MAGNET ROLLER AND DEVELOPING APPARATUS USING THE SAME,MAGNET ROLLER MOLDING METHOD,AND INJECTION MOLDING METAL MOLD

摘要

A magnet roller comprising a magnet main body having a circular or generally circular cross section and a shaft portion. A plurality of ridges made of the same material as the main body are arranged symmetrically with respect to the rotation axis over the entire length of the magent main body. A developing apparatus using the magnet roller is also disclosed. Moreover, by injection molding, a resin layer (21) is formed around a shaft main body (13). The synthetic resin layer (21) is so formed as to protrude from the ends of the shaft main body (13) and to have an inner circumferential surface (21a) apart from the inner circumferential surface of the shaft main body (13) between the ends (13a) of the shaft main body (13) and positions near the ends (13a). Furthermore, in a mold for the hot−runner injection molding, the protrusion amount (t) of the tip end (36a) of a gate pin (36) from the gate surface when a gate (34) is closed is set to a range from 0.1 to 0.5 mm.