1、Lesson1HistoryoftheautomobileLesson2StructureofAutomobilesLesson2StructureofAutomobilesAself-propelledlandvehicleisusuallyhavingfourwheelsandaninternalcombustionengine,usedprimarilyforpersonaltransportation.LayoutofamodernautomobileTheautomobilebodyistheass
2、emblyofsheet-metal,fiberglass,plastic,orcomposite-materialpanelstogetherwithwindows,doors,seats,trimandupholstery,glass,andotherpartsthatformenclosuresforthepassenger,engine,andluggagecompartments.Theassembledbodystructuremayattachthroughrubbermountstoasepara
3、teorfullframe(body-on-frameconstruction),orthebodyandframemaybeintegrated(unitized-bodyconstruction).Inthelattermethod,theframe,bodyparts,andfloorpanareweldedtogethertoformasingleunitthathasenergy-absorbingfrontandrearstructures,andanchorsfortheengine,s
4、uspension,steering,andpower-traincomponents.Athirdtypeofbodyconstructionisthespaceframewhichismadeofweldedsteelstampings.Similartothetubechassisandrollcagecombinationusedinrace-carconstruction,non-load-carryingplasticouterpanelsfastentothespaceframetoform
5、thebody.Theframeisthemainstructuralmembertowhichallothermechanicalchassispartsandthebodyareassembledtomakeacompletevehicle.Inoldervehicledesigns,theframeisaseparaterigidstructure;newerpassenger-cardesignshavetheframeandbodystructurecombinedintoaninte
6、gralunit,orunitizedbody.Subframesandtheirassembledcomponentsattachtothesiderailsatthefrontandrearoftheunitizedbody.Thefrontsubframecarriestheengine,transmissionortransaxle,lowerfrontsuspension,andothermechanicalparts.Therearsubframe,ifused,carriestherea
7、rsuspensionandrearaxle.Thesuspensionsupportstheweightofthevehicle,absorbsroadshocks,transmitsbrake-reactionforces,helpsmaintaintractionbetweenthetiresandtheroad,andholdsthewheelsinalignmentwhileallowingthedrivertosteerthevehicleoverawiderangeofspeedand
8、loadconditions.Theactionofthesuspensionincreasesridingcomfort,improvesdrivingsafety,andreducesstrainonvehiclecomponents,occupants,andcargo.Thespringsmaybecoil,leaf,torsionbar,orair.Mostautomotivevehicleshavecoilspringsatthefrontandeithercoilorleafspring
9、sattherear.Thesteeringsystemenablesthedrivertoturnthefrontwheelsleftorrighttocontrolthedirectionofvehicletravel.Therotarymotionofthesteeringwheelischangedtolinearmotioninthesteeringgear,whichislocatedatthelowerendofthesteeringshaft.Thelinearmotio
10、nistransferredthroughthesteeringlinkagetothesteeringknuckles,towhichthefrontwheelsaremounted.Steeringsystemsareclassedaseithermanualsteeringorpowersteering,withpowerassistprovidedhydraulicallyorbyanelectricmotor.Abrakeisadevicethatusesacontrolledforce
11、toreducethespeedoforstopamovingvehicle,ortoholdthevehiclestationary.Theautomobilehasafrictionbrakeateachwheel.Whenthebrakeisapplied,astationarysurfacemovesintocontactwithamovingsurface.Theresistancetorelativemotionorrubbingactionbetweenthetwosurface
12、sslowsthemovingsurface,whichslowsandstopsthevehicle.Theenginesuppliesthepowertomovethevehicle.Thepowerisavailablefromtheenginecrankshaftafterafuel,usuallygasoline,isburnedintheenginecylinders.Mostautomotiveenginesarelocatedatthefrontofthevehicleandd
13、riveeithertherearwheelsorthefrontwheelsthroughadrivetrainorpowertrainmadeupofgears,shafts,andothermechanicalandhydrauliccomponents.Mostautomotivevehiclesarepoweredbyaspark-ignitionfour-stroke-cycleinternalcombustionengine.Theinlinefour-cylinderengineandV-t
14、ypesix-cylinderenginearethemostwidelyused,withV-8enginesalsocommon.Otherautomotiveengineshavethree,five,ten,andtwelvecylinders.Somepassengercarsandtruckshavedieselengines.Someautomotivespark-ignitionanddieselenginesareequippedwithasuperchargerorturbocharger
15、.Mostautomotiveengineshaveelectronicfuelinjectioninsteadofacarburetor.Acomputer-controlledelectronicenginecontrolsystemautomaticallymanagesvariousemissionsdevicesandnumerousfunctionsofengineoperation,includingthefuelinjectionandsparktiming.Thisallowsoptimizingp
16、owerandfueleconomywhileminimizingexhaustemissions.Thepoweravailablefromtheenginecrankshafttodoworkistransmittedtothedrivewheelsbythepowertrain,ordrivetrain.Inthefront-enginerear-drivevehicle,thepowertrainconsistsofaclutchandmanualtransmission,oratorque
17、converterandanautomatictransmission;driveshaftsandHooke(Cardan)universaljoints;andreardriveaxlethatincludesthefinaldrive,differential,andwheelaxleshafts.Inthetypicalfront-enginefront-drivevehicle,thepowertrainconsistsofaclutchandmanualtransaxle,oratorquec
18、onverterandanautomatictransaxle.Thefinaldriveanddifferentialaredesignedintothetransaxle,anddrivethewheelsthroughhalf-shaftswithconstant-velocity(CV)universaljoints.Thetransmissionisthedeviceinthepowertrainthatprovidesdifferentforwardgearratiosbetweentheengi
19、neanddrivewheels,aswellasneutralandreverse.Thetwogeneralclassificationsoftransmissionaremanualtransmission,whichthedrivershiftsbyhand,andautomatictransmission,whichshiftsautomatically.Toshiftamanualtransmission,theclutchmustfirstbedisengaged.However,someve
20、hicleshaveautomaticclutchdisengagementformanualtransmissions,whileothervehicleshavealimitedmanual-shiftcapabilityforautomatictransmissions.Inthepowertrain,thefinaldriveisthespeed-reductiongearsetthatdrivesthedifferential.Thefinaldriveismadeupofalargeringg
21、eardrivenbyasmallerpinion,orpiniongear.Thisprovidesagearreductionofabout3:1;theexactvaluecanbetailoredtotheengine,transmission,weightofthevehicle,andperformanceorfueleconomydesired.Indriveaxles,thedifferentialisthegearassemblybetweenaxleshaftsthatper
22、mitsonewheeltorotateataspeeddifferentfromthatoftheother(ifnecessary),whiletransmittingtorquefromthefinal-driveringgeartotheaxleshafts.Whenthevehicleiscorneringormakingaturn,thedifferentialallowstheoutsidewheeltotravelagreaterdistancethantheinsidewhe
23、el;otherwise,onewheelwouldskid,causingtirewearandpartiallossofcontrol.Awheelisadiscoraseriesofspokeswithahubatthecenterandarimaroundtheoutsideformountingofthetire.Thewheelsofavehiclemusthavesufficientstrengthandresiliencytocarrytheweightofthe
24、vehicle,transferdrivingandbrakingtorquetothetires,andwithstandsidethrustsoverawiderangeofspeedandroadconditions.Wheelsizeisprimarilydeterminedbytheload-bearingstrengthofthetire.Theuseofsolid-stateelectronicdevicesintheautomobilebeganduringthe1960s,when
25、theelectromechanicalvoltageregulatorofthealternator,wasreplacedbyatransistorizedvoltageregulator.Thiswasfollowedinthe1970sbyelectronicignition,fuelinjection,andcruisecontrol.Sincethen,electronicdevicesandsystemsontheautomobilehaveproliferated.Theseincludeengi
26、neandpowertraincontrol,airbags,antilockbraking,tractioncontrol,suspensionandridecontrol,remotekeylessentry,memoryseats,driverinformationandnavigationsystems,cellulartelephoneandmobilecommunicationssystems,andonboarddiagnostics.Theself-diagnosticcapabilityofthev
27、ehiclecomputer,power-trainorenginecontrolmodule,orsystemcontrollermaybeaidedbyamemorythatstoresinformationaboutmalfunctionsthathaveoccurredandperhapstemporarilydisappeared.Whenrecalledfromthememory,thisinformationcanhelptheservicetechniciandiagnoseandrepair
28、thevehiclemorequickly,accurately,andreliably.Thanksforyourpresence!Aself-propelledlandvehicleisusuallyhavingfourwheelsandaninternalcombustionengine,usedprimarilyforpersonaltransportation.LayoutofamodernautomobileTheautomobilebodyistheassemblyofsheet-metal,f
29、iberglass,plastic,orcomposite-materialpanelstogetherwithwindows,doors,seats,trimandupholstery,glass,andotherpartsthatformenclosuresforthepassenger,engine,andluggagecompartments.Theassembledbodystructuremayattachthroughrubbermountstoaseparateorfullframe(body-
30、on-frameconstruction),orthebodyandframemaybeintegrated(unitized-bodyconstruction).Inthelattermethod,theframe,bodyparts,andfloorpanareweldedtogethertoformasingleunitthathasenergy-absorbingfrontandrearstructures,andanchorsfortheengine,suspension,steering,an
31、dpower-traincomponents.Athirdtypeofbodyconstructionisthespaceframewhichismadeofweldedsteelstampings.Similartothetubechassisandrollcagecombinationusedinrace-carconstruction,non-load-carryingplasticouterpanelsfastentothespaceframetoformthebody.Theframeis
32、themainstructuralmembertowhichallothermechanicalchassispartsandthebodyareassembledtomakeacompletevehicle.Inoldervehicledesigns,theframeisaseparaterigidstructure;newerpassenger-cardesignshavetheframeandbodystructurecombinedintoanintegralunit,orunitized
33、body.Subframesandtheirassembledcomponentsattachtothesiderailsatthefrontandrearoftheunitizedbody.Thefrontsubframecarriestheengine,transmissionortransaxle,lowerfrontsuspension,andothermechanicalparts.Therearsubframe,ifused,carriestherearsuspensionandreara
34、xle.Thesuspensionsupportstheweightofthevehicle,absorbsroadshocks,transmitsbrake-reactionforces,helpsmaintaintractionbetweenthetiresandtheroad,andholdsthewheelsinalignmentwhileallowingthedrivertosteerthevehicleoverawiderangeofspeedandloadconditions.Thea
35、ctionofthesuspensionincreasesridingcomfort,improvesdrivingsafety,andreducesstrainonvehiclecomponents,occupants,andcargo.Thespringsmaybecoil,leaf,torsionbar,orair.Mostautomotivevehicleshavecoilspringsatthefrontandeithercoilorleafspringsattherear.Thestee
36、ringsystemenablesthedrivertoturnthefrontwheelsleftorrighttocontrolthedirectionofvehicletravel.Therotarymotionofthesteeringwheelischangedtolinearmotioninthesteeringgear,whichislocatedatthelowerendofthesteeringshaft.Thelinearmotionistransferredthroug
37、hthesteeringlinkagetothesteeringknuckles,towhichthefrontwheelsaremounted.Steeringsystemsareclassedaseithermanualsteeringorpowersteering,withpowerassistprovidedhydraulicallyorbyanelectricmotor.Abrakeisadevicethatusesacontrolledforcetoreducethespeedof
38、orstopamovingvehicle,ortoholdthevehiclestationary.Theautomobilehasafrictionbrakeateachwheel.Whenthebrakeisapplied,astationarysurfacemovesintocontactwithamovingsurface.Theresistancetorelativemotionorrubbingactionbetweenthetwosurfacesslowsthemovingsurf
39、ace,whichslowsandstopsthevehicle.Theenginesuppliesthepowertomovethevehicle.Thepowerisavailablefromtheenginecrankshaftafterafuel,usuallygasoline,isburnedintheenginecylinders.Mostautomotiveenginesarelocatedatthefrontofthevehicleanddriveeithertherearwh
40、eelsorthefrontwheelsthroughadrivetrainorpowertrainmadeupofgears,shafts,andothermechanicalandhydrauliccomponents.Mostautomotivevehiclesarepoweredbyaspark-ignitionfour-stroke-cycleinternalcombustionengine.Theinlinefour-cylinderengineandV-typesix-cylinderengine
41、arethemostwidelyused,withV-8enginesalsocommon.Otherautomotiveengineshavethree,five,ten,andtwelvecylinders.Somepassengercarsandtruckshavedieselengines.Someautomotivespark-ignitionanddieselenginesareequippedwithasuperchargerorturbocharger.Mostautomotiveengin
42、eshaveelectronicfuelinjectioninsteadofacarburetor.Acomputer-controlledelectronicenginecontrolsystemautomaticallymanagesvariousemissionsdevicesandnumerousfunctionsofengineoperation,includingthefuelinjectionandsparktiming.Thisallowsoptimizingpowerandfueleconomyw
43、hileminimizingexhaustemissions.Thepoweravailablefromtheenginecrankshafttodoworkistransmittedtothedrivewheelsbythepowertrain,ordrivetrain.Inthefront-enginerear-drivevehicle,thepowertrainconsistsofaclutchandmanualtransmission,oratorqueconverterandanautom
44、atictransmission;driveshaftsandHooke(Cardan)universaljoints;andreardriveaxlethatincludesthefinaldrive,differential,andwheelaxleshafts.Inthetypicalfront-enginefront-drivevehicle,thepowertrainconsistsofaclutchandmanualtransaxle,oratorqueconverterandanautomat
45、ictransaxle.Thefinaldriveanddifferentialaredesignedintothetransaxle,anddrivethewheelsthroughhalf-shaftswithconstant-velocity(CV)universaljoints.Thetransmissionisthedeviceinthepowertrainthatprovidesdifferentforwardgearratiosbetweentheengineanddrivewheels,as
46、wellasneutralandreverse.Thetwogeneralclassificationsoftransmissionaremanualtransmission,whichthedrivershiftsbyhand,andautomatictransmission,whichshiftsautomatically.Toshiftamanualtransmission,theclutchmustfirstbedisengaged.However,somevehicleshaveautomaticc
47、lutchdisengagementformanualtransmissions,whileothervehicleshavealimitedmanual-shiftcapabilityforautomatictransmissions.Inthepowertrain,thefinaldriveisthespeed-reductiongearsetthatdrivesthedifferential.Thefinaldriveismadeupofalargeringgeardrivenbyasmaller
48、pinion,orpiniongear.Thisprovidesagearreductionofabout3:1;theexactvaluecanbetailoredtotheengine,transmission,weightofthevehicle,andperformanceorfueleconomydesired.Indriveaxles,thedifferentialisthegearassemblybetweenaxleshaftsthatpermitsonewheeltorotat
49、eataspeeddifferentfromthatoftheother(ifnecessary),whiletransmittingtorquefromthefinal-driveringgeartotheaxleshafts.Whenthevehicleiscorneringormakingaturn,thedifferentialallowstheoutsidewheeltotravelagreaterdistancethantheinsidewheel;otherwise,onewhee
50、lwouldskid,causingtirewearandpartiallossofcontrol.Awheelisadiscoraseriesofspokeswithahubatthecenterandarimaroundtheoutsideformountingofthetire.Thewheelsofavehiclemusthavesufficientstrengthandresiliencytocarrytheweightofthevehicle,transferdrivi
51、ngandbrakingtorquetothetires,andwithstandsidethrustsoverawiderangeofspeedandroadconditions.Wheelsizeisprimarilydeterminedbytheload-bearingstrengthofthetire.Theuseofsolid-stateelectronicdevicesintheautomobilebeganduringthe1960s,whentheelectromechanicalv
52、oltageregulatorofthealternator,wasreplacedbyatransistorizedvoltageregulator.Thiswasfollowedinthe1970sbyelectronicignition,fuelinjection,andcruisecontrol.Sincethen,electronicdevicesandsystemsontheautomobilehaveproliferated.Theseincludeengineandpowertraincont
53、rol,airbags,antilockbraking,tractioncontrol,suspensionandridecontrol,remotekeylessentry,memoryseats,driverinformationandnavigationsystems,cellulartelephoneandmobilecommunicationssystems,andonboarddiagnostics.Theself-diagnosticcapabilityofthevehiclecomputer,power-
54、trainorenginecontrolmodule,orsystemcontrollermaybeaidedbyamemorythatstoresinformationaboutmalfunctionsthathaveoccurredandperhapstemporarilydisappeared.Whenrecalledfromthememory,thisinformationcanhelptheservicetechniciandiagnoseandrepairthevehiclemorequickl
55、y,accurately,andreliably.Thanksforyourpresence!Lesson2StructureofAutomobilesAself-propelledlandvehicleisusuallyhavingfourwheelsandaninternalcombustionengine,usedprimarilyforpersonaltransportation.LayoutofamodernautomobileTheautomobilebodyistheassemblyofshe
56、et-metal,fiberglass,plastic,orcomposite-materialpanelstogetherwithwindows,doors,seats,trimandupholstery,glass,andotherpartsthatformenclosuresforthepassenger,engine,andluggagecompartments.Theassembledbodystructuremayattachthroughrubbermountstoaseparateorfullf
57、rame(body-on-frameconstruction),orthebodyandframemaybeintegrated(unitized-bodyconstruction).Inthelattermethod,theframe,bodyparts,andfloorpanareweldedtogethertoformasingleunitthathasenergy-absorbingfrontandrearstructures,andanchorsfortheengine,suspension,s
58、teering,andpower-traincomponents.Athirdtypeofbodyconstructionisthespaceframewhichismadeofweldedsteelstampings.Similartothetubechassisandrollcagecombinationusedinrace-carconstruction,non-load-carryingplasticouterpanelsfastentothespaceframetoformthebody.T
59、heframeisthemainstructuralmembertowhichallothermechanicalchassispartsandthebodyareassembledtomakeacompletevehicle.Inoldervehicledesigns,theframeisaseparaterigidstructure;newerpassenger-cardesignshavetheframeandbodystructurecombinedintoanintegralunit,o
60、runitizedbody.Subframesandtheirassembledcomponentsattachtothesiderailsatthefrontandrearoftheunitizedbody.Thefrontsubframecarriestheengine,transmissionortransaxle,lowerfrontsuspension,andothermechanicalparts.Therearsubframe,ifused,carriestherearsuspension