Magnetic roll and method of producing same

Abstract

The magnet roll according to the present invention comprising a cylindrical resin-bonded magnet, a first shaft formed by injection molding integrally with the cylindrical resin-bonded magnet at one end thereof, and a second shaft press-fitted into a bore of the cylindrical resin-bonded magnet at the opposite end thereof.A magnetic roll comprises a cylindrical resin- bonded magnet made primarily of a ferromagnetic powder and a thermoplastic resin having a modulus of longitudinal elasticity of at least 2×10 4 kg/cm 2 , a first shaft formed by injection molding integrally with the cylindrical resin - bonded magnet at one end thereof, and a second shaft made of a rigid conductive material and press - fitted into a bore of the cylindrical resin - bonded magnet at the opposite end thereof. The bore has a splined cross section, the second shaft provided with a base portion having a splined cross section complimentary to that of the bore, and the base portion is inserted into the bore. The ferromagnetic powder is made of at least one selected from the group consisting of barium ferrite, strontium ferrite, a rare earth - cobalt alloy and a rare earth - iron - boron alloy, and the thermoplastic resin is at least one selected from the group consisting of nylon - 6, nylon - 12 and nylon - 66.

What is claimed is:  
     
       1. A magnet  magnetic roll comprising a cylindrical resin-bonded magnet made primarily of a ferromagnetic powder and a thermoplastic resin having a modulus of longitudinal elasticity of 1×10 5  kg/cm 2 at least  2 × 10   4    kg/cm   2 , a first shaft formed by injection molding integrally with said cylindrical resin-bonded magnet at one end thereof, and a second shaft made of a rigid conductive material and press-fitted into a bore of said cylindrical resin-bonded magnet at the opposite end thereof. 
     
     
       2. The magnet  magnetic roll according to  claim 1 , wherein said bore has a splined cross section, and said second shaft is provided with a base portion having a splined cross section complimentary to that of said bore, said base portion being inserted into said bore. 
     
     
       3. The magnet  magnetic roll according to  claim 1 , wherein said ferromagnetic powder is made of at least one selected from the group consisting of barium ferrite, strontium ferrite, a rare earth-cobalt alloy and a rare earth-iron-boron alloy. 
     
     
       4. The magnet  magnetic roll according to  claim 1 , wherein said thermoplastic resin is at least one selected from the group consisting of nylon-6, nylon-12 and nylon-66. 
     
     
       5. The magnet  magnetic roll according to  claim 1 , wherein said second shaft is made of steel. 
     
     
       6. A method of producing a magnet  magnetic roll composed of a cylindrical resin-bonded magnet made of a ferromagnetic powder and a thermoplastic resin having a modulus of longitudinal elasticity of 1×10 5  kg/cm 2 at least  2 × 10   4    kg/cm   2 , and first and second shafts concentrically projecting from opposite ends of said resin-bonded magnet, comprising the steps of: 
       (a) mixing said ferromagnetic powder with said thermoplastic resin to prepare a mixture;  
       (b) charging said mixture into an injection-molding die to produce an integrally shaped body of said cylindrical resin-bonded magnet having a first shaft concentrically projecting from one end thereof and a bore at the other end thereof;  
       (c) removing said integrally shaped body from said injection-molding die;  
       (d) press-fitting a separately prepared second shaft made of a rigid conductive material into said bore of said cylindrical resin-bonded magnet; and  
       (e) placing said cylindrical resin-bonded magnet in a magnetic field to form a plurality of magnetic poles on an outer surface of said cylindrical resin-bonded magnet.  
     
     
       7. The method according to  claim 6 , wherein said bore has a splined cross section, and said second shaft is provided with a base portion having a splined cross section complimentary to that of said bore, said base portion being inserted into said bore. 
     
     
       8. The method according to  claim 6 , wherein said ferromagnetic powder is made of at least one selected from the group consisting of barium ferrite, strontium ferrite, a rare earth-cobalt alloy and a rare earth-iron-boron alloy. 
     
     
       9. The method according to  claim 6 , wherein said thermoplastic resin is at least one selected from the group consisting of nylon-6, nylon-12 and nylon-66. 
     
     
       10. The method according to claim  1   6 wherein said second shaft is made of steel. 
     
     
       11. The magnetic roll according to  claim 1 , wherein thermoplastic resin more specifically has a modulus of longitudinal elasticity of at least  1 × 10   5    kg/cm   2 . 
     
     
       12. The method according to  claim 6 , wherein thermoplastic resin more specifically has a modulus of longitudinal elasticity of at least  1 × 10   5    kg/cm   2 . 
     
     
       13. The magnetic roll according to  claim 1 , wherein said thermoplastic resin is a polyamide. 
     
     
       14. The magnetic roll according to  claim 13 , wherein said polyamide is at least one selected from the group of nylon-   6 , nylon -   12  and nylon -   66 .   
     
     
       15. The magnetic roll according to  claim 1 , wherein said thermoplastic resin has a modulus of longitudinal elasticity ranging from  2 × 10   4    kg/cm   2    to  1 × 10     5    kg/cm   2 . 
     
     
       16. The method according to  claim 6 , wherein said thermoplastic resin is a polyamide. 
     
     
       17. The method according to  claim 16 , wherein said polyamide is at least one selected from the group of nylon-   6 , nylon -   12  and nylon -   66 .   
     
     
       18. The method according to  claim 6 , wherein said thermoplastic resin has a modulus of longitudinal elasticity ranging from  2 × 10   4    kg/cm   2    to  1 × 10     5    kg/cm   2 . 
     
     
       19. A magnetic roll comprising a cylindrical resin- bonded magnet made primarily of a ferromagnetic powder and a thermoplastic resin having a modulus of longitudinal elasticity of  1 × 10     5    kg/cm   2    or higher, a first shaft formed by injection molding integrally with said cylindrical resin - bonded magnet at one end thereof, and a second shaft made of a rigid conductive material and press - fitted into a bore of said cylindrical resin - bonded magnet at the opposite end thereof.   
     
     
       20. A method of producing a magnet roll composed of a cylindrical resin- bonded magnet made of a ferromagnetic powder and a thermoplastic resin having a modulus of longitudinal elasticity of  1 × 10     5    kg/cm   2    or higher, and first and second shafts concentrically projecting from opposite ends of said resin - bonded magnet, comprising the steps of:    
       ( a )  mixing said ferromagnetic powder with said thermoplastic resin to prepare a mixture;    
       ( b )  charging said mixture into an injection - molding die to produce an integrally shaped body of said cylindrical resin - bonded magnet having a first shaft concentrically projecting from one end thereof and a bore at the other end thereof;    
       ( c )  removing said integrally shaped body from said injection - molding die;    
       ( d )  press - fitting a separately prepared second shaft made of a rigid conductive material into said bore of said cylindrical resin - bonded magnet; and    
       ( e )  placing said cylindrical resin - bonded magnet in a magnetic field to form a plurality of magnetic poles on an outer surface of said cylindrical resin - bonded magnet.