Liquid-sealed antivibration device

1. A liquid-sealed antivibration device comprising:

a first mounting part to be mounted on one of a vibration source side and a support side;

a second mounting part to be mounted on the other of the vibration source side and the support side;

an antivibration base body formed of an elastomer interposed between the first mounting part and the second mounting part;

a main liquid chamber whose chamber wall is partially formed of the antivibration base body and in which a liquid is sealed;

at least one sub liquid chamber in which a liquid is sealed, each of the at least one sub liquid chamber comprising a chamber wall which is formed of a diaphragm comprising an elastomeric membrane;

a first orifice flow passage which connects the main liquid chamber with any one of the at least one sub liquid chamber;

a second orifice flow passage which is tuned to a frequency range higher than a frequency range of the first orifice flow passage and connects two liquid chambers out of the main liquid chamber and the at least one sub liquid chamber;

a partition element which partitions the main liquid chamber and any one of the at least one sub liquid chamber and forms the second orifice flow passage therein; and

a valve member formed of an elastomeric membrane for opening and closing the second orifice flow passage, the valve member being held orthogonal to the flow direction of the second orifice flow passage in a valve housing chamber formed in the partition element;

wherein the valve member comprises:

an outer peripheral portion which is liquid-tightly held by the partition element; and

a flexible membrane portion which is arranged inside the outer peripheral portion and on which a valve portion and a communication hole are formed,

the valve portion is arranged to face in an opposed manner an opening of the second orifice flow passage leading to the valve housing chamber and is configured to close the opening due to flexural deformation of the flexible membrane portion caused by the flow of a liquid in the second orifice flow passage,

the communication hole is formed at a position not being overlapped with the opening and is configured to bring the second orifice flow passage into communication,

the valve portion comprises a cylindrical buffer portion which projects from a membrane surface of the flexible membrane portion, and is formed into a cylindrical shape for surrounding the opening in a state of flexural deformation of the flexible membrane portion,

the projection height of the cylindrical buffer portion from the flexible membrane portion is set larger than a wall thickness of the cylindrical buffer portion, and is set larger than a wall thickness of the flexible membrane portion outside the cylindrical buffer portion, and

a plurality of auxiliary projections are formed on a distal end of the cylindrical buffer portion.

2. The liquid-sealed antivibration device according to claim 1 ,

wherein the cylindrical buffer portion is formed in a projecting manner from both front and back membrane surfaces of the flexible membrane portion.

3. The liquid-sealed antivibration device according to claim 1 , wherein a slit which extends in the height direction is formed in the cylindrical buffer portion.

4. The liquid-sealed antivibration device according to claim 1 ,

wherein a plurality of projections whose projection height is larger than the projection height of the cylindrical buffer portion are formed on the flexible membrane portion outside the cylindrical buffer portion.

5. The liquid-sealed antivibration device according to claim 4 ,

wherein the plurality of projections comprise a first projection and a second projection which differs from the first projection in projection height and/or cross-sectional area.

6. The liquid-sealed antivibration device according to claim 1 ,

wherein a rib is formed on a membrane portion inside the cylindrical buffer portion.

7. The liquid-sealed antivibration device according to claim 1 ,

wherein the at least one sub liquid chamber comprise a first sub liquid chamber whose chamber wall is partially formed of a first diaphragm mounted on the second mounting part, and a second sub liquid chamber whose chamber wall is partially formed of a second diaphragm mounted on the partition element,

the partition element partitions the main liquid chamber and the first sub liquid chamber,

the first orifice flow passage is formed so as to allow the main liquid chamber and the first sub liquid chamber to communicate with each other, and

the second orifice flow passage is formed so as to allow the second sub liquid chamber and the main liquid chamber or the first sub liquid chamber to communicate with each other.

8. The liquid-sealed antivibration device according to claim 7 ,

wherein the second sub liquid chamber which is partitioned from the first sub liquid chamber by the second diaphragm is formed on the first sub liquid chamber side of the partition element,

the first orifice flow passage is formed so as to allow the main liquid chamber and the first sub liquid chamber to communicate with each other, and

the second orifice flow passage is formed so as to allow the main liquid chamber and the second sub liquid chamber to communicate with each other.