Patent ID: 6856870

Claim:
A power steering system, comprising: a steering valve ( 9 ) for controlling a power cylinder ( 8 ); a variable orifice (a) provided upstream from the steering valve ( 9 ); a solenoid (SOL) for controlling a degree of opening of the variable orifice (a); a controller (C) for controlling a solenoid current instruction value (SI) used for driving the solenoid (SOL); a steering angle sensor ( 14 ) and a vehicle speed sensor ( 15 ) which are connected to the controller (C); and a flow control valve (V) for dividing a flow, supplied from a pump (P), into a control flow (QP) supplied to the steering valve (V) in accordance with the degree of opening of the variable orifice (a), and a return flow (QT) circulating back to a tank (T) or the pump (P), the controller (C) determining the solenoid current instruction value (SI) on the basis of a current instruction value (I 1 ) in accordance with a steering angle supplied from the steering angle sensor, a current instruction value (I 2 ) in accordance with a steering angular velocity, and current instruction values (I 3 , I 4 ) in accordance with a vehicle speed, and comprising a delay control section for lessening the rate of decrease only when an incoming current instruction value is abruptly decreased, the delay control section performing delay control on values (I 1 ×I 3 ) and (I 2 ×I 4 ) obtained by multiplication, and outputting the resulting current instruction value.