车辆工程专业英语PPT课件-UNIT-6--ENGINE-ELECTRICAL-SYSTEMS-TE

No.10039UNIT6ENGINEELECTRICALSYSTEMSTEXTAStarting,ChargingandIgnitionSystemsPROFESSIONALENGLISHNo.10039UNIT5ENGINEELECTRICALSYSTEMSTEXTAStarting,ChargingandIgnitionSystemsChargingSystemStarterSystemIgnitionSystem本次课学习内容No.10039本次课学习目标掌握发动机电气系统的组成掌握点火系统的型式及原理掌握有关的专业名词与术语了解翻译技巧—增词NEWWORDSelectromagnetic[ilektroumæg'netik]a.电磁的trio['tri:ou]n.三件一套，三个一组，三重唱forward-biased['fɔ:wəd-'baiəst]正向偏压的reverse-biased[ri'və:s-'baiəst]反向偏压[偏置]的capacitor[kə'pæsitə]n.=capacitator电容器thermistor[ə:'mistə]n.热敏电阻rope[roup]n.绳,索,绳索；v.围起armature['ɑ:mətjuə]n.电枢collaps[kə'læps]v.&n.倒塌，塌陷，消失，减弱high-tension['hai-'ten∫ən]a.高（电）压的reluctor[ri'lʌktə]n.磁阻轮centrifugal[sen'trifjugəl]n.离心的advent['ædvənt]n.出现，到来，来临chargingsystem充电系统keepupwith跟上，不落后于magneticfield磁场fieldstrength磁场强度contactpoints触点powertransistor功率晶体管integratedcircuit集成电路solidstate固态diodetrio二极管三件组合startingmotor起动机PHRASESANDEXPRESSIONStransmissionhousing变速器壳responsiblefor（应）对…负责，是造成…的（主要）原因，决定着，导致withtheadventof随着…的出现（到来）intimewith与…合拍（同期）in（constant）contactwith（始终）与…保持接触pickupcoil传感线圈electriceye电眼，光电池shutterwheel遮光轮initialtiming初始点火正时vacuumadvance真空式点火提前角调节装置distributorlessignitionsystem无分电器点火系统Starting,ChargingandIgnitionSystemsChargingSystemThechargingsystemusestherotationoftheenginetocreateelectricity.Theelectricityrechargesthebatteryandprovidespowertooperatethevariousvehicleelectricalsystems.Themodernchargingsystemconsistsofthealternatorandregulator.AlternatorThealternatorisabelt-driven,electromagneticdevice.Aftertheengineisstarted,thealternatorproduceselectricitytomeettheneedsofthevehicleandtokeepthebatterycharged.Themodernvehiclecontainsmanycircuitsthatplaceaheavyloadontheelectricalsystem.Sincemanyvehiclesareusedinstop-and-gocitydriving,thismakesitdifficulttomaintainthebatteryinafullychargedstate.Therefore,thealternatormustbeextremelyefficientatallspeeds.Atidle,whentherotoristurningrelativelyslowly,thealternatorcankeepupwiththedemandsofthevehicleelectricalsystem.Atnormalvehiclespeeds,thealternatorcanproducemuchmorevoltageandcurrentthanneeded.Toprotectthealternatorandtherestoftheelectricalsystemfromdamage,ameansofreducingtheoutputmustbefound.VoltageRegulatorToreducealternatoroutput,avoltageregulatorisused.Thevoltageregulatorcontrolsthealternatoroutputbyadjustingtheamountofcurrentreachingtherotor.Thiscontrolsthestrengthofthemagneticfieldpassingthroughthestatorwindings.Theregulatorcontrolsthefieldstrengthbyreadingvoltageoutputfromthealternator.Ifoutputvoltagebecomestoohigh,theregulatorreducesfieldstrength.Iftheoutputvoltagedrops,theregulatorincreasesfieldstrength.ElectromechanicalVoltageRegulatorOldervoltageregulatorsusecontactpointsthatareoperatedbyelectromagneticcoils.Thesewerecalledelectromechanicalvoltageregulators.ElectronicVoltageRegulator(EVR)Allvehiclesmadewithinthelast15yearsuseanelectronicvoltageregulator.Theelectronicvoltageregulatorusespowertransistors,integratedcircuits,diodes,andothersolidstatepartstocontrolalternatoroutput.Theelectronicvoltageregulatoreliminatescontactpointsandmovingpartsthatcanstick,oxidize,orwear.Someelectronicregulatorsareremotelymounted.However,electronicvoltageregulatorsarereliable,durable,andsmallenoughtobeincorporatedintothealternatoritself.Built-inElectronicRegulatorOperationAcommonchargingsystemcircuitwithabuilt-inregulatorisillustratedinFig.6-1.Asmallamountofcurrentpassesfromthestatorthroughthediodetriototheregulator.Thisequalizesthevoltageoneithersideoftheindicatorlight,puttingitout,andtriestogroundthroughresistorR3.Whenthestatorvoltagereachesacertainlevel,voltagegoingtogroundthroughresistorR3willincreasetothepointthatitwillcauseZenerdiodeD1toconduct.Forward-biased(voltageappliedindirectioncausingcurrentflow)transistorTR2conductsandtransistorTR3isreverse-biasedoff.ThisturnstransistorTR1off.ThefieldcurrentandsystemvoltageimmediatelydecreasewithTR1off.Fig.6-1Achargingsystemcircuitwithabuilt-inregulatorWhensystemvoltagedecreases,voltagethroughR3decreasesandD1stopsconducting.ThiscausestransistorTR2tobecomereverse-biasedoffandtransistorsTR1andTR3forward-biasedon.Outputvoltageandfieldcurrentwillincrease.Thiscycleisrepeatedthousandsoftimespersecond,holdingalternatorvoltageoutputtoapresetlevel.SuddenvoltagechangeacrossR3ispreventedbycapacitorC1,andexcessivebackcurrentthroughTR1athightemperatureispreventedbyR4.TR1isprotectedbyD2thatpreventsahighinducedvoltageinthefieldwindingwhenTR1isoff.Voltagecontroltemperaturecorrectionisprovidedbyathermistor(resistancedecreasesastemperatureincreases).Computer-ControlledVoltageRegulationMostvehiclestodayhaveseveralelectroniccontrolunits(ECUs)orpowertraincontrolmodules(PCM)thatcontroltheengineandothersystems.ECUcanalsobeusedtocontrolvoltagetothefieldwinding,whicheliminatestheneedforaseparateregulator.ThedisadvantageofthissystemisiftheportionoftheECUthatcontrolsvoltageregulationbecomesdefective,theentireECUmustbereplaced[1].StarterSystemTostartaninternalcombustionengine,itmustbecranked(rotatedbyanoutsidesource).Smalltwo-strokeenginesareoftencrankedbypullingaropewhichcausestheinternalenginepartstorevolve