一、气门间隙为了保证气门在发动机工作时关闭严密,防止受热膨胀后自动顶开而产生漏气,故在装配发动机配气机构时,必须在气门杆末端与摇臂之间(顶置式气门),或气门杆末端与挺杆上的调整螺钉之间(侧置式气门),保留一定的间隙,这个间隙称气门间隙(用符号△代表之),如图1所示。在国产拖拉机发动机上,广泛地采用了顶置式气门的配气机构。必须注意的是东方红—40拖拉机的发动机(490型),它虽采用了顶置式气门形式,但由于凸轮室位置较高,其气门 First, the valve clearance In order to ensure that the valve is closed tightly when the engine is working, to prevent the top of the valve from being opened automatically after the expansion due to heat, so when the engine is equipped with gas distribution mechanism, it must be between the valve stem end and the rocker (overhead valve) , Or between the end of the valve stem and the adjustment screw on the tappet (side-mounted valve), to maintain a certain gap, the gap that valve clearance (represented by the symbol △), shown in Figure 1. In the domestic tractor engine, widely used overhead valve valve body. It must be noted that the engine is Dongfanghong-40 tractor (490 type), although it uses the overhead valve in the form of, but because of the higher position of the cam chamber, the valve