Design And Experimental Study On Seed Guide Tube Of Maize Precision Seeder

The The mechanized precision sowing of corn has been basically realized.The precision sowing of corn is a technical process that uses the sowing machine to put the corn seeds into the predetermined position in a quantitative and accurate way.It is mainly completed by the cooperation of the parts such as profiling,ditching,seed metering,seed guiding,covering,and pressing.With the continuous improvement of sowing speed,the problem of significantly increasing the coefficient of variation of seed spacing has also been exposed.The process of seed transport can be divided into two processes: from seed box to seed metering tray,and from seed metering tray to seed bed through seed guide tube.In view of the problem that the coefficient of variation of seed spacing increases with the increase of sowing speed,some experts and scholars have optimized and studied the seed metering tray and seed clearing mechanism,However,only a few experts have conducted in-depth research on seed guide tubes.Therefore,it is very necessary to test and study the seed guide tube.This research is to design a new type of seed guide tube based on the pneumatic precision metering device for corn.The variation coefficient of seed spacing after seed implantation under the guidance of the original seed guide tube of the pneumatic seeder is as high as 15.7%.Zhengdan 958 maize seed with large planting area and wide range was selected as the research object,and the physical parameters of maize seed were determined through experiments and literature review.The corn seeds are divided into horse tooth shaped seeds,pyramid shaped seeds and spherical seeds(excluding the special-shaped seeds).Solid Works software is used to accurately model the corn seeds,seed metering device and seed guide tube;Through the analysis of the seed motion image recorded by the high-speed camera,combined with theoretical calculation and bench test,three main factors affecting the coefficient of variation of seed spacing were determined: rebound angle,tangent angle and operating speed,and polyurethane,organic silica gel and eva foam materials were used to replace the curved surface materials of the guide seed tube.EDEM-FLUENT was used to conduct virtual simulation experiments.Three factor and three level experiments were designed for four kinds of materials using Design Expert 8.0.6,with the grain spacing variation coefficient as the evaluation index,and the test results were analyzed and optimized.Because the optimal results of polyurethane seed guide tube are close to those of PP(engineering plastic)seed guide tube,and the coefficient of variability is very low,bench test and field test were conducted to verify the two new seed guide tubes.Through the analysis of the test results,when the positive pressure is 1.6 k Pa,the rotation speed of the seed metering plate is 31.2 r/min,the rebound angle is 4.36 °,the tangent angle is35.49 °,and the working speed of the planter is 9.29 km/h,and the guide seed pipe material is polyurethane,the variation coefficient of the seed spacing in the bench test is 9.35%,and the variation coefficient of the seed spacing in the field test is 9.52%,which are close to the optimal prediction value of 9.47% in the simulation test.The results of bench test,field test and simulation test are basically consistent.The optimized seed guide tube achieved an ideal effect in reducing the coefficient of variation of seed spacing,and completed the goal of this study.