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1、1)The modern automobile engine is a powerful,lightweight,and dependable powerplant.However,it is not perfect for three reasons.First,modern engines do not produce much torque at low engine speeds.Second,engines produce maximum torque between 2000-3000r/min.As a result,engines operate best only withi
2、n this fairly narrow range.Third,much more force is needed to move a car from rest than to keep it moving once it is started.Thus,the vehicle needs a wider range of torque than is available from the engine.,新型的汽车发动机动力强劲、质量轻便而且动力性能可靠。然而它美中不足的原因有三个。首先，新型发动机低速时产生的转矩较小其次，发动机在每分钟2000-3000转时转矩最大结果，发动机只能在这
3、个相当狭窄的转速范围内工作良好第三，起动汽车比它起动后保持其运动需要的力大因此，汽车需要的转距比发动机提供的转距范围大,Review 1:Why is a transmission needed in an automobile?,Review 2:Whats the function of transmission?,Changes the engine torque,Reverses the vehicle movement,Disengages the drive,3.3 transmission,Review 3:List the types of transmission.,Fini
4、te,Infinite,MTManual Transmission（手动变速器）,ATAutomatic Transmission（自动变速器）,AMTAutomatic Mechanical Transmission（液力机械变速器）,CVTContinuously Variable Transmission（无级变速器）,2)In simple terms,a transmission multiplies engine torque and-through gears-sends that power to the drive axle.A driver shifts or change
5、s the gears to increase or decrease the torque produced by the engine.,简而言之，变速器利用齿轮扩大发动机的扭矩，向驱动桥传递动力。驾驶员通过换挡来升高或降低发动机的输出扭矩。,Review 4:Whats the meaning of gear ratio?,DriveGear,DrivenGear,3.3.1 manual transmission,Review 5:List the mesh methods of manual transmission.,Sliding-mesh TransmissionConstan
6、t-mesh TransmissionSynchro-mesh Transimission,Sliding-mesh transmission:Although this type is rarely used today,it is included because the gear layout forms the basic construction of most modern manual gearboxes.The spur gears are mounted on four shafts:primary shaft(input shaft),layshaft(countersha
7、ft),mainshaft and reverse idler shaft.,尽管现在几乎不使用滑动啮合变速器，但在这里仍然要提及，因为它是目前大多数手动变速器的雏形。直齿圆柱齿轮装在四个轴上：输入轴，中间轴，输出轴和倒档轴,Review 6:List the types of transmission gear.,Bevel gear 锥齿轮,Helical gear 斜齿轮,Double helical gear 人字齿轮,Pinion gear 小齿轮,Hypoid gear 准双曲面齿轮,Planetary gear 行星齿轮,External gear 外啮合齿轮,Internal
8、gear 内啮合齿轮,4)Sliding-mesh transmission:In the case of a sliding-mesh gearbox,gear changing demands skill if noise is to be avoided.Crashing(or clashing)of the gears as the result of a bad change suggests the reason why this type is often called a crash type gearbox.,对滑动啮合变速器来说，换挡时要避免噪声是需要技巧的。齿轮打齿是由换
9、挡不当引起的，这也是滑动啮合变速器经常被称为“碰撞”型变速器的原因。,5)constant-mesh transmission:This type uses helical or double helical gears which are always in mesh.The mainshaft gear wheels are mounted on bearings and when a gear is required the mainshaft gear is locked to the shaft by a dog clutch.,常啮合变速器采用斜齿轮或人字形齿轮，这些齿轮总是处于啮
10、合状态。输出轴上的齿轮安装在轴承上，换挡时接合套使输出轴齿轮和输出轴锁止在一起。,6)constant-mesh transmission:Although the mechanical efficiency is lower the helical gears are quieter and any damage resulting from a bad gear change occurs to the dog teeth instead of the actual gear teeth.,尽管斜齿轮的机械效率较低，但其工作噪声较小，而且由于换挡不当所引起的任何损害都不会作用在换挡齿轮的轮
11、齿上，而是作用在接合齿圈的轮齿上。,7)synchro-mesh transmission:As the name suggests this type has a synchronization device which equalizes the speeds of the two members that have to be meshed to obtain the gear.The layout is similar to the constant-mesh but has friction cones fitted between the dog clutch and the ge
12、ar wheel.,顾名思义，同步啮合变速器带有同步装置，使得换挡时要啮合的两齿轮转速达到相同。同步啮合变速器的结构与常啮合变速器类似，不同之处是在接合齿圈和齿轮之间有摩擦锥面。,8)synchro-mesh transmission:The operation of the friction device performs a duty which,in older designs,was carried out by the driver during double-declutching.The synchro-mesh gearbox gives a simpler,quieter a
13、nd quicker gear change.,在老式变速器上，（同步器）摩擦装置完成的工作要通过驾驶员利用两脚离合来实现。同步啮合变速器使得换挡更为简单、安静而快捷。,Review 7:List the types of manual transmission.,Two-shaft MT,Input shaft,Main shaft,Reverse idler shaft,Input shaft(primary shaft),Main shaft,Countershaft(layshaft),Reverse idler shaft,Three-shaft MT,一挡二挡三挡四挡五挡倒挡,Re
14、view 8:List the gear shift actions of MT.,1stGear,Gear shift actions of three-shaft MT,2ndGear,3rdGear,4thGear,5thGear,ReverseGear,Review 9:List the operating system types of MT.,Direct operating system,Remote operating system,Self-lock System,Inter-lock System,Reverse-lock System,Review 10:Whats the function of Power Transfer.,To transfer the engine power to every driving axle.,
