Patent ID: 8213113

Claim:
A disk drive device, comprising: a hub on which a recording disk is to be mounted; a base rotatably supporting the hub through a bearing unit; a core fixed to the base, the core having a ring portion and a plurality of teeth that extend radially from the ring portion; coils wound around the plurality of teeth, the coils being three-phase driven; and a magnet fixed to the hub, the magnet being magnetized for driving with P (P is a natural number) poles along the circumferential direction and arranged to radially face the plurality of teeth, wherein the hub has a convex portion of which the center is a rotational axis, and the convex portion is fit into the central hole of the recording disk, and wherein the rotational frequency N (Hz) of the hub satisfies N<F 0 /(3* P+ 2), where F 0 (Hz) is an Eigen frequency of the second order rocking-mode resonance when not rotating in the situation where the recording disk is mounted on the hub.