Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1999-04-20
2001-05-29
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
Reexamination Certificate
active
06238014
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to electromagnetic valves such as, for example, used in vehicle anti-lock braking systems and, more particularly, to improved electromagnetic valves having a relief for relieving an excessive hydraulic pressure when the hydraulic pressure received by a valve body exceeds a predetermined value when the valve body is closed by excitation of a coil.
2. Background Description
A known electromagnetic valve fitted with a relief means has been disclosed in, for example, Japanese Patent Publication No. 502473/1995. There, a series of guide holes is formed in a valve housing and the central portion of a fixed core. Hollow push bars, which are pushed forward when the coil is excited, are fitted in the respective guide holes. A valve body is slidably fitted in the hollow push bar and contains a relief spring for urging the valve body in the direction of the closing the valve. Furthermore, a valve spring for urging the push bar in the direction of opening the valve body is provided in the valve housing, whereas the push bar is fitted with a stopper for defining a limit to which the valve body is moved forward by the relief spring in the direction of closing the valve body. While the valve body is kept open by defining the limit to which the push bar is moved forward toward the valve body when the moving core is moved back, the valve body is allowed to be opened by a relief valve as the moving core moves forward. This electromagnetic valve demonstrates the relief function in that while the valve body is made to perform the normal opening-closing operation as the coil is excited or demagnetized in addition to the case where even in its closed state, the function of relieving the excessive hydraulic pressure is ensured by allowing the valve body to be opened by the relief spring. Therefore, special relief valves are not needed to be connected to such electromagnetic valves in parallel, so that the hydraulic fluid circuit is simplified further.
However, a valve housing having a relatively large diameter has to be formed because the valve body and the push bar are doubly arranged on the inside and outside of the valve housing and contained therein in the prior art and this has made it difficult to reduce the diameter size of an electromagnetic valve.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an electromagnetic valve which is fitted with relief means and can be made to have a compact diameter without increasing its axial length.
In order to accomplish the above object, an electromagnetic valve, according to the present invention, comprises a valve housing having a valve seat, a valve body which is contained in the valve housing such that the valve body is positioned opposite to the valve seat so that the valve body can be seated on the valve seat. A valve spring urges the valve body in the direction of separating the valve body from the valve seat. A fixed core is coupled to one end of the valve housing and a moving core which is longitudinally movable with respect to the fixed core is used for seating the valve body on the valve seat when moved forward. A coil moves the moving core forward when excited, and is characterized in that a push bar capable of pushing the valve body toward the valve seat and a relief spring for urging the push bar toward the valve body are contained in a guide hole formed in the central portion of the moving core. A stopper is provided to the moving core, the stopper being used for holding the valve body open by defining a limit to which the push bar is moved forward with respect to the valve body when the moving core is moved backward and for allowing the valve body to be closed by the relief spring when the moving core is moved forward.
In the present invention, unlike the prior art structure in which the valve body and the push bar are doubly arranged in the valve housing, the valve body and the push bar are axially arranged separately from each other, so that the valve housing has a more compact diameter. Moreover, an increase in the axial length of the electromagnetic valve can be held in check since the interior of the moving core is utilizable for arranging the push bar and the relief spring.
In addition, the present invention also features that a fitting hole for fitting a valve seat body having the valve seat and a valve opening for slidably fitting the valve body therein are coaxially formed in the valve housing.
According to the second feature of the present invention, the valve seat body and the valve body can readily be arranged coaxially with precision without increasing the production cost, whereby the valve body is restrained from being incompletely closed.
REFERENCES:
patent: 3818927 (1974-06-01), Zeuner
patent: 5167442 (1992-12-01), Alaza et al.
patent: 5318066 (1994-06-01), Burgdorf et al.
patent: 5476313 (1995-12-01), Lauer
patent: 5496100 (1996-03-01), Schmid
patent: 6092781 (2000-07-01), Hohl
patent: 41 29 638 A1 (1993-03-01), None
patent: 7-502473 (1995-03-01), None
Kikuchi Makoto
Masuda Naoki
Sirase Takaomi
Tamai Naotoshi
Bartz C. T.
McGuireWoods LLP
Nissin Kogyo Co. Ltd.
Schwartz Christopher P.
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