SPINDLE MOTOR FOR STORAGE DISK DRIVE, AND STORAGE DISK DRIVE FURNISHED WITH THE SPINDLE MOTOR

摘要

PROBLEM TO BE SOLVED: To provide a spindle motor and a disc driving device that can suppress an eddy-current loss and secure the strength of a base portion.SOLUTION: A motor has a stationary part, a rotation part and a bearing mechanism for supporting the rotation part so that the rotation part is rotatable around the center axis thereof with respect to the stationary part. The stationary part has a substantially plate-like base portion, a stator core 221 and a coil 222 with a conductive wire wound around the stator core, and has a stator 22 disposed above the base portion and a magnetic member 24 located below a rotor magnet 32. The rotation part has a rotor hub disposed above the base portion, and a rotor magnet which is disposed to face the stator through a gap 9 and fixed to the rotor hub. The base portion has a ridge 52 projected from an upwardly facing face which is substantially arcuate or annular around the center axis. In the axial direction, the upper end of the ridge is located to be lower than the lower end 221a of the stator core and the lower end 321 of the rotor magnet and higher than the lower end 222a of the coil. No magnetic member exists on the ridge.