Abstract: In order to obtain the best structural and working parameters of positive and negative air pressure combined seed metering device, the effects of seed variation on seed filling performance and seed feeding accuracy of pneumatic seed metering device were studied. The seed mass, triaxial size, water content, 1 000grain weight, angle of repose and angle of sliding friction of 10 different varieties of pakchoi seeds were tested, and the probability distribution characteristics of seed width and sphericity of pakchoi were analyzed. The results showed that the seed width distribution of pakchoi was concentrated in 1.47-1.61 mm, accounting for more than 80% of the total, the average width was 1.53 mm. The sphericity distribution was concentrated in 85%-95%, accounting for more than 85% of the total, the average sphericity was 90.41%. The average value of sliding friction angle on ABS was 13.75°. The length and width of pakchoi seeds were close to each other, and the seed size distribution was concentrated near the average value in all directions. The shape of pakchoi seeds was similar to spherical, and the width of different varieties of pakchoi seeds was different. The pressurebearing load of pakchoi seeds increased with the increase of the displacement of rupture test probe. As the seed breaks,the maximum value of pressurebearing load was 9.6 N, and its final curve changes was unobvious. It provides an important basis for the design of positive and negative air pressure combined seed metering device, ensures the sowing accuracy of precision direct seeding of pakchoi, meets the agronomic requirements of standardized plant spacing and row spacing of pakchoi, and improves the mechanized production degree of pakchoi and the utilization rate of machines and tools.

Key words: pakchoi seed, metering device, precision seeding, mechanical and physical properties

摘要： 为得到正负气压组合式排种器的最佳结构参数和工作参数，研究种子变异对气力式排种器充种性能和投种准确性的影响，对10个不同品种小白菜种子的质量、三轴尺寸、含水率、千粒重、休止角、滑动摩擦角等进行测试并对小白菜种子宽度及球度概率分布特性进行分析。试验测得小白菜种子宽度分布集中在1.47~1.61 mm，占总体的80%以上，宽度平均值为1.53 mm；球度分布集中在85%~95%，占总体的85%以上，球度平均值为90.41%；滑动摩擦角在ABS材料上的平均值为13.75°。小白菜种子长度和宽度方向尺寸接近，种子尺寸分布集中在各方向的平均值附近，小白菜种子在外形上近似于球形，不同品种小白菜种子之间宽度有差异。小白菜种子的承压载荷随着破裂测试探头位移的增加而增大，种子破裂时承压载荷达到最大值9.6 N，其最终的曲线变化平缓。为正负气压组合式排种器的设计提供重要依据，确保小白菜精量直播的播种精度，满足小白菜标准化株距和行距等农艺要求，以提高小白菜机械化生产程度和机具利用率。

关键词: 小白菜种子, 排种器, 精量播种, 物理特性