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Apparatus to Improve Preload and Bearing Stiffness Control in a Ball Bearing Spindle System Disclosure Number: IPCOM000013813D
Original Publication Date: 2000-Aug-01
Included in the Prior Art Database: 2003-Jun-18

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The disclosed apparatus provides for improved preload and stiffness control in a ball bearing spindle system by vibrating the system for a short duration of time during the initial application of the preload in order to allow the races of the ball bearings to self-align in the presence of frictional forces that would oppose such alignment. The advantage provided by the disclosed apparatus is to provide better ball bearing race alignment, which leads to better bearing stiffness and preload control. Better bearing stiffness and preload control results in better disk drive dynamics, and therefore improves the functional robustness and quality of the disk drive. Figure 1 illustrates superior dynamics (low "S" mode gain) of a disk drive rotary actuator using a ball bearing pivot cartridge with good bearing preload and stiffness properties (b.) compared to relatively poor dynamics (high "S" mode gain) for an actuator using a pivot cartridge with bad bearing preload and stiffness properties (a.). Ball bearing preload and stiffness problems can arise from misalignment of the inner and outer races of the bearing. Figure 2 shows a schematic diagram of aligned and mis-aligned races of a ball bearing. The mis-alignment of Figure 2b. will cause the bearing to have a radial stiffness that is not axisymetric, and can lead to a mis-match with the radial stiffness of the other bearing in the pivot or spindle system. Ultimately, this condition can result in poor dynamics of the disk drive rotary actuator. The disclosed apparatus provides a means to vibrate the ball bearing spindle/pivot structure during assembly and application of the bearing