【作者】 武占华；

【导师】 关德林； 段树林；

【作者基本信息】 大连海事大学 ， 轮机工程， 2008， 博士

【摘要】 为了满足现代车用内燃机对配气机构综合性能要求不断提高的需要，本文对顶置气门下置凸轮轴式配气机构综合性能的分析方法进行全面深入的研究，以6DF1-26柴油机为研究对象，根据所建立配气机构运动学、动力学、润滑和接触应力模型确定配气机构综合性能指标，使配气机构性能评价不再局限于某一个领域。本文首先在对凸轮型线谐波分析的基础上，对配气机构进行时频联合动力学分析，确立了凸轮型线、配气机构动力学响应、机构固有特性之间精确的对应关系，为精确分析实测动力学响应的成分及影响因素提供了理论依据，避免了传统的单纯通过时域或频域对动力学响应分析针对性差、精度低的缺点。通过精确的动力学分析，获得了机构总动变形量、各零部件振动及载荷随转速和气门间隙等影响因素的变化规律。另外，为提高配气机构动力学模型的精度，本文根据最小二乘原理衡量气门动力学理论规律与实测规律的一致性，采用自适应随机搜索优化方法辨识配气机构动力学模型的参数，从而提高了动力学模型对转速、气门间隙、凸轮型线、气门弹簧等大范围变化的适应性，因而可以取代传统的按经验试凑确定动力学模型参数的方法。其次，根据运动学模型和动力学模型提供的精确参数，利用动态油膜厚度和赫兹接触应力模型计算分析了润滑油膜和接触应力的变化规律。经过2000h可靠性实验验证，凸轮-挺柱副出现过度磨损的情况和位置与根据模型理论计算的高应力低膜厚区对应。最后，针对车用内燃机转速范围宽广、工作转速高、凸轮机构个性强的特点，以极限工作转速最高为目标，展开对包括N次谐波凸轮型线和气门弹簧在内的配气机构联合优化设计方法的研究。优化设计以高精度运动学模型、动力学模型及润滑和接触应力模型对配气机构综合性能全面计算为基础，用网格法和随机搜索方法优化确定气门弹簧（n_a，D，d）和参数凸轮型线（ρ₁，ρ₂，ρ₃，ρ₄，ρ₅，ρ₆，ρ₇，R₁，θ_Z等）。对6DF1-26柴油机配气机构联合优化设计的实例表明，联合优化设计方法可以有效折中凸轮负加速度段的气门弹簧特性、凸轮-挺柱副润滑和应力特性的关系，在不降低最高飞脱转速的情况下，可以最大限度的实现换气性能、动力性能、润滑和接触应力性能的最优匹配。本文提出的研究方法紧密联系工程实际，为高速内燃机配气机构综合性能分析和系统优化设计方法的实用化奠定了研究基础。更多还原

【Abstract】 In order to meet the elevated requirement of modern vehicle ICE design to the performances of valvetrain, complete investigation is conducted into the synthetical performances analyzing method of OHV type valvetrain. This dissertation takes 6DF1-26 diesel engine as the objective, kinematic, dynamic, lubrication and friction models are set up, and its relative characteristics & features are analyzed, that makes evaluation to the valvetrain performances not restricted in one field.Based on the harmonic analysis to the lift curve of the cam follower, the time-frequency analysis to the dynamic response of the valvetrain is carried out. The relationship between the valvetrain dynamic response, cam profile and natural characteristics is revealed, and that makes the analysis of the components of the dynamic response of the valvetrain and of its determinants possible. This method is able to avoid the defection of weak pertinence and low precision problem through the traditional method purely in time domain or frequency domain. With the aid of the precise dynamic model, the response sequence including vibration and contact load etc. following the camshaft rotation speed & valve clearance etc. are acquired. In order to improve the precision of the dynamic model of valvetrain, adaptive random search method is used to identifiy the parameters of the dynamic model, such as M, C, K etc., with the least squares criterion to determine the measure of agreement between single mass-spring & （4+N₁+N₂） mass-spring dynamic model of the valvetrain and the physical system, and with the help of it, a method has been developed for converting the measured dynamic response of a system into estimates of its unknown physical parameters. By using a more refined model of the valvetrain with high precision and the greatly improved adaptiveness to variant working conditions, valve clearance, cam profile, valve spring etc., and the traditional try-and-error method that is lack of scientific basis is replaced by identification method.Secondly, the dynamic oil film thickness and contact Herts stress are calculated through the EHL model and Herts contact theory, on the basis of accurate data from the Kinematic and Dynamic model, the low film thickness and high stress zone is located, and that is confirmed by the 2000h reliability test.Lastly, considering the wide speed range, high speed, and individuality features of valvetrain for vehicle internal combustion engine, systemic optimal design methodology is developed which makes valve spring design an integral part of N^th degree harmonic cam profile design, with the aid of the high precision dynamic model and lubrication & friction model. Grid optimal method and random search method is adapted separately to select the best matched parameters of the valve spring （n_a, D, d） and the cam profile （ρ₁,ρ₂,ρ₃,ρ₄,ρ₅,ρ₆,ρ₇, R₁,θ_Z etc.）.The systemic optimal valve-train design methodology practice on 6DF1-26 Dielsel Engine is proved that it makes spring-inertia force match characteristics and lifter-cam lubrication and fatigue-resistant properties in the cam zone more balanced. As a result, the air charging, dynamical, lifter-cam lubrication and fatigue-resistant properties are improved without lowering the valve train jump-up speed.The methodology developed in the dissertation also indicates adaptability and applicability for engineering optimal systemic design of ICE valvetrain.更多还原