| 摘要 |
A control for a hydraulic power boost assembly in a braking system. Located within a housing of the boost assembly is a control piston which has a projection extending therefrom for abutting a spool valve in a valve chamber. The spool valve is responsive to movement of a brake pedal and regulates hydraulic fluid pressure to move a power piston which activates the master cylinder which in turn supplies fluid pressure to the wheel cylinders of a vehicle. The control piston is a stepped diameter piston which has one end thereof exposed to the fluid pressure in the master cylinder and the other end thereof exposed to the fluid pressure acting on the power piston. Upon manual activation by the brake pedal, the fluid pressure from the master cylinder moves the stepped control piston into engagement with the spool valve thereby preventing it from moving until the brake pedal is released. Such an arrangement prevents sudden surges of hydraulic fluid to the power piston in the power chamber which would cause an abrupt stop of the vehicle.
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