Liquid-sealed vibration isolator

A liquid-sealed vibration isolator, comprising:

• a first fixture to be attached to one of a vibration source side and a support side;
• a second fixture to be attached to the other of the vibration source side and the support side;
• a vibration isolating base which is interposed between the first fixture and the second fixture and is formed of a rubber-like elastic body;
• a main liquid chamber, a portion of a chamber wall of the main liquid chamber is formed by the vibration isolating base, and which is sealed with liquid;
• at least one subsidiary liquid chamber, a portion of a chamber wall of the subsidiary liquid chamber is formed by a diaphragm formed of a rubber-like elastic membrane, and which is sealed with liquid;
• a first orifice flow path which connects the main liquid chamber with one of the subsidiary liquid chambers;
• a second orifice flow path which is tuned to a frequency range higher than the first orifice flow path and connects the main liquid chamber with one of the subsidiary liquid chambers;
• and
• a partitioning body which partitions the main liquid chamber and one of the subsidiary liquid chambers and is formed with the second orifice flow path,
• wherein the partitioning body is provided with a second diaphragm formed of a rubber-like elastic membrane in an opening to the main liquid chamber side of the second orifice flow path,
• the second diaphragm comprises a flexible membrane section and an outer peripheral portion, the second diaphragm is configured so that the outer peripheral portion is held against the partitioning body in a liquid-tight manner, the second diaphragm is in contact with an opening periphery portion so as to block the opening, and the flexible membrane section is provided with at least one through hole at a position which does not overlap the opening, and
• the second diaphragm is configured so that, when a flow rate of the second orifice flow path is equal to or greater than a predetermined amount, the flexible membrane section is subjected to a flexural deformation so as to be separated from the opening of the second orifice flow path to the main liquid chamber side, whereby liquid is supplied from the through hole provided in the flexible membrane section to the main liquid chamber side, such that the flexural deformation of the second diaphragm opens a path between the second orifice flow path and the at least one through hole, such that a radially outer most portion is fixed and remains stationary irrespective of the flow rate.