Study On Smoth Shift Of Tractor Hydro-mechanical CVT

The tractor is mainly working on the fields,engaged in plowing,planting,in some cases for road transport,For the complex and multi variant work condition of the tractor,the gear box of the tractor with complex structure always,which leads to the inconvenient operation,the shift is not smooth caused by load fluctuation,which reducing the driver comfort and convenience.In this dissertation,based on "The introduction and development of automatic s hift transmission of large tractor" funded by Ministry of Agriculture(fund No.:2010-Z18),combine with Jiangsu Science&Technology Support Plan(BE2014134)and J iangsu Union Innovation Fund(BY2014128-04),for studying on smooth shift of tra ctor hydro-mechanical CVT,which has an important significance to promote the app lication of the hydro-mechanical CVT in the tractor.In this paper,the main researc h contents and achievements are as follows:(1)Theoretical analysis and Experimental Research on the hydro-mechanical CVT.Analysis of hydro-mechanical CVT speed,torque characteristics of Hydraulic Machinery segment HM1,HM3 and HM2,HM4.Analysis and Research on the transmission characteristics of the hydraulic pump motor system?(2)Research and Analysis on the control system of the wet clutch of the hydro-mechanical CVT.The wet clutch is designed and calculated,the control system is studied.The test results show that the control system designed for the tractor meets the demands of the shift.(3)Research and Analysis on the pump motor speed control system of the hydro-m echanical CVT.Study on the pump-motor displacement ratio and transmission output speed,it is concluded that excitation voltage can change gearbox output speed.(4)Based on the experimental,establish the AMESim simulation model of the hydro-mechanical CVT gearbox.Simulation and analysis of ride comfort in the process o f shitting.There are two main reasons to affect the smooth shift:one is the shiftin g time delay due to the wet clutch combination.Second,during shifting the ratios of transmission are not equal.(5)Simulation Research on the reasons of the shift which not smooth,Binding time of wet clutch delay exists,choose the overlapping shift strategy,and study of overlapping,found that the greater the overlap time sequence,the smaller the speed drop,the better the smoothness of the segment,Research on the transmission ratio on the period of shift and found that by changing the pump motor gear ratio can ensure the transmission ratio equal during shift.The simulation shows that(HM1 switch to HM2)when the pump motor displacement ratio was set to-0.98 for shifting,performed better.(6)Base on overlapping strategy.Overlap timing strategies shows that when the temporal overlap is 0ms,40ms,80ms speed drop respectively:77.210?43.977?20.781 r/min,the degree of impact respectively:656.98,272.398,132.823m/s,dynamic load respectively 1.4255,1.2498,1.1956.The above analysis can be seen in the index,overlapping shift strategy plays a positive role in promoting shift quality.(7)Base on overlap timing and pump motor displacement ratio for simulation analysis,making the 3x2=6 group strategies,and carrying on analysis,After that,the overlap time 150ms and the displacement ratio of 0.98 were tested,the results shows that shift smooth is improved.In summary,through the transmission characteristics of the designed hydro-mec hanical CVT gearbox,smooth for study,tractor ride comfort control provides a theo retical reference and methodological support.