CYLINDRICAL PERMANENT MAGNET

PURPOSE:To facilitate radial arrangement even of rare earth magnet, by setting the difference between outer and inner diameters smaller than 4mm. CONSTITUTION:Lines of magnetic force produced from upper and lower coils 1, 2 pass through upper and lower cores 4, 8 and go to dies 5, 6, 9, 10. Upper dies 5, 6 and lower dies 9, 10 are secured mechanically or integrally with the cores 4, 8. The dies 5, 6, 9, 10 have circular horizontal cross-section. Punches 15-18 have annular horizontal cross-section. A coil 3 is coupled with a core 11 positioned between the upper and lower cores 4, 8, and dies 12-14 are secured mechanically or integrally with the core 11. When current is fed such that the upper coil 1 is provided with N-pole at the underside, while the lower coil 2 is provided with N-pole at the upper side and an intermediate coil 3 is provided with S-pole at the upper side, magnetic powder contained in cavities 19, 20 is oriented radially. Under this orientation, the punches 15-18 are moved and formed with pressure. Then coil current is inverted in order to perform demagnetization, and thus produced radial anisotropic magnet is cured through sintering.