JPH03213668A - Detecting device for misfired cylinder for internal combustion engine - Google Patents

Abstract

PURPOSE:To set a slice level and detect mis-fired cylinders with high accuracy respectively by setting a mis-fire judging value so that the difference in level for an engine operating condition is lessened, and thereby setting the slice level in response to the amplitude of the mis-fire judging value. CONSTITUTION:The rotational period of an internal combustion engine in the range of a specified crank angle is measured by a means A, a mis-fire judging value corresponding to the variation of average effective pressure is operated by a means B correspondingly to each cylinder based on the result of the aforesaid measurement, and the maximum amplitude of the mis-fire judging value is concurrently detected by a means C. In addition, an engine operating condition is detected by a means D, and the mis-fire judging value is corrected by a means E based on the result of the aforesaid detection so that the difference in level due to the engine operating condition is lessened. Furthermore, a slice level is set to be in either the inside or the outside of the maximum amplitude by a means F correspondingly to the amplitude of the mis-fire judging value which is either equal to or more than or less than a specified value. The slice level is then compared with the mis-fire judging value so that a mis-fired cylinder is thereby detected by a means G.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a misfire cylinder detection device for an internal combustion engine, and more specifically, to a misfire detection device for detecting a misfire in an internal combustion engine. The present invention also relates to a misfire cylinder detection device configured to detect a misfire cylinder by comparing the misfire determination value with a slice level.

<Prior Art> Conventionally, a device for detecting a misfiring cylinder calculates a misfire discrimination value that approximately corresponds to the difference in average effective pressure between cylinders based on the engine rotation period as shown below, and then calculates the misfire discrimination value based on this misfire discrimination value. There is a method to determine a misfiring cylinder by
TA-PaperExper-iences
with a new method for a+
easuring the engine roughhn
Ess J by R, Latsch+ E, Maus
ner+V, B 1anchi and patent application Hei 1-27
(See No. 5046).

That is, for example, TDC cycle (180° cycle in a 4-cylinder engine)
is measured sequentially, and the TDC period of 1/2 cycle before is hal
f, 1 cycle previous TDC period old, latest TDC
By setting the period to new and substituting these values into the following equation, the misfire judgment value LU approximately equivalent to the amount of change in the average effective pressure can be obtained.
Calculate.

In the misfire determination value LU based on the above calculation formula, for example, 4
As shown in FIG. 9, which shows a state in which a misfire occurs in the #1 cylinder in a 4-cylinder cycle engine, the misfire determination value LU1 corresponding to the #1 cylinder in the 4-cylinder internal combustion engine varies at each TDC (180°
) is calculated when the latest value of the 180° period measurement result is affected by the in-cylinder pressure of the #1 cylinder, that is, when the combustion stroke of the #1 cylinder is included in the latest 180° period. Therefore, the misfire determination value LU corresponding to each cylinder can be calculated in the same way.

Here, misfire cylinder discrimination based on the misfire discrimination value LU is as follows:
Discriminant value L below slice level SL (minus value) determined by operating conditions (e.g. engine speed and engine load)
When U is detected, it is determined that there is a misfire. However, if the misfire discrimination value LU is negative consecutively and any of them is below the slice level SL, the previous misfire discrimination value LU
indicates the occurrence of a misfire, and if the #1 cylinder continues to misfire as shown in Fig. 9, the misfire discrimination value LU corresponds to the #1 cylinder and #3 cylinder as shown in the figure. The misfire discrimination values LUI and LU3 each become negative values,
However, both are below slice level SL, but #
The misfire discrimination value LUI corresponding to one cylinder comes first (ignition order #1 →
#3→#4→#2), it is determined that the #1 cylinder is misfiring.

<Problems to be Solved by the Invention> By the way, when detecting a misfiring cylinder by comparing the misfire determination value LU and the slice level SL as described above, the first
As shown in Figure 0, the level of the misfire determination value LU varies greatly depending on the engine operating conditions (engine rotation speed and engine load), so it is necessary to change the slice level SL according to the operating conditions. The slice level SL is stored in advance in a map whose parameters are the speed N and the basic fuel injection amount Tp representing the engine load, and the slice level SL of the corresponding operating condition is referenced from the map and used.

However, the method of referring to the slice level SL from the map as described above increases the man-hours for matching the slice level SL, and also requires a non-negligible calculation time to refer to the target slice level SL from two variables. Another problem is that a large amount of ROM capacity is consumed by the map. Furthermore, in determining the slice level SL using a map, if there is a matching error in the map value, there is a problem that the misfire detection accuracy is deteriorated and the misfire detection accuracy is used as is.

For this reason, the applicant first corrected the change rate of the misfire discrimination value by the engine rotation speed (multiplyed by the square value of the rotation speed), thereby reducing the level difference in the misfire discrimination value due to the difference in engine rotation speed. The present invention proposes a misfiring cylinder detection device configured to set the slice level based on the rate of change corrected by the inter-machine rotation speed (filing date: November 22, 1999), and refer to the slice level SL from a map. Instead, the misfire determination value LU is set each time, so that the above-mentioned problem in the map reference method can be avoided.

However, if the misfire discrimination value is corrected by multiplying it by the square value of the rotational speed, as shown in Fig. 11, although the level difference in the misfire discrimination value LU due to the engine speed can be eliminated, Since the misfire determination value LU changes proportionally, there is a difference in the deviation of the misfire determination value LU between when the engine torque is large and when the engine torque is low. It was found that it was not possible to perform proper misfire cylinder detection.

The present invention has been made in view of the above problems, and in setting the slice level from the calculation result of the misfire discrimination value, the slice level is set with high accuracy without being influenced by the engine rotation speed or engine torque (engine load). can be made,
It is an object of the present invention to provide a misfiring cylinder detection device that can maintain good detection accuracy over the entire operating range.

<Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. misfire discrimination value calculation means for calculating a misfire discrimination value, which is a value approximately equivalent to the amount of change in average effective pressure based on the cycle, for each cylinder; maximum runout width detection means for detecting the maximum runout width; engine operating condition detection means for detecting engine operating conditions including at least the engine rotational speed and engine load; and operation including at least the engine rotational speed and the engine load detected thereby. misfire discrimination value correction means for correcting and setting the misfire discrimination value calculated by the misfire discrimination value calculation means based on conditions in a direction that reduces a level difference of the misfire discrimination value depending on engine operating conditions;
When the deviation width of the misfire discrimination value corrected by the misfire discrimination value correction means is equal to or greater than a predetermined value, the slice level is set inside the maximum deviation width detected by the maximum deviation detection means, and the correction setting is performed. slice level setting means for setting a slice level outside the maximum range when the range of deviation of the misfire discrimination value determined is less than a predetermined value; and means for calculating the thus set slice level and the misfire discrimination value. A misfire cylinder detection device for an internal combustion engine is configured to include misfire cylinder detection means for detecting a misfire cylinder by comparing the calculated misfire discrimination value with the misfire discrimination value calculated in the above.

Here, the misfire discrimination value correction means multiplies the misfire discrimination value calculated by the misfire discrimination value calculation means by the parameter of the engine rotation speed, and divides it by the parameter of the engine load, thereby controlling the engine operation according to the misfire discrimination value. It is preferable to configure the correction setting so as to reduce the level difference depending on the conditions.

Further, as shown by the dotted line in FIG. 1, it is preferable to provide a slice level characteristic variable means for variably setting the slice level setting characteristic of the slice level setting means in accordance with the engine rotational speed.

<Operation> According to the misfiring cylinder detection device configured as described above, the misfire discrimination value calculation means detects a misfire that approximately corresponds to the amount of change in the average effective pressure based on the period of the predetermined crank angle range of the engine measured by the rotation period measuring means. A discrimination value is calculated for each cylinder.

The maximum deflection width detection means detects the maximum deflection width of the misfire determination value calculated as described above.

On the other hand, the misfire discrimination value correcting means adjusts the misfire discrimination value to reduce the level difference depending on the engine operating conditions, based on the engine operating conditions including at least the engine rotation speed and the engine load detected by the engine operating condition detection means. Correct and set the misfire discrimination value.

Here, when the deviation of the misfire discrimination value corrected based on the engine operating conditions is equal to or greater than a predetermined value, the slice level setting means sets the maximum deviation of the misfire discrimination value that is not corrected based on the engine operating conditions. If the slice level is set to the inside of the misfire determination value that has been corrected based on the engine operating conditions, and the swing width of the misfire determination value that has been corrected based on the engine operating conditions is less than the predetermined value, Set the slice level outside the maximum deflection width.

The slice level thus set is compared by the misfire detection means with a misfire determination value that has not been corrected based on the engine operating conditions, and a misfired cylinder is detected from the comparison result.

That is, after reducing the level difference depending on the engine operating conditions, the fluctuation range of the misfire determination value is monitored, and when this fluctuation range is large, it is assumed that the fluctuation range has increased due to the occurrence of a misfire, and the misfire determination value is determined before correction. By setting the slice level within the maximum range of values, the misfire determination value changes beyond the slice level, allowing a misfire cylinder to be detected.

Conversely, if the range of misfire discrimination value after correction is small, it is assumed that no misfire has occurred, and the slice level is set outside the maximum range of misfire discrimination value before correction. To avoid erroneous detection of a misfire cylinder by preventing a misfire discrimination value from changing beyond the limit.

As mentioned above, the correction to reduce the level difference in the misfire discrimination value depending on the engine operating conditions is performed by multiplying the misfire discrimination value by the engine speed parameter and dividing it by the engine load parameter. It is preferable to correct the misfire determination value, which tends to increase when the load is low.

Further, the slice level characteristic variable means variably sets the slice level setting characteristic in the slice level setting means in accordance with the engine rotation speed, and the slice level characteristic varying means variably sets the slice level setting characteristic in the slice level setting means in accordance with the engine rotation speed, so that the slice level characteristic is variably set in accordance with the engine rotation speed, and slices due to differences in operating conditions where correction of the misfire discrimination value based on the engine operating conditions is insufficient. Made it possible to respond to changes in level requirements.

<Example> The present invention will be explained in detail below.

In FIG. 2 showing one embodiment, an internal combustion engine 1 includes an air cleaner 2. Intake duct 3. Air is drawn in via the throttle chamber 4 and the intake manifold 5.

An air flow meter 6 is provided in the intake duct 3 to detect the intake air flow rate Q. The throttle chamber 4 is provided with a throttle valve 7 that operates in conjunction with an accelerator pedal (not shown) to control the intake air flow rate Q. The intake manifold 5 is provided with an electromagnetic fuel injection valve 8 for each cylinder (four cylinders in this embodiment), which injects fuel that is fed under pressure from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator. It is injected and supplied into the intake manifold 5.

The fuel injection amount is controlled by a control unit 9 with a built-in microcomputer based on the intake air flow rate Q detected by the air flow meter 6 and the distributor 1.
The basic fuel injection amount Tp corresponding to the opening drive time of the fuel injection valve 8 is calculated based on the engine rotational speed N calculated based on the signal from the crank angle sensor 10 built into the engine 3, and the basic fuel injection amount Tp=KXQ/N.
(K is a constant), and by correcting this basic fuel injection amount TP based on the cooling water temperature Tw detected by the water temperature sensor 14, etc., the final fuel injection fTi is calculated, and this fuel injection amount Ti By outputting a drive pulse signal with a pulse width corresponding to the width of the engine to the fuel injection valve 8 in synchronization with the rotation of the engine, the required amount of fuel is injected and supplied to the engine 1.

Further, each cylinder of the engine 1 is provided with an ignition plug 11, to which a high voltage generated by an ignition coil 12 is sequentially applied via a distributor 13 (the ignition order is #1 → #3 → #4→#2), this causes a spark to ignite and ignite and burn the air-fuel mixture.

Here, the generation timing of the high voltage is controlled via the ignition coil 12a and the attached power transistor 12a. Therefore, ignition timing (ignition advance value) ADV
This control is performed by controlling the on/off timing of the power transistor 12a using an ignition control signal from the control unit 9.

The control unit 9 searches for an ignition timing ADV corresponding to the operating condition from a map that stores ignition timing ADV in advance for each of a plurality of operating regions divided by the basic fuel injection amount Tp and engine rotational speed N. Based on the ignition timing AD■, an ignition control signal is output to control the ignition timing.

The throttle valve 7 is equipped with a throttle sensor 15 that detects its opening TVO with a potentiometer, and from the crank angle sensor 10,
Every 180° in a 4-cylinder engine (BTDC in this example)
A reference angle signal REF (every 70 degrees) and a unit angle signal PO3 every 1 degree or 2 degrees are output.

The reference angle signal REF serves as a reference position for ignition timing control by the control unit 9, and for example, among the reference angle signals REF, the one corresponding to the ignition reference for the #1 cylinder can be distinguished from the others, This allows the reference angle signal REF to correspond to each cylinder so that ignition control can be performed for each cylinder.

In addition, the control unit 9 has a function as a misfire cylinder detection device that performs misfire cylinder detection according to the present invention and displays a cylinder in which a misfire has occurred near the driver's seat of the vehicle. The misfiring cylinder detection control will be explained according to the programs shown in the flowcharts of FIGS. 3 to 5, respectively.

In this embodiment, the functions of the misfire discrimination value calculation means 7 as the maximum runout width detection means, the misfire discrimination value correction means, the slice level setting means, the slice level characteristic variable means, and the misfiring cylinder detection means are as shown in FIGS. They are provided in terms of software as shown in the flowchart of FIG.

In this embodiment, the engine operating condition detecting means corresponds to the air flow meter 6 and the crank angle sensor 10, and the rotation period measuring means corresponds to the crank angle sensor 1.
0 and a control unit 9.

The program shown in the flowchart of FIG. 3 is 15 degrees after compression TDC (ATDC15
This is executed for each angular position (°).

First, step 1 (indicated as Sl in the figure).

(The same applies hereafter) Then, according to another program (not shown),
From TDC 20° to ATDC 180” (angular range where crank angular speed is particularly affected by changes in cylinder pressure)
The results of measuring the period of are stored in memory in chronological order.

That is, as shown in FIG. 7, the control unit 9 detects the positions of ATDC 20° and ATDC 180' based on the signal output from the crank angle sensor IO, and measures the elapsed time (period) between them. In this step 1, the cycle measured just before is set to TO as the latest measurement cycle, and the data of TO where the latest cycle was set when this program was executed last time is set as the previous cycle. Set it to T1, and in the same way, set the cycles Tl, T2゜T3 of the previous one, two, and three times before.
are further set as one-time older data to the two previous (one rotation ago) period T2, the third previous period T3, the fourth previous (two rotations ago) period T4, respectively.

Then, in the next step 2, the period T2 before the latest period TO11 rotations (1/2 cycle before) set in step 1
．． A misfire determination value LU is calculated according to the following formula using the period T4 two revolutions ago (one cycle ago).

The above-mentioned misfire determination value LU is a value that approximately corresponds to the amount of change in the average effective pressure, and from this, the change in the average effective pressure of the cylinder that was in the combustion stroke when measuring the latest period TO is estimated. .

In step 3, a calculation is performed to set the slice level SL to be used for detecting a misfired cylinder based on the misfired cylinder discrimination value LU calculated in step 2 above.

The contents of the calculation for setting the slice level SL are shown in the flowchart of FIG. First, in step 61, it is determined whether or not the misfire discrimination value LU calculated in step 2 is greater than or equal to zero. If the misfire discrimination value LU is greater than or equal to zero, the process proceeds to step 62.

In step 62, a PL is stored in which past data of the misfire discrimination value LU determined to be greater than or equal to zero is stored in chronological order.
Each of LU (0) to PLLU (3) is updated one more time to PLLU [1) to PLLU (4) as old data. That is, PLLU (0) is set to the misfire discrimination value LU that was most recently calculated to be zero or more, excluding this time, and the misfire discrimination value LU that was calculated to be zero or more before this PLLU (0) is set to PLLU (0). (It is set to 13, and since a new misfire judgment value LU of zero or more has been calculated this time, the previous data is updated one more time as old data in order to set this latest data to PLLU [O].) be.

In step 63, each of the past four misfire discrimination values LU updated in step 62 and the currently calculated misfire discrimination value LU are compared, and a total of five misfire discrimination values LU data that are zero or more are selected. To find the maximum value,
A comparison counter i is set to 1, and the currently calculated misfire determination value LU is set to reg.

Then, in the next step 64, it is determined whether or not the comparison counter i has reached 5, which indicates the total number of comparisons. If it has not reached 5, in step 65, the PLLU (1 ) ~ PLLU (4) Compares PLLU (N with the misfire discrimination value LU set in reg, and selects PLLU (N is reg
When it exceeds PLLU (
The misfire discrimination value LU set in i) is updated and set in reg.

In the next step 67, the comparison counter i is incremented by 1 so that the older data of PLLU (1) to PLLU [4] is compared with reg, and again in step 6
Return to 4. Then, the comparison counter i is counted up from 1 to 5, and in step 64, the comparison counter i is counted up from 1 to 5.
If it is determined that this is the case, the process advances to step 68.

In step 68, reg to which the newly obtained maximum value is set and the weighted average of the previous maximum value ma
xjd and are weighted averaged according to the following formula, and the maximum value weighted average max j d is updated.

In step 69, the maximum value MAX up to the previous time is compared with the misfire discrimination value LU calculated this time, and the current misfire discrimination value L
If U is larger, proceed to step 70 and set the current misfire determination value (1iLU) to the maximum value MAX (maximum swing width on the positive side).On the other hand, if the maximum value MAX up to the previous time is greater than the current misfire determination value LU If it is larger, the process proceeds to step 71, where the maximum value weighted average maxjd obtained in step 68 and the maximum value MAX up to the previous time are weighted averaged according to the following formula, and the weighted average result is calculated as a new maximum value M.
Let it be AX.

That is, when an extremely large misfire discrimination value LU is calculated, its instantaneous value is set to MAX, but if a positive misfire discrimination value LU calculated after that does not exceed this MAX, the most recent value is set to MAX. The weighted average value maxjd of the maximum value among the five misfire discrimination values LUO calculated as zero or more and the maximum value MAX are weighted averaged and gradually become the maximum value MAX.
(see Figure 6).

In step 72, the sum of the misfire discrimination value LU calculated this time in step 2 and the misfire discrimination value LU −+ calculated in the same step 2 during the previous execution is added to the engine rotation speed N as the engine operating condition. A correction calculation is performed according to the following formula based on the engine load, and the correction calculation is made to result in a reduction in the level difference of the misfire determination value LU depending on the engine operating conditions.

Dlu← (IU-+I+ILUl)
(←KXQ/N; is a constant), and is used here as a value representative of the engine load. Further, KLU is a constant.

As shown in Figure 8, Dlu calculated by the above formula reduces the level difference in the misfire discrimination value LU due to differences in engine operating conditions, and the misfire discrimination value LU changes only depending on the presence or absence of a misfire. , engine rotational speed N, and engine load conditions.

Therefore, if the level of Dlu is determined, as shown in FIG. 8, depending on whether Dlu is near zero or has an absolute value above a predetermined value, a misfire will occur or not, regardless of the engine operating conditions. can be predicted. As mentioned above, the result of adding the absolute value of the previous value and the current value of the misfire discrimination value LU is corrected based on the engine operating conditions.
In a state where a misfire occurs, as shown in FIG.
There are two cylinders that are calculated on the negative side, but in order to clarify the level difference depending on whether or not a misfire has occurred, there is a demand for increasing the absolute value level and predicting whether or not a misfire will occur. By adding the absolute values of two consecutively calculated misfire discrimination values LU, the level of Dlu increases more clearly when a misfire occurs.

In step 73, a function value S1ga is set for determining the slice level SL based on DIU, which is the misfire determination value LU corrected in step 72 based on the engine operating conditions.
Reference in from the map.

The S1gain is the maximum value MAX as described later.
, and the result is set as the slice level SL. Therefore, if Slgain is less than 1, the slice level SL is set to a value less than the maximum value MAX,
Conversely, when Slgain exceeds 1, the slice level SL is set to a value exceeding the maximum value MAX.

Misfiring cylinder determination is performed based on the slice level S, as described later.
This is done when there is a misfire discrimination value SL that exceeds L.
The value at which the slice level SL exceeds the maximum value MAX (L
When set outside the maximum swing width on the positive side of U), the misfire judgment value LU will not exceed the slice level SL,
If misfire cylinder discrimination is not performed and the slice level SL is set to a value less than the above maximum value MAX (inside the plus side maximum swing width of LU), the misfire discrimination value LU will exceed the slice level SL. The misfiring cylinder is determined.

A large Dlu indicates that the absolute value of the misfire discrimination value LU has increased due to the occurrence of a misfire (see Figure 8). It is necessary to set S)gain smaller than the maximum value MAX, and in step 73, when a misfire occurs when Dlu is greater than a predetermined value, S)gain is set to a value smaller than 1 as Dlu becomes larger than the predetermined value. It's Nishide. Also, when Dlu is a small value near zero, it indicates that no misfire occurs (
(See FIG. 8), in this case, Slgain is set to a value larger than 1 as Dlu becomes smaller than a predetermined value.

In other words, the Dlu eliminates the influence of engine operating conditions and only changes the level depending on whether or not a misfire occurs.
By determining whether a misfire has occurred or not, and when lu is large such that a misfire is predicted to occur, the slice level SL is set inside the maximum value MAX, which is the maximum swing range on the plus side of the misfire determination value LU. A misfire is determined by comparing the misfire determination value LU and the slice level SL, and conversely, it is predicted that no misfire will occur.
When u is small, the slice level SL is set outside the maximum value MAX, which is the maximum swing width in a positive example of the misfire discrimination value LU.
By setting the misfire judgment value LU and slice level S
This prevents a misfire from being determined by comparison with L.

In addition, when setting Slgain based on Dlu as described above, as shown in Fig. 8, the level of Dlu changes depending on the slight change in engine rotational speed N, so Dlu→S Igain
It is equipped with a plurality of conversion characteristics so that the D l u − + S I gain conversion is performed in accordance with the conditions of the applicable engine rotational speed N, and thereby the slice level SL can be set with higher precision. be.

After determining Slgain as described above, in the next step 74, the maximum value MAX (maximum swing width on the positive side of the misfire discrimination value LU) is multiplied by Slgain, and the result is set to the slice level SL. The slice level SL calculated here is a positive value, and as will be described later, the level determination of the positive misfire discrimination value LU will be performed based on the slice level SL calculated here.

In the next step 75, the misfire discrimination value LU calculated in step 2 is set as the latest positive value PLLU (0
3, and in the next step 7G, the misfire determination value LU calculated in step 2 this time is set to LU-, in order to use it as the previous value when the program is executed next time.

On the other hand, when it is determined in step 61 that the misfire determination value LU is not greater than or equal to zero, the maximum runout width on the negative side (minimum value MIN) is detected in the same way as when it is greater than or equal to zero, and the The presence or absence of a misfire is predicted based on Dlu, which is corrected to reduce the level difference of the misfire discrimination value LU based on the Dlu, and Slgain is set according to this prediction.
The slice level S is obtained by multiplying the gain and the minimum value MIN.
Set L (steps 77 to 91).

Even when the above-mentioned misfire discrimination value LU is not greater than zero, Dlu
After predicting whether or not a misfire will occur depending on the level of When this is predicted, the slice level SL is set outside (on the smaller side) of the minimum value MIN, and the level of the misfire discrimination value LU, which is a negative value, is determined based on this slice level SL.

As described above, according to the slice level setting in this embodiment, the engine rotation speed N and the engine load (basic fuel injection amount Tp
) even if the conditions change, the misfire discrimination value LU exceeds the slice level SL when a misfire is predicted to occur, and the misfire discrimination value LU exceeds the slice level SL when it is predicted that no misfire will occur. The slice level SL can be appropriately set under all operating conditions, and the accuracy of misfiring cylinder determination can be improved.

In addition, if the slice level SL is variably set according to the misfire discrimination value LU level at that time as described above, it does not require a large amount of matching man-hours unlike the map reference method, and There is no need to allocate ROM capacity to slice level setting.

Here, to continue the explanation by returning to the flowchart of FIG. 3 again, once the slice level SL is set according to the misfire determination value LU as described above, in the next step 4, the calculation is performed again in step 2. It is determined whether or not the discriminant value LU is greater than or equal to zero. If the discriminant value LU is a negative value, the process proceeds to step 5, and zero is set to the flag F plus for determining whether the discriminant value LU is positive or negative. do.

In the next step 6, the slice level SL set according to the program shown in the flowchart of FIG. Compare with.

In step 6, the misfire judgment value LU is a negative slice level SL.
If it is determined that the count value cnt is equal to or less than 4, the count value cnt is set to 4 in step 7, and then the process proceeds to step 28.
Further, when it is determined that the misfire determination value LU is greater than or equal to zero (positive), step 7 is skipped and the process proceeds to step 28.

In step 28, it is determined whether or not the count value cnt is zero, and if it is not zero, the count value cnt is decreased by 1 in step 29.

Therefore, when the misfire discrimination value LU continues to be in a negative state, when the misfire discrimination value LU becomes equal to or less than the negative slice level SL, 4 is added to the count value cnt, but at the same time it is decreased by 1, and then the misfire If the discrimination value LU does not fall below the negative slice level SL, it is counted down to zero and remains at zero.

On the other hand, when it is determined in step 4 that the misfire determination value LU is greater than or equal to zero, in step 8 the flag F pl
us, and when the flag Fplus is zero and the misfire discrimination value LU calculated at the previous execution of this program is a negative value, that is, when the misfire discrimination value LU is reversed from negative to positive. If so, first set the flag Fplus to 1 in step 9, and set the misfire judgment value LU next time as well.
is greater than or equal to zero, the flag F pl is set in step 8.
so that us is determined to be 1.

Then, in the next step 10, the count value cnt
is 3 or not. The first time that the misfire discrimination value LU is reversed from negative to positive, and the count value cnt is 3.
, the discriminant value L is less than or equal to the negative slice level SL.
This is a case where the misfire determination value LU is reversed from U, and in this case, the count value cnt is set to 2 in step 11.

In step 12, it is determined whether or not the count value cnt is zero, and if it is not zero, the process proceeds to step 13, where the slice level SL set according to the flowchart of FIG. 4 is compared with the misfire determination [LU].

When the misfire determination value LU is larger than the positive slice level SL, the occurrence of a misfire is determined, the cylinder in which the misfire has occurred is specified in steps 14 to 26, and the number of misfire detections for each cylinder is counted up.

First, in step 14, in order to identify the cylinder in which the misfire has occurred, the cylinder counter Cyl indicating the ignition cylinder is
Determine the value of cnt.

The cylinder counter Cylcnt is set according to the program shown in the flowchart of FIG. The program shown in the flowchart of FIG. 5 is executed every time the reference angle signal REF is output from the crank angle sensor 10 (BTD
This is executed every C70°), and the cylinder number whose ignition timing ADV (ignition advance value) is to be controlled next is determined based on the current reference angle signal REF, and the cylinder number is sent to the cylinder counter Cylcnt. (See Figure 7).

That is, first, in step 51, the current reference angle signal R
It is determined whether or not EF is the ignition reference for the #l cylinder. If the current reference angle signal REF is the ignition reference for the #1 cylinder, the process proceeds to step 52, and the cylinder counter Cylcnt is set to indicate the ignition reference for the #1 cylinder. Set to 1 to indicate.

When it is determined in step 51 that it is not the ignition standard for the #1 cylinder, the process proceeds to step 53, where it is determined whether or not it is the ignition standard for the #2 cylinder. If the current reference angle signal REF is the ignition reference for the #2 cylinder, step 5
At step 4, the cylinder counter Cylcnt is set to 2, which indicates the #2 cylinder.

Also, in step 53, the current reference angle signal REF is set to #2.
If it is determined that it is not the ignition standard for the cylinder, it is determined in step 55 whether or not it is the ignition standard for the #3 cylinder, and if it is the ignition standard for the #3 cylinder, 3 indicating the #3 cylinder is set in Cylcnt in step 56. If the ignition standard is set and it is not the ignition standard for the #3 cylinder, it is the ignition standard for the #4 cylinder that remains, so step 57
Set Cylcnt to 4, which indicates cylinder #4.

Returning to the flowchart of FIG. 3 again, Cylcnt set as described above is determined in step 14. For example, when Cylcnt=2, the process proceeds to step 18, and the count value cnt is 2. Determine whether or not. If the count value cnt is 2, it is determined that the #1 cylinder is misfiring, and step 1
At step 9, the LSTI that counts the number of misfire detections in the #1 cylinder is incremented by one.

An actual example of how the #1 cylinder misfire is determined in this way is as follows:
This is shown in FIG. That is, as shown in FIG. 7, #1
When the discrimination value LU is calculated with the cylinder misfiring,
When the discrimination value LU corresponding to the #1 cylinder is calculated as being less than or equal to the negative slice level SL, the count value cnt is set to 4.
After it is set, it is immediately lowered by 1 and becomes 3, but
The next discrimination value LU corresponding to #3 cylinder is also a negative slice level S
When the value is less than L, the count value cut is again set to 3.

Next, the slice level S for which the discrimination value LU corresponding to #4 cylinder is positive
When the value exceeds L and is reversed from negative to positive, the count value cut is set to 2, so the process proceeds to step 14 since the count value cnt is not zero and the discrimination value LU exceeds the positive slice level SL. , In step 14, it is determined that Cylcnt=2, and as a result, it is finally determined that the #1 cylinder has misfired.

Here, for example, the first discriminant value LU corresponding to the #4 cylinder that is reversed to positive may not exceed the positive slice level SL, and the next discriminant value LU corresponding to the #2 cylinder may exceed the positive slice level SL. , in this case, the process proceeds from step 13 to step 28 at the first inversion from negative to positive, and the count value c
It is determined that nt is not zero (count value cnt=2
), the count value cnt is decreased by 1 to 1 in step 29, and when the next discrimination value LU exceeds the positive slice level SL, the process advances from step 8 to step 12, and the count value cnt is 1. The process then proceeds to step 13, where a misfire is detected. At this time, Cylc
Since nt is set to 1, the process proceeds to step 15, but since the count value cnt is 1, the process proceeds from step 15 to step 17, where it is finally determined that the #1 cylinder has misfired, and the #1 cylinder is The number of misfire detections LSTI is incremented by one.

Furthermore, in the example shown in FIG. 7, only one of the discriminant value LU corresponding to the #1 cylinder and the discriminant value LU corresponding to the #3 cylinder may be less than or equal to the negative slice level SL; Also, the first time that the discriminant value LU is reversed to positive, the count value cnt is set to 2, and #1
A cylinder misfire can be determined.

The determination logic in this embodiment is that in a 4-cylinder internal combustion engine, when the firing order is #1 → #3 → #4 → #2, when the #1 cylinder misfires, for example, the misfire discrimination value LU changes from negative → negative → A misfire determination value L that shows a reversal from positive to positive and is continuously negative.
Fewer than U (one exceeds slice level SL,
Furthermore, when at least one of the misfire discrimination values LU that is continuously positive exceeds the slice level SL, the cylinder corresponding to the misfire discrimination value LU one revolution before the first time that is reversed from negative to positive is determined to be a misfire cylinder. It is something that specifies.

Note that the determination logic is not limited to this embodiment, and basically the misfire determination value L that is less than or equal to the negative slice level SL.
It is also possible to detect the occurrence of a misfire when U is calculated. Even in this case, by setting the slice level SL in the same manner as above, the appropriate slice level LU according to the operating conditions can be set each time. It can be calculated based on the misfire discrimination value LU, and the detection accuracy of misfire cylinders can be improved.The reason for using the above-mentioned judgment logic in this embodiment is to avoid engine rotation fluctuations caused by misfires. This is to ensure detection accuracy even when the rotation is likely to fluctuate, such as when the engine is running or when the engine is idling.

After identifying the misfiring cylinder in steps 14 to 26 and incrementing the number of misfire detections LSTI to LST4 for each cylinder, the process proceeds to step 27 and resets the count (direct cnt to zero). If it is positive and the process advances from step 8 to step 12, a determination is made in step 12 that the count value cnt=o, and misfire detection is not performed.

Then, in the next step 28, it is determined whether or not the count value cnt is zero, and if it is not zero, the count value cnt is decreased by 1 in step 29.

In the next step 30 and subsequent steps, the number of misfire detections LSTI
- Control misfire occurrence display for each cylinder based on the misfire occurrence frequency for each cylinder determined by LST4.

First, in step 30, it is determined whether the count value total, which counts the number of times this program is executed, that is, the number of times it is determined whether or not a misfire has occurred, has reached a predetermined value (for example, 1000). Here, if the count value tota 1 has not been counted up to the predetermined value, the process proceeds to step 31, where the count value total is incremented by 1, and this program is ended. In step 39, misfire occurrence is displayed for each cylinder based on the misfire occurrence frequency for each cylinder.

In step 32, by comparing the LSTI to which the number of misfire detections for the #1 cylinder is set with a predetermined value (for example, 50), the number of misfire detections for the #1 cylinder is determined to be a predetermined number of times during a predetermined period in which the count value total is counted up to a predetermined value. If the misfire in the #1 cylinder is detected at the above rate, the process proceeds to step 33, and the occurrence of the misfire in the #1 cylinder is detected by, for example, an LED installed on the dash board of the vehicle in which the engine 1 is mounted.
It is displayed on a display device, etc. to warn the driver.

Similarly, by comparing the number of misfire detections for cylinders #2 to #4 with LST2 to LST4, which are set, and a predetermined value, it is determined whether or not the misfire frequency is high for each cylinder. Regarding cylinders in which misfires occur frequently, the occurrence of misfires is displayed as described above (steps 34 to 39).

As described above, when the count value to ta I has counted up to a predetermined value, the misfire detection frequency is determined for each cylinder and the misfire occurrence display is controlled.
The number of misfire detections for each cylinder during which the LST1 to LST4 and total are reset to zero and the count value total is counted up again to a predetermined value is LS.
It is set to TI to LST4.

Although the above embodiment has been described for a 4-cylinder internal combustion engine, when a misfire occurs in a 6-cylinder internal combustion engine, the ignition order is, for example, #1 → #5 → #3 → #6 → #2 → #4, for example, # 1
If a misfire occurs in a cylinder, the misfire discrimination value LU reverses in the order of negative → negative → negative → positive → positive → positive according to the ignition order, so at least one of the three consecutively negative misfire discrimination values LU
exceeds the slice level SL, and if at least one of the three continuously positive misfire determination values LU exceeds the slice level SL, then
The #l cylinder before rotation may be determined to be the misfiring cylinder.

In this embodiment, when the misfire occurrence frequency for each cylinder is higher than a predetermined value, that cylinder is displayed to warn the driver. Fail-safe control may be performed.

<Effects of the Invention> As explained above, according to the present invention, even if the operating conditions of the engine speed and engine load change, the slice level can be appropriately set according to the misfire discrimination value level at that time. , the detection accuracy of misfiring cylinders can be improved under all operating conditions, and there is no need to require a large amount of matching man-hours or increase the ROM capacity, unlike the method that refers to the slice level from a map. There is.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a system schematic diagram showing an embodiment of the present invention, and FIGS. 3 to 5 each show details of misfiring cylinder detection control in the above embodiment. Flowchart, FIG. 6 is a time chart showing the setting characteristics of the slice level SL in the above embodiment, FIG. 7 is a time chart showing the timing of misfiring cylinder detection in the above embodiment, and FIG. 8 is a misfire discrimination value in the above embodiment. L
A diagram showing the correction results based on the operating conditions of U, Figure 9 is 4
A time chart for explaining the characteristics of misfire detection based on the discrimination value LU in a cylinder engine. Fig. 10 is a line diagram showing the level change of the misfire discrimination value LU depending on the engine rotation speed and engine load. Fig. 11 is a diagram showing misfire discrimination. FIG. 7 is a diagram showing level changes depending on operating conditions when the value LU is corrected only by the engine rotation speed.

Claims (3)

[Claims] (1) A rotation period measuring means for measuring the period of a predetermined crank angle range of the internal combustion engine, and a misfire determination value, which is a value approximately equivalent to the amount of change in average effective pressure, corresponding to each cylinder based on the measured period. misfire discrimination value calculation means for calculating the misfire discrimination value, maximum swing width detection means for detecting the maximum swing width of the misfire discrimination value calculated by the misfire discrimination value calculation means, and engine operating conditions including at least engine rotational speed and engine load. and an engine operating condition detection means for detecting the misfire discrimination value calculated by the misfire discrimination value calculation means based on the operating condition detected by the engine operating condition detection means, and a level difference of the misfire discrimination value depending on the engine operating condition. misfire discrimination value correction means for correcting and setting the misfire discrimination value in a direction to decrease the misfire discrimination value; a slice level setting unit that sets the slice level to be inside the detected maximum run-out width, and sets the slice level to be outside the maximum run-out width when the corrected misfire determination value run-out width is less than a predetermined value; misfire cylinder detection means for detecting a misfire cylinder by comparing the slice level set by the slice level setting means and the misfire discrimination value calculated by the misfire discrimination value calculation means; Misfiring cylinder detection device for internal combustion engines. (2) The misfire discrimination value correction means multiplies the misfire discrimination value calculated by the misfire discrimination value calculation means by a parameter of engine rotation speed, and divides it by a parameter of engine load, thereby determining the misfire discrimination value of the engine. 2. The misfiring cylinder detection device for an internal combustion engine according to claim 1, wherein the misfire cylinder detection device for an internal combustion engine is configured to perform correction settings in a direction that reduces level differences depending on operating conditions. (3) The internal combustion engine according to claim 1 or 2, further comprising slice level characteristic variable means for variably setting the slice level setting characteristic in the slice level setting means in accordance with the engine rotation speed. Misfiring cylinder detection device.