JPH0422745A - Misfire detection method for internal combustion engine - Google Patents

Abstract

PURPOSE:To simply and surely perform detection of misfire with an inexpensive device by detecting the misfire in an engine according to a variation quantity of a calculation quantity which corresponds to load of the engine, under idling or deceleration conditions of the engine. CONSTITUTION:To a control unit 34, there are inputted output signals of an intake air quantity sensor 24, an idle switch 27, a temperature sensor 30, a crank angle sensor 31, a starting switch 35 which detects a starting condition of an internal combustion engine 21. Control of an injector 28, an ignitor 33 and an intake control valve 26 are performed based on the information. When misfire in the engine is detected, a malfunction display lamp 36 is turned on. In this case, in a fuel injection device of the internal combustion engine 21, the variation quantity of the calculation quantity which corresponds to required load as the basic calculation quantity is detected under specified operation conditions such as idling or deceleration conditions of the engine so that the misfire is judged when the variation quantity is more than a specified value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application J This invention relates to a method for detecting a misfire in an internal combustion engine.

[Prior Art] When an internal combustion engine misfires, unburned gas may be released into the atmosphere and cause air pollution, or the unburned gas may react in a catalyst device installed in the exhaust system of the internal combustion engine. , the catalyst device may burn out due to abnormal temperature rise. Therefore, it is necessary to detect such misfires as early as possible and immediately repair the malfunctioning part.

For this reason, a misfire detection method for an internal combustion engine as shown in FIG. 9 has been proposed. As shown in the figure, a signal generator I that converts the ignition timing into an electric signal is provided, and the signal generated in the signal generator 4191 is converted into a rectangular wave by the waveform shaping circuit 2, and the signal generator I converts the ignition timing into an electric signal. It is input to circuit 3. Then, the power transistor circuit 3 interrupts the - secondary side current of the ignition coil 4, so that a high voltage is induced on the secondary side of the ignition coil 4. The high voltage thus generated is distributed by the power distributor 5 to the spark plugs 6 of each cylinder.

In the ignition circuit having such a configuration, a first comparison circuit 9 is connected to the input side of the power transistor circuit 3 via a first timer 7, and a second comparison circuit 9 is connected to the input side of the power transistor circuit 3 via the first timer 7. A second comparison circuit IO is connected via a timer 8. Further, the output signal of the power transistor 3 is input to the first comparison circuit 9 and the second comparison circuit IO, respectively, and the output side of each of the first comparison circuit 9 and the second comparison circuit 10 is It is connected to the OR circuit 11. Then, the input/output signals of the power transistor circuit 3 at the time intervals set by the first timer 7 and the second timer 8 are compared by the first comparison circuit 9 and the second comparison circuit 10, and each comparison circuit 9. IO
An abnormality in the primary side voltage of the ignition coil 4 is detected by the output.

Then, it is detected whether the high tension cord plug side is in the oven state or whether the spark plug 6 is in the ignition state, and it is determined whether the engine is in a misfire state.

[Problems to be Solved by the Invention] In the conventional misfire detection method, engine misfires are detected based on the primary voltage of the ignition coil. Even if the secondary voltage is normal, there is a problem that misfire detection cannot be performed if ignition does not occur completely in the combustion chamber due to other factors such as an abnormal air-fuel ratio. there were.

The present invention was made to solve the above-mentioned problems, and it is possible to easily detect misfires caused by various factors without making any changes to the engine configuration including the conventional fuel injection device. An object of the present invention is to provide a reliable method for detecting misfire in an internal combustion engine.

[Means for Solving the Problems] The present invention makes it possible to detect a misfire in an internal combustion engine by using input information and calculation parameters required in a normal fuel injection device. That is,
The misfire detection method for an internal combustion engine according to the present invention is based on the amount of change in a calculation amount corresponding to the engine load obtained in synchronization with the rotation of the engine in an operating state including at least one of an idling state and a deceleration state of the engine. It is designed to detect engine misfires.

[Operation] In the present invention, the amount of change in the load-equivalent calculation amount required as the basic calculation amount in the fuel injection device of an internal combustion engine is detected in a specific operating state such as the idling state or deceleration state of the engine, and the amount of change is calculated based on the amount of change. When it exceeds a predetermined value, it is determined that a misfire has occurred. By doing so, misfire detection can be easily and reliably performed using an inexpensive device.

[Example] Examples will be described below based on the drawings.

FIG. 1 is an overall system diagram showing an embodiment of the present invention.

In this embodiment, an air cleaner 23 is provided upstream of an intake passage 22 connected to an internal combustion engine 21, and a pot wire type intake air amount sensor 24 and a throttle valve 2 are provided at predetermined locations downstream of this air cleaner 23.
5 is provided.

A bypass passage 22a is provided that connects the upstream and downstream intake passages of the throttle valve 25. In the middle of the bypass passage 22a, a bypass passage control mechanism 26 including an intake control valve (ISC valve) 261, which will be described later, is provided. is provided. The throttle valve 25 also has an idle switch 27 that detects the fully closed position of the throttle valve 25.
is attached. Further, an i:/dijector 28 is disposed downstream of the throttle valve 25 in the intake passage 22 and near the intake boat. Further, an ignition plug 29 is disposed at the top of the combustion chamber of the internal combustion engine 21, and a temperature sensor 30 for detecting the engine temperature is disposed on a jacket provided around the combustion chamber.

The spark plug 29 is connected to an ignition coil 32 and an igniter 33 via a power distributor 31, and
1. A crank angle sensor 311, which will be described later, is installed in the power distributor 31 to pick up a rotation signal and a cylinder identification signal of the internal combustion engine 21.

The control unit 34 includes an intake air amount sensor 24
．． Idle switch 27. Temperature sensor 30 In addition to the output signal of the crank angle sensor 3+1, output signals of a starting switch 35 and the like that detect the starting state of the internal combustion engine 21 are input. Based on this information, the injector 28
．． The igniter 33 and the intake control valve 261 are controlled, and the failure indicator lamp 36 is turned on when a misfire of the engine is detected.

The control unit 34, as shown in FIG.
A CPU 341 with built-in OM, RAM, timer, etc., a rotation signal and a cylinder identification signal from a crank angle sensor 311,
A digital interface 342 receives digital outputs from the start switch 35 and idle switch 27 and outputs them to the CPU 341; analog signals from the intake air amount sensor 24 and temperature sensor 30 are input; the outputs are sent to an A/D converter 343; an analog interface 344 that inputs input to the CPU 341 via the injector 28. FIG. 3 shows a bypass passage control mechanism which is composed of an intake control valve (rsc valve) 26, drive circuits 345, 34, 6, 347, and 348 that output control signals to an igniter 33 and a failure indicator lamp 36, respectively. 26 is a configuration diagram. As shown in the figure, the bypass passage 22a is composed of three passages arranged in parallel, and each passage has an intake control valve (ISO valve) 261, a wax type air valve 262, and an air adjustment valve 263.
is provided. Here, the intake control valve 261 is constituted by a near solenoid valve that controls the amount of intake air by changing the opening area of the bypass passage 22a through duty control. Further, the air valve 262 adjusts the passage area by utilizing the fact that the wax changes between solid and liquid depending on the engine temperature, and the air adjustment screw 263 adjusts the amount of air in the bypass passage 22a. The air adjustment screw 263 absorbs initial variations.

On the other hand, the throttle valve 25 has a throttle adjustment screw 264.
is provided, thereby adjusting the fully open position of the throttle valve 25, and determining the leakage flow rate when the throat valve is fully closed.

Next, the operation of this embodiment will be explained with reference to FIGS. 4 to 8. FIG. 4 is a time chart explaining the operation in the idling state or deceleration state when there is no misfire,
Figure 5 is the same time chart as above when the first cylinder misfires, and Figures 6 to 8 are flowcharts 1 for executing control.
・It is.

In the four-cylinder gasoline engine shown in Fig. 4, the four cylinders (#1.#2.#3.#4) are #l→#3→#4-→#.
Ignition is performed in the order of 2.

The cylinder identification signal in (a) of the same figure is for the compression stroke of cylinder #1
In order for the period including the second dead center (TDC) to become a "bi signal",
A "1.0" signal is generated every four cylinders.

Also, the same figure (b)! The rotation signal here generates a "1.0" signal every 180 degrees of the crank angle.

This rotation signal is a falling signal at the top dead center (TDC) of the CPU 341. i, m are input manually, and CI) tJ3/II accepts this as an interrupt signal.

The air amount signal in FIG. 3(c) is the output of the intake air amount sensor 24 (
Since the sonic speed is choked by the throttle valve 25 during idling or deceleration, the signal remains almost constant.

Furthermore, the rotational angular velocity signal in FIG.
It shows a rotational angular velocity within 0°, and has a periodic small amplitude waveform. Therefore, 18o.

The rotation signal obtained each time is approximately a constant rotation.

A/N in the same figure (e) is the average amount of air per 180° (A)
It is the value obtained by dividing the number of revolutions (N) obtained from the period between top dead center ('1" DC), and indicates the amount of calculation equivalent to the load. If the A/H changes, engine misfire is detected based on the amount of change in A/H.As shown in the figure, the normal value A/H
The amount of change in H is small. Note that the basic fuel injection amount is determined in proportion to this load equivalent calculation 1t (A/N).

Figure (f) shows the intake pressure, D~, 1e [ro
When the fuel injection device based on the NIC system is in H mode, the sulfur fuel injection amount is determined by this intake pressure signal, and in that case, the intake pressure becomes the load-equivalent calculation amount instead of the A/N.

In addition, (g) in the same figure shows the stroke of each cylinder, and (h) in the same figure shows the stroke when the interrupt signal is generated at the above-mentioned top dead center of the rotation signal based on the cylinder identification signal and the rotation signal. Indicates the required cylinder flag. Note that the number of the cylinder flag corresponds to the cylinder before the cylinder at the top dead center (TDC) of the compression stroke.

Next, a case where the #I cylinder misfires will be explained based on FIG. 5.

In this case, as shown in FIG. 4(d), the rotational angular velocity changes greatly, and therefore the number of rotations per 180° also changes. However, the amount of air is not shown in the same figure (C); it hardly changes because it is being moved at the speed of sound. As a result, A, /N is at the time tt, as shown in (e) of the same figure.
(This amount of change is usually about 10%.) Therefore, a misfire state can be detected based on the value of the amount of change in A/H.

In addition, as shown in FIG. 6(f), the average value of the intake pressure for each I80° also changes significantly at time t.

Note that at this time, the cylinder flag is #2, but since the cylinder next to the cylinder flag whose A/N has changed becomes the misfire cylinder, the misfire cylinder is the #1 cylinder. In this way, it is possible to know which cylinder is misfiring.

Further, when a specific cylinder misfires, the misfire detection can be performed periodically for every four cylinders, so that the misfire can be detected more clearly.

Next, the above control will be explained using a flowchart. FIG. 6 shows an interrupt processing routine that is processed for each TDC.

In this flow, first, the level of the cylinder identification signal is determined in step +01, and if the level is "1", the cylinder flag is set to #1 in step 102, and if the level is "0", step 103 Update the previous cylinder flag. This update is the order of power distribution #l → #3 → #4-
Determined according to #2.

Then, in step 104, the average air It (A) between TDCs is determined. This average air It (A) is
For example, the air flow rate between TDCs is determined at each predetermined sampling period, and is determined by averaging at the TDC timing. Next, in step 105, the number of revolutions (N) is determined from the period between TDCs using a well-known method. and,
In the next step 106, the average air ff1(
A) From the rotation speed (N), load equivalent calculation amount (A/N),
Calculate.

Here, the suffix (i) means the current data.

Next, in step 107, in order to determine the misfire detection range, it is determined whether the engine is in an idling state or a deceleration state based on whether the idle switch 27 is turned on.

If the determination is yes, step 108
, the amount of change in the amount of calculation equivalent to the load between the previous time and this time ((
A/N)□(A/N)i-, ) is determined, and it is determined whether this value is larger than a predetermined value. When this is larger than a predetermined value, a misfire detection flag for the relevant cylinder is set in step +09. Here, the relevant cylinder indicates the cylinder next to the current cylinder flag. Note that the relationship between the cylinder flag and the misfiring cylinder becomes a constant relationship by appropriately determining a misfire detection area for the engine.

If the determination in step I07.1.08 is NO, the misfire detection flag for the relevant cylinder is reset in step 110, and the process proceeds to step 113.

After the misfire detection flag is set in step +09 above, step l1. In I, it is determined whether misfires have been detected consecutively n times in the same cylinder. In the case of three consecutive misfires, the misfire determination flag for the relevant cylinder is set in step 112, and the process proceeds to the next step +13. On the other hand, if the determination in step II+ is NO, the process directly advances to step 113. In addition, as described later, when the misfire determination flag in item 1 is set to - degrees, the key switch is turned off.
It is memorized even if F2 is activated, and is retained until the battery is removed.

Next, in step +13, (A/N) is moved to (A/N), -, in preparation for the next time.

Thereafter, the fuel injection pulse width determination process and the like are performed based on this A/N value.

FIG. 7 shows an initialization routine, which is executed only once when the key switch is turned on. In this routine, the determination of cold start in step 201 is made by a control device having a memory backup function. In devices equipped with such a control device, the initialization routine when the power switch is turned on immediately after connecting the battery is called a cold start.
Also, turn off the ghee switch with the battery connected.
After Pt, the next time it is turned on is called a pot star). Such a control device is used when it is desired to retain the memory contents even if the key switch is turned off.

In this flow, if a cold start is determined in step 201, a misfire detection flag is set in step 202.
All misfire determination flags are reset, and if not, the contents of these flags are held. Note that after passing through this flow, the process continues to initialization for the fuel injection device.

Next, FIG. 8 shows a main routine, which is a processing routine performed at predetermined time intervals. In this routine, step 30
If the misfire detection flag is set in step 1, step 3
In step 02, the failure indicator lamp 36 is turned on, and if it has been reset, in step 303, the failure indicator lamp 36 is turned off.

In addition, in the above embodiment, in order to easily perform calculations, misfire detection is performed using the previous and current load-equivalent calculation amounts (A, /
Although the determination is made based on the difference in N), it is also possible to make the determination based on the ratio between the previous value and the current value.

[Effects of the Invention] As described above, according to the present invention, engine misfire is detected based on the amount of change in the calculation amount corresponding to the engine load when the engine is idling or decelerating. Manual information and calculation parameters obtained from the fuel injection device can be used, and misfire detection can be easily and reliably performed using an inexpensive device.

[Brief explanation of the drawing]

Fig. 1 is an overall system diagram showing one embodiment of the present invention, Fig. 2 is a block diagram of its control unit, Fig. 3 is a block diagram of its bypass passage control mechanism, and Fig. 4 is a diagram when no misfire occurs. Figure 5 is a time chart 1 explaining the operation in the idling or deceleration state, Figure 5 is the same time chart when the first cylinder is misfiring), Figures 6 to 8 are time charts for executing the control. [J-char), FIG. 9 is a block diagram of a conventional misfire detection device. In the figure, 21 is an internal combustion engine, 24 is an intake air amount sensor, 2
7 is the idle switch, 34 is the control unit,
311 is a crank angle sensor.

Claims (1)

[Claims] (1) A misfire of the engine is detected based on the amount of change in the calculation amount corresponding to the engine load obtained in synchronization with the rotation of the engine in an operating state that includes at least one of an idling state and a deceleration state of the engine. A misfire detection method for an internal combustion engine.