Research on seed-filling mechanism of vertical shallow basin type seed-metering device with composite filling force

Abstract: On account of the decreasing of filling ability of hole at high operating speed caused miss-seeding, even leaded to reduce production, mechanical precision seed-metering device was gradually eliminated from application markets. How to improve the filling ability of mechanical precision seed-metering device to meet the mechanization requirements at high operating speed was the key point of the research. Because the mechanical precision seed-metering device could only depend on gravity, centrifugal force and interaction force between the seeds to complete filling seeds, mechanics characteristics and regulation of soybean seeds which were in the cavity of seed-metering device in all directions were analyzed from the mechanics point of view. And due to the structure characteristic of seed-metering device and granular mixtures characteristic of soybean seeds, the value of filling force in the form of compressive stress was limited. In this paper the model of filling force of hole was built and it could be easily found that increasing the kinds of filling force was an effective way to improve filling ability of the mechanical precision seed-metering device, so a vertical shallow basin type seed-metering device was innovatively designed. The structure of new type seed-plate was based on the traditional vertical seed-plate. The end plane of vertical seed-plate's hole was been folded into shallow basin shape, and then the filling holes were arranged evenly around the side wall of seed-plate along the circumferential direction, which could not only keep the advantages of vertical seed-plate, but also take full advantage of gravity and centrifugal force to increase the filling force of seed-plate. Owing to the existence of folded edge, soybean seeds could slip off from the inclined plane of seed-plate and leave seed-plate in the process of cleaning seeds, avoiding the negative effects generated by the centrifugal force in the process of cleaning seeds, ensuring the reliability of filling seeds. EDEM (engineering discrete element method) software was utilized to simulate and analyze, and then physical prototype experiment was conducted to verify the theoretical analysis and simulation results. Taking the traditional vertical seed-metering device and shallow basin type seed-metering device as experimental subjects and the rotational speed of seed-plate as experimental factor, the single factor contrast experiments were conducted. The experiment results show that the simulated and experimental values of variation trend of filling rate are basically the same and the simulation value is close to experimental value, the minimum relative error is 0.4%, and the maximum relative error is 2.91%.The filling rate of shallow basin type seed-metering device is higher than vertical seed-metering device, especially at high operating speed. At the rotational speeds of 39.21, 49.12, 58.82 r/min, simulation values are higher by 2.4%, 3.4%, 2.6% and experimental values are higher by 2.59%, 1.58%, 3.04%, and average filling rate is higher by 2.33%, which verifies the components of gravity and centrifugal force which are as composite force can make a contribution to fill seeds and can be obviously helpful for seeds to come into the hole when increasing the rotational speed of seed-plate, and provides the guidance and direction for the research of mechanical precision seed-metering device.