| Under the theme of energy conservation and environmental protection,it has become a consensus to vigorously encourage the development of electric vehicles.The metal belt type continuously variable transmission(CVT)has the advantages of small size,good comfort and strong energy saving,and was more in line with the requirements of energy saving and environmental protection,and has great development potential in the application of the electric vehicle transmission system.However,under the condition of high motor speed,CVT was prone to the problem of metal belt transmission failure.In response to this problem,this paper considered the stress state,lubrication condition and transmission efficiency of the metal belt under high speed conditions.Main work was done as below:(1)The key components and the transmission mechanism of metal belt CVT were introduced.The advantages of CVT in expanding the high efficiency range of the motor were considered.The qualitative analysis of the stress state and flutter effect of the metal belt was realized.The kinematics relationship of CVT was studied.The force analysis of each part of the metal belt was conducted,and the mechanical analysis model of the CVT transmission mechanism was set up.The variation law of the pushing force of the metal piece,the effective tension of the belt ring,and the axial force of the main driven pulley to the working parameters of the CVT was achieved.The finite element analysis of the metal sheet and the pulley needed to be done to find out the stress distribution state of the elementary parts of the metal strip under high speed conditions.(2)The lubrication state of the contact area between the metal piece and the pulley under high speed condition was studied.Founded on the theory of elastic fluid dynamic pressure lubrication,the numerical model of the characteristic analysis of the lubricating oil film was established,and the corresponding relationship between the working parameters of the CVT and the parameters of the lubrication model was established.The pressure and thickness of the lubricant film were calculated by arithmetical calculation.The influence of different working parameters on the pressure and thickness of the oil film was studied.(3)The friction power loss during the working process of CVT was analyzed.The power loss model of the relative sliding part was established.The variation law of the power loss term with speed ratio and speed was studied.The calculation obtained the relationship between the overall transmission efficiency and the speed,torque and speed ratio.(4)The CVT integrated transmission efficiency test was designed,and the variation law of CVT transmission efficiency with speed,torque and speed ratio was reached.The comparison between test data and theoretical calculation results was scheduled for completion.The results show that there is 3% difference between them,but the trend was consistent.The validity of the theoretical analysis results of CVT transmission efficiency under high speed conditions was confirmed. |
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