AN EFFICIENT DESIGN TO REDUCE THE FLUX LEAKAGE OF A SPINDLE MOTOR

A small de brushless spindle motor with small magnetic flux leakage mu st be used for a CD-ROM drive application because the magnetic flux le akage may affect the magnetic and electric control circuit of the pick up head. This paper presents a motor design that efficiently reduces m agnetic flux leakage by using a pair of yokes on the rotor magnet. Usi ng these yokes at a distance of 2.0 mm reduced the magnetic flux leaka ge from 344 to 29 G along the radial direction and from 117 to 10 G al ong the axial direction. After shielding for the magnetic flux leakage , the dynamic performance of the motor cannot be affected. The torque of the CD-ROM spindle motor can be controlled at the same range for sh ielded and unshielded spindle motors. (C) 1996 American Institute of P hysics.