Design and experiment of the orifice-groove combined hole of the oriented filling type precision hill-drop seed-metering device for rice

High-speed seed filling can widely be used in rice planting in recent years. However, rice seeds filling hole in a disorderly manner has been resulted in the low precision separation of seed population. It is also difficulty in the precise adjustment during the seed filling. In this study, an orifice-groove combined hole of oriented filling type precision hill-drop seed-metering device was proposed to deal with the issue. A combination of waist round seed orifice and V-groove slot was also designed to adjust to the attitude change of rice seeds under the churning disturbance of tooth plate. The systematic evaluation was constructed to measure the distribution of rice seeds in the area of seed filling. The attitude change of rice seeds was then clarified with the time. The structural parameters of large and small orifices were determined suitable for the conventional and hybrid rice. Taking the conventional rice Huang Huazhan and hybrid rice Feng liangyou 3948 as the seeding objects, the single-factor, full factor, and variety adaptability experiments were carried out with the large and small orifice widths and vibration frequency as the experimental factors. The single-factor experiment showed that the qualifying rate of the seed-metering device was more than 85% for seeding conventional and hybrid rice, when the width sizes of the large and small orifice were 6.8-7.6 and 4.6-5.2 mm, respectively. Low-frequency vibration was the main vibration condition to dominate the seeding performance. The full factorial test showed that the qualified rate of the seed-metering device was not less than 90%, when the width sizes of the large and small orifice were 7 and 5 mm, respectively, indicating suitable for the different vibration conditions. The variety adaptability test showed that the qualified rates of different size rice seeds were not less than 88.80%, the miss-seeding rates were less than 3.60%, and the damage rates were less than 0.16% under the appropriate effective length of the orifices. The field seeding test showed that the qualified rates of various rows were not less than 89.33%, the miss-seeding and reseeding rates were less than 1.60%, and 9.60%, respectively, the average values of the hole diameter and spacing of various rows were 44.64-54.83, and 133.21-144.67 mm, respectively, when seeding Huang huazhan with the large combined orifice-groove. When seeding Feng liangyou 3948 with the small combined orifice-groove, the qualified rates of various rows were not less than 85.73%, the reseeding, miss-seeding, and empty-seed rates were less than 8.27%, 6.53%, and 1.73%, respectively, the average values of the hole diameter and spacing of various rows were 39.88-45.59, and 200.79-205.56 mm, respectively, all of which fully met the planting requirements of precision dry hill-drop direct seeding of the conventional and hybrid rice. Therefore, through the switching of different combined orifice-grooves and the adjustment of the effective length of the orifices, the seed-metering device can be expected to use for the low damage and precision seeding of various rice varieties with the different sowing amount. The finding can also provide the theoretical reference for the design of rice seed-metering device with the adjustable seeding amount.