Abstract: A brake booster having a constant pressure chamber and a variable pressure chamber formed respectively at both front and rear sides of a power piston within a housing, characterized in that a hollow expansion body expansible axially of the power piston is disposed within the constant pressure chamber and one end of the hollow expansion body is secured fixedly to the housing while the other end of the expansion body is connected to a push rod so that the force magnifying ratio of the brake booster is varied by adjusting the internal pressure in the hollow expansion body.

Abstract: A fluorine-containing aromatic derivative is produced by causing a di(haloacyl)peroxide to react upon benzene, a mono-substituted benzene, naphthalene, or a mono-substituted naphthalene thereby introducing an X(CF.sub.2).sub.n -group into the benzene ring or the naphthalene ring.

Abstract: A brake apparatus has an actuator mechanism for bringing a friction member into tight contact with a braking member so as to obtain a braking force, the actuator mechanism including: a moving piezoceramic member which can be elongated/contracted along a direction in which the friction member is urged; a holder disposed between opposing ends of the friction member and the moving piezoceramic member to couple the friction member and the moving piezoceramic member; and members for selectively restraining movement of the moving piezoceramic element in a direction parallel to the direction in which it is urged with respect to a fixing member.

Abstract: A brake apparatus has an actuator mechanism for bringing a friction member into tight contact with a braking member to generate a braking force, the actuator mechanism comprising:a main actuating unit for moving the friction member to a position where the friction member is in contact with the braking member;a subactuating unit for further urging the friction member which is in contact with the braking member so as to generate the braking force, the subactuating unit being constituted by a piezoceramic element; anda controller for operating the main actuating unit first and then the subactuating unit in accordance with a brake command from a first sensor.

Abstract: A vacuum power servo booster having an improved retainer for an annular seat of a control valve body. A spring seat for a compression spring which presses the annular seat against the valve housing is formed at the front end portion of a retainer. A recess is formed on the front side of the spring seat to receive the skirt of the control valve body. The spring seat is formed by bending a smaller diameter portion of the retainer inwardly prior to assembly. In this manner, the longitudinal axis of the retainer is made to substantially coincide with that of the control valve body.

Abstract: For use in a brake booster of the type having a master cylinder disposed rearwardly of a booster mechanism having a power piston and in which a braking reaction force produced on an output shaft is transmitted therefrom to an input shaft through a reaction disc and a reaction transmitting member, an apparatus is provided for adjusting the magnitude of a clearance defined between the reaction disc and the reaction transmitting member. In this apparatus, the input shaft comprises a first section associated with the reaction transmitting member and a second section on which a valve seat is formed. The valve seat forms a valve mechanism disposed within a valve body for controlling the opening or closing of a passage for hydraulic fluid. The first and the second section of the input shaft are formed by separate members, both of which project toward the front shell and are connected together in a manner to permit their relative position to be adjusted.

Abstract: A reaction force mechanism for a brake power booster includes an elastic member (53) which forms a hydraulic pressure reaction force chamber (50) and is spaced from an end surface (17d) of an input shaft (17) by a predetermined distance (.delta.) so that braking hydraulic pressure is not immediately detected by a driver. In addition, a passage (57) normally provides communication between the hydraulic pressure reaction force chamber and a primary side pressure chamber (45) of the master cylinder, and, alternatively, provides communication between the hydraulic pressure reaction force chamber and a secondary side pressure chamber (46) of the master cylinder when no hydraulic pressure is established in the primary side pressure chamber of the master cylinder.

Abstract: A brake booster includes a master cylinder which is disposed rearwardly of a booster mechanism including a power piston, or toward a brake pedal. A valve mechanism which mechanically cooperates with an input shaft to produce a fluid pressure differential across the power piston includes a first valve seat formed on a valve body defined by a shank portion of the power piston, a second valve seat formed on the input shaft, and a valve head adapted to seat upon the first and the second valve seat in a direction opposite from the direction which is utilized in a conventional brake booster, or in a direction from the front side of the power piston. The valve mechanism is supplied with a fluid pressure from the front side of the power piston, thereby simplifying the construction of a brake booster of the type described.

Abstract: A vacuum power servo booster including a disc-shaped inner shell and a cup-shaped outer shell with a diaphragm secured between the two shells. A radially opening annular groove is formed in peripheral portions of the inner shell by a first annularly bent portion bulging radially inwardly and a second annularly bent portion oriented along the axial direction of the booster. The outer shell includes rectangular recesses into which extend inwardly at the open faces.

Abstract: A vacuum power servo booster including a disc-shaped inner shell and a cup-shaped outer shell with a diaphragm secured between the two shells. A radially opening annular groove is formed in peripheral portions of the inner shell by a first annularly bent portion bulging radially inwardly and a second annularly bent portion oriented along the axial direction of the booster. The outer shell includes rectangular recesses into which extend inwardly at the open faces.