Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C32/00—Bearings not otherwise provided for
  • F16C32/06—Bearings not otherwise provided for with moving member supported by a fluid cushion formed, at least to a large extent, otherwise than by movement of the shaft, e.g. hydrostatic air-cushion bearings
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
  • F16C33/02—Parts of sliding-contact bearings
  • F16C33/04—Brasses; Bushes; Linings
  • F16C33/06—Sliding surface mainly made of metal
  • F16C33/10—Construction relative to lubrication
  • F16C33/1025—Construction relative to lubrication with liquid, e.g. oil, as lubricant
  • F16C33/106—Details of distribution or circulation inside the bearings, e.g. details of the bearing surfaces to affect flow or pressure of the liquid
  • F16C33/107—Grooves for generating pressure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C17/00—Sliding-contact bearings for exclusively rotary movement
  • F16C17/02—Sliding-contact bearings for exclusively rotary movement for radial load only
  • F16C17/026—Sliding-contact bearings for exclusively rotary movement for radial load only with helical grooves in the bearing surface to generate hydrodynamic pressure, e.g. herringbone grooves
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C17/00—Sliding-contact bearings for exclusively rotary movement
  • F16C17/10—Sliding-contact bearings for exclusively rotary movement for both radial and axial load
  • F16C17/102—Sliding-contact bearings for exclusively rotary movement for both radial and axial load with grooves in the bearing surface to generate hydrodynamic pressure
  • F16C17/107—Sliding-contact bearings for exclusively rotary movement for both radial and axial load with grooves in the bearing surface to generate hydrodynamic pressure with at least one surface for radial load and at least one surface for axial load

Definitions

• FIELD OF THE INVENTION Present invention relates to the field of hydrodynamic bearing assemblies which provide support during rotation of a high speed spindle element. More specifically, the present invention relates especially to the use of a hydrodynamic bearing assembly for utilization in an infor ⁇ mation recording system.
• This application is related to and may be used in common with the invention disclosed in attorney's docket A59757 entitled Hub Disc Assembly with Integrated Air Bearing, inventor H. Leuthold, et al., as well as attorney's docket A59756 entitled Single Plate Hydrodynamic Bearing with Self Balancing Fluid Level, inventor Hans Leuthold, et al. and attorneys docket A59788 entitled Single Plate Hydrodynamic Bearing with Self Balancing Fluid Level and Fluid Circulation, inventor Hans Leuthold, et al., and attorneys docket A59715 entitled Sleeve Grooving Tool, inventor Clark et al., all of said applications being assigned to the assignee of the present invention and incorporated herein by reference.
• Disc drive memory systems have been used in computers for many years for storage of digital information. Such information is recorded on concentric memory tracks of a magnetic disc medium, the actual information being stored in the form of magnetic transitions within the medium.
• the discs themselves are rotatably mounted on a spindle, the information being accessed by means of read write heads supported on a pivoting arm which moves radially over the surface of the disc.
• the read write heads or transducer must be accurately aligned with the storage tracks on the disc to ensure proper reading and writing of information.
• the discs are rotated at very high speeds within an enclosed housing by means of an electric motor generally located inside the hub or below the discs.
• an electric motor generally located inside the hub or below the discs.
• One type of motor in common use is known as an in hub or in spindle motor.
• Such in spindle motors typically have a spindle mounted by means of ball bearing systems to a motor shaft disposed in the center of the hub.
• ball bearing systems to a motor shaft disposed in the center of the hub.
• hydrodynamic bearings are being developed. Useful designs are disclosed in the incorporated applications.
• a lubricating fluid functions as the actual bearing surface between a stationary base or housing and the rotating spindle or hub and the surrounding stationary portion of the motor.
• These fluids either gas or liquid must be sealed within the bearing to avoid loss of the lubricant which would result in reduced bearing load capacity. Otherwise, the physical surfaces of the spindle and housing would contact one another, leading to increased wear and eventual failure of the bearing system. Equally seriously, loss of the seal or failure to control the lubricant level within the bearing system could cause contamination of the hard disc drive with lubricant particles and droplets or outgassing related contamination.
• a further critical issue is the need to maintain the stiffness of the hydrodynamic bearing.
• the stiffer the bearing the higher the natural frequencies in the radial and axial direction, so that the more stable is the track of the disc being rotated by a spindle on which reading and writing must occur.
• the stiffness of the bearing in the absence of any mechanical contact between its rotating part becomes critical in the design of the bearing so that the rotating load can be stably and accurately supported on the spindle without wobble or tilt.
• a typical prior art grooving pattern is shown in Figure 1. This pattern was adopted having a constant grooving angle ⁇ which is the angle defined by the groove and the circumference of the cylindrical surface as a constant angle.
• the pattern provides points of high pressure 10 to seek to optimize the stiffness of the bearing, while providing the desired pumping action of the lubricant to maintain the lubricant surface covered with fluid while minimizing the possibilities of fluid escape.
• the grooves are difficult to form, and the tools used to form the grooves wear out quickly.
• a further related objective of the invention is to provide a grooving pattern on the bearing which is easier to define and can be reliably and repeatedly formed on the bearing surface without undue wear on the grooving tool.
• the present invention provides a hydrody- namic bearing characterized in that the continuous grooving pattern along the axis of rotation is designed to have a maximum pumping effect at the bearing boundaries, and an overall optimized load carrying capability independent of journal length and radius.
• This is achieved by providing a sinusoidal grooving pattern having a grooving angle which varies such that the center line of a groove lies on a sinusoidal half period.
• a sinusoidal pattern there are no sharp peaks or points where the groove changes direction, but rather where the grooves change direction a circular segment is formed so that the surface groove forms a sinusoid.
• the result of the adoption of such a pattern is to provide for a greater pressure distribution along the axis of rotation while reducing the total amount of surface area which the grooves actually occupy.
• Figure 1 illustrates a conventional grooving pattern used in hydrodynamic bearings
• Figure 2 illustrates the sinusoidal grooving pattern of the present invention
• Figure 3 is a vertical sectional view of a portion of a motor incorporating a hydrodynamic bearing with which the present grooving pattern is useful;
• Figure 4 illustrates the relative placement of the sinusoidal grooving pattern relative to the structure of the motor of Figure 3.
• FIG. 2 An example of the sinusoidal grooving pattern of the present invention is shown in Figure 2.
• the grooving angle which is the angle between the groove 20 and the axis of rotation 14 of the hydrodynamic bearing varies such that the center line of the groove lies on a sinusoidal half periods (equal to the absolute value of a sinusoid) .
• only the central portion of the pattern is a sinusoid. This provides the advantage of increased lift force in the bearing, because of the reduction in surface area occupied by the grooves while maintaining fluid distribution. This reduction in surface area is clearly illustrated.
• the end portions of the groove pattern are substan ⁇ tially linear.
• the grooved surface can either be on the shaft, or on the surface facing the shaft, and that either the shaft or the bearing surface surrounding it may be the rotating surface. It is the relative rotation of the two surfaces which creates the pumping action which distributes the lubricant between the two surfaces to create the pressure between the surfaces and establish the stiff ⁇ ness and load carrying capacity of the hydrodynamic bearing.
• Figure 3 illustrates a motor in which the present groove design may be utilized. Obviously, use of the design is not limited to motors of the type shown in Figure 3.
• Figure 3 includes a shaft 52 which is rotating past a fixed bushing 70.
• the rotating shaft 52 includes a reser ⁇ voir 54 which supplies fluid through a groove 56 to the surface of the hydrodynamic bearing.
• the hydrodynamic bearing itself is formed between the two relatively rotating surfaces 60, 72.
• the upper end of the bearing terminates in a region generally indicated at 80 where the incline surface 82 slopes away from the recess 84 in the surface 60 to form a meniscus which will hold the fluid within the bearing.
• the lower end of the bearing terminates at a region 90 where the rotating shaft joins a thrust plate 74 the surface 60 including a recess 76 for enabling the joining of the thrust plate to the rotating shaft.
• Figure 4 is an illustrative embodiment of the appli ⁇ cation of the sinusoidal group pattern of the present invention to the bushing 70 which faces the shaft 52.
• the significant portions of the rotating shaft 52 and thrust plate 70 are labeled, especially the angled surface 82 which together with the recess 84 defines the open end of the hydrodynamic bearing, and the region 90 which is defined by thrust plate 74 and recess 75 to denote the closed end of the bearing.
• the distribution of the sinusoidally curved grooving pattern across the surface in this case of the bushing 70 is illustrated by the sine curve 100 of Figure 4 which has a lower circular segment 102 which is positioned to be immediately adjacent the lubricant providing groove 56 and defined there by the region of lowest pressure within the hydrodynamic bearing.
• the regions of highest pressure will be at the curved segments which are the high points of the curve generally indicated in this figure by 104, 106.
• the end points of the sinusoidal pattern are indicated at the thrust bearing end 108 and the hub supporting end 110.
• the only difference between the patterns at the ends of the bearing is that a sufficient extension of the pattern at the open support end 110 will be provided to urge the lubricant toward the center of the hydrodynamic bearing to prevent the lubricant from exiting the bearing region.
• a region of equal pressure 90 is desirably defined so that equal distribution of the fluid across the surface of the hydrodynamic bearing is achieved and maintained.
• This pattern of grooves may be provided either on the rotating shaft, or on the stationary surface facing the rotating shaft. In either event, the pattern will serve to both create pressure between the rotating surface and the fixed surface, and to maintain the fluid within the gap between the rotating and fixed surfaces, without causing the lubricant to be ejected.
• the radial load carrying capacity of the bearing is established by the hydrodynamic lubricant pressure established between the grooved surface and the ungrooved surface.
• this bearing grooving pattern will be highly efficient in creating a stable hydrodynamic bearing system especially for use in disc drives and the like.
• the grooving pattern herein is described as sinusoidal, as this is the preferred format. However other grooved patterns where the transition regions are curved are also possible and would achieve some of the benefits of this invention and are intended to be within the scope of this invention.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Sliding-Contact Bearings (AREA)

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• 1994
  • 1994-11-14 WO PCT/US1994/013136 patent/WO1996015381A1/en not_active Ceased
  • 1994-11-14 EP EP95907190A patent/EP0828952A1/en not_active Ceased
  • 1994-11-14 JP JP51600296A patent/JP3352697B2/ja not_active Expired - Lifetime
  • 1994-11-14 KR KR1019970703307A patent/KR100220149B1/ko not_active Expired - Fee Related

Non-Patent Citations (2)

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