JPH04171250A - Misfire judging method for each engine cylinder - Google Patents

Abstract

PURPOSE:To precisely detect a misfire state by comparing a difference in momentum during a non-working period of combustion between a cylinder before two combustion strokes and a cylinder before one combustion stroke with a misfire judging level set on the basis of an engine combustion state parameter of a cylinder before one combustion stroke so as to determine the misfire state for each cylinder. CONSTITUTION:A combustion state of a cylinder before one combustion stroke is determined based on an average value of momentum during a non-working period of combustion of the cylinder before a combustion stroke before and after the same. A comparison value is compared with a misfire judging level set corresponding to an engine state of the cylinder before one combustion stroke, thereby determining a misfire state of the cylinder before one combustion stroke. Therefore, the misfire state can be precisely detected without any effect of variation of combustion between the cylinders and variation of manufacture of each engine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a misfire discrimination method for each cylinder of an engine, which discriminates the misfire state of each cylinder from the amount of change in motion between the cylinders.

[Problems to be solved by the conventional technology and the invention]-i,
Ideally, combustion in a multi-cylinder engine should be carried out through the same process every cycle in order to obtain stable output, but in a multi-cylinder engine, there are Unevenness in intake air distribution ratio, ■Slight differences in combustion temperature between cylinders caused by the cooling route, ■Manufacturing variations in combustion chamber volume of multiple cylinders, piston shape, etc., ■Fuel injection due to injector manufacturing errors, etc. Combustion tends to vary due to the synergistic effects of slight variations in the air-fuel ratio of each cylinder due to differences in the amount of fuel.

Conventionally, combustion fluctuations between cylinders have been controlled by air-fuel ratio control for each cylinder,
Ignition timing control has minimized the possibility of misfires, but in high-performance engines that have recently become more powerful and fuel efficient, intermittent misfires can occur if the injectors, spark plugs, etc. deteriorate or malfunction. This tends to cause a decrease in output.

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

Therefore, for example, in Japanese Patent Application Laid-Open No. 61-258955, the difference between the minimum value and the maximum value of the engine rotation speed of the cylinder before one combustion stroke, and the difference between the minimum value and the maximum value of the engine rotation speed of the cylinder in the current combustion stroke. The difference is compared, and the combustion state of the cylinder in the current combustion stroke is determined based on whether this comparison value is within a preset reference value. If combustion abnormality occurs more than a predetermined number of times, it is determined that a misfire has occurred and the V? I am trying to inform you.

However, in this prior art, combustion fluctuations in each cylinder are determined from the difference between the minimum engine rotation speed and the maximum engine rotation speed of the combustion stroke cylinder, but the engine rotation speed during combustion increases rapidly. Since a relatively large load is applied to the engine, fluctuations in acceleration become large. Therefore, it is difficult to specify the maximum value of the engine speed, and the accuracy error when determining a misfire becomes large.

Incidentally, the combustion characteristics of an engine vary not only between cylinders but also from engine to engine due to manufacturing errors in parts.

If the reference value for comparing rotational fluctuations is set as an absolute value as in the prior art described above, the reference value will vary relative to each engine due to variations in the combustion characteristics of each engine. This makes it difficult to accurately identify abnormalities.

In engines with a small number of cylinders, the combustion interval between cylinders is relatively long, so the difference in rotational speed is large, and even if the reference value is set as an absolute value, variations in combustion characteristics from engine to engine have a large impact on misfire detection. However, in an engine with a large number of cylinders, the combustion interval between cylinders becomes shorter, and the difference in rotational fluctuation becomes smaller. Therefore, if the judgment level (reference value) is set as an absolute value in advance, it will be easier to determine the combustion characteristics of each engine. Variations have a large effect on misfire determination accuracy.

In particular, in the high rotation range, the fluctuation difference is reduced, so
If the determination level varies relative to each engine, it becomes extremely difficult to accurately determine a misfire.

For example, in Japanese Patent Application Laid-open No. 59-82534, each cylinder #
Difference low rotation ΔN No. 1 (△
N Ii = NH number i - NLIi ) is determined for each cylinder, and then the all-cylinder average value ΔNA of the differential rotation ΔNli of each cylinder #i is compared with the above-mentioned differential rotation ΔN i of each cylinder #j. Thus, the combustion state of each cylinder #i is grasped.

However, in this prior art, since the reference value is the all-cylinder average differential rotation ΔN, the all-cylinder average differential rotation ANA itself is always likely to fluctuate depending on the combustion state, and if this all-cylinder average differential rotation ΔN8 fluctuates, , the combustion state of each cylinder estimated based on this all-cylinder average differential rotation △NA includes the combustion condition factors of other cylinders when setting the above-mentioned all-cylinder average differential rotation △NA. It becomes difficult to accurately identify misfires.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and it is possible to prevent misfires from occurring without jeopardizing the combustion state factors of other cylinders, and to reduce combustion variations between cylinders as well as manufacturing differences between engines. It is an object of the present invention to provide a method for determining engine misfires by cylinder, which can accurately detect misfires without being influenced by variations.

[Means for Solving the Problems] (1) In order to achieve the above object, the second engine cylinder-by-cylinder misfire determination method according to the present invention is based on the momentum of the section in which no work is being done by combustion in the cylinder before two combustion strokes. Find the difference between the average value of the momentum in the section where no work is done by combustion in the cylinder in the current combustion stroke, and the momentum in the section where no work is done by combustion in the cylinder one combustion stroke before, and calculate the difference between this difference and the momentum in the section where no work is done by combustion in the cylinder one combustion stroke before. The misfire state is determined for each cylinder by comparing it with a misfire determination level set based on the engine combustion state parameters of the previous cylinder.

(2) In order to achieve the above object, the second engine cylinder-by-cylinder misfire determination method according to the present invention is based on the momentum of the section where no work is done by combustion of the cylinder before one combustion stroke and the combustion of the cylinder after one combustion stroke. Calculate the difference between the average value of the estimated momentum of the section that is not doing work and the momentum of the section that is not doing work due to combustion in the cylinder in the current combustion stroke, and based on this difference and the engine operating state parameters of the cylinder in the current combustion stroke. The misfire condition is determined for each cylinder by comparing it with the misfire determination level set by the engine.

``Effects (1) According to the first engine cylinder-by-cylinder misfire determination method, the combustion state of the cylinder before one combustion stroke is the average of the momentum in the section where no work is done by combustion in the cylinders of the combustion strokes before and after the combustion stroke. This comparison value is compared with a misfire determination level set corresponding to the engine condition of the whistle before the first combustion stroke to determine the misfire state of the cylinder before the first combustion stroke. It is possible to accurately detect misfire conditions without being affected by combustion variations between cylinders or manufacturing variations between engines.

(2) According to the above-mentioned second engine cylinder-by-cylinder misfire determination method, the combustion state of the current combustion stroke cylinder is determined by calculating the average value of the momentum and estimated momentum in the section where the combustion state of the cylinder in the current combustion stroke is not doing work by combustion in the combustion stroke cylinders before and after the current combustion stroke cylinder. This comparison value is compared with the misfire determination level set corresponding to the engine operating state of the current combustion stroke cylinder to determine the misfire condition of the current combustion stroke cylinder. Accurate detection is possible without being affected by combustion variations between cylinders or manufacturing variations between engines.

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

FIGS. 1 to 8 show a first embodiment of the present invention, and FIG. 1 is a flowchart 1-1 showing a cylinder-by-cylinder misfire discrimination procedure, and FIGS. 2 and 3 are a basic cylinder-by-cylinder misfire discrimination method. A conceptual diagram showing
Figure 4 is a schematic diagram of the engine control system, Figure 5 is a front view of the crank rotor and crank angle sensor, Figure 6 is a front view of the cam rotor and cam angle sensor, Figure 7 is a conceptual diagram of the misfire determination level map, FIG. 8 is a time chart showing cylinder pressure fluctuations, crank pulses, cam pulses, and engine rotation fluctuations.

(Configuration) Reference numeral 1 in FIG. 4 is an engine, and the figure shows a four-cylinder horizontally opposed engine. An intake manifold 3 is attached to an intake boat 2a formed on the cylinder head 2 of this engine 1.
A throttle chamber 5 is communicated upstream of the intake manifold 3 via an air chamber 4,
An air cleaner 7 is attached to the upstream side of the throttle chamber 5 via an intake pipe 6.

Further, an intake air amount sensor (a hot wire air flow meter in the figure) 8 is interposed immediately downstream of the air cleaner 7 in the intake pipe 6, and a throttle valve 5a provided in the throttle chamber 5 is connected to a throttle valve 5a provided in the throttle chamber 5. An opening sensor 9a and an idle switch 9b for detecting fully closed throttle valve are connected.

Further, a multi-point injector (
(hereinafter abbreviated as rMP I J) 10 is provided. Further, reference numeral 11 is a fuel tank, and 12 is a fuel pump that supplies fuel to the MPIIO.

A crank rotor 15 is attached to the crankshaft 13 of the engine 1, and the crank rotor 15 has an electromagnetic pickup on its outer periphery for detecting a protrusion (or a slit) corresponding to a predetermined crank angle. An angle sensor 16 is provided oppositely to the camshaft 14 which rotates by 1/2 with respect to the crankshaft 13.
A cam rotor 17 is connected to the cam rotor 17, and a cam angle sensor 18 is provided on the outer periphery of the cam rotor 17.

As shown in FIG. 5, projections (slits may be used) 1.5a, 15b, and 15c are formed on the outer periphery of the crank rotor 15. Each of these protrusions 15a.

15b and 1.5c are each cylinder's compression top dead center (BTDC)
θ1. θ2. It is formed at the position θ3, and the protrusion 15a
, 15b, the period f 1.2 (here, child = 1/ω ω: angular velocity) is calculated from the passage time between protrusion 1
A periodic element 2.3 is calculated from the transit time between 5b and 15c. Further, the protrusion 15b indicates a reference crank angle when setting the ignition timing.

Generally, the ignition timing during idling is BTDC20'C.
The combustion pressure is around A, and even if ignition occurs at this crank angle, the combustion pressure will not rise sharply until about 10'' CA.

Further, as shown in FIG. 8, in the embodiment, the opening timing of the exhaust valve of each cylinder is set to be slightly retarded than the ignition reference crank angle BTDCθ2 of the next combustion cylinder.
- In general, the combustion pressure immediately after the exhaust valve opens drops rapidly, so at the crank angle BTDCθ3, there is almost no effect of the combustion pressure.

Therefore, the crank angle θ3 of the protrusion 15c is set to BTD.
If the angle is set more advanced than C10'CA, the above protrusion 15b
, 15c between the crank angles BTDCθ2°θ3 are almost unaffected by the combustion between the cylinders, that is, the range is a region in which no work is done by combustion in the combustion stroke cylinder.

Furthermore, as shown in FIG.
b, 1.7c are formed. The protrusion 17a is #3. #
It is formed at the position θ4 after the compression top dead center (ATDC) of the #4 cylinder, and the protrusion 17b is composed of three protrusions, the first of which is formed at the position θ5 after the compression top dead center (ATDC) of the #1 cylinder. Furthermore, the protrusion 17c is composed of two protrusions, and the first protrusion is located after the compression top dead center of the #2 cylinder (A
TDC) is formed at the position θ6.

In addition, in the example shown in the figure, θ1=97℃A, θ2-65℃A
, θ3=10℃A, θ4-20℃A, θ5-5℃A,
θ6 = 20'CA, θ(2-3) = 55°C A, and with this arrangement, as shown in FIG. In this case, it can be determined that the crank pulse subsequently detected by the crank angle sensor 16 is a signal indicating the crank angle of the #3 cylinder.

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

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

Incidentally, the crank angle sensor 16 and the cam angle sensor 18 constitute a crank angle detecting means, and by changing the cam pulse pattern, the crank angle detecting means may be constituted by only the cam angle sensor 18.

On the other hand, a cooling water temperature sensor 20 faces a cooling water passage (not shown) forming a riser formed in the intake manifold 3 of the engine, and the cylinder head 2
The 02 sensor 2 is connected to the exhaust pipe 21 that communicates with the exhaust boat 2b.
2 is coming.

Note that 23 is a catalytic converter, and 24 is a vehicle speed sensor.

(Rotational configuration of control device) On the other hand, reference numeral 3] is a control device consisting of a microcomputer, etc. This control device 31 includes a CPU (central processing unit) 32, ROM3B, R1ΔM34, backup R
An AM (non-volatile RAM) 35 and an I10 interface 36 are connected to each other via a pass line 37, and a predetermined stabilized voltage is supplied from a constant voltage circuit 38.

The constant voltage circuit 38 is connected to a battery 41 via a control relay 39, and supplies control power to each part when the key switch 40 is turned on and the relay contact of the control relay 39 becomes a leap. It is directly connected to the battery 41 and supplies backup power to the backup RA and M35 even when the key switch 40 is turned off.

In addition, each sensor 8, 9a, 16.18, 20°22.24,
And, while the idle switch 9b is connected,
The positive terminal of the battery 41 is connected, the terminal voltage is monitored, and the I10 interface 3
The output port 6 is connected to the MPIIO via a drive circuit 42 and a warning means 43 such as an indicator lamp disposed on a panel or the like to the insulators 1 to 1 (not shown).

The ROM 33 stores control programs, fixed data, and the like. The fixed data includes a misfire determination level map M PΔN1-EVEL, which will be described later.

Further, the RAM 34 stores data after processing the output signals of the sensors, data processed by the CPU 32, and the like. Furthermore, backup RAM3
5, the power is always energized regardless of the key switch 40, the memory contents are not lost even if the key switch 40 is turned OFF and the engine operation is stopped, and trouble data such as misfire data for each cylinder, which will be described later. etc. are memorized.

This trouble data is stored in the I10 interface 36 above.
The data can be read by connecting a failure diagnosis serial monitor 45 to the failure diagnosis connector 44 connected to the output port of the computer.

Furthermore, the CPU 32 performs MP processing according to the control program stored in the ROM 33 and based on various data stored in the RAM 34 and backup RAM 35.
The fuel injection pulse width Ti for IIO and the like are calculated for each cylinder.

In addition to general fuel injection control, the control device 3] individually determines misfire in each cylinder #i (i=1 to 4).

FIG. 2 shows the basic concept of this cylinder-by-cylinder misfire discrimination method.

This will be explained according to FIG.

Figure 3 shows engine speed fluctuations. For example, in the case of a 4-cylinder engine, the combustion stroke cylinder #i switches every 180°C according to the ignition order (for example, #1 → #3 → #2 → #4). Therefore, the combustion strokes do not overlap before and after, and there is no effect of combustion in each cylinder between after the combustion of combustion stroke cylinder #i ends and before the combustion of the next combustion stroke cylinder #t1. , there is a section where no work is done by combustion.

For example, as shown in Fig. 3, if the engine speeds, which are the instantaneous motions of cylinders #1 to #4, are N11 to N#4 in the section where they are not doing work due to combustion, then a certain cylinder #i If a misfire occurs in the engine, the engine output after combustion will drop sharply.

In this example, focusing on the fact that there is a very strong correlation amount I between the combustion state of each cylinder #i and the engine speed Nli, the combustion state is discriminated for each cylinder, and this discrimination value and the misfire Judgment level △N1. ．． EVIEL is compared to determine the misfire state of the cylinder #1.

That is, in this misfire determination method, first, the engine rotational speed N of the current combustion stroke cylinder #i and the second combustion stroke previous cylinder #i are determined.
-2 engine speed N#i-2 and the average value (N $i
-20N Ii) / 2 and 1 combustion stroke previous cylinder #i-
1 engine rotation speed N good i-1, and this comparison value ΔN side i-1 (ΔN number 1-1 = N number, Δ to -11 engineering j)
Y) is compared with a misfire determination level ΔN LEVEL set according to the operating state of the cylinder #i-1, and if the comparison value ΔN11-1 is lower than the misfire determination level ΔN1-EVEL, it is determined that a misfire has occurred. It is something.

By the way, since the comparison value used to determine a misfire is set based on the average value of engine speeds of cylinders that are adjacent to each other in the ignition order, it is a nearly constant value (I) not only when driving at a constant speed but also during acceleration. Under normal conditions, a value close to 0 can be obtained.

In addition, below, the comparison value Δ of cylinder #i-1 before each combustion stroke
A method of calculating N#i-1 will be specifically shown.

ΔN s1= N sl-N $4 + N 13ΔN
, 3=N, 3 N$1+N#2 △N #2=N number 2N? 3+ N #4△N54=
Nt4N #2+Nlt1 Also, below, a correlation equation between the engine rotational speed N in a section where no work is being done by combustion and the combustion state of the cylinder, that is, the indicated mean effective pressure Pi is shown.

First, to express the state in which the engine is rotating using the formula: ■・l・stopΔ−Ti −Tf ・・・・・・(1)
0 dt ■: Moment of inertia)・N ・Engine speed Ti: Indication 1 - Luk Tf: Friction torque, and simplifying this formula (1), we get: Stop ΔcxTi -Tf 4, ... - (2) Then, when expressed in terms of pressure, the old “c<pi −P
f...(3) tP] - Indicated average effective pressure Pf: Friction loss effective pressure.

According to experiments, the engine speed N after combustion in each cylinder #i
As a result of finding dN/dt in the above equation (3) based on li and the temporal change ΔT in the section in which the engine rotation speed Nli is detected (e.g., corresponding to the section (θ2-θ3) in FIG. 6), A very strong correlation was obtained.

Therefore, by determining the engine speed after combustion in each cylinder, it is possible to estimate the indicated mean effective pressure Pi, that is, the combustion state, and by comparing it with the engine speed of the adjacent combustion stroke cylinder, the combustion A comparison value can be set to determine whether there is a misfire in a stroke cylinder.

(Operation) Next, a specific cylinder-by-cylinder misfire determination procedure executed by the control device 31 will be described with reference to the flowchart of FIG. 1.

First, in step (hereinafter abbreviated as "S") 3101, combustion stroke cylinder #i (j, = 1.3°2 .4) is determined, and in 5102, the calculation cycle number C of the combustion stroke cylinder #i is determined.
Count up til (Cfil←C111+
1>.

Next, in 5103, BTDCθ2. which is output from the crank angle sensor 16 is detected. The crank pulse for detecting θ3 is determined by the interruption of the cam pulse, and in step 5104, the BTDC θ2. The elapsed time between crank pulses for detecting θ3 and θ2. From the angle of θ3 (θ2-θ3), the period f
2.3 (f2,3←dt2,3/d(θ2−
θ3)).

After that, in 5105, the engine rotational speed N stored i in the section where no work is done by combustion in the current combustion stroke cylinder #i is calculated from the period f2,3 (Nli←-60/f2.3).
.

Then, at 8106, the engine rotation speed N1-1 of the section where cylinder #1-1 is not doing any work due to combustion after one combustion stroke, which was set in the previous routine and the routine before the previous one and stored at a predetermined address in the RAM 34, and Engine rotation speed N11- in the section where cylinder #i-2 is not doing work due to combustion
2. As shown in Figure 8, the firing order is changed from #1 to #3.
→ #2 → #4, if the current combustion stroke cylinder #i is #3, the 1st combustion stroke previous cylinder #1-1 is #1, and the 2nd combustion stroke previous cylinder #i-2 is #4. .

In addition, the engine speed number 8 i in the first routine
-1, Nti-2 is N #1-1= N N-2= N
It is set to ti.

Next, in 5107, the engine rotation speed Nli in the section where no work is being done by combustion in the current combustion stroke cylinder #i and the engine rotation speed N# in the section where no work is being done by combustion in the 2nd combustion stroke previous cylinder #i-2. Average value with i-2 (N #i+
N #1-2) / 2 and the cylinder #i before the 1st combustion stroke
The combustion state comparison value ΔN#i-1 of the cylinder #i-1 one combustion stroke before is determined from the difference from the engine rotation speed N11-1 in the section where no work is being done by combustion.

ΔN11-1←N#i-1- ((N cloud i+N number 1-2
)/2) After that, in 8108, engine load data (=basic combustion injection pulse width) TP and engine speed Nti- calculated based on the engine speed Nll-1 and intake air amount Q obtained in this routine are calculated. 1 as a parameter, a misfire judgment level ΔN LEVEL is set from NLEVEL to the misfire judgment level map MP.

As shown in FIG. 7, the misfire determination level Matsu 7 M
P △N LEVEL is the engine rotation speed N1ti-1
This is a three-dimensional map with engine load data T+1 and engine load data T+1 as parameters, and each area surrounded by a grid stores a misfire determination level ΔN LEVEL determined in advance through experiments or the like.

As shown in FIG. 3, the combustion state comparison value ΔN11-1 is
It exhibits a relatively large amount of variation during acceleration, but this amount of variation varies depending on the operating conditions of the engine.

Therefore, the amount of variation is determined in advance for each operating condition through experiments, etc., and a misfire is determined according to the amount of variation.
By setting EVEL and creating a map, high misfire determination accuracy can be obtained. Note that during deceleration, fuel is cut, so misfire determination is not substantially performed.

Then, in 5109, the misfire determination level ΔN1. EV
Compare E
-1 is lower than the misfire judgment level △N LEVEL (△N
#1-1〈△NLEVEL) (see Figure 3), it is determined that a misfire has occurred and the process proceeds to 5110, and ∆N LEVEL
If ti-1≧△N LEVEL, it is determined that combustion is normal and the process proceeds to 5111.

If a misfire is determined and the process advances to 5iio, the cylinder #1 before the combustion stroke
Count up the number of misfires by cylinder of i-1 C(#1-1)2 C(#1-1)2←C(嘗1-1)2 +
1), proceed to 3111.

Then, in 5111, the calculation cycle number C number i1 of the current combustion stroke cylinder #i and the preset sampling cycle number C
l1SET (for example, 100cycles), and if the number of calculation cycles Clil does not reach the number of sampling cycles 0 and 1SET (C number i1 < C write is
[T), exits the routine, and the number of calculation cycles Cl
If il reaches the number of sampling cycles Cl1SET (CIi1≧Cl1SET), proceed to 5112,
Clear the calculation cycle number C write i1 ( CIi1
←0).

Next, in 5113, the cylinder-by-cylinder average sampling cycle number Cl1SET of the cylinder #i-1, which has not been calculated in the previous sampling period, and which is stored in a predetermined address of the RAM 34, is stored in the predetermined address of the RAM 34. Based on the number of misfires by cylinder C($1-1)2 of i-1, the current average number of misfires by cylinder C(No. 1-1)2,
It is determined from the weighted average of the weights r shown in the following equation.

C(Ii-1)2 = ((2'-1) XC(Ii
-1)2(-1)+c(Good 1-1)2)/2' By calculating the average number of misfires for each cylinder C(Good 1-1)2 by weighted average, It is possible to correct misfire detection errors and temporary misfire misjudgments due to sudden combustion fluctuations.

Thereafter, at 5115, the number of misfires for each cylinder C(li-1
)2 to clear C(#1-1)2←0), and 5
At 116, the cylinder-specific information calculated in the previous engine matching cycle is stored at a predetermined address in the RAM 34, and at 5117, the current average number of misfires for each cylinder C ($1
-1) 2 and the preset misfire abnormality judgment standard number of times C (#
1-1) Compare with 2SET, C($1-1)2 >
C($1-1)2SET, that is, the average number of misfires by cylinder C(Ii-1)2 is the misfire abnormality determination reference number C(#1-
1) If it exceeds 2SET, the cylinder #i before 1 combustion stroke
-1 is determined to be a misfire abnormality, the process proceeds to 8118, stores the misfire abnormality data of cylinder #i-1 one combustion stroke earlier in a predetermined address of the backup RAM 35, and operates with the warning means 43 such as an indicator lamp turned on. warns the operator of the misfire abnormality and deviates from the routine. On the other hand, C(ti-1)2≦
If it is determined that C(#1-1)23ET, it is determined that the misfire abnormality has not yet occurred in cylinder #i-1 one combustion stroke before, and the routine is exited as is.

Incidentally, the misfire abnormality data of cylinder #1-1 before one combustion stroke stored in the backup RAM (storage means) 35 is as follows:
At a dealer's service station, etc., by connecting the serial monitor 45 to the control device 31 and reading the information, it is possible to determine whether or not a cylinder is misfiring. 45, the misfire abnormality data stored in the backup RAM 35 can be cleared.

(Second Embodiment) FIG. 9 is a flowchart 1 showing a misfire determination procedure for each cylinder according to a second embodiment of the present invention.

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

In this example, the engine speed N #i-1 in the section where no work is being done by combustion after the completion of combustion in cylinder #i-1 before one combustion stroke, and the work done by combustion in cylinder #1+1 after one combustion stroke. The engine rotation speed N ti+1 in the section where no work is done by combustion of the relevant air i#i+1 in the previous cycle is adopted as the estimated value of the engine rotation speed in the section where no work is done.
[-1) and the engine rotation speed N#1 in a section where no work is being done by combustion in cylinder #i in the current combustion stroke to determine whether there is a misfire in the cylinder #1 in the current combustion stroke. This is to set the combustion state comparison value.

First, from 5101 to 5105, the procedure is similar to that of the first embodiment (Fig. 1), and at 5201, the engine is in a section where no work is being done by the combustion of the cylinder #i-1 before one combustion stroke, which is stored in the RAM 34. Rotation speed N kan i-1 and 1 of the cylinder #i ÷ 1, which is adopted as the estimated engine speed in the section where cylinder #i+1 is not doing work due to combustion after one combustion stroke.
The engine rotation speed N #i+1(1) in the section where no work is done by combustion before the cycle is read out, and in 3202,
From the difference between the engine speed Nli of the combustion stroke cylinder #i obtained in 5105 above and the average value of the engine speed N5i-1, N# big 1 (-1) read in 5201 above,
A combustion state comparison value ΔN#1 for the combustion stroke cylinder #i is determined.

ΔN party 1←N #i−((N $i−1+ N $i+
1 (1)) / 2) After that, in 5203, the engine rotational speed N stored i and the intake air amount Q found in this routine
The engine load data (-basic fuel injection pulse width) Tp calculated based on the misfire determination level ΔN1. Set EVEL.

Note that this misfire determination level map MPΔN1−EVE1
, are similar to the first embodiment (FIG. 7).

Then, in 5204, the misfire judgment level △N LEV
E [and the combustion state comparison value ΔN1i of the relevant combustion stroke cylinder #i
The combustion state comparison value ΔNli is determined to be misfire determination 1.
/ /(Le△N LEVEL lower than (△N#i〈△N
LEνEL), it is determined to be a misfire and 520
Proceed to 5, and if ΔNti≧△N LEVEL,
Determine normal combustion and proceed to 5111.

If a misfire is determined and the process proceeds to 5205, the current combustion stroke cylinder #i
Count up the number of misfires per cylinder Cl12.
2←Cti2 +1), proceed to 5111.

Then, in 5111, the calculation cycle number CIil of the current combustion stroke cylinder #i and the preset sampling cycle number C
#iS[T (for example, 100 cycles), and if Iil has not reached the number of sampling cycles Cl1SET (CIil <C
l1SET), exits the routine, and when the number of calculation cycles C#11 reaches the number of sampling cycles Cl1SET (C cloud i11≧C#11SET), 5112
Proceed to and clear the number of calculation cycles CIil (C
tN←O).

Next, in 8206, the cylinder-specific average number of misfires Cti2(-
1), and in 5207, the average number of misfires for each cylinder C.
1i2(-1) and the current sampling cycle number Cl
Based on the cylinder-by-cylinder misfire count C#i2 of the current combustion stroke cylinder #i counted in 1S[T, the current cylinder-specific average misfire count C#i2 is determined from the weighted average of the weight r shown in the following equation.

□ti2 ← (<2 1) XC accumulation 12 (-
1)+C#i2)/2' Then, at 8208, clear the number of misfires by cylinder CIi2 C#i2←0), and at 5209, clear the RAM34
The average number of misfires for each cylinder of cylinder #1 in the current combustion stroke calculated in the previous sampling period stored at the predetermined address of 70- is not calculated this time ←-012)
.

Then, at 5210, the current average number of misfires by cylinder C, average number of misfires by cylinder C, i2 is equal to the misfire abnormality determination reference number Cti.
If it exceeds 2sET, it is determined that the current combustion stroke cylinder #1 has a misfire abnormality, and the process proceeds to 5211, and the backup R
The misfire abnormality data for the current combustion stroke cylinder #i is stored in a predetermined address of the AM 35, the warning means 43 (see FIG. 4) such as an indicator lamp is turned on to warn the driver of the misfire abnormality, and the routine is exited. On the other hand, Cl12≦C1i2s
If it is determined to be ET, it is determined that a misfire abnormality has not yet occurred in the current combustion stroke cylinder #i, and the routine is exited as is.

According to this embodiment, after determining combustion stroke cylinder #1,
Since the combustion state comparison value ΔN#1 for the cylinder #i is immediately set, subsequent calculations become easier.

(Third Embodiment) FIG. 10 is a flowchart showing a cylinder-by-cylinder misfire determination procedure according to a third embodiment of the present invention.

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

First, in step 5101, after determining the combustion stroke cylinder #i,
At 301, the misfire maximum count flag for cylinder #i-1 before one combustion stroke is F [8G
#1-1=1) or reset state (Fl-8G$1
−1=0).

If it is in the set state (FLAGIi-1=1), the process proceeds to 5302, where an indicator lamp or the like serving as the warning means 43 (see FIG. 4) is turned on to warn the driver of the misfire abnormality, and the routine is exited.

On the other hand, the maximum misfire count I-number flag FLAG#i-
1 is determined to be in the reset state (FIJGtti-1=O), the same procedures as in the first embodiment (FIG. 1) described above are executed from 5103 to 5109.

Then, in step 5109, if it is determined that the cylinder #1-1 before one combustion stroke misfires ΔN number i-1 (ΔNLEVEL), the process proceeds to 3303. In addition, normal combustion △N11-1≧ΔN
If it is determined that L[V[[), the process advances to 8306 and the misfire maximum count flag FLAG for cylinder #i-1 before one combustion stroke is set.
After resetting Ii-1 (FLAG number i-1←0),
Falling out of routine.

On the other hand, when the process advances from 5109 to 5303, an indicator lamp or the like is turned on for a short period of time to warn the driver that a misfire has occurred.

By recognizing the frequency with which indicator lamps and the like are lit, the driver can grasp the engine misfire situation, that is, under what engine operating conditions misfires are likely to occur.

Then, at 5110, the number of misfires C(Ii-1)2 of the cylinder #i-1 before one combustion stroke is counted up (C(Ii-1)
)2←C(ti-1)2 + 1) After that, this counted up value C(Ii-1)2 is backed up by R.
It is stored in a predetermined address of AM35.

At a dealer's service station, etc., a serial monitor 45 is connected to the control device 3 via the failed PJ diagnostic connector 44, and the number of misfires for each cylinder C($1-1)2 stored in the backup RAM 35 is displayed. Read the data and refer to the manual to determine the misfire situation.

After that, in 5304, the number of misfires C(#1-1)2 of the cylinder #I-1 before one combustion stroke and the preset maximum count number F
Compare FH (however, it can be set arbitrarily depending on the capacity of the microcomputer), and calculate C(Ii-1)2 = F FH
If C(ti-1)2 <
In the case of F F H, proceed to 5306 .

The above number of misfires C (large 1) 2 is the maximum count number FF
When it is determined that the backup RA has reached H (C(good 1-1)2=FFH) and the process proceeds to step 5305, the backup RA
The number of misfires C (Ii-1
)2 at the maximum count number FFH, 53
At step 07, the misfire maximum count flag FLAGIi-1 of the cylinder good i-1 one combustion stroke before is set (Fl-AG good i-1←-1), and the routine is exited.

In this embodiment, the misfire determination target cylinder may be the current combustion stroke cylinder #1 as shown in the second embodiment.

(Fourth Embodiment) FIGS. 11 and 12 show a fourth embodiment of the present invention.
Figure 1 is a flowchart showing the misfire determination procedure for each cylinder.
Figure 2 is a conceptual diagram of the combustion state learning value map.

In this example, the combustion state is learned for each cylinder, and the difference between this combustion state learning value and the combustion state comparison value obtained based on the engine speed in the section where no work is being done by combustion in the relevant cylinder is determined. This is to determine a misfire condition.

The process will be explained below according to the flowchart.

First, the same procedure as in the first embodiment (Fig. 1) is executed from 5101 to 5107, and at 5401, the above-mentioned 5l (read at 16) is used. The engine speed N#i-1 and the engine load data (-basic fuel injection pulse width) Tp calculated based on the engine speed N i-1 and the intake air amount Q are used as parameters to perform the above 1 combustion. Combustion state learning value △NfJ of pre-stroke cylinder #i-1 is set as combustion state learning value map MPΔ
Set based on NN.

As shown in FIG. 12, the combustion state learning value map MP
ΔNg is a three-dimensional map with the engine speed N#i-1 and engine load data Tp as parameters, and the number corresponding to the cylinders is provided, and each area surrounded by a grid is set in 5403 described later. A combustion state learning value ΔN1 for each cylinder is stored.

Then, in 8108, a misfire judgment level △N LEVEL for the cylinder #i-1 one combustion stroke before is set from a misfire judgment level map MP△N LEVEL using the engine load data Tp and engine speed I'1i-1 as parameters, At 5402, the difference (comparison value) between the combustion state comparison value ΔN$i-1 and the combustion state learned value ΔNl) is compared with the misfire determination level ΔN LEVEL.

And ΔN$1-1-△NfJ <△NLEVEL
In case (1), it is determined that there is a misfire and the process proceeds to 5110, and Δ
In the case of N Book 1-1-△Npn△N LEVEL, it is determined that combustion is normal and the process proceeds to 5403.

In 3403, the cylinder #1 prior to one combustion stroke is determined based on the combustion state learning value ΔNfJ and the combustion state comparison value ΔN #i−1.
The combustion state learning value ΔNρ of i-1 is determined from the weighted average of the following equation.

ΔNN ←((2'-1)x△N, Q +△rli-
1)/2'r: Weight of the weighted average, and with this newly obtained combustion state learning value ΔNg, 1
The data stored in the corresponding address of the combustion state learning value map MPΔNM corresponding to the cylinder #i-1 before the combustion stroke is updated, and the process advances to 5111. Note that the initial set value of the combustion state learning value ΔNIJ for each cylinder stored in this combustion state learning value map MPΔN1 is “0”.
That is, the ideal combustion state discrimination value ΔN11-1 is "O" (uniform combustion in all cylinders), and if the combustion is normal, the combustion state learned value ΔN1 obtained by weighted average will also be 0". This is because it is thought to be approaching.

Combustion state learning value △N during normal operation under each operating condition
By learning fI for each cylinder, it is possible to understand the combustion characteristics of each cylinder individually, and when determining the misfire performed in step 3402 above, one combustion stroke before, which is included in the combustion state discrimination value ΔN5i-t, is used. By correcting the characteristic variation factor of the cylinder (Δ
N ll-1-△In) The above misfire judgment level ΔN1-[
It can be compared relatively with νE[.

Therefore, the determination accuracy is improved, and even in the high rotation range where the difference in rotational fluctuation is relatively small, or even in multi-cylinder engines with six or more cylinders, it is possible to detect misfires without being affected by variations in engine characteristics. Can be judged individually and accurately.

On the other hand, if it is determined in step 5402 that a misfire has occurred and the process proceeds to step 5110, the number of misfires by cylinder C(1-1)2 for cylinder #i-1 one combustion stroke before is counted up.C(ti-1)2←
C (book 1-1) 2 + 1 ), proceed to 5111.

And, 5111 to 5118 are the first embodiment (Fig. 1)
After running a program similar to , it exits the routine.

In this embodiment, the misfire determination target cylinder may be the current combustion stroke cylinder #i as shown in the second embodiment.

(Fifth Embodiment) FIG. 13 is a flowchart showing a misfire determination procedure for each cylinder according to a fifth embodiment of the present invention.

This embodiment is a combination of the third embodiment and the fourth embodiment, in which the combustion state is learned for each cylinder, and this combustion state learning value is used to calculate the engine speed in a section where no work is being done by combustion in the relevant cylinder. The misfire state is determined from the difference with the combustion state determination value calculated based on the number, and the determined number of misfires is stored sequentially for each cylinder. When the number of misfires reaches the maximum count number, the maximum number of misfires is It is fixed and memorized.

In this flowchart, the combustion state learning value setting (S401) shown in the flowchart of the fourth embodiment (Fig. 11) is added to the flowchart shown in the third embodiment (Fig. 10).
, Misfire determination (S402), Combustion state learning value update (S402)
403) to perform cylinder-specific misfire discrimination, and the explanation of flowchart 1- is omitted.6 Note that the present invention is not limited to each of the above embodiments, and for example, the combustion state comparison value is The work due to combustion in each cylinder may be determined as the momentum between specified internal positions using angular acceleration, period, angular velocity, etc.

[Effects of the Invention] -1 As explained above, according to the present invention, the misfire condition can be
Excellent effects such as being able to accurately detect combustion state factors from other cylinders without including combustion state factors, and without being affected by combustion variations between cylinders or manufacturing variations from engine to engine. .

[Brief explanation of the drawing]

1 to 8 show a first embodiment of the present invention, FIG. 1 is a flowchart showing a cylinder-by-cylinder misfire discrimination procedure, and FIGS. 2 and 3 are a concept showing a basic cylinder-by-cylinder misfire discrimination method. Figure, 4th
The figure is a schematic diagram of the engine control system, Figure 5 is a front view of the crank rotor and crank angle sensor, Figure 6 is a front view of the cam rotor and cam angle sensor, Figure 7 is a conceptual diagram of the misfire determination level map, and Figure 8 9 is a time chart showing cylinder pressure fluctuations, crank pulses, cam pulses, and engine rotation fluctuations, FIG. 9 is a flowchart showing a misfire determination procedure for each cylinder according to the second embodiment of the present invention, and FIG. 11 and 12 show a fourth embodiment of the present invention, FIG. 11 is a flowchart showing a misfire judgment procedure for each cylinder according to the third embodiment, and FIG. 12 shows a combustion state FIG. 13, which is a conceptual diagram of the learned value map, is a flowchart showing a misfire determination procedure for each cylinder according to a fifth embodiment of the present invention. #i-1...1 cylinder before combustion stroke, Nli+1...estimated momentum, #1-2...2 cylinder before combustion stroke, N number i,
N11-1゜N11-2... Momentum in the section where no work is done by combustion, △N LEVEL... Misfire judgment level. Figure 7 pod 12 = Figure 100 No. 9 Figure 1 1

Claims (2)

[Claims] (1) The average value of the momentum in the section where no work is done by combustion in the cylinder before the 2 combustion strokes and the momentum in the section where no work is done by combustion in the cylinder in the current combustion stroke, and the work done by combustion in the cylinder before 1 combustion stroke. Calculate the difference between the momentum of the section where no combustion has occurred, and compare this difference with the misfire judgment level set based on the engine combustion state parameters of the cylinder one combustion stroke before.
A method for determining a misfire in each cylinder of an engine, which is characterized by determining a misfire state in each cylinder. (2) The average value of the momentum in the section where no work is done by combustion in the cylinder before one combustion stroke and the estimated momentum in the section where no work is done by combustion in the cylinder after one combustion stroke, and the estimated momentum in the section where no work is done by combustion in the cylinder after one combustion stroke. The misfire condition is determined for each cylinder by determining the difference between the momentum of the section where no work is being done and comparing this difference with a misfire determination level set based on the engine operating status parameters of the cylinder in the current combustion stroke. A misfire detection method for each cylinder of an engine.