| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 2006: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2005: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
The author has performed theoretical and experimental examinations of non-repetitive run-out (NRRO) of ball bearings. Our experience has shown that most of the magnitude of NRRO can be ascribed to the angular frequency of the rolling elements (f_c), which is caused by the dimensional variation between the balls (i.e., maximum ball diameter-minimum ball diameter) in a given bearing. In recent research, however, theoretical calculations have demonstrated that NRRO can also be adversely affected by unequal orbital spacing of the balls (i.e., the angular divergence of the balls from equal spacing). The fc components have been experimentally measured in bearings with retainers having variable pocket clearance; higher values of fc were found in bearings with larger clearances.
Balls are able to shift to arbitrary positions within the clearances permitted by the retainer; thus, the greater the retainer clearance is, the less uniform the orbital spacing of the balls is likely to be. This report
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assumes that the initial non-uniform distribution of ball orbital spacing is preserved during rotation. However, it is difficult to believe that this actually occurs in bearings used in actual applications, where the balls are firmly held in the retainers as the bearing revolves. The following results were obtained:
(1) When the retainer is removed from a stationary loaded bearing, the combined load becomes concentrated upon a single rolling element within a much shorter time (less than 1 s) than the time required for concentration of a pure axial load.
(2) When the rolling elements are clustered about a certain position, this position always represents the center of the axial load distribution, and it occurs where there is the lowest radial distance between the inner and outer races.
(3) It has become clear that the rolling elements move radically within the retainer pockets during rotation of the bearing, thereby diverging from uniform orbital spacing. It has been shown that this is the cause for the increase in the fc component when there is high clearance in the retainer pockets. Less
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