JPH05296101A - Detecting device for misfire of multi-cylinder internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the wrong judgement of the occurrence of misfire by discriminating temporary misfire, and discriminating to be the actual occurrence of the misfire in a multi-cylinder internal combustion engine when only a part of the results of counting temporarily discriminated as the misfire is larger than the fixed number of times. CONSTITUTION:Detection signals issued from a rotating angle sensor 5 which is arrangedly provided on the crankshaft of an internal combustion engine 1 and serves as a rotation signal outputting means and a reference position sensor 6 are inputted into an electronic control unit(ECU) 9. ECU 9 computes the fluctuation of the number of engine revolutions on the detection signal issued from the rotating angle sensor 5, and temporarily discriminates whether the internal combustion engine 1 misfires or not on the result of above computation by a temporary misfire discriminating means. At this time, the misfire of the internal combustion engine 1 is actually discriminated from a counting means to count the number of times of the temporary discrimination of the occurrence of misfire in each cylinder and the result of counting executed through the counting means by an actual misfire discriminating means. Thus the misfire can be accurately judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire detecting device for a multi-cylinder internal combustion engine which detects misfire occurring in the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a means for detecting a misfire occurring in an internal combustion engine, complete combustion cannot be obtained in the combustion chamber of the internal combustion engine when the misfire occurs, and the engine speed (hereinafter referred to as engine speed) is Since it decreases, the instantaneous engine speed is detected at at least two points in one ignition cycle to obtain the engine speed fluctuation amount, and the misfire detection value set from the change amount of the engine speed fluctuation amount and the internal combustion engine state. There is a device for comparing the above with the above and discriminating the misfire when the amount of change in the engine speed fluctuation amount becomes larger than the misfire detection value (for example, Japanese Patent Laid-Open No. 61-25.
8955 publication).

[0003]

However, for example, when the vehicle runs on a bad road, the unevenness of the road surface makes the grounding state between the wheels and the road surface unstable, and the vehicle separates from the road surface or strongly touches the road surface. By doing so, the load state applied to the internal combustion engine fluctuates, the rotational speed of the crankshaft becomes unstable, and the amount of change in the engine speed fluctuation amount may increase despite the fact that misfire has not occurred. Therefore, in such a misfire determination device, there is a risk of misjudging that a misfire has occurred due to the unevenness of the road surface, although the misfire has not actually occurred.

Further, for example, when the vehicle is suddenly decelerated, the engine speed rapidly drops, and although the misfire does not occur, the amount of change in the engine speed fluctuation amount becomes large and the misfire occurs. There was a risk of making a decision.

Therefore, the present invention has been made to solve the above problems, and provides a misfire detection device capable of accurately determining a misfire even when the vehicle is traveling on a bad road or in a decelerated state. The purpose is to do.

[0006]

In order to achieve the above object, an internal combustion engine misfire detection apparatus according to the present invention outputs a rotation signal at every predetermined rotation angle according to the rotation of a multi-cylinder internal combustion engine, as shown in FIG. And a provisional misfire determination means for provisionally determining, for each cylinder, whether or not a misfire has occurred in the multi-cylinder internal combustion engine, based on the output signal of the rotation signal output means, and the provisional misfire determination. In the means, counting means for counting the number of temporary misfires determined to have occurred for each cylinder, counting result storage means for storing the counting result of the counting means for each cylinder, and after performing the temporary misfire determination a predetermined number of times. A main misfire that determines that a misfire has actually occurred in the multi-cylinder internal combustion engine when only the count results of some of the cylinders stored in the count result storage means are greater than a predetermined number Equipped with a discrimination means Adopt the technical means of that.

Further, according to the present invention, vehicle stop detection means for detecting whether or not the vehicle is stopped, and rotation signal output means for outputting a rotation signal for each predetermined rotation angle according to the rotation of the multi-cylinder internal combustion engine. Based on the output signal of the rotation signal output means, a temporary misfire determination means for temporarily determining whether or not a misfire has occurred in the multi-cylinder internal combustion engine, and a misfire occurrence in the temporary misfire determination means. Counting means for counting the determined number of temporary misfires for each cylinder, counting result storage means for storing the counting result of the counting means for each cylinder, and after executing the temporary misfire determination a predetermined number of times, detecting the vehicle stop In the state where the vehicle is not stopped based on the detection result of the means, a misfire actually occurred in the multi-cylinder internal combustion engine when only the count result of some cylinders out of the count result of each cylinder is larger than a predetermined number of times. It is determined that when the vehicle is stopped, a misfire actually occurs in the multi-cylinder internal combustion engine when the count result of at least one cylinder among the count results of each cylinder is larger than a predetermined number of times. It is also possible to employ a technical means that includes a main misfire determination means for determining.

[0008]

According to the present invention, it is determined for each cylinder whether or not a misfire has occurred in the multi-cylinder internal combustion engine based on the rotation signal output at each predetermined rotation angle in accordance with the rotation of the multi-cylinder internal combustion engine. If the misfire is determined to occur, the counting means counts the number of times the cylinder is determined to have misfire, and the count result storage means stores the count result. Then, after performing the provisional misfire determination a predetermined number of times, it is determined that a misfire has actually occurred in the multi-cylinder internal combustion engine when only the count results of some of the cylinders of the counting results of the counting means are larger than the predetermined number of times. To do.

Further, it is detected whether or not the vehicle is in a stopped state, and in the state where the vehicle is not stopped, if only the counting results of some cylinders among the counting results of each cylinder are larger than a predetermined number of times. When it is determined that a misfire has actually occurred in the multi-cylinder internal combustion engine and the vehicle is at a standstill, when the count result of at least one cylinder among the count results of each cylinder is greater than a predetermined number of times, the actual Alternatively, it may be determined that a misfire has occurred in the multi-cylinder internal combustion engine.

[0010]

The present invention will be described below with reference to the embodiments shown in the drawings. FIG. 2 is a block diagram of an apparatus according to an embodiment of the present invention.

In FIG. 2, reference numeral 1 denotes an internal combustion engine, and in the present embodiment, the internal combustion engine has four cylinders. Reference numeral 2 is an intake pipe that guides intake air introduced from an air cleaner (not shown) into the internal combustion engine 1. Reference numeral 3 is an intake pipe pressure sensor that detects the pressure in the intake pipe 2, and a detection signal of the intake pipe pressure sensor 3 is input to an electronic control unit described later.

Reference numeral 5 denotes a crankshaft (not shown) of the internal combustion engine 1, which outputs a signal at every predetermined crank angle (in this embodiment, every 30 ° C. A) according to the rotation of the internal combustion engine 1 to output the signal. Is a rotation angle sensor forming a rotation signal output unit for obtaining a rotation speed Ne (hereinafter, referred to as engine speed) of
A reference position sensor 6 is also incorporated in the distributor 7 and outputs a signal for discriminating the cylinder. More specifically, for example, a signal is output every time the piston 13 of the first cylinder reaches the uppermost position (top dead center). Is. The detection signals from the rotation angle sensor 5 and the reference position sensor 6 are also input to the electronic control device described later.

A water temperature sensor 8 is provided in the cooling water passage of the internal combustion engine 1 and detects the temperature of the cooling water.
The detection signal from is also input to the electronic control unit described later.
Reference numeral 9 is a well-known device that calculates optimum control amounts of the fuel system and the ignition system based on detection signals from the above-mentioned sensors and a sensor (not shown), and outputs a control signal for accurately controlling the injector 10, the igniter 11 and the like. It is an electronic control unit (hereinafter referred to as ECU).

Further, the ECU 9 is a well-known C for performing arithmetic processing.
The PU 9a, the read-only ROM 9b for storing the control program and the control constants necessary for the operation, and the operation data are temporarily stored while the CPU 9a is in operation.
It is composed of a RAM 9c which is a counting result storage means, and an I / O port 9d for inputting and outputting a signal from outside the ECU 9.

Further, the ECU 9 calculates the engine rotation speed fluctuation amount Δω _n based on the detection signal from the rotation angle sensor 5 using a method described later, and based on the calculation result, whether the internal combustion engine 1 has misfired or not. Temporary misfire determination means for temporarily determining whether
At this time, a counting unit that counts the number of times the misfire has been tentatively determined for each cylinder, and a main misfire determination unit that actually determines the misfire of the internal combustion engine 1 from the counting result of the counting unit.

Reference numeral 12 denotes a warning lamp for notifying the driver of the occurrence of misfire when the ECU 9 determines that misfire has occurred, and 14 detects the speed of the vehicle by the rotation of a speedometer cable (not shown) and the vehicle stops. Vehicle speed sensor (vehicle stop detection means) that also detects whether or not
The detection signal of the vehicle speed sensor 14 is also input to the ECU 9 and is used for the temporary misfire determination and the like described later.

Further, the ECU 9 determines the engine rotation speed fluctuation amount Δ of the internal combustion engine 1 based on the detection result of the rotation angle sensor 5.
Engine rotation speed fluctuation amount calculation means for calculating ω, index calculation means for calculating an index indicating the degree of dispersion from the distribution shape of the engine rotation speed fluctuation amount, and a misfire determination value for temporary misfire determination is created based on this index. It also serves as a means for creating a misfire determination value.

Next, a method of creating the misfire determination value in the ECU 9 will be described. 3 (a) and 3 (b) show a plurality of engine rotation speed fluctuation amounts Δω (calculation method will be described later) of all cylinders during normal combustion where no misfire has occurred in the internal combustion engine 1 and their frequency distributions are shown. It is a thing. Ideally, when misfire does not occur in each cylinder, the engine rotation speed fluctuation amount Δω becomes a value near 0. However, for example, the combustion characteristics of a specific cylinder are different from those of other cylinders.
As shown in (a) and (b), the engine rotation speed fluctuation amount Δω has a normal distribution centered around 0. Further, while a certain internal combustion engine has a shape as shown in FIG. 3A, a different internal combustion engine has a shape as shown in FIG. 3B.
Since the combustion characteristics differ for each internal combustion engine, the shape of this normal distribution differs for each internal combustion engine.

Therefore, in order to accurately determine the misfire, it is necessary to create the misfire determination value in consideration of such variations in the engine rotation speed fluctuation amount Δω. Therefore, the inventors of the present invention have shown the engine rotation speed fluctuation amount Δ during normal combustion as shown in FIG.
A method has been found in which the degree of variation in the distribution of ω is obtained, and the misfire determination value is created based on this to set the misfire determination value in consideration of the variation for each internal combustion engine and each cylinder as described above. The method of setting the misfire determination value will be described in detail below.

First, a method of judging whether each cylinder of the internal combustion engine 1 is normally burning will be described. FIG. 4 is a diagram showing the combustion characteristics of the internal combustion engine by detecting a large amount of variation Δω of the engine rotation speed of the internal combustion engine and sampling for each value thereof. Specifically, when the internal combustion engine 1 rotates 200 times in total. The engine rotation speed fluctuation amount Δω of all cylinders is sampled. Further, in FIG. 4, the horizontal axis represents the engine rotation speed fluctuation amount Δω, and the vertical axis represents the frequency of the actually detected fluctuation amount Δω of the engine rotation speed. Also, FIG.
FIG. 4A shows a characteristic at the time of normal combustion, and FIG. 4B shows a characteristic at the time of not combusting normally due to occurrence of misfire several times among many detected engine speed fluctuation amounts Δω.

From this figure, it can be seen that during normal combustion, the fluctuation amount Δω of the engine rotation speed has a normal distribution with the center around 0 (center value). On the other hand, when not burning normally,
A distribution in which the fluctuation amount Δω of the engine rotation speed is centered around 0 (distribution P ₁ ), a distribution in which the fluctuation amount Δω of the engine rotation speed is centered near −150 (distribution P ₂ ), and a fluctuation amount of the engine rotation speed It can be seen that Δω is composed of three distributions (distribution P ₃ ) centered around 150. That is,
Since the fluctuation amount Δω of the engine rotation speed of the cylinder in which the misfire has occurred becomes large, a distribution P ₃ can be obtained by sampling a large amount of the fluctuation amount Δω of the engine rotation speed.

Further, when the distribution of FIG. 4 is rewritten on a known normal probability paper with the cumulative probability on the vertical axis, it becomes as shown in FIG. 5, and the difference in characteristics between normal combustion and occurrence of misfire should be clarified. You can That is, the engine rotation speed fluctuation amount Δω sampled in large numbers during normal combustion is plotted on a substantially straight line (straight line L in FIG. 5A), but is not plotted in this manner when normal combustion is not performed The cumulative probability does not change on the probability paper. In other words, there are parts that are parallel to the horizontal axis (X ₁ and X _{2 in} FIG. 5B).
From the above, the distribution characteristics of the engine rotation speed fluctuation amount Δω can be determined by determining whether or not the internal combustion engine is burning normally as shown in FIG.
It can be seen that it is sufficient to determine whether it is shown in (a) or in FIG. 5 (b).

Next, based on the flow chart shown in the figure,
The misfire determination method will be described in detail. 6 and 7 are flowcharts showing the operation of the misfire detection process in the ECU 9 of the present embodiment, which is performed every predetermined rotation angle (for example,
This is a routine that is interrupted every 30 ° C. Of these FIGS. 6 and 7, FIG. 6 is mainly for the provisional misfire determination, and FIG. 8 is mainly for the main misfire determination.

First, in step 100 of FIG. 7, the deviation between the interrupt time of the previous routine and the interrupt time of the current routine is calculated, and the time T30i required to rotate the crank angle by 30 ° A is calculated. In step 110, it is determined whether or not the interrupt timing at this time is the top dead center (TDC). If it is not the top dead center, this routine ends. On the other hand, if it is the top dead center, the misfire determination process from step 120 onward is executed.

In step 120, the time T180i required for 180 ° C. rotation is calculated by accumulating the data of the past 6 times of the time T30i required for 30 ° A rotation calculated in step 100 (this embodiment). Since the internal combustion engine is a four-cylinder internal combustion engine, the time T180i required to rotate 180 ° C.A was calculated. However, if the internal combustion engine is a six-cylinder internal combustion engine, the time T30i calculated to be 30 ° A. Cumulative data of the past 4 times is 1
The time T120i required for rotating at 20 ° C. A may be calculated).

In step 130, the crank angle is 120 ° C. A
The average rotation speed ω _n between them is calculated. For details, see Step 1
The reciprocal of the time T180i obtained in 20 is obtained and is set as the average rotation speed ω _n .

In step 140, the average rotational speed fluctuation amount Δω _n (engine rotational speed fluctuation amount Δ
ω) is calculated.

[0028]

## EQU1 ## Δω _n = (ω _n-1 −ω _n ) − (ω _n-3 −ω _n-2 ) Here, in the case of a 6-cylinder internal combustion engine, the average rotation speed is calculated based on the following equation (equation 2). The speed fluctuation amount Δω _n (engine rotation speed fluctuation amount Δω) is calculated.

[0029]

## EQU2 ## Δω _n = (ω _n-1 −ω _n ) − (ω _n−4 −ω _n−3 ) where ω _n is the current average rotation speed calculated in step 130, and ω _n−1 Is the previous average rotation speed. Then, (ω _n-1 −ω _n ) is the fluctuation amount of the cylinder in which the explosion stroke is continuous. Further, ω _n-3 is the average rotation speed three times before, and ω _n-4 is the average rotation speed four times before.

Steps 150 to 190 show the processing for determining whether or not the internal combustion engine 1 is in normal combustion. First, at step 150, the cumulative percentage point (cumulative 50%) of the distribution of the average rotational speed variation Δω _n is calculated. Points, cumulative 66% points, cumulative 90
%) Is calculated. The calculation method will be described in detail later. In step 160, the first calculated value MF1 is calculated from the cumulative percentage points (cumulative 50% point, cumulative 66% point) of the distribution obtained in step 150 based on the following equation (Equation 3).

[0031]

MF1 = (u (66) −u (50)) / (Δω ₆₆ −Δω ₅₀ ) Note that u (50) and u (66) are values corresponding to the cumulative 50% point and the cumulative 66% point. Specifically, u (P) is a u value at which the upper probability is (1-P)%. Further, the u value is a value corresponding to the ratio of the deviation and the standard deviation in the normal distribution, and is calculated by the following equation (Equation 4).

[0032]

U = (x−μ) / σ where x = Δω, μ is the average value of Δω, and σ is the standard deviation of Δω.

Further, Δω ₅₀ and Δω ₆₆ are calculated in step 15
The value is calculated as 0, which will be described in detail later. In step 170, the same processing as step 160 is executed to calculate the second operation value MF2 by the following equation (Equation 5).

[0034]

MF2 = (u (90) −u (66)) / (Δω ₉₀ −Δω ₆₆ ) In step 180, the deviation ΔMF between the first calculation value MF1 and the second calculation value MF2 is calculated, and the step At 190, the deviation ΔMF is compared with the predetermined value K, and if the deviation ΔMF is smaller than the predetermined value K, it is determined that the combustion is normal and the routine proceeds to step 200. On the other hand, if the deviation ΔMF is not smaller than the predetermined value K, the process proceeds to step 220.

Here, the process for determining whether or not the internal combustion engine 1 normally burns will be described in more detail with reference to FIG. 8. The first calculated value MF1 indicates the slope of the straight line T1 in FIG. Therefore, the second calculated value MF2 indicates the slope of the straight line T2. Here, during normal combustion, as indicated by almost one straight line as described above, the slopes of the straight line T1 and the straight line T2 are substantially equal, in other words, the first straight line.
The calculated value MF1 and the second calculated value MF2 are substantially the same. Therefore, during normal combustion, the deviation ΔMF calculated in step 180 becomes a value near zero. However, when the combustion is not normal, the first
The calculated value MF1 and the second calculated value MF2 are different values, and the deviation ΔMF does not become a value near 0. From the above, it can be understood that by calculating the deviation ΔMF, FIG. 8 shows the characteristics of the average rotational speed change amount Δω _n and the cumulative percentage point when normal combustion is not performed. Further, the predetermined value K is set to a value near 0.

Returning to FIG. 6, in step 200, the index Sn corresponding to the standard deviation σ of the distribution corresponding to the cylinder of the average rotational speed fluctuation amount Δω _n obtained this time is calculated, and in the following step 210, the following equation (Equation 6 ), The misfire determination value REFn of the cylinder having the average rotation speed fluctuation amount Δω _n is updated. The method of setting the index Sn will be described later in detail.

[0037]

## EQU6 ## REFn = Δω ₅₀ + M × Sn Here, n indicates a cylinder number, and in the present embodiment, since it is a 4-cylinder internal combustion engine, n = 1 to 4. Further, M is a constant associated with the accuracy of misfire detection. For example, if the value of the constant M is 3, the misfire determination value REFn is set at the upper 3σ point of the distribution of the average rotational speed fluctuation amount Δω _n . In this embodiment, the constant M = 4. If the process of step 210 is executed, it is already determined that the internal combustion engine 1 is in normal combustion (step 190), so the misfire determination process of step 220 is not executed and the process proceeds to step 240.

On the other hand, in step 220, the above step 1
The average rotational speed fluctuation amount Δω _n obtained in step 40 is compared with the misfire determination value REFn of this cylinder to determine the average rotational speed fluctuation amount Δω _n.
If ω _n is larger than the misfire determination value REFn, it is determined that the nth cylinder is misfiring and the routine proceeds to step 230, where the provisional misfire counter CMIS _n is incremented (CMIS _n ← CMIS _n +1). Here, the temporary misfire counter CMIS _n is set for each cylinder, and the number of times that the average rotational speed change amount Δω _n is determined to be greater than the misfire determination value REF in the above-mentioned temporary misfire determination is counted for each cylinder, and this counting result is obtained. Is stored in the RAM 9c.
Since the present embodiment is a four-cylinder internal combustion engine, four provisional misfire counters CMIS _n are set in total (n indicates a cylinder, and in this embodiment, n = 1 to 4). At this time, which cylinder is misfiring can be detected in step 220. Therefore, which cylinder is misfiring by changing the lighting interval of the warning lamp 12 in the main misfire determination described later. It may be made known to the driver or the like. If the average rotational speed fluctuation amount Δω _n is equal to or less than the misfire determination value REFn in step 220, it is determined that no misfire has occurred in this cylinder, and step 230 is performed.
Processing proceeds to step 240.

At step 240, the average rotational speed obtained this time
Fluctuation amount Δω_nIs the previous average rotation speed variation Δω_n-1When
Then, the previous average rotation speed fluctuation amount Δω_n-1The average of two times before
Rotational speed fluctuation amount Δω_n-2And the average speed change of the previous two times
Momentum Δω_n-2Average rotation speed variation Δω three times before_n-3When
After that, the process proceeds to the main misfire determination routine of FIG. Where 6
When using the above-mentioned formula 2 in a cylinder internal combustion engine
Is the average rotational speed change three times before in step 240.
Momentum Δω_n-34 times before the average rotational speed fluctuation amount Δω _n-4When
It also executes the process.

Here, the temporary misfire determination method of step 220 will be described. The misfire determination value REFn is expressed by the above equation (6).
As described above, the misfire determination value REFn becomes the value shown in FIG. Therefore, the average rotation speed fluctuation amount Δ
If ω _n is larger than the misfire determination value REFn, it can be determined as misfire because it is not included in the distribution during normal combustion.
Further, as shown in FIG. 3 (b), even in the internal combustion engine in which the average rotation speed fluctuation amount Δω _n has a large variation even during normal combustion, the misfire determination value REFn is set based on the index Sn corresponding to the standard deviation σ of the distribution. Therefore, the misfire judgment value REF
n is set to a value larger than that of the internal combustion engine having the combustion characteristics shown in FIG. As a result, it is possible to accurately detect misfire without erroneously determining misfire, even though the misfire has not actually occurred.

Next, proceeding to the main misfire determination of FIG. 7, in step 400, the counter P ₁ and the counter P ₂ are incremented. The counter P ₁ is a counter that counts the number of ignitions when the vehicle speed is zero (when the vehicle is stopped), and the counter P ₂ is a counter that counts the number of ignitions when the vehicle speed is not zero (during traveling).

In step 410, it is determined whether the vehicle speed SPD = 0 (whether the vehicle is stopped) based on the information from the vehicle speed sensor 14, and if the vehicle speed SPD = 0, the process proceeds to step 420. If the vehicle speed SPD is not 0, the process proceeds to step 430.

At step 420, the counter P ₂ is reset. That is, since the vehicle is currently stopped at this point, the traveling counter P ₂ is always held at zero.
In step 440, it is determined whether or not the value of the counter P ₁ is a predetermined number of times (400 times in this embodiment) or more, and if it is less than the predetermined number of times, this routine is ended. On the other hand, if it is the predetermined number of times or more, the routine proceeds to step 450, where the counter P ₁ is reset. That is, by executing the processing of steps 420 to 440, the misfire determination processing described below is executed only when the state in which the vehicle is stopped for the time when the counter P ₁ reaches the predetermined number of times continues.

In step 460, it is judged whether or not the count value ΣCMIS _n of the temporary misfire counter CMIS _n of each cylinder is larger than a predetermined value α, and if it is larger, the routine proceeds to step 530,
If smaller, go through step 530 and step 540
Proceed to.

On the other hand, at step 430, the counter P ₁ is reset this time. In step 470, the counter P ₂
It is determined whether or not the value of is a predetermined number of times (400 times in the present embodiment) or more, and if it is less than the predetermined number of times, this routine is ended. Here, if it is the predetermined number of times or more, step 480
And the counter P ₂ is reset. That is, by executing the processing of steps 430, 470, and 480, if the state in which the vehicle is traveling for the time when the counter P ₂ reaches the predetermined number of times continues, the misfire determination processing described below is executed.

In step 490, step 230 (see FIG.
Temporary for each cylinder that is finally obtained by incrementing in 6)
Misfire counter CMIS_nRead the value of and count this value
Value ΣCMIS_n(For details, ΣCMIS_n= CMIS₁
+ CMIS₂+ CMIS₃+ CMIS_Four, But CMI
S_n(N = 1 to 4) is the temporary misfire counter CMIS of each cylinder
_nIndicates the value of. ) Is calculated.

In step 500, this count value ΣCMIS
_It is determined whether or not _n is larger than the predetermined value α. If it is larger than the predetermined value α, the process proceeds to step 510, and if not larger, the process proceeds to step 540. The predetermined value α is a value preset according to the required misfire occurrence rate. More specifically, for example, when it is desired to detect a misfire occurrence rate of 5% or more, the predetermined value α is 20 because the misfire determination is performed 400 times in this embodiment.
(400 × 0.05 = 20).

Therefore, when the count value ΣCMIS _n is not larger than the predetermined value α in step 500, it is determined that no misfire has occurred in any cylinder for a predetermined number of times or more, and the processing described later is not executed.

In step 510, the maximum value MCMIS _n of the values of the temporary misfire counter CMIS _n (n = 1 to 4) set for each cylinder is calculated, and this maximum value MCMIS _n is calculated.
Compare _n with a predetermined value β. Therefore, the maximum value MCMIS
_{If n} is larger than the predetermined value β, the process proceeds to step 520, and if maximum value MCMIS _n is smaller than the predetermined value β, step 5
Proceed to 40.

The predetermined value β is a value slightly smaller than the predetermined value α (for example, a value that is slightly smaller than the predetermined value α in consideration of the number of times misfire occurrence and provisional misfire determination are made even though no misfire has actually occurred. (value set from β = α × 0.9).

In step 520, the
Temporary misfire counter CMIS for each cylinder _nMisfire out of the value of
Counter CMIS_nCylinders with the highest value of
Misfire counter CMIS for non-cylinders_nValue of NCMIS
_n(There are three in this embodiment) and a predetermined value γ are compared.
Therefore, these three provisional misfire counters CMIS_nValue of NC
MIS_nIs smaller than the predetermined value γ, the step
Proceed to 530, and if even one is larger than the predetermined value γ,
Proceed to step 540. Here, the predetermined value r
Count value ΣCMIS_nIs a value set by the size of
More specifically, the details are set from the map shown in FIG.

The map of FIG. 10 shows the count value ΣCMIS.
_nThe predetermined value γ increases as
By setting the predetermined value γ in this way, for example,
Count value ΣCMIS_nIs 300 and count value ΣCMIS_nIs 1
50 is the above value NCMIS _nThe former is also a larger value
Therefore, in such a case, the value NCMIS_nWhere
It becomes larger than the fixed value γ and shifts to a direction where it is difficult to detect misfire.
Can be prevented.

Although the predetermined value γ is set as described above, the predetermined value γ (γ = γ is determined from the difference between the predetermined value α and the predetermined value β.
α-β) may be set, or may be set according to the magnitude of the maximum value MCMIS _n .

In step 530, it is assumed that the cylinder in which the value of the temporary misfire counter CMIS _n among the values of the temporary misfire counter CMIS _n of each cylinder is the maximum has a malfunction and misfire has occurred, and the driver etc. The warning lamp 12 is turned on to notify the occurrence of misfire.

In step 540, the temporary misfire count of each cylinder
CMIS_nReset (CMIS _n← 0) and then this book
Finish Chin. The above-described processing of step FIG.
It is the most distinctive part of Ming and performs such processing
By doing so, it is possible to detect misfires more accurately.
The operation will be further described in detail with reference to the drawings.

FIGS. 11A and 11B are views showing the values of the temporary misfire counter CMIS _n for each cylinder when the misfire is determined a predetermined number of times (400 times in this embodiment) as described above. The axis shows the temporary misfire counter CMIS _n of each cylinder and each cylinder number, and the vertical axis shows the count value of the temporary misfire counter CMIS _n . Further, FIG. 11B shows characteristics when the vehicle is running on a bad road (no misfire has occurred), and FIG. 11A shows characteristics when a misfire has occurred.

From this figure, the value of the temporary misfire counter CMIS _n is large for each cylinder when running on a rough road, but when a misfire occurs, the value of the temporary misfire counter CMIS _n only for a specific cylinder (misfire occurrence cylinder). It can be seen that is concentrated and grows.

Therefore, in step 510 described above, the predetermined value β is compared with the maximum value MCMIS _n of the values of the temporary misfire counter CMIS _n for each cylinder, and the values of the temporary misfire counter NCMIS _n of the other cylinders are compared. And a predetermined value γ are compared, the value of the temporary misfire counter NCMIS _n (CMIS ₂ , C in FIG.
(Corresponding to MIS ₃ and CMIS ₄ ) is larger than the predetermined value γ, it is possible to prevent the accidental lighting of the warning lamp 12 by making a final determination that a misfire has occurred.

Although not shown in the figure, since the engine speed fluctuation amount Δω _{n of} all the cylinders becomes large even during sudden acceleration, the provisional misfire is similar to the characteristic when traveling on a rough road shown in FIG. 5B. The counter CMIS _n has a large value for each cylinder. Therefore, by executing the processing shown in FIG. 3, the engine rotation is performed even when the vehicle is suddenly accelerated or a misfire has not occurred during traveling on a rough road. Even if the number variation amount Δω _n becomes large, it is possible to prevent erroneous determination that a misfire has occurred.

Therefore, in the above-described embodiment, the vehicle speed is detected, and when the vehicle speed is zero, there is no fluctuation in the average rotational speed ω _n that occurs during running on a rough road or during rapid acceleration. Therefore, the misfire is detected only by comparing the count value ΣCMIS _n with the predetermined value α. As a result, when the vehicle is running, it is possible to determine the misfire only when a certain specific cylinder is concentrated and the misfire is detected. However, when the vehicle is stopped, the misfire is determined by the above-described process and only the specific cylinder is concentrated. Except for the case, in other words, even if misfiring cylinders occur at random, misfiring can be accurately determined.

FIG. 12 shows step 1 of the routine shown in FIG.
It is a flowchart which shows the process of 50. Step 15
In 1, the average rotational speed fluctuation amount Δω _n obtained this time is compared with the value Δω ₅₀ for calculating the cumulative 50% point of the distribution, and if the average rotational speed fluctuation amount Δω _n is larger than the value Δω ₅₀ , the process proceeds to step 152. , If smaller, go to step 153. The value Δω ₅₀ is a value stored in the RAM 9c in advance.

In step 152, the predetermined value α is added to newly update the value ω ₅₀ , while in step 153, the predetermined value α is subtracted from the previous value ω ₅₀ to newly update the value ω ₅₀ .
As a result, the newly updated value ω ₅₀ can settle at the cumulative 50% point of the distribution of the average rotational speed fluctuation amount Δω _n of all cylinders.

In step 154, the average rotational speed fluctuation amount Δω _n and the value Δω for obtaining the cumulative 66% point of the distribution are calculated.
_66, and the average rotation speed fluctuation amount Δω _n is the value Δω ₆₆
If it is larger, the process proceeds to step 155, and if it is smaller, the process proceeds to step 156. The value Δω _{66 is} also a value stored in the RAM 9c in advance.

In step 155, the value ω ₆₆ is changed to a new value ω ₅₀ by adding a value twice the predetermined value β to the value ω ₆₆ , while in step 156 the predetermined value β is subtracted from the value ω _66. And update the value ω ₆₆ anew. As a result, the newly updated value ω ₆₆ can be settled at the cumulative 66% point of the distribution of the average rotational speed fluctuation amount Δω _n of all cylinders.

In step 157, this time, the average rotational speed fluctuation amount Δω _n and the value Δω for obtaining the cumulative 90% point of the distribution are calculated.
_90, and the average rotation speed fluctuation amount Δω _n is the value Δω ₉₀
If it is larger, the process proceeds to step 158, and if it is smaller, the process proceeds to step 159. The value Δω _{90 is} also a value stored in the RAM 9c in advance.

[0066] by adding 9 times the value of the predetermined value γ to a value omega ₉₀ to step 158 now updates the new value omega _90, whereas subtracting a predetermined value γ from the value omega ₉₀ to step 159 now And update the value ω ₉₀ anew. As a result, the newly updated value ω ₉₀ is the cumulative value 9 of the distribution of the average rotation speed fluctuation amount Δω _n.
You can settle down to the 0% point. When the above-described processing is executed, the process proceeds to step 160 in FIG. Then, in steps 160 and 170, the values ω ₅₀ , ω ₆₆ , and ω ₉₀ newly updated as described above are read, and the first calculated value M
F1 and the second calculated value MF2 are calculated. FIG. 13 is a flowchart showing the process of calculating the index S _n for each cylinder in step 200 of FIG. The average rotation speed variation Δω _50n is the cumulative value 5 of the distribution of the average rotation speed variation Δω _n.
It is a 0% point, and is a value that can be obtained for each cylinder by executing the same processing as the processing shown in steps 151 to 153 of FIG.

In step 201, calculated in step 140
Average rotational speed fluctuation Δω_nIs equivalent to the cumulative 50% point
Average rotation speed variation Δω_50nAnd index S_nDeviation from
ω_{Fifty n}-S_nDetermine if it is greater than
Go to step 202, if not big, go to step 203
move on. In step 202, the average rotation speed fluctuation amount Δω_nBut
Further, the average rotational speed fluctuation amount Δω corresponding to the cumulative 50% point
_50nAnd index S_nValue obtained by adding and_50n+ S_nGreater than
If it is larger, proceed to step 203,
If not larger, go to step 204. That is, Δω
_50n-S_n<Δω _n<Δω_50n+ S_nI'm satisfied
And go to step 204, do not meet this condition
To step 203.

At step 203, a predetermined value ΔS is added to the index S _n.
And the index S _n is updated by adding twice the value of
Update index S _n by 4, from the exponent S _n subtracting the predetermined value [Delta] S.

By executing such processing, the index S _n is the standard deviation σ of the distribution of the average rotational speed fluctuation amount Δω _n.
The value is equivalent to. Here, the reason why the standard deviation σ can be obtained by executing the above processing will be described with reference to FIG.

FIG. 14 shows the distribution of d = Δω _n .
Where d _M is the median (50% cumulative point) of the distribution, d ₋₁ is the −σ point (σ is the standard deviation), and d ₊₁ is the σ point, d ₋₁ <
The probability that d <d ₊₁ can be obtained from the area of the shaded area in the figure, and the probability is about 0.68.

On the other hand, by executing the processing of FIG. 13, the probability that Δω _50n −S _n <ω _n <Δω _50n + S _n becomes
The index S _n is corrected to be about 0.67 (67%). That is, the index S per crank angle 120 ° C A
expected value K _n of variation is defined by Equation 7, also the index S _n converges to a value that the expected value K = 0.

[0072]

[Equation 7]

That is, Δω _50n −S _n <ω _n <Δω _50n
By solving (7) by setting (ΔS) in the range of + S _n and (2ΔS) in other cases, the following formula 8 is obtained.

[0074]

[Equation 8]

Therefore, the exponent S _n can be approximated to σ, and the exponent S corresponding to the standard deviation σ of the distribution of the average rotational speed fluctuation amount Δω _n can be obtained by executing the processing shown in FIG.
_n can be obtained.

Therefore, the misfire determination value REFn is created based on the average rotational speed fluctuation amount Δω _n actually obtained as described above, in other words, by utilizing the nature of the combustion state itself of the internal combustion engine. , The misfire determination value REFn is automatically updated to a value suitable for the internal combustion engine. As a result, a misfire determination value R that is closely matched in advance in consideration of variations in combustion characteristics of each internal combustion engine or each cylinder.
It is not necessary to set EFn. Further, even if the combustion characteristics of the internal combustion engine change with time, etc., the misfire determination value REFn is created from the degree of dispersion (index Sn) of the distribution of the average rotational speed fluctuation amount Δω _n that is actually obtained during normal combustion. Therefore, the misfire determination value REFn also changes with the change in the combustion characteristics of the internal combustion engine, so that an accurate misfire determination value can always be obtained.

Further, in this embodiment, the misfire judgment value RE
Since Fn is obtained for each cylinder, it is possible to obtain a misfire determination value according to the combustion characteristics of each cylinder and to accurately detect which cylinder is misfiring.

In the above-described embodiment, the provisional misfire determination as to whether the internal combustion engine is currently burning normally is made based on the shape of the distribution of the average rotational speed fluctuation amount Δω _n. Although the determination accuracy of whether or not it is inferior is inferior, the method described below may be used and will be described as a second embodiment.

FIG. 15 is a flow chart showing the operation of updating the misfire determination value and the misfire determination processing in the second embodiment, which is used instead of the temporary misfire determination flow chart of FIG. Every (eg,
This is a routine that is interrupted every 30 ° C. It should be noted that the same reference numerals are given to those that perform the same processing as the processing of FIG.

In FIG. 15, if the above-described processing is executed from step 100 to step 140, the process proceeds to step 220, and in step 220, the average rotational speed fluctuation amount Δω _n and the misfire determination value REFn (based on the above-mentioned equation 6). (Calculated from the above) to determine the misfire. If it is determined that a misfire has occurred, the routine proceeds to step 230, where the misfire counter CMISn is incremented as described above, and the routine proceeds to step 240. On the other hand, if there is no misfire, the misfire determination value update process in steps 200 and 210 is executed. That is, in the second embodiment, the internal combustion engine 1 is currently used.
Of normal combustion (step 19 in FIG. 6)
0) and the provisional misfire determination are performed at the same time.

The misfire determination value REFn is also automatically set to a value suitable for the internal combustion engine by executing the above-described processing. However, if the initially set misfire determination value REFn is not a suitable value, Since the misfire determination value REFn may be updated in the wrong direction, it is better to use the method described in the first embodiment of FIG. 6 to determine whether the combustion is normal.

In the first and second embodiments described above, the misfire determination value REFn is updated from the variation in the distribution of the average rotational speed fluctuation amount Δω _n when the internal combustion engine is in normal combustion. Although the misfire determination value may be set to a slightly larger value, the misfire determination value REFn may be constantly updated, not only when the internal combustion engine is in normal combustion.

In the above embodiment, the standard deviation σ of the distribution is detected as an index indicating the degree of dispersion of the distribution. However, even if the 2σ points or 3σ points of the distribution are detected and the misfire determination value is created based on this. Good.

In each of the above embodiments, the misfire determination value REF
Although n is set for each cylinder, it is also possible to set a uniform misfire determination value for all cylinders and update this misfire determination value by the method described above.

Further, in each of the embodiments described above, the misfire determination value in the provisional misfire determination is created based on the index indicating the degree of dispersion of the distribution. However, the misfire determination value is not created, and the third embodiment shown in FIG. As in the example, the provisional misfire may be directly determined based on the index indicating the degree of distribution variation. That is, FIG. 16 is used in place of the temporary misfire determination flowchart of FIG. 6, and in this FIG. 16, steps 200 to 220 are omitted from the flowchart of FIG.
If F is not less than or equal to the predetermined value K, the process proceeds to step 230, and if it is less than or equal to K, the process proceeds to step 210.

The misfire discrimination method will now be described in detail with reference to FIG. 8. The first calculated value MF1 indicates the slope of the straight line T1 in FIG. 8, and the second calculated value MF2 indicates the slope of the straight line T2. ing. Here, during normal combustion, as indicated by almost one straight line as described above, the slopes of the straight line T1 and the straight line T2 are substantially equal, in other words, the first calculated value MF1 and the second calculated value MF2 are almost the same. It will be the same value. Therefore, during normal combustion, the deviation ΔMF calculated in step 180 becomes a value near zero.

However, when a misfire occurs, the first calculated value MF1 and the second calculated value MF2 become different values as shown in FIG. 8, and the deviation ΔMF does not become a value near zero. From the above, it can be seen that by calculating the deviation ΔMF, FIG. 6 shows the characteristics of the average rotational speed change amount Δω _n and the cumulative percentage point when a misfire occurs.

Therefore, in step 190, the deviation ΔM
If F is equal to or less than the predetermined value K, it is determined that the internal combustion engine has not misfired for the above-mentioned reason, and step 230
Processing proceeds to step 240. On the other hand, if the deviation ΔMF is not equal to or less than the predetermined value K, it is determined that the internal combustion engine is misfiring, and the routine proceeds to step 230. Here, the predetermined value K is a value near 0 for the reason described above.

As described above, in the third embodiment, the value of the average rotational speed change amount Δω _n at the cumulative% point is checked out 3 (cumulative 5
0% point, cumulative 66% point, cumulative 90% point), the degree of change from the value at the cumulative 50% point to the value at the cumulative 66% point, and the cumulative 66
When the degree of change from the value of the% point to the value of the cumulative 90% point is different, it is determined that the internal combustion engine 1 has misfired, and therefore it is not necessary to set the misfire determination value. As a result, the misfire determination can be performed without the need for complicated processing such as creating a misfire determination value that matches the combustion characteristics of the internal combustion engine.

In the above-described first and third embodiments, the cumulative percentage points are the cumulative 50% point, the cumulative 66% point, and the cumulative 90%.
Although the average rotational speed change amount Δω _n corresponding to the point is detected and the first calculated value MF1 and the second calculated value MF2 are calculated, even if three other cumulative% points are detected, the misfire is caused by the method described above. Can be detected.

Further, in the above-mentioned first and third embodiments, three cumulative percentage points are detected, but four points are detected and the respective cumulative five points are accumulated.
Misfire detection may be performed based on the ratio of the 0% point values.
By detecting more than one point, the process for detecting the value of each cumulative% point becomes complicated, but the internal combustion engine 1 is more accurate.
The misfire of can be detected.

In each of the above-described embodiments, when the value of the temporary misfire counter CMIS _n of a certain specific cylinder is intensively increased, it is judged that misfire has occurred. In this case, only a single cylinder is misfired. Although it can be determined that misfire has occurred, misfire cannot be determined when a plurality of cylinders (for example, two cylinders) have misfired. A fourth embodiment will be described below in detail as a method for solving such a problem.

FIG. 17 is a flow chart showing a misfire determination operation in the fourth embodiment, which is a routine for the main misfire determination used instead of the flow chart of FIG. Here, components that execute the same processing as the routine of FIG. 7 are assigned the same reference numerals and are as already described, so description thereof is omitted here.

That is, in the routine of FIG.
Step 5 is to execute processing different from the routine
50 to step 570. First, at step 550, the number of cylinders Q at which the value of the temporary misfire counter CMIS _n is larger than the predetermined value ρ is obtained. It should be noted that the predetermined value ρ is a value obtained from the predetermined value α / the number k of cylinders for which misfire detection is desired. Specifically, in the present embodiment, since one cylinder misfire or two cylinder misfire is detected, K = 2. The predetermined value ρ becomes α / 2.

At step 560, the number of cylinders Q is compared with a predetermined value σ. If the number of cylinders Q is not less than the predetermined value σ, the process proceeds to step 540, and if it is less than the predetermined value σ, the process proceeds to step 570. The predetermined value σ is a value set according to the number of misfiring cylinders to be detected. For example, when it is desired to determine a single cylinder misfire or a two cylinder misfire, the predetermined value σ =
It becomes 2.

[0096] The value of the tentative misfire counter CMIS _n in step 570 in step 550 compares the value with a predetermined value φ tentative misfire counter FCMIS _n other than cylinder becomes larger than the predetermined value [rho, the value of the tentative misfire counter FCMIS _n When is larger than the predetermined value φ, the routine proceeds to step 540, and when it is smaller, the routine proceeds to step 530. The predetermined value φ is a value corresponding to the above-mentioned predetermined value γ, and the value is set by the same method as the predetermined value γ.

At step 530, it is judged that misfire has occurred in the cylinder in which the value of the temporary misfire counter CMIS _n becomes larger than the predetermined value ρ at step 550, and the warning lamp 12 is turned on. At this time, the display of the warning lamp 12 may be changed according to the number of cylinders Q (for example, the lighting interval is changed), whereby whether the single cylinder misfire or the two cylinder misfire is determined. The driver can be notified separately.

At step 540, the temporary misfire counter CMI
This routine is ended by resetting _Sn and the number of cylinders Q. Here, FIG. 18 is a diagram showing the characteristics of the temporary misfire counter CMIS _n when a two-cylinder misfire occurs, and the temporary misfire counter CMIS other than the cylinder in which the misfire has occurred is similar to the single-cylinder misfire shown in FIG. It can be seen that the value of _n is small and that value is smaller than the predetermined value φ. Therefore, even if the above-described processing is executed, it is possible to reliably determine whether the misfire is erroneously determined when the vehicle is running on a bad road or the like, or whether a multi-cylinder misfire has occurred.

Further, the judgment of the actual misfire is carried out by the fifth method shown in FIG.
As shown in the embodiment, it is possible to make a determination based on the distributed state of the number of misfire determinations for each cylinder within a predetermined period. The flowchart of FIG. 19 is used instead of the flowchart of FIG. Here, components that execute the same processing as the routine of FIG. 7 are denoted by the same reference numerals, and since they are as already described, the description thereof is omitted. That is, in the routine of FIG. 19, the process different from that of the routine of FIG. 7 is executed in steps 580 to 590. First, in step 580, the misfire determination count CMI of each cylinder is set.
The variance S of Sn is calculated by the following equation.

[0100]

[Equation 9] Next, in step 590, a value obtained by dividing S by the average value of the misfire counter CMIS and normalized is compared with a predetermined value ω, and when this normalized value of S is smaller than the predetermined value ω, the process proceeds to step 540. If it is larger, it is decided that a misfire has occurred, and the routine proceeds to step 530, where the warning lamp 12 is turned on.

FIG. 20 shows the results of obtaining the normalized value of S under each condition. As shown in the figure, by using the normalized value of the variance S of each cylinder misfire determination number, , When driving on a rough road (marked with X) and when a random cylinder misfired (○
(Marked), and the value at the time of misfiring a specific cylinder (marked by Δ) can be made sufficiently large, and by setting a predetermined value ω between them, it is possible to reliably detect misfires when driving on rough roads. It is possible to prevent this, and it is possible to accurately detect all misfire patterns including random cylinder misfire.

In the first to fifth embodiments described above, the average rotational speed ω _n of each cylinder is used to obtain the average rotational speed fluctuation amount Δω _n , and this value is compared with the misfire determination value to determine the misfire. However, as shown in, for example, Japanese Patent Laid-Open No. 58-19532, another misfire determination such as a misfire determination by comparing the instantaneous rotational speed of each cylinder after the expansion process with the instantaneous rotational speed before the expansion process is performed. You may judge misfire by the method.

Further, in each of the above-described embodiments, in the routine for this misfire determination, when the vehicle is stopped, the count value ΣCM is calculated in steps 420 to 460.
Although the misfire is detected only by comparing ISn with the predetermined value, steps 410 to 460 may be omitted and the processing of step 430 and the subsequent steps may be executed even when the vehicle is stopped.

[0104]

As described above, according to the present invention, the provisional misfire determination is executed a predetermined number of times, and only a part of the count results temporarily determined to be misfire for each cylinder is greater than the predetermined number of times. In this case, by determining that a misfire has actually occurred in the multi-cylinder internal combustion engine, it is possible to prevent an erroneous determination that a misfire has occurred when traveling on a bad road, and it is possible to improve the misfire detection accuracy. Play.

Further, the present invention adds a simple process of executing the misfire discrimination by the known misfire discrimination method a predetermined number of times, counting the discrimination result for each cylinder, and discriminating the misfire from the counting result. By doing so, there is an effect that the present invention can be carried out.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is an overall configuration diagram showing a configuration of an apparatus according to an embodiment of the present invention.

3 (a) and 3 (b) are diagrams showing the distribution of the engine rotation speed fluctuation amount Δω when the internal combustion engine is normally burning.

FIG. 4 (a) shows the engine speed fluctuation amount Δ during normal combustion.
It is a figure which shows the frequency of (omega), (b) is a figure which shows the frequency of each engine rotation speed fluctuation amount (DELTA) (omega) at the time of misfire occurrence.

5A and 5B are diagrams in which the characteristics shown in FIG. 3 are rewritten on a normal probability paper, and FIG. 5A shows characteristics upon normal combustion, and FIG. 5B shows characteristics upon occurrence of misfire.

FIG. 6 is a flow chart for explaining a temporary misfire detection operation in the first embodiment of the present invention.

FIG. 7 is a flow chart for explaining a main misfire detection operation in the first embodiment of the present invention.

FIG. 8 is a diagram provided for detailed description of the flowchart shown in FIG. 6;

FIG. 9 is a diagram provided for detailed description of the flowchart shown in FIG. 6;

FIG. 10 is a map for setting a predetermined value γ.

11 is a diagram showing the characteristics of a provisional misfire counter CMIS _n for explaining the misfire detection operation shown in FIG. 7 in detail, where (a) is the characteristics when a misfire occurs and (b) is the normal time and This is a characteristic when driving on a rough road.

FIG. 12 is a flowchart for explaining a cumulative percentage point calculation process of the flowchart shown in FIG. 6;

FIG. 13 is a diagram for explaining the index Sn calculation process of the flowchart shown in FIG. 6;

FIG. 14 is a diagram provided for detailed description of the flowchart shown in FIG.

FIG. 15 is a flow chart for explaining a temporary misfire detection operation of the second embodiment of the present invention.

FIG. 16 is a flowchart for explaining the temporary misfire detection operation of the third embodiment of the present invention.

FIG. 17 is a flow chart for explaining a main misfire detection operation of the fourth embodiment of the present invention.

18 is a detailed description of the misfire detection operation shown in FIG.
Temporary misfire counter CMIS for _nFIG.
It

FIG. 19 is a flow chart for explaining a main misfire detection operation of the fifth embodiment of the present invention.

FIG. 20 is a diagram provided for detailed description of the flowchart shown in FIG. 19;

[Explanation of symbols]

 1 4 Cylinder Internal Combustion Engine 5 Rotation Angle Sensor 6 Reference Position Sensor 9 Electronic Control Unit (ECU) 9c RAM (Count Result Storage Means) 12 Warning Lamp 14 Vehicle Speed Sensor (Vehicle Stop Detection Means)

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 10, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

FIG. 3 is a flowchart for explaining a misfire detection operation in the basic embodiment of the present invention.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

FIG. 4 is a two-dimensional map for obtaining a misfire determination value.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Morishima 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Isamu Nomura 1-1, Showa-cho, Kariya city, Aichi prefecture Nidec Corporation Incorporated (72) Inventor Koichi Shimizu 1-1-1, Showa-cho, Kariya City, Aichi Prefecture

Claims (11)

[Claims] A multi-cylinder internal combustion engine is misfired based on a rotation signal output means for outputting a rotation signal for each predetermined rotation angle in accordance with the rotation of the multi-cylinder internal combustion engine, and an output signal of the rotation signal output means. Temporary misfire determination means for temporarily determining whether or not each cylinder has occurred, counting means for counting the number of temporary misfires determined for each cylinder in the temporary misfire determination means, and counting results of the counting means A count result storage means for storing each cylinder, and after performing the provisional misfire determination a predetermined number of times, only the count results of some of the count results for each cylinder stored in the count result storage means are A misfire detection device for a multi-cylinder internal combustion engine, comprising: a main misfire determination means for determining that a misfire has actually occurred in the multi-cylinder internal combustion engine when the number of times is greater than a predetermined number. 2. A vehicle stop detection means for detecting whether or not the vehicle is stopped, a rotation signal output means for outputting a rotation signal at every predetermined rotation angle according to the rotation of the multi-cylinder internal combustion engine, and the rotation signal. Based on the output signal of the output means, a temporary misfire determination means for temporarily determining whether or not a misfire has occurred in the multi-cylinder internal combustion engine for each cylinder, and the number of temporary misfires determined to have occurred by the temporary misfire determination means. A counting means for counting each cylinder, a counting result storing means for storing the counting result of the counting means for each cylinder, and a detection result of the vehicle stop detecting means after executing the temporary misfire determination a predetermined number of times. Based on the fact that the misfire has actually occurred in the multi-cylinder internal combustion engine when only the counting result of some of the cylinders in the state where the vehicle is not stopped is greater than a predetermined number of times in the state where the vehicle is not stopped, The above In the state where both are stopped, when the count result of at least one cylinder among the count results of each cylinder is larger than a predetermined number, it is determined that a misfire has actually occurred in the multi-cylinder internal combustion engine. And a means for detecting misfire in a multi-cylinder internal combustion engine. 3. The temporary misfire determination means detects the rotational speed of the internal combustion engine based on the signal from the rotational signal output means, and calculates the rotational speed fluctuation amount, and the internal combustion engine. By a predetermined rotation, exponent calculation means for calculating an index indicating the degree of variation in the shape of the distribution of the calculation results obtained by the rotation speed fluctuation amount calculation means, and misfire determination based on the calculation result of the index calculation means. A misfire determination value creating means for creating a value, and a misfire determination means for determining whether or not a misfire has occurred in the internal combustion engine by comparing the calculation result of the rotation speed fluctuation amount calculation means with the misfire determination value. The misfire detection device for an internal combustion engine according to claim 1 or 2, further comprising: 4. The misfire detection / detection apparatus according to claim 3, wherein the index is a value corresponding to a standard deviation of the distribution. 5. The misfire determination value creating means determines whether the shape of the distribution of the plurality of calculation results obtained by the rotation speed fluctuation amount calculating means when the internal combustion engine rotates a predetermined number is a normal distribution shape. 5. A distribution shape determining means and a misfire determination value updating means for updating the misfire determination value when the normal distribution shape determining means determines that the distribution is a normal distribution. A misfire detection device for an internal combustion engine as described. 6. The normal distribution shape determining means detects at least three cumulative% points in the distribution, and determines the normal distribution from the ratio of the values of the detected cumulative% points. The misfire detection and detection device according to claim 5. 7. The temporary misfire determination means detects a rotational speed of the internal combustion engine based on a signal from the rotational signal output means, and calculates a rotational speed fluctuation amount, a rotational speed fluctuation amount calculation means, and the internal combustion engine. And a misfire detection means for determining that the internal combustion engine has misfired when the distribution shape of the plurality of calculation results obtained by the rotation speed fluctuation amount calculation means by a predetermined rotation is not a normal distribution shape. The misfire detection device for an internal combustion engine according to claim 1 or 2, characterized in that. 8. The misfire detection means detects at least three cumulative percentage points in the distribution and determines that the internal combustion engine is misfiring from the ratio of the values of the detected cumulative percentage points. The misfire detection and detection device according to claim 7. 9. The misfire determining means determines all-cylinder misfire count totaling means for summing all values of the counting results of the respective cylinders, and determines whether the sum of all cylinder misfire counts is a first predetermined value or more. A first discriminating means, a second discriminating means for discriminating whether or not the maximum value among the counting results of each cylinder is equal to or more than a second predetermined value set to a value smaller than the first predetermined value; A third discriminating means for discriminating whether or not the values of all cylinders other than the maximum value among the counting results are equal to or less than a third predetermined value which is set sufficiently smaller than the second predetermined value. The first discriminating unit discriminates to be the first predetermined value or more, the second discriminating unit discriminates to be the second predetermined value or more, and the third discriminating unit makes the third discriminator 3. It is determined that a misfire has actually occurred when it is determined that it is less than or equal to a predetermined value of 3. Misfire detecting device according to any one of 8. 10. The all-cylinder misfire count summing means for summing all values of the counting results of each of the cylinders and the all-cylinder misfire count means for judging whether the sum of all cylinder misfire counts is a first predetermined value or more. A first discriminating means, a misfiring cylinder number calculating means for calculating the number of cylinders in which the counting result of each cylinder is equal to or greater than a fourth predetermined value set to a value smaller than the first predetermined value, and the misfiring cylinders. Fourth determining means for determining whether the number is less than or equal to a fifth predetermined value, and values of all cylinders other than cylinders that are equal to or greater than the fourth predetermined value among the counting results of each cylinder are the fourth predetermined value. A fifth discriminating means for discriminating whether or not the sixth predetermined value is set to a sufficiently smaller value, the first discriminating means discriminates that the first predetermined value or more, Is determined to be equal to or less than the fifth predetermined value, and the fifth determination means determines Misfire detecting device according to any one of claims 1 to 8 to determine the actual misfire when it is judged sixth is equal to or less than a predetermined value has occurred. 11. The all-cylinder misfire count summing means for summing all the values of the counting results of each of the cylinders, and the all-cylinder misfire judgment means for judging whether the total sum of all the cylinder misfire counts is a first predetermined value or more. A first discriminating means, a dispersion computing means for obtaining a dispersion of the number of misfire determinations of each cylinder, and a sixth discriminating means for discriminating whether a value obtained by normalizing the dispersion is a seventh predetermined value or more, It is determined that a misfire has actually occurred when it is determined by the first determining means that it is at least the first predetermined value and when it is determined by the sixth determining means that it is at least the seventh predetermined value. The misfire detection device according to any one of claims 1 to 8.