Vibro-impact analysis of AT vehicle driveline system with torque converter under tip-in conditions

Vehicle driveline vibro-impact, induced by the step torque and clearance between connected rotors, often results in serious transient noise problems under tip-in conditions. The torsional element method provides a modular and programmatic approach for dynamic modeling elastic torsional systems. Due to its high modeling efficiency, it is frequently used to establish dynamic models of vehicle drivelines. The main purpose of this paper is to extend the types of torsional elements, establish a dynamic model of a vehicle driveline system by applying the torsional element method, analyze the transient vibro-impact phenomenon, and propose improvement countermeasures. In this paper, a nonlinear hydraulic coupled element and a two-stage cascaded nonlinear clearance element including clearance and inert rotor are developed. A dynamic lumped parameter model with 11 degrees of freedom is established for a front-wheel-drive vehicle driveline with an automatic transmission (AT) by applying these torsional elements. The transient vibro-impact phenomenon generated by the nonlinear clearance element and the unsynchronized speed and torque presented by the nonlinear hydraulic coupled element are numerically investigated under transient tip-in conditions. The real-vehicle experimental results verify the validity of the nonlinear dynamics model. The numerical study reveals that the speed difference between the pump wheel and turbine and the clearance of the driveshaft universal joint significantly affect the driveline vibro-impact, which is verified by experimental results. Finally, countermeasures to reduce the speed difference and clearance are proposed and implemented to improve driveline vibro-impact. Furthermore, the developed torsional element model can be generalized to establish the dynamic model of other elastic torsional systems containing torque converter and clearance nonlinearities.