Patent ID: 6021296
Filing Date: 2000-02-01
Classification: G03G,H01F

Abstract:
In a magnet roller having a plurality of magnet pieces in each of which magnetic powders are dispersed in a resin or rubber binder and the magnet pieces are fixedly disposed around the outer periphery of a shaft, to form a magnet layer around the outer periphery of the shaft,the improvement whereinsaid plurality of magnet pieces comprise at least first magnet pieces and second magnet pieces different from each other in orientation characteristic of magnetic powders;each of said first magnet pieces is a magnet piece in which anisotropic magnetic powders are oriented in such a manner to converge from both side surfaces and a back surface to a specific position on a front surface side; andsaid second magnet pieces are magnet pieces selected from a group consisting of a magnet piece in which anisotropic magnetic powders are oriented at random, a magnet piece in which anisotropic magnetic powders are uniformly or radially oriented in a specific direction from the back surface side to the front surface side, and a magnet piece using isotropic magnetic powders with no orientation characteristic,wherein the first magnet piece in which anisotropic magnetic powders are oriented in such a manner as to converge from both side surfaces and a back surface side to a specific position on a front surface side is molded using a mold in which magnetic material members are disposed on upper and lower sides of a non-magnetic material member; both side surfaces and the back surface side of the cavity are formed of the lower magnetic material member; and a projecting portion is provided on the upper magnetic material member in such a manner that the leading end of the projecting portion is located in the vicinity of a desired position of the cavity on the front surface side.