JP3324795B2 - Engine misfire detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine misfire detection method for detecting misfire from fluctuations in engine rotation.

[0002]

2. Description of the Related Art In general, it is ideal for combustion to be performed in each cycle through the same process in each cycle in order to obtain a stable output. However, in a multi-cylinder engine, the shape of the intake pipe becomes complicated, and the number of cylinders increases. Due to non-uniformity of the intake air distribution ratio due to intake interference between the cylinders, slight differences in combustion temperature between the cylinders caused by the cooling path, and variations in the production of the combustion chamber volume and piston shape of each cylinder, etc. , Combustion tends to vary.

Heretofore, combustion fluctuations between cylinders have been minimized by air-fuel ratio control and ignition timing control for each cylinder. However, in recent high-performance engines, which tend to have high output and low fuel consumption, Deterioration or failure of an injector, a spark plug, or the like may cause intermittent misfire, which may easily cause a decrease in output.

In general, whether a cylinder is in a misfire state is determined by
It can be detected by detecting a rotation speed variation due to misfire and comparing the rotation speed variation with a predetermined determination level. For example, Japanese Patent Application Laid-Open No. Sho 62-118031 measures the interval between a plurality of pulse signals generated for each rotation of a crankshaft, and determines the maximum value of the engine speed fluctuation from the time change of the pulse interval. A technique for determining an abnormal combustion cylinder based on the maximum value and the count value of the pulse signal is disclosed.

Japanese Patent Application Laid-Open No. 2-112646 discloses a method of detecting a plurality of angular positions per one rotation of a multi-cylinder internal combustion engine, and detecting an instantaneous rotational speed of a specific rotational position of each cylinder from the detected angular position intervals. However, there is disclosed a technology for detecting an abnormal cylinder from the fluctuation of the instantaneous rotational speed.

[0006]

However, there are cases where the engine continuously changes in rotation due to causes other than a misfire due to acceleration or deceleration, etc. Also, once a misfire occurs, the engine continuously changes between cylinders. Often misfires occur. In such a case, simply comparing the engine rotation fluctuation with the misfire determination level to make a misfire determination may erroneously determine continuous rotation fluctuation caused by causes other than misfire as misfire, or conversely, There is a possibility that the rotation may be erroneously determined to be continuous.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is intended to reliably detect misfire even when misfires occur continuously without being affected by fluctuations in engine rotation caused by causes other than misfires. It is an object of the present invention to provide a method for detecting a misfire in an engine that can perform the method.

[0008]

According to the first aspect of the present invention,
Engine rotation between the current combustion cylinder and the previous combustion cylinder
The difference between the numbers is the difference between the engine speeds of the current combustion stroke cylinders.
And the engine speed of the combustion stroke cylinder this time.
Of the engine speed of the previous combustion stroke cylinder
The difference is calculated as the differential rotation change of the combustion stroke cylinder this time.
Difference of engine speed of combustion stroke cylinder and judgment threshold
Misfire set based on engine operating conditions
Engine speed of the previous combustion stroke cylinder
The difference between the numbers has dropped below the negative misfire judgment level
At this time, the difference in rotational speed of the combustion stroke cylinder
Compared to the constant level, the change in the differential rotation of the combustion stroke cylinder
If it is higher than the negative misfire judgment level,
Compare the change in differential rotation of the cylinder with the above negative misfire determination level
And the change in the differential rotation of the previous combustion stroke cylinder
When the engine has fallen below the level,
It is characterized by determining that a fire has occurred . Claim 2
According to the invention described in claim 1, a misfire occurs in the invention described in claim 1.
When it is determined that the engine is
Set the difference between the gin rotation speeds as the minimum
The change in the differential rotation of the combustion stroke cylinder is lower than the negative misfire determination level.
Is higher, the misfire of the combustion stroke cylinder is determined
The combustion stroke cylinder is misfired two times before
The difference between the engine speeds of the previous combustion stroke cylinders
Is compared with the above minimum value, and the engine speed of the previous combustion stroke cylinder is
When the number of turns is less than the minimum value,
Misfires occur continuously from the first combustion stroke cylinder to the previous combustion stroke cylinder.
It is characterized in that it is determined to have occurred successively. Claim
The invention according to claim 3 is the invention according to claim 2, wherein
The difference between the engine speeds of the previous combustion stroke cylinders is the minimum value
In the above case, the engine speed of the previous combustion stroke cylinder
Addition of the minimum value to the difference and the misfire determination level
The engine speed of the previous combustion stroke cylinder.
Is smaller than the above addition value, the value of the previous combustion stroke cylinder
It is determined that the misfire has continued, and
Misfire when the difference between the engine speeds of
Is determined to have ended.

[0009]

According to the first aspect of the present invention, the present combustion stroke cylinder and the front
The difference in engine speed between the cylinder and the
Calculated as the difference between the engine speeds of the cylinders,
Of the engine speed of the first combustion stroke cylinder and the previous combustion stroke
The difference between the engine speed difference of the cylinder and the
Is calculated as the differential rotation change. And the last combustion stroke
The difference between the engine speeds of the cylinders
The misfire judgment level set based on the
It has fallen below, and this time
Is higher than the negative misfire determination level and the previous combustion
The change in the differential rotation of the stroke cylinder falls below the negative misfire determination level
When the engine has dropped, misfire has occurred in the previous combustion stroke cylinder.
Is determined. Here, the engine speed of the combustion stroke cylinder
Engine speed between the front and rear combustion stroke cylinders
Using the change in the number of rotations, that is, the difference in rotation,
Judgment allows comparisons to occur due to causes other than misfire
The effect of small engine speed fluctuations
Enables fire detection. According to the second aspect of the invention, a misfire occurs.
The engine of the previous combustion stroke cylinder
The difference between the rotation speeds is set as the minimum value of the difference rotation. Soshi
The change in the differential rotation of the previous combustion stroke cylinder
Higher than the level, and the combustion stroke cylinder misfired two times before
And the difference in engine speed of the last combustion stroke cylinder
When the minute falls below the minimum value, the combustion
Misfires occur continuously from the first cylinder to the previous combustion cylinder.
It is determined that it is produced. That is, the combustion stroke cylinder before last
Is misfired when the engine in the previous combustion stroke cylinder
The difference in engine speed is calculated based on the engine speed difference at the time of misfire.
Compared with the set minimum value, the minimum value of differential rotation at the time of misfire
The difference in engine speed of the previous combustion stroke cylinder
By determining that the engine is
It is possible to accurately detect continuous misfires in the firing stroke cylinder.
It becomes possible. The third aspect of the present invention provides a combustion cylinder having a previous combustion stroke.
When the difference between the engine speeds of the
Engine speed difference of combustion stroke cylinder and misfire judgment level
And the minimum value of the differential rotation at the time of misfire
You. Then, the difference between the engine speeds of the previous combustion stroke cylinders
But it is lower than the above-mentioned added value, lost fire of the previous combustion stroke cylinder
Is determined to be continuing. In addition, the last combustion stroke cylinder
If the difference between the engine speeds is greater than
It is determined that the process has been completed. That is, the air in the previous combustion stroke cylinder
The drop in engine speed difference caused a misfire to the misfire determination level
To a predetermined level by adding the minimum value of the time difference rotation
By judging whether it has recovered, the continuous misfire of the cylinder
It is possible to accurately determine the end of the misfire.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a flowchart showing a subroutine for continuous misfire diagnosis, FIG. 2 is a flowchart showing a misfire diagnosis routine, FIG. 3 is a flowchart showing a misfire diagnosis routine, and FIG. FIG. 5 is a schematic diagram showing an engine control system, FIG. 6 is a front view of a crank rotor and a crank angle sensor, FIG. 7 is a front view of a cam rotor and a cam angle sensor, and FIG. 8 is an electronic control system. FIG. 9 is a time chart showing the relationship between the crank pulse, cam pulse, combustion stroke cylinder, and ignition timing, FIG. 10 is an explanatory diagram showing the differential rotation before correction, and FIG. 11 shows the differential rotation after correction. FIG. 12 is an explanatory diagram of a misfire determination level, and FIG. 13 is an explanatory diagram showing a differential rotation when a continuous misfire occurs.

In FIG. 5, reference numeral 1 denotes an engine,
The figure shows a horizontally opposed four-cylinder engine. An intake manifold 3 communicates with each intake port 2a formed in a cylinder head 2 of the engine 1, a throttle chamber 5 communicates with the intake manifold 3 via an air chamber 4, and an intake pipe is provided upstream of the throttle chamber 5. An air cleaner 7 is attached through the air cleaner 6.

The air cleaner 7 of the intake pipe 6
An intake air amount sensor (hot wire type intake air amount sensor in the figure) 8 is interposed immediately downstream of the throttle valve 5 and a throttle valve 5 provided in the throttle chamber 5.
The throttle sensor 9 is connected to a.

An idle speed control (ISC) valve 11 is interposed in a bypass passage 10 that connects the upstream side and the downstream side of the throttle valve 5a.
Each intake port 2 of each cylinder of the intake manifold 3
An injector 12 is located just upstream of a.

Further, an ignition plug 13a having a tip exposed to the combustion chamber is attached to each cylinder of the cylinder head 2, and an ignition coil 13a connected to the ignition plug 13a is provided.
The igniter 14 is connected to b.

The injector 12 includes a fuel supply passage 15
The fuel tank 16 is in communication with the fuel tank 16 through which an in-tank type fuel pump 17 is provided. The fuel from the fuel pump 17 is pressure-fed to the injector 12 and the pressure regulator 19 through a fuel filter 18 interposed in the fuel supply path 15, and is returned from the pressure regulator 19 to the fuel tank 16 to a predetermined pressure. Regulated to pressure.

A knock sensor 25 is attached to the cylinder block 1a of the engine 1. A cooling water temperature sensor 27 faces a cooling water passage 26 communicating the left and right banks of the cylinder block 1a. An O2 sensor 29 faces a collecting portion of the exhaust manifold 28 communicating with the exhaust port 2b. Reference numeral 30 denotes a catalytic converter.

A crank rotor 31 is mounted on a crankshaft 1b supported by the cylinder block 1a. A crank angle sensor 32 such as a magnetic sensor such as an electromagnetic pickup or an optical sensor is mounted on the outer periphery of the crank rotor 31. And rotation detection means for detecting the rotation of the engine. Further, a cam rotor 33 is connected to the camshaft 1c of the cylinder head 2, and a cam angle sensor 34 for distinguishing a cylinder including a magnetic sensor such as an electromagnetic pickup or an optical sensor is provided on the outer periphery of the cam rotor 33. I have.

As shown in FIG. 6, the crank rotor 3
Projections (may be slits) 31a, 31 on the outer periphery of 1
b, 31c are formed. Each projection 31a, 31b,
31c are the values before the compression top dead center (BTDC) θ1, θ of each cylinder.
2 and .theta.3, the detection signals of the respective projections 31a, 31b and 31c output from the crank angle sensor 32 are shaped and input to the ECU 41 as .theta.1, .theta.2 and .theta.3 crank pulses. The numbers are calculated, and control timings for ignition timing control and fuel injection control are obtained.

As shown in FIG. 7, a cylinder discriminating projection (which may be a slit) 3 is provided on the outer periphery of the cam rotor 33.
3a, 33b and 33c are formed. The projection 33a is formed at a position θ4 after the top dead center (ATDC) of compression of the # 3 and # 4 cylinders, and the projection 33b is composed of three projections. The first projection is the top dead center of the # 1 cylinder. After the point (ATD
C) It is formed at the position of θ5. Further, the protrusion 33c
Are composed of two protrusions, the first of which is formed at a position θ6 after the compression top dead center (ATDC) of the # 2 cylinder.

Each of the projections 33a, 33 of the cam rotor 33
b and 33c are detected by the cam angle sensor 34, waveform-shaped, and provided to the ECU 41 for the cylinder discriminating θ4, θ4.
It is input to the ECU 41 as a 5, θ6 cam pulse.

Thus, when the engine is operating, a cam pulse is generated at a position that does not overlap with the crank pulse as shown in FIG. 9, and it is possible to determine the cylinder based on the number and the state of generation of the cam pulse.

In the embodiment shown in the figure, θ 1 = 97 ° C. A, θ
2 = 65 ° C, θ3 = 10 ° C, θ4 = 20 ° C, θ5
= 5 ° C, θ6 = 20 ° C.

On the other hand, in FIG. 8, reference numeral 41 denotes an electronic control unit (ECU) including a microcomputer or the like, and a CPU 42, a ROM 43, a RAM 44, a backup RAM 44a, and an I / O interface 45 are connected to each other via a bus line 46. Connected, constant voltage circuit 4
7 supplies a predetermined stabilizing voltage.

The constant voltage circuit 47 includes an ECU relay 48
Is connected to the battery 49 through the relay contact of the ECU, and is directly connected to the battery 49.
When an ignition switch 50 connected between the relay coil of the relay 48 and the battery 49 is turned on and the relay contact of the ECU relay 48 is closed, a power supply for control is supplied to each part. When the switch 50 is turned off, the backup RA
Supply backup power to M44a.

The fuel pump 17 is connected to the battery 49 via a relay coil of the fuel pump relay 51 and a relay contact of the fuel pump relay 51.

The input ports of the I / O interface 45 include an intake air amount sensor 8, a throttle sensor 9, a knock sensor 25, a coolant temperature sensor 27, an O2 sensor 29, a crank angle sensor 32, a cam angle sensor 34,
The battery 49 is connected to the vehicle speed sensor 35 and the like, and the battery voltage is monitored.

The igniter 14 is connected to an output port of the I / O interface 45.
Via the drive circuit 52, the ISC valve 11, the injector 12, the relay coil of the fuel pump relay 51, and
ECS installed on the instrument panel (not shown)
(Electronic Control System) Lamp 53 is connected.

The ROM 43 stores a control program and various control fixed data, and the RAM 44 stores output signals of the sensors and switches after data processing and the CPU 42 Stores processed data. Further, power is always supplied to the backup RAM 44a irrespective of the ignition switch 50. Even when the ignition switch 50 is turned off and the operation of the engine is stopped, the stored contents are not lost, and the fault location detected by the self-diagnosis function is not lost. The trouble code etc. corresponding to is stored.

The trouble data can be read out externally by connecting a serial monitor 54 to the ECU 41 via a connector 55. This serial monitor 5
No. 4 is disclosed in Japanese Unexamined Patent Publication No. 2-73 filed earlier by the present applicant.
No. 131 discloses this in detail.

The CPU 42 calculates the fuel injection amount, the ignition timing, the duty ratio of the drive signal of the ISC valve 11 and the like in accordance with the control program stored in the ROM 43 to control the air-fuel ratio, the ignition timing, and the idle speed. Various controls such as cylinder #n (n
= 1 to 4) are individually determined.

Next, the misfire detection procedure executed by the ECU 41 will be described with reference to the flowcharts of FIGS.

The flowcharts of FIGS. 2 and 3 show a misfire diagnosis routine which is interrupted and executed in synchronization with the θ3 crank pulse from the crank angle sensor 32. First, in step S101, each data obtained during the previous execution of the routine is shown. Is stored in the work area, and in step S102, θ2, θ3
The input interval time Tθ23 between crank pulses, θ2, θ3
From the included angle (θ2−θ3) of the crank rotor 31, the engine speed MNXn corresponding to the #n (n = 1, 3, 2, 4) cylinder is determined in consideration of misfire in the low engine speed range. For example, it is calculated in a range of 150 rpm or more.

In the following description, each parameter,
The subscripts n, n-1, n-2,... Of each flag represent each cylinder number.

Next, proceeding to step S103, the engine speed M corresponding to the #n cylinder calculated in step S102
The difference between NXn and the engine speed MNXn-1 corresponding to the # n-1 cylinder one combustion stroke before (calculated when the previous routine is executed) is calculated as the differential rotation DELNEn corresponding to the #n cylinder (DELNEn ← MNXn). -MNXn-1).

Next, at step S104, based on the crank pulse and the cam pulse output from the crank angle sensor 32 and the cam angle sensor 34, the current combustion stroke cylinder #n cylinder is n = 1, 3, 2, 4 Is determined, and in step S105, # n−
One cylinder is determined.

For example, as shown in FIG. 9, when a crank pulse is input from the crank angle sensor 32 after the θ5 cam pulse is input from the cam angle sensor 34, the crank pulse is used to determine the crank angle of the # 3 cylinder. If the θ4 cam pulse is input after the θ5 cam pulse, it can be determined that the subsequent crank pulse indicates the crank angle of the # 2 cylinder.

Similarly, the crank pulse after the input of the θ6 cam pulse indicates the crank angle of the # 4 cylinder.
When a θ4 cam pulse is input after the θ6 cam pulse, it can be determined that the subsequent crank pulse indicates the crank angle of the # 1 cylinder.

Further, after the cam pulse is input from the cam angle sensor 34, it can be determined that the crank pulse input from the crank angle sensor 32 indicates the reference crank angle (θ1) of the corresponding cylinder.

In the embodiment, the ignition order is # 1 → # 3
→ # 2 → # 4 For example, if the misfire diagnosis routine is now executed in synchronization with the θ3 crank pulse of the BTDC θ3 of the # 3 cylinder, the combustion stroke cylinder #n is the # 1 cylinder and one combustion stroke The previous cylinder # n-1 is # 4 cylinder, and the cylinder # n-2 before the two combustion strokes is # 2 cylinder.

Here, the detected position of the crank angle by the crank angle sensor 32 is determined by the manufacturing tolerance of the position and the shape of each of the projections 31a, 31b, 31c of the crank rotor 31, and the engine 1 of the crank angle sensor 32 to the engine 1. There is a permissible error in the mounting position for each engine.

Therefore, the differential rotation DELNE calculated based on the crank pulse from the crank angle sensor 32 is calculated.
Contains variations due to these errors. Particularly, when the engine is running at a high speed, as shown in FIG. 10, the result is that apparently large engine rotation fluctuations occur uniformly.

For this reason, the steps from step S105
In S106, the differential rotation DE calculated in step S103 is calculated.
From LNEn, the differential rotation correction value AVEDN0 of the #n cylinder up to the previous time calculated by statistically processing this differential rotation DELNEn.
n is subtracted, and the rotation is calculated as the corrected differential rotation DELNAn (DELNAn ← DELNEn−AVEDN0n).

As a result, as shown in FIG. 10, the rotation fluctuation due to misfire and the protrusions 31a,
From the uncorrected differential rotation DELNEn, which includes the manufacturing tolerances of the positions and shapes of the 31b and 31c and the apparent rotation fluctuation due to the tolerance of the mounting position of the crank angle sensor 32 to the engine 1, etc. Differential rotation between cylinder # n-1 and # n-1 cylinder, that is, corrected differential rotation DELNA
, And as shown in FIG. 11, the rotation fluctuation due to misfire can be accurately extracted.

10 and 11 and FIG. 1 to be described later.
3 shows differential rotation data calculated in the ECU 41, with one graduation on the vertical axis being 50 rotations and one graduation (1 div) on the horizontal axis being 720 ° CA.

As described above, for example, when the misfire diagnosis routine is executed in synchronization with the BTDC θ3 crank pulse of the # 3 cylinder, the # 4 cylinder as the cylinder # n-1 one combustion stroke earlier is the misfire diagnosis target cylinder. And the # 1 cylinder BTD
The rotation speeds MNX4 (= MNXn-1) of the # 4 cylinder (# n-1 cylinder) one combustion stroke before, calculated based on the input interval time between the θ2 and θ3 crank pulses of Cθ2 and θ3, and B of the # 4 cylinder
Rotational speed MNX of cylinder # 2 (# n-2) two combustion strokes before, based on the input interval time between TDC θ2 and θ3 crank pulses
2 (= MNXn-2) is subtracted and statistically processed, and the corrected differential rotation speed DELNA4 (= DELNAn-1) of the # 4 cylinder (# n-1 cylinder) obtained at the time of execution of the previous routine, and the BT of the # 3 cylinder
From the rotation speed MNX1 (= MNXn) based on the input interval time between the DC θ2 and θ3 crank pulses, the BTDCθ of the # 1 cylinder is
The rotational speed MNX4 (= MNXn-1) based on the input interval time between the 2, and θ3 crank pulses is subtracted, statistically processed, and the corrected differential rotational speed DELNA1 (#n cylinder) of the # 1 cylinder (#n cylinder) obtained in this routine is obtained. = DELNAn), the misfire diagnosis for the corresponding cylinder # 4 (# n-1 cylinder) is performed in the subsequent processing.

Next, steps S106 to S107 are performed.
Then, the difference between the post-correction differential rotation DELNAn of the #n cylinder and the post-correction differential rotation DELNAn-1 of the # n-1 cylinder calculated at the time of execution of the previous routine is calculated as the post-correction differential rotation change DDNEAn.
(DDNEAn ← DELNAn−DELN)
An-1). That is, by capturing the change in the differential rotation speed DELNA after correction, the influence of relatively small engine speed fluctuations caused by causes other than the misfire is eliminated, and accurate misfire detection is enabled.

Thereafter, from the above-mentioned step S107 to step S1
The process proceeds to 08 and thereafter, and it is determined whether or not the misfire diagnosis condition is satisfied in each of steps S108, S109, and S110. That is,
In step S108, it is checked whether or not the fuel is being cut.
At 09, it is checked whether the basic fuel injection pulse width Tp is smaller than the set value TpLWER. In step S110, it is checked whether or not the engine speed NE is equal to or higher than the set speed NEUPER.

Through the steps S108, S109 and S110, the fuel cut is not being performed, and Tp ≧ TpLWER and N
If E <NEUPER, step S1
At 11, the diagnosis permission flag FLGDIAG is set (FLGDIAG
AG ← 1) On the other hand, when the fuel is being cut in step S108, when Tp <TpLWER in step S109, or when NE ≧ NEUPER in step S110, the diagnosis condition is not satisfied and the process branches from step S112 to step S112. And clears the diagnosis permission flag FLGDIAG (FLGDIAG
AG ← 0).

When the process proceeds from step S111 or step S112 to step S113, a continuous misfire diagnosis subroutine described later is executed to detect the start and end of successive misfires. The value of the misfire flag FLGMISn-1 of the # n-1 cylinder one combustion stroke before is referred to.

The misfire flag is set to FL when the misfire is determined in the continuous misfire diagnosis in step S113.
GMISn-1 = 1 is set, and FLGM
If ISn-1 = 0, that is, if no misfire has occurred in the # n-1 cylinder, steps S114 to S115 are performed.
And the difference Δ between the differential rotation DELNEn−1 of the # n−1 cylinder and the differential rotation weighted average value AVEDN0 of all the cylinders up to the previous time.
It is determined whether or not (= DELNEn-1 -AVEDN0) is within a predetermined setting range between upper and lower set values MINDN, MAXDN (MINDN <MAXDN).

In the above step S115, MINDN <Δ <M
AXDN, and if it is within the set range, it is determined that the differential rotation DELNEn is fluctuating due to an error relating to the crank rotor 31 or the crank angle sensor 32, and the differential rotation DELNEn-1 is statistically processed in steps S119 and S120. ,
Proceed to step S121.

That is, in step S119, in order to correct the differential rotation fluctuation due to the error, a new differential rotation weighted average value AVEDN0 of all the cylinders up to the previous time and the corrected differential rotation DELNAn-1 of the # n-1 cylinder are newly calculated. Calculating the total cylinder differential rotation weighted average value AVEDN, (AVEDN ← (3/4) ×
AVEDN0 + (1/4) × DELNAn−1), and in step S120, the new all-cylinder differential rotation weighted average value AVED
The difference between N and the differential rotation DELNEn-1 of the # n-1 cylinder, and the differential rotation correction value AVEDN of the # n-1 cylinder up to the previous time.
0n-1, the difference rotation correction value AVE of the new # n-1 cylinder
Calculate DNn-1 (AVEDNn-1 ← (7/8) × AV
EDN0n-1 + (1/8) × (DELNEn-1-AVED
N)).

On the other hand, in step S114, the FLGMIS
When n-1 = 1, that is, when the # n-1 cylinder misfires,
In step S116, the count value MISCNTn-
Count up 1 (MISCNTn-1 ← MISCN
Tn-1 + 1) Go to step S117.

In step S115, Δ ≦ MIND
When N or Δ ≧ MAXDN, not the fluctuation of the differential rotation DELNEn−1 due to the error relating to the crank rotor 31 or the crank angle sensor 32, but the fluctuation of the differential rotation DELNEn−1 due to other factors (snatch, acceleration / deceleration, etc.). And the process proceeds to step S117.

In step S117, the all-cylinder differential rotation weighted average value AVEDN0 up to the previous time is set as the current all-cylinder differential rotation weighted average value AVEDN (AVEDN ← AVEDN0). In step S118, the difference between the # n-1 cylinder and the previous cylinder is determined. The rotation correction value AVEDN0n-1 is set as a new difference rotation correction value AVEDNn-1 of the # n-1 cylinder (AVEDNn-1 ← AVEDN0).
n-1), and proceeds to step S121.

Then, when proceeding from step 118 or step S120 to step S121, the value of the diagnosis permission flag FLGDIAG is referred to, and when FLGDIAG = 0,
The process jumps to step S127, and when FLGDIAG = 1, in step S122, the count value CRACNT, which is counted every time the misfire diagnosis is performed, is counted up (CRA).
(CNT ← CRACNT + 1), and in a step S123, it is determined whether or not the count value CRACNT has reached 2000.

As described above, this misfire diagnosis routine is executed every time the θ3 crank pulse is input, ie, when the engine 1
/ 2 rotations, the count value CRAC
The value 2000 of NT indicates 1000 revolutions of the engine.

In step S123, CRACNT <2
000, the flow branches to step S127, and CRACNT ≧
In the case of 2000, a misfire determination subroutine, which will be described later, is executed in step S124, and in steps S125 and S126, the count value CRACNT and the count values MISCNT1 to MISCNT4 of the number of misfires for all cylinders are cleared (CRACNT ← 0). , MISCNT1 to 4 ← 0), and the process proceeds to step S127. In step S127, the data such as the differential rotation DELNEn, the corrected differential rotation DELNAn, the all-cylinder differential rotation weighted average value AVEDN, and the differential rotation correction value AVEDNn-1 for the # n-1 cylinder which have been calculated this time are stored in the RAM 44 as monitoring data. Set and exit the routine.

Next, the subroutine for continuous misfire diagnosis in step S113 and misfire determination in step S124 in the above misfire diagnosis routine will be described.

First, in the subroutine for continuous misfire diagnosis shown in FIG. 1, in step S201, a diagnosis permission flag FLG is set.
Referring to the value of DIAG, when FLGDIAG = 0, the misfire flag FLGMISn-1 corresponding to the # n-1 cylinder one combustion stroke before is cleared in step S211 (FLGMI Sn-1).
← 0) Exit the routine, and if FLGDIAG = 1, proceed to step S202.

In step S202, a misfire determination level LVLMIS is set by referring to the misfire determination level map with interpolation calculation using the engine speed NE and the basic fuel injection pulse width Tp as parameters, and the flow proceeds to step S203 and subsequent steps.

The misfire determination level LVLMIS is shown in FIG.
As shown in FIG. 2, a low engine load region where the basic fuel injection pulse width Tp is small is defined as an undiagnosable region, and the slice level increases as the basic fuel injection pulse width Tp increases and the load increases. Are stored as a map in the ROM 43.

Next, steps S202 to S203 are performed.
When the process proceeds to, the negative misfire determination levels -LVLMIS and # n-
One cylinder is compared with the corrected differential rotation DELNAn-1. As a result of the comparison, DELNAn-1> -LVLMIS, and #
When the corrected differential rotation DELNAn-1 of the n-1 cylinder has not fallen below the negative misfire determination level -LVLMIS,
It is determined that it is not a misfire, and the process branches to step S211 described above.
Clear the misfire flag and exit the routine.

On the other hand, as a result of the comparison in step S203, D
ELNAn-1 ≦ −LVLMIS, and the corrected differential rotation DELNAn−1 of the # n−1 cylinder is a negative misfire determination level −L.
If it is below VLMIS,
Proceeding from S203 to step S204, the corrected differential rotation change DDNEAn of the #n cylinder and the negative misfire determination level -LVLMI
S, and the change in the corrected differential rotation DELNA from the # n-1 cylinder to the #n cylinder is examined.

Then, in the above step S204, DDNEA
When n ≦ −LVLMIS, and when the corrected differential rotation speed DELNA drops stepwise from the # n-1 cylinder to the #n cylinder, it is determined that there is a rotation fluctuation due to a cause other than a misfire, and the routine proceeds through the aforementioned step S211. Through D DN
EAn> −LVLMIS, negative misfire determination level−
If the post-correction differential rotation DELNA dropped below LVLMIS fluctuates around the negative misfire determination level -LVLMIS from cylinder # n-1 to cylinder #n, step
In S205, the corrected differential rotation change DDNEAn of the # n-1 cylinder
-1 and a negative misfire determination level -LVLMIS, and #
Corrected differential rotation D from cylinder n-2 to cylinder # n-1
Examine changes in ELNA.

As a result, in step S205, DDNE
An-1 ≦ −LVLMIS, and the above steps S203, S204
And the corrected differential rotation DELNA
Drops below the negative misfire determination level -LVLMIS from the # n-2 cylinder to the # n-1 cylinder, and decreases from the # n-1 cylinder to the #n cylinder.
When it is in the vicinity, it is determined that misfire has started from the # n-1 cylinder, and the process proceeds from step S205 to step S208.

In step S208, the corrected differential rotation speed DELNAn-1 of the # n-1 cylinder is set as the minimum value DNEAMS (DNEAMS ← DELNAn-1), and then the routine proceeds to step S210, where the misfire flag of the # n-1 cylinder is set. FLGMI
Set Sn-1 (FLGMISn-1 ← 1) and exit the routine.

On the other hand, in step S205, DDNEAn-
1> −LVLMIS, and when the corrected differential rotation DELNA does not drop below the negative misfire determination level −LVLMIS from cylinder # n-2 to cylinder # n−1,
The process branches from step S205 to step S206, where # n-
It is determined whether or not the two-cylinder misfire flag FLGMISn-2 is set, that is, whether or not the # n-2 cylinder is in a misfire state.

In step S206, FLGMISn-2
= 0 and the # n-2 cylinder has not misfired,
The process exits from the routine through the above-described step S211 and proceeds to FLGMI.
If Sn-2 = 1 and the # n-2 cylinder is misfired, the process proceeds from step S206 to step S207, where #n
The drop level of the differential rotation DELNAn-1 after the correction of the -1 cylinder is examined.

That is, in step S207, the corrected differential rotation DELNAn-1 of the # n-1 cylinder and the minimum value DNE of the differential rotation.
Compared with AMS, if DELNAn-1 <DNEAMS, and if the corrected differential rotation DELNAn-1 of cylinder # n-1 is lower than the minimum value of differential rotation DNEAMS at misfire, cylinder # n-2 It is determined that the misfire has occurred continuously from # 1 to # n-1 cylinder, and the aforementioned step S208
To update the minimum value DNEAMS, set the misfire flag FLGMISn-1 in step S210, and exit the routine.

On the other hand, in step S207, DELNAn-
If 1 ≧ DNEAMS, and the corrected differential rotation DELNAn−1 of the # n−1 cylinder is equal to or greater than the minimum value DNEAMS, the process proceeds from step S207 to step S209, and # n−
The corrected differential rotation DELNAn-1 of one cylinder is compared with a value obtained by adding the minimum value DNEAMS to the misfire determination level LVLMIS to determine whether or not the drop of the corrected differential rotation DELNA has recovered to a predetermined level. I do.

Then, in step S209, DELNA
If n-1 <DNEAMS + LVLMIS, and the drop in the corrected differential rotation speed DELNAn-1 of the # n-1 cylinder has not recovered, it is similarly determined that the misfire has continued in the # n-1 cylinder. In step S210, the misfire flag FLGMISn-1 is set, and the routine exits.

On the other hand, in step S209, DELNAn-
If 1 ≧ DNEAMS + LVLMIS, and the drop in the corrected differential speed DELNAn−1 of the # n−1 cylinder has recovered, it is determined that misfire has ended, and the misfire flag FLGMISn−1 is cleared in step S211 described above. Through.

That is, the corrected differential rotation speed DELNA is changed from the # n-2 cylinder to the # n-1 cylinder to the misfire determination level LV.
It falls in the negative direction below LMIS, and from # n-1 cylinder #
When the state continues for n cylinders, # n-
It is determined that the misfire has started from one cylinder, and after the misfire has occurred, it is determined that the misfire has ended when the corrected differential rotation speed DELNA has recovered to a predetermined level or more. It is possible to reliably detect a misfire that occurs continuously in the two cylinders, # 1 and # 3 cylinders.

Next, in the misfire determination subroutine shown in FIG. 4, in step S301, the total number of misfires for the four cylindersΣ
MISCNTn (n = 1 to 4) is divided by the count value CRACNT (= 2000) in the above-described misfire diagnosis routine to obtain a misfire rate MIS per 1000 revolutions of the engine.
Calculate CNT (%) (MISCNT ← ΣMISCN
Tn / CRACNT × 100).

Next, the process proceeds to step S302, in which the misfire rate MISCNT calculated in step S301 is set to the set value LMSC.
It is determined whether it is smaller than NT. This set value LMSC
NT is the engine speed NE and the basic fuel injection pulse width Tp
Are constants stored in the ROM 43 in advance with the parameters

As a result of the determination in step S302, MI
When SCNT ≧ LMSCNT, in step S303,
The misfire rate MISCNT is stored at a predetermined address in the backup RAM 44a.
It is checked whether or not the first misfire determination NG flag FLGNG1 stored at a predetermined address of the AM 44a is set.

Then, in step S304, the first-time misfire determination NG flag FLGNG1 has not been set, and F
When LGNG1 = 0, the process jumps from step S304 to step S306, and the first misfire determination NG flag FLG
When NG1 is set and FLGNG1 = 1, the process proceeds from step S304 to step S305 to set the second misfire determination NG flag FLGNG2 stored at a predetermined address in the backup RAM 44a (FLGNG2 ←
1) A warning is issued to the user by turning on or blinking the ECS lamp 53, and the process proceeds to step S306.

In step S306, the first-time misfire determination NG flag FLGNG1 is set (FLGNG1 ← 1).
In S312, the misfire OK counter for counting the number of determinations of no abnormality is cleared (CNTOK ← 0), and the routine exits.

That is, in order to avoid erroneous diagnosis due to noise or the like, the misfire rate MISCNT is set to the set value L in the first determination.
No warning is issued immediately even if MSCNT or higher
The misfire rate MISCNT continues to be the set value LMS
If CNT or more, the cylinder is determined to be abnormal and a warning is issued.

At this time, the backup RAM 44a
The trouble data of the misfiring cylinder is stored, and the trouble data stored in the backup RAM 44a is read by the blinking code of the monitor lamp of the ECU 41 or the serial monitor 54 at the time of troubleshooting at the dealer. After the misfire cylinder is determined and repaired, the trouble data in the backup RAM 44a is cleared via the serial monitor 54 and the like.

On the other hand, in step S302, the MISCNT
If <LMSCNT, it is determined that there is no abnormality, and step
When the misfire OK counter CNTOK is incremented in step S307 (CNTOK ← CNTOK + 1), step S308 is performed.
Then, it is determined whether or not the value of the misfire OK counter CNTOK has exceeded 80 times. If CNTOK <80, the routine exits as it is.
In S309, S310, and S311, the first-time misfire determination NG flag FLGNG1, the second-time misfire determination NG flag FLGNG2, and the misfire rate MISCNT are cleared (FLGNG1 ← 0, F
LGNG2 ← 0, MISCNT ← 0), step S31 described above.
2, clear the misfire OK counter CNTOK (CN
TOK ← 0) Exit from the routine.

[0083]

As described above, the invention according to claim 1 is described above.
According to the above, the difference between the engine speeds of the combustion stroke cylinders
Of the engine speed difference between the front and rear combustion stroke cylinders
Change, that is, using the change in differential rotation to determine misfire
And a relatively small engine
Accurate misfire detection by eliminating the effects of gin rotation fluctuation
be able to. According to the second aspect of the present invention, the fuel is burnt twice before
When the firing stroke cylinder is misfired, the last combustion stroke cylinder
The difference between the engine speeds of
Compare with the minimum value set by the difference,
Engine speed of the last combustion stroke cylinder with respect to the minimum value of rotation
Since the difference of the difference of
In addition to the effect of light, the combustion stroke from the combustion stroke cylinder two times before
Accurate detection of continuous misfires over cylinders
Has an effect. According to the third aspect of the present invention, the last combustion
The difference in the engine speed of the stroke cylinder is judged to be misfire.
The value obtained by adding the minimum value of differential rotation at misfire to the level
Judgment of whether or not it has recovered to the
The drop in engine speed difference has recovered to a predetermined level
If not, it is determined that the last misfire of the combustion stroke cylinder
And the difference in engine speed of the previous combustion stroke
Is recovered, it is determined that the misfire has ended.
In addition to the effect of the invention described in the second aspect, continuation of the corresponding cylinder
An effect that can accurately determine misfire and end of misfire
Have fruit.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a subroutine for continuous misfire diagnosis.

FIG. 2 is a flowchart illustrating a misfire diagnosis routine;

FIG. 3 is a second flowchart illustrating a misfire diagnosis routine;

FIG. 4 is a flowchart showing a subroutine for misfire determination.

FIG. 5 is a schematic configuration diagram of an engine control system.

FIG. 6 is a front view of a crank rotor and a crank angle sensor.

FIG. 7 is a front view of a cam rotor and a cam angle sensor.

FIG. 8 is a circuit configuration diagram of an electronic control system.

FIG. 9 shows crank pulses, cam pulses, combustion stroke cylinders,
Chart showing the relationship between ignition and ignition timing

FIG. 10 is an explanatory diagram showing a differential rotation before correction.

FIG. 11 is an explanatory diagram showing a differential rotation after correction.

FIG. 12 is an explanatory diagram of a misfire determination level.

FIG. 13 is an explanatory diagram showing a differential rotation when a continuous misfire occurs.

[Explanation of symbols]

 1 Engine DELNA Differential rotation after correction (difference) DDNEA Change in differential rotation after correction (change in difference) LVLMIS Misfire determination level

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 45/00 368 F02D 45/00 362 F02P 17/12

Claims (3)

(57) [Claims] 1. The method of claim 1, wherein a current combustion stroke cylinder and a previous combustion stroke cylinder are connected to each other.
The difference between the engine speeds
Of the combustion stroke cylinder this time.
Engine speed difference and engine speed of previous combustion stroke cylinder
The difference from the number difference is taken as the differential rotation change of the combustion stroke cylinder this time.
Calculated and the difference between the engine speed of the previous combustion stroke cylinder and the
Negative loss set based on engine operating conditions
Compared to the fire determination level, the difference between the engine speeds of the previous combustion stroke cylinders
When it is below the fire judgment level,
The change in the differential rotation of the cylinder is compared with the above-described negative misfire determination level, and the change in the differential rotation of the cylinder during the current combustion stroke is compared with the negative misfire determination level.
When the engine speed is higher than the
Is compared with the above-described negative misfire determination level, and the change in the differential rotation of the previous combustion stroke cylinder is used as the negative misfire determination level.
Misfire in the last combustion stroke cylinder
A method for detecting misfire of an engine, characterized by determining that a misfire has occurred . 2. When it is determined that a misfire has occurred,
The difference between the engine speeds of the multiple combustion stroke cylinders
The value of the negative misfire determination level
If it is higher than the pre-
It is determined whether or not the cylinder is misfired.
Compare the difference in engine speed of the stroke cylinder with the above minimum value
The difference between the engine speeds of the previous combustion stroke cylinders is
When the cylinder is lower than the previous one,
It is determined that misfires have occurred continuously over the combustion stroke cylinders.
The engine misfire according to claim 1, wherein
Detection method. 3. The engine speed of the last combustion stroke cylinder
When the difference is equal to or greater than the minimum value, the value of the previous combustion stroke cylinder
The minimum difference between the engine speed difference and the misfire determination level
Comparing the sum value obtained by adding the value, the engine rotational speed difference of the previous combustion stroke cylinder the pressure
If it is lower than the calculated value, the misfire of the previous combustion stroke cylinder continues.
And the difference between the engine speeds of the previous combustion stroke cylinders is added.
When the value is equal to or greater than the calculated value, it is determined that the misfire has ended
The method for detecting misfire of an engine according to claim 2, wherein