Low-profile spindle motor for 5-mm-height PCMCIA disk drive

We developed a new spindle motor with a unique structure for PCMCIA Type-II magnetic disk drives. The motor has extremely small dimensions and has to be highly efficient. The magnetic circuit has radial gaps, axial cores, and a pole-anisotropic ring magnet. We found that the core material and the joints of the core and yoke strongly influenced the motor efficiency and the torque constant. We achieved a motor efficiency 5 times greater than the conventional axial gap motor.