Contact pressures in internally toothed gears

Internally toothed gears are used in planetary gearsets, a type of mechanical power transmission with high transmission ratios and a very compact design. The MATLAB scrip that acts as the basis for the results that have been obtained, was already capable of analysing the static transmission error, load sharing factor and contact pressures of a set of spur or helical gears. Starting from this software, the necessary modifications have been performed to achieve the same study for the meshing of an internal, or ring gear, with the planet of the epicyclic gearing. Particular attention has been aimed at correctly determining the contact pressures generated by the gear meshing. Contact pressures are of fundamental importance in determining the surface strength of gears, and even though the technical standards offer much literature to account for the different loading conditions and possible coupling between different gears, a more detailed result can lead to a better evaluation of the contact stresses, especially in the tip and root region of the tooth. To achieve these results the static loading condition of the coupling is considered, calculating the load sharing factor and static transmission error. As a final step the relative distances between the statically loaded profiles is computed, leading to the computation of the teeth profiles deformation and of the contact pressures. This approach allows to evaluate the difference between various possible tooth modifications that can enhance the performance and durability of gears.