Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
2001-12-22
2003-11-04
Schwartz, Christopher P. (Department: 3683)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
C267S140400, C267S141000
Reexamination Certificate
active
06641119
ABSTRACT:
INCORPORATED BY REFERENCE
The disclosure of Japanese Patent Application No. 2001-020207 filed on Jan. 29, 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 vibration-damping device which exhibits a vibration damping or isolating effect on the basis of an elastic deformation of a rubber elastic body, and more particularly to such a vibration-damping device which is novel in construction and which is suitably applicable to an engine mount, a body mount, and a suspension bushing for an automotive vehicle, for example.
2. Description of the Related Art
As one kind of vibration dampers such as an engine mount or a suspension bushing for an automotive vehicle, for flexibly connecting two members in a vibration system or mounting one of the two members on the other member in a vibration damping fashion, there is known a vibration-damping device having an elastic body made of rubber, which elastically connects a first and a second mounting member that are disposed in a mutually spaced-apart relationship with each other and attachable to these two members of the vibration system. Keeping pace with a recent demand on upgrading damping capability of the vibration dampers, a fluid-filled vibration-damping device has been developed. The fluid-filled vibration-damping device includes a fluid chamber partially defined by the elastic body and filled with a non-compressible fluid, and exhibits an improved vibration-damping device on the basis of resonance or flows of the non-compressible fluid in the fluid chamber induced when the vibration-damping device is subjected to a vibrational load.
Upon application of the vibrational load to such a vibration-damping device, the elastic body is elastically deformed periodically. Since the elastic body itself constitutes a vibration system, the elastic body is likely to suffer from a surging thereof upon application of the vibrational load whose frequency band corresponds to a natural frequency of the elastic body. The surging of the elastic body may deteriorate vibration damping characteristics of the vibration-damping device, whereby the vibration-damping device is incapable of exhibiting a desired damping effect.
A surging frequency: fn of the elastic body may be obtained according to the following equation on the basis of a basic model of the vibration-damping device including the first and second mounting members and the elastic body elastically connecting the first and second mounting members:
fn
=(
N
/2
L
){square root over ( )}(
G
/&rgr;)
where,
L: distance of effective free length of the elastic body;
G: dynamic modulus of elasticity;
&rgr;: density of the elastic body; and
N: degree of a mode of vibration.
In general, the surging of the elastic body in a first mode or harmonic of vibration (N=1) is required to be damped, since an amplitude of the surging of the elastic body is maximized in the first mode.
To cope with the problem of surging of the elastic body, various kinds of surging limiting members incorporated in the vibration-damping device has been proposed. For instance, JP-A-2-256933 discloses a surging limiting member of dynamic damper type in which a pair of support arm protrude from the elastic body so as to support mass members at their protruding end portions, respectively. These support arms and the mass members cooperate to constitute a dynamic damper serving as a subsidiary vibration system, so that the vibration-damping device equipped with this surging limiting member enables to limit or restrict the surging of the elastic body owing to resonance of the subsidiary vibration system. Further, JP-A-10-267069 discloses a surging limiting member of mass damper type in which a ring member serving as a mass damper is fixedly disposed in the elastic body so as to adjust the mass of a surging portion of the elastic body.
However, the disclosed surging members of the dynamic damper type and the mass damper type exhibit their surging limiting effects with respect only to very limited frequency bands, to which these surging members are tuned. This makes it difficult to desirably tune a natural frequency of the subsidiary vibration system, i.e., the dynamic damper of the vibration-damping device, and a natural frequency of a primary vibration system of the vibration-damping device equipped with the mass damper in the form of the ring member.
Moreover, the surging frequency of the elastic body of the vibration-damping device varies depending upon a spring stiffness of the elastic body which is changed due to a change of the ambient temperature. Therefore, even if the disclosed vibration-damping device having the surging limiting members are desirably tuned in their initial or static states, the surging limiting member may possibly become incapable of exhibiting intended surging limiting effects, due to the above-indicted change of the surging frequency of the elastic body. Thus, the conventional vibration-damping devices equipped with the surging limiting members still suffer from difficulty in exhibiting desired surging limiting effects with high stability.
SUMMARY OF THE INVENTION
It is therefore one object of this invention to provide a vibration-damping device, which is novel and simple in construction, which is able to eliminate or minimize a problem of deterioration of vibration damping capability thereof due to a surging of an elastic body thereof, and which is capable of exhibiting an excellent vibration damping effect over a wide frequency band.
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 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 whose 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 vibration-damping device for elastically connecting two members of a vibration system in a vibration damping fashion, the vibration-damping device comprising: (a) a first mounting member attachable to one of the two members of the vibration system; (b) a second mounting member disposed away from the first mounting member and attachable to an other one of the two members of the vibration system; (c) an elastic body disposed between and elastically connecting the first and second mounting members, the elastic body including a connecting portion that extends between the first and second mounting members and has a hollow housing portion; and (d) an independent mass member accommodated in the housing portion such that the independent mass member is independently displaceable relative to the housing portion without being bonded to the housing portion, and such that the independent mass member is brought into direct and elastic impact against the housing portion.
In the vibration-damping device constructed according to the mode (1) of the invention, the independent mass member is displaced relative to the housing portion when a vibrational load is applied between the first and second mounting members and the elastic body undergoes elastic deformation or displacement thereof. In particular, upon application of a specific vibrational load whose frequency corresponds to a surging frequency of the elastic body, an amount of the elastic deformation or displacement of the elastic body increases, resulting in an increase in an amount of displacement of the independent mass member relative to the housing portion of the connecting portion of the elastic body. This effectively i
Beyer Weaver & Thomas LLP
Schwartz Christopher P.
Tokai Rubber Industries Ltd.
Torres Melanie
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