Motors: expansible chamber type – Working member position feedback to motive fluid control – Follower type
Patent
1997-12-22
1999-11-09
Nguyen, Hoang
Motors: expansible chamber type
Working member position feedback to motive fluid control
Follower type
91376R, F15B 910
Patent
active
059792930
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum brake power booster for automotive vehicles.
German patent application No. 43 24 688 discloses a vacuum brake power booster for automotive vehicles, including a booster housing having an interior subdivided by a movable wall into a vacuum chamber and a working chamber, a control housing carrying the movable wall and accommodating a control valve which is operable by an actuating rod and governs a difference in pressure that acts upon the movable wall, and a solenoid which acts upon the control valve and permits ventilating the working chamber irrespective of the actuating rod.
An object of the present invention is to provide an improved vacuum brake power booster, wherein an actuating piston for the actuation of a release switch, which is used to release the solenoid, is arranged particularly favorably so as to achieve a simple and low-cost manufacture of the vacuum brake power booster.
SUMMARY OF THE INVENTION
This object is achieved in that, for operating a release switch which is used to release the solenoid, an actuating piston is paraxially slidably mounted at the edge of the control housing and provides a mechanical connection between the release switch in the vacuum chamber and a stationary stop in the working chamber.
Because the control housing, along with the solenoid and the release switch, is axially movable in the booster housing, a stationary stop is required to actuate the release switch by way of the actuating piston. According to the present invention, the stationary stop is arranged on a sealing ring interposed between the movable control housing and the stationary booster housing. Thus, the stop is independent of the shape or design of the booster housing in this area. This favorably eliminates the need to adapt the booster housing in a specific way for designing a stop. Straightforwardly, the sealing ring itself provides the stationary stop for the actuating piston.
In a preferred aspect of the present, the actuating piston has a slim connecting portion which extends through a bore in the control housing. This permits a simple mounting of the actuating piston on the control housing by easily inserting the slim connecting portion of the actuating piston from the inside in an outward direction through the bore in the control housing. Subsequently, the free end of the connecting portion is provided with an enlarged stop element which prevents the connecting portion and the entire actuating piston from slipping back into control housing. The end face of the stop element is used for abutment on the sealing ring provided between the booster housing and the control housing.
Further advantageous features are directed to improve the sealing effect at the point where the connecting portion extends through the bore in the control housing. Because the actuating piston provides a mechanical connection between the vacuum chamber and the working chamber, a corresponding sealing is required. Sealing can be effected by an annular lip seal which is slipped onto the connecting portion and abuts with a circumferential sealing lip on the connecting portion in a radial direction. In an axial direction, the lip seal abuts around the bore on the control housing. This axial abutment can still be improved if the actuating piston includes a helical wire spring, the one end of of which bears against the stop element, and the other end of which bears with axial preload against the lip seal.
To retain the actuating piston in the preassembled state on the control housing and to secure it against dropping out before the control housing is connected with other component parts and is installed on the booster housing, the actuating piston may have an enlarged retaining element on the inside of the bore of the control housing. The enlarged retaining element limits an axially outwardly directed movement of the actuating piston by abutment on the inside of the control housing.
If the actuating piston has an axially resiliently supported sleeve on its
REFERENCES:
patent: 5460074 (1995-10-01), Balz et al.
patent: 5605088 (1997-02-01), Balz et al.
Elektronisch Geregelter Bremskraftverstarker Von Josef Pickenhahn pp. 36-37, 1995.
Drott Peter
Kramer Horst
ITT Manufacturing Enterprises Inc.
Nguyen Hoang
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