Axial bearing fly-height measurement to detect oil deficiency

Details Axial bearing fly-height measurement to detect oil deficiency Axial bearing fly-height measurement to detect oil deficiency

1998-08-05

2001-01-09

Assouad, Patrick (Department: 2857)

Data processing: measuring, calibrating, or testing

Measurement system in a specific environment

Mechanical measurement system

C310S090500

Reexamination Certificate

active

06173234

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to hydrodynamic fluid bearings for motors such as are utilized in hard disk drives, and more particularly to methods for determining whether sufficient oil resides within the bearing following assembly thereof.
2. Description of the Prior Art
Hydrodynamic fluid bearing motors are utilized in applications that require high speed reliable performance, such as in hard disk drives. Such motors have close tolerances and require the insertion of an adequate quantity of fluid into the hydrodynamic fluid bearing during manufacturing. If insufficient fluid is inserted into the bearing during the manufacturing process, the operational lifetime of the motor can be shortened significantly. However, because such motors are sealed following the fluid insertion step, there has been no way to determine, following sealing of the motor, whether sufficient oil was inserted therewithin. Therefore, while an important step in the quality control evaluation of such motors should involve a determination of whether sufficient fluid has been inserted into the hydrodynamic fluid bearing during the manufacturing thereof, there has been no method to make this determination.
The present invention provides a solution to this problem in a recognition that the fly-height of the hydrodynamic fluid bearing is affected by the quantity of fluid within the bearing, and in the development of a device and method for determining the fly-height of the hydrodynamic fluid bearing. As a result, the present invention provides a device and method for determining the fly-height of the bearing as a measure of the sufficiency of oil therewithin, and thus a measure of the quality of the motor.
SUMMARY OF THE INVENTION
The method for determining the sufficiency of fluid in a hydrodynamic fluid bearing motor involves making a first determination of a range of fluid bearing fly-heights for motors having a sufficient quantity of fluid within the hydrodynamic fluid bearing, and for motors having an insufficient quantity of fluid within the hydrodynamic fluid bearing. Thereafter, the fly-height of a particular hydrodynamic fluid bearing motors can be determined and compared with the range of hydrodynamic fluid bearing fly-heights to provide a determination of the sufficiency of fluid within the particular hydrodynamic fluid bearing motor. Determining the fly-height of a particular hydrodynamic fluid bearing motor involves the utilization of non-contact displacement probes that generate a first signal indicative of the displacement of a rotating component of the bearing at a time when the component is rotating at a maximum fly-height. The probes then generate a second signal indicative of the displacement of the rotating component at a time when said component has ceased its flying within the hydrodynamic bearing. The difference between the first and second signals is an indication of the fly-height of said hydrodynamic fluid bearing of said particular motor.
It is an advantage of the present invention that a method for determining the quality of hydrodynamic fluid bearing motors is provided.
It is another advantage of the present invention that the sufficiency of fluid within a hydrodynamic fluid bearing can be determined.
It is a further advantage of the present invention that the fly-height of components of a hydrodynamic fluid bearing can be determined.
It is yet another advantage of the present invention that improved hydrodynamic fluid bearing motors are produced.
It is yet a further advantage of the present invention that improved hard disk drive motors are produced.
These and other features and advantages of the present invention will become apparent to those skilled in the art upon reading the following detailed description of the invention which makes reference to the several figures of the drawings.


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