The Effect Of Dual Mass Flywheel On Starting And Shifting Performance Of DCT Vehicles

Dual clutch transmission(DCT)has the advantages of uninterrupted shifting power,high transmission efficiency,compact structure,good production inheritance and so on.It has developed rapidly in recent years.As one of the research focuses in the field of DCT,start-up and gearshift performance have been widely concerned.Based on the key project "DCT intelligent control and evaluation method considering dynamic service performance,driving behavior and driving environment" jointly funded by NSFC,this paper studies the effect of dual mass flywheel torsional damper(DMF)on the starting and shifting performance of DCT vehicles under the condition that the engine excitation torque is more accurate.According to the research task,this paper mainly carried out the following research work.(1)Modeling of engine excitation torque Based on the engine structural parameters and test data provided by the enterprise,the engine’s reciprocating moment of inertia and the corresponding working point’s gas acting moment are calculated,and the engine’s average torque model is established.The harmonic components of the gas action moment corresponding to the working point are obtained by Fourier series expansion.On this basis,the harmonic characteristic parameters of the gas action moment at different working points of the engine are obtained by function fitting.Thus,the engine torque model is established,which provides a more accurate dynamic torque excitation for DCT vehicle transmission system.(2)Modeling of DCT vehicle transmission system A dynamic model of general DMF is established for DCT vehicle transmission system modeling,and the effect of DMF parameters on DMF damping performance is analyzed.Based on the clutch stick slip state,the transmission torque characteristics of the clutch are analyzed.Based on the research on the characteristics of DMF,clutch and other key components,the dynamic model of DCT vehicle transmission system is established,and the dynamic equations of DCT vehicle starting and shifting are given.The above work laid a foundation for the study of DMF’s effect on DCT’s starting and shifting performance.(3)Analysis of the effect of DMF on the starting performance of DCT vehicle The effect of DMF on the clutch engagement stability of DCT vehicle during starting is analyzed by simulation.The results show that DMF has a certain effect on the clutch engagement stability,and DMF with reasonable parameter design makes the clutch engagement more stable.Compared with the effect of clutch driven disk torsional damper on DCT vehicle starting judder,the effect of two kinds of damper stiffness and damping on DCT vehicle starting judder is discussed.The results show that DCT vehicle with DMF is in good starting judder condition.The effect of the stiffness and damping parameters of DMF on DCT vehicle starting is analyzed.The results show that the changes of stiffness and damping parameters have a certain effect on the starting shuffle of DCT vehicles.(4)Analysis of the effect of DMF on the shifting performance of DCT vehicle The effect of DMF on the clutch engagement stability of DCT vehicle is analyzed by simulation.The results show that DMF has a certain effect on the engagement stability of the clutch,and DMF with reasonable parameter design makes the engagement of the clutch more stable in the process of shifting.The effect of DMF’s stiffness and damping on DCT vehicle’s shifting judder and shuffle is simulated and analyzed.The results show that,in the given range of parameters,the change of damping has a greater impact on the vehicle’s shifting judder and the change of stiffness has a greater impact on the shuffle.In addition,based on the analysis of the impact of DMF on the starting and shifting performance of DCT vehicles,a Dual Mass Flywheel-Circumferential Short Spring(DMF-CSS)is designed for DCT vehicles developed by the cooperative enterprise.Simulation analysis shows that the DMF-CSS can make the DCT vehicle have better starting and shifting performance.