Patent ID: 7474502

Claim:
A rotor hub for use in a motor installed in a recording disk driving device to spin a recording disk, to which the recording disk including an inner side surface along a center circular through-hole is arranged, the rotor hub comprising: a convex portion engaging the center circular through-hole of the recording disk; a disk engaging surface defined by an outer side surface of the convex portion, a portion thereof engaging the inner surface of the circular center opening of the recording disk; a disk placing portion, arranged around the convex portion, on which the recording disk is placed; a disk placing surface defined by a portion of an upper surface of the disk placing portion, at least a portion of the disk placing surface abutting against a bottom surface of the recording disk; a relief portion defined by a substantially circular concave portion extending inwardly from the disk engaging surface, and arranged between the disk placing surface and the disk engaging surface along the convex portion; and an upper edge of the relief portion provided between the relief portion and the disk engaging surface, and opposing the inner side surface of the recording disk; wherein the upper edge of the relief portion is arranged lower than an upper edge of the inner side surface along the center circular through-hole of the recording disk.