Braking pressure control valve unit

In a fluid pressure control device for a vehicle braking system incorporating between a master cylinder and rear wheel brake cylinders, said master cylinder being operated by a push-rod of a brake pedal, which control device comprises a housing adapted to be mounted on a vehicle body frame, said housing being provided thereon with an inlet port for connection to said master cylinder and an outlet port for connection to said rear wheel brake cylinders and provided therein with a valve chamber in communication with said inlet and outlet ports;

• a valve seat provided within said valve chamber to permit fluid flow therethrough;
• and an inertia-controlled ball disposed within said valve chamber for normally permitting fluid communication between said inlet and outlet ports through said valve seat but adapted to co-operate with said valve seat to cut-off the fluid communication when said ball is subjected to a deceleration in excess of a predetermined value;
• the improvement comprising:
• solenoid means having a solenoid winding attached to said housing and a plunger extending through said solenoid winding into said valve chamber and located behind said ball, said plunger being moved forwardly by energization of said solenoid winding to engage said ball against said valve seat;
• a normally open switch means attached to a portion of said push-rod for connecting said solenoid winding to a source of electricity when closed;
• and
• a movable element slidable on said push-rod to be displaced toward said switch means by inertia force acting thereon when said brake pedal is rapidly depressed, said movable element closing said switch means when engaged with said switch means.