Investigation and Improvement of a Bouncing Torsional Vibration in Automotive Dual Mass Flywheel by Combining Testing and 1D CAE Modeling Approach 2019-01-1556

Dual mass flywheel (DMF) is a well-known isolation system for vehicle drivetrain. DMF has two typical elastic energy storage systems: long travel arc springs and in-series spring units (including two or more springs) and sliding shoes connected in series. DMF has such complex nonlinear characteristics as torque-dependent torsional stiffness and rotational speed-dependent hysteresis friction due to its dependency of centrifugal force that is applied to components and radial force of springs. Because of this complexity, sub-harmonic vibration (SHV) may occur under certain circumstances, such as under light-load and high-rotational conditions. In general, since SHV’s frequency is 1/2 or 1/3 of the engine’s combustion frequency and may cause human discomfort, DMF must be designed robust against such nonlinear vibration. In this paper to reduce the SHV occurrence and to show a more robust design indicator, the SHV causing the mechanism is researched by testing and 1D CAE modeling. In detail, DMF interior behavior in high-speed rotation is clarified with high-speed cinematography on a test bench, and high-resolution relative torsional angle of DMF is obtained by evaluating the actual vehicle with a conventional four-cylinder gasoline engine, which is equipped with in-series spring unit type DMF. As a result, bouncing torsional vibration (BTV) might occur when sliding shoe and secondary-side driven flange contact each other, and that is triggering the SHV excitation. 1D CAE model, whose development is based on the tested mechanism, is verified since the substantially same BTV and SHV occur between tests and simulation results. According to 1D CAE, highly sensitive parameters and ideas for reducing SHV can be found with sensitivity analysis of the physical DMF parameters. The effect of those parameters was confirmed with vehicle tests.