Structural Optimization And Dynamic Characteristics Analysis Of One Power Take-off

The vehicle power take-off(PTO) is an important component to transmit power between special vehicle and its proprietary equipment, which is in most cases installed on the outside of the transmission as additional device. Its weight and life directly affects the use and the manufacturing cost of special vehicles. In order to reduce manufacturing costs and improve market competitiveness, this paper take the PTO system as the research object to analyze and research. The main contents are as follows:(1) Outlines the current research status of automotive lightweight technology and dynamic characteristics of meshing gear system at home and abroad and predicts the future development trend and put forward the analyzing idea of structural optimization and dynamic characteristics analysis of PTO and establish a three-dimensional entity model of PTO system. Modal analysis is based on accurate modeling using the finite element analysis software to PTO box and gear meshing system. The natural frequency of PTO box provide important index for the evaluation of the optimized box dynamic characteristics.(2) Take structural stiffness and strength analysis for the PTO box, respectively study the stress and displacement distribution contours under statics and dynamics to provide theoretical basis for the structural optimization. The analysis results show that the maximum displacement under the statics and dynamics is far less than the allowed value of maximum displacement and the box structure has sufficient stiffness, moreover the maximum stress is also much less than the maximum allowable stress value and the box structure also has enough strength. Analysis results also show that the gear meshing process will produce a greater impact on the vibration of box, so as long as the start time is greater than a certain time, in the process of work the maximum stress box can withstand is acceptable, so the moment of impact point obtained by simulation and the box maximum stress of time-varying curve obtained by different action time can provide reliable basis for the control of motor speed. In addition, the PTO shaft are respectively carried on theoretical strength analysis and dynamic strength analysis. Considering the researched shaft only subjected to bending, the shaft is checked by bending strength. The results show that working strength of PTO shaft is enough under theoretical strength and dynamic strength analysis.(3) Based on the dynamic numerical analysis of the meshing gear system, determine the stress size and its position distribution in the transmission process of the meshing gear pair, and the maximum stress of meshing gear is reduced with the increase of input shaft effect time, and as the friction factor decreasing, maximum stress overall trend is increasing, although there are fluctuations but range is not big. To carry on the dynamic performance analysis of meshing gears, it is concluded that meshing frequency corresponding to gear rotational speed close to natural frequency of the gear, gear resonant vibration amplitude is strong. Analysis also show that the meshing gear and input shaft angle acceleration time-varying curves are basically the same and that the vibration of the input shaft have a great effect on gear meshing dynamic performance, reduce the input shaft vibration helps to improve the performance of gear meshing transmission. While gear axial channeling move is small, PTO system basically have no effect.(4) Ensure PTO box performance were similar with the original structure under the premise of minimizing material and combining with the use of low density,light, new materials such as light metals to optimize the original box structure on the target of the box minimum total weight according to the principle of blue areas thinning and red areas thickening with the constraint conditions of maximum deformation value and the maximum stress value of box, then static, dynamic analysis and modal analysis is carried out on the optimized box structure. Analysis results show that the maximum displacement of the improved box is within the allowable range under statics and dynamics, so the improved box structure can meet stiffness requirements. Although the stress value of the improved box increases slightly, it is still less than the maximum allowable stress value, so the improved box structure also can meet the strength requirements. In addition, the first order natural frequency of the improved box in free mode is far higher than the rotational frequency for transmission and oil pump as external excitation, so the improved box structure also can meet the requirements of dynamic characteristics.To sum up, dynamic analysis can effectively realize the real simulation of the PTO based on reasonable working state to obtain stress and displacement distribution and its time-varying curve under the dynamic load, guide to complete structural optimization design of the box, realized in the enterprise product design and development stage to take structural stiffness and strength analysis for the key parts such as PTO box and dynamic characteristics analysis for meshing gear and prediction, lay the foundation for the study of the meshing gear failure and the influence factors and improving ways of working life, reduce the manufacturing cost of the products, improve the level of the design and development of the product and enhance core competitiveness of enterprises to provide ideas and methods.