Study On Slippage And Wedge Losses Of Continuously Variable Transmission

Recently,along with the increment of consciousness of environment protection,the passenger cars of low fuel consumption and emissions attract attention of people increasingly. Reducing fuel consumption and emissions become the focus of technological innovation and play an important role in market competition of the automobile. Continuously Variable Transmission(CVT),as a type of ideal transmission for passenger cars,not only can reduce emissions but also improve fuel economy. At the same time,it can provide more driving drivability for automobile,and make drivers experience superior drive enjoyment. In despite of Continuously Variable Transmission has a lot of excellences above,the efficiency is the development bottleneck to it. In addition,because Continuously Variable Transmission is an integration,which integrates lots of techniques,but it stile has much improvement space in hardware and software,consequently fuel economy and transmission efficiency get father improvement. They play a positive role in extending proportion of Continuously Variable Transmission in automobile transmission.Therefore,improving efficiency of Metal Belt Continuously Variable Transmission turns into core of CVT research.In Continuously Variable Transmission device,there are a good many factors which affect transmission efficiency,in hardware including torque converter,clutch,transmission shaft,pulley,belt,idler shaft gear,final drive gear,hydraulic pump,hydraulic pipeline,bearing and so on;in software including clutch control,ratio control,clamp control,temperature control,slip control,lock-up torque converter control,improvement on hydraulic driving return line or start-stop control ect. The mechanism and proportion of energy loss which result from factors above are different,Hydraulic system and the variator are important modules,which result in more energy loss. The energy loss in variator includes energy loss between pulleys and belt,segments and segments,segments and bands,bands and bands. In this thesis,the author does deep study on the energy loss between pulleys and belt,mostly including several aspects below:(1) Through referring to a great lot bibliography,the author analyses virtue of Continuously Variable Transmission and its course or area of development,otherwise,the author also analyses the mechanism and types of energy loss.(2) By right of the draw software of three dimensions-CATIA,the author sets up the model of the Variator,which fits FEA software ASNSYS/LS-DYNA.(3) By means of theory analysis,the author sets up mathematical model,what is used to calculate torque loss in entrance and exit of pulleys and wedge loss.(4) In order to find the reasons of correlative movement,getting the level axis displacement of some typical position elements and analysis the movement track of some segments with the lsprepostd of ASNSYS/LS-DYNA.(5) In order to get the torque loss and wedge loss in different stiffness,the torque loss and the wedge loss of the pulleys model based two different stiffness is compared. The research on the torque loss and wedge loss of the metal belt of the CVT at the point,namely in entrance and exit of primary pulleys and second pulleys,with the software of ASNSYS/LS-DYNA which can help get the value of the loss and the percent of torque loss indicate that the effect of changes the loss in different work conditions by improving the stiffness of the metal pulleys.In the proceeding of studying this project,researcher has met lots of difficulties because of the lack of mature experience. Suck as, what degree the transmission can be predigested,and how this model would influent the result. There are lots of steel segments,how to write command language in order to set model parameter and plot meshing on the steel segments,consequently increase its ability of reusing. Whereas the complexity of steel belt model,how much gaps between steel segments would be reasonable;but in the other hand,in order to save time of CPU's computing,how many layers of steel bands would be feasible. What way could researcher to choose a mode of plot meshing and its density. How to achieve the transmission's limit conditions,how to deal with the huge simulation data,how to winkle high frequency interferential signal which influent the result much,and how to disposal data with MATLAB to get torque and loss of power.Cheeringly,through my own favor,all of these problems have been solved effectively.During the researching,I found the precision of transmission model,especially the precision of steel belt model has important influence to results.Meanwhile,the transmission's limit conditions and control parameter of the whole model have mainly influence also. It's necessary to balance the aptness of model and control parameter many times in order to find appropriate model and control parameter to get a satisfactory result finally.It is first time to analysis power loss of CVT using ANSYS/LS-DYNA in domestic area. Through researching of this project,we have proved feasibility of using ANSYS/LS-DYNA to analysis energy lose of CVT,set a good sample for further researching and this paper has an upper referencing value.