| Based on the "floating" principle and four-wheel drive,the boat-type tractor can overcome the disadvantages of crawler tractor and wheeled tractor in paddy field operation by taking advantage of the features of low hull ground pressure and large traction.Boat-type tractor are stimulated by mud,puddles,crops and other external excitations and internal excitations of key components of transmission system,which cause vibration of the whole machine and aggravate the damage of key components.The main research contents of this dissertation is as follows:(1)According to the design requirements of the transmission system of the boat-type tractor,the positions of the key components of the transmission system(engine,clutch,gearbox,transfer case,front axle and rear axle)should be reasonably arranged to ensure the axis of the driving shaft is parallel and in the same vertical plane,so as to improve the smoothness and stability of power transmission.(2)According to the power of the boat-type tractor and the transmission ratio of the gearbox,the key component of the drive shaft is checked for strength.It is to ensure that the reliability of the component design,it lay the foundation for the subsequent analysis of related dynamic characteristics.(3)The three-dimensional finite element model of key components and the frame are established.The strength and inherent characteristics of the frame and optimize the design of the frame are analyzed.The finite element model of the transfer case is established and the inherent characteristics of the system are analyzed.The results are compared with those of the following dynamic response analysis of the transfer case.(4)The three-dimensional finite element model of the first gear pair of the transfer case is established.The contact problem of the the gear meshing process and the influence of different friction coefficients on the contact pressure and contact force of the gear tooth surface are analyzed.By analyzing and processing data,the time-varying meshing stiffness of gears is obtained.It provides a reference for calculating the time-varying meshing stiffness of gears.(5)The thermo-elastic coupling gear pair model is established,the meshing characteristics of thermo-elastic coupling gear pair are analyzed.The internal and external excitations are applied to the transfer case,and the dynamic response is analyzed to ensure that the vibration response of the gear transmission meets the vibration standard of the gear device.(6)The finite element model of the transmission system and the frame is established,and the coupling excitation of the gearbox and the transfer case is applied in the fixed position of the gearbox,the transfer case and the frame respectively,and the vibration response of the frame is analyzed.The thermoelastic coupling and dynamic characteristics of the transmission system of boat-type tractor are analyzed,which can improve the reliability of the keycomponents and transmission system of the boat-type tractor,and has important significance for improving the working efficiency of the boat-type tractor. |
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