JPS62282237A - Misfire detector - Google Patents

Abstract

PURPOSE:To detect a misfire simply and accurately, by counting the change rate of the pressure in a combustion chamber during a compression/combustion process. CONSTITUTION:The pressure value P in a combustion chamber 12 is detected by a pressure sensor 42 and, after a necessary signal is discriminated by a noise filter 64, the change rate dp/dt of the pressure value P is detected by a differentiator 66. Subsequently, only the positive value of the change rate is extracted by a wave-form shaping device 68 and inputted to a misfire detector 62. Because a peak value due to compression pressure at a compression top dead center and a peak value due to the explosion of a gaseous mixture at the point of time passing the compression upper dead point appear in a normal ignition state at the time of light load, the positive value obtained by differentiation becomes twice. On the contrary, because no peak value appears after the passage of the compression top dead center in a misfire state, the output of the shaping device 68, that is, the positive change rate becomes once. Because the positive part of the change rate of the pressure in a combustion chamber during a compression/combustion process is counted to judge a misfire as mentioned above, an erroneous operation factor such as the deterioration of a sensor or the variation in a compression ratio can be excluded and the misfire can be judged simply and accurately.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) This invention is a misfire detection '! In particular, the present invention relates to a misfire detection device that determines engine misfire from the rate of change in pressure within a combustion chamber.

(Prior Art) It is known that engine misfires are likely to occur when the engine is under light load due to factors such as a drop in compression pressure in the combustion chamber, dilution of the a-air gas, or failure to ignite the spark plug. This causes harmful effects such as unpleasant vibrations and a reduction in engine output.

Therefore, various devices have been proposed as means for detecting such a misfire condition.
An example of this is disclosed in Publication No. 5.

The misfire detection device disclosed in this publication focuses on the backflow of exhaust gas that occurs in the exhaust passage when a misfire occurs, and installs two vibrators perpendicular to each other in the exhaust passage. A misfire is determined by detecting changes in the differential pressure between the two.

However, since this device detects a misfire based on exhaust gas, there is a time delay, and the pressure in the exhaust passage fluctuates due to pulsations, making it difficult to accurately determine a misfire.

Therefore, the present applicant (Yoko) has proposed a misfire detection device that solves these drawbacks in Japanese Patent Application No. 148,000/1982.

The misfire detection device according to this application directly measures the pressure in the combustion chamber of the engine with a pressure sensor to determine the misfire state, but this device also has the following problems.

(Problem to be Solved by the Invention) The misfire detection device of the present applicant detects that when the pressure inside the combustion chamber is normal from the start of the engine's compression stroke to the end of the combustion stroke, the engine reaches compression top dead center. A peak value due to compression appears, and another peak value due to combustion appears after the top dead center, whereas in a misfire state, a peak value due to combustion does not appear, and the pressure inside the combustion chamber follows an almost normal distribution curve. This was done by focusing on the fact that the combustion chamber changes in the same way, and it is determined that a misfire has occurred if the pressure inside the combustion chamber is equal at positions shifted by the same crank angle before and after compression top dead center. .

However, with this misfire detection device, it is necessary to set a position that is offset by an equal crank angle before and after the peak (peak position), but this is difficult if accurate rank angle information is not obtained. Hot Iζ.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a misfire detection device that can reliably detect misfires with a simple configuration.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a misfire detection 8i
a pressure sensor that detects the pressure within the combustion chamber; a differentiator that receives an output signal from the pressure sensor and detects the rate of change in the pressure; and a number of times the rate of change of the output value of the differentiator becomes positive. The misfire determination means is configured to send out a misfire detection signal if the measured value of this counter is once during one compression/explosion stroke period when the engine is lightly loaded.

(Function) The misfire detection device configured as described above converts the pressure inside the combustion chamber during the compression and explosion strokes of the engine into a rate of change, and determines whether a misfire has occurred based on whether the rate of change becomes positive once or twice. Because we judge
Misfire conditions can be easily and reliably detected without the need for troublesome standard settings.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 to 3 show an embodiment of a misfire detection device according to the present invention.

The misfire detection device shown in the same figure is an example in which the present invention is applied to a combustion engine with four injections.
The combustion chamber 12 is formed by a piston 18 disposed in a cylinder chamber 16 provided within a cylinder block 14, and a cylinder head 20 coupled above the cylinder block 14.

The cylinder head 20 is formed with an intake/exhaust boat 22.24 that communicates with the combustion chamber 12, and between the combustion chamber 12 and each of these boats 22.24, an intake/exhaust boat that blocks or opens the communication state is formed. Valves 26 and 28 are respectively provided.

Intake and exhaust passages 30 and 32 are connected to the intake and exhaust boats 22 and 24, respectively, and throttle valves 34 and 32 are connected to the intake passages 30 to open and close the intake passages in order from the upstream side. Intake vent 't8
A first pressure sensor 36 for detecting the pressure inside the fuel injection nozzle 30 and a fuel injection nozzle 38 are installed.

A spark plug 40 for exploding the compressed fuel is provided within the combustion chamber 12, and a second pressure sensor 42 for detecting the pressure within the combustion chamber 12 is attached.

A gear plate 46 is fixed to a crankshaft 44 which is rotated by the up and down reciprocating motion of the piston 18.
A driven gear plate 48 is meshed with this gear plate 46 .

An arc-shaped slit hole 50 having a length corresponding to the compression/combustion stroke of the piston 18 is bored in the driven gear plate 48, and a light source 52 and a light sensor 54 are arranged to face the slit hole 50. If the engine 10 is in the compression/combustion stroke, the optical sensor 54 is in the “ON” state and the
signal is output.

Furthermore, electromagnetic pickups 56 are arranged on the outer periphery of the driven gear plate 48 at predetermined intervals, and an F/V converter 58 is connected to the electromagnetic pickups 56 to convert the surrounding signals into voltage. .

Ignition timing by the above spark plug 40 and fuel injection nozzle 3
The control of fuel injection timing and fuel injection amount by
The misfire signal A from the misfire detector 62 is input to the control device 60, and when the engine 10 misfires, the amount of fuel injected by the fuel injection nozzle 38 and the ignition timing by the spark plug 40 are controlled. Correction is done by control device 6
Implemented at 0.

The misfire detector 62 receives a pressure signal B in the intake passage 30 from the first pressure sensor 36, a compression/combustion stroke signal C from the optical sensor 54, and a signal from the F/1 converter 58. An engine rotational speed signal N is inputted, and a signal from a second pressure sensor 42 installed in the combustion chamber 12 is inputted after being processed by the following circuit.

That is, first, the pressure value P inside the combustion chamber detected by the second pressure sensor 42 is input to the differentiator 66 after a necessary signal is discriminated by the noise filter 64.
The rate of change dP/d't of pressure [tP is detected by
Next, only the positive value (dP/dt) of the rate of change dP/dt is extracted by the waveform shaper 68 and sent to the misfire detector 62.
is man-powered.

FIG. 2 shows the output IP of the second pressure sensor 42 at the time of ignition and misfire, the rate of change dP/dt of the differentiator 66, and the waveform shaping from the start of the compression stroke of the engine 10 to the end of the combustion stroke. The output signal (dP/dt) of the device 68 is shown in comparison.

Under normal ignition conditions under light load, as mentioned above, a peak value due to compression pressure at compression top dead center and a peak value due to explosion of the air-fuel mixture after compression top dead center appear; Positive rate of change (dP/dt
)” will be repeated twice.

On the other hand, in a misfire state, the peak value well past the compression top dead center does not appear, so the output value of the waveform shaper 68, that is, the positive rate of change (dP/dt) is one time.

Therefore, in the present invention, misfire is determined by measuring these differences during the compression and combustion strokes.

FIG. 3 shows an example of a misfire determination procedure performed by the misfire detector 62. When the judgment flow starts, first, the signal C is taken in at step 100, and its value becomes “1”.
If it is 1, it is engine 1.
0 is not in the combustion/compression stroke, so it waits, and the signal C is 1''
If so, the process moves to step 101.

At step 101, the engine speed signal N and the intake passage 3
After taking in the pressure signal B within 0, it is determined from these values in step 102 whether the engine 10 is being operated in a light load region.

Note that information regarding the operating range determined based on the relationship between the engine speed and the intake passage pressure is set in advance and stored in the memory device of the misfire detector 62, and the map value is set in the light load T1 range. The map value is set to "1'', and the map value is O" in other areas.

If it is determined in step 102 that the MAP (direct) is not "1", the misfire signal "Opa" is outputted in step 103 and the process returns to the start, since this is a region in which misfire is hardly a problem.

On the other hand, if it is determined in step 102 that the map value is "1", then steps 104 and subsequent steps are executed.

In step 104, the value of the counter i is set to 0, and in step 105 it is determined whether the signal C is 0. It is determined whether the output signal (dP/dt) 9 is "1", and if it is "1", step 107 is executed immediately, but if it is "o", step 1 is executed.
Returning to 05, the standby state is repeated, and only when (dP/dt) '' becomes 1'', the process moves to step 107. In step 107, it is again determined whether the signal C is ``O'', and this is 0°''. If so, the process moves to step 108.

In step 108, the output signal 8 (dP/
dt) If * is "O"', the process moves to the next step 109, but if it is not "O", the process returns to step 107 (dP
/dt)” becomes “0” and then step 109.
to move to.

In step 109, 1 is added to the counter i and step 1
Returning to step 05, in steps 105 to 109, the judgment of the signal C and the (dP/dt) signal is repeated twice each during one compression/combustion stroke of the engine 10. (dP/dt> This is a step to ensure that the counter counts by 1 with the signal, and avoids the old school error when the width of the (dP/dt) signal is uneven, for example.

Then, when it is determined in steps 105 and 107 that the signal C is ○'', that is, the engine 10 has passed the compression/combustion stroke, it is determined in step 110 whether or not the value of the counter 1 is greater than 2''. If it is determined that i is greater than or equal to ``2'', a misfire signal ``o'' is issued in step 103.
” and return to the start.

On the other hand, if it is determined in step 110 that 1 is smaller than °°2'', a misfire signal "1" is outputted in step 111 and the process returns to the start.

In this ¥11 constant procedure, in a normal ignition state, steps 105 to 109 are repeated twice in one compression/combustion stroke, and step 110 is executed, and the output signal of the misfire detector 62 is ``O''. becomes.

Furthermore, in a misfire state, steps 105 to 109 are executed only once during one compression/combustion stroke, so the output signal of the misfire detector 62 is 1''.

Now, in the misfire detection procedure performed as described above,
Since the judgment is made by counting the positive component (dP/dt) of the rate of change of pressure in the combustion chamber 12 during one compression/combustion stroke, malfunctions such as sensor deterioration and compression ratio fluctuations can be avoided. Misfires can be easily and accurately determined without the need for rank angle information.

In the above embodiment, the engine speed N and the pressure inside the intake passage 30 are used to determine the light load region, but the engine speed N and the throttle opening may also be used.

Further, the signal of the rate of change dP/dt extracted by the waveform shaper 6B may be a negative signal.

Furthermore, although the misfire detector 62 has been described in the above embodiment using a microcomputer that operates according to a program flow, it may of course be constructed from an individual circuit such as a counter.

(Effects of the Invention) As explained in detail in the embodiments above, the misfire detection device according to the present invention determines the presence or absence of a misfire based on the rate of change in the pressure in the combustion chamber during the compression/combustion stroke. , a misfire can be reliably detected through simple data processing, and the engine operating condition fF4. There is no need to change the judgment criteria accordingly.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of the device of the present invention, FIG. 2 is an explanatory diagram of the misfire detection principle of the device, and FIG. 3 is a flowchart showing the operating procedure of the device. 12... Combustion chamber 42... Second pressure horn sensor 62... Misfire detector 66...
... Differentiator 68 ... Waveform shaper Fig. 2

Claims (1)

[Claims] A pressure sensor that detects the pressure in the combustion chamber, a differentiator that receives an output signal from the pressure sensor and detects a rate of change in the pressure, and a counter that measures the number of times the rate of change of the output value of the differentiator becomes positive. and a misfire determining means for sending out a misfire detection signal if the measured value of the counter is once during one compression/explosion stroke period when the engine is lightly loaded.