JP2890094B2 - Misfire diagnosis device for multi-cylinder internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misfire diagnosis apparatus for a multi-cylinder internal combustion engine.

[0002]

2. Description of the Related Art As a conventional misfire diagnosis apparatus for a multi-cylinder internal combustion engine, a crank angle sensor detects a crank angle of 720 ° / n (n).
Is generated for each cylinder) and the cycle of the reference signal corresponding to the combustion state of each cylinder is continuously measured. Based on the cycle of the continuously measured reference signal, the presence or absence of a misfire is determined according to these fluctuation states. There is one that makes a judgment (Japanese Utility Model Laid-Open No. 5-171).
No. 72).

[0003]

However, when misfire diagnosis is performed in accordance with the fluctuation state of the cycle of the reference signal, the cycle of the reference signal corresponding to the combustion state of each cylinder is as follows.
Even if the engine operating condition is constant, there is a problem that accurate misfire diagnosis cannot be performed unless this effect is removed because not only the presence or absence of misfire but also the combustion variation between cylinders is affected. .

SUMMARY OF THE INVENTION [0004] In view of the above-mentioned conventional problems, an object of the present invention is to improve the accuracy of misfire diagnosis by learning the variation in combustion between cylinders for each region of the engine operating state.

[0005]

To this end, the present invention is configured as shown in FIG. That is, the crank angle is 720 °
/ N (n is the number of cylinders), a reference signal generating means A for generating a reference signal including a cylinder discrimination signal, a cycle measuring means B for measuring a cycle of the reference signal corresponding to the combustion state of each cylinder, and And misfire determining means C for determining the presence or absence of a misfire in each cylinder based on the cycle of the reference signal.

The cycle average value calculating means D for calculating the average value of the cycle of the reference signal of all the cylinders while the misfire determination means C determines that there is no misfire, the cycle of the reference signal of each cylinder, Ratio calculating means E for calculating the ratio to the average value
And a correction coefficient storage means F for storing a correction coefficient for each cylinder set based on the ratio for each region of the engine operating state.

[0007] Between the cycle measuring means B and the misfire determination means C, the cycle of the reference signal of each cylinder obtained by the cycle measuring means B is stored in the storage means F for each region of the engine operating state. The misfire determination means C is corrected based on the corrected cycle for each cylinder, and based on the corrected cycle.
Is provided. Here, the storage means F sets a new correction coefficient based on the correction coefficient for each cylinder already stored for each region of the engine operating state and the ratio calculated by the ratio calculation means E, It is preferable to have a correction coefficient updating means f for updating the stored value.

When the correction coefficient for each cylinder corresponding to the area of the current engine operation state is not stored in the storage means F, the period correction means G determines whether the engine speed in the engine operation state is low. It is preferable to have a correction coefficient estimating means g for estimating a correction coefficient from a correction coefficient for each cylinder stored corresponding to another equal region.

[0009]

In the above arrangement, prior to the misfire determination,
The cycle of the reference signal measured corresponding to the combustion state of each cylinder is corrected by the correction coefficient for each cylinder in each region of the engine operation state, thereby avoiding the combustion variation between cylinders. For this reason, the average value of the cycle of the reference signal of all the cylinders during which it is determined that there is no misfire is calculated, and the ratio between the cycle of the reference signal of each cylinder and the average value is calculated.
Then, a correction coefficient for each cylinder is set based on the ratio and stored for each region of the engine operating state. By using such a correction coefficient for each cylinder and each region of the engine operating state,
It is possible to avoid combustion variations between cylinders.

When setting and storing the correction coefficient,
By setting a new correction coefficient based on the already stored correction coefficient and the ratio, and updating the stored value,
Learning reliability can be improved. Until the learning of each region of the engine operating state is completed, by estimating by referring to the correction coefficient stored corresponding to another region of the engine operating state having the same engine speed, Correction can be started immediately.

[0011]

An embodiment of the present invention will be described below. Incidentally, 4
In the cylinder internal combustion engine, the ignition order is # 1 → # 3 → # 4 → # 2
And FIG. 2 shows a system configuration. The control unit 10 has a built-in microcomputer, performs arithmetic processing based on signals from various sensors, and has a fuel injection valve 2 provided for each cylinder (# 1 to # 4) of the engine 1.
And controls the operation of the ignition coil 3.

The various sensors include a crank angle sensor 11, an air flow meter 12, and an idle switch 13. The crank angle sensor 11 detects the crank angle.
A reference signal for every 180 ° and a unit signal for every unit crank angle (1-2 °) are output, whereby the crank angle can be detected and the engine speed N can be detected. The reference signal includes a cylinder discrimination signal. For example, by increasing the pulse width of the reference signal corresponding to the # 1 cylinder,
Cylinder discrimination is possible. This crank angle sensor forms reference signal generating means.

The air flow meter 12 is, for example, a hot wire type,
The intake air flow rate Q can be detected. Idle switch 13
Turns ON when the fully closed position of the throttle valve is detected. Here, the control unit 10 determines the basic fuel injection amount Tp = K based on the intake air flow rate Q and the engine speed N.
Calculate Q / N (K is a constant), make various corrections to this, and make the final fuel injection amount Ti = Tp · COEF (COFF
Are determined, and a drive pulse signal having a pulse width corresponding to the Ti is output to the fuel injection valve 2 of each cylinder at a predetermined timing synchronized with the engine rotation to cause fuel injection. However, during deceleration, the idle switch 13 is ON,
When the engine speed N is equal to or higher than the predetermined fuel cut speed as a trigger, the output of the drive pulse signal to the fuel injection valve 2 is stopped, and the fuel is cut. This fuel cut is released when the engine speed N becomes lower than a predetermined recovery speed or when the idle switch 13 is turned off.

The control unit 10 determines an ignition timing based on the engine speed N and the basic fuel injection amount Tp, and controls the operation of the ignition coil 3 at that timing.
Cause ignition. Further, the control unit 10 determines the presence or absence of a misfire in each cylinder according to a misfire diagnosis routine shown in FIGS. 3 and 4, and issues a warning by a warning lamp or the like in a predetermined case.

The misfire diagnosis routine shown in FIGS.
This will be described with reference to FIG. This routine is executed in synchronization with the generation of the reference signal from the crank angle sensor. In step 1 (shown as S1 in the figure, the same applies hereinafter), in the case of four cylinders, the latest value of the cycle of the reference
(T1 to T5) are stored and the misfire determination is performed based on these, so that the previously used cycle is replaced as follows.

T5 ← T4, T4 ← T3, T3 ← T2, T2 ← T1 In addition, the time count value of the timer is read and set as T1 (T
1 ← timer). This timer starts at 0 in the previous routine, and the cycle of the latest reference signal is measured as T1. Therefore, this part corresponds to the period measuring means. In step 2, the timer is reset and started at 0 for the next measurement.

In step 3, the cylinder is discriminated, that is, the cylinder for which the combustion has almost finished at the present time is determined. Here, the cylinder whose cylinder has been determined is defined as i. Thus, the current misfire determination cylinder becomes the cylinder i, and the cycle of the reference signal corresponding to the combustion state of the cylinder i is measured as T1.
Since the ignition order is # 1 → # 3 → # 4 → # 2,
Assuming that the cylinder preceding the cylinder i in the ignition order is i-1, the cylinder preceding the cylinder i is i-2, and the cylinder preceding the cylinder i is i-3, the correspondence is as shown in the following table.

[0018]

[Table 1]

In step 4, it is determined whether a learning condition is satisfied. Here, the learning conditions include the engine speed N and the basic fuel injection amount (load), which are determined to be no misfire during the previous four periods T2 to T5, and are parameters of the engine operating state. ) Assume that there is no extreme change in Tp. Only when the learning condition is satisfied, steps 5 to 9 are executed for learning.

In step 5, as the cycle of the reference signal of all cylinders, the average value of the preceding four cycles T2 to T5 is calculated as T _AVE according to the following equation. This part corresponds to a period average value calculation unit. T _AVE = (T2 + T3 + T4 + T5) / 4 In step 6, the ratio (correction coefficient) KT1 between the cycle (latest cycle) T1 of the reference signal of the cylinder i and the average value T _AVE is calculated according to the following equation. This part corresponds to the ratio calculating means.

KT1 = T1 / T _{AVE In} step 7, the map of the cylinder i is selected from the maps provided for each cylinder, and the engine speed N and the basic fuel injection amount (load) Tp are selected from the selected map. DOO correction coefficient is stored as a parameter KT _i (correction factor corresponding to the current engine speed N and the basic fuel injection amount Tp KT
Read _i ). Note that KT _i = 1 before learning.

In step 8, based on the correction coefficient KT _i read in step 7 and the ratio (correction coefficient) KT1 calculated in step 6, a new correction coefficient K
Setting the T _i. x is a weighting constant. KT _i = [(x−1) / x] KT _i + (1 / x) KT1 In step 9, the newly set KT _i is calculated based on the current engine speed N and the basic fuel injection amount Tp in the map of the cylinder i. And updates the stored value.

Accordingly, the steps 7 to 9 correspond to correction coefficient storage means (including correction coefficient update means). In step 10, it is determined whether learning has been completed, that is, learning (writing to the map) of the correction coefficient has been performed a predetermined number of times or more for each cylinder.

In step 11, it is determined whether or not the area of the current engine operating state (N, Tp) is a learned area. If it is a learned area, the process proceeds to step 12, and if it is not learned, a step is performed. Proceed to 13. In step 12, the correction coefficients KT _{i to} KT _i-3 in the regions corresponding to the current engine speed N and the basic fuel injection amount Tp are searched from the maps of the cylinders i to (i-3), and step 14 is performed. Proceed to.

In step 13, the correction coefficients KT _{i to} KT _i-3 in other areas corresponding to the current engine speed N are searched from the map of the cylinders i to (i-3), and the routine proceeds to step 14.
That is, when the correction coefficient is not stored corresponding to the area of the current engine operating state, by using the correction coefficient stored corresponding to another area having the same engine speed among the engine operating states, Estimate the correction coefficient.

In step 14, the cycle data (T1 to T5) of the reference signal for misfire determination is corrected by the following equation using a correction coefficient for each cylinder, and the corrected cycle data (HT
1 to HT5). HT1 = T1 / KT _i HT2 = T2 / KT _i−1 HT3 = T3 / KT _i−2 HT4 = T4 / KT _i−3 HT5 = T5 / KT _i Therefore, steps 11 to 14 correspond to the period correction means (correction). (Including coefficient estimation means).

In step 15, the misfire determination value M is calculated from the corrected cycle data (HT1 to HT5) according to the following equation.
Calculate ISA. Thereafter, the process proceeds to step 17. MISA = [3 × (HT4-HT5) + (HT4-HT
1)] / HT5 ³ If it is determined in step 10 that the learning has not been completed, the process proceeds to step 16 where the data of the period without correction (T1 to T
From 5), the misfire determination value MISA is calculated according to the following equation. Thereafter, the process proceeds to step 17.

MISA = [3 × (T4-T5) + (T4
In -T1)] / T5 ³ step 17, by referring to a map of the engine speed N and the basic fuel injection quantity Tp as parameters, sets the reference value SL for determining misfire. In step 18, the misfire determination value MI
SA is compared with the reference value SL, and if MISA ≧ SL, the routine proceeds to step 19, where it is determined that a misfire has occurred. Therefore, step 15
Portions to 19 correspond to misfire determination means.

Note that the misfire determination value is the above-mentioned MISA.
Can be used instead of the following MISB. MISB = [2 × (HT3-HT5) + 2 × (HT3-
HT1)] / HT5 ³ or, MISB = [2 × (T3-T5) + 2 × (T3-T
1)] / T5 ³ Also, for this MISB, the latest three values (MISB
1 to MISB3) are stored, and as a misfire determination value,
The following MISC may be used.

MISC = MISB2-MISB3 For these misfire determination values, MISB ≧ predetermined value, M
If ISC ≧ predetermined value, it is determined that a misfire has occurred. If it is determined that a misfire has occurred, it is of course necessary to determine the misfire cylinder,
An alarm or the like is issued according to the number of consecutive times.

[0031]

As described above, according to the present invention, there is obtained an effect that accurate misfire diagnosis can be performed without being affected by combustion variation between cylinders. In addition, when setting and storing the correction coefficient, the reliability of learning can be improved by updating in consideration of the correction coefficient already stored.

Until the learning of the engine operating state for each region is completed, a technique called estimation is used,
Correction can be started immediately.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a system diagram showing one embodiment of the present invention.

FIG. 3 is a flowchart of a misfire diagnosis routine (part 1).

FIG. 4 is a flowchart of a misfire diagnosis routine (part 2);

FIG. 5 is a diagram showing a state of a change in a cycle due to a variation in combustion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Fuel injection valve 3 Ignition coil 10 Control unit 11 Crank angle sensor

Claims (3)

(57) [Claims] 1. A reference signal generating means for generating a reference signal including a cylinder discrimination signal at every crank angle of 720 ° / n (n is the number of cylinders), and measuring a cycle of the reference signal corresponding to a combustion state of each cylinder. In a misfire diagnosis apparatus for a multi-cylinder internal combustion engine, comprising: a cycle measurement means; and a misfire determination means for determining whether or not each cylinder has a misfire based on the cycle of the measured reference signal. Cycle average value calculating means for calculating the average value of the cycle of the reference signal of all cylinders during the operation, ratio calculating means for calculating the ratio of the cycle of the reference signal of each cylinder to the average value, and Correction coefficient storage means for storing the correction coefficient for each cylinder set for each region of the engine operating state, and between the cycle measurement means and the misfire determination means, obtained by the cycle measurement means. Reference signal for each cylinder Cycle correction means for correcting the cycle of the signal by a correction coefficient for each cylinder stored in the storage means for each region of the engine operating state, and making a determination by the misfire determination means based on the corrected cycle. A misfire diagnosis device for a multi-cylinder internal combustion engine, characterized in that: 2. The storage means sets a new correction coefficient based on a correction coefficient for each cylinder already stored for each region of the engine operating state and a ratio calculated by the ratio calculation means, 2. The misfire diagnosis apparatus for a multi-cylinder internal combustion engine according to claim 1, further comprising a correction coefficient updating unit for updating a stored value. 3. The method according to claim 1, wherein the cycle correcting means is configured to determine whether the engine operating speeds are equal when the correction coefficient for each cylinder corresponding to the current engine operating state area is not stored in the storage means. 3. A multi-cylinder internal combustion engine according to claim 1, further comprising a correction coefficient estimating means for estimating a correction coefficient from a correction coefficient for each cylinder stored corresponding to the region of (1). Misfire diagnostic device.