Digital Design Of High Power Tractor Automatic Gearbox

The working environment of high-power tractor is extremely complex,generally working in the environment with extremely terrible road conditions,and the tractor dramatically external load changes making it hard to run smoothly.Traditional tractors generally use manual transmission gear with limited number of stops,it is arduously adapt to complex road conditions,and the traditional tractor regularly apply to high-power engine that likely lead to waste the energy and pollute the environment with the inefficient engine performance.Moreover,the manual variable speed tractor requires the driver to change gears frequently in complex road conditions,which make the driver fatigue and affect the work efficiency easily.If the high-power tractor adopts automatic shifting mode,it will be convenient for the driver to shift gears and greatly simplify the shifting process.Therefore,it is of great significance to design the automatic gearbox of high-power tractor with multi-gear and high transmission efficiency.This paper takes the planetary gear mechanism as the research object and divides the automatic transmission into Simpson type,Lavina type and CR-CR type.According to the design requirement of variable speed mechanism,the equivalent lever method is used to analyze the two to four planetary rows,and a variety of possible matching combinations are obtained.Firstly,the first gear ratio and the range of transmission ratio are determined according to the matching engine parameters.According to the demand of gear number,the general design direction of three and four series of gear shifting mechanism is determined.Using the lever method to analyze the four to five point lever scheme,the core infrastructure of the transmission is designed and extended,and the transmission scheme of the new 26-gear automatic transmission mechanism with 16 forward gears and 10 reverse gears is determined.The gear ratio is configured according to the range of gear ratio,and the power transmission route,transmission efficiency and the working state of the shift actuator of each gear are analyzed.According to the special transmission ratio formula of each gear position and the matched transmission ratio,the characteristic parameters of each planetary row were obtained,and then the number of teeth of each gearwheel was obtained by combining with the law of tooth matching,and then the parameters of the gear shifting mechanism were determined.The key parameters of gear are obtained through relevant calculation,the stress of planetary row under special gear position is analyzed,and the planetary row strength is checked.Then the main input shaft and output shaft are designed and the relevant structural parameters of the shaft are obtained.Finally,the solid modeling of the whole variable speed mechanism is carried out.In order to find the weak part in the structural design quickly,the static analysis of the key parts of the variable speed mechanism is carried out to obtain the distribution of stress,strain and other related parameters along with the position and analyze,and verify that the structure designed fulfil the stiffness strength requirements.The research in this paper provides theoretical basis and technical support for the digital design of automatic gearbox of high-power tractor,which has certain engineering application value.