Research On Meshing Characteristics And Modification Technology Of Gear Transmission System Used In Electric Vehicle Reducer

With the global warming and the increasing energy crisis,energy conservation and emission reduction are hot topics and a worldwide problem that needs to be solved urgently.Electric vehicles can reduce energy consumption and vehicle exhaust emissions,which is one of the important development trends in promoting energy conservation and emission reduction and preventing air pollution in the world.Nowadays,consumers have higher requirements for the comfort of automobiles with the development of technology.Therefore,electric vehicles are required to have better NVH(Noise,Vibration,Harshness)performance.Reducer is an important component of the transmission system.In addition,it is a major contributor for the vibration and noise.Due to the manufacturing error,installation error and time-varying meshing stiffness,gear meshing impact,the eccentric load on the tooth surface and the periodic fluctuation of speed and load are caused,resulting in excitation vibration and noise.A large number of studies have shown that:modification will affect the meshing characteristics of gear pairs.Reasonable modification design can improve the meshing characteristics and NVH performance.Therefore,taking the gear transmission system of an electric vehicle reducer as an example,considering different working conditions,the modification scheme is studied,the main research is as follows:1、In order to reduce the eccentric load in tooth direction,an optimal modification design method of teeth surface for high-speed level helical gears pairs of electric vehicle was proposed.Firstly,the comprehensive flexibility matrix of tooth surface was obtained through ANSYS Workbench.Then,a loaded tooth contact analysis(LTCA)model considering gear errors was established.In order to uniform the meshing load on tooth surface,a modification design method was proposed to obtain high-order modification curve,and the modified gear model was constructed.Finally,the meshing characteristics before and after modification were calculated and compared,and the dynamic meshing stress of high-order curve and traditional modification under rated working conditions were simulated by ANSYS Workbench.Results show that the peak value of transmission error decreases,the load distribution in the tooth direction is more uniform,the maximum contact stress decreases,and the dynamic meshing stress of high-order modified gear reduce 28.5% and 30.2% respectively compared with the traditional parabolic modified gear,in which helps to improve the meshing impact and eccentric load.2、According to the gear transmission system of an electric automotive gearbox,static contact analysis were carried out under rated power,maximum velocity and maximum torque load conditions.A multi-parameter optimization based on permutation and combination increment method of KISSsoft was adopted to obtain the optimal micro-modification scheme of each gear surface under different working conditions,optimizing various objectives such as the transmission error amplitude,the maximum contact stress on the gear flanks,and the minimal safety against scuffing.Finally,ANSYS Workbench was used to carry out transient dynamic analysis of gear transmission system before and after modification.The results show that the meshing performance of the topological optimized gear system is improved,the load distribution area is increased,the dynamic meshing stress and the vibration acceleration is reduced,and the optimization effect is best under the maximum torque condition.3、Constraint modal analysis was performed on the gear transmission system to obtain the front 6 orders modal frequencies and modes shapes.Then the modal superposition method is used to calculate the vibration response of the gear transmission system before and after modification,and gets the vibration velocity and vibration acceleration curve of each measuring point on the gear.Combined the vibration response,the acoustic boundary element method of Harmonic Acoustics was used to estimate the radiated noise of gear transmission system before and after modification at various frequencies.The results show that: except 700 Hz,the maximum value of surface sound pressure level of gear transmission system after modification is reduced at other frequencies,and the radiated noise value of field point is reduced by 6.8d B on average.Compared with the noise experimental results in the literature,the accuracy of the acoustics model is verified.