| The automobile gearbox is the core device of the automobile transmission system.A pure electric automobile which is matched with gearbox can improve the power and economy of the vehicle,but this is based on the premise that the gearbox has high transmission efficiency and excellent NVH performance.Gear shaft tooth parameters and the design of the gear support form affect the NVH performance and transmission efficiency of the gearbox.Here we do research for a two-speed gearbox which is matched up with pure electric vehicle,and the main purpose is to reduce the vibration and noise and improve transmission efficiency of the gearbox.The gear parameters of the gearbox and the support form of the gear were optimized to make the gear change and finally making the gearbox reach the using standard of vehicle.The specific research routes are as follows:1.First we introduced the domestic and international research status of pure electric vehicle gearbox,and then the research status of gearbox noise optimization design and transmission efficiency optimization design are introduced.2.We used the Romax Designer software to build a gearbox model and analyze the vibration and noise of the gearbox.Analyzing the gear transmission error,it was found that the transmission error of the three groups of gears was large under two common working conditions.Next,the dynamic force of the bearing under the excitation of the gear transmission error was simulated,and it was used as the input condition to analyze the harmonic response of the transmission case in Ancys Workbench to obtain the deformation of the case.Then we used the LMS Virtual.Lab software to establish the transmission case Boundary element model of the volume,and then we used the deformation results of the shell as the boundary conditions,the acoustic radiation simulation was performed on the gearbox to obtain the sound pressure radiation cloud diagram and the sound pressure value.The results showed that the noise amplitude was large,and parameter optimization schemes need to be formulated to reduce the noise amplitude.3.Aiming at the problem of unsatisfactory cruising range in the real vehicle test,the efficiency analysis of the gearbox was performed.Based on the Romax model,the overall efficiency simulation was performed to obtain the overall efficiency of the gearbox in two gears.The results showed that the highest efficiency of the first gear was 95.78% and the highest efficiency of the second gear was 93.70%.In order to clarify the power loss distribution,the gear meshing friction loss,oil stirring loss,and bearing friction loss under two common working conditions were obtained by simulation.The results showed that the gear meshing friction loss accounted for the largest proportion of the total power loss and it was needed to be targeted for optimization.There is also room for optimization of the rest of two power losses.4.Based on the simulation results,a parameter optimization scheme was formulated.First,the macroscopic parameters of the gear were optimized to reduce gear transmission errors and gear meshing friction losses.Next,increasing the support rigidity between the idler shaft and the housing,.Then reducing the deformation of the idler shaft and reducing the misalignment of the second gear.Finally,the support stiffness of the first gear of the driven gear on the intermediate shaft was increased to reduce the misalignment of the gear of the first gear.For the gearbox before and after parameter optimization,the vibration and noise simulation,bench test and real vehicle test were compared.The simulation and experimental results showed that the NVH quality of the gearbox after parameter optimization was significantly improved.The efficiency simulation and bench test comparison of the gearbox before and after the parameter optimization showed that the transmission efficiency of the gearbox had been improved after the parameter optimization. |
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