大豆联合收获机对称可调式凹板筛设计与试验

Design and experiment of symmetrical adjustable concave for soybean combine harvester

针对传统大豆联合收获机脱粒间隙调整方法单一、田间作业时工作参数与作物适应性差,导致大豆破碎率、未脱净率和夹带损失率较高的问题,该研究设计了一种对称可调式凹板筛,实现双侧脱粒间隙可调,并对其间隙调整量进行了确定。以大豆联合收获机的前进速度、滚筒转速、脱粒段脱粒间隙、分离段脱粒间隙为影响因素,以大豆破碎率、未脱净率和夹带损失率为评价指标进行四因素三水平响应面试验,利用Desigen-Expert12.0对田间试验结果进行响应面分析,研究不同影响因素对评价指标的影响规律。结果表明,在前进速度为3.3 km/h、前滚筒转速为500 r/min、后滚筒转速为650r/min、脱粒段脱粒间隙19mm和分离段脱粒间隙15mm的参数组合下,采用对称可调式凹板筛的破碎率为2.69%,未脱净率为0.57%,夹带损失率为0.13%,相较于现有的竖直调节式凹板筛,破碎率、未脱净率和夹带损失率分别降低了0.46%、0.71%、0.55%,对称可调式凹板筛的各项指标均优于现有的竖直调节式凹板筛。研究结果可为南方地区大豆联合收获机差速脱粒分离装置的调节以及自适应调节系统的研究提供参考。

Threshing has been one of the most fundamental steps to separate the grains from the harvested crop.An adjustment device of threshing clearance can greatly contribute to matching the feeding amount and working parameters in a combine harvester,in order to reduce the damage or loss rate of clean grain in the field.Two parameters are often used to adjust the threshing clearance at present,including the diameter of the cylinder and the position of the concave.In terms of cylinder diameter,there is a relatively larger structure of the device to control the expansion and contraction of the threshing teeth,leading to high power consumption and production cost.Therefore,the vertical adjusting concave has been commonly used to adjust the position of the concave in the combine so far.However,the vertical concave body can normally move up and down to result in the limited threshing clearance at the bottom of the threshing cylinder in the device.In this study,a symmetrically adjustable concave screen was designed to adjust the threshing clearance at the bottom of the cylinder in both sides.Among them,a hinged shaft was welded between the concave body and the upper cover plate that was installed on the frame,and an electric cylinder was positioned on the screen body.Specifically,a mobile phone in Bluetooth mode was utilized to extend or contract the electric cylinder during operation,further to drive the concave body for the rotation around the articulated shaft,and finally to quickly adjust the threshing clearance at the bottom in both sides of the threshing cylinder.A circular curve function was also selected to calculate the cross-sectional area of threshing clearance for the two concaves in the rectangular coordinate system before and after adjusting the threshing clearance.After that,a comparison was made to determine the working performance of the new symmetrically adjustable concave and vertical one on threshing clearance.The results showed that the symmetrically adjustable concave body was realized to bilaterally adjust the threshing clearance at the bottom at both sides of the cylinder.The cross-sectional area of the threshing clearance also varied greater than that of the vertical one.The grain logistics density was directly proportional to the rubbing effect inside the grain logistics.Once the feeding amount decreased,the threshing clearance was reduced to improve the grain logistics density for the internal rubbing effect and the low rate of unthreshed grains.Once the feeding amount increased,the threshing clearance needed to increase for the low grain logistics density,where the internal rubbing effect and the breakage rate of grain were reduced to directly tailor the density of grain flow via the cross-sectional area of threshing clearance.Correspondingly,the performance of the symmetrically adjustable concave was better than that of the vertical one,according to the cross-sectional area of threshing clearance.A field experiment showed that an optimal combination of parameters was achieved,where the forward speed of 3.3 km/h,the cylinder speed ratio of 500:650,the threshing clearance of 19 mm in the threshing section,and 15mm in the separation section.The optimal performance was obtained in this case,where the breakage rate of grain was 2.69%,the rate of unthreshed grains was 0.57%,and the loss rate of separation grains was 0.13%,indicating the higher reduction by 0.46%,0.71%,and 0.55%,respectively,compared with the vertical one.The indexes of the symmetrically adjustable concave were also better than before.The findings can provide a strong reference for the differential threshing and separation in the adaptive regulation system of soybean combine harvester.