Patent ID: 7202583

Claim:
A motor comprising: a stator comprising a housing, a sleeve fixed to a central portion of the housing and having an axial hole formed at a central portion thereof, and a core fixed around the central portion of the housing and having a coil wound around it; and a rotor rotatably supported on the stator using bearing means, the rotor comprising a shaft rotatably inserted into the axial hole, and a hub coupled to an upper end portion of the shaft and having a downwardly extending portion to an inner surface of which a magnet generating an electromagnetic force due to an interaction with the core is attached, wherein the fluid dynamic bearing generates a fluid dynamic pressure by forming an oil gap between the axial hole of the sleeve and the shaft such that oil is accommodated in the oil gap; wherein the the sleeve has flow grooves formed on an inner circumferential surface thereof, and the bearing means comprises: a fluid dynamic bearing generating a fluid dynamic pressure by forming an oil gap between the rotor and the stator such that oil is accommodated in the oil gap; and an air dynamic bearing generating an air dynamic pressure by forming an air gap between an inner circumferential surface of the hub and an outer circumferential surface of the sleeve wherein when a length of a journal fluid dynamic bearing formed between the sleeve and the shaft is L, a clearance of the journal fluid dynamic bearing is F, and a diameter of the journal fluid dynamic bearing is E, a length of a journal air dynamic bearing formed between the outer circumferential surface of the sleeve and the inner circumferential surface of the hub ranges from 0.4 to 0.8L, a clearance of the journal air dynamic bearing ranges from 1.3 to 1.5F, and a diameter of the journal air dynamic bearing ranges from 6 to 8E.