Patent ID: 7663280

Claim:
A spindle motor comprising: a rotor hub including a disk-like flange having a disk mounting portion for placing a disk thereon, on one main surface of the rotor hub; and a shaft with a cylinder-shaped outer circumference, formed at a central part of one main surface of the flange, opposite to the disk mounting portion; a ring-shaped rotating magnet fastened on one main surface of the flange, opposite to the disk mounting portion, concentrically with a central axis of the shaft; an armature facing the rotating magnet and generating a rotating force with a central axis of the shaft as a center, for the rotating magnet; a sleeve facing one main surface of the flange, opposite to the disk mounting portion, and rotatably supporting the shaft; and a chassis fixing the armature and the sleeve, wherein the flange and the shaft of the rotor hub are integrally formed with magnetic material; and wherein a protrusion is not provided between a mounting surface for mounting the rotating magnet thereon and a counter-face surface facing an end surface of the sleeve, on one main surface of the flange, opposite to the disk mounting portion, and additionally the mounting surface and the counter-face surface are orthogonal to a direction of a central axis of the shaft, and are in a level plane; or the mounting surface is recessed stepwise from the counter-face surface toward the disk mounting portion.