A fluid-filled elastic mount for flexibly connecting two members, comprising:
- a first support member and a second support member which are respectively fixed to the two members to be flexibly connected, and which are spaced apart from each other in a load-receiving direction in which vibrations are applied to the elastic mount;
- an elastic body interposed between said first and second support members for elastically connecting the first and second support members;
- a partition structure supported by said second support member and extending in a direction substantially perpendicular to said load-receiving direction;
- said elastic body at least partially defining a pressure-receiving chamber disposed on one of opposite sides of said partition structure on the side of said first support member, said pressure-receiving chamber being filled with a non-compressible fluid, a pressure of said fluid in said pressure-receiving chamber changing due to elastic deformation of said elastic body upon application of the vibrations in said load-receiving direction;
- a first flexible diaphragm cooperating with said partition structure to define a first equilibrium chamber which is filled with said non-compressible fluid, said first flexible diaphragm being elastically deformable so as to permit volume changes of said first equilibrium chamber to absorb pressure changes of said fluid in said first equilibrium chamber;
- means for defining a first orifice passage which communicates with said pressure-receiving chamber and said first equilibrium chamber so as to permit flow of said fluid therebetween;
- a second flexible diaphragm cooperating with said partition structure to define a second equilibrium chamber which is filled with said non-compressible fluid, said second flexible diaphragm being elastically deformable so as to permit volume changes of said second equilibrium chamber to absorb pressure changes of said fluid in said second equilibrium chamber;
- means for defining a second orifice passage which communicates with said pressure-receiving chamber and said second equilibrium chamber so as to permit flow of said fluid therebetween, said second orifice passage having a ratio of a cross sectional area thereof to a length thereof, which ratio is higher than that of said first orifice passage;
- a flexible partition wall disposed on one of opposite sides of said second flexible diaphragm remote from said second equilibrium chamber, said flexible partition wall cooperating with said second flexible diaphragm to define therebetween an air chamber which is exposed to the atmosphere to permit elastic deformation of said second flexible diaphragm;
- biasing means for applying a biasing force to said second flexible diaphragm, thereby forcing said second flexible diaphragm to close an opening of said second orifice passage;
- said flexible partition wall partially defining a fluid-tightly enclosed operating chamber which is separated from said air chamber by said flexible partition wall;
- and
- pressure control means for applying a vacuum pressure to said operating chamber to draw said second flexible diaphragm away from said opening of said second orifice passage against said biasing force of said biasing means, thereby opening said second orifice passage for fluid communication with said second equilibrium chamber.