| In this paper, a rice water direct-seeding reciprocating fork type metering device was developed aimed at the requirements of rice mechanization planting based on system analysis of rice seed metering device research status at home and abroad, and its overall structure and working principle was introduced.By using of Pro/Engineer software, key parts’ design, three-dimensional modeling and virtual assembly has been done on the basis of the rice bud seed material mechanical properties according to the requirements of metering performance, and the metering device prototype has also been made and debugged. This paper has finished the simulation analysis of metering process and the simulation optimization of device structure with the help of EDEM discrete element software. On the developed test-bed, the metering device test-bed experiments have been carried out, and the effect of structure parameters and operating parameters on the metering performance have also been analyzed.The main contents and conclusions of this study are as follows:(1) Taking rice bud seeds of Japonica rice, Indica rice and Hybrid rice as research objects, this study has determined the rice bud seed material mechanical properties which has impact on the metering performance and gained the parameters of rice bud seed’s three axis dimensions, 1000-grain weight, slip friction factor and natural angle of repose on the condition of wet basis moisture content 18%. This issue’s study has provided theoretical foundation for the design of metering device’s key parts.(2) According to the requirements of reciprocating fork type metering device’s metering performance, the design of overall structure, working principle and dynamic route were determined. This paper has designed the structural style of type hole block, transmission shaft, stirring device and seed scarping device, and determined the parameters of eccentric wheel’s eccentricity and fork rod’s critical velocity. Taking advantage of Pro/Engineer software, the key parts’ three-dimensional modeling, virtual assembly and interference checking of metering device have been done, and key parts have been manufactured and debugged.(3) In allusion to reciprocating fork type metering device, this study has built its discrete element model in EDEM discrete element software, and analyzed rice bud seeds’ motion and the reason of re-seeding and miss-seeding during metering process, and finished seed scraping device’s simulation optimization. The simulation results show that metering quantity has a lot to do with rice bud seeds’ motion when they fill the seed-filling hole. During the simulation time from 0.47 s to 0.57 s, the effect curve of compressive force and revolving speed changing with time were ensured, and the curve showed that the rice bud seeds’ maximum compressive force was 81.02 N and maximum velocity was 0.90m/s. At the same time, the effect curve of all rice bud seeds’ average revolving speed, average compressive force and average distance changing with time were analyzed, the curve showed that maximum average velocity was 0.033m/s, minimum average velocity was 0.003m/s; maximum average compressive force was 0.1N; average distance was 0.008 mm.When revolving speed was 300r/min and seed-filling hole was Ⅳ, the simulation analysis of metering devices with three different structural style seed scraping devices had been done and the effect curve of metering performance changing with scraping devices were ensured. The results showed that metering performance was best when brush style seed scraping device was choice, and its qualified rate was 80.0%, cavity rate was zero, reseeding rate and miss-seeding rate were all below 8.00%.(4) This study has carried out the test-bed experiments of reciprocating fork type metering device and analyzed the influence of transmission shaft revolving speed, seedfilling hole, and seed scraping brush on metering performance. The experiment results showed that metering performance was best when seed-filling hole was Ⅳ, and its qualified was 86.00%, miss-seeding rate, re-seeding rate, cavity rate and breakage rate were all below 6.80%. With revolving speed increasing, the qualified rate and cavity rate were appreciable impacted, the miss-seeding rate, re-seeding and breakage rate were significantly affected; when revolving speed was 270r/min, metering performance was the best.The cavity rate was appreciable impacted with seed scraping brush adjusting, but other performance indexes were not appreciable influenced.(5) In order to analyze the influence of interaction between seed-filling hole and transmission shaft revolving speed on the metering performance, double-factor experiment was carried out, the results showed that seed-filling hole had significant influence on qualified rate, cavity rate and breakage rate, and had appreciable impact on miss-seeding rate and re-seeding rate; seed-filling hole, revolving speed and thare interaction all had significant effect on breakage rate; when seed-filling hole was Ⅳ and revolving speed was 270r/min, metering performance was best, and its qualified rate, miss-seeding rate, reseeding rate,cavity rate and breakage rate were 86.00%,6.80%,4.13%,3.07%,4.495%。(6) Three factors and three levels orthogonal experiment has been done to study the influence primary sequence of three factors on metering performance, the results showed that the influence primary sequence was revolving speed > seed scraping brush > seedfilling hole, and the optimum combination level was revolving speed(270r/min), seed scraping brush position(3mm), seed-filling hole(Ⅳ), and its qualified rate was 87.33%, miss-seeding rate and cavity rate were both below 2.00%. Under the condition of the optimum combination level, the compatibility test of metering device has been developed in allusion to Japonica rice and Hybrid rice, the results showed that reciprocating fork type metering device had a good compatibility to the rice bud seeds which had significant differences on overall dimensions. |
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