Influence of Micro Geometry Modification on Gear Dynamics

Gearbox behavior is strictly affected by gears, shaft, bearings and casing stiffnesses. As a matter of fact, their contribution to gear dynamics is fundamental for mechanical transmissions design. In this paper a semi-analytical model developed for the estimation of the dynamic behavior of two mating gears is presented and tested on two case studies. Starting with the estimation of the Static Transmission Error, intended as the difference between the theoretical and actual angular position between the two mating gears, the dynamic behavior of the mating elements is estimated by means of a Dynamic Model. The Dynamic Model takes into account the gears, the contact between teeth exchanging loads and the other mechanical elements reduced by means of a DOF reduction technique. Based on the block-oriented approach, Dynamic Model allows the user to easily manage the complexity of the system with further or less elements by adding or removing DOFs. The outputs of the Dynamic Model are the Dynamic Transmission Error and the actual dynamic overload due to teeth mating. The main outputs of this model are the overloads in gear mating; such information is useful because the standards provide limited information about these parameters. In the present paper, two sets of gears are analyzed for testing the procedure and highlighting the advantages of the proposed technique. The gears are loaded at different torques, with increasing and decreasing spin speed and with different micro-geometrical teeth profile modifications (linear and parabolic tip relief, ...). Spur gears are tested and an important focus on the effect of micro-geometry on the dynamic behavior of the system is shown. The technique is also useful for analyzing torque inversion events during working conditions.