JPH05332193A - Misfire detection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent misjudgment of misfire by detecting rough road running time by a comparatively simple structure. CONSTITUTION:A device in which a crank angle position of an internal combustion engine is detected and misfire is judged from a crank angle position signal has a vehicle height sensor 13 and a G sensor 14 as vehicle body fluctuation rate detection means. Fluctuation of the vehicle body is detected based on at least one of signals from the sensors 13 and 14, and it is judged whether a road is rough or not. When it is judged to be rough misfire judgment is inhibited.

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, and more particularly to a misfire detection device for an internal combustion engine which is capable of preventing an erroneous misfire determination when traveling on a bad road.

[0002]

2. Description of the Related Art Conventionally, as this type of misfire detection device, for example, there is one shown in FIGS. FIG. 7 is a functional block diagram of this conventional misfire detection device, where M1 is an engine,
M2 is a crank angle detecting means that is connected to the engine M1 and outputs a reference crank angle position used for ignition control. M3 is a misfire detection unit which is connected to the crank angle detection unit M2 and includes a time detection unit that detects a time ratio and a misfire determination unit that determines misfire.
3 indicates the engine M1 based on the signal from the crank angle detecting means M2.
The misfire is determined from a specific reference angle of, for example, the time ratio of the reference period signals before and after the top dead center, or the acceleration of this time ratio.

FIG. 8 is a block diagram embodying FIG.
In FIG. 8, 1 is an engine having cylinders 2 to 5 of # 1 to # 4, 6 is connected to a crank shaft or a cam shaft of the engine 1, and is provided for each crank angle reference position corresponding to the ignition position of the cylinders 2 to 5 ( It is a crank angle sensor that outputs a periodic signal at 180 degrees, for example. Reference numeral 7 denotes a misfire detection unit that receives the output of the crank angle sensor 6 and detects a time ratio, and detects a misfire based on this time ratio. The misfire detection unit 7 outputs a signal from the crank angle sensor 6 to a microcomputer 9 (hereinafter Interface (I / F) 8 for transmission to a microcomputer)
And a memory 9 that stores processing procedures and control information, a timer counter (free running counter) 11 that counts up every fixed time clock, and a microcomputer 9 that includes a CPU 12 that executes misfire detection calculation processing. There is. 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 will be described with reference to FIGS. First, the relationship between the crank angle sensor 6 and ignition and combustion will be described. 9 (a) and 9 (b) show the pressure change of each cylinder 2 to 5 and the waveform of each part with respect to the crank angle of the four-stroke cycle four-cylinder engine. In FIG. 3A, 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 indicates the third cylinder #
3, the one-dot chain line is the second cylinder # 2, the two-dot chain line is the fourth cylinder # 4
Is a pressure waveform of. As shown in FIG. 9, in the four-cylinder engine, the combustion cycles of each cylinder have a phase difference of 180 degrees in crank angle. The second cylinder # 2, the third cylinder # 3,
Regarding the pressure waveform of the fourth cylinder # 4, only the compression and explosion strokes are described, and the intake and exhaust strokes are omitted.

As shown in FIG. 9 (b), the crank angle sensor 6 corresponds to the ignition timing of each of the cylinders 2 to 5 at a cycle of 180 degrees with respect to the position 6 degrees before TDC, for example, at a cycle of 180 degrees. A periodic signal is generated which is distributed into a Low section of 110 degrees (hereinafter referred to as L) and a High section of 70 degrees (hereinafter referred to as H). Generally, ignition control refers to this signal,
The energization of an ignition coil (not shown) is controlled.

That is, taking the first cylinder # 1 as an example, the energization of the ignition coil is started in the H section of the compression stroke at the crank angle of 180 to 360 degrees, and the ignition timing determined corresponding to the rotational speed load. With reference to the signal of the crank angle sensor 6 which changes from H to L in the vicinity of TDC, 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. 9 (a), the in-cylinder pressure is ignited in the explosion stroke at a crank angle of 360 ° to 540 °, and the combustion pressure increases. In the same manner, the ignition order is # 1 → # 3 → # 4 → # in 180 degree cycles.
The combustion cycle is repeated from 2 → # 1.

Next, a specific method for detecting misfire will be described. 9 (a) and 9 (c) show the relationship between combustion and angular velocity. In addition,
This figure 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 centering on the crank angle of 360 degrees is the case of normal combustion, and the air-fuel mixture charged in the intake stroke is pressurized in the compression stroke and compressed. Is ignited in the vicinity of the 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. A pressure waveform centered on a crank angle of 1080 degrees corresponds to this, and is symmetrical with respect to TDC. In the case of this example, there is no combustion, that is, a state of complete misfire is shown. However, if the degree of misfire is slight, the pressure transition in the explosion stroke is at a crank angle of 360 ° to 540 ° during normal operation. It becomes an intermediate value of the pressure waveform. Further, as shown in the crank angle of 0 to 1080 degrees in FIG. 9C, the angular velocity has a characteristic that the angular velocity increases in accordance with the torque increase due to the explosion of each cylinder and decreases in accordance with the compression.

When a misfire occurs, the crank angle is 1
As shown after 080 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 third cylinder # 3 occurs. Therefore, in the method of the conventional example, attention is paid to this, and the misfire is determined from the fluctuation of the angular velocity in the predetermined section of the crank angle caused by the presence or absence of the misfire.

FIG. 10, FIG. 11 and FIG. 12 are a time chart and calculation flowchart of the microcomputer 9. In this conventional example, the ignition cycle signal of the crank angle sensor 6, for example, an H section TL of a crank angle of 70 degrees before 6 degrees before the top dead center TDC shown in FIG. 9B, and an L section TU of 110 degrees sandwiching the TDC. The time required for is measured and the misfire is detected from the time ratio.

FIG. 10 shows a detailed time chart of the crank angle and the calculation process. Before TDC 7 based on TDC
An interrupt is generated in the microcomputer 9 via the interface 8 by the signal of the crank angle sensor 6 every 6 degrees (hereinafter referred to as BTDC 76 °), and the flow of FIG. 11 is executed as an interrupt processing routine, and 6 degrees before the top dead center. (Hereinafter BTDC
The flow of FIG. 12 is executed every 6).

First, in FIG. 11, in step S61, the CPU 12 reads the counter value of the timer 11 that counts up every predetermined time clock and stores it in the memory MB76 (not shown) provided in the memory 10. Here, this stored value indicates the time at BTDC 76 degrees. Next, the process proceeds to step S62, and it is determined whether or not this process is the first time from the start time of the program by referring to a flag (not shown). This flag is set to indicate the first time at the start of the program. In this case, clear this flag and set 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 BTDC 6 degrees shown in FIG. 10, an interrupt is generated again by the signal of the crank angle sensor 6,
The second flow is executed. In step S71, the timer 1
The counter value of 1 is read and a value indicating the time at 6 degrees BTDC is stored in the memory MB6 (not shown). Next, at step S72, the time required for the section TL shown in FIG. 10 is determined by referring to the time at BTDC 76 degrees given at step S61 of FIG.

TL = MB76-MB6 (1)

Memory MTL (not shown) calculated by
And the process ends. Next, when the position of BTDC 76 degrees corresponding to the ignition signal of the next cylinder is reached, the processing of FIG. 11 is executed again. Here, the value of the memory MB76 is updated in step S61, and the next process is prepared, and the initial flag is cleared in the previous process in step S62. Therefore, the process proceeds to step S63. Step S
In 63, the BTD given in step S71 of FIG.
The section TU shown in FIG. 10 with reference to the time at C6 degrees
The time required

TU = MB6-MB76 (2)

Then, the time ratio is calculated by

Time ratio = TU / TL (3)

It is calculated by Then, step S64
Then, it is determined whether or not this time ratio is larger than a predetermined value corresponding to a preset misfire. If it is larger, it is determined that the process branches to step S65, and if it is smaller,
The process branches to step S66, is determined to be normal, and the process ends. In the same manner, the flow of FIG. 11 is executed at 76 degrees of BTDC and the flow of FIG. 12 is executed at 6 degrees of BTDC, and the time ratios corresponding to each cylinder are sequentially calculated.

FIG. 9 (d) shows misfire and time ratio TU / TL.
It is a figure which shows the relationship of (%). In the figure, the solid line is the time ratio value calculated for each of the cylinders # 1 to # 4. For example, the value of 158 (%) indicated by the broken line in the figure is used in step S64 of FIG. If set to a value, the time ratio TU / TL increases corresponding to the misfire of the first cylinder # 1 centering on the crank angle of 1080 degrees, and becomes greater than or equal to a predetermined value, so it is clear that misfire can be determined.
In addition, there is also a method in which the arithmetic expression of the misfire determination value is an arithmetic expression based on the crank angle cycle other than the equation (3) in order to increase the misfire detection sensitivity.

As described above, in the conventional method, since the crank angle sensor used for ignition control is used, it is not necessary to provide a special sensor, and the time ratio is divided by the time based on the compression stroke. The load fluctuation of the engine can be normalized.

[0022]

However, since the above-mentioned conventional device is constructed as described above, when the angular velocity or the angular acceleration of the crank angle fluctuates due to a force other than combustion of the engine, that is, the vehicle is bad. When a force is irregularly applied to the crankshaft by the force transmitted from the wheels when traveling on a road, the cycle between the predetermined crank angles fluctuates despite the normal combustion (the above TL and TU). Fluctuated), and there was a problem of misjudging that there was a misfire.

In view of the above points, the present invention has been made to solve the above problems, and misfires an internal combustion engine that does not make an erroneous determination even when the vehicle is traveling on a bad road. The purpose is to obtain a detection device.

[0024]

In order to achieve the above object, an internal combustion engine misfire detection device according to the present invention is arranged such that a vehicle travels on a rough road by means of a vehicle acceleration detection means or a vehicle height detection means. If it is determined that the road is bad, the misfire determination is prohibited and the misfire misjudgment is prevented.

[0025]

Therefore, according to the present invention, when the vehicle is traveling on a bad road, it is possible to determine the bad road by the vehicle acceleration detection means or the vehicle height detection and prohibit the misfire determination.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. Embodiment 1 FIG. 1 is a block diagram showing a first embodiment of the misfire detection device of the present invention. In the figure, 1 is an engine having cylinders 2 to 5 of # 1 to # 4, 6 is connected to a crank shaft or a cam shaft of the engine 1, and is provided for each crank angle reference position corresponding to the ignition position of the cylinders 2 to 5 ( It is a crank angle sensor that outputs a periodic signal at 180 degrees, for example. Reference numeral 7 is a misfire detection unit that receives the output of the crank angle sensor 6 and detects the time ratio, and detects misfire based on this time ratio. The misfire detection unit 7 transmits the signal of the crank angle sensor 6 to the microcomputer 9. An interface (I / F) 8, 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 CPU 12 that executes misfire detection calculation processing.
It is constituted by a microcomputer 9 having built-in components such as.

Further, 13 is a vehicle height sensor for detecting the vehicle height, and a digital signal interface 8 is provided according to the vehicle height.
To the microcomputer 9 via. Reference numeral 14 is an acceleration sensor for detecting the acceleration of the vehicle body, that is, a G sensor, and outputs an analog signal to the microcomputer 9 via the interface 8 according to the acceleration. That is, this embodiment is different from the conventional example shown in FIG. 8 in that the vehicle height sensor 13 and G
The detection signal from the sensor 14 is used to determine whether the vehicle is traveling on a bad road, and the misfire determination is prohibited when the vehicle is judged to be a bad road. Since the other configurations are the same as those in FIG. 8 described in the conventional example, the description thereof will be omitted.

Next, the operation of the above embodiment will be described with reference to FIGS. 2 to 4 are flowcharts showing the operation of the microcomputer 9, FIGS. 2 and 3 are executed at regular intervals, and FIG. 4 is executed at every 76 degrees of BTDC. First, FIG. 2 shows the processing by the vehicle height sensor 13. Step S21
At this time, the vehicle height sensor value Ai is read. Next, in step S22, the absolute value ΔA of the difference from the previous sensor value A _i-1 is calculated. Next, in step S23, the rough road judgment value k _H and Δ
Compare A.

Here, k _H is the amount of change of the vehicle height sensor within a predetermined time for determining a bad road, which is a value obtained experimentally. If ΔA> k _H , it is determined that the road is a bad road, the process proceeds to step S24, the misfire determination prohibition timer (counter) C _H is set to an initial value, and the process ends. If ΔA ≦ k _H in step S23, it is determined that the road is not a bad road, the process proceeds to step S25, the misfire determination prohibition timer C _H is decremented, and the process ends. However, the timer C _H is clipped at zero. Here, the vehicle height sensor 13 detects the amount of change in the vertical direction of the vehicle body to determine a bad road.

FIG. 3 shows processing by the G sensor 14.
In step S31, the current G sensor value Bi is read.
Next, in step S32, the absolute value ΔB of the difference from the previous sensor value B _i-1 is calculated. Next, in step S33, the rough road determination value k _G is compared with ΔB. Here, k _G is a change amount of the G sensor within a predetermined time for determining a bad road, and is a value obtained experimentally. Then, if ΔB> k _G , it is determined that the road is a bad road, the process proceeds to step S34, an initial value is set in the misfire determination prohibition timer (counter) C _G , and the process ends. If ΔB ≦ k _G in step S33, it is determined that the road is not a bad road, the process proceeds to step S35, the misfire determination prohibition timer C _G is decremented, and the process ends. However, the timer C _G is clipped at zero. Here, G
The sensor 14 detects the amount of change in the vehicle body in the horizontal direction or the vertical direction to determine a bad road.

In FIG. 4, first, in step S41, it is determined whether or not the misfire determination prohibition timer C _H is operating (C _H > 0). If it is operating, the misfire determination is prohibited, so the process ends. If C _H = 0, the process proceeds to step S42. Again, misfire determination prohibition timer C
It is determined whether or not _G is in operation ( _CG > 0). If it is in operation, the misfire determination is prohibited, so the process ends. C
_{If G} = 0, the process proceeds to step S43, misfire determination is performed, and the process ends. The content of step S43 is the same as the content described in FIG. 11 of the conventional example.

As described above, according to this embodiment, the device for detecting the misfire of the internal combustion engine is provided with the vehicle height sensor 13 for detecting the vehicle height and the G sensor 14 for detecting the acceleration of the vehicle.
Based on the detection signals of these sensors 13 and 14, it is determined whether the vehicle is traveling on a bad road, and if it is determined that the vehicle is a bad road, the misfire determination is prohibited, so that the misfire misjudgment at the time of traveling on the bad road is determined. Can be prevented.

Embodiment 2 FIG. 5 is a block diagram showing a second embodiment of the present invention. This embodiment differs from the embodiment of FIG. 1 in that a vehicle height suspension is achieved by driving an actuator (not shown) based on signals from the vehicle height sensor 13 and the G sensor 14 and signals from throttle sensors, vehicle speed sensors, etc. (not shown). The suspension control unit 15 for controlling the above is provided, and the suspension control unit 15 and the misfire detection unit 7 are connected by the communication line 16 so that information can be transmitted. The same reference numerals in the drawings indicate the same or corresponding parts, and the description thereof will be omitted.

Next, the operation will be described. In the suspension control unit 15, the processing of FIGS. 2 and 3 shown in the first embodiment is executed at regular time intervals. In this case, the misfire determination prohibition timers C _H and C _G have C _H > 0.
Alternatively, when C _G > 0, a misfire determination prohibition signal is transmitted to the misfire detection unit 7 via the communication line 16. Here, when a misfire determination prohibition 80 _H, if not prohibited shall send the 00 _H.

Next, the operation of the misfire detector 7 will be described. FIG. 6 is a flowchart showing the operation of the microcomputer 9, which is executed every 76 degrees of BTDC. First, step S5
It is determined whether the data received in 1 is 80 _H.
If the received data is 80 _H , the misfire determination is prohibited, so the process ends. If not, the process proceeds to step S52 and the misfire determination process is performed. The processing content of step S52 is the same as the content described in FIG. 11 of the conventional example. Thus, according to the present embodiment, it is not necessary to add a new sensor,
It has an advantage that it can be an inexpensive device.

Embodiment 3 In the first and second embodiments, the method of using both the signals of the vehicle height sensor 13 and the G sensor 14 is shown, but it is possible to use only one of them. Good.

Fourth Embodiment In the first and second embodiments, it is determined whether or not the misfire determination is prohibited only by the vehicle height sensor 13 and the G sensor 14, but not shown throttle opening, vehicle speed, engine rotation. It may be configured by adding conditions such as the number.

Fifth Embodiment In the second embodiment, the configuration in which the suspension control unit 15 is connected has been described, but any control unit that inputs at least one of the vehicle speed sensor and the vehicle height sensor may be used.

[0039]

As described above, according to the present invention, in a device for detecting a crank angle position of an internal combustion engine and determining a misfire based on the crank angle position signal, a vehicle body variation amount detection such as a G sensor and a vehicle height sensor is detected. Since the misfire is detected by detecting the bad road from at least one signal of the means, it is possible to prevent the misjudgment of the misfire when traveling on the bad road with a simple configuration.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a calculation flowchart for explaining the operation of the first embodiment of the present invention.

FIG. 3 is a calculation flowchart for explaining the operation of the first embodiment of the present invention.

FIG. 4 is a calculation flowchart for explaining the operation of the first embodiment of the present invention.

FIG. 5 is a configuration diagram showing a second embodiment of the present invention.

FIG. 6 is a calculation flowchart for explaining the operation of the second embodiment of the present invention.

FIG. 7 is a block diagram showing functional blocks of a conventional device.

FIG. 8 is a specific configuration diagram of a conventional device.

FIG. 9 is a time chart for explaining the operation of the conventional device.

FIG. 10 is a time chart for explaining the operation of the conventional device.

FIG. 11 is a flowchart for explaining the operation of the conventional device.

FIG. 12 is a flowchart for explaining the operation of the conventional device.

[Explanation of symbols]

 1 Engine 2, 3, 4, 5 Cylinder 6 Crank Angle Sensor 7 Misfire Detection Section 13 Vehicle Height Sensor 14 G Sensor 15 Suspension Control Unit

Claims (2)

[Claims] 1. A crank angle position detection means for detecting a crank angle position of an internal combustion engine, a misfire determination means for determining a misfire from the crank angle position signal, and a vehicle body variation amount detection means for detecting a variation amount of a vehicle body. A misfire detection device for an internal combustion engine, comprising: a misfire determination prohibiting unit that prohibits the misfire determination when the detected vehicle body variation amount is outside a predetermined range. 2. The vehicle body variation amount detecting means detects the vehicle body based on at least one of signals from an acceleration sensor for detecting an acceleration of the vehicle body and a vehicle height sensor for detecting a vehicle height. The misfire detection device for an internal combustion engine according to claim 1.