【作者】 强超；

【导师】 谢宗法；

【作者基本信息】 山东大学 ， 车辆工程， 2013， 硕士

【摘要】 当代社会中,汽车已经成为人类生活的重要组成部分。汽车在为人类提供舒适和便捷的同时,也带来了环境污染、能源危机等一系列问题。这些问题都对汽车,特别是其核心——发动机提出了更高的要求。传统发动机的配气机构采用的是固定配气定时,很难兼顾高速和低速时的进气性能,节气门的节流作用使换气过程中的泵气损失增大,导致发动机燃油经济性和排放性恶化。所以,研究气门最大升程、开启持续角和配气相位三者的连续可变的全可变气门机构便有着十分重要的现实意义。本文所研究的就是一种发动机全可变液压气门机构(简称SDFVVS)。该机构取消了节气门,由机械-液压机构联合控制气门运动,从而实现气门最大升程和开启持续角的连续可变。本文以K157FMI发动机为样机,从运动学和动力学两方面对SDFVVS机构的气门运动规律进行了研究,主要内容有以下几个方面。首先分析SDFVVS机构的基本结构和传动链形式,将结构划分为高压和低压部分或者控制和驱动部分。机构的工作过程主要有气门开启、气门关闭及落座以及挺柱回落等三个阶段,分别阐述其工作原理。另外对机构主要的控制部件——泄油控制器与落座缓冲机构加以分析,同时对液压活塞、气门弹簧、液压挺柱等主要部件加以设计,为后续工作打下基础。然后对SDFVVS机构进行运动学分析与设计。介绍了平底液压挺柱及配气凸轮的运动规律,并结合SDFVVS机构的实际情况分析凸轮型线设计的基本思想与要求。将凸轮型线分为缓冲段和工作段两部分,首先选定合适的缓冲段类型并设计其曲线方程,之后利用计算机编程的方法计算得到工作段曲线方程的设计结果并对其准确性加以验证。设计结果表明,通过对SDFVVS机构凸轮型线的合理设计,可以使SDFVVS机构的气门在理想的时刻开启和落座,从而实现理想的气门运动规律。最后对SDFVVS机构进行动力学仿真分析。在配气机构单质量动力学模型的基础上建立SDFVVS机构的动力学模型并分析其计算方法,利用ADINA软件建立相应的有限元仿真分析模型并计算得到不同转速和泄油角条件下SDFVVS机构的动力学仿真分析的结果,将该结果与实验测得的气门运动规律加以对比,验证动力学仿真模型的准确性并分析误差产生的原因。仿真分析结果进一步表明,SDFVVS机构可以实现对气门运动规律的直接控制,并在很大范围内改变发动机进气门的最大升程和开启持续角,使气门运动规律能够根据泄油角和转速的不同进行相应的改变,从而实现气门最大升程、开启持续角和配气相位的连续可变。更多还原

【Abstract】 In modern society, the automobile is becoming an important part of people’s life. The automobile brings a series of questions such as the environmental pollution and energy crisis while offers comfort and convenience to people. These questions put forward higher request to the automobile, especially the engine, as the core of the engine. The fixed valve timing which is used by the valve train of traditional engines cannot take into account inlet performance both in the high-speed and low speed condition. The throttling action increases the pumping loss during the gas exchange process, which leads to the deterioration of the fuel economy and the emission, so it makes a great difference to research the fully variable valve train, of which the maximum valve lift, the opening angle and the valve timing are continuously variable.A kind of fully variable hydraulic valve system or SDFVVS for short is introduced in this paper. The throttle is removed in this system and the valve is driven by a mechanical-hydraulic system, thus realizing the continuous variability of the maximum valve lift and the opening angle. A K157FMI engine was taken as a prototype in this paper, and the research about the valve movement characteristics was done from both kinematics and dynamics aspects. The main contents are as follow:First of all, the basic structure and the transmission chain of SDFVVS were analyzed and the structure was divided into high-pressure and low-pressure section or control and drive section. The working process, including the valve-opening, valve-seating and tappet back stages, was also respectively stated. In addition, the main control units were introduced and designed to lay the foundation for the follow-up work.Then it was introduced that the kinematics analysis and design of SDFVVS. The movement characteristics of the hydraulic tappet and the valve cam were stated and the basic guideline and requirement of the cam profile design were analyzed considering the practical situation of SDFVVS. The cam profile was divided into buffer section and working section. The proper type of the buffer section was selected and the equation of it was designed. Then the equation of working section was calculated by the way of computer programming and the accuracy of the result was also verified. The result showed that the valve of SDFVVS can be opened and closed at the ideal moment to realize the ideal valve movement characteristics by a rational design of the cam profile.In the last place, it was introduced that the dynamical simulated analysis of SDFVVS. The dynamical model of SDFVVS was built at the basis of the one-mass dynamic model of the valve train, and the calculation method was also stated. The finite element model of dynamical simulated analysis was built by the software ADINA and the results in variable engine speed and oil drainage angle were obtained. The correctness of the model was checked by comparing with the experimental results and the reasons of the error were also analyzed. The result showed further that SDFVVS can control the valve directly and change the maximum valve lift and the opening angle in a large range, which makes the valve movement characteristics change by the engine speed and oil drainage angle and realizes continuously variability of the maximum valve lift, the opening angle and the valve timing.更多还原