Method for producing sintered body that forms rare-earth permanent magnet and has non-parallel easy magnetization axis orientation

Patent metadata

Field	Value
Publication number	US-10867729-B2
Application number	US-201615559652-A
Country	US
Kind code	B2
Filing date	Mar 24, 2016
Priority date	Mar 24, 2015
Publication date	Dec 15, 2020
Grant date	Dec 15, 2020

Abstract

Provided is a method for producing a sintered body that forms a rare-earth permanent magnet, has a single sintered structure and an arbitrary shape, and has easy magnetization axis orientations of different directions applied to the magnet material particles in a plurality of arbitrary regions. This method forms a three-dimensional first molded article from a composite material formed by mixing a resin material and magnet material particles containing a rare-earth substance. The first molded article is then subjected to a deforming force and a second molded article is formed in which the orientation direction of the easy magnetization axis of the magnet material particles in at least the one section of the horizontal cross-section is changed to a direction which differs from the orientation direction of the first molded article. The second molded article is heated to a sintering temperature and kept at the temperature for a period of time.

First claim

The invention claimed is:

1. A method for producing a rare-earth magnet-forming sintered body wherein a number of magnet material particles including rare-earth substances and each having an easy magnetization axis are integrally sintered; comprising,
a first shaped body forming step for forming a first shaped body of a three dimensional shape which has a lengthwise dimension in a lengthwise direction, a thickness dimension defined between a first surface and a second surface in a thickness direction in a cross-section perpendicular to the lengthwise direction, and a widthwise dimension taken in a widthwise direction which is perpendicular to the thickness direction, the first shaped body being formed from a compound material which is formed by mixing the magnet material particles with a resin material;
an orientation step for orienting the easy magnetization axes of the magnet material particles by applying to the first shaped body an external parallel magnetic field, while heating the first shaped body to a temperature higher than a softening temperature of the resin material, to have the easy magnetization axes of the magnet material particles oriented in a direction parallel with the direction of the magnetic field;
a second shaped body forming step for forming a second shaped body by applying a bending force to the first shaped body to produce a bending deformation in the first shaped body such that at least a portion of the first shaped body is changed in shape in the cross-section to thereby change the orientations of the easy magnetization axes of the magnetic material in the at least a portion in the cross-section to a direction different from the direction in the first shaped body; and
a sintering step wherein the second shaped body is heated to a sintering temperature and held in the sintering temperature for a predefined time so that the resin material in the second shaped body is dissipated and the magnet material particles are sintered together to produce the sintered body, the sintering step being carried out with a pressing force applied to the second shaped body in the lengthwise direction.

2. The method as claimed by claim 1 , wherein said magnetic field is directed along the cross-section of the first shaped body from the first surface to the second surface.

3. The method as claimed by claim 1 , wherein the resin material contained in the compound is a thermoplastic resin material.

4. The method as claimed by claim 1 , wherein the sintering temperature is 800° C. to 1200° C.

5. The method as claimed by claim 4 , wherein the pressing force applied to the second shaped body is controlled in the range between 0.01 MPa and 100 MPa, and the pressing force is applied continuously or intermittently.

6. The method as claimed by claim 2 , wherein the sintering step is carried out in an atmosphere of 15 MPa or less, with a temperature raised up to the predefined sintering temperature at a temperature raising rate of 3° C./min to 100° C./min, and the pressing force applied to the second shaped body in the sintering step is maintained until the dimension change of the second shaped body in the direction of pressing force becomes substantially 0.

7. The method as claimed by claim 2 , wherein the sintering step is carried out under an atmosphere of reduced pressure of 6 Pa or less, by raising the temperature up to a predefined sintering temperature at a temperature raising rate of 3° C./min to 30° C./min, and the pressing force applied to the second shaped body in the sintering step is maintained until the dimension change of the second shaped body in the direction of pressing force becomes substantially 0.

8. The method as claimed by claim 1 , wherein after the second shaped body forming step and before the sintering step, a calcining step is carried out for removing carbon, by heating the second shaped body in a hydrogen atmosphere to have the carbon content in the thermoplastic resin contained in the second shaped body reacted with the hydrogen.

9. The method as claimed by claim 8 , wherein the calcining step is conducted at a temperature raising rate of 10° C./min or less.

10. The method as claimed by claim 8 , wherein a de-oiling step is carried out before the calcining step, and the calcining step is conducted at a temperature raising rate of 10° C./min or less.

11. The method as claimed by claim 8 , wherein the calcining step is conducted under a temperature range of 250° C. to 600° C.

12. The method as claimed by claim 8 , wherein the calcining step is conducted under a temperature range of 300° C. to 500° C.

13. The method as claimed by claim 8 , wherein the calcining step is conducted under a pressure of 0.1 MPa to 70 MPa.

14. The method as claimed by claim 8 , wherein the magnet material particles have an average size of 6 μm or less.

15. The method as claimed by claim 14 , wherein the magnet material particles are produced in an inert gas atmosphere having oxygen concentration of 0.5% or less.

16. The method as claimed by claim 3 , wherein the thermoplastic resin is a polymer which does not contain oxygen in its structure.

17. The method as claimed by claim 16 , wherein the thermoplastic resin is a polymer which comprises one or more polymers or copolymers formed from a monomer represented by the following general formula (1):

(where each of R1 and R2 denotes one of a hydrogen atom, a lower alkyl group, a phenyl group and a vinyl group.)

18. The method as claimed by claim 16 , wherein the thermoplastic resin is selected from a group including: polyisobutylene (PIB); polyisoprene (isoprene rubber (IR)); polypropylene; a poly(α-methylstyrene) polymerized with α-methylstyrene; polyethylene; polybutadiene (butadiene rubber (BR)); polystyrene; a styrene-isoprene-styrene block copolymer (SIS); butyl rubber (IIR); a styrene-butadiene-styrene block copolymer (SBS); a styrene-ethylene-butadiene-styrene copolymer (SEBS); a styrene-ethylene-propylene-styrene copolymer (SEPS); an ethylene-propylene copolymer (EPM); EPDM obtained by copolymerizing diene monomers together with ethylene and propylene; a 2-methyl-1-pentene polymerized resin as a polymer of 2-methyl-1-pentene; and a 2-methyl-1-butene polymerized resin as a polymer of 2-methyl-1-butene.

19. The method as claimed by claim 16 , wherein the thermoplastic resin is of the one which has a glass transition temperature or fluidity starting temperature of 250° C. or lower.

20. The method as claimed by claim 3 , wherein the thermoplastic resin does not contain oxygen atom, nitrogen atom and other hetero-atoms.

21. The method as claimed by claim 1 , wherein the first shaped body formed in the first shaped body forming step has a straight central region, end regions contiguous with and provided at the opposite end portions of the central region, wherein each of the end regions is of an arcuate configuration with the second surface being of a convex shape and the first surface being of a concave shape and, in the second shaped body forming step, each of the end regions contiguous with the corresponding end portion of the central region is deformed to be straight with the corresponding end portion of the central region, whereby the orientations of the easy magnetization axes in the second shaped body become such that, in the central region, the easy magnetization axes are oriented in the thickness direction from the first surface to the second surfac

Assignees

• Nitto Denko Corp

Inventors

• Fujikawa Kenichi
• Kume Katsuya
• Ouchi Kazuo
• Hoshino Toshinobu
• Morimoto Masakazu
• Ono Hirofumi
• Nakabayashi Katsuyuki
• Yamaguchi Miho
• Matsuo Hiroshi
• Okuno Toshiaki
• Fujihara Makoto
• Imoto Eiichi
• Ebe Hirofumi
• Omure Tomohiro
• Ozeki Izumi
• Yamamoto Takashi
• Kato Yuki
• Matsuda Tomoya
• Saito Shoichiro

Classifications

• H02K1/27

  Rotor cores with permanent magnets · CPC title

• H01F41/0293

  diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets · CPC title

• H01F41/0273 Primary

  Imparting anisotropy (methods and devices for magnetising permanent magnets H01F13/003) · CPC title

• H01F7/02

  Permanent magnets {[PM]} · CPC title

• H01F1/442

  the magnetic component being a metal or alloy, e.g. Fe (H01F1/447 takes precedence) · CPC title