JP2000064901A - Misfire detector foe internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance misfire detection accuracy during the high speed rotation of an engine. SOLUTION: A crank rotation speed ω(n) is calculated by the explosion stroke of each cylinder. Then, a difference Δω3(n) between a rotational speed variation Δω1(n) in two cylinders having the successive explosion strokes and a rotational speed variation Δω2(n) before a secondary ignition is calculated. By calculating a difference Δω4(n) between a value Δω30LD2 (=Δω3(n-2)) calculated before the secondary ignition and a value Δω3(n) calculated this time, and comparing the difference Δω4(n) with a misfire criterion value K, occurrence of misfire is determined. When misfire occurs before the secondary ignition, such a relation is established that the value Δω30LD2=(the speed variation at misfire) - (the speed variation at normal) becomes more than 0 and the value Δω3(n)=(the speed variation at normal) - (the speed variation at misfire) becomes less than 0. Consequently, such a relation is established that the value Δω4(n)=Δω30LD2-Δω3(n)=positive value-negative value, and then the value Δω4(n) is equal to the increased value Δω30LD2 (the speed variation at misfire) by |Δω3(n)| only. It is thus possible that the speed variation at misfire Δω4(n) becomes a large value, even during the high speed rotation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire detection device for an internal combustion engine that detects misfires occurring in respective cylinders of the internal combustion engine using fluctuations in the rotational speed of a crankshaft.

[0002]

2. Description of the Related Art When a misfire occurs during an explosion stroke of a certain cylinder during the operation of an internal combustion engine, attention is paid to the fact that the rotational speed of the crankshaft is reduced. There is one that detects a misfire every time. In this type of misfire detection device, as shown in, for example, Japanese Patent Application Laid-Open No. 4-365958, a fluctuation amount (first fluctuation amount) of a rotation speed between two cylinders having a continuous explosion stroke.
And the amount of change (second amount of change) in the rotational speed of the cylinder 360 ° A before the cylinder for which the first amount of change was calculated, and calculates the first and second amounts of change. In some cases, misfire is detected based on a difference. Also,
As disclosed in Japanese Patent Application Laid-Open No. H10-54295, in order to increase the misfire detection accuracy, in addition to the first and second fluctuation amounts, the fluctuation amount of the rotation speed of the cylinder before 720 ° C.
Is calculated, and misfire is detected from the first to third fluctuation amounts.

[0003]

However, when the engine is running at high speed, the decrease in the rotation speed due to misfiring is small. Therefore, according to the above-mentioned two publications, even if misfiring occurs at high speed, misfiring is determined. There is a possibility that the first to third fluctuation amounts serving as parameters become small, and that misfire cannot be detected.

The present invention has been made in view of such circumstances, and accordingly, has as its object to provide a misfire detection device for an internal combustion engine that can accurately detect misfire even at high rotation speeds. Is to do.

[0005]

According to a first aspect of the present invention, there is provided an apparatus for detecting a misfire of an internal combustion engine according to the present invention. A signal is output, and the rotation speed of the crankshaft (hereinafter referred to as “cylinder rotation speed”) is calculated by the rotation speed calculation means for each explosion stroke of each cylinder based on the rotation signal. The first speed fluctuation calculating means calculates the fluctuation amount of the cylinder-specific rotational speed between the two cylinders (hereinafter referred to as “first fluctuation amount”), and the second speed fluctuation calculating means calculates the first fluctuation. The amount of change in the cylinder-by-cylinder rotational speed between the two cylinders at a predetermined crank angle before the cylinder for which the amount has been calculated (hereinafter referred to as the “second amount of change”) is calculated. By calculating the difference between the first fluctuation amount and the second fluctuation amount, a fluctuation amount (hereinafter, referred to as a “third fluctuation amount”) in which a rotational speed fluctuation amount generated due to a factor other than misfire is removed.
). Further, the difference between the third variation calculated in the past and the third variation calculated this time (hereinafter referred to as “fourth variation”) for each explosion stroke of each cylinder by the fourth speed variation calculating means is calculated. The misfire is determined by the misfire determination means based on the fourth variation amount.

In this case, the first fluctuation amount increases when a misfire occurs in the current ignition cylinder, and the second fluctuation amount increases when a misfire occurs in the ignition cylinder a predetermined crank angle before the current position. Become larger. Further, since the third fluctuation amount = (the first fluctuation amount)-(the second fluctuation amount), when the misfire occurs, the third fluctuation amount = (the fluctuation amount at the time of misfire)-(the normal fluctuation amount). Fluctuation amount), and the third fluctuation amount becomes a positive value.
When the crankshaft rotates a predetermined crank angle after the occurrence of the misfire, the third fluctuation amount = (the normal fluctuation amount) − (the misfire fluctuation amount), and the third fluctuation amount becomes a negative value. On the other hand, since the fourth fluctuation amount = (past third fluctuation amount) − (this time third fluctuation amount), the past (at the time of misfire) third fluctuation amount is a positive value, and this time (normal) If the third fluctuation amount at (time) is a negative value, the fourth fluctuation amount is a value obtained by increasing the third fluctuation amount at the time of misfire. Therefore, even when the engine is running at a high speed, at the time of misfire, the fourth variation amount serving as a misfire determination parameter can be taken out as a large value, and it is possible to accurately detect misfire based on the fourth variation amount. Can be.

Further, when calculating the third variation amount this time, a parameter including at least one of the parameters used for calculating the past third variation amount is used for calculating the third variation amount. It is preferable to calculate the third variation. In this way, when a misfire occurs, the parameter at the time of the misfire is reflected in the calculation of the third variation in the past and the third variation this time, and the fourth variation in the misfire occurs. The amount can be further increased.

[0008]

[Embodiment (1)] An embodiment (1) of the present invention will be described below with reference to FIGS.
First, a schematic configuration of the entire system will be described with reference to FIG. In the present embodiment (1), for example, a four-cylinder engine 11 (internal combustion engine) is to be controlled. The four-cylinder engine 11 has four cylinders, a first cylinder (# 1) to a fourth cylinder (# 4). In the present embodiment (1), the ignition order is changed from # 1 to # 2 for convenience of explanation. → # 3 → # 4.

A throttle valve 13 is provided in an intake pipe 12 of the engine 11, and an intake pipe pressure sensor 14 for detecting an intake pipe pressure PM is provided downstream of the throttle valve 13. A fuel injection valve 16 is provided at an intake port of each cylinder. The engine 11 is provided with a distributor 18 for sequentially distributing a high voltage generated by an ignition device 17 to a spark plug (not shown) of each cylinder. The distributor 18 has a reference position sensor for distinguishing each cylinder. 19 is built-in. The reference position sensor 19 is, for example, a piston 20 of the # 1 cylinder.
Outputs a reference position signal CYL each time the signal reaches the compression top dead center (# 1 TDC).

On the other hand, a crankshaft (not shown) of the engine 11 is provided with a rotation angle sensor 21 (rotation signal output means) for outputting a rotation signal NE at every predetermined crank angle. The rotation signal NE output from the rotation angle sensor 21
The rotation speed of the crankshaft of the engine 11 is calculated based on the frequency. Further, cylinder discrimination is performed based on the number of pulses of the rotation signal NE from the generation timing of the reference position signal CYL. A water temperature sensor 22 for detecting an engine cooling water temperature is attached to a cylinder block of the engine 11. On the other hand, the exhaust pipe 23 of the engine 11 is provided with an oxygen sensor 24 for detecting the oxygen concentration in the exhaust gas.

The outputs of the various sensors described above are input to an electronic control unit (hereinafter referred to as “ECU”) 25. The ECU 25 is mainly composed of a microcomputer, and includes a CPU 26, a ROM 27 (storage medium), a RAM
28, a backup RAM 29 backed up by a battery (not shown), an I / O port 30, and the like. By executing various engine control programs stored in the ROM 27, the ECU 25 calculates a fuel injection amount, an ignition timing, and the like using engine operating parameters detected by various sensors, and outputs a signal corresponding to the calculation result. Is output from the I / O port 30 to the fuel injection valve 16 and the ignition device 17 to perform fuel injection control and ignition control, and also to perform air-fuel ratio feedback control based on the output of the oxygen sensor 24.

Further, the ECU 25 executes a misfire detection program shown in FIG. 3, which will be described later, stored in the ROM 27 to determine the presence or absence of a misfire for each cylinder. 31 is turned on or flashed to notify the driver or the like of the occurrence of misfire, and an appropriate fail-safe process is executed.

Next, an outline of the misfire detection processing by the ECU 25 will be described with reference to FIG. FIG. 2 is a functional block diagram showing the function of the ECU 25 as a misfire detection device.
The rotation speed calculating means 41 is for each TDC of each cylinder (every 180 ° A) based on the rotation signal NE and the reference position signal CYL.
Next, the crankshaft rotation speed (crank rotation speed) ω (n) is calculated. This crank rotation speed ω (n) corresponds to the cylinder-specific rotation speed in the claims. Note that, instead of the crank rotation speed (rpm), the crank angular speed (rad /
s) may be calculated.

The first speed fluctuation calculating means 42 calculates the fluctuation ΔΔ of the crank rotation speed between two cylinders whose explosion strokes are continuous.
ω1 (n) (first variation) is calculated by the following equation. Δω1 (n) = ω (n-1) −ω (n) (1) where ω (n) is the current crank rotation speed, and ω (n-1) is one ignition before (180 ° C. before A). ) Is the crank rotation speed.

The second speed fluctuation calculating means 43 calculates Δω1
In this embodiment (1), the fluctuation amount of the crank rotation speed Δω2 (n) between the two cylinders a predetermined crank angle before the cylinder for which (n) was calculated, and before the second ignition (before 360 ° A).
Is calculated by the following equation (2). Δω2 (n) = ω (n−3) −ω (n−2) (2) where ω (n−2) is the crank rotation speed before two ignitions, ω (n
-3) is the crank rotation speed before three ignitions. Where Δ
Since ω2 (n) = ω (n−3) −ω (n−2) = Δω1 (n−2), the second fluctuation amount Δω2 (n) of this time is two ignition before (36
The first variation Δω1 (n−2) before 0 ° C. A).

The third speed fluctuation amount calculating means 44 calculates the current fluctuation amount Δω1 (n) calculated by the first speed fluctuation amount calculating means 42.
The difference Δω3 (n) (third fluctuation amount) between the fluctuation amount Δω2 (n) before two ignitions calculated by the second speed fluctuation amount calculating means 43 is calculated by the following equation. Δω3 (n) = Δω1 (n) −Δω2 (n) (3) As a result, Δω3 (n) is not affected by a transient increase / decrease in rotational speed due to operating conditions of the engine 11, such as acceleration and deceleration. This is the amount of fluctuation that has been eliminated. In the case where the cylinders are separated from each other by 360 ° C. (one rotation of the crankshaft), the rotation angle sensor 2
At 1 the same tooth of the signal rotor (not shown) is detected,
Since the crank rotation speed is calculated based on this, the influence of the dimensional variation of the signal rotor is also eliminated. This is the same also in the case of cylinders separated by 720 ° C. in an embodiment (2) described later. Therefore, Δω3 (n) calculated by the above equation (3) is a variation mainly due to only misfire.

The third speed fluctuation amount storage means 45 includes a RAM 2
8 each time the third speed fluctuation amount calculating means 44 calculates the third fluctuation amount Δω3 (n).
(n) is stored.

The fourth speed variation calculating means 46 calculates a difference Δω4 (n) between the third variation Δω3OLD calculated in the past and the third variation Δω3 (n) calculated this time (fourth variation). Is calculated by the following equation. Δω4 (n) = Δω3OLD-Δω3 (n)

In this embodiment (1), Δω3 OLD is the third fluctuation amount calculated two ignitions (360 ° C. A) before the second speed fluctuation amount calculating means 43 calculates Δω2 (n). Δω3 (n-2) is used. Δω4 (n) = Δω3OLD2-Δω3 (n) ... (4) (However, Δω2 (n-2) = Δω1 (n-4)) (However, Δω2 (n) = Δω1 (n-2))

For example, if the cylinder two ignitions before the current position is a misfire cylinder, the first variation Δω1 before the two ignitions
(n-2) is the fluctuation amount at the time of misfire and becomes a relatively large fluctuation amount, but otherwise becomes the fluctuation amount at the normal time and becomes a small fluctuation amount. In this case, Δω3OLD2, which is the third fluctuation amount before the second ignition, is as follows: Δω3OLD2 = Δω1 (n−2) −Δω1 (n−4) = (fluctuation amount at misfire) − (fluctuation amount at normal time) (5) and Δω3OLD2 becomes a plus value.

On the other hand, the third variation Δω3 (n) at this time is: Δω3 (n) = Δω1 (n) −Δω1 (n−2) = (normal variation) − (variation at misfire) (6), and Δω3 (n) becomes a negative value.

Therefore, the fourth variation Δω4 (n) is And the fourth variation Δω4 (n) becomes a large value obtained by increasing Δω3OLD2 (the third variation at the time of misfire) by | Δω3 (n) |. Further, for simplicity of explanation, when the fluctuation amount in the normal state is regarded as 0, from the above equations (5) and (6), Thus, a fluctuation amount almost twice as large as the actual fluctuation amount at the time of misfire can be obtained.

As described above, the present third variation Δω
The first variation Δω1 (n−2) (= Δω2 (n)) before two ignitions is used as one of the parameters used to calculate 3 (n) and the third variation Δω3OLD2 before two ignitions. In order to use the third variation Δω3 (n) and 2
The variation Δω1 (n−2) at the time of misfire can be reflected in both the third variation Δω3OLD2 before ignition, and the fourth variation at the time of misfire can be reflected.
Can be reliably increased.

The determination level calculation means 47 sets a misfire determination value K by a map or a function formula based on the rotation signal NE and the intake pipe pressure PM, for example. Note that the intake air amount may be used instead of the intake pipe pressure PM.

The misfire determination means 48 compares the fourth variation Δω4 (n) calculated by the fourth speed variation calculation means 46 with the misfire determination value K, and determines whether the fourth variation Δω4 (n) is misfire. Value K
It is determined that there is a misfire when it is larger than.

The misfire detection by the ECU 25 described above is executed by a misfire detection routine shown in FIG. This routine is an example in which the amount of change before two ignitions (before 360 ° A) is calculated as the second amount of change Δω2 (n), and misfire is detected after two ignitions from the occurrence of misfire. This routine is started by interrupt processing at every crank angle of 60 ° C. based on the rotation signal NE. When this routine is started, first, in step 100, a time T60 (i) required for the crankshaft to rotate at 60 ° C. A is calculated from the difference between the previous interruption time of this routine and the current interruption time.

Thereafter, in step 110, based on the number of pulses of the rotation signal NE from the generation timing of the reference position signal CYL, it is determined whether or not the current interruption timing is the compression top dead center (TDC) of any cylinder. Is determined. If the current interrupt timing is not TDC, the routine proceeds to step 120, where T6 stored in the RAM 28
0 (i-1) is updated at T60 (i), and T6 (i-1) is updated.
The data of 0 (i-2) is updated at T60 (i-1), and this routine ends. Here, the subscript (i) indicates the number of times of processing by the ECU 25.

Each time the interrupt timing of this routine reaches TDC, that is, every explosion stroke (each 180 ° C.)
In step 110, "Yes" is determined, and step 1
The misfire determination process after 30 is executed as follows. First,
In step 130, the T6 calculated in step 100 is calculated.
The data of the past three times of 0 are integrated, and the crankshaft becomes 18
The time T180 (i) required for 0 ° C. A rotation is calculated. T180 (i) = T60 (i) + T60 (i-1) + T60 (i-
2)

Thereafter, the routine proceeds to step 140, where the current crank rotation speed ω (n) is calculated by the following equation. ω (n) = KDSOMG / T180 (i) Here, KDSMG is a conversion coefficient for converting T180 (i) into crank rotation speed (rpm).

In the next step 150, the first variation Δω
After calculating 1 (n) = ω (n-1) −ω (n), step 16
At 0, a second variation Δω2 (n) = ω (n−3) −ω (n−2) is calculated.

Then, in the next step 170, the RAM 2
The data of Δω3OLD2 stored in 8 is updated with Δω3OLD1, and the data of Δω3OLD1 is updated with the third variation Δω3 (n) calculated last time. Thereby, Δω3
OLD2 is the third variation Δω3 calculated two ignitions before (360 ° C before), and Δω3OLD1 is one variation before one ignition (180 ° C before).
The third fluctuation amount Δω3 calculated in the previous step). Then, the third fluctuation amount Δω3 (n) = Δω1 (n) −Δω2 (n) at this time
Is calculated.

In the next step 180, the fourth variation Δω
After calculating 4 (n) = Δω3OLD2−Δω3 (n), in step 190, the presence or absence of a misfire is determined based on whether or not the calculated fourth variation Δω4 (n) is larger than the misfire determination value K. .
At this time, the misfire determination value K is set by a map or a functional expression based on, for example, the rotation signal NE and the intake pipe pressure PM. If this step 190 determines that the fourth variation Δω4
If it is determined that (n) is equal to or less than the misfire determination value K, it is determined that no misfire has occurred, and the routine proceeds to step 200, where the misfire detection flag XMF is reset to "0" meaning no misfire.

On the other hand, if it is determined in step 190 that the fourth variation Δω4 (n) is larger than the misfire determination value K, it is determined that a misfire has occurred, and step 21 is performed.
The process proceeds to 0, and the misfire detection flag XMF is set to "1" which means that there is misfire. In this case, the emission lamp may be deteriorated due to misfire, the catalyst may be damaged, and the like.
1 is turned on or blinked to warn the driver. It should be noted that the misfire detection flag XMF may be provided for each cylinder so that it is possible to determine which cylinder has a misfire.

After resetting or setting the misfire detection flag XMF in step 200 or 210, the process proceeds to step 220, where the crank rotation speed data ω (n-3), ω (n-2), ω stored in the RAM 28 are stored. (n-1) is updated with the data ω (n-2), ω (n-1), and ω (n) after one ignition, respectively, and the routine ends.

An example of execution of the misfire detection routine of the embodiment (1) described above will be described with reference to the time chart of FIG. FIG. 4 shows that the engine 11 rotates at a high speed (6000 rpm).
An example in which misfire has occurred in the # 4 cylinder while rotating at m) is shown. In this case, Δω3OLD2
Swings to the plus side, and the value of the third variation Δω3 (n) after two ignitions from the misfire swings to the minus side. This allows
Two ignitions after the misfire, the fourth variation Δω4 (n), which is the difference between Δω3OLD2 and Δω3 (n), is a value obtained by increasing the third variation Δω3OLD2 at the time of misfire almost twice, and the misfire determination value It exceeds K and it is determined that there is a misfire.

As described above, in this embodiment (1), even when the engine 11 is rotating at a high speed, the amount of fluctuation at the time of misfiring can be almost doubled and taken out. Can be prevented, and the misfire detection accuracy can be improved.

[Embodiment (2)] Next, an embodiment (2) of the present invention will be described with reference to FIGS. In the above embodiment (1), as the second variation Δω2 (n), the variation before two ignitions (before 360 ° A) is calculated, and the misfire is detected two ignitions after the occurrence of the misfire. In the present embodiment (2), as the second fluctuation amount Δω2 (n), the fluctuation amount before four ignitions (before 720 ° C. A) (that is, the fluctuation amount of the previous explosion stroke of the same cylinder) is calculated, and misfire occurs. Misfire is detected after 4 ignitions.

The misfire detection routine of FIG. 5 executed in the second embodiment (2) performs the processing of steps 160, 170, 180, and 220 of FIG. , 221 and the other steps are the same as those in FIG.
In this routine, every TDC of each cylinder (each 180 ° C.)
In addition, the crank rotation speed ω (n) and the first variation Δω1 (n)
= Ω (n-1) -ω (n) (steps 100 to 15)
0), in the next step 161, the second variation Δω2 (n)
Is calculated by the following equation. Δω2 (n) = ω (n-5) −ω (n-4) Here, ω (n-4) and ω (n-5) are ω (n) and ω (n
-1) is the crank rotation speed four ignitions (720 ° C before). As a result, the second variation Δω2 (n) is calculated for the same cylinder as the cylinder for which the first variation Δω1 (n) has been calculated.

Thereafter, in step 171, the data of the third variation Δω3OLDi (i = 1 to 4) stored in the RAM 28 is converted into Δω3OLD3 → Δω3OLD4, Δω3OLD2 → Δω
3OLD3, Δω3OLD1 → Δω3OLD2, Δω3 (n) → Δω3
OLD1 is sequentially updated with the stored data of the third variation after one ignition, and the third variation Δω3
(n) = Δω1 (n) −Δω2 (n) is calculated.

Then, in the next step 181, in accordance with the calculation of the second variation Δω2 (n), the fourth variation Δω4 (n) becomes an increased value when a misfire occurs. The fourth variation Δω4 (n) this time is calculated by the following equation using Δω3OLDd4 calculated before four ignitions (before 720 ° A). Δω4 (n) = Δω3OLD4-Δω3 (n)

Thereafter, the fourth variation Δω4 (n) is compared with the misfire determination value K to determine the presence or absence of a misfire, and the misfire detection flag XMF is reset or set according to the result of the determination (step 190). ~ 210), in the next step 221,
Crank rotation speed data ω stored in RAM 28
(n-5) to ω (n-1) are converted to data ω (n-
4) Update with ~ ω (n) and end this routine.

In the misfire detection processing of the embodiment (2) described above, as shown in FIG.
The value of OLD4 swings to the plus side, and the value of the third variation Δω3 (n) after four ignitions from misfire swings to the minus side. As a result, the fourth variation Δω4 (n), which is the difference between Δω3OLD4 and Δω3 (n) after four ignitions from the misfire, becomes a value obtained by increasing the third variation Δω3OLD2 at the time of misfire almost twice. Misfire can be detected with high accuracy even when the engine 11 is rotating at high speed. Moreover, the fluctuation amount between the same cylinders (Δω1 (n) and Δω2 (n))
Is used to calculate the third variation Δω3 (n), so that the third variation Δω3 (n) is not affected by the variation between cylinders.
Consequently, the fourth variation Δω4 (n) can be calculated with high accuracy, and the misfire detection accuracy can be further improved.

[Embodiment (3)] Next, an embodiment (3) of the present invention will be described with reference to FIGS. In the present embodiment (3), the amount of change before one ignition (before 180 ° A) is calculated as the second amount of change Δω2 (n),
Misfire is detected after ignition.

The misfire detection routine of FIG. 8 executed in this embodiment (3) performs the processing of steps 160, 170, 180, and 220 of FIG. , 222, and the other steps are the same as those in FIG.

In this routine, the first variation Δω1 (n)
After calculating (Step 150), in Step 162,
The second variation Δω2 (n) is calculated by the following equation. Δω2 (n) = ω (n-2)-ω (n-1)

Thereafter, in step 172, the data of the third variation Δω3OLD1 stored in the RAM 28 is updated with the previously calculated third variation storage data Δω3 (n), and the current third variation Δω3 (n) is updated. Variation Δω3 (n) = Δω1 (n)-Δω
2 (n) is calculated. Thereafter, in step 182, one ignition before (in accordance with the calculation of the second variation Δω2 (n)) so that the fourth variation Δω4 (n) becomes an increased value in the event of misfire. Using Δω3OLDd1 calculated before (180 ° C. before), the fourth variation Δω4 (n) of this time is calculated by the following equation. Δω4 (n) = Δω3OLD1-Δω3 (n)

Thereafter, the fourth variation Δω4 (n) is compared with the misfire determination value K to determine the presence or absence of a misfire, and the misfire detection flag XMF is reset or set according to the result of the determination (step 190). 210), in the next step 222,
Crank rotation speed data ω stored in RAM 28
(n-2) and ω (n-1) are converted to data ω (n-
1) Update with ω (n) and end this routine.

In the misfire detection of the embodiment (3) described above, as shown in FIG. 8, Δω3OLD1
Swings to the plus side, and the value of the third variation Δω3 (n) after one ignition from the misfire swings to the minus side. This allows
One ignition after the misfire, the fourth variation Δω4 (n), which is the difference between Δω3OLD1 and Δω3 (n), is a value obtained by increasing the third variation Δω3OLD1 at the time of misfire almost twice, and the engine 1
Even at the time of high rotation of 1, the misfire is accurately detected.

[Embodiment (4)] By the way, in the above-mentioned embodiment (1), when a continuous misfire occurs in the opposed cylinder (cylinder whose explosion stroke is 360 ° A away), and in the above-mentioned embodiment (2)
In the case of continuous misfiring in the same cylinder (cylinders separated by 720 ° C.), and in the embodiment (3), in the case of continuous misfiring in adjacent cylinders (cylinders separated by 180 ° A), the rotation speed fluctuations The amounts are offset making misfire detection difficult.

Therefore, in the embodiment (4) of the present invention, the misfire detection processes of the above embodiments (1) to (3) are performed in combination with each other, and the rotational speed fluctuation amount between cylinders separated by 360 ° A is provided. , A misfire detection based on the rotational speed fluctuation between cylinders separated by 720 ° C., and a misfire detection based on the rotational speed fluctuation between cylinders separated by 180 ° A may be performed at the same time. .

In this way, it is possible to detect the occurrence of misfires for various misfire occurrence patterns (continuous misfire of the opposite cylinder, continuous misfire of the same cylinder, continuous misfire of the adjacent cylinder). The above embodiments (1) to (3)
May be implemented in combination.

In addition, the present invention may be applied to engines having a number of cylinders other than four. In an N-cylinder engine, the ignition cycle (interval of TDA) is 720 / N (° C. A).

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire system according to an embodiment (1) of the present invention.

FIG. 2 is a functional block diagram illustrating functions of a misfire detection device.

FIG. 3 is a flowchart showing a processing flow of a misfire detection routine according to the embodiment (1).

FIG. 4 is a time chart showing the behavior of ω, Δω3, and Δω4 in the embodiment (1).

FIG. 5 is a flowchart showing a processing flow of a misfire detection routine according to the embodiment (2) of the present invention.

FIG. 6 is a time chart showing the behavior of ω, Δω3, and Δω4 in the embodiment (2).

FIG. 7 is a flowchart showing a processing flow of a misfire detection routine according to the embodiment (3) of the present invention.

FIG. 8 is a time chart showing the behavior of ω, Δω3, and Δω4 in the embodiment (3).

[Explanation of symbols]

11 engine (internal combustion engine) 19 reference position sensor
21: rotation angle sensor (rotation signal output means), 25: EC
U, 41: rotational speed calculating means, 42: first speed fluctuation calculating means, 43: second speed fluctuation calculating means, 44: third speed fluctuation calculating means, 45: third speed fluctuation storing means, 4
6: fourth speed fluctuation amount calculation means, 47: misfire determination value calculation means, 48: misfire determination means.

Claims (2)

[Claims] 1. A rotation signal output means for outputting a rotation signal corresponding to the rotation of a crankshaft of an internal combustion engine, and a rotation speed of the crankshaft (hereinafter referred to as "cylinder Rotation speed calculation means for calculating a rotation speed), first speed fluctuation amount calculation means for calculating a fluctuation amount of the cylinder-by-cylinder rotation speed between the two cylinders (hereinafter referred to as "first fluctuation amount"), A second speed fluctuation calculating means for calculating a fluctuation amount of a cylinder-specific rotational speed between two cylinders at a predetermined crank angle before the cylinder for which the first fluctuation amount is calculated (hereinafter referred to as a “second fluctuation amount”); By calculating a difference between the first fluctuation amount and the second fluctuation amount, a fluctuation amount obtained by removing a rotation speed fluctuation amount generated due to a factor other than misfire (hereinafter, referred to as a “third fluctuation amount”) Third speed fluctuation amount calculating means for determining A fourth speed fluctuation amount calculating means for calculating a difference between the third fluctuation amount calculated in the past and the third fluctuation amount calculated this time (hereinafter, referred to as a “fourth fluctuation amount”) for each explosion stroke; A misfire detecting device for an internal combustion engine, comprising: a misfire determining means for determining the presence or absence of a misfire based on a fourth fluctuation amount. 2. The third speed fluctuation amount calculating means uses a parameter including at least one of the parameters used for calculating the past third fluctuation amount when calculating the current third fluctuation amount. The misfire detection device for an internal combustion engine according to claim 1, wherein the third variation amount is calculated this time.