Dynamic Performance Matching And Experimental Study On Dual Mass Flywheel In A Car Drive System

With the rapid development of automobile industry,consumers have higher requirements on automotive comfort.Therefore,the auto industry pay close attention to vehicles’NVH problems.The engine not only provides driving power,but also continuously generates vibration and noise.Engine excitation is one of main factors of vehicle vibration.The fluctuating torque of the engine generates torsional vibration of the vehicle transmission system,which leads to the life reducing of the transmission system parts.Dual mass flywheel(DMF)can effectively attenuate the engine speed fluctuation,so it is of great significance to study the DMF.In this paper,torsional vibration characteristics of DMF were studied based on the vehicle drive train.Firstly,basic working principle,composition structure and advantages and disadvantages of the DMF were summarized and analyzed.The DMF development history was described.Combined with the research results of domestic and foreign scholars,it showed that it was necessary to study the torsional vibration characteristics of DMF.Secondly,the main excitation source of the transmission system was introduced.The main excitation order components of the engine were analyzed.And the second-order excitation was determined as the main analysis object.According to the basic simplification principle of the driveline,the parts of the driveline were simplified.The shaft system components,engine components,acceleration and deceleration systems and other drive trains were equivalently converted,so as to establish the mechanical model of the vehicle drive train under idle conditions and driving conditions.Based on this,the mechanical equations of the transmission system were established.The natural frequencies and modes of idle model and driving model were obtained by solving the mechanical equation using the subspace iteration method,and the inherent characteristics were analyzed.Thirdly,according to the DMF design structure,the AMESim model was built.The static stiffness curve,dynamic stiffness curve and damping angle curve were obtained by testing DMF,which were compared with the simulated curves to verify the accuracy of the AMESim model.The driveline model was established to analyze the DMF torsional vibration attenuation under different working conditions.Results showed that the DMF could effectively attenuate the engine speed fluctuation and the torsional vibration attenuation was above 30%.The second-order slice value of the primary mass is greater than that of the secondary mass under full-throttle acceleration and sliding conditions.The second-order slice value of the second-order mass was below 300rad/s~2.Then,the test verification analysis was carried out.According to the test scheme,the LMS test equipments were applied to test the car under different working conditions to obtain the speed fluctuation of primary and secondary mass,vibration of the gearbox and driver seat guide rail,and sound pressure level in the right ear of the driver and the rear passenger.Tests data showed that the DMF could attenuate the speed fluctuation.The gearbox and the driver’s seat rail were greatly affected by the engine second-order excitation.The sound pressure level at the right ear of the left rear passenger was significantly larger than that of the driver’s right ear.Comparing the test and simulation data,the rotational speed fluctuation error was under5%and the difference between the second-order slice curve and speed curve was small,which verified the accuracy of the vehicle transmission system model.Finally,the joint simulation model of AMESim and MATLAB was established.According to the optimization range,the inertia ratio,torsional stiffness and damping were optimized for the secondary mass rotational speed amplitude.Under idle conditions and the driving conditions,the optimal value of the damping was 0.02 Nm/(rev/min),the optimal value of the moment of inertia ratio is 0.71,and the torsional stiffness and the inertia ratio needed to be determined according to the actual conditions.According to the speed fluctuation amplitude,the rotation speed stability and the flywheel resonance peak,the optimal value of foundation friction torque was 10Nm.