【Listening】

【Vocabulary & Phrases】

Power Train System传动系

Transmission system传动系

drive wheel驱动轮

engine发动机

transmission变速器

clutch离合器

differential差速器

drive shaft驱动轴

half shaft半轴

flywheel飞轮

clutch disk离合器盘

pressure plate压盘

release bearing分离轴承

linkage分离机构

crankshaft曲轴

clutch pedal离合器踏板

master cylinder主缸

reservoir储液罐

slave cylinder从动缸

 

manual transmission手动变速器

automatic transmission自动变速器

gear ratios齿轮比、传动比

four-wheel-drive四轮驱动

front-wheel-drive前轮驱动

rear-wheel-drive后轮驱动

transaxles变速驱动桥

final drive主减速器

 

input shaft输入轴

output shaft输出轴

forward gear前进挡

neutral position空挡

reverse gear倒挡

multiple-disk clutch多片离合器

one-way clutch单向离合器

friction band制动带

【Reading】

PowerTrain System

The functions of the power train system

The power train serves two functions: it transmitspower from the engine to the drive wheels, and it varies the amount of torque. Thepower train includes:

1）The engine:which produces the power;

2）The transmission:either manual or automatic;

3）The clutch:on vehicles with manual transmissions;

4）The differential:which sends the power to the two rear wheels through the wheel axles;

5）The driveshaft: which carries the power from the transmission to the differential;

6）The halfshaft

Power train system’s component

1.Clutch

Driving a car with a manual transmission, youdepress the clutch, select a gear, and release the clutch while applying powerto get the car to move. The clutch allows engine power to be applied graduallywhen a vehicle is starting out, and interrupts power to avoid gear crunchingwhen shifting. Engaging the clutch allows power to transfer from the engine totransmission and drive wheel. Disengaging the clutch stops the power transferand allows the engine to continue turning without force to the drive wheels.

The clutch basic components are: the flywheel,clutch disk, pressure plate, release bearing and linkage.

The flywheel is bolted to the crankshaft of theengine. Its main function is to transfer engine torque from the engine to thetransmission.

The clutch disk is basically a steel plate, coveredwith a frictional material that goes between the flywheel and the pressureplate.

    Apressure plate is bolted to the flywheel. It includes a sheet metal cover,heavy release springs, a metal pressure ring that provides a friction surfacefor the clutch disk.

The release bearing is the heart of clutchoperation. When the clutch pedal is depressed, the throw-out bearing movestoward the flywheel, pushing in the pressure plate’s release fingers and movingthe pressure plate fingers or levers against pressure plate spring force.

The linkage transmits and multiplies the driver’sleg force to the fork of the clutch pressure plate. A mechanical clutch linkageusually consists of the clutch pedal, a series of linkage rods and arms, or acable. A hydraulic clutch linkage typically includes a clutch master cylinderand reservoir, a hydraulic line and a slave cylinder.

2.Transmission

1）manualtransmission

The manual transmission provides a means of varyingthe relationship between the speed of the engine and the speed of the wheels.Varying these gear ratios allows the right amount of engine power at manydifferent speeds. 

Manual transmission requires use of a clutch toapply and remove the engine torque to the transmission input shaft. The clutchallows this to happen gradually so that the car can be started from a completestop.

Modern manual transmissions do not disengage any ofthe forward drive gears, they are simply connected to their shafts through theuse of “synchronizers”. Reverse is achieved reverse idler gears ,which areengaged to move the car backwards.

Manual transmissions usually have four or fivespeeds , and often have “overdrive”, which means that the output shaft can turnfaster than the input shaft for fuel economy on the high way. When you use it,it will reduce the engine speed by one-third, while maintaining the same roadspeed.

2）Automatictransmission

Both an automatic transmission and a manualtransmission accomplish exactly the same thing, but they do it in totallydifferent ways. The key difference between a manual and an automatictransmissions is that the manual transmission locks and unlocks and differentsets of gears to the output shaft to achieve the various gear ratios, while inan automatic transmission, the same set of gears produces all of different gearratios. The planetary gear-set is the device that makes this possible in anautomatic.

 Automatictransmissions are used in many rear-wheel-drive and four-wheel-drive vehicles.Automatic transaxles are used in most front-wheel-drive vehicles. The majorcomponents of a transaxle are the same as those in a transmission, except thetransaxle assembly includes the final drive and differential gears, in additionto the transmission.

An automatictransmission receives engine power through a torque converter, which is drivenby the engine’s crankshaft. Hydraulic pressure in the converter allows power toflow from the torque converter to the transmission’s input shaft. The inputshaft drives a planetary gear set that provides the different forward gears, aneutral position, and one reverse gear. Power flow through the gears iscontrolled by multiple-disk clutches, one-way clutches, and friction bands.

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