Mold for and method of producing polar anisotropic ring-shaped bonded magnet molded articles

Patent metadata

Field	Value
Publication number	US-12040128-B2
Application number	US-202318296959-A
Country	US
Kind code	B2
Filing date	Apr 6, 2023
Priority date	Sep 27, 2018
Publication date	Jul 16, 2024
Grant date	Jul 16, 2024

Abstract

Provided are molds for polar anisotropic ring-shaped bonded magnet molded articles which enable the production of bonded magnet molded articles with a high degree of roundness and only slight distortion, without the need for mold modification and preparation of a test mold, and a method of preparing such molds. The present invention relates to a method of preparing a mold for a polar anisotropic ring-shaped bonded magnet molded article, the method including: 1) determining the shrinkage length (Tc) of a desired polar anisotropic ring-shaped bonded magnet molded article using the following equation: Tc=T×(α1/100−α2/100); 2) determining the radius (Dm) of a magnetic pole portion of a mold cavity using the following equation: Dm=D/(1−α2/100); and 3) defining the outer peripheral shape of the mold cavity from the Tc, the Dm, and the number (P) of magnetic poles of the molded article.

First claim

What is claimed is:

1. A mold for a polar anisotropic ring-shaped bonded magnet molded article, comprising a cavity whose outer periphery is defined by the following equation in polar coordinates (r,θ), with an origin at a center of the mold cavity:
r =( Dm+β×Tc/ 2)+(β× Tc/ 2)sin( P θ)

wherein α1 represents a shrinkage ratio of a molded specimen in a direction vertical to a magnetic field; α2 represents a shrinkage ratio of the molded specimen in a direction parallel to the magnetic field; T represents a wall thickness of a desired polar anisotropic ring-shaped bonded magnet molded article; P represents a number of magnetic poles of the molded article; D represents an outer radius of the molded article; Tc represents a shrinkage length of the molded article as defined by T×(α1/100−α2/100); Dm represents a radius of a magnetic pole portion of the mold cavity as defined by D/(1−α2/100); and β represents a correction factor and 0.7≤β≤1.0.

2. The mold according claim 1 , further comprising a partition wall,
wherein the outer periphery of the cavity is the inside of the partition wall.

3. The mold according claim 2 , wherein the partition wall is made of a non-magnetic steel material.

4. The mold according claim 2 , further comprising metal steel components and orientation magnets.

5. The mold according claim 4 , wherein the metal steel components are made of a magnetic steel material.

6. The mold according claim 4 , wherein the orientation magnets are made of a magnetic material.

7. A mold for a polar anisotropic ring-shaped bonded magnet molded article, comprising a cavity whose outer periphery is defined by the following equations in rectangular coordinates (x,y), with an origin at a center of the mold cavity:
x ={( Dm+β×Tc/ 2)+(β× Tc/ 2)sin( P θ)}×cos θ, and

y ={( Dm+β×Tc/ 2)+(β× Tc/ 2)sin( P θ)}×sin θ

wherein α1 represents a shrinkage ratio of a molded specimen in a direction vertical to a magnetic field; α2 represents a shrinkage ratio of the molded specimen in a direction parallel to the magnetic field; T represents a wall thickness of a desired polar anisotropic ring-shaped bonded magnet molded article; P represents a number of magnetic poles of the molded article; D represents an outer radius of the molded article; Tc represents a shrinkage length of the molded article as defined by T×(α1/100−α2/100); Dm represents a radius of a magnetic pole portion of the mold cavity as defined by D/(1−α2/100); β represents a correction factor and 0.7≤β≤1.0; and 0≤θ≤2π.

8. The mold according claim 7 , further comprising a partition wall,
wherein the outer periphery of the cavity is the inside of the partition wall.

9. The mold according claim 8 , wherein the partition wall is made of a non-magnetic steel material.

10. The mold according claim 8 , further comprising metal steel components and orientation magnets.

11. The mold according claim 10 , wherein the metal steel components are made of a magnetic steel material.

12. The mold according claim 10 , wherein the orientation magnets are made of a magnetic material.

13. A method of producing a polar anisotropic ring-shaped bonded magnet molded article, the method comprising:
preparing a mold according to claim 1 ; and

injection molding a bonded magnet composition in the mold.

14. A method of producing a polar anisotropic ring-shaped bonded magnet molded article, the method comprising:
preparing a mold according to claim 7 ; and

injection molding a bonded magnet composition in the mold.

Assignees

• Nichia Corp

Inventors

• Abe Masahiro
• Ihara Kohei

Classifications

• B29C45/26

  Moulds · CPC title

• H01F1/0577

  sintered · CPC title

• B29C33/3835

  Designing moulds, e.g. using CAD-CAM · CPC title

• B29C45/7693

  using rheological models of the material in the mould, e.g. finite elements method · CPC title

• B29C45/0013

  using fillers dispersed in the moulding material, e.g. metal particles · CPC title