A bearing unit includes: an impregnated bearing that rotatably supports a shaft of a rotor; a storage part which is formed in a manner that an end surface of a housing incorporating the rotor in an axial direction becomes convex toward an outer side and which stores the impregnated bearing in a non-rotatable manner; and an oil return washer which is placed to face an end surface of the impregnated bearing stored in the storage part and which integrally rotates with the shaft. The storage part has a bottom tubular shape, and includes an inner surface and a bottom surface, and the oil return washer is placed in a manner that the facing surface overlaps with the inner surface of the storage part when viewed from a radial direction, and includes a circulation part that receives oil leaked from the impregnated bearing and returns the oil to the impregnated bearing.

A porous gas bearing is disclosed. The porous gas bearing includes a housing having a fluid inlet and an aperture. A porous surface layer is disposed within the housing surrounding the aperture in a circumferential direction. The porous surface layer is in fluid communication with the fluid inlet. A damping system includes a damping system including a biasing member, the biasing member being disposed in a passageway that extends along the longitudinal direction of the aperture and circumferentially about the aperture, wherein the biasing member is arranged radially outward from the porous surface layer.

An oil-impregnated sintered bearing in which a FeCu-based sintered body is impregnated with a lubricant and which has a bearing hole that is configured to support a rotary shaft inserted therethrough, in which an inner circumferential surface of the bearing hole includes at least a first region including a central portion in a shaft direction and a second region forming a portion from a first end portion of the first region to a first opening of the bearing hole, and, in a friction surface of the second region, an area of a Fe phase is larger and an area of a Cu phase formed of Cu powder including Cu-based flat raw material powder is smaller than those in a friction surface of the first region.

A fan dynamic pressure structure having a plastic frame integrally formed around an oil-containing sintered metal powder bearing includes an oil-containing sintered metal powder bearing, a plastic frame having a middle tube integrally formed around a peripheral of a bushing body of the oil-containing sintered metal powder bearing, a blade assembly having an axial shaft penetrating through a shaft hole of the oil-containing sintered metal powder bearing, the axial shaft protruding downwardly and having an annular groove, and an annular dynamic pressure piece having an insertion hole and an annular body surrounding the insertion hole. The insertion hole is engaged with the annular groove of the fan assembly, the annular body has a plurality of curved radial dynamic pressure ditches on a surface adjacent to the oil-containing sintered metal powder bearing, of the annular body.

A porous gas bearing is disclosed. The porous gas bearing includes a housing having a fluid inlet and an aperture. A porous surface layer is disposed within the housing surrounding the aperture in a circumferential direction. The porous surface layer is in fluid communication with the fluid inlet. A damping system includes a damping system including a biasing member, the biasing member being disposed in a passageway that extends along the longitudinal direction of the aperture and circumferentially about the aperture, wherein the biasing member is arranged radially outward from the porous surface layer.

A charging amount of lubricating oil (11) into an internal space of a housing (7) is adjusted so that, within a range of a use temperature, an oil level of the lubricating oil (11) is positioned on a lower side with respect to an upper end portion of a chamfered portion (8f) formed in an upper-end inner peripheral edge portion of a bearing member (8). The bearing member (8) integrally includes: a small-diameter cylindrical portion (81); and a large-diameter cylindrical portion (82). Under a state in which an upper end surface (8c) of the small-diameter cylindrical portion (81) is exposed to an atmosphere, the large-diameter cylindrical portion (82) is sandwiched from both sides in the axial direction with an annular member (9) and a bottom portion (7b) of the housing (7) so that the bearing member (8) is fixed along an inner periphery of the housing (7).

On an inner peripheral surface of a bearing hole into which a shaft is inserted, concave oil supply surfaces arranged dispersively like separated islands and a sliding surface continuous around the oil supply surfaces to hold an outer peripheral surface of the shaft are formed: a maximum height difference between the sliding surface and the oil supply surfaces is not less than 0.01% and not more than 0.5% of an inner diameter Di of the sliding surface; a surface aperture area ratio of pores at the sliding surface is not more than 10%; a surface aperture area ratio of pores at the oil supply surfaces is more than 10% and less than 40%; and an area of each of the oil supply surfaces is not less than 0.03 mm.sup.2 and not more than 0.2Di.sup.2 (mm.sup.2).

A porous gas bearing is disclosed. The porous gas bearing includes a housing having a fluid inlet and an aperture. A porous surface layer is disposed within the housing surrounding the aperture in a circumferential direction. The porous surface layer is in fluid communication with the fluid inlet. A damping system includes a damping system including a biasing member, the biasing member being disposed in a passageway that extends along the longitudinal direction of the aperture and circumferentially about the aperture, wherein the biasing member is arranged radially outward from the porous surface layer.

Provided is a method of manufacturing a sintered bearing including, on an inner peripheral surface, a cylindrical portion and a one-side increased-diameter portion (increased-diameter portion), which are provided so as to be continuous in the axial direction. When sizing is performed on a sintered compact, the cylindrical portion and the one-side increased-diameter portion are molded on an inner peripheral surface of the sintered compact by press-fitting a cylindrical portion molding surface formed on a core into an inner peripheral surface of the sintered compact from the one side in the axial direction, and then by pressing a one-side increased-diameter portion molding surface provided so as to be continuous with the cylindrical portion molding surface in the axial direction against an inner peripheral surface of the sintered compact under a state in which an outer peripheral surface of the sintered compact is retained by a die.

An oil-impregnated sintered bearing (8) includes a copper-iron-based sintered compact containing 40 mass % or more of copper, and has inner pores impregnated with an oil. The sintered compact has: a copper structure derived from copper powder (13) of partially diffusion-alloyed powder (11) in which copper powder (13) having a particle diameter of 20 m or less is diffused on and joined to a surface of iron powder (12) in advance; and a copper structure derived from elemental copper powder (14).