The influence of mesh misalignment on the dynamic characteristics of helical gears including sliding friction

Due to either elastic deformations or errors in the manufacturing or assembling of gears, shafts, bearings and their housings, it is an inevitable consequence that mesh misalignment between teeth occurs. The change in length of the contact line or the change in load distribution along the length of the contact line induced by mesh misalignment causes changes in the dynamic characteristics of helical gears. There is currently no satisfactory solution for the modeling and calculation of the internal excitation in helical gears with mesh misalignment and sliding friction that would reveal the changes in the dynamic characteristics. In this study, an improved calculation method of friction excitation is proposed based on the time-varying length of the contact line and the time-varying friction coefficient model in helical gears. By considering the change in the mesh position and the change in the length of the contact line or the change of the displacement error along the contact line induced by mesh misalignment, the time-varying sliding friction force and the dynamic mesh force may be obtained. An eight degree-of-freedom analytical helical gear pair model is developed by incorporating the time-varying sliding friction force and dynamic mesh force and considering the mesh misalignment. By assuming a constant mesh stiffness density along the contact line, the rules governing the variation of the dynamic response are obtained using simulations of helical gear pair examples with different friction coefficient models and mesh misalignment. The developed analytical model provides a new method for the study of excitation characteristics in helical gears with mesh misalignment.