Passive magnetic bearings for a spindle motor

• US 5,610,463 A
• Filed: 06/02/1995
• Issued: 03/11/1997
• 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 O.
• Application Number:
  US08/459,113
• Time in Patent Office: 648 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 multipole 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. In a disc drive, an apparatus for journaling a rotor about a stator of a spindle motor comprising:

a pivot, said pivot for pivotally displacing said rotor about said stator;

a raised magnetically permeable flange, said raised flange disposed on a top portion of said stator, said flange substantially annular in shape having an outer radius X;

a first outer annular disc having inner radius greater than X, said outer annular disc comprising a first axially oriented magnetic pole, said outer disc fixably attached to said top portion of said stator and flush with said flange;

a second opposing annular disc, said opposing annular disc comprised of a second axially oriented magnetic pole oriented similarly to said pole of said outer annular disc in the direction facing said outer annular disc, said opposing annular disc fixably attached to said rotor and centrally disposed so as to oppose said flange.

2. The apparatus of claim 1 wherein said raised magnetically permeable flange is constructed from magnetic steel.

3. A spindle motor as claimed in claim 1 wherein said raised flange is spaced from said pivot by an annular gap having a axial depth substantially the same as the axial depth of said axially aligned magnetic pole.

4. A spindle motor as claimed in claim 3 wherein said gap extends radially from said pivot at least to a point opposite said opposing annular disc comprising:

said second axially aligned magnetic pole.

5. A spindle motor as claimed in claim 4 wherein said pivot comprises a rotor which is substantially drum shaped and includes centrally disposed rotating shaft rotating within said stator, a top surface of said drum shaped rotor extending radially over said stator and supporting said second axially aligned magnetic pole over said stator and said magnetically permeable flange.

6. A spindle motor as claimed in claim 5 wherein said stator supports a stator assembly comprising one or more permanent magnets and coil windings radially outside of said first axially aligned magnetic pole, said rotor supporting a ring shaped rotor magnet radially aligned with said stator assembly.

7. A spindle motor as claimed in claim 1 wherein said first axially aligned magnetic pole is oriented in a repulsion mode relative to said second axially aligned magnetic pole.

8. A spindle motor as claimed in claim 7 wherein said first axially aligned magnetic pole lies entirely radially beyond said second axially aligned magnetic pole so that no axial alignment exists between said first and second magnetic poles.

9. A spindle motor as claimed in claim 2 wherein said first axially aligned magnetic pole is oriented in a repulsion mode relative to said second axially aligned magnetic pole.

10. A spindle motor as claimed in claim 5 wherein said first axially aligned magnetic pole is oriented in a repulsion mode relative to said second axially aligned magnetic pole.