Design and experiment of self-disturbance inner-filling cell wheel maize precision seed-metering device

Abstract: In order to increase the rate of single seed and reduce the missing and multiple rate of the mechanical precision seed-metering device, and from the perspective of reducing the seeds friction in the filling area and increasing the seeds activity, a kind of self-disturbance inner-filling cell wheel maize precision seed metering device was designed. For the mechanical metering device, the process of seeds filling into hole depends more on gravity, because of seed layer thickness is limited, the size of filling gravity will not change too much, and disturbing the seed to a certain extent will cause the seed to produce normal beating, which is not conducive to fill. So a seed disturbing strip on the inner surface of a certain inclined cone disc was designed. The advantage is that the seed on the top of the hole gets a small normal jump to decrease the seed friction, simultaneously it can ensure that the seed gets enough filling force to be filled into the hole. The movement of the seed on the disturbing strip and the principle of seed filling were analyzed, and then the parameter design of the seed metering device was completed. The hole parameters of seed metering disc were calculated, and the optimum hole size for seed filling was determined. Different types of disturbing strip are set on the conical surface of the seed metering disc, which are non-disturbing strip, direct disturbing strip, decline disturbing strip and spiral disturbing strip. The force acting on the seed disturbing strip and the relative limit velocity of the seed filling into hole were analyzed. It was determined that the radius of the seed disturbing strip, the cone angle of the cone and the rotation speed of the seed disc all affected the filling process. In order to determine the optimal seed metering parameters of the seed metering device, a discrete element software EDEM was used to simulate the seed metering device. The single factor test and the multiple quadratic rotation orthogonal combination test were carried out with the test factors of the rotation speed of the seed plate, the strip form of disturbing the seed, the cone angle of the seeding plate and the radius of the disturbing strip. Using Design-Expert 8.0.6 to analyze the test data, the mathematical model between the rate of single seed, missing , multiple sowing and the test index was obtained. The optimum parameters were as follows: The speed of the seed disc was 8.40 r/min, the disturbing strip form was spiral, the cone angle of the seed plate was 38.6(, and the radius of the disturbing strip is 1.24 mm, respectively. The single, multiple and missing rate were 96.29%, 2.55% and 1.15%, respectively. Under the optimal parameter combination, the bench test proved that the of single、multiple and missing rate were 95.4%, 2.55% and 1.15%, respectively. When the speed of the seed disc during 8.40~16.67 r/min, the single rate was more than 91.4%, multiple and missing rate were less than 2.55% and 1.15%, the seed damage rate was less than 0.44%, respectively, and the seeding effect is 3.2% higher than the scoop wheel type metering device. which could meet the agronomic requirements of the precision sowing of maize. The simulation test of the seed metering device based on EDEM discrete element method has provided references for determining the performance parameters of the seed metering device and shortens the design period. This study can provide references for improving the performance of the mechanical seed metering device.