Patent ID: 8723375

Claim:
A linear actuator comprising: a coil portion including a plurality of coils, said coils adapted to receive AC currents respectively having different phases from one another; and a shaft portion configured to pass through a center of said plurality of coils, wherein said shaft portion includes: a plurality of permanent magnets located along a central axis such that adjacent pairs of said plurality of permanent magnets have a same pole facing each other along the central axis; and a plurality of intermediate members, each of said intermediate members being located between an adjacent pair of said plurality of permanent magnets, wherein each of said plurality of intermediate members has a saturation magnetic flux density that is higher than a saturation magnetic flux density of each of said plurality of permanent magnets, wherein each of said plurality of intermediate members has a thickness in the central axis direction that increases further from the central axis, and wherein each of said plurality of permanent magnets has a thickness in the central axis direction that decreases further from the central axis.