Vibration Characteristics Analysis And Optimization Of Longitudinal Axial Threshing Drum Of Rape Combine Harvester

In recent years,the whole process mechanization of rape has been continuously promoted,and the harvest link is one of the most important processes.Combine harvester is widely used and developed because of its high efficiency and time-saving characteristics.However,most domestic rape combine harvesters are improved from rice wheat combine harvesters,and the vibration and noise of the whole machine is still violent,resulting in problems such as easy damage to the structure and poor stability.The longitudinal axial flow threshing drum is not only the most loaded component in the whole machine,but also a key link in the threshing and cleaning link.The stable operation of the drum affects not only the threshing performance,but also the stability of the whole machine.The combine harvester is affected by multiple excitation sources in operation,and the threshing drum is not only one of the vibration sources,but also affected by other vibration sources,so there is a risk of resonance.In the field operation,the feeding amount fluctuates,and the uneven crop feeding and its own imbalance will make its vibration more intense.The bending and torsional vibration of the threshing drum during high-speed rotation will deform the working structure in the drum and affect its normal threshing effect.Therefore,this paper will start from two aspects: the operation stability of the drum itself and avoiding structural resonance.The main research contents of this paper include:(1)Vibration test of rape combine harvester.Aiming at the problem of large field vibration of longitudinal axial flow drum rape harvester,taking ward Ruilong 4lz-7.0rape combine harvester as the object,the vibration characteristics of the whole machine under five working conditions were studied by dhdas dynamic signal analyzer.Analyze the vibration acceleration of both ends of the threshing and cleaning frame and the main vibration sources such as engine and header.The overall vibration is concentrated in the low-frequency range of 0 ～ 150 Hz.The main vibration source at the front end of the drum is the transverse vibration of the cutter,with a frequency of 6.8hz.The rear end is greatly affected by the vertical vibration of double frequency 59.4hz caused by the engine.After the rape was fed,the amplitude on the drum increased from 2.4 m · S-2 to 3.6m · S-2,an increase of 51%,mainly in the transverse and vertical directions.(2)According to the theory of rotor dynamics,two main causes of vibration deformation,self-excited vibration and forced vibration,are proposed,and the effects of whirl and rotation of the rotor system on its critical speed and natural frequency are obtained.Finally,according to the load and damping of the drum under field conditions,the vibration mechanical model of the threshing drum is established,and the vibration differential equation is obtained,which provides a theoretical basis for the subsequent simulation model.(3)Use Solid Works to establish the three-dimensional model of the longitudinal axial flow threshing drum,import it into ANSYS Workbench for pretreatment,add bearing constraints to its main moving rotor,solve the Campbell diagram and analyze its critical speed.By comparing the critical speed of bearing damping and non bearing damping rotation,it is concluded that the oil film bearing as the boundary condition of the rotor will reduce the value of its first-order critical speed.And the first-order critical speed is1127 rpm.Within ± 15% of the normal working speed of 900 rpm,there is a risk of self-excited vibration at a lower threshold.The harmonic response of the drum is analyzed.According to the G40 dynamic balance standard,1kg imbalance is added at the toothed rods of the front feeding inlet,the middle and the rear discs respectively to simulate the influence of Rape Stalk winding and its own accuracy.The results show that the resistance of the middle plate to the unbalance is poor,and the maximum radial deformation of the rod teeth in the resonance range is 16 mm.The first 8 natural frequencies and vibration modes of the damped drum model are obtained.Compared with the vibration data measured in the whole machine test,it is concluded that the drum overlaps near the frequencies of 23 Hz and 59 hz,which is prone to vibration coupling.(4)The simulation analysis of the longitudinal axial flow threshing drum may have modeling or accuracy problems.Therefore,in order to verify the reliability of the simulation theoretical results,the test mode of the longitudinal axial flow drum is tested.The simulation results show that the natural frequency is 23.4%.Aiming at the resonance problem of longitudinal axial flow threshing drum,topology optimization is carried out to reduce the overall weight,reduce the power consumption of rotor and strengthen the thickness of middle plate.Increase its overall natural frequency to avoid 23 Hz and 59 hz.In view of the irregular vibration of crops in the drum,it is proposed to add damping devices at the supports of bearing seats at both ends.This reduces the transmission of vibration caused by the drum to the vehicle body.