necessary to set the average air-fuel ratio of all cylinders on the leaner side. This makes it possible to reduce NOx emissions and improve fuel efficiency.

Note that in cylinders where the amount of torque fluctuation is relatively small, it is not necessarily necessary to retard the ignition timing, and it is also possible to maintain the current magnitude.

Further, the cylinders in which fuel is injected simultaneously are not limited to those having a stroke difference of 360° CA as in the above embodiment, and the present invention can also be applied to a system in which fuel is injected simultaneously in all cylinders, for example. .

〔Effect of the invention〕

As described above, according to the present invention, in a multi-cylinder internal combustion engine in which fuel is injected into two or more cylinders simultaneously, torque fluctuations in the cylinders become uniform, and the air-fuel ratio can be made leaner. , it becomes possible to reduce the amount of NOx emissions and improve fuel efficiency.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the invention, Figure 2 is a diagram showing a multi-cylinder internal combustion engine according to an embodiment of the invention, Figure 3 is a diagram explaining fuel injection timing, and Figure 4 is control of torque fluctuation. Routine chart 11. Figure 5 is a graph showing the relationship between ignition timing and torque fluctuation amount. Figure 6 is a graph showing the relationship between ignition timing, torque fluctuation amount, and NOx emissions using air-fuel ratio as a parameter. It is a graph. 22... Spark plug, 28... Fuel injection valve. Fig. 1 Fig. 2 22. ・Sobi hydrant 28 8 Fee・Prize υ cat Fig. 3

Claims (1)

[Scope of Claims] A fuel injection valve that simultaneously injects fuel into one or more cylinders, a spark plug provided for each cylinder, means for detecting the amount of output torque fluctuation in each cylinder, and Ignition timing control means advances the ignition timing of a spark plug provided in a cylinder with a large output torque fluctuation amount to equalize the output torque fluctuation amount of the cylinder, and the equalized output torque fluctuation amount becomes a set value. 1. A control device for a multi-cylinder internal combustion engine, comprising means for increasing and decreasing fuel.