Dynamic magnetic information storage or retrieval – Record transport with head stationary during transducing – Disk record
Patent
1997-12-19
2000-10-24
Heinz, A. J.
Dynamic magnetic information storage or retrieval
Record transport with head stationary during transducing
Disk record
360 9908, G11B 1708
Patent
active
061376507
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to magnetic disc drive storage systems, and more specifically, the present invention relates to a hydrodynamic fluid bearing for use in a magnetic disc drive storage system.
BACKGROUND OF THE INVENTION
Magnetic disc drives are used for magnetically storing information. In a magnetic disc drive, a magnetic disc rotates at high speed and a transducing head "flies" over a surface of the disc. This transducing head records information on the disc surface by impressing a magnetic field on the disc. Information is read back using the head by detecting magnetization of the disc surface. The transducing head is moved radially across the surface of the disc so that different data tracks can be read back.
Over the years, storage density has tended to increase and the size of the storage system has tended to decrease. This trend has lead to greater precision and lower tolerance in the manufacturing and operating of magnetic storage discs. For example, to achieve increased storage densities the transducing head must be placed increasingly close to the surface of the storage disc. This proximity requires that the disc rotate substantially in a single plane. A slight wobble or run-out in disc rotation can cause the surface of the disc to contact the transducing head. This is known as a "crash" and can damage the transducing head and surface of the storage disc resulting in loss of data.
From the foregoing discussion, it can be seen that the bearing assembly which supports the storage disc is of critical importance. One typical bearing assembly comprises ball bearings supported between a pair races which allow a hub of a storage disc to rotate relative to a fixed member. However, ball bearing assemblies have many mechanical problems such as wear, dents in balls or raceways, run-out and manufacturing difficulties. Moreover, resistance to operating shock and vibration is poor because of low damping. Thus, there has been a search for alternative bearing assemblies for use with high density magnetic storage discs.
One alternative bearing design which has been investigated is a hydrodynamic bearing. In a hydrodynamic bearing, a lubricating fluid such as air or liquid provides a bearing surface between a fixed member of the housing and a rotating member of the disc hub. In addition to air, typical lubricants include oil or ferromagnetic fluids. Hydrodynamic bearings spread the bearing interface over a large surface area in comparison with a ball bearing assembly which comprises a series of point interfaces. This is desirable because the increased bearing surface reduces wobble or run-out between the rotating and fixed members. Further, the use of fluid in the interface area imparts damping effects to the bearing which helps to reduce non-repeat runout.
However, hydrodynanic bearings themselves suffer from a number of disadvantages. These disadvantages include a low stiffness-to-power ratio.
SUMMARY OF THE INVENTION
Thus, it is an object of the present invention to create an improved hydrodynamic fluid bearing which is relatively insensitive to shock, vibration, changes in load and rotational speed and is dynamically more stable.
A related objective of the invention is to provide a hydrodynamic bearing open at both ends in which the balance of fluid flow within the bearings is maintained.
Yet another object of the present invention is to provide a hydrodynamic bearing assembly which is more easily assembled, and in which the gaps are easily adjusted.
A further objective of the invention is to provide a hydrodynamic bearing design in which the tolerances for assembly of the various components is minimized; that is, the critical nature of many of the gaps is diminished.
Another objective of the invention is to provide a hydrodynamic bearing useful in a spindle motor or the like which is stiffer than known standard spindle motors which are supported only at one end.
These and other objectives of the invention are achieved by a hydrodynamic fluid bearing useful in a bearin
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patent: 5488521 (1996-01-01), Lemke et al.
patent: 5969448 (1999-10-01), Liu
Heine Gunter Karl
Khan Raquib Uddin
Leuthold Hans
Rahman Mohamed Mizanur
Heinz A. J.
Seagate Technology L.L.C.
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