| 摘要 |
PURPOSE:To prevent the steering auxiliary effort of a power steering unit from largely varying, by keeping off a sudden variation in motor revolution at the time of operating a switching device. CONSTITUTION:A comparator circuit 22 outputs a voltage signal commensurate to a new car speed to a duty control circuit 44 via a selector switch 46 even when a change in car speed or in motor revolution due to the variation of load in a motor 13 occurs. For this reason, the control circuit 44 compares both values between a signal outputted by a generator circuit 50 and a signal outputted by the comparator circuit 22 and then outputs a square wave-base current to a transistor 23 whereby a continuous rating current flowing into the motor 13 is controlled by a chopper. Since the motor 13 drives a pump 14 with a revolution commensurate to the car speed irrespective of its load, the quantity of an operating (hydraulic) fluid discharged out of the pump 14 varies with the car speed so that the steering auxiliary effort produced by a power steering unit 12 enjoys dependability on the car speed, thus steering performance is made yet better. |
