| 摘要 |
PURPOSE:To improve the accuracy in centering of the inside and outside diameters, by molding an outer periphery retaining frame first when the outer periphery retaining frame and an inner periphery retaining frame, both formed of a resin material, are insert-molded separately in a disk magnet having an axial hole in the central part. CONSTITUTION:Both obverse and reverse surfaces of a disk magnet 1 having an axial hole 2 formed in the central part are ground, and an outer periphery retaining frame 3 is molded on an outer peripheral edge 1a ground and an inner periphery retaining frame 4 on the inner peripheral edge 1b of the axial hole 2, separately from each other, by using an insert of resin material and by means of a mold. On the occasion, the outer periphery retaining frame 3 is molded first so that the outer peripheral part of the magnet 1 be compressed to oppose an internal pressure, i.e. an expansion force, generated in molding of the inner periphery retaining frame 4, and thereby to prevent cracks or damages. According to this method, only plane grinding of both obverse and reverse surfaces is required even when sintered ferrite is used for the disk, and no damage is caused by an impact force when the disk magnet is fitted to an electromagnetic apparatus. |
