Patent ID: 7456530

Claim:
A magnetostrictive actuator comprising: displacement-generating means configured to generate a displacement caused by magnetic material having a magnetostrictive characteristic; movable means configured to move in a displacement direction of the displacement-generating means, said movable means being connected with the displacement-generating means and made of a ferromagnet; magnetic-field-generating means configured to apply a magnetic field to the displacement-generating means, said magnetic-field-generating means being arranged around the displacement-generating means; and an enclosing device configured to enclose the displacement-generating means, in the enclosing device, magnetic-circuit-forming member including a plurality of magnetic circuit forming members and a plurality of permanent magnets for applying static magnetic bias field to the displacement-generating means are arranged in a displacement direction around the enclosed displacement-generating means at fixed intervals, wherein the movable means is arranged relative to the enclosing device to form a gap therebetween, allowing magnetic bias force exerted between the movable means and the enclosing means to apply prestress to the displacement-generating means, and wherein the gap, plurality of magnetic circuit forming members and plurality of permanent magnets are arranged in a linear direction parallel to an axis of the displacement-generating means.