Design and experiment of precision air-suction plate seed metering device for super hybrid rice

Abstract: Seed-metering device is the key equipment for factory seedling, however the metering precision of the existing rice seed-metering device was in 2~5 seeds per sampling area, it couldn't meet the super rice sowing requirements of the 2 ± 1 seeds per seedlings area when machine plug seedling. Air-suction metering device has become the main equipment of super rice sowing because of its high accuracy, low injury, adaptability and other characteristics. But the existing air-suction seeding device widely used the metering methods that row box was vertically vibrated and sowing plate was parallel moved back and forth for filling seeds, then it has complicated structure, large overall volume of the gas chamber, uneven pressure distribution and unstable air flow, it was also affected easily by the air flow and pressure factors. To overcome these shortcomings, a new kind of air-suction plate metering device was designed in this paper, which was composed of conveyor belt, slider, combination of airway gas chamber, suction plate, linear guide way, vibrator ,Seed box, cylinder, seeding tray, electric sensor, and so on. The working principle of new type metering device was the suction plate swung back and forth,the seed box moved up and down along the suction plate. To meet the super hybrid rice precision sowing requirements of 2 ± 1 seeds per sowing unite，the suction plate was designed as 544 suction units, each unit was arranged two suction holes diagonally. According to the rice seedling plate size, the size of the overall structure of gas cavity plate was determined, its length is 600 mm, width is 300mm and the height is 25 mm. The gas cavity plate was divided into eight airway with the horizontal, each airway width is 30mm, height is 20 mm, two ends of each horizontal airway communicated with the longitudinal airway, airway suction slot longitudinally at both ends connected with a negative pressure air source, multi gas cavity plate connected with seed suction plate under the sealing state, its two ends can be vacuumed by interconnected aspiratory airway. Seed box was designed to the half open type shape, opening bottom width is 100mm, high is 120 mm, up width is 40mm, the gap left between the lower edge of the box and a seed suction plate, both sides of box respectively through the sliding block and the fixed installed in the ceiling which consists of linear guide plate on both sides of the moving pair. The traditional single chamber structure was changed to combination chamber by more horizontal airways and longitudinal grooves on both sides of chamber. Take liangyoupeijiu super hybrid rice as the research object, select the vacuum pressure, seed box moving speed, seed-filling the position angle and suction hole diameter as test factors，the single factor and orthogonal experiments were carried out. The results showed that metering device had the optimal seed-filling performance under these conditions of the seed box moving speed 0.12 m/s, vacuum pressure 1.5 kPa, seed-filling the position angle 120°, and the suction hole diameter 1.0mm, the qualified rate was 94.26%, the miss index was 2.47%, and the multiple index was 3.27%. And the seeding performance was tested by different efficiency under the optimal parameter combination of seed-filling performance. When the efficiency is 300 plates per hour，the qualified rate is 90.52%, it showed the new air-suction seeding device not only meet the super rice seedling sowing requires precision, but also has important implications for the quality assurance of super rice breeding, mechanized cultivation, increase productivity and profitability.