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链勺式玉米精量排种器设计与试验

Design and experiment of chain-spoon type maize precision seed metering device

  • 摘要: 针对传统机械式玉米排种器作业性能不稳定、播种穴距合格率低、漏播率高的问题,该研究设计了一种链勺式玉米精量排种器。根据西南地区玉米种子的物理特性对排种器进行结构设计;对排种过程中玉米种子的受力和运动状态进行分析,确定了影响排种性能的关键参数;基于EDEM-Recurdyn耦合方法对排种器的工作过程进行仿真,模拟验证种子运动过程;进行二次回归正交旋转组合台架试验,得到各参数对穴距合格率和漏播率的影响大小依次为:充种型孔半径、种勺斜角、主动链轮转速,当充种型孔半径为5.45 mm、种勺斜角为3.42°、主动链轮转速为45.62 r/min时,排种性能最佳,穴距合格率为83.14%、漏播率为1.73%;田间试验结果表明,安装链勺式玉米精量排种器的播种机播种平均穴距合格率为81.67%、平均漏播率为1.67%,满足国内玉米精量播种要求。与现有玉米排种器相比,链勺式玉米精量排种器播种结构简单、成本低,适用于小型玉米播种机使用。

     

    Abstract: Precision seed metering is a crucial process to ensure maize yield. In order to solve the problems of unstable operational performance, seed damage, seed clogging, and poor versatility of traditional mechanical seed metering devices, a chain scoop maize precise seed metering device was designed for this study. Based on the physical characteristics of maize seeds, the structural design of the chain scoop type maize precise seed metering device and its core component, the seed scoop, was carried out. The dimensions of key parts, such as the seed-filling hole and the bottom groove, were determined. The seed metering chain was selected as the 06B chain number with a K-type attachment plate. The seed scoop was designed in a "7"-shaped structure, with the length A1 determined as 20.00 mm, the width B1 as 27.00 mm, and the height C1 as 12.50 mm. To ensure the seeds rest obliquely within the seed scoop, the seed-filling hole and the bottom groove were designed in a spherical shape, with evenly distributed elliptical notches. The seed-filling hole radius was calculated to range from 4.5 to 6 mm (6 mm≥R1≥4.5 mm), the short diameter of the elliptical notch (r1) was determined to be 1.05 mm, and the radius of the bottom groove was calculated as 4.17 mm. The seed metering device primarily consists of housing, seed scoop, seed metering chain, sprockets, drive shaft, bearings, mounting base, and seed box. The chain-scoop assembly is formed by evenly attaching seed scoops to the seed metering chain. The device encompasses four working areas: seed filling, seed clearing, seed protection, and seed delivery, and operates through a seed metering motor. A theoretical analysis of the motion states of the target seeds during each process was conducted, identifying the key factors influencing seed metering performance, such as the speed of the driving sprocket, the seed-filling hole's radius, and the seed scoop's inclination angle. This study employed the discrete element method (DEM) coupled with multibody dynamics (MBD) for simulation analysis, examining the operational process of the chain scoop type maize precise seed metering device. The established simulation model was utilized to validate the motion process of maize planting. The simulation results demonstrated that maize seeds successfully passed through each working area of the seed metering device. The simulation test results indicate that the seeding function of the planter designed using chain-scoop technology successfully meets the expected performance requirements. Bench tests were conducted on the chain-scoop maize precise seed metering device. This study utilized Design Expert 12.0 software to perform a three-factor, three-level, second-order orthogonal rotational combination experiment. The operating parameters were fine-tuned to optimize performance, and the effects of these parameters—such as the speed of the driving sprocket, the radius of the seed-filling hole, and the inclination angle of the seed scoop—on seeding performance, including the qualified rate of planting hole spacing and the miss-seeding rate, were analyzed. Subsequently, a regression equation corresponding to the collected data was established. The experiment identified the optimal operating parameters for maize seed planting: a sprocket speed of 45.6 r/min, a seed-filling hole radius of 5.45 mm, and a seed scoop inclination angle of 3.42°. The results demonstrated that under these parameters, the planting test achieved a qualified planting hole spacing rate of 83.14% and a miss-seeding rate of 1.73%. The optimization results predict a feasibility rate of 98.3%. The precise seed metering device prototype, designed with chain-scoop technology, has been completed and is ready for installation. Field tests were conducted based on the optimal operating parameter combination determined from the maize seed bench tests. The field trials achieved an average qualified planting hole spacing rate of 81.67% and an average missing rate of 1.67%. These results conform to the standards for precise maize seed planting in China. Compared with the existing corn seed metering device, the chain-spoon type maize precision seed metering device has a simple seeding structure, low cost, and is suitable for use in small corn seeders.

     

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