A hollow shaft includes a hollow portion extending in an axial direction from an opening that is open at one end of the hollow shaft in the axial direction. The hollow shaft further includes a first communicating hole establishing radial communication between the hollow portion and an axial space between an upper lubricating oil and a lower lubricating oil. The hollow shaft further includes a second communicating hole establishing radial communication between the hollow portion and an unsealed space inside the motor. The unsealed space is connected to an external space outside the motor. The hollow shaft further includes a sealing member closing the opening. The hollow shaft has, in an inner peripheral surface facing the hollow portion, a recess recessed radially outward. A part of the sealing member is fitted into the recess.

A pivot assembly bearing device includes a shaft having an outer peripheral surface and a rolling bearing fixed to the shaft. An annular sealing surface axially overlapping with at least a part of an end surface of the rolling bearing is provided on an axially outer side of the rolling bearing. An oil-repellent film is annularly formed on at least one of the sealing surface and a part of the outer peripheral surface of the shaft located axially outward from the rolling bearing.

A fluid bearing apparatus includes a stationary member and a rotating member. A bearing surface of the stationary member and a bearing surface of the rotating member are arranged opposite to each other with a minute gap therebetween. The minute gap has a fluid arranged therein. At least one of the bearing surfaces includes a first dynamic pressure groove array. The first dynamic pressure groove array includes a plurality of first dynamic pressure grooves arranged unevenly at irregular intervals in a circumferential direction.

A tolerance ring has a band with outwardly extending corrugated protrusions forming waves that engage an outer surface of a shaft. At one end of the tolerance ring is an inwardly flared guide surface extending axially and radially from the band. The guide surface acts as a tapered entrance to a bore of a housing to assist during assembly.

An apparatus is provided including a shaft, wherein the shaft is stationary. A rotatable component is configured to rotate with respect to the shaft. A fluid is operable to flow between the shaft and the rotatable component. A limiter is at a first axial end of the shaft, and a cup is at a second axial end of the shaft. An axially extending grooved region is between the limiter and the rotatable component.

The fluid dynamic bearing including: a pair of bearing surfaces (8a1 and 8a2) having dynamic pressure generating grooves (G1 and G2) on an inner peripheral surface (8a); a pair of first smooth surfaces (8a4 and 8a5) formed between both the bearing surfaces (8a1 and 8a2) so as to be adjacent to the respective bearing surfaces (8a1 and 8a2); and a relief portion (8a3), which is formed between both the first smooth surfaces (8a4 and 8a5), and has a diameter larger than those of the pair of bearing surfaces (8a1 and 8a2).

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).

A tolerance ring has a band with outwardly extending corrugated protrusions forming waves that engage an outer surface of a shaft. At one end of the tolerance ring is an inwardly flared guide surface extending axially and radially from the band. The guide surface acts as a tapered entrance to a bore of a housing to assist during assembly.

A fluid bearing apparatus according to a preferred embodiment of the present invention includes a shaft arranged to extend along a central axis extending in a vertical direction; a rotating portion arranged opposite to an outer circumferential surface of the shaft, and arranged to be capable of rotating about the central axis with respect to the shaft; a lubricating oil arranged in a gap between the rotating portion and each of upper and lower outer circumferential surfaces of the shaft; a first groove defined in at least one of a middle outer circumferential surface of the shaft and a portion of an inner circumferential surface of the rotating portion, the portion being opposite to the middle outer circumferential surface, the first groove being arranged to extend along a circumferential direction; a plurality of second grooves each of which is defined in an upper surface of the rotating portion; and a plurality of communicating holes each of which is defined in the rotating portion, and is in communication with the first groove and a corresponding one of the second grooves.

In certain embodiments, a motor includes a shaft positioned adjacent a sleeve for relative rotation. The sleeve includes a first radial recirculation channel. The shaft and sleeve form first and second gaps. The first gap is configured to form a pump seal, is positioned above the first radial recirculation channel, and has a width measured between the shaft and sleeve. The second gap is configured to form a journal bearing, is positioned below the first radial recirculation channel, and has a width measured between the shaft and sleeve. The width of the first gap is greater than the width of the second gap.