JP2679468B2 - Misfire detection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire detecting device for detecting a misfire occurring in each cylinder in an internal combustion engine mounted on a vehicle or the like.

[0002]

2. Description of the Related Art Conventionally, when a misfire occurs in a multi-cylinder internal combustion engine, not only the engine torque fluctuates but unburned fuel is discharged from the misfired cylinder as it is or leaks around the internal combustion engine. It may happen. Therefore, various techniques for detecting occurrence of a misfire and notifying a driver of the misfire have been proposed to cope with a misfire abnormality of the internal combustion engine at an early stage.

For example, in Japanese Unexamined Patent Publication No. 61-258955, the rotational fluctuation of the internal combustion engine is detected in synchronization with the explosion stroke of each cylinder, and if the change in the rotational fluctuation is large, it is determined that a misfire has occurred. Was notified to the driver.

[0004]

However, during the control of the internal combustion engine, there are various controls that intentionally reduce the engine torque. For example, an ECT shift torque control delay for reducing a shift shock of a transmission, a traction control delay for smoothly starting a vehicle on a snowy road, and an auto for smoothing a constant speed running. There are retard correction during drive control, fuel cut control in deceleration state, reduction correction at fuel cut recovery, deceleration increase correction, or reduced cylinder operation, and these controls include control that intentionally changes the engine torque. Has been done.

[0005] For example, in the reduced cylinder operation control, in the operating cylinder next to the reduced cylinder, the influence of the previous reduced cylinder is dragged and the engine speed decreases, so that even if the combustion is normally performed. The rotation fluctuation becomes large. As a result, the technique described in the above publication has a problem that if the rotation fluctuation is large, misfire is determined and an erroneous determination is made.

Therefore, when the engine speed in the first cylinder explosion after the completion of the various control commands as described above is lowered, the driver is informed of the misfire many times, and the correct judgment of the misfire is made. It could not be distinguished from erroneous judgment, and there was a risk that the reliability of misfire notification would be reduced.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to prevent misjudgment of misfire during intentional engine torque fluctuation and to prevent the influence of control for torque fluctuation. An object of the present invention is to provide a misfire detection device for an internal combustion engine, which can properly detect an abnormal cylinder while eliminating it.

[0008]

In order to achieve the above object, in the present invention, as shown in FIG. 1, a rotation detecting means M2 for detecting the rotation of an internal combustion engine M1 and a detection of the rotation detecting means M2. Based on the result, the rotation variation indexing means M3 for determining the rotation variation for each explosion stroke of each cylinder of the internal combustion engine M1 and each cylinder when the indexation result of the rotation variation indexing means M3 exceeds a predetermined determination value. A misfire detection device including a misfire determination means M4 for determining a misfire in an explosion stroke, and a rotation fluctuation command means M5 for commanding an intentional rotation fluctuation of the internal combustion engine according to an operating state of the internal combustion engine. the rotational fluctuation indexing means M3 is rotary converter
Rotational speed in the cylinder explosion immediately before the command of the dynamic command means is executed
And the rotational speed in the first cylinder explosion after the end of the command, the rotational fluctuation after the end of the command is calculated, and the misfire determination means M4
Determines values and compared with set rotational fluctuation after finger Ordinance ends higher than normal determination value, and performs the misfire determination.

[0009]

According to the above construction, as shown in FIG. 1, the rotation detecting means M2 detects the rotation of the internal combustion engine M1 during operation, and the rotation variation indexing means M3 detects the rotation based on the detection result. Determine the rotation fluctuation for each. Further, when the rotation fluctuation indexing result exceeds a predetermined value, the misfire determination means M4
Is judged as misfire in each cylinder explosion stroke. By rotation variation command means M5, when a deliberate rotation change command of the internal combustion engine M1 is performed according to the operating state of the internal combustion engine M1, the rotational fluctuation indexing means M3, the times
In a cylinder explosion immediately before execution of the command of the rolling change command means M5
The rotation fluctuation after completion of the command is calculated from the rotation speed and the rotation speed in the first cylinder explosion after the completion of the command. Further, the misfire determining means M4 determines values and compared with set rotational fluctuation after finger Ordinance ends higher than normal determination value, performs a misfire determination.

Accordingly, in the cylinder next to the cylinder corresponding to the control for intentional torque fluctuation, even if the rotational speed of the internal combustion engine decreases and the post-command rotational fluctuation fluctuates significantly due to the influence of the torque fluctuation, Misfire is determined according to the fluctuation. As a result, it is possible to properly detect the misfiring cylinder while eliminating the influence of the control due to the torque fluctuation, thereby preventing the misdetection of the abnormal cylinder and improving the accuracy of the misfire determination.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the misfire detection device for an internal combustion engine according to the present invention will be described in detail below with reference to FIGS.

FIG. 2 is a schematic configuration diagram showing a gasoline engine system to which the misfire detection device in this embodiment is applied. Engine 1 as an internal combustion engine mounted on a car
Has an intake passage 2 forming an intake system and an exhaust passage 3 forming an exhaust system. An air cleaner 4 is provided at an inlet of the intake passage 2. A surge tank 5 is provided in the middle of the intake passage 2. This surge tank 5
Downstream of each cylinder of the engine 1 (four cylinders in this embodiment).
Injectors 6A, 6 for injecting fuel for each cylinder)
B, 6C and 6D are provided respectively. On the other hand, a catalytic converter 7 having a built-in three-way catalyst for purifying exhaust gas is provided on the outlet side of the exhaust passage 3.

Then, the engine 1 takes in outside air from the air cleaner 4 through the intake passage 2. At the same time as taking in the outside air, the engine 1 is connected to each of the injectors 6A to 6A.
The fuel injected and supplied from D is taken in. Also, Engine 1
After exploding and burning the mixture of the taken fuel and the outside air in each combustion chamber to obtain a driving force, the exhaust gas is discharged from the exhaust passage 3 to the outside via the catalytic converter 7.

On the upstream side of the surge tank 5, there is provided a throttle valve 8 which opens and closes in conjunction with the operation of an accelerator pedal (not shown). When the throttle valve 8 is opened and closed, the amount of intake air in the intake passage 2 is adjusted.

A throttle opening sensor 21 for detecting the throttle opening TA is provided near the throttle valve 8. A well-known movable vane type air flow meter 22 for measuring the amount of intake air passing through the intake passage 2 is provided on the downstream side of the air cleaner 4.

An oxygen sensor 23 for detecting the oxygen concentration in the exhaust gas, that is, for detecting the exhaust air-fuel ratio is provided in the middle of the exhaust passage 3 for feedback control of the air-fuel ratio of the engine 1. Further, the engine 1 is provided with a water temperature sensor 24 for detecting a temperature (cooling water temperature) THW of the cooling water.

The ignition signal distributed by the distributor 10 is applied to the ignition plugs 9A, 9B, 9C and 9D provided for each cylinder of the engine 1. The distributor 10 synchronizes the high voltage output from the igniter 11 with the crank angle of the engine 1 to each of the ignition plugs 9A to 9A.
It is for distribution to 9D. The ignition timing of each of the ignition plugs 9A to 9D is determined by the high voltage output timing from the igniter 11.

The distributor 10 incorporates a rotor (not shown) that rotates in association with the rotation of the engine 1. The distributor 10 receives the rotation speed of the engine 1 (engine rotation speed) N from the rotation of the rotor.
A rotation speed sensor 25 is provided as rotation detection means for detecting E. Similarly, for the distributor 10,
A cylinder discrimination sensor 26 is provided which detects a change in the crank angle CA of the engine 1 at a predetermined rate according to the rotation of the rotor. In this embodiment, the engine 1 is used for one stroke.
, The cylinder discrimination sensor 26
The crank angle is detected at the rate of ° CA. An automatic transmission (not shown) that is drivingly connected to the engine 1 is provided with a vehicle speed sensor 27 for detecting a vehicle speed SP.

Further, in this embodiment, the instrument panel of the driver's seat is provided with a misfire indicator lamp 12 for informing the driver of the occurrence of misfire. Then, the injectors 6A to 6D, the igniter 11 and the misfire indicator lamp 12 are provided.
Is electrically connected to an engine electronic control unit (hereinafter simply referred to as “engine ECU”) 30 that constitutes a rotation fluctuation indexing unit, a misfire determination unit, and a rotation fluctuation command unit, and drives them by the operation of the engine ECU 30. Timing is controlled.

As described above, the engine ECU 30 is a control device that mainly controls the fuel injection control and ignition timing control of the engine 1, and also constitutes a misfire detection device that determines and detects misfire in each cylinder explosion stroke. There is. In addition to this, in this embodiment, as shown in FIG. 2, an electric controlled transmission (ECT) ECU 4
1, a traction control (TRC) ECU 42 and an auto drive ECU 43 are provided respectively.

In order to reduce the shift shock of the automatic transmission (not shown), the ECT ECU 41 controls the direct connection clutch control and shift control of the automatic transmission by the torque control delay angle during ECT shift, and intentionally changes the torque of the engine 1. Let Therefore, the ECT ECU 41 inputs a shift position signal indicating the shift position of the automatic transmission. Also, EC
The TECU 41 exchanges signals with the engine ECU 30, and inputs the detection values of the air flow meter 22 and the sensors 21, 23 to 27 from the engine ECU 30 as data signals. Then, the ECT ECU 41 determines a shift pattern according to the shift condition at each time based on various input signals, and outputs a shift control signal for suitably controlling the actuator of the automatic transmission according to the shift pattern.

The TRCECU 42 intends the torque of the engine 1 by retarding the traction control and the like in order to suppress the wheel spin due to an excessive driving force and secure the directional stability and the driving force of the vehicle at the time of starting acceleration on a snowy road. Fluctuate. Therefore, the TRCECU 42 is connected to the engine ECU 3
Signals to and from the engine ECU 30
From the air flow meter 22 and each sensor 21, 23-2
The detected value of 7 or the like is input as a data signal. And T
The RC ECU 42 determines a target torque amount according to the acceleration state at each time based on various input signals, and a traction communication signal for causing the engine 1 to perform fuel cut or the like so as to perform torque control according to the target torque amount. Is output to the engine ECU 30.

The automatic drive ECU 43 controls the opening of the throttle valve 8 by correcting the retard angle during the automatic drive control so that the torque of the engine 1 is controlled in order to smoothly drive the vehicle at a constant speed for a long time on a highway or the like. Fluctuate. Therefore, the auto drive ECU 43 operates from a set switch (not shown) operated by the driver,
Input a set signal to instruct auto drive.
Further, the auto drive ECU 43 exchanges signals with the engine ECU 30, and inputs the detection values of the throttle opening sensor 21 and the vehicle speed sensor 27 from the engine ECU 30 as data signals. Then, the auto-drive ECU 43 outputs an opening degree control signal to an actuator (not shown) that is driven to control the opening degree of the throttle valve 8 so that the vehicle travels at a speed specified by the driver based on various input signals. To do.

In this embodiment, the ECT ECU described above is used.
41, TRCECU 42 and auto drive ECU 43
Constitutes a rotation fluctuation command means for commanding an intentional rotation fluctuation of the engine 1 in accordance with the operating state of the engine 1.

FIG. 3 is a block diagram illustrating the structure of the engine ECU 30. The engine ECU 30 includes a central processing unit (CPU) 31, a read-only memory (ROM) 32 in which a predetermined control program and the like are stored in advance, and a random access memory (R) for temporarily storing the calculation results of the CPU 31 and the like.
AM) 33, a backup RAM 34 for storing data stored in advance, and the like, and a logical operation circuit in which these components are connected to an external input circuit 35 and an external output circuit 36 by a bus 37. And the CPU 31
Represents the air flow meter 22 and the sensors 21, 23 to 27
Is read as an input value through the external input circuit 35. The CPU 31 also controls the injectors 6A to 6A through the external output circuit 36 based on these input values.
D, the igniter 11 and the misfire indicator lamp 12 are suitably controlled. Further, the engine ECU 30 receives the ECT ECU 4 through the external input circuit 35 and the external output circuit 36.
1, the TRCECU 42 and the auto-drive ECU 43, and the air flow meter 22 and the sensors 21 and 23.
Data signals such as detection values of 27 to 27 and calculation results are exchanged.

Next, the processing operation for detecting the occurrence of an abnormal cylinder due to a misfire in the misfire detecting device for an internal combustion engine configured as described above will be described with reference to the flow charts of FIGS.

FIGS. 4 to 6 show an abnormal cylinder detection processing routine executed by the engine ECU 30, which is executed by a regular interruption every predetermined time. When the processing shifts to this routine, first, at step 300, the intake air amount Q is calculated from the detection values of the air flow meter 22 and the rotation speed sensor 25.
And engine speed NE etc. are read and ECTE
CU41, TRCECU42 and auto drive ECU
Data signals such as those control signals are read from 43.

Next, in the series of determination processing from step 311 to step 318, whether or not the abnormal cylinder due to misfire is detected based on the previously read data signal and the like,
That is, it is determined whether to enable or disable the misfire determination.

That is, in step 311, ECT
Based on the data signal from the ECU 41, it is determined whether or not the ECT torque control command is being executed. Where EC
When the T torque control is not being performed, it is determined at step 312 based on the data signal from the auto drive ECU 43 whether or not the command for the auto drive torque control is being executed. If the automatic drive torque control is not being performed, then in step 313, TRCECU
Based on the data signal from 42, it is determined whether or not the TRC torque control command is being executed. If the TRC torque control is not in progress, in step 314, the engine 1
It is determined whether or not the deceleration amount is increasing to cause the intentional torque fluctuation.

If the deceleration amount is not increasing, it is determined in step 315 whether or not the fuel cut return reducing amount for similarly intentionally changing the torque is in progress, that is, the fuel injection is returned after the fuel cut. Therefore, it is determined whether or not the moderation process of the injection amount control is performed. Then, when the fuel cut return reduction amount is not in progress, it is determined in step 316 whether or not the cylinder is the stopped cylinder by the reduced cylinder operation control for causing the intentional torque fluctuation. The reduced-cylinder operation control is to reduce the number of operating cylinders by stopping fuel injection in some cylinders when the engine 1 has a light load, so that the operating load is increased in the operating cylinder even if the engine 1 as a whole has a light load. This is the control for improving the combustion state in the cylinder.

Here, if the cylinder is not the stopped cylinder by the cut-off cylinder operation control, it is determined in step 317 whether or not the fuel cut for intentional torque fluctuation is being performed. Then, when the fuel cut is not being performed, it is determined in step 318 whether or not two control cycles have elapsed after the fuel cut is returned.

Here, if only two control cycles have elapsed after the return of the fuel cut, the process proceeds to step 330. That is, when the determination at step 318 described above is affirmative, the steps 311 to 317 before that are executed.
Since the series of determinations in No. are all negative, and control for intentional torque fluctuation of the engine 1 is not performed, it is determined that abnormal cylinder detection is performed, that is, misfire determination is performed, and the process proceeds to step 330.

On the other hand, the above-mentioned steps 311 to 317
If each of the determinations in step 1 is affirmative or the determination in step 318 is negative, various cylinder control for intentional torque fluctuation of the engine 1 is performed, so abnormal cylinder detection is not performed. As a result, that is, the misfire determination is invalidated, the process proceeds to step 320.

Then, in step 320, the intake air amount Q of this time is similarly divided by the engine speed NE of this time, and the result is set as the load value L. Further, in step 325, the function f3 (L) having the previously set load value L as a parameter is obtained by referring to a predetermined map (not shown), and the value of the function f3 (L) is corrected by the correction value α ( It is set as 0 <α <1), and the subsequent processing is temporarily terminated.

In step 330 after the step 318, whether or not the elapsed time CD from the start of the process of detecting the abnormal cylinder due to the misfire is "0",
That is, it is determined whether or not it is immediately after the start of the detection process.

Here, if it is not immediately after the start of the detection process, the process directly proceeds to step 350. If the detection process has just started, in step 340,
After resetting the cylinder number n indicating the number of the cylinder to "0", the process proceeds to step 350. The value of the cylinder number n is a number assigned to each cylinder in the order of reaching the explosion stroke, and is not the actual cylinder number. The cylinder number n takes a value of "1 to 4" because the engine 1 has four cylinders.

In step 350, it is determined whether or not the count value Ccrnk representing the rotation timing of the crankshaft of the engine 1 is "3, 9". This count value C
As shown in the flowchart of FIG. 7, crnk is a value set by the “30 ° CA interrupt routine” executed by the engine ECU 30. That is, step 152
In the above, the count value Ccrnk is incremented by "1" every time the crankshaft rotates 30 °. In step 154, it is determined whether the count value Ccrnk has been counted up to "12". Then, when the count value Ccrnk is not counted up to "12", the processing is temporarily terminated as it is. On the other hand, when the count value Ccrnk is counted up to “12” in step 154, the count value Ccrnk is counted in step 156.
Is reset to "0", and the subsequent processing is temporarily terminated.

The condition that the count value Ccrnk is "3, 9" is that the crank angle is "90 ° CA, 270 ° CA, 450".
° CA, 630 ° CA ”for each crank angle. That is, the judgment becomes affirmative at the timing of the middle of the explosion stroke of each cylinder.

Returning again to the processing routines of FIGS.
In step 350, the count value Ccrnk is "3.
If it is not “9”, the process directly proceeds to step 460. On the other hand, in step 350, the count value Ccrnk
If the value is "3, 9", first, in step 360, the cylinder number n is incremented by "1". Next, in step 370, it is determined whether or not the cylinder number is "5", and if the value is not "5", the process directly proceeds to step 390.

In step 370, the cylinder number n
Is “5”, the cylinder number n is set to “1” in step 380, and the process proceeds to step 390. That is, in the processing of steps 360 to 380, the cylinder number n is incremented by "1" within the range of "1 to 4".

Then, after shifting from steps 370 and 380, in step 390, the engine speed NE at this time is set to the engine speed NEn of the cylinder of the cylinder number n,
The rotation speed NEn and the rotation speed NE in the previous cylinder number
A rotational fluctuation amount ΔNE which is a difference from B is obtained.

Next, at step 400, the function f1 (L) having the previously set load value L as a parameter is obtained by referring to a predetermined map (not shown), and the value of the function f1 (L) is obtained. Set as the reference value X. Similarly, a function f2 (L) having the load value L as a parameter is obtained by referring to a predetermined map (not shown), and the function f2 (L) is obtained.
The value of 2 (L) is set as the reference value Y.

Thereafter, in step 410, the magnitude of the rotation fluctuation amount ΔNE is determined. This rotation fluctuation amount ΔNE
Becomes smaller when there is no abnormal cylinder due to misfire. When the engine misfires for some reason, the rotational speed NEn of the misfiring cylinder decreases and the rotational fluctuation amount ΔNE, which is the difference from the rotational speed NEB of the preceding cylinder, increases.

Therefore, in step 410, when the rotation fluctuation amount ΔNE is larger than the value obtained by adding the correction value α to the predetermined reference value X, it is determined in step 420 that the rotation speed NEn in the cylinder is abnormal. The number of abnormal rotations in the cylinder of cylinder number n, CDINJn, is set to A
Just increase. Furthermore, the rotational speed NE of the cylinder this time
A value obtained by adding the reference value X and the correction value α to n is updated as the rotation speed NEB in the previous cylinder in the process in the next cylinder.

On the other hand, when the rotation fluctuation amount ΔNE is smaller than the predetermined reference value Y in step 410, it is determined in step 430 that the rotation speed NEn of the cylinder is normal, and the number of abnormal rotations CDINJn is equal to the value B. Reduce. Further, the rotational speed NEn of the current cylinder is directly changed to the rotational speed NE of the previous cylinder in the process of the next cylinder.
Update as B.

If the rotation fluctuation amount ΔNE exceeds the value Y and is less than the reference value X plus the correction value α in step 410, the number of abnormal rotations CDINJn is increased or decreased in step 440. Instead, the rotational speed NEn of the current cylinder is updated as it is to the rotational speed NEB of the previous cylinder in the process of the next cylinder. In this way, the number of abnormal rotations CDIN
Jn is increased correctly.

Incidentally, the steps 420 and 43.
0 or in step 440, NEB is updated
However, each judgment in each of the above steps 311 to 317
Is affirmative, or the determination in step 318 is
If the result is negative and the process proceeds to step 320, the
This is the case when the fire check is disabled and therefore NEB
Will not be updated as a new rotation speed of. Obedience
The NEB will continue until the misfire determination is restarted (returned).
, The misfire determination is invalidated (the misfire determination is not performed)
The value updated immediately before will be retained. this
Therefore, the fingers for various controls for intentional torque fluctuations
Immediately after the decree ends, if the misfire determination is restarted,
In 390, the above misfire determination is invalidated.
Value updated immediately before (no misfire determination is performed)
And the rotational fluctuation that is the difference between the engine speed NEn of this time
The amount ΔNE will be obtained . Misfire determination, as above
Immediately before is invalidated (misfire determination is not performed)
NEB, which is the updated value, is the rotation variation implementation of the present invention.
Equivalent to the number of revolutions in the cylinder explosion immediately before the command of the example means,
The engine speed NEn of this time is the same as that of the present invention.
Corresponding to the number of revolutions in the first cylinder explosion after the end of the command
You. When the process proceeds to step 450 through step 420, step 430 or step 440, the correction value α is reset to “0” in step 450. Here, the correction value α is set by the function f3 (L) in step 325 only when the current cylinder corresponds to the control for intentional torque fluctuation. Therefore, if the cylinder this time supports control for intentional torque fluctuations , and the next control cycle
When entering, do not enter control for intentional torque fluctuation.
If the rotation fluctuation amount ΔNE is larger than the value obtained by adding the predetermined correction value α to the reference value X in step 410, the process proceeds to step 420.

Then, at step 420, the rotational speed NE
The correction value α is further added to the reference value X to be added to n. Alternatively, the rotation fluctuation amount ΔNE exceeds the reference value Y,
If it is less than the value obtained by adding the correction value α to the reference value X, the process proceeds to step 440. Then, the correction value α
Is reset to "0" in step 450, the correction value α is "0" until it is determined in the subsequent control cycle that control for torque fluctuation is being performed in another cylinder next time. Will remain. That is, the correction value α is set to a predetermined value as the function f3 (L) only when it corresponds to the control for the intentional torque fluctuation, and the next value of the cylinder corresponding to the control for the torque fluctuation is set. In step 410, the reference value X to be compared with the rotation fluctuation amount ΔNE is added to the correction value α and is set to a large value only for the cylinders No. Further, the correction value α becomes “0” for the second and subsequent cylinders counted from the cylinders corresponding to the control for torque fluctuation, and in step 410, the reference value X to be compared with the rotation fluctuation amount ΔNE is the correction value. It is not added by α.

Then, step 350 or step 4
After shifting from 50, in step 460, it is determined whether or not "1 second" has elapsed from the start of the processing of this routine. Here, if "1 second" has not elapsed, the process directly proceeds to step 480. On the other hand, if “1 second” has elapsed, then in step 470 the elapsed time C
Increment D by "1" and then step 480
Move to.

In step 480, the elapsed time CD
Is greater than or equal to a predetermined value L (“25 seconds” in this embodiment). Here, when the elapsed time CD is not equal to or greater than the predetermined value L, it is determined that the data that can be used to determine the abnormality of each cylinder has not been collected, and the subsequent processing is temporarily terminated.

In step 480, the elapsed time C
When D is equal to or greater than the predetermined value L, it is determined in step 490 whether the number of abnormal rotations CDINJn in the cylinder number n is equal to or greater than the predetermined value M ("100 times" in this embodiment). Then, the number of times CDINJn is a predetermined value M
In the above case, it is determined that there is abnormal rotation in the cylinder of cylinder number n, that is, misfire is determined, and step 50
At 0, a process of outputting a misfire determination signal and turning on the misfire display lamp 12 in the driver's seat is performed. At the same time, the misfire determination signal is stored in the backup RAM 34 as diagnosis data.

Then, in step 510, the injectors 6A to 6D corresponding to the current cylinder are stopped, and the fuel injection in that cylinder is stopped thereafter. In step 520, the control for intentional torque fluctuation is stopped.

Further, in step 530, each variable used for detecting the abnormal cylinder, that is, the elapsed time CD due to the counting of the counter, the number of abnormal rotations CDIN in the cylinder number n,
A process of resetting Jn to "0" is performed. Then, the subsequent processing is temporarily terminated.

On the other hand, in step 490, the number of times CD
If INJn is not equal to or more than the predetermined value M, the number of times CD
Since the number of times before INJn can be determined to be abnormal has not been reached, it is determined to be normal and the process proceeds to step 530. Then, in the same step 530, each variable used for detecting the abnormal cylinder, that is, the elapsed time CD measured by the counter, the number of times of abnormal rotation CDI in the cylinder number n
A process of resetting NJn to "0" is performed.
Then, the subsequent processing is temporarily terminated.

As described above, according to the misfire detecting device for the internal combustion engine in this embodiment, steps 311 to 31 are executed prior to the abnormal cylinder detection, that is, the misfire determination.
In 8, it is determined whether or not to invalidate the misfire determination depending on whether or not the control for intentional torque fluctuation of the engine 1 is performed. And the ECT ECU 41,
The misfire determination is invalidated when the TRCECU 42, the automatic drive ECU 43, or the engine ECU 30 performs various controls for intentional torque fluctuation of the engine 1. That is, the misfire determination is not performed.

Therefore, while various controls for intentional torque fluctuation of the engine 1 are being performed, it is determined that each cylinder is abnormal due to misfire even if the engine 1 fluctuates in rotation. It is possible to prevent the misjudgment of misfire in advance. Therefore, the misfire indication lamp 12 is prevented from being turned on by the misjudgment of misfire, and the driver is not notified of the result of the misjudgment. At the same time, the result of the erroneous determination is prevented from being stored in the backup RAM 34 as the diagnosis data. As a result, the reliability of misfire notification by the misfire indicator lamp 12 or diagnosis can be enhanced, and in the event of a misfire abnormality, reliable misfire determination information can be given to a driver or the like to prompt early measures for misfire.

Further, in this embodiment, the rotational fluctuation amount ΔNE, which is the difference between the rotational speed NEn of the cylinder concerned in the present control cycle and the rotational speed NEB of the previous operating cylinder, is corrected to a predetermined reference value X. When the value becomes larger than the value α added, the rotational speed NEB in the previous operating cylinder in the next control cycle is added by the correction value α added to the reference value X from the engine rotational speed NEn in the cylinder. I am trying to set a large value. Therefore, even if there is an abnormality due to misfire in any of the cylinders, and even if accidental misfire, that is, irregular misfire occurs in the cylinder that reaches the explosion stroke immediately before that cylinder, the abnormal state continues. The cylinder in which it is occurring can be correctly determined to be abnormal. In such an irregular misfire, when a failure occurs due to foreign matter being caught in any of the injectors 6A to 6D and the air-fuel ratio of the corresponding cylinder is overrich and misfires, the air-fuel ratio feedback control causes the air-fuel ratios of other cylinders to change. It becomes easy to occur by becoming an overrun. In this embodiment, in response to the above-mentioned irregular misfire, the occurrence of abnormal cylinders due to misfire can be continuously and accurately detected.

Furthermore, in this embodiment, even if the rotational speed NEn at that time is judged to be abnormal and the number of abnormal rotations CDINJn is increased for the cylinder in which the misfire has occurred, the rotational fluctuation amount ΔNE is next determined. If it is less than the reference value Y of, the number of times CDINJn is reduced by the value B. Therefore, when the engine speed NE is accidentally reduced due to an irregular misfire, the relevant cylinder is not erroneously determined to be abnormal due to the misfire, and the determination accuracy of the abnormal cylinder, that is, the accuracy of the misfire determination. Can be increased.

Furthermore, in this embodiment, the correction value α is obtained only when various controls for intentional torque fluctuation are performed.
Is set to a predetermined value, and in the cylinder next to the cylinder corresponding to the control for the torque fluctuation, the reference value X to be compared with the rotation fluctuation amount ΔNE is added to the correction value α to be set large. Therefore, in the cylinder next to the cylinder corresponding to the control for intentional torque fluctuation, the engine speed NE decreases due to the influence of the torque fluctuation, and the rotation fluctuation amount ΔNE
Even if fluctuates greatly, it is possible to determine the abnormal cylinder according to the fluctuation. That is, even if misfire occurs in a cylinder that should be operating during control for intentional torque fluctuation, an abnormal cylinder is properly detected while eliminating the influence of the control for torque fluctuation. Therefore, it is possible to prevent erroneous detection of an abnormal cylinder and further improve the accuracy of misfire determination.

In addition, in this embodiment, in the case of misfire,
Since fuel injection is stopped for the misfiring cylinder,
It is possible to prevent discharge of unburned gas, and thus prevent damage to the three-way catalyst in the catalytic converter 7 in advance. Further, in this embodiment, in the case of misfire, various controls for intentional torque fluctuation are stopped,
Control for torque fluctuation and misfire are combined, and engine 1
It is possible to prevent an extreme output shortage and an engine stall.

The present invention is not limited to the above-described embodiment, but may be implemented as follows with a part of the structure appropriately changed without departing from the spirit of the invention. (1) In the above embodiment, in addition to the engine ECU 30, the ECT ECU 41 and the TRCECU 4 serve as rotation fluctuation command means.
Although the ECU 2 and the automatic drive ECU 43 are provided, a control device that causes an intentional torque fluctuation in the engine 1 may be provided as the rotation fluctuation command means. (2) In the above embodiment, the misfire detection device for an internal combustion engine is applied to a gasoline engine, but it may be applied to other internal combustion engines such as a diesel engine. (3) In the above embodiment, the correction value α is added to the reference value X to be compared with the rotation fluctuation amount ΔNE in step 410. However, the value obtained by adding “1” to the correction value α is the reference value X. May be multiplied, and the multiplication result may be compared with the rotation fluctuation amount ΔNE. (4) In the embodiment described above, in step 420, the reference value X and the correction value α are added to the rotational speed NEn of the cylinder this time, and the addition result is set as the rotational speed NEB. However, the correction value α is "1". It is also possible to multiply the reference value X by a value obtained by adding and add the multiplied value to the rotation speed NEn and set the result as the rotation speed NEB.

[0062]

As described above in detail, according to the present invention, when the intentional rotation fluctuation of the internal combustion engine is executed as a command according to the operating state of the internal combustion engine, the intentional torque fluctuation is caused. In the cylinder next to the cylinder corresponding to the control of, even if the rotation speed of the internal combustion engine decreases due to the influence of the torque fluctuation and the post-command rotation fluctuation fluctuates significantly, the misfire is determined according to the fluctuation. The misfiring cylinder can be properly detected while eliminating the influence of the control for torque fluctuation, and thus the erroneous detection of the abnormal cylinder can be prevented and the accuracy of misfire determination can be improved.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram of the present invention.

FIG. 2 is a schematic configuration diagram showing a gasoline engine system to which a misfire detection device according to an embodiment of the present invention is applied.

FIG. 3 is a block diagram showing a configuration of an engine ECU of the same.

FIG. 4 is a flowchart illustrating an abnormal cylinder detection processing routine that is also executed by the engine ECU.

FIG. 5 is a flowchart illustrating the continuation of an abnormal cylinder detection processing routine that is also executed by the engine ECU.

FIG. 6 is a flowchart illustrating the continuation of an abnormal cylinder detection processing routine that is also executed by the engine ECU.

FIG. 7: 30 ° also executed by the engine ECU
It is a flow chart explaining a CA interruption routine.

[Description of Reference Signs] 1 ... Engine as internal combustion engine, 25 ... Rotation speed sensor as rotation detecting means, 30 ... Rotation fluctuation indexing means, misfire determining means, and rotation fluctuation commanding means
U, 41 ... ECT ECU, 42 ... TRCECU, 43 ...
Auto-drive ECU (41, 42, 43 constitute rotation fluctuation command means).

Claims (1)

(57) [Claims] 1. A rotation detecting means for detecting the rotation of an internal combustion engine, and a rotation fluctuation calculating means for calculating a rotation fluctuation for each explosion stroke of each cylinder of the internal combustion engine based on a detection result of the rotation detecting means. When the indexing result of the rotation fluctuation indexing means exceeds a predetermined determination value, in a misfire detection device including a misfire determination means for determining misfire in each cylinder explosion stroke, the internal combustion engine according to the operating state of the internal combustion engine A rotation fluctuation command unit for commanding an intentional rotation fluctuation of the engine is provided, and the rotation fluctuation indexing unit executes a command of the rotation fluctuation command unit.
The rotational speed in the immediately preceding cylinder explosion and the rotational speed in the first cylinder explosion after the end of the command are used to determine the rotational fluctuation after the end of the command, and the misfire determination means determines the rotational fluctuation after the end of the command from the normal determination value. misfire detecting device also determined value and compared set to increase, and performs the misfire determination.