Patent ID: 7328888

Claim:
A hydraulic antivibration device comprising: a first attachment fitting, a second cylindrical attachment fitting, a vibration-isolating base joining the second attachment fitting and the first attachment fitting and composed of a first elastomer, a diaphragm attached to the second attachment fitting and forming a liquid-filled chamber between the diaphragm and the vibration-isolating base, and a partitioning means comparting the liquid-filled chamber into a first liquid chamber on the vibration-isolating base side and a second liquid chamber on the diaphragm side, and an orifice formed between an outer peripheral face of the partitioning means and an inner peripheral face of the second attachment fitting and putting the first liquid chamber and the second liquid chamber into communication with each other, the partitioning means including an elastic partition membrane composed of a second elastomer and a pair of displacement-regulating members regulating the displacement amount of the elastic partition membrane from both sides thereof, the pair of displacement-regulating members having respective openings; wherein the openings consist of a first opening defined at a radially central location of each of the displacement-regulating members and a plurality of second openings defined around the first opening in a distributed manner; wherein the elastic partition membrane includes; a thick-walled portion at a radially central location thereof located within the first openings when viewed in an axis center direction thereof, a thin-walled portion located radially outwardly of the thick-walled portion and formed to be thinner than the thick-walled portion thereby being located to be spaced apart from the pair of the displacement-regulating members, a stationary portion situated in a peripheral marginal area of the thin-walled portion and pinched and fixed between the pair of the displacement-regulating members radially outwards of the second openings, first ribs situated on a first face side of the thin-walled portion around the thick-walled portion in a distributed manner and formed integrally with a boundary between the thick-walled portion and the thin-walled portion in a spaced relation to the one of the pair of the displacement-regulating members, and second ribs situated on a second face side of the thin-walled portion around the thick-walled portion in a distributed manner and formed integrally with the boundary between the thick-walled portion and the thin-walled portion in a spaced relation to the other of the pair of the displacement-regulating members; and wherein the first attachment fitting is constructed as a body frame side coupling means to be coupled to a body frame side and the second attachment fitting is constructed as a vibration generator side coupling means to be coupled to a vibration generator side, and thereby, part of a vibration transmitting path from the partitioning means to a body frame is constituted by the vibration-isolating base.