JPH04159438A - Misfire detection method for internal combustion engine - Google Patents

Abstract

PURPOSE:To enable high-precision misfire detection by providing gear ratio detection means and a clutch ON/OFF state detection means and changing the misfire determination condition according to the outputs in the misfire detection from engine rotational fluctuation. CONSTITUTION:During operation of an engine, in a control circuit 15, a reference comparative rotational speed B(n) is obtained from a rotational speed (n) obtained by an engine rotational sensor 1 and then the clutch on/off state is determined. When the clutch is ON, a misfire determination level (f) is obtained on the basis of the gear ratio (g), the engine load l and the engine rotational speed (n). Then, the value obtained by subtracting the engine rotational speed (n) from the reference comparative rotational speed B(n) is compared with the misfire determination level (f), and when the misfire determination level (f) is larger than the other, this is determined as a misfire. When the clutch is off, on the other hand, a misfire determination level (h) is obtained from the engine rotational speed (n) and the engine load l. The value obtained by subtracting the engine rotational speed (n) from the reference comparative rotational speed B(n) is compared with the misfire determination level (h). When the misfire determination level (h) is larger than the other, this is determined as a misfire.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects a misfire in an internal combustion engine based on engine rotational fluctuations, and in order to improve the detection accuracy,
The slice level is changed depending on the gear ratio.

[Conventional technology]

Conventionally, misfires have been detected based on the rate of fluctuation in engine speed, as described in Japanese Patent Application Laid-Open No. 62-228929.

[Problem to be solved by the invention]

The purpose of the present invention is to detect a misfire in an internal combustion engine by measuring the engine speed or angular velocity of the internal combustion engine and comparing it with a value determined by the position of the transmission and the engine state (load) as to whether or not power is being transmitted. It's about doing. Since the inertial mass of the engine changes depending on the gear shift position and the presence or absence of power transmission, the engine speed fluctuation value also changes, so let's provide a highly accurate misfire detection method by changing the speed fluctuation comparison value used to determine a misfire. That is.

[Means to solve the problem]

In order to achieve the above object, a means for detecting a gear ratio;
Means for detecting the presence or absence of power transmission is provided to determine the moment of inertia of the entire internal combustion engine.

Furthermore, means for detecting the engine state of the internal combustion engine and means for detecting the engine speed are provided, and the misfires are detected by comparing them with a value determined from the moment of inertia.

[Effect]

If a misfire occurs while the internal combustion engine is running, the rotational speed will drop, but during power transmission, the moment of inertia of the entire system is large, so the drop in rotational speed is small, and when the gear ratio is small, the rotational speed decreases even more than when the gear ratio is large. The drop in rotational speed becomes smaller. Furthermore, when there is no power transmission, the inertia of the internal combustion engine alone increases the drop in rotational speed in the event of a misfire. Furthermore, when the internal combustion engine decelerates, there is an obvious drop in the rotational speed, so it is necessary to detect this by means of detecting the state of the internal combustion engine.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1 is a sensor that measures engine speed or angular velocity. 3 is an intake air amount sensor, and part of the intake air that has passed through the air cleaner 17 passes through the bypass passage 2. The intake air amount sensor outputs a signal according to the amount of intake air.

9 is a throttle valve that controls the amount of intake air. A throttle valve opening sensor 16 outputs a signal corresponding to the position of the throttle valve 9. 13 is a water temperature sensor, which outputs a signal according to the cooling water temperature.

8 is a thermowax which moves the throttle valve 9 in the direction of opening when the water temperature is low, depending on the cooling water temperature. 14 is an air-fuel ratio sensor. The output changes depending on the state of the exhaust gas components from the internal combustion engine. The air-fuel ratio sensor outputs a signal depending on the air-fuel ratio. The signal of the sensor that measures the engine speed of 1 appears as engine speed 101 in FIG.
The reference comparison rotation speed 102 obtained from 1 is also shown. The position of the transmission at this time is 2nd gear. Figure 3 shows the 2nd gear.

An engine speed 101 at the time of misfire occurrence 106, a reference comparison speed 102, and a difference 105 between these speeds are shown.

Similarly, FIG. 4 shows the top gear, the engine speed 101 at the time of misfire occurrence 110, the reference comparison speed 102, and the difference 109 between these speeds. As can be seen from FIGS. 4 and 5, there is a difference in the rotational speed difference 105, 109 when a misfire occurs depending on the position of the gear ratio, and the difference becomes smaller as the inertia increases.

FIG. 1 shows the control flow. Engine rotation sensor 1,
The reference comparison rotation speed B (n) is calculated from the rotation speed obtained from 111, and then the clutch is turned on.

Branch 112 due to OFF. When the clutch is ON, the misfire determination level f (grQ+n) is determined by means of determining the gear ratio g, the engine load Q, and the engine speed n. Next, the value obtained by subtracting the engine speed n from the reference comparison speed B (n) is compared with the misfire determination level f (g+Q+ n), and if the misfire determination level f (g+Ω, n) is large, it is determined that a misfire has occurred. Next, when the clutch is OFF, the misfire determination level h (n, Q) is determined from the engine speed n and the engine load Ω.

Next, compare the value obtained by subtracting the engine speed n from the standard comparison speed B (n) with the misfire judgment level h (n, Q),
When the misfire determination level h (n, Q) is large, it is determined that a misfire has occurred. Therefore, this embodiment has the effect of reliably realizing engine misfire determination.

〔Effect of the invention〕

According to the present invention, since the determination conditions are changed depending on the load,
This has the effect of reliably detecting misfires.

[Brief explanation of the drawing]

Fig. 1 is a flowchart of an embodiment of the present invention, and Fig. 2 shows a constant engine rotation speed of 101 when the engine is in 2nd gear.
FIG. 3 shows the engine speed of the 2nd gear when a misfire occurs and the standard comparison speed 102. FIG. 4 shows the engine speed of the top gear when a misfire occurs and the standard comparison speed. FIG. 5 is a system diagram of the entire engine according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Sensor, 2... Bypass passage, 3... Intake air amount sensor, 9... Throttle valve, 13... Water temperature sensor. Fig. 2 3rA f, i fakee th +l2I tI#Ie

Claims (1)

[Claims] 1. In an internal combustion engine that detects a misfire from engine rotational fluctuations, there is a means for detecting a gear ratio and a clutch ON/O
1. A method for detecting a misfire in an internal combustion engine, comprising means for detecting an FF state, and means for changing a misfire determination condition thereby.