活塞直驱发动机凸轮机构几何特性分析

Geometric Characteristics Analysis of Cam Mechanism in Direct-Drive Piston Engine

随着机械系统不断向小型化、轻量化方向发展,围绕小体积、高能效及高功率密度发动机传动机构的构型研究一直是该领域的研究热点.本文以一种活塞直驱输出凸轮的反凸轮机构为对象,在系统分析机构的结构、工作原理及工况特点的基础上,探讨了适用于活塞-凸轮机构高能效转换的运动函数形式.在此基础上,建立了圆柱凸轮的曲面方程、凸轮曲面与活塞滚子间的诱导曲率及其啮合角的解析式.随后,分析了影响凸轮机构几何特性、力与运动的传递特性及凸轮曲面与滚子间滑动率的主要因素,进一步建立了凸轮曲面与滚子避免产生曲率干涉的参数设计条件.最后,根据任选的活塞行程等工况参数,设计出可行的反凸轮机构尺度参数算例,并在Adams环境下建立了样机的仿真模型,经样机仿真结果与所设计的运动规律理论曲线比较,验证了设计方法的有效性.研究结果为活塞直驱发动机的凸轮机构尺度设计提供了一种有效的方法.

The configuration of a small size,high energy efficiency,and high power density engine has always been the focal point of study in this field.The focus of this paper is an inverse cam mechanism driven directly by pistons.Based on the systematic analysis of the structure,operating principle,and operating condition features of the mechanism,the motion function form applicable to high-efficient energy conversion between pistons and cam mechanism was discussed.Based on the established motion law,the curved surface equation of the cylindrical cam and analytical equations for the induced curvature and the meshing angle between the cam surface and the piston rollers were established.Then,the principal factors affecting the geometric characteristics,force and motion transmission characteristics,and sliding ratio between the cam surface and rollers of the cam mechanism were analyzed,and the parametric design condition for preventing curvature interference between the cam surface and rollers was established.Finally,given arbitrary working condition parameters such as piston travel,feasible dimensional parameter examples for the inverse cam mechanism were designed,and the simulation model of the prototype was built in the Adams environment.The validity of the design method was verified by comparing the simulation results of the prototype with the theoretical curves of the designed motion law.The research provides an efficient method for designing the cam mechanism of direct-drive piston engines.