Patent ID: 6843342

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 distributing a flow supplied from a pump (P), to 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) calculating or storing a current instruction value (I 1 ) in accordance with a steering angle received from the steering angle sensor and a current instruction value (I 2 ) in accordance with a steering angular velocity, multiplying each of the current instruction value (I 1 ) based on the steering angle and the current instruction value (I 2 ) based on the steering angular velocity by a current instruction value (I 3 , I 4 ) set on the basis of a vehicle speed, applying a current instruction value (I 7 , I 8 ), according to the vehicle speed, serving as a limit value to each of the current instruction value based on the steering angle and the current instruction value based on the steering angular velocity obtained by the multiplication, selecting a larger value out of the two current instruction values below these limit values, and determining the selected value as a solenoid current instruction value (SI).