Abstract: A hydraulic braking pressure control system includes a shut-off valve (4) which is provided in an oil passage (58) connecting a brake device with an output port in a master cylinder and which is brought into a closed state by a control circuit when a braking operation is detected by an operation-amount detector, and a locking device (5) for inhibiting the closing of the shut-off valve when the output hydraulic pressure from a hydraulic pressure supply source in equal to or less than a predetermined value. The shut-off valve is opened when there is no braking operation, thereby ensuring that even if a hydraulic pressure is delivered from a hydraulic pressure control valve when there is no braking operation, such hydraulic pressure can be released into a reservoir.

Abstract: A fluid pressure booster device includes a booster body, a control piston in the booster body for forward and rearward movements to define a boosting chamber between the control piston and a rear surface of a master piston of a master cylinder, a valve piston in the control piston for forward and rearward movements and communicating at its front face with the boosting chamber, a reaction piston in the control piston for forward and rearward movements and connected to an operating member, the reaction piston defining a reaction chamber between itself and a rear face of the valve piston, a stroke accumulator having an accumulation chamber connected to the reaction chamber, an inlet valve disposed between the control piston and the valve piston and interposed in a flow passage extending between the boosting chamber and a fluid pressure source, the inlet valve being closed when the valve piston is retracted and opening when the valve piston advances, and an outlet valve disposed between the control piston and the

Abstract: A hydraulic booster for a master cylinder in which an inlet valve is interposed between an output pressure chamber at the back of the booster piston and an input pressure chamber connected to a pressure source. Advance of the valve piston opens the inlet valve. An outlet valve between the output chamber and an outlet chamber connected to an oil tank closes at advance of the valve piston relative to the booster piston. The booster chamber is exposed to a rear of a master cylinder operation piston. The valve piston oil feed passage connects input pressure chamber with booster chamber at opening of the outlet valve. The reaction chamber at the front surface of the booster piston is reduced in volume with the advancing movement and is connected to an accumulator making it possible to smooth initial operation of the master cylinder and reduce booster system size.

Abstract: In a hydraulic pressure booster comprising a booster piston slidably fitted in a booster cylinder coupled to a rear end of a master cylinder, the piston having at a leading end thereof an output rod abutting against a rear end of a master piston slidably fitted in the master cylinder, an inlet valve interposed between an output hydraulic oil chamber defined to face a back surface of the booster piston and an input hydraulic oil chamber leading to a hydraulic pressure supply source, the inlet valve being opened in response to an advancing movement, relative to the booster piston, of a valve piston connected to an operating member and slidably fitted in the booster piston, an outlet valve interposed between the output hydraulic oil chamber and an outlet chamber leading to an oil tank, said outlet valve being adapted to be closed in response to the advancing movement of the valve piston relative to the booster piston, and a reaction mechanism provided between the valve piston and the output rod for transmitting

Abstract: A hydraulic booster device comprises a booster cylinder coupled with a rear end of a cylinder body of a master cylinder, a booster piston slidably received in a piston guide mounted in the booster cylinder and spring-biased in a retreating direction, a valve piston connected to an operating member and slidably received in the booster piston, an output hydraulic pressure chamber defined to face a back of the booster piston, an input hydraulic pressure chamber leading to a hydraulic pressure supply source, an inlet valve interposed between the input and output hydraulic pressure chambers and opened in response to the advancing operation of the valve piston relative to the booster piston, an outlet valve interposed between the output hydraulic pressure chamber and an outlet chamber leading to an oil reservoir and closed in response to the advancing operation of the valve piston relative to the booster piston, and a booster chamber facing a back of the operating piston and defined between the operating piston and