Design Of Electric Vehicle Helical Gear Transmission Tooth Surface Based On Equal Strength And Modification

Compared with fuel vehicles,electric vehicles have the advantages of pollution-free and fast acceleration,and their widespread use has become the general trend of the development of The Times.Helical gear is the core part of electric vehicle transmission.The design of macro-geometric parameters and micro-tooth surface modification has a direct influence on the transmission quality of the transmission system.At present,the helical gear of electric vehicle mostly adopts the gear shape of addendum modification,modification and high teeth,which makes the design and calculation of its geometric parameters complicated and redundant.Moreover,the enterprise engineers often use the trial-and-error method and empirical method in gear design,which only meets the working strength requirements of the gear pair,but ignores the strength difference between the bull gear and pinion pair.In addition,most electric vehicles adopt the motor directly coupled with the reducer,and the output speed of the motor is high(the peak speed has reached 17900r/min),which puts forward more demanding design requirements for the modification of the helical gear transmission tooth surface of electric vehicles.Therefore,based on the constant strength and modification,this paper studies the design of helical gear transmission tooth surface for electric vehicles.The main research contents are as follows:(1)According to the formation machining principle of helical gear and the meshing principle of spatial gear teeth,the helical gear tooth surface model of electric vehicle with addendum modification and high teeth was established,and the helical gear tooth contact analysis(TCA)model considering the edge contact and installation error was constructed.The geometric contact characteristics of helical gear transmission of electric vehicle were studied by using MATLAB self-programming.(2)Static strength analysis was carried out for all levels of gear pairs of a two-stage reducer of an electric vehicle.Considering the strength differences between large and small gear pairs,a multi-objective macro-geometric parameter optimization design method for helical gear transmission was proposed,and multi-objective particle swarm optimization algorithm(MOPSO)with variation strategy was adopted to optimize the solution.The load bearing capacity and bending strength difference of helical gear pair are improved after optimization.(3)Considering the influence of installation error on the geometric contact performance of helical gear transmission of electric vehicles,a tooth surface modification design method was established,which included three modification methods: axial modification,profile modification and topological modification.The influence of three modification methods on the geometric contact characteristics of helical gear transmission was investigated by the gear tooth analysis algorithm with edge contact,and the topological modification methods of pinion tooth surface were determined.In order to avoid the edge contact phenomenon of helical gear transmission,the contact trace and geometric transmission errors in the contact characteristics were taken as the optimization objectives,and the topological modification parameters were optimized.After optimization,the contact trace of the tooth surface is close to a straight line,which reduces the sensitivity of the contact trace of the tooth surface to the installation error,and no edge contact phenomenon.(4)The professional gear transmission simulation software MASTA was used to carry out static simulation on the helical gear pair before and after the equal strength design optimization in Chapter 3,verifying the feasibility of the equal strength design method for electric vehicle helical gear transmission,and comparing the influence of TCA analysis in this paper and the topological modification design of tooth surface on the geometric contact characteristics of helical gear transmission,the results were basically consistent.The reliability of the theoretical derivation is verified.