电液式柴油机可变气门系统结构强度分析

Analysis of Structural Strength in Diesel Engine Electro-hydraulic Variable Valve Timing System

利用有限元法,对比分析原机配气机构与改进后可变气门机构关键零部件的结构强度,同时利用名义应力法对零部件的疲劳寿命进行对比。结果表明:相比原机气门机构,当液压缸内出现最大稳态压力载荷,可变气门机构零部件总体静应力分布与原机相差不大,应力最高增幅出现在挺柱组件中,应力最高增加20.2%;当缸内出现瞬态压力振动幅值,挺柱组件的应力增加到原机的127.4%,但零部件最大应力依旧远低于材料屈服极限,静应力满足强度要求。此外,分别使用Goodman方程和Gerber方程来描述应力幅和平均应力之间的关系时,零部件的应力幅低于材料的疲劳极限,零部件寿命满足发动机零部件无限寿命设计要求。

Finite element method was used to analyze and compare the components and parts structural strength of initial valve sys-tem and variable valve timing system. In addition, nominal tension stress method was used to calculate the life of components and parts. The result shows that the part and components, stress of variable valve timin g system increases a l i t t le compared with in i t ia l valve system when the load is maximum steady pressure, and the maximum stress is in tappet component, which increases 20. 2% com-pared to the initial system. When the load is maximum fluctuation pressure, the maximum pressure in tappet component increases 127. 4% compared to the initial system but is still much smaller than yield strength, which means the design satisfies the requirement of static stress. Additionally, Goodman and Gerber equation were used respectively to describe the relation of stress amplitude and average stress. The result shows that the stress amplitude for all components and parts is smaller than the relative materials, fatigue strength and the life of components and parts satisfies the requirement of infinite life.