Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
2001-05-25
2003-12-16
Graham, Matthew C. (Department: 3683)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
C267S140110
Reexamination Certificate
active
06663090
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hydraulic engine mount, i.e., a hydramount, including a supporting bearing and a bearing member, which are supported on each other by an essentially frustoconical, first elastic spring element made of an elastomer material, and including a working chamber and a compensating chamber, which are each filled with hydraulic fluid, are separated from each other by a partition, and are in fluid communication via a first damping opening.
BACKGROUND INFORMATION
Such hydramounts are described, for example, in German Published Patent Application No. 41 41 332. Conventional hydramounts are especially used as engine, gearing or transmission suspensions in motor vehicles. The action of these hydramounts is substantially axial, in the direction of the hydramount, liquid constituents being displaced back and forth through the damping opening, between the working chamber and the compensating chamber, in order to damp low-frequency, high-amplitude engine vibrations. High-frequency, low-amplitude vibrations, e.g., vibrations induced by the internal combustion engine itself, are isolated by a diaphragm, which is made of an elastomer material and is mounted inside the partition so as to be capable of vibrating.
In the radial direction of the hydramount, supporting action is substantially attained by locally hard, rubber spring segments, while isolation is provided by locally soft, rubber spring segments. This variable adjustment of the first elastic spring element to different requirements renders the cost of developing appropriate elastomer springs high. Nevertheless, the result is generally a compromise, because only the material of the elastic spring element damps in the radial direction. The choice of suitable materials is very limited since, to achieve effective axial damping action, materials that have a very low damping capability and only harden to a small extent are necessary for the first elastic spring element.
SUMMARY
It is an object of the present invention to provide a hydramount that, in addition to the improved working properties of the hydramount in the axial direction, improved working properties may also be attained in regard to the damping in the radial direction.
The above and other beneficial objects of the present invention are achieved by providing that the supporting bearing is in the form of an internal, first supporting body, which is enclosed by an external, second supporting body at a radial distance, that the first and second supporting bodies are connected by the first elastic spring element and a second elastic spring element, that the first and the second supporting bodies delimit at least two chambers filled with hydraulic fluid, and that the chambers are positioned perpendicularly to the axis, substantially in diametric opposition to each other in the radial direction, and are in fluid communication via at least one second damping opening. The hydramount according to the present invention includes the advantage of possessing, on one hand, the usual working properties with regard to the damping and the isolation of vibrations in the axial direction, and on the other hand, an improved damping effect in the radial direction, i.e., perpendicularly to the axis. The additional configuration of the chamber pair, in which the two chambers of the chamber pair are in fluid communication via the second damping opening, also allows low-frequency, high-amplitude vibrations to be damped in the radial direction.
For example, damping in the radial direction is necessary in order to damp pitching motions of an engine mounted longitudinally in a motor vehicle. Engine shaking motions in transversely mounted engines may also be effectively damped by the hydramount damping that acts in the radial direction. Depending on the particular application case and the design of the second throttle opening, there is also the possibility of isolating shaking motions of the engine, using an absorption effect. The dynamic reduction in stiffness caused by the absorption effect allows comparatively high radial spring constants for supporting the engine in the direction of travel, e.g., while accelerating and braking, which is very improved for the driving comfort.
Engine shaking motions in engines mounted longitudinally in motor vehicles may be damped by the hydramount according to the present invention, in the transverse direction of the vehicle, or they may be isolated by an absorption effect when the second damping opening is appropriately designed. In the case of absorbing vibrations, the cornering performance of a motor vehicle can be improved by a higher static spring constant. That is, the engine does not strike the end stop too early in the radial direction, which means that the noise is minimized, and reverberation, e.g., post-vibration of the engine is prevented in the transverse direction.
Therefore, the improved working properties result from integrating at least one additional chamber pair, e.g., in the form of a hydraulic sleeve, into a conventional hydramount, the additional chamber pair acting in the radial direction.
The second supporting body and the bearing member may be formed from a uniform material and/or may be formed in one piece. The one-piece design allows the hydramount to be manufactured inexpensively and to be assembled from a small number of parts. However, if the second supporting body and the bearing member are formed in two pieces, then undercuts may be produced in the radial direction. When removing the part from the vulcanization tool, neither the part itself nor the tool is damaged/destroyed.
The first and the second elastic spring elements may be formed in one piece or multiple pieces. The one-piece design of the two elastic spring elements allows the hydramount to be manufactured easily and inexpensively, the choice of material depending mainly on the required spring stiffnesses of the elastic spring elements.
For example, the first damping opening may be designed in the shape of a channel and may form the circumference of the partition. In this connection, it may be advantageous that the comparatively large channel length of the damping opening allows a large mass of fluid to vibrate back and forth between the working chamber and the compensating chamber and therefore allows low-frequency, high-amplitude vibrations to be damped effectively.
The second damping opening may be in the form of a choke, a throttle or an absorption channel. If the second damping opening is in the form of a throttle, the radially induced vibrations are damped by forcing hydraulic fluid between the chambers of the chamber pairs, through the second damping opening having a comparatively small cross-section. A condition for the throttle damping is that the chamber walls should be very resistant to inflation. This is achieved by short, thick spring segments made of elastomer. The second damping opening may also be in the form of an absorption channel. In this context, the length of the damping opening is small, and its cross-section is large, in order to attain a dynamic stiffness in the frequency range of 20 to 80 Hz, which is lower than the static stiffness. A plurality of absorption channels may be arranged in a functionally parallel circuit.
The first and the second elastic spring elements may define two chamber pairs, which are positioned adjacently to each other in the axial direction, the chambers of each chamber pair being positioned transversely to the axis, substantially in diametric opposition to each other in the radial direction, and being in fluid communication with each other, and the chamber pairs being positioned so as to be offset 90° from each other. Vibrations may be damped in all three spatial directions. In the application case of a motor vehicle, this means that vibrations may be damped in the travel direction, transversely to the travel direction, and perpendicularly to the road surface. In this case, the degree of undesirable vibration transmission, e.g., into the passenger compartment of the motor vehicle
Hettler Werner
Simuttis Arnold
Firma Carl Freudenberg
Graham Matthew C.
Kenyon & Kenyon
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