Abstract: A vehicle brake system includes a first fluid chamber whose volume changes corresponding to the amount of advancement and retraction of the input piston, a second fluid chamber into which hydraulic pressure from a hydraulic pressure source is introduced after adjustment in a pressure regulator, a third fluid chamber kept at the atmospheric pressure, a stroke simulator which generates a reaction force to the brake operation corresponding to a change in volume of the first fluid chamber, a master cylinder, a partition member partitioning each of the second and third fluid chambers from the first fluid chamber, first and second seal members disposed in respective fitting gaps, and an annular member having both ends abutting respective seal members. The annular member divides a space into first and second space portions whose volumes respectively increases and decreases by the same amount when the annular member moves in one axial direction.

Abstract: In order to address a problem with the effectiveness of a brake booster device, provision is made for the latter to be produced in the form of hydraulic servo control. In such an instance, a master cylinder (7-10) of a braking circuit (3-4) is provided with a pressure chamber (19) upstream of the braking circuit. This pressure chamber is then subjected to an injection (28) of hydraulic fluid by a pump (34). The pump is operated (39) according to the braking requirements. The servo control comprises a set of moving gear (54) sensitive to these requirements and that work an injection valve (29-30).

Abstract: A normally closed secondary solenoid opening/closing valve 36 is provided along a secondary branched fluid pipe 35 establishing a communication between an accumulator 11 and a reservoir 8 through a fluid pressure input side to a fluid pressure output side of a regulator valve 3, and in the event that a fluid pressure supplied to the regulator valve 3 decreases down to or lower than a predetermined range due to something abnormal occurring in the accumulator 11, the state of the secondary solenoid opening/closing valve 36 is changed over from a closed state to an opened state, whereby a residual pressure in the accumulator 11 and a residual pressure in the output fluid pressure chamber 15 can be released through the reservoir 8 which is in communication therewith through an output fluid pipe 31 and the secondary branched fluid pipe 35 along which the secondary opening/closing valve 36 is provided.

Abstract: A fully hydraulic brake booster/master cylinder unit (10) for a vehicle brake system has a housing (12) and a bore (14) which is formed therein and in which is arranged sealingly and displaceably a primary piston (16) which is coupled to an input member (40) for transmitting an actuating force to the primary piston (16). Located in the bore (14) are a first pressure chamber (22), one boundary wall of which is formed by one end wall (20) of the primary piston (16), and a first booster chamber (46), one boundary wall of which is formed by the other end wall (50), located opposite the end wall (20), of the primary piston (16). The first booster chamber (46) has an inlet for hydraulic fluid under pressure which is used for boosting the actuating force. In order to bring about additional brake boosting comfortably and as required, there is arranged in the bore (14) a second booster chamber (48), to which hydraulic fluid under pressure can be supplied independently of the first booster chamber (46).

Abstract: A vehicle hydraulic system is disclosed comprising a hydraulic fluid reservoir; a pressure force supplying pressurized hydraulic fluid to a discharge header; a fluid conduit between the discharge header and the reservoir; a back pressure valve operative in the fluid conduit to maintain a desired pressure in the discharge header; and a vehicle braking system having a hydraulically operated boost piston assembly for supplementing a force exerted by a vehicle operator to operate brakes of the vehicle braking system. The system further includes a boost pressure control valve responsive to an input from the vehicle operator for selectively directing pressured hydraulic fluid from the discharge header to the boost piston assembly and venting hydraulic fluid from the boost piston assembly to the reservoir.