LOW HYSTERESIS BEARING
A low hysteresis pivot bearing suitable for a variety of applications. The relationship between torque and angular displacement is substantially linear, with negligible residual hysteresis. The pivot bearing includes a pivot shaft and an inner sleeve pivotally attached to the pivot shaft by an inner bearing. An outer sleeve is pivotally attached to the inner sleeve by an outer bearing. An inner sleeve actuator continuously rotates the inner sleeve relative to the stationary shaft.
1 . A pivot bearing for use in a rotary actuator of a hard disk drive, the pivot bearing comprising:
a pivot shaft;
an inner sleeve pivotally attached to the pivot shaft by an inner bearing;
an outer sleeve pivotally attached to the inner sleeve by an outer bearing;
an inner sleeve actuator adapted to rotate at least one of the inner sleeves relative to the stationary shaft.
2 . The pivot bearing of claim 1 wherein the inner sleeve actuator is coupled to the pivot shaft and one of an inner surface of the inner sleeve or a distal end of the inner sleeve.
3 . The pivot bearing of claim 1 comprising hydrodynamic features at one or more interfaces between the pivot shaft, the inner sleeve, and the outer sleeve.
4 . The pivot bearing of claim 1 wherein the inner sleeve actuator comprises a DC motor with a magnet mounted to one of the inner sleeve or the stationary shaft and a stator mounted to the other of the inner sleeve or the stationary shaft.
5 . The pivot bearing of claim 1 wherein the inner sleeve actuator rotates the inner sleeve at about 1 revolution per minute to about 100 revolutions per minute.
6 . The pivot bearing of claim 1 wherein a relationship of torque applied to the pivot bearing to angular displacement of the pivot bearing is substantially linear.
7 . The pivot bearing of claim 1 comprising a controller programmed to actuate the inner sleeve actuator only during position critical rotation.
8 . The pivot bearing of claim 12 wherein the controller is the servo controller for a hard disk drive.
9 . A pivot bearing, the pivot bearing comprising:
a pivot shaft;
an inner sleeve pivotally attached to the pivot shaft by an inner bearing; and
an outer sleeve pivotally attached to the inner sleeve by an outer bearing.
10 . A hard disk drive comprising:
at least one suspension arm that positions magnetic transducers over selected information tracks on rotating magnetic disks; and
a pivot bearing rotatably supporting the suspension arms relative to the rotating magnetic disks, the pivot bearing including at least one inner sleeve pivotally attached to a pivot shaft by an inner bearing, at least one outer sleeve pivotally attached to the inner sleeve by an outer bearing, and at least one inner sleeve actuator adapted to rotate the inner sleeve relative to the stationary shaft.
11 . The hard disk drive of claim 10 further comprising a controller programmed to actuate the inner sleeve actuator of the pivot bearing only during position critical rotation.
12 . The hard disk drive of claim 10 further comprising a controller programmed to rotate the inner sleeve of the pivot bearing continuously or intermittently.
13 . The hard disk drive of claim 11 wherein the controller is at least a portion of a servo controller for the hard disk drive.
14 . The pivot bearing of claim 10 further comprings a controller programmed to rotate the inner sleeve in a same direction or opposite direction of rotation of the outer sleeve.
15 . The hard disk drive of claim 10 further comprising a controller programmed to apply one of a current or voltage to a voice coil motor attached to the suspension arm that is proportional to a current or voltage applied to the inner sleeve actuator.
16 . A method of operating a hard disk drive comprising the steps of:
supporting at least one suspension arm by an outer sleeve of a pivot bearing;
rotating an inner sleeve of the pivot bearing arranged concentric with the outer sleeve relative to a pivot shaft; and
rotating the suspension arms and the outer sleeve independently from the rotation of the inner sleeve to position magnetic transducers attached to the suspension arms over selected information tracks on rotating magnetic disks.
17 . The method of claim 16 comprising the step of rotating the inner sleeve in a range of about 1 revolution per minute to about 100 revolutions per minute.
18 . The method of claim 16 comprising the step of rotating the inner sleeve at a rate sufficient to create an air bearing between at least one of the inner sleeve and the pivot shaft or the inner sleeve and the outer sleeve.
19 . The method of claim 16 comprising rotating an upper portion of the inner sleeve in a first direction and rotating a lower portion of the inner sleeve in a second opposite direction.