发动机润滑系统英文翻译.doc

英文翻译原文：English Lubricating SystemThere are a great many moving metal parts in the engine. There parts must be protected by lubricating oil so that there will be no actual metal-to-metal contact. The moving parts , in effect , float on films of oil .Two types of lubricating systems have been used on four-cycle automotive engines , splash and combination splash and pressure feed.In the splash lubricating system , oil is splashed up from the oil pan or oil trays in the lower part of the crankcase .Theoil is thrown upward as droplets or fine mist and provides adequate lubrication to valve mechanisms , piston pins , cylinder walls ,and piston rings.In the combination splash and prcssure fcad lubricating system , an oil pump takes oil from the oil pan and forces it through holes drilled in the engine block and crankshaft.This oil thereby reaches the various bearings that support rotating shafts and the different moving parts in the engine. It covers the surfaces of the moving parts to prevent metal-to-metal contact and undue wear of the parts.In this system , cylinder walls are lubricated by splashing oil thrown off frem the connecting-rod bearings.The lubricating oil circulating through the engine to all moving parts requiring lubricarion through the engine to all moving parts requiring lubrication performs other jobs.(1) Lubricate moving parts to minimize wear.(2) Lubricate moving parts to minimize power loss from friction.(3) Remove heat from engine parts by acting as a cooling agent.(4) Absorb shocks between bearings and other engine parts , thus reducing engine noise and extending engine life.(5) Form a good seal between piston rings and cylinder walls.(6) Act as a cleaning agent , washing the working surfaces free of chemical deposits , dust and to protect them from corrosion.A satifactory engine lubricating oil must have certain characteristics . or properties . It must have proper viscosity (body and fluidity) and must resist oxidation , and foaming . Also , it must act as a good cleatning agent , must pour at low temperatures , and must have good viscosity at extremes of high and must have good viscosity at extremes of high and low temperature.Any mineral oil , by itself , does not have all there properties . Lubricating-oil manufactures therefore put a number of additives into the oil during the manufacturing process . An oil for severe service may have many additives , as follows:(1) usually a viscosity-index improver;(2) pour-point depressants;(3) oxidation inhibitors;(4) corrosion inhibitors;(5) rust inhibitors;(6) foam inhibitors;(7) detergent-dispersants;(8) extreme-pressure agents.English Cooling SystemThe purpose of the cooling system is to keep the engine at its most efficient operating temperature at all engine speeds and all driving conditions . A great deal of heat is produced in the engine by the burning of the air-fuel mixture. Some of this heat escapes from the engine through the exhaust gases ( the hot gases left after the gasoline is burned ) . But enough remains in the engine to cause serious trouble unless removed by some other means . The cooling bybtem take care of this additional heat.The cooling system is built into the engine . There are hollow spaces around each engine cylinder and combustion chamber . These hollow spaces are called water jackets , since they are filled with water . When the engine is running , the water takes heat from the engine , becoming hot in the process . A water pump pumps the hot water from the engine water jackets into the radiator . The radiator has two sets of passages . One set carries water . The other set carries aie ( pulled thrugh by car motionand the engine fan ) . As the hot water passes through ,it gives up its heat to the air passing through . The cooled water then reenters the engine , where it can pick up more heat . In operation , water continuously circulates between the engine and radiator , carrying heat form the engine to the radiator . By this means , excessive engine temperatures are prevented.Two general types of cooling systems are used , air cooling and liquid cooling . Most automotive engines now employ liquid cooling . The liquid cooling system consists of water pumps , water jackets , engine fan , radiator and so on . The water pump , driver by a belt from the engine crankshaft , circulates the cooling liquid between the radiator and engine water jackets . The cooling liquid is water . Antifreeze compounds are added to the water during the winter . The water jacket are cast into the cylinder blocks and heads . The engine fan is usually mounted on the water pump shaft and is driven by the same belt that drives the pump and the generator . The purpose of the fan is to provide a powerful draft of air through the radiator . The radiator is a device for holding a large volume of water in close contact with a large volume of air so that heat will transfer from the water to the air . The radiator core is divided into two separate and intricate compartments ; water passes through one , and air passes through the other .Battery GeneratorThe electric system does several jobs . It cranks the engine for starting . It supplies the high voltage surges that ignite the compressed air-fuel mixture in the combustion chambers . It includes the battery , generator , starting system , ignition system , lighting system , horn system , radio and other devices . The starting system and the ignition system have been discussed ; the others are discussed in the following pages . BatteryThe purpose of battery is to supply current for operation of the cranking motor and the ignition system when the engine is being cranked for starting . It also supplies current for light , radio , and other electrical accessories at times when the generator is not operating fast enough to handle the electrical load . The amount of current the battery can supply is strictly limited by the “capacity” of the battery , which in turn depends on the amount of chemicals it contains . In making the battery , several similar plates are properly spaced and welded to a strap to form a plate group . Plates of two types are used , one for the positive plate group , the other for the negative plate group . A positive plate is nested with a negative plate group , with separators placed between the plates to from an element . Separators are designed to hold the plates apart so that they do not touch , and at the same time they must be porous enough to sheets , spun glass matted into sheets , and polyvinyl chloride have been used as separators . The liquid , called the electrolyte , is made up of about 40 percent sulfuric acid and about 60 percent water . When sulfuric acid is placed between the plates , chemical actions take place that remove electrons one group of plates and mass them at the other . The chemical actions that take place are rather complicated and we cannot discuss it here . The GeneratorThe generator is a device that converts mechanical energy from the automobile engine into a flow of electric current . The generator replaces in the battery the current used in starting the engine and also supplies current for operation of electrical devices , such as the ignition system , lights , radio , and so on . The generator is usually mounted on the side of the engine block . It is driven by the engine fan belt .For many years , all automotive generators were direct current (d-c) units . In recent years , alternating current (a-c) generators , or alternators , as they are also called , have come into widespread use . Direct current flows in one direction and then in the other . The a-c generator , or alternator , produces alternating current . The battery , ignition system , and other electrical components on the automobile cannot use ac , however , they are all d-c units . The a-c output must therefore be rectified , or changed to dc .Many charging circuits use an indicator lamp to indicate whether or not the alternator is charging the battery . However , and ammeter is used on many cars . It provides a better idea to the driver of what is happening in the charging circuit . The ammeter shows in a general way how much current is flowing to the battery during charge , and how much is flowing from the battery if the alternator is not charging the battery .译文：发动机润滑系统发动机中有大量的运动的金属零件。要保护这些零件就必须进行润滑，这样可以避免金属零件之间的直接接触。实际上，在运动零件的表面总是覆盖着一层油膜。四行程发动机使用两种润滑系统：飞溅式润滑和飞溅压力结合送油式润滑。在飞溅润滑系统中，油从机体下部的油盘或油底壳中飞溅上来。飞溅上来的油形成油滴或油雾，使气门机构、活塞销、汽缸壁和活塞环得到充分的润滑。在飞溅压力结合送油润滑系统中，油泵从油盘中把油抽上来并压入发动机机体上和曲轴上的油滴，被输送到发动机的曲轴和各种运动零件的每个轴承上。润滑油在运动零件表面，形成油膜，以防金属零件表面直接接触，以及零件的过度磨损。在这一系统中，汽缸壁是由连杆轴承运动飞溅起来的油进行润滑的。润滑油在发动机的所有活动部件之间循环流动，其作用是：1， 润滑运动零件，减少磨损。2， 润滑运动零件，减少因摩擦一起的功率损耗。3， 起冷却剂作用，带走发动机零件产生的热量。4， 吸收轴承和其他发动机零件产生的冲击力，减少发动机的噪音，并延长其寿命。5， 在活塞环和汽缸壁之间形成良好的密封。6， 起清洁剂作用，冲洗运动零件表面的化学杂质、灰尘和污物，以避免部件受到腐蚀。理想的发动机润滑油必须具有某些特性：必须具有一定的粘性（粘稠度和流动性），并且必须具有抗氧化、防止碳膜生成、防腐、防锈、抗积压和防泡沫的作用、润滑油必须具有良好清洁作用和良好的低温流动性，以及在高温和低温时都具有良好的粘性。任何矿物油自身都不具备所有这些特性。因此，润滑油厂家在制造润滑油的过程中，加入了许多添加剂。高级润滑油中可能加入以下这些添加剂：(1)常常加入黏度指数添加剂；（2）抗凝剂；（3）抗氧化剂；（4）防腐剂；（5）防锈剂；（6）抗泡剂；（7）净化分散剂；（8）极压剂。发动机冷却系统冷却系统的作用是使发动机在各种转速和各种行驶状态下都能有效的控制温度。混合起的燃烧在发动机这产生大量的热，其中部分热量通过废气被排出。但是，残留在发动机这的预热仍足以使发动机手到严重损坏，除非用其他的方法排除这些余热的。冷却系统就设置在发动机中。在每个汽缸体和燃烧室周围都留有空腔。这些空腔装满水，因此称之为水套。在发动机运行中水被加热，并以水循环方式把热量从发动机中带走。水泵从发动机水套中把热水抽到散热器中。散热器有两条通道：一条是水道，另一条是气道 空气是通过汽车行驶和发动机的风扇抽入的 。当热水流过水道时，气道中流通的空气使热水冷却。冷却后的水又重新进入发动机，再把发动机中的热量传导出去。在这一过程中，水不断的在发动机与散热器之间循环，水携带着热量从发动机流到散热器再散发出去。通过这个方法可避免发动机温度过高。通常使用的冷却系统有两种形式：空气冷却系和液体冷却系。现在大多数汽车发