上海牌轿车用的680Q 汽油机采用顶置凸轮式配气机构(参看图1)。从图1不难看出,这种配气机构的摇臂比是凸轮转角的函数。函数的参变量有下列五个:1.气门杆端部上下位置(反映在图2的 FG、GE 和 EF 中);2.摇臂轴中心位置(反映在图2的 AF、FG、GE 和 EF 中);3.凸轮轴中心位置(反映在图2的 AF 中);4.摇臂圆弧面圆心位置(反映在图2的 BF、GE 和 EF 中); The 680Q gasoline engine used on the Shanghai brand sedan adopts the overhead cam type gas distribution mechanism (see Fig. 1). It is not difficult to see from Figure 1 that the rocker ratio of such a valve train is a function of the cam angle. The parameter of the function has the following five variables: 1. Up-down position of the valve stem end (reflected in FG, GE and EF in Fig. 2); 2. Center position of the rocker arm (reflected in AF, FG, GE and EF); 3. camshaft center position (reflected in AF in Figure 2); 4. rocker arm arc center position (reflected in Figure 2 BF, GE and EF);