JPH02220971A - H-bridge circuit in all electrical type power steering gear - Google Patents

Abstract

PURPOSE:To aim at generation of breaking force with a simple construction at the time of trouble of a CPU, by providing, in an H-bridge circuit, a gate voltage applying means for supplying, output voltage of a battery for supplying electric power to an electrical motor for assisting steering, to the gate of a lower step transistor. CONSTITUTION:Lower step driving circuits 6, 7 are driven by signals outputted respectively from the terminals T3, T4 of a CPU 1, so that lower step transistors 13, 14 are controlled by the output thereof. Resistances 8, 9 having high resistance values as gate voltage applying means are provided between a battery 23 and the lower step transistors 13, 14. When the driving circuit 6, 7 come to provide high impedances by turning off an ignition key 2 at the time of any trouble of the CPU 1, voltage of the battery 23 is supplied to respective gates of the transistors 13, 14. Thereby, the transistors 13, 14 are turned on so that a short-circuit condition takes place between the terminals of an electric motor 10, then power generation brake becomes effective. It is thus possible to provide simple constitution for the title device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an H-bridge circuit for an all-electric power steering system, and particularly to measures against a CPU failure.

[Conventional technology]

In a steering system whose power source is a steering assist motor that is bridge-connected between the connection point of the upper transistor and the lower transistor in an H-bridge circuit, for example in a 4WS, when the CPU fails, the power is turned off and the steering wheel is moved to the neutral position using a spring or the like. I was putting it back. However, in this case, there is a danger that the steering wheel may return suddenly, so the electric motor is used as a generator.
In order to return the motor slowly using dynamic braking, a relay contact can be configured to short the motor terminals, or power can be supplied from a separate power source to the drive circuit to turn on the upper or lower transistors that make up the H-bridge circuit. I was doing a lot of things.

[Problem to be solved by the invention]

However, the method of shorting between the terminals of a motor using a relay contact requires a large-capacity contact to allow a large short-circuit current to flow, and also requires a transistor that constitutes an H-bridge circuit with the drive circuit in an active state. When turned on, it has the disadvantage of continuously consuming power.

[Means to solve the problem]

In order to eliminate such drawbacks, the present invention provides a gate voltage applying means for supplying the output voltage of the battery that supplies power to the steering assist motor to the gate of the lower stage transistor.

[Effect]

In the H-bridge circuit of the all-electric power steering system according to the present invention, when the power is turned off when the CPU fails, the lower stage transistor is turned on by supplying power supply voltage from the battery.

〔Example〕

FIG. 1 shows a control system to which an H-bridge circuit of an all-electric power steering system according to the present invention is applied. In the same figure, 1
is a signal controller including a CPU, 2 is an ignition key switch, 3 is a relay, 4 and 5 are upper drive circuits, 6 and 7 are lower drive circuits, and 8.9 is a high resistance value as a gate voltage application means. 10 is a steering assist electric motor, 11.12 is an MO3 field effect transistor (MOSFET) as an upper stage transistor, 13.
14 is a MOSFET as a lower stage transistor, 15~
18 is a diode, 19 to 22 are Zener diodes for gate protection, and 23 is a battery.

The upper stage drive circuit 4 is driven by a signal from the terminal T1 of the signal controller 1, and controls the on/off of the upper stage transistor 110 by its output.

The upper stage drive circuit 5 is a circuit having the same configuration as the drive circuit 4, and is driven by a signal from the terminal T2 of the signal controller 1, and controls the on/off of the upper stage transistor 12 by its output. Further, the lower drive circuits 6 and 7 are connected to terminals T3. Driven by the signal from T4, its output drives the lower transistors 13 and 14.
control on/off.

The lower drive circuits 6 and 7 are three-state drive circuits of rHJ level, "L" level, and high impedance, and are in high impedance when the signal controller 1 is powered off. Battery 23 and lower transistor 13
．． A resistor 8.9 having a high resistance value is provided between the signal controller 14 and the drive circuit 6 when the power is turned off by turning off the ignition key switch 2 when the signal controller 1 fails.
When transistor 7 becomes high impedance, transistor 1
3. Supply battery voltage to the gate of 14. This turns on transistors 13 and 14, causing motor 1
0 terminals are short-circuited by the transistor 13 or 14, and the electric motor 10 is subjected to a dynamic brake, thereby preventing the steering wheel from suddenly returning to the neutral position. In addition,
Either one of the resistors 89 may be used. For example, if resistor 9 is not present, the battery voltage will be reduced to resistor 8. The signal is supplied to the gate of the transistor 14 via the drive circuit 6 and the drive circuit 7.

When the ignition key switch 2 is on and the signal controller 1 is in normal operation, the transistors 13 and 14 are controlled on and off by rHJ level or rLJ level signals from the drive circuits 6 and 7. resistance 8
, 9 have a high resistance value, so that the normal operation of the signal controller 1 is not affected in any way.

FIG. 2 is a circuit diagram showing another embodiment of the H-bridge circuit, showing a drive circuit 6 and a transistor 13 as an example. In this embodiment, the battery voltage is divided by resistors 8a and 3b having high resistance values. The voltage is applied to the gate of transistor 13 and similarly to transistor 14, so that transistors 13 and 14 are brought into a semi-conducting state to generate an appropriate braking force.

FIG. 3 is a circuit diagram showing still another embodiment of the H-bridge circuit and another embodiment of the drive circuit 6. In FIG.

The gate voltage supplied to the transistor 13 is a constant voltage determined by the Zener diode 24, and the gate voltage supplied to the transistor 13 is a constant voltage determined by the Zener diode 24.
The conduction resistance of No. 3 can be set accurately.

Since the drive circuit 6 needs to output both rHJ and rLJ levels, an appropriate impedance element is inserted in series.

FIG. 4 is a circuit diagram showing another embodiment of the relay 3, in which the normally open contacts a are connected to the drains of transistors 11 and 12 for supplying power to the H-bridge circuit, and the normally closed contacts a are connected to the drains of transistors 11 and 12. This is a configuration in which the contacts 1 and 2 are used to supply voltage to the gates of transistors 13 and 14.

〔Effect of the invention〕

As explained above, the H-bridge circuit of the all-electric power steering system according to the present invention is provided with a gate voltage applying means for supplying the output voltage of the battery that supplies power to the steering assist motor to the gate of the lower stage transistor. As a result, braking force can be generated using this gate voltage, which eliminates the need for conventional large contact capacity relays and the associated thick wire wiring, and also makes it possible to activate the drive circuit as in the conventional case. Since it is not necessary, power consumption is eliminated, and the effect is that the electric motor can be completely braked at low cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a control system to which an H-bridge circuit of an all-electric power steering system according to the present invention is applied, and FIG.
FIG. 3 is a circuit diagram showing another embodiment of the bridge circuit, FIG. 3 is a circuit diagram showing still another embodiment of the H-bridge circuit and another embodiment of the lower drive circuit, and FIG. 4 is a circuit diagram showing another embodiment of the relay. FIG. ■... Signal controller, 2... Ignition key switch, 3... Relay 4.5... Upper drive circuit, 6, 7... Lower drive circuit, 8, 9... Resistor, 10 ...Electric motor for steering assist, 11.12...
・Upper stage transistor, 13.14...Lower stage transistor, 15-18...Diode, 19-22...Zener diode for gate protection, 23...Battery patent applicant Jidosha Kiki Co., Ltd.

Claims (1)

[Claims] It has an upper transistor driven by an upper drive circuit and a lower transistor driven by a lower drive circuit,
An H-bridge circuit for an all-electric power steering device in which a steering assist electric motor, which is bridge-connected between a connection point between the upper transistor and the lower transistor, is rotated forward or reverse by selectively driving the upper transistor and the lower transistor. H-bridge of an all-electric power steering system, characterized in that the H-bridge of an all-electric power steering device is provided with gate voltage applying means for supplying the output voltage of a battery that supplies power to the electric motor to the gate of the lower stage transistor when an abnormality occurs in the drive circuit. circuit.