Chassis Design And Lightweight Research Of 25 Horsepower Pure Electric Tractor

With the development of "green and ecological" agricultural machinery and equipment in China,the development of high-efficiency and energy-saving agricultural machinery and equipment has attracted much attention,so the in-depth research on electric tractors is of great significance.Based on the liquid-cooled heat dissipation system of the 25-horsepower electric tractor power battery pack,this paper designs a chassis structure that can carry its power battery pack and drive system and other components.In addition,in order to prevent the damage of the chassis structure or the reduction of the tractor’s cruising range due to the excessive mass of the whole vehicle,the reliability of the chassis structure and the quality of the whole vehicle cannot be ignored in the design.Therefore,the chassis design of the 25 horsepower electric tractor should not only consider Its bearing applicability,but also the lightweight design of its chassis structure,to ensure the good overall performance of the electric tractor.In this paper,on the basis of a fuel tractor chassis of a traditional model,based on the actual size of the dual-motor independent drive system and power battery and the installation position on the chassis,the chassis structure design frame is first determined,and then the chassis structure design index is obtained according to the design parameters of the whole vehicle.,design a complete chassis structure through its design indicators,and also determine the use of chassis structural materials and the connection method of each component,and finally carry out a theoretical check calculation of strength and stiffness based on the load on the chassis,and get the check result that the strength exceeds the standard.nuclear index.In order to verify the accuracy of the calibration and find out the problems existing in the chassis structure,it is necessary to further carry out the finite element analysis of the chassis structure.The finite element model of the chassis structure of the electric tractor is established by Hyper Mesh software,and the bending condition,torsion condition and traction condition are selected according to the actual working conditions of the tractor,and the chassis structure is calculated and analyzed by Opti Struct software.The research shows that the strength and stiffness amplitudes of the chassis structure are higher than the check indexes under the three working conditions.The L-section structure is optimized and improved.Aiming at the problems of stress concentration and sudden change in stiffness of the L-section of the front frame structure of the chassis,a structural optimization and improvement plan was formulated.The specific solution is to strengthen the inner and outer sides of the L-shaped section of the rear of the chassis front frame,and to strengthen the inner side of the L-shaped section of the middle of the front frame of the chassis.At the same time,the supporting plate structure of the front axle of the chassis is optimized and improved.The flat structure is replaced by a grooved steel structure.Based on the improved chassis structure,the finite element analysis under three working conditions is carried out.The research shows that: the strength and stiffness of the chassis structure under the three working conditions are lower than the check indexes,indicating that the structural improvement plan is effective.Compared with the check,the strength and stiffness of the chassis structure have a larger safety margin,which lays the foundation for the lightweight research of the chassis structure below.Finally,the chassis vibration characteristics are evaluated by modal analysis for the improved chassis structure,and it is concluded that the chassis structure is not easy to resonate,and there is no sudden change,and the structure is good through the mode shape diagram.Based on the reason that the chassis structure has a large safety margin in terms of strength and stiffness,size optimization and variable density topology optimization are adopted for the chassis structure to achieve the purpose of lightweight chassis structure.The size optimization is mainly aimed at the longitudinal beam structure of the front frame of the chassis.The thickness of the longitudinal beam is reduced from 12 mm to 10.89 mm,the structural mass of the longitudinal beam is reduced from 97.60 kg to about 89.46 kg,and the mass of the chassis structure is reduced from 330 kg to about 322 kg.The weight is about 2.5%;the variable density topology optimization is mainly aimed at the gearbox and the drive axle housing.After the optimization,the chassis structure reduces the weight by67 kg,from the original 322 kg to about 255 kg.Compared with the optimized chassis structure,the weight reduction is about 20.8%,the overall weight loss effect obviously achieves the purpose of lightweight.Finally,the vibration characteristics of the chassis are evaluated by modal analysis of the lightweight optimized chassis structure,and the comparison of the chassis vibration diagrams before and after optimization shows that the natural frequency of the lightweight chassis structure is increased,about 2 Hz,which is not easy to Resonance and no sudden change,the mode shapes of each order are also similar to the previous ones.In conclusion,the chassis structure of the 25-horsepower electric tractor has high practical value.