JPS63240466A - Safety device for power steering gear - Google Patents

Abstract

PURPOSE:To promote the prevention of abnormal steering due to a transistor in trouble, by deciding voltage across emitter-collector of the transistor in a motor driving circuit of an electric type power steering (PS) to be in abnormal combination through a decision circuit and cutting off the supply of an electric current to a transistor bridge circuit in the time of deciding abnormality. CONSTITUTION:A predetermined electric type power steering (PS) is actuated being based on a signal of a signal generating control circuit 1 in accordance with a steering amount through a driving circuit 3 of a motor 2 constituted of bridge-arranged transistors 3a-3d and driving transistors 30a-30d. A device, taking out voltage across emitter and collector of each transistor by arithmetic amplifiers 4a-4d, 40a-40d to be compared with reference voltage generating circuits 41a, 41b, decides abnormality of the voltage. When the abnormality is decided, the device, actuating a relay 5c in a cutoff circuit 5 and closing a contact 5d, suspends supply of a current to each transistor 3a-3d in the motor driving circuit 3. In this way, the device promotes the prevention of abnormal steering due to the transistor in trouble.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a safety device for a power steering device that ensures safety in the event of a failure of the power steering device that drives a steering assist motor using a transistor bridge. 0 [Prior Art] Conventionally, a power steering device has been used in which a cylinder is actuated by the hydraulic pressure of an oil pump driven by an engine, but in recent years, all-electric steering devices that do not require troublesome piping have been used. A power steering device has been proposed.

However, electrical circuits are subject to accidental failures, and countermeasures are required. For this reason, JP-A-60-13918
As shown in Publication No. 1, a system that prevents abnormal operation due to transient conditions when the power is turned on,
As shown in Japanese Patent No. 366, a safety device has been proposed that detects short circuits and disconnections in the motor.

[Problems that the invention attempts to resolve]

However, such conventional systems cannot prevent incorrect rotation of the motor due to malfunction of the transistors that make up the transistor bridge, and therefore cannot prevent abnormal steering due to defective parts, which poses a problem in terms of safe operation. 0 It is extremely dangerous for the steering wheel to be suddenly turned in one direction against the driver's will, especially due to a short circuit in the transistor, and it is absolutely necessary to avoid this situation instantly. There was no suitable method.

[A precautionary measure to resolve the problem]

In order to solve this problem, the present invention monitors the operations of the transistors forming the transistor bridge and the transistors that drive the transistors.

[For production]

By monitoring the emitter-collector voltage of both the drive transistor and the transistor driven by the transistor, it is possible to monitor whether the transistor is on or off, and to detect that the state of the transistor is abnormal. ．． -fc, the flow to this transistor bridge is cut off to prevent malfunction and damage from spreading.

〔Example〕

Figure c-t? :' is a circuit diagram showing an embodiment of the invention.

In the figure, 1 is a control circuit that generates nine control signals according to the amount of steering, 2 is a motor, 3 is a motor drive circuit, 4 is a failure determination circuit that determines failure of the motor drive circuit 3, and 5 is a failure of the motor drive circuit. This is a cutoff circuit that cuts off the current supplied to the motor drive circuit. The motor drive circuit 3 is configured in a bridge type and includes nine transistors 3 &~3as and drive transistors 30a~30a for driving them.
It is made up of many things. Failure determination circuit 4 is transistor 3
Operational amplifiers 4a to 4d1 that amplify the emitter-collector voltages of transistors a to 3d; operational amplifiers 40&- that amplify the emitter-collector voltages of transistors 30a to 30d;
A reference voltage generation circuit 41a generates a reference voltage by dividing the 40d% power supply voltage using resistors.

41b1 Compare the output of each operational amplifier 41 to 4d, 40a to 40d with the voltage generated from the reference voltage generation circuit Comparators 42a to 42h % Calculate the non-transitive OR of the comparator outputs E OR43a to 43d1 NOR circuit 44m, 44d %AND circuit 44b, 446
%FOR and an OR circuit 45 that performs a logical sum operation of the NOR circuit output. The cutoff circuit 5 includes directly connected transistors 5m, 5m,) transistors 5b.
Contact 5d of relay 5e and relay 5c driven by
, bias resistors 5s and 5f.

The operation of the device thus constructed is as follows. The control circuit 1 sends a signal having a duty ratio according to the amount of steering to a transistor 30 and a transistor 30a.
t or to the bare terminals of transistor 30b and transistor 30c. For this reason, the transistor 30a.

When a signal is supplied to the bare terminal 30d, those transistors and transistors 3a and 3d are turned on, and a current flows from right to left in the ζ-Meta 2 diagram, and the average value of the current is the duty ratio. Therefore, the amount of rotation of the motor 2 is controlled by the duty ratio. When a signal is supplied to the bare terminals of the transistors 30b and 30c, the direction of the current flowing through the transistors 30b and 30c is reversed, and steering is performed in the opposite direction.

Now, the transistors 30a r 3a, 30d,
When transistor 3a is on, the emitter-collector voltage of those transistors is saturated and is about 0.3 volts. These voltages are connected to operational amplifiers 40m, 4m,
4d? comparator 42d via 40d;
It is supplied to the inverting input terminals of 42c r42F and 42h, respectively. A predetermined reference voltage is supplied to the non-inverting input terminals of these comparators from the reference voltage generation circuits 41m and 41b, and this reference voltage is output from the operational amplifier when the transistor of the motor drive circuit 3 is on. It is set higher than the level, and lower than the level output from the operational amplifier when the transistor of the motor drive circuit 3 is off. Ninth, as in the above condition, transistors 30a and 3m
, 3d, and 30d are on, the comparator 42a
, 42e t 42ft 42h are sending out a "1" level signal.

On the other hand, since the control circuit 1 is designed to drive only the transistors in the diagonal direction among the transistors forming the bridge, the transistors 30b and 3b.

3c and 30c are off, and therefore, for the reason mentioned above, the comparators 42e and 42t are turned off.
42b.

42m is sending out a "0" level signal. This next EOR43a ~ 43d %NOR circuit 44a * 44
d.

The input and output of the AND circuit N 44b t 44e is as shown in the truth table shown in Table M2. However, in Table 2, ■～X
■ indicates the state shown in Table 1.

Table 1 No. 2 The condition of ■ and ■ is E
OR circuit 431L to 43as OR circuit 44ar44ds Since both AND circuits 44b and 446 output a "0" level signal, OR circuit 45 outputs a "0" level signal. Therefore, the transistors 5a*5b of the cutoff circuit 5 are turned off, and the relay 5c is not energized, so that the relay contact 5d is connected to the motor drive circuit 3.
Current is supplied through.

However, in the abnormal states ■ to Relay 5c, which turns on t 5b, is energized. As a result, the relay contact 5d is turned off and the current supplied to the motor drive circuit is cut off. Next, even if any transistor in the motor drive circuit 3 becomes short-circuited or disconnected, the current is cut off, and an accident in which the motor 2 rotates incorrectly can be prevented.

In addition, by inserting a retrigger pull type one-shot multivibrator into the base of the transistor 5b of the cutoff circuit 5, the relay 5 can be operated even in chopper control.
The operation can be made continuous instead of intermittent.

〔Effect of the invention〕

As explained above, the present invention has the effect of being able to prevent abnormal steering due to defective parts because the operation of the transistor bridge and the transistors that drive it are monitored.

[Brief explanation of drawings]

The figure is a circuit diagram showing one embodiment of the present invention. 1*...Control circuit, 2...Motor, 3...Motor drive circuit, 4...Failure determination circuit, 5...Connection circuit, 3a to 3d, 30a to 30d. 5a, 5b... dispute/transistor, 43a-43d
...EORl 44&, 44d and...Noah circuit, 44b, 44c fist---and circuit, 5 C self @ @
11 relay~.

Claims (1)

[Claims] A power steering device that maintains safety in the event of a failure of the power steering device, which turns on and off the transistors in the transistor bridge generated by supplying a signal corresponding to the amount of steering to drive the motor and performs steering using the torque. In the safety device of the control device, there is a judgment circuit that judges whether the combination of emitter-collector voltage of each transistor that is on or off used in the transistor bridge is a normal combination, and a judgment circuit that judges whether the combination is abnormal or not. A safety device for a power steering device, comprising a cutoff circuit that cuts off current supplied to a transistor bridge when a state is determined.