汽车专业英语读译教程 第3版 课件 8-U4TB Operation of the Motronic System

UNIT4

GASOLINEFUELINJECTION

TEXTB

OperationoftheMotronicSystem

PROFESSIONALENGLISH

UNIT4

GASOLINEFUELINJECTION

TEXTB

OperationoftheMotronicSystem

StartControl(Fuel,IgnitionTiming,Air)

Post-Start

Warm-Up

Closed-LoopOperation

Part-ThrottleAcceleration

Full-LoadAcceleration

KnockControl

RPMLimitation

CoastingCut-Off本次课学习内容本次课学习目标掌握MOTRONIC系统的控制原理掌握有关控制原理的专用术语了解翻译技巧—句子成分转换NEWWORDSflood[flʌd]v.充满，淹没，溢出；n.洪水compensate['kɔmpenseit]v.补偿，偿还formation[fɔ:'mei∫ən]n.形成，形成量turbocharge['tə:bout∫ɑ:ʤ]v.用涡轮增压turbo['təbou]n.涡轮增压，涡轮增压器intercooler[ֽintə'ku:lə]n.中间冷却器，中冷器sense[sens]v.理解，感到，感受，检测override[ֽouvə'raid]v.超过（越），越过，压倒，占优势overswing['ouvəswiŋ]v.摆动过大lambda['læmdə]n.λ值，过量空气系数，氧传感器NEWWORDSflood[flʌd]v.充满，淹没，溢出；n.洪水compensate['kɔmpenseit]v.补偿，偿还formation[fɔ:'mei∫ən]n.形成，形成量turbocharge['tə:bout∫ɑ:ʤ]v.用涡轮增压turbo['təbou]n.涡轮增压，涡轮增压器intercooler[ֽintə'ku:lə]n.中间冷却器，中冷器sense[sens]v.理解，感到，感受，检测override[ֽouvə'raid]v.超过（越），越过，压倒，占优势overswing['ouvəswiŋ]v.摆动过大lambda['læmdə]n.λ值，过量空气系数，氧传感器endanger[in'deinʤə]v.危及trait[treit]n.特性，显著的特点harmonics[hɑ:'mɔniks]n.谐波[音]，谐波分量NEWWORDSrecognition[ֽrekəg'ni∫(ə)n]n.承认，赏识，赞誉modify['mɔdifai]v.更改，修改stratification[ֽstrætifi'kei∫ən]n.成层，分层cutback['kʌtbæk]n.减少scope[skoup]n.范围，领域，见识，示波器，指示器simultaneous[ֽsiməl'teinjəs]a.同时的，同时发生的，同步的coast[koust]v.滑行，滑翔，沿海岸航行；n.海岸，沿岸cut-off['kʌtəf]n.切断，关闭，停车coastdown['koustdaun]n.降低，下降，滑行blank[blæŋk]ad.空白的，空着的，没有表情的；n.空白stall[stɔ:l]v.失速，熄火，（速度不够）停车[停止转动]refinement[ri'fainmənt]n.精致，文雅，精巧resume[ri'zju:m]v.恢复,重新开始

PHRASESANDEXPRESSIONS

portinjector进气道喷油器startinjector起动喷油器，冷起动喷油器thermo-timeswitch温控定时开关turbochargedcar涡轮增压轿车air-fuelratio空燃比knocksensor爆燃传感器passengercompartment乘客舱，乘员室knockcontrolregulator爆燃控制调节器besortedfrom与…分开，从…拣出scopeset示波器Inthissection,let'slookatoperatingconditionstoseehowMotroniccontrolsinjectionandignitionaswellasidle-speedbypassairforgoodenginemanagement[1].StartingStartControl,FuelInmostMotronics,startenrichmentisprovidedbytheportinjectorsratherthantheseparatestartinjector/thermo-timeswitch.Forstartcontrol,theimportantinputsarerpmandenginetemperature.Thecontrolunitmonitorscrankingrpm,andalsothenumberofrevolutionssincethetimecrankingbegan[2].Theinjectionpulsesmaybelongerthannormal.

OperationoftheMotronicSystem

OperationoftheMotronicSystem

Butatlowenginetemperatures,thecontrolunitmaydeliverinsteadseveralshorterinjectionpulsesperrevolutiontoimprovestarting.Remember,theseare10millisecondpulsesinapulseperiod,orcrankshaftrevolutiontimeof200ms.Forhotstarts,orhighintakeairtemperatures,timingwillberetardedbecauseahotcylindercanfireeasierwhilethepistonisrisingatcrankingrpm.Retardedtimingpreventsknockingthatcanoccurinhigh-compressionengines,andmaybemaskedbythestartersound.

OperationoftheMotronicSystem

Topreventflooding,fuelquantitywillcutbackafterameasurednumberofrevolutions,oraftertheenginehasreachedacrankingrpmthatistemperaturerelated,forexample200-300rpm.StartControl,IgnitionTimingWithacoldengineatlowcrankingspeeds,timingwillbecontrollednearTDC.Fornormalcrankingrpm,alargeadvanceintimingmightfiretooearly,damagingthestarter.Further,startingwouldbedifficultifnotimpossible.Withacoldengineathighercrankingrpm,however,timingwillbeadvancedforbetterstarting.

OperationoftheMotronicSystem

StartControl,AirAsinL-Jetronic,theidle-speedstabilizerisnormallydrivenopenmorebyincreaseddwellsignalstoprovideextrabypassairforcoldstarting.Post-StartPost-start-the5-30secondswhenyouwanttheenginetokeeprunningafteryoureleasethekeyfromCRANK-isaffectedbyenginetemperatureaswellasatimerinthecontrolunit.Colderenginesgetmorefuelinjected.Also,colderenginesgetmoretimingadvance.Basedonthestart-uptemperature,andthetimesincestart,post-startenrichmentisgraduallyreduced.Theidle-speedstabilizermaintainsrpm.

OperationoftheMotronicSystem

Warm-UpDuringwarmup,themostimportantinput,besidesengineloadandrpmforbasicpulsetime,isenginetemperature.ThecontrolunitincludesaROMmapofwarm-upcharacteristicstoapplyacorrectionfactorbasedonloadandenginespeed,greateratlowloadsandrpmthanathighloadsandrpms[3],SeeFig.4-7.Controlunitoutputsincludeinjectionpulsesforthepropermixture,ignitiontimingfordriveability(advanceunderpart-loadacceleration,retardondecelerationtoreduceHCemissions),andidlestabilizationtohelpkeeptheenginerunningatidle.

OperationoftheMotronicSystem

Remember,duringwarm-up,thetemperatureofthelambdasensorisimportant.Unheatedlambdasensorscanbeheatedfasterbychangingignitiontiming.Motronicretardstimingtocauseahotterexhaust.Thatheatstheoxygensensormuchquickerandalsoheatsthecatalyticconverterfasterformoreefficiency.Fig.4-7Warm-upcorrectionfactors

OperationoftheMotronicSystem

Closed-LoopOperation

Basedontheinputsofawarmengine,andoxygen-sensorvoltagewhenhot,thesystemnormallyoperatesclosed-loop.Theoxygensensorfine-tunesthefuel-injectiondeliveryforproperair-fuelratios.Foreverycombinationofinputs,thecontrolunitlooksinitsmemoryforthebesttiming,thebestdwellangle,thebestlambda,orair-fuelratio[4].Onthebasisofenginetemperature,Motroniccontrolsignitiontimingwithindependentcalibrationsforstarting,idling,deceleration,andacceleration,bothpart-loadandfull-loadorWOT(WideOpenThrottle).Forexample,controloftimingadvanceatidlereducestheneedforidlefuelenrichment.

OperationoftheMotronicSystem

OperationoftheMotronicSystem

Part-ThrottleAccelerationJustasinL-Jetronic,theoverswingsignaloftheair-flowsensorincreasesfueldelivery,compensatedbytemperature.Forair-masssensors,therateofincreaseofthevoltagesignalsacceleration.Duringpart-throttleacceleration,thenormalpulseforsteadycruiseincreasesforjustaboutonesecondwhileyouopenthethrottle.Thenthepulsecutsbackevenastheenginepicksupspeed;thissavesfuelandreducesemissions.

OperationoftheMotronicSystem

Inaddition,ignitiontimingcanberetardedtoavoidthebriefaccelerationknockthatcouldoccurforthefirstfewcyclesofengineacceleration.IgnitiontimingcontrolalsoreducestheformationofNOx,whichisnormalwithacceleration.Rateofignitiontimingchangeisalsocontrolled;·toavoidknocking,thecontrolunitallowsfastchange·toreducejerkduringtransition,thecontrolunitnormallychangesignitionadvancegraduallyFull-LoadAccelerationFull-loadenrichmentissignaledbythethrottleswitch.Aslongasthethrottleisfull-open,longerinjectionpulseswillbedeliveredforenrichment.Richmixturesreducethetendencytoknock.Thisenrichmentisbasedsolelyonrpm,andprogrammedfromenginetests.Theair-flowsignalisignored.Atthesametimeasrpmandthrottlepositioncontrolfull-loadinjectionenrichment,airtemperatureandenginetemperaturesupplyinputstocontroltheadvanceofignitiontimingforbestaccelerationwithoutapproachingknock[5].

OperationoftheMotronicSystem

OperationoftheMotronicSystem

Forengineswithoutknocksensors,timingadvanceisbasedonenginetestdatastoredinthetimingmap.Theenginecanoperateclosetotheignition-advancelimit,developingmaximumtorqueovertheentirerpmrangewithleastchanceofknockingbasedonthreefactors:1.thetimingcurvecanbeprogrammedspecificallyforeachengineoperatingpoint。2.thesystemoperateswithnarrowtolerancesandfreedomfrommechanicalwear3.timingiscompensatedaccordingtoenginetemperatureandintake-airtemperature

OperationoftheMotronicSystem

Insometurbochargedcars,asecondair-temperaturesensorismountedinthemanifolddownstreamoftheturboortheintercoolertosensethetemperatureoftheairenteringtheengine.Thisisaspecialfast-responsesensoroverridingthefirstair-temperaturesensortohandlethequickchangesintemperaturethatcanoccurduringfull-throttleacceleration.

OperationoftheMotronicSystem

KnockControlProgrammedtimingaccuracy,evenwithcompensations,canbeimprovedbyaknock-sensorsystemthatcausestimingtoadvancetojustbeforethepointwhereknockcoulddamagetheengine.Withaknocksensorcontrollingtimingadvanceinaseparateclosed-loopsystem,poweroutputcanbemaximizedwithoutendangeringtheengine.Someengines,particularlyturbochargedengines,includeknocksensorstopickupvibrationsfromtheengineatthefirstsignsofknock.TSomesystemsusetwocontroltraits,mountedinsidethepassengercompartment,oneforMotronic,andarelatedknockcontrolregulator,calledKLR.Knock-sensinginputshelpbothcontrolunitstoworktogether.hefirstandfastestoutputchangesthetiming.Iftheengineisturbocharged,thesecondoutputcontrolstheboost.IntheMotronicknownasML3,knocksensingandenginemanagementarecombinedinonecontrolunit.Whentheengineknocks,itvibrateswithcharacteristicfrequenciesof5-10kilohertztogetherwithcorrespondingharmonics.Thesevibrationsmustbesortedfromotherenginevibrationsinarecognitioncircuitinthecontrolunit.

OperationoftheMotronicSystem

OperationoftheMotronicSystem

TheMotroniccontrolunithasaccurateinformationoncrankshaftpositionandfiringordersoitispossibletodeterminewhichcylinderisknocking(onecylinderusuallyknocksbeforetheothers).Further,circuitsoperatewithsuchspeedthatignitiontimingcanberetardedonlyfortheknockingcylinder,andadvancedforthefiringofthenextcylinder.Eachknocksignalcanmodifytiminginmilliseconds.Whenignitionretardeliminatestheknock,timingisadvancedslowlyinstepstotheoriginalvalueoruntilknockingagainoccurs.

OperationoftheMotronicSystem

Onturbochargedengines,ifknockcontinuesforseconds,boostcontrolreducesmanifoldpressure.Knockcontrolpermitsmoreboost,andhighercompressionratiosforgreaterpower.Automatically,ittendstoadjustfortheoctane-ratingofthefuelbeingburned.Withprecisecontrolofignitiontimingandturboboost,enginescanbedesignedwithhighercompressionratiosforgreaterpoweroutput.Onallengines,theknockinglimitsdependonmanyfactors:·intakeairtemperature·enginetemperature·enginedeposits·combustion-chamberform·mixturecomposition,A/Fratio,andstratification·fuelquality·airdensity

OperationoftheMotronicSystem

OperationoftheMotronicSystem

Foryears,drivershaveknownthatusinghigher-octanefueldidnotaddtoenginepowerunlessignitiontimingwasadjustedatthedistributortotakeadvantageoftheimprovedanti-knockindex.Now,withknocksensorsandclosed-loopignition-advancecontrol,poweroutputcandependontheanti-knockindexofthefuelbeingburned.Itisnotunusualtoseeenginepowerspecificationsincludetheanti-knockindexofthefueltobeused[6].

OperationoftheMotronicSystem

RPMLimitationIftherpmsignalisgreaterthanmax-allowablerpmstoredinthecomputermemory,thecontrol-unitsignalsacutbackofthefuel-injection