自动变速器英文文献翻译

1、毕业设计外文翻译THE RESEARCHS OFAMT SHIFTING SCHEDULESThe modern automatictransmissionisby far ， the most complicatedmechanicalcomponent intodays automobile.Itisa typeoftransmissionthatsiftsitself.A fluidcouplingor torque converterisused insteadof a manually operatedclutchto connect the transmission to the

2、engine.There are two basic types of automatic transmission based on whether thevehicle is rear wheel drive or front wheel drive. On a rear wheel drive car，the transmission is usually mounted to the back of the engine and is locatedunder the humpin the centerofthefloorboardalongside the gas pedal pos

3、ition.A drive shaft connects the transmission to the final drive which is located inthe rear axle and is used to send power to the rear wheels. Power flow on thissystem is simple and straightforwardgoing from the engine ，throughthetorqueconverter ，then trough the transmission and drive shaft until i

4、t reaches thefinal drive where it is split and sent to the two rear transmission.On a front wheel drive car，the transmission is usually combined with thefinaldrivetoform what iscalleda transaxle.The engineon a frontwheel drivecar is usually mounted sideways in the car with the transaxle tucked under

5、 iton the side of the engine facing the rearof the car. Front axles are connecteddirectly to the transaxle and provide power to front wheels. In this example，power floesfrom the engine ， throughthetorqueconvertertoa largerchainthatsends the power througha 180 degree turntothetransmissionthatisalongs

6、idethe engine.From there ， the power isrouted throughthe transmissionto the finaldrivewhere itis splitand senttothetwo frontwheels through thedriveaxles.There are a number of otherarrangements includingfrontdrivevehicleswherethe engine is mounted front to back instead of sideways and there are other

7、systems that drive all four wheels but the two systems described here are byfar the most popular.A much less popular rearand isconnected by a driveshaftto the torque converter which is still mounted on the engine. This system isfound on the new Corvetteand isused inorder to balancethe weightevenly b

8、etweenthe front and rear wheels for improved performance and handling. Another reardrivesystem mounts everything，theengine ， transmissionand final drivein therear. This rear engine arrangement is popular on the Porsche。The modern automatic transmission consists of many components and systemsthatdesi

9、gned towork togetherin a symphonyof planetarygear sets ，the hydraulicsystem, seals and gaskets ， thetorqueconverter， thegovernor and the modulatoror throttle cable and computer controls that has evolved over the years intowhat many mechanical inclined individuals consider to be an art from. Here try

10、to used simple ，generic explanation where possible to describe these systems.1） Planetary gear setsAutomatic transmission contain many gears in various combinations. In amanual transmission ，gears slide along shafts as you move the shift lever fromone position to another，engaging various sizes gears

11、 as required in order toprovide the correct gear ratio.In an automatictransmission，how ever ，the gearsare never physically moved and are always engaged to the same gears. This isaccomplished through the use of planetary gear sets.The basic planetary gear set consists of a sun gear，a ring and two or

12、moreplanet gears ，all remaining in constant mesh. The planet gears are connectedto each other througha common carrierwhich allows thegears tospin on shaftscalled “ pinions ” which are attached to the carrier.One example of a way that this system can be used is by connecting the ringgear to the input

13、 shaft coming from the engine， connecting the planet carrierto the output shaft，and locking the sun gear so that it cant move. In thisscenario ，when we turn the ring gear，the planets will“walk ” along the sungear ( which isheldstationary) causing the planetcarrier to turnthe outputshaft in the same

14、direction as the input shaft but at a slower speed causinggear reduction ( similar to a car in first gear ).Ifwe unlock the sun gear and lock any two elements together ，thiswillcauseall three elements to turn at the same speed so that to output shaft will turnat the same rate of speed as the input s

15、haft. This is like a car that is thirdor high gear. Another way we can use a planetarygear set is by lockingthe planetcarrier from moving，then applying power to the ring gear which will cause thesun gear to turn in opposite direction giving us reverse gear.The illustrationin Figureshows how the simp

16、le system describedabove wouldlook in an actual transmission. The input shaft is connected to the ring gear，the output shaft is connected to the planet carrier which is also connected toa “Multi-disk ” clutch pack. The sun gear is connected to drum which is also connected to the other half of the cl

17、utch pack. Surrounding the outside of the drum is a band that can be tightened around the drum when required to prevent the drum with the attached sun gear from turning.The clutch pack is used， in this instance，to lock the planet carrier withthe sun gear forcing both to turn at the same speed. If bo

18、th the clutch packand the band were released， the system would be in neutral. Turning the inputshaft would turn the planetgears against the sun gear ，but since noting is holdingthe sun gear ，it will just spin free and have no effect on the output shaft.To place the unit in first gear， the band is ap

19、plied to hold the sun gear frommoving. To shift from first to high gear， the band is released and the clutchis appliedcausing the outputshaftto turnat thesame speed as the inputshaft.Manymore combinationsarepossibleusingtwo or more planetarysetsconnected in various way to provide the different forwa

20、rd speeds and reverse that are found in modern automatic transmission.2 ）Clutch packA clutch pack consists of alternating disks that fit inside a clutch drum. Half of the disks are steel and have splines that fit into groves on the inside of the drum. The other half have a friction material bonded t

21、o their surface and have splines on the inside edge that fit groves on the outer surface of theadjoining hub. There isa piston inside the drum thatis activatedby oilpressureat the appropriate time to squeeze the clutch pack together so that the twocomponents become locked and turn as one.3 ）One-way

22、ClutchA one-way clutch (alsoknown as a “sprag ” clutch) isa devicethatwillallow a component such as ring gear to turn freely in one direction but not inthe other. This effect is just like that bicycle，where the pedals will turnthe wheel when pedaling forward，but will spin free when pedaling backward

23、.A commonplace where a one-way clutchis used isinfirstgear when the shifterisinthedriveposition.When youbegintoacceleratefrom astop ， thetransmission starts out in first gear. But have you ever noticed what happensif you release the gas while it is still in first gear ? The vehicle continuesto coast

24、 as if you were in neutral. Now， shift into Low gear instead of Drive.When you let go of the gas in this case，you will feel the engine slow you downjust like a standard shift car. The reason for this is that in Drive， one-wayclutch is used whereas in Low，a clutch pack or a band is used.4） Torque Con

25、verterOnautomatictransmission，the torque convertertakestheplace ofthe clutchfound on standard shift vehicles. It is there to allow the engine to continuerunningwhen the vehiclecomes toa stop.The principlebehind a torqueconverteris like taking a fanthat is plugged into the wall and blowing air into a

26、notherfanwhich isunplugged.If you grab thebladeon theunplugged fan ，you areableto hold it from turning but as soon as you let go，it will begin to speed upuntil it comes close to speed of the powered fan. The difference with a torqueconverter is that instead of using air it used oil or transmission f

27、luid，tobe more precise.A torqueconverteris a lagerdoughnut shaped devicethatismounted betweenthe engine and the transmission. It consists of three internal elements thatwork together to transmit power to the transmission. The three elements of thetorqueconverterare the pump，the Turbine ， and theStat

28、or.The pump ismounteddirectly to the torque housing which in turn is bolted directly to the engines crankshaft and turns at engine speed. The turbine is inside the housing andis connected directly to the input shaft of the transmission providing powerto move the vehicle. The stator is mounted to a o

29、ne-way clutch so that it canspin freely in one direction but not in the other. Each of the three elementshasfinsmounted inthemtopreciselydirecttheflowofoilthroughtheconverter.Withtheengine running ，transmissionfluidispulledintothepumpsectionand ispushed outwardby centrifugalforceuntilitreachesthetur

30、binesectionwhich stars it running. The fluid continues in a circular motion back towardsthe center of the turbine where it enters the stator. If the turbine is movingconsiderably slower than the pump，the fluid will make contact with the frontof the stator fins which push the stator into the one way

31、clutch and preventit from turning. With the stator stopped，the fluid is directed by the statorfins to re-enter the pump at a“help ” angle providing a torque increase. Asthespeed oftheturbinecatches up withthe pump， the fluidstartshittingthestatorblades on theback-sidecausing thestatortoturninthe sam

32、e directionas thepumpand turbine.As thespeed increase ，allthree elementsbegin toturnat approximatelythe samespeed. Sine the 80s，in orderto improvefueleconomy，torqueconvertershave been equipped witha lockupclutchwhich lockstheturbineto the pump as the vehicle reaches approximately 40-50 mph. This loc

33、kup iscontrolled by computer and usually wont engage unless the transmission is in3rd or 4th gear.5） Hydraulic SystemThehydraulicsystem isa complex maze ofpassage and tubesthatsends thatsends transmission fluid and under pressure to all parts of the transmissionandtorqueconverterand.Transmissionflui

34、dservesanumberofpurposeincluding:shiftcontrol,generallubricationand transmissioncooling。Unliketheengine,whichuses oilprimaryforlubrication,everyaspectof atransmission s function is dependant on a constant supply of fluid is sendpressure. In order to keep the transmission at normal operating temperat

35、ure，a portion of the fluid is send to through one of two steel tubes to a specialchamber thatissubmerged inanti-freezeintheradiator.Fluidpassingthroughthis chamber is cooled and then returned to the transmission through the othersteel tube.A typicaltransmissionhas an avenge of tenquartsof fluidbetwe

36、enthe transmission， torque converter， and cooler tank， In fact， most of thecomponents of a transmission are constantly submerged in fluid including theclutch packs and bands. The friction surfaces on these parts are designed tooperate properly only when they are submerged in oil.6） Oil PumpThe trans

37、missionoilpump ( notto confusedwith thepumpelementinsidethetorque converter ) is responsible for producing all the oil pressure that isrequiredinthe transmission.The oilpumpismounted to frontofthe transmissioncase and is directly connected to a flange onthe engine crankshaft，the pumpwill produce pre

38、ssure whenever the engine is running as there is a sufficientamount oftransmissionfluidavailable.The oilenters the pumpthrougha filterthat is located at bottom of the transmission oil pan and travels up a pickuptube directlytothe oilpump. The oilisthen sent ，under pressure to the pressureregulator ，

39、the valve body and the rest of the components， as required.7 ）Valve BodyThe valve body is the control center of the automatic transmission. Itcontains a maze of channels and passages that direct hydraulic fluid to thenumerous valves which when activate the appropriate clutch pack of band servoto smo

40、othly shift to the appropriate gear for each driving situation. Each ofthe many valves in the valve body has a specific purpose and is named for thatfunction. For example the 2-3 shift valve activates the 2nd gear up-shift orthe 3-2 shift timing valve which determines when a downshift should occur.T

41、he most important valve and the one that you have direct control overis the manual valve. The manual valve is directly connected to the gear shifthandle and covers and uncovers various passages depending on what position thegear shift is paced in. When you place the gear shift in Drive， for instance

42、，the manual valvedirectsfluidto the clutchpack ( s )thatactivates1st gear.It also sets up to monitor vehicle speed and throttle position so that it candetermine the optimal time and the force for the 1-2 shift. On computer controlled transmission ，you will also have electrical solenoids that are mou

43、nted in thevalve body to direct fluid to the appropriate clutch packs or bands under computer control to more precisely control shift points.8） Seals and GasketsAn automatic transmission has many seals and gaskets to control the flow ofhydraulic fluid and to keep it from leaking out. There are two m

44、ain externalseals : the front seal and the rear seal. The front seal seals the point wherethe torque converter mounts to the transmission case. This seal allows fluidto freely move from the converter to the transmission but keeps the fluid fromleaking out. The rear seal keeps fluid from leaking past

45、 the output shaft.A seal is usuallymadeof rubber ( similarto the rubber in a windshieldwiperblade ) and is used to keep oilfrom leakingpast a moving partsuch as a spinningshaft. In some cases，the rubber is assisted by a spring that holds he rubberin close contact with the spinning shaft.A gasket is

46、a type of seal used to seal two stationary parts that are fastedtogether.Somecommongasket materialsare : paper ，cork ，rubber ， siliconeandsoft metal.Aside from the main seals ， there are also a number of othersealsand gasketthat vary from transmission to transmission. A common example is the rubberO

47、-ring that sealsthe shaft for theshiftcontrol lever.This is the shaftthatyou move when you manipulate the gear shifter. Another example that is commonto most transmissionis the oilpan gasket.In fact ，seals are requiredanywherethat a device needs to pass through the transmission case with each one be

48、inga potential source for leaks.9） Computer ControlsThe computer uses sensors on the engine and transmissionto detectsuch thingsas throttleposition，vehiclespeed，engine speed，engine load ，stop lightswitchposition，etc. to control exact shift points as well as how soft or firm theshift should be. Some

49、computerized transmission even learn your driving styleand constantlyadapt to itso thatevery shiftis timed preciselywhen you wouldneed it.Because ofcomputer controls，sportsmodels are coming outwith the abilityto take manual controlofthe transmissionas throughitwere a stickshiftleverthrough a special

50、 gate ，then tapping it in one direction or the other in orderto up-shift at will. The computer monitors this activity to make sure that thedriver dose not select a gear that could over speed the engine and damage it.Anotheradvantage to these“ smart ” transmissionisthattheyhave a selfdiagnosticmodewh

51、ich can detecta problem earlyon and warn you withan indicatorlight on the dash. A technician can then plug test equipment in and retrievea list of trouble codes that will help pinpoint where the problem is.VehicularAutomaticTransmissioncan be divided intothreetypes:AutomaticTransmission(AT),AutomatedMechanicalTransmission(AMT)and ContinuouslyVariable Transmission(CVT). LMT has become a kind of