| Potato is the fourth largest staple food crop in China.Its production has a long history.And China has a wide area of potato planting and ranks first in the world.However,the yield of potato in China is relatively low,with an average yield of only about 1 ton per mu.Yields are far below the average for other developed countries.Among them,mechanization of cultivating tillage is one of the important reasons leading to the low yield of potato,except for the effects of seeding potato,mechanized sowing and harvesting.The main effects of tillage operations for loose soil,moisture and drought,improve soil physical properties,and improve soil fertility,eliminate weeds,improve crop yield.At present,the large-scale cultivators are widely used in foreign countries,the plowshare and the hoe shovel are mainly included.The cultivator is hauled by a tractor and used for linear towing.Although the operation efficiency is relatively high,the soil crushing effect also has poor phenomenon,the soil-broken rate of traditional shovel-type cultivator is from 85% to 90%,soil-broken rate in the sticky heavy soil are more lower,in addition,most foreign cultivators throughout the working width are installing tillage components,potato are easy damaged in the mid-tillage operations;most of the domestic cultivator has hoe shovel and spring tines as tillage components,the advantage of tillage depth is consistency,but most of the tillage machine ridge spacing are only applicable to corn,major grain crops such as wheat are not suitable for potato with slightly ridge width,and their soil-broken rate is also lower.After cultivation,there are many large-sized soil blocks,which can easily result in the phenomenon of large soil blockage and seedling,which is not suitable for sticky soil compaction board work.Therefore,how to solve the problems of low soil-broken rate and high applicability of potato when planting potato has become the key to improve the quality and efficiency of potato cultivation.Therefore,in view of the above problems,the key components of the drive-type potato cultivator are designed and studied.The key components are analyzed theoretically and simulation of soil crushing process,as well as the design and optimization of the parameters and corresponding test.The main contents are as follows:(1).According to the requirements of agronomy potato cultivator work,soil-broken rate is not less than 85%,depth of tillage is not less than 150 mm,compared the advantages and disadvantages of different types of cultivator,overall program design of driving-type potato cultivator was got,while designing the corresponding soil crushing plant and device in the rational arrangement of potato cultivator,targeted to solve the problem of low soil-broken rate,small plowing depth,high injury rate.(2).Consider the overall structure and characteristics of the machine,the structure and arrangement of the soil broken knife,which is the key component of the crushing device were designed.The crusher with the chisel blade is designed so that the device meets the effect of the soil-broken and can meet the agronomic requirements for potato cultivation.(3).Through the analysis of the soil broken performance of the breaking parts,the structural factors and the movement parameters that affect the soil breaking were obtained,and the range of each structural parameter is solved by MATLAB software.The EDEM discrete element software is used to analyze the performance of the designed soil-broken components,and the rate of soil-broken of components in the simulation process is obtained.The theoretical analysis of the structural parameters was validated.(4).According to the national industry standards and relevant national standards for agricultural machinery test method for bench test,test bench device was designed,soil-broken parts of soil crushing performance test were analysis,taking soil-broken rate as test index,according to the theoretical analysis of the impact of soil-broken effect of experimental factors,the quadratic regression rotation combination design test method was used to compare the performance of soil-broken device at different levels of experimental research,the soil-broken rate(evaluation index)and the mathematical model between the factors were establishment,the factors and interactions on the index of experiment results was also analyzed,and finally optimize the structural parameters of the device to get a more reasonable device structure to meet the effect of the ground.And verify the test to confirm the level of structural parameters to meet the soil-broken requirements of cultivator work to verify the feasibility of broken effect.The results are as follows:(1)In this paper,the design of driving-type potato cultivator is reasonable.After theoretical analysis and experiment,the design form of monolithic rotating monomer was determined,which can reduce injury seedlings and has deep tillage.The rotary parts of this design adopted two inner knives.Plate was symmetrically installed on the inside of the driven shaft.The left knife disc and the right knife disc were installed symmetrically on the outside of the driven shaft.All the disc heads had a radius of 227 mm and a diameter of 70 mm.In order to adapt to the ridge distance of potato planting,the distance between the outermost two turrets was about 445 mm.Taking into account the prevention of the phenomenon of soil plowing in the process of soil broken,the distance between two adjacent soil-broken knife in the same disc was 12 mm.Both sides of the disc symmetrically arranged way to ensure smooth work,uniform shaft load,and ground disc with chisel straight knife,it can also reduce the cutting resistance,so that the cutting stress is more concentrated,the soil performance was good,the blade thickness was 10 mm.The angle of the knife edge was 45°,the width of the knife edge was 1.5 mm,the length of the side edge was 11 mm,the corner of the soil-broken knife was 150 and the length of the edge was 70 mm.(2)Through the analysis of the rotaty parts and the analysis of the cutting stress of the soil-broken knife,the conclusion was drawn that when the rotating parts work,the terminal velocity decreased continuously with the penetration of the disc into cutting process,and increased with the increase of the motion parameters.The range of motion parameters was determined to be 3~9,and the operating speed range of rotating parts was 175-325 r/min.The cutting stress increased with the increase of soil entrainment time.When the bending angle of soil-broken knife was 150°,when the length of the cutting edge is between 0.05 and 0.11 m,the cutting stress is larger than the shear strength of the soil,which can cut and break soil.The results showed that under the condition of sticky soil,the design range of the soil-broken knife can be selected to break the soil.By using the EDEM software and using the API function replacement method,the large particle size soil particles were replaced by small particle size.The simulation experiments of the broken particles of the bonded particles to simulate the actual situation of the soil in the complex situation,the test results of the soil-broken rate was 95.62%,to meet the requirements of soil cultivator crushing operations to verify the rationality of theoretical analysis,while provide the basis test parameters to choose.(3)The performance of key components of driving-type cultivator was verified by bench test.The design of the key components of the driving-type cultivator of potato tiller was obtained,which could solve the problem of poor soil crushing effect in the work of sticky heavy plate soil.Test bench test to determine the best soil cutter structural parameters,when the soil moisture content was 11.6%,the solidity of was 94.3 kPa,the rotation speed was 275 r/min,the advancing speed was 0.75 m/s,depth of cultivation was 0.18 m,soil-broken knife angle was 150°,cutting edge length was 0.07 m,the soil-broken rate was 93.8%,The result meet the requirements of potato tillage operations.At the same time,the rationality of simulation model and theoretical formula were also verified.The research in this paper provided new ideas and new methods for the design and research of potato cultivator,and provides theoretical support and technical reference for the design improvement and optimization of potato cultivator,and promotes the further development of mechanized cultivating of potato. |
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