| Electric vehicle is the development direction of the future automotive industry,and the light weight of drive motor and the density increase of power volume are its main trends.According to the roadmap on the “roadmap” of the electric drive motor for electric vehicles issued by the US govement,the power density of the drive motor will reach 50 KW/L in 2025.This means that the speed for drive motor will be further increased from the current 6000~12000 to 15000~20000 r/min.Meanwhile,the NVH problem of reducer/transmission gear becomes an important technical problem,especially.For China,the reducer/transmission vibration noise problem of electric vehicle has not been effectively captured,so that it has become a crucial bottleneck restricting the power density and the speed increase for the drive system of electric vehicle.The reducer/transmission for electric vehicle usually adopt a fixed gear ratio of 1gear or a transmission system of 2 gear and 3 gear.With the reducer/transmission input speed increasing,vibration and noise will be generated under the excitation of the transmission error when it occurs in the gear transmission system.Consequently,the transmission error is not only the main driving source of reducer/transmission gear vibration and noise,but also the key to settle the problems for vibration and noise.The research herein of this dissertation mainly focuses opon the transmission gear error and vibration excitation of electric vehicles.The main source of gear transmission errors is gear tooth deformation and manufacturing errors.During the analysis of this dissertation,the gear tooth deformation of the spur gear is chosen as the starting point to investigate the calculation method for transmission error and the excitation response of the reducer /transmission helical gear.The main research contents are as follows:(1)Based on the analysis of the tooth deformation of spur gears,the helical gear was converted into a series of spur gears by the slicing method,and then,deformation curves and tooth contact during the process the deformation compatibility principle and the helical gears are quickly meshed using the load integration.This provides a simple and efficient calculation method for the meshing performance and transmission error calculation of the reducer/transmission helical gear.i.e.,the Romax software was used to confirm of the correctness of the method,and the LTCA and deformation calculationfunctions of the finite element software are utilized to compare the calculation results and testify its reliability.(2)The influence of gear macro parameters(helix angle,tooth width,pressure angle,addendum coefficient,top clearance coefficient,contact ratio)on the transmission error was analyzed,and the results displayed that the influence of helix angle and overlap ratio was greater.It is also proved that when the axial coincidence εβ was an integer,the change trend of gear transmission error was gentle and the peak-to-peak value was the smallest.(3)The influence of various modification parameters including tooth profile modification and axial modification on transmission error was explored,and the method of selecting the modification parameters and reducing the transmission error was proposed.The verification analysis was carried out with Romax software and the reliability of the calculation method was verified.(4)The vibration excitation response of the gear transmission system to the transmission error is studied.Based on the calculation optimization and spectral characteristics of the transmission error,using the frequency spectrum characteristic of the transmission error spectrum of the gear transmission system and the frequency characteristics of the forced vibration under excitation,the gear multi-freedom vibration model is simplified to a double mass vibration model,and a gear transmission system is established.The direct relationship between the quality,stiffness,transmission error frequency spectrum and the gear vibration spectrum provides key vibration response laws and evaluation parameters such as gear amplitude,gear vibration force,vibration force on the bearing and the case,etc.The impact of mass,stiffness,and transmission error spectrum on vibration,which provides a clear and reliable method for the analysis and resolution of NVH(noise,vibration,and harshness)problems in electric vehicle reducer/transmission.(5)By means of the setting up a transmission error test-bed,high precision test of gear transmission errors were performed.The gear transmission errors under different working conditions were tested,and the test results were analyzed and processed.After the theoretical calculation results compared,the accuracy and reliability of the theoretical calculation method were demonstrated. |
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