JPH03260356A - Misfire diagnostic device of internal combustion - Google Patents

Abstract

PURPOSE:To improve accuracy of a misfire diagnosis by performing the misfire diagnosis while correcting a period based on its deviation when the misfire diagnosis is performed by means of the deviation obtained between mutual periods measured in the single period of a detection signal output from a crank angle detecting means and compared with each other. CONSTITUTION:A crank angle detecting means A, which outputs a detection signal per crank angle corresponding to a stroke phase difference between cylinders, is provided, and also a period measuring means B, which measures a period of outputting the detection signal from this means A, is provided. A deviation between mutual periods, measured in the single period of the detection signal output from the means A, is obtained by weight averaging by means of a period deviation setting means C, next generation of a misfire is diagnosed in a misfire diagnostic means D by comparing the mutual periods during the single period of the detection with each other while correcting the periods based on the deviation of periods obtained by the means C.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a misfire diagnosis device for an internal combustion engine, and more specifically, a misfire diagnosis device for diagnosing a misfire based on fluctuations in the crank angle period corresponding to the stroke phase difference of each cylinder. Concerning what is composed.

<Prior Art> As a device for diagnosing a misfire in an internal combustion engine, devices that directly detect the in-cylinder pressure for each cylinder and diagnose a misfire have been proposed. Various devices have been previously proposed that can diagnose misfires based on engine rotational fluctuations. The cycle of the detection signal output every 120° in the cylinder is measured, and based on this cycle variation, engine rotational fluctuations due to a decrease in cylinder pressure due to a misfire are detected and misfire diagnosis is performed.

By the way, in order to detect rotational fluctuations caused by misfires, it is necessary to accurately detect changes in the cycle. A detection signal is output every 180' crank angle by detecting two protrusions A and B facing each other across the center of rotation on a signal plate that rotates at the same angular velocity as the angular velocity of t. In the case of a configuration in which the engine rotates, the angle CA1 from protrusion A to protrusion B and the angle CA2 from protrusion B to protrusion A along the engine rotation direction may not be exactly 180° due to production variations. , there is a habit of erroneously detecting rotational fluctuations due to angle variations between the protrusions A and B.

Note that in a six-cylinder engine, protrusions are provided at 3 m locations at 120° intervals, and in this case as well, variations in the 120° intervals pose a problem.

Therefore, if there is a possibility that the detected crank angle varies as described above, it is possible to compare the periods of measuring the same angle range (angle CAI or angle CA2) on the sensor in time series. It was necessary to detect rotational fluctuations and diagnose misfires.

Moreover, as shown in FIG. 5, instead of the protrusions corresponding to the TDC period, protrusions (teeth) are provided at every minute angle, and at every minute angle! In some cases, a sensor such as a magnetic pickup generates a detection signal, and by counting the detection signal for each minute angle, a detection signal for each crank angle corresponding to the stroke phase difference between cylinders is generated in the same way as above. In this case, for example, if there is a chip in the protrusion provided for each minute angle, the desired angle cannot be detected accurately, so Must be configured to diagnose misfires.

In this way, considering the angular variation of the crank angle sensor, it is necessary to compare the cycles of the same angular range on the sensor. For this reason, conventionally, the detected part (signal plate) that rotates at the same angular velocity as the engine rotation has been used. ), the crank angle (TDC period) corresponding to the stroke phase difference between cylinders is sequentially measured based on the detection signal from the sensor, and the latest measurement result T0 of the period and the crank angle Using the cycle T2 of the same angular range measured by the angle sensor one engine revolution ago, and the cycle T4 of the same angular range measured two engine revolutions ago, the degree of engine rotational fluctuation can be calculated using the following formula, for example. The misfire was diagnosed based on the magnitude of the LU value (
(See Japanese Patent Application No. 1-275046).

<Problems to be Solved by the Invention> However, in the configuration described above in which misfire diagnosis is performed by comparing cycles (TDC cycles) in the same angular range on the sensor,
For example, the firing order in a 4-cylinder engine is #1 → #3 → #4 →
A misfire occurs in both cylinders where the pistons are at the TDC position (compression top dead center, exhaust top dead center) at the same angular position, such as the combination of #1 cylinder and #4 cylinder when #2 is set. When a misfire occurs, it may not be possible to detect a misfire.

In other words, since the influence of cylinder pressure reduction in both misfiring cylinders appears in the same crank angle range of 180 m in 4 cylinders,
Even if we compare the cycles in the same crank angle range of 180', the comparison is actually between misfiring cylinders, although the cycles are actually longer than the cycles affected by the in-cylinder pressure of the cylinders that are not misfiring. Since there is a difference in the period from
.

Similarly, in a 6-cylinder engine, if two cylinders whose pistons are at TDC (compression top dead center, exhaust top dead center) at the same crank angle position both misfire, the crank angle range affected by the in-cylinder pressure of these cylinders will change. are the same, misfire diagnosis cannot be performed by comparing these cycles.

In this way, if we compare the cycles of the same part of the crank angle range divided by crank angle corresponding to the stroke phase difference between the cylinders, it is possible that multiple cylinders that reach top dead center TDC at the same crank angle position If both misfires occur, misfire diagnosis cannot be performed. Therefore, even if there are variations in the measured crank angles, the cycles of different crank angle ranges can be compared (for example, the cycle of CAI and C
A comparison with the A20 cycle) to accurately capture rotational fluctuations, and even if multiple cylinders with pistons at the same crank angle position are at top dead center, the misfire can be diagnosed. There was a request to make it possible.

The present invention has been made in view of the above-mentioned problems, and when diagnosing a misfire using a sensor that outputs a detection signal at each crank angle corresponding to the stroke phase difference between cylinders, it is possible to The purpose is to be able to accurately capture rotational fluctuations even when comparing the engine speeds, and to be able to perform misfire diagnosis even when multiple cylinders that are at the top dead center at the same crank angle position misfire together. .

Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. a period measuring means for measuring the period at which the detection signal is output from the means;
a period deviation setting means for obtaining a weighted average of deviations between the periods measured by the period measuring means in one period of the detection signal output from the crank angle detecting means; A misfire diagnosing device for an internal combustion engine is configured to include a misfire diagnosing means for diagnosing a misfire by comparing and correcting the period between the two on the basis of the period deviation determined by the period deviation setting means.

<Operation> According to this configuration, the detection signal output from the crank angle detection means is not output accurately for each crank angle corresponding to the stroke phase difference between the cylinders, but is output with a predetermined angular error. Even in the case of a misfire diagnosis, the deviation between the periods measured in one period of the detection signal, that is, the detected angle deviation in the crank angle' detecting means, is obtained by weighted averaging, and the periods are compared with each other to diagnose a misfire. Since the detection is performed while correcting based on the deviation, periodic fluctuations can be accurately captured, and the accuracy of misfire diagnosis can be maintained.

Therefore, even if a plurality of cylinders that reach top dead center at the same crank angle position misfire, it is possible to diagnose the misfire by comparing the cycles measured in one cycle of the detection signal.

<Example> The present invention will be explained in detail below.

In FIG. 2 showing one embodiment, a crankshaft (not shown) of a 4-stroke, 4-cylinder internal combustion engine 1 is formed of a magnetic material, and around the crankshaft is formed a magnetic material at every 3° (3" CA) of the crank angle.
Signal disc plate 2 with 20 convex parts formed
is pivotally supported, and the signal disk plate 2 rotates at the same angular velocity as the engine rotation.

The temperature near the periphery of the signal disk plate 2 is 3°C.
TM Pinkup 3 for A detection is fixedly supported,
The open end of the magnet of the electromagnetic pickup 3 is configured to obtain an induced electromotive force pulse by opening and closing a convex portion on the periphery of the signal disk plate 2 as the crankshaft rotates, and the electromagnetic pickup 3 is connected to the signal disk plate 2 by 3° CA.
A detection signal is obtained every 3° CA by the electromagnetic pickup 3 for detection.

Further, on one end surface of the signal disk plate 2,
A pair of protrusions 2a and 2b are provided on the same circumference with the rotation axis in between, and an electromagnetic pickup 4 for TDC detection that detects the protrusions 2a and 2b generates an induced electromotive force pulse every 180''CA. Obtained, signal disc plate 2
The protrusions 2a, 2b and! Detection signal of 180°CA (reference angle signal) by combination with magnetic pickup 4
This is so that it can be obtained. Here, the protrusion 2a,
2b's! By aligning the detection position by the magnetic pickup 4 with the top dead center position (TDC), for example, the compression TD of each cylinder is determined by the ignition signal and the TDC position detection.
The C position can be detected.

The induced electromotive force output from each of the TM pickups 3 and 4 is input to zero cross comparators 5 and 6, respectively, and converted into a pulse wave centered at 0 based on the magnitude with respect to the O level, and further passed through the next waveform shaping circuit. In 7.8, 0
It is shaped into a pulse wave with ■ being a low level.

The output pulse of the waveform shaping circuit 7 that rises (falls) every 3° CA (hereinafter abbreviated as 3@CA pulse) is a control built in a computer that diagnoses misfires and controls fuel supply to the engine 1. The timer 1 of the unit 9 counts the number of these 3'' CA pulses. Also, the output pulse of the waveform shaping circuit 8 rises (falls) every 180' CA at the TDC position of each cylinder. (
The TDC pulse (hereinafter referred to as TDC pulse) is input to the trigger 1 of the control unit 9.

The control unit 9 measures the period of the TDC pulse input to the trigger 1, that is, the 180° CA (TDC) period, which is a crank angle corresponding to the stroke phase difference between the cylinders in the four-cylinder engine 1 of this embodiment. In addition, T.D.
The 3° CA pulse is counted using the C pulse as a trigger, and the interrupt execution timing of the misfire diagnosis program is detected, for example near ATDC 30', and the misfire diagnosis is performed at a 180° CA cycle.

Incidentally, the crank angle detection means for detecting the rotational position of the crankshaft may include a device of the type that obtains the induced electromotive force pulses,
It may be an optical type that detects the rotational position of the crankshaft by detecting light passing through a slit provided in the signal disk plate, and is not limited to the device of this embodiment.

Next, the execution timing immediately after TDC (ATDC30
The misfire diagnosis program that is executed by interruption when the engine temperature reaches 100°C will be explained in accordance with the flowchart shown in FIG.

In this embodiment, the functions of the period measuring means 1 period change setting means and the misfire diagnosis means are provided in the form of software as shown in the flowchart of FIG. 3 above. Further, the crank angle detection means in this embodiment is constituted by a combination of protrusions 2a and 2b of the signal disk plate 2 and an electromagnetic pickup 4.

First, step 1 (denoted as Sl in the figure).

(Similarly below), a process of setting the measurement result of the period T of the TDC pulse input to the trigger 1 in a time series manner is performed. That is, the most recently measured TDC cycle is set in To, the TO cycle data for which the latest measurement result was set in the previous execution of this program is set in T1, and similarly, the cycle data in the previous execution of this program is set in T1. Each data TI, T
2. T3 is made one more time old data and T2. T3. T4
Set to . Therefore, among the periodic data To-T4, To, T2 . T4 is signal disc plate 2
Two 180 degrees separated by protrusions 2a and 2b at
This is time series data obtained by measuring the period on one side of the range, and similarly, Tl and T3 are time series data obtained by measuring the period on the other side of the 180° range.

In the next step 2, the deviation between TO and T1 of the periodic data set in step 1 is determined, that is, the deviation between TO and T1 of the periodic data set in step 1 is determined, that is, the difference between the periodic data TO and T1, that is, the deviation of the detection signal from either of the protrusions 2a, 2b on the signal disk plate 2 as the reference point until it returns to the reference point again. 2 measured in one period)
Find the absolute value of the deviation of the two periods and set the result to Ilt.

In step 3, the periodic deviation Df calculated in step 2 is
Weighted average value Df of t! tav is determined according to the following formula.

In the next step 4, while correcting the deviation (first-order differential value of the period) between the periods measured in different 180' ranges on the signal disk plate 2 using the weighted average value Dltav, the second-order differential value of the period T is corrected. is calculated according to the following formula, and the result is set to misfire determination (jiZu).

2 As mentioned above, the deviation between the periods T1 and T2 and the periods To and T
1, the deviation from DI! , if corrected by tav, T1
and T2 and between To and T1, protrusions 2a, 2
There is an angular position error of b, so one actually measures a cycle of 180 degrees or more, and the other one measures 18 degrees.

Even when the following periods are measured, the period difference due to the difference in detection angles can be corrected to decrease, and rotational fluctuations can be detected with high accuracy.

For example, To, T2. The detected crank angle corresponding to T4 is T
It is larger than the I, T3 side, and the TO, T2. T4
is longer than TI, T3, Tl
-72 should be corrected by subtracting the crank angle error, and TO-TI should be corrected by adding the crank angle error, but (Tl-72) (T.

-T1) is calculated, so as above (TI
-72) and (To-TI), if one is additively corrected using the absolute value of the deviation, DJ2tav, and the other is subtractively corrected, then (TI-T2) and (To-TI)
This means that the detected crank angle error has been corrected for the difference.

Therefore, the protrusion 2a on the signal disc plate 2,
Even if the periods of one of the two 180° ranges separated by 2b are not compared, it is possible to prevent the actual crank angle error in the 180° range from having a negative effect on the detection of period fluctuations.

In step 5, the smallest value is found among the multiple data calculated below zero among the recently calculated misfire discrimination values Zu including the Zu calculated in step 4, and this latest minimum value is compared with the previous one. The minimum value m1nZu of Zu that has been set up to now is weighted averaged, the result is set as a new minimum value m1nZu, and the minimum value m1nZu is updated.

In the next step 6, the minimum value m1nZu obtained as described above is compared with the Zu calculated in step 4 this time, and it is determined that the latest calculation result is better than the average minimum value m1nZU. If it is smaller, the process proceeds to step 7 and the currently calculated Zu is set to the minimum value m1nZu. Therefore, if Zu calculated in step 4 falls below the average level, the minimum value minZu will immediately follow this change.

After setting the minimum value m1nZu of the misfire discrimination value Zu as described above, in the next step 8, in order to determine the level of the misfire discrimination value Zu calculated this time, the absolute value of the currently calculated Zu is set as the engine rotation speed N. In response to an increase in the engine load, an increase is corrected, and in response to an increase in the engine load, a decrease is made, and the result of this correction is set in DZu. The engine rotation speed N is TD
It can be calculated based on the C cycle, and the basic fuel supply amount TP when electronically controlling the fuel supply amount to the engine to an amount commensurate with the intake air amount may be used as the engine load.

The above-mentioned Zu tends to be calculated to a smaller value as the engine rotational speed N is higher, and to a larger value as the engine load is higher. It is possible to set a value that indicates the true degree of engine rotation variation that is unrelated to the conditions of .

In the next step 9, a coefficient ga i is used to set the slice level SL1 for determining the negative level of the misfire discrimination value Zu as a predetermined multiple of the minimum value m1nZu.
n is found by searching from the map based on the DZu calculated in step 8 above.

Here, the larger the DZu, the larger the coefficient gain
is set to a small value, and the DZu
When the engine speed fluctuation exceeds a certain level and the engine rotational fluctuation is large, the coefficient gajn is set to a value of 1 or less, and the slice level S on the side different from the minimum (iminZu to zero) is set.
LI is set, and conversely, the DZu
When engine rotation fluctuation is small below a certain level, the coefficient gain is set to a value of 1 or more, and the slice level SLI is set to a value even smaller than the minimum value m1nZu.

As a result, the larger the engine speed fluctuation is, the more easily the misfire determination 4ffi-Zu is determined to be smaller than the slice level SLI and the misfire diagnosis is made. Conversely, when the engine speed fluctuation is small, the slice level SL is determined to be smaller than the slice level SLI.
This is to prevent the misfire discrimination value Zu from becoming smaller than I, thereby making it difficult to diagnose a misfire.

In step 10, the minimum value m1nZu is multiplied by the coefficient gain obtained by searching from the map in step 9, and the result is set as the slice level SLI.

In the next step 11, it is determined whether or not the misfire discrimination value Zu calculated in step 4 is greater than or equal to zero. If it is not greater than or equal to zero, that is, if the misfire discrimination value Zu is less than zero, the process proceeds to step 12. The misfire determination value Zu is compared with the slice level SLI set in step 10 above.

Here, if it is determined that the misfire determination value Zu is smaller than the slice level SLI, it is assumed that the engine rotation fluctuation has exceeded a predetermined level J due to the occurrence of a misfire, and a misfire is detected. ), the process proceeds to step 13 and LSTD, which counts the number of misfire detections, is incremented by one.

In addition, when one cylinder misfires alone, the misfire determination value Zu greatly changes to the negative side as the TDC period affected by the cylinder pressure of that cylinder becomes longer, and misfire occurrence is diagnosed, but the TDC position Even if two cylinders with the same misfire (for example, #1 and #4 when the firing order is #1 → #3 → #4 → #2) both misfire, the period corresponding to one of the misfiring cylinders When is set to To, Zu changes significantly to the negative side, making it possible to perform a misfire diagnosis. Furthermore, even if two consecutive cylinders in the firing order both misfire, the occurrence of such two-cylinder consecutive misfire can be detected. Therefore, the number of misfire detections LSTD is the number of detections of individual misfires in one cylinder, and the number of times LSTD detects misfires in one cylinder, and two
This includes the number of misfire detections for a cylinder and the number of misfire detections for two consecutive cylinders in the firing order.

In the next step 14, a misfire discrimination value LU is calculated according to the following formula in the same way as the misfire discrimination value Zu.

The above-mentioned misfire discrimination value LU is determined by 180 degrees separated by the protrusions 2a and 2b on the signal plate 2, as shown in the above formula.
The results of measuring cycles on the same side of the range are compared, and the misfire determination value LU based on the above calculation formula is:
If two cylinders with TDC at the same crank angle position both misfire, the value will be close to zero, so if two cylinders one after the other in the firing order misfire as described above, this should be detected. This is something that cannot be done.

In the next step 15, a slice level SL2 for determining the negative level of the misfire determination value LU is set to a basic fuel supply amount TP representing the engine rotational speed N and the engine load.
Search and find from the map based on.

Then, in the next step 16, it is determined whether the misfire determination value LU calculated in the step 14 is smaller than the slice level SL2 obtained in the step 15. Here, when it is determined that the misfire determination value LU is smaller than the slice level SL2, it is a state in which a misfire occurrence has been detected, but such a misfire diagnosis is also performed when one cylinder misfires alone. This is also done when two adjacent cylinders in the firing order are both misfiring.

However, it has been confirmed from experiments that when two cylinders misfire in succession, the misfire determination value LU swings more toward the negative side than when one cylinder misfires alone, so in the next step 17, the slice level SL2 is By comparing the result of increasing the absolute value of the misfire determination value LU with the misfire determination value LU, it is determined whether or not the misfire determination value LU has swung more to the negative side than when one cylinder misfires alone. It is determined whether the determination is based on the detection of a single misfire in one cylinder or the detection of a state in which two cylinders are misfiring in succession.

In step 17, when it is determined that the misfire determination value LU is smaller than the value obtained by increasing the absolute value of the slice level SL2, the misfire determination value LU becomes significantly negative due to two cylinders consecutively misfiring. When it is determined that the misfire determination value LU is less than the slice level 312 set in step 15, but has not changed to the negative side as much as seen when two cylinders consecutively misfire, That is, only when a one-cylinder individual misfire is detected, the process proceeds to step 18, and the LSTS, which counts the number of such one-cylinder individual misfire detections, is incremented by one.

In the next step 19, the number of times of misfire diagnosis is counted.
It is determined whether or not mr has reached a predetermined value (for example, 1000), and if it has not reached the predetermined value, the tmr is incremented by 1 in step 20 and the program is terminated.

When it is determined in step 19 that tmr has reached a predetermined value, in step 21, it is determined whether or not the number of misfires LSTD detected based on the misfire determination value Zu exceeds a predetermined value, that is, the count of the tmr. It is determined whether misfires are detected at a rate equal to or higher than a predetermined rate per ignition number corresponding to a predetermined value that is an increase target.

In step 21, the number of misfires LSTD is calculated based on the misfire discrimination value Zu.
If it is determined that exceeds a predetermined value, the process proceeds to step 22, and it is then determined whether or not the number of times LSTS of single cylinder misfires detected based on the misfire determination value LU exceeds a predetermined value. .

The number of misfires LSTD based on the misfire determination value Zu includes the number of times when two cylinders are detected to be misfiring, as well as the number of times when one cylinder misfire is detected. This step 2 is intended to be counted up only when it is detected.
When it is determined in step 2 that LSTS exceeds a predetermined value, it is assumed that the number of misfires LSTD is mainly counted up based on the result of detecting a single cylinder misfire. If the number of misfires LSTD exceeds the predetermined value even though the number of misfires LSTS does not exceed the predetermined value, the number of misfires LSTD exceeds the predetermined value as a result of detection of a state in which two cylinders are misfiring. It is estimated that

Therefore, when it is determined in step 22 that the number of times 5 LTS of single cylinder misfires detected by the misfire determination value LU does not exceed a predetermined value, it is determined that misfires in two cylinders are occurring at a rate higher than a predetermined rate; Proceeding to step 23, control is performed to display the two-cylinder misfire condition on the driver's seat or the like.

Then, in a state where tmr has been counted and amplified to a predetermined value, tmr, LST
D. LSTS is reset to zero, and the number of misfire detections is counted up in LSTD and LSTS until tmr is counted up to a predetermined value again.

In addition, in the misfire diagnosis based on the misfire discrimination value Zu,
If two cylinders adjacent to each other in the firing order misfire in succession, and
Like the #1 cylinder and #4 cylinder in the ignition order of this embodiment, the same crank angle position is TDC (two cylinders with one ignition order skipped), and the same 180° on the signal plate 2. Since a misfire is detected even when the influence of a misfire appears in the cycle of the range, the two-cylinder misfire display in step 23 indicates the consecutive two-cylinder misfires (for example, #1, #3) and two-cylinder misfires that occur one after another (for example, #1 and #3). For example, both #1 and #4) are possible.

In addition, although the case of a four-cylinder engine was described in this example,
12 on the signal disc plate 2 as shown in Figure 2.
Even in the case where detected parts such as protrusions are provided at 0° intervals so that a TDC period of 6 degrees can be detected, the three 120° points detected during one period of the detection signal are similar to the above.
By calculating the weighted average of the deviations between the surroundings and correcting them based on this weighted average period deviation when comparing the periods, even if there is a variation in the 120° interval, the period fluctuation will be affected by this. Erroneous detection can be prevented, and even in a six-cylinder engine, it is possible to detect a state in which two cylinders at the same TDC position are both misfiring.

<Effects of the Invention> As explained above, according to the present invention, cycles measured in different angle ranges on a sensor that outputs a detection signal for each crank angle corresponding to the stroke phase difference between cylinders are compared with each other. This method also has the effect of being able to accurately capture periodic fluctuations, and making it possible to perform a misfire diagnosis even if multiple cylinders that are at the top dead center at the same crank angle position all misfire.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a system schematic diagram showing an embodiment of the present invention, and FIG. 3 is a flowchart showing the contents of misfire diagnosis control in the above embodiment.
FIGS. 4 and 5 are schematic diagrams showing examples of crank angle sensors, respectively, and FIG. 6 is a time chart for explaining problems with conventional misfire diagnostic control. 1... Engine 2... Signal disc plate 3
．． 4... tM1 pickup 5, 6... Zero cross comparator 7, 8... Waveform brightness circuit 9...
·control unit

Claims (1)

[Claims] a crank angle detecting means for outputting a detection signal for each crank angle corresponding to a stroke phase difference between cylinders; a period measuring means for measuring a cycle in which a detection signal is output from the crank angle detecting means; and the crank angle detecting means. a period deviation setting means that calculates a weighted average of mutual deviations between the periods measured by the period measuring means in one period of the detection signal output from the period measuring means, and a period between one period of the detection signal measured by the period measuring means; A misfire diagnosing device for an internal combustion engine, comprising a misfire diagnosing means for diagnosing a misfire by comparing and correcting each other based on the periodic deviation determined by the periodic deviation setting means.