Dynamic Analysis And Structural Optimization Design Of Hydro-mechanical Continuously Variable Transmission Box

The working environment of the gearbox is very bad,which is accompanied by variable excitation loads in the working process.Especially under the conditions of low speed and heavy load,the transmission box bears a large impact load.If the strength and stiffness of the transmission box are insufficient,it will cause the cracking and deformation of the box,and affect the life cycle and overall performance of the transmission.Transmission is one of the main noise sources of the tractor transmission system,and transmission box plays as the main radiation noise of the gearbox,which is account for more than 90% of the radiation noise.When the natural frequency and excitation frequency of box body is consistent,it can cause resonance,producing vibration and noise.Therefore,the design of the transmission box is important in improving the reliability of transmission.Focusing on the problem of lightweight design and vibration control for the hydro-mechanical continuously variable transmission of heavy tractor,the research conducted in this paper is as follows:1)Dynamic analysis of the initial design for the transmission box is conducted to determine the objective function and constraints of the optimization design.Using Optistruct module in Hyperworks,the thin wall of the box is meshed by the shell element,and the flange plate and the thick plate near the bearing block are meshed by the tetrahedron element.The finite element model of the coupling is established between the shell elements and the solid elements.The modal analysis and transient dynamic analysis are performed to solve the first ten order natural frequencies and the maximum stress and displacement of box.The results show that the low frequency enclosure can effectively avoid the road excitation frequency,but the first six order natural frequencies of box is within the engine excitation frequency range.The ninth order natural frequencies areclose to the gear mesh frequency,563.33 Hz,which will cause resonance.Although the strength and stiffness of the box can meet the design requirements,there is still a large potential for optimization.2)Based on the structural optimization method,the optimal design of lightweight and vibration and noise control is achieved.The optimization mathematical model of transmission box is developed by using the Hyperworks Optistruct module,in which the method of topology and topography optimization are employed.The density of the solid element and the morphology of the shell element are set as design variables.The mass of the optimized box is reduced by 12.6%,and the first ten order natural frequencies and the excitation frequency are staggered.,The objective of lightweight,anti-vibration reduction are achieved via the structural optimization design which provide significant reference for the optimization design of the similar transmission box.