# US 11,028,853 B2 · Electromagnetic unit, magnetic bearing device, and vacuum pump > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,028,853 B2 - Document ID: US11028853B2 - Status: Granted - Kind: B2 - Application number: 15/741,945 - Filed: 2016-07-01 - Published: 2019-01-24 - Granted: 2021-06-08 - Earliest claimed: 2015-07-07 - Assignees: Edwards Japan Limited - Applicants: Edwards Japan Limited - Inventors: Toshiaki Kawashima - Web page: https://patentgrep.com/patent/US11028853B2 ## CPC - F04D 19/042: {Turbomolecular vacuum pumps} - F04D 17/168: {Pumps specially adapted to produce a vacuum} - F04D 19/048: {comprising magnetic bearings} - F16C 32/0446: {Determination of the actual position of the moving member, e.g. details of sensors} - F16C 32/048: {with active support of two degrees of freedom, e.g. radial magnetic bearings} - H02K 7/09: with magnetic bearings - H02K 11/21: Devices for sensing speed or position, or actuated thereby (specially adapted for machines having non-mechanical commutating devices H02K29/06, H02K29/14) - F16C 2360/45: Turbo-molecular pumps - F16C 2380/26: Dynamo-electric machines or combinations therewith, e.g. electro-motors and generators - F04D: NON-POSITIVE-DISPLACEMENT PUMPS (engine fuel-injection pumps F02M; ion pumps H01J41/12; electrodynamic pumps H02K44/02) - F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) ## 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. ## Claims ### Claim 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. ### Claim 2 (depends on 1) 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. ### Claim 3 (depends on 2) 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. ### Claim 4 (depends on 2) 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. ### Claim 5 (depends on 1) 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. ### Claim 6 (depends on 1) 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. ### Claim 7 (depends on 1) 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. ### Claim 8 (depends on 1) 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. ### Claim 9 (depends on 8) 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. ### Claim 10 (depends on 1) 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. ### Claim 11 (depends on 1) 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. ### Claim 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. ### Claim 13 (depends on 12) 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. ### Claim 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 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.