Top Dead Center上止点 intake yalve进气阀 exhaust valve排气阀 oil pan( oil sump)油底壳,油盆 Notes 1. Of all automobile components, an automobile engine is the most complicated assembly with domi nant efTects on the function of an automobile 汽车发动机是切汽车部件中结构最复杂,对汽车功能起支配作用的一个总成。 2. In the 4-stroke engine, four strokes of the piston in the cylinder are required to complete one of full operating cycle 在四冲程发动机中,需要四个行程来完成一个工作循环 3. To obtain the maximum filling of the cylinder the intake valve opens about 10 before t de ing20° overlap 为了使进气充分,进气门在活塞到达上止点之前约10打开,使进、排气门有20的打开 重合角 4. The spark plug is fired to ignite the air-fuel mixture prior to the piston being at the t.d. c 在活塞到达上止点前,火花塞发火点燃可燃混合气 5. Aluminum is a relatively light metal, weighing much less than cast iron 铝是比较轻的金属,其重量比铸铁轻多了。 Unit two Connecting Rods and Crankshaft In a reciprocating engine, the power mechanism is called the crankshaft and connecting rod assem- bly. In this assembly, all of the major units such as the engine crankcase and cylinder block, the piston and connecting rd, and the crankshaft and flywheel work in close cooperation to convert thermal energy into mechanical energy used to drive the vehicle. The engine crankcase and block are usually cast into one piece and therefore can be seem as the largest and most intricate piece of metal in automobile. They are usually made of high-grade cast alloy iron to improve wear characteristics of the cylinder. This major unit must be strong and rigid enough to withstand any bending or distortion The piston converts the potential engines of the fuel into the kinetic energy that tuns the crankshaft The piston is a cylindrical shaped hollow part that moves up and down inside the engines cylinder. The piston is composed of piston head, piston ring, piston lands, piston skirt and piston pin hole. see Fig 1-3.)The piston head or"crown is the: top surface against which the explosive force is exerted. It may be flat, concave, and convex or any one of a great variety of shapes to promote turbulence or help control combustion. In some application, a narrow groove is cut into the piston above the top ring to serve as a heat dam"to reduce the amount of heat reaching the top ring. The piston rings carried in the ring groove are of two basic types: compression rings and oil-control ring. Both types are made in a wide variety of designs. The upper ring or rings are to prevent cormpression leakage; the lower ring or rings control the