Production method for anisotropic bonded magnet and production apparatus for same

Patent metadata

Field	Value
Publication number	US-9666341-B2
Application number	US-201113639785-A
Country	US
Kind code	B2
Filing date	Apr 5, 2011
Priority date	Apr 5, 2010
Publication date	May 30, 2017
Grant date	May 30, 2017

Abstract

A method for production of an anisotropic bonded magnet includes: aligning magnetic pole bodies which include an even number of permanent magnets arranged uniformly around an outer periphery of an annular cavity filled with magnetic raw material, aligning magnetic fields to cause rare-earth anisotropic magnet powder to be semi-radially aligned; compressively molding the semi-radially aligned magnet raw material to obtain an annular compact; discharging the compact from the annular cavity; demagnetizing causing the aligning magnetic pole bodies to relatively move only in circumferential direction with respect to the compact after the molding step thereby to apply demagnetization magnetic fields to the compact; The demagnetization magnetic fields are applied from the aligning magnetic pole bodies with opposite poles to those during the alignment step, and the demagnetization magnetic fields are in directions for cancelling the magnetization of the compact caused by the aligning magnetic fields.

First claim

The invention claimed is:

1. A production apparatus for an annular anisotropic bonded magnet, comprising:
a molding die that comprises an annular cavity;
an inner part that includes intermediate yokes arranged uniformly around the outer periphery of the molding die, the inner part is tubular shaped; and
an outer part that includes main permanent magnets arranged uniformly around the outer periphery of the inner part, the outer part is tubular shaped,
wherein directions of magnetic fields of the main permanent magnets are alternately reversed, the main permanent magnets as a magnetic field source capable of providing an aligning magnetic field to the annular cavity,
wherein the outer part comprises a pair of auxiliary permanent magnets arranged adjacent to both sides, in a circumferential direction, of each of the main permanent magnets, same poles of the auxiliary permanent magnets face each other,
wherein the outer part is rotatable about the inner part in a circumferential direction by a predetermined angle without a movement in a rotation center axis direction.

2. The production apparatus for an annular anisotropic bonded magnet as set forth in claim 1 , wherein the outer part comprises outer subsidiary permanent magnets each having N-pole side and S-pole side and being arranged in the circumferential direction, wherein adjacent two of the outer subsidiary permanent magnets are arranged in a opposite direction and face at one of the N-pole sides and the S-pole sides.

3. The production apparatus for an annular anisotropic bonded magnet as set forth in claim 1 , wherein the inner part comprises inner subsidiary permanent magnets each having N-pole side and S-pole side and being arranged in the circumferential direction, wherein adjacent two of the inner subsidiary permanent magnets are arranged in a opposite direction and face at one of the N-pole sides and the S-pole sides.

4. The production apparatus for an annular anisotropic bonded magnet as set forth in claim 1 , wherein an outer peripheral length of the intermediate yokes is longer than inner peripheral gaps between neighboring ones of the main permanent magnets.

5. The production apparatus for an annular anisotropic bonded magnet as set forth in claim 1 , wherein the molding die is a hollow cylindrical body that surrounds a hollow cylindrical or solid cylindrical core.

6. The production apparatus for an annular anisotropic bonded magnet as set forth in claim 5 , wherein the hollow cylindrical body comprises non-magnetic material and contacts with an inner peripheral surface of the intermediate yokes.

7. The production apparatus for an annular anisotropic bonded magnet as set forth in claim 1 , wherein the molding die comprises a movable die and a fixed die for injection molding.

8. The production apparatus for an annular anisotropic bonded magnet as set forth in claim 1 , wherein the annular cavity comprises a mold, a core, an upper punch and a lower punch.

9. The production apparatus for an annular anisotropic bonded magnet as set forth in claim 1 , wherein the inner part includes an even number of the intermediate yokes.

10. The production apparatus for an annular anisotropic bonded magnet as set forth in claim 1 , wherein the outer part includes an even number of the main permanent magnets.

11. A production method using the production apparatus for an anisotropic bonded magnet according to claim 1 , comprising:
a filling step of filling the annular cavity with a magnet raw material including one or more types of rare-earth anisotropic magnet powder and a binder resin;
an alignment step of applying aligning magnetic fields to the magnet raw material in the annular cavity to cause the rare-earth anisotropic magnet powder to be aligned in the binder resin being in softened state or in molten state, the aligning magnetic fields being applied from an even number of aligning magnetic pole bodies arranged uniformly around outer periphery of the annular cavity such that directions of magnetic fields thereof are alternately reversed, each of the aligning magnetic pole bodies having a permanent magnet as a magnetic field source;
a molding step of subjecting the magnet raw material during the alignment step or after the alignment step to a molding to obtain an annular compact; and
a discharging step of discharging the compact from the annular cavity;
the production method further comprising:
a demagnetizing step of causing the aligning magnetic pole bodies to relatively move with respect to the compact only in circumferential direction after the molding step and before the discharging step to apply demagnetization magnetic fields to the compact, the demagnetization magnetic fields being applied from the aligning magnetic pole bodies with opposite poles to those during the alignment step, the demagnetization magnetic fields being in directions for cancelling magnetization of the compact caused by the aligning magnetic fields.

12. The production method for an anisotropic bonded magnet as set forth in claim 11 , wherein the demagnetizing step is a step of causing the aligning magnetic pole bodies to relatively rotate with respect to the compact from during the alignment step by an odd multiple of a magnetic pole unit angle that is a minimum angle required for inverting magnetic poles of the aligning magnetic pole bodies arranged around the compact.

13. The production method for an anisotropic bonded magnet as set forth in claim 11 , wherein the discharging step is a press-fitting step of press-fitting the compact into a tubular body while discharging the compact from the annular cavity, the tubular body being provided coaxially with the annular cavity and including an inner peripheral surface capable of being contacted with outer peripheral surface of the compact.

14. The production method for an anisotropic bonded magnet as set forth in claim 11 , wherein the molding step is a compression molding step or an injection molding step.

15. The production method for an anisotropic bonded magnet as set forth in claim 11 , further comprising a filling preparation step of disposing, before the filling step, the aligning magnetic pole bodies at non-magnetic field positions which exert no magnetic field to the annular cavity.

16. The production method for an anisotropic bonded magnet as set forth in claim 11 , further comprising a discharging preparation step of disposing, before the discharging step, the aligning magnetic pole bodies at non-magnetic field positions which exert no magnetic field to the annular cavity.

17. The production method for an anisotropic bonded magnet as set forth in claim 11 , wherein the tubular body is a magnetic tubular body comprised of a magnetic material.

18. The production method for an anisotropic bonded magnet as set forth in claim 17 , wherein the magnetic tubular body is a yoke of an electric motor.

Assignees

• Honkura Yoshinobu
• Mitarai Hironari
• Matsuoka Hiroshi
• Kato Masayuki
• Okumura Ikuzou
• Aichi Steel Corp

Inventors

• Honkura Yoshinobu
• Mitarai Hironari
• Matsuoka Hiroshi
• Kato Masayuki
• Okumura Ikuzou

Classifications

• H01F1/0578

  bonded together · CPC title

• B29C43/003

  characterised by the choice of material · CPC title

• H01F1/01

  of inorganic materials (H01F1/44 takes precedence) · CPC title

• H01F1/28 Primary

  dispersed or suspended in a bonding agent · CPC title

• H01F41/0266 Primary

  Moulding; Pressing (H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11) · CPC title