Design And Vibration Analysis Of Low-loss Rape Header With Double Vertical Cutters

As an important oil crop,rapeseed is widely cultivated in our country that has a trend of steady rising.However,the mechanized harvest of rapeseed in China is still at a low level(49.55%)in 2016,which is far behind the crops such as rice,wheat,corn and so on.One of the main reasons for restricting the development of rape mechanization in China is the high loss rate.The total loss rate is above 10%,and the rapeseed header loss can account for half of the total loss.The main reasons for the large loss of the rapeseed header are as follows:(1)Cutting loss:Due to the thickness of pod,upper branches,and intertwine of the branches,it's must for vertical cutter.The pod which was cut but not fall into the header make the cutting loss is high in vertical cutter.(2)Rape pod loss:Mature pod is easy splash by collision and vibration.Vibration source and vibration amplitude are complex and large.The swing of vertical cutter make the rape pod loss is high.Rapeseed table vibration not only causes larger header loss,but also seriously affects the comfort of drivers,makes drivers irritable and depressed,and seriously affects the physical and mental health of operators.The reducing of loss and vibration about rapeseed combine harvester has become an urgent problem.Based on the practice of combine harvester,this paper aims at the problems that the loss rate of the harvester is too high,the vibration of the header is heavy and the reliability is poor.The prototype of header come from 4LZ-4.3(TH988)rapeseed combined harvester produced by Wuxi United harvester Co.,Ltd.A low loss rapeseed header with a double vertical cutter was designed and a vibration test based on the field harvest of a rapeseed harvester was tested.Through the modal test and the finite element analysis technique,the rapeseed header was optimized to reduce the vibration of the rapeseed combined harvester and reduce the loss of the header.The main content of this paper is as follows:(1)The paper analysis each component of rapeseed header.The parameters of the cutter type,the transmission mode and the relative position of the vertical cutter are designed and calculated.The paper calculated the main cutter cutting path and power,designed the rational allocation,speed and power and designed the rational allocation,speed and power of the reel.And the paper designed right,left and behind curtain on the header.(2)The study of the relationship between the header vibration and the loss of the header.The DH5902 dynamic signal testing and analysis system was used to test and analyze the vibration during the harvest of combined harvester in the field.It was found that the loss rate of the vertical cutter accounts for 29.7~44.7%of the total loss rate of the header by the sample groove method.Comparing the header's vibration loss,it was found that when the root mean square of vibration acceleration is<3.24m/s~2,the change of header vibration has little effect on the total loss of header.But when the root mean square of vibration acceleration is greater than or equal to 3.24m/s~2,the increase can cause a larger increase in the total loss of the header.The loss rate of vertical cutter increased with the increase of vibration displacement amplitude in the middle part of the vertical cutter in the X direction,but the growth rate decreased and the loss rate of vertical cutter was stable near 1.96%finally.(3)In order to reduce the vibration of the rapeseed header,the modal characteristics of the header frame were analyzed and optimized.According to the modal results obtained by the experimental modal and finite element analysis,the frame of the header was optimized and improved.The natural frequencies of the 1st order mode and the second order mode of improved header increased from 8.59Hz and 11.45Hz to 12.2Hz and14.15Hz,respectively,which increased by 42%and 24%,avoiding the exciting frequency of each exciting source.In addition,the maximum amplitude of the 1st order mode was reduced from 8.31mm to 6.56mm,which was reduced by 21%.Meanwhile,the amplitude of the middle part of the vertical cutter was reduced obviously after the improvement of the first three modes,and the dynamic performance of the header was improved effectively.(4)Through the field harvest test,the vibration test of the prototype header and improved header was carried out.The vibration characteristics of the improved header were analyzed.It was found that the total vibration of the rape header decreased by20~55%,and the loss rate of the cutting platform decreases by 34~58%.This shows that the structure improvement of the rapeseed cutting platform is very effective in reducing the cutting loss.The low vibration and low loss of rapeseed cutting platform were improved.