中英文文献翻译具有车架结构车辆的怠速震动分析.docx
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中英文文献翻译具有车架结构车辆的怠速震动分析.docx
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中英文文献翻译具有车架结构车辆的怠速震动分析
附录
附录A
AnAnalysisofIdlingVibrationforaFrameStructuredVehicle
ABSTRACT
Afiniteelementmodelforanentireframe-structuredsportsutilityvehiclewasmadetoevaluatethecharacteristicsoftheidlingvibrationsforthevehicle.TheengineexcitingforcesweredeterminedbySouma'smethodtosimulatetheidlingvibrations.Themodelingofthepowerplantandtheentirevehiclewasverifiedbythereasonableagreementoftheexperimentandcalculationresults.Attentionwasfocusedonthefrequencyofthefirst-orderverticalbendingmodefortheframe.Ithasbecomeclearthattheidlingvibrationlevelofthevehicleisloweredbydecreasingthefrequencyofthefirst-orderframebendingmode.
INTRODUCTION
Oneofthedefectsofadieselvehicle,whichhasfuelandeconomicalefficiency,isidlingvibrationforavehiclebody.Inadieselengine,sharppressurerisecausedbythegenerationofthethermalenergyaffectsthepistons.Inthecranksystem,whichconvertsthelinearmotionintotherotarymotion,twotypesofreactionforcesexcitetheengineblock:
thereactioncausedbythealternationofthevelocityvectorineachmovingparts,andbythenon-uniformrotarymotiongeneratedbythefinitenumberofcylinders.Theforcestransmittoanengineblock,anenginefoot,arubberenginemount,aframe,arubbercab-mount,andthenavehiclebody,whichmakeoccupantsuncomfortable.
Theidlingvibrationforlarge-sizedcommercialvehicleswasestimatedattheearlydevelopmentstage,andthemeasuresagainstthevibrationweretakenbysimulatingtheengineexcitingforceswithSouma‘smethod,andenteringthemtoavehiclemodel.
Inthispaper,theidlingvibrationwasdeterminedbyenteringtheengineexcitingforcestothevehiclemodel,whichwasmadeofthefiniteelementoftheframeandthebodyforasmall-sizedrecreationalvehicle(RV).Alsointhispaper,howthenaturalmodesfortheframechangesinthevehicleconditionisanalyzed,anditwasindicatedthatthenaturalfrequencyofthefirst-orderverticalbendingfortheframehadasignificanteffect.
ANALYSISOFTHEVEHICLEBODYVIBRATION
Figure1showstheresultsofanalyzingthefrequenciesoftheaccelerationinverticalvibrationgeneratedontheseatrailwhileidlinginsmall-sizedRVpoweredby4-cylinderdieselengine.Themainpartoftheidlingvibrationisthesecond-orderenginerotation.The0.5th,1st,and1.5th-ordersarealsocritical.However,theseordersarecausedbythevariedcombustionbetweencylinders.Ameasureagainstthevariedcombustioncanbeexpectedbyimprovingtheinjectionsystem.Inthisresearch,only24Hzofthesecond-orderattheidlingrotationspeedof720rpmisfocusedonasameasureinthevehiclestructure.Besides,ameasureforloweringthevibrationisstudiedbecausetheverticalvibrationonseatshasagreatdamagingeffectonhumansense.
IDENTIFICATIONOFTHEENGINEEXCITINGFORCE
Therearethreepathsfortheenginetoexcitevibrationtoavehiclebody:
throughanenginemount,adrivingsystem,andatailpipe.Inthispaper,thepaththroughanenginemount,whichhasagreatesteffect,isstudied.Thevarioustypesofmethodstoidentifytheexcitingforcethroughanenginemountareknown.Inthispaper,Souma’smethodisused.
OUTLINEOFSOUMA’SMETHOD
Thecauseoftheexcitingforcetoanengineblockinthecontroversialfrequencydomainoftheidlingvibrationisconsidered.First,thecombustionpressurethatactsonthepistonsisconsideredtocausethevibration.However,assumingthatapistoncrankshaftdoesnotmovewithaflywheelandanengineblockfixedinsomeway,theenginecomponentsaresupposedtobecompletelyrigidinthisfrequencydomain.Inthissituation,theengineblockwillnotvibrateifthepistoncrankshaftdoesnotmoveinspiteoftherapidpressureriseinacombustionchamberduetothedieselcombustion.
Accordingly,thedirectcauseoftheengineblockvibrationisnotthecombustionpressurebutthereactionagainstthepistoncrankshaftmovement.Todeterminetheexcitingforcetotheengineblock,thereactionforcesagainstthemovementofthemass(mainlyincranksystemandpistonsystem),whichworksinsideandoutsideoftheengineblock,maybecalculated.
InSouma’smethod,thenon-uniformrotarymotioninthecranksystemisfoundbymeasuringthepulsegeneratedinaringgearoftheflywheel.Then,theverticalmotionintheconnectedpistonsystemiscalculatedtodeterminetheexcitingforcetotheengineblockusingeachmassspecificationvalue.
VERIFICATIONOFTHEACCURACYINTHEEXCITINGFORCE
Theexcitingforcesareaddedatthepointcorrespondingtothecrankshaftontheentirevehiclemodel(describedlater).Thevibrationontheheadcoverandtherightenginefoot,whichtheexcitingforcesmostlyaffect,isestimated.TheresultsofcomparingthecalculationwiththeexperimentareshowninFigure2and3.InFigure2and3,5typesofcalculatedresultsareshownconsideringtheidlingrotationspeedchanges.
InFigure2and3,thecalculationandtheexperimentareidentifiedaround24Hz,48Hz,and72Hzof2nd,4th,and6th-ordersatthespeedof720rpm.Thedataoftheleftenginefoot,whichisnotshowninthispaper,isalsoalmostidentified.Inthisfrequencydomain,asforthevibration,theengineandthevehiclebodyareinsulatedbytheenginemount.Thebodyhardlyaffectstheenginevibration.Asthedataoftheexperimentandthecalculationisidentifiedinthisdomain,thepowerplantmodelingandtheexcitingforcecanbeconsideredreasonable.
However,around12Hzof1st-orders,dataisnotmuchidentified.Inthisfrequencydomain,thevibrationoftheengineandthevehiclebodyaremutuallycoupledthroughtheenginemount.Therefore,theaccuracyofthevehiclebodymodelhasadamagingeffect.
IMPROVEMENTOFTHEMEASURINGACCURACYINLOW-FREQUENCYVIBRATION
TheengineexcitingforcewasdeterminedusingSouma’smethod,andthevibrationineachpartoftheenginewascalculatedbyaddingtheexcitingforce.Sofar,however,thecalculateddatahasnotbeenmuchidentifiedwiththeactualmeasurement.Therefore,theaccuracyoftheactualmeasurementisimproved.Inthesurfacevibrationoftheengine,thelow-frequencyvibration,whichcausestheidlingvibration,andthehigh-frequencyvibration,whichcausesnoise,aremixed.Whenthemixedvibrationismeasuredwithapiezoelementaccelerationpickup,thehigh-frequencyorderisemphasizedandthetargetlow-frequencyorderbecomesrelativelysmall.Forexample,themeasuredaccelerationtotimewaveformfortheverticalvibrationintherightenginefootisshowninFigure4.
Inthispaper,astraingageaccelerationpickup,whichmeasuresforceactingontheinnerweightbystrain,isused.Thisdevice,whichislargerthanapiezoelementaccelerationpickup,ismoresensitivetotheacceleration.Besides,siliconoilisfilledinsidetoprotectthedetectingpartsinthisdevice,whichmechanicallyblocksoffthehigh-frequencyorder.ThemeasuredaccelerationtotimewaveformfortheverticalvibrationwiththedeviceisshowninFigure5.ComparedwithFigure4,Figure5showsonlythelow-frequencyorderalthoughthesameareawasmeasured.Inthisway,thehigh-frequencyorderisblockedoff,whichresultsinthehighersensitivitywiththedevice.Thistime,thedevice,whichmeasurestheaccelerationrangingfrom0to20m/s2,wasused.ThisdeviceiseasilycalibratedusingG-forcesbecauseithasthehighersensitivity.Whenapiezoelementaccelerationpickupwasused,thedifferencesbetweenthecalculationandtheexperimentwere20-40%inthemainorderofthevibration,andafewtimesinotherorders.Therefore,theprincipleofSouma’smethodusingapiezoelementacceleration
pickuphasbeenindoubt.However,thedataoftheexperimentandthecalculationhasbeenidentifiedasshowninFigure2and3sinceastraingageaccelerationpickup,whichhasbeenusedintheexperimentofmovementperformance,wasusedforanengine.
Fig.1SeatrailverticalvibrationFig.2Headcoverlateralvibration
Fig.3RightenginefootverticalvibrationFig.4Measurementwithpiezoelementaccelerationpickup
ENTIREVEHICLEMODEL
Figure6showsthebodymodel.Interiorandexteriorequipmentssuchasdoorsandseatareaddedintheformof85masspointstothemainstructuremodelingdetailedwithsheetmetalfiniteelements.Thegridpointsare61,912.Figure7showsthemodelwhereaframe,asuspension,andanenginearecombined,andafueltankandabumperisaddedintheformofconcentratedmass.Thegridpointsare39,262.
CombiningthemodelsshowninFigure6and7usingcabmountmakestheentirevehiclemodel.Totalgridpointsmountsto101,174.Thecalculationtimeis3,293secondsusingIBMSP2,MSC/NASTRANVersion70.5.2.Thecalculatingmethodispackagecalculation.Ifthemodelbecomesonlargerscale,themodelmustbecalculatedbytheblockstructure.
Figure8showsthefrequencyresponsefunction,indicatingtheresponsesoftheframewiththerightbackenginemountafterexcitingthedriver’sseatrail.Inthefrequencyrangingfrom20to30Hz,whichisrequiredfortheanalysis,thedataoftheexperimentisqualitativelyidentifiedwiththatofthecalculation.
Fig.5MeasurementwithstraingageaccelerationpickupFig.6Bodymode
Fig.7Frame,powerplantandsuspensionmodelFig.8Frequencyresponsefunction
CORRELATIONANALYSISOFTHEMODES
Fromtheviewpointofvibrationcharacteristics,itcanbeconsideredthatanentirevehicleisinsulatedbytheenginemountandthecabmount,whichhaverelativelysmallspringconstants,althoughtheinsulationisnotcomplete.Whentheentirevehicleisdivide
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