Design And Experiment Of Belt Conveyor Header For Soybean Combine Harvester

Soybean production reached 15.28 million tons in 2018 in China.Soybean planting has high planting cost,high labor intensity and low degree mechanization.In recent years,the mechanized harvest level of soybean is less than 70%.Low level soybean mechanization technology has become the factor restricted the further development of soybean industry in China.At present,rice-wheat combine harvester is used to harvest soybean in Huang-huai-hai region of China,but the loss rate in this way is particularly high.The reason is that rice-wheat combine harvester is difficult to adapt to the characteristics of soybean.Therefore,it is important to develop a special soybean header suitable for this area.In this paper,aiming at the problems in mechanized soybean harvesting in Huang-huai-hai region,a special soybean cutting table was developed.The main research contents include:(1)The agronomic and morphological characteristics of soybean related to header in mechanized soybean harvesting were studied,and the structural design scheme of special cutting table for soybean was determined.The agronomic and morphological characteristics related to mechanized harvesting of 20 main soybean varieties in Huang-huai-hai region were measured,the result is: the row spacing is 36 cm,the plant spacing is 10-25 cm,the plant height is 40-90 cm,the bottom pod height is 7-30 cm,and the maximum diameter is 10-37 cm.According to the characteristics of soybean plant,this paper introduces the working principle of the header and analyses the movement process of soybean stalk on the header,and the overall design scheme of the uniform conveying cutting table was determined: 1 design and install anti-explosion pod reel;2 design a longer header length;3 add auxiliary conveying device between cutter and screw pusher;4 motion parameters of key components are optimized for soybean harvest.(2)The structure and motion parameters of key parts of header are designed.Eccentric Five-bar type used in reel,the anti-explosion pod board was installed on the reel teeth.The reel can not only reduce the impact on soybeans,but also enhance the ability of poaching.Through theoretical calculation,it was deduced that the rotational speed of the reel was between 35 and 45 r/min.The height of the reel relative to the cutter was 720 mm,and the maximum forward distance relative to the cutter was 196 mm.Auxiliary conveying device was added between cutter and screw pusher.The device could transport the soybean stalks accumulated on the cutter to the screw pusher in time.The speed of conveyor belt was 0.5-0.9 m/s.Anti-splash cover was installed at the back of the header to prevent the beans and pods from flying out of the header.(3)Finite element analysis of header frame was carried out.In order to ensure the reliability of the designed header structure,the static and modal analysis of the header was carried out by using ANSYS Workbench finite element analysis software.Stress analysis shows that the maximum stress occurs in the middle of the lower cross beam of the rack,the maximum stress is 100.03 MPa,and the maximum deformation occurs in the lower cross beam of the rack far from the contact point,which is 1.97 mm.The first six order modal parameters were obtained by modal analysis of the header.The deformation of the header concentrates on the left and right side plates,left and right crossbeams,bottom plates and cutter frame crossbeams.(4)Taking the loss rate of the cutting table as the objective,the structure parameters and motion parameters of the header were optimized through field experiments.Through single factor test,the horizontal position of the reel was determined to be 60 mm in front of the cutter.Then,the three key parameters of harvester forward speed,conveyor belt speed and reel speed are tested and optimized by Box-Benhnken central combination test method.The regression mathematical model of header loss rate was established and its variance analysis was carried out.Variance analysis shows that the rotation speed of the reel was the most important factor that affects the loss rate of the header,followed by the forward speed of the harvester,and the least influential factor was the speed of the conveyor belt.The response surface method was utilized to analyze the effects of factors’ interaction on loss rate,and the objective optimization of the influencing factor carried out based on the Design-expert software.The optimum combination of operating parameters of the header was as follows: harvester forward speed was 1.35m/s,reel speed was 40r/min,conveyor belt speed was 0.83m/s.Under the optimum combination of parameters,the loss rate of header was 1.44%,which meets the requirements of national standards.The special soybean header was adjusted according to this parameter and tested in the field.Under this condition,the loss rate of header was 1.39%.(5)In order to solve the problem of large vibration of the cutting table,the dynamic signal acquisition and analysis system was used to test the vibration,and the vibration characteristics of the cutting table were analyzed.Vibration tests showed that: The reciprocating motion of the cutter is the main reason for the vibration of the cutting table.The vibration intensity of the front part of the cutting table is greater than that of the back part of the cutting table,and the vibration intensity of the transverse part is greater than that of the front,back and vertical part.Compared with the traditional soybean header,the vibration intensity near the cutter of soybean special cutter is smaller,which decreases by 27.25% and 10.67% in the left and right directions and in the front and back directions,respectively.Therefore,soybean special header not only has better reliability,but also could reduce the loss rate.