发动机配气机构凸轮-从动件接触应力分析

配气机构中凸轮与从动件是一对重要的摩擦副,较易出现磨损、擦伤、劈裂等破坏。针对凸轮与从动件之间容易产生破坏的情况,通过改变气门弹簧的预紧力与刚度,以降低凸轮与从动件之间的接触应力,减少凸轮从动件间的接触破坏。利用AVL EXCITE Timing Drive建立某发动机配气机构单阀系动力学模型,对不同转速下的模型进行动力学分析。在Design Explorer中进行拉丁超立方试验设计,再通过Nelder-Mead算法对得到的试验数组进行优化,得出最佳的接触应力、弹簧预紧力与刚度的组合。试验与优化过程中,通过设置接触损失角和气门落座速度两个约束条件对优化结果进行约束,以防止弹簧预紧力与刚度的变化对机构整体的影响。优化得到的弹簧预紧力与刚度使得不同转速下最大接触应力均有所降低,且未出现飞脱现象。

Analysis of Cam-Follower Contact Stress in Engine Valve Train

Cam and follower are a pair of important friction pairs in the engine.It prones to wear, abrasion, splitting and other damage. For the case of easy damage between the cam and the follower, changing the preload and rigidity of the valve spring can reduce the contact stress,thus reduces contact damage. The dynamical model of single valve system of engine train is established by AVL EXCITE Timing Drive. And the dynamic analysis of the model under different speed is carried out. In the Design Explorer, the Latin hypercube test design is carried out.Then the Nelder-Mead algorithm is used to optimize the experimental array to obtain the best contact stress, spring preload and stiffness combination. During the experiment and optimization process, the optimization results are constrained by setting the contact loss angle and the valve closing velocity.And the two parameters can prevent the influence of spring preload and stiffness changes on the whole mechanism. The maximum contact stress at different speeds are reduced by the optimized spring preload and stiffness and no fly-off occurred.