汽车悬架液压减振器热机耦合动力学模型

Thermo-mechanical Coupling Dynamics Model of Automotive Suspension Hydraulic Shock Absorber

针对汽车悬架液压减振器建立了由路面不平度激励模型、非线性悬架振动模型、考虑温度影响的减振器阻尼力试验数据模型、减振器热动力学模型子模型组成的耦合动力学效应的理论分析模型.通过减振器阻尼力特性试验数据建立了考虑温度影响的非线性阻尼力试验模型,利用减振器发热特性试验数据辨识了减振器热动力学模型参数.利用所建立的耦合动力学理论模型预测了减振器温度上升动态过程,并进行了影响因素的仿真分析.研究表明,减振器的热机耦合效应在高速行驶和较差路面条件下表现突出,而在低速或者良好路面条件下不明显;行驶车速、路面等级、环境温度与减振器周围空气流动速度、悬架非簧载质量、减振器壳体换热面积对减振器发热平衡温度高低具有很大影响,而悬架等效刚度、簧载质量和减振器壳体比热容参数对之影响很小.

A theoretical thermo-mechanical coupling dynamical model was established, which consists of road irregularity excitation model, two-degree-of-freedom suspension vibration model, empirical shock absorber damping force model by taking temperature effect into consideration and shock absorber thermodynamic model. The empirical shock absorber damping force model was formed as a nonlinear look- up-table by using the damping force, relative velocity and temperature measured under various sine and stochastic displacement excitation. And the parameters of the shock absorber then＇nodynamic model were identified based on the shock absorber thermodynamic characteristics test. Using the thermo-mechanical coupling dynamics model, shock absorber＇s operational temperature was predicted and the influence of factors was also numerically investigated. Results show that the thermo-mechanical coupling effect of shock absorber is obvious when vehicle runs on low-grade pavement with high speed. And the simulation results show that vehicle speed, pavement grade, ambient temperature and air flow rate around shock absorber, unsprung mass, shock absorber tube radiating area have great effect on equilibrium temperature, while sprung mass, suspension stiffness and shock absorber thermal capacity coefficient have little effect on equilibrium temperature.