STUDY OF DUAL-CLUTCH TRANSMISSION GEAR RATTLE UNDER LOW SPEED DRIVING CONDITION

Gear rattle is an important factor affecting vehicle sound quality. The paper describes the rattle phenomena and control method for a powerplant with a dual-clutch transmission at vehicle low speed driving condition. The parameters influencing the rattle, which contains rotational speed fluctuation, drag torque and moment of inertia of gear, etc, are analyzed theoretically. A detailed model including engine, torsional damper, dual-clutch, equivalent vehicle and gears inside transmission is built. Angular acceleration and contact force between gears are identified as the most important parameters to evaluate rattle intensity, thus they are called rattle index. The paper analyzes the sensitivities between rattle index and the torsional damper hysteresis torque, and between rattle index and moment of inertia of input shaft. The analysis results show that moment of inertia of unloaded gears is the most important parameter influencing the rattle, and dual-mass flywheel, a special kind of torsional damper, is the most effective way to reduce the rattle. A powerplant with dual-mass flywheel is tested and the data show good coincidence with the simulation results.