AutomotiveenginecamshaftBriefintroductionThecamshaftisapartofthepistonengine.Itsroleistocontroltheopeningandclosingoperationofthevalve.Althoughthecamshaftrotationalspeedinafour-strokeengineisahalfofthecrankshaft(thesameasthecamshaftrotationalspeedinatwo-strokeenginewiththecrankshaft),butusuallyitisstillveryhighspeed,butalsoneedtowithstandthelargetorque,sothedesignrightdemandingcamshaftintermsofstrengthandsupportmaterialisgenerallyaspecialcastiron,occasionallyusingforgings.Valvemotionlawrelatedtoenginepowerandoperationcharacteristics,thedesigninthedesignprocessoftheenginecamshaftoccupiesaveryimportantposition.StructureThemainbodyofthecamshaftisthesameastheonewiththecylinderlengthofthecylindricalrod.Theabovesetshaveseveralcamfordrivingthevalve.Oneendofthecamshaftcamshaftbearingsupportandtheotherendisconnectedtothedrivewheels.Camsidewasegg-shaped.Thedesignaimstoensurethethecylindersufficientairintakeandexhaust,specifically,withintheshortestpossibletimetocompletethevalveopeningandclosingmovements.Inaddition,takingintoaccountthedurabilityoftheengineandthesmoothnessofoperation,thevalvecannotbegeneratedduetothedecelerationprocessofopeningandclosingmovementstoomuchtoolargetheimpactofseriouswearandtearofthevalve,otherwiseitwillcauseanincreaseinnoiseorotherseriousconsequences.Therefore,thecamandthepoweroftheenginetorqueoutputaswellastheoperationoftheridethereisadirectrelationship.Generallyinlineengine,acamcorrespondingtoavalveV-typeengineorhorizontalopposedtypeengine,everytwovalvesshareacam.Therotaryenginethevalvelesswithgasenginebecauseofitsspecialstructure,doesnotneedtocamPositionInthelongperiodoftime,thebottom-mountedcamshaftinaninternalcombustionengineismostcommon.Typicallysuchengines,thevalveislocatedinthetopoftheenginecamshaftmachine,i.e.,so-calledtheOHV(OverHeadValve,OHV)engines.Usuallycamshaftlocatedonthesideofthecrankcase,throughthegasdistributionagencies(suchastappet,pushrod,rocker,etc.)valvecontrol.Bottom-mountedcamshaftgeneralalsocalledside-mountedcamshaft.Fardistancevalve,andeachcylinderisusuallyonlytwovalvesinsuchanenginecamshaft,sothespeedisusuallyslower,ridecomfortispoor,theoutputpowerisalsorelativelylow.However,theengineoutputtorqueandlow-speedperformanceofthisstructureisrelativelygood,relativelysimplestructureandeasymaintenance.Nowmostoftheproductioncarsengineisequippedwithoverheadcamshaft.Theoverheadcamshaftsstructureclosertothecamshaftvalve,toreducethekineticenergyofthewastecausedbythebottom-mountedcamshaftduetothelargerdistancebetweenthecamshaftandthevalveshuttle.Overheadcamshaftoftheenginevalveopeningandclosingactionisrelativelyrapid,andhencehigherspeed,andthesmoothrunningisalsobetter.TheengineofthetheoverheadcamshaftsstructureappearedearliertheSOHC(SingleOverHeadCam,overheadsinglecamshaft)engine.Thisengineisonlyinstalledatthetopofacamshaft,andthereforegenerallyonlytwotothreevalvesofeachcylinder(theintakeairatotwoexhaust),thehigh-speedperformancehasbeenlimited.TechnologyupdatesDOHC(DoubleOverHeadCam,doubleoverheadcamshaft)engine,thisenginewithatwocamshaftspercylindercanbeinstalledfourtofivevalves(intaketwotothree,Paigastwo),high-speedperformancesignificantlyimproved,butatthesametimethelow-speedperformancewillbeaffectedtosomedegree,thestructurewillbecomplicatedanddifficulttorepair.ClassificationAccordingtothethecamshaftnumberofhowmany,canbedividedintosingleoverheadcamshaft(SOHC)anddoubleoverheadcamshaft(DOHC),twokinds.Thesingleoverheadcamshaftcamshaftisonlyonecamshaft,doubleoverheadcamshaftistwo,thisistoostraightforwardexplanation.Thesingleoverheadcamshaftwithacamshaftinthecylinderhead,directdriveintotheexhaustvalve,ithasasimplestructure,suitableforhigh-speedengine.Generallyusedinthepastsidecamshaft,thecamshaftinthecylinderside,isdrivendirectlybyatiminggear.Thevalveliftertotherotationofthecamshaftisconvertedintoreciprocatingmotionofthevalvemustbeusedtotransferpower.Thus,morepartsofthereciprocatingmotion,theinertialmass,isnotconducivetohigh-speedmovementoftheengine.Moreover,theslendertappethasacertaindegreeofflexibility,pronetovibration,acceleratedcomponentwear,eventhevalvecontrolislost.DOHCcylinderheadequippedwithtwocamshafts,oneisusedtodrivetheintakevalve,theotherfordrivingtheexhaustvalve.Doubleoverheadcamshaftcamshaftandvalvespringdesignlessdemanding,especiallyforthehemisphericalcombustionchamberofthevalveV-shapedconfiguration,butalsofacilitateandusedinconjunctionwithfour-valvegasdistributionagencies.FaultCamshaftcommonfaultsincludingabnormalwearandtear,abnormalwearofthesymptomsoftenfirstappearbeforetheoccurrenceofabnormalsoundaswellasfracture,abnormalsoundandfracture.(1)Camshaftalmostattheendoftheenginelubricationsystem,lubricationsituationisnotoptimistic.IftheoilpumpistoolongandsoinsufficientoilpressureorthelubricantsRoadblockagecausedbylubricatingoilcannotreachthecamshaftbearingcapfasteningboltstighteningtorquecausedbyexcessiveoilcannotenterthethecamshaftgapwillcausingabnormalwearofthecamshaft.(2)theabnormalwearofthecamshaftcausesthegapincreasesbetweenthecamshaftbearing,thecamshaftmovementoccurswhentheaxialdisplacement,resultinginabnormalnoise.Abnormalwearwillleadtoincreasedgapbetweenthedrivecamwithhydraulictappets,camcombinedwithhydraulictappetswillcollide,resultinginabnormalnoise.(3)camshaftsometimesfractureandotherseriousfault,commoncausesofhydraulictappetcrackedorseverelyworn,seriouspoorlubricationthecamshaftpoorqualityandcamshafttiminggearrupture.(4)Insomecases,thefailureofthecamshaftisman-madecauses,inparticularthemaintenanceoftheenginecamshaftnotcorrectdisassembly.Suchasdemolitionofthecamshaftbearingcapswithahammerstrengthknockingorpryingwithascrewdriver,orinstallthebearingcapinstalledthewrongpositiondoesnotmatchtheresultinthebearingcapandbearing,orbearingcoverthefasteningbolttighteningtorqueistoolarge.Installbearingcapshouldpayattentiontothedirectionofthearrowandthepositionnumbermarkedonthesurfaceofthebearingcap,andinstrictaccordancewiththeprovisionsoftorqueusingthetorquewrenchtightenthebearingcapfasteningbolts.RefitInordertoenhancethepoweroftheengine,someconvertedstoresamodifiedcamshaftenginefacelifthighanglecamshaft(Hi-camshaftCAM)isacommonformofmodifiedmethod.Thismodificationoperationisnotcomplicated,butbecauseofthelackofunderstandingofsomemodificationcamonthecamshaftangleandworkssothatthemodifiedeffectisnotobviousevenleadtothedeteriorationoftheperformanceoftheengine.Highanglecamshaftrelativetoordinarycamshaftcamangleofabout240,highanglecamshaftcamanglecanoftenreachover280.Thelargeangleofthecamshaftcanextendthevalveopentime,increasethevalvelift,theintakevalveandtheexhaustvalveopenasearlyandlateoff,sothatmoreairintothecylinder,inordertoimprovetheengine,thepowerofthehighspeedoutput.Shouldchooseforcivilianvehicles,modifiedcamcamshaftangle278,willbeasignificantincreaseinworkingananglegreaterthan278camshaftvalveoverlapangle,sothatthepoweroftheenginehighspeedimprovealot,butenginecylindersealisnotgoodatlowspeedandcausetheidlingseriousjitteroreventurnoff,sothatthevehiclecannotadapttoeverydayuse,andcanonlybeusedforcompetitionpurposes.ProductiontechnologyThecamshaftisoneofthekeypartsoftheengine,thehardnessofthecamshaftpeachapicalandwhitelayerdepthistodeterminethekeytechnicalindicatorscamshaftlifeandengineefficiency.,Shouldbeconsideredtoensurethatthecamhasasufficientlyhighhardnessandafairlydeepwhitelayerpremisejournaldoesnotappearhighcarbide,sothatithasabettercuttingperformance.Currently,themainmethodofdomesticandforeignproductioncamshaft:steelforgingblankbycuttingthecampeachtipmartensiticlayerformedsomeofthehigh-frequencyquenchingprocess.Theendofthe1970s,GermanyandFrancehavedevelopedanewcamshaftargonarcremeltingprocess；hardenedcastironcamshaftotherwisedominatedbytheUnitedStates；chilledcastironcamshaftmainlytoJapanandFrance；wellcampartsoftheCr-Mn-Moalloycoatingscastingsurfacealloyingproduction.汽車發(fā)動機凸輪軸簡介凸輪軸是活塞發(fā)動機里的一個部件。它的作用是控制氣門的開啟和閉合動作。雖然在四沖程發(fā)動機里凸輪軸的轉(zhuǎn)速是曲軸的一半（在二沖程發(fā)動機中凸輪軸的轉(zhuǎn)速與曲軸相同），不過通常它的轉(zhuǎn)速依然很高，而且需要承受很大的扭矩，因此設(shè)計中對凸輪軸在強度和支撐方面的要求很高，其材質(zhì)一般是特種鑄鐵，偶爾也有采用鍛件的。由于氣門運動規(guī)律關(guān)系到一臺發(fā)動機的動力和運轉(zhuǎn)特性，因此凸輪軸設(shè)計在發(fā)動機的設(shè)計過程中占據(jù)著十分重要的地位。構(gòu)造凸輪軸的主體是一根與汽缸組長度相同的圓柱形棒體。上面套