Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
2003-01-22
2003-07-29
Schwartz, Christopher P. (Department: 3683)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
C267S140110
Reexamination Certificate
active
06598865
ABSTRACT:
INCORPORATED BY REFERENCE
The disclosure of Japanese Patent Application No. 2002-019956 filed on Jan. 29, 2002 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 fluid-filled vibration damping device capable of exhibiting a vibration damping effect on the basis of flows of a non-compressible fluid filling a fluid chamber formed therein and suitably applicable to an engine mount for use in an automotive vehicle, for example. More particularly, the present invention is concerned with such a fluid-filled active vibration damping device including: a primary fluid chamber adapted to exhibit fluid pressure variation due to a vibrational load applied thereto; and a movable rubber plate partially defining the primary fluid chamber and adapted to be displaced toward and away from an interior of the primary fluid chamber owing to its elastic deformation for regulating or controlling the fluid pressure variation induced in the primary fluid chamber.
2. Description of the Related Art
As one type of a vibration damping device to be interposed between two members of a vibration system, there is known a fluid-filled vibration damping device capable of exhibiting a vibration damping effect with the help of flows of a non-compressible fluid filling a fluid chamber formed therein. A known example of the fluid-filled vibration damping device is disclosed in JP-A-57-9340, JP-A-62-101979 and JP-A-10-184769, wherein the fluid-filled vibration damping device includes: a rubber elastic body elastically connecting a first and a second mounting member that are disposed in mutually spaced-apart relationship with each other; a primary fluid chamber partially defined by the rubber elastic body and filled with a non-compressible fluid, while being adapted to induce fluid pressure variation due to an elastic deformation of the rubber elastic body caused by a vibrational load applied between the first and second mounting members; and a movable rubber plate partially defining the primary fluid chamber such that a peripheral portion of the movable rubber plate is bonded to and fluid-tightly supported by a rigid wall portion of the primary fluid chamber so that the fluid pressure variation induced in the primary fluid chamber is regulated or controlled by displacement of the movable rubber plate owing to its elastic deformation.
The known fluid-filled vibration damping device constructed as described above is capable of moderating or eliminating the fluid-pressure variation induced in the primary fluid chamber with the help of a slight displacement of the movable rubber plate, for improving its vibration isolating effect with respect to high and small-amplitude vibrations. Alternatively, the known fluid-filled vibration damping device can exhibit an active vibration damping effect, when being arranged such that an air chamber is formed on a rear-side of the movable rubber plate, and an air pressure in the air chamber is actively controlled so as to adjust vibration characteristics of the device depending on input vibrations by regulating a spring rigidity of the primary fluid chamber. Also, the air pressure in the air chamber is actively controlled so that the movable rubber plate is actively oscillated at a frequency corresponding to that of vibrations to be damped. For the above-described advantages, the known fluid-filled vibration damping device has been applied to engine mounts, body mounts or other damping devices for use in automotive vehicles.
In the known or conventional fluid-filled vibration damping device, as described above, the peripheral portion of the movable rubber plate is bonded to and supported by the rigid wall portion of the primary fluid chamber, thereby establishing an excellent fluid-tightness of the primary fluid chamber, while preventing a relatively large amount of displacement of the movable rubber plate in its entirety. However, the conventional fluid-filled vibration damping device may suffer from inherent problems. For instance, a durability of the movable rubber plate itself may be deteriorated due to an excessively large amount of displacement of the movable rubber plate. Further, the conventional fluid-filled vibration damping device may fail to exhibit desired damping effects on the basis of flows of the non-compressible fluid, since an effective fluid pressure variation induced in the primary fluid chamber is undesirably absorbed by the displacement of the movable rubber plate, even when the vibration damping device is subjected to low and medium frequency vibrations.
To cope with the above-described problems, a modified fluid-filled vibration damping device has been proposed, as disclosed in JP-A-57-9340 and JP-A-62-101979, in which a pair of displacement limiting plates are disposed on the opposite sides of the movable rubber plate with spacing therebetween. The displacement limiting plates have a plurality of holes formed therethrough so that a fluid pressure in the primary fluid chamber can act on the movable rubber plate through the plurality of holes. Also, the displacement limiting plates can limit an amount of displacement of the movable rubber plate such that the movable rubber plate is brought into abutting contact with one of the displacement limiting plates when the amount of displacement of the movable rubber plate increases.
The proposed fluid-filled vibration damping device, however, needs the pair of displacement limiting plates to be disposed on the both sides of the movable rubber plate, thus increasing the number of components, leading to complicated or cumbersome manufacturing operations. Further, the movable rubber plate is exposed to the primary fluid chamber through the plurality of holes formed through one of the displacement limiting plates, in other words, the fluid pressure variation induced in the primary fluid chamber is transmitted to the movable rubber plate only through the plurality of holes. This means that the displacement limiting plates possibly restrict transmission of the fluid pressure variation from the primary fluid chamber to the movable rubber plate, leading to decrease in an effective pressure receiving area of the movable rubber plate. Therefore, it is difficult for the fluid-filled vibration damping device to sufficiently improve its damping capability with the help of the elastic deformation of the movable rubber plate. Yet further, the movable rubber plate and one of the displacement limiting plates cooperate to form a slight gap in the primary fluid chamber, making it difficult to remove an air remained in the gap upon filling the primary fluid chamber with the non-compressible fluid. The air remained in the slight gap formed between the movable rubber plate and the displacement limiting plate may possibly deteriorate an intended vibration damping capability of the fluid-filled vibration damping device.
SUMMARY OF THE INVENTION
It is therefore one object of this invention to provide a novelly structured fluid-filled vibration damping device including a primary fluid chamber partially defined by a movable rubber plate, which is able to effectively restrict an amount of displacement of the movable rubber plate toward and away from an interior of the primary fluid chamber by means of a simple structure with the reduced number of components, which is easy to manufacture, and which enables a fluid pressure variation in the primary fluid chamber to effectively act on the movable rubber plate for thereby exhibiting its improved vibration damping capability with the help of elastic displacement or deformation of the movable rubber plate.
The above and/or other 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 inventio
Beyer Weaver & Thomas LLP
Schwartz Christopher P.
Tokai Rubber Industries Ltd.
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