Passive magnetic bearings for a spindle motor

• US 5,619,083 A
• Filed: 06/02/1995
• Issued: 04/08/1997
• Est. Priority Date: 02/25/1994
• Status: Expired due to Term

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology plc (Seagate Technology Holdings Plc)
• Inventors: Heine, Gunter K., Oveyssi, Kamran, Dunfield, John C.
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US08/458,570
• Time in Patent Office: 676 Days
• Field of Search: 310/90, 310/90.5, 384/112-115, 384/120, 384/121, 384/100, 384/107, 360/97.02, 360/98.07, 360/99.04, 360/99.08
• US Class Current: 310/90.5
• CPC Class Codes: F16C 17/08 for supporting the end face of a shaft or other member, e.g. footstep bearings
• CPC Class Codes: F16C 2370/12 Hard disk drives or the like
• CPC Class Codes: F16C 25/045 with magnetic means to preload the bearing
• CPC Class Codes: F16C 32/0417 for axial load mainly
• CPC Class Codes: F16C 32/0425 for radial load mainly
• CPC Class Codes: F16C 39/063 Permanent magnets
• CPC Class Codes: G11B 19/2009 Turntables, hubs and motors for disk drives; Mounting of motors in the drive means for clamping of disk to turntable G11B17/022 and subgroups
• CPC Class Codes: H02K 7/09 with magnetic bearings

Abstract

An apparatus for rotatably journaling a rotor of a spindle motor about a shaft comprising a plurality of annular ring multi-pole magnets, each ring comprised of a plurality of axially aligned magnets whose polarity is alternated along the radius of the ring. The annular ring multi-pole magnets are disposed on both the rotor and stator of a spindle motor in opposition in attraction mode, or a complete offset repulsion mode with like poles facing one another with an full offset, thereby forming a radially stable magnetic bearing for maintaining rotor displacement about a shaft in conjunction with a conventional axial pivot.

Claims

1. A magnetic bearing for journaling a rotor about a stator of a spindle motor comprising:

a pivot for pivotally supporting said rotor for rotation about said stator;

a first plurality of axially aligned magnetic poles supported from and radially extending along said stator; and

a second plurality of axially aligned magnetic poles, said poles are fixably attached to said rotor and opposing said first annular plurality of poles having each of said plurality of poles aligned exactly with each of said like plurality of poles, said first plurality of poles magnetically oriented oppositely from said second plurality of poles so that alignment of said rotor and said stator is maintained by attraction of said first and second plurality of poles, and stiffener means supported on said stator and establishing magnetic interaction with said magnetic poles on said rotor to provide directional stiffness substantially perpendicular to the axis of orientation of said magnetic poles.

2. The apparatus of claim 1 wherein said stiffener means comprises at least one additional pole located adjacent said whereby said additional pole is aligned completely axially offset from either an innermost or outermost pole of said first annular ring.

3. The apparatus of claim 1 wherein said plurality of poles comprises at least 3 axially aligned magnetic poles.

4. The apparatus of claim 1 wherein said first annular disc is disposed 0.25 mm beneath said second annular disc.

5. The apparatus of claim 1 wherein said pivot is a hydrodynamic bearing.

6. The apparatus of claim 1 wherein said pivot is a conventional ball bearing.

7. The apparatus of claim 1 wherein said pivot is a ruby ball bearing.

8. The apparatus of claim 1 wherein said pivot is a ceramic ball bearing.

9. A magnetic bearing as claimed in claim 1 wherein said axially aligned magnetic poles are physically adjacent.

10. A magnetic bearing as claimed in claim 9, said stiffener means comprising an additional, unpaired pole radially adjacent said plurality of poles on said stator but not axially aligned with any of said second plurality of poles on said rotor, said additional poles magnetically interacting with one of said poles on said rotor to provide stability against radial shocks.

11. A magnetic bearing as claimed in claim 1 wherein radially adjacent ones of said poles are oppositely axially aligned.

17. A magnetic bearing as claimed in claim 2, wherein said magnetic pole of said stiffener means is oppositely axially aligned to the nearest of said magnetic poles on said rotor.

12. A motor comprising a fixed support shaft supporting a stator near one end and a bearing support bracket near another end, a rotor supported for rotation around said support shaft, said rotor having a magnet fixed to an inner surface and aligned with said stator, said rotor being supported and aligned relative to said stator by a magnetic bearing comprising:

a pivot for pivotally supporting said rotor for rotation about said stator;

a first plurality of axially aligned magnetic poles supported from and radially extending along said stator; and

a second plurality of axially aligned magnetic poles, said poles are fixably attached to said rotor and opposing said first annular plurality of poles having each of said plurality of poles aligned exactly with each of said like plurality of poles, said first plurality of poles magnetically oriented oppositely from said second plurality of poles so that alignment of said rotor and said stator is maintained by attraction of said first and second plurality of poles, and stiffener means supported on said stator and establishing magnetic interaction with said magnetic poles on said rotor to provide directional stiffness substantially perpendicular to the axis of orientation of said magnetic poles.

13. The apparatus of claim 12 wherein said stiffener means comprises at least one additional pole located adjacent said whereby said additional pole is aligned completely axially offset from either an innermost or outermost pole of said first annular ring.

14. A magnetic bearing as claimed in claim 13 wherein said axially aligned magnetic poles are physically adjacent.

15. A magnetic bearing as claimed in claim 12, said stiffener means comprising an additional, unpaired pole radially adjacent said plurality of poles on said stator but not axially aligned with any of said second plurality of poles on said rotor, said additional poles magnetically interacting with one of said poles on said rotor to provide stability against radial shocks.

16. A magnetic bearing as claimed in claim 12 wherein radially adjacent ones of said poles are oppositely axially aligned.

18. A magnetic bearing as claimed in claim 12, wherein said magnetic pole of said stiffener means is oppositely axially aligned to the nearest of said magnetic poles on said rotor.