JPS61255446A - Program run-away detecting circuit for vehicle control device - Google Patents

Abstract

PURPOSE:To execute the discharging of the capacitor of the time constant circuit at the rise part of the watch dog output and to detect the run-away by the watch dog output continuation by connecting the differentiating element between the watch dog output terminal and the time constant circuit. CONSTITUTION:A capacitor C is connected between a watch dog output terminal 18 of a run-away detecting circuit 19 and a resistance R1, a watch dog output is differentiated, and at the rise and fall parts, negative and positive pulses are supplied to the base of a transistor Q1. At such a time, by selecting the transistor with the sufficiently high electric current amplifying ratio as the transistor Q1, the transistor Q1 is only energized by the watch dog output differentiated by the capacitor C for a short time and discharging is sufficiently executed. When the program is normally processed, the charge of the capacitor C is discharged periodically, and the electric power of the capacitor C will not reach the threshold to energize a transistor Q2.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a program runaway detection circuit for a vehicle control device, and particularly to a program runaway detection circuit of the above type that can more reliably detect program runaway.

<Prior Art> In recent years, CPtJs comprising microprocessors have been increasingly used in vehicle control devices such as constant-speed running devices. Such a CPU performs various control operations according to programs stored in a ROM, but there are cases where the CPU malfunctions mainly due to electromagnetic noise, and normal program processing is not performed. Therefore, various means for detecting program runaway have been proposed in the past. For example, an output terminal for detecting program runaway called a watchdog output terminal is provided in CPtJ, and periodic lock pulses are generated according to the normal processing of the program. It is possible to monitor whether or not the program is being processed normally.

As a circuit connected to such a watchdog output terminal, there is a time constant circuit. For example, when the watchdog output is at a low level, a built-in capacitor in the time constant circuit is charged, and when the watchdog output is at a high level, the capacitor is charged. If the capacitor is discharged and the program runs out of control and the watchdog output terminal continues to be at a low level, when the potential of the capacitor exceeds a predetermined threshold, it is determined that the program has run out of control. I'm trying to make a decision.

<Problem to be solved by the invention> However, depending on the degree of runaway of the program, the watchdog output may continue to be at a high level, and in such a case, the capacitor will continue to be discharged. , a runaway program will not be detected.

In view of these drawbacks of the prior art, a main object of the present invention is to provide a program runaway detection circuit that can more reliably detect program runaway in a vehicle control device.

<Means for Solving the Problems> According to the present invention, an object of the present invention is to provide a circuit for detecting runaway of a program using a watchdog output of a CPLJ used in a vehicle control device. Connect the terminal and the time constant circuit via a differential element,
This is achieved by providing a program runaway detection circuit characterized in that a program runaway is detected based on a change in the level of the output of the time constant circuit.

<Operation> If a differential element is connected between the watchdog output terminal and the time constant circuit in this way, the capacitor in the time constant circuit will be discharged at the rising edge of the watchdog output, and the Program runaway is detected not only when the dog output continues to be at a low level, but also when the watchdog output terminal continues to be at a high level.

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

FIG. 1 is an explanatory diagram schematically showing a constant speed traveling device to which the present invention is applied. The actuator unit 2 is provided with three electromagnetic valves including a vacuum valve 3, a vent valve 4, and a safety valve 5. A diaphragm 7 biased in one direction by a coil spring 8 is provided inside the housing 6 of the actuator unit 2, and one end of the electromagnetic valve communicates with a negative pressure chamber 9 defined by the diaphragm 7. are doing. A link member 10 is fixed to the center of the diaphragm 7, and a negative pressure chamber 9 is connected to the link member 10.
The link member 10 moves according to the magnitude of the negative pressure within the
For example, the supply of fuel to the engine is controlled by driving an accelerator pedal.

The other end of the vacuum valve 3 is connected to the intake pipe of the engine via a pipe line 11 and a check valve 13.
By opening the vacuum valve 3, the negative pressure in the negative pressure chamber 9 can be increased, and the movement of the diaphragm 7 can increase the vehicle speed.

The accumulator 12 connected to the pipe line 11 is connected to the negative pressure chamber 9
It functions to store the negative pressure introduced into the tank.

The other end of the vent valve 4 communicates with the atmosphere via a filter 14, and by opening the vent valve 4, the negative pressure in the negative pressure chamber 9 can be reduced, and the movement of the diaphragm 7 can reduce the vehicle speed. can.

Like the vent valve 4, the safety valve 5 communicates with the atmosphere via the air filter 14, and is used to deactivate the constant speed traveling device or detect some kind of abnormality and turn the constant speed traveling device on. Open when stopping the function, negative pressure chamber 9
It functions to communicate with the atmosphere.

FIG. 5 is a circuit diagram showing a conventional program runaway detection circuit used in the constant speed cruise control 6II device 1. C.P.
U15 has an output terminal 16 for valve control and a watchdog output terminal 18.

The output terminal 16 is connected via a resistor R3 to the base of a transistor Q4, whose emitter is grounded and whose collector is connected via R4 to the base of a transistor Q5. The emitter of transistor Q5 is connected to the power supply v8, and its collector is connected to the common terminal 17
are respectively connected to one end of three solenoid valves 3.4.5 via.

Therefore, if the output level of the output terminal 16 is high, transistors Q4 and Q5 are turned on, and the safety valve 5
is closed, and the vacuum valve 3 and vent valve 4 can be opened and closed according to the levels of the vacuum valve control output and the vent valve control output, respectively. Conversely, if the level of the output terminal 16 is -, the transistor Q4
, Q5 are turned off, and the vent valve 4 and safety valve 5 are opened unconditionally.

On the other hand, watchdog output terminal 18 is connected to the base of transistor Q1 via resistor R1. The emitter of transistor Q1 is directly grounded, and its collector is grounded via capacitor C1 and connected to the base of transistor Q2 and to the stabilized power supply VCC via resistor R2. Transistor Q2
Its collector is connected to the power supply VCC, and its emitter is connected to the base of transistor Q3. The emitter of transistor Q3 is directly grounded, while its collector is connected to the base of transistor Q4.

Pulses with a relatively small width are generated from the dog output terminal 18 at a constant cycle, and if the program is processed normally, such pulses will continue to occur at a fixed cycle. (See Figure 6). Therefore, when the watchdog output is at a low level, the transistor Q1 is off, so the capacitor C1 is charged by the power supply VCC via the resistor R2. However, when the watchdog output is at a high level, the transistor Q1 is charged.
conducts and the capacitor C1 is discharged. Here, the voltage of the capacitor C1 rises while the output of the dog dog is at a low level, but by appropriately setting the time constant C1 and R2, the voltage of the capacitor C1 increases before the potential of the capacitor C1 reaches the threshold that turns on the transistor Q2. Transistor Q1 conducts so that the charge on capacitor C1 is rapidly discharged. Therefore, when the watchdog output is generated at regular intervals, transistor Q3 is always in the off state.
There is no interference with the output of the output terminal 16.

However, for example, if the program goes out of control at time T1 and the watchdog output level is low and held at a level (-line margin), transistor Q1 is always turned off, and capacitor C1 is not discharged. , whose potential gradually increases, making transistors Q2 and Q3 conductive (see FIG. 6). As a result, the output of the output terminal 16 is always grounded, and the transistors Q4 and Q5 are always off. Therefore, the safety valve 5 is always open, and the constant speed traveling device is released.

However, depending on the degree of runaway of the program, the seventh
As shown in the figure, the tchdog output may be held at a high level after time T2. In that case, transistor Q1 is always on, capacitor C1 is continuously discharged, and transistors Q2 and Q3
is always off and does not interfere with the output of the output terminal 16 in any way, so runaway of the program is not detected.

FIG. 2 shows a runaway detection circuit 19 according to the present invention, which is similar to the known circuit described above except that a capacitor C is connected between the 1-quote dog output terminal 18 and the resistor R1. In this case, the watchdog output is differentiated by the capacitor C, and as shown in the middle part of FIG. 3, positive and negative pulses are supplied to the base of the transistor Q1 at the rising and falling portions of the watchdog output. At this time, if a transistor with a sufficiently high current amplification factor is selected as the transistor Q1, the watchdog output differentiated by the capacitor C will only make the transistor Q1 conductive for a short time, and the capacitor C
1 can be sufficiently discharged.

Therefore, when the program is normally processed, the charge in the capacitor C1 is periodically discharged, and the potential of the capacitor C1 never reaches the threshold value that makes the transistor Q2 conductive.

As shown in Figure 3, when the watchdog output remains at a low level at time T1, capacitor C1 is no longer discharged, and its potential turns on transistor Q2. As a result, program runaway can be detected as described above.

Moreover, as shown in FIG. 4, even if the watchdog output is held at a high level at time T2, the transistor Q1 becomes conductive at the final rising edge of the watchdog output, discharging the capacitor C1. However, since capacitor C is connected in series, even though the watchdog output is at a high level, transistor Q1 remains off and capacitor C1 is charged, and the potential of capacitor C1 becomes lower than transistor Q2. This makes it possible to detect program runaway.

In the above embodiment, the time constant circuit is formed by using a simple CR circuit and a transistor, but a monostable circuit having a required time constant may also be used. The present invention is particularly suitable as a program runaway detection circuit for a control device in a constant speed traveling system, but it can also be applied to other electronic control devices for vehicles.

<Effects of the Invention> As described above, according to the present invention, simply adding one capacitor greatly improves the accuracy of detecting program runaway using the watchdog output. It is possible to achieve great effects of improvement at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing the functional configuration of a constant speed traveling device to which a program runaway detection circuit according to the present invention is applied. FIG. 2 is a circuit diagram showing the main parts of a constant speed running control device to which a program runaway detection circuit according to the present invention is applied. FIG. 5 is a circuit diagram showing the main parts of a constant speed cruise control device to which a conventional program runaway detection circuit is applied. FIGS. 6 and 7 are waveform diagrams of the program shown in FIG. This is a waveform diagram in the runaway detection circuit. 1...Constant speed travel control device 2...Actuator unit 3...Vacuum valve 4...Vent valve 5...
・Safety valve 6...Housing 7...Diaphragm 8...Coil spring 9...Negative pressure chamber
10...Linkage member 11...Pipe line
12...Accumulator 13...Check valve 1
4...Air filter 15...CPLJ 1
6...Output terminal 17...Common terminal 18...
Watchdog terminal 19.20...Program runaway detection circuit Patent applicant Honda Motor Co., Ltd. Mitsuka Electric Manufacturing Co., Ltd. Representative Patent attorney Yo Oshima - Figure 1 Figure 2 Figure 3 Figure 4 Figure 4 Figure 5 Figure 6 Figure 7 Procedural amendment (voluntary) December 6, 1985 Director General of the Patent Office Mr. Ubuya Michibu 1. Indication of the case 1985 Patent application No. 097398 @ 2. Name of the invention Vehicle control device Relationship between the program runaway detection circuit 3 and the amended case Patent applicant name (532) Honda Motor Co., Ltd. and 1 other person 4, agent address 1-8-Iidabashi, Chiyoda-ku, Tokyo 102
6 Shibusawa Building Telephone 262-17616, Number of inventions increased by amendment 07, Subject of amendment Detailed explanation column of invention of specification and drawing 8, Contents of amendment As attached (1) Specification page 9, No. 8 Correct "constant speed running device" in the line to "constant speed running state". (2) Figure 5 of the drawings is corrected as shown in the attached drawing. (Symbol C in the figure is deleted, and there is no correction in Figure 4.) (The following
Above) 9J1. Figure 5

Claims (1)

[Scope of Claim] A circuit for detecting runaway of a program using a watchdog output of a CPU used in a vehicle control device, comprising: a watchdog output terminal and a time constant circuit connected via a differential element; A program runaway detection circuit is characterized in that a program runaway is detected based on a change in the level of the output of a time constant circuit.