Analysis of Fluctuations in Bearing Preload and Optimal Design of Tapered Roller Bearings for Pinion Shaft Support in Differential Gearboxes

Regarding tapered roller bearings used on pinion shafts in differential gearboxes, it has been observed that some cases of bearing failure, like flaking or seizure, occurred much earlier than expected. As to the cause of this kind of failure, it has been clarified that on the shaft system supported by a pair of tapered roller bearings, the actual bearing load, including the preload of the bearings, fluctuates not only under the dynamic state but also under the static state because of the temperature distribution around the bearings. This fluctuation of the actual bearing load and preload greatly affects rolling fatigue life, seizure performance and the stiffness of the shaft support system. This paper discusses optimal design concepts for improving the rolling fatigue life, frictional torque, rigidity and seizure performance of a pair of tapered roller bearings. The design concepts are based on analysis results of the dynamic preload situation under actual operating conditions. Also introduced is a downsized shaft support system devised with a pair of tapered roller bearings developed using these design concepts.