Magnetic encoder and roller bearing unit having magnetic encoder

Abstract

The magnetic encoder is constituted by integrally bonding a magnet portion obtainable by forming a magnetic material containing a magnetic powder and a binder for the magnetic powder in a circular ring shape to a slinger. The binder contains at least a thermoplastic resin and an impact resistance-improving agent.

The invention claimed is: 
     
       1. A magnetic encoder comprising:
 a magnet portion formed by circularly arranging a magnetic material comprising a magnetic powder and a binder for the magnetic powder, wherein 
 the binder comprises at least a thermoplastic resin and an impact resistance-improving agent, and 
 a bending deflection amount of the magnetic portion falls within a range of 2 to 15 mm in an experimental condition that a thickness of magnetic material is 3.0 mm, span distance is 50 mm and temperature is 23° C. under ASTM D790, wherein 
 the thermoplastic resin is a polyamide 12 resin, and 
 the impact resistance-improving agent is a modified polyamide 12 resin which is a block copolymer comprising: 
 a hard segment of the polyamide 12; and 
 a soft segment of at least one of a polyester component and a polyether component. 
 
     
     
       2. The magnetic encoder according to  claim 1 , wherein
 the thermoplastic resin is a polyamide resin, and   the impact resistance-improving agent is at least one of vulcanized rubber particles and a modified polyamide resin.   
     
     
       3. The magnetic encoder according to  claim 1 , wherein the thermoplastic resin is a polyester-based resin, and
 the impact resistance-improving agent is at least one of vulcanized rubber particles and a modified polyester resin.   
     
     
       4. The magnetic encoder according to  claim 1 , wherein the thermoplastic resin is a polyphenylene sulfide resin, and
 the impact resistance-improving agent is vulcanized rubber particles.   
     
     
       5. The magnetic encoder according to  claim 2 , wherein the thermoplastic resin is selected from the group consisting of polyamide 12, polyamide 11, polyamide 612, polyamide 610, modified polyamide 6T, polyamide 9T and polymide MXD6. 
     
     
       6. The magnetic encoder according to  claim 1 , wherein the thermoplastic resin is a polyamide resin, and
 the binder further comprises an aromatic amine-based antioxidant.   
     
     
       7. A roller bearing unit comprising:
 a fixed ring; 
 a rotating ring; 
 a plurality of rolling elements rotatably arranged in a circumferential direction between ring and rotating ring; and 
 the magnetic encoder according to  claim 1 , wherein 
 the magnet portion is fixed to a slinger composed of a magnetic material with an adhering agent, and 
 the slinger is fixed to the rotating ring. 
 
     
     
       8. The magnetic encoder according to  claim 1 , wherein,
 the thermoplastic resin is a polyamide 12 resin, and   the impact resistance-improving agent is a modified polyamide 12 resin which is a block copolymer comprising:
 a hard segment of the polyamide 12; and 
 a soft segment of at least one of a polyester component and a polyether component. 
   
     
     
       9. The magnetic encoder according to  claim 1 , wherein
 the thermoplastic resin is a polybutylene terephthalate, and   the impact resistance-improving agent is a modified polybutylene terephthalate which is a block copolymer comprising:
 a hard segment of the polybutylene terephthalate; and 
 a soft segment of at least one of the polyester component and the polyether component. 
   
     
     
       10. The magnetic encoder according to  claim 1 , wherein
 the thermoplastic resin is a polybutylene naphthalate, and   the impact resistance-improving agent is a modified polybutylene naphthalate which is a block copolymer comprising:   a hard segment of the polybutylene naphthalate; and   a soft segment of at least one of the polyester component and the polyether component.   
     
     
       11. The binder of the magnetic encoder according to  claim 2 , further comprising;
 antioxidant selected from diphenylamine-based compounds and p-phenylenediamine-based compounds.   
     
     
       12. The binder of the magnetic encoder according to  claim 5 , further comprising;
 antioxidant selected from diphenylamine-based compounds and p-phenylenediamine-based compounds.   
     
     
       13. The binder of the magnetic encoder according to claim  8   1 , further comprising;
 antioxidant selected from diphenylamine-based compounds and p-phenylenediamine-based compounds. 
 
     
     
       14. The binder of the magnetic encoder according to  claim 2 , wherein a diameter of the vulcanized rubber particles falls within a range of 30 to 300 nm, and
 the vulcanized rubber particles are selected from the group consisting of acrylic rubber, carboxyl-modified acrylonitrile-butadiene rubber and carboxyl-modified hydrogenated nitrile rubber.   
     
     
       15. The binder of the magnetic encoder according to  claim 8 , wherein a diameter of the vulcanized rubber particles falls within the range of 30 to 300 nm, and
 the vulcanized rubber particles are selected from the group consisting of acrylic rubber, carboxyl-modified acrylonitrile-butadiene rubber and carboxyl-modified hydrogenated nitrite rubber.   
     
     
       16. The binder of the magnetic encoder according to  claim 4 , wherein a diameter of the vulcanized rubber particles falls within the range of 30 to 300 nm, and
 the vulcanized rubber particles are selected from the group consisting of carboxyl-modified acrylonitrile-butadiene rubber and carboxyl-modified hydrogenated nitrite rubber.   
     
     
       17. The magnetic encoder according to  claim 1 , wherein
 the magnet portion and a slinger are bonded by at least one of a phenolic resin based adhering agent and an epoxy resin based adhering agent.   
     
     
       18. The magnetic encoder according to claim  8   1 , wherein
 the magnet portion and a slinger are bonded by at least one of a phenolic resin based adhering agent and an epoxy resin based adhering agent. 
 
     
     
       19. The magnetic encoder according to  claim 17 , wherein
 the magnet portion and the slinger are bonded by insert molding.   
     
     
       20. The magnetic encoder according to  claim 18 , wherein
 the magnet portion and the slinger are bonded by insert molding.