The maximum allowable misalignment in hydrodynamic rolling hybrid bearings

A hydrodynamic rolling hybrid bearing (HRHB) assembled coaxially by a rolling bearing and hydrodynamic bearing is developed to achieve two functions at low and high speeds. At low speeds, the rolling bearing of the HRHB can be utilized to avoid wear in the hydrodynamic bearing. While at high speeds, the rotor is entirely supported by the hydrodynamic bearing, keeping away the interference of the rolling bearing. However, because the HRHB is mounted coaxially by two bearings, a misalignment cannot be avoided. This can lead two unexpected consequences: either the malfunction of the rolling bearing at low speeds or the interference of rolling bearing applied on the rotor. In this paper, a computational method to calculate the maximum allowable misalignment based on the noninterference conditions of the locus of the shaft center and rolling bearing at high speeds is proposed, and the influence of the rotating speed, the spindle, and bearing structural parameters on the maximum allowable misalignment is also analyzed. The results show that the locus of the maximum allowable misalignment forms a circle along the circumferential direction. The noninterference conditions are satisfied when the maximum allowable misalignment is inside the circle.