JPH0754705A - Misfire detection device for internal combustion engine - Google Patents

Abstract

(57) [Abstract] [Purpose] When misfire is detected based on the rotational fluctuation of an internal combustion engine, it is possible to prevent erroneous determination of misfire due to rotational fluctuation of wheels caused by a change in road surface. [Structure] Rotational speed VF of wheels of a vehicle equipped with an engine
R, VFL, VRR, and VRL are measured (step S5
1), their speed difference (speed difference ΔVRI between right and left front wheels,
Speed difference ΔVLE between left and right front wheels, speed difference ΔVF between left and right front wheels
R or the rear wheel left / right speed difference ΔVRE) is a predetermined value Δ
When it is larger than VLMT, it is determined that there is a wheel speed fluctuation (steps S53 to S56, S58). When it is determined that the wheel speed has changed, the misfire determination is prohibited.

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 misfire of an internal combustion engine.

[0002]

2. Description of the Related Art Various misfire detection devices for internal combustion engines have been proposed in the past, but the applicant of the present application has found that transient illegal combustion occurs depending on the operating condition of the engine or the operating condition of the vehicle in which the engine is mounted. Considering the pressure in the intake pipe of the engine,
It has been proposed that the misfire determination be prohibited during a transient operation state in which a change in the throttle valve opening or the traveling speed of the vehicle is large, or during low-load traveling such as traveling downhill in a highland. Wishhei 4-148930
issue). This is because the misfire detection device is intended to detect a steady misfire state caused by an abnormality (system abnormality) of the engine and its control device.

[0003]

However, in a device that detects a misfire based on engine speed fluctuations, for example, when traveling on a bad road, wheel rotation fluctuations occur due to road surface changes even in steady operation. As a result, the crankshaft of the engine may fluctuate in rotation, and misfire may be erroneously determined.

The present invention has been made in view of this point, and provides a misfire detection device capable of preventing misjudgment during traveling on a bad road or the like and more reliably detecting misfire caused by system abnormality. The purpose is to do.

[0005]

In order to achieve the above object, the present invention provides a misfire detecting device equipped with a misfire determining means for determining a misfire state of an internal combustion engine mounted on a vehicle based on a rotational fluctuation of the engine. A wheel speed detecting means for detecting a rotation speed of a wheel of the vehicle; a wheel speed fluctuation amount calculating means for calculating a fluctuation amount of the detected wheel speed; and a calculated wheel speed fluctuation amount larger than a predetermined fluctuation amount. The prohibiting means for prohibiting the judgment by the misfire judging means is provided.

[0006]

When the fluctuation amount of the vehicle wheel speed is larger than the predetermined fluctuation amount, the misfire determination is prohibited.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of an internal combustion engine (hereinafter referred to as “engine”) and a control system therefor according to an embodiment of the present invention. A throttle valve 3 is arranged in the middle of an intake pipe 2 of an engine 1. Has been done. A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3 and outputs an electric signal according to the opening of the throttle valve 3 to supply it to an electronic control unit (hereinafter referred to as “ECU”) 5. .

The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve (not shown) of the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). The valve opening time of fuel injection is controlled by a signal from the ECU 5 that is electrically connected to the ECU 5.

On the other hand, a pipe 7 is provided immediately downstream of the throttle valve 3.
The intake pipe absolute pressure (PBA) sensor 8 is provided via the, and the absolute pressure signal converted into an electric signal by the absolute pressure sensor 8 is supplied to the ECU 5. Further, an intake air temperature (TA) sensor 9 is attached downstream thereof,
EC is detected by detecting the intake air temperature TA and outputting the corresponding electric signal.
Supply to U5.

The engine water temperature (TW) sensor 10 mounted on the main body of the engine 1 is composed of a thermistor or the like, detects the engine water temperature (cooling water temperature) TW, outputs a corresponding temperature signal and supplies it to the ECU 5.

A signal pulse (hereinafter referred to as "CYL signal pulse") is generated around a cam shaft (not shown) or a crank shaft of the engine 1 at a predetermined crank angle position of a specific cylinder of the engine 1.
Cylinder discrimination sensor (hereinafter referred to as “CYL sensor”) 13 for outputting a crank angle position that is a predetermined crank angle before the top dead center (TDC) at the start of the intake stroke of each cylinder (a crank angle of 180 for a 4-cylinder engine). Every °) T
A TDC sensor 12 that generates a DC signal pulse, and one pulse (hereinafter “CRK signal pulse”) at a constant crank angle (for example, 30 °) cycle shorter than the cycle of the TDC signal pulse.
A crank angle sensor (hereinafter, referred to as “CRK sensor”) 11 for generating a CYL signal pulse, a TDC signal pulse, and a CRK signal (crank angle signal) pulse are supplied to the ECU 5.

A spark plug 19 is provided in each cylinder of the engine 1.
It is provided and is connected to the ECU 5 via the distributor 18.

The three-way catalyst (catalyst device) 15 is arranged in the exhaust pipe 14 of the engine 1 and is used for HC and C in the exhaust gas.
Purify components such as O and NOx. An oxygen concentration sensor 16 (hereinafter referred to as “O ₂ sensor 16”) as an air-fuel ratio sensor is attached to the exhaust pipe 14 on the upstream side of the three-way catalyst 15. The O ₂ sensor 16 is an oxygen sensor in the exhaust gas. The ECU 5 detects the concentration and outputs an electric signal according to the detected value.
Supply to.

In the ECU 5, the rotational speed VFR (right front wheel), VFL (left front wheel), and driven wheel (rear wheel) rotational speed VRR (right rear wheel) of a drive wheel (front wheel) of a vehicle further equipped with the engine 1 are provided. ) And VRL (left rear wheel) are respectively connected to wheel speed sensors 21 to 24, and these detection signals are supplied to the ECU 5. The traveling speed VSP of the vehicle is calculated based on the driven wheel speeds VRR and VRL.

A switch 25 for various electric loads such as an air conditioner and a speed change mechanism 26 are connected to the ECU 5, and signals indicating the on / off state of the switch 25 and the state of the speed change mechanism are input to the ECU 5. The transmission mechanism 26 is a known automatic transmission mechanism or manual transmission mechanism.

The ECU 5 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, and the like, a central processing circuit (hereinafter referred to as "the central processing unit"). "CPU"),
It is composed of storage means for storing various calculation programs executed by the CPU and calculation results, an output circuit for supplying drive signals to the fuel injection valve 6, the distributor 18, and the like.

The CPU of the ECU 5 discriminates various engine operating states such as a feedback control operating region and an open loop control operating region according to the oxygen concentration in the exhaust gas based on the various engine parameter signals described above, and at the same time, the engine operating Depending on the state, the fuel injection time Tout of the fuel injection valve 6 synchronized with the TDC signal pulse is calculated based on the following equation (1).

Tout = Ti × KO2 × K1 + K2 (1) Here, Ti is the basic fuel injection time determined in accordance with the basic fuel amount, specifically, the engine speed NE and the intake pipe absolute pressure PBA. , Ti for determining this Ti value
The map is stored in the storage means.

[0020] KO2 represents an air-fuel ratio correction coefficient calculated based on the output of the O ₂ sensor 16, the air-fuel ratio in the feedback control the air-fuel ratio detected by the O ₂ sensor 16 (oxygen concentration) of the target air-fuel ratio Set to match,
During open loop control, it is set to a predetermined value according to the engine operating state.

K ₁ and K ₂ are other correction coefficients and correction variables calculated according to various engine parameter signals, respectively, and various characteristics such as fuel consumption characteristics and engine acceleration characteristics according to the engine operating state can be optimized. It is set to the value as shown.

The CPU of the ECU 5 further controls the ignition timing θIG.
Is calculated according to the engine operating state, and a drive signal for the fuel injection valve 6 according to the Tout value and a drive signal for the spark plug 19 according to the θIG value are output via the output circuit.

The ECU 5 constitutes misfire determination means, wheel speed fluctuation amount calculation means and prohibition means.

FIG. 2 is a flow chart of a program for making a misfire determination based on the rotation fluctuation of the crankshaft of the engine 1 and a system abnormality determination based on the result, and this program is synchronized with this every time a TDC signal pulse is generated. To be executed.

In step S1, it is determined whether or not a monitor condition, that is, a condition for permitting execution of misfire determination is satisfied. Whether or not this monitor condition is satisfied is determined by the program shown in FIG. 3 described later.

When the monitor condition is not satisfied, the process immediately proceeds to step S10, and the monitor condition judgment program (FIG. 3).
Restart (monitor restart).

When the monitor condition is satisfied, the process proceeds to step S2 to measure the rotation fluctuation of the crankshaft.

That is, the rotation time T of 210 ° of the crankshaft
REV (n) is measured based on the CRK signal pulse,
Crankshaft rotation time TREV (n-1) during the previous loop
The deviation ΔTREV (n) from

Then, this deviation ΔTREV (n) is converted into three deviations ΔTREV (n−1), Δ calculated previously.
The average value of TREV (n−2) and ΔTREV (n−3) is compared, and the difference is calculated as the rotation fluctuation amount ΔΔTREV (n).

Next, in step S3, the transmission 26
A misfire determination map is selected according to the type of the above and the clutch engagement state, and the misfire determination value MFDEL is calculated. The rotation fluctuation amount ΔΔTREV (n) is the misfire determination value MF.
When it is larger than DEL, it is determined that a misfire has occurred, and the flag FMF is set to "1". On the contrary, when it is smaller, the flag FMF is set to "0".

Here, the misfire determination map is the misfire determination value MFD based on the engine speed NE and the intake pipe absolute pressure PBA.
The EL is searched, and the misfire determination value MFDEL is searched based on the selected misfire determination map.

Next, in step S4, it is determined whether or not the flag FMF is "1", and if it is "0", immediately in step S4.
8, the process proceeds to step S5 if "1", and the misfiring cylinder is discriminated. Specifically, the misfiring cylinder is determined by the number of times the TDC signal pulse is generated after the CYL signal pulse is generated and the misfire is detected.

After determining the misfiring cylinder, step S6
Then, it is determined whether or not the misfire has continued for a predetermined number of times Nc or more. Here, the predetermined number of times Nc is four in the case of a four-cylinder engine.

That is, in the case of continuous misfire, the misfire cylinder determination routine determines the misfire cylinder each time the TDC determination signal is generated. Therefore, the number N of consecutive misfires is counted to determine whether or not the N value is equal to or greater than the Nc value. .

When the number of consecutive misfires N is less than Nc, the process proceeds to step S8. When the number of consecutive misfires is Nc or more, the process proceeds to step S7. The number of consecutive misfires N is not regarded as a misfire as the number of misfires NMF, and the process proceeds to step S8.

In step S8, T after the monitor restart
The number of times the DC signal pulse is generated is a predetermined number C (for example, 100
It is determined whether or not the number of times exceeds 0. If the number of times is not exceeded, this program is terminated, and when the number of times is exceeded, the first step S
Proceed to 9 to make an abnormality determination.

In step S9, it is first determined whether or not the crankshaft rotation fluctuation is measured without causing fluctuations in the operating state such as acceleration operation within a predetermined rotation speed after the monitor restart. If the answer is no, Only when the misfire detection process is finished and the answer is affirmative, the misfire rate φ is calculated, and if the predetermined value φ ₀ or more, it is determined to be abnormal, and if less than that, it is determined to be normal. Here, the misfire rate φ is the ratio of the number of misfires NMF to the predetermined number of times C.

After this abnormality determination, the monitor condition determination program (FIG. 3) is restarted (step S10), and this program ends.

FIG. 3 is a flowchart of a program for determining whether or not the monitor condition is satisfied, and this program is executed in the background.

In steps S11 to S16, it is determined whether the engine water temperature TW is lower than a predetermined water temperature TWFMES (for example, 0 ° C.) (step S11), and the intake air temperature TA is the predetermined intake air temperature TA.
Whether it is lower than FMES (for example, 0 ° C.) (step S1)
2), the absolute pressure PBA in the intake pipe is the predetermined pressure PBLMT (15
0 mmHg) or less (step S13), whether fuel cut is in progress (step S14), whether air-fuel ratio lean control is being performed (step S15), and the throttle valve opening θTH is more than a predetermined lower limit opening θTHMONIL. It is determined whether it is small. When any of these determination results is affirmative (YES), the process proceeds to step S26, the down-count timer tMFMONIDLY is set to a predetermined time (for example, 1 second) and started, and it is determined that the monitor condition is not satisfied (step S27). .

On the other hand, when all the answers in steps S11 to S16 are negative (NO), it is judged whether or not the cruise is in progress, that is, whether or not the vehicle is in a constant speed steady running state (step S1).
7). For example, the fluctuation of the vehicle speed VSP is ± 0.8 km / se
If the state within c continues for 2 seconds or more, it is determined that the cruise is in progress.

If the cruise is not in progress, the vehicle is stopped (VSP =
0) or not (step S18), and when the vehicle is stopped, the engine speed NE is a predetermined upper and lower limit value NE when there is no load.
NLLMTH, NENLLMTL (eg 4500 rp
m, 500 rpm) is determined (step S19). If the answer to either step S18 or S19 is negative (NO), then step S2
6, the process proceeds to S27, while it is determined that the monitor condition is not satisfied,
Both answers in steps S18 and S19 are affirmative (YES).
In the case of, it is determined whether or not there is a change in the operating state (step S23). Specifically, the determination in step S23 is performed by the program of FIG. 4 described later.

When there is a change in the operating state, the routine proceeds to steps S26 and S27, where it is determined that the monitor condition is not satisfied, and when there is no change, it is determined whether or not the count value of the timer tMFMONIDLY is 0 (step S2).
4). When tMFMONIDLY> 0, the monitor condition is not satisfied before the predetermined time has elapsed (step S27), and tM
After FMONIDLY = 0, it is determined that the monitor condition is satisfied.

The answer to step S17 is affirmative (YE
S), that is, the predetermined intake pipe internal pressure PBM during cruise
ONI is calculated according to the engine speed NE and the atmospheric pressure PA (step S20), and the detected absolute intake pipe pressure PB is detected.
It is determined whether A is the PBMONI value or more (step S
21). When PBA ≧ PBMONI is satisfied, the engine speed NE is further equal to a predetermined upper and lower limit value NE under load.
RLLMTH, NERLLMTL (for example, 6000 rp
m, 500 rpm).
When both the answers in steps S21 and S22 are affirmative (YES), the process proceeds to step S23. When the answers in step S21 or S22 are negative (NO), the process proceeds to steps S26 and S27, and it is determined that the monitor condition is not satisfied.

As described above, according to the program shown in FIG. 3, it is determined that the monitor condition is satisfied when the operating state of the vehicle including the engine operating state is in a predetermined steady state.

FIG. 4 is a flow chart of a program for judging the fluctuation of the driving state of the vehicle, and the result of the judgment by this program is used in step S23 of FIG.
It should be noted that this program is executed in synchronization with each generation of the TDC signal pulse.

In steps S31 to S39 of FIG. 4, it is determined whether or not the amount of change ΔθTH in the throttle valve opening θTH (calculated as the difference between the previous value and the current value) is larger than a predetermined value THMFDFL (step S31). Absolute pressure PBA
Whether the change amount ΔPBA of the intake air is larger than a predetermined value PBMDFDEL (step S32), whether there is a change in the intake pipe absolute pressure PBA (step S33), an electric load change, specifically, an output current change of the generator. Amount is a predetermined value ΔACGFL
Whether it is larger than MT (step S34), whether the air conditioner switch is turned on or off (step S3)
5) Whether or not the brake switch that is turned on when the brake is activated is turned on or off (step S36), and whether the power steering switch that is turned on when the power steering is activated is turned on or off (step S3)
7), whether or not traction control is in progress (step S38),
It is determined whether there is a wheel speed fluctuation (step S39).

Whether or not there is a change in the PBA value in step S33 is determined by P for a fixed time (for example, 100 msec).
This is different from step S32 in which it is determined whether or not the change amount of the BA value is larger than a predetermined value (for example, 40 mmHg), and it is determined whether or not the change amount ΔPBA at each TDC signal pulse generation is less than or equal to the predetermined value.

The traction control is a control for reducing the output torque of the engine by making the air-fuel ratio lean when the excessive slip state of the drive wheels is detected based on the driven wheel speed and the drive wheel speed.

If any of the answers in steps S31 to S39 is affirmative (YES), it is judged that the driving condition has changed (step S41), and if all the answers are negative (NO), it is judged that the driving condition has not changed. (Step S4
0).

Next, with reference to FIG. 5, the specific contents of the determination of the presence or absence of wheel speed fluctuation (FIG. 4, step S39) will be described.

In step S51 of the figure, the drive wheel speed V
FR, VFL, driven wheel speeds VRR, VRL are measured, and then the speed difference ΔVRI between the right and left front wheels, the speed difference ΔVLE between the left and right front wheels, the speed difference ΔVFR between the left and right front wheels, and the speed difference ΔVRE between the left and right rear wheels are calculated by the following equations. Is calculated (step S
52).

ΔVRI = | VFR-VRR | ΔVLE = | VFL-VRL | ΔVFR = | VFR-VFL | ΔVRE = | VRR-VRL | In the subsequent steps S53 to S56, the speed difference ΔVRI, Δ
It is determined whether or not VLE, ΔVFR, and ΔVRE are larger than a predetermined value ΔVLMT. If any of these determination results is affirmative (YES), it is determined that there is wheel speed fluctuation (step S58) and all are negative (step S58). If NO, it is determined that there is no wheel speed fluctuation (step S57).

As described above, according to the programs shown in FIGS. 3 to 5, when there is a wheel speed fluctuation, it is determined that there is a fluctuation in the operating state of the vehicle (FIG. 4, steps S39 and S41), and the monitor condition is not satisfied. So (FIG. 3, steps S23, S
27), misfire determination by the program of FIG. 2 is prohibited. Therefore, it is possible to avoid a situation where a misfire is erroneously determined due to a change in the wheel speed caused by a change in the road surface while traveling on a rough road, and it is possible to more reliably detect a misfire due to a system abnormality. .

[0055]

As described above in detail, according to the present invention, when the fluctuation amount of the wheel speed is larger than the predetermined fluctuation amount, the misfire determination is prohibited, so that the wheel speed caused by the change of the road surface during the traveling on the rough road. It is possible to avoid a situation where a misfire is erroneously determined due to fluctuations, and it is possible to more reliably detect a misfire due to a system abnormality.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an internal combustion engine and a control device therefor according to an embodiment of the present invention.

FIG. 2 is a flowchart of a program for performing misfire determination and abnormality determination.

FIG. 3 is a flowchart of a program for determining a monitor condition.

FIG. 4 is a flow chart of a program for determining whether or not a driving state of a vehicle has changed.

FIG. 5 is a flowchart of a program for determining whether or not the wheel speed has changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Electronic control unit (ECU) 21 Wheel speed sensor (right front wheel) 22 Wheel speed sensor (left front wheel) 23 Wheel speed sensor (right rear wheel) 24 Wheel speed sensor (left rear wheel)

Claims (1)

[Claims] 1. A misfire detection device including a misfire determination means for determining a misfire state of an internal combustion engine mounted on a vehicle, the wheel speed detection detecting a rotational speed of a wheel of the vehicle. Means, wheel speed fluctuation amount calculating means for calculating the detected fluctuation amount of the wheel speed, and prohibiting means for prohibiting the judgment by the misfire judging means when the calculated wheel speed fluctuation amount is larger than a predetermined fluctuation amount. A misfire detection device for an internal combustion engine, characterized in that