Influence of asymmetry on noise excitation be-haviour of involute gears

Involute gears are broadly in use for many decades now, in a vast number of applications: automotive, tool machines, wind power or medicine, to name but a few. The great majority of gears produced up to now show a symmetric tooth shape, i.e. curvature and profile angle progression being symmetric for the loaded flank and the rear flank of each tooth of a gear. So, each tooth has a symmetry line radial to the gear. Gears with non-symmetric gear teeth, i.e. different profile angles for loaded flank and rear flank, introduce at least one more degree of freedom to the process of gear design and optimization. This is especially relevant for applications with high power densities and strict requirements regarding e.g. gear set mass and load carrying capacity. This is one of the reasons why asymmetric gears are already being produced in series e.g. for aviation uses. The noise excitation behaviour of classic symmetric involute gears has been researched intensely in the past. Estimation methods for dynamic tooth forces - being the main source of gear-induced machine noise - are well documented and standardized. One central element of these methods is formed by the stiffness of the gear mesh. For calculating the mesh stiffness for common involute gears, analytical calculation approaches of good accuracy exist. In this paper, the well-validated methods of gear stiffness calculation and gear noise excitation estimation are enhanced to be applicable to asymmetric gear geometries. Additionally, a parameter variation is presented which describes the effects of different kinds of gear asymmetry on mesh stiffness and noise excitation behaviour.