Method for manufacturing magnetic encoder

Patent metadata

Field	Value
Publication number	US-10203222-B2
Application number	US-201515311379-A
Country	US
Kind code	B2
Filing date	May 18, 2015
Priority date	May 16, 2014
Publication date	Feb 12, 2019
Grant date	Feb 12, 2019

Abstract

Provided is a method for a magnetic encoder having a magnetic body comprised of a magnetic rubber molded article, comprising a mixing step of mixing and then kneading a nitrile rubber (A), a ferrite magnetic powder (B) and a vulcanizing agent (C) to provide a magnetic rubber composition; and a molding step of molding and vulcanizing the magnetic rubber composition in a mold to which a magnetic field is applied to provide the magnetic rubber molded article, wherein a content of the ferrite magnetic powder (B) is 700 to 1500 parts by mass based on 100 parts by mass of the nitrile rubber (A); and a compressed density of the ferrite magnetic powder (B) is 3.5 g/cm 3 or more. According to this method, a magnetic encoder having a magnetic body with high coercivity and residual magnetic flux density can be produced by vulcanizing a magnetic rubber composition having favorable moldability.

First claim

The invention claimed is:

1. A method for manufacturing a magnetic encoder having a magnetic body comprised of a magnetic rubber molded article, comprising
a mixing step of mixing and then kneading a nitrile rubber (A), a ferrite magnetic powder (B) and a vulcanizing agent (C) to provide a magnetic rubber composition; and
a molding step of molding and vulcanizing the magnetic rubber composition in a mold to which a magnetic field is applied to provide the magnetic rubber molded article,
wherein a content of the ferrite magnetic powder (B) is 700 to 1500 parts by mass based on 100 parts by mass of the nitrile rubber (A);
a compressed density of the ferrite magnetic powder (B) is 3.5 g/cm 3 or more; and
a minimum torque ML of the magnetic rubber composition is 3 to 8 kgf·cm as determined in a vulcanization curve at 180° C.

2. The method for manufacturing a magnetic encoder as claimed in claim 1 , wherein the ferrite magnetic powder (B) has a particle size distribution with a plurality of peaks.

3. The method for manufacturing a magnetic encoder as claimed in claim 2 , wherein the ferrite magnetic powder (B) is an anisotropic magnetic powder.

4. The method for manufacturing a magnetic encoder as claimed in claim 1 , wherein the ferrite magnetic powder (B) is an anisotropic magnetic powder.

5. The method for manufacturing a magnetic encoder as claimed in claim 1 , wherein in the mixing step, the nitrile rubber (A), the ferrite magnetic powder (B) and the vulcanizing agent (C) are mixed and then kneaded at 60 to 130° C. for 10 to 60 min to provide the magnetic rubber composition.

6. The method for manufacturing a magnetic encoder as claimed in claim 1 , wherein vulcanization is conducted at 140 to 250° C. for 1 to 30 min in the mold to which a magnetic field is applied.

7. The method for manufacturing a magnetic encoder as claimed in claim 1 , wherein the magnetic encoder comprises a supporting member attachable to a rotator and an annular magnetic rubber molded article mounted on the supporting member, in which the magnetic rubber molded article is circumferentially alternately magnetized in N-pole and S-pole.

8. A magnetic encoder having a magnetic body comprised of a magnetic rubber molded article, wherein
the magnetic rubber molded article is obtained by vulcanizing a magnetic rubber composition comprising a nitrile rubber (A) and a ferrite magnetic powder (B),
a content of the ferrite magnetic powder (B) is 700 to 1500 parts by mass based on 100 parts by mass of the nitrile rubber (A),
a compressed density of the ferrite magnetic powder (B) is 3.5 g/cm 3 or more,
an average particle diameter of the ferrite magnetic powder (B) is 0.5 to 2 μm,
the ferrite magnetic powder (B) has a particle size distribution with a plurality of peaks, and
a minimum torque ML of the magnetic rubber composition is 3 to 8 kgf·cm as determined in a vulcanization curve at 180° C.

9. The magnetic encoder as claimed in claim 8 , wherein the ferrite magnetic powder (B) is an anisotropic magnetic powder.

10. The magnetic encoder as claimed in claim 8 , comprising a supporting member attachable to a rotator and an annular magnetic rubber molded article mounted on the supporting member, in which the magnetic rubber molded article is circumferentially alternately magnetized in N-pole and S-pole.

11. A method for manufacturing the magnetic encoder as claimed in claim 8 , comprising
a mixing step of mixing and then kneading the nitrile rubber (A), the ferrite magnetic powder (B) and a vulcanizing agent (C) to provide the magnetic rubber composition; and
a molding step of molding and vulcanizing the magnetic rubber composition to provide the magnetic rubber molded article.

12. The method for manufacturing the magnetic encoder as claimed in claim 11 , wherein in the mixing step, the nitrile rubber (A), the ferrite magnetic powder (B) and the vulcanizing agent (C) are mixed and then kneaded at 60 to 130° C. for 10 to 60 min to provide the magnetic rubber composition.

13. The method for manufacturing the magnetic encoder as claimed in claim 11 , wherein in the molding step, the vulcanization is conducted at 140 to 250° C. for 1 to 30 min.

14. The method for manufacturing the magnetic encoder as claimed in claim 11 , wherein in the molding step, the magnetic rubber composition is molded and vulcanized in a mold to which a magnetic field is applied.

Assignees

• Uchiyama Mfg

Inventors

• Sakate Kazushi
• Kasamoto Tadashi
• Katayama Tatsuo

Classifications

• H01F1/117

  Flexible bodies · CPC title

• B29K2995/0008

  Magnetic or paramagnetic · CPC title

• G01D5/14 Primary

  influencing the magnitude of a current or voltage · CPC title

• B29C35/02

  Heating or curing, e.g. crosslinking or vulcanizing {during moulding, e.g. in a mould}(cold vulcanisation B29C35/18 {; vulcanising tyres, presses therefor B29D30/0601}) · CPC title

• B29K2019/00

  Use of rubber not provided for in a single one of main groups {B29K2007/00 - B29K2011/00,} as moulding material · CPC title