外文翻译--分析和实验输出式凸轮阀系统的液压挺杆 英文版【优秀】.pdf
40KSMEJournal,VolA,No.1,pp.40-47,1990.ANALYTICALANDEXPERIMENTALMOTIONANALYSISOFFINGERFOLLOWERTYPECAM-VALVESYSTEMWITHAHYDRAULICTAPPETWon-JinKim-,Hyuck-SooJeon-andYoun-SikPark-(ReceivedSeptember11,1989)Inthispaper,themotionofafinger·followertypecamvalvesystemwithahydraulictappetwasanalyticallyandexperimentallystudied.First,theexactcontactpointbetweencamandfollowerforeachcorrespondingcamanglewassearchedbykinematicanalysis.Thena6degreeoffreedomlumpe<jspring·damper·massmodelwasconstructedtosimulatethevalvemotionanalytically.Whenconstructingthemodel,mostoftheparameterswereexperimentallydetermined.Butseveralvalueswhicharedifficulttoderiveexperimentallysuchasdampingcoefficientsweredeterminedwithengineeringintuition.Inordertoshowtheeffectivenessoftheanalyticalmodel,thepredictedcam·valvemotionwasdirectlycomparedwiththemeasuredvalveandtappetmotions.KeyWords:Finger·Follower(OscillatiwRollerFollower),OverheadCam(OHC),Cam·ValveSystem,Jump,BounceNOMENCLATURE-Ae:Equivalentcross-sectionalareaofoilchamberintappet,m2C."C.2C.3:Equivalentdampingcoefficientsofvalvespring,N/mC.e:Dampingcoefficientofvalveseat,N-s/mc,f,CVf,Cfe:Equivalentdampingcoefficientsofcontactpoint,N·s/mc,p:Equivalentdampingcoefficientoftappet:N-s/m/0:Fundamentalnaturalfrequencyofvalvespring,HzFo:Initialcompressionforceofvalvespring,NFifFvfFfe:Contactforcesateachcontactpoint,NFifO,Fvfo,Ffeo:Initialcontactforcesateachcontactpoint,Nh:Clearancebetweencylinderandplunger,mmHe:Lengthofcompressedoilchamber,mmIf:Followermomentofinertia,kg-m2Ko:Valvespringstiffness,N/mKe:Equivalentstiffnessoftappetoilchamber,N/mK.1K.2K.3:Equivalentstiffnesscoefficientsofvalvespring,N/mK.:Stiffnessoftappetsoftspring,N/mK,f,Kvf,Kfe:Equivalentstiffnesscoefficientsofcontactpoint,N/mL:Plungerlength,mmLf:LeverarmofforceFfmmLvf:LeverarmofforceFvf,mmme:Massofoilinsidetappetoilchamber,kgMf:Followermass,kgMt:Equivalenttappetmass,kgMv:Equivalentvalvemass,kg°DnpartmentofMechanicalEngineering,KoreaAdvancedInsti·tuteofScienceandTechnology,P.O.Box150Cheongruarlg,Seoul130-650,Koeram"m2:Equivalentvalvespringmasses,kgRp:Radiusoftappetplunger,mmRe:Radiusofcambasecircle,mmRab:Distancefromcampivottofollowerpivot,mmR,:lengthofoscillatingrollerfollower,mmRf:Radiusofrollerinrollerfollowermodel,mmYf:Followerdisplacement,mmY,:Tappetdisplacement,j.tmYe:Camlift,mmYv:Valvedisplacement,mmY."Y.2:Displacementsofequivalentvalvespringmasses,mm8f:Angularrotationoffollower,radianj.t:Oilviscositycoefficient,Pa-sE:Bulkmodulus,N/m28:Angularrotationofcam,radian1.INTRODUCTIONWhendesigningacam-valvetrainofinternalcombustionengine,therearemanythingstobeconsideredsuchasvalveliftarea,peakcamacceleration,propercameventangle,rampvelocity,etc.Asincreasingtheoperationspeedofinternalcombustionengine,thedynamiceffectofcam-valvesystembecomesmoreimportant.Recently,someresearcheshavebeendonefocusingthedynamiceffectsoncam-valvesystem.Akiba,etal.(1981)constructeda4degreeoffreedommodeltoanalyzeanOHV(OverheadValve)typecam-valvesystemandstudiedthedynamiceffectsonthesystemmotion.JeanandPark(1989)triedtoanalyzethesametypeofvalvesystemwithalumpedmassdynamicmodelanddesignedanoptimalcamshapeconsideringdynamiceff.PisanoandFreudenstein(1982)developedadynamicmodelofahighspeedvalvesystemcapableofpredictingbothnormalsystemresponseaswellaspathologicalbehaviorassociatedwithonsetofjumping,bounce,andspringsurge.Previousresearchesinhigh-speedcamsystemhadbeenalmostfocusedonsystemswithaconstantrocker-armratioandonthevalve.ANALYTICALANDEXPERIMENTALMOTIONANALYSISOFFINGERFOLLOWERTYPECAM-VALVESYSTEMWITH.41trainseparationphenomena.Especially,theanalysisforcamsystemhavingahydraulictappethasnotbeenthoroughlystudied.Inthiswork,anOHCcam-valvetrainwithahydraulictappetandafingerfollower,wasanalyzedanalyticallywithlumpedmassmodelanditsreliabilitywasverifiedexperimentally.Thecam-followersystemusedinthisworkischaracterizedwithitscomplexdynamicsofhydraulictappetandthenonlinearityfromvaryingrocker-armratio.Therocker-armratiodeviatesasmuchas34percentfromabaselinevalueofI.47asthecontactpoirUbetweencamandfollowermoves.Thepivotendoftheoscillatingfollowerissupportednotatafixedpointbutataverticallymovingpivotmountedattopahydraulictappet.Themajorroleofthehydraulictappetistoremovethevalvelashwhichgivesharmfulimpactwithinvalvetrain.Butinhighoperatingspeedregion,thehydraulictappetcanbeopratedabnormallyandcanmakeanunusualvalvetrainmotion.Therefore,thecharacteristicsofthehydraulictappetmustbeconsideredinvalvetraindynamicmodel.TheprimaryresearchforasimilarcamsystemwasdonebyChanandPisano(1987).Theyestablishedsixdegreesoffreedommodelconsideredtranslationalandrotationalmotionofoscillationgfollowerandvalve.Buttheyusedasimplesingledegreeoffreedommodelforthehydraulictappet.Theyfocusedonlyonanalyticalworkanddidnotattempttoverifytheresultsexperimentally2.VALVETRAINMODELINGTAPPETFig.1:0:bIiP:VALVEI()ISPRINGIf0:IIVALVESEATSchematicoffingerfollowervalvetrainTheactualoverallshapeofanOHCtypecam-valvetrainisshowninFig.I.Inordertodescribethevalvemotionprecisely,thevalvetrainwasmodeledwith6degreeoffreedom.Thosearevalveopeningandclosingmotion,Yv,hydraulictappettranslationalmotion,Y"finger-followertranslationalandrotationalmotion,Y/and8/,andtwoadditionaldegreeoffreedomYS!andYS2whichrepresentvalvespringtranslationalmotion.ThereasonfortakingvalvespringmotionsYS!andYS2istoconsidervalvespringsurgephenomenon.Itisknownthatvalvespringsurgeaffectsgreatlyonvalvemotionespeciallywhentheoperationspeedishigh.Becausecamshaftcanbeconsideredasrigidandfixedonitsbearing,itsdynamiccharacteristicswasneglectedinthemodel.Allthecompotsandthecontactpointsofthecam-valvesystemwererueledwithequivalentmass,springsanddampersasshoinFig.2.Thedetailsofmodelingprocedureareexplainedasfollows.2.1ContactPointModelingAsshowninFig.1thefinger-followertypecam-valvetrainCAMTAPPETIVALVESEATVALVESPRING.CseFig.2Usedmodel42Won-inKim,Hyuck-SooJeonandYoun-SikParkTheequivalentmass(Me)offingerfollowerateachcontactpointcanbeobtainedfromEq.(2)asconsideringthefollowermomentofinertia(If).whereMfisthefollowerequivalentmassandIisthedistancebetweenfollowermasscenterandeachcorrespondingcontactpoint.Theequivalentmassofcamshaftatcontactpointisestimatedtoinfinityasassumingthatitisrigidandhas4contactpointsbetweenvalvetraincomponents.Thosearebetweenfollowerandtappet,follwerandcam,followerandvalve,andvalveseatandvalve.Thecontactatvalveseatoccursperiodicallyasdifferentwithotherswhichshouldmaintaincontinuouscontact.Theequivalentvalveseatstiffness(Kse)anddamping(Cse)cofficientsweretakenfromthepreviouslypublishedliterature(ChanandPisano,1987).Ontheotherhand,theequivalentdampingandstiffnesscoefficientsatothercontactpointswerepredictedbyHertzcontacttheoryutilizingshapefactor,modulusofelasticity,andPossonsratio.AJ;assumingtheproperrangeofcontactforces,thecorrespondingcontactstiffnesswascalculatedbyHertzcontacttheory.Thentheequivalentstiffnessesateachcontactpointweredeterminedbyleastsquareerrorcurvefitfromobtainedcontactstiffnesses(RoarkandYoung,1976).Itwasassumedthatthecontactbetweentappetandfollowerisaninternalcontactoftwospheres,betweencamandfollwerisacontactoftwocylinders,andbetweenfollowerandvalveisacontactofacylinderonaplane.Thedampingcoefficientsateachcontactpointwereassumedas0.06andthecriticaldampingcoefficient(Ccr)canbecalculatedusingEq.(I).WhereM,andMzaretheequivalentmassesofeachcontactingcomponent.itwasassumedthattheequivalentmassesofeachcontactingcomponent(M,andMz)areconnectedbyaspringandadamper.(3)2m,=mz=:rKol(flo)8Kl=K.a=:rKo,K.z=4Ko2.3HydraulicTappetModelingTheleftsideofFig.3showsthecrosssectionshapeofhydraulictappet.Oilentersthroughentranceandfillsthecentralcavityoftappetplunger.Astheplungermovesdown,thecheckvalveisclosedandtheoilflowsfromoilchamberthroughnarrowclearancebetweenplungerandcylinderandgeneratesdampingforce.Innextstep,whentheplungermovesupwardduetothespringpositionedinsideofoilchamber,thecheckvalveisopenedandoilisrefilledinoilchamber.ThehydraulictappetwassimplifiedasshownintherightsideofFig.3andtheequivalentstiffnessofthetappetwasestimatedbyassumingthatthefluidistotalycompressiveandthereisnoflowthroughdiametralclearance.TheThespringrateandfundamentalnaturalfrequencyofusedvalvespringare35KN1mand504.46Hz,respectively.Thedampingisassumedas4%proportionalviscousdamping.fixedonitsbearing.TheequivalentmassesoftappetandvalveatothercontactpointsareM,andMv.2.2ValveSpringModelingInordertoconsidervalvespringsurgeeffect,thevalvespringwasmodeledwith2masses(m,andmz),3springs(KShKsandKsa),and3dampers(CshCszandC.a)with2degreeoffreedom(¥sand¥z).Severalassumptionsweremadeinthevalvespringmodeling.Thoseare;(i)symmetricity(K.,=KsaandC.,=Csa),(ii)equivalencyofstaticstiffnessandfundamentalnaturalfrequencybetweenmodelandfundamentalnaturalfrequencybetweenmodelandactualsystem,(iii)properdampingassumption.Asconsideringthatvalvespringisinclamped-clampedboundaryconditon,thesecondarynaturalfrequencyofvalvespringbecomestwiceofthefundamentalspringnaturalfrequency.Alltheaboveassumptionsgive(1)(2)C=2/KM,MzcrM,+M.OILENTRANCE-<TAPPETPLUNGERIW-CENTRALCAVITYCHECK-1,.Io"-J:>-""<hJ.-<.-lVECOMPRESSIVEFOACEOILLEAKAGEDIAMETRALCLEARANCEOILTAPPETBASEFig.3Hydraulictappetanditssimplifiedoperationdrawing.ANALYTICALANDEXPERIMENTALMOTIONANALYSISOFFINGERFOLLOWERTYPECAM-VALVESYSTEMWITH···43Table1TappetdimensionsandpropertiesParameterValueA.H.EfJ.RphL1.213x10-m21O.15mm1.375x109N/m20.015Pa·s7.9325mm0.009mm13.58mmTable2UsedmodelparametersstiffnessofplungerspringMass(kg),(kg-m2)Stiffness(N1m)Damping(N·s/m)M,0.04567K,p6.648x10C,p2.635x106(y,>0)Mf0.05981K:5.92x10;1.1280,<0)h1.1527X10-·Kif5.52X10Cf118.97Mv0.08544Kfc8.37x10Cfc197.97m,0.0092KVf4.33x10CVf94.13m20.0092K1.31x10C634.77K.K.9.33xlOCu.C.a2.35!5K.21.40x10·C.23.534relationshipis(4)wascarefullycalculatedconsideringitsgeometricalshape.Alltheusedmass.stiffnessanddampingvaluesweresummarizedinTable2.whereaandpcanbedeterminedbycomparingmodelsimulationresultwithexperimentallymeasuredrecord.2.4MassandMomentofInertiaModelingValve,tappetplunger,andfollowermass(Mv,Mt,andMf)weredirectlymeasured.Thefollowermomentofinertia(If)whereEisbulkmodulus,Heisthelengthofcompressedoilchamber,andAeisplungerarea.Ontheotherhand.theequivalentdampingcoefficientwasestimatedbyassumingthattheoilistotallyincompressive.Itwasassumedthattheexcessiveoilduetoplungermotionflowscompletelythroughthediametralclearance.Thentheequivalentdampingvaluecanbepredictedfromthetheoryoffluidmechanics.Itisknownthatthedampingcoefficientchangeswiththedirectionofplungermotion.Thoseare(7)X=(Rc+S)cosO-sinOY=(Rc+S)sinO+cosO3.1KinematicalAnalysisWhensearchingthepointwherecamandfollowercontacts,thetappetwasconsideredfixedpoint.Itwasfoundthattheinfluenceoftappetmotionuponcontactpointisnegligible.Thetappetmotion,whichisatmostO.I(mm).isenoughsmallandcanbeconsiderednegligibleanddiffersinorderofmagnitudewithcamlift.Whenthecamdataisgivenwithdesiredcamlift(S),theactualcamshape(X,.Y),contactingwithaflatfollower,canbeobtainedfromEq.(7)Thebaselinerocker-armratiois1.47andthefluctuatingrangeofrocker·armratiovariesfrom1.15to1.97duringthecycle.Thefinger-followertypeORCcam-valvesystemischaracterizedwithvaryingrocker-armratiowithcamshaftrotations.Sothekinematicalanalysistosearchtheexactcontactpointsbetweencamandfollowerisinevitablebeforedoingdynamicanalysis.3.ANALYSISwhereRciscambasecircle.0iscamangle,Sisflatfollowerdisplacement,andXandYspecifycamshape.Theincre·mentofSabout0canbecalculatedwithcubicsplineinter·polation(Shoup.1979).Whenthecamshape(X.Y)isgiven,thecontactpointbetweencamandfollowercanbefoundbykinematicalanalysis.Fig.4showstheideahowtofindthecontactpoint.Theproceduresare.first,rotatethefolloweraroundafixedcam.thenfindoutthelocusoffollowercenter(CC)Next.searchthecontactpointforeachfollowerrotatingangle(Oc)usingtheprinciplethatthecontactpointis(6)whereJ1.isoilviscouscoefficient,Lisplungerlength,Rpisplungerradius,andhisclearancebetweencylinderandplunger.AlltappetdimensionsandpropertiesaregiveninTable1.Equations(4,5)derivedabovearetwoextremecases.oneisassumedtotallycompressiveandtheotheristotallyincom·pressive.Butinactualsituation,thedragforce(Fd)duetoplungermotionwillbeplacedsomewhereinthemiddleofthetwovalues(KreuterandMass.1987).AsintroducingtwocoefficientsaandP(O<a<I,O<p<1),thedragforcecanbemodeledasEq.(6).