教学材料《汽车构造英语》-Unit8

UnitEightWhatIsTransmissionInadditiontothevariousforwardgears，atransmissionalsohasaneutralpositionwhichdisconnectstheenginefromthedrivewheels，andreverse，whichcausesthedrivewheelstoturnintheoppositedirectionallowingyoutobackup.2Finally，thereistheParkposition.Inthisposition，alatchmechanism(notunlikeadeadboltlockonadoor)isinsertedintoaslotintheoutputshafttolockthedrivewheelsandkeepthemfromturning，therebypreventingthevehiclefromrolling(seeFig8-1).3

上一页返回下一页UnitEightWhatIsTransmissionTherearetwobasictypesofautomatictransmissionsbasedonwhetherthevehicleisrearwheeldriveorfrontwheeldrive.Notes1.Anautomobileenginerunsatitsbestatacertainrpm(revolutionsperminute)rangeanditisthetransmission’sjobtomakesurethatthepowerisdeliveredtothewheelswhilekeepingtheenginewithinthatrange.汽车发动机在一定的转速（rpm，每分钟转）范围内以最佳状态运转，而变速器的任务就是保持发动机转速在最佳范围内时，确保动力被传递到车轮。上一页返回下一页UnitEightWhatIsTransmissionmakesurethat后接宾语从句。bedeliveredto意为“被传递到”。whilekeepingtheenginewithinthatrange为时间状语从句。上一页返回下一页UnitEightWhatIsTransmission2.Inadditiontothevariousforwardgears，atransmissionalsohasaneutralpositionwhichdisconnectstheenginefromthedrivewheels，andreverse，whichcausesthedrivewheelstoturnintheoppositedirectionallowingyoutobackup.除了各前进挡外，变速器还有一个空挡，和一个倒挡，空挡能使发动机与驱动轮断开连接；当要倒车时，倒挡能使驱动轮向相反的方向运转。上一页返回下一页UnitEightWhatIsTransmissionwhichdisconnectstheenginefromthedrivewheels和whichcausesthedrivewheelstoturnintheoppositedirection均是定语从句，修饰先行词position。allowingyoutobackup为现在分词作定语，修饰先行词direction。上一页返回下一页UnitEightWhatIsTransmission3.Inthisposition，alatchmechanism(notunlikeadeadboltlockonadoor)isinsertedintoaslotintheoutputshafttolockthedrivewheelsandkeepthemfromturning，therebypreventingthevehiclefromrolling.在停车挡，一个锁止机构（像门锁插销一样）插入输出轴，以锁住驱动轮，阻止车轮转动，防止汽车滑移。keepsb.fromdoingsth.=preventsb.fromdoingsth.阻止某人做某事preventingthevehiclefromrolling为现在分词作结果状语。上一页返回下一页UnitEightWhatIsTransmissionExtraReadingAutomobileSuspensionSystemAutomobilesuspensionsystemshavetwobasicfunctions,tokeepcarwheelsinfirmcontactwiththeroadandtoprovidecomfortablerideforthepassengers.1Alotofthesystem’sworkisdonebythespring.Undernormalconditions,thespringssupportthebodyofthecarevenlybycompressingandreboundingwitheveryup-and-downmovement.Thisup-and-downmovement,however,causesbouncingandswayingaftereachbumpandisveryuncomfortabletothepassenger.上一页返回下一页UnitEightWhatIsTransmissionThisuncomfortableeffectisreducedbytheshockabsorbers.Mostsuspensionsystemshavethesamebasicpartsandoperatebasicallyinthesameway.Therearefourbasictypesofspringsusedinsuspension:leafspring,coilspring,airspring,andtorsionbar,asshowninFig8-2.Theymaybepairedoffonvehiclesinvariouscombinationsandareattachedtovehiclesbyseveraldifferentmountingtechniques.上一页返回下一页UnitEightWhatIsTransmissionThecoilspringisthemostpopulartypeofspringinbothfrontandrearsuspensionsystems.Theadvantagesofthecoilspringareitscompactness,lackofmovingparts,andexcellentweightsupportingcharacteristics.Thedisadvantageofacoilspringisitsweaknessinsupportingside-to-sideorlateralmovement.Whencoilspringsareusedatthedrivewheels,heavytractionbarsortorquetubesareoftenrequiredtomaintainaxlehousingalignment.上一页返回下一页UnitEightWhatIsTransmissionAnumberofvehiclesuseatorsionbarspring.Itisalong,solidsteelshaftthatisanchoredatoneendtothesuspension’scontrolarmandattheotherendtothevehicl’sframe.Thetorsionbarcanstoreasignificantlyhighermaximumamountofenergythaneitheranequallystressedleaforcoilspring.Thetorsionoffersimportantweightsavingsanditisadjustable.Inaddition,itrequiressignificantlylessspacethanacoilspring.上一页返回下一页UnitEightWhatIsTransmissionTheleafspringmostcommonlyusedinautomobilesismadeupofseverallongplates,orleaves.Theleafspringactslikeaflexible.Becausetheleafspringconsistsofaseriesofthinleaves,oneontopofanother,itdoesnotbreakwhenbent.Whenthespringisbent,theindividualleavesbendandslopeoveroneanother.Thisprovidesaspringwithgreatflexibilityandstrength.Themainadvantageofleafspringsistheirabilitytocontrolvehicleswayandlateralmovement.Forthesereasons,leafspringsareoftenusedontherearsuspensionofreardrivevehicle.上一页返回下一页UnitEightWhatIsTransmissionManylate-modelluxurycarsuseairsprings.Thespringisessentiallyarubberbagorbladderfullofair.Apistonisattachedtothelowercontrolarm.Movementofthelowercontrolarmcausesthepistontomoveintotheairbladderandcompresstheairinthebladder.Airpressureisusedtoregulatehoweasyorhardthebladdercanbecompressed.Theairbladderisusuallyconnectedtoanaircompressor,whichregulatestheactionoftheairspringbasedonroadconditions.2

上一页返回下一页UnitEightWhatIsTransmissionInthepast,awidevarietyofdirectandindirectshockabsorbingdeviceswereusedtocontrolspringactionofpassengercars.Today,direct,double-actinghydraulicshockabsorbersandshockabsorberstrutshavealmostuniversalapplication.Theoperationprincipleofdirect,double-actinghydraulicshockabsorbersisforcingfluidthroughrestrictingopeningsinthevalves.Thisrestrictedflowservestoslowdownandcontrolrapidmovementinthecarspringsastheyreacttoroadirregularities.上一页返回下一页UnitEightWhatIsTransmissionUsually,fluidflowingthroughthepistonsiscontrolledbyspring-loadedvalves.Hydraulicshockabsorberautomaticallyadaptstoseverityoftheshock.Iftheaxlemovesslowly,resistancetotheflowoffluidwillbelight.Iftheaxlemovementisrapidorviolent,theresistanceisstronger,sincemoretimeisrequiredtoforcefluidthroughopenings.上一页返回下一页UnitEightWhatIsTransmissionBytheseactionsandreactions,theshockabsorberspermitasoftrideoversmallbumpsandprovidefirmcontroloverspringactionforcushioninglargebumps.3Thedoubleactingunitsmustbeeffectiveinbothdirectionsbecausespringreboundcanalmostbeasviolentastheoriginalactionthatcompressedtheshockabsorber.上一页返回下一页UnitEightW