Research On The Technology Of Multi-Point Lifting And Lowering Chassis About The Tracked Combine Harvester

The crawler combined harvester was an important agricultural machinery.In paddy field operations,the minimum clearance of the chassis walking device affected the field permeability of the harvester.When the combined harvester had a minimum ground clearance,the center of the machine had a low center of gravity and good stability,which is suitable for high-speed operation.When the ground clearance was increased,the field had a fine passability,and it was suitable for operation in wet fields and deep paddy fields.Therefore,the study of the chassis walking device with adjustable ground clearance can adapt to the change of field topography by actively adjusting the height of the ground clearance of the chassis,improve the field passability and stability of the combine harvester,which has a very broad application prospect.In this paper,based on the design of the crawler chassis walking device of the combine harvester,a crawler-type chassis lifting and leveling device was proposed.According to the design requirements of the project,the overall design scheme was formulated.The rationality of the scheme was verified by theoretical analysis,kinematics simulation and hydraulic system simulation were performed on the multi-point lifting model,and the rationality of the simulation was verified by the prototype test.The main work had been done as follows:(1)A crawler type chassis lifting and leveling device was proposed.According to the overall requirements of designing 7 tons of the whole machine,the power of the whole machine was calculated to be 79kw.The chassis has a total length of 4146mm and a total width of 2177mm.The four-point adjustment lifting and leveling scheme was adopted,and the distance between the shafts of the front and rear lifting mechanisms of the same side was 1550 mm.Calculated and analyzed the movement mechanism of the lifting mechanism on the crawler type chassis lifting and leveling device,and the degree of freedom of the single-side lifting mechanism was 2,which corresponds to the arrangement of two hydraulic cylinders on one side,indicated the feasibility of the scheme.According to the calculation results of the lifting and lowering,the chassis frame of the lifting and leveling device can be raised horizontally by 140 mm.The track-type chassis had a gauge of1550mm,and the horizontal angle of the chassis on the horizontal ground was±4.01°,and The maximum forward angle is 6.11 degrees.The design speed of the hydraulic cylinder was 0.1m/s,and the hydraulic cylinder was initially determined to be 63 cylinders,the cylinder diameter was 63mm,the rod diameter was 35mm,the front cylinder stroke was100mm,and the rear cylinder stroke was 200mm.(2)Established an ADAMS model for lifting and lowering chassis.The loading mass acts as a load on the chassis frame that simulates the working part.The simulation results showed that when the front cylinder elongation was 50mm,the chassis frame can be adjusted with an inclination angle of 4.54 degrees with respect to the ground;the overall lifting height range was 140mm,it can accommodate the left and right lateral height drop of 140mm;when the one-side rear hydraulic cylinder extended 100 mm,the lateral inclination angle was plus or minus 3.71 degrees.In the process of synchronous adjustment of the left and right,the maximum speed of the hydraulic cylinder and the hinge joint point was 71.56mm/s,and the acceleration was 75.67/s~2.The maximum angular velocity of the boom of the lifting mechanism was 14.38°/s.The maximum acceleration of the center of mass movement of the chassis was 50 mm/s~2.(3)According to the actual working conditions of the model,load-sensitive loops are designed and modeled in AMESim software.Through the modeling and simulation of the hydraulic control circuit of the lifting hydraulic cylinder,the signal of the opening degree of the reversing valve was adjusted,the flow rate and moving speed of the hydraulic cylinder were controlled,and the hydraulic circuit of the no-load sensitive system was set as the control group.In the left and right load adjustment,the hydraulic cylinder load was reduced from 35116N to 26317N in 10 seconds,and then maintained at 26317N.The hydraulic cylinder start and stop moving smoothly in the load-sensitive circuit.The pressure of the hydraulic cylinder inlet port changes uniformly from 14.3MPa to 12.4MPa during the movement,the pressure fluctuation and the dynamic impact turned small.The hydraulic cylinder piston rod of the no-load sensitive system fluctuates greatly when starting and stopping,and the oil pressure was greatly beaten when the movement stop.The eccentric load simulation results showed that under the action of load-sensitive loop,although the load of the two hydraulic cylinders was quite different,they can all reach the predetermined motion state,and the flow rate of the hydraulic cylinder inlet port was always stable with the load change.However,the load of the large-capacity cylinder was less,so the movement was relatively slow.The simulation verifies that the load-sensitive loop can reduce unnecessary throttling losses and greatly improve energy utilization.At the same time,the hydraulic cylinder was operated smoothly,reducing the vibration shock at the start and stop.(4)Carried out the lifting and leveling operation test,compared and analyzedthe simulation results.The displacement sensor and the oil pressure sensor are selected to detect the displacement of the hydraulic cylinder and the pressure change of the inlet and outlet ports,the attitude sensor detects the attitude information of the chassis frame,and the analog quantity acquisition module records the sensor data in real time.Obtained the attitude of the chassis tilting posture of the lifting and lowering device in different working modes.The displacement of the hydraulic cylinder of the lifting actuator,and the internal parameters of the hydraulic part,and the relationship between the hydraulic cylinder displacement and the tilting attitude was obtained.It was found that the combined harvester had little effect on the change of the hydraulic port inlet pressure under both static and low speed conditions.The simulation model was modified with the prototype.After re-simulation,the results were compared with the experimental data.It was found that the hydraulic cylinder synchronous lifting inlet pressure and test error were 5.3%,which verified the simulation.