Design and experiment of side positive pressure seed metering device

Abstract: Precision seeding device was one of the important parts of precision seeder. Among the seeding devices, mechanical seeding device had simple structure and lower cost of manufacture. So it was widely used in China now. Meanwhile, it caused damage of seeds and needed frequent maintenance. As to its unstable working condition, it can not adapt to high speed operation. At present, pneumatic seeding device was used to achieve precision seeding. It mainly accomplished precision seeding by means of pressure difference. But air suction seeding device required precise structure to avoid pressure loss and it often consumed more electric power. Due to the problems, a set of side positive pressure seeding device was designed in order to realize maize precision seeding. The working principle of seeding device was analyzed, and the dynamics of seeding process was studied. It accomplished better filling seeds and carrying seeds by positive pressure air. The basic requirements were also researched to meet reliable seeding by force analysis of seeds in filling hole. A suitable filling hole was designed to realize precise filling seeds. According to the analysis, the pressure must reach 1.2 kPa to guarantee the seeds in the filling hole reliably. Three factors have great effect on seeding device performance: air pressure, rotation speed of seed plate and size of filling hole. In order to figure out the degree of influence of all the factors and confirm the best working parameters of seeding device, uniform design was arranged on influence factors for basic performance, and the regression mathematical model of three indexes was set up. The test results have showed that, the speed of planter plate was the most significant factor to qualified index and loss index, filling hole size was the most remarkable factor to the reseeding index. Fan pressure affected the row index insignificantly. When fan pressure reaches 1.2kPa, the speed of planter plate 18r/min, filling hole width 11mm, the requirements of sowing was remarkable. Seed size also influenced seeding performance. Accordingly seeds' three-dimensional size was measured for grading. The seeds with width size between 8.5mm to 9.5mm accounted for 85%. On this basis, seeds were graded by DSX computer filter through seed grading test, and then the seed metering performance was significantly improved. Qualified index reached 89.36% and loss index was 4.26%. The side positive pressure seeding device had simple structure and it consumed less energy. More importantly it worked efficiently under a wide pressure range. It provided a new method for design of seeding device.