Hydrodynamic type oil-impregnated sintered bearing

A spindle motor for information equipment comprising:

• a rotating shaft rotating with rotating components of the information equipment;
• a bearing for supporting the rotating shaft;
• and
• a rotor and stator arranged to face each other via a prescribed gap, wherein:
• said bearing comprises a porous bearing body of sintered metal having a bearing surface opposed to a sliding surface of the rotating shaft via a bearing clearance, and hydrodynamic pressure generating grooves slanting against an axial direction provided in the bearing surface, and lubricating oil or lubricating grease impregnated in pores inside the bearing body,
• wherein the rate of area of surface holes on the bearing surface is set within a range of 3%-15%, the surface holes being distributed substantially uniformly over the whole area of the bearing surface including areas of the hydrodynamic pressure generating grooves,
• wherein said lubricating oil or a base oil of said lubricating grease forms a lubricating film in the bearing clearance due to the hydrodynamic pressure generating grooves while circulating between an inside of the bearing body and the bearing clearance through the surface holes on the bearing surface, so that the lubricating film continuously supports the rotating shaft in a non-contact manner, and
• wherein said lubricating oil or a base oil of said lubricating grease is a lubricating oil selected from among mixtures of poly-α-olefin or hydrogenated compound thereof and ester, and further includes phosphoric ester defined by the following general formula: