Apparatus and method for producing a solid magnet roller using a movable mold

Abstract

An apparatus and a method for manufacturing a magnet roller makes it possible to remarkably reduce defects on the surface or the inside of a magnet roller and also to control “warp” of the magnet roller sufficiently so that it does not adversely affect the functions of the magnet roller. A metal mold for magnetic field injection molding is composed of two fixed mold counterparts and a movable mold counterpart. The movable mold counterpart is moved to increase the volume of the cavity of the metal mold as a resin-bonded magnet material is injected into the mold.

What is claimed is:  
     
         1 . An apparatus for producing a magnet roller, comprising: 
 a fixed mold having a cavity for forming a solid magnet body;    a movable mold disposed in the cavity, which is capable of increasing or decreasing a volume of the cavity in accordance with an injected amount of the melted resin-bonded magnet material composed primarily of magnetic powder and a binder; and    a magnetic field generator disposed around the fixed mold.    
     
     
         2 . An apparatus for producing a magnet roller according to  claim 1 , wherein the movable mold moves in a lengthwise direction of the cavity against a biasing force provided by biasing means extending in the cavity.  
     
     
         3 . An apparatus for producing a magnet roller according to  claim 1 , wherein the movable mold moves in a lengthwise direction of the cavity with a back pressure of 0.5 to 50 kg/cm 2  against a biasing force provided by biasing means extending in the cavity.  
     
     
         4 . An apparatus for producing a magnet roller according to  claim 1 , wherein the movable mold moves in a lengthwise direction of the cavity against a biasing force provided by biasing means extending in the cavity, the biasing means provided with force by a coil spring or an air cylinder.  
     
     
         5 . A method for producing a magnet roller in which a resin-bonded magnet material, which is composed primarily of magnetic powder and a binder, is injected into a cavity of a metal mold while applying a magnetic field thereto, 
 wherein a fixed mold having a cavity for forming a solid magnet body and a movable mold disposed in the cavity and capable of increasing or decreasing a volume of the cavity are used as the metal mold; and    while injecting a melted resin-bonded magnet material into the cavity, the movable mold is moved such that the volume of the cavity is increased in accordance with the injected amount of the melted resin-bonded magnet material, and a magnet body molded within the cavity is magnetized by a magnetic field generator disposed around the fixed mold.    
     
     
         6 . A method for producing a magnet roller according to  claim 5 , 
 wherein the movable mold moves in a lengthwise direction of the cavity against a biasing force provided by biasing means extending in the cavity.    
     
     
         7 . A method for producing a magnet roller according to  claim 5 , wherein the movable mold moves in a lengthwise direction of the cavity with a back pressure of 0.5 to 50 kg/cm 2  against a biasing force provided by biasing means extending in the cavity.  
     
     
         8 . A method for producing a magnet roller according to  claim 5 , wherein a surface roughness of the magnet roller is 20 mm or less based on Japanese Industry Standard (JIS) 10-point average roughness scale Rz, and when magnetic force is measured at intervals of 1 mm in a direction parallel to axial direction, a difference in magnetic force between adjacent points is 10 gauss or less.