The Design And Optimization Of Changing-wheels Mechanism For Boat Type Tractor

China is a big country, the geographical features are complex, and it’s rich of water in the southern of China, plots narrow disperses, paddy field and dry-land crosses.A type of tractor is named ship-tractor witch can work freely on the land and swamp water, the south region is badly in need of it. In the case Changing-wheels mechanism is a important part of ship-tractor. This article is written about the main research object of designing ship tractors’ wheel mechanism, try to make sure automatically converting movements state, high mechanical strength, reasonable and reliable product. Mainly jobs divided into the following steps:Firstly, Using TRIZ theory of system evolution to find the direction of the design on wheel structure, clearly defined the five basic requirements, completed the preliminary figure in gear system. Two system internal contradictions encountered in the design process, one was time-consuming increasing, speed slowing down and the other was being poor of automation, using the corresponding standards on the theory of invention principle and methods in TRIZ to solve, finally completed the reasonable plan witch can meet all the requirements in wheel mechanism.Secondly,based on the plan of Changing-wheels mechanism, the parameterized helical gear library have been built, and then set up input and output shaft, synchronous ring, push rod, impeller, lugs as so on,the assembly of virtual model of changed wheel mechanism was completed. Using simulation software to simulate the working whole process.Proved gear transmission system inspection mechanism has a stable transmission ratio 2.6; add the cosine function of the motor input,studied the laws of motion, verifted the rationality of the preliminary plan for wheel mechanism.Thirdly, base on kinematics analysis, accouting to seven fuzzy reasons in manufactor,the minimum volume of gear set as the optimization’s goal and bending strength reliability and so on set as constraint conditions,;modulus, tooth number, spiral Angle and coefficient of tooth width parameter fuzzy optimization model is established, and on the basis of fuzzy theory into the general optimized,it has made the optimized gears volume decreased by 39%.The last, Analyzed before and after the optimization of the gears in the process of meshing gear on the whole, and in radial tooth width direction the change of the maximum contact stress, contact stress are slightly improve after optimized, but the value is not big, shows that the optimization result made little effect on the strength to significantly reduce the whole volume.In a word, through the design and analysis, the plan had finished which has the advantages of small volume-light and weight strength enough for wheel mechanism design, had realizated of the need for amphibious tractor changing-wheels fastly and stably, to promote the development of boat type tractor.