Self-contained hydrodynamic bearing unit and seals

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.

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.

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.