770561 NoiseControlIn PlanetaryTransmissions W.E.PalmerandR. R.Fuehrer DetroitDieselAllison DivisionofGeneralMotorsCorporation NOISELEVELSofvehicularsystemsarein creasingly becomingthesubjectofgovernment regulation. The1982EPAstandardformediumand heavytrucks,asshowninFig.1,necessitates an8 dB(A)reductionfromthepresentindustryvolun tarystandardof88dB(A)atadistanceoffiftyfeet to80dB(A)(1)*.Morestringentstandards are plannedbytheEPAinthefuture.Futurefederal standardshavebeenforeshadowed bysomelocal legislation andcustomerspecifications. Forexam ple,arecenttransitbusspecification required passbynoisetobe83dB(A)orless. Thechallengetothevehiclemanufacturer isob viousandiscompounded bythenumberof differentcomponents fromwhichnoiseoriginates. Thestudyofaline-haultruck(2),providesanex ample.AsshowninFig.2,atthebaselinenoise level88dB(A),fanandexhaustnoisedominated whiletransmission noisewasinsignificant. After modification ofthevehicletoreduceoverallnoisetoalevelequivalent totheEPA1982standardof80 dB(A),theunmodified manualtransmission becamesignificant contributing 1dB(A)tothe total.Ingeneraltomeetfurthernoisereductions ABSTRACT Noisegeneratedbyvehicleshasbecomeofin creasingconcern,inrecentyears,initseffectboth insideandoutsidethevehicle.Althoughthenoise contributed byheavy-duty automatic transmis sionsinon-andoff-highway vehiclesisinsignifi cantinrelationtothatgenerated byothervehicle components, aprogramwasinitiatedtoinvestigate sourcesandcausesoftransmission noiseandtodevelopmethodsofreducingoreliminating that noise. Inpowertransmission, themostcommonsource ofnoiseisvibrationofindividual gearsinmesh. Twomethodsofdecreasing gearmeshvibration have been foundsuccessful: improving geartooth profileandcounterphasing planetarygearing. *Numbersinparentheses designateReferencesat endofpaper. 2134 0096-736X/78/8603-2134$02.50 Copyright ©1978SocietyofAutomotive Engineers, Inc. Downloaded from SAE International by University of New South Wales, Sunday, August 26, 2018after1982,noisecontrolimprovements willhaveto bemadeonanumberofcomponents including presentlyinsignificant noisesourcessuchas transmission, compressors, andaxles. DDAsuppliesacompletefamilyoflight,medium andheavy-duty automatic transmissions forboth on-andoff-highway vehicles.Theseproductshave demonstrated widemarketacceptance duetotheir contribution toeaseofoperationandvehicle economics(3).Theinherentdesignfeaturesofthese transmissions whichcontribute tooverallvehicle economics alsoenhancetheirlownoisefeatures.A torqueconverter smoothlymultiplies torque, minimizing drivelinetorsionals -torsionalswhich arefrequentlythesourceofdrivelinedurability problemsandnoise.Automatically controlledshifts eliminateunintentional engineoverspeeding. Asacomponent supplierDetroitDieselAllisonis continuously evaluatingandimprovingitsproducts tomeetallmarketneedsincludingthatofnoise reduction. Aspartofthesecontinuingdevelopment activities, severaltransmission noisecontrol refinements wereinvestigated inatestbedvehiclea transitcoach- wheretransmissionplanetarygearnoisewasaudible.Thispaperwillpresentthe resultsof twosuccessfulmodificationsto theplanetary gearing;improvedgeartoothprofileandgear toothmeshtiming(counterphasing).TRANSITCOACH NOISE- Transitcoachnoise levelsarecriticalfortworeasons;one,tomeetgovernment legislation,and two,toassurerider acceptance.For example,a recentcontractof coaches limitedexteriorpass-bynoiseto83dB(A)at fiftyfeet.Thecharacterof interiornoiseisalsoimportant;rapid changesin levelor dominanttones, suchas transmissionshift "chirp"andgearwhine,canbeannoyingto therider.Noise certificationtests tendtoreflectworstcasenoise operationfor thecoachengineandtransmission. Thecertificationtestissimilarto SAE366c;thevehicleacceleratesfroma standingstartatfullpower withthe transmissionin automaticmode.The startingpointis chosento obtaina fullpowerautomatic first-to-secondrange shiftattheclosestpointtothetestmicrophone,fifty feet.Sincea firstto-secondshift typicallyoccursat vehiclespeeds