PURPOSE: To prevent the pressure reduction of a sealed liquid to an enclosed chamber resulting from the diameter expanding deformation of a rubber sleeve.

CONSTITUTION: A pair of two face plates 2 and 3 are installed to a rod 1 by separating them in the axial direction, a tubular member 4 positioned by placing specific intervals from them is provided around the rod 1 between both face plates 2 and 3, and the end parts of the tubular member 4 are connected liquidtight to the face plates 2 and 3 through rubber sleeves 5 and 6 respectively, so as to form an enclosed chamber 7, and at the position to seal the liquid in the enclosed chamber 7, an inner pressure compensating means of the liquid in the enclosed chamber is provided relating to at least one side face plate. And the inner pressure compensating means is composed of a movement part 15 to displace or deform in the direction from the inner side to the outer side of the enclosed chamber under the liquidtight condition, and a pressing part 16 to press the movement part 15 to the inner direction of the enclosed chamber.