Radial and torsionally controlled magnetic bearing

• US 4,634,191 A
• Filed: 11/21/1985
• Issued: 01/06/1987
• Est. Priority Date: 11/21/1985
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Studer, Philip A.
• Primary Examiner(s): SKUDY, ROBERT
• Application Number:
  US06/800,193
• Time in Patent Office: 411 Days
• Field of Search: 308/10, 361/143, 361/146
• US Class Current: 310/90.5
• CPC Class Codes: F16C 32/0444 Details of devices to control the actuation of the electromagnets
• CPC Class Codes: F16C 32/0465 with permanent magnets provided in the magnetic circuit of the electromagnets
• CPC Class Codes: F16C 32/0487 with active support of four degrees of freedom

Abstract

A magnetic bearing including a circular stator member having a plurality of circumferential pole faces and a suspended annular ring member with corresponding number of inward facing circumferential pole faces separated by respective air gaps. A source of DC magnetic flux circulates flux between the circumferential pole faces of the stator and the ring to provide axial stability along a central longitudinal axis. Flux coil means are included on the stator member for providing variable flux density along predetermined radial paths to provide active radial stabilization. Additionally, flux coil means are included on the stator to actively modulate the magnitude of the magnetic forces as well as their direction of differential flux control involving the DC magnetic flux to produce torquing moments about a pair of mutually orthogonal axes which are perpendicular to the central axis.

Claims

1. An active magnetic bearing system for producing both radial and torsional forces on a suspended body, comprising:

an inner generally circular stator member having a plurality of peripheral outer surfaces defining a set of curvilinear exterior pole faces;

an outer annular magnetically permeable ring member coaxial with said stator member about a longitudinal axis and having a like plurality of inwardly projecting rims including surfaces defining a like set of curvilinear interior pole faces disposed opposite said set of exterior pole faces of said stator member and being separated therefrom by respective circumferential air gaps;

said stator member further being comprised of at least one permanent magnet member lying in a plane perpendicular to said longitudinal axis and providing a substantially uniform DC magnetic flux across said circumferential air gaps, a first and second set of segmented magnetically permeable members respectively located on opposite sides of said at least one permanent magnet member and including means for magnetically coupling pairs of segments of the same set diametrically to direct flux across said air gaps along first and second mutually orthogonal axes perpendicular to said longitudinal axis, flux coil means selectively energized to produce a first variable magnetic control flux alono predetermined radial paths which interacts with said DC magnetic flux to modulate radial forces across said circumferential air gaps for providing active radial stabilization of ring member about said longitudinal axis and flux coil means selectively energized to produce a second variable magnetic control flux which differentially interacts with said DC magnetic flux across said circumferential air gaps to generate torsional forces of said ring member about said first and second orthogonal axis.

2. The magnetic bearing system of claim 1 and further comprising sensor means located in relative close proximity to said ring member for sensing radial displacement of said ring member from said longitudinal axis along said first and second orthogonal axes and for sensing angular displacement of said ring about said first and second orthogonal axes and electrical circuit means coupled between said sensor means and said flux coil means for energizing said coil means.

3. The magnetic bearing system of claim 1 wherein said at least one permanent magnet member comprises at least one disc magnet centered on said longitudinal axis and wherein said first and second set of segmented members, comprise mutually separated quadrants of first and second magnetically permeable discs centered on said longitudinal axis.

4. The magnetic bearing system of claim 3 wherein said means for coupling flux between pairs of segments comprises first and second magnetically permeable members respectively covering at least a portion of first and second sets of disc quadrants.

5. The magnetic bearing system of claim 4 wherein said first and second magnetically permeable members comprises respective disc members contacting the outer surface of first and second sets of disc quadrants.

6. The magnetic bearing system of claim 3 wherein said flux coil means energized to produce said first and second variable magnetic flux comprises first and second sets of coil windings located on said disc quadrants.

7. The magnetic bearing system of claim 3 wherein said first and second sets of disc quadrants provide two curvilinear interior pole faces and said ring member includes two inwardly projecting rims providing two curvilinear exterior pole faces separated therefrom by two circumferential air gaps.

8. The magnetic bearing system of claim 1 wherein said at least one permanent magnet member comprises a pair of magnetically opposed permanent magnets and additionally including a magnetically permeable member located between said pair of permanent magnets wherein said first set of segmented magnetically permeable members are located on the outside surface of one of said pair of magnets;

and wherein said second set of segmented magnetically permeable members are located on the outside surface of the other of said pair of magnets.

9. The magnetic bearing system of claim 8 wherein said magnetically permeable member between said pair of permanent magnets comprises a generally flat circular plate member having a peripheral outer surface defining one of said plurality of exterior pole faces, wherein the peripheral outer surface of said first and second sets of segmented permeable members define two more of said plurality of exterior pole faces, providing three exterior pole faces thereby, and wherein said ring member has three inwardly projecting rims defining three interior pole faces, whereby a structure having three circumferential air gaps is provided.

10. The magnetic bearing system of claim 9 wherein said first and second set of segmented magnetically permeable members comprise quadrants of a generally circular ferrous disc and wherein the vertices of said quadrants are directed toward said longitudinal axis.

11. The magnetic bearing system of claim 10 and wherein said flux coil means comprises respective winding means located on each of said disc quadrants.

12. The magnetic bearing system of claim 11 wherein each said disc quadrant includes an outwardly projecting magnetically permeable core member and wherein said respective coil winding means is wound on said core member.

13. The magnetic bearing system of claim 12 and wherein said means for magnetically coupling pairs of segments comprises a first and second magnetically permeable flux bridge member respectively located across and in contact with the top of the core members of said first and second sets of disc quadrants.

14. The magnetic bearing system of claim 13 wherein mutually opposing upper and lower coil winding means of said first and second sets are energized in opposition for producing a unidirectional control flux which interacts with said DC magnetic flux for producing differential forces for selectively producing said torsional forces.

15. The magnetic bearing system of claim 10 wherein said means for magnetic coupling said segments comprises a first and second magnetically permeable disc member affixed respectively to the top surface of said first and second set of disc quadrants, and wherein said coil winding means includes a respective coil winding located on the surface of each of said disc quadrants for producing said second variable control flux and a set coil winding located on magnetically permeable members between said pair of permanent magnets for producing said first variable control flux.

16. An active magnetic bearing system for producing both radial and torsional forces comprising:

an inner generally circular stator member having a plurality of peripheral outer surfaces defining a set of curvilinear exterior pole faces;

an outer annular magnetic permeable ring assembly coaxial with said stator member about a longitudinal axis, said ring assembly having a like plurality of inwardly projecting rims separated by rings of permanent magnets which are mutually magnetically opposed to one another, said rims having surfaces defining a set of curvilinear interior pole faces disposed opposite said set of exterior pole faces and being separated therefrom by respective circumferential air gaps;

said stator member being further comprised of a central magnetically permeable disc member having a pair of opposing faces lying in a plane perpendicular to said longitudinal axis, a pair of disc type permanent magnets located on said opposing faces and being oriented so that their magnetic polarities are mutually opposed, a first and second set of magnetically permeable disc segments respectively located on the outer surface of said permanent magnets and including means for magnetically coupling diametrically opposite segments to direct flux across said air gaps along first and second mutually orthogonal radial axes perpendicular to said longitudinal axes, said permanent magnets providing a substantially uniform radial DC flux across said circumferential air gaps which by itself provides axial stabilization of said ring member about said stator member, and coil winding means located on said disc segments and being selectively energizable to produce a first control flux which combines with said DC flux to radially stabilize said ring about said longitudinal axis and a second control flux which combines with said DC flux for producing differential forces across said circumferential air gaps to generate a torque of said ring member about said first and second orthogonal axes.

17. The magnetic bearing system of claim 16 wherein said first and second set of segmented magnetically permeable member comprise respective quadrants of a magnetically permeable disc, said quadrants being arranged so as to be in alignment with said first and second orthogonal axes and wherein the vertices thereof are convergent upon said longitudinal axis.

18. An active magnetic bearing, comprising:

an inner generally circular stator member having two peripheral outer surfaces defining curvilinear exterior pole faces;

an outer annular magnetically permeable ring member coaxial with said stator member about a longitudinal axis and having two inwardly projecting rims having surfaces defining a set of curvilinear interior pole faces disposed opposite said exterior pole faces of the stator member and being separated therefrom by a first and second circumferential air gap;

said stator member being further comprised of a central permanent magnet member providing a DC flux across said first and second air gaps and having a pair of opposing faces lying in a plane perpendicular to said longitudinal axis, a first and second set of segmented magnetically permeable disc members respectively located on said pair of opposing faces and including means for being magnetically coupled to direct flux across said first and second air gaps along first and second mutually orthogonal radial axes perpendicular to said longitudinal axis and coil winding means located on said stator member and being selectively energized to produce a first control flux for producing radial stabilizing forces of said ring member about said longitudinal axis when summed with said DC flux and to produce a second control flux to generate a torque of said ring member about said first and second orthogonal axis in a predetermined direction when summed with said DC flux.

19. The magnetic bearing of claim 18 wherein said first and second set of segmented magnetically permeable members comprise quadrants of a magnetically permeable disc arranged about said longitudinal axis and being centered about said first and second mutually orthogonal axes.

20. The magnetic bearing of claim 19 and wherein said coil winding means includes coil windings on each of said quadrants.