Magnetostrictive actuator

Abstract

A magnetostrictive actuator has magnetostrictive element having a magnetostrictive, a driving rod moving in a displacement direction of the magnetostrictive element, which is connected with the magnetostrictive element and made of a ferromagnet, a solenoid coil applying magnetic field to the magnetostrictive element, which is arranged around the magnetostrictive element, an enclosure enclosing the magnetostrictive element and the solenoid coil. In the enclosure, a permanent magnet for applying static magnetic bias field to the magnetostrictive element and tubular cases including a ferromagnet are arranged around the enclosed magnetostrictive element, and the driving rod is arranged in the enclosure with a space. Magnetic pull-in force caused between the driving rod and the enclosure can apply prestress to the magnetostrictive element.

1 . A magnetostrictive actuator comprising: 
 displacement-generating means configured to generate a displacement caused by magnetic material having a magnetostrictive;    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 magnetic field to the displacement-generating means, said magnetic-field-generating means being arranged around the displacement-generating means; and    enclosing device configured to enclose the displacement-generating means and the movable means,    wherein in the enclosing means, magnetic-circuit-forming member including a ferromagnet and a permanent magnet for applying static magnetic bias field to the displacement-generating means are arranged around the enclosed displacement-generating means; and    wherein the movable means is arranged in the enclosing means with a space, thereby allowing magnetic pull-in force caused between the movable means and the enclosing means to apply prestress to the displacement-generating means.    
   
   
       2 . The magnetostrictive actuator according to  claim 1 , wherein sealing member having flexibility seals the space between the movable means and the enclosing means.  
   
   
       3 . The magnetostrictive actuator according to  claim 1 , wherein in the enclosing means, a plurality of permanent magnets are arranged in a displacement direction of the displacement-generating means with an interval therebetween.  
   
   
       4 . A magnetostrictive actuator comprising: 
 displacement-generating device configured to generate a displacement caused by magnetic material having a magnetostrictive;    movable member configured to move in a displacement direction of the displacement-generating device, said movable member being connected with the displacement-generating device and made of a ferromagnet;    magnetic-field-generating device configured to apply magnetic field to the displacement-generating device, said magnetic-field-generating device being arranged around the displacement-generating device; and    enclosing device configured to enclose the displacement-generating device and the movable member,    wherein in the enclosing device, magnetic-circuit-forming member including a ferromagnet and a permanent magnet for applying static magnetic bias field to the displacement-generating device are arranged around the enclosed displacement-generating device; and    wherein the movable member is arranged in the enclosing device with a space, thereby allowing magnetic pull-in force caused between the movable member and the enclosing device to apply prestress to the displacement-generating device.