JPH05195856A - Misfire detecting method for internal combustion engine - Google Patents

Abstract

PURPOSE:To correctly detect misfire of a multicylinder engine in a wide running load range. CONSTITUTION:Speed measuring periods against many cylinders are set to be a constant value in the range of crank angles from 45 deg. to 180 deg., and elapsed times from the start point to the end point of respective speed measuring terms are measured in order. Difference between the elapsed time measured at the last time and that at the present in a same cylinder is computed, and the computed difference at each cylinder is set as a misfire parameter MISP (i). When the respective parameters MISP (i) are over a prescribed value, the cylinders of the parameters MISP (i) are judged to be misfiring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine misfire detection method mainly applied to a multi-cylinder engine for automobiles.

[0002]

2. Description of the Related Art As a prior art relating to this type of misfire detection method, for example, as disclosed in Japanese Patent Application Laid-Open No. 2-112646, there is a method for detecting the presence or absence of misfire based on the change in the rotational speed of a crankshaft. Are known.

Conventionally, in the case of detecting a misfire based on a change in the rotational speed of a crankshaft, for example, a speed measurement period located near the top dead center of each cylinder is set to about 8 ° crank angle and each speed is set. The speed change amount is calculated by calculating the difference between the elapsed time corresponding to the previous cylinder and the elapsed time corresponding to the current cylinder while sequentially measuring the elapsed time from the start point to the end point of the measurement period. When the amount exceeds a certain level, it is determined that a misfire has occurred.

[0004]

However, in the high speed region and the light load region, the influence of the change in the rotation speed due to the vibration or the combustion difference between the cylinders cannot be ignored even in the normal combustion state. Therefore, it becomes difficult to determine whether or not the detected rotational speed change of a certain level or more is due to an actual misfire. Therefore, in the conventional method, the misfire detection range is limited to the low rotation and high load operation range.

An object of the present invention is to eliminate such a problem.

[0006]

The present invention takes the following means in order to achieve such an object. That is, in the misfire detection method for an internal combustion engine according to the present invention, the speed measurement period for each cylinder is set to a constant value in the range of 45 ° crank angle or more and 180 ° crank angle or less, and The elapsed time from the start point to the end point is sequentially measured, and the difference between the previously measured elapsed time of the same cylinder and the currently measured elapsed time is calculated, and the difference calculated for each cylinder is used as the misfire parameter for each cylinder. It is characterized in that when each misfire parameter exceeds a preset predetermined value, it is determined that the cylinder having the misfire parameter has misfired.

Here, the reason why the speed measurement period is 45 ° crank angle or more is to suppress the influence of vibration in the high rotation range. That is, this type of misfire detection is greatly affected by the vibration of the frequency of the fourth-order component of the rotation speed. Less susceptible to impact. On the other hand, the reason why the speed measurement period is set to 180 ° crank angle or less is to enable the presence or absence of misfire to be determined for each cylinder.

[0008]

With such a structure, when the normal ignition continues, the previously measured elapsed time of each cylinder and the currently measured elapsed time become substantially equal to each other. The misfire parameter becomes substantially zero and does not exceed a preset predetermined value. On the other hand, when a misfire occurs, there is a difference between the previously measured elapsed time of each cylinder and the currently measured elapsed time, and only in that case, the misfire parameter indicates a value apart from zero and It will exceed the specified value. Therefore, according to the present invention, misfire determination can be made for each cylinder without misdetection.

Further, since the speed measuring period is set to 45 ° crank angle or more, it is possible to suppress the influence of vibration in the high rotation range.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The internal combustion engine 1 schematically shown in FIG. 1 has four cylinders and has a 180 ° CA (crank angle).
It is set so that the ignition is performed in the order of the first cylinder → the third cylinder → the fourth cylinder → the second cylinder, and the electronic control unit 2 for controlling the ignition is provided. Although not shown, the internal combustion engine 1 is provided with an intake pressure sensor for detecting the pressure in the surge tank of the intake system, a rotation speed sensor for detecting the engine speed, and the like. The signals from these sensors are sent to the electronic control unit 2 described later.
Central processing unit 7 via the input interface 5 of
Is input to.

The electronic control unit 2 comprises a central processing unit 3,
Mainly composed of a microcomputer unit including a storage device 4 including a ROM and a RAM, an input interface 5 and an output interface 6,
It has a function of detecting misfiring as well as an air-fuel ratio control function, a control function of ignition for each cylinder, and the like. The input interface 5 includes a crank angle reference position sensor 7 built in a distributor (not shown) and N (cylinder discrimination) indicating a compression top dead center (compression TDC) of each cylinder, as shown in FIG.
A signal is input every 180 ° CA, and a P signal for knowing the output rotation speed is input from the electromagnetic pickup 8 every 18 ° CA.

The electromagnetic pickup 8 is a usual one in which a coil (not shown) is wound around the outer circumference of a magnetized iron core 8a, and the iron core 8a is arranged close to the outer circumference of the sensing gear 9. The sensing gear 9 has 20 teeth 9a protruding from the outer periphery at equal intervals, and is fixed to the end of the crankshaft 10. Then, when the sensing gear 9 rotates, the magnetic field generated in the iron core 8a is interrupted to generate an AC voltage in the coil, and the AC voltage is shaped by a waveform shaping circuit (not shown) and the input interface 5 receives the P voltage. It is designed to be input as a signal.

The electronic control unit 2 incorporates a program as schematically shown in FIG. 2 in order to carry out the misfire detection method of the present invention. This program executes the conditions for executing the misfire detection, for example, the engine is not in the transient operation state, the engine water temperature is not too low, the fuel is not cut, and the engine speed is from 600 rpm to 2
Between 800 rpm, intake pressure is 450 mmHg
If the above conditions are satisfied, then 18
An interrupt process is performed every 0 ° CA, that is, each time an N signal is input (N timing interrupt process).

First, at step 51, the elapsed time S from the start point to the end point of the current speed measurement period for each cylinder is S.
_{(I) n} (i indicates the cylinder number, and n indicates the order of measurement periods) is measured. In this embodiment, as shown in FIG. 3B, the speed measurement period for each cylinder is 72 ° crank angle (72 ° CA) near the top dead center.
The output rotation speed T72CA _(n) is the elapsed time S _{(i) n} from the start point to the end point of this speed measurement period, that is, the P signal at the bottom dead center is 0, and that at the top dead center is 9 obtained from the P signal to measure the elapsed elapsed time S _{(i) n} 4 pieces of signals leading to the No. 2 P signals of the next cycle. In this measurement, the crank angle is every 180 °,
Further, the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder are performed in this order, and the measured elapsed time S _{(i) n} is stored in the storage device 4. The obtained elapsed time S _{(i ) n} is theoretically zero as shown in FIG. 4 (a), but has a characteristic peculiar to each cylinder and deviates to a positive or negative value. ing. Then, the misfire parameter MISP for each cylinder is calculated from the measured elapsed time S _{(i) n} by the following formula.

MISP _(i) = S _{(i) n-} S _{(i) n-1} (i is ₁ , 3, 4, 2,) In step 52, the obtained misfire parameter MISP
Misfire determination processing is performed by comparing _(i) with a preset predetermined value. If misfire occurs, the process proceeds to step 53, and if not misfire, proceeds to step 54. The misfire is determined as misfire when the misfire parameter MISP _{(i )} exceeds a predetermined value, and as normal ignition when the misfire parameter MISP _{(i )} is less than the predetermined value. It should be noted that the predetermined value may be set to a value that sufficiently considers the error when the elapsed time is long due to vibration or the like. In the case of normal ignition, the misfire parameter MISP _(i) is substantially zero, whereas the misfire parameter MISP in the case of misfire
_(I) is deviated from the normal value by more than the predetermined value, as indicated by an arrow A in (a) of FIG. Step 5
In step 3, a process for counting the cumulative number of misfires of the misfiring cylinder is performed, and the process proceeds to step 54. To count the cumulative number of misfires, a dedicated counter may be prepared for each cylinder and programmed so that the counter is incremented each time a misfire occurs. Thereafter, in step 54, in order to detect that the measurement of the once elapsed time S _{(i) n} is completed, the current elapsed time S _{( i) n} is detected.
1 is added to the 200-rotation flag NCNT indicating the number of times of measurement, and stored in the processing RAM for every 200 rotations.

Next, at step 55, it is judged if the 200-rotation flag NCNT is 400, and if it is judged that the 200-rotation flag NCNT is not 400, the routine returns to the main routine (not shown). Proceeds to step 61. 200 rotation flag NCNT is 40
0, that is, when the crankshaft 10 has made 200 revolutions from the measurement of the first elapsed time S _{(i) n} , the cumulative number of misfires at the time when the crankshaft 10 made 200 revolutions in step 61 is greater than or equal to the first reference value EMSL1. It is determined whether or not, and if it is above, the process proceeds to step 62, and if not, the process proceeds to step 63. At step 62, a warning light M is issued to notify that there is an abnormality.
Illuminate IL. As a warning method in this case, in addition to the above-mentioned method of turning on the warning lamp MIL, the electronic control unit 2
It is also possible to provide a diagnostic output terminal in and to detect the abnormality by a tester or the like connected to the terminal. Then, in step 63, in order to detect that the abnormal judgment of the number of misfires has been executed once, 1 is added to the 1000 rotation flag JCNT indicating the current abnormal judgment number.
Every 000 revolutions is stored in the processing RAM. In step 64, it is determined whether or not the 1000 rotation flag JCNT is 5, and if it is 5, the process proceeds to step 65, and if not, the process proceeds to step 71.

In step 71, the 200 revolution flag NC
The contents of the processing RAM for every 200 rotations storing NT are cleared (NCNT = 0), and the process returns to the main routine (not shown). On the other hand, in step 65, the cumulative number of misfires at the time when the crankshaft 10 rotates 1000 times is the second
It is determined whether or not the value is equal to or greater than the reference value EMSL2 (≧ first reference value EMSL1). If it is equal to or more than the reference value, the process proceeds to step 66. In step 66, as in step 62, the warning lamp MIL is turned on to notify that there is an abnormality. In step 67, 100 which stores the 1000 rotation flag JCNT is stored.
The contents of the processing RAM for every 0 revolutions are cleared (JCNT = 0) and the process proceeds to step 71.

In the above configuration, misfire detection is 180
Control is performed in step 51 by interrupt processing for each CA.
→ 52 → (53) → 54 → 55, and if the crankshaft 10 is not rotating 200 times, the interrupt process is ended and the process returns to the main routine. If the crankshaft 10 is rotating 200 times, the process proceeds to step 61. And crankshaft 10
When the number of misfires detected corresponding to the number of revolutions is equal to or greater than the reference value, control is performed so that an alarm is issued. The control in this case is step 61 → 62 → 63 → 64 → 71 or step 61 after the control of the misfire detection described above.
→ 62 → 63 → 64 → 65 → 66 → 67 → 71, the crankshaft 10 rotates 200 times, and if the cumulative number of misfires is the first reference value EMSL1 or more, an alarm is issued, and further 1000 rotations are performed. And, when the cumulative number of times is equal to or larger than the second reference value EMSL2, an alarm is issued. The present invention is not limited to the embodiment described above, and the speed measurement period for each cylinder may be set appropriately within the range of 45 ° crank angle or more and 180 ° crank angle or less. Further, in the misfire determination, assuming that a misfire has occurred twice or more consecutively in the same cylinder, the misfire is determined first, and the misfire parameter MIS calculated next is determined.
If P becomes a value near zero without becoming a negative value equal to or less than a negative set value, it may be programmed to determine that the misfire parameter MISP also has calculated the speed measurement period in which the speed has been calculated. desirable. That is, when the previous time is a misfire, the elapsed time S _{(i) n} measured last time is larger than that during normal combustion, and the elapsed time S _{(i) n + 1} measured this time is also the same as that during normal combustion. Since it is a larger value, the difference between them is the misfire parameter MIS.
P _(i) becomes a value near zero. If misfires continuously occur in the same cylinder, the misfire parameter MIS
P _(i) continuously shows a value near zero. After this, when the combustion is normal without misfire, the measured elapsed time S _{(i) n} becomes small, so the misfire parameter MISP
_(I) has a negative value. Therefore, it is only necessary to determine that no misfire has occurred because the misfire parameter MISP _(i) becomes negative after such misfire determination.

In addition, the configuration of each part is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0021]

As described above in detail, according to the present invention, the misfire parameter is calculated independently for each cylinder to determine the misfire. Therefore, the misfire can be determined more reliably without erroneous detection. You can Since it is not necessary to learn the amount of speed change for each cylinder, the control is simplified and the accuracy of misfire determination is improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flow chart schematically showing a control procedure of the embodiment.

FIG. 3 is a timing chart showing the control mode of the embodiment.

FIG. 4 is a timing chart showing the relationship between the elapsed time S _{(i) n} and the misfire parameter MISP _(i) in the example.

[Explanation of symbols]

1 ... Internal combustion engine 2 ... Electronic control device 7 ... Crank angle reference position sensor 8 ... Electromagnetic pickup 9 ... Sensing gear 10 ... Crank shaft MISP _(i) ... Misfire parameter

Claims (1)

[Claims] 1. A speed measurement period for each cylinder is set to a constant value in the range of 45 ° crank angle or more and 180 ° crank angle or less, and the elapsed time from the start point to the end point of each speed measurement period is sequentially set. While measuring, calculate the difference between the previously measured elapsed time of the same cylinder and the currently measured elapsed time, and use the calculated difference for each cylinder as the misfire parameter for each cylinder, and set each misfire parameter in advance. A misfire detection method for an internal combustion engine, comprising: determining that a cylinder having the misfire parameter has misfired when the predetermined value is exceeded.