JP2586565B2 - Output fluctuation detecting device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting an output torque difference between cylinders of an internal combustion engine.

[Conventional technology and issues]

Conventionally, for controlling the operation of the engine, a torque difference in each cylinder is detected. JP-A-59-5272
Patent Document 6 discloses a configuration for comparing a change in the number of revolutions of each cylinder during an explosion stroke as a method of detecting a torque difference between the cylinders.

However, in the conventional configuration, in the transient state in which the engine load changes, the change in the rotational speed based on the change in the load is not taken into account. If the engine returns to the steady state after a long period of time, the output torque difference between the cylinders increases, and the operating state of the engine temporarily becomes unstable.
There is a problem.

The present invention relates to an output fluctuation detecting device capable of detecting an output torque difference between cylinders with high accuracy even when the engine is in a transient state, improving the accuracy of engine operation control and stabilizing the engine operation state. The purpose is to provide.

Japanese Patent Application Laid-Open No. Sho 60-1356 discloses a configuration for correcting an output fluctuation error caused by a change in engine speed in a transient state based on a difference in engine speed change. It does not suggest a configuration in which the output fluctuation error is corrected using the amount of change in the average required time of the explosion stroke of all cylinders as in the present invention.

[Means for solving the problem]

Means A for determining the time required for the explosion stroke required for the crankshaft to rotate between the predetermined rotation angles during the explosion stroke of each cylinder, and the average value obtained by averaging the time required for the explosion stroke for a plurality of cylinders in a continuous explosion order Means B for calculating the amount of change in the average value, and calculating the amount of change in the average value based on the amount of change in the average value. A means C for correcting the time, a means D for calculating the output fluctuation equivalent value based on the corrected explosion stroke required time of each cylinder, and a difference between the cylinders of the output fluctuation equivalent value being smaller than a predetermined value. When it is large, it is characterized by comprising means E for judging that the output fluctuation between the cylinders is large and detecting the output fluctuation.

Here, the above-mentioned output fluctuation equivalent value represents a variation in the rotational speed of each cylinder during the explosion stroke, such as a ratio or a deviation between the explosion stroke required time of each cylinder and the average value of the required time. Value.

(Operation)

Based on the amount of change in the average required time of the explosion stroke of all cylinders, the difference in output torque due to the variation between cylinders excluding the effect of the change in engine load is determined.

〔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. Intake manifold 1
The throttle valve 1 is provided in the intake passage 14
A throttle sensor 16 is connected to a valve shaft of the throttle valve 15. The throttle sensor 16 outputs an ON signal when the throttle valve 15 is substantially fully closed. The distributor 17 is driven to rotate by a cam shaft (not shown), and supplies a high voltage to each of the ignition plugs 21, 22, 23, and 24. The reference position sensor 18 is connected 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).

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. Each sensor 16, 18, 19 is connected to an input port 44, and the fuel injection valves 31, 32, 33, 34 are connected to an output port 45.

FIG. 3 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., cylinders 3, 4, and 2 are in compression TDC, respectively. If the predetermined cylinder is not currently in the compression TDC, step 101
This routine is immediately terminated by the execution of, but 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 duration T180 _i in the explosion stroke is calculated on the basis of the output signal and the timer of the crank angle sensor 19. The required time T180 _i is proportional to the inverse of the output torque of the cylinder. In step 103 the cylinder counter i is incremented by 1, in step 104, whether the calculation of required time T180 _i in step 102 has been finished is determined for all the cylinders. If the execution of step 102 has been completed for all cylinders, the process proceeds to step 105, but if not completed, this routine is immediately terminated. In this embodiment, since the engine has four cylinders, it may be determined in step 104 whether 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. Then step 10
Prior to determining the ratio K _i between the average duration T180AV period 180 ° C. A required time T180 _i and all the cylinders of 180 ° C. A period of the cylinder at 9, at step 106 to 108, the load of the current engine , And the required time T180 _i of the 180 ° C. period of each cylinder is corrected by the change in the load.
The required time T180 _i that takes into account the change in the load is required.

Before explaining steps 106 to 108, referring to FIG.
Described above K _i = method of obtaining (T180 _i / T180AV) during transients.

In this figure, Nos. 1 and 3, each required time T180 _i at 180 ° C. A power stroke of the fourth and the second cylinder is a solid line S ₁ in the first cycle, a solid line S ₂ in the second cycle, third cycle in each changed as indicated by a solid line S _3. Average required time T180AV at 180 ° C for the explosion stroke of all cylinders
Changes as indicated by a solid line V _i for the first cycle, a solid line V ₂ for the second cycle, and a solid line V ₃ for the third cycle. That is, in this example, the second
The steady state continues until the cycle, but the time required for the explosion stroke from the third cycle is shortened, and the load, that is, the torque is increased.

Steady state, the ratio K _i is calculated by dividing the 180 ° C. A duration T180 _i of each cylinder at 180 ° C. A Average duration of all the cylinders T180AV, the magnitude of the ratio K _i of each cylinder, by a solid line L ₁ as shown, it becomes similar to the magnitude of 180 ° C. a duration T180 _i of each cylinder. In contrast, as with steady even during the transient, simply Dividing 180 ° C. A duration T180 _i of each cylinder at 180 ° C. A Average duration of all cylinders, the ratio K _i of each cylinder by the solid line L ₃ As shown, it shows the same tendency as the 180 ° C. required time T180 _i (solid line S ₃ ) of each cylinder, which decreases with time, and is affected by changes in load. Therefore, in this embodiment, the transient load is assumed to change linearly in each cycle, as indicated by the following equation, the time required T180 _i of each cylinder to the average time required T180AV those prorated in each cycle Correct for

That is, the first cylinder is the actually measured required time T1
Average time T180A in previous cycle for 80 _i
What is necessary is just to reduce by 3/8 of the difference between V _j-1 and the average required time T180AV _j in the current cycle. T180 ₁ ← T180 ₁ −3 / 8 × (T180AV _j−1 −T180AV _j ) (1) ), The effect of the load change is corrected. Similarly, the required times T180 _i of the third, fourth, and second cylinders are respectively T180 ₃ ← T180 ₃ −1 / 8 × (T180AV _j−1 −T180AV _j ) …… (2) T180 ₄ ← T180 ₄ −1 / 8 × (T180AV _j-1 −T180AV _j ) …… (3) T180 ₂ ← T180 ₂ −3 / 8 × (T180AV _j-1 −T180AV _j ) The correction for the effect of the load change is performed by (4). As a result, the ratio K _i of each cylinder will denote the similar tendency to the ratio K _i during steady-state as indicated by the dashed line B _3, the influence of load changes have been removed.

In step 106 to 108, such modifications are made to the time required T180 _i of each cylinder. First, in step 106, the average required time of all cylinders in the previous cycle (T180AV
A difference DLT180 between O) and the average required time T180AV of all cylinders in the current cycle obtained in step 105 is obtained. In step 107, using the difference DLT180, (1) to (4) as well as modifying the effect of load change relative duration T180 _i of each cylinder is performed. Step 108
Then, the current average required time T180AV is replaced with the average required time T180AVO for execution of step 106 in the next cycle. Next, in step 109, for each cylinder, the time required for the 180 ° C. A period of that cylinder and the 180 ° C.
The ratio K _i between duration of period A is determined. That this ratio K _i indicates the difference between the average value of the torque of the torque and all the cylinders of the cylinder.

In step 110, 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 otherwise, it is determined that fuel cut is not being performed, and then step 111 and subsequent steps are executed.

In step 121, the integrated value SKFC _i is determined is the ratio K _i is accumulated for each cylinder, also the cycle counter J _f 1
Is only incremented. That is, the integrated value SKFC _i is
During fuel cut, it is obtained by integrating the ratio K _i between the average power stroke duration power stroke duration and all the cylinders of each cylinder. Magnitude relationship between the integrated value SKFC _i of each cylinder during a fuel cut, because each cylinder is not in the combustion state, means an error of the angle detection of the crank angle sensor.

At step 122 the cycle counter J _f whether reached 50, that is, in step 121 the ratio K _i is determined whether been accumulated 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, the routine here ends, and thereafter, the ratios _Ki (step 109) are again obtained for all the cylinders. In step 122, the cycle counter _Jf becomes 5
If it is 0, in step 123, the integrated value SKFC
i is replaced by the accumulated value SKFi, integrated value SKFCi and cycle counter J _f is cleared to zero.

In step 111, the ratio K _i of each cylinder during fuel supply
There cumulative value SK _i is accumulated is determined and also the cycle counter J is incremented by 1. Integrated value of each cylinder
The magnitude relationship of SK _i corresponds to the difference in the output torque of each cylinder. Before the counter J reaches 50, the process proceeds from step 112 to step 117, where the cylinder counter i is set to 1 and this routine ends. If the counter J has reached 50, step 113 is executed. That is, for the two cylinders whose explosion strokes are continuous, the integrated value SK _i ,
The difference between SK _{i-1 and} the difference between the integrated values SKF _i and SKF _i-1 during the fuel cut are obtained, and the difference (SK _i −SK _i−1 ) and the difference (SKF _i −SKF _{i−1) are obtained.} ) calculates the change amount DSK _i with. This change amount DSK _i indicates the amount of torque drop in the cylinder.

This variation DSK _i is judged whether or not the determination value or more in step 114. If the change amount DSK _i is equal to or greater than the judgment value,
In step 115, the fuel injection correction coefficient KTAU _i is increased by β, and if the change amount DSK _i is smaller than the determination value, step
115 the fuel injection correction coefficient KTAU _i currently not performed 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 is obtained by TAU _i by TAU _i = FAF × KTAU _i × α _i × TP, where FAF is a feedback coefficient,
α _i is a correction coefficient, and TP is a basic injection amount.

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

Thus, in the present embodiment, first, at the time of a load change transition, the required 180 ° C. A required time T180 _{i of} each cylinder, in which the influence of the load change is removed, is obtained. Then then one cycle (7
20 ° C. A) each ratio K _i between the average 180 ° C. A period of 180 ° C. A period and all the cylinders of the explosion stroke of each cylinder is determined, the integrated value of 50 cycles in the fuel supply or the fuel cut is SK _i ,
SKF _i is required. This integrated value is updated every 50 cycles. Next, the difference (SK _i −SK _i−1 ) between the integrated values SK _i and SK _i−1 and the integrated values SKF _i and SKF for the two cylinders in which the explosion stroke is continuous
_i-1 of the difference (SKF _i -SKF _i-1) and is calculated, as long as these differences variation DSK _i determination value or more, the cylinder counter i
Is determined to be too small, the fuel injection amount is increased.

As described above, the magnitude relation of the integration value SKF _i of each cylinder during a fuel cut, because each cylinder is not in the combustion state, means an error of the angle detection of the crank angle sensor. Therefore, when the torque generated by the explosion stroke is uniform in each cylinder, the magnitude relation of the integration value SK _i of each cylinder in the fuel supply is substantially the same as the magnitude of the integrated value SKF _i of each cylinder during the fuel cut become.

FIGS. 5A to 5E show the case where the air-fuel ratio of the air-fuel mixture in each cylinder is made uniform and the case where the air-fuel ratio of the air-fuel mixture in one cylinder is made larger than that of the other cylinders. The integrated value SK _{i of} each cylinder is the integrated value S at the time of fuel cut.
It is the result of the examination of whether or not there in any relationship to the KF _i. As shown in FIG. 5 (a), the air-fuel ratio of each cylinder
When the A / F (solid line A), that is, the output torque is substantially uniform, the integrated value SK _i (solid line S) at the time of fuel supply and the integrated value SKF _i (dashed line C) at the time of fuel cut substantially coincide with each other. Therefore, the change amount DSK _i (solid line D) takes a constant value in each cylinder. On the other hand, when the air-fuel ratio of one cylinder, for example, the second cylinder is increased, that is, the output torque is reduced, as shown in FIG. 5 (b), the integrated value SK _i (solid line S) at the time of fuel supply is obtained. It differs from the integrated value SKF _i (dashed line C) at the time of fuel cut in each cylinder. That is, the integrated value SK _i of the second cylinder becomes larger than the integrated value SKF _i , and the integrated values SK _i and SKF _i of the other cylinders change. As a result, only the change amount DSK _i of the second cylinder Is the amount of change in other cylinders DSK _i
Is clearly larger than that. Similarly, 1st, 3rd, 4th
When the air-fuel ratio of the cylinder No. is increased, the change amount DSK _{i of the} cylinder increases as shown in FIGS. 5 (c), (d) and (e), respectively. Then, FIGS. 5 (a) to 5 (e)
Accordingly, the cylinder variation DSK _i is greater than a predetermined judgment value so small that the output torque, thus if caused to increase the amount of fuel injection that the output torque of each cylinder is uniform is familiar with this cylinder.

As described above, in the present embodiment, the pulse signal for each 720 ° C.
From the pulse signal at every 30 ° C. obtained by the above and the throttle fully closed signal of the throttle sensor 16, the time required for the explosion stroke of each cylinder at the time of fuel supply and fuel cut is obtained.
It detects the output torque difference between the cylinders. Therefore, the configuration of a normal engine can be applied as it is, and it is not necessary to add a sensor or the like. Further, since the angle detection error of the crank angle sensor is removed by calculating the explosion stroke required time at the time of fuel cut, the output torque difference between the cylinders is detected with high accuracy irrespective of engine-specific variations. be able to. Furthermore, in the present embodiment, when the load changes, the effect of the load change is removed from the time required for the explosion stroke of each cylinder. Can be obtained exactly.

As described above, according to the present embodiment, since the detection accuracy of the output torque difference between the cylinders is improved, the air-fuel ratio of each cylinder can be made uniform with high accuracy. As a result, the idling operation can be further stabilized, and the idling speed can be reduced to improve fuel efficiency. In addition, in the case of the lean burn control system, the output torque difference between the cylinders is reduced, so that the torque fluctuation of the entire engine is reduced, and the air-fuel ratio can be further made lean, thereby improving the fuel efficiency. emissions of the NO _X can be reduced. Furthermore, when the fuel injection amount of each cylinder is independently controlled in the stoichiometric control system, since the air-fuel ratio of each cylinder is made uniform, it is possible to improve the purification rate of the three-way catalyst, and further reduce exhaust emissions. Can be improved.

In order to adjust the output torque of each cylinder, 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〕

As described above, according to the present invention, even if the engine is in a transient state, the output torque difference between the cylinders is detected with high accuracy, and the accuracy of engine operation control can be improved.

[Brief description of the drawings]

FIG. 1 is a block 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 flowchart of an output fluctuation detection routine, and FIG. graph showing the ratio K _i of FIG. 5 (a) ~ (e) the air ratio a / F of each cylinder, the integrated value S
K _i, is a diagram showing an SKF _i and variation DSK _i. 16 ... Throttle sensor, 18 ... Reference position sensor, 19 ... Crank angle sensor.

Claims (1)

(57) [Claims] An output fluctuation detecting device for detecting an output fluctuation due to a variation between cylinders of a multi-cylinder internal combustion engine, wherein a crankshaft is predetermined in an explosion stroke of each cylinder by detecting an engine crankshaft rotation angle. Explosion stroke time detection means for detecting the explosion stroke time required to rotate the rotation angle section, and the explosion stroke time detected by the explosion stroke time detection means is averaged for each of a plurality of cylinders in a continuous explosion order. An explosion stroke required time average value change amount calculating means for calculating the average value, and calculating the amount of change in the average value; and based on the amount of change in the average value, when the average value is determined to decrease, the order of the explosion is determined. Correction means for correcting the required explosion stroke time of each cylinder with a correction amount that increases as the vehicle advances, and output variation based on the required explosion stroke time of each cylinder corrected by the correction means. Output fluctuation equivalent value calculating means for calculating the dynamic equivalent value, and when the difference between the respective cylinders of the output fluctuation equivalent value calculated by the output fluctuation equivalent value calculating means is larger than a predetermined value,
An output fluctuation detecting device comprising: an inter-cylinder output fluctuation detecting means for determining that output fluctuation between cylinders is large.