Mixed Lubrication Analysis for the Interface between Wave Generator Outside Surface and Flexspline Inside Surface in Strain Wave Gearing (Numerical Analysis under No-Load Torque Operation)

Abstract

This paper represents a mixed lubrication analysis for the interface between the Wave Generator (WG) outside surface and the Flexspline (FS) inside surface in Strain Wave Gearing (SWG). The analytical model consists of the FEM model of the WG outer race and FS and the mixed lubrication model combined with the pressure-compliance equation of surface roughness contact developed by Greenwood and Williamson and the average Reynolds equation by Patir and Cheng. The lubricant film thickness, the hydrodynamic and asperity contact pressures and the lubricant flow vectors at the WG/FS interface are calculated as a function of the input rotational speed. The numerical results show that in the present operating conditions the SWG works primarily in the regime of mixed lubrication and the roughness contacts are made at both edges of the WG outside surface. In addition, axial lubricant flow from the inside to the outside at WG/FS interface is found at the relatively low rotational speed of the WG.