1、Unit TwoEngine ConstructionPassage A Crank Mechanism and Its Main Components Crank mechanism is one of the major motion mechanisms of the engine Its function is to transform the reciprocating movement of pistons into rotary movement of the crankshaft,offering torque to make the drive wheels turn(see
2、 Fig.2-1).Crank mechanism is divided into 3 groups:block group;piston and connecting-rod group;and crankshaft and flywheel group The block group contains the following main components(see Fig.2-2):Cylinder head is bolted to the top of the cylinder block with a gasket in between sealing the block and
3、 forming the combustion chambers with the cylinders Cylinder head holds camshafts,valves,spark plugs and injectors Oil panis at the bottom of the cylinder block It is a container for storage of engine oil Piston and connecting-rod group has some main components as follows(see Fig.2-3):Pistonis a cyl
4、indrical shaped hollow part made of aluminum alloy It can be divided into three parts:crown,ring groove and skirt(see Fig.2-4).Its reciprocating movements in the cylinder transform the energy of the expanding gases into mechanical energy Piston rings are inserted in the ring grooves on the top of th
5、e piston Most pistons have three rings:the top two are compression rings and the lower ring is an oil ring They function as sealing between the piston and cylinder wall,lubricating,heat transferring and piston supporting in the cylinder Connecting rod connects the piston to the crankshaft It has a s
6、mall end and a big end The small end attaches to the piston with the piston pin and the big end connects to the crank pin of the crankshaft Crankshaft and flywheel group includes the following components(see Fig.2-5):Crankshaftis one of the most important parts in the engine It is held in the crankc
7、ase in the cylinder block and converts the reciprocating motion of the pistons into a rotary motion for the drive wheels In a 4-cylinder engine,the crankshaft usually has three main journals and four crank pins attached to the big ends of the connecting rods Every crankshaft has counter weights whos
8、e purpose is to balance the weight of the connecting rods Its front end is used to drive the valve train,water pump and cooling fan,and its rear end is used to install the flywheel Flywheel is a rotating disk located on one end of the crankshaft It has a ring gear around the disk Its purposes are to
9、 reduce vibration caused by the power stroke through its inertia,and to start the engine when the starter meshes with itNew Words and Expressions mechanism meknizm n 机制;机械装置 component kmpunnt n 部件,零件 transform trnsfm vt 改变,转换 torque tk n 扭矩,转矩 aluminum lummm n 铝 lubricant lubriknt n 润滑剂;润滑油 bolt bul
10、t n 螺栓 vt 用螺栓固定 seal sil vt 密封 container kntein n 容器 storage strid n 存储 hollow hlu adj 空的,空腹的 skirt skt n 裙部 attach tt vi 连接,固定 reduce ridjus vt 减少,降低 inertia in n 惯性 cast iron铸铁,生铁 cast aluminum铸铝 aluminum alloy铝合金 ring groove活塞环槽,环槽 mechanical energy机械能 mesh with(齿轮)啮合Common Automobile Terms crank
11、case krkkeis n 曲轴箱 gasket gskit n 气缸垫,垫圈 camshaft kmft n 凸轮轴 injector indekt n 喷油器 flywheel flaiwil n 飞轮 crank mechanism曲柄连杆机构 block group机体组 cylinder block气缸体 water jacket水套,冷却管 lubricant passage润滑油道 oil pan油底壳 engine oil机油 piston and connecting rod group活塞连杆组 piston ring活塞环 compression ring气环 oil ring油环 small end连杆小头 big end连杆大头 cylinder wall气缸壁 piston pin活塞销 crank pin曲柄销,曲轴销 crankshaft and flywheel group曲轴飞轮组 main journal主轴颈 counter weight平衡重 ring gear齿圈
