Patent ID: 7884509

Claim:
A linear motor comprising: a movable magnet yoke taking a hollow shape; a plurality of magnet constructs attached to a circumferential surface of the magnet yoke at an equiangular distance; coil yokes, wherein the magnet yoke is movable relative to the coil yokes; and a plurality of coils attached respectively to the coil yokes and arranged to respectively face the plurality of magnet constructs; and wherein: each of the magnet constructs comprises at least one pair of magnet members juxtaposed in the moving direction of the magnet yoke and arranged with their polarities of magnet pole being opposite to each other, the poles of the pair of magnet members of each magnet construct being arranged such that lines of magnetic force extend through the magnet yoke between the pair of magnet members of each magnet construct, and an auxiliary magnet interposed between the magnet members of each of said pairs of magnet members and having poles arranged to prevent lines of magnetic force passing between the pair of magnet members from diffusing; respective pairs of the magnet members attached to the circumferential surface form first and second rows spaced from each other in the moving direction of the magnet yoke; each magnet member in the first row is arranged to be opposite in polarity of magnet pole to each of the magnet members next thereto in the circumferential direction, and the poles of each magnet member in the first row are arranged such that lines of magnetic force extend through the magnet yoke between each of the circumferentially adjacent magnet members in the first row and the magnet members next thereto in the circumferential direction; and each magnet member in the second row is arranged to be also opposite in polarity of magnet pole to each of the magnet members next thereto in the circumferential direction, and the poles of each magnet member in the second row are arranged such that lines of magnetic force extend through the magnet yoke between each of the circumferentially adjacent magnet members in the second row and the magnet members next thereto in the circumferential direction.