PERMANENT MAGNET FOR MOTOR, MOTOR AND MAGNETIZING METHOD

摘要

A tubular permanent magnet which is used in a micro DC brushless motor used in a miniature hard disc, and employs an Sm-Co based magnetic material. The permanent magnet has radially magnetized domains formed in the circumferential direction at a constant interval, wherein the inside diameter D of the permanent magnet is set at 20 [mm] or less, and the radial thickness t of the permanent magnet is set to satisfy a relation t<= piD/(NM-pi), assuming the average of the inner circumferential length and the outer circumferential length included in one domain is a pitch P, the number of domains is N, and the number of phases of an AC current for driving the motor is M.