Servo valve device in power steering apparatus

Claim 1

In a power steering apparatus having a fluid pressure motor supplementing manual steering torque, a first rotatable steering rod member rotating in response to the action of said fluid pressure motor, a manually rotatable second steering rod member aligned with said first steering rod member, and a servo valve device serving to distribute fluid under pressure to said fluid pressure motor in response to rotational phase difference between said first steering rod member and said second steering rod member due to manual steering torque, said servo valve device comprising: a main valve member mounted on one of said two steering rod members nd having an axial slot extending from one open axial end thereof toward a closed axial end in a plane containing a rotational axis thereof; partition means housed in said axial slot and separably fixed to said main valve member for fluid-tightly partitioning said axial slot into at least two axially spaced slots so as to respectively define a first valve chamber and a second valve chamber being axially spaced apart, said first valve chamber being connected to a fluid supply line and being provided with a pair of distribution ports, one of which communicates with one of the operative ports of said fluid pressure motor and the other of which communicates with the other of said operative ports of said fluid pressure motor, said second valve chamber being connected to a fluid exhaust line and being provided with a pair of injection ports, one of which communicates with said one of said distribution ports and the other of which communicates with said other of said distribution ports; a radially extending first flap valve member mounted on the other of said two steering rod members and located in said first valve chamber for controlling flow of said fluid being supplied under pressure to said two distribution ports; and a radially extending second flap valve member integrally formed with said first flap valve member and located in said second valve chamber for controlling flow of said fluid under pressure from said two injection ports.