Oil-impregnated sintered bearing and fluid dynamic bearing device provided with the bearing

An oil-impregnated sintered bearing comprising:

• a sintered metal bearing obtained by compression-molding a metal powder into a tubular shape to form a green compact, and sintering the formed green compact;
• a lubricating fluid impregnating an internal pore of the sintered metal bearing;
• a radial dynamic pressure generation portion formed on an inner peripheral surface of the sintered metal bearing;
• and
• a thrust dynamic pressure generation portion formed on an end surface of the sintered metal bearing on one side of the sintered metal bearing in an axial direction, an end surface of the sintered metal bearing on another side of the sintered metal bearing in the axial direction having a flat shape, wherein
• an axial dimension L of the oil-impregnated sintered bearing is 0.8 mm or more and 1.8 mm or less,
• a thickness dimension t of the oil-impregnated sintered bearing is 0.5 mm or more and 1.5 mm or less,
• a ratio L/D2 of the axial dimension L to an outer diameter dimension D2 of the oil-impregnated sintered bearing is 0.24 or more and 0.6 or less,
• a density ratio of the oil-impregnated sintered bearing is 86% or more and 92% or less,
• an inner diameter dimension D1 of the oil-impregnated sintered bearing is 1.2 mm or more and 2.5 mm or less,
• the outer diameter dimension D2 is 2.5 mm or more and 5.0 mm or less, and
• the radial dynamic pressure generation portion includes a plurality of dynamic pressure generating grooves.