Hydraulic reaction device for power steering apparatus

Claim 1

A hydraulic reaction device for a power steering apparatus for supplying a pressure oil to left and right chambers of a power cylinder via a flow path switching valve for switching the pressure oil in a main flow path extending from a main pump in accordance with a steering operation, said hydraulic reaction device selectively constraining relative pivotal displacement between input and output shafts which comprise a rotary flow path of the flow path switching valve, and including an oil pressure reaction mechanism provided between the input and output shafts, a reaction plunger actuated according to the oil pressure reaction mechanism, and a hydraulic reaction chamber, comprising: a sub flow path independently arranged from said main flow path; a vehicle-speed responsive pump responsive to vehicle-speed to change a discharge flow rate, and for supplying oil pressure to said sub flow path; a reaction oil pressure control means having a reaction oil pressure control valve for variably controlling a flow rate via an oil pressure supplied from said vehicle-speed responsive pump and via an oil pressure of said main pump; and said hydraulic reaction chamber for supplying a reaction oil pressure to said reaction plunger being provided between said vehicle-speed responsive pump and said reaction oil pressure control means in said sub flow path, whereby the reaction oil pressure caused by said reaction oil pressure means is controlled in accordance with a magnitude of the oil pressure in said main flow path flowing from said main pump to said left and right chambers of the power cylinder.