The Static And Dynamic Characteristics Analysis Of The Dual Mass Flywheel In Vehicle Powertrain System

There are many factors that can affect the comfort, among which the vibrationand noise of the powertrain system have more influences. Torsional moment is themain one among excitation sources causing the vibration and noise of the powertrainsystem. Installing a torsional damper is the easiest and most effective way to controlthat. At the beginning, the torsional damper was installed on the clutch and then it wason the two parts that the flywheel was divided into, which forms the widely-used dualmass flywheel now. The appearance of dual mass flywheel preferably solves thevibration and noise of the powertrain system.This thesis adopts the dual mass flywheel circumferential spring (DMF-CS) thatcomposed of the primary、secondary mass and circumferential spring torsional damper.Deducing elastic characteristics of the circumferential spring by a section spring andcomparing the influence of DMF-CS with clutch torsional damper(CTD) on inherentcharacteristics and forced vibration of the powertrain system can provide thetheoretical basis and simulation data.By reading the relevant literature, this thesis makes a brief introduction ofvibration and noise of vehicle, describes the development and category of DMF athome and abroad, and compares advantages and disadvantages of DMF and CTD.Torsional characteristic curves are obtained by deducing the torsional rigidity formulaof circumferential spring on the DMF-CS. This thesis simplifies and meshes the keycomponents of DMF using Hypermesh and makes a finite element analyses withAbaqus on the following aspects such as the torque transmitting capacity of forceplate, the torque transmitting capacity of spline plate, the interference analysis of gearring and front shell, the torque transmitting capacity of spring system, and the ultraspeed analysis of primary mass. Also, the thesis establishes the powertrain torsional equivalent model on idling conditions and driving conditions and obtains the naturalfrequency and natural mode of vibration of the powertrain system equipped withDMF-CS and CTD using Matlab. Besides, excitation frequencies of main harmonic ofengine are calculated, and resonance conditions on idling conditions and drivingconditions are analyzed. What’s more, the thesis establishes the forced vibrationsimplified models on idling conditions and the fifth gear driving conditions of thepowertrain system to calculate the angle acceleration and angular velocity contrastcurves on input end and output end of torsional damper of the powertrain systemequipped with DMF-CS and CTD using Hypermesh and Abaqus.The important conclusions analyzed are as follows:1、On the idling condition: DMF-CS can effectively reduce the natural frequencyof second mode and slightly affect natural frequencies of the third and fourth mode,but it has little influence on higher modes of the powertrain system in contrast to CTD.On the fifth gear driving condition: DMF-CS can effectively reduce naturalfrequencies of the second and forth mode and slightly affect those of the first and thirdmode, but it has little influence on higher modes of the powertrain system in contrastto CTD2、Resonance analysis on idling conditions: the resonance of the powertrainsystem equipped with DMF-CS will not happen, but the natural frequency of secondmode of the powertrain system equipped with CTD is easy to resonate with thesecond main harmonic frequency of engine. On the fifth gear driving condition: thenatural frequency of the fifth mode of the powertrain system equipped with DMF-CSis easy to resonate with the seventh, eighth, ninth and tenth harmonic frequency ofengine. In addition to the powertrain systems having the same resonant frequency ofDMF-CS, its natural frequency of second mode equipped with CTD is easy toresonate with the first and second harmonic frequency of engine.3、Forced vibration analysis on idling conditions of the powertrain system: theamplitude of angular acceleration on output end with DMF-CS decreases by81.0%contrast to that with CTD, and the amplitude of angular velocity on output end withDMF-CS decreases by76.7%contrast to that with CTD, proving that the powertrain system equipped with DMF-CS has a good vibration isolation.