Design And Research On A Drive Mechanism Of Vibrating Screen With Three Translations And Two Rotations

Vibrating sieve for corn cleaning is a vital component of combine harvester cleaning system.Its structure and movement have an important influence on cleaning efficiency and performance.To further improve the screening efficiency of corn threshed mixture on the screen,a new type of driving mechanism of vibrating screen for corn cleaning is designed in this paper.Three translations and two rotations of the screen can be realized based on the plane reciprocation mechanism with only two translation.A variety of methods were used to study the motion laws and sieving performance in this article mainly including design of drive mechanism,motion simulation,numerical simulation,parameter optimization,and experimental verification.The main research contents are as follows:A drive mechanism of vibrating screen with three translations and two rotations was designed based on the main mechanism of traditional plane reciprocating vibration sieve,and the composition and working principle of the new drive mechanism were analyzed.Translations along the direction of x,y,and z,and rotations around the x axis and the z axis of the upper screen was realized under the action of the driving mechanism.The driving mechanism was divided into several parts such as crank rocker mechanism, double-rocker mechanism and several link mechanisms,and the kinematic sketch was drawn according to the working principle of the drive mechanism with three translations and two rotations.The displacement equation of any point on the screen were derived using the closed vector polygon method.The curve of x and y direction velocity of marker point on the screen were generated using Matlab numerical simulation,compared with the velocity curve of the same point in motion simulation,and the correctness of the derivation of motion equation was affirmed.The motion of the screen that is cyclical and not simply harmonic was showed by the velocity curve of numerical simulation.The lengths of each drive rod were determined using optimal design of Isight software.The optimization objective is that the displacement of the screen in the rear would be minimum,and the scope angle of the screen was taken as a constraint.The back amplitudes of the screen optimized was 15.4 mm.The greatest influence on the amplitude of the screen is the crank,the lower rocker and the limit bar,the connecting rod and the upper rocker have relatively large influence on the amplitude of the screen,and the T rod and V rod have relatively small influence,which were drawn by the correlation analysis of the objective function.The motion laws of the mechanism optimized were obtained by numerical simulation combining Matlab software,and the effect on the sieving performance was analyzed.The tilted angle of screen swinging back and forth changes in the range of 4.24 degrees to 3.85 degrees,and its swinging left and right floats in the range of plus or minus 18 degrees.The motion of the screen was proved to be cyclical and not simply harmonic.The amplitude of x displacement in the rear screen is 4.6 mm higher than that in the front and increases gradually along the screen.The amplitude of y displacement in the front screen is 7.6 mm higher than that in the rear and reduces gradually along the screen and gradually increasing from the middle to both sides.The displacement of the screen in z direction is simple harmonic motion and its amplitude is relatively small.The law of the acceleration of the points on the screen is similar to that of the y displacement.That the change of y displacement has a direct effect on the acceleration was indicated.The non-simple harmonic motion of screen was also confirmed by the non-simple harmonic variation of acceleration.Displacement coordinates of the front and rear screen in x and y direction were recorded respectively with high-speed camera.That the motion law of the two curve is consistent was indicated by comparing the fitting curve that generated by Matlab and numerical simulation.The correctness of the derivation of the kinematic equation and the reasonableness of the kinematic analysis were proved.To compare the screen performance,comparative experiment were conducted on the new type of driving mechanism and the plane reciprocation mechanism.Different speed of spindle and the mass of corn feed mixture were taken as the factors,and the screening time and screening rate were taken as the performance index.The conclusion was drawn that the screening time of the new mechanism was shorten by 18.7% than that of plane reciprocating vibration screen,when corn feed mixture were fed into 6kg once.The optimized speed of spindle is 260 r/min when the maximum feed mass is 6kg/s continuously.The corresponding sieving rate was increased by 5.75% and energy consumption was reduced by 16.1%.The superiority of this drive mechanism of vibrating screen with three translations and two rotations is proven.