Permanent magnet suitable for magnetic angle encoder

Patent metadata

Field	Value
Publication number	US-9715959-B2
Application number	US-201414758447-A
Country	US
Kind code	B2
Filing date	Jan 3, 2014
Priority date	Jan 5, 2013
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

The present invention relates to a permanent magnet suitable for a magnetic angle encoder. The permanent magnet has an annular cylindrical structure and comprises a first permanent magnet unit and a second permanent magnet unit. The first permanent magnet unit and the second permanent magnet unit are geometrically symmetrical with respect to a diametral cross section. The magnetization intensity of the first permanent magnet unit and the magnetization intensity of the second permanent magnet unit are parallel to the axial direction of the annular cylinder and are in opposite directions, or the magnetization intensity of the first permanent magnet unit and the magnetization intensity of the second permanent magnet unit are perpendicular to the diametral cross section and are parallel to one another and in the same direction.

First claim

The invention claimed is:

1. A magnetic angle encoder, comprising:
a permanent magnet having an end face, the permanent magnet configured to provide a magnetic field in a detection plane adjacent and parallel to the end face, the permanent magnet including:
a cylindrical ring permanent magnet having an inner radius R i and an outer radius R o , the cylindrical ring permanent magnet including a first permanent magnet unit having a first direction of magnetization and a second permanent magnet unit having a second direction of magnetization,
wherein the cylindrical ring permanent magnet has a diametrical cross-section and the first and second permanent magnet units are symmetrically placed on opposite sides of the diametrical cross-section; and

a magnetoresistance sensor in a detection region of the detection plane at a radial distance r from a center of the cylindrical ring permanent magnet,
wherein:
the first direction of magnetization and the second direction of magnetization are aligned along the axial direction of the cylindrical ring in antiparallel directions, and the detection region is defined by a ratio of the radial distance r to the outer radius Ro, where r/R o <0.2 or where 0.5<r/R o <0.95, or
the first and second directions of magnetization are aligned perpendicular to the diametrical cross-section, and aligned parallel to the each other, and the detection region is defined by a ratio of the radial distance r to the outer radius Ro, where r/R o r/Ro<0.5.

2. The magnetic angle encoder of claim 1 , wherein the magnetization of the first permanent magnet unit and the magnetization of the second permanent magnet unit are the same size.

3. The magnetic angle encoder of claim 1 , wherein the outer diameter of the cylindrical ring permanent magnet is between 3 and 200 mm.

4. The magnetic angle encoder of claim 1 , wherein the inner diameter of the cylindrical ring permanent magnet is between 1 and e100 mm.

5. The magnetic angle encoder of claim 1 , wherein the axial length of the cylindrical ring permanent magnet is between 1 and 50 mm.

6. The magnetic angle encoder of claim 1 , wherein the cylindrical permanent magnet has a detection plane located adjacent and parallel to a cylindrical end face of the permanent magnet.

7. The magnetic angle encoder of claim 6 , wherein the distance between the detection plane and the cylindrical ring end face is 1 to 5 mm.

8. The magnetic angle encoder of claim 1 , wherein the magnetic field from the permanent magnet has a component in the detection plane.

9. The magnetic angle encoder of claim 1 , further comprising a specific detection area located within the detection plane and within a specified distance along the cylindrical ring radius from the axis, wherein the rotational angle (φ) of the magnetic field components within the specific detection area varies linearly with the rotational angle (α) of the permanent magnet.

10. The magnetic angle encoder of claim 1 , wherein the permanent magnet is composed of Alnico.

11. The magnetic angle encoder of claim 1 , wherein the permanent magnet is composed of a ceramic ferrite material with composition MO.6Fe 2 O 3 , and M is Ba, Sr, or combinations of both.

12. The magnetic angle encoder of claim 1 , wherein the permanent magnet is composed of an alloy with composition RECo 5 , where RE=Sm and/or Pr; RE 2 TM 17 , where RE=Sm, TM=Fe, Cu, Co, Zr and/or Hf; or RE 2 TM 14 B, where RE=Nd, Pr and/or Dy, TM=Fe and/or Co.

13. The magnetic angle encoder of claim 1 , wherein the permanent magnet is composed of an alloy NbFeB or FeCrCo.

14. The magnetic angle encoder of claim 1 , wherein the permanent magnets are comprised of permanent magnet powder embedded in plastic, rubber, or a resin composite.

15. The magnetic angle encoder of claim 14 , wherein the permanent magnet powder is comprised of any of various permanent magnetic materials including MO.6Fe2O3, where M is Ba, Sr or combinations of both; RECo 5 , RE=Sm and/or Pr; RE 2 TM 17 , RE=Sm, TM=Fe, Cu, Co, Zr and/or Hf; or RE 2 TM 14 B, where RE=Nd, Pr, and/or Dy, TM=Fe and/or Co; or an alloy of NbFeB or FeCrCo; and the permanent magnet powder is embedded in plastic, rubber, or resin composite.

16. A magnetic angle encoder, comprising:
a permanent magnet having an end face, the permanent magnet configured to provide a magnetic field in a detection plane adjacent and parallel to the end face, the permanent magnet including:
a cylindrical ring permanent magnet including two permanent magnet units, the two permanent magnet units includes a first permanent magnet unit and a second permanent magnet unit, the cylindrical ring permanent magnet having an inner radius R I and an outer radius R O , the cylindrical ring permanent magnet including a first permanent magnet unit having a first direction of magnetization and a second permanent magnet unit having a second direction of magnetization,
wherein the cylindrical ring permanent magnet has a diametrical cross-section and the first and second permanent magnet units are symmetrically placed on opposite sides of the diametrical cross-section, and
wherein the first permanent magnet unit and second permanent magnet unit have directions of magnetization aligned in parallel with each other and aligned perpendicular to the diametrical cross-section; and

a magnetoresistance sensor in a detection region of the detection plane at a radial distance r from a center of the cylindrical ring permanent magnet, wherein the detection region and the detection region is defined by a ratio of the radial distance r to the outer radius Ro, where r/Ro<0.5.

17. The magnetic angle encoder of claim 16 , wherein the cylindrical ring permanent magnet includes two permanent magnet units, the two permanent magnet units including the first and the second permanent magnet units.

18. A permanent magnet suitable for a magnetic angle encoder, comprising:
a cylindrical ring permanent magnet including two permanent magnet units, the two permanent magnet units include a first permanent magnet unit and a second permanent magnet unit,
wherein the cylindrical ring permanent magnet has a diametrical cross-section and the first and second permanent magnet units are symmetrically placed on opposite sides of the diametrical cross-section, and
wherein the first permanent magnet unit and the second permanent magnet unit have a magnetization that is aligned along the axial direction of the cylindrical ring, and in antiparallel directions.

19. The permanent magnet of claim 18 , wherein the cylindrical ring permanent magnet has an end face and further has an inner radius R i and an outer radius R o , the cylindrical ring permanent magnet, the permanent magnet configured to provide a magnetic field in a detection plane adjacent and parallel to the end face, and provide a detection region in a detection plane for a magnetoresistance sensor, the detection region is defined by a ratio of the radial distance r to the outer radius Ro, where r/R o <0.2 or where 0.5<r/R o <0.95.

20. The permanent magnet of claim 18 , wherein the cylindrical ring permanent magnet includes two permanent magnet units, the two permanent magnet units including the first and the second permanent magnet units.

Assignees

• Multidimension Technology Co Ltd

Inventors

• Deak James Geza
• Zhou Zhimin

Classifications

• H01F7/0289

  Transducers, loudspeakers, moving coil arrangements · CPC title

• H01F1/0551

  in the form of particles, e.g. rapid quenched powders or ribbon flakes · CPC title

• H01F1/047

  Alloys characterised by their composition · CPC title

• H01F1/06

  in the form of particles, e.g. powder (H01F1/047 takes precedence {; record carriers G11B5/70605}) · CPC title

• G01D5/145 Primary

  influenced by the relative movement between the Hall device and magnetic fields (see G01R33/06) · CPC title