JPH04198732A - Internal combustion engine misfire detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a misfire detection device for an internal combustion engine.

[Conventional technology]

Conventionally, there are various types of misfire detection devices for internal combustion engines, and one equipped with a misfire detection method based on a change in rotational speed is disclosed, for example, in Japanese Patent Laid-Open No. 19532/1983. This device has crank angle detection sensors corresponding to the first and second stages of the expansion stroke of the internal combustion engine, and determines that a misfire has occurred when the difference in rotational speed between the two is equal to or less than a set value.

[Problem to be solved by the invention]

By the way, a misfire in an internal combustion engine not only causes direct air pollution due to unburned gas, but also causes unburned gas to react within the catalyst, causing abnormal temperature rise and burning out the catalyst.It is important to detect this as early as possible. It is necessary to repair the malfunctioning part.

However, even with the conventional device described above, the aim is to increase the sensitivity of misfire detection by detecting the difference in rotational speed at locations where the rotational speed changes greatly, but since the deviation is at a fixed angle of the crankshaft, the ignition timing changes. It was not possible to cope with changes in the angle where the rotational speed changed significantly. (Normally, ignition timing varies from BTDC40" to ATDCIO° (width: about 50°), which is determined by the rotational speed and load.) The present invention solves these problems in view of the above points. It is an object of the present invention to provide a misfire detection device for an internal combustion engine that can detect misfires with high sensitivity over a wide range of operating regions.

[Means to solve the problem]

The misfire detection device according to the present invention is equipped with an ignition control means that optimally controls the ignition timing according to the operating state of the internal combustion engine, and generates a plurality of pulses as an angle signal per revolution of the crankshaft of the internal combustion engine. and a first rotation angular velocity near the ignition timing and a second rotational angular velocity at a point a predetermined crank angle from the ignition timing based on the angle signal and the ignition timing signal accompanying the ignition control means. The misfire detection means determines the rotational angular velocity of the engine and determines an abnormal combustion cylinder of the engine based on the first rotational angular velocity and the second rotational angular velocity.

[Effect]

In the present invention, the rotational angular velocity is detected near the ignition timing and after a predetermined angle using the ignition timing as a reference, and a misfire is determined based on the angular velocity deviation or angular velocity change, that is, the angular velocity ratio. Misfires can be detected.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment in which a misfire detection device according to the present invention is applied to a vehicle electronic control system. In FIG. 1, reference numeral 11 indicates a four-cylinder gasoline engine, and a thermal air flow sensor 12 is disposed in its intake passage, and an air flow rate signal Sa output from the sensor is input to a control unit 15, which will be described later. 13 is a cylinder identification sensor 13 attached to the camshaft of the engine 11 to obtain cylinder identification and rotation information. and a rotation signal sensor 13°, which detects one pulse per rotation of the camshaft as a cylinder identification signal Sb (see Fig. 2 (a)), and detects four pulses as a rotation signal. Sc (Figure 2 (
b)), and these signals Sb and Sc are input to the control unit 15. Reference numeral 14 denotes a crank angle signal generating means attached to the crankshaft, and, for example, a crank angle pulse Sd (FIG. 2(C)) every 1° is inputted to the control unit 15 as an angle signal.

This control unit 15 includes a digital interface (DIF) 15 to which the cylinder identification signal Sb, rotation signal Sc, and crank angle pulse Sd are input, and an analog interface (AIF) to which the air flow signal Sa and the like are input.
)15□ and CPU as a microcomputer
15 x and a driver (I
DR) 154 and an ignition driver (
TDR) 15s, a lamp driver (RDR) 156 that drives the misfire detection warning lamp 19, and the like.

The control unit 15 has functions such as ignition control and fuel control that optimally control the ignition timing according to the operating state of the engine 11, and also has functions such as ignition control and fuel control that output the ignition signal Se (see FIG. 2(d)) to the ignition system. ), the rotational angular velocity immediately after the ignition timing and the rotational angular velocity at a point after a predetermined crank angle from the ignition timing are determined, and the abnormal combustion cylinder of the engine is determined based on the angular velocity deviation or angular velocity ratio. It has a function to detect a misfire, and in the event of a misfire, the driver 15.
The alarm lamp 19 is driven through the alarm lamp 19.

Here, the control unit 15, that is, the CPU 153,
The falling edge (mark in the figure) of the rotation signal Sc shown in Figure 2 is the engine TDC, and at the rising edge of the signal Sc, the cylinder identification signal sb is used to identify a specific cylinder (in the figure, 1 cylinder (Ill)). After that, each cylinder (
#2 to #4). However, the in-cylinder pressure waveform shown in Fig. 2(e) is a reference diagram for considering the rotation speed; under normal conditions (#4), as shown in part A, the in-cylinder pressure rises rapidly due to the explosion after the ignition timing; The rotational angular velocity also increases. On the other hand, when there is a misfire (heat 2), there is no explosion as in part B, so the increase in cylinder pressure is small and the increase in rotational angular velocity is small.

The present invention focuses on this point and attempts to detect a misfire by determining the rotational angular velocity at a predetermined crank angle based on the ignition timing of the engine.The principle of operation is shown in Fig. 3. I will explain using

That is, in the present invention, the cycle between crank angle pulses immediately after ignition is set to tl, and the period between crank angle pulses is set to a predetermined crank angle, for example, 45°, immediately after ignition.
If the period between subsequent crank angle pulses is t7, then the instantaneous angular velocity ω immediately after these ignitions.

The instantaneous angular velocity ω7 at n° after ignition is given by the following formula, respectively:
By calculating the rotational angular velocity deviation Δω or the angular velocity ratio between ω1 and ω7 using the following equations, misfire can be determined based on the calculation results.

ω 1 1゜; □ ・ ・ ・ ・(4)t
, l Figure 4 shows the instantaneous rotational angular velocity ω (every 1°) in this embodiment.
and rotational angular velocity deviation Δω6 (=ω, -ω, ,) corresponding to normal conditions and misfires, respectively. In the case of a misfire, the second cylinder (#2) is misfired in fc in the same figure. I know that there is. Therefore, there is a significant difference in the amount of variation in Δω6 between normal conditions and misfires, and misfires can be determined based on this.

FIG. 5 is a flowchart showing an overview of the fuel injection and ignition control of the control unit in the above embodiment, and the control unit 15 has the following functions. That is, the control unit 15 first determines the engine rotation speed N from the cycle of the rotation signal Sc in step 51, and then determines the air amount A from the average of the outputs of the intake air amount sensor 12 between the rotation signals (step 52). Load amount A/N
(Step 53). Next, in step 54, the basic pulse width τl of the injector 16 is set to *(A/N)(
However, K is a constant) and then the final pulse width τ-τm*c (C is a constant) after various fuel corrections is determined (step 55). Next, the rotation speed N and the load amount (A/N
) is used to determine the basic ignition timing (step 56), and then the injector 1 is
6. Fuel control timing control 2 Ignition timing control timing control of the simmering device is performed (step 57).

FIG. 6 is a flowchart showing an example of misfire determination and alarm operation based on the angular velocity deviation Δω shown in FIG. 4 in the control unit 15 having such a control function. That is, the control unit 15 first measures the period t1 between crank angle pulses immediately after the ignition timing in step 61, and then measures the period t7 between crank angle pulses of n-n+1 in crank angle from immediately after the ignition timing (step 62). ).

Next, based on these tll tll, the above (1),
(After determining the rotational angular velocity ω8 immediately after the ignition timing and the rotational angular velocity ω7 after a predetermined crank angle using Equation 21 (step 63), the angular velocity deviation Δω4 is further determined (step 64).Next, in step 65, the Δω4 is calculated. It is determined that the preset value α is the preset value α, and if the result is YES, the process proceeds to step 66, where the misfire flag for the corresponding cylinder is set and the warning lamp 19 is turned on (step 67).

If the answer is No, the process proceeds to step 68 and resets the misfire flag.

Set the alarm lamp 19 accordingly.

The light is turned off (steps 67 and 69). Thereby, a misfire can be notified by lighting the lamp 190.

FIG. 7 is a flowchart showing a modification of the misfire determination and alarm operation in the above embodiment. Here, the difference from the one in FIG. 6 is that instead of Δω4, the rotational angular velocity ratio Δωr (
=ω7/ω1), and its operation is basically the same as that shown in FIG. 6, so its explanation will be omitted. Note that β in step 75 in FIG. 7 is Δ
This is a desired setting value set in advance corresponding to ω.

〔Effect of the invention〕

As described above, according to the misfire detection device of the present invention, the rotational angular velocity is detected near the ignition timing and after a predetermined angle based on the ignition timing, and a misfire is determined based on the angular velocity deviation or angular velocity ratio. Misfires can be detected with high sensitivity over a wide range of areas.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an embodiment of the misfire detection device according to the present invention applied to a vehicle electronic control system, and Fig. 2 shows signals and cylinder pressure waveforms of various parts to explain the above embodiment. FIG. 3 is an explanatory diagram showing the operating principle of the present invention,
FIG. 4 is a diagram showing the instantaneous rotational angular velocity ω and the rotational angular velocity deviation Δω6 corresponding to normal and misfire conditions in the above embodiment, and FIG. 5 is an overview of the fuel injection and ignition control of the control unit in the above embodiment. A flowchart showing
FIG. 6 is a flowchart showing an example of the misfire determination and alarm operation based on Δ&d shown in FIG. 4 in the control unit of the above embodiment, and FIG. 7 is a flowchart showing a modification of FIG. 6. 11... Engine, 12... Air flow sensor, 1
3...sensor section, 13. ... Cylinder identification sensor, 13
□ ... Rotation signal sensor, 14 ... Crank angle signal generation means, 15 ... Control unit, 16 ... Injector, 17 ... Igniter, 18 ... Distributor with built-in coil, 19 ... Alarm lamp.

Claims (1)

[Claims] In an engine equipped with an ignition control means for optimally controlling ignition timing according to the operating state of the internal combustion engine, the angle signal generation means generates a plurality of pulses as an angle signal per revolution of the crankshaft of the internal combustion engine; Based on the signal and the ignition timing signal accompanying the ignition control means, a first rotational angular velocity near the ignition timing and a second rotational angular velocity at a point after a predetermined crank angle from the ignition timing are determined, and these first rotational angular velocities are determined. A misfire detection device for an internal combustion engine, comprising a misfire detection means for determining an abnormal combustion cylinder of the engine based on a rotational angular velocity of the engine and a second rotational angular velocity.