Self-expanding mount

A self-expanding mount for controlling transmission of vibration of a vibration source to a base, including a resilient member fixed to one of said vibration source and said base, a casing fixed to the other of said vibration source and said base, a main liquid chamber defined between said resilient member and said casing and filled with liquid, liquid pressure-changing means for changing pressure of said liquid within said main liquid chamber in response to a control signal corresponding to vibration of said vibration source, an auxiliary liquid chamber, and a communication passage having a restriction and communicating said auxiliary liquid chamber with said main liquid chamber, wherein a variation in pressure of said liquid is caused by said liquid pressure-changing means to cause contraction and expansion of said resilient member to thereby control the transmission of vibration from said vibration source to said base,

• the improvement wherein said liquid pressure-changing means comprises a cylinder formed in said casing and defining part of said main liquid chamber, a driven member received in said cylinder for axial displacement therein, and electromagnetic driving means for driving said driven member, and wherein said communication passage includes pressure-relieving means for allowing liquid from one of said main liquid chamber and said auxiliary liquid chamber to the other when an excessive change occurs in the pressure of liquid within said main liquid chamber.