Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
2001-04-17
2003-03-04
Lavinder, Jack (Department: 3613)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
C267S140150
Reexamination Certificate
active
06527262
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2000-118062 filed on Apr. 19, 2000 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 elastic engine mount including a fluid-filled pressure-receiving chamber, wherein a pressure of the fluid in the pressure-receiving chamber is suitably controlled so that the engine mount exhibits an active or positive vibration damping or isolating effects. More particularly, the present invention is concerned with such a fluid-filled active elastic engine mount which is novel in construction and which is capable of exhibiting an excellent active damping or isolating effect with respect to any vibrations including low frequency vibrations such as engine shakes, medium frequency vibrations such as engine idling vibrations, and high frequency vibrations such as booming noises.
2. Description of the Related Art
In an automotive vehicle having a power unit including an internal combustion engine, there has been used an elastic engine mount which is interposed between the power unit and a body of the vehicle for elastically mounting the power unit on the vehicle body in a vibration damping fashion, thereby attenuating or reducing vibrations transmitted from the power unit to the vehicle body. To cope with recent increasing demands for vibration damping characteristics of the engine mount, there has been developed an active engine mount which includes a first and a second mounting members, an elastic body elastically connecting the first and second mounting members and partially defining a fluid-filled pressure receiving chamber to which vibrations to be damped is applied, and an oscillating plate partially defining the pressure receiving chamber. The oscillating plate is oscillated at a frequency and amplitude which correspond to those of vibrations to be damped, and the oscillating movement of the oscillating plate may acts to offset or absorb periodic fluid pressure change in the primary fluid chamber due to elastic deformation of the elastic body upon application of the input vibrations. Thus, the active elastic mount exhibits an active or positive vibration damping effect based on the oscillation of the oscillating plate.
Generally, an engine mount is required to exhibit high vibration damping or isolating effects with respect to various kinds of input vibrations having different frequencies bands or ranging over a wide frequency band.
A known example of a modified engine mount proposed in an attempt to meet such a high requirement for the engine mount, is disclosed in Japanese Laid-Open Publication No. JP-A-10-331908. The disclosed engine mount includes a partition member which divides the pressure receiving chamber into a primary fluid chamber partially defined by the elastic body and an auxiliary fluid chamber partially defined by the oscillating plate, which are located on the opposite sides of the partition member. The primary fluid chamber is held in fluid communication with the equilibrium chamber through a first orifice passage, and is also held in fluid communication with the auxiliary fluid chamber through a second orifice passage. The first and second orifice passage are tuned to a low frequency band corresponding to engine shakes and a medium frequency band corresponding to engine idling vibrations, respectively. The disclosed engine mount constructed as described above is capable of exhibiting excellent vibration damping effects with respect to both of the engine shakes and the engine idling vibrations based on flows of the fluid through the first and second orifice passages, and is also capable of exhibiting active damping effects based on a periodic fluid pressure change generated in the auxiliary fluid chamber by the oscillation of the oscillating plate and transmitted to the pressure receiving chamber through the second orifice passage.
However, the proposed engine mount suffers from a problem of deterioration of the active damping characteristics thereof, upon application of vibrations whose frequency is higher than the medium frequency to which the second orifice passage is tuned. Namely, the engine mount is incapable of transmitting the periodic fluid pressure from the auxiliary fluid chamber to the primary fluid chamber through the second orifice passage, upon application of the higher frequency vibrations, since substantially no flow of the fluid through the second orifice passage is permitted due to a significant increase of resistance to the fluid flows through the second orifice passage. Therefore, the proposed engine mount having the first and second orifice passages tuned to engine shakes and engine idling vibrations, respectively, suffers from a significant deterioration of its vibration damping characteristics with respect to high frequency vibrations such as booming noises whose frequency is higher than the frequency of the engine idling vibration.
To cope with this drawback of the proposed engine mount, another modified engine mount has been proposed, wherein the first and second orifice passages are formed parallel to each other between the pressure receiving chamber and the equilibrium chamber, and the oscillating plate is disposed in a portion which is independent of or isolated from the first and second orifice passages, so that the oscillating plate is directly faced to the pressure receiving chamber. As a result of an extensive study of the thus constructed engine mount by the present inventors, it was found that the engine mount is prone to suffer from a significant deterioration of the vibration damping characteristics thereof due to a significant increase in a dynamic spring constant thereof upon application of vibration in a high frequency band. It seems that the engine mount has a resonance frequency in a higher frequency band that is higher than the medium frequency band corresponding to the engine idling vibrations.
While the reasons why the engine mount exhibits the significantly increased dynamic spring constant in the frequency band higher than the frequency band to which the second orifice passage is tuned, has not yet been revealed, it may be considered that the oscillating plate and an elastic support member elastically supporting the oscillating plate with respect to the second mounting member cooperate to constitute a mass-spring system, and the resonance of this mass-spring system may cause the above-indicated significant increase of the dynamic spring constant of the engine mount. In this respect, the engine mount is prone to suffer from the increase in the dynamic spring constant thereof upon application of vibrations having frequencies ranging from a few dozen to a few hundred Hz, corresponding to the booming noise, especially, ranging from 50 to 100Hz.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a fluid-filled active elastic engine mount which is capable of exhibiting an excellent vibration damping or isolating effect with respect to vibrations over a wide frequency range, especially to low frequency vibrations such as engine shakes, medium frequency vibrations such as engine idling vibrations, and high frequency vibrations such as booming noises.
The above object may be achieved according to the principle of the present invention, which provides a fluid-filled elastic engine mount comprising: a first and a second mounting member which are spaced apart from each other; an elastic body elastically connecting the first and second mounting members and partially defining a pressure-receiving chamber filled with a non-compressible fluid; a flexible diaphragm partially defining an equilibrium chamber filled with the non-compressible fluid, the flexible diaphragm being displaceable to permit a change in a volume of the equilibrium chamber; a movable oscillating plate partially defining the pressure-receiving chamber, the movable oscillating plate being oscillated by means of an oscillating device, for controlling
Goto Katsuhiro
Hagino Yoshihiko
Suzuki Tatsuya
Beyer Weaver & Thomas LLP
Lavinder Jack
Siconolfi Robert A.
Tokai Rubber Industries Ltd.
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