Abstract: A brake system for a vehicle comprises a booster unit including a power piston disposed slidably in a housing for defining a first chamber and a second chamber in the housing, a regulator disposed slidably in the power piston, a flow restrictor formed between the first chamber and a fluid pressure source for restricting flow of fluid in response to movement of the regulator, a pilot pressure chamber disposed upstream of the flow restrictor, a movable member moved by the internal pressure of the pilot pressure chamber thereby permitting communication between the second chamber and the fluid pressure source, and a reaction spring disposed between the power piston and the regulator. A master cylinder is connected to the power piston of the booster unit to supply braking hydraulic fluid at controlled pressure to front and rear brakes, and a brake pedal actuates the regulator of the booster unit to cause movement of the regulator relative to the power piston.

Abstract: A brake system for a vehicle comprises a booster unit including a piston disposed for sliding movement in a cylinder, a pressure chamber defined between the cylinder and the piston, and a valve member arranged for interlocking movement with the brake pedal and disposed slidably in the piston for controlling flow of hydraulic fluid from a fluid pressure source into the pressure chamber. A pressure control valve is disposed between the fluid pressure source and the booster unit for controlling the maximum internal pressure of the pressure chamber of the booster unit depending on the weight of the vehicle sensed by a sensor, and a master cylinder is connected to the piston of the booster unit to supply braking hydraulic fluid at controlled pressure to the front and rear brakes.