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1、猥揸妨阊汝旧绐运烊懈哏AutomobileTransmissionsandPowerSteering琶某怿掇怆姹鳗统髦茱蛋Automobiles,trucks,buses,andtractorsalldependontransmissionstodeliverpowerfromtheenginetothewheels,Thegasolineanddieselenginesthatpowerthesevehiclescannotbeconnecteddirectlytothewheels,becausetheenginesmustkeepturni
2、ngatacertainseedtokeepfromstalling.Also,differentamountoftorque(turningforce)mustbedeliveredtothewheelsatdifferenttimes.Alargeamountofforceisneededtogetacarmovingfromastandstill.Lessforceisneededtokeepthecarmovingonceitisrolling.Goingupahillofdrivingathighspeedrequiresstillot
3、heramountofforce.Itisthejobofthetransmissiontodelivertheparticularamountofforcethatisneeded.Thetransmissionalsoallowsamotorvehicletobackup-----gasolineanddieselenginescanruninonlyonedirection,butthetransmissioncanreversethedirectionoftheforce.Andwhenacarstops,thetransmissionl
4、etstheenginekeeprunningwithoutmovingthewheels.祺彗蝠筌疟薰镂绡睃濞猖Theheartofanytransmission——evenanautomaticone—isasetofgears.Gearsdonotchangethepowerofanengine,buttheycanincreasethetorquebydecreasingthespeed.Theycanalsoincreasethespeedbydecreasingthetorque.圾燃新啵狡戳挞忄目蓼圆Theautomobiletra
5、nsmissionusesaseriesofgearswhichenablestheenginetocontinuetooperateatmaximumefficiencywhenthevehicle’sspeedisaltered.Settinganautomobileinmotionrequiresalargeamountofpowertoovercometheinertiaofthevehicle’sweight.Thisprocessrequireshighenginespeed,neededforhighpower,andagradua
6、lincreaseinavehicle’sspeedtoavoidajerkystart.Todothis,alowgearratioisallowsthecrankshafttorevolveseveraltimesinordertoturntherealaxleonce.Thelowgearratioisusedforstarting,climbingsteepslops,andothersituationsinwhichmaximumpowerisrequired.Aspowerneedsarereduced,asecond,higherg
7、earratioisusedwhichrotatestherearaxlewithfewerrevolutionsofthecrankshaft.Asthecar’sspeedincreases,successivelyhighergearratiosareuseduntilthedrivefromtheenginetotherearwheelspassesthroughthetransmissionwithoutreduction.Twoprincipletypesoftransmissionareused,manualandautomatic
8、.贾儆纱撸圬蠊缀谯贾滥庭Themanualtransmissionsystempermitsthedrivertoselectthede
