Study On Thermo-hydro-mechanical Coupling Characteristics And Influence Of Wet Clutch

In recent years,with the rapid development of China’s self-owned brand transmission companies and breakthroughs in independent technology,the proportion of automatic transmissions based on wet clutch research and development in the domestic passenger car transmission market has increased year by year.During the working process of the wet clutch,a large amount of friction heat is generated by the sliding friction of the friction pair.The cooling lubricating oil in the friction pair oil groove takes away part of the heat,and the remaining heat is absorbed by the friction pair,causing its temperature to rise sharply.It is prone to thermal failure phenomena such as friction factor decline,surface burning,local deformation and overall deformation,which reduce the working performance and thermal reliability of the wet clutch,thereby affecting the shifting performance and life of the transmission system.Relying on the wet clutch development project of a domestic enterprise,this subject conducts an in-depth study of the thermo-hydro-mechanical coupling characteristics of the wet clutch friction pair,and analyzes the influence of the cooling oil flow rates and the inclination angles of the oil groove on the temperature characteristics,stress and strain characteristics and flow field characteristics during the engagement process of the friction pair of the wet clutch.The main research contents of the thesis are as follows:(1)The engagement process of the wet clutch friction pair is analyzed based on the friction contact mechanism.An effective mathematical model of the engagement process is established by applying the average Reynolds equation and the rough surface elastic contact model.At the same time,considering the viscosity-temperature characteristics of the oil film between the friction pairs,the sliding friction temperature field model of the wet clutch friction pair is established.Finally,the changes in the sliding friction temperature field,relative speed difference,transmission torque and equivalent friction coefficient during the engagement process are analyzed,which provide initial input conditions for the subsequent thermo-hydro-mechanical coupling finite element analysis of the friction pair of the wet clutch.The validity of the simulation results is verified by experiments.(2)The mutual coupling relationship of temperature field,stress strain field and flow field during the actual engagement of the friction pair of the wet clutch is studied,the boundary conditions of the three-field coupling during the engagement process of the friction pair of the wet clutch are determined.And based on the simulation results of the mathematical model of the wet clutch friction pair engagement process,a thermo-hydro-mechanical coupling finite element analysis model of the wet clutch friction pair is established.(3)Based on the established thermo-hydro-mechanical coupling finite element analysis model of the wet clutch friction pair,the temperature field,stress strain field and flow field during the engagement process of the wet clutch friction pair are analyzed.Then,a simplified model of thermal-fluid-solid coupling analysis of wet clutch friction pair is established,and compared with the original model,it was verified that the simplified model can effectively analyze the thermo-hydro-mechanical coupling characteristics of wet clutch friction pair.(4)Simplified thermo-hydro-mechanical coupling finite element analysis model for wet clutch friction pairs with different cooling lubricating oil flow rates and different oil groove inclination angles are established.And the influence of cooling lubricating oil flow rates and oil groove inclination angles on the temperature field,stress-strain field and flow field of wet clutch frication pair during engagement are studied.