Sound Quality Analysis And Optimization Of Hybrid Transmission With Double Planetary Mechanism

With the rapid development of the automotive industry,the subjective feeling of noise has been paid more and more attention by customers.As one of the main noise sources of hybrid electric vehicles,the sound quality research of gearbox has become an important part of automotive research and development.In this dissertation,a double planetary hybrid electromechanical coupling transmission used in bus is taken as the research object.Based on the theory of multi-body dynamics,finite element method,boundary element method and psychoacoustics,the sound quality of the radiated noise of the gearbox is analyzed.According to the analysis results,the sound quality of the radiated noise of the gearbox is improved by optimizing the structure of the gearbox.The main contents of this paper are as follows:Firstly,the generating principle of gear meshing excitation in gearbox is expounded.Then,the dynamic model of double planetary row coupling mechanism is established by professional dynamic simulation software.The speed of main components,meshing force between gear pairs and dynamic backing force of bearing seat on gearbox are solved.Secondly,based on the finite element theory,the finite element model of the double planetary hybrid power transmission is established.The modal of the transmission is solved,and the natural frequency and modal mode of the shell are analyzed.In addition,the transient response of the box under extreme conditions is solved by using the dynamic response of each bearing seat as the dynamic load.Violent vibration is also concentrated at the end cover of the output shaft and the shell of the driving motor.At the same time,the gearbox in pure electric mode is selected to carry out frequency response analysis in this dissertation,and the vibration acceleration and displacement of the shell are obtained.Through the vibration and noise test of the gearbox,the test data are compared with the simulation results,and the correctness of the simulation model is verified.Thirdly,the boundary element model of a double planetary hybrid electromechanical coupling transmission is established,and the sound power,surface sound pressure level and field sound pressure level of the box are obtained by solving the vibration displacement of the node of the box as the boundary condition.Besides,the sound pressure levels of three near sound field points obtained by simulation are compared with the experimental data to verify the correctness of the simulationBesides,the loudness,sharpness,roughness,fluctuation and annoyance of noise signals at designated field points are evaluated,and the radiated noise of five parts of gearbox is simulated individually,coming to the result that the parts with poor sound quality are the output end cap and the drive motor.Finally,the sound quality of the radiated noise of the cabinet is improved.The annoyance degree,which represents a comprehensive evaluation index of sound quality,is selected as the optimization objective,and the structure is improved by adding reinforcement and free damping layer to the target parts.After the optimization,the sound pressure and sound quality of the improved radiated noise are reduced,which verifies the rationality and feasibility of the optimization scheme.