Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
2001-06-07
2002-12-10
Graham, Matthew C. (Department: 3613)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
C267S140130
Reexamination Certificate
active
06491290
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2000-214108 filed on Jul. 14, 2000 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 in general to a fluid-filled vibration-damping device, which exhibits a vibration damping or isolating effect based on flows or resonance of a non-compressible fluid contained therein. More particularly, the present invention is concerned with a novel fluid-filled vibration damping device which has a plurality of orifice passages tuned to respective different frequency bands of input vibrations and exhibits an excellent vibration damping effect with respect to the input vibrations having different frequencies or over a wide frequency range, based on the flows of the non-compressible fluid through these orifice passages.
2. Discussion of the Related Art
As one type of a vibration damper interposed between two members of a vibration system so as to connect these two members in a vibration damping manner or mount one of these members on the other member in a vibration damping manner, there is known, as disclosed in JP-U-61-190051, for example, a fluid-filled vibration damping device which includes: a first and a second mounting member that are disposed in mutually spaced-apart relationship with each other; an elastic body elastically connecting the first and second mounting members and partially defining a pressure-receiving chamber filled with a non-compressible fluid; and an easily deformable flexible diaphragm partially defining an equilibrium chamber filled with the non-compressible fluid and held in fluid communication with the pressure-receiving chamber through a first orifice passage. Such a known fluid-filled vibration-damping device is capable of exhibiting an excellent vibration damping effect based on resonance of the fluid flowing through the first orifice passage, which effect would not be achieved by only the elasticity of the elastic body. Therefore, the fluid-filled vibration-damping device is preferably usable as an engine mount for an automotive vehicle, for example.
Generally, the vibration damping or isolating effect of the known fluid-filled vibration damping device based on the flows or resonance of the fluid is exhibited with respect to only the particular input vibrations over a limited frequency range to which the first orifice passage is tuned. In particular, when the frequency of the input vibration is higher than the frequency band to which the first orifice passage is tuned, a resistance to flow of the fluid through the first orifice passage tends to be increased, making it difficult for the device to exhibit a satisfactory damping effect based on the fluid flows through the first orifice passage. In this case, the fluid-filled vibration-damping device exhibits a high dynamic spring constant, resulting in significant deterioration of the vibration damping characteristics.
To cope with this drawback, there is proposed another structure of the fluid-filled vibration damping device wherein the pressure-receiving chamber is partially defined by an elastically displaceable elastic wall member, as disclosed in JP-A-2-129427, for example. In this structure, the elastic wall member is displaced at a suitable frequency so that a periodic pressure change generated in the pressure-receiving chamber upon application of the higher frequency vibrations is reduced or absorbed, for preventing or minimizing an excessive increase in the dynamic spring constant of the device. There is also proposed yet another structure, as disclosed in JP-A-7-71506, wherein a partition member is disposed within the pressure-receiving chamber so as to divide the pressure-receiving chamber into two sections, namely a primary fluid chamber partially defined by the elastic body and a auxiliary fluid chamber partially defined by the elastic wall member, and a second orifice passage is formed for fluid communication between the primary and auxiliary fluid chambers. In this structure, the vibration damping device exhibits a low dynamic spring constant and an accordingly high vibration isolating effect based on flows of the fluid through the second orifice passage, upon application of high-frequency vibrations.
However, even in the provision of the elastic wall member or the second orifice passage, as described above, the fluid-filled vibration damping device still suffers from significant increase in the dynamic spring constant when the frequency of the input vibration is higher than the frequency band to which the elastic wall member or the second orifice passage is tuned, resulting in significant deterioration of the vibration damping characteristics of the device with respect to the higher frequency vibrations. Thus, the known fluid-filled vibration damping device suffers from significant difficulty in exhibiting an excellent vibration damping or isolating effect with respect to the input vibrations over a sufficiently wide frequency range.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a fluid-filled vibration damping device which is novel in construction and which is capable of exhibiting an excellent vibration damping or isolating effect based on flows or resonance of a non-compressible fluid contained therein, with respect to input vibrations over a sufficiently wide frequency range.
The above and other objects of this invention may be attained according to the following modes of the invention. Each of these modes of the invention 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. It is to be understood that the principle of the invention is not limited to those modes of the invention and combinations of the technical features, but may otherwise be 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 and a second mounting member which are spaced apart from each other; an elastic body elastically connecting the first and second mounting members and partially defining a pressure-receiving chamber, the pressure-receiving chamber being filled with a non-compressible fluid whose pressure is changed upon application of a vibrational load between the first and second mounting members; an easily deformable flexible diaphragm partially defining an equilibrium chamber on one of opposite sides thereof, the equilibrium chamber being filled with the non-compressible fluid and has a volume easily variable; a first orifice passage for fluid communication between the pressure-receiving chamber and the equilibrium chamber; an elastic wall member being elastically displaceable and partially defining the pressure-receiving chamber; a restricting member disposed on one of opposite sides of the elastic wall member which is remote from the pressure-receiving chamber, the elastic wall member being elastically pressed to the restricting member; a working air chamber partially defined by the other side of the flexible diaphragm remote from the equilibrium chamber; and a negative pressure-regulating device adapted to apply different negative pressures to the working air chamber, depending upon frequencies of vibrations to be damped.
In the above-indicated mode (1) of the present invention, the pressure of the fluid within the pressure-receiving chamber is varied due to the elastic deformation of the elastic body, upon application of vibrational loads between the first and second mounting members. (a) Upon application of the vibrational loads over a low frequency band, the fluid is forced to flow through the first orifice passage between the pressure-receiving chamber and the equilibrium chamber, based
Hatano Motohiro
Kato Kazuhiko
Muramatsu Atsushi
Beyer Weaver & Thomas LLP
Burch Melody M.
Tokai Rubber Industries Ltd.
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