JPH05202800A - Misfire detecting device of internal combustion engine - Google Patents

Abstract

PURPOSE:To make a correct judgement of the misfire over the extensive operational range of an engine, with a simple constitution. CONSTITUTION:The high level interval and the low level interval of the reference periodical pulse to give the position of the crank angle according to the ignition timing of a 6-cylinder engine 1 are measured by a crank angle detecting means 2, the required time for the specified angle range below and over the reference speed of the crank angle is calculated from the measured value by a misfire detecting means 3, and a judgement on the misfire is made from the calculated value. Thus, it is unnecessary to add a sensor, leading to a simplified and inexpensive constitution with high accuracy, and normalization of the load fluctuation of the engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an ignition system for an internal combustion engine,
The present invention relates to a misfire detection device for an internal combustion engine for detecting misfire due to an abnormality in a fuel system or the like.

[0002]

2. Description of the Related Art Conventionally, an apparatus of this type is disclosed in, for example, Japanese Patent Laid-Open No. 62-26345. This is the cylinder pressure of the engine is detected by the cylinder pressure sensor, and the crank angle at which this cylinder pressure reaches its peak is calculated.
When this peak position exists within a predetermined crank angle period, it is determined to be normal.

[0003]

However, in such a conventional device, in order to detect the peak position of the in-cylinder pressure, it is necessary to continuously measure the in-cylinder pressure for each crank angle in a predetermined period unit. Becomes complicated, and under light load operating conditions, there are two peak values of the in-cylinder pressure, a compression top dead center and a peak due to combustion, and it is difficult to determine that, and when there is a peak before the compression top dead center, There was a problem that misfire could not be judged.

The present invention has been made in order to solve the above-mentioned conventional problems, and has a relatively simple structure, which enables accurate misfire determination in an internal combustion engine over a wide range of engine operating regions. Aim to get.

[0005]

A misfire detecting device for an internal combustion engine according to the present invention utilizes a crank angle reference period signal, and
A misfire detection means is provided for detecting a required time ratio of a predetermined crank angle section dividing one cycle before and after sandwiching a specific reference angle of the cylinder engine, and detecting a misfire from this time ratio. ..

[0006]

The misfire detection device according to the present invention detects the above-mentioned time ratio which differs depending on the presence or absence of misfire, and judges the misfire from the difference between the ratios or the acceleration of the ratio.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an internal combustion engine misfire detection device of the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram of the embodiment. In FIG. 1, 1 is an engine, 2 is a crank angle detecting means for outputting a reference crank angle position used for ignition control, 3 is a misfire detecting means, and a specific reference of the engine 1 is obtained from a signal of the crank angle detecting means 2. It is a misfire detection means for determining a misfire from an angle, for example, a time ratio of a reference period signal before and after a top dead center or acceleration of the time ratio.

FIG. 2 is a block diagram showing the construction of a concrete embodiment constructed by applying the present invention. In FIG. 2, 1 is an engine having cylinders 21 to 26 of # 1 to # 6, 6 is a crankshaft or camshaft of the engine 1, and is a crank angle reference position corresponding to an ignition position of the cylinders 2 to 5. It is a crank angle sensor that outputs a periodic signal every (120 degrees), and corresponds to the crank angle detecting means 2 in FIG.

Reference numeral 7 is a misfire detecting section for detecting the misfire by receiving the output of the crank angle sensor 6, and an interface 8 for transmitting the signal of the crank angle sensor 6 to a microcomputer 9 (hereinafter abbreviated as a microcomputer). , A processing procedure, a memory 10 that stores control information, a timer counter (free running counter) 11 that counts up every fixed time clock, and a C that executes misfire detection calculation processing.
It is configured by a microcomputer 9 having a PU 12 and the like built therein. In the above configuration, the signal of the crank angle sensor 6 is input to the microcomputer 9 via the interface 8 and the arithmetic processing is executed.

Next, the operation of the present invention will be described with reference to the embodiment shown in FIG. 3 (a) and 3 (b) show the pressure change of each cylinder 21 to 26 and the waveform of each part with respect to the crank angle of the 4-stroke cycle 6-cylinder engine. Figure 3
In (a), the solid line is the pressure waveform of the first cylinder # 1 of the engine 1, BDC is the bottom dead center, and TDC is the top dead center. The broken line is the third cylinder # 3, and the alternate long and short dash line is the second cylinder # 3.
The two and two-dot chain lines represent the pressure waveform of the fourth cylinder # 4.

As shown in FIG. 3 (a), in the 6-cylinder engine, the combustion cycle of each cylinder has a phase difference of 120 degrees in crank angle. Note that # 2, # 3, # 4, #
In the pressure waveforms of 5 and # 6, only the compression and explosion strokes are described, and the intake and exhaust strokes are omitted.

As shown in FIG. 3B, the crank angle sensor 6 outputs a signal of 6 ° B falling and a signal of 76 ° B rising of a cycle of 120 degrees corresponding to the ignition timing of each cylinder 21-26. .. This is because the ignition timing control is also performed on the basis of this signal, and therefore the ignition timing control required range is 60 ° B to 20 ° A.
In order to improve the control accuracy of the
A signal of 6 ° B is used to secure the ignition timing as a backup in the case where the control computer fails, which is a position near 76 ° B.

As shown in FIG. 3B, with respect to TDC, for example, a low level section of 50 degrees (hereinafter referred to as L) and a high level of 70 degrees with a cycle of 120 degrees with respect to a position 6 degrees before. Periodic signals distributed to sections (hereinafter referred to as H) are generated.

Generally, the ignition control refers to this signal to control the energization of an ignition coil (not shown). That is, taking the first cylinder # 1 as an example, the crank that starts energization of the ignition coil in the H section of the compression stroke and changes from H to L in the vicinity of TDC at the ignition timing determined corresponding to the rotational speed load. With reference to the signal from the angle sensor 6, the ignition coil is de-energized and the high voltage generated thereby is applied to the ignition plug to ignite it.

Correspondingly, as shown by the solid line in FIG. 3 (a), the in-cylinder pressure is ignited in the explosion stroke at a crank angle of 0 to 720 degrees, and the combustion pressure increases. Similarly, the ignition sequence is # 1 → # 2 → # 3 → # 4 in a cycle of 120 degrees.
→ The combustion cycle is repeated in the order of # 5 → # 6 cylinders.

Next, a specific method for detecting misfire will be described. FIG. 3A and FIG. 3C show the relationship between combustion and each angle. Note that FIG. 3 shows the case where the engine speed is 1000 rpm.

In the first cylinder # 1 shown by the solid line in FIG. 3 (a), the waveform centered on the crank angle of 0 degree is the case of normal combustion, and the air-fuel mixture charged in the intake stroke is pressurized in the compression stroke. It is ignited in the vicinity of compression TDC, rapidly expanded in the explosion stroke, and discharged outside the cylinder in the exhaust stroke.

Next, a misfire state that occurs when ignition fails or the mixing ratio of air and fuel is inappropriate will be described. The pressure waveform centered around a crank angle of 720 degrees corresponds to this, and T
It becomes symmetrical about DC. In the case of this example, there is no combustion, that is, the state of complete misfire is shown. However, if the extent of misfire is slight, the pressure transition in the explosion stroke is at the normal crank angle of 360 to 480 degrees. It becomes an intermediate value of the pressure waveform.

Further, the angular velocity is 0 crank angle in FIG. 3 (c).
As shown at 720 to 720 degrees, the angular velocity increases in response to the torque increase due to the explosion of each cylinder, and decreases in response to the compression.

When a misfire occurs, the crank angle 7
As shown after 20 degrees, since the torque increase due to the explosion cannot be obtained, the angular velocity decreases and continues to decrease until the next explosion of the cylinder # 2 occurs.

In view of this, the present invention intends to judge the misfire from the fluctuation of the angular velocity in the predetermined section of the crank angle generated by the presence or absence of the misfire. FIG. 4 is a time chart of the arithmetic processing of the microcomputer 9 according to the first embodiment of the present invention, and FIG. 5 is a flowchart showing the arithmetic flow of the microcomputer 9. In this embodiment, an ignition cycle signal of the crank angle sensor 6, for example, an H section TL having a crank angle of 70 degrees before 6 degrees before the top dead center TDC shown in FIG. The required time is measured and the misfire is detected from the measurement result.

As shown in FIG. 4 which is a detailed time chart of the crank angle sensor 6 and the calculation process, the signal of the crank angle sensor 6 is obtained every 76 degrees before top dead center (hereinafter referred to as BTDC 76 degrees) with reference to the top dead center TDC. As a result, an interrupt is generated in the microcomputer 9 via the interface 8, the flow of FIG. 5 is executed as an interrupt processing routine, and the flow of FIG. 6 is executed every 6 degrees before top dead center (hereinafter referred to as BTDC 6 degrees). ..

First, in FIG. 5, in step S1, the CPU 12 reads the counter value of the timer counter 11 which counts up every predetermined time clock and stores it in the memory MB76 provided in the memory 10. Here, this stored value indicates the time at BTDC 76 degrees.

Next, the process proceeds to step S2, and it is determined whether or not this process is within the second time from the start of the program by referring to a flag (not shown). This flag is set so as to indicate within the second time at the start of the program. In this case, the flag is cleared, the process branches to YES, and the process ends.

Next, the CPU 12 waits until the signal from the crank angle sensor 6 reaches BTDC 6 degrees. When the engine rotates and reaches the time point of BTDC 6 degrees shown in FIG. 4, an interrupt is generated again by the signal of the crank angle sensor 6, and the flow of FIG. 6 is executed. In FIG. 6, in step S7, the counter value of the timer counter 11 is read,
A value indicating the time at 6 degrees BTDC is stored in the memory MB6.

Then, in step S8, step S of FIG.
1, the required time of the section TL shown in FIG. 4 is calculated by TL = MB76−MB6 (1) and the previously calculated required time TL is stored in the memory 10
After the store to TL _O, it stores the required time calculated in (1) to TL memory 10, the process ends.

Next, B corresponding to the ignition signal of the next cylinder
When the position at TDC 76 degrees is reached, the processing of FIG. 5 is executed again. Here, in step S1, the value of the memory MB76 is updated to prepare for the next process, and in step S1.
In step 2, since the initial flag has been cleared in the previous process, the process proceeds to step S3.

In step S3, the required time of the section T _U shown in FIG. 4 is calculated by T _U = MB6-MB76 (2) with reference to the time at BTDC6 ° given in step S7 of FIG. Then, the time ratio is calculated by T _U + TL / 2 / TL _O (3).

As described above, the crank angle sensor output 7
The 6 ° B and 6 ° B angles are necessary for other reasons. In the present invention which is intended to determine a misfire based on the speed ratio between the crankshaft rotation speed in the compression stroke and the crankshaft rotation speed in the explosion stroke, the L period T _U of the measured crank angle signal output is measured.
If the (50 ° CA period) is used as it is, the measurement section changes from 6 ° B to 44 ° A when viewed in the same cylinder, which is a measurement section in the middle of the explosion stroke (less than half). Therefore, in this embodiment, as the measurement interval of the explosion stroke, were selected _{T U + L L / 2 =} 50 + 70/2 = 85CA ··· (4).

In order to improve the speed detection accuracy, it is advantageous that the measurement section is long. However, in the case where each stroke of each cylinder is independently performed every 180 ° CA, such as four cylinders, the compression stroke and the explosion stroke have 90 measurement sections each.
More than ° CA is possible, but 120 ° CA for 6 cylinders
Since ignition is performed every time, it becomes easy to be influenced by combustion of the adjacent cylinders. Therefore, it is necessary to adopt a method in which the crankshaft velocity measurement section of the explosion stroke is set to 85 ° CA as in the expression (3) and the measurement section is overlapped with two cylinders as in this embodiment.

Next, in step S4, it is judged whether or not this time ratio is larger than a predetermined value corresponding to a preset misfire, and when the judgment result is large, step S5
Branch to and determine that there is a misfire. Also, step S
As a result of the judgment in 4, if the time ratio is smaller than the predetermined value,
The process branches from the NO side of step S4 to step S6. In step S6, the process is determined to be normal, and the process ends.

Thereafter, similarly, the flow of FIG. 5 is executed for 76 degrees of BTDC and the flow of FIG. 6 is executed for 6 degrees of BTDC, and the time ratio corresponding to each cylinder is sequentially calculated.

Figure (d) shows misfire and time ratio T _U + TL / 2.
It is a figure which shows the relationship of / TL _O (%). In the figure,
The solid line is the time ratio value calculated for each of the cylinders # 1 to # 4, and is shown by the broken line in the figure, for example, 158
If the value of (%) is set to the misfire determination value used in step S4 of FIG. 5, cylinder # 1 centered at a crank angle of 720 degrees is used.
It is clear that the misfire can be determined because the time ratio T _U + TL / 2 / TL ₀ increases corresponding to the misfire and is above the predetermined value.

[0034]

As described above, according to the present invention, the rotation fluctuation due to the misfire is measured by measuring the high level period and the low level period of the reference period signal of the crank angle sensor.
Since the required time ratio of the crank angle section representing the compression stroke and the explosion stroke before and after the specific reference angle of each cylinder is calculated, and the misfire is detected from this time ratio, the detection sensitivity is good, and moreover, Since a crank angle sensor used for ignition control is used, there is no need to provide a special sensor, the device can be inexpensive with a simple configuration, and
There is an effect that a highly accurate one can be obtained.

Further, since the time ratio is configured to be divided by the time based on the compression stroke, it has the feature that the load fluctuation of the engine can be normalized.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a configuration of a misfire detection device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a misfire detection device for an internal combustion engine according to a specific embodiment of the present invention.

FIG. 3 is a time chart for explaining the operation of the embodiment of FIG. 2 above.

FIG. 4 is a time chart of the arithmetic processing of the microcomputer in the embodiment of FIG. 2 above.

5 is a flowchart showing a calculation flow for each 76 ° of BTDC of the microcomputer in the embodiment of FIG.

6 is a flowchart showing a calculation flow for every 6 ° of BTDC of the microcomputer in the embodiment of FIG. 2 above.

[Explanation of symbols]

 1 engine 2 crank angle detecting means 3 misfire detecting means 21 cylinder 22 cylinder 23 cylinder 24 cylinder 25 cylinder 26 cylinder 6 crank angle sensor 7 misfire detecting section 8 interface 9 microcomputer 10 memory 11 timer counter 12 CPU

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[Procedure amendment]

[Submission date] June 22, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

Next, the CPU 12 waits until the signal from the crank angle sensor 6 reaches BTDC 6 degrees. When the engine rotates and reaches the time point of BTDC 6 degrees shown in FIG. 4, an interrupt is generated again by the signal of the crank angle sensor 6, and the flow of FIG. 6 is executed. In FIG. 6, in step S7, the counter value of the timer counter 11 is read,
A value indicating the time at 6 degrees BTDC is stored in the memory MB6.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

In step S3, the required time of the section T _U shown in FIG. 4 is calculated by T _U = MB6-MB76 (2) with reference to the time at BTDC6 ° given in step S7 of FIG. Then, the time ratio is calculated by (T _U + TL / 2) / TL _O (3).

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

As described above, the crank angle sensor output 7
The 6 ° B and 6 ° B angles are necessary for other reasons. In the present invention which is intended to determine a misfire based on the speed ratio between the crankshaft rotation speed in the compression stroke and the crankshaft rotation speed in the explosion stroke, the L period T _U of the measured crank angle signal output is measured.
If the (50 ° CA period) is used as it is, the measurement section changes from 6 ° B to 44 ° A when viewed in the same cylinder, which is a measurement section in the middle of the explosion stroke (less than half). Therefore, in this embodiment, As the measurement section of the explosion stroke, T _U + T _L / 2 = 50 + 70/2 = 85 CA (4) was selected.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction content]

Figure (d) shows misfire and time ratio (T _U + TL /
2) it is a graph showing the relationship / TL _O (%). In the figure, the solid line is the time ratio value calculated for each of the cylinders # 1 to # 4.
If the value of 8 (%) is set as the misfire determination value used in step S4 of FIG. 5, the cylinder # centered at a crank angle of 720 degrees is
Time ratio (T _U + TL / 2) / TL corresponding to 1 misfire
It is clear that misfire can be determined because ₀ increases and becomes equal to or greater than a predetermined value.

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (1)

[Claims] 1. A crank angle detecting means for measuring a high level period and a low level period of a reference cycle pulse signal which gives a crank angle position corresponding to an ignition timing of a 6-cylinder engine, and a measurement measured by the crank angle detecting means. A misfire detection device for an internal combustion engine, comprising means for calculating a required time in a predetermined angle section before and after sandwiching a reference angle of the crank angle from the value, and determining misfire based on the calculation result.