Shigeo Obata

Development of FDB spindle motors for HDD use

The areal recording density of an HDD has increased noticeably at a rate of 60% to 100% a year, and further increases are expected in the future. In line with this trend, increasingly exacting tolerances are required regarding off-track errors of heads. Ball bearings have been conventionally used in spindle motors. However, off-track errors caused by non-repeatable run outs (NRRO) are approaching the control limit. Expectations for the implementation of spindle motors incorporating fluid dynamic bearings (FDBs) are rising. In this paper, we discuss FDB spindle motors, which are thought of as the future mainstream of HDD.

Automatic design method of brushless DC motors for VCRs

An automatic design method for all types of brushless DC motors for VCRs was developed. Quick and easy motor design with no trial manufacture was realized, enabling a motor of minimum size to achieve maximum efficiency. In carrying out this work, the authors systematized the parameters governing the motor characteristics of a brushless DC motor and theoretically analyzed and clarified the correlations between parameters and characteristics. Various experiments were conducted to increase the reliability of the theoretical analysis of the magnetic circuit. Some motor rules vital in motor design were identified and used to devise an algorithm for automatic motor design, and interactive software was developed on the basis of this algorithm. The resulting design method is a highly practicable one and permits an optimum motor design that satisfies all the conditions imposed by the equipment in which the motor is to be used. >