汽车专业英语Chapter3Engine.ppt

* Chapter 3 Valve and Gasoline Fuel System * * * Automotive Engineering English * Qu.1: What’s the main function of the Valve System? Open and close the valves at just the right time. 2.5: valve system Remove the burned gases as much as possible and increase the volumetric efficiency (容积/充气效率). Qu.2: How many types of Valve Train?(气门传动) OHC ( Overhead Camshaft) 顶置凸轮轴 Push-rod Qu.3: How many types of Camshaft Drive Mechanism? Belt Drive Gear Drive Chain Drive Rocker-arm（摇臂） Camshaft Tappet (Cam follower) （挺柱） Push-rod Valve clearances Valve Spring Valve stem Valve seat（insert） （气门座） Valve head Piston Rocker-shaft The cam is an egg-shaped piece of metal on a shaft that rotates in coordination with the crankshaft. The metal shaft, called the camshaft, typically has individual cams for each valve in the engine. （p26） 凸轮是一个蛋形的金属块，它安装在同曲轴协调运转的一根轴上，该轴称为凸轮轴，其上通常有单独的凸轮与发动机每一个气门对应。 1) Valve operation In this arrangement, the cam lobes push against round metal cylinders called cam follower. As the lobe of the cam comes up under the cam follower, it pushes the cam follower upward (away from the camshaft). 在这种布置方案中，凸轮凸圆推动圆形的金属筒，也就是凸轮挺杆（挺柱）。凸轮凸圆运动到挺杆下方时，推动挺杆远离凸轮轴向上运动。 挺柱带着推动摇臂的推杆，摇臂绕摇臂轴的中心转动。摇臂的一端升起，另一端就落下，这类似于跷跷板。摇臂向下运动的一端推动气门杆打开气门。 The cam follower rides against a push rod, which pushes against a rocker arm. The rocker arm pivots on a shaft through its center. As one side of the rocker arm moves up, the other side moves down, just like a seesaw. The downward-moving side of the rocker arm pushes on the valve stem to open the valve. （p27） When the engine runs in compression stroke and power stroke, the valves must close tightly on their seats to produce a gas-tight seal and thus prevent the gases escaping from the combustion chamber. 当发动机在压缩冲程和做功冲程工作时，气门必须紧贴在气门座上，形成良好的气密性以防止燃烧室漏气。 2) Valve clearance 气门间隙 如果气门关闭不严，发动机就不能发挥出全部的功率。而且气门头部容易被经过的高温气体烧蚀，活塞顶部也可能会碰到气门使发动机严重损坏。 2) Valve clearance 气门间隙 If the valve