JPH09112334A - Misfire detecting device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the position of a misfire decision section proper to both of low and high rotation areas and to ensure high misfire detecting precision throughout a whole rotation area by changing the position of a misfire decision section (a crank angle) according to an engine rotation speed. SOLUTION: An engine control circuit 22 computes a fuel injection amount and an ignition timing according to various engine control programs stored at an ROM 24 to control operation of an engine 11, and the presence of the misfire of each cylinder is decided according to a misfire decision program stored at an ROM 24. Namely, during operation of an engine, the time of a misfire decision section is integrated from the pulse interval of a crank angle signal outputted in a misfire decision section. By calculating a difference therebetween through comparison of the integrating result with the time of a preceding misfire decision section, a rotation speed fluctuation amount is computed, and when a rotation speed decrease amount exceeds a misfire decision value, it is decided that the misfire occurs. This constitution improves misfire detection precision throughout a whole rotation area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire detection device for an internal combustion engine (hereinafter referred to as "engine"), which detects misfire from an amount of decrease in rotational speed.

[0002]

2. Description of the Related Art If a misfire occurs while the engine is operating, the engine speed will decrease.
As shown in Japanese Patent Publication No. 962, a misfire determination section having a predetermined crank angle width is set for each explosion stroke, and within this misfire determination section, the misfire is detected from the pulse interval of the crank angle signal output from the crank angle sensor at constant crank angles. By accumulating the time in the judgment section and comparing it with the time in the previous misfire judgment section, the fluctuation amount of time in the misfire judgment section, that is, the rotation speed fluctuation amount is calculated, and the rotation speed decrease amount (time fluctuation amount) Is judged to be a misfire when exceeds the misfire judgment value. A conventional general misfire detection device has a certain specific misfire determination section (for example, ATDC 145 ° C A to 2 in a 4-cylinder engine).
Between 35 ° C and 90 ° C or ATDC 175 ° C to 295
(Between 120 ° C and 120 ° C) is set.

[0003]

By the way, as shown in FIG. 5, in the low rotation speed region and the high rotation speed region, the degree of decrease in the engine rotation speed after the occurrence of misfire differs, and the position of the lowest point of the engine rotation speed decrease. The (crank angle) tends to shift to the rear side in the higher rotation range, and the return of the engine rotation speed from the lowest point also tends to become slower in the higher rotation range. Therefore, if the position of the misfire determination section (crank angle) is fixed as in the conventional case, the position of the lowest point may deviate from the misfire determination section or be displaced near the boundary of the misfire determination section depending on the rotation range. This reduces the accuracy of detecting the amount of decrease in the rotation speed, which causes the accuracy of misfire detection to decrease.

When the crank angle width in the misfire determination section is increased, the rotation range in which the lowest point falls within the misfire determination section can be expanded. However, the rotation speed reduction amount is the average value of the rotation speed reduction amounts in the misfire determination section. Therefore, if the misfire determination section becomes unnecessarily large, the rotational speed decrease amount will be detected relatively small, and the misfire detection accuracy will decrease (however, the influence of instantaneous fluctuations in rotation due to external disturbances It is necessary to increase the angle width of the misfire determination section to some extent in order to make it difficult to receive). Therefore, ideally, the lowest point is located near the middle of the misfire determination section, and the angular width of the misfire determination section is a range in which the time measurement accuracy is not deteriorated while being less affected by the instantaneous rotation fluctuation due to disturbance. Although it is preferable to narrow it within the range, for the conventional configuration, either one of the setting for the low speed range (prior art 1 in FIG. 5) or the setting for the high speed range (prior art 2 in FIG. 5) is used. However, there is a drawback that the accuracy of misfire detection is reduced in either the low speed range or the high speed range.

The present invention has been made in view of the above circumstances, and therefore an object thereof is to provide a misfire detection device for an internal combustion engine which can ensure high accuracy of misfire detection over the entire rotation range. is there.

[0006]

In order to achieve the above object, the misfire detecting device for an internal combustion engine according to claim 1 of the present invention changes the position (crank angle) of the misfire determination section according to the engine speed. . As a result, the position of the misfire determination section becomes appropriate for both the low speed range and the high speed range,
High misfire detection accuracy can be secured over the entire rotation range.

Further, according to the second aspect, the angular width of the misfire determination section is also changed according to the engine speed. That is, as shown in FIGS. 4 and 5, in the low rotation speed range, the engine rotation speed decreases and rises faster with respect to the crank angle after the occurrence of misfire than in the high rotation speed range. Therefore, in the low rotation speed region, it is possible to accurately detect the rotation speed reduction amount near the lowest point by narrowing the angular width of the misfire determination section to some extent.

On the other hand, in the high revolution range, the engine speed decreases and rises slowly with respect to the crank angle after the occurrence of misfire, and the vicinity of the lowest point becomes almost flat, so the misfire determination section has a certain angular width. Even if it is increased, it is possible to detect the rotation speed decrease amount with high accuracy. Furthermore, since the pulse interval (time) of the crank angle signal also becomes shorter in the high rotation range, increasing the angle width of the misfire determination section is not only advantageous in terms of time measurement accuracy, but also instantaneous rotation due to disturbance occurs. Less susceptible to fluctuations. According to the second aspect of the present invention, the misfire determination section is changed not only in its position but also in its angular width in accordance with the rotation range in consideration of the rotation variation characteristic according to the rotation range.

According to a third aspect of the present invention, when the engine speed is equal to or higher than a predetermined value, the position of the misfire determination section is delayed by a predetermined crank angle and the angular width of the misfire determination section is lengthened. It is a composition. With this configuration,
Both the position and the angular width of the misfire determination section are the best for both the low rotation range and the high rotation range, and the misfire detection accuracy can be further improved over the entire rotation range.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG.
4 through FIG. First, the schematic configuration of the entire engine control system will be described with reference to FIG. An intake pipe 12 of an engine 11, which is an internal combustion engine, is provided with a throttle valve 13 and an intake pipe pressure sensor 14, and a fuel injection valve 15 is provided for each cylinder of the engine 11. The engine 11 is equipped with a distributor 17 that sequentially distributes the high voltage generated by the igniter 16 to spark plugs (not shown) of each cylinder. The distributor 17 is installed once every two revolutions of the crankshaft of the engine 11. Cylinder discrimination sensor 18 for generating pulse signals at a rate
Further, there is provided a crank angle sensor 19 which is a crank angle signal output means for outputting a pulsed crank angle signal each time a predetermined crank angle (30 ° C. in the present embodiment) rotates. Furthermore, the water jacket 20 of the engine 11
A water temperature sensor 21 for detecting the engine cooling water temperature is attached to the.

Detection signals from these respective sensors are input to the engine control circuit 22. This engine control circuit 2
Reference numeral 2 is a microcomputer including a CPU 23, a ROM 24, a RAM 25, a backup RAM 26, an input / output port 27 and the like. The engine control circuit 22 calculates the fuel injection amount and the ignition timing according to various engine control programs stored in the ROM 24 to control the operation of the engine 11, and is also stored in the ROM 24 as shown in FIGS. Whether or not there is a misfire in each cylinder is determined according to the misfire determination program, and when a misfire is detected, the warning lamp 28 is turned on to warn the driver.

Next, the misfire determination method will be described based on FIG. 4 (an example of a four-cylinder engine). In this embodiment, for example, it is divided into a low rotation range and a high rotation range at 5000 rpm, and in the low rotation range, the misfire determination section starts from ATDC 145 ° C and the misfire determination section has an angular width of 90 ° C. on the other hand,
In the high rpm range, the position of the lowest point (crank angle) of the engine speed decrease after misfire occurs is shifted to the rear side compared to the low rpm range, and the engine speed decreases with respect to the crank angle after misfire occurrence.・ Since the rise is delayed and the vicinity of the lowest point becomes almost flat, the misfire judgment section is 3 from the low rotation range.
Start from ATDC 175 ° C with a delay of 0 ° C, and set the angle width of the misfire determination section to 30 ° C from the low rotation range.
Expanded to 120 ° C.

Then, during engine operation, the time TMF0 of the misfire determination section is integrated from the pulse interval of the crank angle signal output in the misfire determination section, and this is calculated as the previous misfire (180 ° C before the 4-cylinder engine). Time of judgment section TMF
By calculating the difference DMF between them by comparing with 1, the fluctuation amount of time in the misfire determination section, that is, the rotation speed fluctuation amount is calculated, and the rotation speed decrease amount (time fluctuation amount DMF) is the misfire judgment value M.
When it exceeds FREF, it is judged as misfire.

This misfire determination process will be described with reference to FIG.
And according to the program of FIG. The T30 interrupt routine shown in FIG. 2 is executed by interrupt processing each time the crank angle signal falls. When this routine is started, first, at step 101, the time T30 from the last fall of the crank angle signal to the next fall of the crank angle signal, that is, the time required for the crankshaft to rotate 30 ° C. ( Hereinafter, it will be referred to as “30 ° C. A time”).

Then, in the subsequent processing of steps 102 to 107, 30 ° C time data T3 from the past 150 ° C before
05 to T300 are sequentially updated. Here, T300 is the current 30 ° C time, and T301 is the previous time (30 ° CA).
It is 30 ° C A hour before, and T302 is two times before (60 ° C).
30 ° C time before A), T303 is 30 ° C time before 90 ° C, and T304 is 30 ° C before 120 ° C.
It is A time, and T305 is 30 ° C. A time before 150 ° C. The numbers in the squares of T30 □ are the crank N in Fig. 4.
o. It corresponds to.

On the other hand, the misfire detection routine shown in FIG. It is executed by interrupt processing at each falling input of the crank angle signal of 0. When this routine is started, first, in step 201, the engine speed NE is read, and in the following step 202, it is determined whether the engine speed NE is lower than 5000 rpm, that is, whether it is a low rotation range or a high rotation range. If the low speed range (NE <
If it is 5000 rpm), the routine proceeds to step 203, where the time TMF0 of the misfire determination section in the low rotation speed region is calculated by the following formula.

TMF0 = T304 + T303 + T302 Here, the misfire determination section in the low speed range is ATDC145.
This is a section with an angular width of 90 ° C that starts from ° C A and ends at ATDC 235 ° C. Within this section, T304, which is the 30 ° C time calculated by the T30 interrupt routine of Fig. 2,
The time TMF0 of the misfire determination section in the low rotation speed region is calculated by adding T303 and T302.

If it is determined in step 202 that the engine speed is in the high rotation range (NE ≧ 5000 rpm), step 2
04, misfire determination section time TMF0 in the high speed range
Is calculated by the following equation. TMF0 = T303 + T302
+ T301 + T300 Here, the misfire determination section in the high revolution range starts from ATDC 175 ° C and then ATDC 295.
This is a section with an angular width of 120 ° C ending at 0 ° C, and T303, T302, T30 which is 30 ° C time in this section.
1, T300 is summed up to calculate the time TMF0 of the misfire determination section in the high speed region.

After the time TMF0 of the misfire determination section is calculated according to the rotation region as described above, the routine proceeds to step 205, where the time TMF0 of the misfire determination section calculated this time is set to the previous time (180 ° C. before the four cylinder engine). By calculating the difference DMF between the two in comparison with the time TMF1 in the misfire determination section, the amount of time variation in the misfire determination section, that is, the rotation speed variation is calculated. The processing of these steps 202 to 205 functions as a rotation speed fluctuation amount calculation means in the claims.

Thereafter, at step 206, the time variation D
MF (rotational speed decrease amount) is compared with the misfire determination value MFREF. If DMF> MFREF, misfire is determined. At this time, the misfire determination value MFREF is equal to the engine speed NE.
It is calculated based on the engine rotation speed NE and the engine load from a two-dimensional map with the engine load as a parameter. If it is determined that the misfire (DMF> MFREF), the process proceeds to step 207, the warning lamp 28 is turned on to warn the driver, and the misfire information is stored in the backup RAM 26 in the following step 208. In step 209, the time TMF0 of the misfire determination section calculated this time is stored as the time TMF1 of the previous misfire determination section and used for the next misfire determination. If it is not determined in step 206 that a misfire has occurred (DMF ≦ MFREF), the process immediately proceeds to step 209, the time TMF0 of the misfire determination section calculated this time is stored as the time TMF1 of the previous misfire determination section, and Exit the routine. Step 20 above
The processing of No. 6 functions as a misfire determination means in the claims.

According to the embodiment described above, both the position and the angular width of the misfire determination section are changed between the low rotation range and the high rotation range. That is, as shown in FIGS. 4 and 5, the position of the lowest point (crank angle) of the engine speed decrease after the occurrence of misfire is shifted to the rear side in the higher rotation range, and the engine speed from the lowest point is changed. The return condition also tends to be slower in the higher rotation range. In other words, in the low speed range, the engine speed decreases and rises faster with respect to the crank angle after the occurrence of misfire than in the high speed range. Therefore, in the low rotation range, the position of the misfire determination section is shifted to the front side compared to the high rotation range,
By narrowing the angular width of the misfire determination section to some extent, it is possible to accurately detect the rotational speed decrease amount near the lowest point.

On the other hand, in the high engine speed range, the position of the lowest point (crank angle) of the engine speed decrease after occurrence of misfire shifts to the rear side, and the engine speed decreases or rises with respect to the crank angle after occurrence of misfire. Becomes slower and the vicinity of the lowest point becomes almost flat, so in the high rotation range, the position of the misfire determination section is shifted to the rear side and the angular width of the misfire determination section is increased to some extent to reduce the rotation speed decrease amount. Can be detected accurately. Further, since the pulse interval (time) of the crank angle signal becomes short in the high rotation range, it is advantageous to increase the angle width of the misfire determination section in terms of time measurement accuracy, and instantaneous rotation fluctuation due to disturbance. Less susceptible to.

In this embodiment, the rotation fluctuation detection accuracy is improved over the entire rotation range by changing both the position and the angular width of the misfire determination section in consideration of the rotation fluctuation characteristic according to the rotation range. Although it improves the misfire detection accuracy, only the position of the misfire determination section may be changed according to the engine rotation speed without changing the angular width of the misfire determination section. The purpose of the period can be achieved.

Further, in this embodiment, the boundary between the high rotation speed region and the low rotation speed region is set to 5000 rpm.
00 rpm, 4500 rpm, 4000 rpm, 350
It may be either 0 rpm, .... Further, the rotation region may be divided into three or more regions, and the position and the angular width (may be only the position) of the misfire determination section may be changed for each region.

Further, in step 205 of FIG. 3, the difference DMF between the time TMF0 of the misfire determination section calculated this time and the time TMF1 of the previous misfire determination section is calculated to estimate the rotation speed fluctuation amount. The rotational speed fluctuation amount may be estimated by calculating the difference DMF between the angular velocity K / TMF0 in the present misfire determination section and the angular velocity K / TMF1 in the previous misfire determination section by the following formula. DMF = K / TMF1-K / TMF0 (K: constant) Further, JP-A-61-114040 and JP-A-57-
The method for calculating the rotation fluctuation amount described in Japanese Patent No. 106834 may be used.

In this embodiment, the crank angle signal is set to 3
Although it is set to occur every 0 ° C A, it is not limited to this.
For example, it may be generated every 15 ° C. Also,
It goes without saying that the number of engine cylinders is not limited to four.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire system showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a processing flow of a T30 interrupt routine.

FIG. 3 is a flowchart showing a processing flow of a misfire detection routine.

FIG. 4 is a time chart illustrating the relationship between the engine rotation range and the position / angle width of the misfire determination section.

FIG. 5: Positions of conventional engine rotation range and misfire determination section
Time chart explaining the relationship with the angular width

[Explanation of reference numerals] 11 ... Engine (internal combustion engine), 14 ... Intake pipe pressure sensor, 18 ... Cylinder discrimination sensor, 19 ... Crank angle sensor (crank angle signal output means), 22 ... Engine control circuit (rotation speed fluctuation amount calculation) Means, misfire determination means).

Claims (3)

[Claims] 1. A crank angle signal output means for periodically outputting a crank angle signal in accordance with rotation of an internal combustion engine, and a rotational speed by obtaining a time of a misfire determination section having a predetermined crank angle width based on the crank angle signal. A rotation speed fluctuation amount calculation means for calculating a fluctuation amount, and a misfire determination means for determining the presence or absence of a misfire based on the rotation speed fluctuation amount are provided, and the rotation speed fluctuation amount calculation means determines the position of the misfire determination section. A misfire detection device for an internal combustion engine, which is changed according to an engine rotation speed. 2. The misfire detection device for an internal combustion engine according to claim 1, wherein the rotational speed fluctuation amount calculation means also changes the angular width of the misfire determination section in accordance with the engine rotational speed. 3. The rotation speed fluctuation amount calculating means delays the position of the misfire determination section by a predetermined crank angle and lengthens the angular width of the misfire determination section when the engine rotation speed is equal to or higher than a predetermined value. The misfire detection device for an internal combustion engine according to claim 2.