Tokico, Ltd.

Hitachi, Ltd.

Kabushiki Kaisha Hitachi Seisakusho

Kabushiki Kaisha Hitachi Seiksakusho

Yasuhiko Amari

Naganori Koshimizu

Tomonori Mouri

Nobumaro Osaka

Hiromi Ando

Takato Ogiwara

Takanobu Enomoto

Yoshinari Iwai

Daigoro Kamase

A piston seal is provided in a circumferential groove formed in a cylinder body. The piston seal is capable of sealing a pressure chamber, which supplies fluid pressure to a discharge passage, from a supply passage, which communicates with a reservoir. The piston seal comprises: an annular base portion; an inner circumferential lip portion projecting from an inner circumferential side of the base portion and being in slidable contact with an outer circumferential surface of a piston; an outer circumferential lip portion projecting from an outer circumferential side of the base portion and being in abutment with the circumferential groove of the cylinder body; and an intermediate projecting portion which is formed between the inner circumferential lip portion and the outer circumferential lip portion of the base portion and which is projected beyond the outer circumferential lip portion. Cutout grooves are formed on a tip side of the intermediate projecting portion. Therefore, when releasing air, a sufficient amount of brake fluid can be supplied through a gap between the piston seal and a bottom surface of the circumferential groove, and the cutout groove. As a result, the number of repetitions of an air releasing operation can be minimized.

Master cylinder

A large-diameter bore portion is formed in a portion defining a pressure chamber in a cylinder body on a side opposite to a circumferential groove relative to a slidable inner-diameter portion. A communication groove capable of allowing communication between the circumferential groove and the large-diameter bore portion is formed in an upper portion of the slidable inner-diameter portion. A point of maximum depth of the communication groove is located radially outward of a bottom of the circumferential groove. The master cylinder of the present invention is capable of preventing the supply of a brake fluid from being restricted in an evacuation process, and enables a reduction in length to be machined of the communication groove, thus reducing the time for machining and suppressing an increase in cost.

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.

Master cylinder and method of producing the same

A master cylinder comprises a cylinder body in a cylindrical form having one end closed and including a discharge passage and a supply passage for a brake fluid, the supply passage being communicated with a reservoir. A piston is slidably disposed in the cylinder body, so as to form a pressure chamber for supplying a fluid pressure to the discharge passage. A piston seal is provided in a circumferential groove formed in the cylinder body, which has an inner circumferential surface thereof in slidable contact with the piston and is capable of sealingly disconnecting the supply passage and the pressure chamber. The cylinder body includes a communication groove which opens into the circumferential groove and extends from the circumferential groove toward the closed end of the cylinder body to thereby connect the circumferential groove and the discharge passage. The communication groove is formed outwardly beyond a bottom surface of the circumferential groove relative to a radial direction of the cylinder body.

A pneumatic booster has a valve member arranged to operate stably even under a large differential pressure. The inside of a housing is divided into a constant-pressure chamber and a variable-pressure chamber by a diaphragm. A plunger and a valve member are disposed in a valve body supported by the diaphragm such that the plunger and the valve member are slidable relative to each other. The valve member is formed from a rigid reinforcing member and an elastic member bonded to the reinforcing member. The plunger is movable in association with an input shaft. The movement of the plunger is transmitted to the valve member through a valve spring, causing the valve member to separate from a seat portion provided on the plunger. Thus, compressed air is introduced into the variable-pressure chamber from a pneumatic device through passages to produce a differential pressure between the variable-pressure chamber and the constant-pressure chamber, which is supplied with a negative pressure from an engine, thereby driving the valve body.

Pneumatic booster

The present invention provides a booster of the gaseous pressure type. The booster of the gaseous pressure type comprises: a power piston dividing the inside of a shell between a constant pressure chamber the inside of which is maintained in an approximately constant pressure, and a variable pressure chamber into which an operation gas can be introduced, wherein the power piston comprises a valve body projecting to the outside of the shell and a movable partition means for dividing the inside of the shell, with the inner periphery of the partition means fixed to the valve body; a valve for introducing the operation gas into the variable pressure chamber through a communication passage, according to a movement relative to the valve body of an input shaft which is connected to a brake pedal, and provided in the valve body; a cover for supporting the valve body and for forming an operation gas chamber which can store the operation gas, together with the shell, provided outside the portion of the valve body projecting from the shell; a gas source generating the operation gas; and a path for supplying the operation gas from the gas source to the operation gas chamber.

Booster of gaseous pressure type

A pneumatic booster comprises a piston dividing a housing into front and rear chambers, the front chamber being is constant communication with a vacuum source, the rear chamber being selectively supplied with an atmospheric pressure source or a compressed air source, wherein a valve body of the piston includes a bore having a retainer mounted within, and an input rod movable within the retainer and having a compressed air passage extending therein, the bore of the valve body also having a first rear control valve and a second front control valve, such that movement of the input rod opens the first rear control valve to allow atmospheric air into the booster chamber and a further movement of the input rod opens the second front control valve to allow compressed air into the booster chamber, resulting in an increased output force of the booster.

Growing community of inventors

Kofu, Japan

Yasuhiko Amari