| Power shift tractor has the advantages of sufficient power,high efficiency,low fuel consumption and easy operation,and has no interruption in the process of shifting.With the development of China's agricultural modernization,its domestic demand is increasing.At present,the domestic market of high-power power shift tractors are mainly the products of foreign agricultural machinery enterprises,while the products of domestic agricultural machinery enterprises are either imitation or import foreign advanced technology directly.Power shift transmissions are all imported products,which can not be developed independently.Therefore,the research and development of full power shift and reversing transmission for heavy tractors with proprietary intellectual property rights are suitable for our agricultural characteristics,which will play a great role in promoting the development of our high-powered tractor industry,promoting the industrialization of domestic heavy-duty tractors and entering the international market.The characteristics of typical power shift transmission schemes were analyzed.Based on the domestic manufacturing level,several different transmission schemes were proposed.Through comparative analysis,the most suitable transmission scheme was determined.The transmission scheme was elaborated in detail,and the engagement state of wet clutches was determined when each gear was working.Detailed parameter design was carried out for the determined transmission system of full power shift transmission.The center distance of each gear pair,gear modulus,gear teeth number,gear transmission ratio and gear pair transmission ratio were determined.The minimum diameter of shaft,gear-to-gear ratio and inter-segment ratio were ensured.Relevant parameters of wet clutches were designed,and the speeds and traction force of tractor in each gear position were calculated.The three-dimensional model of full power shift transmission was built by NX software.No interference phenomenon was found after preliminary examination.The simulation model of the full power shift transmission was established by Romax Designer software.Load spectrum analysis of gears in transmission system showed that the life of all gears is more than 8000 h of design value.By analyzing the safety factor of load spectrum,it was concluded that the contact safety factor and bending safety factor of all gears are greater than 1.According to the analysis of the stress in the worst working condition,the contact stress and bending stress of gear set Z19-Z20 are the largest,which are 1443.879 MPa and 822.570 MPa,respectively.The displacement offset of the transmission system was analyzed.The maximum displacement offset value of the transmission system is 175.56?m.The analysis of bearing life showed that the minimum life of bearing S5-2 is 8269.791 h.The meshing dislocation of each gear pair was analyzed,it was concluded that the maximum meshing dislocation of gear pair Z19-Z20 is 40.49?m.The transmission error and contact stress of gear pair Z19-Z20 were analyzed,It was concluded that the transmission linear error range of gear pair Z19-Z20 is 42.63~48.10?m,the axial coincidence range is 1.550~1.681,and the maximum load per unit length is 1572N/mm.The three-dimensional model of the transmission housing was built in NX software,and then the mesh was divided by HyperMesh software.Finally,the rigid-flexible coupling model was built in Romax Designer software.Static analysis of the transmission housing showed that the maximum displacement amplitude is 2.640)?m the maximum stress is about 76.848 MPa,the maximum strain is 9.4130),the material of the transmission housing is HT200,and the minimum tensile strength is 200 MPa.It showed that the transmission housing designed in this paper meets the performance requirements.Through modal analysis of the transmission housing,the modal modes of the transmission housing under the first eight modes were obtained.By analyzing the dynamic characteristics of the transmission housing,the weak links of the rigidity of the transmission housing were obtained,which provides a reference for the optimization of the transmission housing structure. |
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