Designand Experimental Studyon Differential Inverse Gearbox Of Tracked Rice Field Combine Harvester

The traditional single-side braking steering mode is mostly used in the domestic tracked combine harvesters.The steering mode not only causes the subsidence of harvester and the oversized steering radius,but also causes the shear failure and rolling damage of the soil.The gearbox of Kubota and Yanmar combine harvester solve the above problem by using inverse differential steering mode,and have good passing and steering performance in field.The key technology of them is blocked to the outside.It is important to design a gearbox which could use differential inverse steering mode.Based on the principle of differential inverse steering,an differential inverse steering gearbox that can perform differential inverse steering mode is designed in this paper.The electro-hydraulic control system is designed based on the steering principle to control the steering mode of the gearbox.The steering performance of gearbox is tested by the dynamic simulation test and field test.The main work of this paper is as follows:1.The design of differential inverse steering gearbox.The initial parameters is determined based on the different working condition of combine harvester.The installing space of gearbox is determined based on the chassis walking mechanism of Taihu 988 combine harvester.The component parameters of gearbox are designed.The displacement transmission mode and modification coefficient are designed based on the movement of meshing gears.The 3D model of gearbox is determined,and the components are assembled.The minimum area is set as the object function by obtaining the topology diagram of the gearbox 3D model.The integral type gear-box is designed to overcome the poor sealing of intermediate separation gear-box,and the opening of gearbox is determined.Using ANSYS Workbench to conduct static simulation of the transmission case,the results show that the maximum stress of the case is 73.21 MPa,which is different from the tensile strength of 250 MPa,indicating that the strength requirement is satisfied.The finite element modal simulation of the box was performed.The results show that the natural frequency of the box is greater than the excitation frequency and not the frequency multiplication relationship to avoid resonance.The DH5902 dynamic signal acquisition instrument was used to test the gear-box by hammer modal test to obtain the first 6 natural frequencies of the box and compare with the finite element simulation.The results show the results of the finite element calculation is basically same with the experimental modal results.2.The dynamic simulation based on RecurDyn.In order to simulate the performance of the differential reverse steering and the effect of non-uniform load distribution on the turning radius and steering time when the combine harvester works in a silt field,it provides data support for the further study of the chassis lift.Using RecurDyn and Pro/E to establish the dynamics model of crawler combine harvester chassis.The track?LM?low-speed track module is used to establish the left and right track sub-systems.The chassis running mechanism is constrained and the load is defined,the virtual motor-driven walking mechanism and clay road surface parameter are set.By loading different masses to simulate changes in the load distribution and entering different time functions to obtain different steering modes,various steering parameters are obtained,such as minimum turning radius of the traveling mechanism,steering time.The results show that the uneven distribution of the load ratio on the harvester has a great influence on the steering time and turning radius.Under the differential reverse steering mode,the uneven distribution of the centroid of the dynamic model has a greater influence on the turning radius and has a smaller influence on the steering time;The non-uniform distribution of the centroids during braking and steering has a greater influence on the steering time and less on the steering radius.The closer the steering to the concentrated side of the load,the larger the turning radius and the greater the slip,the longer the turning time.3.Gearbox assembling and testing.The operation of the gearbox is tested through a bench test,and an electro-hydraulic control system is designed according to the gearbox movement mechanism to complete the assembly of the chassis and electro-hydraulic operating system in the test vehicle.A test study was conducted on the crawler-type harvester chassis running mechanism by selecting different road surfaces.The results show that compared to unilateral braking and steering,the steering mode of the differential reverse steering mode has higher steering efficiency and the steering radius is very small.The driving speed V₀ of the harvester has a great influence on the steering time T,and the harvester's mass M is the steering time T.The impact is not significant,the driving speed V₀ and the weight of the harvester M are all important factors affecting the turning radius.