| 摘要 |
PURPOSE:To effectively perform injection molding with high accuracy in size while preventing the breakage of a work by injecting a resin into an inner wall in a hollow of said work with low pressure to form a resin layer of a simple shape and then injecting a resin inside said resin layer with high pressure, thereby filling a resin in a desired shape. CONSTITUTION:A work 1 is a thin cylindrical shape, and is held by a mold 2, namely, an upper mold 20 and a lower mold 21. A core of a predetermined shape is set in a room 4 inside the work 1. A resin is injected into the core with low pressure thereby to form a resin layer 6 of a simple shape. Then, another core for molding a rotor shaft 5 and a hollow part, etc., being of complicated shape is set in the hollow inside the resin layer 6, and a resin is injected with high pressure thereby to fill and form a resin part 7 of a desired shape. Accordingly, the work 1, i.e., a cylindrical magnetic material formed of ferrite or the like and the rotor shaft 5 are integrally molded via the resin layer 6 and resin part 7 thereby forming a mold rotor. At this time, although high pressure is applied to the work 1, the resin layer 6 being formed previously works as a reinforcing member for the work 1 and therefore prevents the work 1 from breaking. |
