JPH0436044A - Diagnostic device for misfire of engine - Google Patents

Abstract

PURPOSE:To prevent mistakes in diagnosing misfire that could be caused by rotary fluctuations during cranking and at the initial period of complete ignition by providing a misfire judgement stopping means for stopping judgement of misfire from the start of driving of a starter motor until a predetermined time elapses after driving of the starter motor is stopped. CONSTITUTION:Judgement of misfire is stopped by a misfire judgement stopping means M1 from the start of driving of a starter motor until a predetermined time elapses after driving of the starter motor is stopped. Then judgement of misfire is started by a misfire judging means M2 after the stopping period of misfire judgement elapses.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine misfire diagnosis device that temporarily stops misfire determination during engine startup.

[Prior Art] In general, in a multi-cylinder engine, it is ideal for combustion to occur through the same process every cycle in order to obtain stable output, but in a multi-cylinder engine, Unevenness in intake air distribution ratio due to intake air interference between cylinders, ■Slight differences in combustion temperature between cylinders caused by cooling routes, ■Manufacturing variations in combustion chamber volume of multiple cylinders, piston shape, etc., ■Injectors Combustion tends to vary due to slight variations in the air-fuel ratio of each cylinder due to differences in fuel injection lids due to manufacturing errors, etc.

Conventionally, this so-called combustion fluctuation has been solved by cylinder-specific air-fuel ratio control,
Ignition timing control has minimized the possibility of misfires, but in high-performance engines that have recently become more powerful and fuel efficient, intermittent misfires can occur if the injectors, spark plugs, etc. deteriorate or malfunction. This causes a decrease in output.

In multi-cylinder engines, even if intermittent misfires occur in one cylinder, the engine is often operated without being noticed.
It is difficult to diagnose during operation whether the cause of the misfire is temporary or caused by deterioration of the injector, spark plug, etc.

Therefore, for example, in Japanese Patent Application Laid-Open No. 61-258955, the difference between the minimum and maximum engine speeds of the cylinders in the previous combustion stroke and the minimum and maximum values of the engine speeds in the cylinders in the current combustion stroke are The combustion status of the relevant cylinder is determined based on whether this comparison value is within a preset reference value, and if combustion abnormality occurs more than a predetermined number of times, it is determined to be a misfire and a warning is issued. I have to.

[Problems to be Solved by the Invention] Incidentally, in the above-mentioned prior art, the misfire condition is determined by detecting engine rotational fluctuations, but the misfire diagnosis is not performed during cranking, where the engine rotational fluctuations are large, or at the beginning of a complete explosion. Doing so can easily lead to misdiagnosis and pose reliability problems.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an engine misfire diagnosis device that is capable of reducing misdiagnosis and achieving high reliability.

[Means for Solving the Problems] In order to achieve the above object, the engine misfire diagnosis device according to the present invention is provided, as shown in FIG. Misfire determination stopping means M that stops misfire determination until the time elapses
1, and a misfire determination means M2 that starts misfire determination after the misfire determination stop period has elapsed.

[Operation] In the above configuration, first, the misfire determination stopping means M1 stops the misfire determination from the start of driving the starter motor until a predetermined period of time elapses after driving of the starter motor stops.

Then, the misfire determination means M2 starts misfire determination after the misfire determination stop period has elapsed.

[Embodiments of the invention] Hereinafter, the present invention will be explained in detail based on the drawings.

Figures 2 to 9 show the first embodiment of the present invention, Figure 2 is a schematic diagram of the engine control system, Figure 3 is a front view of the crank rotor and crank angle sensor, and Figure 4 is a diagram of the cam rotor and crank angle sensor. A front view of the cam angle sensor, Fig. 5 is a time chart of cylinder pressure fluctuations, crank pulses, cam pulses, and engine speed, Fig. 6 is a conceptual diagram of the misfire determination level map, Fig. 7
The figure is a time chart of differential rotational speed and misfire determination level, FIG. 8 is a flowchart showing a misfire diagnosis stop procedure, and FIG. 9 is a flowchart showing a misfire determination procedure.

(Configuration) Reference numeral 1 in FIG. 2 is the engine body, and the figure shows a four-cylinder horizontally opposed engine.

An air cleaner 5 of an intake pipe 4 communicating with the intake boat 2a of this engine body 1 via an intake manifold 3
An intake air amount sensor 6 is installed immediately downstream of the intake manifold 3 , and an idle switch 8 that is turned ON when the throttle is fully closed is connected to the throttle valve 7 installed midway through the intake pipe 4 . Direct the injection port toward the intake boat 2a side on the downstream side (multi-point)
An injector 9 is provided.

Further, a crank rotor 15 is pivotally attached to the crankshaft 1b of the engine main body 1, and a crank angle sensor 16 consisting of an electromagnetic pickup or the like for detecting the crank angle is provided on the outer periphery of the rotor 15, and a crank rotor 15 is mounted on the crankshaft 1b. A cam rotor 17 is pivotally attached to a camshaft lc that rotates 1/2 of the rotation, and a cam angle sensor 18 is provided on the outer periphery of the cam rotor 17.

As shown in FIG. 3, projections 15a, 15b, and 15c are formed on the outer periphery of the crank rotor 15. These protrusions 15a, 15b, 15c are located before the compression top dead center of each cylinder (
BTDC) θ1. θ2. It is formed at the position θ3,
The engine rotation speed N is determined from the passage time between the protrusions 15b and 15C.
Calculate.

By the way, in general, the crank angle indicating the maximum combustion pressure in MBT (optimal ignition timing) control is almost constant over the entire operating range, and is about 10 BTDC, about 1 armpit, and as shown in FIG. , the opening timing of the exhaust valve of each cylinder is set to be slightly retarded than the ignition reference crank angle BTDCθ2 of the next combustion cylinder, but in general, the combustion pressure immediately after the exhaust valve opens drops rapidly. Therefore, the crank angle B
At TDC θ3, there is almost no effect of combustion pressure.

Therefore, the crank angle θ3 of the protrusion 15c is set to BTD.
Cl If set to the advance side from 0℃A, the above protrusion 15
The section between the crank angles BTDC θ2 and θ3 of b and 15c is almost unaffected by the combustion between the cylinders, that is, the section where no work is done by the combustion between one combustion stroke cylinder and the next combustion stroke cylinder. become.

Further, as shown in FIG. 4, cylinder discrimination protrusions 17a, 17b, and 17c are formed on the outer periphery of the cam rotor 17. The protrusion 17a is #3. It is formed at the position θ4 after the compression top dead center (ATDC) of the #4 cylinder, and the protrusion 17b
consists of three protrusions, the first of which is formed at the position θ5 after compression top dead center (ATDC) of the #1 cylinder, and furthermore, the protrusion 17c consists of two protrusions, the first of which is formed at a position θ6 after compression top dead center (ATDC) of #2 cylinder.

In addition, in the example shown in the figure, θ1=97℃A, θ2=65℃A
, θ3; 10℃A, θ4=20℃A, θ5=5℃A, θ
6 = 20'CA, θ(2-3) = 55°C,
With this arrangement, as shown in FIG. 5, for example, when the cam angle sensor 18 detects a cam pulse of θ5 (protrusion 17b), the crank pulse subsequently detected by the crank angle sensor 16 will change to the crank angle of #3 cylinder. It can be determined that the signal indicates

Also, after the cam pulse of θ5, θ4 (protrusion 17a
), it can be determined that the subsequent crank pulse detected by the crank angle sensor 16 indicates the crank angle of the #2 cylinder. Similarly θ6
The crank pulse after detecting the cam pulse of (protrusion 17c) indicates the crank angle of the #4 cylinder, and
When a cam pulse of θ4 (protrusion 17a) is detected after the cam pulse of θ6, it can be determined that the crank pulse detected thereafter indicates the crank angle of the #1 cylinder.

Further, after the cam pulse is detected by the cam angle sensor 18, it can be determined that the crank pulse detected by the crank angle sensor 16 indicates the reference crank angle (θ1) of the cylinder.

(Circuit configuration of control device) On the other hand, reference numeral 21 is a control device consisting of a microcomputer, etc., and this control device (ECU) 21 includes a CPU (central processing unit) 22, ROM 23, RAM 24, backup RAM 25, and I10 interface. 26 are connected to each other via a pass line 27, and each sensor 6.16° 18, idle switch 8, vehicle speed sensor 19, and starter switch 32 are connected to the input port of this I10 interface 26, and To the output port of the above I10 interface 26,
The injector 9 is connected via a drive circuit 28 to a warning means 29 such as an indicator lamp disposed on an instrument panel (not shown) or the like.

The ROM 23 stores control programs, fixed data, and the like. Fixed data includes a misfire determination level map M P /!, which will be described later. There is UN LEVEL.

Further, the RAM 24 stores the output signals of the Kamikita sensors after data processing and the data processed by the CPU 22, and the backup RAM 25 stores trouble data such as misfire determination data for each cylinder.

Furthermore, a failure diagnosis connector 30 is connected to the output port of the I10 interface 26, and a failure diagnosis serial monitor 3 is connected to the failure diagnosis connector 30.
By connecting 1 to 1, the l-rable data stored in the backup RAM 25 can be read.

Further, a starter motor 33 and a power source 34 are connected via the starter switch 32.

The ECU 21 is supplied with control power from the power supply 34 via the ignition relay 35 and the constant voltage circuit 36, and the backup RAM 25 is supplied with backup power. Also, code 37
is the ignition switch.

Further, the function of diagnosing a misfire of the control device 21 includes:
Includes misfire determination stopping means for stopping leap misfire determination from the start of driving of the starter motor until a predetermined period of time has elapsed since driving of the starter motor stops, and misfire determination means for starting misfire determination after the misfire determination stop period has elapsed. It is.

(Function) Next, the misfire diagnosis procedure in the control device 21 will be explained according to the flowcharts of FIGS. 8 and 9.

: Misfire diagnosis stop procedure: This flowchart starts at the same time as the ECU power is turned on.

As shown in FIG. 8, step (hereinafter abbreviated as "S") 1
01 clears the misfire diagnosis stop flag FLAGA to set the initial value (FLAGA←0, misfire diagnosis stop cancelled), and 8
102 or less, it is determined whether to stop the misfire diagnosis.

First, in 5102, it is determined whether the starter switch 32 is ON. When the starter switch 32 is OFF, 5
Return to 101. Note that while the starter switch 32 is not turned on after the ECU is powered on, the misfire diagnosis stop flag FLAGA maintains the stop release (FLAGA←0) state, but since the engine is not started, the following will be explained later. The misfire diagnostic program will never be executed.

On the other hand, if it is determined in 5102 that the starter switch 32 is ON, the process proceeds to 8103, where the delay timer TIMER1 is set to a set value n5ET (e.g., equivalent to 2 SeC), and the misfire diagnosis is stopped in 5104. Set the flag FLAGA (F
LAGA-1, misfire diagnosis stopped).

When cranking is performed by the starter motor 33, the crank rotor 15 and the cam rotor 17 rotate, so the crank angle sensor 16 and the cam angle sensor 18 generate crank pulses.
Cam pulse is detected.

This is because the engine speed during cranking is unstable and fluctuates widely, so if the misfire diagnosis stop flag FLAGA is not set, there is a risk that a misfire condition will be erroneously diagnosed in the misfire diagnosis program described later.

Next, proceeding to 5105, the starter switch 32
is OFF. If the starter switch 32 is ON, it is determined that cranking is in progress and the process returns to 8103; if it is OFF, it is determined that the engine has completely exploded and the process returns to 8106.
Proceed to.

Proceeding to 8106, the set value n SET of the delay timer TIMERI set in 5103 above is subtracted (T
IMER1←TIMERI−1).

Then, in 5107, the above-mentioned delay timer TIMER1
Determine whether T I MER1≠0 has become 0.
In this case, it is determined that the timer is being subtracted, and the process returns to step 5105, where it is again determined whether the starter switch 32 is OFF. If the engine does not start on the first cranking,
This is because there is a possibility that the cranking operation will be performed again.

If TIMER1=O, it is determined that a predetermined period of time has elapsed, the process proceeds to 5108, and the misfire diagnosis stop flag FLA is
Clear G^ (FLAGA←0) and exit the routine.

As a result, misfire diagnosis is stopped during the ranking of relatively large rotational fluctuations and for a predetermined period of time after complete detonation, reducing misdiagnosis, improving diagnostic accuracy, and achieving high reliability. can.

: Misfire diagnosis procedure: This misfire diagnosis is executed interruptively for each cylinder in synchronization with the engine speed.

As shown in FIG. 9, first, in step 5201, the misfire diagnosis stop flag of the misfire diagnosis stop program)=゛LAG^
is in a reset state (FLAGA = 0, misfire diagnosis stop canceled). If the misfire diagnosis is stopped when FLAG 8 = 1), it is determined that the engine is cranking or in the early stage of a complete explosion, and the routine is exited without performing a misfire diagnosis.

On the other hand, if FLAGA = O (misfire diagnosis stop canceled),
In order to perform a misfire diagnosis, first, in 5202, the combustion stroke cylinder $i (i=1.3, 2°4) is determined based on the crank pulse and cam pulse output from the crank angle sensor 16 and the cam angle sensor 18, respectively. , 520
3, the calculation cycle number Ci1 of the combustion stroke cylinder #i is counted up (C11←Cil+1).

Note that when the engine is stopped, no pulses are output from the sensors 16 and 18 even if FLAGA=O, so this diagnostic program is not executed.

Next, in 5204, BTDCθ2. output from the crank angle sensor 16 is determined. The crank pulse for detecting θ3 is determined by the interruption of the cam pulse, and in step 5205, the BTDC θ゛2. The elapsed time between crank pulses for detecting θ3 and θ2. Calculate the period f2.3 from the angle of θ3 (θ2-θ3) (chi2゜3←dt2,3/d(θ2
-θ3)).

After that, in 8206, the current engine rotation speed NNE- is calculated from the periodic element 2.3.NNE-←60/(2π
・Second 2.3)) At 5207, the section where no work is being done by combustion in combustion stroke cylinder #1 is determined from the difference between the current engine speed NNE- and the engine speed NOLD calculated in the previous routine. Calculate the difference rotational speed ΔNi (i = 1.3, 2.4) of (θ2-θ3) (
ΔNi←NNEW-NOLD).

As shown in Fig. 5, in the case of a 4-stroke, 4-cylinder engine, the calculation of the engine rotational speed N NEW is performed every 180°C in the section where no work is being done by combustion. If we pay attention to this, if we subtract the previously calculated engine speed NO[0 from the currently calculated engine speed N NEW, we will get the differential rotational speed ΔN of cylinder #1.
1 is obtained, and on the other hand, looking at cylinder #3, the cylinder #1 is
By setting the engine rotation speed NNE- to N OLD,
The differential rotational speed ΔN3 can be determined from the subsequent engine rotational speed N NEW of cylinder #3.

The common engine speed between the cylinders is N.
4.1, N1.3, N3.2, and N2.4, the differential rotational speed of each cylinder is as follows.

ΔNi = NNEW -NOLD ΔN 1 = N1.3 - N4.1 ΔN5 = N3.2 - N1.3 ΔN 2 = N2.4 - N3.2 ΔN4 = N4.
1 -N2.4 By the way, experiments have revealed that the differential rotation angle ΔNi has a strong correlation with the indicated mean effective pressure Pi, that is, the combustion state of the cylinder. Therefore, by determining this differential rotational speed ΔNi, it is possible to estimate whether the combustion state n (indicated mean effective pressure) of each cylinder #i is good or bad.

The relationship between the differential rotational speed 1UNi and the indicated average effective pressure is shown below.

First, the state in which the engine is rotating is represented by an equation: I: Moment of inertia N: Engine speed Ti: Commanded torque Tf: Friction torque.This equation (1) is simplified, and then the pressure is Replaced and expressed, Pi; indicated average effective pressure Pf: friction loss effective pressure.

According to experiments, if the crank angular width θ2.3 for detecting the rotational speed is set before and after the combustion stroke, in the case of a 4-cycle 4-cylinder engine, the above-mentioned difference rotational speed ΔNi and the temporal change between them JT <180℃A), the above (
3) As a result of calculating dN/dt in the equation, a very strong correlation is obtained.

In this case, if we consider that the variation in ΔT (180°C A) is negligible and the friction loss effective pressure Pf is also constant,
From the above formula (3), ΔN=KxPi 10PF = 14) Pi
, PF: A constant holds true.

Therefore, by determining the differential rotational speed ΔNi of each cylinder, the indicated mean effective pressure Pi, that is, the combustion state can be estimated for each cylinder.

Then, the differential rotational speed ΔNi of each cylinder #i is individually “
If the value approaches 01, the combustion state for each cylinder can be made uniform.

On the other hand, in the above equation (3), if the frictional average effective pressure Pf is assumed to be constant, and the constant C is set, and the proportionality constant is K, then N - = - Pi - C t (5), and therefore, K , C in advance, the indicated mean effective pressure Pi can be determined.

According to the equation (5), by differentiating the rotational speed difference ΔNi with respect to time, the indicated mean effective pressure Pi can be estimated from the rotational speed difference ΔN with higher accuracy.

The engine speed NNEI calculated in this interval (θ2 - θ3) where no work is done by combustion does not include the fluctuation factor of the engine speed due to combustion pressure, so it is relatively stable. Engine speed NNEW
,, Since N0LD is detected under the same conditions, the correlation between the differential rotational speed ANi and the combustion state of the combustion stroke cylinder #i becomes clear, and therefore the combustion state can be estimated with high accuracy. .

After that, in 8208, engine load data (=basic fuel injection pulse width) TP is calculated based on the engine speed NNE- and intake air amount Q obtained in this routine (TI
) 4-KXQ/NNEW K: constant).

Then, in step 5209, the misfire judgment level ΔN is calculated from the misfire judgment level map MPΔNLEVEL using the engine load data Tp and the engine speed N NEW as parameters.
Set LEVEL.

As shown in FIG. 6, the misfire determination level map MPΔ
N LEVEL is a three-dimensional map with engine speed N NEW and engine load data Tp as parameters.
A misfire determination level ΔN LEVEL determined in advance through experiments or the like is stored in each area surrounded by a grid.

As shown in FIG. 7, the differential rotational speed ΔNi exhibits a relatively large value during a transient period, but the range of this variation differs depending on the operating conditions of the engine. Therefore, high misfire determination accuracy can be obtained by determining the fluctuation range for each operating condition through experiments, etc., setting the misfire determination level ΔN LEVE [according to the fluctuation range, and creating a map.

Then, at 5210, the difference rotation speed/! UNi is compared with the misfire determination level AN LEVEL. 1UN
i <4 N LEVEL, that is, the differential rotational speed JNi of the combustion stroke cylinder #1 is the misfire determination level, 4 N
If it is determined that it is lower than LEVEL (see Figure 7),
It is determined that a misfire has occurred and the process proceeds to 5211, and ANi ≧ΔNL
If EVEL is NO, it is determined that combustion is normal and the process proceeds to 5212.

When proceeding to 5211, the number of misfires Ci2 for each cylinder of the combustion stroke cylinder #i is counted up, C+2←Ci2+1
), proceed to 5212.

Then, in 5212, the number of calculation cycles Cil of the combustion stroke cylinder #i is compared with the preset number of sampling cycles C1ISET (for example, 100 cycles), and if the number of calculation cycles Cil has not reached the number of sampling cycles C1ISET (Cil<C11s
ET), jumps to 5220, and if the number of calculation cycles Cil reaches the number of sampling cycles C11SET (Ci11≧C1lsET), proceed to 5213 and reset the number of calculation cycles Ci1 (Ci1←
0).

Next, in 5214, the cylinder-specific average number of misfires C for the combustion stroke cylinder #i calculated in the previous sampling period is calculated.
12(-1) is read out, and in 5215, this average number of misfires by cylinder C12(-1) and the number of misfires by cylinder C counted in the current sampling cycle number C1lsET.
Based on i2, the current average number of misfires for each cylinder Ci2 is calculated from the weighted average of the weighting coefficient r (Ci2←((2-1)
XCi2(-1)+C12)/2).

By determining the average number of misfires Ci2 for each cylinder using a weighted average, it is possible to correct misfires in the combustion stroke cylinder #i, discrimination errors, and temporary misjudgments of misfires due to sudden combustion fluctuations.

After that, in 5216, reset the number of misfires for each cylinder Ci2 (C12←0), and in 5217, the average number of misfires for each cylinder C12 (C12←0) calculated in the previous sampling period
-1) is updated with the currently calculated average number of misfires for each cylinder C12 (C12(-1)←C12).

Then, in 8218, if the current average number of misfires for each cylinder C12 exceeds the preset misfire abnormality determination reference number C12sET■, it is determined that the cylinder #i has a misfire abnormality, and the process proceeds to 5219, where the backup RAM 25 is After storing the misfire abnormality data of the cylinder #i in a predetermined address and warning the driver of the misfire abnormality by lighting the warning means 29 such as an indicator lamp, proceed to 5220, C12≦C
If it is determined that 12sET has occurred, it is determined that a misfire abnormality has not yet occurred in the cylinder #i, and the process proceeds to 5220.

5220, the engine rotation speed N NEW calculated this time
The engine rotation speed N0LD calculated in the previous routine is updated (NOLD 4-NNEW), and the routine is exited.

The misfire abnormality data for the cylinder #i stored in the storage means (backup RAM>25) is stored on the serial monitor 31 at a dealer's service station, etc.
The misfire abnormality data stored in the storage means 25 can be cleared via the serial monitor 31.

(Second Embodiment) FIG. 10 is a flowchart showing a misfire determination procedure according to a second embodiment of the present invention.

Note that steps having the same functions as those in the first embodiment are given the same reference numerals as in the first embodiment, and explanations thereof will be omitted.

In this embodiment, the number of misfires is sequentially stored for each cylinder, and when the number of misfires reaches the maximum count, the maximum number of misfires is fixed and stored.

First, cancel the misfire diagnosis stop with 5201 (FLAGA = 0
), the process proceeds to 5202, and after determining the combustion stroke cylinder #, it is determined in 5301 whether the misfire maximum count number 7 lag Fi of the combustion stroke cylinder #1 is set (Fi==1), or
Determine whether it is in the reset state (Fi = O). If it is in the set state (Fi = 1), the process proceeds to 5302, where the warning means 29 such as an indicator lamp is turned on to warn the driver of the misfire abnormality, and the routine is exited.

On the other hand, if it is determined that the misfire maximum count flag Fi is in the reset state (Fi = O),
Up to this point, the same procedure as in the first embodiment described above is performed.

Then, in the above 5210, it is determined that the combustion stroke cylinder #1 has misfired (ΔNi <, 6NLEVEL)), and the process proceeds to Relto 5303, and the normal combustion (ΔN1≧ΔNLEV
If it is determined that the misfire maximum count flag Fi is reset (Fi←0), the process proceeds to step 3304.

If you proceed to 5303, warning means 2 such as indicator lamps etc.
9 is turned on for a short period of time to warn the driver that a misfire has occurred.

By recognizing the frequency with which the warning means 29 lights up, the driver can grasp the engine misfire situation, that is, whether misfires are likely to occur under the engine operating conditions.

Then, in 5305, after counting up the number of misfires Ci2 of the cylinder #i (Ci2←ci2+1), this counted up value Ci2 is stored in the storage means (backup R
Store at a predetermined address of AM>25.

At a dealer's service station or the like, the serial monitor 31 is connected to read the misfire count data for each cylinder stored in the storage means 25, and the misfire situation is determined by referring to a manual or the like.

After that, in 8306, the number of misfires Ci2 of the cylinder #i is compared with a preset maximum count number C12HAX (for example, 2 bytes is FFH), and Ci2=C12HA
If X (7), proceed to 8307, and if Ci2<C1
In the case of 2HAX, proceed to 5304.

It is determined that the number of misfires Ci2 has reached the maximum count number C12HAX (C12HAX in C12), and 53
07, the number of misfires Ci2 stored in the predetermined address of the storage means 25 is set to the maximum count number Ct2H^X.
At 8308, the misfire maximum count flag Fi is set (Fi←1).

Then, when proceeding from 8308 or 5304 to 5309, the previously calculated engine speed N OLD is updated with the currently calculated engine speed NNE- (N OL
D←NNEI11) , the routine is removed.

(Third Embodiment) FIG. 11 is a flowchart showing a misfire determination procedure according to a third embodiment of the present invention.

Note that steps having the same functions as those in the first embodiment and the second embodiment are designated by the same reference numerals, and the explanation thereof will be omitted.

In this embodiment, misfire determination is performed during idling operation.

Since the engine speed during idling is low and load fluctuations are small, the misfire determination level ΔN LEVE[ is
There is no need to use a variable value (6209) as in the first embodiment described above, and a fixed value determined in advance through experiments will not cause erroneous determination.

Therefore, the misfire determination procedure according to this embodiment is almost the same as the flowchart shown in FIG.
At 01, the misfire diagnosis stop flag FLAGA is in the reset state (
FLAGA = O1 misfire diagnosis stop cancellation) is determined,
Proceeding to step 5401, judgment is made based on the ON state of the idle switch 8 (throttle fully closed, OFF (fully open)) and the output value of the vehicle speed sensor 19, the idle determination is made, and the idle state is canceled (idle switch OFF, or vehicle speed ≠ 0). If it is determined that the
If it is determined that the idle switch is ON and the vehicle speed is O,
The point of proceeding to 5202 and 5208.5209 of the first example
The difference is that instead of 5402, the fixed misfire determination level ΔN LEVEL stored in advance in the ROM 23 is read out and % is calculated.

(Fourth Embodiment) FIG. 12 is a flowchart showing a misfire determination procedure according to a fourth embodiment of the present invention.

Incidentally, steps having the same functions as those in the second embodiment and the third embodiment are given the same reference numerals, and the explanation thereof will be omitted.

In this embodiment, the number of misfires during idling is sequentially stored for each cylinder, and when the number of misfires reaches the maximum count, the maximum number of misfires is fixed and stored.

The misfire determination procedure according to this embodiment is almost the same as the flowchart shown in FIG. 10, but first, the idle determination is performed at 5401, and the preset misfire determination level is set at 5402. The difference is that I N LEVEL is read.

Note that the above-mentioned 5401 and 5402 are the same as those in the third embodiment (FIG. 11) described above, so the explanation will be omitted.

Note that the present invention is not limited to the above-mentioned embodiments. For example, in each embodiment, the engine rotation speed is used as the momentum, but instead of this, the period, angular velocity,
Alternatively, angular acceleration may be used.

[Effects of the Invention] As described above, according to the present invention, there is provided a misfire determination stopping means for stopping the misfire determination from the start of driving the starter motor until a predetermined period of time has elapsed since the driving of the starter motor has stopped; Since the engine is equipped with a misfire determination means that starts misfire determination after the misfire determination stop period has elapsed, misfires are less likely to be erroneously disconnected due to rotational fluctuations during cranking and in the early stages of complete combustion, improving diagnostic accuracy and achieving high Excellent effects such as reliability can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to claims of the present invention, Figs. 2 to 9 show a first embodiment of the invention, Fig. 2 is a schematic diagram of an engine control system, and Fig. 3 is a crank rotor and crank angle sensor. Figure 4 is a front view of the cam rotor and cam angle sensor, Figure 5 is a front view of the cylinder pressure fluctuation, crank pulse, cam pulse,
6 is a conceptual diagram of a misfire determination level map, FIG. 7 is a time chart 1 of differential rotational speed and misfire determination level, and FIG. 8 is a flowchart showing a misfire diagnosis stop procedure. 9 is a flowchart showing the misfire determination procedure, FIG. 10 is a flowchart showing the misfire determination procedure according to the second embodiment of the present invention, FIG. 11 is a flowchart showing the misfire determination procedure according to the third embodiment of the present invention, and FIG. The figure is a flowchart showing a misfire determination procedure according to a fourth embodiment of the present invention. Ml... misfire determination stop means, M2... misfire determination means. Figure 1 Figure 6 Figure 711 Figure 8

Claims (1)

[Scope of Claims] Misfire determination stopping means for stopping misfire determination from the start of driving of the starter motor until a predetermined period of time has elapsed since driving of the starter motor has stopped, and for starting misfire determination after the misfire determination stop period has elapsed. What is claimed is: 1. A misfire diagnostic device for an engine, comprising: misfire determining means.