JPH0534505B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a control device for a main relay that turns on and off power supplied from an automobile battery to an automobile electronic control device.

Prior Art and Problems In this type of conventional main relay control system, for example, as shown in Fig. 1, the ignition switch 1
output signal a and the control microcomputer 2
The output b of a certain output port is input to the NOR circuit 3, and the output of the NOR circuit 3 excites the coil of the main relay 4. That is, when the ignition switch 1 is closed, the signal a becomes high level and the output of the NOR circuit 3 becomes low level, and the current flowing from the automobile battery 5 to the NOR circuit 3 turns on the main relay 4, which includes the microcomputer 2. Power is supplied to each part of the automobile electronic control device 6. Furthermore, the microcomputer 2 monitors the open/close state of the ignition switch 1 by detecting the level of the signal a, and when the signal a becomes low level, that is, the ignition switch 1
When the ignition switch is opened, necessary measures are taken after the ignition switch is turned off, such as initializing the stepper motor 7 that controls the bypass air flow rate under ISC control, and then the output b is set to a low level and the main relay 4 is shut off. It is. In FIG. 1, 8 has a so-called watch-dog timer function that detects an abnormality in the microcomputer 2 by monitoring a certain output signal c of the microcomputer 2 whose level changes intermittently during normal operation. An abnormality detection circuit 9 to be realized, and upon detection thereof, output an initialization signal (Reset) d for the microcomputer 2 to initialize the microcomputer 2, and output a fail signal e to inform the outside of an abnormality in the microcomputer 2. At the same time, when the microcomputer 2 is being initialized, the switches 10 and 11 are switched from the output port side of the microcomputer 2 to the self side.
This is a backup circuit equipped with a control circuit 13 that outputs a signal to the actuator to prevent the stepper motor 7 and other actuators 12 from becoming in a dangerous state via the terminals 0 and 11, and backs up the operation of the microcomputer. This circuit is especially required for automotive electronic control devices, which strongly require the following.

By the way, according to the configuration shown in FIG. 1, when the microcomputer 2 becomes abnormal, a dangerous situation can be avoided by the backup circuit 8, but when the microcomputer 2 becomes abnormal, the level of the signal b becomes undefined. Even if the ignition switch 1 is turned off, there is no guarantee that the main relay 4 will be cut off, and there is a risk that an unexpected accident may occur due to the continued supply of power.

OBJECT OF THE INVENTION The present invention has improved the conventional drawbacks, and its purpose is to improve the ignition switch 1.
When the microcomputer 2 is turned off, the main relay 4 is reliably cut off even if the microcomputer 2 is abnormal, and the power to the electronic control device for the automobile can be cut off.

Structure of the Invention The gist of the present invention is to detect abnormalities in the microcomputer by monitoring a control microcomputer and a specific signal that is output from the microcomputer and whose level changes intermittently during normal operation. In a control device for a main relay that turns on and off power supplied from an automobile battery to an automobile electronic control device that is equipped with a backup circuit that sometimes generates a fail signal to indicate a fail signal, the backup circuit is an ignition control device. When the cutoff of the ignition switch is detected, a fail signal is output, and the output signal indicating the cutoff of the ignition switch and the fail signal are taken in. When the output signal is detected and the fail signal is detected, the main relay is activated. This is a main relay control device in an electronic control device for an automobile, characterized in that a control means for shutting off is provided. Therefore, when the ignition switch is turned on, the main relay is immediately turned on by the output signal of the ignition switch, and when the ignition switch is turned off, the main relay is turned on by the fail signal output from the backup circuit. The relay will be cut off. Therefore, even if the microcomputer is abnormal when the ignition switch is turned off, the main relay will be reliably cut off by the fail signal.

Embodiment of the Invention FIG. 2 is a block diagram showing an example of the hardware configuration of an embodiment of the invention, and the same reference numerals as in FIG. 1 indicate the same parts. The difference between the configuration in FIG. 2 and the configuration in FIG. 1 is that in terms of hardware, the output signal b of the microcomputer 2 is
Instead of inputting the fail signal e to the NOR circuit 3,
It is located at the point entered in . Regarding the software of the microcomputer 2, as shown in the flowchart example in FIG. Instead of setting the output signal b to a low level after taking necessary measures after turning off the ignition switch 1, the intermittent level changes of the signal c are forcibly stopped. According to this configuration, when the ignition switch 1 is turned on, the main relay 4 is immediately turned on by the signal a, and when the ignition switch 1 is turned off, the microcomputer 2 is turned on when it is normal. After completing necessary initialization processing and the like for the actuator, the level change of the signal c is stopped. As a result, the backup circuit 8 determines that the signal c is abnormal and outputs a fail signal e. The main relay 4 is cut off by the fail signal e. Also, microcomputer 2
In the event of an abnormality, the microcomputer 2 is unable to control the signal c as described above, but due to the original operation of the backup circuit 8, the main relay 4 is immediately cut off by the fail signal e from the backup circuit 8. .

In any case, when the ignition switch 1 is turned off, a fail signal is inevitably output.

Note that the signal output from the microcomputer 2 to switch the input channel of the A/D converter that AD converts multiple analog outputs such as a throttle opening sensor and a vehicle speed sensor (not shown) is intermittent when the microcomputer 2 is normal. Therefore, this channel initialization signal can be used as signal c.

In addition, the conventionally provided fail signal e
Since it uses the same signal line, there is no need to provide a new dedicated line for relay control, and it is very effective in terms of hardware.

Effects of the Invention As explained above, according to the present invention, when the ignition switch 1 is turned off, even if the microcomputer 2 is abnormal, the main relay 4 is reliably shut off and the electronic control device for the automobile is not connected. The power can be cut off. In addition, in the conventional configuration shown in FIG. 1, it is necessary to allocate a 1-bit output port to control the main relay 4, but in the present invention, this is not necessary and the output port can be used for other controls. This is very effective when using a so-called one-chip microcomputer with a limited number of output ports.

Furthermore, since no new dedicated line for relay control is required, it is very effective in terms of hardware.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional example, FIG. 2 is a block diagram showing an example of the hardware configuration of an embodiment of the present invention, and FIG. 3 is a flowchart showing an example of processing by the microcomputer 2. 1 is the ignition switch, 2 is the microcomputer, 3 is the Noah circuit, 4 is the main relay,
5 is a car battery, 6 is a car electronic control unit, 8 is a backup circuit, 9 is an abnormality detection circuit,
13 is a control circuit, c is a specific signal whose level changes intermittently during normal operation of the microcomputer 2, and e
is a fail signal.

Claims (1)

[Claims] 1 A backup device that detects an abnormality in the microcomputer by monitoring a control microcomputer and a specific signal that is output from the microcomputer and whose level changes intermittently during normal operation, and generates a fail signal to indicate the abnormality. In a main relay control device that is attached to an automobile electronic control device and turns on and off power supplied from an automobile battery, the backup circuit generates a fail signal when it detects that the ignition switch is cut off. A control means is provided for outputting, receiving an output signal indicating that the ignition switch is shut off, and the fail signal, detecting the output signal, and shutting off the main relay when the fail signal is detected. Main relay control device in automotive electronic control device.