为了提高机械除草的作业效率、降低地头频繁调头引起的伤苗率,该文研制了3GY-1920型宽幅水田中耕除草机.该机由12 kW水田拖拉机提供动力,工作幅宽为5.7 m,一次作业可覆盖6行插秧机3个行程的作业宽度,并配备了4个双作用液压缸,控制整个机架的展开闭合与除草轮位置的横向调节.该文结合水田土壤特性和现有除草部件的特点,通过对除草轮的运动学与显式动力学仿真分析,设计并优化了螺旋刀齿式样除草轮,该除草轮通过与土壤及杂草的剪切、翻耕作用实现中耕除草作业.田间除草试验结果表明:在机具不同前进速度(0.3、0.6、0.9 m/s)和除草轮入土深度(3、6、9 cm)条件下,该机平均除草率为82%,伤苗率为4.8%;根据机具作业速度和幅宽可知该机作业效率为0.6~1.8 hm2/h;整机工作性能和作业效率满足水稻田机械中耕除草作业的技术要求.机械除草与化学除草产量对比试验结果表明:在试验区域内,机械除草产量高于化学除草,该研究可为中耕除草对水稻田产量的影响提供参考.%In order to improve the mechanical weeding efficiency and reduce the injury rate of seedling caused by frequent swerve at the end of the field, a wide-swath machine, named 3GY-1920 type wide-swath weeder, was designed for intertillage and weeding in paddy field. This weeding machine driven by the paddy tractor mounted relevant components including the wide-swath adjustable frame, the hydraulic control system, the weeding unit and profiling mechanisms. To match triple working widths of ride style high-speed rice transplanter, this weeder was equipped with 19 weeding rolls. The working width was designed to be 5.4 m according to line spacing of rice seeding, which was normally 0.3 m. As the transplanter could not follow one path line in 3 different processes, the whole frame was divided into 3 parts including the left-side frame, the right-side frame and the bearing frame. A hydraulic system, including oil pump, different types of electromagnetic valves, hand valve, 4 hydraulic cylinders, relief valve, throttle valves and so on, were equipped to control the 4 single-rod double-acting hydraulic cylinders, which could adjust the frames to fold or unfold for transportation or weeding, and the real-time motion of rolls on the side frames. The weeding roll was designed as the spiral cutter weeding roll referring to the existing rollers and the bearing capacity and shearing strength of paddy. And the different parameters for weeding rolls such as the working resistance and the capacity to damage soil were tested with the explicit finite element software ANSYS/LSDYNA. The weeding roll was composed of 6 cutters; every cutter was sharpened and rotated around the axis by 720° and welded into the reel. A spring type profiling mechanism was also designed and applied to ensure the stable working depth. The installation height and working depth of weeding machine were adjusted before weeding so as to avoid injuring the plants due to the difference of the size of the rice seedlings. When the weeding machine moved forward at a certain speed, the weeding rolls were rotated by the force of soil resistance, elastic force of spring, and forward stress of traction. And the spiral cutters on the roll moved downward into and out of the soil for shearing weeds and stirring soils to cover weeds at the same time. An all-factor experiment on the weeding rate and injury rate of seedlings was conducted to test the performance of this weeding machine. Depth of the weeding and travel speed were selected as 2 factors in this experiment. Results showed that the operating efficiency of this weeding machine was 0.6-1.8 hm2/h, the average weeding rate was 82%, and the average seedling injury rate was 4.8%. With the increment of travel velocity, the weeding rate rose and then fell, and the injury rate kept rising. With the increase of working depth, the weeding rate continued to rise, and the seedling injury rate went up at first and then declined. The weeder showed the optimal operation effect when the weeder's speed was 0.6 m/s, and the roll's working depth was maintained at 6 cm. Under the parameter combination, the average weeding rate was 87.2% and no seedlings were damaged. A yield test was also performed to compare the differences between 2 weeding methods (mechanical weeding and chemical weeding). Results were as follows: The average yield of rice under mechanical weeding was 686.56 g/m2while that under chemical weeding was 659.83 g/m2. The average number of useful spikes per hole in the testing zone was 13.25 under the condition of mechanical weeding and 9.36 using chemical method of weed control. The average number of holes per square meter was 19.71 and 21.68 based on mechanical and chemical weeding respectively. The result suggests that the mechanical weeding may hurt the seedlings compared to chemical weeding method, however, its weeding and inter-cultivation function can promote the tilling of plants and improve the yield of rice.
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