专业英语ppt课件汽车专业英语ppt课件-与汽车专业英语读译教程配套-宋进桂制作11-U6TB

UNIT6ENGINEELECTRICALSYSTEMSTEXTBDirectIgnitionSystemsandElectronicTriggeringDevices,PROFESSIONALENGLISH,UNIT6ENGINEELECTRICALSYSTEMSTEXTBDirectIgnitionSystemsandElectronicTriggeringDevicesDirectIgnitionSystemElectronicTriggeringDevices,本次课学习内容,本次课学习目标,掌握直接点火系统的组成掌握主要部件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,NEWWORDS,coil-on-pluga.点火线圈在火花塞上的saturationstreinn.饱和(状态),浸润,浸透，饱和度intermittentint(:)mitnta.间歇的,断断续续的misfiremisfaiv.不发火，缺火confirmationknfmeinn.证实,确认,批准verifyverifaiv.检验,校验,查证,核实commandkm:ndn.命令,掌握,司令部；v.命令,指挥，支配recommendrekmendvt.推荐,介绍,劝告,使受欢迎swapswpv.交换；n.交换expectancyikspektnsin.期待,期望,waferweifn.晶片,圆片,薄饼tabtbn.标签,制表符,短小突出部shuttertn.关闭者,百叶窗,快门slitslitn.裂缝,狭长切口；v.切开,撕裂incidenceinsidnsn.发生，影响，发生率,PHRASESANDEXPRESSIONS,autoshutdownrelay自动关闭继电器lifeexpectancy预期寿命，预计使用期限magneticpickup电磁式传感器triggerwheel磁阻轮airgap气隙reluctorwheel磁阻轮Hall-effectswitch霍尔效应开关opticalsensor光电式传感器rotorplate遮光板lightemittingdiode发光二极管(LED)photosensitivediode光电二极管，光敏二极管photodiode光电二极管,DirectIgnitionSystemsandElectronicTriggeringDevicesDirectIgnitionSystemSomeenginesuseadistributorlessignitionsystemthateliminatestheneedforsparkplugwires.Thedirectignitionsystem(DIS)utilizesacoiltowerthatisinstalledontoacoverplateandplugbootsthatfitdirectlyontothesparkplugs.Theignitionmoduleandcoilsareinstalledunderthecoiltower.Thesparkistransmittedtotheplugbootsthroughsecondaryconductorslocatedinthetower.Thissystemoperatesusingthesameprinciplesasthedistributorlessignitionsystem.ElectronicIgnitionSystemswithCoilsConnectedDirectlytotheSparkPlugsTheseEIsystemshavethesamereluctorringandmagneticsensorasotherelectronicinjection(EI)systems.However,ontheseEIsystems,thesparkplugwiresareeliminatedandthecoilsecondaryterminalsareconnecteddirectlytothesparkplugs.,Sincethesparkplugwiresareeliminated,thechanceofhigh-voltageleaksisreduced.Thecoilmoduleandcoilsaremountedunderaplatethatispositionedbetweenthecamcoversontopoftheengine(Fig.6-3).Eachcoilisconnectedtoapairofsparkplugs,andthesparkplugpairsare1-4and2-3.Sincethecoilmodulecontactsthemountingplate,thisplateactsasaheatshield.Themountingplatemustbegroundedtotheenginetoprovideignitionoperation.Remotesparkplugwiresmaybeconnectedbetweenthesparkplugsandthecoilsecondaryterminalsfortestpurposes,butthecoilmountingcovermustbegroundedwithajumperwireduringthistestprocedure.Theoperationandelectricalconnections(Fig.6-4)fortheseEIsystemsaresimilartotheEIsystemexplainedpreviously.ThePCMreducesthesparkadvanceforafewmillisecondsduringtransmissionshiftingtolowertheenginetorqueloadonthetransmissionclutches.,Fig.6-3Ignitionsystemswithcoilsconnecteddirectlytothesparkplugs,Fig.6-4Adistributorlessignitionsystemcircuit,IndependentIgnitionSystem(Coil-On-PlugorCoil-Near-Plug)Theindependentignitionsystemisalsoknownasacoil-on-plugsystemorcoil-near-plugandusesonecoilforeachcylinder.Theindependentignitionsystemmountsanignitioncoilasanassemblydirectlytoasparkplugornearthesparkplugwithaveryshortsecondaryignitionwire.Thecoilonplugdesignallowsforincreasedcoilsaturationtimebetweencylinderfiring.Coilsaturationtimeistheperiodwhencurrentflowsthroughtheprimarywindings,increasingthemagneticfieldgenerated,andtherebyincreasingthesecondaryvoltagewhenrequired1.Misfiresaremorelikelytooccurunderhigherenginespeedsandincreasedloadconditions.Theabilitytoincreasefiringvoltagewhenrequiredlowerstheriskofintermittentmisfires.,Thecoilonplugindependentignitionsystemeitherusesoneignitionmoduletocontroltheprimarycircuitofallcoils(Fig.6-5)orintegratestheignitionmoduleintoeachcoilassembly(Fig.6-6)orintegratestheignitionmoduleintothePCM(CHRYSLER).TheignitionmoduleiscontrolledbythePCM.ThePCMsuppliesanignitiontimingsignaltotheignitionmodule.Next,theignitionmodulecommandsthetransistorsinthedrivercircuittoturnontheprimarycircuitintheindependentcoilcircuit.TheignitionmodulesendsaconfirmationsignalbacktothePCMtoverifythecommand.Thecoilassemblyusesahigh-voltagediodeinthesecondarycircuit(Fig.6-7)forrapidcutoffofthesecondaryignitionvoltage.Iftheignitionmoduleisnotintegratedintothecoilassembly,boththeprimaryandsecondarycircuitsmaybecheckedusingaconventionaldigitalohmmeterforcircuitintegrity.Alwayscomparereadingstomanufacturerspecifications.Itisgenerallyrecommendedtoswapcoilswhentestingforafaultyignitioncoilsinceallcoilsarethesameontheengine.,Fig.6-5Aindependentignitionsystemthatusesoneignitionmoduletocontroltheprimarycircuitofallcoils,Fig.6-6Aindependentignitionsystemthatintegratestheignitionmoduleintoeachcoilassembly,Theindependentignitionsystemwithintegratedignitionmodulesintoeachcoilassemblytypicallyusefourwiresconnectedtotheprimarysideoftheassembly(Fig.6-6).Thefourwiresconsistofbatterypositive,ground,ignitiontimingsignal,andignitionconfirmationsignal.ThePCMusestheignitionconfirmationsignaltodetermineifacoilisnotoperating.Theprimarycircuitsofthesecoilscannotbetestedwithanohmmeter.Someenginesdonothavethephysicalspacetointegratethecoil-on-plugdesign.Inthesesituations,manufacturershaveplacedtheindividualcoilassembliesasclosetothesparkplugsaspossible,typicallyontopofthevalvecover,andintegratedshortplugwiresfromeachofthecoilstotheirrespectivesparkplugs.,Fig.6-7Thecoilassemblyusesahigh-voltagediodeinthesecondarycircuit,Theindependentignitionsystemoffersgreaterreliabilityandalowerincidenceofcylindermisfirescomparedtopastignitionsystems.Thecoil-on-plugsystemeliminatesthesparkplugwires,whichhavebeenacommonsourceofshortsinthepast3.Theindependentignitionsystemhasbecomethepreferredignitionsystembymostvehiclemanufacturers.Thecoil-on-plugsystem,sometimesreferredtoasacoil-over-plugignitionsystem,issubjecttothesameproblemsasprevioussystems,suchasfaultysparkplugs,misfire,hardstart,andno-startconditions.Ifthecrankpositionsensorsignalislost,theignitionsystemwillshutdown.,ElectronicTriggeringDevicesSomesystemsalsoincludeanautoshutdownrelaycontrolledbythePCM,whichsuppliesbatterypowertoboththeignitioncoilsandthefuelinjectors4.2.Whenthestartermotorarmaturebeginstoturn,thestartergearmovesoutandengagestheringgear,whichspinsthecrankshaft.Whentheenginestarts,thedriverbreaksthestarterelectricalcircuitbyreleasingtheignitionkeyswitch.Thiscausesthestartergeartomoveoutofmeshwiththeringgear3.Electronictriggeringdevicessendasignalcurrenttotheignitionmodule,whichthenbreakstheprimarycircuit.Thepartsofthetriggeringdevicedonotwear,whichgivesthemamuchlongerlifeexpectancythancontactpoints.Sincethetriggeringdevicedoesnotwear,enginetimingdoesnotchange.Thisimprovesengineperformance,emissionsoutput,andreliability.Therearethreetypesoftriggeringdevicescurrentlyinuse:magnetic,Halleffectandoptical.,Mostofthetriggeringdevicesareoperatedbyrotationofthedistributorshaft.Sometriggeringdevicesareinstalledintoorontheengineblockandareoperatedbytherotationofthecrankshaftand/orcamshaft.MagneticPickupThemagneticpickupshowninFig.6-8ismountedinthedistributorandreactstodistributorspeed,whichisonehalfofcrankshaftspeed.Thissensorgeneratesalternatingcurrent.Thecurrentproducedissmall(about250millivolts),butcanbereadeasilybytheignitionmodule.Therotatingtoothassemblyiscalledareluctor,ortriggerwheel.Thestationaryassemblyiscalledthepickupcoilorstator.,Fig.6-8Amagneticcrankshaftpositionsensor,Somesensorsaremountednearthecrankshaft.Areluctorwheelispartofthecrankshaftandisplacedatitsmidpoint.Anairgapalsoexistsbetweenthissensorandthereluctor.Whenthesensorisinthemiddleofeachslot,thetransistoristurnedoffandinterruptscurrentflowtotheignitioncoil,causingasparkplugtofire.Theairgapiscriticalonallmagneticsensorsandmustbesettospecifications.Hall-EffectSwitchTheHall-effectswitchcanbemountedinthedistributororatthecrankshaft,Fig.6-9.TheHall-effectsensorisathinwaferofsemiconductormaterialwithvoltageappliedtoitconstantly.Amagnetislocatedoppositethesensor.Thereisanairgapbetweenthesensorandmagnet(Fig.6-9a).,Themagneticfieldactsonthesensoruntilametaltab,usuallycalledashutter,isplacedbetweenthesensorandmagnet(Fig.6-9b).Thismetaltabdoesnottouchthemagnetorsensor.Whencontactbetweenthemagneticfieldandsensorisinterrupted,itcausesitsoutputvoltagetobereduced.Thissignalstheignitionmoduletoturnthepowertransistoroff.Thisinterruptsprimarycurrenttotheignitioncoil,causingittofire.,OpticalSensorTheopticalsensorisusuallylocatedinthedistributor,asshowninFig.6-10a.Therotorplate,Fig.6-10b,hasmanyslitsinitthroughwhichlightpassesfromthelightemittingdiode(LED)tothephotosensitivediode(lightreceiving)5.Astherotorplateturns,itinterruptsthelightbeamfromtheLED)tothephotodiode.Whenthephotodiode