Research On The Key Techniques Of Self-propelled Carrots Combine Harvester

Planting area and total output of carrot are ranked among the top of the whole world in China, which still maintain fast and continue growth.However, the mechanization technology of carrot harvesting is not advanced. with the goal of high efficient harvesting mechanization of carrots, this paper was aimed at the key technologies in the process of carrot harvesting (e.g. digging, pulling up, clamping, transportation, separation,etc) based on the agronomic characteristics in different carrots planting regions. The analysis was conducted mainly to solve the bottleneck problems such as digging shovel, injured carrot and rhizomes separation of carrot harvester. New and high efficient carrot harvester was devised by theoretical analysis and experimental research.At last, a series of field trials for prototype were tested. The main research contents and conclusions are as follows.Firstly, basic physic features, tensile strength and pulling force of carrot were tested, the data was analyzed using statistics theory and liner regression analysis methods.The database of carrot’s physical and mechanical properties was established. The key parts’parameters of carrot harvester are provided by the database, it mainly contained structural parameters of digging shovel, spacing of unit clamping, the size of unit clamping of pulley, belt tension,spacing of horizontal directional device, structural parameters of cutting blades, stems transporting device and roots transporting device, etc.Secondly, main parameters and transmission ratio of various working parts with mechanical driving by means of harvester transmissions system were analyzed and calculated theoretically. Based on the calculated result of the working parts driven by hydraulic motor, we can choose the type of BMM-12.5 cycloidal hydraulic motor to drive profiling grain lifter, and choose type of BMM-50 cycloidal hydraulic motor to drive stems transporting device and roots transporting device.Thirdly, based on users’requirements,digging shovel structure suitable for carrot harvester was designed and the structural parameters were determined by analogy and analysis of the structure and working principles of digging shovel for root crops. Considering the influence of physical and mechanical properties of soil which influenced the digging shovel work resistance, the dynamic model between soil and digging shovel was established by applying soil dynamic theories.Finite element analysis was analyzed for the two kinds of structure digging shovels, results showed that the strength of two kinds of digging shovels was both fulfilled design requirements and the stress distribution of triangle digging shovel was with more homogeneous force, less stress and smaller strain. The mining effect of chisel shovel was better than triangle shovel, but soil blocking of chisel shovel was more difficult with more energy consumption under condition of sticky and wet soil when dealing with the same work by field comparing tests. Analogy analysis and working principle of rhizome separation device for root crops was conducted in order to separate roots from stems which was suitable for carrot harvester The paper focused on theoretical analysis of the cutting stems device to calculate its structure and working parameters systematically. Combined two kinds of structure of disc blades, the results showed that they can all satisfy job requirements,but the work effects of serration blade was superior to ordinary disc blade under the same experimental working conditions. By research of the analysis force condition of carrot stems and the working mechanism of double disc blades, necessary condition to ensure cutting quality when separating roots from stems was proposed. After analysis of the motion trajectory of double disc cutter, the movement rule of disc blade was figured out and a solid theoretical foundation was established using kinematics analysis. In order to improve cutting rate, reduce injury rate and optimize better working parameters, simulation software was used to analyze the working principles of double disc blades when the device was separating roots from stems.