Vibro-Impact Motions of a Three-Degree-of-Freedom Geartrain Subjected to Torque Fluctuations: Model and Experiments

In this study, a multimesh gear system subjected to torque fluctuations is employed as an example to study vibro-impacts of multidegree-of-freedom systems having multiple clearances. Such rotational systems are common in various automotive geared drivetrains where external torque fluctuations lead to contact loss at gear mesh interfaces to result in sequences of impacts. The specific configuration considered here is a three-axis, two-gear mesh drivetrain that is commonly used in engine timing gear systems, known for its vibro-impacts resulting in rattling noise. On the theoretical side, a discrete torsion model is developed and solved using a piecewise-linear solution method. Its predictions are compared to measurements from a three-axis geartrain to demonstrate its accuracy. The validated model is employed to characterize the sensitivity of vibro-impact motions and associated nonlinear behavior to key excitation parameters for two kinematic configurations. For the idler configuration where the middle gear is not subject to any external disturbance, double-sided impacts of one gear mesh were shown to induce separation on the other gear mesh such that vibro-impacts are localized in a single mesh. For the torque-split configuration, the ratio of the torques carried by the outputs was identified as a major parameter defining regions and types of rattle motions.