Fluid-filled vibration-damping device having gas-retaining hole

1. A fluid-filled vibration-damping device for an automotive vehicle, comprising:

a first mounting member adapted to be fixed to a member on a power unit side of the vehicle;

a second mounting member adapted to be fixed to a member on a body side of the vehicle, and having a cylindrical configuration, the first mounting member being disposed underneath a lower open-end of the second mounting member with an axial spacing therebetween;

an elastic body elastically connecting the first and second mounting members so that the lower open-end of the second mounting member is fluid-tightly closed by the elastic body and the first mounting member;

a flexible layer is disposed so as to fluid-tightly close an upper open end of the second mounting member so that a fluid-sealing area is formed within the second mounting member and is filled with a non-compressible fluid that is forced to flow within the fluid-sealing area upon application of a vibrational load to the fluid-sealing area so as to exhibit vibration-damping effect; and

at least one gas-retaining hole is formed on a side of the first mounting member so as to open to the fluid-sealing area through an opening thereof facing vertically upward, and capable of retaining a predetermined volume of gas therein with the opening thereof facing vertically upward within the non-compressible fluid, and discharging the gas retained therein into the liquid sealing area when the device is installed between the power unit and the body of the vehicle.

2. A fluid-filled vibration-damping device according to claim 1 , wherein the at least one gas-retaining hole is adapted to discharge the predetermined volume of gas retained therein from the opening thereof into the fluid-sealing area in an event of application of a given external force to the device.

3. A fluid-filled vibration-damping device according to claim 1 , wherein a wall of the fluid-sealing area is partially defined by a rigid member, and the at least one gas retaining hole is formed into a portion of the wall in which deformation due to a force applied thereto is prevented by means of the rigid member.

4. A fluid-filled vibration-damping device according to claim 1 , wherein the fluid-sealing area includes a pressure-receiving chamber partially defined by the elastic body and an equilibrium chamber partially defined by a flexible layer and held in fluid communication with the pressure-receiving chamber through an orifice passage, and the at least one gas-retaining hole is open to the pressure-receiving chamber of the fluid-sealing area.

5. A fluid-filled vibration-damping device according to claim 4 , wherein a partition structure is disposed within and supported by the second mounting member so as to divide the fluid-sealing area into the pressure receiving chamber and the equilibrium chamber on the opposite sides thereof, and the at least one gas-retaining hole is open in an inner surface of the sealing end portion.

6. A fluid-filled vibration-damping device according to claim 1 , wherein the at least one gas-retaining hole comprises a plurality of gas-retaining holes, and the plurality of gas-retaining holes are oriented to be open in a same direction.

7. A fluid-filled vibration-damping device according to claim 1 , wherein the at least one gas-retaining hole has an inner surface made of an elastic material such as rubber and a synthetic resin material.

8. A fluid-filled vibration-damping device according to claim 1 , wherein the at least one gas-retaining hole is formed into a portion of the elastic body, which portion does not undergo elastic deformation upon application of a vibrational load between the first and second mounting members.