A fluid bearing includes a foil assembly that supports a journal inside a stationary retaining member includes a cylindrical top foil that is positioned radially inward, a cylindrical mid-foil that is positioned outside the top foil and corrugated bump foils positioned outside the mid-foil. In order to suppress a small amplitude vibration of the journal in the low rotational rate region, the bump foils, are separated into six in the circumferential direction. In order to suppress the synchronous vibration instability phenomenon, the top foil and the mid-foil are wound in opposite directions from each other. In order to suppress the whirl instability phenomenon, the sum of the frictional damping forces generated by the lower bump foils is set to be larger than the sum of the frictional damping forces generated by the upper bump foils.

An improved foil thrust bearing having a thrust runner and a thrust plate includes an underspring element positioned adjacent to the thrust plate. The underspring element comprises, in one embodiment, a plurality of alternating first apertures and spring portions, with at least one spring portion having a periodic configuration and comprising a leading edge and a trailing edge. The periodic configuration is defined by a plurality of pitches that vary between the leading and trailing edges. Also defining the periodic configuration is a plurality of periodic elements that vary in longitudinal length between the leading and trailing edges. A thrust bearing disk is disposed intermediate the underspring element and the thrust runner. The disk comprises a plurality of transition areas that provide a stepped configuration to the disk. The transition areas match a plurality of circumferential positions of the first apertures in the underspring.

A compliant hydrodynamic fluid film journal bearing for handling high loads. The bearing assembly includes a first thin smooth compliant sheet for facing a shaft, one or more corrugated foils, and a second sheet between the foils and the compliant sheet for supportedly underlying the compliant sheet for preventing sagging of the first sheet between ridges of the foils. A foil element is anchored at a position intermediate its ends to the bearing sleeve whereby both ends thereof are unanchored. A pair of radially outer and inner corrugated foils have outer foil ridges which underlie some inner foil ridges and outer foil furrows which underlie others of the inner foil ridges. A bearing assembly includes a plurality of rows of corrugated foil elements wherein ends of foil elements are offset circumferentially from ends of foil elements in adjacent rows symmetrically from the radial centerplane to provide a herringbone pattern effect. At least some ridges on at least one of inner and outer corrugated foils have truncated apex portions.

A turbocharger includes a foil bearing assembly mounted in a center housing between a compressor and a turbine of the turbocharger. The bearing assembly forms a unit installable into the center housing from one end thereof, and the center housing is a one-piece construction. The bearing assembly includes a foil thrust bearing assembly disposed between two foil journal bearings. The journals foils are mounted in annular bearing carriers fixedly mounted in the center housing. A radially inner portion of a thrust disk of the thrust bearing assembly is captured between a shaft and a shaft sleeve of the turbocharger. The center housing defines cooling air passages for supplying cooling air to the foil bearings, and optionally includes a water jacket for circulating engine coolant through the center housing.

A high load capacity hydrodynamic journal foil bearing system is disclosed, which comprises a top foil and a plurality of undersprings. Preload forces are transferred from the undersprings to internal circumferential compressive forces within a top foil, resulting in low preload forces against the shaft, allowing the shaft to expand at high speeds without increasing the preload forces or overloading the fluid film. One underspring may have a different spring rate than another underspring. The top foil may be normalized to shaft shape and dimensions. These features may be accomplished with using less mechanical parts than other journal foil bearing system designs.