Study On The Design Method Of Air Spring Life Cycle For Vehicle

In recent years, with the development of industrial technology and the improvement of people's income level, the demand for the car is growing, more and more attentions are paid onpassenger comfort and running safety.Compared with other types of elastic elements, air spring, a kind of elastic element of the automobile suspension, has several advantages such as variable rigidity, low self vibration frequency, high controllability and strong vibration absorption capability.It can make the car get better ridingcomfort and handling stability.Therefore, air spring has got increasingly extensive applicationin large and medium-sized buses, heavy trucks and high-class cars. But it also brings a series of problems, such as excessive consumption of resources, energy shortage and environmental pollution with the increased production and sales. Therefore, research on the life cycle design method of air springs can not only improve the design level of our country air spring and enhance the international competitiveness of China's air spring products, but also have an important practical significanceon realizing the goals ofenergy saving and cleaner production of the China's rubber industry.In this paper, some key technologies of the life cycle design of air spring will be studied. The main research work is as follows:(1) Based on expanding the theory of Quality Function Deployment for Environment (QFDE)andconstructing a hierarchical house of quality, the weights of user demandsareobtained by using Analytic Hierarchy Process (AHP), the weights of the basic engineering parameters are gained by using the transformation matrice between user demands and basic engineering parameters. Based on the sensitivity analysis method and the analytic hierarchy process of the life cycle theory, the comprehensiveenvironmental engineering parameters corresponding to theenvironment requirements of the air spring and the cost requirements of the life cycles are determined. To obtain the final air spring life cycle engineering parameter weights, the comparison matrix between user requirements engineering parameters and comprehensive environmental engineering parameters should be established. And on this basis, the life cycle design and planning model of the air spring is constructed.(2) Based onthe air spring basic principle and design theory, the design and calculation method is presented for the air spring stiffness and natural frequency.Based on the knowledge of thermodynamics, the influence of the polytropic index n value on air spring stiffness is analyzed from three aspects, namely, power loss coefficient, vibration frequency and spring size. The results shows that it is not reasonable to set the polytropic index n euqal to 1.33 under any circumstances.The polytropic index n should be taken different values according to the operation conditions of the air spring. Based on the built finite element simulation model of air spring, the influence of air spring parameters on the air spring stiffness is further analyzed.Thus, the design ideas and design methods are provided for the performance design of air spring life cycle design.(3) By building the virtual simulation model of air spring, the influence of the structure parameters and working parameters of the air spring on the ride comfort is analyzed. Based on the virtual prototype model of multi body dynamics software, the dynamic analysis of air spring suspension is carried out. The optimization variables and the optimization goal are determined through the study of ride comfort simulation of the virtual prototype;the functions and status of the optimization variables in the model are evaluated by analyzing the sensitivity of the optimization variables;the correctness and effectiveness of the optimization model is validated by the comparison between the results of simualtion and real vehicle tests before and after the optimization.It can be seen from the optimization process that the whole vehicle virtual prototyping technology is an effective evaluation and optimization method for the design results of the air spring performance parameters.(4) Based on the basic theory of life cycle assessment, the Life Cycle Inventory(LCI) of air spring is analyzed by using Gabi4 software. On this basis, a multi-objective optimization model,using the Mooney viscosity and carbon emissions as the optimization objectives and usingthe plasticization process of the roller line speed, roller spacing and roller speed ratio as the optimization variables, is built by analyzing the Mooney viscosity and energy consumption of the air spring during mastication. The optimization model is solved by the improved genetic algorithm. The validity of the proposed model is verified by a specific air spring, and the sensitivities of the optimization results and the optimization variables are analyzed. The calculation and analysis process provides a theoretical basis and practical method for the environmental assessment and improvement in the air spring life cycle design.(5) Based on the basic theory of life cycle cost and combined with the phase characteristics analysisin the process of life cycleof the air spring, the life cycle cost framework and the phased cost model were constructed. By analyzing the factors that affect the cost, the blind number theory based model of the life cycle cost of air spring is established based on the blind number theory and improved confidence level method. The feasibility of the proposed model is indicated by a number of examples of the model. The construction of the blind number cost model provides an effective theoretical basis and calculation method for the cost estimation in the life cycle design of air spring.