JPH01267362A - Fail safe device for ignition control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To enable the common use of a hardware and to enable reduction of a cost, by a method wherein, in a device which stops an ignition signal from a microcomputer during the occurrence of abnormality and outputs an ignition signal from a different output means, the output means is so formed that an ignition signal is outputted at intervals of a given time. CONSTITUTION:During running of an engine, a microcomputer 20 inputs a reference signal REF from a crank angle sensor and a position signal POS to generate an ignition signal at an optimum timing responding to an engine running condition, and outputs the ignition signal to an ignition device 22 through a switching circuit 21. In this case, a program run signal inverted at a given period is monitored by a run away monitoring circuit 23, and when the period is out of a given range, it is decided that the microcomputer 20 is in a run-away state to output a reset signal. This constitution causes switching of the switching circuit 21 by means of a microcomputer abnormality detecting circuit 24 when abnormality occurs, and outputs an ignition signal, generated at intervals of a given time by a dividing circuit 25, to the ignition device 22.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an ignition control device for an internal combustion engine, and more particularly to a fail-safe device in the event of an abnormality in a microcomputer or the like.

<Prior art> In modern internal combustion engines, a microcomputer determines the optimal ignition timing according to engine operating conditions, and an ignition signal is sent to the ignition system at the optimal ignition timing based on a signal from a crank angle sensor. It is outputting.

Incidentally, such a system in which the ignition timing is controlled by a microcomputer is equipped with a fail-safe device so that the vehicle can run at a minimum level even in the event of a failure of the microcomputer or the like.

Conventional examples of such fail-safe devices for ignition control devices for internal combustion engines include the following, for example.

That is, when the microcomputer malfunctions, the output of the ignition signal from the microcomputer to the ignition device is stopped.
This is to switch to a counter as another ignition signal output means. As shown in Fig. 3, this counter receives a reference signal REF every 180 degrees from the crank angle sensor to the reset terminal R in the case of a 4-cylinder engine, and also inputs the reference signal REF every 180 degrees to the input terminal C.
A position signal PO3 is input every 1° or 2° from the crank angle sensor. Then, as shown in FIG. 4, the reference signal REF is generated (for example, 7 seconds before top dead center
Start energizing the ignition device from 0°), and at the same time,
The number of occurrences of the position signal PO3 from this point on is counted, and when the count value matches the data set in advance in the counter, the power supply to the ignition device is stopped, and this is used as an ignition signal to cause spark ignition. ing. The above data is set so that the ignition signal is output at 10° to 20' before top dead center.

<Problems to be Solved by the Invention> However, in such conventional fail-safe devices, data must be set in accordance with the type of crank angle sensor, that is, the reference signal generation timing and position signal generation interval. The problem is that it is necessary to prepare each counter for each type of vehicle, and it is not possible to share hardware between car models, which increases costs.
Furthermore, there is also the problem that if the crank angle sensor breaks down, there is no backup method available.

In addition, as shown in Japanese Patent Application Laid-open No. 61-286584, when an abnormality occurs in the position signal of the crank angle sensor, there is a type that outputs an ignition signal after a predetermined time elapses from the generation of the reference signal using the reference signal as a reference. There is also a fail-safe device, but in this case as well, if the crank angle sensor itself fails, there is no fail-safe method, as in the above example.

In view of these conventional problems, the present invention eliminates the need for individualization of hardware due to different models of crank angle sensors, makes them common, and reduces costs. The purpose is to maintain a minimum level of ignition function even if the ignition system malfunctions.

<Means for Solving the Problems> For this reason, the present invention stops the output of an ignition signal from the microcomputer to the ignition device when there is an abnormality in at least one of the crank angle sensor or the microcomputer, and outputs another ignition signal. In the apparatus in which the ignition signal is outputted from the output means to the ignition device, the ignition signal output means on the side is constituted by means for outputting the ignition signal at predetermined time intervals.

In the above configuration, the output of the ignition signal from the microcomputer is stopped in the fail-safe mode, and the ignition signal is output from another ignition signal output means at predetermined intervals. The ignition signal can be output to the ignition device without relying on a computer or crank angle sensor. Note that even if the ignition signal is sent at predetermined time intervals that are not synchronized with the crank angle, it is possible to maintain the ignition function that ensures minimum vehicle running.

<Example> An example of the present invention will be described below based on FIGS. 1 and 2.

FIG. 2 shows the system configuration of an ignition control device for an internal combustion engine. Fuel is injected and supplied from fuel injection valves 3 provided in the branch portion for each cylinder.

Each cylinder of the engine 1 is provided with an ignition plug 4, to which a high voltage generated by an ignition coil 5 is sequentially applied via a distributor, thereby igniting a spark to ignite the air-fuel mixture. Ignite and burn. Here, the timing of generation of high voltage in the ignition coil 5 is controlled via a power transistor 7 attached thereto. Therefore, the ignition timing is controlled by controlling the on/off timing of the power transistor 7 using an ignition signal from a control unit 8, which will be described later. In addition, power transistor 7° ignition coil 5
．． The distributor and the spark plug 4 constitute an ignition device.

The Distributoro has a built-in photoelectric crank angle sensor 9. The photoelectric crank angle sensor 9 includes a signal disk plate 11 that rotates together with a distributor shaft 10 and a detection section 12. The signal disc plate 11 is formed with 360 slits 13 for position signals (1° signal) and, in the case of a 4-cylinder engine, 4 slits 14 for reference signals (180° signal). Reference signal slit 1
One of the four is also used to determine No. 1 cylinder. The detection unit 12 detects these slits 13 and 14 and generates a reference signal REF including position signals (720 position signals from 6360 slits 13 per 1001 rotations of the distributor shaft) PO5 and Nα1 cylinder discrimination signal. Outputs .

The control unit 8 includes a CPU and a ROM.

It is equipped with a microcomputer 20 (FIG. 1) that includes a RAM and an input interface, and determines the ignition timing based on signals from various sensors (not shown).
While monitoring the reference signal REF and position signal PO3 from the crank angle sensor 9, an ignition signal is output to the ignition device at a timing synchronized with the ignition timing.

To explain the ignition timing control in more detail, an ignition advance angle ADV predetermined according to engine operating conditions such as engine speed and basic fuel injection amount is searched for, and the control is performed based on this search value. When the ignition advance angle is determined, if the reference signal REF from the crank angle sensor 9 is output at 70 degrees before compression top dead center, the register (70-AD
After setting V) and inputting the reference signal REF, the positilon signal PO8 from the crank angle sensor 9
The value in the register is subtracted by one each time the value is input, and when the value in the register reaches O, an ignition signal is output to the power transistor 7.

Here, a fail-safe device shown in FIG. 1 is incorporated into the control unit 8.

As described above, the reference signal REF and position signal PO3 from the crank angle sensor 9 are input to the microcomputer 20, and the ignition signal is switched to the ignition system via the switching circuit 21 at the optimum timing according to the engine operating conditions. 22 (directly to the power transistor 7). The switching circuit 21 normally connects the microcomputer 20 and the ignition device 22, and in the case of fail-safe, this connection is cut off as described later to prevent the ignition signal from the microcomputer 2o from being input to the ignition device 22. do.

Here, from the microcomputer (CPU) 20,
A program run (P-RUN) signal that is inverted at a predetermined cycle is always output to the runaway monitoring circuit 23. This runaway monitoring circuit 23 monitors the inversion cycle of the program run signal, and when the cycle deviates from a predetermined range, determines that it is JLt of the microcomputer 20 and outputs a reset signal to the microcomputer 20.

On the other hand, the reset signal from the runaway monitoring circuit 23 is simultaneously input to the microcomputer abnormality detection circuit 24. This microcomputer abnormality detection circuit 24 detects the presence or absence of an abnormality in the microcomputer 20 by the number of resets within a predetermined time (for example, twice per second), and when an abnormality exists, the switching circuit 21 switches the ignition signal output means. The microcomputer 20 is switched to the frequency divider circuit 25, which is another ignition signal output means (means for outputting an ignition signal at predetermined time intervals), and the frequency divider circuit 25 is started to operate.

The frequency dividing circuit 25 counts the clock signal and outputs an ignition signal at predetermined intervals, and this ignition signal is sent to the switching circuit 2.
1 to the ignition device 22.

As a result, in the event of an abnormality in the microcomputer 20,
Stopping the output of the ignition signal from the microcomputer 20, outputting the ignition signal from the frequency dividing circuit 25 at a predetermined time,
Perform ignition operation. If you set the ignition signal at each predetermined time to have the optimum cycle when the engine speed is 1 soo to 200 rpm, you can send the ignition signal to each cylinder in turn even if it is not synchronized with the crank angle. Since the fuel can be distributed, the vehicle can run with a minimum ignition function.

Although this embodiment has described fail-safe processing when the microcomputer is abnormal, it is possible to detect this and perform similar fail-safe processing even when the crank angle sensor is abnormal.

In this way, when there is an abnormality in at least one of the crank angle sensor or the microcomputer, the ignition signal from the microcomputer is stopped and the ignition signal is output from the frequency dividing circuit. There is no need for counters, which are individualized hardware depending on the model, and the parts can be shared, making it possible to reduce costs. This allows the vehicle to run for a limited amount of time.

Further, in this embodiment, the ignition device is equipped with a distributor, but in a so-called electronic power distribution system that does not have a distributor, it is possible to output the ignition signal to all cylinders at the same time at a predetermined time interval. It is possible to ensure that the vehicle can run for a limited time.

<Effects of the Invention> As described above, according to the present invention, the ignition signal from the microcomputer is stopped at the time of fail-safe, and the ignition signal is output from another ignition signal output means at predetermined intervals. It is possible to reduce costs by sharing hardware, and to maintain the minimum ignition function not only when the microcomputer is abnormal, but also when the crank angle sensor is abnormal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a fail-safe device showing one embodiment of the present invention, FIG. 2 is a system diagram of the same embodiment, and FIG.
FIG. 4 is an explanatory diagram of a conventional example. 1... Engine 4... Spark plug 8... Control unit 9... Crank angle sensor 20.
...Microcomputer 21...Switching circuit
22...Ignition device 23...Runaway monitoring circuit 2
4...Microcomputer abnormality detection circuit 25.
... Frequency divider circuit patent applicant Japan Electronics Co., Ltd. Representative Patent attorney Fujio Sasashima Figure 2 Figure 3 Figure 4 P-week Door/Dog

Claims (1)

[Claims] An ignition control device for an internal combustion engine that controls ignition timing by a microcomputer based on a signal from a crank angle sensor, wherein when at least one of the crank angle sensor or the microcomputer is abnormal, the microcomputer sends an ignition signal to the ignition device. The output of the ignition signal is stopped and the ignition signal is output from another ignition signal output means to the ignition device, wherein the another ignition signal output means is configured to output an ignition signal at predetermined time intervals. A fail-safe device for an ignition control device for an internal combustion engine, characterized by: