Filling performance analysis and verification of cell-belt rice precision seed-metering based on friction and repeated filling principle

Precision seeding of rice is key technology to achieve the modernization of rice cultivation. At present, most seeding precision of rice in China is 1 to 7 per hole, which is hard to achieve the requirements of seeding precision. A cell-belt type precision seed-metering device based on friction and repeated filling principle was developed aimed at meeting the production requirement of sowing (2±1) seeds into per hole to solve the problem on the precision seeding of low sowing quantity for hybrid rice seedling production. Structure and working principle of the cell-belt type precision seed-metering device was described, and the result showed the feasibility of precision of the seed-metering device. Structure size of key components was analyzed, included the shape and dimensions of cell, the distribution of cell, the dimensions of cell-belt. The mechanics and kinematics on seed-filling processing mechanism was analyzed, from which the filling conditions was found out. And the factors influenced the filling performance was received, including the angle of cell, velocity of the cell-belt and thickness of seed layer. And this provided theoretical basis for the design of metering device. With the consideration of the motion direction, the resistance and the processing difficulty, the directional angle of cell was designed as 90°, which meant the direction of the long side of the cell was in accordance with the motion direction of the belt. Multiple and repeated seed filling process was simulated. And the single factor tests on the effects of cell-belt velocity, cell-belt inclined angle and seed layer thickness on seed filling performance was performed by EDEM software. It showed that: the leakage rate decreased first and then increased as the increases of the cell-belt velocity; the circulation layer formed and the range of it became larger gradually as increasing the seed layer thickness, which caused the longer of the filling interval and could decrease the leakage rate; the filling interval decreased and leakage rate increased as increasing the cell-belt inclined angle. On this basis, the prototype device was designed in accordance with the parameters of the metering device. According to the tests and the analysis based on the simulation, the optimal conditions were selected for experimental verification. The optimal parameters combination of the cell-belt inclined angle, cell-belt velocity and seed layer thickness was 43°, 0.11 m/s, 50 mm, respectively. The text response parameters of the result were the seed-filling qualified rate (the rate of sowing (2±1) seeds into per hole), the multiple seed rate (the rate of sowing >3 seeds into per hole) and the leakage rate (the rate of sowing 0 seed into per hole), respectively. The result was that: The seed-filling qualified rate, the multiple seed rate, the leakage rate were 96.4%, 1.4% and 2.2%, respectively. Under the same condition, the crushing test was done, and the average of 3 tests result showed that the broken rate was 0.18%, which was enough for the practical production. The cell-belt rice precision seed-metering device based on friction and repeated filling principle could meet the requirements of precision seeding. The research results provide a reference for the design of precision seeding machine for factory plug seedlings. © 2019, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.