JPH03246347A - Abnormality detector for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the wrong detection of misfiring at the time of travel on a bad road or the like, by calculating a difference at a predetermined crank angle between a real engine revolution velocity value and a revolution velocity value which, and deciding that misfiring has occurred at an internal combustion engine when this difference has surpassed a reference value. CONSTITUTION:A revolution velocity detecting means M2 detecting the engine revolution velocity of an internal combustion engine M1, is equipped, and a real engine revolution velocity value continuously detected by means of this detecting means M2, is moderation-controlled by means of a moderating control means M3. And a difference between a revolution velocity value after the moderating control and a real engine revolution velocity value at a predetermined crank angle at the internal combustion engine M1, is calculated by means of a velocity difference calculating means M4, and when a velocity difference calculated hereat has surpassed a previously set reference value, it is decided by means of a misfiring decision means M5 that misfiring has occurred at the internal combustion engine M1. As a result, at the time of travel on a bad road, it is arranged so that misfiring may not be decided just because of a small difference between the real engine revolution velocity value and the revolution velocity value after.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an abnormality detection device for an internal combustion engine, and more particularly to an abnormality detection device for detecting misfires such as poor ignition and flame propagation in an internal combustion engine. .

[Prior Art] Conventionally, a device for detecting a misfire in an internal combustion engine detects the crankshaft rotational speed after and before the expansion stroke of a reciprocating engine, as shown in Japanese Patent Laid-Open No. 19532/1983. However, it is known that a misfire is determined when the rotational speed difference is less than a set value. In other words, the rotational speeds are different between the expansion stroke and the compression stroke, and the former is faster when ignition occurs normally, but when a misfire occurs,
Based on the fact that the difference is almost eliminated, a misfire is determined when the rotational speed difference is less than a predetermined value, that is, when the crankshaft is not accelerated during the expansion stroke.

In addition, there is also known a device that detects the rotational speed of the internal combustion engine at each top dead center, and determines that a misfire has occurred when the speed difference is greater than or equal to a set value. In other words, when the internal combustion engine is burning normally, the difference in rotational speed at each top dead center is small;
When a misfire occurs, the rotational speed decreases and the speed difference increases, so when this speed difference is equal to or greater than a set value, it is determined that a misfire has occurred.

[Problems to be Solved by the Invention] However, with such a device, when a vehicle drives on a rough road, the crankshaft rotation speed becomes unstable due to unevenness of the road surface, and even though no misfire has occurred, the crankshaft rotation speed becomes unstable. Regardless of the situation, it may be determined that there is a misfire. This is because the contact between the wheels and the road surface is not constant due to unevenness of the road surface, and the wheels may leave the road surface or make strong contact with the road surface, causing the load on the internal combustion engine to fluctuate, resulting in unstable crankshaft rotation speed. This is because. Therefore, even though the rotational speed is originally supposed to increase in a stroke, the load increases and the rotational speed does not increase, or vice versa. Therefore, a problem has arisen in that accurate misfire detection is not performed.

The abnormality detection device for an internal combustion engine of the present invention has been made to solve the above-mentioned problems, and its purpose is to improve misfire detection accuracy even when driving on rough roads.

[Means for Solving the Problems] An abnormality detection device for an internal combustion engine according to the present invention (as illustrated in FIG. 1, an abnormality detection device for detecting a misfire in an internal combustion engine M1, a rotational speed detection means M2 for detecting the engine rotational speed of the internal combustion engine M]; a smoothing processing means M3 for smoothing the actual engine rotational speed value continuously detected by the rotational speed detection means M2; a speed difference calculation means M4 for calculating a difference between the rotation speed value after the smoothing process and the actual engine rotation speed value at a predetermined crank angle; and the speed difference calculation means M
The present invention further comprises a misfire determining means M5 that determines that a misfire has occurred in the internal combustion engine M1 when the difference calculated in step 4 exceeds a preset reference value.

[Operation] The abnormality detection device for an internal combustion engine of the present invention having the above configuration (the speed difference calculation means M4 calculates the actual engine rotational speed value continuously detected by the rotational speed detection means M2 and the smoothing processing means M
3, the difference at a predetermined crank angle between the actual engine rotational speed value and the rounded rotational speed value is calculated. Then, the misfire determining means M5 determines that a misfire has occurred in the internal combustion engine M1 when this difference reaches a preset reference value.

Therefore, in the event of a misfire where the rotational speed value changes only in a decreasing direction, the difference between the actual engine rotational speed value and the rotational speed value after smoothing is large, so it is determined that a misfire has occurred, but when driving on a rough road Since the rotation speed value repeats increases and decreases, the difference between the actual engine rotation speed value and the rotation speed value after the smoothing process is small and is not determined to be a misfire.

[Embodiments] In order to further clarify the configuration and operation of the present invention described above, preferred embodiments of the abnormality detection device for an internal combustion engine of the present invention will be described below.

FIG. 2 is a schematic configuration diagram of an abnormality detection device for detecting a misfire in an internal combustion engine as an embodiment of Yoshiki's invention.
The internal combustion engine targeted for abnormality detection in this embodiment is a 4-cylinder, 4-cycle engine.

As shown in the figure, the abnormality detection device 1 includes a rotation angle sensor 3.
Intake air amount sensor5. Warning light7. An electronic control device 9 is provided.

The rotation angle sensor 3 detects every ]/24 revolutions of the camshaft of a distributor (not shown), that is, every crank angle of 3
It outputs one pulse signal every 0°CA ('CA is an abbreviation for crank angle), and the period of this pulse signal determines the rotational speed of the internal combustion engine 10 (the rotational speed corresponds to the number of revolutions, so (Hereinafter, it will be explained as the rotation speed Ne)
is required.

That is, the rotation speed Ne is obtained as follows. Further, each time the crank angle reaches the top dead center TDC (every 180° CA), a separate signal is output, and the timing of the top dead center can also be detected.

The intake air amount sensor 5 is provided on the air intake side of the internal combustion engine 10 to detect the intake air amount of the internal combustion engine 10, and uses a well-known air flow meter.

The warning light 7 is provided in the inner panel of the vehicle (not shown), and is an indicator light that notifies the riding equipment of an abnormality when a misfire is detected by the misfire detection process described later.

The electronic control device 9 includes a CPU 91 .
ROM92. RAM93. Backup RAM94
, an input/output interface 95, and a bus 96 that interconnects these. The backup RAM 94 is
Power is directly supplied from a battery (not shown) 2 This is a memory that retains data regardless of whether an ignition switch (not shown) is turned on or off. The input/output interface 95 also includes a waveform shaping circuit, an A/D converter, a drive circuit, etc., and the rotation angle sensor 3. A detection signal from the intake air amount sensor 5 is input, and a drive signal is output to the warning light 7 in the event of an abnormality.

Next, the misfire detection process executed by the electronic control unit 9 will be explained with reference to the flowchart of FIG. 3. This process is performed based on the signal from the rotation angle sensor 3.
Executed every 0'CA. First, a signal from the rotation angle sensor 3 corresponding to the rotation speed Ne is acquired (step) 00
), then the intake air amount sensor 5 corresponding to the intake air amount O
A signal from the camera is captured (step 110). Subsequently, the rotational speed Ne is smoothed (step 120).

This process smoothes the transition of the rotational speed Ne obtained for each crank angle of 30'CA, and is performed as follows.

The rotation speed N s after the previous smoothing process obtained by executing the misfire detection process every 306 CA of crank angle
From i-1 and the current rotation speed Nei, the rotation speed Nsi after the smoothing process is determined as Ns,=(n-1)Nsi-1+Ne (n is a constant).

FIG. 4(A) shows the transition between the rotational speed Ns obtained by this smoothing process and the actual rotational speed Ne.

The waveform shown by the broken line is the rotation speed Ns after the smoothing process,
The waveform shown by the solid line is the actual rotation speed Ne. This figure shows that the vehicle is running on a smooth road surface, and the internal combustion engine
This is the waveform when combustion is complete. In this case, the rotational speed Ne for each top dead center TDC has almost the same value, and the rotational speed Ns after the smoothing process has a small amplitude fluctuation near the center of the waveform of the rotational speed Ne. From this state, the waveform when a misfire occurs in the internal combustion engine 10 is as follows:
It is shown in the same figure (a). As shown in the figure, when a misfire occurs at time t1, the rotational speed Ne further decreases even though the crank angle is at the top dead center TDC, and when the next top dead center TDC
It increases at (time t2). Then, after time t3, the original normal state is restored. Therefore, at the next top dead center TDC (time t2) where a misfire occurs, the rotational speed Ne decreases greatly, but the rotational speed Ns after the smoothing process is slightly smaller than the average value of the rotational speed Ne up to that point. Since it only decreases, the difference between the two is large.

That is, when a misfire occurs, the rotational speed Ns after the smoothing process, which had been changing near the center between the maximum value and the minimum value of the rotational speed Ne, decreases at time t2; Since the rotation speed Ne is higher than the center (intermediate value) of the thick minimum values, the difference between the rotation speed Ne and the rotation speed Ns is large.

On the other hand, while driving on a rough road, even if combustion in the internal combustion engine 10 is completely performed, due to the influence of the unevenness of the road surface, as shown in FIG. The waveform is not the same every 80° CA, and its maximum and minimum values vary, and the rotational speed Ne increases and decreases as a whole. Therefore, the rotational speed Ns after the smoothing process changes along the entire flow, and takes a value approximately near the center of the waveform of the rotational speed Ne. Therefore, although the amplitude of the rotational speed Ne is large, the difference from the rotational speed Ns after the smoothing process is not very large.

In this way, it has been confirmed through experiments that the difference between the rotational speed Ns after smoothing and the actual rotational speed Ne becomes relatively large when the difference is due to a misfire, and relatively small when the difference is due to driving on a rough road. There is.

Based on this, a misfire in the internal combustion engine 10 is detected by the process from step 30 in FIG. 3 below.

In step]30, it is determined whether the crank angle is at the top dead center TDC. If it is not the top dead center TDC, this process is once terminated, and if it is the top dead center TDC, the difference △Ne (△Ne =
N s −N e (hereinafter referred to as rotational difference ΔNe) is calculated (step 40).

That is, every time the crank angle is rotated to 180° C., a rotational difference ΔNe, which is the difference between the rotational speed Ne at the top dead center TDC and the rotational speed Ns after the smoothing process, is calculated.

Subsequently, it is determined whether the value of the rotational difference ΔNe is negative (step 50). When a misfire occurs in the internal combustion engine 10, the rotation speed Ne is always smaller than the rotation speed Ns after the smoothing process, so if △Ne≧0,
This process is temporarily terminated assuming that no misfire has occurred in the internal combustion engine 10. In the case of △Ne〈O, the rotation difference △Ne
Determine whether the absolute value of the reference value is greater than 1 (
Step] 60). As shown in FIG. 5, this reference value 1 is determined based on a map M set from the rotational speed Ne and the engine load Q/Ne. Therefore, 1 is set as the reference value according to the engine load Q/Ne and the rotational speed Ne.

The judgment in step 160 is rNOJ, that is, 1△Nel≦
If Ki, it is assumed that no misfire has occurred in the internal combustion engine 10, and this process is temporarily terminated. If YES, it is assumed that a misfire has occurred in the internal combustion engine 10, and the process proceeds to step 170. That is, as shown in Fig. 4 (a), the absolute value of the rotational difference △Ne increases during a misfire, so
If LΔNe1>Ki, it is determined that a misfire has occurred.

In addition, the reference value Kil&, as shown in Figure 4 (T),
By setting a value larger than the absolute value of the rotational difference ΔNe that is normally considered when driving on a rough road, when normal combustion is performed even when driving on a rough road, the determination at step 160 becomes "No".

The process at step 170 is a misfire diagnosis process. This process outputs a drive signal to turn on the warning light 7 in order to notify the occupants that an abnormality has been detected in the internal combustion engine 10, and also stores a code indicating misfire detection in the backup RAM 93. . Therefore, by lighting the warning light 7, it is possible to know whether there is an abnormality in the internal combustion engine [O], and by reading the code at a checker (on the illustrated route) after driving, it is possible to know the nature of the abnormality. When the process of step 170 is completed, this misfire detection process is temporarily ended.

Although the reference value K11t and the conversion map M were set in this embodiment,
It may be set to a constant value regardless of the intake air amount O.

The abnormality detection device for an internal combustion engine according to the present embodiment described above calculates the rotation speed Ne for each crank angle of 30°C and the rotation speed Ns obtained by smoothing this, and calculates the rotation speed of both at each top dead center TDC. A difference ΔNe is calculated, and when the absolute value of the rotation difference ΔNe is greater than a reference value of 1, it is determined that a misfire has occurred in the internal combustion engine 10. In other words, when driving on a rough road, the rotational speed N
Although the variation in e is large, the rotational difference ΔNe is smaller than when there is a misfire, so misfires are not detected erroneously when driving on rough roads. As a result, misfire detection can be performed without being affected by road surface conditions, and misfire detection accuracy is improved.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way. For example, the crank angle at which the rotational difference ΔNe is calculated is set to the top dead center TDC.
Instead, it may be calculated for each predetermined crank angle interval before or after that, and it goes without saying that the present invention can be implemented in various ways without departing from the gist of the present invention.

Effects of the Invention As detailed above, according to the internal combustion engine abnormality detection device of the present invention, the difference at a predetermined crank angle between the actual engine rotational speed value and the rotational speed value obtained by smoothing the actual engine rotational speed value is calculated, When this difference exceeds a reference value, it is determined that a misfire has occurred in the internal combustion engine. In other words, while the rotational speed at a given crank angle varies greatly when driving on rough roads, the difference between the two obtained by smoothing is smaller than when there is a misfire, so misfire misdetection when driving on rough roads is Not done. As a result, misfire detection can be performed without being affected by road surface conditions, and misfire detection accuracy is improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the basic configuration of the present invention, FIG. 2 is a schematic configuration diagram of an abnormality detection device, FIG. 3 is a flowchart showing misfire detection processing, and FIG. 4 is a graph showing changes in rotation speed. FIG. 5 is a map for determining the reference value of 1. 3...Rotation angle sensor 9...Electronic control device]O
・・・Internal combustion engine

Claims (1)

[Claims] 1 An abnormality detection device for detecting a misfire in an internal combustion engine, comprising a rotation speed detection means for detecting the engine rotation speed of the internal combustion engine, and an actual engine rotation speed value continuously detected by the rotation speed detection means. a smoothing processing means for performing smoothing processing; a speed difference calculation means for calculating a difference between the rotational speed value after the smoothing processing and the actual engine rotational speed value at a predetermined crank angle of the internal combustion engine; and the speed difference calculation means. An abnormality detection device for an internal combustion engine, comprising misfire determining means for determining that a misfire has occurred in the internal combustion engine when the difference calculated by the means exceeds a preset reference value.