汽车专业英语翻译及课后答案解析__黄韶炯

Unit 1 Automotive Basics

Automobiles, trucks, and buses are essential forms of transportation. They are complex machines made up of many parts. These parts can be grouped into a number of systems. An understanding of how the system work will help you understand how the automobile works.

轿车、卡车和客车是交通运输的重要组成部分。它们都是由许多部件组成的复杂机器。这些部件可以归类为汽车的几个组成系统。了解这些各个小系统是如何工作的将有助于我们理解整个汽车系统是如何工作。

An automobile can be divided into two basic parts: a body and a chassis. The body is the enclosure that houses the engine, passengers, and cargo. It is the part of the automobile that you see. The chassis is that part of the automobile beneath the body.

汽车可以分为两个基本部分：车身和底盘。车身包围发动机、乘客和行李，它是汽车你所看到的部分。而车身以下的部分就是底盘。

1.1 THE BODY An automobile body is a sheet metal shell with windows, doors, a hood, and a trunk deck built into it. It provides a protective covering for the engine, passengers, and cargo. The body is designed to keep passengers safe and comfortable. For example, insulation in the body reduces noise and protects against heat and cold. The body styling provides an attractive, colorful, modern appearance for the vehicle. It is streamlined to lessen wind resistance and to keep the car from swaying at driving speeds.

轿车车身是一个钣金件壳体，它上面有车窗、车门、发送机罩和行李舱门等部件，它给发动机、乘客和行李提供防护。车身设计来确保乘客乘坐的安全和舒适。比如：车身绝热层可以减少噪音和抵御冷热。车身造型设计使得汽车有一个华美、现代、吸引人的外观。车身的流线型设计可以减少风阻，防止汽车行驰过程中发生摆动。

The automobile body has two basic parts-the upper body and the under body.

车身有两个基本部分-车身上部和车身下部。

1.2 The chassis The chassis is an assembly of those systems that are the major operating parts of a vehicle. The chassis includes everything except the body. The three important parts of the chassis are the frame, the engine, and the power train (also called the drive train). Each of these three parts is made up of a number of systems. A system is a mechanical or electrical unit that performs a specific function. Thus, each system (such as steering, brake, or fuel) has a certain job to do in running a vehicle. We shall look at each of these parts and systems to see how they fit together to form the automobile chassis.

底盘集中了汽车大部分的运动组件，它包括除了车身以外的所有部件。底盘有三个重要的系统：车架、发动机和传动系统。这三个系统又都有许多个完成某一个特定功能的机械或电气系统组成。为了保证汽车正常运转，每个系统（比如：转向、制动或燃油系统）都要实现一定的功能。下来我们看看这些系统和组件是如何相互连接从而组成汽车底盘的。

1.2.1 The frame The first major part of the chassis is the frame. It is made from tough steel sections welded, riveted, or bolted together. The frame looks like a steel ladder, though it sometime has an X shape for extra strength. It forms a foundation for the car body and the parts of the several systems. The body is joined to the frame with bolts. Rubber shock mounts or washers are used at each joint. These

reduce vibration and road noise. In most modern cars the frame is built into the body. A car with the frame built into the body has a unitized body or unibody. The frame supports the suspension system, steering system, and the braking system. 底盘最重要的部分就是车架。车架由钢件通过焊接、铆接或螺栓联接而成，看上去就像一架钢梯。有时为了得到额外的强度，车架做成了X形状。车架为车身和很多系统部件提供了底座。车身和车架使用螺栓联接。每个联接使用橡胶防震支架或垫圈来减振降噪。现代轿车车架和车身做在了一起。采用这个形式的汽车车身叫做承载式车身。车架支撑悬架、转向和刹车系统。

The front and rear wheels are attached to the chassis by a suspension system. This system is made up of springs, shock absorbers, control arms, and stabilizers. These support the vehicle and cushion it from road bumps for better ride and handling. 前后轮通过悬架系统和底盘相连。悬架系统由弹簧、减振器、控制臂和横向稳定杆组成。它们支撑着车身，并减缓由于路面不平引起的颠簸，以获得更好的乘坐舒适性和操作稳定性。The steering system controls the car’s direction of travel. It includes a wheel and column, steering gears, rods, and linkages. As the steering wheel is turned, its motion is transferred to the idler arm and tie rods. These cause the front wheels to turn to the right of left. On some cars, a power unit (called power steering) makes steering easier.

转向系统控制车辆行驰的方向。它包括方向盘、转向管柱、转向器、转向拉杆和转向传动装置。当转动方向盘，方向盘的运动被传递到随动臂和横拉杆，从而使得前轮向左或向右转动。有些车辆使用助力转向装置，从而使得转向更加轻便。

The brake system gives the automobile its stopping power. Hydraulic brakes are found on all modern cars. As the brake pedal is pushed with the foot, brake fluid is forced through brake lines into cylinders that press the brake shoes against a drum. This stops the motion of the car. Power units (power brakes) are used to make braking easier. Most modern cars have disc brakes on the front wheels. (Some have them on both the front and rear wheels.) Disc brakes work like a pair of pliers squeezing a rotating disc. Drum brakes are also used.

制动系统给车辆制动的动力。现代轿车都使用液压制动。当踩下制动踏板，制动液通过制动管路流入制动缸，强迫制动蹄接触制动鼓，从而阻止车辆运动。为了使刹车更加轻便，车辆也使用助力制动。现代轿车在前轮装备盘式制动器。（一些轿车在前后轮都使用盘式制动器。）盘式制动器工作原理类似一对钳子夹住旋转的盘片。也有前后轮都使用鼓式制动器的汽车。

1.2.2 The engine The engine provides power to move the automobile. The most common type of automobile engine is the gasoline-burning piston engine. It is found in most automobiles. Diesel-fuel burning engines are also used in modern passenger cars, as well as in large trucks. All engines have fuel, exhaust, cooling, and lubrication systems. Gasoline engines also have an ignition system.

发动机给汽车提供动力。最常见的发动机是汽油机。大多数汽车都使用它。现代客车和大型卡车使用柴油机。所有的发动机都具有燃油、排放、冷却和润滑系统。汽油发动机还有一套点火系统。

The ignition system supplies the electric spark needed to ignite the air-fuel mixture in the cylinders. When the ignition switch is turned on, current flows from the 12-volt storage battery to the ignition coil. The coil boosts the voltage to produce the strong spark of 20,000V needed to ignite the engine fuel. The distributor directs

the electrical current to the right spark plug at the right time. Diesel engines use the heat caused by engine compression to ignite the fuel charge. These engines are called compression ignition engines.

点火系统提供点燃气缸内油气混和物的电火花。当打开点火开关，电流从12V电池流向点火线圈。点火线圈升高电压，产生用于点火的20000V尖峰电压。分电器引导电流在正确的时刻流向正确的火花塞。柴油机使用压缩发动机产生的热量来点燃燃料，因此被称为压燃式发动机。

The automobile supplies all the electricity it needs through its electrical system. For example, the electrical system supplies electricity for the ignition, horn, lights, heater, and starter. The electricity level is maintained by a charging circuit. This circuit consists of the battery, alternator (or generator), and the regulator. The battery stores electricity. The alternator changes the engine’s mechanical energy into electrical energy and recharge the battery. The regulator prevents damage to the system by regulating the maximum voltage in the circuit 汽车通过自身的电气系统给自身供电。比如：电气系统给点火系统、喇叭、灯光、供暖系统和起动器供电。系统电压通过充电系统保持稳定。充电系统由电池、发电机和调节器组成。电池储存电能。发电机将发动机的机械能转变为电能，并给电池充电。调节器调节电气系统的最大电压，提供过压保护。

The fuel system stores liquid fuel and delivers it to the engines. The fuel is stored in the tank, which is connected to a fuel pump by a fuel line. The fuel is pumped from the fuel tank through the fuel lines. It is forced through a filter (which removes moisture and dirt) into the carburetor, where it is mixed with air, or into the fuel injection system. The fuel is mixed with air to form a combustible mixture in the carburetor, the manifold, or the cylinders themselves.

燃油系统储存液态燃料，并且把燃料送至发动机。燃料储存在通过油管与油泵连接的油箱里。油泵通过油管将油箱内的油泵出，并通过滤清器（去除湿气和杂污）送达化油器与空气混合或者喷油系统。燃油在化油器、歧管或气缸自身内与空气混合，形成可燃混和物。

The exhaust system has four jobs:

1. To collect burned gases from the engines.

2. To remove dangerous emission that pollutes the air.

3. To reduce exhaust noises.

4. To get rid of the exhaust gases.

排放系统要实现四个功能：

1、收集发动机的废气。

2、去除污染空气的排放物。

3、减少排放噪音。

4、排出废气。Exhaust gases contain carbon monoxide, unburned hydrocarbons, and oxides of nitrogen. Since all of these are harmful, the exhaust system is designed to reduce them as much as possible. In the United Stares all modern automobiles have emission control systems.

汽车废气包含一氧化碳，未燃烧的碳氢化合物和氮氧化合物。所有的这些都是有害的，排放系统设计要尽可能多减少这些有害物质。美国所有的现代车都配备了排放系统。

The cooling system removes excessive heat from the engine. The temperature in engine combustion chambers is about 1094°C. Since steel melts at around 1354°C, this heat must be carried away to prevent engine damage. Air and a coolant are used to carry away the heat. The radiator is filled with a coolant. The water pump circuits this

coolant through the engine and the walls of the engine block and head. Heat also is removed by the radiator fan, which draws air through the narrow fins of the radiator. This system also supplies heat to the passenger compartment and the window defroster.

冷却系统去除发动机多余的热量。发动机燃烧室的温度可以达到1094摄氏度。钢的熔点大约是1354摄氏度，发动机多余的热量必须消除来防止发动机过热。空气和冷却剂用来带走这个热量。散热器内装满了冷却剂。水泵使冷却剂在发动机、发动机壳体和发动机盖循环流动。也可以使用冷却风扇来降温。冷却风扇将风从散热器狭窄的孔径吹出，从而带走热量。这个系统可以给乘客舱和车窗除霜器提供热量。

The lubrication system is important in keeping the engine running smoothly. Motor oil is the lubricant used in the system. The lubrication system has four functions:

1. It cuts down friction by coating moving parts with oil.

2. It produces a seal between the piton rings and the cylinder walls.

3. It carries away sludge, dirt, and acids.

4. It cools the engine by circulating the motor oil.

润滑系统非常重要，它使得发动机平滑工作。润滑系统使用机油作为润滑剂。润滑系统有四个功能：1、通过运动部件油膜，它可以减小摩擦。2、它在活塞环和气缸壁之间产生油封。

3、它可以带走金属碎屑、杂污和酸。

4、通过机油的循环，它可以冷却发动机。

To keep this system working effectively, oil filters and motor oil must be change regularly. All other moving parts in an automobile must also be lubricated. These include the transmission, differential, wheel bearings, and steering linkage. 为了使得润滑系统有效工作，机油滤清器和机油必须定期更换。汽车内所有的运动部件都必须要润滑，这包括变速器、差速器、轮轴轴承和转向传动机构。

1.2.3 The power train The power train, or drive system, delivers power from the engine to the wheels. The power from the engine moves through the transmission. Transmissions are either standard, with a manual shift lever and foot clutch, or automatic.

传动系统将发动机动力传给车轮。来自发动机的动力传递给变速器。变速器可以是一个带手动换档杆和离合器的手动变速器或者自动变速器。

The transmission has gears that control the amount of power delivered to the wheels. The transmission increases the power (torque) to start the car moving. This torque is reduced when the transmission changes gears at higher speeds. The transmission also contains a set of gears that can reverse the direction of the wheels. The transmission delivers the power to the differential. A drive (or propeller) shaft with universal joints at either end of the drive shaft allows axle movement of front-engine, rear-wheel drive cars. These flexible universal joint prevent the drive shaft from breaking. The differential delivers power to the wheels through axle. Certain gears allow one wheel to turn faster than the other wheel when the vehicle is turning a corner.

变速器使用齿轮来控制传递到车轮力矩的大小。当车辆起步时，变速器增大扭矩。当车速增大，变速器改变齿轮来减小扭矩。变速器还有一套使得车轮反向运动的齿轮。变速器将扭矩传递给差速器。发动机前置后轮驱动轿车的驱动轴两侧装有万向节，可允许产生轴向运动。万向节防止驱动轴断裂。差速器通过半轴将扭矩传递给车轮。当车辆转弯时，齿轮使得一侧车轮比另一侧车轮旋转得更快。

These are the basic systems of the automobile. Each of the systems is designed for a specific job.

以上就是汽车的基本系统。每个系统都为了一个专门的功能而设计。

1 Exercises

The automobile’s further development will be determined by already existing and steadily increasing requirements, by additional further requirements and by the technical possibilities for meeting these requirements. The following focal points for development and research efforts can be discerned:

汽车的进一步发展取决于已经存在的、目前稳定增长和未来的需求以及为了满足这些需求的技术。下来给出发展研究的几个要点：

Further improvements of the automobile through products innovation in all classis functions, i. e. performance, fuel economy, environmental impact, safety, comfort and reliability.

Further development of new technologies such as electrics, alternative materials, new test and production methods.

Long-range solutions for traffic problems such as highway congestion, smog in cities and carbon dioxide enrichment of our atmosphere.

传统功能的产品革新，比如：性能、燃油经济性、环境友好、安全、舒适性和可靠性。

新技术的发展，比如：电气、替代材料、新型测试和生产技术。

解决交通问题的技术，比如：交通拥堵，城市烟雾和温室效应。

Unit2 Automotive engine

2.1 Purpose and locations of engines The purpose of an automobile engine is to supply the power needed to move the vehicle. The engine produces this power by burning fuel inside it. Because the engine burns fuel inside, or internally, the engine is known as an internal combustion engine (ICE).

汽车发动机的功用是提供汽车行驰所需的动力。发动机通过发动机内部燃烧燃料来产生这个动力。由于燃料燃烧在发动机内部进行，这种发动机被称作内燃机。

Most automobile engines are located at the front of the vehicle. Many engines drive the rear wheels. This requires a long drive shaft extending from the front wheels to the rear wheels. Other engines drive the front wheels. In the rear-wheel-drive arrangement, the engine sits longitudinally. Its long dimension is from front to back.

对于大多数汽车，发动机布置在汽车前部。许多发动机驱动后轮，这就要求从前轮到后轮的长驱动轴。其余发动机驱动前轮。对于后轮驱动的汽车而言，发动机由前到后纵向布置。

In the front-wheel-drive arrangement, the engine sits crosswise, transversely. With either arrangement, the power is carried to the drive wheels (rear or front) by gears and shafts.

对于前轮驱动的布置，发动机横置。无论哪种布置方式，能量都是通过齿轮和传动轴传到驱动轮（前轮或后轮）。

Some cars have the engine mounted in back of the front seat. This is called a mid-engine arrangement. Other cars have been built with the engine mounted at the rear, in back of rear seat. The Volkswagen “beettle” is an example of rear.

有些汽车的发动机位于前排座椅的后面。这种布置被称为发动机中置。还有些汽车的发动机位于后部，安置在后排座椅后面。大众汽车的甲壳虫就是发动机后置的一个例子。

2.2 Engine types Various kinds of engine are used in automotive vehicles. The two major types are:The piston engine inwhich pistons move up and down, or reciprocate, in the engine cylinder. This is the engine used in all cares today, except for some models of Mazda.

2. The Wankel rotary engine in which rotate, or spin. The Mazda Motor Corporation of Japan is the major manufacturer of this engine.

汽车上使用着不同种类的发动机。它们可以分成两大类：

1、往复活塞式发动机：发动机在气缸内作上下往复运动。除了马自达公司的几款以外，现今几乎全部轿车都采用这种发动机。

2、转子发动机：活塞在气缸内作旋转运动。日本的马自达公司是这类发动机的主要生产商。There are two types of piston engines-spark ignition (SI) and compression ignition (CI). Spark-ignition engines use an electric system with spark plugs. Electric sparks at the spark plugs ignite, or set fire, the fuel in the engine cylinders. The combustion of the fuel makes the engine run and produce power. This is the engine used in most produce power. This is the type of engine used in most automotive vehicles.

活塞式发动机可以分为两类：点燃式和压燃式。点燃式发动机使用带火花塞的点火系统。火花塞的电火花点燃发动机气缸内的燃料。燃料燃烧驱动发动机，并做功。这是大多数动力源采用的发动机，也是大多数汽车采用的发动机形式。

The compression-ignition engine uses the heat of compression to ignite the fuel.When air is compressed, it gets very hot. In the diesel engine, the air is compressed so much that its temperature goes up to 538 degrees Celsius or higher. The diesel fuel is sprayed into this very hot air and is ignited by the heat. Some automobiles have diesel engines. Many heavy-duty trucks and buses are powered by diesel engines. 压燃式发动机使用压缩产生的热量来点燃燃料。当空气被压缩，它可以达到非常高的温度。对于柴油式发动机，压缩空气可以使得空气温度达到538度或者更高。此时，柴油被喷射到这炽热的空气中，被空气的热量点燃。一些轿车使用柴油发动机。重型卡车和客车普遍使用柴油发动机。

There are other engines still in the experimental stage that might someday become important. These include gas-turbine engines, steam engines, Stirling engines, and electric motors.

还有一些目前尚且处于试验阶段，但未来可能会非常重要的发动机，比如：燃气涡轮机、蒸汽机、斯特灵发动机和电动机。

2.3 Basic engine systems A spark-ignition engine requires four basic systems to run. Diesel engines requires three of these systems. They are fuel system, ignition system (expect diesel), lubricating system and cooling system. Each performs a basic job in making the engine run. These are described briefly below.

点燃式发动机运转需要4个基本系统，而柴油发动机需要3个基本系统。它们是燃油系统、点火系统（柴油发动机不需要），润滑系统和冷却系统。每个系统实现一个基本功能来使得发动机运转。下文将简短介绍这些系统。

2.3.1 fuel system The fuel system supplies gasoline or diesel fuel to the engine. This fuel is mixed with air to make a combustible mixture (a mixture that will run). Each cylinder is repeatedly filled with the mixture. Then, the mixture is ignited or burned, producing high pressure. The high pressure makes the piston move (or

rotors spin). This turns shafts that rotate the wheels, causing the vehicle to move. 燃油系统给发动机提供汽油或柴油燃料。燃油与空气混合形成可燃混合气。发动机的每个气缸重复充满这种可燃混合气，然后它们被点燃或压燃，产生高压。这个高压使得发动机活塞运动（或者转子旋转），驱动轴来旋转车轮，从而使得汽车行驶。

2.3.2 ignition system Every time the fuel system delivers air/fuel mixture to

a cylinder, the ignition system follows up by a delivering an electric spark. This ignite the mixture which creates the high pressure that moves the pistons and turns the car wheels. The action is repeated many times each second while the engine is running.

每当燃油系统将可燃混合气送至气缸，点火系统接着就发出电火花来点燃缸内的可燃混合气，从而产生高压，使得活塞运动和汽车行驶。当发动机运转时，每秒钟要点火多次。The ignite system takes the low voltage of the battery and builds it up to a very high voltage: as high as 47,000 volts in some systems. This high voltage jumps the gaps in the spark plugs, producing the sparks that ignite the air/fuel mixture in the engine cylinders.

点火系统将电池的低电压升压到高压。对于某些系统，可以达到47000伏。这个高压击穿火花塞间隙，产生电火花，点燃发动机气缸内的可燃混合气。

2.3.3 The lubricating system The engine has many moving metal parts. If metal parts rub against each other, they will wear rapidly.To prevent this, engines have lubricating oil. The oil gets between the metal parts so they slide on the oil, and not on each other.

发动机有许多运动金属部件。如果这些金属部件相互摩擦，那它们磨损就会很快。为了防止这种情况，发动机使用润滑油。润滑油在金属部件之间，使得金属部件在油膜上滑动，而不是彼此之间的摩擦。

The lubricating system has an oil pan at the bottom of the engine which holds several quarts (liters) of oil. An oil pump, driven by the engine, sends oil from this reservoir through the engine. After circulating through the engine, the oil drops back to the oil pan. The oil pump continues to circulate the oil as long as the engine is running.

发动机润滑系统在发动机底部有一个储存几升汽油的油底壳。由发动机驱动的油泵将油从油底壳泵到发动机循环流动。在发动机循环后，润滑油流回到油底壳。只要发动机在运转，油泵就始终使润滑油循环流动。

2.3.4 Cooling system Where there is fire (combustion), there is heat. Burning of the air/fuel mixture raises the temperature inside the engine cylinders several thousand degrees. Some of this heat produces the high pressure that moves the pistons to produce power. Some of the heat leaves the cylinders with the exhaust gas. The exhaust gas is what is left after the air/fuel mixture burns. It is cleared out of the cylinders after the combustion is complete.

哪里有燃烧，哪里就有热量。可燃混合气的燃烧使得发动机气缸内温度上升数千度。部分热量产生高压来驱动活塞产生动力。部分热量伴随排放气体被带出气缸。排放气体指的是可燃混合气燃烧后剩余物。当燃烧结束，排放气体被排出气缸。

Some of the heat is removed by the circulating oil. After the hot oil drops down into the oil pan, the oil gives up some of this heat to the air passing under the

oil pan. The rest of the heat is removed by the cooling system.

部分热量被循环油带走。当温度较高的油流回到油底壳，热量通过油底壳下流动的空气带走。剩余的热量就要使用冷却系统来带走。

2.3.5 Other engine system An engine will run with the four basic systems described above-fuel, ignition, lubricating and cooling. However, three other related systems are also necessary. These are the exhaust system, the emission-control system, and the starting system.

具备上述的燃油、点火、润滑和冷却系统，发动机就可以运转。但是，其余相关的3个系统也是非常必需的。它们是排放系统、排放控制系统和启动系统。

The exhaust system reduces the noise of the burned gases leaving the engine cylinders and carries these exhaust gases safely away from the people in the car. The emission-control system is required by law to reduce the air pollution the engine could produce. The starting system is needed to crank the engine. A battery provides the electric power to operate the starting motor and the ignition system during cranking.

排放系统减少发动机气缸可燃混合气燃烧时的噪音，并且将废气安全带走，使其远离车厢内的人。排放控制系统是法律强制要求的，用来减少发动机产生的空气污染。启动系统是用来启动发动机。启动过程中，由电池给启动电机和点火系统提供能量。

2.4 Energy conversion The internal combustion engine is a device used to convert the chemical energy to the fuel (gasoline or diesel fuel) into heat energy, and then to convert this heat energy into usable mechanical energy. This is achieved by combining the appropriate amounts of air and fuel, and burning the mixture in an enclosed cylinder at a controlled rate. A movable piston in the cylinder is forced down by the expanding gases of combustion.

发动机是一个将燃料（汽油或柴油）的化学能转化成热能，再将热能转化成可利用的机械能的装置。实现这个能量的转化是通过混合适当的空气和燃油，并在密封的气缸内以一个可控的速率燃烧这个可燃混合气来实现的。燃烧产生的膨胀气体强迫气缸内的活塞运动。An average air/fuel ratio for good combustion is about 15 parts of air to 1 part of fuel by weight. This means that for every gallon of gasoline burned, the oxygen is about 9,000 to 10,000 gallons of air is required. Air is about 21% oxygen and 78% nitrogen.

可燃烧良好的空燃比，按质量大约是15：1。这就意味着燃烧1加仑汽油需要的9000到10000加仑的空气里的氧气。空气大约有21%的氧气和78%的氮气。

Diesel engine operate on a much wider air/fuel ratio, since air intake is not regulated on most diesels. Ratios may range from about 20:1 to 100:1. The fact, plus the high compression of the diesel, makes it a very fuel efficient engine.

由于大多数的柴油机并不控制进气，柴油机的空燃比范围很宽，从20：1到100：1。再加上柴油混合气具有很高的压缩比，这使得柴油机的效率很高。

The movable piston in the cylinder is connected to the top of a connecting rod. The bottom of the connecting rod is attached to the offset portion of a crankshaft. As the piston is forced down, this force is transferred to the crankshaft, causing the crankshaft to rotate. The reciprocating (back and forth or up and down) movement of the piston is converted to rotary (turning) motion of the crankshaft, which supplies the power to drive the vehicle.

气缸内的活塞与连杆的上部相连，而连杆的下部与曲轴的偏移部连接。因此，当活塞向下运动时，这个运动传递到曲轴，使得曲轴旋转。活塞的往复运动（前后或者上下）就转化为曲轴的旋转运动，从而给汽车行驶提供动力。

The efficiency of the internal combustion, reciprocating piston engine in converting the potential energy in fuel into mechanical energy is only about 33%. Of the available heat energy in the fuel, about one-third is lost through through the exhaust system and one-third is absorbed and dissipated by the cooling system. Of the remaining one-third, about one-half is lost through available at the vehicle’s drive wheels.

往复活塞式内燃机将燃料的能量转化为机械能的效率大约是33%。燃料中可利用的热量有三分之一通过排气系统丢失掉，另有三分之一被冷却系统吸收和带走，剩下的三分之一大约有一半的能量在汽车的驱动轮消耗掉。

The overall efficiency of the diesel engine is considerably higher than that of the gasoline engine. The reason for this are: the higher compression ratio, the higher air/fuel ratio, and the higher heat value of the fuel. The useful power developed at the drive wheels by a diesel engine is about 25% compared to 15% by a gasoline. 与汽油机相比，柴油机的总体效率要高很多。这是因为柴油机具有更高的压缩比，更高的空燃比，柴油的热量也要更高。对于柴油机，驱动轮得到的能量大约可以达到总能量的25%，而汽油机只有15%。

2.5 four stroke-cycle gasoline engine operation The movement of the piston from its uppermost position (TDC, top dead center) to its lowest position (BDC, bottom dead center) is called a stroke. Most automobile engines operate on the four stroke-cycle principle. A series of events involving four strokes of the piston completes one cycle. These events are: (1) the intake stroke, (2) the compression stroke, (3) the power stroke, and (4) the exhaust stroke. Two revolutions of the crankshaft and one revolution of the camshaft are required to complete one cycle. 活塞从它在气缸内的最高位置(上止点)运动到最低位置(下止点)称为一个冲程。大多数汽车发动机采用四冲程工作循环，由活塞的四个冲程组成一个工作循环，分别是：进气冲程、压缩冲程、作功冲程和排气冲程。发动机的一个工作循环需要曲轴旋转两次，凸轮轴旋转一次。 On the intake stroke the piston is pulled down in the cylinder by the crankshaft and connecting rod. During this time the intake valve is held open by the camshaft. Since the piston has moved down in the cylinder, creating a low-pressure area (vacuum), atmospheric pressure forces a mixture of air and fuel past the intake valve into the cylinder. Atmospheric pressure is approximately 14.7 pounds per square inch (about 101.35 kilopascals) at sea level. Pressure in the cylinder during the intake stroke is considerably less than this. The pressure difference is the force that causes the air/fuel mixture to flow into the cylinder, since the liquid or a gas (vapor) will always flow from a high-pressure to a low-pressure area.

吸气冲程过程中，气缸内的活塞被曲轴和连杆向下拉动。此时，凸轮轴使得进气门打开。由于活塞在气缸壁向下运动，产生了一个低压区（真空区），大气压力使得可燃混和气从进气门进入气缸。海平面的大气压大约是每平方英寸14.7磅（大约101.35千帕）。吸气冲程时，气缸内的压力要远远小于大气压。由于液体和气体总是从高压区流向低压区，因此，气缸内外的压力差就使得可燃混和气流入气缸。

As the piston is moved up by the crankshaft from BDC, the intake valve closes.

The air/fuel mixture is trapped in the cylinder above the piston. Further piston travel compresses the air/fuel mixture to approximately one-eighth of its original volume (approximately 8:1 compression ratio) when the piston has reached TDC. This completes the compression stroke.

当曲轴推动活塞从下止点起向上运动，进气门关闭。可燃混和气被限制在活塞以上的气缸区域内。当活塞达到上止点时，活塞压缩可燃混合气至其原有容积的1/8（大约8:1的压缩比）。此时，压缩冲程结束。

When the piston is at or near TDC, the air/ fuel mixture is ignited. The burning of the air/fuel mixture (combustion) takes place at a controlled rate. Expansion of the burning mixture causes a rapid rise in pressure. The increased pressure forces the piston down on the power stroke, causing the crankshaft to rotate.

当活塞达到或接近上止点时，可燃混和气被点燃，并且在一个可控的节奏下进行。可燃混和气的膨胀使得压力急剧上升，并推动活塞向下运动作功，使得曲轴旋转。

当活塞达到或接近上止点时，可燃混和气被点燃，并且在一个可控的节奏下进行。可燃混和气的膨胀使得压力急剧上升，并推动活塞向下运动作功，使得曲轴旋转。

At the end of the power stroke, the camshaft opens the exhaust valve, and the exhaust stroke begins. Remaining pressure in the cylinder, and upward movement of piston, force the exhaust gases out of the cylinder. At the end of the exhaust stroke, the exhaust valve closes and the intake valve opens, repeating the entire cycle of events over and over again.

作功冲程结束时，凸轮轴打开排气门，排气冲程开始。气缸内剩余的压力和活塞向上的运动把废气排出气缸。排气冲程结束时，排气门关闭，进气门开启，从而再次重复整个循环。 To start the engine, some method of cranking the engine is required to turn the crankshaft and cause piston movement. This is done by the starter motor when the ignition key is in the start position. When sufficient air/fuel mixture has entered the cylinders and is ignited, the power strokes create enough energy to continue crankshaft rotation. At the point, the ignition key is released to the run position and starter is disengaged.

为了起动发动机，需要转动曲柄来使得活塞运动。当点火开关置于起动位置时，起动电机转动曲柄，起动发动机。当足量的可燃混和气进入气缸并被点燃，作功冲程产生的能量足以使得曲轴连续转动。此时，点火开关释放到正常位置，起动机推出啮合。

Sufficient energy is stored in the flywheel and other rotating parts on the power stroke to move the piston and related parts through the other three strokes (exhaust, intake, and compression). The amount of air/fuel mixture allowed to enter the cylinder determines the power and speed developed by the engine.

在作功冲程中，大量的能量被储存在飞轮和其他旋转部件上，从而在其余三个冲程中可以使得活塞和相连部件运动。进入气缸的可燃混合气的数量决定了该发动机的功率和转速。

2 Exercises

Ⅰ What is the purpose of an automotive engine?Ⅰ

To supply the power needed to move the vehicle.

What is the difference between a gasoline engine and a diesel engine?

A gasoline engine uses an electric ignition system with spark plugs to ignite the fuel. And a diesel engine uses the heat of compression to ignite the fuel. What are the basic systems to run a spark-ignition engine required?

Fuel system, ignition system, lubricating system and cooling system.

List the strokes of a four-stroke-cycle gasoline engine operation.

The intake stroke, the compression stroke, the power stroke and the exhaust stroke.

What is the function of the flywheel?

It is used to store sufficient energy to move the piston and related parts through the other strokes (exhaust, intake and compression).

Ⅱ 1 A car usually has a piston engine. It consists of several moving part: pistons, connecting rods, crankshaft, camshaft, valve lifters, intake valves and exhaust valves. The cast iron or aluminum engine block holds the moving parts. The engine block has a series of holes which are called cylinders. The cylinders can be arranged in line or in a V-shape and in the upper part of the block. Each cylinder holds a piston and the connecting rod. A circular ring is used to seal the small gap between the piston and the cylinder wall. The lower part of the block is called crankcase which holds the crankshaft with bearing mounts. Pistons are connected to the crankshaft by connecting rods.

汽车一般使用活塞式发动机。活塞式发动机由活塞、连杆、曲轴、凸轮轴、气门挺杆、进气门和排气门等运动部件组成。这些运动部件安置在铸铁或铝合金机体内。发动机体上有些凹洞，这些凹洞被称作气缸。气缸在机体上部呈直列式或V型排列。每个气缸都有活塞和连杆。活塞和气缸壁之间的微小缝隙通过一个圆环密封。机体的下部是曲轴箱，里面是带有轴承的曲轴。活塞和曲轴之间通过连杆连接。

2 The cylinder heads are the top covers of the cylinders which are tightly bolted to the top of the block. The cylinder heads contain combustion chambers. Each combustion chamber contains at least one intake and exhaust valve and one spark plug per cylinder. The valves are opened and closed in a specific sequence with valve lifters controlled by the camshaft. The camshaft is connected to the crankshaft through a time belt.

气缸盖是气缸的上盖，其通过螺栓与上机体连接。气缸盖下是燃烧腔。每个气缸的每个燃烧腔都至少要有一个进气门，一个排气门和一个火花塞。气门被由凸轮轴控制的气门挺杆按一定的顺序打开和关闭。凸轮轴和曲轴之间通过正时带连接。

Unit 3 Automotive Lubrication System

3.1 Lubrication principles Reducing friction to minimize wear and loss of power is the primary job of a lubrication system must perform. Residual oil on engine parts also provides lubrication for engine start-up.

减少摩擦，降低磨损和动力损失是润滑系统必须完成的主要工作。发动机部件上残余的油也可以为起动发动机提供润滑。

The engine oil forms a seal between the pistons, rings, and cylinders. It also helps to cool engine parts. Without the cleaning action of the lubrication system, carbon and varnish buildup would be excessive. The engine oil also absorbs the shock and dampens the noise of moving parts.

发动机油在活塞、活塞环和气缸之间形成了密封。它也有助于冷却发动机。如果没有润滑系统的清洁作用，气缸内就会累积过量的积炭。发动机油也有助于吸收振动和减少运动部件产生的噪音。

3.2 Parts of the pressure-lubrication system

3.2.1 oil pan How successful the lubrication system is in performing all these functions depends on a number of factors and conditions. There must be an adequate supply of good-quality lubricant delivered to all moving engine parts under sufficient pressure to provide hydrodynamic lubrication for rotating parts and oil adhesion to surface subject to sliding friction.

一个润滑系统成功实现以上功能取决于许多条件和状态。润滑系统必须要有足够量的高品质润滑油，并在充足的压力下将润滑油提供给发动机所有运动的部件，从而给旋转部件提供液力润滑，并给滑动的表面提供油膜。

The oil pan bolts under the engine block, where it seals off the bottom of engine. Shaped like a trough, this sheet-metal pan serves as the reservoir for about 5 quarts of oil. As oil flows from the engine, it drains downward into the oil pan. The oil pump sucks oil from the top of the oil pan, the oil sump. Many oil pans have baffles, which are thin metal partitions. These keep the oil in the sump when the car corners hard or brakes suddenly. A drain plug at the bottom of the sump allows oil to be drained from the engine. The oil-pan gasket fits between the oil pan and the bottom of the engine block.

油底壳使用螺栓与发动机气缸体连接，并对发动机底部形成密封。油底壳是一个钣金件槽形体，可以储存5夸脱的润滑油。油从发动机流出，并流回到油底壳。机油泵从油底壳上层吸油。许多油底壳有薄金属的挡油板。当车辆急拐弯或者急刹车时，挡油板可以把油保持在油底壳内。油底壳下部有一个放油螺栓，可以把发动机的油排干。油底壳和气缸体之间有油底壳垫圈。

In most engines, the oil circulates in the engine, and then returns to the pan. It stays in the pan until drawn back into the engine by the oil pump. During operation, the sump usually holds 2 to 3 quarts oil. The rest of the oil moves through the passageways of the lubrication system. With the engine off, the pan holds about four quarts of oil. The fifth quart is in the oil filter. Because a pool of oil always rests in the sump, the type of lubrication system is called a wet-sump oiling system. 对于大多数发动机，机油在发动机循环，然后流回到油底壳，并储存在油底壳内，直至被机油泵再次吸回到发动机。在这个循环过程中，油底壳通常储存2-3夸脱油，剩余的油在润滑系统的油管内流动。当发动机停止时，油底壳储存大约4夸脱油，剩余的一夸脱油在机油滤清器内。因为油底壳内总是有机油，这种润滑系统被称作湿式油底壳润滑系统。

A dry-sump oil system is used in many racing engines. This system has a separate storage tank for the oil. A second oil pump draws oil from the oil pan as soon as the oil drains from the engine. As a result, a dry-sump system can circulate more oil through the engine than a wet-sump system.

干式油底壳润滑系统在许多赛车中得到应用。这种系统有一个单独的机油箱。一旦发动机的机油开始循环，一个单独的油泵从油底壳吸油。因此，这个系统能够比湿式油底壳循环更多的油。

3.2.2 oil pump In most cars, the oil pump is in the crankcase above the sump. It draws oil through a tube that extends downward into the sump. This tube, called the oil-pump pickup tube, has a filter screen over its bottom end. The screen keeps large pieces of sludge and dirt from being drawn into the pump. The tube may be hinged on the pump end so that it can move up and down as the oil level changes in the sump. Thus, the pump always draws oil from the top of the sump, not from the bottom where

the dirt and sludge tend to settle. Modern cars use one of two common types of oil pump-the gear-type and rotor-type.

对于大多数汽车，机油泵位于油底壳上部的曲轴箱内。机油泵通过延伸到油底壳的油管吸油。这个油管被称作机油吸油管，在它的末端有一个滤网，可以阻止大块的油泥和污垢吸入到油泵内。油管可以绞接在机油泵底部，这样它就可以随着油底壳内油面的变化上下漂动，从而保证油泵总是从油底壳上部吸油，而不是从油泥和污垢易于沉淀的下部。现代汽车一般使用齿轮式油泵或者转子式油泵。

3.2.3 oil filters A modern engine uses a full-flow filtering system. In this system, the output of the oil pump flows through the oil filter before moving through engine. In other words, the oil is filtered and cleaned before each trip through the engine. When an engine runs at 3,000 rpm, its entire five quarts of oil pass through the filter at least once every minute. Thus the oil filter ensures that only clean oil enters the engine.

现代发动机使用全流式滤清器系统。在这个系统，机油泵输出的机油在流入发动机之前先通过机油滤清器。也就是说，在发动机的每次循环之前机油都进行了滤清。当发动机转速为3000转/分时，油底壳内的全部5夸脱油每分钟都得到一次滤清。这样，机油滤清器就确保进入发动机的机油是干净的。

Modern engines use replaceable oil filters. When dirty, such a screw-on filter is replaced with a new one. Inside the steel outer casing of the unit, a special paper acts as a filter. Folded and tightly packed, this paper has just the right porosity. These tiny holes in the paper allow oil to pass through, but filter out dirt and sludge. The paper is treated to protect it from acid or water in the oil.

现代发动机采用可替换型机油滤清器，滤清器和机体采用螺纹固定。这样，可以拆下脏的滤清器，换上新的滤清器。在滤清器钢外壳的内部是特殊的纸滤芯。纸滤芯具有适当的微孔，被折叠并压紧在滤清器里。这些微孔可以让机油通过，但把油泥和杂质截流在滤芯上。滤纸经过特殊的处理，可以抵御机油里的酸和水（抗腐蚀性和抗湿性）。

Normally, oil enters the oil filter from the outside. Oil enters the filter around the outer edge of the base. The oil flows through the paper to the center of the container. It then flows out to the engine. Most filters also have a pressure-relief valve, or bypass valve. Such a valve allows oil to flow to the engine without going through the filter. This is necessary when the filter becomes too clogged for oil to pass through it. Thus, a plugged filter allows dirty oil to circulate through the engine. To prevent this, the oil and oil filter should be changed regularity. 一般而言，机油从滤清器底部的外边缘流入滤清器，并通过滤纸流入滤清器的中心，然后流进发动机。多数滤清器设置了卸压阀或者旁通阀。这个阀可以使机油不通过滤清器直接流入发动机。当滤清器被严重堵塞以至机油无法通过滤芯时，卸压阀就非常必要。被堵塞的滤清器使得没有滤清的机油在发动机内循环。因此，需要定期更换机油和机油滤清器。

3.3 Engine lubrication An internal combustion engine would not run for even a few minutes if the moving parts were allowed to make metal-to-metal contact. The heat generated due to the tremendous amounts of friction would melt the metals, leading to the destruction of the engine. To prevent this, all moving parts ride on a thin film of oil that is pumped between all the moving parts of the engine. Once between the moving parts ,the oil serves two purposes. One purpose is to lubricate the bearing surfaces. The other purpose is to cool the bearing by absorbing the

friction-generated heat. The flow of oil to the moving parts is accomplished by the engine’s internal lubricating system.

如果发动机的运动部件是金属与金属的直接接触，内燃机运行无法超过几分钟。摩擦产生的巨大热量可以熔化金属，从而损坏发动机。因此，发动机所有的运动部件之间都要有一层薄油膜。作用在运动部件之间的机油有两个功用。一个作用是润滑轴承面，另一个作用是吸收摩擦产生的热量，冷却轴承。发动机的内润滑系统使得机油流到各个运动部件。

The oil pump is of the gear type, consisting essentially of two gears in mesh and requires no attention or adjustment. It is housed in the sump, being driven by a shaft and skew gearing from the camshaft.

齿轮泵式燃油泵实际上由两个相互啮合的齿轮组成，无需调整。它位于油底壳底部，由来自凸轮轴的一根轴和斜齿轮驱动。

3.4 Lubrication oils Motor oils for automobile engines fall into two basic categories: petroleum-based oils and synthetic oils. Petroleum-based oils, however, contain a variety of additives, so in fact they, too, are partly synthetic. Some of the major additives include those described here.

发动机机油可以分为两类：石油基润滑油和合成润滑油。实际上，石油基润滑油也包含大量的添加剂，因此，部分上它也是合成润滑油。主要使用的添加剂如下所述。

Antiscuff additives help to polish moving parts, including cams, pistons, and cylinder walls. This is particularly important during new engine break-in and after an engine overhaul. Since heat is the prime enemy of antiscuff additives, operating conditions that produce excessively high engine temperatures reduce the life expectancy of these additives. This type of the operation requires more frequent oil changes than does normal operation.

抗磨损添加剂可以抛光运动部件，比如：凸轮、活塞和气缸壁。这对于新发动机磨合和大修后的发动机尤其重要。热量是这种添加剂最大的敌人，使得发动机过热的运行工况就会减小抗磨损添加剂的使用寿命。因此，这种运行工况下要比正常使用要求更加频换的更换机油。Corrosion inhibitors reduces the formation of harmful acids by attacking the acid-forming ingredients. Combustion produces a number of by-products, including acid and water. Corrosion inhibitors neutralize these combustion by-products before they can do any harm to the engine. A cold engine, rich fuel mixture, a poorly turned engine and much short trip, cold-weather driving increases the amount of acid produced

腐蚀抑制剂可以通过攻击酸形成的成分从而减小有害酸的形成。燃烧会生成大量的副产品，比如：酸和水。腐蚀抑制剂中和这些燃烧副产品，避免其对发动机腐蚀。冷机、成分丰富的可燃混合气、工况较差的发动机以及短途和寒冷天气下的行驰会加剧这些酸的产生。Detergent-dispersants clean engine parts during operation and keep these contaminants in suspension in the oil. As the oil is forced through the filter, the majority of these contaminants are trapped by the filter.

当发动机运行时，清洁分散剂可以清洁发动机部件，并使得污垢悬浮在油中。当机油通过滤清器，大部分污垢被滤清器过滤掉。

Viscosity index improvers tend to stabilize or improve the viscosity of engine oils at various temperatures. They tend to give the oil more body when the oil is cold. In other words, they improve the body and fluidity of the oil. The ability of the oil to carry a load at high temperature is improved by this additive, and the ability

of the oil to flow when cold is also improved

黏度改善剂可以稳定或改善机油在不同温度下的黏度。当机油过冷时，它可以提高机油的流度。也就是它可以改善机油的黏度和流度。高温时，黏度改善剂提高了机油承载的能力，低温时，黏度改善剂提高了机油的流度。

Foam inhibitors reduce the tendency of oil to foam. Heat and agitation mix the the oil with air to create foam. Oil foam reduces the lubrication ability of the oil and causes oil starvation and failure of engine parts. Loss of oil pressure due to foaming increases this problem.

泡沫抑制剂可以阻止机油形成泡沫。热量和搅动使得机油和空气混合形成泡沫。泡沫减少了机油的润滑能力，造成了发动机部件表面的供油不足。泡沫形成降低了油压，这也加剧了这个问题。

3 Exercises

1 What is the purpose of automobile lubrication system?

Reducing friction to minimize wear and loss of power

3 Explain what the function of oil is.

Form a seal between the pistons, rings, and cylinders.

Cool engine parts.

Clean carbon and varnish.

Absorb the shock and dampen the noise.

4 Name at least three common additives used in compounding oils.

Antiscuff additives.

Corrosion inhibitor.

Detergent-dispersant.

Foam inhibitor.

Viscosity index improver.

6 Explain how oil reduces friction.

All moving parts ride on a thin film of oil instead of metal-to-metal contact.

7 Define the word viscosity.

The body and fluidity of the oil.

8 What is detergent oil?

Clean engine parts during operation and keep contaminants in suspension in the oil.

What is the difference between the full flow filter system and the bypass filter system?

1 The bypass filter system allow oil to circulate through the engine when the filter becomes too clogged for oil to pass through it.

The purpose of the lubrication system is to circulate oil through the engine. Many parts inside the engine, such as the camshaft, crankshaft, connecting rods, and pistons are connected to other metal parts. When parts rub together, friction is created. Friction produce heat. Although two metal surfaces may appear smooth to the naked eye, they may look rough when seen through a microscope.

润滑系统的作用是让润滑油在发动机循环。发动机内部许多部件，如：凸轮轴，曲轴，挺杆和活塞都与其他金属部件相连。当这些部件相互接触，就产生了摩擦。摩擦就会产生热量。肉眼看上去，两个金属的表面非常光滑，但通过显微镜观察，它们实际上非常粗糙。

2 An engine must have a good lubrication system. Without it, the friction heat from the contact of the moving parts would wear the parts and causes loss. Oil, when placed between two moving parts, separates them with a film. This oil film prevents the parts from rubbing against each other. This oil film also cushions the parts, giving quieter and smoother engine operation.

发动机必须要有好的润滑系统。没有润滑系统，运动部件之间摩擦产生的热量会磨损部件和耗费功率。当润滑油位于两个运动部件之间时，就会产生一层油膜来分离这两个部件。油膜可以防止两个部件相互摩擦，还起到类似缓冲垫的作用，可以让发动机安静平稳的工作。Unit 4 The Cooling System

The purpose of the eng ine’s cooling system is to remove excess heat from the engine, to keep the engine operating at its most efficient temperature, and to get the engine up to the correct temperature as soon as possible after starting. Ideally, the cooling system keeps the engine running at its most efficient temperature no matter what the operating conditions are.

发动机冷却系统的作用就是取出发动机多余的热量，保持发动机在最佳效率温度点运行，并在启动发动机后尽可能快使得发动机达到适合的温度。理想状态下，无论什么样的运行状态，冷却系统都可以使得发动机运行在最佳效率温度点。

Fuel burning engines produces enormous amounts of heat, tem perature can reach up to 4000 F when the air-fuel mixture burns. However, normal operating temperature is about 2000F.

发动机要产生大量的热量。当可燃混和气燃烧时，温度可以达到4000F，而发动机的运行温度大约是2000F。

The exhaust system takes away much of the heat, but parts of the engine, such as the cylinder walls, pistons, and cylinder head, absorb large amounts of the heat. If a part of the engine gets too hot, the oil film fails to protect it. This lack of lubrication can ruin the engine

排放系统可以带走大量的热量，但是发动机的一些部件，如：气缸壁，活塞和气缸盖会吸收许多热量。如果发动机的部件过热，油膜就会失去保护作用。而缺乏油膜的润滑就会损坏发动机。

On the other hand, if an engine runs at too low a temperature, it is inefficient, the oil gets dirty (adding wear and subtracting horsepower), deposits form, and fuel mileage is poor- not to mention exhaust emissions! For these reasons, the cooling system is designed to stay out of the action until the engine is warmed up.

另一方面，如果发动机运行在过低的温度下，发动机的效率就会低下，燃油变脏（增加损耗，减少马力），积炭形成，燃油里程数变差，更不要说排放了。正是因为这些原因，冷却系统被设计为并不工作直到发动机变热。

There are two types of cooling systems, liquid cooling and air cooling. Most auto engines are cooled by the liquid type, air cooling is used more frequently for airplanes, motorcycles and lawnmowers.

目前有两种冷却系统：液体冷却系统和空气冷却系统。大多数汽车发动机使用液体冷却系统，空气冷却系统经常在飞机、摩托车和除草机上得到应用。

The cooling system of a water-cooled engine consists of the engine’s water jacket, a thermostat, a water pump, a radiator and radiator cap, a cooling fan (electric or belt-driven), hoses, and usually an expansion (overflow) tank.

水冷式发动机冷却系统由发动机水套、节温器、水泵、散热器、散热器盖、冷却风扇（电或皮带驱动）、水管和溢流槽。

The pump sends the fluid into the engine block, where it makes its way through passages in the engine around the cylinders. Then it returns through the cylinder head of the engine. The thermostat is located where the fluid leaves the engine. The plumbing aro und the thermostat send the fluid back to the pump directly if the thermostat is closed. If it is open, the fluid goes through the radiator first and then back to the pump.

水泵将冷却液泵入发动机壳，然后冷却液沿着发动机内的通道在气缸周围流动，接着通过发动机气缸盖流回到水泵。节温器位于冷却液离开发动机的位置。如果节温器关闭，节温器周围的水管将冷却液直接送回到水泵。如果节温器打开，冷却液先流经散热器，之后再流回到水泵。The water pump is a simple centrifugal pump driven by a belt connected to the crankshaft of the engine. The pump circulates fluid whenever the engine is running. 冷却系统的水泵是简单的离心式水泵，由与发动机曲轴相连的皮带驱动。只要发动机在运转，水泵就要循环冷却液。

4.1 The water pump The water pump uses centrifugal force to send fluid to the outside while it spins, causing fluid to be drawn from the center continuously. The inlet to the pump is located near the center so that fluid returning from the radiator hits the pump vanes. The pump vanes fling the fluid to the outside of the pump, where it can enter the engine.

水泵一旦旋转，水泵产生的离心力将冷却液甩向外侧，源不断从中心吸取冷却液。水泵的入水口位于中心周围，这样当冷却液从散热器流回。冷却液冲击水泵叶片。水泵叶片将冷却液甩向水泵外侧，并进入到发动机。

4.4 The water jacket The water jacket is a collection of passages within the block and head. There passages let the coolant circulate around the hot spots (valve seats and guides, cylinder walls, combustion chamber, etc.) in order to cool them off. 水套是发动机壳体和发动机盖内部冷却液通道的集合。这些通道使得冷却液在热点（气门座和导管，气缸壁，燃烧室等）周围流动，从而冷却它们。

Temperature in the combustion chamber of the engine can reach 4500F, so cooling the area around the cylinder is critical. Areas around the exhaust valves are especially crucial, and the almost all of the space inside the cylinder head around the valves that is not needed for structure is filled with coolant. If the engine goes without cooling for very long, it can seize. When this happens, the metal has actually gotten hot enough for the piston to weld itself to the cylinder. This usually means the complete destruction of the engine.

燃烧室的温度可以达到4500F ，气缸周围区域的冷却非常重要，尤其排气门周围的区域是至关重要的。因此，在满足结构强度的要求下，缸盖内排气门周围几乎所有的空间都充满了冷却液。如果发动机没有长时间冷却，发动机就会损坏，此时，金属的温度已经可以使得活塞与气缸焊接在一起。这通常意味着发动机彻底的损坏。

One interesting way to reduce the demands on the cooling system is to reduce the amount of heat that is transferred from the combustion chamber to the metal parts of the engine. Some engines do this by coating the inside of the top of the cylinder head with a thin layer of ceramic. Ceramic is a poor conductor of heat, so less heat is conduced through to the metal and more passes out of the exhaust.

一个有趣的减少冷却系统需求的方法是减少燃烧室到发动机金属部件热量的传递。一些发动机通过在发动机盖顶端内侧覆盖上一层薄陶瓷层来实现减少热量的传递。陶瓷导热性很差，这样较少的热量传递到金属，而较多的热量由排放系统带出。

4.3 radiator A radiator is a type of heat exchanger. It is designed to transfer heat from the hot coolant that flows through it to the air blown through it by the fan.

散热器是一种热交换器。它的设计是将流经散热器较热的冷却液的热量传递至由风扇吹过的空气。

Most modern cars use aluminum radiators. These radiators are made by brazing thin aluminum fins to flattened aluminum tubes. The coolant flows from the inlet to the outlet through many tubes mounted in a parallel arrangement. The fins conduct the heat from the tubes and transfer it to the air flowing through the radiator.

大多数现代轿车使用铝散热器。这些散热器由将薄的铝叶片焊接到扁平的铝管上制成。冷却液通过并联布置的铝管从入口流向出口。叶片将热量从铝管导出，并传给流过散热器的空气。The tubes sometimes have a type of fin inserted into them called turbulator, which increases the turbulence of the fluid flowing through the tubes. If the fluid flowed very smoothly through the tubes, only the fluid actually the tubes would be cooled directly. The amount of heat transferred to the tubes from the fluid running through them depends on the difference in temperature between the tube and the fluid touching it. So if the fluid that is in contact with the tube cools down quickly, less heat will be transferred. By creating turbulence inside the tube, all of the fluid mixes together, keeping the temperature of the fluid touching the tubes up so that more heat can be extracted, and all of the fluid inside the tube is used effectively. 有时候铝管插有叫做湍流管的叶片，用来增加管道中冷却液的湍流现象。如果冷却液平滑从管道中流过，实际上只有与管道接触的冷却液能够直接冷却。从管道内流过的冷却液交换到管道的热量取决于管道和与管道接触的冷却液的温度差。因此，如果与管道接触的冷却液迅速冷却，较少的热量被传递。通过制造管道内的湍流，所有的冷却液混合在一起，保持与管道接触的冷却液温度较高，从而更多的热量被传递，有效地利用管道内的所有冷却液。

4.4 pressure cap The radiator cap actually increases the boiling point of your coolant by about 45F. How does this simple cap do this? The same way a pressure cooker increases the boiling temperature of water. The cap is actually a pressure release valve, and on cars it is usually set to 15 psi. The boiling point of water increases when the water is placed under pressure.

散热器盖实际上将冷却液的沸点提高了大约45F。它是如何做到的呢？高压锅使用同样的方法增加水的沸点。压力盖实际上是个压力释放阀。轿车上，它一般被设定为15psi。当水在压力下，水的沸点会提高。

When the fluid in the cooling system heats up, it expands, causing the pressure to build up. The cap is the only place where this pressure can escape, so the setting of the spring on the cap determines the maximum pressure in the cooling system. When the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the overflow tube into the bottom of the overflow tank. This arrangement keeps air out of the system. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the

overflow tank to replace the water that was expelled.

当冷却系统的冷却液被加热，冷却液体膨胀，引起压力上升。散热器盖是压力唯一可以逃离的地方，因此散热器盖的弹簧设置决定了冷却系统的最大压力。当压力达到15psi，压力推开阀门，使得冷却液流出冷却系统。冷却液从溢流管流向溢流箱底部。这个设置使得空气排出冷却系统。当散热器冷却下来，冷却系统内形成一个真空，从而将另一个弹簧阀拉开，将之前排到溢流箱底部的冷却液再次吸回到散热器。

4.5 Thermostat Any liquid-cooled car engine has a small device called the thermostat that sits between the engine and the radiator. The thermostat’s main job is to allow the engine to heat up quickly, and then to keep the engine at a constant temperature. It does this by regulating the amount of water that goes through the radiator. At low temperature, the outlet to the radiator is completely blocked –all of the coolant is re-circulated back through the engine.

任何一个液体冷却的轿车发动机都有一个叫做节温器的装置，位于散热器和发动机之间。节温器使得发动机快速升温，然后保持发动机在一个恒定的温度。节温器通过调节流过散热器冷却液的流量实现以上目的。低温下，节温器的出口完全堵塞，所有的冷却液在发动机内部循环。

Once the temperature of the coolant rises to between 180F to 195F, the thermostat starts to open, allowing fluid to flow through the radiator. By the time the coolant reaches 200F to 218F, the thermostat is open all the way.

一旦冷却液温度升到180F与195F之间，节温器开始工作，使得冷却液流向散热器。当冷却液温度位于200F与218F之间，节温器处于全开状态。

The secret of the thermostat lies in the small cylinder located on the engine-side of the device. This cylinder is filled with a wax that begins to melt at around 180F (different thermostats open at different temperatures, but 180F is a common one).

A rod connected to the valve presses into this wax. When the wax melts, it expands significantly, pushing the rod out of the cylinder and opening the valve. By letting the engine warm up as quickly as possible, the thermostat reduces engine wear, deposits and emissions.

节温器工作的秘密就在节温器发动机侧的一个小圆缸内。这个圆缸充满了蜡，蜡的熔点大约在180F（不同的节温器在不同的温度下开启，但180F是常用值）。一个与阀门联接的连杆推入到蜡里。当蜡开始溶化，蜡会显著膨胀，从而将连杆推出圆缸，并打开阀门。通过让发动机尽可能快升温，节温器减小了发动机损耗，积炭和排放。

4.6 Fan Like the thermostat, the cooling fan has to be controlled so that it allows the engine to maintain a constant temperature.

和节温器一样，冷却风扇也需要进行控制来使得发动机在恒定的温度下运行。

Front-wheel drive cars have electric fans because the engine is usually mounted transversely, meaning the output of the engine points toward the side of the car. The fans are controller either with a thermostatic switch or by the engine computer, and they turn on when the temperature of the coolant goes above a set point. They turn back off when the temperature drops below that point.

前轮驱动式轿车使用电风扇冷却，这是因为前轮驱动式轿车的发动机通常是横向安置。这就意味着发动机的输出正对着轿车的侧面。冷却系统使用温控开关或者发动机计算机来控制风扇。当冷却液温度高于设定点时，打开风扇。一旦温度低于设定点，风扇关闭。

Rear-wheel drive cars with longitudinal engines usually have engine-driven cooling

fans. These fans have a thermostatically controlled viscous clutch. This clutch is positioned at the hub of the fan, in the airflow coming through the radiator. 采用发动机纵置的后轮驱动轿车通常采用发动机驱动冷却风扇。这种风扇使用一种温控液体粘性离合器进行控制。这个离合器位于风扇的中心，面向来自散热器的气流。

4 Exercises

1 What is the function of the cooling system?

To remove excess heat from the engine, to keep the engine operating at its most efficient temperature, and to get the engine up to the correct temperature as soon as possible after starting.

2 What are the most common causes of engine overheating?

Fuel burning engines produce enormous amounts of heat. The exhaust system takes away much of the heat, but parts of the engines, such as the cylinder walls, pistons, and cylinder head, absorb large amounts of the heat.

3 Will installing a lower temperature thermostat help the engine run cooler and prevent it from overheating?

No. The thermostat’s main job is to allow the engine to heat up quickly, and then to keep the engine at a constant temperature.

4 Why are liquid-cooling system pressurized?

It can increase the boiling point of the coolant.

1The fan’s activity is not always necessary, and it take power from the engine to spin. For this reason a thermostatic control, or fan clutch, is often used to reduce drive torque when it isn’t needed (variable-speed fan).

因为风扇需要从发动机吸取能量来旋转叶片，风扇并不需要持续运转。因此，当不需要风扇运转时，温度控制器或者风扇离合器经常被用来减小转矩（变速风扇）

2A different type of fan uses centrifugal force to move its flexible plastic blades, by flattening them when the engine rpm is high (flexible-blade fan). The less angle the blade have, the less power they use. The idea of these units is to save horsepower and to reduce the noise the fan makes.

当发动机转速较高时，有一种风扇使用离心力来移动可动的塑料叶片（变叶片风扇）。叶片的迎风角越小，风扇所消耗的功率越小。这些部件的设计是用来减小功率和风扇产生的噪音。3A fan can have from four to six blades to suck the air through the radiator. Often the radiator has a shroud for the fan to keep it from re-circulating the same hot air that has collected behind the radiator. Many fans have irregularly spaced blades to reduce resonant noise.

风扇拥有4到6个叶片来吸取来自散热器的空气。通常散热器被裹盖，防止风扇将散热器后部聚集的热空气重复循环。许多风扇有着不规则的叶片来减小共振噪音。

4Another function of the expansion tank is to remove air bubbles from the cooling system. Coolant without air-bubbles is much more efficient than coolant with air bubbles, because it absorbs heat much faster. The advantage of the expansion tank is that while the level of coolant contained in it rises and falls, the radiator is always full.

溢流箱的另一个作用是去除来自冷却系统的气泡。没有气泡的冷却液要比含有气泡的冷却液更有效，因为它可以更快地吸收热量。无论溢流箱内的液位上升或下降，散热器总是满的。Unit 5 Fuel Injection System