Contribution of the deflection of tapered roller bearings to the misalignment of the pinion in a pinion-rack transmission

The misalignment of the gears is one of the main causes of premature failure in gear transmissions. This misalignment can be caused by different phenomena where the deformation of the elastic elements of the transmission usually has a major importance. In this paper, a pinion and rack transmission is used to investigate the misalignment of the pinion produced by the deflection of both shaft and bearings, focusing in the contribution of the bearings to this misalignment. For this task, a design space with 261 different cases of pinion and rack transmission has been explored. For each case, a realistic 3D FEM model (including gears, shaft and roller bearings) has been created and the coupled structural and contact problem has been solved. From the results of the FEM models, the different parameters of misalignment of the pinion have been computed and analyzed through five studies. These studies revealed the high importance of the elasticity of the bearings in the misalignment of the pinion and, in general, the important error that can be assumed when the bearings are not included in the structural models of gear transmissions.The authors express their deep gratitude to the Spanish Ministry of Science and Innovation (MICINN) for the financial support of research project ref. DPI2013-47702-C2-2-P