Jidosha Kiki Co., Ltd.

Atushi Satoh

Tohru Satoh

Haruo Suzuki

Junichi Ohki

A power piston assembly for booster, in particular, an improvement of an axial portion of a power piston and a retainer which is engaged therewith is disclosed. A front power piston is formed with a first and a second tubular section around its inner periphery, and the first tubular section is fitted around a flange of a valve body and is prevented from disengagement therefrom by an annular retainer. Around its outer peripheral edge, the retainer is formed with a peripheral tubular portion, which is disposed as a press fit around the second tubular section of the front power piston from the front side, thereby connecting the front power piston to the flange of the valve body. With this arrangement, the front end of the first tubular section of the front power piston may be located rearward of the front end of the valve body (or its flange). Accordingly, the axial size of the first tubular section and hence of the booster may be reduced as compared with a conventional arrangement.

Power piston assembly for booster with diaphragm retainer

A brake booster such as of a tandem type having a center plate disposed within a shell is disclosed. A valve body has a stepped end face, from which a cylindrical portion extends rearwardly. The cylindrical portion extends through a rear power piston and a rear diaphragm while maintaining a hermetic seal therebetween, with a distal end of the cylindrical portion being disposed within a variable pressure chamber of a rear chamber. The internal space of the cylindrical portion defines the rear end of a variable pressure passage. This arrangement allows the rear end of the variable pressure passage (the cylindrical portion) to be disposed in radially overlapping relationship with the rear power piston, thereby allowing the external diameter of the valve body to be reduced. In this manner, the effective area of the front power piston connected to the valve body may be increased as compared with the prior art.

Brake booster

A brake booster includes a center plate disposed within a shell. A seal member is provided to interrupt a communication between a variable and a constant pressure chamber which are located across the center plate. The seal member is formed with a lip, acting as a check valve which releases to the variale pressure chamber any pressure developed in the constant pressure chamber which is to be sealed by the seal member and which rises above the pressure in the variable pressure chamber.

Brake booster with one-way valve on centerplate

A seal unit for a brake booster such as of a tendem type including a centerplate disposed within a shell is disclosed. Annular seal means maintains a hermetic seal between the centerplate and a valve body. According to the invention, the annular seal means is formed with a passage which provides a communication between the inner and the outer periphery thereof. This allows a communication between the inner and the outer periphery of the annular seal means to be maintained by the passage formed therein in the event the opening of a constant pressure passage (or variable pressure passage) formed in the valve body is closed by the annular seal means. This allows a spacing between the annular seal means and a power piston or pistons mounted on the valve body to be reduced, contributing to reducing the overall length of the brake booster.

Seal unit for brake booster

In the negative pressure booster equipment 1 according to the present invention, a groove 27 is provided on the inner peripheral beads 14a and 16a of the diaphragms 14 and 16, fixed on the valve body 8 and forming the power pistons in order to communicate the variable pressure chambers 5b and 7b divided by the diaphragms 14 and 16 with the passages 26 and 28 corresponding to the variable pressure chambers 5b and 7b. Accordingly, the air passages are opened to the variable pressure chambers 5b and 7b through the groove 27 formed on the beads 14a and 16a of the diaphragms 14 and 16. According to this invention, therefore, there is no need to provide wide gap between the fixed portion of the beads and the center plate in order to open the air passages to the variable pressure chambers. This makes it possible to shorten overall length of the negative pressure booster equipment 1.

Negative pressure booster equipment

The negative pressure booster equipment according to the present invention is provided with a variable orifice, by which the area of the air passage in the pathways other than one pathway, of two or more pathways communicating two or more variable pressure chambers with atmospheric air, is gradually decreased as the valve plunger moves forward, and it is gradually increased as the valve plunger moves backward in relation to the valve body. Consequently, the pathways other than one pathway are throttled by the variable orifice as the valve plunger moves forward. As the result, most of the air flowing through the control valve is intensively introduced into the variable pressure chamber communicating with the pathway, which is not throttled by the variable orifice, and the pressure in this variable pressure chamber is rapidly increased. As the result, the power pistons under the pressure in this variable pressure chamber is quickly operated, and the rising of the output of the negative pressure booster equipment occurs earlier.

Growing community of inventors

Saitama, Japan

Atushi Satoh