单顶置凸轮轴式汽油机可变凸轮机构的研究

Study on VCS of Single Overhead Camshaft Gasoline Engine

针对摩托车用汽油机气门机构的结构特点,提出了一种移动摇臂轴式可变凸轮机构(VCS)。该VCS机构通过移动进气摇臂轴实现高速摇臂和低速摇臂的结合与分离,进而实现工作凸轮在高速凸轮和低速凸轮之间切换。在高、低速摇臂的端面结合齿上设置锁止角,防止其在气门开启状态下实现结合。通过控制轴向力的大小,使高低速摇臂在一个工作循环内的进气门关闭期间实现完全结合。采用仿真计算,确定了低速凸轮和高速凸轮的型线及其配气相位。试验结果表明:该可变凸轮机构在全转速范围内实现了高低速摇臂的平稳结合和分离,且与原机相比发动机的高速和低速进气充量系数有明显的改善。

Based on the structural characteristics of valve mechanism for a motorcycle gasoline engine, a variable cam system（VCS） with movable rocker arm shaft is proposed in this paper. By shifting intake rocker arm shaft, the combination and separation between the high and low-speed rocker arm were achieved. The high and low-speed rocker arms are separated during the period of intake valve opened by setting locking angle on the end face of the engaged gear. The high and low -speed rocker arms are completely combined during the inlet valve closed period for one engine cy- cle by controlling the axial force. The cam profile and valve timing are determined by simulation cal- culation. The experimental results show： the combination and separation between the high and low- speed rocker arm were smoothly achieved in whole speed range. Compared with the original engine, volumetric efficiencies of both high and low speed conditions are significantly improved.