Patent ID: 8094410

Claim:
A spindle motor for rotatably driving at least one recording disc, said spindle motor comprising: a base plate; a stator disposed on said base plate, said stator having an outer circumference side; a rotor hub configured to have the recording disc attached thereto; an annular yoke disposed on said rotor hub; an annular rotor magnet disposed on said yoke and located adjacent said outer circumference side of said stator so as to be opposite said stator in the radial direction; and a hydrodynamic bearing disposed on said base plate, and configured to rotatably support said rotor hub relative to said base plate; said rotor hub including a disc support cylindrical portion configured to support said recording disc in the radial direction, and having an end surface, an annular disc mount portion disposed around an outer circumference of said end of said disc support cylindrical portion, said annular disc mount portion protruding from the outer circumference of said end of said disc support cylindrical portion in the radial direction, said annular disc mount portion having an annular disc receiving face arranged so as to enable the recording disc to be mounted thereon by contacting the recording disc in the axial direction, a side axially opposite said annular disc receiving face, and an annular non-contact surface arranged so as to face the recording disc via a gap in the axial direction in a position that is outside said disc support cylindrical portion in the radial direction and inside said annular disc receiving face in the radial direction, the annular non-contact surface including a corner flat portion, a step portion between said corner flat portion and said annular disc receiving face, and a corner portion between an outer circumference face of said disc support cylindrical portion and said corner flat portion, and an annular projection formed on said annular disc mount portion on said side axially opposite said annular disc receiving face and having an outer circumference face to which said yoke is fixed, wherein the outer diameter of the annular projection is smaller than the outer diameter of said step portion.