【作者】 李震；

【导师】 桂长林； 李志远；

【作者基本信息】 合肥工业大学 ， 机械设计及理论， 2005， 博士

【摘要】 内燃机曲轴-轴承系统是内燃机的关键部件,其摩擦学、动力学性能不仅直接影响到内燃机工作的可靠性和耐久性,还限制了内燃机潜力的发挥。因而,摩擦学、动力学性能分析历来是该系统设计理论基础的重要组成部分。然而,长期以来,由于曲轴-轴承系统特殊的结构形式和复杂的受力状况,理论研究难度较大,其摩擦学和动力学行为的分析是在两个独立的领域里分别进行的。因此,进行曲轴-轴承系统摩擦学和动力学的耦合研究、提高曲轴-轴承系统理论分析的准确性,具有重要的理论意义和现实的应用价值。 首先,本文在分析现有内燃机轴承润滑分析、曲轴动力学分析和转子动力学相关领域研究现状的基础上,探讨了轴-轴承系统摩擦学、动力学耦合的必要性。认为轴-轴承系统所承受的最普遍、最常见的载荷形式是变载荷,即使是工作在恒定载荷工况下轴-轴承系统,其在加载与卸载过程中也是承受变载荷作用;对变载荷轴承的分析必须同时考虑轴的动力学效应和轴承的摩擦学效应。据此提出将轴和轴承视为一个整体系统,根据轴的动力学方程和滑动轴承的油膜力方程,采用数值积分方法直接耦合求解轴-轴承系统的摩擦学、动力学行为。 其次,本文采用控制理论的基本观点,详细分析了轴-轴承系统中轴承的摩擦学行为与轴动力学行为间的相互联系,提出了轴-轴承系统摩擦学、动力学耦合研究的分析模型,把轴、轴承分别看作是受控对象和控制器,该模型全面客观地反映了轴、轴承之间的内在联系,物理意义清晰,可以涵盖所有类型的轴-轴承系统,为轴-轴承系统的摩擦学、动力学耦合分析提供了新的研究思路。 第三,本文根据轴-轴承系统摩擦学、动力学耦合研究的分析模型,提出了轴-轴承系统摩擦学、动力学耦合研究分析方法:首先建立轴-轴承系统的仿真模型,采用ADAMS和MATLAB联合仿真,实现轴-轴承系统摩擦学、动力学的耦合分析。该方法建模快捷迅速、仿真过程直观、数据处理方便,为研究复杂轴-轴承系统摩擦学、动力学效应的耦合作用建立了有效的方法和手段。 第四,采用本文提出的轴-轴承系统的摩擦学、动力学耦合分析方法,研究了刚性轴-轴承系统在冲击载荷、径向变载荷和旋转载荷作用下的摩擦学、动力学行为,采用扫频法研究了刚性轴-轴承系统的共振频率,详细分析了转速、轴承间隙、轴承宽度、润滑油粘度等因素对刚性轴轴承系统摩擦学、动力学行为的影响。 第五,以弹性轴的柔体动力学分析为基础,建立了弹性轴-轴承系统的仿真模型,通过ADAMS与MATLAB联合仿真,研究了弹性轴-轴承系统在径向正弦载荷作用下的摩擦学、动力学行为,比较了弹性轴-轴承系统和刚性轴-轴承系统的摩擦学、动力学特性。更多还原

【Abstract】 Crankshaft bearing system is one of the most important components in Internal Combustion Engines (ICE). The performances of the crankshaft bearing system not only have direct effect on the reliability and durability of the engine, but also restrict the development of the engine potentiality. As a result of the complicated structure and loading conditions, it is hard to understand or analyze the coupling tribological and dynamical behaviors of the crankshaft bearing system. The tribological and dynamical behaviors have to been studied independently on the domain of tribology or dynamic over a long period of time. Therefore, to study the behaviors of the crankshaft bearing system coupling bearing tribology with crankshaft dynamics is very important both in theoretical and practical sense.At the beginning of this dissertation, the present status of the tribological analysis of ICE journal bearings, dynamical calculation of crankshaft and correlative researches of rotor dynamics are reviewed. To reveal the relationships between tribological and dynamical behaviors of shaft bearing system, an analytical model of the shaft bearing system is brought forward. According to the model, the shaft bearing system is taken as an auto-control system, and the bearings and shaft are taken as controllers and controlled object. The analytical model has a clear physic sense and can be applied to nearly all the types of shaft bearing system.According to the analytical model, a new coupling analyzing method for shaft bearing system is put forward. With this method, a simulating model of the shaft bearing system is set up at first. Then the simulation model is analyzed by the joint simulation of ADAMS and MATLAB. This method provides an effective tool to analyze the coupling tribological and dynamical behaviors of complicated shaft bearing systems.By using the new coupling analyzing method, the tribological and dynamical behaviors of rigid shaft bearing system exciting with impact, sine and rotating loads are studied. The frequency response of shaft bearing system is evaluated with frequency-sweeping method. It is shown that the resonance frequency of the shaft bearing system has relation with the shaft rotating speed, bearing clearance, lubricant viscosity. The influences of rotating speed of shaft, width and clearance of bearing, lubricant viscosity on the behaviors of shaft bearing system are discussed.Based on the theory of flexible multi-body dynamics, a simulating model of flexible shaft bearing is set up. By the joint simulation of ADAMS and MATLAB, the flexible shaft-bearing system is analyzed. The coupling tribological and dynamical behaviors are compared between flexible and rigid shaft bearing systems.Experiments of flexible shaft-bearing system are done on the test set designed by the author. A non-contact electromagnetic actuator is used in the experiments. The results of the experiments are introduced and discussed. The influences of rotational speeds of the shaft, length and clearance of the bearing on the vibration amplitude of the journal center are analyzed. It is shown that the experimental results are coincident with the theoretical analysis.The crankshaft bearing system of N485 diesel engine is analyzed with the method presented above.The coupling simulation model of crankshaft bearing system is built with the finite element model of crankshaft. The tribological behaviors of main bearings and the three dimension vibrations of the crankshaft are discussed in detail. It is shown that the coupling method is efficient to analyze the tribological and dynamical behaviors of crankshaft bearing system.更多还原