Abstract
A high rotational speed spindle motor for a high-performance hard disk drive (HDD) beyond the current high-end drives was investigated. If a high rotational speed is achieved, the I/O-performance of the drive is improved because of a shorter access time, although the power consumption increases. The major factors causing high power consumption are windage loss, motor loss, and ohmic loss of the electric circuit. The relationships between windage loss and motor loss with the rotational speed were estimated by dimensional analysis. The result indicated that a drive with a single 48mm disk achieved a rotational speed of 35,000 min^<-1> and power consumption equivalent to a current server HDD with the 3.5-inch form factor. Moreover, two types of prototype spindle motors were fabricated. They are equipped with fluid dynamic bearings of either oil or air, and can rotate a single 48mm disk at up to 35,000 min^<-1>. The power consumptions and vibration responses of the motors were measured. The experimental results agreed well with the estimations and showed that the vibration response gain of the oil bearing motor were smaller than that of the air bearing motor.
