Electromagnetic unit, magnetic bearing device, and vacuum pump

Patent metadata

Field	Value
Publication number	US-11028853-B2
Application number	US-201615741945-A
Country	US
Kind code	B2
Filing date	Jul 1, 2016
Priority date	Jul 7, 2015
Publication date	Jun 8, 2021
Grant date	Jun 8, 2021

Abstract

An electromagnet unit, a magnetic bearing device, and a vacuum pump with which displacement of a rotating body in a radial direction can be detected with precision. An upper electromagnet unit includes: radial electromagnets for supporting a rotor in a radial direction without contact; radial sensors for detecting displacement of the rotor in the radial direction; and a core around which coils are wound. Two radial electromagnets that are adjacent to each other in a circumferential direction of the core are disposed such that adjacent magnetic poles belonging respectively to the two radial electromagnets are homopolar, and a low magnetic flux interference region is formed between the two radial electromagnets. Each of the radial sensors is disposed in the low magnetic flux interference region.

First claim

What is claimed is:

1. An electromagnet unit comprising:
a plurality of radial direction magnetic force generating means for supporting a rotating body in a radial direction by magnetic force without contact;
a plurality of radial direction displacement detecting means for detecting displacement of the rotating body in the radial direction; and
a core around which coils of the plurality of radial direction magnetic force generating means and coils of the plurality of radial direction displacement detecting means are wound, wherein
two of the plurality of radial direction magnetic force generating means that are adjacent to each other in a circumferential direction of the core are disposed such that adjacent magnetic poles belonging respectively to the two of the plurality of radial direction magnetic force generating means are homopolar,
a low magnetic flux interference region is formed between the two of the plurality of radial direction magnetic force generating means,
each of the plurality of radial direction displacement detecting means is disposed in the low magnetic flux interference region,
the plurality of radial direction displacement detecting means comprise two mutually different magnetic poles arranged in an axial direction of the rotating body, and
magnetic poles to which the coils of the plurality of radial direction magnetic force generating means are wound do not overlap, in the radial direction, magnetic poles to which the coils of the plurality of radial direction displacement detecting means are wound.

2. The electromagnet unit according to claim 1 , further comprising a magnetic shielding means for reducing a magnetic coupling between the plurality of radial direction magnetic force generating means and the plurality of radial direction displacement detecting means.

3. The electromagnet unit according to claim 2 , wherein the magnetic shielding means is a conductive shield ring attached to the plurality of radial direction magnetic force generating means.

4. The electromagnet unit according to claim 2 , wherein the magnetic shielding means is a conductive shield tube covering each of the coils of the plurality of radial direction displacement detecting means.

5. The electromagnet unit according to claim 1 , wherein the plurality of radial direction magnetic force generating means comprise three magnetic poles arranged in the circumferential direction of the core so as to form two magnetic fluxes oriented in mutually opposite directions.

6. The electromagnet unit according to claim 1 , wherein the plurality of radial direction magnetic force generating means comprise four magnetic poles arranged in the circumferential direction of the core so as to form two magnetic fluxes oriented in mutually opposite directions.

7. The electromagnet unit according to claim 1 , wherein the plurality of radial direction magnetic force generating means comprise five or more magnetic poles arranged such that different polarities occur alternately in the circumferential direction of the core.

8. The electromagnet unit according to claim 1 , wherein the core comprises an eddy current reducing means for reducing eddy currents generated when magnetic flux generated by the plurality of radial direction displacement detecting means in the axial direction passes through the core.

9. The electromagnet unit according to claim 8 , wherein the eddy current reducing means is structured to reduce a passage sectional area where the magnetic flux generated by the plurality of radial direction displacement detecting means in the axial direction passes through the core.

10. The electromagnet unit according to claim 1 , wherein
each of the coils of the plurality of radial direction displacement detecting means is wound around two pawl portions projecting from the core toward an inner side in the radial direction, and
a distance from a radial direction outer side end of each of the coils to a base end of the pawl portion is set to be greater than a distance between the two pawl portions.

11. The electromagnet unit according to claim 1 , wherein a magnetic pole center of at least one of the plurality of radial direction magnetic force generating means and a magnetic pole center of at least one of the plurality of radial direction displacement detecting means are disposed on an identical plane.

12. A magnetic bearing device comprising:
an electromagnet unit comprising:
a plurality of radial direction magnetic force generating means for supporting a rotating body in a radial direction by magnetic force without contact;
a plurality of radial direction displacement detecting means for detecting displacement of the rotating body in the radial direction; and
a core around which coils of the plurality of radial direction magnetic force generating means and coils of the plurality of radial direction displacement detecting means are wound, wherein
two of the plurality of radial direction magnetic force generating means that are adjacent to each other in a circumferential direction of the core are disposed such that adjacent magnetic poles belonging respectively to the two of the plurality of radial direction magnetic force generating means are homopolar,
a low magnetic flux interference region is formed between the two of the plurality of radial direction magnetic force generating means,
each of the plurality of radial direction displacement detecting means is disposed in the low magnetic flux interference region,
the plurality of radial direction displacement detecting means comprise two mutually different magnetic poles arranged in an axial direction of the rotating body, and
magnetic poles to which the coils of the plurality of radial direction magnetic force generating means are wound do not overlap, in the radial direction, magnetic poles to which the coils of the plurality of radial direction displacement detecting means are wound; and

a control means for controlling the electromagnet unit.

13. The magnetic bearing device according to claim 12 , further comprising a magnetic shielding means configured to reduce a magnetic coupling between the plurality of radial direction magnetic force generating means and the plurality of radial direction displacement detecting means, wherein the magnetic shielding means is a conductive shield plate interposed between the electromagnet unit and a substrate for connecting the coils of the plurality of radial direction displacement detecting means.

14. A vacuum pump comprising:
a magnetic bearing device comprising:
an electromagnet unit comprising:
a plurality of radial direction magnetic force generating means for supporting a rotating body in a radial direction by magnetic force without contact;
a plurality of radial direction displacement detecting means for detecting displacement of the rotating body in the radial direction; and
a core around which coils of the plurality of radial direction magnetic force generating means and coils of the plurality of radial direction displacement detecting means are wound, wherein
two of the plurality of radial direction magnetic force generating means that are adjacent to each other in a circumferential direction of the core are disposed such that adjacent magnetic poles belonging respectively to the two of the plurality of radial direction magnetic force generating means are homopolar,
a low magnetic flux interference region is formed between the two of the plurality of radial direction magnetic force generating means,
each of the plurality of radial direction displacement detecting means is disposed in the low magnetic flux interference region,
the pluralit

Assignees

• Edwards Japan Ltd

Inventors

• Kawashima Toshiaki

Classifications

• F04D19/048

  comprising magnetic bearings · CPC title

• F16C2380/26

  Dynamo-electric machines or combinations therewith, e.g. electro-motors and generators · CPC title

• F16C32/0446

  Determination of the actual position of the moving member, e.g. details of sensors · CPC title

• F16C32/048

  with active support of two degrees of freedom, e.g. radial magnetic bearings · CPC title

• F16C32/04 Primary

  using magnetic or electric supporting means · CPC title