Self-contained hydrodynamic bearing unit and seals

• US 5,558,445 A
• Filed: 12/22/1994
• Issued: 09/24/1996
• Est. Priority Date: 07/22/1994
• Status: Expired due to Term

• Current Assignee: Maxtor Corporation (Seagate Technology Holdings Plc)
• Original Assignee: Quantum Corporation (Chi Ko Investment Co., Ltd.)
• Inventors: Chen, Shuo-Hao, Hatch, Michael R., Zang, Yan
• Primary Examiner(s): Hannon, Thomas R.
• Application Number:
  US08/363,566
• Time in Patent Office: 642 Days
• Field of Search: 384/100, 384/107, 384/108, 384/109, 384/111, 384/112, 384/119, 384/124, 384/130, 384/132, 384/135, 310/90, 277/80, 277/135
• US Class Current: 384/132
• CPC Class Codes: F16C 17/107 with at least one surface for radial load and at least one surface for axial load
• CPC Class Codes: F16C 2370/12 Hard disk drives or the like
• CPC Class Codes: F16C 33/10 Construction relative to lubrication lubrication in general F16N
• CPC Class Codes: F16C 33/103 retained in or near the bearing
• CPC Class Codes: F16C 33/107 Grooves for generating pressure
• CPC Class Codes: F16C 33/745 by capillary action

Abstract

A self-contained hydrodynamic bearing unit includes a shaft and a shaft housing defining an opening for receiving the shaft for relative rotation. The shaft and bearing define at least one radial hydrodynamic bearing and an annular thrust bearing, formed as a disk portion extending radially outward of a main cylindrical surface of the shaft which cooperates with an adjacent annular face of the shaft housing. A gap between an outer cylindrical wall of the thrust bearing disk portion and an adjacently facing cylindrical surface of the shaft housing provides a primary annular capillary seal segment. An annular bushing ring extends from the housing radially inwardly to enclose the thrust bearing disk, and cooperates with an adjacent outer face of the thrust bearing disk to provide a secondary containment capillary seal segment. Normally, lubricating liquid is in the bearing unit at the radial hydrodynamic bearing, at the hydrodynamic thrust bearing and in the primary annular capillary seal segment. However, if liquid overflows from, or extends beyond the primary seal segment as by thermal expansion, it is contained in the secondary seal segment and urged to return by centrifugal force to the primary seal segment. A tertiary containment seal may also be provided to prevent escape of liquid to the external ambient.

Claims

1. A self-contained hydrodynamic bearing unit comprising a shaft and a shaft housing defining an opening for receiving the shaft for relative rotation, at least one radial hydrodynamic bearing defined between the shaft and the shaft housing, the shaft defining an annular thrust bearing disk portion extending radially outward of a main cylindrical surface of the shaft and cooperating with an adjacent annular face of the shaft housing to define a hydrodynamic thrust bearing, a gap being formed between an outer cylindrical wall of the thrust bearing disk portion and an adjacently facing cylindrical surface of the shaft housing for defining a primary annular surface tension capillary seal, and an annular bushing ring extending from the housing radially inwardly to enclose the thrust bearing disk, at least one of the annular bushing ring and an adjacent outer face of the thrust bearing disk forming a secondary containment capillary seal, there normally being lubricating liquid in the bearing unit at the radial hydrodynamic bearing, at the hydrodynamic thrust bearing and in the primary annular capillary seal, the secondary containment capillary seal for containing overflow of lubricating liquid from the primary annular capillary seal, the trapped lubricating liquid being urged toward the primary annular capillary seal by centrifugal force generated by the relative rotation between the shaft and the shaft housing.

2. The self-contained hydrodynamic bearing unit set forth in claim 1 wherein one of the annular bushing ring and the adjacent outer face of the thrust bearing disk define an interior annular plateau region for trapping lubricating liquid otherwise escaping from the primary annular capillary seal.

3. The self-contained hydrodynamic bearing unit set forth in claim 2 wherein the secondary containment capillary seal is coated with a thin film barrier material for impeding surface flow of the lubricating liquid droplets.

4. The self-contained hydrodynamic bearing unit set forth in claim 1 wherein the outer cylindrical wall of the thrust bearing portion and the adjacently facing cylindrical surface define a divergent gap for the primary annular capillary seal.

5. The self-contained hydrodynamic bearing unit set forth in claim 1 further comprising a tertiary containment capillary seal for trapping lubricating liquid droplets otherwise escaping from the secondary containment capillary seal, the tertiary containment capillary seal being formed by a narrow cylindrical gap defined between the shaft and an inner face of the annular bushing ring.

6. The self-contained hydrodynamic bearing unit set forth in claim 5 wherein the tertiary containment capillary seal is coated with a thin film barrier material for impeding surface flow of the lubricating liquid droplets.

7. A self-contained hydrodynamic bearing unit comprising a shaft and a shaft housing defining an opening for receiving the shaft for relative rotation, a plurality of spaced apart radial hydrodynamic bearings defined between the shaft and the shaft housing and separated by a central reservoir region containing a lubricating liquid, a pair of end reservoirs containing the lubricating liquid and located axially outside of the plurality of radial bearings, a pair of annular hydrodynamic thrust bearing ring portions of the shaft extending toward the shaft housing outwardly adjacent the pair of end reservoirs, a pair of primary annular surface tension capillary seals formed at annular gaps defined by oppositely facing cylindrical faces of the thrust bearing ring portions and the shaft housing, and a pair of annular static bushings secured to the shaft housing and aligned with and overlying the thrust bearing ring portions, one of each static bushing and an outer face of an adjacent thrust bearing ring portion defining an annular plateau forming a narrowed gap secondary containment capillary seal for trapping lubricating liquid droplets otherwise escaping from an adjacent primary capillary seal due to shock forces or vibration, the lubricating liquid being trapped at the secondary containment capillary seal being drawn back into to the adjacent primary annular capillary seal by centrifugal force during relative rotation between the shaft and shaft housing.

8. The self-contained hydrodynamic bearing unit set forth in claim 7 wherein each pair of annular static bushings define an annular plateau which faces the oppositely facing outer face of an adjacent thrust bearing ring portion thereby to form each said narrowed gap secondary containment seal.

9. The self-contained hydrodynamic bearing unit set forth in claim 7 wherein the annular gaps defined by oppositely facing cylindrical faces of the thrust bearing ring portions and the shaft housing are outwardly divergent.

10. The self-contained hydrodynamic bearing unit set forth in claim 7 further comprising a pair of tertiary containment capillary seals defined by narrow, axially extending cylindrical spaces adjacent inside walls of the annular static bushings.

11. The self-contained hydrodynamic bearing unit set forth in claim 10 wherein the tertiary containment capillary seals are coated with a thin film barrier material for impeding surface flow of the lubricating liquid droplets.

12. The self-contained hydrodynamic bearing unit set forth in claim 7 wherein the secondary containment capillary seals are coated with a thin film barrier material for impeding surface flow of the lubricating liquid droplets.

13. A self-contained fluid bearing disk spindle assembly for a hard disk drive comprising:

a base,

a shaft secured to the base,

a shaft sleeve defining an opening for receiving the shaft for relative rotation,

a disk hub secured to the shaft sleeve,

at least one data storage disk secured to the disk hub,

DC brushless spindle motor means having a fixed stator assembly secured to the base and an annular permanent magnet assembly secured to an inner cylindrical face of the disk hub, for rotating the disk hub relative to the base at a predetermined unidirectional angular velocity,

the shaft and the shaft sleeve cooperatively defining a pair of radial hydrodynamic bearings spaced apart along the shaft, a central reservoir for lubricating liquid between the pair of radial hydrodynamic bearings and a pair of end reservoirs axially outside of the pair of radial hydrodynamic bearings,

a lower thrust bearing ring secured to the shaft axially beyond a lower one of the end reservoirs and facing a lower radial wall of the shaft sleeve for defining a lower fluid thrust bearing communicating with a lower one of the end reservoirs,

an upper thrust bearing plate secured to the shaft axially beyond an upper one of the end reservoirs and facing an upper radial wall of the shaft sleeve for defining an upper fluid thrust bearing communicating with an upper one of the end reservoirs,

an upper annular primary surface tension capillary seal formed in an annular gap defined by oppositely facing cylindrical faces of the upper thrust bearing plate and the shaft sleeve,

a lower annular primary surface tension capillary seal formed in an annular gap defined by oppositely facing cylindrical faces of the lower thrust bearing ring and the shaft sleeve,

an upper containment bushing secured to the shaft sleeve and having an inside wall cooperating with a facing outer wall of the upper thrust bearing plate to define an upper secondary containment capillary seal,

a lower containment bushing secured to the shaft sleeve and having an inside wall cooperating with a facing outer wall of the lower thrust bearing ring to define a lower secondary containment capillary seal, and

lubricating liquid in the central reservoir, end reservoirs and primary capillary seals, and forming lubricating films at the pair of radial hydrodynamic bearings and at the upper and lower thrust bearings, the upper secondary containment capillary seal, and the lower secondary containment capillary seal for for holding lubricating liquid flowing from one of the primary capillary seals and for urging the lubricating liquid to flow toward an adjacent one of the primary capillary seals in response to centrifugal force generated during relative rotation of the fluid bearing disk spindle assembly.

14. The self-contained fluid bearing disk spindle assembly set forth in claim 13 wherein the upper containment bushing and the lower containment bushing cooperate with respective adjacent facing outer walls of the upper and lower thrust bearings to define narrowed annular gap regions including plateaus enabling the upper and lower secondary containment capillary seals to trap and capture droplets of lubricating liquid otherwise escaping from an adjacent one of the primary capillary seals.

15. The self-contained fluid bearing disk spindle assembly set forth in claim 14 wherein the facing walls forming the annular gaps of the upper and lower annular primary capillary seals are outwardly axially divergent.

16. The self-contained fluid bearing disk spindle assembly set forth in claim 13 further comprising an upper tertiary containment capillary seal formed in a cylindrical gap between the upper thrust bearing plate and the upper bushing, and a lower tertiary containment capillary seal formed in a cylindrical gap between the shaft and the lower bushing, for trapping and containing lubricating liquid droplets escaping from an adjacent one of the secondary containment capillary seals.

17. The self-contained fluid bearing disk spindle assembly set forth in claim 16 wherein adjacent gap faces forming the upper and lower tertiary containment capillary seals are coated with a thin film barrier material.

18. The self-contained fluid bearing disk spindle assembly set forth in claim 13 wherein adjacent faces of the cylindrical gap between the upper thrust bearing plate and the upper bearing are coated with a thin film barrier material.

19. A self-contained hydrodynamic bearing unit having a first surface tension capillary seal, the bearing unit comprising:

a shaft and a sleeve defining an opening for receiving the shaft and being dimensioned relative to the shaft to enable relative rotation about an axis,

a first hydrodynamic journal bearing defined between a main cylindrical surface of the shaft and the sleeve,

the shaft including a first annular thrust bearing disk portion extending radially outwardly from the main cylindrical surface and cooperating with an adjacent annular face of the sleeve to define a first hydrodynamic thrust bearing,

a first gap defined between an outer wall of the first thrust bearing disk portion and an adjacently facing surface of the sleeve comprising an axial segment of the capillary seal,

a first annular bushing ring extending from the sleeve radially inwardly toward the shaft to enclose the first annular thrust bearing disk portion and defining in combination with the shaft a radially inward axial opening to ambient,

a second gap defined between the bushing ring and an adjacent face of the thrust bearing disk portion comprising a radial segment of the first surface tension capillary seal,

the axial segment of the first surface tension capillary seal being contiguous with the radial segment of the capillary seal,

hydrodynamic lubricating liquid in the bearing unit at the first hydrodynamic journal bearing, at the first hydrodynamic thrust bearing and in at least the axial segment of the first surface tension capillary seal,

the radial segment for receiving and holding lubricating liquid otherwise flowing out of the axial segment of the seal capillary seal,

the lubricating liquid in the radial segment being forced toward the axial segment of the capillary seal by centrifugal force resulting from relative rotation between the shaft and the sleeve.

20. The self-contained hydrodynamic bearing unit set forth in claim 19 wherein the outer wall of the first thrust bearing disk portion and the adjacently facing surface of the sleeve define a divergent wall gap which diverges in an axial direction away from a region of the first hydrodynamic thrust bearing.

21. The self-contained hydrodynamic bearing unit set forth in claim 20 wherein an inside radial wall of the first annular bushing ring and the adjacent face of the first thrust bearing disk portion diverge toward the axis of rotation.

22. The self-contained hydrodynamic bearing unit set forth in claim 19 wherein adjacently facing walls of the shaft and the first annular bushing ring defining the axial opening to ambient are coated with a thin film barrier material.

23. The self-contained hydrodynamic bearing unit set forth in claim 19 further comprising:

a second hydrodynamic journal bearing defined between the main cylindrical surface of the shaft and the sleeve and axially spaced away from the first hydrodynamic journal bearing,

the shaft including a second annular thrust bearing disk portion extending radially outwardly from the main cylindrical surface and cooperating with an adjacent annular face of the sleeve to define a second hydrodynamic thrust bearing,

the first and second hydrodynamic journal bearings being located inwardly of the first and second annular thrust bearing disk portions,

a central hydrodynamic lubricant reservoir defined in a gap between the shaft and sleeve between the first and second hydrodynamic journal bearings,

a second gap defined between an outer wall of the second thrust bearing disk portion and an adjacently facing surface of the sleeve comprising an axial segment of a second surface tension capillary seal,

a second annular bushing ring extending from the sleeve radially inwardly toward the shaft to enclose the second annular thrust bearing disk portion and defining in combination with the shaft a second radially inward axial opening to ambient,

a second gap defined between the second bushing ring and an adjacent face of the second thrust bearing disk portion comprising a radial segment of the second surface tension capillary seal,

the axial segment of the second surface tension capillary seal being contiguous with the radial segment of the second capillary seal,

hydrodynamic lubricating liquid also present in the bearing unit at the central hydrodynamic lubricant reservoir, at the second hydrodynamic journal bearing, at the second hydrodynamic thrust bearing and in at least the axial segment of the second surface tension capillary seal,

the radial segment for receiving and holding lubricating liquid otherwise flowing out of the axial segment of the second capillary seal,

the lubricating liquid in the radial segment of the second capillary seal also being forced toward the axial segment of the second capillary seal by centrifugal force resulting from relative rotation between the shaft and the sleeve.

24. The self-contained hydrodynamic bearing unit set forth in claim 23 wherein the outer wall of the second thrust bearing disk portion and the adjacently facing surface of the sleeve define a divergent wall gap which diverges in an axial direction away from a region of the second hydrodynamic thrust bearing.

25. The self-contained hydrodynamic bearing unit set forth in claim 24 wherein an inside radial wall of the second annular bushing ring and the adjacent face of the second thrust bearing disk portion diverge toward the axis of rotation.

26. The self-contained hydrodynamic bearing unit set forth in claim 23 adjacently facing walls of the shaft and the second annular bushing ring defining the axial opening to ambient are coated with a thin film barrier material.