Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
2000-12-08
2002-10-29
Buiz, Michael Powell (Department: 3753)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S514000, C137S493800
Reexamination Certificate
active
06470909
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a hydraulic system, more particularly for motor vehicles having a damping device or at least one pressure restricting valve, wherein at least one closing body which can be moved against the action of an axially active energy accumulator seals a conduit cross-section of the hydraulic system.
Hydraulic systems of this kind are used in particular in motor vehicles as devices for operating brakes, as power steering systems and as a device for operating friction clutches, for example in the force flow between an internal combustion engine and a gearbox and/or an electric machine and a drive train. Damping devices such as illustrated for example in GB 20 32 581, are thereby used to dampen pressure shocks in the pressure medium. Damping devices of this kind have at least one closing body axially biased by an energy accumulator and producing at a predetermined closing pressure the connection between the two connector members. Arrangements of this kind are particularly susceptible to periodically recurring pressure shocks in the pressure medium and react when excited in this way for example with noises such as squeaking noises.
If a pressure restricting valve of this kind is installed in a conduit train with the formation of two individual lines, then there is the further drawback that when filling the hydraulic system with pressure medium the two conduit trains have to be filled individually since the pressure restricting valve sealingly separates the two conduit parts from each other.
OBJECT OF THE INVENTION
The object of the invention is therefore to provide a hydraulic system which dampens vibrations entering into the pressure medium and which has an improved method of operation with regard to reducing the development of noise, is more cost-effective to produce and which is easier to assemble. Furthermore the hydraulic system is to be able to be filled entirely from one filling station.
SUMMARY OF THE INVENTION
The foregoing objective is achieved through a hydraulic system which has at least one pressure restricting valve comprising a housing with at least two connections and at least one conduit cross-section which can be closed by a closing body which is axially movable against the action of an energy accumulator, wherein at least a part of the axial travel of the closing body is damped. In this way it is possible to avoid any resonance excitation of the closing body through the pulsating medium, whereas an undamped closing body which is only biased with one energy accumulator can enter into resonance with the pressure medium and thus cause onerous noises.
According to the inventive idea for this purpose the damping device can be formed from an energy accumulator element and at least one friction element. By way of example an energy accumulator which axially biases at least one closing body of a damping device can be provided to act in parallel or serially with a friction device, wherein the case of a parallel method of operation the axial movement of the closing body is combined immediately or after a predetermined axial travel of the closing body with an adjusting friction moment. The friction moment can thereby be adjusted linearly, progressively or degressively by the axial path. Furthermore the friction moment can be from the speed of the axial movement of the closing body.
By way of example energy accumulator elements which axially impinge on the closing body can be coil compression springs, rubber elements and/or compressible fluids which for this purpose can be housed in a practically closed chamber and against which the closing body is moved axially under the volume contraction of the chamber. The energy accumulator is for this purpose advantageously supported fixed on the housing indirectly through a piston or the like or directly, for which suitably formed stops can be provided on the housing, connected in one piece with the housing, or additional component parts can be brought to stop with the housing, so that the closing body can be supported against the action of the energy accumulator. It is evident that any type of energy accumulators can also be installed under pretension or with play in the force flow between the closing body and the housing.
An advantageous friction element according to the inventive idea can be active hydraulically—for example hydrodynamically and/or hydrostatically—and/or mechanically. Thus for example a friction element can be formed on the basis of a shearing action of a viscous fluid, whereby the viscous fluid can be introduced between a component part of the closing body and a component part fixed on the housing, and in the event of relative movement between the two parts can act as a fluid friction element.
Furthermore when using an internally hollow closing body in conjunction with an axially acting spring element, for example a coil compression spring which engages axially in the closing body and is supported axially on the base of the closing body on one side and on the housing of the pressure restricting valve on the other, an advantageous behaviour can be observed, for example a noise-dampening effect, without having to provide a separate friction device. Tests have shown that the cause for this is an internal friction of the arrangement and/or the position of the point of engagement of the spring element in the closing body so that the connecting point which has been placed axially forwards has positive effects on the tilting behaviour of the closing body. Through this hollow design with an adequate axial guidance of the closing body the connecting point of the spring element can be moved towards the conduit cross-section or sealing edge of the pressure restricting valve. Advantageously the connecting point can be moved into the front half, preferably into the front third of the axial extension of the closing body. Furthermore mass concentrations axially between the connecting point and the front part of the closing body facing the sealing edge can have advantageous effects, for example a shock absorber effect for vibrations in the pressure medium. It is evident that the connection of the spring element inside the closing body can also be advantageous for designs having a friction element.
According to an inventive idea it can be advantageous to arrange at least two pressure restricting valves in a housing wherein these can advantageously be arranged to act opposite one another. The housing can be a separate housing introduced in a conduit, and it is furthermore possible to arrange one or more pressure restricting valves in a functional component part belonging to the hydraulic system, for example a master cylinder and/or a slave cylinder, whereby particularly favourable arrangements can be formed with regard to the number of component parts.
The arrangement of two or more pressure restricting valves in a housing produces in a particularly advantageous way so-called “vibration filters” of high quality since a bi-directional damping of pressure fluctuations in the pressure medium can be filtered effectively and bi-directional. These damping devices can be particularly advantageous if designed and fitted with damped pressure restricting valves according to the inventive idea.
One advantageous development of a hydraulic system of the said type provides at least one closing body which consists of at least two relatively displaceable parts. These parts can engage radially into each other—and can be formed hollow on the inside so that during displacement of the two parts relative to each other a changing volume can be formed in a chamber enclosed by the two parts. The two parts, for example the closing body itself and a component part, such as for example a piston, radially adjoining the inside walls of the closing body with sealing action, and which can likewise be hollow, can contain a compressible fluid, for example a gas such as air or a foam body, for example formed from compressible hard foam which is reversibly deformable. In this way an energy accumulator element can be contai
Fidline Alexandre
Heller Jean-Francois
Homm Manfred
Kremer Eugen
Osterlänger Jürgen
Buiz Michael Powell
Darby & Darby
Krishnamurthy Ramesh
LuK Lamellen und Kupplungsbau Beteiligungs KG
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