Torque Characteristic Analysis And Experimental Research Of Wet Clutch On DCT

The wet clutch is the core component of the wet DCT.During the engagement and disengagement of the clutch,the torque transmitted during the sliding phase and its precise control determine the starting and shifting quality of the DCT vehicle.If the torque characteristics of the wet clutch are not understood,or the torque estimation of the real-time transmission is not accurate,which will lead to inaccurate control of the clutch torque,resulting in vehicle starting shock,or the clutch slipping time is too long and even overheat problems such as ablation.Therefore,it is necessary to study the torque characteristics and real-time accurate torque estimation of DCT wet clutch in order to provide guidance for the design and control of wet clutch and improve the comfort and economy of DCT vehicles.For this reason,this article carried out the following research work:(1)The drag torque modeling and simulation of DCT wet clutch.Based on laminar flow theory in viscous fluid mechanics and Yang-Laplace equation in surface physicochemistry,the centrifugal inertia force and surface tension of cooling lubricating oil film are also considered to improve the surface contact model of oil film and friction pair.Then the influence of oil pressure difference at the inlet and outlet of clutch and groove is also considered to establish the drag torque model of DCT wet clutch.The effects of relative speed,lubricating oil temperature and viscosity on the drag torque of wet clutch in DCT are obtained.Finally,the sensitivity analysis of the factors affecting the drag torque of DCT wet clutch is also made.(2)Dynamic torque modeling and simulation of DCT wet clutch.The DCT wet clutch engagement process is analyzed,and the wet clutch micro-convex friction torque model and oil film viscous torque model are established.On this basis,the wet clutch dynamic torque model is established.In order to explore the dynamic torque characteristics in the engagement process of the wet clutch,the power transmission system modeling is carried out for the vehicle equipped with the wet DCT,and the dynamic analysis of the single clutch start and dual clutch start process of the DCT vehicle and the simulation analysis of the dynamic torque of the wet clutch are carried out.The trend of oil film thickness and clutch viscosity torque,rough torque and total torque in the process of engagement at different oil temperatures are compared and analyzed,as well as the variation of DCT wet clutch dynamic torque calculation model and traditional torque calculation model at different oil temperatures.(3)Research on real-time torque estimation of DCT wet clutch.Firstly,the discrete state space model of torque estimation of DCT wet clutch is designed,and the torque estimation flow of DCT clutch is established,then the discrete state space model is established when the single clutch and the double clutch of DCT are sliding respectively.On this basis,the simulation analysis of DCT wet clutch torque estimation based on Kalman filter algorithm is made.The results show that the torque estimation method designed has certain accuracy and practicability.It can not only estimate the torque transmitted by single wet clutch of DCT in real-time accurately,but also estimate the torque transmitted by double wet clutches of DCT in sliding phase respectively.(4)Design and development of DCT wet clutch comprehensive performance test bench.It mainly includes the scheme design of the test bench,the design and selection of the instruments and the development and design of the measurement and control system.Based on the designed test bench,the drag torque experiment of DCT wet clutch is carried out to explore the influencing factors of the drag torque and the law of its influence on the drag torque.The test result also verifies the rationality of the drag torque model.Based on the friction coefficient test,the influencing factors and influence laws of the friction coefficient are explored.The friction coefficient model established by the experiment is applied to the clutch torque simulation model above to obtain the actual change trend of the wet clutch torque more accurately.