Patent ID: 8240920

Claim:
A fluid dynamic bearing for a motor, the fluid dynamic bearing comprising: a substantially cylindrical sleeve centered about a central axis, the central axis extending in an upward/downward direction; a shaft inserted in the sleeve to be opposed to an inner circumferential surface of the sleeve with a radial gap therebetween; an upper cap including an opening arranged to have the shaft inserted therein, a top portion having a substantially annular shape and arranged to cover an upper surface of the sleeve, and a cylindrical portion extending downward from an outer circumferential portion of the top portion to cover an outer circumferential surface of the sleeve; a first capillary seal portion arranged radially outward of the radial gap to define a gap extending in an axial direction of the radial gap; a second capillary seal portion arranged above the radial gap to define a gap extending in the axial direction to the radial gap and the first capillary seal portion; lubricating oil disposed in the radial gap, the first capillary seal portion, and the second capillary seal portion; a first channel filled with the lubricating oil and arranged to connect a bottom portion of the radial gap with the first capillary seal portion, the first channel having a channel cross-sectional area including a first gap extending radially outward from the sleeve; and a second channel filled with the lubricating oil and arranged to connect the first capillary seal portion with the second capillary seal portion, the second channel having a channel cross-sectional area including a second gap extending radially between the sleeve and the cylindrical portion of the upper cap, a radial dimension of the second gap is larger than a radial dimension of the first gap.