A zero wear assembly of a hydrodynamic bearing and a rolling bearing

Hydrodynamic bearings (HBs) are prone to initial wear due to contact friction between the bushing and shaft under the condition of insufficient hydrodynamic pressure (IHP). This problem is usually solved by adding a hydrostatic bearing as a secondary bearing. But it increases complication, expense and power consumption by employing external high pressure pumps. In this paper, a HB and a rolling bearing (RB) with a fixed clearance is assembled to form a Journal-Rolling Hybrid Bearing (JRHB). Two regimes characterized by distinct hydrodynamic pressure are expected in this new design. Under the condition of IHP, the rotor is supported by the RB, which protects the HB from direct contact wear. While under the condition of sufficient hydrodynamic pressure (SHP), i.e. under working condition, the rotor is supported by the HB alone. A test rig was designed and fabricated to investigate the stability behavior of the JRHB to demonstrate its feasibility. Clearance circles of the hybrid bearing, shaft orbits, and load sharing of the RB were measured. The experimental results show that the RB plays a protective role under the condition of IHP; and that the hydrodynamic pressure levitates the rotor at high speeds, and consequently the RB no longer shares the load.