Efficiency And Thermal Analysis Of The Two-speed AMT For Pure Electric Vehicle

With the continuous development of pure electric vehicles,taking the driving range,speed performance and other performance into account,equipment with two-speed AMT of pure electric vehicle has become a hot research at home and abroad.Many of energy losses including gear meshing power loss,bearing power loss and churning oil power loss are incurred during power transmission.Its small size and high integration of the structural characteristics will reduce the heat dissipation area with limited cooling capacity.If the power losses cannot be dissipated in time,the transmission will be subject to higher heat load.Excessive oil temperature will not only cause the system temperature rise,but also affect the performance of lubrication and transmission.In addition,high tooth surface temperature is also one of the main factors of causing glue.Therefore,it is necessary to research on the overall thermal analysis for the drive system of electric vehicle.Studying the rule of heat transfer of the transmission system and the distribution of temperature field has very important theoretical significance and practical value.The study is carried out relying on a college-enterprise cooperative program.A two-speed AMT is selected as research object.Based on theory of heat transfer,the temperature rising and distribution under different conditions were studied combined with thermal network method and finite element method.The main researches are as following:(1)The power loss model of the two-speed AMT.An energy transfer model of the gear system is developed based on the power plane,thermal plane and the lubrication plane.The theory of efficiency loss of transmission has been analyzed,and the power losses including gear mesh loss,oil churning loss and bearing friction loss have been calculated in detail.The power loss model of the two-speed AMT has been established.Meanwhile,the percent of the subsystem power losses in total power losses has been studied under different working condition,which provides the theory base for the gearbox thermal analysis.(2)The thermal balance analysis and the thermal properties.Without regard to the effect on the heat transfer properties of the internal temperature difference,the nodes substitute for all of the parts.The thermal resistances are employed to simulate the couple between the parts and the thermal network model of the two-speed AMT was constructed by integrating the nodes.With the thermal network model,the thermal balance of the two-speed AMT under different working condition has been studied.(3)Finite element simulation analysis.Considering that the thermal network cannot describe the temperature distribution of components accurately,the finite element analysis method is adopted.Based on SolidWorks and Ansys interface,the three-dimensional solid model and finite element analysis model of transmission are established.At the same time,the boundary condition and the heat balance equation of the gear temperature are established based on the calculation results of the thermal network.Through ANSYS thermal analysis and calculation,the gear temperature distribution is systematically analyzed.(4)Experimental study on the temperature rise and transmission efficiency of the two-speed AMT.The tests of the temperature rises of the main parts and the transmission efficiency under different operating condition are obtained.Then compare them with the numerical results gotten before.The test results are good agreement with the numerical results and it is shown that the thermal balance model can be available to estimate the temperature rise of two-speed AMT.