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外文资料--Dynamic Analysis of Fo ur -Bar Be ating -upMechanismwith Joint Cle arance.pdf

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外文资料--Dynamic Analysis of Fo ur -Bar Be ating -upMechanismwith Joint Cle arance.pdf

DynamicAnalysisofFourBarBeatingupMechanismwithJointClearance¹XUEWenliangÏÓ1,CHENGuozhençS2,CHENGeçê3,ZHUZhangchenc71,CHENGLongdiñHš11KeyLaboratoryofTextileScienceTechnology,MinistryofEducation,DonghuaUniversity,Shanghai201620,China2ShanghaiShenAnTextileCo.,Ltd.,Shanghai200020,China3CollegeofMechanicalEngineering,DonghuaUniversity,Shanghai201620,ChinaAbstractForthefourbarbeatingupmechanismofairjetloom,theplainbearingoflinkageisthebearingwithdynamicload,andisimmersedinthelubricantbox.Ifthejointclearanceisconsidered,theresearchonlinkagemovementcouldbeverycomplicated.Inthispaper,thekinematiccharacteristicsoffourbarbeatingupmechanismwithjointclearancewerestudiedbyanalyzingthetraceofjournalcenterandthebalanceofradial,tangentialforces,andbearingload.Theregionofprincipalvibrationanditsformingcauseswerediscussed.Andtheresultscouldinterpretthemeasuringcurvesoffourbarbeatingupmechanismcompletely.KeywordsdynamicanalysisfourbarlinkagebeatingupmechanismjointclearanceCLCnumberTS193.3DocumentcodeAArticleID16725220201004055907IntroductionForthefourbarbeatingupmechanism,thecrankshaftbearingandrockshaftbearingaretheballbearing,andthecouplejournalbearingandcrankjournalbearingarethejournalbearing.Thecrank,coupler,rocker,andtwojournalbearingsareallimmergedinthelubricant,andthereistheradialclearancebetweentheringandpinofjournalbearing.Theclearanceishelpfultotherelativemotionoflinksbyprovidingthespaceofmovingandlubricating,butitalsoleadstothediscontinuousmotionofkinematicpair,whichisthemainreasontoaffectthemechanismdynamiccharacteristics13.Forthemechanismstransferringtheforceandmomentappliedintheindustrymanufacturing,asthejointclearanceenlargingthedynamiccharacteristicswillbedestructiveundertheconditionofhighspeedandhighload.Thejointclearanceoffourbarbeatingupmechanismiswithintherangeoftolerance.Ifrunningsmoothlysomeclearanceinthejointofmechanismisalwaysnecessary.Buttheclearanceisoftenincreasedbywearing,thentheimpactforcescouldcausethevibration,noise,bearingdeterioration,andthewearcouldalsobeincreased.Therefore,thevibrationsbecomeonebasicstudycontentaboutmechanismkinetics.Xietal.studiedtherelationbetweenthedynamicbalanceandthevibration4,andSoongetal.studiedthedynamiccharacteristicsofcranksliderwithjointclearance5.Thedynamicalternatingloadisenduredbythejournalbearingoffourbarbeatingupmechanism.Theforcesoflinksaretransferredbytheoilfilm,andthepincenterofcouplejournalmovesonthetrace.Whentheeccentricityislittle,themotionofrockerisunstable,whichshouldleadtotheinstantaneousimpactbetweentheringandthepinandmoreseriouswear,sothestrongvibrationwillhappenmorefrequently.1FourBarLinkagewithJointClearanceIfthejointclearanceofmechanismiszero,thecentersofbearingandjournalareinthesameposition.Butiftheclearanceappears,twocenterswillbeseparated,whichcanresultintheeccentricity,andthereistheextradegreeoffreedomforthemechanism.ThebeatingupmechanismwithjointclearanceisshowninFig.1,whichisthecrankrockerinversion.ThebearingBismadeupofcrankandcoupler,thebearingCismadeupofcouplerandrocker,therockershaftbearingDismadeupofrockerandgroundlink,andthecrankshaftbearingAismadeupofgroundlinkandcrank.Forthebeatingupmechanism,theconnectingarmpinbearingCiseasiesttobeworn,soitisassumedthatthereisonlytheclearancebetweenthecouplerpinandring,andnoclearanceinotherthreebearings.Inthispaper,themeasuringloomistheZA203airjetloomanditsspeedis450r/min.XYreferencecoordinateframeofmechanismshowninFig.1issetaccordingtothepracticalworkingposition.TheoriginisthebearingcenterofcrankshaftA,andthecoordinateofrockershaftbearingDcenterarexD8mmandyD159.8mm.Theotherparametersare559JournalofDonghuaUniversityEng.Ed.Vol.27,No.42010¹Receiveddate20090115CorrespondenceshouldbeaddressedtoXUEWenliang,Emailxwldhu.edu.cnshowninTable1.Fig.1FourbarlinkageusedforbeatingweftupintoclothTable1MainparametersoffourbarmechanismLinkageLength/mmMass/kgMomentofinertial/kgcm2CrankAB3535.80155CouplerBC752.27114RockerCD14510.42528SleyandsleyswordDE64.953728GroundlinkAD160ThesleyandsleyswordDEistheworkinglinkoffourbarmechanism,whichisintegratedwiththerocker.Whenthesleyreciprocates,thereedpushestheweftintothefellofclothfortheinertiaofsleyandsleysworddrivenbytherockerandelbowpositionofmechanism.Forthelinksoffourbarbeatingupmechanism,themassofsleyandsleyswordincludingtherockerismuchheavierthanotherlinks.Themainbodyofrockingshaftisthesteeltubeoflargediameter.Themotionofrockerisstableanditspropertyofantijammingiswell,sothesleyswordischosenasthemeasuringobjectiveofbeatingupmechanismaccelerationcurve.Apiezoelectricaccelerometerisadsorbedonthesleysworddirectlybythemagneticseat,whichisshowninFig.2.Thesleyswordisshortandstrong,whichoutputsignalcouldreflectsensitivelythedynamiccharacteristicsoffourbarlinkage.ThemeasuringaccelerationcurveofsleyswordisshowninFig.3,whichaccordswiththetheoreticalaccelerationcurve,andcharacterizedin.1Thecurveisnotsmooth,whichmeansthatthetheoreticalsmoothcurvehasbeenaddedbytheoscillationswithdifferentfrequenciesandamplitudesseeFig.4.Fig.2SketchofmeasuringpositionFig.3MeasuringcurveFig.4Contrastbetweenmeasuringcurveandtheoreticalsmoothcurve2Theoscillationswithdifferentfrequenciesexpressstrictperiodical,andthedifferenceisonlytheamplitudesseeFig.3.Forthefourbarbeatingupmechanismwithfixedgeometricalandkinematicparameters,inthefirsttwoor560JournalofDonghuaUniversityEng.Ed.Vol.27,No.42010threeyearstheoutputaccelerationsignalofmechanismwillappearagaincorrectlyinthenextperiod,andthevibrationpulsewithfixedfrequencyandamplitudewillalsoappearagaineveryperiodofcrankangle.Sotheoutputaccelerationsignaloffourbarbeatingupmechanismwithjointclearanceisnottherandomsignal,butthemainbodyofsignalisthesignalwiththestrictperiodicity.Theoutputcurveofmechanismismainlymadeupofsignalswiththestrictperiodicity,andalsoincludessomerandomcomponent.3Therandomcomponentofvibrationwillincreaseastheworkingtimeofloom.Thatistosayastheworkingtimeofmechanismincreases,therandomcomponentofoutputcurvewillbegraduallyimproved.ShowninFig.5,Bistheincludedangleofcoupleroritsextendedlineandcrank.WhenB0bor180b,thecrankandthecouplerareinthesameline,andwhentheaccelerationofcrankiszero,themechanismisinthepositionofelbowlink.WhenB90bor270b,thecrankandthecouplerareverticaleachother,andtheaccelerationofcrankislarge.Accordingtothefourspecialpositionsabove,theswingprocessofsleycouldbedividedintofourregions.Fig.5Bangleoffourbarmechanism2RelativeTraceofCouplerPinCenterwithJointClearanceatStaticBalancePositionAccordingtothemeasuringcurve,thereistheimpactoflinksinthejointclearance.Bymeasuringtheclearanceofcrankbearingis2Lm,andtheclearanceofcouplerpinjournalis42Lm.Soitcouldbeconcludedthattheimpactinthejointclearancewillhappenmainlyinthecouplerpinjournal.2.1CouplerpinjournalwithclearanceTherearetwocylindersofpinholeandjournalshowninFig.6.TheradiusofjournalbearingholeisR,theradiusofjournalisr,andtheradiusclearanceiscRr.ThedistancebetweentwocentrallinesofcylindersistheeccentricityeC1C2.Thecouplerandtherockerconnectedbythecouplerjournalbearingarebothmovableparts,sothebearingandthejournalarealsobothturning.Thereistheoilbetweentwocylinders,andthethicknesshofextrusionfilmishcesinHc1EsinH,1whereEe/cistheeccentricityHistheangleincludedbetweenhandC1C2intheverticaldirection.Fig.6GeometricdimensionofjournalforradialloadFisthetotalloadofjournalbearing,Ubcisthelinearvelocityofpinalongthepinsurface,andUcdisthelinearvelocityofjournalalongtheringsurfaceseeTable2.Table2MainparametersofcouplerpinbearingNominaldimensionofjournalbearingholeandjournal2R/mmWidthofplainjournalbearingL/mmViscositycoefficientoflubricantG/Nsm1RadiusclearancecRr/mm40420.01750.0212.2JournalcentertraceofstaticbalancepositionThecrankandthecouplerarebothimmersedinthelubricantbox.Thelubricantinthejointclearanceofjournalandbearingwillturnwiththem.Thereisthehigherhydrodynamicpressureintheregionoflessclearance,andthelowerhydrodynamicpressureintheregionoflargerclearance,whichleadstothedeliveryhead.Thebearingloadisenduredbythehydrodynamicpressureoflubricantfortheeffectofoilwedge.Thestaticbalancepositionofjournalcenteristhebalancepositionofoilfilmforceandbearingforce.Thereisthedifferencebetweencouplerpinjournalandordinaryradialbearing.1Thedirectionandintensityofloadonthecouplerpinjournalalternateasthetime.2Theswingvelocityofjournalandbearingchangesasthetime.TherelationbetweenbearingloadFanddimensionlessoilfilmforce–isshowninEq.26.5Fc/R2GUbcUcdL,2561JournalofDonghuaUniversityEng.Ed.Vol.27,No.42010whereFisthebearingload,Gisthedynamicviscosity,andUbcandUcdareshowninFig.6.AccordingtothedatainTable3,thebalanceposition7NF,C1C2couldbesolvedbytheinterpolation.Table3BearingparametersofcircularcylinderratioofwidthandradiusL/2R1.0EccentricityE0.100.200.300.400.500.600.70Eccentricangle7/b75.1163.5955.5550.0845.3240.5436.02Oilfilmforce–X0.1970.4150.6801.0291.5242.2963.654Thejournalcentertracecouldbedrawnaccordingtotheeccentricangleandtheeccentricity.Thejournalcentertraceofbearingwiththestaticloadusuallyissemicircle.Buttheloadofcouplerpinjournalwillvaryinthesizeanddirectionastheturningofcrank,sothejournalcenterwillmovealongthetraceofstaticbalanceposition.TherelativetraceofjournalcenterstaticbalancerelativetothecouplerpinjournalholeshowninFig.7is8shaped.ThepolarangleshowninFig.7isthedirectionangleofhole,andthepolarradiusistheeccentricity.Accordingtothefigure,therearethreetimesforthejournalcentercomingintothecircleofE0.1.Whenthecrankangleisat72b114b,itisthefirsttimeforthejournalcentercomingintothecircle,andtheleasteccentricityis0.001.Lesseccentricity,Fig.7Relativetraceofjournalcenterstaticbalancerelativetoholethemargentangleisthecrankanglethesystemstabilityisworseandworse.Whenthecrankangleisat178b192b,itisthesecondtimeforthejournalcentercomingintothecircle,andtheleasteccentricityis0.098.Whenthecrankangleisat302b338b,itisthethirdtimeforthejournalcentercomingintothecircle,andtheleasteccentricityis0.001.AndtherearetwotimesforthecentertouchingtheoutercircleofE1,wheretheangularvelocitiesofcouplerandrockerrelativetothebearingloadFarethesame,buttheirdirectionsarereverse,andtheimpactwillhappenbetweentwolinks.2.3BalancebetweenoilfilmforceandbearingloadFnisthereactionforcecomponentinthedirectionoflinkBClength,andFtisthereactionforcecomponentintheverticaldirectionoflinkBC.Between80band150b,Ftisclosetozero,andat92bFnistheleast.Thebearingreactionforceisenduredmainlybytheoilfilmthicknessh,andifaverticalloadwasplacedonthejournal,theoilwouldsqueezeandthereisthesufficientpressuretosupporttheload.ThepressurecouldbedividedintotheradialforceF0ninthedirectionoftielineandthetangentialforceF0tintheverticaldirectionoftieline.F0nGUbcUcdL5c2E21E22,MC1C2F0t14GUbcUcdL5c2PE1E25/2,LC1C23whereUbcistherelativelinearvelocityofholesurface,Ucdistherelativelinearvelocityofjournalsurface.Thereactionforceofjournalfortheoilfilmwillchangeastheturningofcrank.Thebearingloadistheconcentratedforce,andthereactionforceisthedistributionforce.ThefunctionofradialforceF0nistosupportthejournal.Inthedirectionofturning,thejournalcenterwillmovefortheactionoftangentialforceF0t,andtheeccentricitywillincrease.Thetangentialforcewilldestroythebalanceofjournal.Whenthemainbearingloadisinthedirectionofcouplerlength,thecomponentofforceFtintheverticaldirectionisverylittle.ThepressurecurvesofF0ninthedirectionofcoupleandF0tintheverticaldirectionareshowninFig.8.BecausetheoilfilmforceF0tisnotlikethebearingforceFtwhichisaroundzero,inthisconditionF0tiseasytodestroythestabilityofjournalmotion.562JournalofDonghuaUniversityEng.Ed.Vol.27,No.42010

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