JPH09166041A - Misfire detector of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect misfires with a simple structure. SOLUTION: When an engine revolution number Ne(n) exceeds a switching determination revolution number NeA, an ECU 30 calculates the angular acceleration Dω (n) of a crankshaft 23 based on a timing for moving away of a rear end from a sensor main body 26 (that is, BTDC 5 deg.) instead of a timing for entering of each vane tip formed in a rotor plate 25 into the sensor main body 26 (that is, BTDC 75 deg.). Then, the ECU 30 calculates an average angular acceleration Dave (n) corresponding to each cylinder from angular acceleration Dω (n) in a misfire determining region, determines whether this is lower than a misfire determination threshold value Dω A or not and if this determination is Yes, a misfire alarm lamp 31 is lit or the like in a misfire processing subroutine and then the process returns to START and control is repeated.

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 technique for enabling accurate misfire detection even in a high engine speed range.

[0002]

2. Description of the Related Art In a spark ignition internal combustion engine mounted on an automobile or the like, a misfire often occurs when a failure occurs in an ignition device, a fuel supply device or the like. In this case, HC (hydrocarbon)
Since unburned fuel, mainly composed of methane, flows into the exhaust system, resulting in overheating of the catalyst device and an increase in harmful exhaust gas components, it has been necessary to promptly detect misfire. Further, in recent years, in order to improve fuel efficiency and reduce harmful exhaust gas components, a lean burn engine has been proposed in which a lean air-fuel mixture is burned. In this type of engine, fuel injection control is often performed near the misfire limit by gradually diluting the air-fuel ratio of each cylinder, and it is necessary to accurately detect misfire for each cylinder.

As a misfire detection device for an internal combustion engine, a device for detecting a misfire based on a change in a pressure in a combustion chamber (hereinafter referred to as an in-cylinder pressure) disclosed in Japanese Patent Laid-Open No. 4-58052, etc. has been conventionally used. There is proposed a device for detecting misfire based on the fluctuation of crank angular acceleration, which is described in, for example, Kaihei 6-22931. The former device detects a misfire of a V-type 2-cylinder 2-cycle engine that retards the ignition timing at a high rotation speed, and uses a finger pressure sensor mounted on a cylinder head bolt to detect a cylinder before and after top dead center (TDC). The deviation of the internal pressure is detected, and when it falls below a predetermined threshold value, it is determined that a misfire has occurred. At the time of high rotation, the appearance timing of the peak value of the in-cylinder pressure fluctuates due to the retardation of the ignition timing, so the detection timing after TDC is also retarded. Further, in the latter device, a vane type crank angle sensor consisting of a rotor having a plurality of vanes and a sensor body is attached to a crankshaft, and for example, the rise of the crank angle signal (the moment when each vane begins to cross the sensor body) Calculate the crank angular acceleration from the interval,
When this falls below a predetermined threshold value, it is determined that a misfire has occurred.

[0004]

By the way, the conventional misfire detecting device described above has various problems and drawbacks as described below. For example, in a device that detects a misfire based on a change in cylinder pressure, when applied to a multi-cylinder engine for a passenger car, the device configuration becomes complicated and an increase in cost is unavoidable. That is, in-line 4-cylinder and V-type 6
In a cylinder engine or the like, since a plurality of cylinders share a cylinder block and a cylinder head, a finger pressure sensor having a simple structure cannot be used to detect the cylinder pressure of each cylinder, and a relatively expensive cylinder is used. It was necessary to install the internal pressure sensor in a cylinder block or the like for the number of cylinders. Further, in order to transmit the signal from each in-cylinder pressure sensor, the wiring and connectors around the engine are increased, and the control program for the engine control device for processing the signal tends to be complicated.

On the other hand, in a device for detecting a misfire based on a change in crank angular acceleration, if the phase of a torque curve (that is, a change in crank angular acceleration) deviates due to an increase in engine speed, it is difficult or impossible to determine a misfiring cylinder. Sometimes it was possible. For example, in a low engine speed range, a predetermined crank angle (for example, BTDC75 ° in each cylinder)
When the average angular acceleration is obtained by measuring each time, a crank angle region (for example, 12
The angular acceleration at 0 °) is significantly reduced, and the average angular acceleration falls below the misfire determination threshold value, and misfire is determined. However,
In the high engine speed range, the phase of the torque curve shifts to the advance side due to the advance of the ignition timing, etc., so the torque due to misfire not only in the misfiring cylinder but also in the crank angle range corresponding to the cylinder immediately preceding in the ignition sequence. Occurs. As a result, the average angular accelerations of the misfiring cylinder and the cylinder immediately before it both become less than or equal to the misfire determination threshold value, and misfire prevention processing is performed on the cylinders that are not actually misfiring (for example, enrichment of the air-fuel ratio in a lean burn engine. Etc.) may be performed. On the contrary, depending on the setting of the misfire determination threshold value, neither cylinder may be determined to be misfire, and the vehicle may continue to run in the misfire state and the harmful exhaust gas component may increase.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a misfire detecting device for an internal combustion engine, which can accurately detect misfire while adopting a simple device configuration.

[0007]

Therefore, in claim 1 of the present invention, a crank angle sensor that outputs a crank angle signal at a plurality of crank angles in accordance with the rotation of the internal combustion engine, and a predetermined angle input from the crank angle sensor. Is obtained from the crank rotation state amount calculation means for calculating the crank rotation state amount in a predetermined crank angle region of the internal combustion engine, and the calculation result of the crank rotation state amount calculation means. And a misfire determination means for determining a misfire of a predetermined cylinder of the internal combustion engine based on the fluctuation of the crank rotation state quantity, wherein the crank rotation state quantity calculation means calculates the engine rotation state quantity in calculating the crank rotation state quantity. A plurality of crank angle signal sets are selectively used as the reference crank angle signal set according to the change of To propose a misfire detection apparatus of the combustion engine.

According to a second aspect of the present invention, in the misfire detection device according to the first aspect, the misfire determination means determines that the predetermined cylinder has misfired when the crank rotation state amount falls below a predetermined threshold value. Suggest what to do. According to a third aspect of the present invention, in the misfire detection device according to the first or second aspect, the engine operating state quantity is an engine rotation speed, and the crank rotation state quantity calculating means has the engine rotation speed exceeding a predetermined threshold value. Therefore, it is proposed to use the crank angle signal set on the advance side as the reference crank angle signal set.

According to a fourth aspect of the present invention, in the misfire detection device according to the first to third aspects, the crank angle sensor rotates in accordance with the rotation of the crankshaft of the internal combustion engine, and a plurality of vanes are arranged on the circumference. The crank rotation state quantity calculating means includes: rotating members formed at substantially equal intervals; and signal generating means for generating a crank angle signal when the vanes formed on the rotating member enter and leave. As the reference crank angle signal set, it is proposed to selectively use the crank angle signal set when the vane enters and the crank angle signal set when the vane leaves.

According to a fifth aspect of the present invention, in the misfire detection device according to the first to fourth aspects, the crank rotation state quantity calculating means, when switching the crank angle signal set to be used, for a predetermined period, the crank rotation state quantity. We propose to suspend the calculation of.

[0011]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an engine control system to which a rotation fluctuation detecting method according to the present invention is applied. In FIG. 1, reference numeral 1 is a V-type 6-cylinder gasoline engine for an automobile (hereinafter simply referred to as an engine). In the intake port 2 of the engine 1, a fuel injection valve 3 is provided for each cylinder.
Via an intake manifold 4 to which an air cleaner 5, an air flow sensor 6, a throttle valve 7, I
An intake pipe 9 including an SC (idle speed controller) 8 and the like is connected. An exhaust pipe 11 including an O ₂ sensor 12, a three-way catalyst 13, and a muffler (not shown) is connected to the exhaust port 10 via an exhaust manifold 11. In FIG. 1, 15 is the opening θ of the throttle valve 7.
A throttle sensor for detecting TH, a water temperature sensor 16 for detecting a cooling water temperature TW, an atmospheric pressure sensor 17 for detecting an atmospheric pressure Pa, and an intake air temperature sensor 18 for detecting an intake air temperature Ta.

The engine 1 has a cylinder head 20
An ignition plug 22 is screwed to face the combustion chamber 21 of each cylinder, and a crank angle sensor 24 is arranged on the front end side of a crankshaft 23. The crank angle sensor 24 includes a rotor plate 25 directly attached to the crankshaft 23 and a sensor body 26 that detects the rotation of the rotor plate 25. As shown in FIG. 2, three vanes 27a, 27b, 27c having an angular width of 70 ° are formed on the rotor plate 25 at equal intervals (120 ° intervals). These vanes 27a-27c
Indicates that the crank angle of either cylinder is 75 ° before top dead center (B
At the moment when TDC reaches 75 °, the tip enters the sensor body 26, and the crank angle of the cylinder is 5 ° before top dead center (BTDC).
The rear end is set to separate from the sensor main body 26 at the moment of 5 °). In FIG. 1, 28 is a spark plug 22.
It is an ignition coil that outputs a high voltage to.

An input / output device (not shown) and a storage device (ROM, RA) containing a large number of control programs are provided in the vehicle compartment.
M, BURAM, etc.), central processing unit (CPU), timer counter, etc., ECU (engine control unit)
30 is installed and performs comprehensive control of the engine 1. Detection information from the various sensors described above is input to the input side of the ECU 30. The ECU 30 drives the fuel injection valve 3, the ignition coil 28, and the like by calculating an optimum value of the fuel injection amount, the ignition timing, and the like based on the detection information, and when the misfire occurs in any of the cylinders, the driver's seat. The misfire warning light 31 provided in the.

The control procedure in this embodiment will be described below with reference to the control flowcharts of FIGS. 3 to 8 and the graphs of FIGS. 9 and 10. When the driver turns on the ignition key to start the engine 1, the ECU 30
Repeats the misfire detection subroutine shown in the flowcharts of FIGS. 3 to 6 at a predetermined control interval (for example, 10 ms).

When this subroutine is started, the ECU 3
In step S1, 0 is first determined whether a switching flag FCHG, which will be described later, is 0. If this determination is Yes (affirmative), the operation information from each sensor described above in step S3 is stored in the RAM. Read into. Next, in step S5, the ECU 30 determines the engine speed Ne (n) for this time based on the input interval of the output signal from the crank angle sensor 24.
Is calculated, and this is the preset switching determination rotation speed NeA.
(In the case of this embodiment, it is determined whether it is 4,000 rpm or less. Then, if this determination is Yes, the ECU 30 determines in step S7 whether the previous engine rotation speed Ne (n-1) was also the switching determination rotation speed NeA or less. Then, if this determination is Yes, the ECU 30 determines in step S9 that each vane 2
Based on the timing at which the tips of 7a to 27c enter the sensor body 26 (that is, BTDC 75 °), the crank angle region (= 120 ° ... The angular acceleration Dω (n) of the crankshaft 23 in (Note) is sequentially calculated.

When the calculation of the angular acceleration Dω (n) is completed, EC
In step S11 of FIG. 4, the U30 calculates the average angular acceleration Dωave (n) corresponding to each cylinder from the angular acceleration Dω (n) in the misfire determination area. Thereafter, the ECU 30 determines in step S13 whether the average angular acceleration Dωave (n) is below the misfire determination threshold DωA, and this determination is Yes.
If s, the misfire processing subroutine described later is executed in step S15, and then the process returns to the start and the control is repeated. On the other hand, if the determination in step S13 is No (negative), the normal processing subroutine described later is executed in step S17, and then the process returns to the start and the control is repeated. FIG.
Shows the angular acceleration Dω and the average angular acceleration Dωave of the crankshaft 23 during low-speed steady operation,
From this figure, it is understood that when a cylinder misfires, the angular acceleration Dω mainly falls in the misfire determination region of the cylinder, and the average angular acceleration Dωave also falls below the misfire determination threshold DωA. 9 and 10 to be described later, the amount of decrease in the angular acceleration Dω is shown by hatching.

The determination in step S5 of FIG. 3 is No, that is, the engine rotation speed Ne (n) at this time is the switching determination rotation speed NeA.
If it exceeds, the ECU 30 determines in step S21 whether the previous engine rotation speed Ne (n-1) has also exceeded the switching determination rotation speed NeA. Then, if this determination is Yes, the ECU 30 causes the misfire of the cylinder targeted this time based on the timing (that is, BTDC 5 °) at which the rear ends of the vanes 27a to 27c are separated from the sensor body 26 in step S23. The angular acceleration Dω (n) of the crankshaft 23 in the determination area is calculated.

When the calculation of the angular acceleration Dω (n) is completed, EC
U30 proceeds to step S11 of FIG. 4 and executes misfire determination and subsequent processing, as in the case where the engine speed Ne (n) is equal to or lower than the switching determination speed NeA. In FIG.
The angular acceleration Dω and the average angular acceleration Dωave of the crankshaft 23 during high-speed steady operation are shown. From this figure, when a cylinder misfires, the angular acceleration Dω mainly in the misfire determination region corresponding to that cylinder is shown. It can be seen that the average angular acceleration Dωave also falls below the misfire determination threshold DωA. In the conventional device described above, when the phase of the crank angular acceleration change is shifted to the advance side due to the advance of the ignition timing, etc., not only the misfire determination region of the misfiring cylinder but also the broken line The angular acceleration Dω also decreases in the misfire determination region of the cylinder positioned immediately before the misfire cylinder in the ignition order. As a result, the average angular acceleration Dωave in both cylinders is equal to the misfire determination threshold D.
Below ωA, false detection will occur.

On the other hand, step S7 or step S2
If the determination result in step 1 is No, the ECU 30 first sets the switching flag FCHG to 1 in step S31 of FIG. 5, and then sets the countdown timer TCD to the predetermined value Tx in step S33.
(0.1 second in this embodiment) is substituted, and the process returns to the start without performing the subsequent processing. The switching flag FCHG determines whether or not the engine speed Ne (n) has increased or decreased at the switching determination speed NeA, that is, the output signal of the crank angle sensor 24 serving as the reference of the misfire determination region is BTDC75 ° and BTDC5. It indicates whether or not the angle has been switched to or from. When the switching flag FCHG is set to 1 in step S31, the determination in step S1 of FIG.
The U30 determines in step S35 of FIG. 6 whether or not the value of the countdown timer TCD is 0. Then, while this determination is No, the ECU 30 repeats the control without performing any specific processing. This is because when the output signal of the reference crank angle sensor 24 is switched, the crank angle width and the like in the misfire determination region may be misaligned and erroneous detection may occur. When the countdown of the countdown timer TCD is completed and the determination in step S35 becomes Yes, the ECU 30 resets the switching flag FCHG to 0 in step S37 and returns to the start.

If the determination in step S15 is Yes, the ECU 30 executes the misfire processing subroutine shown in FIG. When this subroutine is started, E
The CU 30 illuminates the misfire warning light 31 in step S41 to call attention to the driver, stores the failure code for diagnosis in the ROM in step S43, and then returns to the misfire detection subroutine. If the determination in step S15 is No, the ECU 30 executes the normal processing subroutine shown in FIG. When this subroutine is started, the ECU 30 starts the misfire warning light 3 in step S51.
After turning off 1 and erasing the fault code for diagnosis from the ROM in step S53, the process returns to the misfire detection subroutine.

Although the specific embodiment has been described above, the aspect of the present invention is not limited to this embodiment.
For example, although the present invention is applied to the V-type 6-cylinder engine in the above-described embodiment, it may be applied to various engines having different numbers of cylinders and their arrangement, such as a single-cylinder engine and an in-line 4-cylinder engine. Further, as a measure at the time of misfire, instead of turning on the warning light, enrichment of the air-fuel ratio, retardation of ignition timing, or the like may be performed. Further, in the above-described embodiment, the one having the vane type rotor plate is used as the crank angle sensor, but the one that detects the rotation of the crankshaft every 1 ° may be used. Further, in the above embodiment, the determination is interrupted at the time of switching the misfire determination region for a predetermined time,
This may be performed over a predetermined process. Also,
In the above embodiment, the misfire is detected based on the fluctuation of the crank angular acceleration, but the crank angular velocity, the crank rotation speed, etc.
The misfire may be detected based on the variation of the crank rotation state amount of another type. In addition, the specific device configuration, control procedure, and the like can be appropriately changed without departing from the scope of the present invention.

[0022]

According to the misfire detection device of the first aspect of the present invention, a crank angle sensor that outputs a crank angle signal at a plurality of crank angles according to the rotation of the internal combustion engine, and a predetermined angle input from the crank angle sensor. Is obtained from the crank rotation state amount calculation means for calculating the crank rotation state amount in a predetermined crank angle region of the internal combustion engine, and the calculation result of the crank rotation state amount calculation means. And a misfire determination means for determining a misfire of a predetermined cylinder of the internal combustion engine based on the fluctuation of the crank rotation state quantity, wherein the crank rotation state quantity calculation means calculates the engine rotation state quantity in calculating the crank rotation state quantity. Since a plurality of crank angle signal sets are properly used as the reference crank angle signal set according to the change of Even out of phase of the accompanying angular acceleration change curve rise in the emission speed it will be able to pay the majority of the decrease in the crank angular acceleration at a predetermined crank angle region, to improve the accuracy of misfire detection.

According to a second aspect of the present invention, in the misfire detecting device according to the first aspect, the misfire determination means misfires the predetermined cylinder when the crank rotation state amount falls below a predetermined threshold value. Since it is determined that there is a misfire, it is not erroneously detected that a misfire has occurred during deceleration operation or sudden load increase. According to claim 3, in the misfire detection device according to claim 1 or 2, the engine operating state quantity is an engine rotation speed, and the crank rotation state quantity calculating means determines that the engine rotation speed is a predetermined threshold value. Since the crank angle signal set on the advance side is used as the reference crank angle signal set, the phase shift of the angular acceleration change curve due to the advance control of the ignition timing or the like can be reliably captured. it can.

According to a fourth aspect of the present invention, in the misfire detection device according to the first to third aspects, the crank angle sensor rotates in accordance with rotation of the crankshaft of the internal combustion engine, and a plurality of vanes surround the crankshaft. The crank rotation state amount calculating means includes a rotating member formed on the upper side at substantially equal intervals, and signal generating means for generating a crank angle signal when the vanes formed on the rotating member enter and leave. As the reference crank angle signal set, the crank angle signal set when the vane enters and the crank angle signal set when the vane leaves are used separately, so that a false detection is prevented while adopting a relatively simple configuration. it can.

According to a fifth aspect of the present invention, in the misfire detection device according to the first to fourth aspects, the crank rotation state quantity calculating means is configured to rotate the crank rotation for a predetermined period when switching the crank angle signal set to be used. Since the calculation of the state quantity is interrupted, it is possible to prevent erroneous detection due to an error in the reference crank angle signal set.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an engine control system to which a misfire detection device according to the present invention is applied.

FIG. 2 is a perspective view showing a crank angle sensor.

FIG. 3 is a flowchart showing a procedure of a misfire detection subroutine.

FIG. 4 is a flowchart showing a procedure of a misfire detection subroutine.

FIG. 5 is a flowchart showing a procedure of a misfire detection subroutine.

FIG. 6 is a flowchart showing a procedure of a misfire detection subroutine.

FIG. 7 is a flowchart showing a procedure of a subroutine for misfire processing.

FIG. 8 is a flowchart showing a procedure of a normal processing subroutine.

FIG. 9 is a graph showing angular acceleration and average angular acceleration during low-speed steady operation.

FIG. 10 is a graph showing angular acceleration and average angular acceleration during high-speed steady operation.

[Explanation of symbols]

 1 Engine 22 Spark Plug 23 Crank Shaft 24 Crank Angle Sensor 25 Rotor Plate 26 Sensor Body 27a-27c Vane 28 Ignition Coil 30 ECU 31 Misfire Warning Light

Claims (5)

[Claims] 1. A crank angle sensor that outputs crank angle signals at a plurality of crank angles as the internal combustion engine rotates, and a predetermined crank angle signal set input from the crank angle sensor as a reference crank angle signal set. Crank rotation state amount calculation means for calculating the crank rotation state amount in a predetermined crank angle region of the internal combustion engine, and based on the fluctuation of the crank rotation state amount obtained from the calculation result of the crank rotation state amount calculation means, And a misfire determination means for determining misfire of a predetermined cylinder, wherein the crank rotation state quantity calculation means calculates the crank rotation state quantity according to a change in the engine operating state quantity, and outputs a plurality of reference crank angle signal sets. A misfire detection device for an internal combustion engine, wherein different crank angle signal sets are used properly. 2. The internal combustion engine according to claim 1, wherein the misfire determination means determines that the predetermined cylinder is misfired when the crank rotation state amount falls below a predetermined threshold value. Misfire detection device. 3. The engine operating state quantity is an engine rotation speed, and the crank rotation state quantity calculating means determines that the engine rotation speed exceeds a predetermined threshold value, and thus the crank rotation state quantity calculation means advances as the reference crank angle signal set. 3. The misfire detection device for an internal combustion engine according to claim 1 or 2, wherein the crank angle signal set is used. 4. The crank angle sensor rotates with the rotation of a crankshaft of the internal combustion engine, and a plurality of vanes are formed on the circumference at substantially equal intervals, and the crank member is formed on the rotary member. A crank angle signal at the time of advancing the vane as the reference crank angle signal set. The misfire detection device for an internal combustion engine according to any one of claims 1 to 3, wherein a set and a crank angle signal set when the vane is disengaged are used properly. 5. The crank rotation state quantity calculation means suspends the calculation of the crank rotation state quantity for a predetermined period when switching the crank angle signal set to be used. 13. A misfire detection device for an internal combustion engine according to any one of 1.