Fluid pressure controlling device for vehicle braking system

Claim 1

An improved fluid pressure controlling device for vehicle braking system comprising a valve housing provided with an input chamber communicating with an output port of a master cylinder and an output chamber communicating with a rear wheel brake, a resilient valve seat separating said input and output chambers and provided with a valve port through which said input and output chambers communicate with each other, a valve member including a valve rod slidably held by said valve housing and extending through said valve port and a pressure-receiving piston formed integrally with said valve rod and received in said output chamber, said pressure-receiving piston being adapted to open and close said valve port, and a biasing means adapted to resiliently bias said valve member in a direction as to move said pressure-receiving piston away from said valve port, the improvement comprising: a conical valve seat surface formed at an inner peripheral portion of said resilient valve seat for cooperating with said pressure-receiving piston, an annular thin-walled portion adjoining and surrounding said inner peripheral portion, said thin-walled portion being formed at its opposite surfaces with a pair of annular grooves in an opposing relation with each other to define an annular narrowed, flexible portion for greater axial flexibility of said thin-walled portion, and a set spring disposed between said valve seat and said valve member for resiliently urging said valve seat against an end wall of said input chamber, said set spring being received at one end in one of said annular grooves.