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首页> 外文期刊>Proceedings of the institution of mechanical engineers >Synthesis and kinematic and dynamic analysis of a variable valve lift mechanism with general contact curve
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Synthesis and kinematic and dynamic analysis of a variable valve lift mechanism with general contact curve

机译：具有一般接触曲线的可变气门升程机构的综合，运动学和动力学分析

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摘要

In this paper, a new type of continuously variable valve lift (WL) system is presented. The mechanism comprises a standard roller finger follower, the camshaft, and an intermediate rocker arm used between them. When the adjustment shaft rotates, the intermediate rocker arm is repositioned with respect to the cam and the roller of the rocker finger. This means that, when the rotation angle of the adjustment shaft is controlled, the valve lift height is also controlled. The intermediate rocker arm is equipped with a special developed contact surface, which is one of the novelties of this paper. The profile of the contact surface is analytically determined using the theory of the envelope curves. Using a certain cam profile, the kinematic analysis of the mechanism proceeds, resulting in the family of the valve lift laws. This paper also establishes the general conditions to design a variable valve timing (WT) mechanism with continuous WL and mechanical actuation. Numerical simulation shows that the mechanism continuously varies valve lift height and timing phases, while the valve's opening time remains constant. The last parts of the paper are dedicated to different aspects concerning the elastohydrodynamic lubrication and valve train dynamics. The study is performed by comparing the optimized cam and a standard harmonic one which achieves the same maximum displacement of the valve. The optimized cam ensures better safety in functioning, a smaller preload, leading to a greater oil film thickness, and not causing excessive deformations in the engine. The calculation model is a general one, and it may be applied to other mechanisms with similar configuration.
机译：本文提出了一种新型的无级气门升程（WL）系统。该机构包括一个标准的滚指从动件，凸轮轴以及在它们之间使用的中间摇臂。当调节轴旋转时，中间摇臂相对于摇臂指的凸轮和滚子重新定位。这意味着，当调节调节轴的旋转角度时，气门升程高度也得到控制。中间摇臂配备了专门开发的接触表面，这是本文的新颖之处之一。接触面的轮廓通过包络曲线的理论进行分析确定。使用一定的凸轮轮廓，进行机构的运动学分析，从而得出气门升程定律系列。本文还建立了设计具有连续WL和机械致动的可变气门正时（WT）机构的一般条件。数值模拟表明，该机构不断改变气门升程高度和正时相位，而气门的打开时间保持恒定。本文的最后一部分致力于涉及弹性流体动力润滑和气门机构动力学的不同方面。该研究是通过比较优化凸轮和实现相同最大阀门位移的标准谐波进行的。经过优化的凸轮可确保更好的功能安全性，较小的预紧力，导致更大的油膜厚度，并且不会引起发动机的过度变形。该计算模型是通用的，并且可以应用于具有类似配置的其他机制。

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