Power plants – Pressure fluid source and motor – Pulsator
Reexamination Certificate
2001-02-28
2003-04-15
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Pulsator
C137S493000, C137S493800
Reexamination Certificate
active
06546727
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an hydraulic system, particularly for motor vehicles, including a master cylinder, a slave cylinder, a connecting pressure-medium conduit, as well as a pressure relief valve that is integrated into the hydraulic system and that is governed as a function of the pressure of the pressure medium.
2. Description of the Related Art
Such hydraulic systems are utilized particularly in motor vehicles as arrangements to operate brakes, as power steering systems, and as arrangements to operate friction clutches, for example in the power flow between an internal-combustion engine and a transmission, and/or an electric motor and a drive train. Dampers such as are shown in British patent No. 2,032,581 are utilized for damping pressure pulses in the pressure medium. Such damping devices include at least one closing element that is axially actuated by an energy accumulator and which, when a predetermined closure pressure is exceeded, will produce a connection between the two elements. Such arrangements are especially susceptible to periodically recurring pressure pulses in the pressure medium and react to such stimulation with, for example, screeching noises. Moreover, the sealing seats of the closure elements are susceptible to soiling, so that absolute sealing of the pressure relief valve is frequently unattainable over its lifetime.
Such situations can be a drawback if pressure conditions within the hydraulic system change, caused for example by temperature changes. Changing pressure conditions develop in the conduit before and after the pressure relief valve, so that non-negligible flows of pressure medium can take place in the hydraulic system, which can increase the moisture level in the pressure medium and therewith as a consequence can impair the quality of the pressure medium.
It is therefore an object of the present invention to provide an hydraulic system in which damping of pressure oscillations that are introduced into the pressurized medium can take place, and one that produces improved operation relative to reducing induced noises, that is more economical to manufacture, that tightly seals secondary conduits of the hydraulic system, and that is easier to assemble. Furthermore, the hydraulic system is to be filled completely through one filling point.
SUMMARY OF THE INVENTION
The object is achieved by an hydraulic system that includes a slave cylinder, a master cylinder, a pressure-medium line connecting the cylinders, as well as at least one pressure-medium controlled pressure-relief valve integrated into the system, with at least two connections for inlet and outlet of pressure medium and at least one port connecting the inlet and outlet and that is sealingly closable by an elastic element.
The port, whose one opening points in the outlet direction and whose other opening points in the inlet direction, thereby advantageously has closed by an elastic body its opening that points away from the direction of the pressure, for example in the form of an opening-spanning elastic tube valve. If a pressure is applied from the first connection through the port in the direction of the opening that is closed by the elastic, at least part of the elastic body will be displaced by the pressing force of the pressure medium and a path of pressure medium is formed away from the opening in the direction of the second connection.
The closing pressure of such a valve is determined at least by the tension force in the elastic body, by which it presses closed the opening. Furthermore, the type and extent of the closing pressure between the bearing surfaces, against which the elastic body presses, and the pressure medium path formed by the elastic body, depends upon the type and arrangement of such as, for example, the diameter of the opening, the elastic modulus of the elastic body. As well, the surface characteristics of the elastic body and the bearing surfaces can enter into the magnitude of the closing pressure and the damping characteristics. In that manner pressure spikes can be damped and the pressure relief valve can be adapted to prevailing conditions and can be matched with them. The return movement of the elastic body against the opening and the surrounding material after the decline of the pressure spike ideally is elastic, and when compared with the impact of a spring-loaded sealing element on a valve seat it is practically noiseless.
An advantageous embodiment provides an arrangement of the connections that is approximately coaxial, whereby both connections can be placed in communication with each other by a predominantly radially-extending port. It is especially advantageous—by a radially nested arrangement of the chambers that communicate with respective terminal ends of the port, which chambers communicate with the connections—that the approximately coaxial connections are axially spaced from each other, so that at least one pressure relief valve in accordance with the invention can be arranged axially between the two connections, in which a port is formed between the respective connections to the axially adjacent chambers, one that provides communication between the two connections, whereby an elastic body is arranged on an opening of the port that closes the opening as a function of the pressure of the pressure medium. The port can thereby run substantially radially from one terminal end to the other, that is, that one terminal end communicates with one chamber, or extends to it, and that it extends radially further than the chamber of the second terminal end and that forms a port that leads from radially outside to radially inside to provide communication between the two chambers.
It is to be understood that in addition the chambers can be axially overlapped by the use of a common wall, for example, a sleeve-shaped wall that is closed at one end, and the port in its radial extent also can have axial portions and can be inclined from outside to inside, or can be provided as an axially-formed open slot in the common wall, through which a simpler structure can be achieved by means of an injection molding process, and by which radial undercuts can be avoided. By the use of a sleeve-shaped construction of the common wall between the first and second connections, in each case at lease one wall surface can be cylindrically constructed and on those cylindrical surfaces, inner or outer cylindrical surfaces, the elastic body can be sealingly applied over the discharge opening. It has proved to be especially advantageous in addition to utilize tube sections, which are pulled onto the outer cylindrical surface or are put—introduce into the inner cylindrical surface to seal radially outwardly.
The tube sections can each be formed as an insert—on the inner cylinder or on the outer cylinder—for different respective opening pressures, whereby experience has shown that for the arrangement of the tube section on the inner cylinder less closing pressure is required, that is, it opens at a lower pressure of the pressure medium. Both arrangements can be constructed to be self-reinforcing, that is, the sealing function can be reinforced by counterpressure in dependence upon the applied pressure of the pressure medium. For special application cases, the bearing surfaces of the elastic body can be formed with grooves to avoid self-reinforcement and to ensure a minimal flow of pressure medium.
All kinds of elastic materials can be advantageous for the elastic body, materials that are resistant to the pressure medium, for example, brake fluid of the customary specification, and especially materials that have no negative adhesive effects such as bonding, vulcanization, adhesion, and the like with the material from which the housing is formed, which can be composed of metal, ceramic, plastic, and the like, to receive the at least one pressure relief valve. Advantageous materials have proved to be plastics, preferably elastomers, rubber, and silicon, such as silicon rubber or silicon resin. When utilizing tube sections th
Böckling Marcus
Grabenstätter Jan
Pfeiffer Joachim
Rammhofer Thomas
Kershteyn Igor
Look Edward K.
Luk Lamellen und Kupplungsbau Beteiligungs KG
Mangels Alfred J.
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