Hydraulic power steering apparatus

Claim 1

A power steering apparatus comprising: a hydraulic actuator for generating steering assisting force by hydraulic pressure being supplied from a pressure source to a low pressure side; a hydraulic control valve for controlling said hydraulic pressure to be supplied to said hydraulic actuator according to a quantity of relative movement between a valve body and a casing thereof accompanying a steering operation; a first restriction means for exerting restriction force corresponding to at least vehicle speed against the relative movement between said valve body and said casing, wherein said first restriction means has plungers being installed movably at a part of said casing and a reaction chamber being formed at one side in the direction of movement of said plunger so as to supply hydraulic pressure from a vehicle speed pump to said plungers corresponding to vehicle speed, said first restriction means applying its restriction force corresponding to said hydraulic pressure being introduced to said reaction chamber so as to exert it against said relative movement through said plungers wherein said first restriction means exerts restriction force corresponding to hydraulic pressure being supplied from a vehicle speed pump for generating hydraulic pressure corresponding to vehicle speed; a second restriction means for exerting restriction force corresponding to said quantity of relative movement against the relative movement between said valve body and said casing; wherein said second restriction means has a throttled path being provided between said reaction chamber and low pressure side and whose opening is controlled according to the movement of said plungers being generated due to said relative movement.