On the dynamics of lubricated hypoid gears

The torsional dynamics of a vehicle differential hypoid gear pair is investigated. The model comprises applied torque, representing transmitted engine power, including engine order vibration. A number of gear teeth pairs transmit the applied torque through their lubricated conjunctions. Tooth contact analysis (TCA) is used to obtain the appropriate geometrical, kinematic and meshing parameters. These enable the evaluation of contact loads, film thickness and friction for conjugate teeth pairs, which are subject to mixed thermo-elastohydrodynamic regime of lubrication. It is shown that the lubricant undergoes non-Newtonian shear in line with the Eyring regime of traction. The inclusion of combined thermal non-Newtonian shear and boundary interactions has not hitherto been reported for the tribo-dynamics of hypoid gear pairs. When rate of change of gear teeth contact radii is included in the analysis more complex system dynamics (loss of teeth contact) result, particularly at higher speeds. The stated features constitute the main contributions of the current work, which have not hitherto been reported in literature. It is also shown that teeth contact separation ensues when resonant conditions are noted. This is regarded as the main root cause of a noise and vibration phenomenon, known as axle whine.