JP2001173509A - Misfire detecting device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve a problem that, in a misfire detecting device for an internal combustion engine to perform detection of running on an adverse road and detection of a misfire, a rotation speed fluctuation amount after the occurrence of a misfire induces an aftershock occasioned by the occurrence of a misfire, and thus an aftershock of the rotation speed fluctuation amount after the occurrence of a misfire is erroneously detected as a state during running on an adverse road through detection of running on an adverse road, and when the presence of a final misfire is decided, erroneous decision that detection of a misfire is rendered ineffective is performed. SOLUTION: This misfire detecting device comprises an adverse road running detecting means, and first and second misfire detecting means. By using a prohibiting means in a given section after detection of a misfire, it is prevented from occurring that the adverse road running detecting means is counted due to an aftershock occurring in a given period after detection of a misfire. This constitution, since an aftershock is not counted as a state during running on an adverse road when the second misfire detecting means to decide a final misfire is used, prevents the occurrence of erroneous decision that an engine is in a normal state despite of the engine being in a misfire state.

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 which detects a misfire occurring in the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a device for detecting misfire in an internal combustion engine, the rotational speed of each cylinder during an explosion stroke is detected. There is something to judge. That is, since the rotational speed of the misfired cylinder during the explosion stroke is lower than the rotational speed of the normal ignition cylinder, the rotational speed fluctuation amount of these cylinders becomes large. In addition, since the amount of rotation speed fluctuation between the normally ignited cylinders is small, misfire can be detected based on the amount of rotation speed fluctuation.

When the vehicle is traveling on a rough road, the rotational speed of the internal combustion engine fluctuates due to the load from the vehicle. Since there is a possibility that this fluctuation may be erroneously detected as a misfire, a technique is conventionally known in which it is determined whether the vehicle is traveling on a bad road, and if the vehicle is traveling on a bad road, the misfire determination is prohibited. (For example, Japanese Patent Application Laid-Open No. 7-1910
No. 3). According to this conventional publication, when the rotation fluctuation amount is larger than a first determination value, a first determination value for determining that a misfire has occurred, that is, a misfire determination level, and a second determination value smaller than the first determination value. That is, a rough road determination level is provided. Each time a rotational speed fluctuation amount occurs between the misfire determination level and the rough road determination level, the number of occurrences is counted for a predetermined period. When the total number counted for a predetermined period is larger than a predetermined value, the determination of misfire is invalidated to prevent erroneous detection of running on a rough road as misfire.

[0004]

However, when a misfire occurs, the rotational speed of the internal combustion engine fluctuates, causing the vehicle to roll back. The rolling back of the vehicle refers to a phenomenon in which when the rotational speed of the internal combustion engine is reduced due to misfire, the internal combustion engine is rotated by the inertial force of the vehicle. As a result, the rotation speed of the internal combustion engine increases due to the reaction that the rotation speed has decreased. However, the rotation speed drops due to the recoil that has risen too much. When such a phenomenon is repeated, the rotation speed becomes as shown in FIG. When the rotation fluctuation amount Δω is obtained by using the signal of the rotation speed ω, the behavior as shown in FIG. 1 is obtained, and the swing back after the misfire is determined as the misfire determination level as the first determination level and the bad determination as the second determination level. Occurs during the road determination level. Therefore, even if a misfire is detected, there is a possibility that the misfire actually generated by the rough road determination may be invalidated. In particular, when the internal combustion engine and the vehicle drive shaft (transmission) are directly connected to each other, such as a manual transmission vehicle (hereinafter simply referred to as a manual vehicle) or a vehicle having a continuously variable transmission, the effect of the backlash is remarkable. Appear. The same phenomenon occurs when the automatic transmission vehicle locks up.

[0005]

According to a first aspect of the present invention, there is provided an internal combustion engine misfire detecting apparatus for detecting a misfire for each ignition of an internal combustion engine and counting the detected misfires. No. 1 misfire detecting means, bad road running detecting means for detecting that the vehicle is running on a bad road and counting the number of times that the vehicle is running on bad road, and misfire detected by the misfire detecting means Then, in a predetermined section, a prohibiting means for prohibiting the detection of bad road running by the bad road running detecting means, the number of misfire determinations detected by the first misfire detecting means, and a bad count counted by the bad road running detecting means. A second misfire detecting means for judging the presence or absence of a final misfire based on the number of times of road determination.

[0006] Thus, it is possible to prevent the bad road running detecting means from being counted by the reversal occurring during a predetermined period after the detection of the misfire. It is possible to prevent erroneous determination that the road is bad due to the influence of the swingback and erroneous determination that the road is normal despite the misfire state. In addition, the prohibition of the rough road traveling detecting means by the prohibiting means may prohibit counting when the rough road traveling is detected,
The detection of rough road travel itself may be prohibited.

In the misfire detection apparatus for an internal combustion engine according to the second aspect, the bad road traveling detecting means may include a second speed variation amount smaller than the first determination value and smaller than the first determination value.
By counting when the value is larger than the determination value, it is possible to more accurately detect the rotation speed detection amount that fluctuates due to running on a rough road.

According to a third aspect of the present invention, there is provided the internal combustion engine misfire detection apparatus according to any one of the first to second aspects, wherein the prohibition means is activated when it is detected that the engine is in a predetermined operating state. Used. As a result, the prohibition means is used in an operating state in which reversal is likely to occur after the occurrence of a misfire, so that erroneous determination due to reversal can be prevented with high accuracy.

According to a fourth aspect of the present invention, there is provided the internal combustion engine misfire detecting apparatus according to the third aspect, wherein the operating state detected by the operating state detecting means is the internal combustion engine of a manual transmission vehicle. The prohibition means is used when it is detected that the operation state of the vehicle is at the time of low rotation and high load.

Accordingly, the prohibiting means is used in the predetermined section where the swinging is likely to occur. In particular, in a manual transmission vehicle, since the internal combustion engine and the vehicle drive shaft (transmission) are directly connected, if a single-shot misfire occurs, the vehicle is likely to swing back. Further, by using the prohibiting means when the internal combustion engine is at a low rotation speed and a high load as a state in which the vehicle is likely to roll back, it is determined that the vehicle is traveling on a rough road even though the vehicle is not traveling on a rough road. Can be prevented beforehand.

According to a fifth aspect of the present invention, there is provided a misfire detecting apparatus for an internal combustion engine according to the third aspect, wherein the operating state detected by the operating state detecting means is a vehicle having a continuously variable transmission. The prohibiting means is used when it is detected that the operating state of the internal combustion engine is at low rotation and high intake pipe pressure.

Thus, the prohibiting means is used in the predetermined section in which swinging is likely to occur. Particularly, in a vehicle having a continuously variable transmission, since the internal combustion engine is directly connected to the vehicle drive shaft (transmission), if a single misfire occurs, the vehicle is likely to roll back. Also, by using the prohibiting means when the internal combustion engine is at a low rotation speed and a high load as a state in which the vehicle is likely to roll back, it is determined that the vehicle is traveling on a rough road even though the vehicle is not traveling on a rough road. Can be prevented beforehand.

According to a sixth aspect of the present invention, there is provided a misfire detection apparatus for an internal combustion engine according to the third aspect.
As the operating state detected by the operating state detecting means, the prohibiting means is used particularly when it is detected that the operating state of the internal combustion engine of the automatic transmission vehicle is at low rotation speed and high load.

Thus, in particular, in the automatic transmission, the internal combustion engine is in a state where the drive shaft of the vehicle is directly connected, the torque converter of the automatic transmission vehicle is in a lockup state, and the operation state of the internal combustion engine is a low rotation high intake air. By using the prohibiting means at the time of pipe pressure, it can be prevented beforehand that it is determined that the vehicle is traveling on a rough road even though the vehicle is not traveling on a rough road.

[0015]

<First Embodiment> A first embodiment of the present invention will be described below with reference to the drawings. First, FIG. 2 is a schematic configuration diagram showing a six-cylinder internal combustion engine 2 (hereinafter, simply referred to as an internal combustion engine) to which the present invention is applied and peripheral devices thereof. As shown in FIG. 2, the internal combustion engine 2 has an intake pressure sensor 6 for detecting the pressure in the intake pipe 4 (intake pipe pressure) and a water temperature sensor 8 for detecting the temperature of the cooling water. A rotation angle sensor 10 attached to a crankshaft of the internal combustion engine 2 and generating a pulse signal every time the internal combustion engine 2 rotates a predetermined crank angle (30 ° CA in this embodiment), and a high voltage generated by the igniter 12 Attached to a distributor 14 that sequentially distributes to a spark plug (not shown) provided in each cylinder of the internal combustion engine 2, once per rotation of the distributor 14 (two rotations of the internal combustion engine 2).
A cylinder discrimination sensor 16 that generates a pulse signal at a rate of once per rotation) is provided.

The detection signals from these sensors are input to an electronic control unit (ECU) 20. The ECU 20
It is composed of a well-known microcomputer mainly composed of a CPU 21, a ROM 22, and a RAM 23, and inputs detection signals from the above-mentioned sensors via an input / output port 25. Further, the CPU 21 follows the control program stored in the ROM 22 in advance and controls the fuel injection amount injected from the fuel injection valve 27 provided in each cylinder of the internal combustion engine 2 and the generation timing of the high voltage of the igniter 12 (that is, the ignition timing ) To perform the engine control process,
From the rotational speed of each cylinder of the internal combustion engine for each explosion stroke, the internal combustion engine 2
Then, a misfire detection process of detecting the misfire of the engine and lighting the warning lamp 29 is executed.

Hereinafter, a misfire detection process, which is a main process according to the present invention, which is executed by the ECU 20 configured as described above, and a failure diagnosis process for turning on the warning lamp 29 in accordance with a misfire detection result by the misfire detection process will be described. , FIG. 3, FIG. 4, FIG. 5, and FIG.

The misfire detection process is performed by the CPU 21 based on an output signal from the rotation angle sensor 10 according to the internal combustion engine 2.
Is interrupted every predetermined crank angle (30 ° CA in this embodiment). When this process is started, first, in step 100, the internal combustion engine 2 is set at 30 ° from the difference between the previous interrupt time and the current interrupt time.
The time T30i required for CA rotation is calculated. Then, in the following step 110, it is determined whether or not any of the cylinders is at the top dead center (TDC). If it is not the top dead center, the process proceeds to step 120, and if it is the top dead center, the process proceeds to step 130. .

In step 120, T30i is set to T30i-1, T30i-1 as a pre-stage for calculating the time required for the internal combustion engine 2 to rotate at 120 ° CA in step 130.
30i-1 is T30i-2, and T30i-2 is T30i-
The routine is terminated after 3 is reached. In step 130, the time T30i required for the 30 ° CA rotation calculated in step 100 is determined by comparing the time T30i with the previous time, the previous time,
T30i, T30i− obtained at the time of the previous execution
The time T120i required for the internal combustion engine 2 to rotate at 120 ° CA is calculated by accumulating the data of all four times, 1, T30i-2, and T30i-3. And step 1
In 40, by calculating the reciprocal of the calculated time T120i, calculates the average rotational speed omega _n between the internal combustion engine 2 rotates 120 ° CA.

Next, in step 150, the average rotational speed omega _n and the previous calculated this time, 3 times before, and the average four times was calculated before the rotation speed _{ω n-1, ω n-} 3, and omega _n-4 Based on
The change amount Δω _n of the rotation speed of the internal combustion engine 2 is calculated as follows using the following equation.

[0021]

Δω _n = (ω _n−1 −ω _n ) − (ω _n−4 −ω _n−3 ) In the above equation 1, (ω _n−1 −ω _n ) and (ω
_{n−4− ω n−3} ) is the rotation speed fluctuation amount in the cylinder where the explosion stroke is continuous, and (ω _n−1 −ω _n ) is the latest (ω _n−4).
−ω _n−3 ) is a value before 360 ° CA. Here, in the present embodiment, the internal combustion engine 2 is a six-cylinder internal combustion engine, and the period during which one cylinder is in the explosion stroke alone is 120 ° CA before the top dead center of the cylinder that enters the next explosion stroke. Therefore, first, at steps 100 to 140, the internal combustion engine 2
By calculating the average speed for each CA omega _n, it calculates the rotational speed at power stroke of each engine cylinder. Then, in step 150, the latest rotational speed fluctuation is obtained from the rotational speed and the previously obtained rotational speed, and the internal combustion engine used for the misfire determination is determined from the rotational speed fluctuation and the rotational speed fluctuation before 360 ° CA. and to calculate the second rotation speed variation [Delta] [omega _n.

In this embodiment, the latest rotational speed fluctuation amount and the rotational speed fluctuation amount before 360 ° CA are obtained at the same time by using the above equation (1). If you store it in 360
° By reading CA rotational fluctuation amount before the RAM 23, it is also possible to determine a change amount [Delta] [omega _n without calculating the rotational speed variation of the 360 ° CA before.

Next, at step 160, the current operating state (rotational speed NE, intake pipe pressure PM) is detected.
Proceed to step 170. In step 170, based on the operation state (rotation speed NE, intake pipe pressure PM) detected in step 160, the rotational speed NE and the intake pipe pressure PM stored in the ROM 22 in advance are used as parameters (FIG. 7).
A first determination value (misfire determination value REF) for determining misfire is set by searching a two-dimensional map (REF map) shown in FIG.

Similarly, at step 180, the rotational speed NE
By searching a two-dimensional map (REF ′ map) shown in FIG. 8 in which the vehicle and the intake pipe pressure PM are used as parameters, a second determination value (rough road) for determining that the vehicle is traveling on a rough road is obtained. Determination value REF ′) is set. FIG. 11 shows the relationship between the value of Δω and the frequency during normal ignition (graph A), and the relationship between the value of Δω and the frequency during misfire (graph B). As can be seen from the figure, these are each a graph of a normal distribution. In the present embodiment, as shown in FIG. 11, the map of the misfire determination value REF represents the average value of Δω at the time of misfire measured under each operating condition as xRE.
F, where σ is the standard deviation,

[0025]

## EQU2 ## It is created based on the value set by REF = xREF-3σ. Similarly, in the map of the rough road determination value REF ′, if the average value of Δω during normal ignition measured in each operation state is xREF ′ and the standard deviation is σ ′,

[0026]

## EQU3 ## It is created based on the value set by REF ′ = xREF ′ + 3σ ′. That is, the misfire determination value REF is at least smaller than the variation Δω when misfire occurs on a flat road. Further, the bad road determination value REF ′ is set to a value at least larger than the variation Δω when normal ignition is performed on a flat road. Further, it is assumed that the relationship between REF and REF 'satisfies REF>REF'.

It should be noted, [Delta] [omega _n of the present embodiment REF 'and has been determined from an independent map the REF, the normal and the misfire
If there is a sufficient difference in the values of

[0028]

REF ′ = k × REF (0.45 <k <0.55) The number of bytes in the ROM 22 may be reduced by obtaining REF ′ from the following equation. Note that the k value does not necessarily need to be in the above range, and may be changed as needed as long as it is in the range of 0 <k <1.

In step 200, a misfire determination process for each ignition is executed. Hereinafter, the subroutine of this processing will be described with reference to the flowchart of FIG.

In step 201, step 15 in FIG.
Rotational speed fluctuation Δω calculated at 0 _nAnd the steps in Figure 3
The first determination value REF (hereinafter referred to as REF) calculated in 170 is
Compare. Δω_nIs greater than REF,
Proceed to step 202. In step 202, rough road detection is prohibited.
Input the initial value KCRFSTP to the stop counter CRAFSTP
Power. Initial value KCRFSTP occurs after misfire occurs
Set based on the number of ignitions that will be affected by the bounce
Value. Next, in step 203, step 201
Δω_n> Count of misfire count in response to REF
Increment CMIS.

The process proceeds to step 204 if the [Delta] [omega _n is determined to REF less at step 201, the rough road detection inhibit counter for inhibiting rough road detecting means after the misfire C
It is determined whether or not RAFSTP is 0. If it is 0, it is a section where there is no swaying effect after a misfire, so that step 2 is performed.
Go to 05. In Step 205, Step 15 in FIG.
RE obtained in [Delta] [omega _n and step 180 calculated in 0
Compare F '. [Delta] [omega _n is incremented rough road detection inhibit counter CRAF If REF 'greater. If it is determined in step 204 that CRAFSTP is not 0, the process proceeds to step 207, where CRAFSTP is decremented. In step 208, the discrimination ignition number counter CSPK for making the final misfire determination is incremented, and the step 200 in FIG. 3 ends.

In the flowchart of FIG. 5, by inputting the initial value KCRFSTP to the rough road detection prohibition counter CRAFSTP, the rough road detection prohibition counter CRAFST is input.
Uneven road detection is prohibited until P becomes zero. In other words,
Predetermined section is prevented from being detected despite rough road not being rough road by the reacting roll rotational speed variation [Delta] [omega _n occurring sway-back period after the misfire detection by the rough road detection is not performed. Then, when determining whether or not there is a final misfire, an erroneous determination in which the misfire determination result is invalidated by swinging back is prevented.

The rough road detection prohibition counter CRAFSTP
The same effect can also be obtained by inputting 0 to, and continuing to increment the rough road detection prohibition counter CRAFSTP until it reaches a predetermined value.

Next, at step 210 in FIG.
ω_nΩ for calculation_n-1, Ω_n-2, Ω _n-3And now each
Used ω_n, Ω_n-1, Ω_n-2Is stored in the RAM 23
I do. In step 220, every time the internal combustion engine 2 rotates a predetermined number of times.
To determine whether or not there is a misfire state that should be used for failure determination
It is. This process will be described with reference to the flowchart of FIG.
I do.

In FIG. 4, in step 201, it is determined whether or not the value of the counter CSPK incremented for each ignition in step 208 described above has reached a predetermined value J1. The value of the predetermined value J1 is 10 in a six-cylinder internal combustion engine.
When a failure is determined every 00 rotations, J1 = 3000. Therefore, every predetermined rotation of the internal combustion engine, Step 2
02 and the following processes are executed.

When the ECU 20 determines in step 201 that the predetermined rotation has elapsed, the routine proceeds to step 202, where the value of the misfire number integrating counter CMIS is compared with the misfire state determination value J2. The value of J2 is calculated as follows: if the misfire state to be displayed as a fault every 1000 revolutions is 1% or more of the misfire occurrence rate, J1 = 30.
At 00, J2 = 30. The CMIS value is the prescribed value J2
If it is larger than the predetermined value, the process proceeds to step 20
Go to step 3; if smaller, go to step 205.

In step 203, the rough road discrimination counter C
The value of RAF is compared with the value obtained by multiplying the CMIS value by the rough road discrimination coefficient J3. The value of J3 is a value that is adapted by actually traveling on a rough road that leads to a misfire state erroneous determination, and is, for example, a value of about J3 = 1 to 2. In this embodiment, the rough road is determined by comparing with CMIS × J3, but may be determined by comparing with a predetermined constant such as J2 × J3. If it is determined in step 203 that the bad road determination counter value CRAF is smaller, it is determined that there is no misfire misjudgment due to running on a bad road, and step 2 is performed.
At 04, the misfire detection flag XMF is set to "1".
Otherwise, it is determined that there is a high possibility of misfire detection due to running on a bad road, and the routine proceeds to step 205, where the misfire detection flag XMF is set to "0".

Next, at step 206, each counter CM
IS, CRAF, and CSPK are cleared to 0, and the misfire detection processing ends. Next, the failure diagnosis processing shown in FIG.
The PU 21 performs an interrupt process at predetermined time intervals. First, in step 310, an abnormality detection flag storing information from various sensors for detecting whether the actuator is operating normally, or the misfire detection process When a misfire is determined in step (1), various abnormality detection flags such as a misfire detection flag XMF set to "1" are read.

In the following step 320, step 3
The state of the various abnormality detection flags read in step 10 is determined,
For example, if the misfire detection flag XMF is set to "1", the process proceeds to step 330, and if it is set to "0", the process returns to the main routine. And step 3
In step 30, for example, in order to protect the catalyst and prevent an increase in the concentration of HC in the exhaust gas, the fuel supply to the cylinders determined to be misfired is cut off, or a driver or the like is notified of the misfire occurrence. A well-known fail-safe process corresponding to abnormality detection, such as turning on the warning lamp 29, is executed, and the routine ends.

[0040] Incidentally, in this embodiment, the first misfire detecting means, a result of comparison between the [Delta] [omega _n and REF map is performed in step 150, each time the misfire performed in step 203 is detected This operation corresponds to an operation of incrementing the ignition number integration counter.

The rough road detecting means, bad road and the result by comparison with [Delta] [omega _n and REF 'map, which is performed in step 205, each time it is detected that rough road running performed in step 205 This corresponds to an operation of incrementing the determination counter CRAF.

The prohibition means used in the predetermined section corresponds to an operation of inputting the initial value KCRFSTP to the rough road prohibition counter CRAFSTP in step 202 and an operation of decrementing CRAFSTP to 0 performed in step 207.

The second misfire detecting means compares the misfire count counter CMIS in step 202 with a predetermined value J2, multiplies the misfire count counter CMIS in step 203 by a correction coefficient J3, and a bad road discrimination counter CRAF. , And finally corresponds to the processing of inputting 1 or 0 to the misfire detection flag in steps 204 and 205.

The rotational speed fluctuation amount detecting means performs step 11
The processing is performed in 0, 120, 130, 140, and 150, and corresponds to a routine for calculating Δω _n .

<Second Embodiment> In the first embodiment,
The problem was solved by using the prohibition means in a predetermined section after the misfire was detected. The present embodiment is particularly applied to a manual transmission vehicle in which a vehicle drive shaft is directly connected to an internal combustion engine or a vehicle having a continuously variable transmission. In such a configuration, by applying the prohibition means based on the driving state,
It is possible to prevent an erroneous road from being erroneously detected in a predetermined section in which swinging after a misfire occurs is likely to occur.

Hereinafter, the present embodiment will be described in detail with reference to the flowchart of FIG. The difference from the first embodiment is that a prohibition unit is used between steps 201 and 202 in FIG. 5 based on the parameters detected by the operation state detection unit. The operating state detecting means detects the rotational speed and the high load state (for example, the intake pipe pressure) of the internal combustion engine 2, but may include the gear position in addition to this condition. Furthermore, different parameters may be used as long as the occurrence of swaying can be detected. Internal combustion engine 2
The operation state in which the backlash occurs in the range is a region where the internal combustion engine 2 has a low rotational speed and a high load (for example, a high intake pipe pressure). Therefore, in step 501, it is determined whether or not the rotation speed of the internal combustion engine 2 is, for example, 1500 rpm or less, and if it is 1500 rpm or more, the process proceeds to step 203. When the rotation speed is equal to or less than 1500 rpm, the process proceeds to step 502. In step 502, it is determined whether the intake pipe pressure of the internal combustion engine 2 is larger than, for example, 300 mmHg. If it is smaller than 300 mmHg, the process proceeds to step 203;
Step 202 and subsequent steps are the same as in the first embodiment.

Further, in the case of an automatic transmission vehicle (hereinafter, referred to as an AT vehicle), a backlash occurs while the torque converter is locked up. Therefore AT
In a car, the locked-up state may be determined.
For example, a lock-up signal is input from a control unit for an AT vehicle, or if there is no signal, a parameter signal (for example, vehicle speed, throttle opening, etc.) for controlling lock-up is used.

In the first embodiment, in the failure diagnosis process shown in FIG. 4, the judgment values of the misfire number integrating counter CMIS and the bad road detection prohibition counter CRAF are individually provided, but as shown in FIG. Step 203: CMIS and CRAF
May be determined to be misfire if CMIS is large.

Further, in the first embodiment, the fixed value of KCRFSTP is set as the initial value of the bad road determination prohibition section after the misfire determination, and the section using the prohibition means is the same in all operating states. However, the present invention is not limited to this, and a map for each driving state may be provided according to the amount of influence of the swing back. Since a predetermined section according to the driving state can be set by this map, misfire determination can be performed with higher accuracy.

In this embodiment, the operating state detecting means comprises:
This corresponds to a process of reading the intake pipe pressure PM and the rotational speed NE of the internal combustion engine performed in step 160.

[Brief description of the drawings]

FIG. 1 is an actual timing chart of the present embodiment.

FIG. 2 is a configuration diagram of an embodiment in which the present invention is applied to a six-cylinder internal combustion engine.

FIG. 3 is a main flowchart of a misfire detection process executed by an ECU of the embodiment.

FIG. 4 is a flowchart of a failure diagnosis process executed by the ECU of the embodiment.

FIG. 5 is a flowchart of a misfire determination process for each ignition executed by the ECU of the embodiment.

FIG. 6 is a flowchart of a failure diagnosis process executed by the ECU of the embodiment.

FIG. 7 is an explanatory diagram illustrating a REF map according to the present embodiment.

FIG. 8 is an explanatory diagram showing a REF ′ map according to the present embodiment.

FIG. 9 is a flowchart of a misfire determination process executed by the ECU of the embodiment.

FIG. 10 is a flowchart of a misfire determination process executed by the ECU of the embodiment.

FIG. 11 is a normal distribution diagram showing the relationship between the value of Δω and the frequency of appearance during misfire and during normal ignition.

[Brief description of reference numerals]

 Reference Signs List 2 internal combustion engine 4 intake passage 6 intake pressure sensor 8 engine water temperature sensor 10 rotation angle sensor 20 ECU (electronic control device) 21 ROM (read only memory) 22 RAM (random access memory) 24 input / output port 29 warning lamp

Claims (6)

[Claims] A first misfire detecting means for detecting a misfire for each ignition of the internal combustion engine and counting the number of times the misfire is detected; and detecting that the vehicle is traveling on a bad road. A bad road running detecting means for counting the number of times that the running is detected, a predetermined section which is affected by a backfire due to the misfire after the first misfire is detected by the first misfire detecting means, Prohibiting means for prohibiting detection of bad road travel; final misfire detection based on the number of misfire determinations detected by the first misfire detection means and the number of bad road determinations counted by the bad road travel detection means. The second to determine the presence
And a misfire detecting means for an internal combustion engine. 2. The misfire detection device for an internal combustion engine according to claim 1, wherein the rotational speed fluctuation amount calculating means for calculating the fluctuation amount of the rotational speed based on the rotational speed of the internal combustion engine; When the rotation speed fluctuation amount calculated by the rotation speed fluctuation amount calculation means is smaller than a first determination value and larger than a second determination value smaller than the first determination value, the vehicle is traveling on a rough road. A misfire detection device for an internal combustion engine, wherein the misfire is detected and counted. 3. An apparatus for detecting a misfire of an internal combustion engine according to claim 1, further comprising an operating state detecting means for detecting an operating state of the internal combustion engine, wherein said prohibiting means is provided with a predetermined operating state by said operating state detecting means. A predetermined section after misfire detection when it is detected that the vehicle is in the operating state,
An apparatus for detecting misfire of an internal combustion engine, which prohibits detection of running on a rough road. 4. An apparatus for detecting a misfire of an internal combustion engine according to claim 1, wherein the operating state detecting means is configured to operate the internal combustion engine of the manual transmission vehicle at a low rotational speed and a high load. Means for detecting whether or not there is, when the prohibition means, when the operating state detection means detects that the internal combustion engine of the manual transmission vehicle is at low rotation high load, after the misfire detection An apparatus for detecting a misfire of an internal combustion engine, which prohibits detection of running on a rough road in a predetermined section. 5. The apparatus for detecting a misfire of an internal combustion engine according to claim 1, wherein the operating state detecting means is configured such that the internal combustion engine of a vehicle having a continuously variable transmission has a low rotational speed. Means for detecting whether or not a load is present, wherein the prohibiting means is that the internal combustion engine of the vehicle equipped with the continuously variable transmission is at a low rotation speed and a high intake pipe pressure by the operating state detecting means. A misfire detection device for an internal combustion engine, wherein the misfire detection device is used in the predetermined section where the swingback is large when detected, and the prohibiting means is used in the predetermined section. 6. The misfire detecting device for an internal combustion engine according to claim 1, wherein the operating state detecting means is configured to lock a torque converter of an automatic transmission vehicle, and The automatic transmission vehicle is a means for detecting whether the internal combustion engine of the automatic transmission vehicle is at low rotation high load, the prohibition means, the operating state detection means the automatic transmission vehicle torque converter is locked up, and, A misfire detection device for an internal combustion engine, wherein when the internal combustion engine of the automatic transmission vehicle is detected to have a low rotation and a high load, detection of traveling on a bad road for a predetermined section after the detection of the misfire is prohibited.