JPH01172729A - Misfire detecting apparatus of engine - Google Patents

Abstract

PURPOSE:To issue a misfire warning when abnormal burning or complete misfire is repeated by several times, by judging the abnormal burning and the complete misfire when the maximum value of pressure in a cylinder is measured within a certain crank angle range after a compression stroke. CONSTITUTION:A signal from a pressure sensor 13 is imparted to a maximum pressure detecting means 20. The detecting means 20 detects the maximum value of the signal from the pressure sensor 13 and detects a crank angle at this time. In a crank angle judging means 21, the crank angle at the time of the maximum pressure is compared with a preset crank angle. When the maximum pressure is detected on the advanced angle side from the preset crank angle, a memory region corresponding to the operating region at that time is specified in a map, which is formed in a memory means 24, then one is added to the number in the memory region. The value, which is counted in the crank angle judging means 21, is imparted to a misfire judging means 23 and compared with a specified value. When the value exceeds the specified value, an energizing signal is imparted to a display lamp of a warning means 15.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an engine misfire detection device.

[Conventional technology]

Engine misfire detection includes a pressure detection means such as a pressure sensor for each cylinder; in addition, a crank angle sensor detects a predetermined crank angle position in the relevant cylinder, and a misfire state of the engine is detected based on these conditions. The device is described in, for example, Japanese Patent Laid-Open No. 61-23876. Here, two crank angle positions are determined before and after the compression top dead center, and the pressure values detected at these two positions are compared, and it is determined that these detected values are in the determined large-bore f system. Sometimes it is determined to be a misfire. 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).

[Problems to be solved by the invention]

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 detect the allowable gap between large and small rJJ. Depending on the settings, this cannot be detected. Also, due to unforeseen circumstances,
There is no need to issue a misfire alarm even if the engine misfires in a situation where the engine misfires for only one cycle and runs normally thereafter, unless the cause is investigated. The present invention was made based on the above circumstances, and the combustion state is determined by comparing the crank angle at which the cylinder pressure is maximum within the crank angle range after the compression stroke with the set crank angle, and the combustion state is determined by An engine misfire detection system that detects a misfire when the cylinder pressure does not reach its maximum value within the crank angle range, including abnormal combustion, and issues a misfire alarm only when this occurs a predetermined number of times. The aim is to provide equipment.

[Means to solve the problem]

Therefore, in the present invention, the pressure detection means detects the cylinder internal pressure, the maximum pressure detection means detects the maximum pressure value and the crank angle at that time from the signal from the pressure detection means, and the maximum pressure detection means detects the pressure. crank angle determination means for comparing the crank angle at the maximum pressure set and the set crank angle;
A misfire determining means is provided for determining a misfire when a state in which the crank angle at the maximum pressure is more advanced than the set crank angle is detected a predetermined number of times in the same operating range based on the result of the crank angle determining means. .

[For production]

Therefore, when the maximum value of the cylinder pressure is measured within the crank angle range after the compression stroke, abnormal combustion or complete misfire can be determined, and if this is repeated several times,
It is possible to issue a misfire warning in anticipation of a failure in the relevant cylinder.

【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, and as a result of electronic calculation, a signal is output to a display lamp 15 as an alarm means. 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 signal of angular pulse 2 is given, and at the timing determined by this, the control unit 14 outputs a signal to energize the ignition plug 5, and also receives the signal from the throttle opening sensor 17 and the intake air temperature. A signal is given to the fuel injection valve 8 to inject the amount of fuel calculated from the signal from the sensor 18 and the engine speed from the crank angle sensor 16. Next, aspects of the misfire detection device in the control unit 14 will be specifically explained with reference to the block diagram of FIG. 2. In the figure, a signal from a pressure sensor 13 is given to maximum pressure detection means 20. The maximum pressure detection means 20 detects a predetermined crank angle (for example, one crank angle from the reference crank angle) which is a predetermined phase shift from the detection position of the crank angle pulse 1 as the reference crank angle for each cylinder.
80°), the maximum value of the signal from the pressure sensor 13 is detected, and the crank angle at that time is detected.6Then, the crank angle determining means 21 compares the crank angle at the time of the maximum pressure with the set crank angle. However, if the maximum pressure is detected on the advanced side of the set crank angle, the operation at that time w4
A storage area corresponding to the area is specified in a map (a two-dimensional map of engine speed and load prepared for each cylinder) configured in the storage means 24, and a number within the specified force area is specified. Increment the counter by 1 and write it. Further, the value counted up by the crank angle determining means 21 is given to the misfire determining means 23, where the value is compared with a predetermined value, and if it exceeds the predetermined value, an indicator lamp 15 as an alarm means is sent. Give an auxiliary signal. 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 of the crank angle sensor 16, and then in step 5102, the pressure sensor is detected.Next, based on FIG. Step 5
In step 101, 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, it is determined whether the current crank angle θ is within the period from the reference crank angle (crank angle pulse 1) θ0 to the predetermined crank angle θ and is in the misfire detection period, and if it is not within the period. If it is during the period, the process moves to step 5104, where the maximum pressure detection means 20 compares the cylinder pressure P detected in step 5102 with the maximum pressure (MPaX) up to now. The angle θ is the measurement period of the maximum pressure value P 1ax etc. from the compression stroke to the end of combustion. Then, if the cylinder pressure P is equal to or larger than the maximum pressure value Pla×, in the next step 5105, the above The cylinder pressure P is set to the maximum pressure value Pnax, and in step 8106,
The crank angle θ at that time is updated as θpIlaX. Next, in step 5107, the crank angle θ is compared with (reference crank angle θ0 + predetermined crank angle θk), and if they do not match, the process goes to EXIT, and if they match, the process goes to step 3108. It is determined whether the crank angle is advanced or retarded from the set crank angle θINIT. This is based on the fact that the maximum value of in-cylinder pressure in normal combustion is measured around 10 degrees after compression top dead center, and the maximum value in abnormal combustion or complete misfire is measured near compression top dead center. A set crank angle (5 degrees after compression top dead center) is set for misfire determination, and when the maximum in-cylinder pressure value is retarded than the set crank angle, it is determined to be normal combustion, and when it is advanced, it is determined to be a misfire. be. Here, if θpnax<θINIT, in step 8109 the existing number of times C stored corresponding to the operating range determined by the engine speed and load is read out from the map, and in step 5110 the count is increased (C-C+l). is performed and written in the corresponding storage area of the map.Furthermore, in step 5111, the misfire determination means 23 sets the counted up number of times C to a predetermined number of times C.
It is compared with INIT to determine whether C≧CINIT. If the conditions are met, in step 5112, the indicator lamp 15 is turned on for a warning. If step 310
8 or if a negative determination is made in step 5111,
PTDC=O in step 5113, step 5114
Reset Plax to 0 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】

According to the present invention, as described in detail above, abnormal combustion or complete misfire can be determined when the maximum value of the cylinder pressure is measured within the crank angle range after the compression stroke, and this is repeated several times. At this time, a misfire warning can be issued based on the assumption that there is a failure in that 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... Maximum pressure detection means, 21... Crank angle determination means, 23...
Misfire determination means. Patent applicant: Fuji Heavy Industries Co., Ltd. Agent: Nobu Kobashi, patent attorney

Claims (1)

[Claims] a pressure detection means for detecting the cylinder pressure; a maximum pressure detection means for detecting the maximum pressure value and the crank angle at that time from a signal from the pressure detection means; and a crank at the maximum pressure detected by the maximum pressure detection means. and a crank angle determining means that compares the crank angle with the set crank angle, and based on the determination of the crank angle determining means, a state in which the crank angle at the maximum pressure is more advanced than the set crank angle is detected a predetermined number of times in the same operating region. 1. A misfire detection device for an engine, comprising a misfire determination means for determining a misfire when a misfire occurs.