




已阅读5页,还剩3页未读, 继续免费阅读
版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
40KSMEJournal,VolA,No.1,pp.40-47,1990.ANALYTICALANDEXPERIMENTALMOTIONANALYSISOFFINGERFOLLOWERTYPECAM-VALVESYSTEMWITHAHYDRAULICTAPPETWon-JinKim-,Hyuck-SooJeon-andYoun-SikPark-(ReceivedSeptember11,1989)Inthispaper,themotionofafingerfollowertypecamvalvesystemwithahydraulictappetwasanalyticallyandexperimentallystudied.First,theexactcontactpointbetweencamandfollowerforeachcorrespondingcamanglewassearchedbykinematicanalysis.Thena6degreeoffreedomlumpejspringdampermassmodelwasconstructedtosimulatethevalvemotionanalytically.Whenconstructingthemodel,mostoftheparameterswereexperimentallydetermined.Butseveralvalueswhicharedifficulttoderiveexperimentallysuchasdampingcoefficientsweredeterminedwithengineeringintuition.Inordertoshowtheeffectivenessoftheanalyticalmodel,thepredictedcamvalvemotionwasdirectlycomparedwiththemeasuredvalveandtappetmotions.KeyWords:FingerFollower(OscillatiwRollerFollower),OverheadCam(OHC),CamValveSystem,Jump,BounceNOMENCLATURE-Ae:Equivalentcross-sectionalareaofoilchamberintappet,m2C.C.2C.3:Equivalentdampingcoefficientsofvalvespring,N/mC.e:Dampingcoefficientofvalveseat,N-s/mc,f,CVf,Cfe:Equivalentdampingcoefficientsofcontactpoint,Ns/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,kgDnpartmentofMechanicalEngineering,KoreaAdvancedInstituteofScienceandTechnology,P.O.Box150Cheongruarlg,Seoul130-650,Koeramm2: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,Yfinger-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(sandz).Severalassumptionsweremadeinthevalvespringmodeling.Thoseare;(i)symmetricity(K.,=KsaandC.,=Csa),(ii)equivalencyofstaticstiffnessandfundamentalnaturalfrequencybetweenmodelandfundamentalnaturalfrequencybetweenmodelandactualsystem,(iii)properdampingassumption.Asconsideringthatvalvespringisinclamped-clampedboundaryconditon,thesecondarynaturalfrequencyofvalvespringbecomestwiceofthefundamentalspringnaturalfrequency.Alltheaboveassumptionsgive(1)(2)C=2/KM,MzcrM,+M.OILENTRANCE-hJ.-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.21.40x10C.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-armratiois1.47andthefluctuatingrangeofrockerarmratiovariesfrom1.15to1.97duringthecycle.Thefinger-followertypeORCca
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 2025年地铁隧道二维位移自动监测系统项目建议书
- 以学生为中心的教育心理学课堂实践
- 智慧城市安防升级保障公共安全技术合作新篇章
- 提升学生自主学习动力的教育心理学方法论
- 数字化校园教育园区的智能升级
- 商业教育中技术应用的新趋势
- 教育心理学在个人自学策略中的应用
- 教育大数据下的学生个性化发展研究
- 2025届河北省秦皇岛市卢龙中学物理高二下期末学业质量监测模拟试题含解析
- 学习动力与学业成就的关系研究
- 2024-2029全球及中国福利管理系统行业市场发展分析及前景趋势与投资发展研究报告
- 新标准英语小学五年级下各模块习题
- 中华护理学会成人肠内营养支持护理团标解读
- 2022-2023年人教版八年级化学上册期末测试卷(及参考答案)
- DLT 5175-2021 火力发电厂热工开关量和模拟量控制系统设计规程-PDF解密
- 全国中医优才计划
- 排风工程全过程BIM建模与协同设计
- 提升员工服务能力的实用培训方案
- 数字化系列研究之财务数智化篇:大型集团企业财务管理的数智化
- 锅炉安装知识讲座
- 30题产业研究员岗位常见面试问题含HR问题考察点及参考回答
评论
0/150
提交评论