Advantages associated with low friction rotor bearings are well known in the field of turbomachinery where rotor speeds often exceed 100,000 RPM. Such high-speed applications, owing to the fact that rotor imbalance force increases as a square function of rotor speed, typically include a mechanism for radial damping of the rotor bearing. In addition, changes in operating conditions can generate significant axial thrust forces that act on a bearing; these forces should also be damped or absorbed.
One type of low friction bearing is referred to as a fully floating bearing. Fully floating bearings rely on hydrodynamic films, in particular, an inner hydrodynamic film or films between the rotor shaft and the bearing and an outer hydrodynamic film or films between the bearing and the housing. Fully floating bearings can spin in the housing, typically, at between about 20 and about 40 percent of the rotor shaft speed. However, floating bearings can become unstable due to resonant frequencies in the shaft/bearing system driven by such rotation. To prevent such instabilities a semi-floating approach has been used.
In a cylindrical coordinate system, a bearing may be defined with respect to radial, azimuthal and axial coordinates (e.g., r, Θ, z, respectively). See, e.g., Beyer, W. H., CRC Standard Mathematical Tables, 28th ed. Boca Raton, Fla.: CRC Press, p. 212, 1987. Within a bearing housing, referred to as housing in subsequent text, a semi-floating bearing is normally located axially and azimuthally via one or more mechanisms. To prevent rotation (i.e., spinning in Θ), a semi-floating bearing may employ a radial pin locating mechanism. Such a mechanism allows some movement in a radial direction along a radial line defined by the pin but prevents rotation of the bearing in the housing. While such a radial pin may provide for axial positioning as well, thrust forces can cause wear and misalignment issues; hence, other mechanisms are sometimes used for axial positioning (e.g., a pin oriented with its axis parallel to that of the bearing and fit into a notch in the end of the bearing).
Overall, an industry need exists for bearing and bearing components housings that allow for better alignment and/or reduced wear. Various exemplary bearings, bearing components and housings presented herein address such issues.
USPTO Backgrounds
USPTO Backgrounds