Contact Mechanics and Elasto-Hydrodynamic Lubrication Analysis of Internal-External Straight Bevel Gear Mesh in a Pericyclic Drive

The focus of this work is development of a comprehensive tooth contact analysis model and characterization of lubricant performance in a Pericyclic mechanical transmission utilizing modified straight bevel gears. The Pericyclic drive is kinematically similar to an epicyclic bevel gear train, and is characterized by load sharing over large number of teeth, large shaft angles (175°-178°), nutational gear motion, and high reduction ratio. The load sharing calculation model described in this paper takes into account contact outside involute region and is easily generalized to all bevel epicyclic gear drives. The resulting contact stress field, calculated using Hertz contact stress theory, was validated against FEA solution. A 3-D kinematic analysis of the pericyclic drive was carried out to determine rolling and sliding velocities at contact points. Thereafter, Elastohydrodyamic lubrication (EHL) characteristics viz. film thickness, friction coefficient, and flash temperature were calculated for a sample lubricant. Power losses due to film friction are calculated to determine mesh efficiency. Finally, the effect of input power and profile crowning parameter was studied for all of the above mesh characteristics. The friction coefficient values were found to be in the lower range of EHL contact leading to high efficiency values and a small flash temperature for surfaces in contact.