Spindle motor and disk drive utilizing the spindle motor

A disk-drive device including a housing, a spindle motor fixed inside said housing for spinning recording disks, and an information access means for writing information into and reading information out from needed locations on the recording disks, wherein said spindle motor comprises:

• a shaft;
• a sleeve formed with a through-hole for rotary-play insertion of the shaft;
• a rotor having a round top plate in the rotational center of which the shaft is furnished united, and a circular cylindrical wall depending from the top plate along its outer rim;
• a cover member for closing over one end of the through-hole formed in the sleeve;
• a circular cylindrical casing member fitted to said shaft over its outer circumferential surface;
• micro-gaps formed continuing between an upper-end face of said sleeve and a bottom face of said rotor top plate, an inner circumferential surface of said sleeve and an outer circumferential surface of said casing member, and an inner face of said cover member and end faces of said shaft and said casing member;
• oil retained continuously without interruption within said micro-gaps throughout their entirety;
• a radial dynamic-pressure bearing section configured intermediarily by at least one surface of either said sleeve inner-circumferential surface or said casing member outer-circumferential surface, and by said oil when said rotor spins, and provided with, as dynamic-pressure-generating striations, herringbone grooves for inducing into said oil when said rotor spins hydrodynamic pressure;
• a thrust bearing section configured on at least one of either said sleeve upper-end face or said top plate bottom face, and furnished with dynamic-pressure-generating striations for imparting to said oil radially inward-heading pressure when said rotor spins;
• an axial support section, formed between said cover member inner face and said shaft end face, having pressure essentially balancing radially inward-heading pressure generated in said thrust bearing section, wherein said rotor is lifted through cooperation of said thrust bearing section and said axial support section;
• and a communicating pathway formed in between said shaft along its outer circumferential surface and said casing member along its inner circumferential surface, for communicating said oil retained in, and enabling it to circulate between, the micro-gap formed between said sleeve upper-end face and the bottom face of said rotor top plate, and the micro-gap formed between said cover member inner face and said shaft and casing member end faces.