JPH01172728A - Misfire detecting apparatus of engine - Google Patents

Abstract

PURPOSE:To issue a misfire alarm at first when the misfiring states occur specified number of times, by judging the misfiring state based on the pressure difference between the maximum value of the internal pressure in a cylinder after a compression top dead center and the value of pressure at the compression top dead center. CONSTITUTION:A signal from a compression sensor 13 is imparted to an top-dead-center- pressure detecting means 20. A signal from a crack angle sensor 16 is supplied to a top-dead- center detecting means 21. The top-dead-center detecting means 21 imparts the detected signal of the position of the top dead center to the top-dead-center-pressure detecting means 20. Then, the top-dead-center-pressure detecting means 20 sets the pressure at the pressure top dead center. Then, a maximum-pressure detecting means 22 detects the maximum pressure value during the time a counter 23 counts the crack angles. Thereafter, a pressure-difference operating means 24 computes the pressure difference between the detected 20 pressure value at the compression top dead center and the detected 22 maximum pressure value. A pressure- difference judging means 25 compares the pressure difference with a specified value. When the result is less than the specified value, misfire or abnormal burning is judged. When that is repeated specified number of times, the misfire is judged with a misfire judging means 26, and the misfire is warned through a warning means (display lamp) 15.

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FE] The present invention relates to an engine misfire detection device. fPrior Art] Each cylinder is equipped with a pressure detection means such as a pressure sensor, and a crank angle sensor detects a predetermined crank angle position in the corresponding cylinder, and a misfire state of the engine is detected from these conditions. In the engine misfire detection device disclosed in, for example, Japanese Unexamined Patent Publication No. 61-23876, two crank angle positions are determined before and after the compression top dead center, and the engine misfire is detected at these two positions. The detected pressure values are compared, and a misfire is determined when these detected values have a predetermined magnitude relationship. This takes advantage of the fact that the pressure waveform at the time of a misfire appears symmetrically around compression top dead center (see Fig. 4).

[Prayer point while the invention is trying to solve the problem]

The problem here is that even if combustion is delayed due to some reason and the combustion state does not result in a complete misfire, but is inconvenient for engine operation, the misfire detection device described above can still In order to investigate the cause of the engine misfire, which may not be detected due to the settings, or if the engine misfires due to an unexpected reason, only one cycle misfires, but the rest of the engine is working normally. There is no need to issue a misfire warning. . The present invention was made based on the above circumstances, and determines the combustion condition and combustion level based on the difference between the maximum value of the in-cylinder pressure that occurs after the compression top dead center and the pressure value at the compression top dead center. To provide a misfire detection device for an engine which determines a misfire state including abnormal combustion when no pressure value is generated, and issues a misfire alarm only when this occurs a predetermined number of times.

[Means to solve the problem]

Therefore, in the present invention, the pressure detection means detects the pressure in each cylinder, the top dead center pressure detection means detects the pressure at compression top dead center from the output signal of the crank angle sensor, and the top dead center pressure detection means detects the maximum value of the cylinder pressure. pressure difference calculation means that compares the output signal of the top dead center pressure detection means and the output signal of the maximum pressure detection means to calculate a pressure difference; and a pressure difference calculation means that compares the pressure difference with a predetermined value. , when the value is below a predetermined value, the number of times it is detected is
The engine is equipped with a pressure difference determining means for writing in a storage area corresponding to the operating region at that time, and a misfire determining means for determining a misfire when the number of detections in one operating region exceeds a predetermined value.

[For production]

Therefore, if there is not a sufficient pressure difference between the cylinder pressure at compression top dead center and the maximum cylinder pressure, it can be determined that abnormal combustion or a complete misfire has occurred.Moreover, when this is repeated several times, it is assumed that there is a failure in the relevant cylinder. A misfire alarm can be issued.

【Example】

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. In the figure, reference numeral 1 indicates the engine body, and intake valves 3 and 3 correspond to combustion chambers 2 and 3 of the engine body, respectively. There is an exhaust valve 4 and an ignition plug 5. Further, an intake manifold 7 is connected to the intake boat 6, and a fuel injection valve 8 is provided here. A throttle valve 11 in the intake pipe 10 is connected from the air cleaner 9 to the intake manifold 7.
Air is further supplied through the intake chamber 12. Further, in line with the ignition plug 5, a pressure sensor 13 is installed in the combustion chamber 2 as pressure detection means. The output signal of the pressure sensor 13 is supplied to a control unit 14, which outputs a signal to an indicator lamp 15 as an alarm means as a result of the electronic calculation. The control unit 14 receives a crank angle pulse 1 as a reference signal from a crank angle sensor 16 provided on the crankshaft of the engine body 1, as shown in FIG. The control unit 14 outputs a signal to energize the ignition plug 5 at a timing determined by the angular pulse 2 signal, and the signal 2 from the throttle opening sensor 17 is output from the control unit 14. signal from sensor 18,
Furthermore, a signal is given to the fuel injection valve 8 to inject the amount of fuel calculated from the engine rotational speed from the crank angle sensor 16. Next, in FIG. 0, a mode of the misfire detection device in the control unit 14 will be specifically explained with reference to the block diagram of FIG. It will be done. Further, two signals, crank angle pulse 1 and crank angle pulse 2, from the crank angle sensor 16 are supplied to a top dead center position detecting means 21, and the top dead center position detecting means 21 detects a reference crank angle for each cylinder. After detecting the crank angle pulse 1, a compression top dead center crank angle having a predetermined phase difference from the crank angle pulse 1 as an angle is detected by counting a predetermined number of crank angle pulses 2, and is sent to the top dead center pressure detecting means 20. , gives a top dead center position detection signal. As a result, the top dead center pressure detection means 20
sets the pressure at compression top dead center. Further, the signal from the pressure sensor 13 is supplied to the maximum pressure detection means 22, while the crank angle pulse 1 detected by the crank angle sensor 16 is supplied to the counter 23 as a counter start fIIJ signal. The signal from the angle sensor 16 is counted up to a predetermined crank angle (for example, 180 degrees after the start of counting). While the counter 23 is counting the crank angle, the maximum pressure detection means 22 detects the maximum pressure value. A compression top dead center pressure value detected by the top dead center pressure detection means 20;
The maximum pressure value obtained by the maximum pressure detection means 22 is calculated by the pressure difference calculation means 24, and the pressure difference calculation means 24 sends the pressure difference between the maximum pressure value and the top dead center pressure value to the pressure difference determination means 25. give. The pressure difference determining means 25 compares the pressure difference with a predetermined value, and if the result is less than the predetermined value, it is determined that there is a misfire or abnormal combustion, and each time the determination is made, the pressure difference is compared with a predetermined value. The recording/filling area is specified in the map (two-dimensional map of engine speed and load prepared for each cylinder) configured in the storage means 27, and the counter is incremented by 1 for the number in the storage area. and write. Further, the value counted up by the pressure difference determining means 25 is given to the misfire determining means 26,
Here, the value is compared with a predetermined value, and if it exceeds the predetermined value, an energizing signal is given to the indicator lamp 15 as a warning means. Next, the sequence of misfire detection will be explained based on FIG. First, in step 5101, the current crank angle θ is detected from the signal from the crank angle sensor 16, and then in step 5102, the current cylinder pressure P is detected from the signal from the pressure sensor 13. In step 5103, the current crank angle θ is set to the reference crank angle (crank angle pulse 1
) It is determined whether or not the misfire detection period is within the period from θ0 to the predetermined crank angle θ counted by the counter 23, and if it is not within the period, proceed to EXIT, and if within the period, proceed to step 5104. , the current crank angle θ is counted a predetermined number of times from the reference crank angle θ0 by the top dead center position detecting means 21 for the cylinder concerned, and is determined to be the compression top dead center crank angle θTDC with a predetermined phase shift. do. Here, the predetermined crank angle θ
is the maximum pressure value P I'l from the compression stroke to the end of combustion.
This is the measurement period for aX, etc. Then, if the compression top dead center crank angle θTDC is determined, in the next step 5105, the cylinder pressure P at that time is stored as the compression top dead center pressure P TDC by the top dead center pressure detection hand Fi20, and the process moves to the next step 8106. . In step 8106, the cylinder pressure P is compared with the maximum pressure fIip l1aX detected and stored by the maximum pressure detection means 22 at that time. and,
If the cylinder pressure P is equal to or larger than the maximum pressure value pHa×, in the next step 5107, the cylinder pressure P is updated as the maximum pressure value PlaX. Next, in step 8108, the current crank angle θ is compared with (reference crank angle θ0 + predetermined crank angle θk), and if they do not match, E
Go to XIT, and if they match, go to step 3109,
In the pressure difference calculation means 24, ΔP=PIax −PTDC
! - Calculate and use the pressure difference determining means 25 in step 5.
At 110, it is compared with a predetermined value ΔP INIT. Rashi, Δ
If P is ΔPINIT, in step 5111, the stored number of times C corresponding to the operating range determined by the engine speed and load is read out from the map, and in step 5112, the count up < C-C+-1) is performed. , write this to the corresponding storage area of the map, and then proceed to step 5.
At step 113, the misfire determining means 26 compares the count value C counted up by the pressure difference determining means 25 with the predetermined number of times C1 old ■, and determines whether C≧CINIT.
If the conditions are met, in step 5114, the indicator lamp 15 is turned on for a warning. If step 51
10 or if a negative determination is made in step 5113, PTDC=O in step 5115, and step 5116
Reset pnax=o and EXIT. Incidentally, by providing a pressure sensor for each cylinder and executing the determination based on the above-described flowchart for the gold cylinder, more accurate misfire detection becomes possible.

【Effect of the invention】

The present invention has been described in detail above, and if there is no sufficient peak value in the pressure measured within a predetermined crank angle from compression top dead center, abnormal combustion or complete misfire can be determined.
When this is repeated several times, a misfire alarm can be issued assuming a failure in the relevant cylinder.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention, FIG. 2 is a block diagram of a control unit for misfire detection,
FIG. 3 is a flowchart, and FIG. 4 is a graph showing the relationship between crank angle and cylinder pressure. DESCRIPTION OF SYMBOLS 1... Engine body, 5... Ignition plug, 8... Fuel injection valve, 13... Pressure sensor, 14...
...Control unit, 15...Indication lamp, 1
6... Crank angle sensor, 17... Throttle opening sensor, 18... Intake temperature sensor, 20... Top dead center pressure detection means, 21... Top dead center position detection means, 22...
- Maximum pressure detection means, 24...pressure difference calculation means, 25
. . . Pressure difference determination means, 26 . . . Misfire determination means. Patent applicant: Fuji Heavy Industries Co., Ltd. Agent: Patent attorney: Makoto Kobashi Ukiyo Patent attorney: Susumu Murai

Claims (1)

[Claims] A pressure signal from a pressure detection means for detecting the cylinder pressure;
A top dead center pressure detection means for detecting the pressure at compression top dead center from the crank angle signal of the crank angle sensor, a maximum pressure detection means for detecting the maximum value of the cylinder pressure, and an output of the top dead center pressure detection means. A pressure difference calculation means that compares the signal and the output signal of the maximum pressure detection means to calculate the pressure difference; and a pressure difference calculation means that compares the pressure difference with a predetermined value, and when the pressure difference is less than the predetermined value, calculates the number of times of detection and calculates the pressure difference in the operating range at that time. A misfire detection device for an engine, comprising: a pressure difference determining means for writing in a storage area corresponding to the above, and a misfire determining means for determining a misfire when the number of detections in one operating region exceeds a predetermined value.