一种带有内三速后轴机构(俗称“内三飞”)的变速自行车,既能适应骑车者在平直路上快速行驶,也能在遇逆风或爬坡时驾骑省力.这种“三飞”变速机构虽在我国各地已有不少工厂生产,但对其内在质量尚缺乏一定的分析研究,至今还没有系统的质量指标。为此,我们采用新型的台架试验装置,对上海自行车零件二厂生产的“三飞”,抽样进行了效率等性能测试和分析,现介绍如下。一、“内三飞”的传动原理及结构“内三飞”的结构如图1所示,它是利用2K-H 负号行星机构来实现变速的。变速换档是靠装在车把上 A kind of variable speed bicycle with an internal three-speed rear axle mechanism (commonly known as “Nei-San-Fei”) can both ride fast on a straight road and save labor while riding a headwind or climbing a hill. Although the “three-speed” transmission mechanism has been manufactured in many factories all over China, it still lacks some analytical studies on its inherent quality. So far there is no systematic quality indicator. To this end, we use a new type of bench test device, the Shanghai Bicycle Parts Factory production of “three fly”, sampling and other performance testing and analysis of efficiency, are presented below. First, the “three-fly” transmission principle and structure “Three-fly” structure shown in Figure 1, which is the use of 2K-H negative planetary gear to achieve speed. Gear shift is mounted on the handlebars