JP2626298B2 - Engine misfire detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine misfire detection device capable of accurately detecting a misfire state over a wide operating range of the engine.

[0002]

2. Description of the Related Art Internal combustion engines (hereinafter simply referred to as engines)
In order to purify the harmful components in the exhaust gas emitted from vehicles equipped with the engine, a catalytic converter has been incorporated in the exhaust passage connected to this engine to reduce the amount of harmful components in the exhaust gas. In the exhaust gas purifying device, if the exhaust gas contains a large amount of unburned gas that has failed to be burned, the unburned gas burns when passing through the catalytic converter and rapidly increases the temperature of the catalytic converter. There is a possibility that the catalytic converter may be deteriorated or melted.

A major cause of a large amount of unburned gas contained in exhaust gas is a misfire phenomenon in which fuel supplied to a combustion chamber of an engine is not ignited for some reason. The misfire phenomenon of this engine is
In particular, not only makes the idling control of the engine extremely difficult, but also has problems such as the deterioration and melting of the catalytic converter as described above. It is important to take steps.

Conventionally, as a method of detecting engine misfire, attention has been paid to the fact that the angular speed of the crankshaft during the expansion stroke does not temporarily increase when a misfire occurs in the engine. Japanese Patent Application Laid-Open No. 58-19532, etc., which detects misfires of the engine based on the fact that the oxygen concentration in the exhaust gas increases when a misfire occurs in the engine. Japanese Patent Publication No. 59-30895 discloses a technique for detecting a misfire of an engine based on a change in oxygen concentration in a gas.

[0005]

In the high-speed operation region of the engine where the crankshaft rotates at a high speed, the fluctuation of the crankshaft angular velocity of the engine is reduced by the inertial rotation of the crankshaft. The method of detecting the misfire of the engine by using this method has a disadvantage that the reliability of the detection gradually decreases as the engine speed increases.

On the other hand, in an operating region where the temperature in the exhaust passage is low, such as when the engine is idling immediately after a cold start, an oxygen concentration sensor for detecting the oxygen concentration in the exhaust gas (hereinafter referred to as an O ₂ sensor). Is not activated, it is not possible to detect a misfire of the engine based on the fluctuation of the oxygen concentration in the exhaust gas until the O ₂ sensor is activated.

An object of the present invention is to provide an engine misfire detection device capable of reliably detecting a misfire state over a wide operating range of the engine.

[0008] The misfire detection apparatus of the engine according to the present invention, institutions
An angular velocity detecting means for detecting a crank shaft angular velocity, the angular
Based on the change in the angular velocity detected by the speed detection means
First misfire detecting means for detecting misfire of the engine;
Oxygen concentration detecting means for detecting oxygen concentration in exhaust gas of Seki
And whether the oxygen concentration detection means is activated
Activation determination means and the oxygen concentration detection means.
Detects misfire of the engine based on the change in oxygen concentration
The second misfire detecting means for setting the engine speed and the engine speed are preset.
The first misfire determination area when the rotation speed exceeds the predetermined rotation speed.
The engine speed and the load of the engine
When the rotation speed is less than or equal to or less than the predetermined load
The engine is determined to be in a second misfire determination area, and the engine speed and
The load is less than the predetermined rotation speed and the predetermined load
Misfire determination area to determine the third misfire determination area when exceeds
Area determination means and the misfire determination area determination means.
The first or second misfire corresponding to each misfire determination area.
Misfire of the engine based on at least one of the fire detection means.
A misfire determination means for determining, wherein the misfire determination means,
In the first misfire determination area, the second misfire detection means
Misfire is determined, and in the second misfire determination area, the second misfire is determined.
The misfire is determined by the first misfire detection means, and the third misfire
In the constant region, the activation determination means determines the oxygen concentration.
When it is determined that the delivery means is in the activated state,
One of the first and second misfire detecting means detects misfire of the engine.
It is determined that a misfire has occurred and the oxygen concentration detecting means is activated.
The first misfire detection when it is determined that the first misfire is not present.
It is characterized in that misfire is determined by means .

When the engine speed is equal to or less than a predetermined speed and the load
Is in the second misfire determination region below a predetermined load.
Since the oxygen concentration detection means <br/> for detecting the oxygen concentration in the exhaust gas it is considered that not activated, the first loss
The misfire of the engine is detected by the fire detection means based on the crankshaft angular velocity of the engine.

[0010] The engine speed is set to a predetermined speed.
In the first misfire determination region, the fluctuation of the crankshaft angular velocity of the engine is reduced due to the inertial rotation of the crankshaft,
Since detecting the misfire of the engine based on fluctuations of engine crankshaft angular velocity is problematic in terms of reliability, the second loss
The misfire of the engine is detected by the fire detecting means based on the components in the exhaust gas discharged from the engine.

The engine speed is less than a predetermined speed and the engine
In the third misfire determination region where the load of
The activation determination means activates the oxygen concentration detection means.
The first or second misfire when it is determined that the
When the misfire of the engine is detected by one of the detection means,
It is determined that the oxygen concentration detecting means is not in the activated state.
When set, a misfire is detected by the first misfire detection means.
judge.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1 showing the concept of an embodiment in which an engine misfire detecting apparatus according to the present invention is applied to a V-type six-cylinder internal combustion engine provided with a catalytic converter, the apparatus is adapted to the operating state of a vehicle and the like. An amount of fuel set by the electronic control unit 11 is supplied via fuel supply means (not shown), and a combustion chamber (not shown) of an engine 13 having a cylinder block 12 arranged in a V-shape is provided with the cylinder block 12. An exhaust passage 15 in an exhaust pipe 14 having one end fixed thereto communicates. The exhaust passage 15 is for discharging exhaust gas generated in the combustion chamber, and in the middle of the exhaust passage 15 for purifying harmful components in the exhaust gas flowing through the exhaust passage 15. Is built in. Further, in the middle of the exhaust pipe 14 between the catalytic converter 16 and the combustion chamber, an exhaust passage 15 is provided.
A well-known O ₂ sensor 17 for electrically detecting the concentration of oxygen in the exhaust gas flowing through the inside is provided.

On the other hand, the cylinder block 1 of the engine 13
A detection ring 19 having gear-shaped irregularities formed at regular intervals on an outer peripheral surface thereof is fitted coaxially and integrally with the crankshaft 18 rotatably supported by the rotary shaft 2. The detection ring 19 faces the outer peripheral surface of the detection ring 19. Further, the pickup 20 that magnetically detects the passage of the convex portion formed on the outer peripheral surface of the detection ring 19,
Together with this detection ring 19, it constitutes a crank angle sensor.

The pickup 20 and the O ₂ sensor 17 are electrically connected to the electronic control unit 11, respectively.
3 is electrically converted and output to the electronic control unit 11 while the O ₂ sensor 17 detects the concentration of oxygen occupied in the exhaust gas flowing through the exhaust passage 15 from the theoretical air. Based on the exhaust gas in the state of the fuel ratio, it is electrically determined whether the state is larger (hereinafter referred to as a lean state) or smaller (hereinafter referred to as a rich state). Control unit 1
1 is output.

In this embodiment, a misfire indicator lamp 21 is provided in a passenger compartment (not shown) so that an occupant can confirm that a misfire has occurred, and the misfire indicator lamp 21 is turned on. When the electronic control unit 11 determines that the engine 13 has misfired, the power from the power supply 22 is supplied to the electronic control unit 11 via a switch (not shown) incorporated in the electronic control unit 11. Are supplied to the misfire indicator lamp 21.

The electronic control unit 11 includes an engine 13
A misfire determination circuit (not shown) for determining the misfire of the engine 13 is incorporated, and the present invention employs different determination methods in three determination regions as shown in FIG. ing. Specifically, an engine speed N calculated based on a detection signal from a crank angle sensor, and an air flow sensor (not shown) that detects the engine speed N and the amount of intake air A sucked into the combustion chamber of the engine 13 are used for electronic control. Intake charging efficiency (ratio of intake air amount A to engine speed N) A / N calculated in electronic control unit 11 based on a detection signal output to control unit 11
Thus, in this embodiment, the low load determination region selected when the engine speed N is less than 2500 rpm and the intake charging efficiency A / N is less than 40%, and the intake charging efficiency A / N when the engine speed N is less than 2500 rpm. The electronic control unit 11 has three determination areas, a high load determination area selected when N is 40% or more and a high rotation determination area selected when the engine speed N is 2500 rpm or more. I have.

In the low load determination region, the crank angle sensor
Change in the crankshaft angular velocity based on the detection signal from the
Read, near the compression top dead center of the engine 13 (for example, ATDC0
° to 20 °) of the crankshaft 18_RWhen,
A position on the way from compression top dead center to bottom dead center (for example, ATDC
40 ° to 60 °) and the angular velocity ω of the crankshaft 18 _D
And ω_R≧ ω_DIs determined to be misfire in the case of. example
If a misfire occurs in the fifth cylinder of the engine 13,
As shown in FIG. 3, which shows the change in the crankshaft angular velocity,
Changes in the crankshaft angular velocity during the expansion stroke indicate normal combustion.
Significantly changed with changes in the crankshaft angular velocity of the other cylinders
It turns out to be different.

In this case, when the engine 13 is suddenly accelerated or decelerated, for example, when the fluctuation amount ΔN of the engine speed N per unit time corresponding to several revolutions of the crankshaft 18 is expected to be large, an erroneous determination for misfire is made. Therefore, in the present embodiment, the engine 13 based on the detection signal from the crank angle sensor is only used when the absolute value | ΔN | of the variation ΔN | of the engine speed N per unit time is 50 rpm or less. Misfire determination is performed. Incidentally, as a method of determining misfire of the engine 13 based on a detection signal from the crank angle sensor, JP-A-58-19532 and JP-A-2-112646
Can be adopted.

In the high rotation determination region, the change in the oxygen concentration in the exhaust gas is read out based on the detection signal from the O ₂ sensor 17 and the engine 13 is read out according to the method disclosed in Japanese Patent Publication No. 59-30895. However, as is well known, when the O ₂ sensor 17 is inactive, the change in the oxygen concentration in the exhaust gas cannot be read out based on the detection signal from the O ₂ sensor 17. Although the reliability is low, the misfire of the engine 13 can be detected based on the detection signal from the crank angle sensor.

When the engine 13 is burning normally, the air-fuel ratio of the exhaust gas repeats a rich state and a lean state according to a predetermined control time constant of the feedback control system, and the equivalent air-fuel ratio becomes the stoichiometric air-fuel ratio. Therefore, the output of the O ₂ sensor 17 is a signal having a frequency corresponding to the control time constant as shown by a broken line in FIG. Here, for example, when a misfire occurs in the first cylinder of the engine 13,
The exhaust gas contains a large amount of unburned gas during the exhaust stroke of the first cylinder, and the O ₂ sensor 17 detects excess oxygen during the exhaust stroke of the first cylinder and outputs a lean signal. As a result, the air-fuel ratio feedback control is performed, so that the air-fuel mixture supplied to the engine 13 is in a rich state, and the O ₂ sensor 17 outputs a signal corresponding to the rich state during the exhaust stroke of a cylinder other than the first cylinder. However, since the exhaust gas of the first cylinder is the unburned gas, the O ₂ sensor 17 outputs a signal corresponding to the lean state during the exhaust stroke of the first cylinder.

As a result, when a misfire occurs in the engine 13
O_TwoThe output signal frequency of the sensor 17 is represented by a solid line in FIG.
Under normal operating conditions where no misfire has occurred as shown
O _TwoAbout several times to ten times the output signal frequency of the sensor 17
Therefore, it is possible to detect the misfire of the engine 13 based on this.
it can. In addition, in a normal operating state where no misfire has occurred
O_TwoThe output signal frequency of the sensor 17 is the engine speed.
In this embodiment, a misfire occurs because the temperature fluctuates almost corresponding to N.
O in normal operating conditions that are not generated_TwoSensor 17
The output signal frequency is adjusted according to the engine speed and its output.
The map as shown in FIG. 5 stored in the control unit 11
From the actual O_TwoOutput signal frequency of sensor 17
If this is higher than the preset ratio,
It is determined that it has occurred.

On the other hand, in the high load determination region, in the present embodiment, the engine 13 is determined by the above-described method based on the detection signal from the O ₂ sensor and the detection signal from the crank angle sensor.
, Respectively, so that even if one of the methods cannot be adopted for some reason, the remaining method can detect the misfire of the engine 13.

As shown in FIG. 6 showing an example of the misfire determination procedure in this embodiment, first, in S1, it is determined whether or not the engine speed N is less than 2500 rpm. If it is determined that the engine speed N is less than 2500 rpm, then at S2, the intake charge efficiency A / N
Is less than 40%.

In the step S2, the intake charging efficiency A /
If N is less than 40%, that is, if it is determined that the operating state of the engine 13 is in the low load determination region, then in S3, it is determined whether or not the absolute value of the fluctuation width ΔN of the engine speed N is within 50 rpm. The absolute value of the fluctuation width ΔN of the engine speed N is within 50 rpm, that is, even if misfire of the engine 13 is detected based on a detection signal from the crank angle sensor, there is little possibility of erroneous determination. If it is determined that the engine 13 has misfired in S4 based on the detection signal from the crank angle sensor, it is determined in S5 whether the engine 13 has misfired. If it is determined in step S5 that the engine 13 has misfired, the current from the power source 22 is supplied to the misfire indicator lamp 21 in S6, and the misfire indicator lamp 21 is turned on to execute the above-described S1. Returning to the step,
If it is determined in step 5 that the engine 13 has not failed, the power supply 22 for the misfire indicator lamp 21 is determined in step S7.
Is turned off, and the process returns to step S1.

In step S3, the absolute value of the fluctuation width ΔN of the engine speed N exceeds 50 rpm, that is, there is a possibility that an erroneous determination is made when the misfire of the engine 13 is detected based on the detection signal from the crank angle sensor. Is higher, the process returns to step S1 without doing anything.

In the step S2, the intake charging efficiency is determined.
A / N is 40% or more, that is, the operating state of the engine 13
If it is determined that the vehicle is in the high load determination region, it is determined in step S8 that O_Two
It is determined whether or not the sensor 17 is activated. Soshi
In step S8, O _TwoThe sensor 17 is activated
That is, feedback control of the air-fuel ratio is performed.
If it is determined that the_TwoFrom the sensor 17
Misfire detection of the engine 13 is performed based on the detection signal.
It is determined whether or not the engine 13 has misfired. And
At step S10, it is determined that the engine 13 has misfired.
If the power supply is disconnected, the process proceeds to step S6 and the power supply 2
2 is supplied to the misfire indicating lamp 21 and
Turn on the fire indicator lamp 21 and return to the step S1.
You.

If it is determined in step S10 that the engine 13 has not misfired, it is determined in step S11 whether the absolute value of the fluctuation width ΔN of the engine speed N is within 50 rpm. Then, in step S11, the absolute value of the fluctuation width ΔN of the engine speed N is within 50 rpm.
That is, based on the detection signal from the crank angle sensor, the engine 1
If it is determined that the possibility of erroneous determination is small even when the misfire of No. 3 is detected, the process proceeds to step S4, and the misfire of the engine 13 is detected based on the detection signal from the crank angle sensor. However, in step S11, the absolute value of the fluctuation width ΔN of the engine speed N exceeds 50 rpm, that is, it is determined that there is a high possibility of erroneous determination when detecting misfire of the engine 13 based on a detection signal from the crank angle sensor. If you do
Since it is determined in step S10 that the engine 13 is not in a misfire state, the process proceeds to step S7 and the power supply 22 to the misfire indicator lamp 21 is cut off.

Since the O ₂ sensor 17 is not activated in the step S8, that is, the feedback control of the air-fuel ratio is not reliable, it is difficult to detect the misfire of the engine 13 by the O ₂ sensor 17. If it is determined that the engine is misfired, the process proceeds to step S3 to detect misfire of the engine 13 based on the detection signal from the crank angle sensor.

On the other hand, the engine speed is determined in step S1 is equal to or greater than 2500 rpm, i.e. if the operating state of the engine 13 is determined to be in the high rotation determination area, activated O ₂ sensor 17 at S12 Is determined. When the O ₂ sensor 17 is determined to be activated, i.e. the feedback control of the air-fuel ratio has been made at this step S12, the O ₂ sensor 17 in S13
Misfire detection of the engine 13 based on the detection signal from the
At 14, it is determined whether or not the engine 13 has misfired. If it is determined in step S14 that the engine 13 has misfired, the process proceeds to step S6 in which the current from the power supply 22 is supplied to the misfire indicator lamp 21.
The misfire indicator lamp 21 is turned on. If it is determined in step S14 that the engine 13 has not misfired,
In step S7, the power supply from the power supply 22 to the misfire indicating lamp 21 is cut off.

In this embodiment, since the O ₂ sensor 17 is not activated in the step S12, that is, the feedback control of the air-fuel ratio is not reliable, the misfire detection of the engine 13 by the O ₂ sensor 17 is not performed. If it is determined that it is difficult to perform the process, the process returns to the step S1 without doing anything. However, although the reliability is low, the process proceeds to the step S3 and the engine is started based on the detection signal from the crank angle sensor. 13 may be detected. In this embodiment, the misfire of the engine 13 is detected by the O ₂ sensor and the crank angle sensor in the high load determination region. However, the misfire of the engine 13 can be detected by using only one of the sensors. It is.

[0031]

According to the engine misfire detecting apparatus of the present invention,
Angular velocity detecting means for detecting the crankshaft angular velocity of the engine;
Based on the change in angular velocity detected by the same angular velocity detection means
A first misfire detecting means for detecting a misfire of the feeder the engine, before
Oxygen concentration detection to detect the oxygen concentration in the exhaust gas of the engine
Means and whether the oxygen concentration detecting means is activated or not.
Activation determining means for determining, and the oxygen concentration detecting means
The engine is misfired based on the detected change in oxygen concentration.
The second misfire detection means to be detected and the engine speed are predicted.
The first misfire determination area when the set number of rotations exceeds
And the engine speed and load are
When the rotation speed is equal to or less than a predetermined rotation speed and equal to or less than a predetermined load.
Is determined to be the second misfire determination region, and the engine speed is further determined.
And the load is less than or equal to the predetermined rotational speed and the predetermined
Misfire judgment to determine the third misfire determination area when the load is exceeded
Determined by the fixed area determination means and the misfire determination area determination means
Corresponding to each of the determined misfire determination areas.
Of the engine based on at least one of the misfire detection means of
A misfire determination means for determining a fire, wherein the misfire determination means
Is, in the first misfire determination region, said second misfire detection hand
A misfire is determined by a step, and in the second misfire determination area,
The misfire is determined by the first misfire detecting means, and the third misfire is determined.
In the fire determination region, the activation determination unit determines the oxygen concentration.
If the degree detection means is determined to be in the activated state,
One of the first and second misfire detecting means, the misfire of the engine;
Is detected, a misfire is determined, and the oxygen concentration detecting means
When it is determined that the engine is not in the activated state, the first misfire
Since the misfire is determined by the detection means , a highly reliable misfire detection can be reliably performed over a wide operating state of the engine.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an embodiment in which an engine misfire detection method according to the present invention is applied to a multi-cylinder internal combustion engine equipped with a catalytic converter.

FIG. 2 is a map showing a determination area for misfire detection according to the present embodiment in association with an engine speed and an intake charging efficiency.

FIG. 3 is a diagram illustrating an example of a variation state of a crankshaft angular velocity when a misfire occurs in an engine.

FIG. 4 is a diagram illustrating an example of output fluctuation of an O ₂ sensor when a misfire occurs in an engine.

FIG. 5 is a map showing a relationship between an engine speed in a normal operation state of the engine, its output, and a setting region of an output signal frequency of an O ₂ sensor 17;

FIG. 6 is a flowchart illustrating a determination procedure according to the embodiment.

[Explanation of symbols]

11 is an electronic control unit, 12 is a cylinder block, 1
3 is an engine, 14 is an exhaust pipe, 15 is an exhaust passage, 16 is a catalytic converter, 17 is an O ₂ sensor, 18 is a crankshaft,
9 is a detection ring, 20 is a pickup, 21 is a misfire indicator lamp, and 22 is a power supply.

Claims (1)

(57) [Claims] An angular velocity for detecting a crankshaft angular velocity of an engine.
Degree detecting means and the angular velocity detected by the angular velocity detecting means.
First misfire detecting means for detecting misfire of the engine, and oxygen concentration detecting means for detecting oxygen concentration in exhaust gas of the engine.
It is determined whether the output means and the oxygen concentration detecting means are activated.
Activation determining means, and a change in oxygen concentration detected by the oxygen concentration detecting means.
Second misfire detection means for detecting misfire of the engine based on
And the number of revolutions of the engine exceeds a predetermined number of revolutions
Sometimes it is determined that the engine is in the first misfire determination area,
And the load are not more than the predetermined number of revolutions and
The second misfire determination area when the load is equal to or less than the predetermined load,
Further, when the engine speed and load
A third misfire determination when the number is equal to or less than the predetermined load and exceeds the predetermined load.
A misfire determination area determining means for determining an area; and each of the misfire determinations determined by the misfire determination area determination means.
The first or second misfire detection means may
Misfire judgment to judge misfire of the engine based on at least one
Setting means, wherein the misfire determining means, in the first misfire determination area, the second misfire detecting means
More misfire is determined, and in the second misfire determination area, the first misfire detection means
Misfire is further determined, and in the third misfire determination region, the activation determination means
It was determined that the oxygen concentration detection means was in the activated state
Sometimes one of the first or second misfire detecting means is
When the misfire of the engine is detected, the misfire is determined and the oxygen concentration is determined.
When it is determined that the detecting means is not in the activated state,
A misfire detection device for an engine, wherein misfire is determined by first misfire detection means .