Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
1999-11-23
2001-06-26
Oberleitner, Robert J. (Department: 3613)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
C267S219000
Reexamination Certificate
active
06250616
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fluid-filled vibration damping device which exhibits a vibration damping effect based on flows of a non-compressible fluid enclosed therein, and which are particularly suitable for use as, e.g., automotive-vehicle engine mounts, body mounts, and differential mounts.
2. Related Art Statement
There is known a fluid-filled vibration damping device as a sort of vibration-damping connecting or supporting device that is interposed between two members of a vibration transmitting system, for connecting the two members in a vibration damping fashion. The fluid-filled vibration damping device includes a first mounting member adapted to be attached to one of the two members; a second mounting member adapted to be attached to the other of the two members; and an elastic rubber body which elastically connects the first and second mounting members to each other and which provides a portion of a fluid-chamber wall defining a fluid chamber filled with a non-compressible fluid. When a vibrational load is applied to the vibration damping device, it exhibits a vibration damping effect based on flows of the fluid in the fluid chamber, in particular, resonance of the fluid.
Meanwhile, there has been proposed another fluid-filled vibration damping device which includes, in addition to the above-indicated members, a working or umbrella-shaped member which is supported by the first mounting member such that the umbrella member extends, in the fluid chamber, in a direction substantially perpendicular to a direction in which a main vibrational load is applied to the vibration damping device, and thereby divides the fluid chamber into two divided chambers which are located on opposite sides of the umbrella member, respectively, and which are communicated with each other via a fluid-flow restricting passage defined by at least the umbrella member.
Upon application of the main vibrational load to the second vibration damping device including the umbrella member, the umbrella member is reciprocatively moved in the fluid chamber, so that the fluid flows through the fluid-flow restricting passage. The second vibration damping device can exhibit a vibration damping effect based on the flows of the fluid through the restricting passage, in particular, the resonance of the fluid.
However, even in the second vibration damping device, the vibration damping effect based on the flows of the fluid through the restricting passage defined by the umbrella member is effective against only vibrations having frequencies in a pre-tuned frequency range. In particular, when a vibration having a frequency higher than the pre-tuned range is input to the vibration damping device, the resistance to the flows of the fluid through the restricting passage is excessively increased so that the vibration damping device exhibits an inappropriate (i.e., high) dynamic spring characteristic, which leads to largely lowering the vibration damping performance of the device. Thus, the prior vibration damping device cannot exhibit an appropriate or low dynamic spring characteristic in a 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 has an improved structure for exhibiting, based on a working member provided in a fluid chamber, a low dynamic spring characteristic in a wide frequency range and thereby exhibiting an excellent vibration damping effect against vibrations in the wide frequency range.
The present invention provides a fluid-filled vibration damping device which has one or more of the technical features that are described below in respective paragraphs given parenthesized sequential numbers (1) to (13). Any technical feature which includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to that technical feature. Thus, two or more of the following technical features may be combined, if appropriate. Each technical feature may be accompanied by a supplemental explanation, as needed. However, the following technical features and the combinations thereof are just examples to which the present invention is by no means limited. Rather, the concept of the present invention should be construed based on the overall description of the specification and the drawings.
(1) According to a first feature of the present invention, there is provided a fluid-filled vibration damping device for connecting two members to each other in a vibration damping fashion, comprising a first mounting member which is adapted to be attached to one of the two members; a second mounting member which is adapted to be attached to the other of the two members; an elastic rubber body which elastically connects the first and second mounting members to each other and which provides a portion of a fluid-chamber wall defining a fluid chamber filled with a non-compressible fluid; and a working member which is supported by the first mounting member such that the working member extends, in the fluid chamber, in a first direction substantially perpendicular to a second direction in which a main vibrational load is applied to the fluid-filled vibration damping device, and thereby divides the fluid chamber into two divided chambers which are located, in the second direction, on opposite sides of the working member, respectively, and which are communicated with each other via a fluid-flow restricting passage defined by at least the working member, at least one of a length of the fluid-flow restricting passage in the second direction and a width of the restricting passage in the first direction changing in a circumferential direction of the working member, the restricting passage consisting of (a) a pair of first fluid-flow portions which are opposed to each other in the first direction, each of the two first fluid-flow portions extending over an angle of from 30 degrees to 80 degrees in the circumferential direction of the working member, and having a first ratio, A
s
/L
s
, of a cross-section area, A
s
, thereof to the length, L
s
, thereof; and (b) a pair of second fluid-flow portions which are opposed to each other in a direction perpendicular to each of the first and second directions, each of the two second fluid-flow portions extending over an angle of from 150 degrees to 100 degrees in the circumferential direction of the working member, and having a second ratio, A
w
/L
w
, of a cross-section area, A
w
, thereof to the length, L
w
, thereof, the second ratio A
w
/L
w
being greater than the first ratio A
s
/L
s
, and a ratio, (A
s
/L
s
)/(A
w
/L
w
), of the first ratio A
s
/L
s
to the second ratio A
w
/L
w
being not smaller than {fraction (1/10)} and being not greater than ½.
The fluid-flow restricting passage may consist of an annular space or gap defined by, and between, respective opposed portions of an outer circumferential surface of the working member and an inner circumferential surface of the fluid-chamber wall, or may consist of the annular gap and through-holes formed through the thickness of the working member. In the case where the restricting passage consists of the annular gap and the through-holes, the width of the restricting passage in the first direction is defined as the sum of the respective widths of the annular gap and each through-hole in the first direction.
The Applicants have found, from their various experiments and studies, that the fluid-filled vibration damping device according to the first feature (1) wherein the fluid-flow restricting passage consists of the two first fluid-flow portions and the two second fluid-flow portions and each of the two first fluid-flow portions extends, in the circumferential direction of the working member, over the predetermined angle relative to each of the two second fluid-flow portions, and has the predetermined ratio of cross-section area to length relative to that of each of the two second fluid-flow portions, can exhibit, based on the resona
Kato Kazuhiko
Suzuki Tatsuya
Burr & Brown
Oberleitner Robert J.
Talavera Melanie
Tokai Rubber Industries Ltd.
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