Abstract: A master cylinder apparatus for a BBW system is provided, which eliminates a risk of brake delay, even with the use of a plunger-type master cylinder, and which therefore is able to achieve a reduction in size of a master cylinder. The master cylinder apparatus comprises a tandem-type master cylinder connected to wheel cylinders through fail-safe valves and a stroke simulator for ensuring a desired stroke of a brake pedal upon receiving a brake fluid introduced from a fluid pressure chamber in the master cylinder. The master cylinder is arranged in the form of a plunger-type master cylinder in which cup seals are provided on an inner surface of a bore of the cylinder body. A spring force of a second return spring for a secondary piston is set to be larger than that of a first return spring for a primary piston. A retracted position of the secondary piston is limited by a stopper pin extending through an oblong hole formed in the secondary piston.

Abstract: A master cylinder that can sufficiently compensate for an ineffective fluid amount at an initial stage of a stroke, even at a time of sudden braking in a case where a hydraulic control unit is disposed between the master cylinder and a brake device, is provided. The master cylinder includes a control valve that releases hydraulic pressure in a large diameter pressurizing chamber to a reservoir side when the hydraulic pressure in the large diameter pressurizing chamber reaches a fluid-release pressure corresponding to hydraulic pressure introduced via a branched flow path that branches from a communication flow path that connects a hydraulic control unit and a small diameter hydraulic chamber. A restrictor is disposed in the branched flow path for introducing the hydraulic pressure to the control valve.

Abstract: A master cylinder of the invention supplies a brake fluid from a large diameter pressurizing chamber 56 to a small diameter hydraulic chamber 49 by opening a reverse flow checking opening and closing portion 61 by sliding movement of a stepped piston 16 forwardly, that is, fast fill and when the hydraulic pressure of the large diameter pressurizing chamber 56 rises, a control valve 86 escapes the hydraulic pressure of the large diameter pressurizing chamber 56 to a reservoir 12 to gradually lower in accordance with rise of the hydraulic pressure of the small diameter hydraulic chamber 49, thereby capable of reducing a strange feeling in a pedal feeling caused by sudden pressure release of the large diameter pressuring chamber 56.

Abstract: A master cylinder has a cylinder member in the shape of a cylinder, one end of which is closed, and a piston inserted in the cylinder member to form a pressure chamber in the cylinder member. The cylinder member is formed with a port for providing communication between the pressure chamber and a reservoir. The port is formed during casting of the cylinder member, thereby eliminating the need to form the port by boring, and forming the port into an elongated-hole shaped sectional configuration.

Abstract: A master cylinder that can sufficiently compensate for an ineffective fluid amount at an initial stage of a stroke, even at a time of sudden braking in a case where a hydraulic control unit is disposed between the master cylinder and a brake device, is provided. The master cylinder includes a control valve that releases hydraulic pressure in a large diameter pressurizing chamber to a reservoir side when the hydraulic pressure in the large diameter pressurizing chamber reaches a fluid-release pressure corresponding to hydraulic pressure introduced via a branched flow path that branches from a communication flow path that connects a hydraulic control unit and a small diameter hydraulic chamber. An aperture is disposed in the branched flow path for introducing the hydraulic pressure to the control valve.

Abstract: A master cylinder including a cylinder having one end open to the outside. A secondary piston guide ring, a sleeve and a primary piston guide ring are adapted to be fitted in this order into the cylinder from the one open end. A piston is slidably fitted in an axial direction of the cylinder, into each of the secondary piston guide ring, the sleeve and the primary piston guide ring. A retainer is provided at the open end of the cylinder, and adapted to abut against the primary piston guide ring so as to prevent escape of the primary piston guide ring from the cylinder. An elastic member is provided between a rearward end portion of the sleeve and a forward end portion of the primary piston guide ring.

Abstract: A master cylinder of the invention supplies a brake fluid from a large diameter pressurizing chamber 56 to a small diameter hydraulic chamber 49 by opening a reverse flow checking opening and closing portion 61 by sliding movement of a stepped piston 16 forwardly, that is, fast fill and when the hydraulic pressure of the large diameter pressurizing chamber 56 rises, a control valve 86 escapes the hydraulic pressure of the large diameter pressurizing chamber 56 to a reservoir 12 to gradually lower in accordance with rise of the hydraulic pressure of the small diameter hydraulic chamber 49, thereby capable of reducing a strange feeling in a pedal feeling caused by sudden pressure release of the large diameter pressuring chamber 56.

Abstract: A master cylinder of the present invention comprises a cylinder having one end open to the outside. A secondary piston guide ring, a sleeve and a primary piston guide ring are adapted to be fitted in this order into the cylinder from the one open end. A piston is slidable fitted in an axial direction of the cylinder, into each of the secondary piston guide ring, the sleeve and the primary piston guide ring. A retaining means is provided at the open end of the cylinder, and adapted to abut against the primary piston guide ring and prevent escape of the primary piston guide ring from the cylinder. An elastic member is provided between a rearward end portion of the sleeve and a forward end portion of the primary piston guide ring.

Abstract: A master cylinder includes a cylinder, a piston slidably provided in the cylinder, an annular cup seal held on an inner circumferential surface of the cylinder, and a relief port formed in the piston. The piston and the cylinder define a pressure chamber for generating fluid pressure in front of the piston, and the cylinder and an outer circumferential surface of the piston define a fluid supply chamber which communicates with a reservoir. The cup seal is adapted to slide against the outer circumferential surface of the piston to separate the fluid supply chamber from the pressure chamber. The relief port provides communication between the pressure chamber and the fluid supply chamber. A control taper surface is formed on the outer circumferential surface of the piston rearwardly from the relief port. The control taper surface is tapered toward the front of the piston and is capable of abutting against an inner circumferential surface of the cup seal.

Abstract: In the master cylinder of the present invention, a cylindrical portion of a grommet seal includes at least two outer sealing projections on an outer circumferential surface thereof, an inner sealing projection on an inner circumferential surface thereof at a position corresponding to a recess between the outer sealing projections, and an abutting portion adapted to abut against a positioning stepped portion provided in a supply fitting of a reservoir. When the supply fitting is inserted into the grommet seal fitted in a boss of a cylinder body, deformation of the inner sealing projection is relieved by a cavity constituted by the recess between the outer sealing projections. When a hydraulic pressure is applied to the cylindrical portion of the grommet seal, because the abutting portion of the grommet seal abuts against the positioning stepped portion of the supply fitting of the reservoir, the cylindrical portion is axially compressed, so that sealability of the sealing projections can be improved.