4-汽车专业英语课件-汽车设计制造部分-section 4汽车专业英语ppt课件-修改2017022714 starging system designVIP

Chapter11AutomotiveDesign,DesignofDryClutchesEngineandTransmissionMatching11.1Changingratios-matchingofthetransmissiontothevehicle11.2Brakingsystemdesignmethodology;11.4DevelopingandTestingtheEngineManagementSoftware11.3StartingSystemDesign,学习内容,本次课学习内容、目标和重点难点,学习目标,难点重点,AutomotiveDesign11.3StartingSystemDesign,1.掌握有关起动系统设计的专业术语与词汇2.掌握长句分析要点，提高翻译技巧3.了解离合器设计需要考虑的几个重要问题,1.重点：长句翻译方法；相关术语的记忆2.难点：长句翻译,回顾,起动系统电学术语,AutomotiveDesignStartingSystemDesign,NewWords,AutomotiveDesignStartingSystemDesign,NewWords,AutomotiveDesignStartingSystemDesign,1.EnginestartingrequirementsAninternalcombustionenginerequiresthefollowingcriteriainordertostartandcontinuerunning:Combustiblemixture.Compressionstroke.Aformofignition.Theminimumstartingspeed(about100rev/min).Inordertoproducethefirstthreeofthese,theminimumstartingspeedmustbeachieved.Thisiswheretheelectricstartercomesin.Theabilitytoreachthisminimumspeedisagaindependentonanumberoffactors.Ratedvoltageofthestartingsystem.Lowestpossibletemperatureatwhichitmuststillbepossibletostarttheengine.Thisisknownasthestartinglimittemperature.,AutomotiveDesignStartingSystemDesign,Enginecrankingresistance.Inotherwordsthetorquerequiredtocranktheengineatitsstartinglimittemperature(includingtheinitialstalledtorque).Batterycharacteristics.VoltagedropbetweenthebatteryandthestarterStarter-to-ringgearratio.CharacteristicsofthestarterMinimumcrankingspeedoftheengineatthestartinglimittemperature.Itisnotpossibletoviewthestarterasanisolatedcomponentwithinthevehicleelectricalsystem.Thebatteryinparticularisofprimeimportance.Anotherparticularlyimportantconsiderationinrelationtoenginestartingrequirementsisthestartinglimittemperature.,AutomotiveDesignStartingSystemDesign,AutomotiveDesignStartingSystemDesign,Figure11-5startertorqueandtheenginecrankingtorque,Figure11-5showshow,astemperaturedecreases,startertorquealsodecreasesandthetorquerequiredtocranktheenginetoitsminimumspeedincreases.,AutomotiveDesignStartingSystemDesign,Typicalstartinglimittemperaturesare-18to-25forpassengercarsand-15to-20fortrucksandbuses.Figuresfromstartermanufacturersarenormallyquotedatboth+20and-20.5.2StartingsystemdesignThestartingsystemofanyvehiclemustmeetanumberofcriteriainexcessof(超过,较.为多)theeightlistedabove.Longservicelifeandmaintenancefree.Continuousreadinesstooperate.Robust,suchastowithstandstartingforces,vibration,corrosionandtemperaturecycles.Lowestpossiblesizeandweight.,AutomotiveDesignStartingSystemDesign,Figure11-6Startersystemgenerallayout,AutomotiveDesignStartingSystemDesign,Figure11-6showsthestartingsystemgenerallayout.Itisimportanttodeterminetheminimumcrankingspeedfortheparticularengine.Thisvariesconsiderablywiththedesignandtypeofengine.Theratedvoltageofthesystemforpassengercarsis,almostwithoutexception,12V.Trucksandbusesaregenerally24Vasthisallowstheuseofhalfthecurrentthatwouldberequiredwitha12Vsystemtoproducethesamepower.Itwillalsoconsiderablyreducethevoltagedropinthewiring,asthelengthofwiresusedoncommercialvehiclesisoftengreaterthanpassengercars.,AutomotiveDesignStartingSystemDesign,Theratedoutputofastartermotorcanbedeterminedonatestbench.Abatteryofmaximumcapacityforthestarter,whichhasa20%dropincapacityat-20,isconnectedtothestarterbyacablewitharesistanceof1m.Thesecriteriawillensurethestarterisabletooperateevenunderthemostadverseconditions.Theactualoutputofthestartercannowbemeasuredundertypicaloperatingconditions.Theratedpowerofthemotorcorrespondstothepowerdrawnfromthebatterylesscopperlosses(duetotheresistanceofthecircuit),ironlosses(duetoeddycurrentsbeinginducedintheironpartsofthemotor)andfrictionlosses.,AutomotiveDesignStartingSystemDesign,Figure11-7showsanequivalentcircuitforastarterandbattery.Thisindicateshowthestarteroutputisverymuchdeterminedbylineresistanceandbatteryinternalresistance.Thelowerthetotalresistance,thehighertheoutputfromthestarter.Therearetwootherconsiderationswhendesigningastartingsystem.Thelocationofthestarterontheengineisusuallypre-determined,butthepositionofthebatterymustbeconsidered.Otherconstraints（限制）maydeterminethis,butifthebatteryisclosertothestarterthecableswillbeshorter.Alongerrunwillmeancableswithagreatercross-sectionareneededtoensurealowresistance.Dependingontheintendeduseofthevehicle,specialsealingarrangementsonthestartermaybenecessarytopreventtheingressofcontaminants.Thismaybeappropriateforoff-roadvehicles.,Chapter11AutomotiveDesign11.3StartingSystemDesign,Figure11-7Equivalentcircuitforastartersystem,AutomotiveDesignStartingSystemDesign,5.3ChoosingastartermotorAsaguide,thestartermotormustmeetallthecriteriapreviouslydiscussed.ReferringbacktoFigure5-1(thedatashowingenginecrankingtorquecomparedwithminimumcrankingspeed)willdeterminethetorquerequiredfromthestarter.Manufacturersofstartermotorsprovidedataintheformofcharacteristiccurves.Thesearediscussedinmoredetailinthenextsection.Thedatawillshowthetorque,speed,powerandcurrentconsumptionofthestarterat+20and-20.Thepowerratingofthemotorisquotedasthemaximumoutputat-20usingtherecommendedbattery.Figure11-8showshowtherequiredpoweroutputofthestarterrelatestotheenginesize.,Chapter11AutomotiveDesign11.3StartingSystemDesign,Figure11-8Poweroutputofthestartercomparedwithenginesize,Chapter11AutomotiveDesign11.3StartingSystemDesign,Asaverygeneralguidethestalled(locked)startertorquerequiredperlitreofenginecapacityatthestartinglimittemperatureisasshowninTable11-1.Agreatertorqueisrequiredforengineswithalowernumberofcylindersduetothegreaterpistondisplacementpercylinder.Thiswilldeterminethepeaktorquevalues.Theothermainfactoriscompressionratio.Toillustratethelinkbetweentorqueandpower,wecanassumethat,undertheworstconditions(-20),afour-cylinder2-litreenginerequires480Nmtoovercomestaticfrictionand160Nmtomaintaintheminimumcrankingspeedof100rev/min.Withastarterpinion-t