Hydraulic control system for automatic transmissions of motor vehicles

Claim 1

A hydraulic control system for an automatic transmission having a housing and a shaft therein, said system comprising, in combination: (a) a cylinder member engaged with the housing of the transmission and having a pair of fluid passages defined therethrough; (b) a piston member mounted in said cylinder member and having a valve for controlling the opening and closing of one of said fluid passages, said piston member being movable within a predetermined angular limit about said shaft, means for blocking the angular movement of said piston member about the shaft of said transmission; (c) a spring retainer rigidly secured to said cylinder member; (d) a spring between said spring retainer and said piston member and engaged with said piston member for applying a reaction force thereto in the axial direction as well as in the circumferential direction of the shaft of the transmission; (e) a fluid pressure chamber defined by said cylinder member and said piston member, said chamber being connected with said fluid passages; (f) a reaction member rigidly secured to said cylinder member; (g) a first friction element between said reaction member and said piston member and slidably engaged in the axial direction of said transmission with said cylinder member; and (h) a second friction element adapted to engage said first friction element and engaged with a friction element carrying member connected to said shaft, said piston member detecting the direction of rotation of the friction element carrying member relative to the cylindrical member when said first and second friction members are engaged with each other to thereby control the fluid pressure to be supplied to said fluid chamber.