Liquid-sealed type vibration isolator

1. A liquid-sealed type vibration isolator comprising:

a first fixture to be fixed to one of a vibration source side and a support side;

a second fixture to be fixed to the other one of the vibration source side and the support side;

a vibration-isolating base member made of an elastomer interposed between the first fixture and the second fixture;

a main liquid chamber having liquid sealed therein and a chamber wall thereof defined partly of the vibration-isolating base member;

at least one auxiliary liquid chamber having liquid sealed therein and a chamber wall thereof defined partly of a diaphragm formed of an elastomeric membrane;

a first orifice flow channel configured to communicate the main liquid chamber and the at least one auxiliary liquid chamber;

a second orifice flow channel tuned to a higher frequency range than the first orifice flow channel and configured to communicate any two of the main liquid chamber and the at least one auxiliary liquid chamber;

a partitioning member configured to partition the main liquid chamber and the at least one auxiliary liquid chamber and formed with the second orifice flow channel; and

a valve member formed of an elastomeric membrane for opening and closing the second orifice flow channel,

wherein the partitioning member includes a valve housing chamber configured to house and hold the valve member in a part of the second orifice flow channel so as to be orthogonal to the direction of flow in the flow channel,

the valve member is held at an outer peripheral portion thereof between wall surfaces of the valve housing chamber, and includes inside the outer peripheral portion thereof a flexible membrane portion configured to be subjected to flexural deformation by the liquid flow in the second orifice flow channel and thereby close an opening of the second orifice flow channel to the valve housing chamber provided in the partitioning member, and

the membrane portion includes a communication hole configured to bring the second orifice flow channel into communication at a position not being overlapped with the opening of the partitioning member to open the second orifice flow channel in a state in which the membrane portion is apart from the opening.

2. The liquid-sealed type vibration isolator according to claim 1 , wherein the membrane portion includes a projection provided on a membrane surface thereof at a position not being overlapped with the opening of the partitioning member, and the projection is configured to be compressed to an opposed wall surface of the valve housing chamber by the flexural deformation of the membrane portion.

3. The liquid-sealed type vibration isolator according to claim 2 , wherein the communication holes are provided at a plurality of positions on a circumference surrounding a plug portion positioned at the center of the membrane portion, and the projections are provided at a plurality of positions on the circumference alternately with the communication holes.

4. The liquid-sealed type vibration isolator according to claim 2 , wherein the projection has a conical shape.

5. The liquid-sealed type vibration isolator according to claim 1 , wherein an annular projecting portion is provided on a peripheral edge portion of the opening of the partitioning member or on the membrane portion opposing the peripheral edge portion so as to surround the opening.

6. The liquid-sealed type vibration isolator according to claim 5 , wherein the annular projecting portion is provided on the membrane portion and a radially projecting portion extending from the center of the annular projecting portion in the radial direction is provided inside the annular projecting portion.

7. The liquid-sealed type vibration isolator according to claim 5 , wherein the membrane portion includes a projection provided on a membrane surface thereof at a position not being overlapped with the opening of the partitioning member, and the projection is configured to be compressed to an opposed wall surface of the valve housing chamber by the flexural deformation of the membrane portion.

8. The liquid-sealed type vibration isolator according to claim 1 , wherein the second orifice flow channel is provided so as to communicate the main liquid chamber and the at least one auxiliary liquid chamber.

9. The liquid-sealed type vibration isolator according to claim 1 , wherein the at least one auxiliary liquid chamber comprises a first auxiliary liquid chamber which includes a chamber wall defined partly by a first diaphragm attached to the second fixture, and a second auxiliary liquid chamber having a chamber wall defined partly by a second diaphragm provided on the partitioning member,

the partitioning member partitions the main liquid chamber and the first auxiliary liquid chamber,

the first orifice flow channel is provided so as to communicate the main liquid chamber and the first auxiliary liquid chamber, and the second orifice flow channel is provided so as to communicate the second auxiliary liquid chamber and the main liquid chamber or the first auxiliary liquid chamber.

10. The liquid-sealed type vibration isolator according to claim 9 , wherein the second auxiliary liquid chamber is provided at the center of the partitioning member,

the second orifice flow channel includes a first flow channel portion extending in the thickness direction of the partitioning member and a second flow channel portion connected to the first flow channel portion and extending along the periphery of the second auxiliary liquid chamber,

the partitioning member includes the valve housing chamber at an intermediary position of the first flow channel portion so as to be orthogonal to the direction of flow in the flow channel portion, and

the valve member is arranged so that the center thereof is deviated from the center of the second auxiliary liquid chamber so that the first flow channel portion is not overlapped with the second auxiliary liquid chamber in the thickness direction of the partitioning member.

11. The liquid-sealed type vibration isolator according to claim 10 , wherein the partitioning member is formed into a circular shape in plan view, the valve member is formed into a disk shape, and the valve member is arranged so that the center thereof is deviated from the center of the partitioning member by an extent corresponding to a radius of the valve member or more.

12. The liquid-sealed type vibration isolator according to claim 1 , wherein the opening of the partitioning member opposing a membrane surface of at least one of the front and back of the membrane portion is deviated from the center of the valve member.

13. The liquid-sealed type vibration isolator according to claim 12 , wherein the membrane portion includes a projection provided on a membrane surface thereof at a position not being overlapped with the opening of the partitioning member, and the projection is configured to be compressed to an opposed wall surface of the valve housing chamber by the flexural deformation of the membrane portion.

14. The liquid-sealed type vibration isolator according to claim 12 , wherein the at least one auxiliary liquid chamber comprises the first auxiliary liquid chamber which includes a chamber wall defined partly by a first diaphragm attached to the second fixture, and the second auxiliary liquid chamber having a chamber wall defined partly by a second diaphragm provided on the partitioning member,

the partitioning member partitions the main liquid chamber and the first auxiliary liquid chamber, and the second auxiliary liquid chamber partitioned from the first auxiliary liquid chamber by the second diaphragm is provided on the side of the first auxiliary liquid chamber of the partitioning member, and

the first orifice flow channel is provided so as to communicate the main liquid chamber and the first auxiliary liquid chamber, and the second orifice flow channel is provided so as to communicate the main liquid chamber and the second auxiliary liquid chamber.

15. The liquid-sealed type vibration isolator according to claim 1 , wherein the rigidity of the membrane portion is set to be non-uniform over a circumference surrounding a plug portion positioned at the center of the membrane portion.

16. The liquid-sealed type vibration isolator according to claim 15 , wherein the communication holes are arranged at non-uniform intervals at a plurality of positions on the circumference surrounding the plug portion, so that the rigidity of the membrane portion is set to be non-uniform over the circumference.

17. The liquid-sealed type vibration isolator according to claim 15 , wherein the membrane portion includes projections provided on a membrane surface thereof at positions not being overlapped with the opening of the partitioning member, the projection is configured to be compressed to an opposed wall surface of the valve housing chamber by the flexural deformation of the membrane portion, and the projections are arranged at non-uniform intervals at a plurality of positions on the circumference surrounding the plug portion so that the rigidity of the membrane portion is set to be non-uniform on the circumference thereof.

18. The liquid-sealed type vibration isolator according to claim 1 , wherein flexural deformation restricting projections configured to restrict the flexural deformation by coming into abutment with the membrane portion at least at the time of the flexural deformation of the membrane portion are provided on a wall surface of the valve housing chamber opposing at least one of the membrane surfaces on the front and back sides of the membrane portion non-uniformly on the circumference.

19. The liquid-sealed type vibration isolator according to claim 1 , wherein the outer peripheral portion of the valve member is formed to be thicker than the membrane portion, and a ring-shaped restricting projection configured to come into abutment with the inner peripheral surface of the thick outer peripheral portion and restrict inward displacement of the outer peripheral portion is provided on the wall surface of the valve housing chamber.