Analysis And Optimization Of Contact Fatigue Of Hybrid Planetary Gear Train Based On Working Conditions

As a key component of a new hybrid vehicle transmission system,planetary gear trains have become one of the research hotspots in the field of new energy vehicles in recent years due to their high transmission efficiency,wide transmission ratio range and strong carrying capacity.The hybrid planetary gear system can change the speed,torque and driving direction,and can meet the needs of different cycle conditions of the vehicle.However,due to the abundant internal nonlinear excitation of the gears,the load between the gear pairs is more complicated,which makes it prone to gears.Contact fatigue damage affects the gear transmission performance and greatly reduces the safety performance of the vehicle.In order to improve the reliability of hybrid electric vehicles and ensure the personal safety of drivers and passengers,it is necessary to study and analyze the contact fatigue of hybrid planetary gear trains based on actual cycle conditions,which mainly include the following aspects:First,according to the load distribution characteristics of the planetary gear train,a plan for the preparation of the contact fatigue load spectrum of the hybrid planetary gear train is determined;the eigenvalue statistics and analysis are carried out based on the typical cycle conditions,and the working mode switching decision of the hybrid planetary gear train is made,combined with the vehicle Longitudinal force analysis during driving has established a working condition model of hybrid planetary gear train.Through simulation analysis,the relationship between required torque,speed and time history is obtained.Combined with the requirements of finite element simulation analysis and experimental analysis,a close-to-practical model is compiled.The contact fatigue load spectrum under cyclic conditions provides a theoretical basis for subsequent contact fatigue analysis.Secondly,the structural characteristics of the planetary gear train are analyzed,and the gear transmission model of the planetary gear train is established.The finite element method is used to analyze the tooth surface contact stress of the planetary gear train,and the dangerous fault parts of the tooth surface are determined,and the contact fatigue is simulated and predicted.The life value is calculated by the nominal stress method and the linear fatigue cumulative damage theory to obtain the contact fatigue life value of the planetary gear train.Compared with the simulation result analysis,the simulation analysis verifies the feasibility of predicting the contact fatigue life of the planetary gear train under random loads.Thirdly,a test bench for the contact fatigue reliability of the hybrid planetary gear train was built,and the test was run in accordance with the operating procedure.The damage of the planetary gear train gears in the test results was analyzed and summarized,and the results were compared with the finite element simulation analysis results of the contact fatigue life of the planetary gear train.,Verified the reliability of the dynamic model of the planetary gear train,and provided an important basis for the following tooth profile optimization.Finally,combined with the consistency of the results of the finite element simulation of the contact fatigue of the planetary gear train and the experimental analysis,the necessity of the tooth profile optimization method is proposed for the problems of uneven load distribution on the tooth surface and edge stress concentration,and the tooth profile is also introduced.Compared with the theory and method of tooth profile modification,the planetary gear system is modified based on the micro-modification software,and the results before and after the tooth profile optimization are compared to improve the uneven distribution of contact stress on the tooth surface of the planetary gear system.The load-bearing capacity of the planetary gear train avoids stress concentration and is beneficial to prolong the service life,which proves the effectiveness of the tooth profile optimization method.