为提高具有成群分布小孔的水稻气力式精量穴播排种器对粳稻种子的排种精度，设计了一种直线型搅种齿，并采用二次回归正交旋转组合试验的方法，以吸种真空度、吸种盘转速、直线型搅种齿与吸孔边沿间距离以及搅种齿高度为影响因素对排种器排种精度进行了试验研究，依据试验结果建立了该排种器对粳稻种子的不同穴粒数的排种回归模型。结果显示：以（3～4）粒/穴率、3粒/穴率、4粒/穴率和≥5粒/穴率为评价指标建立的回归方程均拟合很好，并且均在0.05水平显著；基于生产需要对比确定最优吸附条件为真空度2.40 kPa、吸种盘转速30 r/min、直线型搅种齿距吸孔边沿8 mm且搅种齿高度3 mm。以含水率21.30%～21.79%的粳稻盐丰47号破胸芽种为对象，在吸孔直径1.8 mm、吸孔之间距离6.5 mm以及有清种装置时，进行了该排种器吸附精度验证试验，结果表明该排种器排出（3～4粒）/穴种子的概率为77.28%；≤2粒/穴种子的概率为3.04%，≥5粒/穴种子的概率为19.67%；试验结果与回归模型模拟结果接近，表明所获得的排种回归模型正确，并可用来预测排种效果。该研究结果可为水稻气力式排种器精量播种粳稻芽种时的结构、运动参数设计与优化以及排种性能预测提供重要参考依据。%There are two rice varieties in China. One is Japonica rice and another is Indica rice, and there are obvious differences between them. Due to the need to accurately obtain seed quantity for each hill in direct rice seeding, a novel precise pneumatic metering device was designed with a group sucking holes plate in a seed metering device, by which 3-4 seeds can be sucked and dropped at the same time. Existing experiments were conducted to investigate the sucking characteristics of the group holes on the sucking plate under vacuum, the diameter of the hole, and the seed-clearing device. For optimization of the pneumatic precise metering device structure and motion parameters, improving its capability on accurately sucking different rice varieties of seed, a kind of line-churning tooth was designed. A quadratic orthogonal rotation regression experiment was conducted to investigate the sucking characteristics of the precise pneumatic metering device under vacuum, the rotation speed of the plate, the distance between the sucking-hole center, and the line-churning tooth and height of the line-churning tooth. A probability about the quantity for each hill was used to evaluate the capability of the pneumatic precise metering device. The experimental equipment consisted of a pneumatic metering device with group holes, a U-shaped manometer, a positive and negative pressure air pipeline, a cut-off valve, and a vortex pump. In the experiments, the rotating speed of a sucking plate was 15-45 r/min and its diameter was 165 mm. The diameter of the sucking hole was 1.8mm, and the distance between sucking holes were 6.5mm, while the distance was 65 mm between the middle hole and the center of the plate. There were ten group holes on the plate, and every group had three sucking holes on a straight line of radius direction. A fingerlike clearing device was set on the plate while the distance was 123.75 mm between it and the center of the plate, its length was 38 mm, and the installation angle was 25° to vertical axis of the plate. The rice variety was pregnant Japonica rice seed whose name was Yanfeng 47. Its moisture content (wet basis) was 21.30%-21.79%, its 1000-grain was 30.03 g, its sphericity was 0.54, and its overall dimension (length×width×thickness) was 6.82 mm×3.23 mm×2.24 mm. Its sliding friction angle was 36.15°, and its natural repose angle was 27.12°. With a probability of (3-4) seeds per hill, a probability of three seeds per hill, a probability of four seeds per hill, and a probability of≥5 seeds per hill, four regression equations were established. Every equation’s evaluation of fitting was very good, and all equations were significant at the 0.05 level. The experimental results showed that there existed an optimization condition on the capability of the metering device to meet the needs of production. The optimization condition included that the vacuum was 2.4 kPa, the rotation speed was 30r/min, the distance between the churning tooth and sucking hole was 8mm, the seed churning tooth height was 3mm, the sucking hole diameter was 1.8 mm, and the distance between the holes was 6.5 mm. With the cleaning device, the probability of (3-4) seeds per hill of the metering device was 77.28%; in addition the ≤2 seeds probability was 3.04%, and ≥5 seeds probability was 19.67%, while the experimental results were very close to the regression model calculation results. The study proved that the metering device could accurately obtain seed quantity for each hill of pregnant Japonica seeds, and the regression model could be used to predict probable seed quantity for each hill. This study was an important reference basis for the pneumatic metering device on structure design and motion parameters optimization on seeding pregnant Japonica seeds.
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