Design And Research Of Hilly Mountain Tractor Chassis

There are many hills and mountains in China,which make the traditional tractor chassis difficult to adapt to their complex working environment.It is mainly manifested in the poor adaptability of chassis on sloping land,low trafficability and stability,large turning radius,poor obstacle climbing performance,etc.The mechanization degree of hilly and mountainous areas is low,which can not meet the needs of farmland operation in hilly and mountainous areas.The purpose of this paper is to solve the key technical problems of power transmission,steering control and automatic leveling of chassis,and to provide reference for the transmission layout,in-situ steering and leveling profiling of agricultural tractor chassis in hilly areas,which is of great significance to improve the degree of agricultural mechanization and the design level of agricultural machinery in hilly areas.According to the knowledge of tractor design manual,automobile tractor science,chassis structure and vehicle theory,agricultural machinery manual,mechanism design science,etc.,using ADAMS,ANSYS,Auto CAD,Solid Works and other computer software,the chassis transmission and walking system,steering system and leveling system were studied,and a 504-type hilly mountain tractor chassis was designed.The main research contents and conclusions of this paper are as follows:(1)Determination of overall technical scheme.The chassis of 504-type hilly mountain tractor adopts wheel type walking system,with matching power of 50 hp,tread and wheelbase are both of 1200 mm,and adhesion coefficient of 0.55,the maximum traction force is 10.78 k N.Adopt mechanical transmission system,the forward and backward speed is 0-5km/h,and can be stepless speed regulation.The car body can be automatically leveled and turned in place,which can meet the needs of farmland operation in hilly and sloping fields below 25 degrees.(2)Design of transmission system and walking system.The chassis of model 504 hilly tractor adopts 7.50-16 herringbone tread tire.The driving wheel is connected with the vehicle body through the leveling mechanism to ensure that the tire is always in a vertical state under various working conditions and prevent sideslip when walking on the slope.The engine power is transmitted to the four driving wheels through the main clutch,MB75 continuously variable transmission,R77 helical gear reducer,transfer case,front and rear drive axles.The speed range of MB75 CVT is 1-5,and the reduction ratio of R77 reducer is 77.24.The transfer case divides the driving force into two outputs,which are respectively transmitted to the left and right driving wheels through the front and rear drive axles.Through the control of the two power flows,the vehicle can move forward,backward and turn left and right.(3)Design of steering system.The clutch type steering transfer case is used to control the different operation states of the chassis through the combination of the teeth clutch in the steering transfer case.The two-way power forms a combination of four states: forward rotation + forward rotation,reverse rotation + reverse rotation,forward rotation + reverse rotation,reverse rotation + forward rotation,realizing the tractor’s forward,backward,left and right radius steering and in-situ steering.(4)Design of leveling system.The leveling mechanism of 504-type hilly mountain tractor is composed of body,front and rear drive axle,wheel side transmission box support beam and upper beam.The engine is suspended under the longitudinal beam by hinged way to form the basis of body balance.The action range of the leveling mechanism is 732 mm,which can ensure the lateral level of the car body on the slope of 25 degrees.The calculation results of the longitudinal stability show that the limit tilt angle of uphill is 45°,the limit tilt angle of downhill is 45°,the longitudinal slip angle of uphill is 33.69°,and the downhill is 16°.The force analysis of the obstacle climbing performance shows that the obstacle climbing height of the front and rear driving wheels is 214 mm,and the profiling obstacle climbing performance is good.(5)Virtual prototype modeling and dynamic simulation analysis.Through ADAMS software simulation analysis,the maximum roll angle of the vehicle body under the leveling state of the 504-type hilly mountain tractor is 37.5°,which is very close to the theoretical calculation of 35.93°.The results show that the front and rear drive axles of the 504-type hilly mountain tractor can be leveled independently under the leveling state of the chassis,with strong climbing and obstacle crossing capabilities,good in-situ steering stability,and good road profiling and passing performance.(6)Finite element simulation analysis of main working parts.The chassis of 504-type hilly mountain tractor adopts H-type frame with only one longitudinal beam in the center and running through the chassis,which has good torsional rigidity.The results of finite element analysis of the longitudinal beam frame show that the maximum deformation of the longitudinal beam frame occurs at the joint of the longitudinal beam and the power input,with the total displacement of 1.2896 × 10-3mm and the maximum stress of 3.0022 Mpa at the middle power transmission joint.The finite element analysis results of the wheel side transmission box show that the maximum stress is 30.229 Mpa at the hinge joint of the wheel side transmission box and the drive axle,and the maximum deformation occurs at the joint of the transmission box and the wheel hub,and the displacement is 2.8104 × 10-2mm.The strength and stiffness meet the use requirements.