Unit7AboutCars..doc

Unit 7 About Cars Structure of Automobile（字典P236图） It is well-known that automobile is composed of four sections such as engine, chassis(底盘), body and electrical system. The automobile engines can be classified according to: number of cylinders; arrangement of cylinders; arrangement of valves; type of cooling; number of cycles (two or four)(周期、循环); type of fuel burned; type of ignition(点火). The engine which is called the “heart” of a vehicle is used to supply power for an automobile. It includes the fuel, lubricating, cooling, ignition and starting systems. Generally, an automobile is operated by internal combustion engine(内燃机). The internal combustion engine burns fuel within the cylinders and converts the expanding force of the combustion or “explosion” into rotary force used to propel(推进) the vehicle. The chassis is a framework used to assemble auto components on it. The chassis itself is divided into four systems like transmission(传动) system, suspension(悬浮) system, steering system and brake system. The transmission system applies to the components needed to transfer the drive from the engine to the road wheels. The main components are clutch(离合器), gearbox(变速箱), drive shaft(驱动杆), final drive(后桥?) and differential(差速器?). The primary purpose of the suspension system is to increase strength and durability of components and to meet customers’ requirements for riding comfort and driving safety. In automobile suspension, the major component is springs. The springs used on today’s vehicles are engineered in a wide variety of types, sizes, rates and capacities. Spring types include leaf springs(板簧片簧), coil springs(卷簧螺旋弹簧) and torsion bars(扭力杆). Springs are paired off(成对) on vehicles in various combinations, and are attached to vehicle by different mounting(装配) techniques. The function of the steering system is to provide the driver with a means for controlling the direction of the vehicle as it moves. The steering system consists of steering wheel, steering shaft, worm