某机械厂承担了一批水管的铸造业务,为了便于检查和清洗管道,使用单位要求在90°弯头上开一个检查孔,盖上盖子后,管內仍保持圆滑无阻.这个孔盖的周边曲线该怎么画线?这一问题颇有实际意义.所要求的曲线,显然是平面切割圆环的相贯线,我们叫它圆环曲线.本文介绍了圆环曲线的直角坐标方程及该曲线的几何画线方法. In order to facilitate the inspection and cleaning of the pipelines, a machine shop undertakes a number of pipe casting operations. The user requests to open a check hole in the 90 ° elbow and keep the pipe smooth and open after the lid is closed. Curves how to draw lines? This question is quite practical. The required curve is obviously the intersection of plane cutting ring, we call it the torus curve.This paper describes the torus curve Cartesian equation and the curve Geometry drawing line method.