发布时间 : 星期三 文章《发动机配气机构动力学分析及优化》硕士学位论文更新完毕开始阅读0f9ee38c84868762caaed5e9
哈尔滨工业大学工学硕士学位论文
Abstract
Valve train is an important part in the internal combustion engine, whether its structure is appropriate or not will directly affect the engine’s economic performance, noise pollution, vibration and working reliability． Valve pair's working condition is not only a direct scale of the valve train's state, but also a key factor to work on the valve pair's impact fatigue wear． This thesis analyzes all the factors that affect the valve pair's impact fatigue wear both on theory and experiment． Moreover, it also presents the improving method accordingly．
So, the dynamic analysis of valve train plays an important role in the engine designs． The methods in common use include Single-Mass Model, Multi-Mass Model and Finite Element Method． With a view to the result’s veracity and the use of computation, the Multi-Mass Model is often used to analysis the valve trains dynamic performance． This article discuss the computation and analysis of the Multi-Mass Model, and a kind of multi-mass model was established．
With regard to the impact fatigue wear between the valve and the valve seat (it’s the origin of noise pollution in the valve train, and it always causes the valve train disabled．), a valve friction and wear test-bed was devised． It take CA488 valve train as its structure frame, and it can be used to test CA488、CA6102、CA6110 valve train’s valve impact fatigue wear．
To analyze the testing result on theory, a new kind of multi-mass dynamic model was presented． The model aims at the test-bed factual structure, gives attention to CA6102’s structure trait． Reasonable centralized mass distributions is used to replace the mass of moving accessory, “Hertz” contact method is used to calculate the stress and deformation, more simple and reasonable origin of coordinate is chosen for the model calculation． Applied to the model presented, the dynamic performance of valve train of the test-bed is calculated, the result of the calculation is compared with the testing result of the test-bed． At the same time, the relationship between max seated impact force and Cam speed and valve clearance is calculated．
Key Words Engine；Valve train; Dynamic Analysis
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哈尔滨工业大学工学硕士学位论文
目 录
摘 要 ··························································································· I Abstract ······················································································ II
第1章 绪论 ......................................................................................................... 1 1.1 课题研究的目的与意义 ...................................... 1 1.2 课题在国内外的发展动态 .................................... 2 1.2.1 配气机构动力学计算 .................................... 2 1.3 本课题的主要研究内容 ...................................... 4 第2章 配气机构动力学模拟 ............................................................................. 5 2.1 单质量模拟系统 ............................................ 5 2.2 多质量模型建立 ............................................ 7 2.2.1 动力学模型 ............................................ 7 2.3 微分方程组与初始条件确定 .................................. 9 2.3.1 微分方程组 ............................................ 9 2.3.2 方程组初始条件确定 ................................... 10 2.4 模型处理与参数确定 ....................................... 11 2.4.1 模型处理 ............................................. 11 2.4.2 参数确定 ............................................. 14 第3章 模型应用 ........................................................................................... 17 3.1 N次谐波凸轮逼近方法 .................................... 17 3.2 微分方程组的数值解法与编程 ............................... 19 3.3 计算参数确定 ............................................. 20 3.4 计算初始条件 ............................................. 21 3.5 计算结果分析 ............................................. 21 3.5.1 气门加速度计算值曲线分析 ............................. 21 3.5.2 气门落座冲击力计算值与实测值对比 ..................... 26 3.5.3 气门落座冲击力峰值与凸轮轴转速、气门间隙的关系 ...... 35 3.6 本章小结 ..................................................................................................... 37 结 论……………………………………………………………………………．．38 参考文献 ····················································································· 40
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哈尔滨工业大学工学硕士学位论文
攻读硕士学位期间所发表的论文 ······················································ 45 哈尔滨工业大学硕士学位论文原创性声明 ·········································· 46 哈尔滨工业大学硕士学位论文使用授权书 ·········································· 46 致谢 ··························································································· 47 个人简历 ····················································································· 48
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哈尔滨工业大学工学硕士学位论文
第1章 绪 论
配气机构是发动机的重要组成部份，它直接关系到发动机运转的可靠性，在一定程度上影响发动机性能，并且又常是发动机噪声的主要来源，造成发动机运转过程中的振动。气门系统的振动是发动机高速运转的关键问题，这种振动可以引起发动机性能下降、挺柱和凸轮脱离接触、气门的运动失去凸轮控制、凸轮—挺杆副和气门座磨损、噪声增大等问题，甚至出现活塞与气门相碰、气门座或气门损坏。随着现代发动机技术的迅猛发展，发动机转速和功率逐渐提高，配气机构各零件的负荷不断增加，传动链的畸变越来越大。这种由于构件本身弹性所导致的工作异常，很可能使配气机构正常工作遭到严重破坏，直到发动机不能正常运转。只有在知道了气门及其驱动零件的真实运动和载荷变化情况后，才能对其工作条件和可靠性做出正确结论，从而提出有效的改进措施。
1.1 课题研究的目的和意义
随着计算机技术的飞速发展，考虑机构弹性变形和弹性振动的配气机构动态模拟计算在发动机的设计和改进中起着越来越重要的作用，可以用它来预测发动机性能，优化配气机构的参数设计，特别是凸轮型线的优化，以获得较接近理想的充气效率和配气正时。同时，还可以对配气机构的寿命和可靠性进行估计。从而达到大大节省试验时间，缩短配气机构的研制和开发周期，以节省大量人力、物力、财力的目的。
气门副（气门—气门座）在工作中承受极高的机械负荷、热负荷及腐蚀性气体的冲刷，润滑状态极为不良，因而在工作中磨损比较严重，常造成气门下沉，燃烧室的有害容积增大，使发动机性能变坏，严重时气门—气门座的密封作用失效，影响发动机的正常工作和大修期，因此在发动机配气机构设计中应给予足够的重视。[1]
气门和气门座处于燃烧室和气道之间，由于缺乏有效的润滑油供应，在气门工作表面上不可能形成润滑油膜。但在排气门工作面上，有一层由残留在排气中的油烟、金属灰末和烟粒组成的非金属层。在非增压发动机的进气门工作面上，有一些在进气过程中从气门导管吸入的润滑油形成的非金属层。
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