Patent ID: 8451558

Claim:
A disk drive device comprising: a base member; a hub on which a recording disk is to be placed; a bearing unit arranged on the base member for rotatably supporting the hub; and a spindle drive unit for rotationally driving the hub, wherein the spindle drive unit includes: a stator core having salient poles; a three-phase coil wound around each of the salient poles; and a magnet having a plurality of magnetic poles arranged in a circumferential direction so as to be opposed to the salient poles, the hub includes an outer cylindrical portion formed of a magnetic material and adapted to be engaged with an inner periphery of the recording disk, and an inner cylindrical portion fixing an outer periphery of the magnet, the bearing unit is configured to be encircled by the recording disk in a radial direction, and includes a portion for at least partially overlapping the recording disk in an axial direction, the number of magnetic poles is an even number in a range of 10 to 16, and the number of salient poles is a multiple of 3 in a range of 12 to 24.