Design of bidirectional electric driven side vertical cutter for rape combine harvester

Abstract: The side vertical cutter of the rape combine harvester header is generally composed of a moving blade and a fixed blade which were driven by mechanical structure. This kind of cutting form and transmission structure result in high loss and strong working vibration of the rape combine harvester header. In response to the above problems, bidirectional electric driven side vertical cutter was designed. Bidirectional electric driven side vertical cutter mainly includes driving mechanism and 2 blades. The driving mechanism was composed of motor, a pair of driving gears, symmetric double eccentric wheel and 2 cranks. Symmetric double eccentric wheel mechanism was used as transmission mechanism and its kinematic characteristics were analyzed. The displacement, velocity and acceleration curves of the 2 blades had the same shape, but the phase difference was π, and the acceleration inertial forces cancel each other out, which could reduce the influence on the vibration of the header. According to the mechanical model of blade cutting rape stem, main parameters of the transmission mechanism and the blade were determined. The mechanical model of side vertical cutter cutting rapeseed stem was established. According to the mechanical condition that rape stem was clamped by blades but does not slide, the blade slip angle was determined to be 19°. Double action cutters cutting trajectory equations were established. Based on numerical simulation, the cutting effects under different cutting speed ratios (the ratio of the average speed of the cutter to the forward speed of the harvester) were compared. The relationships between missing rate, repeated rate and cutting speed ratio were fitted. Take the minimum of missing rate and repeated rate as constraint, the optimum cutting speed ratio was determined to be 1.1. Bidirectional electric driven side vertical cutter was applied to 4LZ-6T rapeseed combine harvester. Header vibration test showed that header vibration acceleration was 0.11g when only the side vertical cutter working. When the cross cutter and side vertical cutter working at the same time, the vibration acceleration of the header was 1.09g, which was only 0.08g higher than that of the cross cutter working. Field tests showed that the total loss rate of rapeseed combine harvester equipped with bidirectional electric driven side vertical cutter was 6.15%, among which the loss rate of the header was 3.37%, and the loss rate of the side vertical cutter was 1.03%. When the cutting speed ratio were 1.08, 1.63, 2.40, the siding loss rate of vertical cutter were 0.90%, 1.04%, 1.14%, respectively. When cutting speed ratio was close to the optimal value 1.1, siding loss rate of vertical cutter was 0.90%, which was 13.5% and 26.7% lower than that of the other 2 cutting speed ratios, appropriate cutting speed ratio could effectively reduce the siding loss. This study can provide the basis for the improvement of rapeseed headers structure and the performance of rape combine harvester.