As one side of the rocker arm moves up, the other side moves down, just like a seesaw.当摇臂的一侧上升，其另一侧下降，正如一块跷跷板一样。
The downward-moving side of the rocker arm pushes on the valve stem to open the valve.摇臂向下移动的那一边推动气门杆以打开气门。