A Proposal of Optimum Groove Design Concepts of Spiral-Grooved Journal Bearings Applied to Spindles of Precisieon Equipments (1st Report, A Guide for Reduction of Amplitude of Repeatable Run-Out in Incompressible Fluid Film Bearings)

Spiral-grooved bearings have lately attracted considerable attentions as better substitutions for current ball bearings, especially in motor spindles of precision equipments such as hard disk drive systems. In this paper, optimum designs of the groove dimensions of the spiral-grooved journal bearings specialized for a reduction of amplitude of the operating repeatable run-out (RRO), which is a major characteristic to be considered for applications to precision equipments, are theoretically discussed. The operating RRO of the bearing is formulated in a kinematical model in this study to be attributed to an unbalanced rotor mass, so that an evaluation index concerning the amplitude of the RRO is proposed. Theoretical results show that the appropriate groove designs, which make the proposed evaluation index to be minimum, can improve the RRO performances several times as good as the currently recommended groove design.