JPH0833142B2 - Misfire diagnosis device for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a misfire diagnosis device for an internal combustion engine.

<Prior Art> When an internal combustion engine misfires, unburned gas is discharged, which causes post-combustion, and the catalyst provided in the exhaust passage is burned out.

Therefore, it is necessary to detect a misfire, and as a method therefor, a time period of a predetermined crank angle section in an explosion stroke determined based on a reference pulse signal from a crank angle sensor is conventionally measured and compared with that of other cylinders. By doing so, he is trying to diagnose a misfire.

In other words, if a misfire occurs in any of the cylinders, the rotation speed drops, so that it is monitored that the cycle becomes long.

<Problems to be Solved by the Invention> By the way, as the installation location of the crank angle sensor, it is impossible to determine the cylinder on the crankshaft side.
The rotation is transmitted from the crankshaft via a timing belt (chain), and the camshaft side is rotated once for every two rotations of the crankshaft.

Therefore, if the crank angle section for time period counting is determined based on the signal from the crank angle sensor, a signal output from the crank angle sensor due to backlash, expansion or contraction of the timing belt during acceleration / deceleration ( There is a deviation between the time of occurrence of the reference pulse signal or unit pulse signal) and the actual crank angle, and the deviation also fluctuates, causing a deviation in the predetermined crank angle section that is the reference for the misfire diagnosis, resulting in a time cycle. However, there was a problem that the timekeeping became inaccurate and a misdiagnosis of whether or not there was a misfire was made.

The present invention has been made in view of the above problems, and an object thereof is to provide a misfire diagnosis device for an internal combustion engine, which enables accurate diagnosis.

<Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention relates to rotation of a shaft which is driven by a crankshaft of an engine and makes one rotation for every two rotations of the crankshaft, as shown in FIG. Separately from the crank angle sensor that outputs the reference pulse signal at every 720 ° / n (n is the number of cylinders) at the crank angle in synchronization, the auxiliary pulse signal for each minute crank angle is directly synchronized with the rotation of the crankshaft. A pickup type sensor for outputting is provided, and counting of the auxiliary pulse signal from the pickup type sensor is started by generation of the reference pulse signal from the crank angle sensor, and the first signal is output when the counting of the first predetermined number is completed. First counting means (a) for outputting
And second counting means (b) for starting the counting of the auxiliary pulse signal from the pickup type sensor by the generation of the first signal and outputting the second signal when the counting of the second predetermined number is completed. , A clocking means (c) for timing the time from the generation of the first signal to the generation of the second signal, and a misfire determination means (d) for determining the presence or absence of a misfiring cylinder from the change state of the clocked time. And a third counting means (e) for counting the auxiliary pulse signal from the pickup type sensor between the reference pulse signals from the crank angle sensor, and the count value is compared with a reference value to detect the pickup type sensor. A configuration is provided that includes a determination stopping unit (f) that detects the presence or absence of an abnormality and stops the misfire determination by the misfire determination unit when the abnormality is detected.

<Operation> According to the above configuration, the auxiliary pulse signal output directly in synchronization with the crankshaft is counted with reference to the time of generation of the reference pulse signal from the crank angle sensor,
After counting the first predetermined number, the first signal is output to determine the timing start timing.

Next, the auxiliary pulse signal is further counted after the generation of the first signal, and after the second predetermined number is counted, the second signal is output to determine the timing end timing.

In this way, the timing start timing and timing end timing are determined, the time between them is clocked, and the presence or absence of the misfiring cylinder is determined based on the change state of this time.

That is, the presence / absence of the misfiring cylinder can be determined based on the signal output in direct synchronization with the rotation of the crankshaft.

Furthermore, the first predetermined number is counted with reference to the time of generation of the reference pulse signal from the crank angle sensor to determine the timing start timing to determine the crank angle section used for determining the presence or absence of the misfiring cylinder. , Can be set so as to be optimal for determination, that is, in a section where the influence of misfire is most likely to appear.

When the reference pulse signal is generated from the crank angle sensor, a shift may occur with respect to the crank angle, but there is no problem if the crank angle section is constant.

Further, in the present invention, since the pickup type sensor is additionally provided, self-diagnosis of the pickup type sensor is indispensable. Therefore, the auxiliary pulse signals between the reference pulse signals are counted and the counted value is compared with the reference value. Then, the presence or absence of abnormality of the pickup type sensor is detected. And
When the abnormality of the pickup type sensor is detected, the misfire determination is stopped to improve the reliability of the misfire diagnosis.

<Examples> Examples of the present invention will be described below with reference to FIGS. 2 to 7.

 First, the system will be described with reference to FIG.

The engine 1 mainly includes a cylinder 2, a piston 3, a connecting rod 4, a crankshaft 5, an intake valve 6, an exhaust valve 7 and a camshaft 8.

The rotation of the crankshaft 5 is transmitted to the camshaft 8 at a rate of one rotation for every two rotations of the crankshaft 5, via the timing pulley 9, the timing belt 10, and the timing pulley 11 provided at one end thereof.

The cam shaft 8 has a crank angle sensor 12 of photoelectric type or the like.
The crank angle sensor 12 is provided with a reference pulse signal REF (including a cylinder discrimination signal) for each 180 ° (in the case of four cylinders) and a unit pulse signal for each 2 °, for example.
The POS is output to the control unit 13.

Further, a pickup type sensor 15 is provided so as to face a toothed surface on the outer circumference of a flywheel 14 provided at the other end of the crankshaft 5, and an auxiliary pulse for each minute angle (for example, 3 °) in crank angle. The signal SUM is output to the control unit 13.

Next, the hardware in the control unit 13 will be described with reference to FIGS. 3 and 4, and the misfire diagnosis and self-diagnosis routines will be described with reference to FIGS. 5 to 7. .

First, the hardware will be described with reference to FIGS. 3 and 4.

The auxiliary pulse signal SUB output from the pickup type sensor (15 in FIG. 1) is the first counter 16 as the first counting means and the second counter 16 as the second counting means.
Entered in 17.

The first counter 16 is a crank angle sensor (1 in FIG. 1).
The reference pulse signal REF output from 2) is used as a trigger to start counting the auxiliary pulse signal SUB.

Then, when the count value reaches the preset first predetermined number, the first signal is output to the second counter 17.

The first predetermined number is set as a number corresponding to the crank angle from the time the reference pulse signal REF is generated to the top dead center.

The second counter 17 starts counting the auxiliary pulse signal SUB by using the first signal as a trigger, and at the same time, raises the output to the clock pulse counter 18. This is substantially the same as the first signal.

When the count value of the second counter 17 reaches the preset second predetermined number, the clock pulse counter 18
Output to. This will be the second signal.

The second predetermined number is set as a number corresponding to the crank angle section from the top dead center to the bottom dead center.

By setting the first predetermined number and the second predetermined number in this way, the crank angle section (explosion stroke) most susceptible to the influence of misfire can be used for determining the presence or absence of the misfiring cylinder.

The output of the second counter 17 is a clock pulse counter
18 and the microcomputer 19.

A clock pulse signal CLK from a clock (not shown) is input to the clock pulse counter 18 through a gate, and the signal output from the second counter 17 rises (first signal) to fall (first signal). 2nd signal) until the clock pulse signal by opening the gate
Timing is performed by counting CLK.

Then, the microcomputer 19 reads the counter value of the clock pulse counter 18 in synchronization with the signal output from the second counter 17, and processes it by a method described later in terms of software.

On the other hand, the reference pulse signal REF and the auxiliary pulse signal SUB are input to the third counter 20 as the third counting means, and when the reference pulse signal REF is input, the reference pulse signal REF is used as a trigger to generate the auxiliary pulse signal. Start counting the signal SUB.
Then, when the next reference pulse signal REF is input, the count value of the auxiliary pulse signal which has been counted so far is output to the microcomputer 19, and the value is reset,
The counting of the auxiliary pulse signal SUB is newly started.

A misfire diagnosis routine will be described with reference to the flowchart of FIG.

Prior to the misfire diagnosis, in step 1 (denoted as S1 in the figure. The same applies hereinafter), the diagnosis stop flag F is set (F =
It is determined whether or not 1).

When F = 1, it means that the abnormality of the auxiliary pulse signal SUB output from the pickup sensor 15 is detected as a result of the self-diagnosis according to the flowchart shown in FIG. 6 or FIG. This routine is ended as it is without judging the presence or absence of.

When F = 0, it means that the output of the pickup type sensor 15 is normal, and therefore, the procedure proceeds to step 2 and thereafter to carry out the misfire diagnosis.

In step 2, the signal output from the second counter 17 is judged, and when it rises, that is, when it is the first signal, the process proceeds to step 3 and the clock pulse counter 18
The current counter value C _{1 of} is read, this is temporarily stored, and this routine ends.

If the result of determination in step 2 is a fall, that is, if it is the second signal, the process proceeds to step 4, where the current counter value C ₂ of the clock pulse counter 18 is read,
In Step 5, the counter value C _2, by subtracting the counter value C ₁ which is temporarily stored in step 2, obtaining the first and at the signal generating time T when the second signal generation.

Then, the process proceeds to step 6 and the previous time T ^-1 and time T
The difference | T−T ⁻¹ | with a predetermined value A that has been set in advance, and when | T−T ⁻¹ | ≦ A, it is determined that there is no misfiring cylinder, and this routine is left as it is. finish.

The predetermined value A corresponds to the limit value of the fluctuation of the time difference that can occur during normal combustion without misfire.

On the other hand, when | T−T ⁻¹ |> A, it is determined that there is a misfiring cylinder, and misfire is displayed in step 7.

At this time, since the misfiring cylinder can be specified by the cylinder discrimination signal included in the reference pulse signal, it is possible to display for each cylinder.

Here, the steps 2 to 5 together with the clock pulse counter 18 correspond to the time counting means, and the steps 6 and 7 correspond to the misfire determination means.

In this embodiment, the presence / absence of a misfiring cylinder is determined by comparing the difference between the time T and the previous time T ⁻¹ with the predetermined value A. However, in addition, the time T and the previous time T ^{−1 are determined.} Ratio with T / T
^-1 may be compared with a predetermined value B, and the time of the number of cylinders (for example, in the case of T ₁ , T ₂ , T ₃ , T ₄ ; Whether or not there is a misfiring cylinder by comparing the time equivalent to the stroke (eg T ₁ ) with the average value of the time equivalent to the explosion stroke of the other cylinders (eg (T ₂ + T ₃ + T ₄ ) / 3) Various methods can be used, such as determining.

A self-diagnosis routine will be described with reference to the flowchart of FIG.

In step 11, the count value C from the third counter 20
Enter (3).

In step 12, the count value C (3) is changed to the reference value 60 (4
In the cylinder, the interval of the reference pulse signal REF is 180 ° in crank angle
Then, during this period, when the number of auxiliary pulse signals output at every 3 ° of crank angle is approximately 60 (C), and when they substantially match (C
In the case of (3) ≈60), the pickup sensor 15 is normal, so this routine is finished as it is, and when there is no coincidence (when C (3) ≠ 60), the pickup sensor 15 is
Is abnormal, the process goes to step 13 to display the misfire diagnosis stop (including the abnormal display of the pickup sensor 15), and in step 14, the diagnosis stop flag F is set (F ←
1), this routine is finished.

As a result, the diagnosis is stopped when the routine shown in FIG. 5 is executed.

Here, the steps 12, 13, 14 and the step 1 in FIG. 5 correspond to the determination stopping means.

As another method of self-diagnosis of the pickup sensor 15, the unit pulse signal P between the reference pulse signals REF is
There is a method of counting the OS and using this as the reference value.

However, in this case, prior to this, the unit pulse signal PO
Perform S self-diagnosis.

Specifically, first, the hardware will be described with reference to FIG.

In addition to the third counter 20, as shown by the broken line, a fourth counter 21 is provided, to which the reference pulse signal REF and the unit pulse signal POS from the crank angle sensor (12 in FIG. 2) are input. Then, when the reference pulse signal REF is input, counting of the unit pulse signal POS is started. Then, when the next reference pulse signal REF is input, the count value C (4) of the unit pulse signal POS which has been counted so far is output to the microcomputer 19, and the value is reset to newly set the unit. The counting of the pulse signal POS is started (see FIG. 4).

Next, the rune for self-diagnosis will be described with reference to the flowchart in FIG.

In step 21, the count value C (3) of the third counter 20 is input, and in step 22, the count value C of the fourth counter 21.
Enter (4).

In step 23, first, for self-diagnosis of the unit pulse signal POS output from the crank angle sensor 12, the count value C (4) is compared with a predetermined value 90, and when they are substantially equal (C
In the case of (4) ≈90), since the crank angle sensor 12 is normal, the routine proceeds to step 24, and the output (auxiliary pulse signal) of the pickup sensor 15 is self-diagnosed.

That is, the count value C (3) is compared with the reference value 2C (4) / 3. Here, 2/3 (= 60/90) is 4 cylinders, the interval of the reference pulse signal REF is 180 °, and the crank angle is 3 ° during this interval.
This means that the number of auxiliary pulse signals output for each is 60, and similarly, the number of unit pulse signals POS output for each 2 ° in the crank angle is 90 during this period.

When the count value C (3) substantially coincides with the reference value 2C (4) / 3 (when C (3) ≈2C (4) / 3), the pickup sensor 15 is normal. To finish.

On the other hand, when C (4) ≠ 90 in step 23, the unit pulse signal POS is not normally output, so the misfire diagnosis should be stopped without stopping the self-diagnosis of the pickup sensor. Display (including the abnormal display of the crank angle sensor 12), and the diagnosis stop flag F is set (F
← 1), this routine is completed.

Further, if C (3) ≠ 2C (4) / 3 in step 24, it means that an abnormality of the pickup sensor is detected as a result of the self-diagnosis of the pickup sensor 15, so the misfire diagnosis is stopped. In order to do so, similarly, in step 25, the display of the misfire diagnosis cancellation is displayed (including the abnormal display of the pickup type sensor 15), and the diagnosis cancellation flag F is set (F ← 1),
This routine ends.

Here, the steps 24, 25 and 26 and step 1 of FIG. 5 correspond to the determination stopping means.

<Effects of the Invention> As described above, according to the present invention, not the signal from the crank angle sensor that detects the rotation of the crankshaft from the shaft transmitted through the timing belt or the like, but the rotation of the crankshaft is directly synchronized. Since the picked-up sensor outputs the generated signal as an auxiliary pulse signal for each minute crank angle, the time used for diagnosis can be accurately timed and reliable misfire diagnosis can be performed.

Further, by performing the counting of the first predetermined number before starting the counting of the second predetermined number, the crank angle section most effective in the diagnosis of the presence or absence of the misfiring cylinder (specifically, in the explosion stroke The corresponding crank angle section) can be set.

Furthermore, since the diagnostic device itself is self-diagnosed by comparing the count value of the auxiliary pulse signal from the pickup type sensor with a reference value, when an abnormality is detected in the output of the pickup type sensor, a misfire determination is made. Thus, the reliability of the diagnosis result can be improved.

[Brief description of drawings]

1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a system diagram of an embodiment according to the present invention, FIG. 3 is a hardware configuration diagram in a control unit, FIG. 4 is a signal waveform diagram, FIG. 5 is a flowchart showing a misfire diagnosis, FIG. 6 is a flowchart showing a self-diagnosis, and FIG. 7 is a flowchart showing another embodiment of the self-diagnosis. 1 ... Engine, 5 ... Crankshaft, 8 ... Camshaft, 10 ... Timing belt, 11 ... Timing pulley, 12 ... Crank angle sensor, 13 ... Control unit, 14 ... Flywheel, 15 ... ... Pickup sensor, 16 ... First counter, 17 ... Second counter,
18 ... Clock pulse counter, 19 ... Microcomputer, 20 ... Third counter, 21 ... Fourth counter

Claims (1)

[Claims] 1. A reference pulse signal for every 720 ° / n (n is the number of cylinders) at least at a crank angle is output in synchronization with the rotation of a shaft which is driven by a crankshaft of an engine and rotates once per two rotations of the crankshaft. In addition to the crank angle sensor, a pickup type sensor that outputs an auxiliary pulse signal for each minute crank angle is provided in direct synchronization with the rotation of the crankshaft, and the pickup type sensor is generated by generating a reference pulse signal from the crank angle sensor. Counting means for starting the counting of the auxiliary pulse signal from the first pulse generator and outputting the first signal when the counting of the first predetermined number is completed, and the auxiliary pulse from the pickup sensor due to the generation of the first signal. Second counting means for starting signal counting and outputting a second signal at the end of counting of the second predetermined number; and issuing the first signal. Between the raw time and the time from the generation of the second signal, a time measuring means, a misfire determining means for determining the presence or absence of a misfiring cylinder based on a change state of the time measured, and a reference pulse signal from the crank angle sensor. Third counting means for counting the auxiliary pulse signal from the pickup type sensor, and comparing the count value with a reference value to detect the presence or absence of abnormality of the pickup type sensor, and at the time of detecting abnormality, misfire by the misfire determination means. A misfire diagnosing device for an internal combustion engine, comprising: a judgment stopping means for stopping the judgment.