Patent ID: 6856049

Claim:
A voice coil linear actuator comprising: an axially-shaped center yoke formed of a ferromagnetic material; an armature coil concentrically disposed so as to move along the axial direction of said center yoke; and ring-shaped permanent magnets which have N and S magnetic poles arranged in the radial direction thereof, and are disposed concentrically as to said armature coil; wherein said armature coil has armature coil units distributed in at least three positions in the axial direction, with adjacent pairs of said armature coil units being arranged so that electric current flows through each in opposite directions, respectively and; wherein said ring-shaped permanent magnets are distributed in at least three positions in the axial direction at positions facing said armature coil units in the radial direction, with adjacent pairs of said permanent magnets being arranged so that N and S magnetic poles of adjacent permanent magnets facing in opposite directions in the radial direction.