Fluid-filled insulating bushing

DETAILED DESCRIPTION It is an object of the present invention to provide an improved insulating bushing which enables effective damping of low frequency and large amplitude vibrations such as engine shake and idling vibration while effectively damping high frequency and small amplitude vibrations that cause booming noise within a vehicle passenger compartment.
The insulating bushing of the present invention is comprised of a support elastic member tightly interposed between the inner and outer cylinder.
The support elastic member is formed with a hollow defining therein a main fluid chamber.
The support elastic member is also formed with an auxiliary fluid chamber which is separate from the main fluid chamber in the peripheral direction.
An orifice passage is formed along the inner periphery of the outer cylinder to communicate the main and auxiliary fluid chambers.
Additionally, a flange plate fixedly connected to a side of the inner cylinder is disposed within the main fluid chamber to divide the main fluid chamber into first and second chambers in the diametrical direction.
The flange plate is such located such that the periphery thereof is separate from the inner wall surface of the main fluid chamber to define therebetween a clearance through which the first and second chambers are in communication with each other.
With the thus configured insulating bushing, the orifice passage for communicating the main and auxiliary fluid chambers is arcuate or annular along the inner periphery of the outer cylinder and therefore can be increased in length and cross-sectional area.
Accordingly, the mass of fluid vibrating in the orifice passage increases thereby to set target vibrations to be damped within a low frequency and large amplitude region.
Furthermore, since the main fluid chamber is divided into two chambers by the flange plate, fluid displacement takes place between the two chambers through the clearance formed around the periphery of the flange plate when the side wall of the main fluid chamber deforms upon receiving input vibration