Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
2002-10-28
2003-07-15
Schwartz, Christopher P. (Department: 3683)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
Reexamination Certificate
active
06592111
ABSTRACT:
INCORPORATED BY REFERENCE
The disclosure of Japanese Patent Application No. 2001-331570 filed on Oct. 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 fluid-filled active vibration damping device having a pressure-receiving chamber filled with a non-compressible fluid and capable of actively offsetting or attenuating a vibrational load applied to the pressure-receiving chamber by suitably controlling a pressure of the fluid filling the pressure-receiving chamber. More particularly, the present invention is concerned with such a fluid-filled active vibration damping device that is suitably applicable to active elastic mounts or active dampers or oscillators for use in automotive vehicles.
2. Description of the Related Art
Vibration damping devices have been used for damping or isolating vibrations (including noises induced by the vibrations) of a subject member such as a body of an automotive vehicle or other members suffering from these vibrations or noises. Known examples of such vibration damping devices include: a vibration-damping coupling or mount, e.g., an engine mount, which is interposed between the subject member and a vibration source, e.g., a power unit, so as to connect these two members in a vibration damping or isolating fashion for eliminating or reducing a vibration transmitted from the vibration source to the subject member; and a vibration damper that is fixed to the subject member for attenuating or absorbing the vibration of the subject member.
A fluid-filled active vibration damping device has been proposed as one type of such vibration damping devices, which includes: an elastic body elastically deformed due to vibrational loads applied thereto; a pressure-receiving chamber partially defined by the elastic body and filled with a non-compressible fluid; an oscillating rubber plate disposed elastically displaceable; an oscillating fluid chamber partially defined by one of opposite sides of the oscillating rubber plate and filled with the non-compressible fluid; an orifice passage permitting a fluid communication between the pressure-receiving chamber and the oscillating fluid chamber; and a working air chamber partially defined by the other side of the oscillating rubber plate so as to be opposed to the oscillating fluid chamber with the oscillating rubber plate interposed therebetween. In the known fluid-filled active vibration damping device, an air pressure variation corresponding to vibrations to be damped is applied from the external area to the working air chamber so as to oscillate the oscillating rubber plate, and an oscillating force generated by the oscillation of the oscillating rubber plate is transmitted to the pressure-receiving chamber through the oscillating fluid chamber and the orifice passage, thus making it possible to actively control a fluid pressure variation induced in the pressure-receiving chamber. Thus, the known fluid-filled active vibration damping device is capable of exhibiting an active vibration damping effect or an offsetting effect with respect to vibrations to be damped, and accordingly ensuring high vibration damping characteristics in comparison with conventional passive vibration damping devices. For this reason, the known fluid-filled active vibration damping device has been applied to an engine mount for automotive vehicles where a demand for higher grade damping has been growing.
In order to induce in the working air chamber the air pressure variation having a frequency corresponding to that of the vibrations to be damped, the known fluid-filled active vibration damping device generally employs: an air conduit connectable to the working air chamber; and a solenoid-operated switch valve operable for alternately connecting and disconnecting the air conduit to and from two different air pressure sources, e.g., a vacuum source and the atmosphere, at a frequency corresponding to that of vibrations to be damped.
However, the conventional fluid-filled active vibration damping device is not able to conform the waveform of the air pressure variation induced in the working air chamber to the waveform of the vibrations to be damped with sufficient accuracy, since the air pressure variation is induced in the working air chamber as a result of the switching operation of the solenoid operated switch valve between the two different air pressure sources, namely the air pressure variation is caused by an “ON/OFF” like operation of the solenoid operated switch valve. Also, undesirable pressure variation is likely to be generated due to compressibility of the air used as a pressure-transmitting medium. For the above reasons, the air pressure variation applied to the working air chamber is likely to include secondary frequency components other than a primary frequency component corresponding to the frequency of the vibrations to be damped, thereby undesirably transmitting to the pressure-receiving chamber the oscillating force having the secondary frequency components, which are not corresponding to the frequency of the vibrations to be damped. Therefore, the conventional fluid-filled active vibration damping device may possibly suffer from deterioration of its damping capability due to the generation of the secondary frequency components in the air pressure variation applied to the working air chamber.
SUMMARY OF THE INVENTION
It is therefore one object of this invention to provide a fluid-filled active vibration damping device, which is novel in construction and which is capable of reducing a transmission of a fluid pressure variation having higher frequency components or other frequency components that do not correspond to a vibration to be damped to a pressure-receiving chamber, for thereby exhibiting a desired active vibration damping effect in an effective and a stable manner.
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 depending 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 these modes of the invention and combinations of the technical features, but may otherwise be recognized based on the teachings of the present invention disclosed in the entire specification and drawings or that may be recognized by those skilled in the art in the light of the present disclosure in its entirety.
The present inventors have conducted an extensive study and a multiplicity of experiments in an effort to solve the conventionally experienced problem or to explore a mechanism of generation of the fluid pressure variation having the higher frequency components in the pressure-receiving chamber. As a result, the present inventors discovered at first that the air pressure variation applied to the working air chamber is converted into the fluid pressure variation generated in the oscillating fluid chamber, and then is transmitted to the pressure-receiving chamber through the orifice passage while being influenced by shapes of the orifice passages in terms of pressure transmission characteristics including pressure transmission efficiency. Namely, the pressure transmission characteristics of the orifice passage may vary depending upon its shape. The present invention was developed as a result of a further extensive study on this finding.
(1) A fluid-filled active vibration damping device including: (a) an elastic body elastically deformed due to a vibrational load applied thereto; (b) a pressure-receiving chamber partially defined by the elastic body and filled with a non-compressible fluid; (c) an oscillating rubber plate disposed elastically displaceable; (d) an oscillating fluid chamber partially defined by the oscillating rubber plate, disposed on one of opposi
Kato Kazuhiko
Matsuoka Hideki
Nishi Naoki
Beyer Weaver & Thomas LLP
Schwartz Christopher P.
Tokai Rubber Industries Ltd.
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