Bearing structure

A bearing structure comprising:

• an inner shaft;
• an outer sleeve;
• a pair of roller bearings axially spaced and interposed between the inner shaft and the outer sleeve;
• and
• a preload means for exerting a preload on the roller bearings;
• wherein coefficients of linear expansion of the inner shaft and the outer sleeve being made different in an axial direction, and the change in rotational torque which, because of the lubricant enclosed in the roller bearings, becomes lower as the temperature rises and higher as the temperature falls being canceled with the change in the preload which, because of the different coefficients of linear expansion, becomes higher as the temperature rises and lower as the temperature falls.

A method of forming a bearing structure, comprising the steps of:

• combining an inner shaft and an outer sleeve, each having coefficients of linear expansion that are different in an axial direction;
• interposing a pair of axially spaced roller bearings between the inner shaft and the outer sleeve;
• exerting a preload on the roller bearings, a first rotational torque derived from the preload increasing with a rise in temperature and decreasing with a fall in temperature as a result of the coefficients of linear expansion of the inner shaft and the outer sleeve being different;
• applying a lubricant to the roller bearings, the lubricant exerting a second rotational torque, the second rotational torque becoming lower as the temperature of the lubricant rises and higher as the temperature of the lubricant falls, the first and second rotational torques being cancelled out.

A disk drive system, comprising:

• a device enclosure having a bottom base and a cover;
• at least one storage disk;
• a motor, coupled to the device enclosure and the storage disk, for rotating the storage disk;
• an actuator assembly, disposed within the enclosure housing, for moving a head arm relative to the disk, the head arm having a magnetic head installed on one end thereof, the head arm being rotatably supported at an intermediate portion on the base through a pivot bearing, the pivot bearing comprising:
• an inner shaft;
• an outer sleeve;
• a pair of roller bearings axially spaced and interposed between the inner shaft and the outer sleeve;
• and
• a preload means for exerting a preload on the roller bearings;
• wherein coefficients of linear expansion of the inner shaft and the outer sleeve being made different in an axial direction, and the rotational torque resulting from a temperature change because of the lubricant enclosed in the roller bearings has been canceled with the change in the preload resulting from the temperature change because of the different coefficients of linear expansion.