JP3230383B2 - Misfire detection device for multi-cylinder internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire detection apparatus for a multi-cylinder internal combustion engine, and more particularly to a misfire detection apparatus for a multi-cylinder internal combustion engine to which a simultaneous ignition system is applied.

[0002]

2. Description of the Related Art When a misfire occurs in an internal combustion engine, unburned gas is discharged into the atmosphere, and there is a risk of damaging a catalyst device for purifying exhaust gas. Important for protection. In order to detect a misfire occurring in a multi-cylinder internal combustion engine having a plurality of cylinders, the time required to rotate a predetermined crank angle in the explosion stroke of one cylinder is longer than the time in the explosion stroke of another cylinder A misfire detection device that determines that a misfire has occurred in a cylinder when is detected is known.

In order to detect the rotation angle of the crankshaft, a rotor having teeth formed on the outer periphery that is rotated synchronously with the crankshaft and an electromagnetic pickup installed close to the teeth of the rotor may be used. In general, a time required for rotating a predetermined crank angle in an explosion stroke is detected as a time for counting a certain number of pulses.

[0004] However, it is difficult to accurately form teeth on the rotor at predetermined fixed angles, and it is inevitable that a considerable error will occur. Occurs. In order to solve this problem, the present applicant uses the same range of the rotor to detect a predetermined crank angle rotation time of the explosion stroke of the two cylinders, and the rotation time corresponding to each cylinder is more than a predetermined deviation. A misfire detection device has been proposed which determines that a misfire has occurred in a cylinder having a longer rotation time when a misfire has occurred (see Japanese Patent Application Laid-Open No. Hei 2-26547).

[0005]

However, in an internal combustion engine to which a so-called simultaneous ignition system is applied, a misfire cannot be detected by the misfire detection device according to the above proposal. In other words, since the same stroke is repeated every 720 ° as a crank angle in a four-cycle internal combustion engine, in a multi-cylinder internal combustion engine, one ignition system is used for two cylinders having different strokes in a 360 ° crank angle. It is possible to adopt a simultaneous ignition system and make the ignition system simple.

In the simultaneous ignition system, the same range of the rotor is used for detecting a predetermined crank angle rotation time during the explosion stroke of two cylinders having different 360 ° strokes, and when an abnormality occurs in the ignition system. There is a high possibility that two cylinders will misfire at the same time. Therefore, if two cylinders having different 360 ° strokes are misfired at the same time, the predetermined crank angle rotation time in the explosion stroke of the two cylinders becomes equally long. Is impossible to detect.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a misfire detection apparatus for a multi-cylinder internal combustion engine capable of reliably detecting misfire even in an internal combustion engine to which a simultaneous ignition system is applied. The purpose is to:

[0008]

FIG. 1 is a basic configuration diagram of a misfire detection apparatus for a multi-cylinder internal combustion engine according to a first invention, which is synchronized with a crankshaft of a multi-cylinder internal combustion engine employing a simultaneous ignition system. A rotor 13 having a plurality of detection elements formed at predetermined angles on the outer circumference at a predetermined angle, and a sensor which is disposed close to the outer circumference of the rotor and outputs a pulse each time a detection element formed on the outer circumference of the rotor passes therethrough. 14 and the time during which the passage of a predetermined number of detection elements present in the same range of the rotor by the sensor is detected, to the rotation time of the predetermined reference crank angle of the explosion stroke of the two cylinders sharing the ignition system. And calculates a time difference between two times corresponding to each of the two cylinders. When the time difference becomes equal to or longer than a predetermined set time, it is determined that a misfire has occurred in the longer cylinder. The detecting a misfire in first and misfire detecting means A, a crank angle difference detecting misfire other ways than a misfire detection used in the first misfire determination means for detecting a misfire by rank angular difference misfire detection method 2
Misfire detection means B, rotation number discrimination means C for discriminating whether or not the rotation number of the internal combustion engine is equal to or higher than a predetermined reference rotation number; When it is determined that the above is the case, when the first misfire detecting means A detects misfire, it is determined that a misfire has occurred, and when the rotational speed determining means C determines that the internal combustion engine rotational speed is less than the reference rotational speed, the second misfire is detected. A misfire state output means D which determines that a misfire has occurred when a misfire is detected by the misfire detection means B;
Is provided.

A misfire detection device for a multi-cylinder internal combustion engine according to a second invention is characterized in that the misfire is detected by the second misfire detection means B when the rotation number discrimination means C determines that the internal combustion engine rotation number is lower than the reference rotation number. The catalyst damage condition establishment determining means for determining whether there is a possibility of catalyst damage based on the cylinder identified as having occurred and the number of misfire occurrences, and the possibility that the catalyst may be damaged by the catalyst damage condition satisfaction determination means And a catalyst damage alarm output means for outputting a catalyst damage alarm by assuming that there is a possibility of catalyst damage even when the internal combustion engine rotation speed is equal to or higher than the reference rotation speed in the rotation speed discriminating means C when the judgment is made. .

In a misfire detection device for a multi-cylinder internal combustion engine according to a third aspect of the present invention, the catalyst damage condition satisfaction determining means may cause misfire in two cylinders sharing an ignition system by the second misfire detection means. Is detected, it is determined that the ignition system is abnormal.

[0011]

In the misfire detection apparatus for a multi-cylinder internal combustion engine according to the first invention, the ignition timings are opposed to each other by using the time required for the rotation of the first rotor in the same region in a high-speed operation state. Since the crank angle difference misfire detection method for detecting misfire of the two cylinders is applied, the influence of the rotor manufacturing error is eliminated. In a low-speed operation state, a time variation caused by a manufacturing error of the rotor can be ignored. Therefore, a misfire detection method other than the crank angle difference misfire detection method is applied.

In the misfire detection apparatus for a multi-cylinder internal combustion engine according to the second invention, the number and number of cylinders in which misfire has been detected in a low-speed operation state are identified, and there is a possibility of catalyst damage due to misfire. Determine whether or not. In the high-speed operation state, this determination is not performed because misfire for each cylinder cannot be detected. In the misfire detection device for a multi-cylinder internal combustion engine according to the third invention, when it is detected that both of the opposed cylinders have misfired in the low-speed operation state, the misfire detection device is common to the opposed cylinders in the ignition system. It is determined that the portion, that is, the ignition system is abnormal.

[0013]

FIG. 2 is a block diagram of a misfire detection apparatus for a multi-cylinder internal combustion engine according to the present invention, and shows a case where the present invention is applied to a four-cylinder internal combustion engine. That is, the internal combustion engine 1 has four cylinders of the first cylinder # 1, the second cylinder # 2, the third cylinder # 3, and the fourth cylinder # 4.

The intake valve side of each cylinder is connected to the surge tank 3 via the corresponding branch pipe 2, and the exhaust valve side is connected to the exhaust manifold 4. Each branch pipe 2 is provided with a fuel injection valve 5 corresponding to a cylinder. The surge tank 3 is connected to an air cleaner 8 via an intake duct 6 and an air flow meter 7, and a throttle valve 9 is arranged in the intake duct 6.

The opening of the throttle valve 9 is detected by a throttle sensor 10 connected to the throttle valve 9, and the coolant temperature of the internal combustion engine is detected by a water temperature sensor 11 attached to the internal combustion engine 1. A disk-shaped first rotor 13 is directly connected to the crankshaft 12 of the internal combustion engine 1, and a crank angle sensor 14 is arranged on the outer periphery of the first rotor 13.

Further, a distributor 15 is installed in the internal combustion engine 1, and the distributor 15 has a shaft 16 that rotates at half the speed of the crankshaft 12.
Is provided. A disk-shaped second rotor 17 is fixed to the shaft 16, and a top dead center sensor 18 is arranged on the outer periphery of the second rotor 17. Further, each cylinder has a spark plug 51, 52, 53, 54 for igniting the mixed gas.
Is installed.

In the four-cylinder internal combustion engine 1 to which the simultaneous ignition system is applied, one ignition circuit is provided for two cylinders having a phase difference of 360 ° in crank angle. That is, the first ignition coil 55 is provided for the # 1 and # 4 cylinders, and the second ignition coil 56 is provided for the # 2 and # 3 cylinders. The internal combustion engine 1
Control and monitoring are performed by an electronic control unit (hereinafter referred to as “ECU”) 20.

The ECU 20 is a microcomputer system.
23, a CPU 24, a timer 25, an input port 26, and an output port 27. The timer 25 is composed of a free running counter, and the count value indicates time.

The air flow meter 7 outputs a voltage proportional to the amount of intake air, and is connected to an input port 26 via an A / D converter 28. The throttle sensor 10 outputs a voltage proportional to the opening of the throttle valve 9, and is connected to an input port 26 via an A / D converter 29. The water temperature sensor 11 outputs a voltage proportional to the internal combustion engine cooling water temperature, and is connected to the input port 26 via the A / D converter 30.

Further, the crank angle sensor 14 and the top dead center sensor 18 are directly connected to the input port 26. On the other hand, the output port 27 outputs an ignition signal and a misfire detection signal. That is, the first ignition signal is output to the first ignition coil 55 via the first power transistor 57, and the second ignition signal is output to the second power transistor 5
8 to the second ignition coil 56.

The misfire detection signal is transmitted to the corresponding driver 31, 3
A warning light 35 indicating that the # 1 cylinder has misfired, a warning light 36 indicating that the # 2 cylinder has misfired, and a warning light 37 indicating that the # 3 cylinder has misfired via 2, 33 and 34. Warning light 3 indicating that # 4 cylinder misfired
8 is connected. FIG. 3 shows that the ignition order is # 1, # 3, # 4,
FIG. 3 is a detailed circuit diagram of an ignition circuit of the internal combustion engine in the order of # 2 cylinders, wherein a first ignition signal output from an output port 27 is connected to a base of a first power transistor 57, and Becomes "H" level, the first power transistor 57 is turned on.

Then, electric power is supplied from the battery bus 59 to the primary coil of the first ignition coil 55,
A high voltage is induced in the next coil. This high voltage is supplied via a high tension cord to a spark plug 51 installed in the # 1 cylinder and an ignition plug 54 installed in the # 4 cylinder. The second ignition signal output from the output port 27 is connected to the base of the second power transistor 58, and when the second ignition signal becomes "H" level, the second power transistor 58 becomes conductive.

Then, electric power is supplied from the battery bus 59 to the primary coil of the second ignition coil 56,
A high voltage is induced in the next coil. This high voltage is supplied via a high tension cord to a spark plug 52 installed in the # 2 cylinder and a spark plug 53 installed in the # 3 cylinder. FIG. 4 is a front view of the first rotor attached to the crankshaft 12 and the crank angle sensor.

The rotor 13 has twelve external teeth 13a to 13l formed at a 30 ° pitch. The crank angle sensor 14 generates an output pulse every time the external teeth cut off the magnetic flux generated by the crank angle sensor 14. . That is, the external teeth constitute a detection element. When the crankshaft 12 rotates, the first rotor 13 rotates in the direction of arrow X, and an output pulse is supplied to the input port 26 every time the first rotor 13 rotates by 30 °.

FIG. 5 is a front view of a second rotor attached to the distributor shaft 16 and a top dead center sensor. The second rotor 17 has one external tooth 17a. External teeth 17a are top dead center sensor 1
An output pulse is output each time the magnetic flux generated in step 8 is turned off. The external teeth 17a of the second rotor 17 are set, for example, to face the top dead center sensor 18 when the # 1 cylinder is at the top dead center of the explosion, and each time the # 1 cylinder reaches the top dead center of the explosion, That is, each time the crankshaft 12 rotates 720 °, an output pulse is input to the input port 26.

Next, the basic concept of the misfire detection method according to the present invention will be described. It is necessary to consider the cause of misfire when the simultaneous ignition method is applied and the manufacturing error when forming external teeth on the first rotor 13. There is. That is, in the ignition circuit shown in FIG. 3, when an abnormality occurs on the upstream side of the first or second ignition coil 55 or 56, that is, on the ECU side, a high voltage is not induced in the secondary coil. A misfire (hereinafter, referred to as "both misfires") occurs in both of the two cylinders ignited by one ignition coil.

On the other hand, if an abnormality occurs on the downstream side of the first or second ignition coil 55 or 56, that is, on the side of the ignition plug, a misfire can occur on both sides, but depending on the cause of the abnormality, one ignition may occur. A misfire (hereinafter referred to as "one-sided misfire") may occur in one of the two cylinders ignited by the coil. FIG. 6 is a comparison graph of the variation caused by misfire and the variation caused by the manufacturing error of the first rotor, in which the horizontal axis represents the internal combustion engine speed and the vertical axis represents the rotation at a predetermined crank angle (for example, 180 °). Take the time it takes.

That is, when a misfire occurs in one cylinder, no driving force is applied, so that the time required for the crank to rotate by a predetermined angle during the explosion stroke becomes longer than when no misfire occurs, and the internal combustion The variation decreases as the engine speed increases. This is because, as the internal combustion engine speed increases, the time required to rotate by a predetermined angle decreases.

On the other hand, the amount of change in the time required for rotating the first rotor 13 by a predetermined angle due to the formation error of the external teeth is substantially constant irrespective of the internal combustion engine speed. Therefore, when the internal combustion engine is operated at a low rotation speed, it is possible to detect a misfire based on the time required for the first rotor 13 to rotate by a predetermined angle without being affected by the external tooth formation error. On the other hand, when the internal combustion engine is operated at a high rotation speed, it is not possible to distinguish between a time variation caused by an external tooth formation error and a time variation caused by a misfire.

That is, it is necessary to use a misfire detection method which is not affected by external tooth formation errors during high-speed operation of the internal combustion engine. The present applicant has already proposed a crank angle difference misfire detection method as a misfire detection method which is not affected by the external tooth formation error (Japanese Patent Laid-Open No. Hei 4-265647).
However, the outline is as follows.

In a four-cylinder internal combustion engine, an explosion stroke is performed in each cylinder every 180 ° crank angle rotation.
The first rotor 13 has a range I from the external teeth 13a to 13f.
The explosion stroke of the # 1 or # 4 cylinder
The explosion stroke of the # 2 or # 3 cylinder is executed in the range II from g to 13l. Accordingly, the rotation time ΔT of the range I of the first rotor 13 when the # 1 cylinder is in the explosion stroke
_First rotor 13 when cylinders # ₁ and # 4 are in the explosion stroke
Can be detected based on the deviation from the rotation time ΔT _{4 in} the range I of the cylinder # 1 or # 4.

That is, for example, when a misfire occurs in the # 1 cylinder, the rotation time ΔT ₁ corresponding to the # 1 cylinder becomes longer than the rotation time ΔT ₄ corresponding to the # 4 cylinder. Misfire is detected by detecting the occurrence of deviation. Similarly # 2
Range of the first rotor 13 when the cylinder is in the power stroke II
Detection of misfire in the # 2 cylinder or # 3 cylinder based on the deviation between the rotation time ΔT ₂ of the first rotor 13 and the rotation time ΔT ₃ of the range II of the first rotor 13 when the # 3 cylinder is in the explosion stroke. Can be.

However, a misfire can be detected by the above-described crank angle difference misfire detection method in the case of one of the misfires, and cannot be detected in the case of both the misfires. This is because in the case of both misfires, the rotation time ΔT ₁ corresponding to the # 1 cylinder and #
This is because the deviation does not increase because the rotation time ΔT ₄ corresponding to the four cylinders is substantially the same.

FIG. 7 is a timing chart of the crank angle difference misfire detection method, in which the top dead center pulse is set to be generated when the # 1 cylinder is at the top dead center of the explosion. Each time it is detected, the count value of the counter C is reset. At times T ₁ , T ₂ , T ₃ , and T ₄ that slightly exceed the top dead center of each cylinder, elapsed times ΔT ₁ , ΔT ₂ , ΔT ₃ , and ΔT ₄ between the respective times are measured.

The same area of the first rotor 13 is used.
Times that are measured as ₁And ΔT_Four, ΔT_Two
And ΔT_ThreeAre compared to perform misfire detection. In contrast
During low-speed operation of the internal combustion engine, a predetermined angle rotation time due to misfire
Fluctuations caused by external teeth formation errors compared to time fluctuations
Because it is large enough, the above-mentioned crank angle difference misfire detection method
Apply other misfire detection methods without using the method
be able to.

For example, when the # 1 cylinder is in the explosion stroke, the rotation time ΔT ₁ of the range I of the first rotor 13 is in the range I, and the # 3 cylinder, which is the next explosion stroke after the # 1 cylinder, is in the explosion stroke. (hereinafter referred to as "continuous cylinder method".) the method for detecting the occurrence of misfire in the # 1 cylinder or the # 3 cylinder based on the deviation between the rotation time [Delta] T ₃ in the range II of the first rotor 13 can be applied .

The operation of the misfire detecting device according to the present invention will be described below with reference to a flowchart of a routine executed by the ECU 20. FIG. 8 is a flowchart of the ignition order counter reset routine. Every time a top dead center pulse is detected by the top dead center sensor 18, the count value of the counter C indicating the ignition order is reset in step 81.

FIG. 9 is a flowchart of the misfire detection routine, which is executed at every 180 ° crank angle, that is, at every time T ₁ , T ₂ , T ₃ , T ₄ in FIG. After incrementing the count value C of the counter C in step 91, the count value Tim of the timer 25 is incremented in step 92.
er is stored in T (C). In step 93, it is determined whether a misfire determination condition is satisfied. For example, when the internal combustion engine speed is deemed to be unstable, such as when the internal combustion engine is started, sudden acceleration or sudden deceleration, it is determined that the misfire determination condition is not satisfied.

Whether or not the internal combustion engine is being started is determined by whether or not the cooling water temperature detected by the water temperature sensor 11 is equal to or higher than a predetermined temperature. Whether or not the internal combustion engine is rapidly accelerating or decelerating is determined by whether or not the throttle valve 9 detected by the throttle sensor 10 is rapidly opened or closed. When an affirmative determination is made in step 93, the routine proceeds to step 94, where crank angle difference misfire determination processing is executed, and subsequently, in step 95, continuous cylinder misfire determination processing is executed.

When a negative determination is made in step 93, this routine is directly terminated. FIG. 10 is a detailed flowchart of the crank angle difference misfire determination process executed in step 94. In steps 94a and 94b, the count value of the counter C is determined. If C = 1, the routine proceeds to step 94c, where the time ΔT ₂ required to rotate the crankshaft by 180 ° from the top dead center of the # 2 cylinder is set.
Is calculated by the following equation.

ΔT_Two= T₁-T_Four In step 94d, the area of the first rotor 13
Crank angle from top dead center of cylinder # 3 explosion detected in region II
Time ΔT required to rotate 180 ° in degrees _ThreeDifference with
Is greater than or equal to a threshold value L. Steps
When a positive determination is made in 94d, the process proceeds to step 94e,
It is determined that a misfire has occurred in the # 2 cylinder, and the flag MFX (2) is set.
To end this processing.

When a negative determination is made in step 94d
Ends this process directly. When C = 2,
To 94f, crank angle from top dead center of cylinder # 1 explosion
Time ΔT required to rotate 180 ° in degrees₁Is
It is calculated by ΔT₁= T_Two-T₁ In step 94g, the area of the first rotor 13
Crank angle from top dead center of cylinder # 1 explosion detected in region I
Time ΔT required to rotate 180 ° in degrees _FourDifference with
Is greater than or equal to a threshold value L.

When an affirmative determination is made in step 94g, the routine proceeds to step 94h, where it is determined that a misfire has occurred in the # 1 cylinder, the flag MFX (1) is set, and this processing ends. If a negative determination is made in step 94g, this process is directly terminated. When C = 3, the routine proceeds to step 94i, in which the crank angle is set at 18 degrees from the top dead center of the # 3 cylinder explosion.
The time ΔT ₃ required for rotating by 0 ° is calculated by the following equation.

ΔT_Three= T_Three-T_Two In step 94j, the area of the first rotor
Crank angle from top dead center of cylinder # 2 explosion detected in region II
Time ΔT required to rotate 180 ° in degrees _TwoDifference with
Is greater than or equal to a threshold value L. Steps
When a positive determination is made in 94j, the process proceeds to step 94k,
It is determined that a misfire has occurred in the # 3 cylinder, and the flag MFX (3) is set.
To end this processing.

When a negative determination is made in step 94j
Ends this process directly. When C = 4,
To 94l, crank angle from top dead center of cylinder # 4 explosion
Time ΔT required to rotate 180 ° in degrees_FourIs
It is calculated by ΔT_Four= T_Four-T_Three In step 94m, the area of the first rotor 13 is also
Crank angle from top dead center of cylinder # 1 explosion detected in region I
Time ΔT required to rotate 180 ° in degrees ₁Difference with
Is greater than or equal to a threshold value L.

When an affirmative determination is made in step 94m, the routine proceeds to step 94n, where it is determined that a misfire has occurred in the # 4 cylinder, the flag MFX (4) is set, and this processing ends. If a negative determination is made in step 94d, this process ends directly. Here, the threshold value L is the internal combustion engine load Q / N
(Where Q is the amount of intake air detected by the air flow meter 7 and N is the number of revolutions of the internal combustion engine detected by the crank angle sensor 14) are stored in the ROM 22 as a function.

FIG. 11 is a flow chart of the continuous cylinder misfire detection process. In steps 94a and 94b, the count value of the counter C is determined. If C = 1, the routine proceeds to step 95c, where the time ΔT ₂ required for rotating the crankshaft by 180 ° from the top dead center of the # 2 cylinder is calculated by the following equation. ΔT ₂ = T ₁ −T _{4 In} step 95d, the difference from the time ΔT ₄ required to rotate 180 ° in crank angle from the top dead center of the explosion of the # 4 cylinder in which the explosion affirmation was executed immediately before the # 2 cylinder. Is greater than or equal to a threshold M.

When an affirmative determination is made in step 95d, the routine proceeds to step 95e, where it is determined that a misfire has occurred in the # 2 cylinder, a flag MFY (2) is set, and this processing is terminated. If a negative determination is made in step 95d, this process is directly terminated. If C = 2, the routine proceeds to step 95f, in which the crank angle is set at 18 degrees from the top dead center of the # 1 cylinder.
The time ΔT ₁ required for rotating by 0 ° is calculated by the following equation.

ΔT ₁ = T ₂ −T _{1 In} step 95g, the time ΔT ₂ required to rotate 180 ° in crank angle from the top dead center of the explosion of cylinder # 2 in which the explosion affirmation was executed immediately before cylinder # 1. It is determined whether or not the difference from is greater than or equal to threshold value M. Step 95g
When the determination is affirmative, the routine proceeds to step 95h, where it is determined that a misfire has occurred in the # 1 cylinder, the flag MFY (1) is set, and this processing ends.

When a negative determination is made in step 95g, this process is directly terminated. When C = 3, the routine proceeds to step 95i, where the time ΔT ₃ required for rotating the crankshaft by 180 ° from the top dead center of cylinder # ₃ is calculated by the following equation. ΔT ₃ = T ₃ −T _{2 In} step 94j, the difference from the time ΔT ₁ required to rotate 180 ° in crank angle from the top dead center of the explosion of cylinder # 1 in which the explosion affirmation was executed immediately before cylinder # 3. Is greater than or equal to a threshold M.

When an affirmative determination is made in step 95j, the routine proceeds to step 95k, in which it is determined that a misfire has occurred in the # 3 cylinder, a flag MFY (3) is set, and this processing ends. If a negative determination is made in step 95j, this process is directly terminated. When C = 4, the routine proceeds to step 95l, where the crank angle is set at 18 degrees from the top dead center of the # 4 cylinder explosion.
The time ΔT ₄ required for rotating by 0 ° is calculated by the following equation.

ΔT ₄ = T ₄ −T _{3 In} step 95m, the time ΔT ₃ required for rotating the crankshaft by 180 ° from the top dead center of the explosion of the # 3 cylinder in which the explosion affirmation was executed immediately before the # 4 cylinder. It is determined whether or not the difference from is greater than or equal to threshold value M. Step 95m
When the determination is affirmative, the routine proceeds to step 95n, where it is determined that a misfire has occurred in the # 4 cylinder, the flag MFY (4) is set, and this processing ends.

If a negative determination is made in step 94d, this process is directly terminated. Here, the threshold value M is stored in the ROM 22 as a function of the internal combustion engine load Q / N. FIG. 12 is a flowchart of a misfire alarm output routine, which is executed as an interruption process at regular time intervals.

In step 121, the internal combustion engine speed N
Is read, and in step 122, the index i representing the cylinder number is set to 1. Engine speed at step 123 N threshold rotational speed N _th (e.g. 1200r
pm) or not. When an affirmative determination is made in step 123, that is, when the internal combustion engine is in a high-speed operation state, it is determined that highly reliable detection cannot be performed unless the crank angle difference misfire detection method is used.
At 4, it is determined whether or not the flag MFX (i) is set.

When a negative determination is made in step 123, that is, when the internal combustion engine is in a low-speed operation state, it is determined that highly reliable detection cannot be performed unless the continuous cylinder misfire detection method is used, and the flag MFY (i) is determined in step 125. Is set or not. If an affirmative determination is made in step 124 or 125, step 12
6 and the warning lights 35, 3 according to the value of the index i.
One of 6, 37 and 38 is turned on, and the process proceeds to step 127.

When a negative determination is made in step 124 or 125, the flow directly proceeds to step 127, where it is determined whether or not the index i is 4 or more. When an affirmative determination is made, this routine ends. If a negative determination is made in step 127, the index i is incremented in step 128 and the process returns to step 123.

When the occurrence of misfire is detected, unburned gas is discharged to the exhaust system and may be burned in the catalyst for purifying exhaust gas to damage the catalyst. Has limitations. FIG. 13 is a graph showing the permissible misfire limit of the four-cylinder internal combustion engine. The horizontal axis represents the internal combustion engine speed, the vertical axis represents the internal combustion engine load, and the parameter is the misfire rate. The misfire rate is defined as the ratio of the number of misfired cylinders to the total number of cylinders of the internal combustion engine.

That is, when the internal combustion engine is operating at a high load and a high speed, a misfire of one cylinder (a misfire rate of 25%) may not be permitted. However, as described above, in the internal combustion engine employing the simultaneous ignition system, if both misfires occur, the misfire rate becomes 50%. However, highly accurate misfire detection cannot be performed by the continuous cylinder misfire detection method. Since one of the misfires cannot be detected by the angle difference misfire detection method, it is impossible to detect both misfires with high accuracy.

On the other hand, during the low-load low-speed operation of the internal combustion engine, there is an operation state (for example, an idling state) in which a misfire rate of 50% is permissible, and the two cylinders facing each other are detected by the continuous cylinder misfire detection method. It is possible to detect a misfire. Therefore, in the present invention, when the misfire of the two opposed cylinders is detected during the low-speed operation of the internal combustion engine, a catalyst damage condition is issued and a catalyst damage alarm is issued, and the misfire detection is performed during the high-speed operation of the internal combustion engine. Regardless of the catalyst damage alarm is held.

Thereafter, when it is determined that the catalyst damage condition is not satisfied when returning to the idling state, the catalyst damage alarm is reset. FIG. 14 is a flowchart of a catalyst damage warning routine, which is executed as a time interruption every predetermined time. Engine speed N is equal to or a threshold rotational speed N _th or more in step 141, the process proceeds to step 142 as is being an internal combustion engine low speed operation if a negative decision.

At step 142, the flag MFY
It is determined whether or not the sum of (i) is 2 or more, that is, whether or not misfire has occurred in two or more cylinders in the continuous cylinder misfire detection processing. If an affirmative determination is made in step 142, the process proceeds to step 143, where a catalyst damage alarm is output, and this routine ends.

If a negative determination is made in step 142, the routine proceeds to step 144, where the catalyst damage alarm is reset, and this routine ends. If an affirmative determination is made in step 141, this routine is directly terminated without determining that the internal combustion engine is operating at high speed, and without determining a catalyst damage alarm. Further, when it is determined in the continuous cylinder misfire determination process that misfire has occurred in two cylinders, it is determined that the two cylinders are opposed to each other with respect to the ignition timing, that is, the cylinders are shifted from each other by 360 ° ignition timing. It is possible to specify that both are misfires and an abnormality has occurred in the ignition system.

FIG. 15 is a flowchart of an ignition coil abnormality determination routine, which is executed as a time interruption every predetermined time. In step 151, it is determined whether or not the sum of the flags MFY (i) is 2 or more, that is, whether or not misfire has occurred in two or more cylinders in the continuous cylinder misfire detection processing.

If the determination in step 151 is affirmative, the routine proceeds to step 152, where it is determined whether MFY (1) + MFY (4) is 2, that is, whether misfire has occurred in cylinders # 1 and # 4. Is determined. If the determination in step 152 is affirmative, in step 153, an abnormality alarm is generated for the ignition coil 55 commonly used in the # 1 cylinder and the # 4 cylinder.

If a negative determination is made in step 152, the flow advances to step 154 to determine whether MFY (3) + MFY (2) is 2, that is, whether misfire has occurred in cylinders # 3 and # 2. Is determined. If an affirmative determination is made in step 154, an abnormality alarm is generated in step 155 for the ignition coil 56 commonly used by the # 3 cylinder and the # 2 cylinder.

Step 151 or step 15
If a negative determination is made in step 4, this routine is directly terminated. The case where the present invention is applied to a four-cylinder internal combustion engine has been described above, but it is apparent that the present invention is also applicable to an internal combustion engine having six or more cylinders.

[0067]

According to the misfire detection apparatus for a multi-cylinder internal combustion engine according to the first invention, misfires other than simultaneous misfires of two cylinders sharing an ignition circuit in a high-speed operation state are detected, and a low-speed operation state is detected. It is possible to detect a misfire for each cylinder at. According to the misfire detection device for a multi-cylinder internal combustion engine according to the second aspect of the present invention, it is possible to generate an alarm from a misfire occurrence condition in a low-speed operation state as a possibility that the catalyst may be damaged even in a high-speed operation state.

According to the misfire detection device for a multi-cylinder internal combustion engine according to the second invention, it is possible to identify the occurrence site of the ignition circuit from the misfire occurrence condition in the low-speed operation state.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of the first invention.

FIG. 2 is a configuration diagram of a misfire detection device.

FIG. 3 is a detailed circuit diagram of a misfire circuit.

FIG. 4 is a front view of a first rotor and a crank angle sensor.

FIG. 5 is a front view of a second rotor and a top dead center sensor.

FIG. 6 is a graph showing variation due to misfire and variation due to rotor manufacturing error.

FIG. 7 is a timing chart of a crank angle difference misfire detection method.

FIG. 8 is a flowchart of an ignition order counter reset routine.

FIG. 9 is a flowchart of a misfire detection routine.

FIG. 10 is a flowchart of a crank angle difference misfire detection process.

FIG. 11 is a flowchart of a continuous cylinder misfire detection process.

FIG. 12 is a flowchart of a misfire detection output routine.

FIG. 13 is a graph showing an allowable misfire limit.

FIG. 14 is a flowchart of a catalyst damage warning routine.

FIG. 15 is a flowchart of an ignition coil abnormality determination routine.

DESCRIPTION OF SYMBOLS 12 ... Crankshaft 13 ... First rotor 14 ... Crank angle sensor 15 ... Distributor 17 ... Second rotor 18 ... Top dead center sensor 20 ... ECU 51,52,53,54 ... Spark plug 55, 56: ignition coil 57, 58: power transistor

Claims (3)

(57) [Claims] 1. A rotor having a plurality of detection elements formed at predetermined intervals on an outer periphery thereof, the rotor being rotated in synchronization with a crankshaft of a multi-cylinder internal combustion engine employing a simultaneous ignition system, A sensor that outputs a pulse each time a detection element formed on the outer periphery of the rotor passes therethrough, and the sensor detects passage of a predetermined number of detection elements existing in the same range of the rotor. Is detected as the rotation time of the predetermined reference crank angle of the explosion stroke of the two cylinders sharing the ignition system, and the difference between the two times corresponding to each of the two cylinders is calculated. First misfire detection means for detecting misfire by a crank angle difference misfire detection method for determining that misfire has occurred in a cylinder having a longer time when a predetermined set time or more has been reached; A second misfire detection means for detecting misfire by a method other than the crank angle difference misfire detection method which is a misfire detection used in the first misfire determination means; A rotational speed determining means for determining whether or not the above is true; and a misfire detected by the first misfire detecting means when the rotational speed determining means determines that the internal combustion engine speed is equal to or higher than a reference rotational speed. If a misfire has occurred, and if the rotational speed discriminating means determines that the internal combustion engine speed is lower than the reference rotational speed, the second misfire detecting means detects misfire and determines that a misfire has occurred. Means,
A misfire detection device for a multi-cylinder internal combustion engine, comprising: 2. The method according to claim 1, wherein the second engine speed determining means determines that the engine speed is lower than a reference engine speed.
Catalyst damage condition satisfaction determining means for determining whether there is a possibility of catalyst damage based on the cylinder identified as having misfired by the misfire detection means and the number of misfire occurrences; and If it is determined that there is a possibility of damaging the engine, the engine speed discriminating means outputs a catalyst damage alarm by assuming that there is a possibility of catalyst damage even when the internal combustion engine speed is equal to or higher than the reference speed by the engine speed discriminating means. The misfire detection device for a multi-cylinder internal combustion engine according to claim 1, further comprising: means. 3. The catalyst damage condition establishment determination means, wherein the second misfire detection means shares an ignition system.
The misfire detection device for a multi-cylinder internal combustion engine according to claim 2, wherein when it is detected that a misfire has occurred in one of the cylinders, it is determined that the ignition system is abnormal.