Patent ID: 6992553

Claim:
A magnetic-field-molding apparatus used for producing a polar-anisotropic ring magnet having magnetization directions in alignment with its normal line at each magnetic pole position and in alignment with its tangential line at each middle position between adjacent magnetic poles, and having a substantially constant angle difference in a magnetization direction between adjacent elements, said elements being obtained by division at an equal angle pitch between said magnetic pole position and said middle position adjacent to said magnetic pole position, said apparatus comprising a molding die having a circular cross-sectional bore; a columnar rod core concentrically disposed in the circular cross-sectional bore of said die to define a ring-shaped cavity; a plurality of recesses opening on the inner surface of said die; and a plurality of coils disposed in each recess, a plurality of coils being aligned along said cavity, and a ratio of a central angle θ 1 defined by a plurality of coils aligned along said cavity in each recess to a central angle θ 2 between coils in the adjacent recesses being 0.8 to 1.2.