Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
2001-08-16
2004-11-23
Pezzlo, Benjamin A. (Department: 3683)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
C267S219000
Reexamination Certificate
active
06820867
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fluid-sealed anti-vibration device which is used in an engine mounting and the like in which a cylindrical bushing and a cone-shaped mounting are integrally provided and dynamic characteristics are improved in a cylindrical bushing.
2. Description of the Prior Art
A cone-shaped mounting is known in the prior art, in which a first connecting member secured to a vibration generating side, a second connecting member secured to a vibration receiving side, and a substantially cone-shaped elastic body section for connecting the first and second connecting members are provided. A fluid chamber is provided inside the elastic body section which forms a part of the elastic wall of the fluid chamber. The fluid chamber is divided into a main fluid chamber and a sub-fluid chamber by a partition member and a first orifice is provided for communicating with both fluid chambers. A cylindrical bushing is also known in the prior art in which inner and outer tubes of a cylindrical shape are connected by an elastic member and a plurality of fluid chambers divided by the elastic member in the circumferential direction is provided. An orifice is arranged to communicate with these fluid chambers.
The present applicant has also filed another patent application (U.S. patent application Ser. No. 09/749,829) concerning a fluid-sealed anti-vibration device similar to the device shown in FIG.
1
and
FIG. 2
of the present application. In this application, a cone-shaped mounting section is integrally provided by using an elastic wall which forms a part of a fluid chamber of a cylindrical bushing section and an elastic body section in common. By this integration, the vibrations in the biaxial directions which meet at right angles can be absorbed by the cylindrical bushing section and the vibrations in the direction perpendicular to these can be absorbed by the cone-shaped mounting section. Accordingly, all the vibrations in the triaxial directions which meet at right angles can be absorbed by a single device. In the following description, the vertical direction (the front and rear direction when a car body is installed) and the lateral direction (the lateral direction when the car body is installed) in a condition shown by
FIG. 1
, and the vertical direction in
FIG. 2
(the vertical direction when the car body is installed) are referred to as the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively.
As described above, when the cylindrical bushing section and the con-shaped mounting section are integrally provided, each is provided with a membrane resonance section. Accordingly, as an overall fluid-sealed anti-vibration device, the dynamic spring characteristics in the medium to high frequency range have been determined by coupling each membrane resonance in the cylindrical bushing section and the cone-shaped mounting section. As a result, it is difficult to realize a low dynamic spring effect in a wider range and to form the minimum value of the dynamic spring constant in a specified frequency. It is therefore desirable to make this possible. (Hereinafter the minimum value of the dynamic spring constant is referred to as “a dynamic spring bottom”. Likewise, the maximum value of the dynamic spring constant is referred to as “a dynamic spring peak”.)
It is therefore a first object of the present invention to realize such a demand and it is a second object to improve dynamic characteristics such as lowering a dynamic spring constant in an optional frequency. The medium to high frequency bands here mean those between about 200 and 1,000 Hz.
In the cylindrical bushing section
2
, the elastic member used therein acts as a rubber spring has spring values, each being peculiar to the front and rear direction and the lateral direction. However, when the recessed sections, which is a space opened to the atmosphere, are provided between the neighboring fluid chambers in a circumferential direction, the spring value is reduced in the direction in which the recessed sections are provided. Accordingly, to improve a comfortable car riding, it is necessary to increase the spring values in this direction. For the increase of spring values, it is also considered that the elastic partition wall, which is a partition wall between the recessed section and the fluid chambers, is thickened to raise the rigidity. However, in a case where the recessed sections are disposed in the lateral direction and the liquid chambers are disposed in the front and rear direction, since the elastic partition wall is elastically deformed relative to the input of vibrations in the front and rear direction, it is required to make the capacity of the side fluid chambers variable. Accordingly, it is not possible to raise the rigidity without limitation. It is therefore required to have such a membrane construction as to raise the rigidity relative to only the vibrations in the lateral direction.
It is therefore a third object of the present invention to realize such a demand.
SUMMARY OF THE INVENTION
To attain the above-mentioned first object, according to a first invention of the present invention, a fluid-sealed anti-vibration device is provided, which comprises a cone-shaped mounting section and a cylindrical bushing section, the cone-shaped mounting section being provided with a first connecting member secured to either of a vibration generating side or a vibration receiving side, a second connecting member secured to the other side, a substantially cone-shaped elastic body section for connecting the first and second connecting members, a fluid chamber of which part of an elastic wall is the elastic body section and of which the inside is divided into a main fluid chamber and a sub-fluid chamber by a partition member, and a first orifice for communicating with the main fluid chamber and the sub-fluid chamber, the cylindrical bushing section being provided with a plurality of side fluid chambers which are provided in the circumferential direction at predetermined intervals on the outer circumstance of the elastic body section and of which part of an elastic wall is the elastic body section, and a second orifice for communicating with each side fluid chamber, characterized in that the cone-shaped mounting section and the cylindrical bushing section are caused to generate a membrane resonance in each different natural frequency, and the maximum value or the minimum value of a dynamic spring constant generated by the natural membrane resonance in the cone-shaped mounting section and the maximum value or the minimum value of the dynamic spring constant generated by the natural membrane resonance in the cylindrical bushing section are coupled to interfere with each other, thereby providing low dynamic spring characteristics.
Each natural membrane resonance in the cone-shaped mounting section and the cylindrical bushing section is a membrane resonance with the natural resonant frequency and the dynamic spring characteristics which can be obtained by filling and sealing a fluid in a fluid chamber on either side of the cone-shaped mounting section or the cylindrical bushing section, and by measuring the dynamic spring characteristics.
At this time, the fluid-sealed anti-vibration device may be provided, wherein the cylindrical bushing section forms the maximum value of the dynamic spring constant in the natural frequency by a plurality of membrane resonances and also forms the minimum value of the dynamic spring constant on a higher frequency side than the natural frequency, while the cone-shaped mounting section generates a membrane resonance which forms the minimum value of the dynamic spring constant near and on a frequency side lower than the natural frequency which gives the maximum value.
Also, the fluid-sealed anti-vibration device may be provided, wherein the cylindrical bushing section forms the maximum value of the dynamic spring constant by the natural membrane resonance, and the cone-shaped mounting section also forms the min
Sakamoto Toru
Satori Kazutoshi
Birch & Stewart Kolasch & Birch, LLP
Pezzlo Benjamin A.
Yamashita Rubber Kabushiki Kaisha
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