JPS5445717A - Preparing magnetic rotor - Google Patents

Abstract

PURPOSE:To prevent a permanent magnet from generating a crack and slit in its peripheral part, by a preparation in such manner that a resing pressure actin in outer circumferential surfaces of the permanent magnet suppress a resin pressure acting in inner circumferential surface. CONSTITUTION:In a cavity part 15 of metal mold, are provided a plurality of partition parts 18 that touches throughout from a top dege 14c to a bottom edge 14d in prepheral surfaces of a permanent magnet 14. Simultaneously with a shoulder part, that touches a part near the top edge of peripheral surfaces of the magnet, provided between each of the partition parts 18, an individual peripheral air space part 16 is constructed. On the other hand, with an inner circumferential air space part 19 constructed in inner circumferential surface of the magnet 14, a synthetic resin is injected at the same time into each of the inner and outer circumferential air space parts, and a filling process is so made that a resin pressure acting in peripheral surfaces of the magnet may be slightly bigger than a resin pressure acting in inner circumferential surfaces, with a hardening processed. Consequently, a resin pressure acting in peripheral surfaces of the magnet can suppress a resin pressue acting in inner circumferential surfaces, thus enabling a prevention from a generation of crack and slit in the peripheral part of the permanent magnet.