Bearings – Rotary bearing – Fluid bearing
Patent
1996-12-09
1998-08-18
Hannon, Thomas R.
Bearings
Rotary bearing
Fluid bearing
384121, F16C 3200
Patent
active
057950741
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to hydrodynamic thrust bearing configuration for a spindle motor assembly. More specifically, the invention relates to the groove configuration of a hydrodynamic thrust bearing for use in a computer hard disc drive spindle motor assembly.
BACKGROUND OF THE INVENTION
Computer hard disc drives generally comprise an array of magnetic discs mounted to a spindle motor assembly. Data is written to, and read from, each magnetic disc by means of a read/write head located at the end of an arm which extends between the discs. Positioning of the arm is accomplished by means of a voice coil motor under the control of disc drive control electronics.
The array of magnetic discs is mounted to a hub of the spindle motor assembly. The hub is mounted for rotation with respect to a base of the spindle motor assembly by means of a bearing arrangement. In use, the hub is rotated by means of an electromagnetic motor.
In order to facilitate the accurate positioning of the read/write heads between the magnetic discs, the bearing arrangement is required to run substantially vibation-free and to have a small deflection under the application of external loads (i.e., have a high bearing stiffness). The bearing arrangement is also expected to have a long, maintenance-free service life. The continuous trend of miniaturization in the computer industry has meant that the above functions have to be accomplished by a bearing arrangement which occupies as little volume as possible.
The bearing arrangements used in computer disc drive spindle motor assemblies are often hydrodynamic bearing arrangements, which include at least one hydrodynamic thrust bearing. The thrust bearing comprises a thrust plate and an opposed counter plate, each of which define a bearing surface. Either one of the bearing surfaces is formed with a pattern of grooves. The two bearing surfaces are separated in use by a film of lubricant. Pressures generated in the lubricant by the relative rotation of the bearing surfaces keep the bearing surfaces apart and ensure smooth rotation of the bearing arrangement.
The axial load bearing capacity and other static and dynamic characteristics of the thrust bearing depend on the pressure rise in the lubricant film and on the distribution of pressure across the thrust bearing. The pressure rise and distribution in turn depend on the design of the grooving pattern, e.g. the angle of the grooves, the groove pitch ratio, the groove depth and the center radius of the thrust or counter plate.
Current grooved thrust bearings have been designed with a view to maximizing bearing performance. This increased performance has been at the expense of ease of manufacture of the grooved bearing surface. In particular, groove densities and configurations have resulted in shortened lifespans of punch and die combinations used to form the groove pattern.
Accordingly, there is a need for a groove pattern which provides good thrust bearing performance without adversely affecting the manufacturability of the thrust bearing.
SUMMARY OF THE INVENTION
The present invention provides a grooved hydrodynamic thrust bearing comprising first and second bearing surfaces. The first and second bearing surfaces are rotatable relative to one another and are separated by a bearing fluid.
The first bearing surface defines a plurality of continuous lands extending from an inner radius to an outer radius. Adjacent continuous lands define between them a continuous groove having an approximately constant depth and extending in unbroken fashion between the inner radius and the outer radius. The continuous groove has an undivided portion in an inner annulus of the first bearing surface and a divided portion in an outer annulus of the first bearing surface, and is divided in the divided portion by an intermediate land located between the two adjacent continuous lands. The divided portion of the continuous groove communicates in unbroken fashion with the undivided portion of the continuous groove.
Other features of the prese
REFERENCES:
patent: 3870382 (1975-03-01), Reinhoudt
patent: 4728201 (1988-03-01), Abbe
patent: 5433529 (1995-07-01), Hensel
patent: 5492341 (1996-02-01), Pecht et al.
Clark Wesley
Leuthold Hans
Rahman Mohamed M.
Hannon Thomas R.
Seagate Technology Inc.
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