Motors: expansible chamber type – Working member position feedback to motive fluid control – Plural input signal means for single motor valve
Patent
1999-04-05
2000-06-06
Ryznic, John
Motors: expansible chamber type
Working member position feedback to motive fluid control
Plural input signal means for single motor valve
91376R, F15B 1316
Patent
active
060705140
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention generally relates to brake systems and more particularly to a pneumatic brake force booster for automotive vehicles.
BACKGROUND OF THE INVENTION
International patent application WO 94/11226 discloses a brake force booster of this general type. The prior art brake force booster suffers from the disadvantage of the effect of annular surfaces on the valve member of the control valve which are delimited by the second and third sealing seats, on the one hand, and the boundary of the mentioned pneumatic chamber, on the other hand, especially in the event of independent activation by switching on the electromagnets. This condition affects adversely the use of the independently actuatable brake force booster especially in control operations. One of the annular surfaces to which a pneumatic differential pressure is applied during the independent activation of the brake force booster produces a force component which counteracts the independent actuating force generated by the electromagnet and tends to close the control valve. This necessitates compensating the force component by an increase of the independent actuating force which must be generated by the electromagnet.
Therefore, an object of the present invention is to disclose measures which permit eliminating the disturbing effects of the mentioned force component.
According to the present invention, this object is achieved because a permanent pneumatic connection between the pneumatic chamber and the vacuum chamber is provided, and in that both the second and the third sealing seat and the valve member in its part delimiting the pneumatic chamber in the control housing have almost identical diameters which, preferably, range in a tolerance width of 1 mm. It is preferred that the pneumatic chamber is delimited by a cylindrical part which cooperates with a sealing lip designed on the valve member.
In a preferred aspect of the subject matter of the present invention, the valve member has two sealing surfaces which preferably have an annular configuration and are arranged one behind the other in the actuating direction, and the first and the third respectively the second sealing seat are movable into abutment with the sealing surfaces.
The present invention will be explained in detail in the following description of an embodiment, making reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal cross-sectional view, partly broken off, of a design of the brake force booster of the present invention in the inactive stand-by position.
FIG. 2 is a view of the control assembly of the brake force booster of FIG. 1 in the full braking position controlled by the driver.
FIG. 3 is a view of the control assembly of the brake force booster of FIG. 1 in the release position, with the electromagnet switched.
FIG. 4 is a diagram showing the force-and-travel characteristic curves of the system illustrated in FIGS. 1 to 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The booster housing 1 (represented only schematically) of the vacuum brake force booster of the present invention which is shown in the drawing is subdivided by an axially movable wall 2 into a working chamber 3 and a vacuum chamber 4. The axially movable wall 2 includes a diaphragm plate 8, deep drawn from sheet metal, and a flexible diaphragm 18 (not shown) abutting on the plate. The diaphragm, configured as a rolling diaphragm, provides a sealing between the outside periphery of the diaphragm plate 8 and the booster housing 1.
A control valve 12 is operable by an actuating rod 7 and accommodated in a control housing 5, which is sealed and guided in the booster housing 1 and carries the movable wall 2. The control valve 12 is composed of a first sealing seat 15 provided on the control housing 5, a second sealing seat 16 provided on a valve piston 9 connected to the actuating rod 7, and a valve member 10 which cooperates with the two sealing seats 15, 16. Valve member 10 is guided in a guide part 21 sealed in control housing 5 and
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Japanese Abstract 2-306870 Published Dec. 20, 1990.
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Bayens Mark
Berthold Thomas
Drott Peter
Kramer Horst
Continental Teves AG & Co. OHG
Ryznic John
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