Fluid-filled type vibration damping device

A fluid-filled type vibration-damping device for elastically connecting two components making up a vibration transmission system in a vibration damping fashion, the device comprising:

• a first mounting member adapted to be attached to one of the two components;
• a second mounting member adapted to be attached to an other one of the two components;
• a main rubber elastic body elastically connecting the first and second mounting members;
• a pressure-receiving chamber whose wall is partially constituted by the main rubber elastic body having a non-compressible fluid sealed therein, and into which vibration is input;
• an equilibrium chamber having the non-compressible fluid sealed therein, whose wall is partially constituted by a flexible film that readily permits change in volume of the equilibrium chamber;
• a partition member supported by the second mounting member and positioned such that the pressure-receiving chamber and the auxiliary fluid chamber are disposed on either side thereof;
• an orifice passage through which the pressure-receiving chamber and the equilibrium chamber communicate with each other;
• and
• a movable rubber plate is positioned housed within a housing space provided in the partition member, the housing space formed with through-holes for connecting the housing space to the pressure-receiving chamber and the equilibrium chamber respectively so that the pressure in the pressure-receiving chamber is exerted on a first face of the movable rubber plate while pressure in the equilibrium chamber is exerted on an other face so that small pressure fluctuations produced in the pressure-receiving chamber during vibration input escape to and are absorbed by the equilibrium chamber via the movable rubber plate,
• wherein the movable rubber plate is formed of a generally disk shaped rubber elastic body, and has at least one concave groove and at least one convex rib formed in alternating fashion on each of the first face and the other face of the movable rubber plate, extending in a circumferential direction about a same center axis, and
• wherein each of the convex ribs has tapered cross section gradually narrowing in width towards an distal end thereof, and the at least one concave groove and convex rib on the first face and the at least one concave groove and convex rib on the other face are disposed at the same locations in a diametrical direction, respectively, so that the thickness of the movable rubber plate is varied in the circumferential direction.