Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
2002-10-16
2004-01-06
Schwartz, Christopher P. (Department: 3683)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
Reexamination Certificate
active
06672574
ABSTRACT:
INCORPORATED BY REFERENCE
The disclosure of Japanese Patent Application No. 2001-320233 filed on Oct. 18, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a cylindrical vibration damping device including: an inner shaft member; an outer sleeve member disposed radially outward of the inner shaft member; and a rubber elastic body elastically connecting the inner shaft member and the outer sleeve member. More particularly, the present invention is concerned with a fluid-filled cylindrical vibration damping device capable of exhibiting a vibration damping or isolating effect based on flows or resonance of a fluid contained therein, and being suitably employed as an engine mount, a body mount a differential mount, a suspension bushing or other mounts for use in automotive vehicles, for example.
2. Description of the Related Art
A fluid-filled cylindrical vibration damping device is known as one type of a vibration damping mount or bushing interposed between two members of a vibration system for elastically connecting two members or for elastically mounting on one of the two members on the other in a vibration damping or isolating fashion. A known example of the fluid-filled cylindrical vibration damping device is disclosed in JP-B-63-3763 or JP-B-5-55739, which includes an inner shaft member attachable to one of the two members of the vibration system, an outer sleeve member attachable to the other member of the vibration system and disposed radially outwardly of the inner shaft member with a radial spacing therebetween, and a rubber elastic body interposed between the inner shaft member and the outer sleeve member for elastically connecting these two members and defining a plurality of fluid chambers between these two members. These fluid chambers are filled with a non-compressible fluid, and are held in fluid communication with each other through at least one orifice passage. An application of a vibrational load to the fluid-filed vibration damping device constructed as described above induces fluid pressure variation between these fluid chambers, thereby causing flows of the fluid through the orifice passage. Thus, the fluid-filled vibration damping device is able to exhibit an excellent vibration damping effect based on flows or resonance of the fluid flowing through the orifice passage, which effect is never achieved by an elastic mount whose damping effects are only based on the rubber elastic body. For this advantage, the conventional fluid-filled cylindrical vibration damping device is preferably employed as an engine mount for use in an automotive vehicle.
However, the above-described conventional fluid-filled cylindrical vibration damping device exhibits an effective vibration damping or isolating effect based on the fluid flows through the orifice passage, with respect to only input vibrations in a relatively narrow frequency range to which the orifice passage is tuned. In particular, the conventional vibration damping device experiences considerable deterioration in its damping capability when the input vibration has a frequency higher than the frequency to which the orifice passage is tuned.
For the above-described inherent problem, the conventional fluid-filled cylindrical vibration damping device, when being used as an engine mount for an automotive vehicle with its orifice passage is tuned to a frequency range corresponding to engine shakes required to be damped upon driving of the vehicle, or corresponding to engine idling vibrations required to be damped upon idling of the vehicle, is not able to exhibit a desired high damping effect upon application of the engine shakes or a desired vibration isolating effect upon application of the engine idling vibrations for a wide frequency range enough to meet requirements. In particular, the damping capability of the conventional vibration damping device is considerably deteriorated immediately after the input vibration has a frequency higher than the frequency to which the orifice passage is tuned.
Meanwhile, JP-A-9-21441 and JP-A-8-14311 disclose another example of the vibration damping device suitably usable as an engine mount for an automotive vehicle, other than the fluid-filled cylindrical vibration damping device directed to the present invention. The disclosed vibration damping device includes a block-shaped first mounting member, a large-diameter cup-shaped second mounting member and a rubber elastic body interposed between the second mounting member and the first mounting member disposed on the side of an open end portion of the second mounting member for elastically connecting the first and the second mounting members with each other and fluid-tightly closing the open end of the second mounting member, thereby defining a fluid chamber filled with a non-compressible fluid. The disclosed non-cylindrical type fluid-filled vibration damping device has a relatively large inner space in comparison with the fluid-filled cylindrical vibration damping device. For this advantage, the non-cylindrical type fluid-filled vibration damping device, as disclosed in the above-mentioned publications, is able to incorporate therein a switch valve for alternately effecting a plurality of orifice passages tuned to different frequency ranges, or a fluid-pressure absorbing mechanism having a movable plate for limiting an amount of flows of the fluid. This arrangement makes it possible for the non-cylindrical type fluid-filled vibration damping device to easily exhibit a desired vibration damping or isolating effect based on resonance or flows of the fluid through the orifice passage over an expanded or a wide frequency range of vibrations. However, the present invention is directed to the fluid-filled cylindrical vibration damping device wherein the inner shaft member is disposed in the central portion of the bore of the outer sleeve member with a substantially coaxial relationship with each other, making it significantly difficult to incorporate such a complicated mechanism of the orifice passages and the switch valve or such a fluid-pressure absorbing mechanism into the bore of the outer sleeve member of the fluid-filled cylindrical vibration damping device. Further, the use of these mechanisms causes considerable deterioration in efficiency and economy of manufacture of the fluid-filled cylindrical vibration damping device, thus being ineffective to improve the damping capability of the fluid-filled cylindrical vibration damping device.
SUMMARY OF THE INVENTION
It is therefore one object of this invention to provide a fluid-filled cylindrical vibration damping device novel in construction and capable of exhibiting an excellent vibration damping and/or isolating effect based on resonance or flows of the fluid through an orifice passage or passages with respect to vibrations over an expanded or wide frequency range, with simple structure.
The above and/or optional objects of this invention may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depending from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the principle of the invention is not limited to these modes of the invention and combinations of the technical features, but may otherwise be recognized based on the teachings of the present invention disclosed in the entire specification and drawings or that may be recognized by those skilled in the art in the light of the present disclosure in its entirety.
(1) A fluid-filled cylindrical vibration damping device including: (a) an inner shaft member; (b) an outer sleeve member disposed radially outwardly of the inner shaft member in a spaced-apart relationship with the inner shaft member; (c) an elastic body interposed between the inner shaft member and the outer sl
Hamada Masaaki
Suzuki Tatsuya
Beyer Weaver & Thomas LLP
Schwartz Christopher P.
Tokai Rubber Industries Ltd.
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