EnginemountsNVH专业资料.ppt

Lotusexperienceofenginemounts,DesignofmountingconceptforengineNTA3point,NTA4point,3point,4pointmountingLocationofenginemountsrelativetoenginetorqueaxis(CAE)EnginesidemountingdesignRefinement,durability(FEA)EnginemountdetaileddesignBodystructuraldesignofenginemounts(FEA)NVHdevelopmentofenginemountrates,bracketsRide/shakedevelopmentofenginemountsTransientengineloadreaction(shuntreaction)Modaltestingofpowertrainmodesinvehicle,Enginemountfunctions,StaticLoadacceptanceHoldthemassoftheengineDynamicloadacceptanceVehicle-braking,cornering,kerbstrike,bumps,crashEngine-inertia/gasforces,torques,abusestarts,hillstartsIsolationRideComfort2-20HzNoiseandVibration20Hz+EngineLocationCompressionsetPowerunit/enginebaypositioningTorquecontrol-tipin/tipout,gearshift,Enginemountingconcepts,Thegenerallyusedenginemountingconceptsuseeither3or4mainmounts.Atleast2mountsmustbearthestaticweightoftheengine.Thedesignlocationmusttakeintoaccountthattheelastomerelementwilldeformunderthestaticloadoftheenginemass.Atleastonemountmustprovidearestrainingreactiontotheenginetorque.Insomemountingconceptsstaticloadandtorquereactionaredonebyseparatemountsinotherconceptsmountsprovidereactiontobothkindsofload.AllmountsmustprovideisolationtovibrationtransmissionSelectionofconceptisbasedonenginedesign,refinementtargets,cost,crashconsiderations,manufacturingstrategy.,3pointmount-milkingstool,All3mountscarrythemassoftheengineandreactenginetorque,4pointplatform,All4mountscarrythemassoftheengineandreactenginetorque-Distributionofforcesvarieswithgeometrytolerances,Torqueaxis-twintiebars,2mountsonthetorqueaxistheoreticallycarrythemassoftheengine1or2tiebarstheoreticallyreactallenginetorque,Enginerigidbodybehaviour,ModesareinfluencedbypowertrainMass,CofG,directionsofinertiaaxisModesareinfluencedbymountingsystemNumberandlocationofmounts,mountorientation,mountstiffnessanddampingSixNaturalmodescanbeexpectedForeaft(x)Lateral(y)Bounce(z)Roll(Rx)Pitch(Ry)Yaw(Rz)Someofthesemodesareoftendifficulttoidentifyespeciallyif2modesarevirtuallyco-incident-e.g.lateral(Y)infollowingexample,EngineBouncemode-10.8Hz,Engineforeaftmode11.8Hz,Enginerollmode14.3Hz,Enginepitchmode14.8Hz,Engineyawmode16.8Hz,EngineFlexuralmodes,GenerallymoreproblematiconRWDinstallationsBendingmodeusuallysub200HzSystemmasshigherIdealmountpositionisonnodalpointsofbendingmodetopreventenergytransferintobodystructure,Powertrainbendingmode138Hz,Practicalenginemountdesign,Thereisnosinglerightlocationforanenginemountsystem.Idealisedmountingpositionsmaynotbeachievableduetogeometryandpackage.Locatingmountswithminimaloffsetsfromstructuralmembersorthemainblockleadstogoodrefinement-thiscanbefarbetterthananidealisedpositionthatrequireslongbracketsorhighoffsets.Bodymountcommonalityfordifferentenginederivativesmaydetermineacompromiselocationisselected.Othervehiclerequirementssuchascrashperformancecaninfluencelocationandstiffnessofenginemounts.Manufacturingrequirementsforengineinstallationcanalsoinfluenceenginemountlocation(e.g.assemblyaccess),Bodysidemountdesign,Themainrequirementofthebodymountsistoreactthestaticanddynamicforcesfromtheenginewithoutallowingvibrationenergyintothebodystructure.ForaforceactingonamountgeneratingvibrationSoundpower(Structuralnoise)MechanicalpowertransferMechanicalPowertransferForcexvelocityBodymountmobilitym/s/NprovidescorrelationtonoisepathsensitivityIfthebodystructurewasinfinitelystiffthennostructuralnoisewouldbegenerated.(bedplate).BodysensitivityismeasuredbyINPUTPOINTMOBILITY,Enginemountexample,Enginemountresponsemeasured,StrongvibrationfoundonengineRHenginemount.Engineside-overalllevelBodyside-overalllevelEngineside2ndorderBodyside2ndorderOverallgoodmountattenuationEnginesidetoBodyside-ElastomerratesarethereforeOK.,Structuralchangestoenginemounts,Reinforcedenginesidemount,Engineblockpickup-improvedcasting,Bodysidebracketfrontreinforced,Bodysidebracketrearreinforced,Improvednoiseat4800rpm,Enginerelationtovehiclemodes,Enginesolidbodymodesareshiftedtoeithercoincideoravoidvehiclesystemmodes.Decouple/avoidmodes-exampleEngineroll8HzEngineBounce10HzEnginepitch14HzAlternative-UseenginebouncetoabsorbwheelhopEnginebounceonlyslightlyhigherthanwheelhopMoreeffectiveifhydromountsareusedtointroducedampingFirststrategyisfarmorecommonapproach.,Wheelhopmode12Hz,Humansensitivitiestovibration,Thehumanbodyhasarangeofnaturalresponseswhichcaninducediscomfortandpain.Theresonantamplificationofresponseandthedissipationofvibrationenergywithinthehumanbodycanresultinvariousphysiologicaleffectsonhumans,suchasincreasedpulserate,respiratoryrateormoreseriouslyailmentsofspinalmuscle,ano-rectalorgastro-intestinalsystems.MotionsicknessinducedbyVerticalvibration4-11HzRoll,foreaft,andlateralvibration0.5-8HzAvoidallmodes3-8HzAvoidverticalenginemodes8Hz(preferably10Hz)HighlydampedverticalresponseVerticalmodesspaced2Hzfromwheelhop,Inputinducedbyroadsurfaceirregularities,LotusShaketestRoad,Shuntcontrol,Resultofsuddentorquechangesduetoengineloading(1-4Hz)Shunt,shuffle,tipin/tipout,shiftqualityInfluencedbyEnginemanagement,Flywheelinertia,Driveshaftstiffness,Clutchtuninganddamping,EnginesuspensionDesignStrategyHighdampingofenginepitchHighdampingdrivelinetorsionmodesCouplefore-aftmode(butnotwithEnginepitch)Progressivestiffnessincreasebyuseofsnubbing,Idlerefinement（怠速定义）,20-40Hzfor4cylinder-createdbytorqueoutputfluctuations（扭矩输出的波动）Unevencombustionbetweencylinderscaninduceexcitationatvarioushalforders.（各个气缸之间不充分的燃烧可导致各种的半阶激励）InfluencedbyModeofbodythatareabove20HzSteeringwheel&columnmodes20-35HzHighdampingreducesisolationathigherfrequencies（较高的阻尼在高频时会降低隔振率）Hydromountsareadirectresultofthiseffect液压悬置是这种现象的直接原因,Hydromounts,Rubbermountshaverelativelylowdamping.Improvinglowfrequencydamping20dBabove30Hz（30Hz以上悬置的隔振率应大于20db）Useofsnubberstogivelowstiffnessatsmalldisplacementswithhighstiffnessathigherdisplacementstocontainsuddenshockloads.（使用减震器，小位移时提供低刚度，大位移时包括突然的冲击载荷提供大刚度）,NonNVHrequirements1,Movementrestriction-typicalvalues（位移限制-限位）X,Ydirections+/-10mmZdirection+/-15mmX,Zrotation+/-1.5degYrotation+/-3.0degStaticenvelope25mmaroundengineCompressionsetof25%oftotalstrokeShippingloads（运输工况）RailtransportlashingManufacture,Assembly,ServiceRemove&refitofengineinserviceAccessforroboticassemblyAbilitytocopewithtolerancevariationsinbuild,Poormanufacturingqualityandhighloadsinducedfailure,NonNVHrequirements2,Durability&reliabilityDesignforvehiclelife150,000kmCrashperformancebehaviourpredi