Self-adjusting magnetic bearing systems

• US 5,783,885 A
• Filed: 08/07/1995
• Issued: 07/21/1998
• Est. Priority Date: 08/07/1995
• Status: Expired due to Term

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Post, Richard F.
• Primary Examiner(s): Stephan, Steve L.
• Assistant Examiner(s): WALLACE, MICHAEL J
• Application Number:
  US08/511,981
• Time in Patent Office: 1,079 Days
• Field of Search: 310/90.5, 310/103, 310/105, 310/80, 310/104
• US Class Current: 310/90.5
• CPC Class Codes: F16C 39/063 Permanent magnets
• CPC Class Codes: H02K 7/025 for power storage
• CPC Class Codes: H02K 7/09 with magnetic bearings
• CPC Class Codes: Y02E 60/16 Mechanical energy storage, e.g. flywheels or pressurised fluids

Abstract

A self-adjusting magnetic bearing automatically adjusts the parameters of an axially unstable magnetic bearing such that its force balance is maintained near the point of metastable equilibrium. Complete stabilization can be obtained with the application of weak restoring forces either from a mechanical bearing (running at near-zero load, thus with reduced wear) or from the action of residual eddy currents in a snubber bearing. In one embodiment, a torque is generated by the approach of a slotted pole to a conducting plate. The torque actuates an assembly which varies the position of a magnetic shunt to change the force exerted by the bearing. Another embodiment achieves axial stabilization by sensing vertical displacements in a suspended bearing element, and using this information in an electrical servo system. In a third embodiment, as a rotating eddy current exciter approaches a stationary bearing, it heats a thermostat which actuates an assembly to weaken the attractive force between the two bearing elements. An improved version of an electromechanical battery utilizing the designs of the various embodiments is described.

Claims

1. A self-adjusting magnetic bearing, comprising:

a stationary bearing element;

a rotatable bearing element magnetically levitated by said stationary bearing element;

wherein said self-adjusting magnetic bearing is intrinsically radially stable; and

active means for automatically adjusting the magnetic parameters of said stationary bearing element with respect to said rotatable bearing element, resulting in axial stability, such that the force balance of said self-adjusting magnetic bearing is maintained near the point of metastable equilibrium,

wherein said stationary bearing element comprises at least one first annular iron pole piece

wherein said rotatable bearing element comprises at least one second annular iron pole piece fixedly attached to an annular conducting plate comprising non-magnetic material,

wherein said at least one first annular pole piece and said at least one second annular pole piece are configured to exert magnetically attractive forces upon each other such that said rotatable bearing element tends to be pulled toward said stationary bearing element, and

wherein said means for automatically adjusting the magnetic parameters comprises a stationary drive screw supporting an assembly comprising a magnetic shunt pair with an internal thread, each shunt of said shunt pair supporting a slotted pole.

2. The self-adjusting magnetic bearing of claim 1, wherein said annular conducting plate comprises copper.

3. The self-adjusting magnetic bearing of claim 1, further comprising:

an eddy-current damper plate fixedly attached to said rotatable bearing element; and

an annular permanent magnet element fixedly attached to said stationary bearing element and having field lines that intersect said eddy current damper plate.

4. The self-adjusting magnetic bearing of claim 3, wherein said eddy current damper plate comprises a plurality of concentric conducting rings separated by material having a conductivity that is less than that of said conducting rings.

5. The self-adjusting magnetic bearing of claim 3, wherein said eddy current damper plate comprises a non-magnetic metal plate having deep circular grooves, wherein only a thin web of supporting material remains on the surface of said eddy current damper plate that is farthest from said annular permanent magnet element.

6. The self-adjusting magnetic bearing of claim 1, further comprising:

an eddy-current damper plate fixedly attached to said stationary bearing element; and

an annular permanent magnet element fixedly attached to said rotatable bearing element and having field lines that intersect said eddy-current damper plate.

7. The self-adjusting magnetic bearing of claim 1, further comprising a vacuum enclosure, wherein said stationary bearing element is located outside said vacuum enclosure and wherein said rotatable bearing element is located inside said vacuum enclosure.

8. The self-adjusting magnetic bearing of claim 1, further comprising:

an eddy-current damper plate fixedly attached to said rotatable bearing element; and

an annular permanent magnet element fixedly attached to said stationary bearing element and having field lines that intersect said eddy-current damper plate.

9. The self-adjusting magnetic bearing of claim 8, wherein said eddy-current damper plate comprises a plurality of concentric conducting rings separated by material comprising with a conductivity that is less than that of said conducting rings.

10. The self-adjusting magnetic bearing of claim 8, wherein said eddy-current damper plate comprises a non-magnetic metal plate having deep circular grooves wherein only a thin web of supporting material remains on the surface farthest from said annular permanent magnet element.

11. The self-adjusting magnetic bearing of claim 1, further comprising a vacuum enclosure, wherein said stationary bearing element is located outside said vacuum enclosure and wherein said rotatable bearing element is located inside said vacuum enclosure.

12. A self-adjusting magnetic bearing, comprising:

a stationary bearing element;

a rotatable bearing element magnetically levitated by said stationary bearing element;

wherein said self-adjusting magnetic bearing is intrinsically radially stable; and

means for automatically adjusting the magnetic parameters of said stationary bearing element with respect to said rotatable bearing element, resulting in axial stability, such that the force balance of said self-adjusting magnetic bearing is maintained near the point of metastable equilibrium,

wherein said stationary bearing element comprises;

a cup-shaped element having a central axis; and

an interior magnetic bearing element comprising a pole having permanent magnet material, wherein said interior magnetic bearing element is fixedly attached to said central axis of said cup shaped element,

wherein said rotatable bearing element comprises an iron disc, and

wherein said means for automatically adjusting the magnetic parameters comprise;

a pole assembly detached from and located between said stationary bearing element and said rotatable bearing element, said pole assembly comprising a disc having a center iron piece and at least one alternating concentric ring of non-magnetic metal and iron, said pole assembly attached to a support structure with a spring;

means for sensing vertical displacements away from equilibrium of said rotatable bearing element; and

a control coil surrounding said interior magnetic bearing element, wherein a feed-back circuit is electrically connected between said means for sensing vertical displacements and said control coil.

13. The self-adjusting magnetic bearing of claim 12, wherein said means for sensing vertical displacements comprises a strain gauge operatively connected to said spring.

14. The self-adjusting magnetic bearing of claim 13, further comprising:

an eddy-current damper plate fixedly attached to said rotatable bearing element; and

an annular permanent magnet element fixedly attached to said stationary bearing element and having field lines that intersect said eddy-current damper plate.

15. The self-adjusting magnetic bearing of claim 14, wherein said eddy-current damper plate comprises a plurality of concentric conducting rings separated by material comprising with a conductivity that is less than that of said conducting rings.

16. The self-adjusting magnetic bearing of claim 14, wherein said eddy-current damper plate comprises a non-magnetic metal plate having deep circular grooves wherein only a thin web of supporting material remains on the surface farthest from said annular permanent magnet element.

17. The self-adjusting magnetic bearing of claim 14, wherein said eddy current damper plate comprises a plurality of concentric conducting rings separated by material having a conductivity that is less than that of said conducting rings.

18. The self-adjusting magnetic bearing of claim 14, wherein said eddy current damper plate comprises a non-magnetic metal plate having deep circular grooves, wherein only a thin web of supporting material remains on the surface of said eddy current damper plate that is farthest from said annular permanent magnet element.

19. The self-adjusting magnetic bearing of claim 13, further comprising a vacuum enclosure, wherein said stationary bearing element is located outside said vacuum enclosure and wherein said rotatable bearing element is located inside said vacuum enclosure.

20. The self-adjusting magnetic bearing of claim 13, further comprising:

an eddy-current damper plate fixedly attached to said stationary bearing element; and

an annular permanent magnet element fixedly attached to said rotatable bearing element and having field lines that intersect said eddy-current damper plate.

21. A self-adjusting magnetic bearing, comprising:

a stationary bearing element;

a rotatable bearing element magnetically levitated by said stationary bearing element;

wherein said self-adjusting magnetic bearing is intrinsically radially stable; and

means for automatically adjusting the magnetic parameters of said stationary bearing element with respect to said rotatable bearing element, resulting in axial stability, such that the force balance of said self-adjusting magnetic bearing is maintained near the point of metastable equilibrium,

wherein said stationary element comprises;

a first cup-shaped element comprising magnetically conducting material and having a first central axis;

a second cup-shaped element comprising magnetically conducting material and having a second central axis;

a permanent magnet piece fixedly connected to said first central axis and said second central axis to fixedly connect said first cup to said second cup;

a third cup-shaped element comprising a third central axis, said third cup shaped element comprising magnetically conducting material and non-magnetic metallic material with at least two through holes; and

a copper eddy current plate supported by two support rods that extend from said copper eddy current plate through said at least two through holes and are fixedly attached to said second cup shaped element;

wherein said rotatable bearing element comprises;

an eddy-current exciter; and

a pole assembly fixedly attached to said eddy current exciter;

wherein said means for automatically adjusting the magnetic parameters comprise a thermostat element fixedly supported between said copper eddy current plate and said non-magnetic metallic material of said third cup shaped element.

22. The self-adjusting magnetic bearing of claim 21, wherein said eddy-current exciter comprises a slotted pole.

23. The self-adjusting magnetic bearing of claim 22, further comprising at least one tension spring fixedly attached between said third cup shaped element and said eddy current plate.

24. The self-adjusting magnetic bearing of claim 21, wherein said eddy-current exciter comprises a planar Halbach array.

25. The self-adjusting magnetic bearing of claim 21, wherein said thermostat element is selected from a group consisting of a sealed sylphon bellows and an assembly comprising a bimetallic element, wherein said sealed sylphon bellows comprises a vaporizable liquid.

26. The self-adjusting magnetic bearing of claim 21, further comprising:

an eddy-current damper plate fixedly attached to said rotatable bearing element; and

an annular permanent magnet element fixedly attached to said stationary bearing element and having field lines that intersect said eddy-current damper plate.

27. The self-adjusting magnetic bearing of claim 26, wherein said eddy-current damper plate comprises a plurality of concentric conducting rings separated by material comprising with a conductivity that is less than that of said conducting rings.

28. The self-adjusting magnetic bearing of claim 26, wherein said eddy current damper plate comprises a non-magnetic metal plate having deep circular grooves wherein only a thin web of supporting material remains on the surface farthest from said annular permanent magnet element.

29. The self-adjusting magnetic bearing of claim 21, further comprising a vacuum enclosure, wherein said stationary bearing element is located outside said vacuum enclosure and wherein said rotatable bearing element is located inside said vacuum enclosure.

30. The self-adjusting magnetic bearing of claim 21, further comprising:

an eddy-current damper plate fixedly attached to said stationary bearing element; and

an annular permanent magnet element fixedly attached to said rotatable bearing element and having field lines that intersect said eddy-current damper plate.