JPH08144838A - Misfire detection device of internal combustion engine - Google Patents

Abstract

PURPOSE: To realize accurate misfire detection by calculating a second change amount from the deviation between this time first change amount and the first change amount calculated before a prescribed integer times rotation by a crank angle and calculating an index which indicates the dispersion degree of the second change amount by using the second change amount at the time of normal ignition. CONSTITUTION: ECU 9 outputs a control signal for controlling an injector 10, an igniter 11, etc., based on the detection result of an intake pipe pressure sensor 3, a rotation angle sensor 5, a standard position sensor 6, etc. A processing for detecting the accidental fire generated in an internal combustion engine 1 is carried out. In this accidental fire detection, when the absolute value |Δωn | of a rotation speed change amount Δωn is smaller than an accidental fire removal level, this absolute value is compared with a standard deviation σn . In the case of |Δωn |>=σn , the standard deviation σn is renewed by adding the twice values of a prescribed value α to the standard deviation σn until now. While, in the case of |Δωn |<σn , σn is renewed by subtracting the prescribed value αfrom the value σn .

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, there is a technique for obtaining the amount of change in the rotational speed of an internal combustion engine (rotational speed fluctuation amount) and determining whether or not a misfire has occurred in the internal combustion engine based on the distribution shape of this amount of change. It is disclosed in Japanese Patent Publication No. 149191. According to the apparatus described in the above publication, the misfire determination is made from the distribution shape of the rotational speed fluctuation amount, so that the misfire determination can be made without creating a misfire determination value that requires close matching.

[0003]

However, even in the device described in the above publication, the operating state of the internal combustion engine (for example, the distribution of the rotational speed fluctuation amount indicating misfire and the distribution of the rotational speed fluctuation amount indicating normality) overlaps with each other (for example, , High rotation, low load), misfire could not be detected well.

Therefore, according to the present invention, a misfire detection device for an internal combustion engine capable of satisfactorily detecting a misfire even in an operating state in which the distribution of the rotation speed fluctuation amount indicating the normal condition and the rotation speed fluctuation amount indicating the misfire overlap. The purpose is to provide.

[0005]

Therefore, in the invention described in claim 1, as illustrated in FIG. 12, a rotation signal output for outputting a rotation signal at every predetermined rotation angle according to the rotation of the internal combustion engine. Means, an actual value calculation means for obtaining an actual value determined by measuring the period required for rotation between predetermined rotation angles in the expansion stroke of each cylinder based on the rotation signal, and an actual measurement of two cylinders in which the expansion stroke is continuous. The first variation amount calculation means for calculating the first variation amount by obtaining the deviation of the values, the current first variation amount calculated by the first variation amount calculation means, and the crank angle of the internal combustion engine. Second variation amount calculation means for calculating the second variation amount by obtaining a deviation from the first variation amount calculated before the integral multiple rotation of 720 degrees, and the second variation amount during normal ignition. An index showing the degree of variation in the appearance frequency distribution A cylinder index calculating means for calculating for each cylinder, based on the calculated index by cylinder Indices calculating means, and misfire determination value creation means for creating a misfire determination value,
Misfire determination means for determining whether or not misfire has occurred in the internal combustion engine by comparing the second variation amount with the misfire determination value created for each cylinder. A detection device is provided.

Further, according to a second aspect of the present invention, there is provided misfire removal level calculation means for calculating the misfire removal level based on an index indicating the degree of dispersion of each cylinder, and the cylinder-by-cylinder index calculation means has an absolute value higher than the misfire removal level. The misfire detecting device for an internal combustion engine according to claim 1, further comprising means for calculating, for each cylinder, an index indicating a degree of variation by using a small second variation amount.

Further, in claim 3, the misfire removal level calculation means is provided with an exponential guard means for guarding the exponent indicating the degree of variation from exceeding a predetermined value, and the misfire removal level is guarded by the exponent guard means. 3. A misfire detecting device for an internal combustion engine according to claim 2, further comprising means for calculating based on an index. Further, in claim 4, the misfire determination value creating means includes means for creating a misfire determination value for each cylinder by multiplying an index indicating the degree of variation by a predetermined value. A misfire detection device for an internal combustion engine according to any one of 3 above.

Further, in the fifth aspect, the misfire determination value creating means, when the index indicating the degree of dispersion of the cylinders for which the misfire determination value is created is smaller than the average value of the indexes indicating the degree of dispersion of each cylinder, the index of each cylinder. The misfire detection device for an internal combustion engine according to claim 4, wherein the misfire determination value is created based on the average value of the above. Further, in claim 6, a continuous misfire detection means for detecting continuous misfire continuously occurring in a specific cylinder is provided, and the internal combustion engine according to any one of claims 1 to 5 is provided. A misfire detection device is provided.

[0009]

According to the first aspect of the present invention, the rotation signal output means outputs a rotation signal at every predetermined rotation angle according to the rotation of the internal combustion engine, and the measured value calculation means expands each cylinder based on the rotation signal. A measured value determined by measuring the period required for rotation between predetermined rotation angles in the stroke is obtained.

Further, the first variation amount calculating means calculates the first variation amount by obtaining the deviation between the measured values of the two cylinders in which the expansion strokes are continuous, and the second variation amount calculating means is the first variation amount. The second variation is obtained by obtaining a deviation between the first variation calculated this time by the variation calculation means and the first variation calculated before the integral multiple rotation of 720 degrees at the crank angle of the internal combustion engine. Calculate the quantity.

Further, the cylinder-by-cylinder index calculating means calculates an index indicating the degree of variation in the appearance frequency distribution of the second fluctuation amount during normal ignition for each cylinder, and the misfire determination value creating means is calculated by the cylinder-by-cylinder index calculating means. A misfire determination value is created based on the calculated index. Here, the second variation amount during normal ignition is
This is the second variation of total ignition minus the second variation of misfire.

Then, the misfire determination means compares the second fluctuation amount with the misfire determination value created for each cylinder,
It is determined whether or not a misfire has occurred in the internal combustion engine. Further, in the apparatus according to the second aspect, the misfire removal level calculation means calculates the misfire removal level based on an index indicating the degree of dispersion of each cylinder. Then, the cylinder-by-cylinder index calculation means calculates an index for each cylinder by using the second variation amount whose absolute value is smaller than the misfire removal level, for each cylinder.

Further, in the apparatus according to the third aspect of the present invention, the misfire removal level calculating means guards the exponent guard means so that the index indicating the degree of variation does not become larger than a predetermined value, and the misfire removal level is set to the exponential guard means. Calculated based on the guarded index. Further, claim 4
In the apparatus described in (1), the misfire determination value creating means creates a misfire determination value for each cylinder by multiplying an index indicating the degree of variation by a predetermined value.

Further, in the apparatus according to the fifth aspect, the misfire determination value creating means is configured such that when the index indicating the degree of dispersion of the cylinders for which the misfire determination value is created is smaller than the average value of the indexes indicating the degree of dispersion of each cylinder. Creates a misfire determination value based on the average value of the indices of each cylinder. Further, in the apparatus according to the sixth aspect, the continuous misfire detecting means detects the continuous misfire continuously occurring in a specific cylinder.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment to which the present invention is applied will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram showing a configuration of an internal combustion engine including a misfire detection device according to this embodiment.
In FIG. 1, reference numeral 1 denotes an internal combustion engine, and in the present embodiment, an internal combustion engine having four cylinders is used. 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 output from the intake pipe pressure sensor 3 is input to an electronic control unit 9 described later.

Reference numeral 5 denotes a rotation angle sensor which is arranged on a crank shaft or a cam shaft of the internal combustion engine 1 and which outputs a signal at every predetermined angle. The electronic control unit 9 determines the engine rotation speed Ne based on this signal. Ask. Reference numeral 6 denotes a reference position sensor incorporated in the distributor 7. The reference position sensor 6 outputs a signal for discriminating the cylinder, more specifically, for example, a signal for each top dead center of the piston 13 of the first cylinder. Reference numeral 8 denotes a water temperature sensor which is arranged in the cooling water passage of the internal combustion engine 1 and detects the temperature of the cooling water.

An electronic control unit (hereinafter referred to as ECU) 9 outputs a control signal for controlling the injector 10 and the igniter 11 based on the detection results of the above-mentioned sensors and other sensors (not shown), and the ignition system and It is a well-known thing which controls a fuel system appropriately. Further, the ECU 9 includes a CPU 9a for actually performing arithmetic processing, a read-only ROM 9b for storing control programs and control constants necessary for arithmetic operation, a RAM 9c for temporarily storing arithmetic data during the operation of the CPU 9a, And an I / O port 9d for inputting / outputting a signal from the outside of the ECU 9, and executes processing for detecting a misfire occurring in the internal combustion engine 1. Reference numeral 12 is a warning lamp for notifying the driver of the occurrence of misfire when the ECU 9 detects misfire.

Next, the principle of misfire detection of this embodiment will be described. First, the principle of misfire detection during inter-firing fire will be described with reference to FIGS. FIG. 2 shows the appearance frequency of the rotation speed fluctuation amount Δω for each cylinder of the four-cylinder internal combustion engine 1 calculated by the following equation.

[0019]

## EQU1 ## Δω _n = (ω _n-1 −ω _n ) − (ω _n-5 −ω _n-4 ) where ω is the rotation speed of the expansion stroke of each cylinder, and n is the cylinder number. ing. It should be noted that n-1 indicates a cylinder one time before the nth cylinder in the ignition sequence (hence, ω _n-4 is the previously detected rotational speed of the nth cylinder).

That is, in this embodiment, the difference (the first fluctuation amount) between the rotational speeds of the n-th cylinder and the cylinders whose expansion strokes are adjacent to each other is obtained by the above equation, and the rotational speed difference obtained this time and the rotation obtained last time are obtained. From the difference with the speed difference, the rotation speed fluctuation amount Δ of the nth cylinder
ω _n (second variation amount) is calculated. Therefore, the appearance frequency distribution of Δω for each cylinder during normal ignition is a normal distribution centered on the zero point as shown in FIG. Further, when misfire occurs at a predetermined rate (hereinafter referred to as "intermissive fire"), the rotational speed fluctuation amount at the time of misfire increases, so as shown in Figs. 2 (b) and (c). There are three peak distributions: the distribution a due to misfire, the distribution b of normal ignition that is not affected by misfire, and the distribution c of normal ignition that is affected by misfire and in which the rotational speed fluctuation amount is small. Note that FIG. 2 (b) shows a case where the distribution due to misfire and the distribution of normal ignition not affected by misfire are separated, and FIG. 2 (c) shows the distribution due to misfire and normal ignition not affected by misfire. It is an appearance frequency distribution of Δω in the case where the distributions of and are overlapped.

In FIG. 2A, Δω_aIs the Δω distribution
(Cumulative) shows the top 16% points, σ _aIs the standard of Δω distribution
Indicates the deviation. The values of the top 16% points of these Δω distributions and
The standard deviation corresponds to an index that indicates the degree of variation in the Δω distribution
I do. Also, since this Δω distribution is a normal distribution, σ_aWhen
Δω_aAnd are almost the same. In Figure 2 (b)
Also, the distribution a due to misfire is set to the first misfire removal level EXMF.
In 1, the distribution c created by the influence of misfire is
The distribution removed by the last level EXMF2, that is, the influence of misfire
The distribution b of the normal ignition that has not been received is the same as that of FIG.
Distribution. In FIG. 2B, Δω_bIs on the distribution b
16% of the points, σ_bIndicates the standard deviation of distribution b.
Since this distribution b is a normal distribution, Δω_bAnd σ_b
And are almost the same value. Furthermore, the Δω distribution of FIG.
And the Δω distribution b in Fig. 2 (b) are the same normal distribution,
The values of quasi-deviation become equal (Δω_a= Δω_b≒ σ_a=
σ_b).

Also, this first misfire removal level EXMF
1 is the average value S of the standard deviation σ of the normal ignition distribution b of each cylinder.
It is obtained by multiplying GM by a predetermined value (3 in this embodiment). This predetermined value is given a value that almost includes the amount of fluctuation in the rotational speed of normal ignition. In the present embodiment, the standard deviation is obtained from the cumulative upper 16% points of the distribution b, so the second misfire removal level EXMF2 is not obtained.

By the way, as shown in FIG. 2C, the distribution a
And the distribution b, and in the low load / high rotation operating region where the distribution b and the distribution c overlap, the first misfire removal level EXM
The first and second misfire removal levels EXMF1 and EXMF1 and EX2 so that the normal ignition range surrounded by F1 and the second misfire removal level EXMF2 almost includes the fluctuation amount of the rotation speed of normal ignition.
When XMF2 is set, a part of the rotational speed fluctuation amount at the time of misfire and the rotational speed fluctuation amount affected by the misfire is included in this range. Therefore, the standard deviation of this cylinder becomes large, and the normal ignition range obtained from the standard deviation becomes wide. When the normal ignition range is widened, the fluctuation amount of the rotational speed at the time of misfire and the fluctuation amount of the rotational speed affected by the misfire are included in the normal ignition range, and the standard deviation becomes larger.

Therefore, it is necessary to prevent the standard deviation of the misfired cylinder and the divergence of the normal ignition range during the low load / high speed operation. In this embodiment, a divergence prevention threshold is set, and when the value of the standard deviation used when calculating the first misfire removal level EXMF1 exceeds this divergence prevention threshold, the divergence prevention threshold is used for guarding. I'm hanging. As a result, the first misfire removal level EXMF1 does not diverge and the normal ignition range does not widen. Therefore, it is possible to prevent divergence of the standard deviation. In the present embodiment, the divergence prevention threshold value is calculated by multiplying the average value SGM of the standard deviations of all cylinders by a predetermined value.

Further, the missing fire judgment level REF between cylinders
I _n is obtained by multiplying the standard deviation σ thus obtained by a predetermined value (for example, 4). Then, by comparing the missing fire determination level and the rotation speed fluctuation amount during this period, it is determined whether or not a misfire has occurred. As described above, even under low-load / high-rotation operating conditions, the standard deviation necessary for creating the intermittent fire determination level can be calculated almost accurately even during intermittent fire, so misfire can be detected well. be able to.

Next, the principle of misfire detection during continuous misfires will be described with reference to FIGS. 3 (a) and 3 (b). FIG. 3 shows the rotational speed fluctuation amount Δ for each cylinder of the internal combustion engine 1 calculated by the following equation.
It represents the appearance frequency of ω.

[0027]

Δω _n = (ω _n-1 −ω _n ) − (ω _n−3 −ω _n−2 ) As shown in FIG. 3, the distribution of the rotational speed fluctuation amount Δω for each cylinder at the time of normal ignition is also The distribution of the rotational speed fluctuation amount Δω at the time of continuous misfire is also a normal distribution, and the misfire cannot be detected from the distribution shape. However, the cumulative frequency 50% point of the rotational speed fluctuation amount Δω during continuous misfire (equal to the average value of the rotational speed fluctuation amount Δω in the case of normal distribution) becomes larger than the cumulative frequency 50% point during normal ignition (misfire). Therefore, the rotation speed fluctuation amount Δω is large). Therefore, the cylinder in which continuous misfires occur can be detected by smoothing the rotational speed fluctuation amount Δω of each cylinder and comparing the magnitudes thereof.

Next, the inter-firing miss detection process executed by the ECU 9 in this embodiment will be described with reference to the flow chart shown in FIG. Note that this flowchart is interrupted at every predetermined rotation angle (in this embodiment, every 30 ° CA (crank angle)). First, step 1
At 00, the deviation between the interrupt time of this routine last time and the interrupt time of this routine this time is calculated, and it is 30 ° C.
The time T30 _i required to rotate A is calculated. In step 101, the interrupt timing this time is the top dead center (T
DC), and if it is not top dead center, in step 112, T30 _{n (n = i, i-1, i-2, i-3, i-4) is changed} to T30 _{n-1 ( After} setting _{n = i, i-1, i-2, i-3, i-4)} , this routine ends. On the other hand, if it is the top dead center, the misfire determination process from step 102 is executed.

In step 102, the cylinder number n of the cylinder whose top dead center was detected in step 101 is identified. In step 103, 30 ° CA calculated in step 100
The time T18 required to rotate 180 ° CA by accumulating the data of the past 6 times of the time T30i required to rotate
Calculate 0i. Since the internal combustion engine has four cylinders in this embodiment, the time T18 required for 180 ° CA rotation is T18.
0i has been calculated, but in the case of a 6-cylinder internal combustion engine, for example, when the data for the past four times of the time T30i required for rotating 30 ° CA calculated in step 100 is accumulated and 120 ° CA rotates. The required time T120i may be calculated.

In step 104, the average rotational speed ω _n between 180 ° CA is calculated. More specifically, the reciprocal of the time T180i obtained in step 103 is obtained and is set as the average rotation speed ω _n . In step 105, the rotation speed fluctuation amount Δω _n is calculated based on the following equation.

[0031]

## EQU3 ## Δω _n = (ω _n-1 −ω _n ) − (ω _n-5 −ω _n-4 ) In the case of a 6-cylinder internal combustion engine, rotation based on the following equation instead of equation 2 The speed variation amount Δω _n is calculated.

[0032]

## EQU4 ## Δω _n = (ω _n-1 −ω _n ) − (ω _n-7 −ω _n-6 ) In the next step 106, the distribution of the rotational speed fluctuation amount Δω _n of the normal ignition of this cylinder is calculated. Calculate the cumulative percentage points. The method of calculating the cumulative percentage points will be described in detail later. Next, the routine proceeds to step 107, where misfire removal level calculation processing is executed, and at step 108, judgment level calculation processing is executed. Details of these processes will also be described later.

In step 109, the rotational speed fluctuation amount Δω _n obtained in step 105 is compared with the missing fire determination level REFI _n for this cylinder set in step 108. As a result, if the rotational speed fluctuation amount Δω _n is larger than the inter-firing loss determination value REFI _n, it is determined that the nth cylinder is misfiring, and the routine proceeds to step 110. In step 110, the value of the temporary misfire counter CMIS _n corresponding to the nth cylinder identified in step 102 is incremented (CMI
S _n ← CMIS _n +1).

Here, the temporary misfire counter CMIS _n is set for each cylinder, and the number of times that the rotational speed fluctuation amount Δω _n is judged to be larger than the inter-firing fire judgment value REFI in the above-mentioned temporary misfire judgment is counted for each cylinder. The result is RAM9
It is stored in c. Since the internal combustion engine is a four-cylinder engine in this embodiment, the temporary misfire counter CMIS _n is 4 in total.
Have been set. Further, in step 109, it is possible to detect which cylinder is misfiring. Therefore, it is possible to determine which cylinder is misfiring by changing the lighting interval of the warning lamp 12 when the misfire is determined. Etc. may be notified.

In step 109, if the rotational speed fluctuation amount Δωn is less than or equal to the inter-firing loss judgment value REFIn, it is determined that no misfire has occurred in this cylinder, and step 110
Processing is passed through to step 111. Step 1
At 11, the rotation speed fluctuation amount of each cylinder is stored in preparation for the next processing. In the present embodiment, the value memorized as the rotational fluctuation amount of the cylinder before ignition for the detected cylinder this time is memorized as the rotational fluctuation amount of the cylinder before ignition for the next detected cylinder (ω _{i ( i = n, n-1, n-2, n-3, n-4)} → ω
_{i-1 (i = n, n-1, n-2, n-3, n-4)} ). Here, in the case of a 6-cylinder internal combustion engine, the rotation fluctuation amount of the cylinders before 6 ignitions is updated in the same procedure.

Next, the processing for obtaining the cumulative Δ% points of the Δω distribution executed in step 106 of FIG. 4 will be described with reference to the flowchart shown in FIG. First, in step 201, in order to obtain the standard deviation σ _n from the Δω distribution at the time of normal ignition, the current rotational speed fluctuation amount Δω _n of the cylinder is compared with the first misfire removal level EXMF1. The Δω distribution during normal ignition is the Δω distribution during full ignition from the Δω distribution during misfire.
It is the distribution excluding the distribution. As a result, if the absolute value of the rotation speed fluctuation amount Δω is smaller than the first misfire removal level EXMF1, the routine proceeds to step 202, and if it is larger, this routine is ended.

In step 202, the rotation speed fluctuation amount Δω
comparing the absolute value and the standard deviation sigma _n of _n, the absolute value of [Delta] [omega _n is greater than the standard deviation sigma _n proceeds to step 203,
If it is smaller, the process proceeds to step 204. In step 203 the standard deviation sigma _n far by adding twice the predetermined value α to update the standard deviation sigma _n. On the other hand, in step 204, σ _n is updated by subtracting the predetermined value α from the previous value σ _n .
As a result, the newly updated σ _n can be settled at the distribution upper 16% point of the rotation speed fluctuation amount Δω _n of the nth cylinder. Next, in step 205, the standard deviation obtained this time is smoothed by the following equation.

[0038]

Equation 5] sigma If _{'n ← (7 × σ'} n + σ n) / 8 above processing is completed, the routine is ended, the process proceeds to step 107 in FIG. 4. By executing the processing shown in FIG. 5, the standard deviation of each cylinder can be obtained by using the rotation speed fluctuation amount (second fluctuation amount) in the first and second misfire removal levels. The standard deviation thus found is almost the same for both the misfiring cylinder and the normal cylinder, as described above.

Next, the misfire removal level calculation processing executed in step 107 of FIG. 4 will be described with reference to the flowchart shown in FIG. First, in step 206, the average value obtained by multiplying a predetermined value a to the SGM of _n 'sigma of _n and all the cylinders' standard deviation sigma smoothed obtained in step 205 of FIG. 5 (divergence prevention threshold) To compare. When σ ′ _n is larger than a × SMG, the process proceeds to step 207, and the value of σ ′ _n is set to a × SMG. Step 206,
By the processing of step 207, it is possible to prevent the phenomenon that the standard deviation of the cylinder in which the intermittent fire has occurred diverges. In the next step 208, the average value SGM of the standard deviations of all cylinders is updated by the following equation.

[0040]

[Equation 6] SMG ← (7 × SMG + σ ′ _n ) / 8 Then, in step 209, the SMG calculated in step 208 is multiplied by the predetermined value b to obtain the first misfire removal level EX.
MF1 is obtained, this processing is terminated, and step 108 in FIG.
Proceed to. The predetermined value b is set so that the region where the rotation speed fluctuation amount is smaller than the first misfire removal level EXMF1 includes the Δω distribution of normal ignition, and is set to 3 in this embodiment.

In the process shown in FIG. 6, the first misfire removal level is calculated using the average value of the standard deviations of the cylinders. Therefore, even if misfire occurs in a certain cylinder, when the standard deviation of the cylinder is obtained by the process of FIG. 5, the rotational speed fluctuation amount exceeding the first misfire removal level is not taken into consideration. Even if the distribution of fluctuation amount and the distribution of misfiring cylinders overlap, it is possible to prevent the standard deviation of this misfiring cylinder from diverging.

Next, step 108 in FIG. 4 is executed.
The misfire removal level calculation process is a flowchart shown in FIG.
Follow the instructions below. When this process is executed,
Σ ′ calculated in step 205 of FIG. 5 at step 210
_nAnd the standard deviation average value S calculated in step 208 of FIG.
Compare with GM. Where the standard deviation σ ′_n<Standard deviation
When the average value SGM, the routine proceeds to step 211, where the standard deviation is
Standard deviation that uses the difference average value SGM to create the judgment level
σ '_nAnd This is σ '_nIf the misfire is small
This is to prevent erroneous detection because the constant level becomes small.
It Then, the process proceeds to step 212. Also, the standard deviation
σ ' _nIf ≧ standard deviation average value SGM,
Proceed to step 212.

[0043] At step 212, the intermittent misfire judgment level REFI _n by multiplying a predetermined value u to the standard deviation sigma _'n. Here, the predetermined value u is set to a value of about 3 to 4 in order to prevent erroneous detection. When this process ends, the process exits this routine and proceeds to step 109 in FIG. In the process of FIG. 7, since the inter-missing fire determination level is created using the standard deviation of the appearance frequency distribution of the rotational speed fluctuation amount at the time of normal ignition, which is the normal distribution, the optimum misfire determination level is easily created. be able to.

By the above-mentioned processing, it is possible to satisfactorily detect the missing fire during the internal combustion engine. Next, the continuous misfire detection processing executed by this embodiment will be described with reference to the flowchart shown in FIG. It should be noted that this processing is executed by an angle interruption for each predetermined angle (for example, 30 ° CA).

When this processing is executed, in steps 301 to 304 and step 309, steps 100 to 104 and step 112 in FIG. 4 are performed.
The same process as is executed (the description is omitted here). In step 305, the rotation speed fluctuation amount Δω _n is calculated based on the following equation.

[0046]

## EQU7 ## Δω _n = (ω _n-1 −ω _n ) − (ω _n−3 −ω _n−2 ) In this embodiment, a four-cylinder internal combustion engine is described as an example. Although calculates the rotation speed variation [Delta] [omega _n, it may be determined rotational speed variation [Delta] [omega _n by the following equation in the case of for example six-cylinder internal combustion engine.

[0047]

Δω _n = (ω _n-1 −ω _n ) − (ω _n-4 −ω _n-3 ) Next, the process proceeds to step 306, where the rotation speed fluctuation amount Δω _n is smoothed by the following equation, and the fluctuation amount is calculated. The smoothed value dΔω _n is calculated.

[0048]

Equation 9] _{dω n = ((k-1} ) × dω n-4 + Δω n) / k , where for d [omega _n-4 is a previous smoothed value of n-th cylinder (4-cylinder internal combustion engine ). The value of the constant k is 8 in this embodiment. The value of this constant k is preferably set to a value of 2 ^{n in} terms of computer processing. In this way, by smoothing the rotation speed fluctuation amount, the characteristics shown in FIG. 11 are obtained.

FIG. 11A shows the amount of fluctuation in the rotational speed when the engine is normal, and FIG. By smoothing the rotation speed fluctuation amount as shown in FIG. 11B, the rotation speed fluctuation amount of the normal cylinder and the continuous misfire cylinder can be separated, and shown in steps 307-1 and 307-2. The misfire can be easily detected by the processing. In step 307-1, dω _n obtained in step 306 is compared with the continuous misfire misfire determination level CREF _n, and dω _n
Is larger, the procedure advances to step 307-2, and the misfire counter CMIS _n corresponding to the cylinder this time is incremented. The value of CMIS _n is used in the misfire detection process shown in FIG.

If dω _n is small in step 307-1, the process proceeds to step 308. In step 308, ω
_{Let i (i = n, n-1, n-2)} be ω _{i-1 (i = n, n-1, n-2)} , and dω
The process is terminated by setting _{i (i = n, n-1, n-2, n-3)} to dω _{i-1 (i = n, n-1, n-2, n-3)} . By executing the above processing, continuous misfire is detected in this embodiment. Next, a process for finally determining whether or not a misfire has occurred in the internal combustion engine will be described with reference to the flowchart shown in FIG. In addition,
This processing is executed by angle interruption for each predetermined angle (for example, 30 ° CA).

When this processing is executed, first, step 4
In 01, it is determined whether or not the interrupt timing this time is the top dead center (TDC) of any cylinder. If the interrupt timing this time is not TDC, this routine is ended. If TDC timing, step 402
Proceed to. In step 402, the judgment counter COUNT
Increments the value of. Then, in step 403, it is determined whether or not the value of COUNT is larger than the predetermined value k ₁ . If a negative determination is made here, this processing ends.
If a positive determination is made, the operation proceeds to the misfire detection routine below.

In step 404, step 11 in FIG.
7 and CMI of each cylinder counted in 307 of FIG.
The total value ΣCMIS of S is calculated. And Step 4
At 05, it is determined whether this ΣCMIS is larger than a predetermined value m ₁ . If an affirmative determination is made here, it is determined that a misfire has occurred, the misfire flag MF is set to 1 in step 406, and the process proceeds to step 408. When a negative determination is made in step 405, it is determined that no misfire has occurred and the process proceeds to step 407. In step 407, the misfire flag MF is set to 0 and the process proceeds to step 408. Then, in step 408, the value of the judgment counter COUNT is cleared, and in step 409, the CMIS of each cylinder is cleared.
The value of _{n (n = 1,2,3,4)} is cleared, and this processing ends.

Further, when the misfire flag MF is 1, the ECU turns on an alarm lamp, executes a fail-safe process, and so on. In this embodiment, if there is a misfire even in one cylinder, it is determined only that the engine has a misfire. However, it is detected whether or not there is a misfire in each cylinder, and the misfire is detected. The cylinder number may be stored.

In the first embodiment, the rotation angle sensor 5 and the reference position sensor 6 are used as the rotation signal output means, step 103 in FIG. 4 is used as the measured value calculation means, and the average rotation speed of the continuous cylinders is used in step 105 of FIG. The process of calculating the difference is performed by the first variation amount calculating means, and the process of calculating the rotation speed variation amount Δω in step 105 of FIG. 4 is performed by the second variation amount calculating means.
Steps 201 to 204 correspond to the cylinder-by-cylinder index calculation means, steps 210, 211, and 212 in FIG. 7 correspond to the cylinder-specific misfire determination value creating means, and step 109 in FIG. 4 corresponds to the misfire determination means. To do.

Further, step 209 of FIG. 6 is executed by the misfire removal level calculating means, and steps 206 and 20 of FIG.
7 corresponds to the index guard means, and the processing shown in FIG. 8 corresponds to the continuous misfire detection means, and functions. Next, a second embodiment of continuous misfire detection will be described with reference to FIG. In the second embodiment, in step 307 of FIG. 8 in the first embodiment.
-1 and 307-2 are executed by executing the process shown in FIG. 10 for the continuous misfire detection process.

In the second embodiment, when the process of step 306 of FIG. 8 is completed, the process proceeds to step 501 of FIG. 10, and the fluctuation amount smoothing value dω _n calculated in step 306 of FIG.
Is the maximum value (dω) of the variation smoothed values calculated so far
Determine if it is greater than _max . Here, if an affirmative decision is made, the operation proceeds to step 502. In step 502, the fluctuation amount smoothed value calculated this time is newly set as the maximum value (dω) _max of the fluctuation amount smoothed value, and the process proceeds to step 503. If a negative determination is made in step 501, step 50 is continued.
Go to 3. In step 503, it is determined whether the fluctuation amount smoothed value dω _n calculated this time is smaller than the minimum value (dω) _{min of} the fluctuation amount smoothed values calculated so far. Here, if the result is affirmative, the routine proceeds to step 504. In step 504, the fluctuation amount smoothed value calculated this time is newly set as the minimum value (dω) _min of the fluctuation amount smoothed value, and the process proceeds to step 505. When a negative determination is made in step 503, the process directly proceeds to step 505. At step 505, the maximum / minimum deviation d ² ω is obtained from the following equation.

[0057]

D ² ω = (dω) _max − (dω) _min Then, in the next step 506, the maximum / minimum deviation d
^It is determined whether _{2ω is} larger than the continuous misfire determination level V _REF1 . If an affirmative determination is made here, it is determined that continuous misfires have occurred and the routine proceeds to step 509. In step 509, the cylinder index number is stored in the misfiring cylinder memory CMF1 on the assumption that misfiring has occurred in the cylinder for which the misfire detection processing has been performed this time. Then, the process proceeds to step 511, the misfire determination flag XMF is set to 1, and the process proceeds to step 512.

When a negative determination is made in step 506, the process proceeds to step 507. In step 507,
It is determined whether the maximum / minimum deviation d ² ω is larger than the continuous misfire determination level V _REF2 . Here, if an affirmative decision is made, it is considered that a plurality of cylinders have misfired, and the routine proceeds to step 510.
In step 510, the multi-cylinder misfire determination flag XMF2 is set to 1. The misfires of a plurality of cylinders can be detected by the processes of these steps 507 and 510. Then, the process proceeds to step 511 and the misfire determination flag XMF is set to 1
Then, the process proceeds to step 512.

When a negative determination is made in step 507, it is determined that no misfire has occurred, and the routine proceeds to step 508, where the misfire discrimination flag XMF and the multiple cylinder misfire discrimination flag XMF2 are set to 0 and the routine proceeds to step 512. In step 512, it is determined whether the interrupt timing this time is the interrupt timing of the # 1 cylinder. If a negative determination is made here, this processing is ended as it is. If an affirmative decision is made, in steps 513 and 514,
The values of the maximum value (dω) _max and the minimum value (dω) _min of the fluctuation amount smoothed value dω _n are reset, the present process is terminated, and the process proceeds to step 308 of FIG. 8.

In step 308, ω _{i (i = n, n-1, n-2) is set} to ω _{i-1 (i = n, n-1, n-2)} , and dω
The process is terminated by setting _{i (i = n, n-1, n-2, n-3)} to dω _{i-1 (i = n, n-1, n-2, n-3)} . By executing the above processing, it is possible to detect a continuous misfire, and it is possible to determine which cylinder has a continuous misfire in this embodiment. FIG. 11A is a characteristic diagram in which the rotation speed fluctuation amount at the time of normal ignition is smoothed, and FIG. 11B is a characteristic diagram when misfires continuously occur in a predetermined cylinder.

As shown in FIG. 11A, during normal ignition, there is a large difference between the maximum value (dω) _max and the minimum value (dω) _min of dω _n . Therefore, as in the above embodiment, the misfire can be easily detected by comparing the d ² ω calculated by Expression 7 with the continuous misfire determination level V _REF1 . In the second embodiment described above, the process shown in FIG. 10 corresponds to the continuous misfire detecting means and functions.

[0062] In the present embodiment uses the cylinder of the standard deviation sigma _'n when calculating the intermittent misfire judgment level, the average value SG of the standard deviation obtained during misfire removal level calculated
M may be used as it is for all cylinders to create the inter-missing fire determination level.

[0063]

As described above, in the device according to the first aspect, the first fluctuation amount of this time and the first fluctuation amount calculated before the integral multiple rotation of 720 degrees in the crank angle of the internal combustion engine. The second variation amount is calculated from the deviation from the variation amount, and the index indicating the degree of variation of the second variation amount is calculated using the second variation amount during normal ignition. Therefore, the index indicating the degree of variation between the intermittently fired cylinder and the normally ignited cylinder becomes almost the same value, and even when the distribution of the rotational fluctuation amount at misfire and the rotational fluctuation amount at normal ignition overlap during high-speed / low-load operation. The misfire determination level of the inter-missing fire occurrence cylinder can be created by using the index indicating the degree of dispersion of the normal ignition cylinders, and the misfire detection can be performed well. The misfire determination level may be obtained for each cylinder, for example, by multiplying an index indicating the degree of dispersion by a predetermined value as described in claim 4.

Further, in the apparatus according to claim 2,
By calculating the index indicating the degree of variation for each cylinder using the second variation amount whose absolute value is smaller than the misfire removal level, the index indicating the variation degree is calculated using only the second variation amount during normal ignition. It can be calculated. Also,
In the apparatus according to the third aspect, the index indicating the degree of variation used when creating the misfire removal level is set not to be larger than a predetermined value. As a result, it is possible to prevent a phenomenon in which the misfire removal level diverges when a missing fire occurs at high rotation and low load.

Further, in the apparatus according to the fifth aspect, when the index indicating the degree of dispersion of the cylinders for which the misfire determination value is created is smaller than the average value of the index indicating the degree of dispersion of each cylinder, the average of the indexes of the cylinders is calculated. The misfire judgment value is created based on the value. Therefore, even if the index indicating the degree of variation becomes relatively small, it is possible to prevent the misfire determination level calculated from this index from becoming small, and it is possible to prevent erroneous misfire detection.

Further, in the apparatus according to the sixth aspect, by additionally providing a misfire detecting means for newly detecting continuous misfires, it is possible to reliably detect both missed fires and continuous misfires occurring at a predetermined rate. can do.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an internal combustion engine used in a first embodiment to which the present invention is applied.

2 (a) to (c) are explanatory views for explaining a method for detecting inter-firing fire in the first embodiment.

3A and 3B are explanatory views for explaining a method of detecting continuous misfires in the first and second embodiments.

FIG. 4 is a flowchart of an inter-missing fire detection process executed in the first embodiment.

FIG. 5 is a flowchart of an inter-deletion fire detection process executed in the first embodiment.

FIG. 6 is a flowchart of inter-missing fire detection processing executed in the first embodiment.

FIG. 7 is a flowchart of inter-missing fire detection processing executed in the first embodiment.

FIG. 8 is a flowchart of a continuous misfire detection process executed in the first embodiment.

FIG. 9 is a flowchart of misfire detection processing executed in the first embodiment.

FIG. 10 is a flowchart of a continuous misfire detection process executed in the second embodiment.

11A and 11B are time charts for explaining a method of detecting continuous misfires in the first and second embodiments.

FIG. 12 is a configuration diagram showing the configuration requirements of the present invention.

[Explanation of symbols]

 1 Internal Combustion Engine 5 Rotation Angle Sensor 6 Reference Position Sensor 9 ECU

Claims (6)

[Claims] 1. A rotation signal output means for outputting a rotation signal for each predetermined rotation angle according to the rotation of an internal combustion engine, and rotation for a predetermined rotation angle in an expansion stroke of each cylinder based on the rotation signal. A measured value calculation means for calculating a measured value determined by measuring a period, and a first fluctuation amount calculation for calculating a first fluctuation amount by calculating a deviation between the measured values of two cylinders in which the expansion stroke is continuous. Means and the first variation of this time calculated by the first variation amount calculation means.
Second variation amount calculation for calculating a second variation amount by obtaining a deviation between the variation amount of the first internal combustion engine and the first variation amount calculated before an integral multiple rotation of 720 degrees at the crank angle of the internal combustion engine. Based on the index calculated by the cylinder-specific index calculation means, and a cylinder-specific index calculation means for calculating, for each cylinder, an index indicating the degree of variation in the appearance frequency distribution of the second fluctuation amount during normal ignition. By comparing the second variation amount with the misfire determination value created for each cylinder, it is possible to determine whether or not a misfire has occurred in the internal combustion engine. A misfire detecting device for an internal combustion engine, comprising: a misfire judging means for judging. 2. A misfire removal level calculating means for calculating a misfire removal level based on an index indicating a degree of dispersion of each cylinder, wherein the cylinder-by-cylinder index operation means has a first absolute value smaller than the misfire removal level. The misfire detection device for an internal combustion engine according to claim 1, further comprising means for calculating an index indicating the degree of variation for each cylinder using the variation amount of 2. 3. The misfire removal level calculation means includes an exponent guard means for guarding the exponent indicating the degree of variation from exceeding a predetermined value, and the misfire removal level is guarded by the exponent guard means. The misfire detection device for an internal combustion engine according to claim 2, further comprising: a calculation unit based on the above. 4. The misfire determination value creating means includes means for creating a misfire determination value for each cylinder by multiplying an index indicating the degree of variation by a predetermined value. 4. The misfire detection device for an internal combustion engine according to any one of 3 above. 5. The misfire determination value creating means averages the indexes of the respective cylinders when the index indicating the degree of variation of the cylinders for creating the misfire determination value is smaller than the average value of the indexes indicating the degree of variation of each cylinder. The misfire detection device for an internal combustion engine according to claim 4, wherein the misfire determination value is created based on the value. 6. A misfire detection for an internal combustion engine according to claim 1, further comprising a continuous misfire detection means for detecting a continuous misfire continuously occurring in a specific cylinder. apparatus.