Prediction of mechanical gear mesh efficiency of hypoid gear pairs

This study proposes a new spiral bevel and hypoid gear mechanical efficiency model for both face-milling and face-hobbing type cutting methods. The proposed efficiency model combines a computationally efficient contact model and a mixed elastohydrodynamic lubrication (EHL) based surface traction model to predict friction power losses. The employed contact model simulates the cutting process to compute all required geometric parameters of the contacting surfaces. It computes the unloaded contact positions between the tooth surfaces utilizing an ease-off approach and estimates the tooth compliance using a shell model. It also computes pressure distribution and rolling and sliding velocities. The EHL traction model considers typical ranges of the key contact parameters governed by hypoid gear applications, including Hertzian pressure, contact radii, surface speeds, lubricant temperature and surface roughness amplitude of hypoid type of gears, covering a wide range of conditions from full-film to boundary lubrication regime. At the end, the efficiency model is applied to two face-hobbed examples with similar overall dimensions, but different shaft offsets to investigate the influences of key operating and design parameters on the mechanical gear mesh power losses.