《机电工程英语》PPT课件.ppt

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1、Lesson 21:Introduction to Automobile,词汇讲解课文分析练习答案,本课教学目标：,理解汽车差速器、燃油喷射器的作用；掌握与汽车相关的专业词汇；熟悉独立主格、伴随壮语等语法现象。,Section：words and phases,重点专业名词解析词性转换专有名词的通用含义,Now you will have 5 minutes to skim over the new words and phrases,marking the special words you cant understand.,1.重点专业名词解析,differential suspensio

2、n transmission driving axle&driving shaft,differential,汽车发动机的动力经离合器、变速器、传动轴，最后传送到驱动桥再左右分配给半轴驱动车轮，在这条动力传送途径上，驱动桥是最后一个总成，它的主要部件是减速器和差速器。减速器的作用就是减速增矩，这个功能完全靠齿轮与齿轮之间的啮合完成，比较容易理解。而差速器就比较难理解，什么叫差速器，为什么要“差速”？汽车差速器是驱动轿的主件。它的作用就是在向两边半轴传递动力的同时，允许两边半轴以不同的转速旋转，满足两边车轮尽可能以纯滚动的形式作不等距行驶，减少轮胎与地面的摩擦。,suspension,车身好比是

3、人的上半身,轮胎好比是人的脚,悬挂系统就好比是人的腿。汽车悬架包括弹性元件，减振器和传力装置等三部分，这三部分分别起缓冲，减振和力的传递作用。,transmission,发动机的输出转速非常高，最大功率及最大扭矩在一定的转速区出现。为了发挥发动机的最佳性能，就必须有一套变速装置，来协调发动机的转速和车轮的实际行驶速度。变速器可以在汽车行驶过程中，在发动机和车轮之间产生不同的变速比，通过换挡可以使发动机工作在其最佳的动力性能状态下。变速器的发展趋势是越来越复杂，自动化程度也越来越高，自动变速器将是未来的主流。,driving axle&driving shaft,驱动桥处于动力传动系的末端，其基

4、本功能是增大由传动轴或变速器传来的转矩，并将动力合理的分配给左、右驱动轮，另外还承受作用于路面和车架或车身之间的垂直立、纵向力和横向力。驱动桥一般由主减速器、差速器、车轮传动装置和驱动桥壳等组成。,2.词性转换,ignition n ignite vt 点燃；激起 vi 着火lubrication n lubricate vt 使润滑 vi 起润滑作用cylinder n cylindrical adj 圆柱形的intermittent adj intermission n 间歇，休息时间；intermittence n 断续性，周期性compensate v compensation n补偿

5、，补偿金，报酬 Did you get any compensation when you were dismissed from your job?The job is hard but the compensation is good.,3.专业名词的通用含义,differential n 差别，差速器；adj 差别的muffler n 消声器，围巾，厚手套tire n 轮胎；vt 使疲劳；vi 疲劳，厌烦（+of）She never tires of talking about her hometown.transmission n 变速器，传送，传播the transmission o

6、f diseasesmanifold n 多种，管；adj 种种的manifold duties,Now please read the new words after me for 2 times.After that,you will have 10 minutes to remember as many words as you can.,Section：text,At first,read the first paragraph silently in two minutes,please.,paragraph:,Automobile（）is a self-propelled vehi

7、cle used for travel on land.The term is commonly applied to a four-wheeled vehicle designed to carry two to six passengers and a limited amount of cargo,as contrasted with(与.比较)a truck,which is designed primarily for the transportation of goods and is constructed with larger and heavier parts,or a b

8、us(or omnibus or coach),which is a large public conveyance designed to carry a large number of passengers and sometimes additionally small amounts of cargo.,一般来说，汽车是指陆地上行驶的机动式车辆，具有四个轮子，用来搭载两至六名乘客和少量货物。我们可以把它与卡车或公汽对比一下，卡车的零部件更大更重，主要用来运输货物；公共汽车(或公共马车、长途汽车)是一种大型的公共运输工具，用来搭载大量的乘客，有时也附加地运输少量的货物。,Oral Eng

9、lish practice:,Please describe the functions of an automobile,a truck and a bus separately!,Read the second paragraph silently in two minutes,please.,paragraph:,Differential,fuel injection,ignition,internal-combustion engine,lubrication,muffler,odometer,shock absorber,speedometer,steering system,sus

10、pension,tachometer,tire and transmission are the main operation and technical features of automobiles.差速器、燃油喷射器、点火器、内燃机、润滑装置、消声器、里程表、减震器、速度计、驾驶装置、悬挂、转速计、轮胎和变速器反应了小汽车的主要操作特性和技术特性。,paragraph:,Differential and fuel injection system are introduced in this lesson,with other components presented in the fo

11、llowing lessons.本课介绍了差速器和燃油喷射系统，其他零部件将在后续几课中介绍。,独立主格结构,（一）：独立主格结构的构成：名词(代词)+现在分词、过去分词；名词(代词)+形容词；名词(代词)+副词；名词(代词)+不定式；名词(代词)+介词短语构成。（二）独立主格结构的特点：1）独立主格结构的逻辑主语与句子的主语不同，它独立存在。2）名词或代词与后面的分词，形容词，副词，不定 式，介词等是主谓关系。3）独立主格结构一般有逗号与主句分开。,The test finished,we began our holiday.=When the test was finished,we be

12、gan our holiday.考试结束了，我们开始放假。The president assassinated,the whole country was in deep sorrow.=After the president was assassinated,the whole country was in deep sorrow.总统被谋杀了，举国上下沉浸在悲哀之中。Weather permitting,we are going to visit you tomorrow.如果天气允许，我们明天去看你。This done,we went home.工作完成后，我们才回家。The meeti

13、ng gone over,everyone tired to go home earlier.会议结束后，每个人都想早点回家。He came into the room,his ears red with cold.他回到了房子里，耳朵冻坏了。He came out of the library,a large book under his arm.他夹着本厚书，走出了图书馆。,Now well come to paragraph four,the most difficult one in this passage,please read the it silently in 5 minut

14、es,.,paragraph:,Differential in the automobile is a set of gears used on the driving axle.The two wheels on the driving axle must be interconnected in order to receive their energy from the same source,the driving shaft;at the same time they must be free to revolve at different speeds when necessary

15、(e.g.,when rounding a curve,the outer wheel travels farther and thus must revolve faster than the inner wheel in order to prevent skidding).,汽车差速器由装在驱动桥上的一套的齿轮组成。驱动桥两端的车轮必须互连，以便从同一个动力源即传动轴上获取能量；同时，必要时，两个车轮必须能自由地以不同的速度旋转（例如，拐弯时，外侧的轮子比内侧的行驶的距离更远，为了避免打滑，故其转速应更快）。,These two requirements are met by the d

16、ifferential gearing.Furthermore,through it the rotating motion of the driving shaft is transmitted to the axle and the wheels.The axle is in two halves;to each half is attached a wheel at one end and,at the inner end,a gear.The end of the driving shaft is also equipped with a gear.By an ingenious ar

17、rangement(Fig.6.2)of these and other gears,together constituting the differential,a difference in speed of the two wheels is compensated for without a loss of tractive force.,使用差动传动装置能同时满足这两个要求。此外,通过差速传动装置可以把传动轴的旋转运动传递给驱动轴和车轮。驱动轴由两个半轴组成；每个半轴外端装了一个车轮，内端装了了一个(半轴)齿轮。传动轴的一端也装了一个齿轮。通过精巧地布置上述和其他的一些齿轮组成差速器

18、，两个车轮的速度差异就能得到补偿，且不损失牵引力。,左侧大图表示其基本结构。右上图表示2侧半轴同步转动时，行星齿轮不转，而带着两侧半轴同步转动。右下图表示当右侧半轴转速超过左侧半轴时，其极端情况是左半轴停止转动时，由于传动轴强迫盆齿以一定的速度继续转动，2个行星齿轮便会产生左右相反的转动，而该转动又会使右侧半轴在原来跟随盆齿转动的基础上又产生一个向前的转动量。这时右半轴的转速来自于两部分原因：第一，盆齿的转动，第二，行星齿轮的转动。因此，行星齿轮组转动的结果相当于把不转动或转动慢的一侧半轴的转速传递给了另一侧半轴。所以，当盆齿转动速度一定的时候，两侧半轴的转速和是一个定值，而差速器的作用就是在

19、这个前提下，使左右半轴的速度可以自由分配。,A disadvantage of the conventional differential is that when one wheel is on a dry and the other on a slippery surface,the differential causes the wheel on the slippery surface to revolve at double speed while the other wheel remains stationary.This hazard can be avoided by use

20、 of a limited slip differential,which feeds power to one wheel when the other wheel starts to slip and thus keeps the automobile moving.,常见的差速器的缺点是：当一个车轮走在干硬的地面上而另一个车轮走在湿滑的地面上时，差速器会导致走在打滑地面上的轮子转速加倍，而使另外一个轮子保持静止。使用防滑差速器则能避免出现这一危险情况，这种分速器在某个车轮开始打滑时只给另一个车轮供给能量，从而保持汽车移动。,Oral English practice:,Is a diff

21、erential a part of driving axle?and whats its function?Do driving axle and driving shaft refer to the same thing?If not,whats the difference between them?,Now we will come to the last paragraph,read it silently in 5 minutes,please!,paragraph:,Fuel injection system in an internal-combustion engine de

22、livers fuel or a fuel-air mixture to the cylinders by means of pressure from a pump.It was originally used in diesel engines because of diesel fuels greater viscosity and the need to overcome the high pressure of the compressed air in the cylinders.A diesel fuel injector sprays an intermittent,timed

23、,metered quantity of fuel into a cylinder,distributing the fuel throughout the air within.,内燃机上的燃油喷射系统通过泵产生的压力来将油或油气混合物传递给汽缸。燃油喷射系统最早用在柴油机上，因为柴油的黏度较大,且需克服汽缸里受压缩空气的高压。柴油喷射器间歇地、定时地将一定量的柴油喷洒到汽缸中，使燃油与空气充分混合。,Fuel injection is also now used in gasoline engines in place of a carburetor.In gasoline engines

24、 the fuel usually is injected into the intake manifold and mixed with air,and the resulting mixture is delivered to the cylinder.Modern fuel injection systems use computers to regulate the process.Fuel injection results in more efficient fuel combustion,improving fuel economy and engine performance

25、and reducing polluting exhaust emissions.,内燃机上的燃油喷射系统通过泵产生的压力来将油或油气混合物传递给汽缸。燃油喷射系统最早用在柴油机上，因为柴油的黏度较大,且需克服汽缸里受压缩空气的高压。柴油喷射器间歇地、定时地将一定量的柴油喷洒到汽缸中，使燃油与空气充分混合。,Oral English practice:,Fuel injection system can be used both in diesel engine and gasoline engine,however,is there any difference between them?,Section：exercises,Now its time to do the exercises.And please finish them in five minutes.,This is the end for lesson 21.It will be pretty good if you could review lesson 21 and preview lesson 22 in your spare time.,