JPH06146996A - Misfire detector for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent erroneous judgement of misfire by stopping idle correction control when misfire happens during the idle correction control. CONSTITUTION:When an ignition counter CSPK reaches a specific ignition number K at step 250, and when the number of misfire counted by a misfire counter CMF in a current misfire judgement cycle is larger than a specific number KMREF at a step 260, while it is judged by a step 270 that a misfire flag XMFISC during idle correction control is 1, it is judged that misfire happens during execution if idle correction control in the current misfire judgement cycle. An idle correction control execution flag XISC is reset to zero level at a step 290, to stop idle correction control. Erroneous judgement of misfire can thus be prevented due to hunting generated in a case where single misfire thus happens recovers to normal ignition during idle correction control.

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 a multi-cylinder internal combustion engine, which detects misfire occurring in the multi-cylinder internal combustion engine from the rotational state of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a device for detecting a misfire of an internal combustion engine, as disclosed in, for example, Japanese Patent Laid-Open No. 61-258955, when a misfire occurs in the internal combustion engine, complete combustion is performed in the combustion chamber of the internal combustion engine. Since it is not obtained, and the rotation speed of the internal combustion engine decreases, at least 2 during each cylinder explosion stroke
The rotation speed of the internal combustion engine for each cylinder explosion stroke is obtained by detecting the instantaneous rotation speed at each point, and the rotation fluctuation amount Δω is calculated from the rotation fluctuation amount and the rotation fluctuation amount of the previous explosion stroke cylinder. A device configured to determine the misfire of the internal combustion engine when the change amount Δω is compared with a predetermined misfire determination value and the change amount Δω becomes larger than the misfire determination value is known. .

[0003]

However, in general, in an internal combustion engine, in order to stabilize the rotation speed during idling,
Correction control is performed by detecting the amount of rotation fluctuation and performing feedback control of the intake air amount, ignition timing, and the like.
Therefore, when a misfire occurs and the rotation speed drops, the correction amounts such as the intake air amount and the ignition timing are reflected so as to increase the rotation speed. However, during this idle correction control, after a single misfire occurs and the rotation speed temporarily drops, the torque may be generated by the next normal ignition, and the rotation speed may rise and return.

In this case, the idle correction control makes a meaningless correction for the internal combustion engine, and the rotational speed after the occurrence of a single misfire may hunt. Then, there is a state in which the rotation speed decreases until the hunting converges, which may cause misfire detection. For this reason, misfire is detected too much,
There was a problem that the misfire was not correctly detected due to incorrect identification of the misfire cylinder.

The misfire detection device for an internal combustion engine of the present invention is made to solve the above problems, and an object thereof is to accurately detect misfire in an internal combustion engine having a control for stabilizing the rotation speed. And

[0006]

In order to achieve the above object, the present invention outputs a rotation signal at every predetermined rotation angle according to the rotation of a multi-cylinder internal combustion engine as shown in the block diagram of FIG. A rotation signal output means, a rotation speed variation calculation means for calculating a rotation speed variation amount for each explosion stroke of each cylinder of the multi-cylinder internal combustion engine based on a signal from the rotation signal output means, and the multi-cylinder internal combustion engine. Misfire determination value setting means for setting a misfire determination value based on the engine state of the engine, and a misfire for determining the misfire of the multi-cylinder internal combustion engine by comparing the calculation result of the rotation speed fluctuation calculation means and the misfire determination value. Judgment means, storage means for storing the result of the misfire judgment means, and a control amount for controlling the rotation speed of the multi-cylinder internal combustion engine to a desired rotation speed are calculated. Place Rotation speed stabilization control means for stabilizing the rotation speed and, while executing the rotation speed stabilization control, when the misfire determination means determines that a misfire has occurred in the multi-cylinder internal combustion engine, the control amount is suppressed. The technical means of a misfire detection device for an internal combustion engine, which comprises:

[0007]

According to the configuration of the misfire detection device for an internal combustion engine according to the present invention described above, the rotation speed fluctuation amount calculation means determines whether each cylinder of the multi-cylinder internal combustion engine is operated based on the rotation signal output from the rotation signal output means. The rotation speed fluctuation amount for each explosion stroke is calculated. On the other hand, the misfire determination value setting means sets the misfire determination value of the multi-cylinder internal combustion engine. Then, the misfire determination means determines the misfire of the multi-cylinder internal combustion engine based on the set misfire determination value and the calculation result of the rotational speed fluctuation calculation means, and the misfire is stored in the storage means. Further, the rotational speed stabilizing means calculates a control amount for controlling the rotational speed of the multi-cylinder internal combustion engine to a desired rotational speed, and the rotational speed of the multi-cylinder internal combustion engine is stabilized to the desired rotational speed by this control amount. It

Here, when the rotational speed stabilization control is being executed by the rotational speed stabilization means and the misfire determination means determines that a misfire has occurred in the multi-cylinder internal combustion engine, the control amount is suppressed by the suppression means. To be done.

This excludes the case where misfire is erroneously determined by hunting that occurs when a single misfire occurs during execution of the rotational speed stabilization control. Therefore, accurate misfire detection is performed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 is a schematic configuration diagram showing a 6-cylinder internal combustion engine (hereinafter, simply referred to as an internal combustion engine) 2 to which the present invention is applied and its peripheral devices.

As shown in FIG. 2, the internal combustion engine 2 includes an intake pressure sensor 6 for detecting the pressure in the intake pipe 4 (intake pipe pressure) as a sensor for detecting the operating state of the internal combustion engine 2, and a temperature of cooling water. A water temperature sensor 8 for detection and a rotation angle as a rotation signal output means which is attached to the crankshaft of the internal combustion engine 2 and generates a pulse signal every time the internal combustion engine 2 rotates a predetermined crank angle (30 ° C. in this embodiment). The high voltage generated by the sensor 10 and the igniter 12 is attached to a distributor 14 that sequentially distributes to a spark plug (not shown) provided in each cylinder of the internal combustion engine 2, and the distributor 1
The cylinder discriminating sensor 16 is provided for generating a pulse signal once for every four rotations (for every two rotations of the internal combustion engine 2).

Detection signals from these sensors are input to an electronic control unit (ECU) 20. ECU20 is C
It is configured by a well-known microcomputer mainly including the PU 21, the ROM 22, and the RAM 23, and inputs the detection signals from the above-mentioned sensors through the input / output port 25.

Further, the CPU 21 has the ROM 2 in advance.
2 according to the control program stored in the internal combustion engine 2
Fuel injection amount from the fuel injection valve 7 provided in each cylinder of
An engine control process for controlling the high voltage generation timing (ie, ignition timing) of the igniter 12 is executed.

In this engine control processing, idle correction control, which is rotational speed stabilization control for correcting the ignition timing and stabilizing the idle rotational speed when the internal combustion engine 2 is in the idle state, is executed. The idle correction control will be described below with reference to the flowchart shown in FIG.

In step 400, it is determined whether the internal combustion engine 2 is in the idle state. Here, when the rotational speed of the internal combustion engine 2 is equal to or lower than the predetermined rotational speed and an idle switch (not shown) is ON, it is determined that the internal combustion engine 2 is in the idle state. If in step 400 it is determined that engine 2 is not idle, then step 470
Then, the idle correction ignition timing θisc = 0 is set, and the routine proceeds to step 450. Note that this idle correction ignition timing θ
isc is a corrected ignition timing calculated so as to control the rotation speed of the engine 2 to the target idle rotation speed when the engine 2 is in the idle state.

On the other hand, when it is determined in step 400 that the engine is in the idle state, the routine proceeds to step 410, where it is determined whether or not the idle correction control execution flag XISC = 1. Here, this idle correction control execution flag XISC
When is set to 1, idle correction control is executed, and when set to 0, this control is stopped.

When XISC = 0,
Proceed to step 480. In step 480, the idle correction ignition timing θisc is fixed to the predetermined value A, and the execution of this correction control is stopped. Then, it progresses to step 450. The predetermined value A is, for example, 1 (° C
It may be A). Further, θisc calculated until the idle correction control is stopped may be stored and the average value thereof may be set as the predetermined value A.

On the other hand, when XISC = 1, the routine proceeds to step 420, where idle correction control is executed. In step 420, the rotation speed NEn of the internal combustion engine 2 is fetched from the rotation angle sensor 10. Then, in step 430,
A deviation ΔNE between the preset target idle rotation speed NEo and the rotation speed NEn is calculated. And
In step 440, ΔNE calculated in step 430
The idle correction ignition timing θisc corresponding to the above is calculated. This θisc is calculated in step 450 as the basic ignition timing θba calculated from the intake pipe pressure and the engine rotation speed.
Then, the final ignition timing θig is calculated. Then, in step 460, an ignition signal corresponding to this θig is output.

The idle correction control execution flag XISC in step 410 is set so as to be in a reset state when the internal combustion engine 2 is started. Also, CPU2
Reference numeral 1 executes the engine control processing described above, and also executes misfire detection processing that detects misfire of the internal combustion engine 2 from the rotational speed of each cylinder of the internal combustion engine for each explosion stroke.

The misfire detection process and the engine state detection process, which are the main processes of the present invention executed by the ECU 20 having the above-described configuration, will be described below with reference to the flowcharts shown in FIGS. 4 and 5.

In the misfire detection process shown in FIG. 4, a predetermined crank angle of the internal combustion engine 2 (30 ° C. in this embodiment) is determined by the CPU 21 based on the output signal from the rotation angle sensor 10.
The interrupt process is performed every A). When this process is started, first, at step 100, the internal combustion engine 2 rotates at 30 ° C. A from the deviation between the previous interrupt time and the current interrupt time. The time T30i required for the calculation is calculated.
Then, in the following step 110, it is determined whether or not any cylinder is currently at top dead center (TDC). If it is not top dead center, this routine is ended, and if it is top dead center, the routine proceeds to step 120. .

In step 120, the time T30i calculated in step 100 for rotating at 30 ° C. is calculated.
And, the internal combustion engine 2 rotates at 120 ° C. A by accumulating the data of all four times of T30i-1, T30i-2, and T30i-3 obtained at the time of execution of the previous time, two times before, and three times before, respectively. The required time T120i is calculated. Then, in step 130, the reciprocal of the calculated time T120i is calculated to calculate the average rotation speed ωn while the internal combustion engine 2 is 120 ° C.

Next, at step 140, based on the average rotational speed ωn calculated this time and the average rotational speeds ωn-1, ωn-3, ωn-4 calculated last time, three times before, and four times before,
The change Δωn in the rotational fluctuation amount of the internal combustion engine 2 is calculated using the following equation.

[0024]

## EQU1 ## Δωn = (ωn-1−ωn) − (ωn−4−ωn−3) In the above formula 1, (ωn−1−ωn) and (ωn−4)
−ωn−3) is the rotation fluctuation amount in the cylinder in which the explosion stroke is continuous, and (ωn−1−ωn) is the latest, (ωn−4−ωn−).
3) is the value before 360 ° C.

Here, the above steps 100 to 14
The process of 0 corresponds to the above-described rotation speed fluctuation amount calculation means. That is, in this embodiment, the internal combustion engine 2 is a 6-cylinder internal combustion engine, and the period during which one cylinder alone has an explosion stroke is 120 ° C. before top dead center of the cylinder that enters the next explosion stroke. 1 to 1 of the internal combustion engine 2 from 100 to step 130
By calculating the average rotation speed ωn every 20 ° C.,
The rotation speed at the time of the explosion stroke of each cylinder of the internal combustion engine is calculated, and in step 140, the latest rotation fluctuation amount is calculated from this rotation speed and the previously calculated rotation speed.
The change amount Δωn of the rotation variation amount of the internal combustion engine used for the misfire determination is calculated from the rotation variation amount before 60 ° C. A. In this embodiment, the latest rotational fluctuation amount and the rotational fluctuation amount before 360 ° C. are obtained at the same time by using the above formula 1, but the latest rotational fluctuation amount may be stored in the RAM 23. For example, the amount of rotation fluctuation before 360 ° C is stored in RAM
It is also possible to obtain the variation amount Δωn without calculating the rotation variation amount before 360 ° C. A by reading the variation amount Δωn.

At the next step 150, the current operating state (rotational speed NE, intake pipe pressure PM) is determined, and the routine proceeds to step 160. In Step 160, Step 1
Operating conditions (rotational speed NE, intake pipe pressure P
Based on M), the misfire determination value REF is set by searching a two-dimensional map (REF map) shown in FIG. 6 with the rotational speed NE and the intake pipe pressure PM stored in the ROM 22 in advance as parameters. .

Next, at step 170, this misfire determination value R
The misfire determination is performed by comparing the EF and the variation Δωn obtained in step 140. That is, if the change amount Δωn is larger than the cylinder determination value REF, it is determined that a misfire has occurred, and the process proceeds to step 180. If the change amount Δωn is equal to or less than the misfire determination value REF, it is determined that a misfire has not occurred. Move to 190.

Then, in step 180, a misfire detection flag XMFn indicating that misfire has occurred in the cylinder is set. Then, in the next step 182, the idle correction control execution flag XISC = shown in FIG.
It is determined whether or not the value is 1, and it is determined whether or not a misfire has occurred during this idle correction control. And XISC = 1
In the case of, the process proceeds to step 184, and it is determined that a misfire has occurred during the idle correction control, and the misfire flag during idle correction control XMFISC is set to 1. On the other hand, step 182
If XISC = 0, the process proceeds to step 200.

In step 190, the misfire detection flag XMFn is reset, and the process proceeds to next step 200. In step 200, the latest average rotation speed ωn obtained in step 130 is set as the previous average rotation speed ωn-1 for the next process execution, and the previous average rotation speed ωn-1 is set as the previous average rotation speed ωn-. 2, the average rotational speed ωn-2 of the previous two times is set as the average rotational speed ωn-3 of the three times before, and the average rotational speed ωn-3 of the three times before is set as the average rotational speed ωn-4 of the four times before. Store and end this processing routine.

Next, the engine state detection processing shown in FIG. 5 is executed in the interrupt processing by the crank angle sensor 10 after the misfire detection processing of FIG. Hereinafter, description will be given along this flowchart.

First, in step 210, it is determined whether or not any cylinder is currently at top dead center (TDC). If it is not top dead center, this routine is terminated, and if it is top dead center, step 220. Proceed to. In step 220, if the flag XMFn is set based on the result of the misfire detection flag XMFn in steps 180 and 190 in FIG. 4,
After incrementing the misfire number counter CMF in step 230, the process proceeds to step 240, and directly proceeds to step 240 when the flag XMFn is reset.
In step 240, the misfire number counter CSPK is incremented. The ignition number counter CSPK is a counter for determining the timing for checking the state determination as to whether or not the engine is in the misfire state, and in this embodiment, 1 is set for each predetermined number of ignitions K as determined in step 250. Check is carried out as a cycle. Step 25
When it is determined that the predetermined ignition number K has elapsed at 0, it is determined in step 260 whether or not the number of misfire determinations in the present cycle is equal to or greater than the predetermined value KMREF, the misfire number counter C.
It is judged by comparing with MF. Also, step 250
If it is determined that the one cycle has not been completed, the present routine is ended.

If it is determined in step 260 that the number of misfires counted by the misfire number counter CMF in the present misfire determination cycle is greater than the predetermined number KMREF, the process proceeds to step 270. At step 270, FIG.
It is determined whether or not the misfire detection flag XMFISSC = 1 during the idle correction control shown in the misfire detection process. Based on this result, it is possible to determine whether or not a misfire has occurred during the current misfire determination cycle and the idle correction control has been executed.

Then, in step 270, XMFISC =
If it is 0, during the misfire determination cycle this time,
This means that misfires occurred more than the predetermined number of times KMREF other than the idle correction control. Therefore, step 280
Then, it is stored in the RAM 23 that the internal combustion engine 2 is in the misfire state, and the warning lamp 29 is turned on.

On the other hand, in step 270, XMFISC =
If the value is 1, it is determined that a misfire has occurred during execution of the idle correction control. Therefore, the process proceeds to step 290, in which the idle correction control execution flag XISC is reset to 0 and the execution of the idle correction control is stopped.
The processing of steps 270 and 290 corresponds to the suppressing means of the present invention.

If it is determined in step 260 that the number of misfires counted by the misfire number counter CMF in the present misfire determination cycle is smaller than the predetermined number KMREF, the process proceeds to step 300. And step 300
Then, it is stored in the RAM 23 that the internal combustion engine 2 is in the normal ignition state. Further, the routine proceeds to step 310, where the idle correction control flag XISC is set to 1.

After these processes are completed, in step 320, the idle correction control misfire flag XMF is set.
The ISC, the misfire number counter CMF, and the misfire number counter CSPK are reset, and this routine ends.

Here, when a single misfire occurs during execution of the idle correction control shown in FIG. 3 and then normal ignition is restored, the rotational speed of the engine 2 temporarily decreases. At this time, the ignition signal corrected by the idle correction control so as to increase the rotation speed is output from the ECU 20.
However, after a single misfire, the engine 2 returns to normal ignition and the rotation speed also rises, so that the rotation speed of the engine 2 increases more than the rotation speed increase due to the correction control.
Therefore, the rotation speed of the engine 2 hunts. Then, when the rotation speed decreases in this hunting, it may be erroneously determined that a misfire has occurred.

Therefore, as in the above processing, the misfire flag XMFFISC during idle correction control during the misfire determination cycle is performed.
It is possible to determine whether or not a misfire has occurred during the idle correction control by determining whether is 1 or 0.
When the FISC is set to 1, the idle correction process is stopped and the misfire detection process of the engine 2 is performed again. As a result, it is possible to exclude a case where the misfire state is suspicious, such as whether the engine 2 has really misfired or whether the hunting has caused an erroneous determination. For this reason,
Misfire misjudgment can be prevented. Further, by the above processing, the idle correction control can be executed when it is surely detected that no misfire has occurred, so the idle rotation speed can be reliably controlled to the target rotation speed.

In the above embodiment, the idle correction ignition timing θisc is fixed to the predetermined value A when the idle correction control execution flag XISC is reset to 0. But,
Not limited to this, to the extent that it does not hinder the misfire determination process,
This correction control may be executed by reducing the value of θisc according to the deviation ΔNE of the rotation speed. For example, the value of θisc may be reduced to about ¼.

[0040]

According to the configuration and operation of the misfire detection device for an internal combustion engine of the present invention described above, when a misfire occurs during execution of the rotational speed stabilization control, the rotational speed of the multi-cylinder internal combustion engine is controlled by the suppressing means. The control amount for controlling the rotation speed to a desired rotation speed is suppressed. As a result, accurate misfire detection can be performed without being affected by the rotation speed stabilization control.

[Brief description of drawings]

FIG. 1 is a block diagram showing the present invention.

FIG. 2 is a schematic configuration diagram showing a 6-cylinder internal combustion engine and its peripheral devices to which the present invention is applied.

FIG. 3 is a flowchart showing an idle correction process of this embodiment.

FIG. 4 is a flowchart showing a misfire detection process of this embodiment.

FIG. 5 is a flowchart showing an engine state detection process of this embodiment.

FIG. 6 is an explanatory diagram showing a REF map of the present embodiment.

[Explanation of symbols]

 2 Internal combustion engine 10 Rotation angle sensor 16 Cylinder discrimination sensor 20 ECU 29 Warning lamp

Claims (2)

[Claims] 1. A rotation signal output means for outputting a rotation signal for each predetermined rotation angle according to the rotation of the multi-cylinder internal combustion engine, and each cylinder of the multi-cylinder internal combustion engine based on a signal from the rotation signal output means. Rotation speed fluctuation amount calculation means for calculating the rotation speed fluctuation amount for each explosion stroke, misfire judgment value setting means for setting a misfire judgment value based on the engine state of the multi-cylinder internal combustion engine, and the rotation speed fluctuation calculation means The misfire determination means for determining the misfire of the multi-cylinder internal combustion engine by comparing the calculation result and the misfire determination value, the storage means for storing the result of the misfire determination means, the rotational speed of the multi-cylinder internal combustion engine To calculate a control amount for controlling the rotation speed to a desired rotation speed, and by the control amount, a rotation speed stabilization control unit that stabilizes the multi-cylinder internal combustion engine at a desired rotation speed, and executes the rotation speed stabilization control. In the above, there is provided a misfire detection device for an internal combustion engine, comprising: a suppression means for suppressing the control amount when the misfire determination means determines that a misfire has occurred in the multi-cylinder internal combustion engine. 2. The suppressing means fixes the control amount to a predetermined value when the misfire determining means determines that a misfire has occurred in the multi-cylinder internal combustion engine while the rotational speed stabilization control is being executed. A means as a means.
A misfire device for an internal combustion engine as described.