Abstract:In order to solve the problem of the lack of accurate and controllable seed metering device for mechanical film mulching and hole sowing of rapeseed in actual production,a combined device of positive and negative pressure for rapeseed was designed,which adopted negative pressure seed sucking,positive pressure seed unloading,duck mouth hole forming and secondary seed feeding,so as to meet the requirements of 1-3 seeds for mechanical film mulching and hole sowing of rapeseed. By establishing the mechanical model of seed sucking,seed carrying and unloading process and combining with FLUENT simulation analysis,the structure and parameters of the combined positive and negative pressure seeding device for rapeseed were determined.The negative pressure,the height of seed layer,rotation speed of seed metering wheel spindle and positive pressure were selected to carry out the single factor test of seed metering performance with the right rate of seeds per hill and rate of no seed hill as the test index,and the optimization and verification of working parameters were carried out according to the quadratic orthogonal rotation center combination test of response surface method. The results showed that:the primary and secondary factors affecting the right rate of seeds per hill were negative pressure,rotation speed of seed metering wheel spindle and positive pressure.The optimal working parameters of seed metering performance was rotation speed of seed metering wheel spindle at 7.5 r/min,negative pressure at -2 000 Paand positive pressure at 850 Pa.The results of bench verification test showed that the right rate of seeds per hill (1-3) was 88.15%,and the rate of no seed hill was 4.43%,which met the requirements of rapeseed production requirements of mechanical film laying and hole sowing. This study provides a reference for the improvement of rapeseed seed metering device structure.