Research On Effect Of The Wet Clutch Engagement Characteristics For CVT Starting Process

CVT is a ideal transmission for cars especillay economical cars.It has the advantages of compact structure,excellent performance,easy to electronic control,low cost, high efficiercy and low emissions of harmful gases,therefore it have brood prospects for the development and market space.Such transmission is still in the research and development stage in China,there are some challenging issues either in the drive mechanism or in systemic design and control technologies.Grasp these theories and key technologies has great realistic significance for enhancing our country's self-development capacity in domestic cars and shortening the gap with developed countries.This is also a common goal for the contemporary major automobile companies in the world.The key technologies of CVT control including the speed ratio control,champing force control and starting clutch control,and only these three aspects of control are in the best condition can contribute to the full performance of motor vehicles.The common starting clutch used on CVT including hydraulic torque converter,the electromagnetic clutch and wet multi-plate clutch.Wet multi-plate clutch with its unique characteristics and also its higher efficiency and low price has been widely used in various types of vehicles.Therefore the research on effect of the wet multi-plate clutch engagement characteristics on CVT starting process has great theoretical significance for the formulation of the control strategy of CVT starting clutch.In view of this,the paper combined the project cooperated with Shuangling Group Co.LTD,that is the developing project of CVT and launched its foucs on the following aspects by concentrating the effect of the wet multi-plate clutch engagement characteristics on CVT starting process:(1)On the basis of reading alarge number of domestic and foreign reference books,the structure and working principles of the CVT and the wet multi-plate clutch were analyzed.(2)On the basis of the analysis of the dynamics of the engagement process of wet multi-plate clutches,the friction mechanism of the sliding friction state and the composition of the transmission torque were analyzed.(3)In order to simulate the engagement process of wet multi-plate clutch,proceed the wet milti-plate clutch bed test.The test results confirmed the reasonableness of the analysis of the process of the engagement and the sliding friction state.(4)Established the starting engagement process model of CVT wet multi-plate cluth on the basis of the model of engine output torque,the clutch output shaft torque and the torque transferred in the clutch starting engaging process and analyzed the evaluation indicators of the strating process of the clutch.(5)On the basis of wet milti-plate clutch bed test,with the application of Matalb/Simulink software established the simulation system of the starting engaging process of the wet multi-plate clutch.Simulate the process of ground starting of the 50 percent and 80 percent throttle opening,and analyzed the effect of the engage characteristics of the wet multi-plate clutch on sliding wear and impact.The outcomes and methods of the paper will providing a favourable guidance for the research of the engagement strategy of CVT wet multi-plate clutch starting and for the development of CVT products.