Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1997-04-28
1999-11-02
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
25112902, 251117, 1375992, B60T 836
Patent
active
059756543
DESCRIPTION:
BRIEF SUMMARY
The invention pertains to a valve unit, in particular, for hydraulic brake systems with antilock and/or wheel-slip control.
A valve unit of the type constituting this class is known from EP 0,353,635 B1.
This valve unit comprises a housing, into which a piston that functions as a flow control valve is inserted. This flow control valve regulates the volume flow between a pressure medium source and a pressure medium sink as a function of the switching position of an electromagnetic actuating element. In order to fulfill this function, the piston has a relatively long shaft, the through-holes of which are provided with control edges that override the pressure medium channels of the pressure medium sink or the pressure medium source which open radially into the valve housing. Not only the relatively large size of the flow control valve, but also the activation of the flow controller by letting off the pressure medium after opening the electromagnetically controlled pressure medium connection to a reservoir result in a substantial structural volume of the valve unit.
Consequently, the present invention is based on the objective of improving a valve unit of the initially mentioned type in such a way that a functionally reliable operation is ensured and the structural volume is reduced to a minimum with simple means.
The invention proposes to support an electromagnetic actuating element on one end face of the flow control valve against the force of a compression spring in its normal position, and that the piston of the flow control valve separates from the actuating element in the operating position of the actuating element and assumes an intermediate position in which it controls the volume flow of the pressure medium between the pressure medium source and the pressure medium sink.
The invention proposes to arrange the piston of the flow control valve between the actuating element and the compression spring that is supported on a holding part of the valve unit. Due to this measure, the graduated bore required for the flow control valve can have relatively short dimensions and it is ensured that the piston of the flow control valve is directly contacted by the actuating element.
The further elaboration of the invention provides that the piston is guided in the valve housing in axially movable fashion while it is metallically sealed by means of several annular grooves arranged on its circumference, such that the annular grooves fulfill the function of labyrinth seals. This means that only negligible small leakage flows are formed along the outer contour of the piston and the length of the piston can be significantly reduced.
In order to ensure a favorable arrangement of the metering orifice required for the flow control valve, it is proposed to integrate the metering orifice within the region of the end face that is contacted by the actuating element.
A realization of the control edge function between the flow control valve and the valve housing required for regulating the pressure which is particularly favorable for manufacturing reasons is disclosed. The valve housing comprises a graduated bore that provides advantages with respect to the pressure control as well as the arrangement of the actuating element and the compression spring.
With regard to the aforementioned advantage of a favorable pressure medium flow, it is proposed that the piston comprise at least one control edge at the elevation of the bore graduation so as to ensure an unobstructed pressure medium flow between the pressure medium source and the pressure medium sink in the normal position of the actuating element.
Due to the design of the piston in the shape of a pot, it is possible either to insert the actuating element as deep as possible into the flow control valve or, alternatively, support the compression spring therein, i.e., the characteristics result in a drastic reduction of the structural length.
A practical measure for adjusting the actuating element in the graduated bore is disclosed. For this purpose, a spacer is inserted into the gr
REFERENCES:
patent: 5076588 (1991-12-01), Mohr et al.
patent: 5356211 (1994-10-01), Fritsch
patent: 5673980 (1997-10-01), Schwarz et al.
Linhoff Paul
Zaviska Dalibor
ITT Manufacturing Enterprises Inc.
Oberleitner Robert J.
Williams Thomas J.
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