【作者】 宫燃；

【导师】 周晓军；

【作者基本信息】 浙江大学 ， 机械制造及其自动化， 2009， 博士

【摘要】 重载车辆传动系统使用涨圈型密封环作为动态密封装置,主要解决旋转件与固定件之间的密封问题。从实际运行情况看,密封环的使用寿命一般都达不到设计要求,出现提前失效的现象。其失效形式是密封环的密封面的严重磨损,导致密封实际接触面积减小,影响传动装置的正常运行。因此在密封环的设计和试验阶段,分析密封环失效原因,延长密封环使用寿命是传动装置设计开发过程中的重要研究课题。结合密封环的应用条件和工作环境,研究密封环的润滑特性,通过建立油膜模型求解雷诺方程,得到油膜压力、承载力和摩擦力矩的表达式,并获得它们随密封参数和工况状态的变化规律,从流体油膜的角度来研究密封环的润滑状况。通过密封环的受力分析,比较密封开启力与闭合力的平衡关系,确定影响密封环摩擦状态的规律。同时,建立密封环泄漏模型,研究其泄漏情况。密封环的磨损分为正常磨损与非正常磨损,根据它们的不同特点,提出采用试验分析法与理论建模法来分别研究。建立了密封环的磨损分析模型,讨论了密封环随轴转动与扰动对磨损的影响。通过磨损试验,分析密封环在不同速度、压力和油温条件下的摩擦磨损规律。利用扫描电子显微镜观察了磨损程度不同的密封环端面的表面形貌,并探讨了其磨损机理。根据密封环、油膜和密封介质组成的传热系统,以摩擦热为热源,研究了密封环的传热特性,得到密封环导热计算的热边界条件,提出了密封端面摩擦热的计算方法,推导了密封环温度分布的计算公式,得到了密封环的温度场以及影响摩擦热和密封环传热性能的因素。模拟实际运行工况,采用热-结构耦合分析方法获得密封环在压力和摩擦热作用下的变形特征。自主开发研制了一台高转速、高油压,适用于旋转运动用的密封性能试验台。通过试验系统可以完成静态与动态的泄漏检测,密封环的温升试验和磨损试验,具备良好的通用性和实用性。对密封环进行试验,获取其性能参数及其影响规律曲线,与理论计算进行对比论证,探讨了各环境参数对密封性能的影响。试验台的研制为失效分析、结构设计与改进及其理论验证提供了基础保证。研究失效的评价技术指标,从压力、转速、润滑状态、摩擦热、温度分布、热变形等几个方面讨论了失效评价参数。提出以磨损为主导的失效模式,而油膜承载力与闭合力的不平衡以及摩擦热是引起摩擦机制变化,导致密封环失效的主要原因。从密封环结构参数、结构型式和工况环境参数三个方面进行优化设计,提出优化方案。基于虚拟设计思想,对优化后的密封环进行仿真计算,结果表明,经过优化设计后的密封环在抵抗磨损、降低端面温升、限制泄漏方面有很大改善。更多还原

【Abstract】 The piston ring type seals,as the rotary sealing devices,are one of the most important components in the wet clutch unit of a heavy load vehicle,whereas the failure of the rings occurred only after a service of about a month,the expected service life was more than 3 months.The failure ring was subjected to serious wear on the sealing surfaces,but the mating metal surfaces had slight abrasion.So it is necessary to investigate the wear mechanism and failure cause of sealing rings in order to provide the essential evidence and critical feedback into the design process,and thus contributing to the prevention of the sealing failures and more successful application of this rings in the future.According to the environmental and service conditions of seals in the transmission,the characteristics of the fluid film were studied,and pressure,friction torque and their regular pattern with working conditions were obtained.The lubrication of seals was researched by fluid film.Based on the force analysis of sealing ring,the balance between closing force and bearing force was confirmed to discuss the patterns of sealing friction and wear behavior.A model to simulate leak was constructed and then leakage rate was calculated.The wear of these rings can be divided into two categories:normal wear and abnormal wear.In accordance with the different characteristics,experimental analysis and modeling method were applied respectively.In order to obtain the influence of abnormal wear,a model was established for the small perturbation and rotation of ring.To assess the friction and wear behavior of seals made from PTFE composites under heavy-pressure and high-speed conditions,effects of normal load,sliding speed and oil temperature on tribological properties were investigated using a test rig.Scanning electron microscopy(SEM) was utilized to examine composite microstructures and study the wear mechanism.According to the working conditions of sealing rings,the transfer regularity in the sealing system was investigated.This heat transfer system consists of the ring,the fluid film and the sealed medium.Then the method to calculate the frictional heating of the end face and the partition ratios of the frictional heat were presented.The temperature distribution in the sealing rings was given,and the heat transfer analysis results indicate that the temperature distribution is related to the geometric parameters,the material parameters of the sealing rings,the frictional heat of the fluid film and the coefficient of heat transfer from the sealing rings to the sealed medium.A coupled method based on heat transfer theory and experimental analysis was put forward to estimate thermal loads on sealing rings.Selecting reasonably boundary conditions exerted on seals and simulating the actual operations of the transmission,thermal responses such as temperature field and distribution,thermal deformation,and their variabilities with pressure and rotating speed were obtained by computation of heat transfer.A test rig for dynamic sealing performance under high pressure and high speed was developed and built that can be used for rotary seal.This testing system is developed to simulate the real conditions of sealing rings and its functions include measuring statistical and dynamic fluid leakage rate,evaluating sealing performance during running in process and detecting the temperature of seals,which is of high quality of practicability and universality from the results.Conducted experiments with several seals by this testing system,the performance parameters and relation curves had been obtained,and the effect of each performance parameter on sealing performance was discussed primarily.The development and exploitation of this test rig for rotary seal provides potent guarantee for design and testing verification of seals with low friction coefficient,high reliability and high values of pressure-velocity.There are some indexs that cause sealing failure including working pressure,rotation, lubrication of seals,frictional heat,temperature distribution,deformation of the end face and so on.Those key technical indexes of failure mode were discussed,which indicated that failure mechanism was mainly wear-out-failure by heat and unbalance between closing force and bearing force.The optimum design methods based on working condition parameters,geometric parameters and seals-Types were put forward.The virtual design was applied in the optimized sealing ring and the results show that the leakage rate could be reduced and the effect of the frictional heat and thermal deformation of the end faces on the characteristics of the seals were within a appropriate range.更多还原