汽車實(shí)用英語Unit3EngineMechanicalSystemServiceUponcompletionofthisunit,youshouldbeableto:OverallObjectives總體目標(biāo)?Learnkeytermsaboutenginemechanicalsysteminthisunit?Understandtherepairingprocessofeveryassembly?UsemaintenancemanualtodealwiththepracticalproblemsTask3.1InspectingEngineAssembly發(fā)動(dòng)機(jī)總成的檢查Task3.2ReplacingChainSub-assembly正時(shí)鏈條的更換Task3.3InspectingCrankshaftandPiston曲軸和活塞的檢查Task3.4OverhaulingCylinderHead氣缸蓋的檢修Task3.5ReplacingCamshaft更換凸輪軸TasksIntroduction任務(wù)導(dǎo)入Task3.1Inspectingengineassembly發(fā)動(dòng)機(jī)總成檢修Task3.2Overhaulingcylinderblockassembly氣缸體檢修Task3.3InspectingcrankshaftandpistonTask3.4OverhaulingcylinderheadTask3.5ReplacingcamshaftTask3.6Replacingchainsub-assemblyTasksIntroduction任務(wù)導(dǎo)入Servicingenginemechanicalsystemdescribestheactofinspectingtheconditionofengineassemblyandreplacingparts.Properoperationiscriticaltoensuretheenginerunningsafely,smoothlyandcorrectively.Thefollowingtasks(e.g.overhaulingcylinderblockassembly,inspectingcrankshaftandpiston,replacingcamshaft,replacingchainsub-assemblyetc.)aretheimportantitemsinenginemechanicalsystemtoavoidmajordamageorforsafetyreasons.TaskDescription任務(wù)描述

Task3.1InspectingengineassemblyLearningPreparation學(xué)習(xí)準(zhǔn)備inspecting檢查engineassembly發(fā)動(dòng)機(jī)總成coolingsystem冷卻系統(tǒng)radiatorcap散熱器蓋install安裝reinstall重新安裝

Keyterms:LearningPreparation學(xué)習(xí)準(zhǔn)備fin散熱器片compressedair壓縮空氣oilpressure油壓socketwrench套筒扳手oilpressureswitch油壓開關(guān)Keyterms:Step1Amaintenancecaseisprovided;Step2Learntheprocessofinspectingengineassemblyviaamaintenancemanual;Step3Requirestudentstograspthekeytermsinthistask;Step4Trytodescribetheprocessofengineassemblyinspection;Step5Studentsreadrelativematerial;Step6AssessmentPlanandImplement計(jì)劃和實(shí)施()1.Theenginecoolantlevelshouldbebetweenthe”LOW”and”FULL”line.()2.Youcanremovetheradiatorcapwhiletheengineandradiatorarestillhot,asfluidandsteamcanbeblownoutunderpressure.()3.Oillevelshouldbebetweenthe”L”and”F”marksontheoillevelgage.()4.CheckidlespeedwithcoolingfanON.()5.Ifaddingoilhelpsthecompression,itislikelythatthepistonringsand/orcylinderborearewornordamaged.AssessmentandFeedback評(píng)價(jià)和反饋TrueorFalse()6.Ifcompressionpressurestayslow,theremaybeleakagepastthegasket.()7.Theminimumcompressionpressureis1,500kPa(10.2kgf·cm2,145psi).()8.Theengineidlespeedis700–800rpm.()9.Ifthedistancebetweenthesteamcleanerandcoreistooclose,thereisapossibilityofdamagingthefins.()10.Iffinsareclogged,washthemwithgasolinecleaneranddrywithcompressedair.AssessmentandFeedback評(píng)價(jià)和反饋TrueorFalseAnenginewhichiscalledthe“heart”ofavehicleisusedtosupplypowerforanautomobile.Generally,anautomobileisoperatedbyinternalcombustionengine（內(nèi)燃機(jī)）.Mostinternalcombustionenginesoperateonthefourstrokecycle.ThistypeofengineisalsoknownasOttocycle,afterthenameofitsinventor,NikolausOtto.Eachcylinderofthefourstrokecycleenginehasapistonwhichreciprocates（往復(fù)運(yùn)動(dòng)）withinthecylinder.Thepowerproductioncycleconsistsoffourstrokesofthepistoninareciprocatingengine.Thesefourstrokesareintakestroke,compressionstroke,powerstrokeandexhauststroke,showninFig.3-1.3.1.1BriefIntroductiontoEngine3.1.1BriefIntroductiontoEngineFig.3-1workingprincipleTheintakestroke,asthepistonmovesdownwardtotheBottomDeadCenter,avacuumiscreatedinthecylinder.Theintakevalveopensandair-fuelmixture（混合氣）entersthecylinder.Thecompressionstroke,theair-fuelmixtureiscompressedasthepistonmovesupward.Thesparkplugisfiredtoignitetheair-fuelmixturepriortothepistonbeingattheTopDeadCenter.Notethatbothvalvesareclosed.3.1.1BriefIntroductiontoEngineThepowerstroke,theair-fuelmixtureexplodes（爆炸，膨脹）,whichforcesthepistondownward.Notethatbothvalvesareclosed.Theexhauststroke,asthepistonstartstomoveupward,theexhaustvalveisopened.Thepistonmovingupforcestheexhaustgasesoutofthecylinder.Thisfourstrokecycleofpistonwithinthecylinderisrepeatedtimeandagaintopushthevehicleforward.3.1.1BriefIntroductiontoEngineThemostcommonenginecomprisescrankshaftandconnectingrodmechanism,valvegear,coolingsystem,lubricatingsystem,fuelsystem,startingsystem,ignition（點(diǎn)火）system(thereisnoignition

systemindieselengines),showninFig.3-2.3.1.2MainComponentsofEngineThepowermechanismoftheengineisactuallycalledthecrankshaftandconnectingrodmechanism.Itsfunctionistoconvertheatenergyintomechanicalenergyusedtodrivethevehicles.Thevalvegearprovidestimelyadmissionofthefreshchargeintothecylindersandexhaustofspentgasesfromthem.Thefunctionofthecoolingsystemistomaintainthehighestandmostefficientoperatingtemperaturewithintheengineandtoremoveexcessheat（余熱）fromtheengine.3.1.2MainComponentsofEngineThelubricationsystemisdesignedtokeepalltheenginepartslubricatedsothatfriction（摩擦）isreduced.Thefuelsystemworksaccordingtotherequirementsoftheengineasitprovidesanair-fuelmixturewhichmustbeinproportiontothespeedandloadplacedontheengine.Thefuelsystemsendstheair-fuelmixturetothecylinderforburningandsimultaneously（同時(shí)地）exhauststheeffluentgasthroughtheexhaustpipe.3.1.2MainComponentsofEngineTheignitionsystemisdesignedtoignitetheairandfuelthathavebeenmixedinthefuelsystem.Thestartingsystemprovidesthepowertoturntheinternalcombustionengineoveruntilitcanoperateunderitsownpower.3.1.2MainComponentsofEnginePractice—MaintenanceManualReadingInspectingengineassemblyPractice—MaintenanceManualReading1.Inspectcoolant

1)INSPECTCOOLINGSYSTEMFORLEAKSWarning!

Toavoidthedangerofbeingburned,donotremovetheradiatorcapwhiletheengineandradiatorarestillhot,asfluidandsteamcanbeblownoutunderpressure.(a)Filltheradiatorwithcoolantandattacharadiatorcaptester.(b)Warmuptheengine.(c)Pumpitto118kPa(1.2kgf/cm2,17.1psi),andcheckthatthepressuredoesnotdropPractice—MaintenanceManualReadingNote!

Ifthepressuredrops,checkthehoses,radiatororwaterpumpforleaks（泄露）.Ifnoexternalleaksarefound,checktheheatercore,cylinderblockandhead.Practice—MaintenanceManualReading2)CHECKENGINECOOLANTLEVELATRESERVOIR(a)Theenginecoolantlevelshouldbebetweenthe”LOW”and”FULL”lineNote!

Iflow,checkforleaksandadd”ToyotaLongLifeCoolant”orequivalent（相等的）uptothe”FULL”line.Practice—MaintenanceManualReading3)CHECKENGINECOOLANTQUALITY(a)Removetheradiatorcap.Warning!

Toavoidthedangerofbeingburned,donotremovetheradiatorcapwhiletheengineandradiatorarestillhot,asfluidandsteamcanbeblownoutunderpressure.Practice—MaintenanceManualReadingNote!Ifexcessivelydirty,replacethecoolant.(c)Reinstalltheradiatorcap.(b)Checkifthereisanyexcessivedepositsofrustorscalearoundtheradiatorcapandradiatorfillerhole;thecoolantshouldbefreefromoil.Practice—MaintenanceManualReading4)INSPECTFINSBLOCKAGE(a)Iffinsareclogged（堵塞）,washthemwithwaterorasteamcleaneranddrywithcompressedair.Practice—MaintenanceManualReadingWarning!Ifthedistancebetweenthesteamcleanerandcoreistooclose,thereisapossibilityofdamagingthefins,sokeepthefollowinginjectiondistance.·Ifthefinsarebent,straightenthemwithascrewdriverorpliers.·Becarefulnotpourwaterdirectlyontoelectroniccomponents.Practice—MaintenanceManualReading2.Inspectengineoil

1)CHECKENGINEOILLEVEL(a)Afterwarminguptheengineandthen5minutesaftertheenginestops,oillevelshouldbebetweenthe”L”and”F”marksontheoillevelgage（油位表）.Iflow,checkforleakageandaddoiluptothe”F”mark.Warning!Donotfillwithengineoilabovethe”F”mark.Practice—MaintenanceManualReading2)CHECKENGINEOILQUALITY(a)Checktheoilfordeterioration,entryofwater,discoloringorthinning.Ifthequalityisvisiblypoor,replacetheoil.Oilgrade:UseAPIgradeSL”Energy–Conserving”,orILSACmultigradeengineoil.SAE5W–30isthebestchoiceforgoodfueleconomy,andgoodstartingincoldweather.Practice—MaintenanceManualReadingIfSAE5W–30isnotavailable,SAE10W–30maybeused.However,itshouldbereplacedwithSAE5W–30atthenextoilreplacement.Practice—MaintenanceManualReading3)INSPECTOILPRESSURE(a)Disconnecttheoilpressureswitchconnector.(b)Usinga24mmdeepsocketwrench,removetheoilpressureswitch.Practice—MaintenanceManualReading(c)Installtheoilpressuregauge.(d)Warmuptheengine.(e)Inspecttheoilpressure.Practice—MaintenanceManualReadingOilpressure:(f)Applyadhesiveto2or3threadsoftheoilpressureswitch.

Adhesive:PartNo.08833–00080,THREEBOND1344,LOCTITE（樂泰，一種美國(guó)品牌膠水）242orequivalentPractice—MaintenanceManualReading(g)Usinga24mmdeepsocketwrench,installtheoilpressureswitch.Torque:15N·m(153kgf·cm,11ft·lbf)(h)Connecttheoilpressureswitchconnector.(i)Checkfortheengineoilleaks.Practice—MaintenanceManualReading3.InspectfanandgeneratorVbelt

Note!

Youdon’tneedtocheckthebeltdeflection（撓曲）becauseautotensionerisadopted.Practice—MaintenanceManualReading4.Inspectengineidlespeed

(a)Warmupengine.(b)Whenusinghand–heldtesterorOBDIIscantool.(1)Connectthehand–heldtesterorOBDIIscantooltotheDLC3.Note!Pleaserefertothehand–heldtesterorOBDIIscantooloperator’smanualforfurtherdetails.(c)Checktheidlespeed.Idlespeed:650–750rpmPractice—MaintenanceManualReading(c)Checktheidlespeed.Idlespeed:650–750rpmWarning!·CheckidlespeedwithcoolingfanOFF.·Switchoffallaccessoriesandairconditioning.Practice—MaintenanceManualReading5.Inspectcompression(a)Warmupandstopengine.(b)Removeignitioncoil.(c)Removesparkplugs.(d)Inspectcylindercompressionpressure.SST09992–00500(1)Insertacompressiongaugeintothesparkplughole.(2)Fullyopenthethrottle.(3)Whilecrankingtheengine,measurethecompressionpressure.Practice—MaintenanceManualReading5.InspectcompressionCompressionpressure1,300kPa(13.3kgf·cm2,189psi)Minimumpressure:1,000kPa(10.2kgf·cm2,145psi)Differencebetweeneachcylinder:100kPa(1.0kgf·cm2,15psi)Practice—MaintenanceManualReadingWarning!·Alwaysuseafullychargedbatterytoobtainenginespeedof250rpmormore.·Checkothercylinder’scompressionpressureinthesameway.·ThismeasurementmustbedoneinasshortatimeasPossible.(4)Ifthecylindercompressioninonemorecylindersislow,pourasmallamountofengineoilintothecylinderthroughthesparkplugholeandrepeatsteps(1)through(3)forcylinderswithlowcompression.Practice—MaintenanceManualReading

Note!·Ifaddingoilhelpsthecompression,itislikelythatthepistonringsand/orcylinderborearewornordamaged.·Ifpressurestayslow,avalvemaybestickingorseatingisimproper,ortheremaybeleakagepastthegasket（襯墊）.Task3.2Replacingchainsub-assemblyLearningPreparation學(xué)習(xí)準(zhǔn)備revolve旋轉(zhuǎn)valve氣門hexagonalwrench六角扳手align對(duì)齊，排列chaintensioner鏈條張緊器slipper滑塊Keyterms:Step1Amaintenancecaseisprovided;Step2Learntheprocessofreplacingchainsub-assemblyviaamaintenancemanual;Step3Requirestudentstograspthekeytermsinthistask;Step4Trytodescribetheprocessofchainsub-assemblyreplacement;Step5Studentsreadrelativematerial;Step6AssessmentPlanandImplement計(jì)劃和實(shí)施()1.Timingchainmustbereplacedatthemanufacturer'srecommendeddistanceand/ortimeperiods.()2.Theowner'smanualmaintenancescheduleisthesourceoftimingchainreplacementintervals,typicallyevery30,000to50,000miles.()3.Don’treplacethetimingchaintensioneratthesametimeasthechainisreplaced.AssessmentandFeedback評(píng)價(jià)和反饋TrueorFalse()4.Incaseofrevolvingthecamshaftswiththechainoffthesprockets,turnthecrankshaft1/5revolutionforvalvesnottotouchthepistons.()5.Twoyellowcolorlinksareonthechain.()6.Timingchainsaregenerallymoredurablethantimingbelts.()7.Failuretoreplacethechaincanresultincompletebreakdownorcatastrophicenginefailure.AssessmentandFeedback評(píng)價(jià)和反饋TrueorFalse()8.Removethetimingchainwiththecrankshafttiminggearplyingscrewdrivers.()9.WhenInstallingchainsub-assy,Usingacrankshaftpulleybolt,turnthecrankshaftandsetthesetkeyonthecrankshaftupward.()10.Installthetimingchainonthecrankshafttimingsprocketwiththeyellowcolorlinkalignedwiththetimingmarkonthecrankshafttimingsprocket.AssessmentandFeedback評(píng)價(jià)和反饋TrueorFalse3.6.1Chain(TimingBelt)Atimingbeltortimingchainisapartofaninternalcombustionenginethatsynchronizes（同步）therotationofthecrankshaftandthecamshaft(s)sothattheengine’svalvesopenandcloseatthepropertimesduringeachcylinder’sintakeandexhauststrokes,showninFig.3.2.1.Inaninterferenceenginethetimingbeltorchainisalsocriticaltopreventingthepistonfromstrikingthevalves.3.6.1Chain(TimingBelt)Atimingbeltisabeltthatusuallyfeaturesteethontheinsidesurface,whileatimingchainisarollerchain.3.6.1Chain(TimingBelt)Mostmodernproductionautomobileenginesutilize（使用）atimingbeltorchaintosynchronizecrankshaftandcamshaftrotation;someenginesinsteadutilizegearstodirectlydrivethecamshafts.Theuseofatimingbeltorchaininsteadofdirectgeardriveenablesenginedesignerstoplacethecamshaft(s)furtherfromthecrankshaft,andinengineswithmultiplecamshaftsatimingbeltorchainalsoenablesthecamshaftstobeplacedfurtherfromeachother.3.6.1Chain(TimingBelt)Timingchainswerecommononproductionautomobilesthroughthe1970sand1980s,whentimingbeltsbecamethenorm,buttimingchainshaveseenaresurgence（復(fù)活）inrecentyears.Timingchainsaregenerallymoredurablethantimingbelts–thoughneitherisasdurableasdirectgeardrive–however,timingbeltsarelighter,lessexpensive,andoperatemorequietly.3.6.2ChainFailureTimingbeltsmustbereplacedatthemanufacturer‘srecommendeddistanceand/ortimeperiods.Failuretoreplacethebeltcanresultincompletebreakdownorcatastrophic（毀滅性的）enginefailure,especiallyininterferenceengine.Theowner’smanualmaintenancescheduleisthesourceoftimingbeltreplacementintervals（周期）,typicallyevery60,000to100,000miles.Itiscommontoreplacethetimingbelttensioneratthesametimeasthebeltisreplaced.3.6.2ChainFailureTheusualfailuremodesoftimingbeltsareeitherstrippedteeth(whichleavesasmoothsectionofbeltwherethedrivecogwillslip)ordelamination（剝落）andunraveling（變形）ofthefibercores.Breakageofthebelt,becauseofthenatureofthehightensilefibers,isuncommon.3.6.2ChainFailureCorrectbelttensioniscritical-toolooseandthebeltwillwhip（拍擊，拍打）,tootightanditwillwhine（嘎嘎響）andputexcessstrainonthebearingsofthecogs（齒輪）.Ineithercasebeltlifewillbedrasticallyshortened.Asidefromthebeltitself,alsocommonisafailureofthetensioner,and/orthevariousgearandidlerbearings,causingthebelttoderail.Practice—MaintenanceManualReadingReplacingchainsub-assembly(a)Removethetimingchainwiththecrankshafttiminggearplyingscrewdriversasshownintheillustration.1.Removechainsub-assyWarning!·Putshopragtoprotecttheengine.·Incaseofrevolvingthecamshaftswiththechainoffthesprockets,turnthecrankshaft1/4revolutionforvalvesnottotouchthepistons.Practice—MaintenanceManualReadingReplacingchainsub-assembly1.Removechainsub-assyPractice—MaintenanceManualReadingReplacingchainsub-assembly2.Installchainsub-assy(a)SetNo.1cylindertoTDC/compression.(1)Turnthehexagonalwrenchheadportionofthecamshafts,andalignthepointmarksofthecamshafttimingsprockets.Practice—MaintenanceManualReadingReplacingchainsub-assembly2.Installchainsub-assy(2)Usingacrankshaftpulleybolt,turnthecrankshaftandsetthesetkeyonthecrankshaftupward.Practice—MaintenanceManualReadingReplacingchainsub-assembly2.Installchainsub-assy(b)Installthetimingchainonthecrankshafttimingsprocketwiththeyellowcolorlinkalignedwiththetimingmarkonthecrankshafttimingsprocket（鏈輪）.Practice—MaintenanceManualReadingReplacingchainsub-assembly2.Installchainsub-assyThreeyellowcolorlinksareonthechain.(a)SetNo.1cylindertoTDC/compression.(1)Turnthehexagonalwrenchheadportionofthecamshafts,andalignthepointmarksofthecamshafttimingsprockets.Note!Practice—MaintenanceManualReadingReplacingchainsub-assembly2.Installchainsub-assy(c)UsingSST,installthecrankshafttimingsprocket.SST09223–22010Practice—MaintenanceManualReadingReplacingchainsub-assembly2.Installchainsub-assy(d)Installthetimingchainonthecamshafttimingsprocketswiththeyellowcolorlinksalignedwiththetimingmarksonthecamshafttimingsprockets.Practice—MaintenanceManualReadingReplacingchainsub-assembly3.Installchaintensionslipper(a)Installthechaintensionerslipperwiththebolt.Torque:19N·m(194kgf·cm,14ft·lbf)Task3.3InspectingcrankshaftandpistonLearningPreparation學(xué)習(xí)準(zhǔn)備crankshaft曲軸piston活塞thrustclearance軸向間隙screwdriver螺絲刀thrustwasher止推墊圈runout跳動(dòng)micrometer千分尺Keyterms:Step1Amaintenancecaseisprovided;Step2Learntheprocessofinspectingcrankshaftandpistonviaamaintenancemanual;Step3Requirestudentstograspthekeytermsinthistask;Step4Trytodescribetheprocessofcrankshaftandpistoninspection;Step5Studentsreadrelativematerial;Step6AssessmentPlanandImplement計(jì)劃和實(shí)施()1.Thecrankshaftthruststandardthrustclearanceis0.04to0.24mm(0.0016to0.0094in.).()2.UsingadialindicatorandV–blocks,measurethecrankshaftcirclerunout.()3.Ifreplacingabearing,selectanewonehavingthesamenumber.()4.Usingamicrometer,measurethepistondiameterataanywhereangletothepistonpinhole.AssessmentandFeedback評(píng)價(jià)和反饋TrueorFalse()5.Usingapiston,pushthepistonringalittlebeyondthebottomoftheringtravel,thatmeans110mm(4.33in.)fromthetopofthecylinderblock.()6.Thenumberofbearingsusedusuallydependsonthenumberofcylindersintheengine,andthedesignoftheengine.()7.Thecrankshaftisboltedtothebottomofthecylinderblock.AssessmentandFeedback評(píng)價(jià)和反饋TrueorFalse()8.Pistonpinsarebothstrongandlightweight.()9.Pistonskirtformsabearingareaincontactwiththecylinderwall.()10.Insomeapplication,anarrowgrooveiscutintothepistonabovethetopringtoserveasa“heatdam”toreducetheamountofheatreachingthetopring.AssessmentandFeedback評(píng)價(jià)和反饋TrueorFalse3.3.1CrankshaftThecrankshaftassemblyincludesthecrankshaft,bearings,flywheel,timinggear,andfrontandrearseals（前后油封）.Thecrankshaft,regardedasthe“backbone”oftheengine,servestochangethereciprocatingmotionofthepistonintorotarymotionandhandlestheentirepoweroutput.Itisboltedtothebottomofthecylinderblock.3.3.1CrankshaftTheperiodic（周期的）gasandinertia（慣性）forcestakenbythecrankshaftmaycauseittosufferwearandbendingordistortion.Thecrankshaftthereforemustbeadequatelystrongandwear-resistant（耐磨）.Sothecrankshaftiseitherforgedfromhighqualitysteelorcastinhigh-strongiron.ThecrankshaftsshowninFig.3-4isactuallymadeupofvariouspartssuchasmainbearingjournal,rodjournal,crankarm,counterbalancedweightandetc.3.3.1Crankshaft1-front;2-mainbearingjournal;3-rodjournal;4-crankarm;5-counterbalancedweight;6-rearflange3.3.1CrankshaftThenumberofbearingsusedusuallydependsonthenumberofcylindersintheengine,andthedesignoftheengine.Theflywheelismadefromcarbonsteel.Itfitsontotherearofthecrankshaft.Aswellasitsfunctionistohelptheenginetorunsmoothlybyabsorbingsomeoftheenergyduringthepowerstrokeandreleasingitduringtheotherstrokes；italsocarriestheclutch,whichtransmitsthedrivetothegearbox；andhasthestarterringgeararounditscircumference（周圍）.3.3.2PistonThepistoncantransmittheforceofexpansiontocrankshaftthroughconnectingrod.Itisthickatthetopwhereittakesthebruntoftheheatandtheexpansionforce.Itisthinatthebottom,wherethereislessheat.Thepistoniscomposedofpistonhead,pistonlands,pistonskirtandpistonpinhole,showninFig.3-5.3.3.2PistonThepistoncantransmittheforceofexpansiontocrankshaftthroughconnectingrod.Itisthickatthetopwhereittakesthebrunt（沖擊）oftheheatandtheexpansionforce.Itisthinatthebottom,wherethereislessheat.Thepistoniscomposedofpistonhead,pistonlands,pistonskirtandpistonpinhole,showninFig.3-5.3.3.2Piston3.3.2PistonThetoppartofthepistonisthehead,orcrown.Itmaybeflat,concave,andconvexoranyoneofagreatvarietyofshapestopromote（促進(jìn)）turbulence（紊流）orhelpcontrolcombustion.Mostpistonshavethreeringgroovesatthetop.Thethinpartistheskirt.Itformsabearingareaincontactwiththecylinderwall.Thesectionsbetweentheringgroovesarecalledringlands.3.3.2PistonThelandsprovideaseatingsurfaceforthesidesofpistonrings.Insomeapplication,anarrowgroove（凹槽）iscutintothepistonabovethetopringtoserveasa“heatdam”toreducetheamountofheatreachingthetopring.Thepistonpinholeinthepistonalsoservesasabearingforthepistonpin,whichisusedtoconnecttheconnectingrod.3.3.2PistonThepistonringscarriedintheringgrooveareoftwobasictypes:compressionrings（氣環(huán)）andoil-controlring（油環(huán)）.Bothtypesaremadeinawidevarietyofdesigns.Theupperringorringsaretopreventcompressionleakage;thelowerringorringscontroltheamountofoilbeingdepositedonthecylinderwall.Thelowergrooveorgroovesoftenhaveholesorslotsinthebottomofthegroovestopermitsoildrainagefrombehindtherings3.3.2PistonPistonpins,alsoknownaswristpins（活塞銷）,areusedtoattachthepistontotheconnectingrodandmadeofhigh-qualitysteel.Theyarebothstrongandlightweight.Practice—MaintenanceManualReadingInspectingCrankshaftandpistonPractice—MaintenanceManualReading

1.Inspectcrankshaftthrustclearance(a)Usingadialindicator,measurethethrustclearancewhilepryingthecrankshaftbackandforthwithascrewdriver.Standardthrustclearance:0.04to0.24mm(0.0016to0.0094in.)Maximumthrustclearance:0.30mm(0.0118in.)

·Ifthethrustclearanceisgreaterthanmaximum,measurethethrustwasherthickness.·Ifthethicknessisnotspecified,replacethethrustwasherPractice—MaintenanceManualReadingThrustwasherthickness:2.430to2.480mm(0.0957to0.0976in.).Note!Practice—MaintenanceManualReading2.Inspectcrankshaft

(a)UsingadialindicatorandV–blocks,measurethecirclerunout,asshownintheillustration.Maximumcirclerunout:0.03mm(0.0012in.)Ifthecirclerunoutisgreaterthanmaximum,replacethecrank-shaft.Practice—MaintenanceManualReading2.Inspectcrankshaft

(b)Usingamicrometer,measurethediameterofeachmainjournalatthepointsshownintheillustration.Diameter:47.988to48.000mm(1.8893to1.8898in.)Ifthediameterisnotasspecified,checkthecrankshaftoilclearance.(c)Checkeachmainjournalfortaperandout–of–roundasshown.Maximumtaperandout–of–round:0.02mm(0.0008in.)Practice—MaintenanceManualReading2.Inspectcrankshaft

Ifthetaper（錐角）andout–of–roundisgreaterthanmaximum,replacethecrankshaft.Practice—MaintenanceManualReading2.Inspectcrankshaft

(d)Usingamicrometer,measurethediameterofeachcrankpinatthepointsshownintheillustration.Diameter:43.992to44.000mm(1.7320to1.7323in.)Ifthediameterisnotasspecified,checktheconnectingrodoilclearance.(e)Checkeachcrankpinfortaperandout–of–roundasshown.Maximumtaperandout–of–round:0.02mm(0.0008in.)Practice—MaintenanceManualReading2.Inspectcrankshaft

Ifthetaperandout–of–roundisgreaterthanmaximum,replacethecrankshaft.Practice—MaintenanceManualReading3.InspectcrankshaftoilclearanceDonotturnthecrankshaft.

(a)Cleaneachmainjournalandbearing.(b)Placethecrankshaftonthecylinderblock.(c)LayastripofthePlastigageacrosseachjournal.Warning!Practice—MaintenanceManualReading3.Inspectcrankshaftoilclearance(d)UsingSST,tightentheboltsinseveralpasses,inthesequenceshown,bythespecifiedtorque.SST09011–38121Torque:44N·m(449kgf·cm,33ft·lbf)Practice—MaintenanceManualReading3.Inspectcrankshaftoilclearance(e)Markthefrontofthebearingcapboltswithpaint.