| 摘要 |
PURPOSE:To obtain a mold equipped with an inner cylindrical part, which has a high abrasion-resistant surface, and having high saturation magnetic flux density, by a method wherein a concentric circular high hardness magnetic material is used in the outer periphery of the inner cylindrical part for molding the inner diameter part of a plastic magnet and a magnetic material having high saturation magnetic flux density is used in the central part of said cylindrical part to constitute a magnetically double structure. CONSTITUTION:When a plastic magnet is molded, a heated plastic magnet having viscosity is injected in a mold from a left-hand spool 8 and the magnetic field applied from a magnetic field generating coil 1 passes through a route to be applied to the plastic magnet in the mold to mold the same. When molding is completed, the mold is separated into left and right sections and an ejector plate 9 is pushed from the right and the plastic magnet 11 is pushed out from the mold by 1-4 rods per one plastic magnet. In the mold of the plastic magnet, the inner cylindrical part connected to the inner diameter of the plastic magnet is the mold for molding the plastic mold and has the role of a yoke heel piece forming an one-way magnetic path and, since the circumference thereof is made of a non-magnetic material, the magnetic flux through the mold mount plate entirely passes through the inner cylindrical part to give an oriented magnetic field to the plastic magnet. |
