Patent ID: 6450688
Filing Date: 2002-09-17
Classification: F16C

Abstract:
A fluid bearing having a stationary retaining member surrounding an outer circumference of a rotating journal with an annular cavity formed therebetween and a foil assembly positioned in the cavity and supporting the journal, the foil assembly comprising:a top foil having one end facing a first slit formed therein in the axial direction thereof and being cylindrically wound in one circumferential direction from the one end to the other end and partially disposed around the outer circumference of the rotating journal, the one end being fixed to the stationary retaining member on the upper half of the stationary retaining member relative to the direction of gravity, and supporting the outer circumference of the rotating journal through a fluid film layer, a mid-foil having one end facing a second slit formed therein in the axial direction thereof and being cylindrically wound in the opposite circumferential direction from the one end to the other end, the mid-foil being fixed to the stationary retaining member on the upper half of the stationary retaining member relative to the direction of gravity, the inner circumference of the mid-foil frictionally and slidably contacting an outer circumference of the top foil, thereby generating a fictional damping force counteracting the radially outward movement of the rotating journal, a plurality of bump foils positioned between the mid-foil and the stationary retaining member, the bump foils being circumferentially separated, wherein each of the bump foils is formed as a wave to elastically deform in the radial direction and to stretch and contract circumferentially, one end of each bump foil being fixed to the stationary retaining member, and wherein a frictional damping force counteracting the radially outward movement of the journal is generated by first contacts of the bump foils frictionally and slidably with an inner circumference of the stationary retaining member and second contacts of the bump foils frictionally and slidably with a radially outer circumference of the mid-foil, and wherein the sum of the frictional damping forces generated by the lower bump foils positioned on the lower half of the stationary retaining member relative to the direction of gravity is set to be larger than the sum of the frictional damping forces generated by the upper bump foils positioned on the upper half of the stationary retaining member.