Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
2000-08-07
2002-04-30
Schwartz, Christopher P. (Department: 3613)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
C267S219000
Reexamination Certificate
active
06378850
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a fluid-filled vibration damping device having a fluid chamber filled with a non-compressible fluid and constructed to provide a vibration damping effect based on flows of the fluid in the fluid chamber. More particularly, the present invention is concerned with such a fluid-filled vibration damping device which is novel in construction and suitably used in an engine mount, a body mount or other mounts for an automotive vehicle.
2. Description of the Related Art
As one type of a vibration damping device, such as a vibration damping coupling (bushing) or mount, which is interposed between two members of a vibration system for flexibly connecting these two members or mount one of these members on the other member in a vibration damping manner, there is know a fluid-filled vibration damping device which includes a first mounting member and a second mounting member which are spaced apart from each other and which are elastically connected to each other by an elastic body that partially defines a primary fluid chamber filled with a non-compressible fluid. The damping device further includes a partition structure supported by the second mounting member and flexible diaphragm which partially defines an auxiliary fluid chamber also filled with the non-compressible fluid, the volume of which is variable. The primary and auxiliary fluid chambers are located on the opposite sides ofthe partition structure, respectively, and communicated with each other through an orifice passage formed through the partition structure. Upon application of vibrational loads between the first and second mounting members, a pressure of the fluid in the primary fluid chamber changes due to elastic deformation of the elastic body, generating a pressure difference ofthe fluid between the primary and auxiliary fluid chambers. Based on this pressure difference of the fluid, the non-compressible fluid forcedly flows through the orifice passage between the primary and auxiliary fluid chambers, so that the vibration damping device exhibits an excellent vibration damping effect with ease, owing to resonance or flow of the fluid flowing through the orifice passage, which vibration damping effect is not attained by a non-fluid-filled type vibration damping device whose damping effect owing to only an elasticity of an elastic body thereof. In the light of this excellent vibration damping effect, the fluid-filled vibration damping device has been used as an engine mount for an automotive vehicle, for example.
Such a known fluid-filled vibration damping device as described above suffers from a problem of a significant increase of its dynamic spring constant upon application of vibrations having a frequency band higher than the frequency band to which the orifice passage is tuned, due to a significant increase of resistance to the fluid flow through the orifice passage. As a method to cope with this problem, it is proposed to constitute the partition structure by a combination of an annular orifice member which is fixedly supported by the second mounting member and which has an orifice passage extending in its circumferential direction along an inner circumferential surface of the second mounting member, and a flexible rubber plate which is supported at its peripheral portion by the inner peripheral portion of the annular orifice member such that the center opening of the orifice member is fluid tightly closed by the flexible rubber plate, for example. The thus constructed partition structure permits an effective formation of the orifice passage formed therein so as to extend its circumferential direction thereof, while allowing a substantive flow of the fluid between the primary and auxiliary fluid chambers, owing to the elastic deformation of the flexible rubber plate, upon application of a high frequency vibration. Therefore, the fluid-filled vibration damping device equipped with such a partition structure can exhibit its reduced dynamic spring constant, resulting in avoiding or reducing the undesirable significant increase of the dynamic spring constant of the device.
For fluid-tightly closing the center opening of the annular orifice member with the flexible rubber plate, JP-A-10-252813 disclosing a partition structure wherein the orifice member is constituted by a thick annular block member and the flexible rubber plate which is bonded at its peripheral portion to the inner circumferential surface of the orifice member. The orifice member in the form of the annular block has an inner circumferential surface whose area is enough large so that the flexible rubber plate is bonded to the inner circumferential surface of the orifice member with a sufficiently large bonding area. However, the orifice member needs to be formed of a metallic material by cutting or die-casting, resulting in low-efficiency and increased cost of manufacture of the orifice member.
Another partition structure of the fluid-filled vibration damping device is disclosed in JP-B-7-56314 wherein the partition structure is constituted by a combination of a plurality of metallic plates which are superposed on each other in the axial direction of the device in which the first and second mounting members are spaced apart from each other, and are fixedly secured together by press-fitting or welding. The metallic plates are partially bent so as to form the inner circumferential surface to which the outer periphery of the flexible rubber plate is bonded. This arrangement permits both of a sufficiently large bonding area of the flexible rubber plate and a efficient and economical manufacture of the orifice member by use of the metallic plates which are available at a relatively low cost and which permit excellent productivity. However, the partition structure consisting of the mutually press-fitted metallic plates may suffer from a problem of difficulty to assure with high stability a sufficient bonding strength at the interfaces of the metallic plates. On the other hand, the partition structure consisting of the mutually welded metallic plates may possibly suffer from a problem of deterioration or change of the property of the flexible rubber plates due to an adverse effect of heat upon welding the metallic plates to form the partition structure. Therefore, the conventional fluid-filled vibration damping device suffers from a problem of significant difficulty to assure a desired fixing strength of the orifice member and a desired elasticity of the flexible rubber plate, with high stability.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a fluid-filled vibration damping device having a partition structure which is novel in construction and easy and economical to manufacture, and which assures a sufficiently large bonding area of a flexible rubber plate with respect to an orifice member of the partition structure. The partition structure also permits a desired fixing strength of an orifice member, while exhibiting a desired elasticity of the flexible rubber plate with high stability.
The above object may be achieved according to the following modes of the invention each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. However, it is to be understood that the present invention is not limited to those modes of the invention and combinations of the technical features, but may be otherwise recognized based on the thought of the present invention that disclosed in the whole specification and drawings or that may be recognized by those skilled in the art in the light of the disclosure in the whole specification and drawings.
(1) A fluid-filled vibration damping device comprising: a first mounting member and a second mounting member which are spaced-apart from each other, the second mounting member having a cylindrical portion open to the first mounting member; an elastic body elastically connectin
Rossi & Associates
Schwartz Christopher P.
Sy Mariano
Tokai Rubber Industries Ltd.
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