R-TM-B RADIAL ANISOTROPIC RING MAGNET, PROCESS FOR PRODUCTION OF THE SAME, METAL MOLD FOR PRODUCING THE SAME, AND ROTOR FOR BRUSHLESS MOTOR

摘要

A process for the production of a radial anisotropic ring magnet having an axial groove on the inside face in at least one place, characterized by using a metal mold composed of a cylindrical magnetic core, a magnetic sleeve which has an axial protrusion corresponding to the groove on the outer face and which is set on the outer periphery of the core, and a cylindrical outer die for forming a cavity for forming a ring magnet between the outer die and the magnetic sleeve and compression-molding a magnetic powder put in the cavity while applying a radial magnetic field to the powder; and a radial anisotropic ring magnet which is made substantially of R-TM-B (wherein R is at least one member selected from among rare earth elements including Y; TM is at least one transition metal; and B is boron) and has an axial groove on the inside face in at least one place and which is magnetized in such a way that the center line between magnetic poles does not overlap with the groove.