| 摘要 |
PURPOSE:To prevent abrupt steering operation of a power steering apparatus at high speed running time of a vehicle by increasing steering oil flow rate until an engine speed reaches predetermined value and gradually decreasing it when the engine speed exceeds predetermined value to thereby enhancing the steering characteristics of the steering apparatus at parking time and at low speed running time. CONSTITUTION:When an engine rotation frequency is low and a pump discharge is small, the differential pressure between the front and the rear of a sub piston 34 does not reach a value to move a spool 10 of a control valve. All the discharge oil from a pump 3 is fed into a supply passage 42. When a spool 47 is displaced upon steering of a power steering apparatus, total steering oil flow from cylinder port 62 or 64 into a cylinder 5 is increased as the engine rotation speed is accelerated. When the engine speed is accelerated to increase the discharge oil from the pump 3, the sub piston 34 and the spool 10 are moved to bypass excessive oil flow to thereby feed oil through the passage 42 into a switching valve 8 to thus reduce the steering oil flow rate in response to the opening of a restricted passage 19. |
