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AT03 simpson planetary gear.pdf

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AT03 SIMPSON PLANETARY GEAR
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Automatic Transmissions - Course 262 1. Manipulate transmission components to demonstrate power flow through a simple planetary gear set for: w Gear reduction w Gear increase (overdrive) w Reverse 2. Identify the three major components of the simple planetary gear set. 3. Describe the function of the simple planetary gear set to provide: w Rotational speed change w Rotational torque change w Change in rotational direction 4. Demonstrate the measurement for wear on planetary carrier assembly and determine serviceability. 5. Describe the operation of the following holding devices: w Multiplate clutch w Brake band w One-way clutch Section 3 SIMPSON PLANETARY GEAR UNIT Lesson ObjectivesSECTION 3 22 TOYOTA Technical Training ToyotaautomatictransmissionsusetheSimpson-typeplanetarygear unit.Thisunitismadeupoftwosimpleplanetarygearsetsarranged onthesameaxiswithacommonsungear.Thesegearsetsarecalled thefrontplanetarygearsetandtherearplanetarygearset,basedon theirpositioninthetransmission.Thesetwoplanetarygearsetsresult inathree-speedautomatictransmissionhavingthreeforwardgears andonereversegear. Simpson Planetary Gear Set Made up of two simple planetary gear sets arranged on the same axis with a common sun gear. Theseplanetarygearsets,thebrakesandclutchesthatcontroltheir rotation,andthebearingsandshaftsfortorquetransmissionarecalled theplanetarygearunit. Theplanetarygearunitisusedtoincreaseordecreaseenginetorque, increaseordecreasevehiclespeed,reversedirectionofrotationor providedirectdrive.Itisbasicallyaleverthatallowstheengineto moveheavyloadswithlesseffort. Thereisaninverserelationshipwhichexistsbetweentorqueandspeed. Forexample:whenavehicleisstoppeditrequiresagreatdealoftorque togetittomove.Alowgearisselectedwhichprovideshightorqueat lowvehiclespeed.Astheheavyloadbeginstomove,lessleverageis requiredtokeepitinmotion.Astheloadremainsinmotionandspeed increases,torquerequirementsarelow.Withasuitablenumberoflevers ortorqueratios,improvedperformanceandeconomyarepossible. Beforegettingintosimpleplanetarygears,itisnecessaryto understandgearrotationandgearratiosorleverage.Whentwo Gear Rotational Direction and Gear RatioSIMPSON PLANETARY GEAR UNIT Automatic Transmissions - Course 262 externalgearsareinmeshasillustratedbelow,theywillrotatein oppositedirections.Thatis,whenthesmallgearisrotatedina clockwisedirection,itwillcausethelargergeartorotateina counter-clockwisedirection.Thisisimportanttoobtainachangein outputdirection,suchasinreverse. Gear Rotational Di- rection When two external gears are in mesh, they will rotate in opposite directions. Thegearratiothatthesetwogearsprovidewillbealeveradvantage. Therotatingspeedofanoutputgearisdeterminedbythenumberof teethofeachgear.Thegearratio,andthustherotationalspeedofthe outputgear,canbefoundbydividingthenumberofoutputgearteeth bythenumberofinputgearteeth.Thesegearratiosaredeterminedby theengineersandfixedinthemanufactureofthetransmission. Gear ratio Numberofoutputgearteeth Gearrat io= Numberofinputgearteeth Gear ratio 24 1 6:1 Gearrat io= 15 =1.6:1 Intheillustrationabove,iftheinputgearhas15teethandtheoutput gearhas24teeth,thegearratiois1.6to1(1.6:1).Inotherwords,the inputgearhastoturnslightlymorethanoneandone-halfturnsto havetheoutputgearturnonce.Theoutputgearwouldturnslower thantheinputgearwhichwouldbeaspeeddecrease.Theadvantagein thisexampleisanincreaseintorquecapability.SECTION 3 24 TOYOTA Technical Training Tocontrastthisillustration,let’sassumethatasetofgearshavethe samediameterwiththesamenumberofteeth.Ifwedeterminethe gearratiousingtheformulaabove,theratiois1to1(1:1).Inthis examplethereisnoleverageorspeedincrease.Onerotationofthe inputgearresultsinonerotationoftheoutputgearandthereisno leveradvantage. Whenanexternalgearisinmeshwithaninternalgearasillustrated below,theywillrotateinthesamedirection.Thisisnecessarytogeta changeinoutputgearratio.Thegearratioherecanbedeterminedin thesamemanneraswasjustdiscussed.Sincetheratioisonly accomplishedwhenallmembersoftheplanetarygearsetfunction together,we’llexaminegearratiosoftheplanetarygearsetunderthe SimplePlanetaryGearSet. Gear Rotational Di- rection When an external gear is in mesh with an internal gear, they will rotate in the same direction.SIMPSON PLANETARY GEAR UNIT Automatic Transmissions - Course 262 OurintroductiontoToyotaautomatictransmissionswillbeginwitha simpleplanetarygearset.Aplanetarygearsetisaseriesofthree interconnectinggearsconsistingofasungear,severalpiniongears, andaringgear.Eachpiniongearismountedtoacarrierassemblybya pinionshaft.Thesungearislocatedinthecenteroftheassembly; severalpiniongearsrotatearoundthesungear;andaringgear surroundsthepiniongears.Thisgearassemblyiscalledthe planetary“gearsbecausethepiniongearsresembleplanetsrevolving aroundthesun. Inaplanetarygeardesign,weareabletogetdifferentgearratios forwardandreverse,eventhoughthegearshaftsarelocatedonthe sameaxis. Simple Planetary Gear Operation Carrier Ring gear Sun gear Sun gear Carrier Ring gear Ring gear Carrier Sun gear HELD POWER INPUT Sun gear Ring gear Ring gear Carrier Sun gear Carrier POWER OUTPUT ROTATIONAL SPEED TORQUE ROTATIONAL DIRECTION Gearratioscanalsobedeterminedinaplanetarygearsetalthoughit isnotsomethingthatcaneasilybechanged.Thegearratioofthe planetarygearsetisdeterminedbythenumberofteethofthecarrier, ringgear,andsungear.Sincethecarrierassemblyhasnoteethand thepiniongearsalwaysoperateasidlegears,theirnumberofteethis notrelatedtothegearratiooftheplanetarygearset.However,an arbitrarynumberneedstobeassignedtothecarrierinorderto calculatetheratio.Simplycountthenumberofteethonthesungear andtheringgear.Addthesetwonumberstogetherandyouhavethe carriergearnumberforcalculationpurposes. Simple Planetary Gear Set Planetary Gear RatiosSECTION 3 26 TOYOTA Technical Training Thenumberofcarrierteeth(Zc)canbeobtainedbythefollowing equation: Zc=Zr+Zs where Zc=Numberofcarrierteeth Zr=Numberofringgearteeth Zs=Numberofsungearteeth Forexample,assumethenumberofringgearteeth(Zr)tobe56and thatofsungear(Zs)tobe24.Whenthesungearisfixedandthering gearoperatesastheinputmember,thegearratiooftheplanetarygear setiscalculatedasfollows: Gear ratio Numberofoutputgearteeth Gearrat io= Numberofinputgearteeth Numberofcarrierteeth(Zc) = Numberofringgearteeth(Zr) = 56+24 80 56 = 56 = 1.429 Inotherwords,theinputmemberwouldhavetoturnalmostoneanda halftimestooneturnoftheoutputmember. Nowlet’sassumethatthecarrieristheinputmemberandthering gearistheoutputmember.Wewouldusethesameequationin determiningthegearratio. Gear Ratio 56 56 Gear Ratio= 56+24 = 80 = 0.7 Inthiscase,theinputmemberwouldonlyturnalittlemorethana halfturnfortheoutputmembertoturnonce.SIMPSON PLANETARY GEAR UNIT Automatic Transmissions - Course 262 Theoperationofasimpleplanetarygearsetissummarizedinthe chartbelow:differentspeedsandrotationaldirectionscanbeobtained byholdingoneoftheplanetarymembersinafixedpositionproviding inputtorquetoanothermember,withthethirdmemberusedasan outputmember. Thischartrepresentsmoreratiosandcombinationsthanareusedin Toyotaautomatics,butarerepresentedheretoshowthescopeofits design.TheshadedareasrepresentthecombinationsusedinToyota transmissionsandare,therefore,theonlycombinationswewill discuss. HELD POWER POWER ROTATIONAL ROTATIONAL HELD POWER INPUT POWER OUTPUT SPEED TORQUE ROTATIONAL DIRECTION Ring gear Sun gear Carrier Reduced Increased Same direction as Ring gear Carrier Sun gear Increased Reduced direction as drive member S n gear Ring gear Carrier Reduced Increased Same direction as Sun gear Carrier Ring gear Increased Reduced direction as drive member Carrier Sun gear Ring gear Reduced Increased Opposite direction as Carrier Ring gear Sun gear Increased Reduced direction as drive member Operation Simple Planetary Gear OperationSECTION 3 28 TOYOTA Technical Training Whentheringgearorsungearisheldinafixedposition,andeitherof theothermembersisaninputmember,theoutputgearrotational directionisalwaysthesameastheinputgearrotationaldirection. Whentheinternalteethoftheringgearturnsclockwise,theexternal teethofthepiniongearswalkaroundthefixedsungearwhilerotating clockwise.Thiscausesthecarriertorotateatareducedspeed. Reduction Example: Speed reduction - torque increase Sun gear - Held member (15 teeth) Ring gear - Input member (45 teeth) Carrier - Output member (45 + 15 teeth) Thegearratioiscomputedasfollows: Gear ratio = Numberofoutputgearteeth Gearra tio= Numberofinputgearteeth Gear ratio 45+15 1 3:1 Gearrat io= 45 = 1.3:1 Inthisexample,theinputgear(ringgear)mustturn1.3timesto1 rotationoftheoutputgear(carrier).Thisexampleisusedinsecond gear. Forward DirectionSIMPSON PLANETARY GEAR UNIT Automatic Transmissions - Course 262 Whenthecarrierturnsclockwise,theexternaltoothedpiniongears walkaroundtheexternaltoothedsungearwhilerotatingclockwise. Thepiniongearscausetheinternaltoothedringgeartoacceleratetoa speedgreaterthanthecarrierspeedinaclockwisedirection. Overdrive Example: Speed increase - torque reduction Sun gear - Held member (15 teeth) Carrier - Input member (45 + 15 teeth) Ring Gear - Output member (45 teeth) Thegearratioiscomputedasfollows: Gear ratio 45 75:1 Gearrat io= 45+15 = .75:1 Inthisexample,theinputgear(carrier)mustturnthree-quartersofa turn(.75)to1rotationoftheoutputgear(ringgear).Thisexampleis usedinoverdrive.SECTION 3 30 TOYOTA Technical Training Wheneverthecarrierisheldandeitheroftheothergearsareinput members,theoutputgearwillrotateintheoppositedirection. Withthecarrierheld,whentheexternaltoothedsungearturns clockwise,theexternaltoothedpiniongearsonthecarrieridleinplace anddrivetheinternaltoothedringgearintheoppositedirection. Reverse Example: Speed reduction - torque increase Carrier - Held member (45 + 75 teeth) Sun gear - Input member (15 teeth) Ring gear - Output member (45 teeth) Thegearratioiscomputedasfollows: Gear ratio 45 3:1 Gearrat io= 15 = 3:1 Inthisexample,theinputgear(sun)mustturnthree(3)timesto1 rotationoftheoutputgear(ringgear).Thisexampleisusedinfirst gearandreversegear. Whenanytwomembersareheldtogetherandanothermember providestheinputturningforce,theentireassemblyturnsatthesame speedastheinputmember. Nowthegearratiosfromasingleplanetarysetdonotgiveusthe desiredratioswhichtakeadvantageoftheoptimumtorquecurveofthe engine.Soitisnecessarytousetwosingleplanetarygearsetswhich shareacommonsungear.Thisdesignisbasictomostallautomatic transmissionsinproductiontoday. Reverse Direction Direct Drive - (One-To-One Ratio)SIMPSON PLANETARY GEAR UNIT Automatic Transmissions - Course 262 Theplanetarygearassemblyisaverystronggearunit.Inputtorqueis transmittedtobothfrontandrearplanetarygearassemblies,which makesthisunitverydurable.However,sincetherearenosealsand0 ringstoreplace,thisunitcanbeeasilyoverlookedduringinspection.It isverycriticalthatitbeinspectedandmeasuredforexcessivewear duringtheoverhaulprocess.Excessivewearmaybethesourcefor futurefailureornoise. Beginwithavisualinspectionofthegearteeth.Anychipsofthegears wouldwarrantreplacement.Alsocheckthrustsurfacestoensurethat thebushingorbearinghasasmoothsurfacetomateto.Withthe visualinspectioncomplete,measurethebushinginsidediameterand compareittotherepairmanualspecifications.Ifitisoutsidethewear tolerance,replacetheassembly. Bushing Inside Diameter Measure the diameter in three positions. If any is outside the wear tolerance, replace the assembly. Useafeelergaugetomeasuretheclearanceofthepiniongearto carrierhousingandcomparetothespecifications.Standardclearance is0.0079“to0.0197“.Clearanceinexcessofthestandardonany planetarygearwouldrequirethereplacementofthecarrierassembly. Pinion Gear Clearance Excess clearance at any planetary gear requires replacement of the assembly. Inspection and Measurement Planetary Gear AssemblySECTION 3 32 TOYOTA Technical Training Therearethreetypesofholdingdevicesusedintheplanetarygearset. Eachtypehasitsspecificdesignadvantage.Thethreeinclude multiplateclutches/brakes,brakebandsandone-wayclutches. w MultiplateClutchholdstworotatingplanetarycomponents w Brakeholdsplanetarycomponentstothehousing - multiplatebrake - brakeband w RollerorSpragOne-WayClutchholdsplanetarycomponentsin onerotationaldirection Themultiplateclutchandmultiplatebrakearethemostcommonof thethreetypesofholdingdevices;theyareversatileandcanbe modifiedeasilybyremovingorincludingmorefrictiondiscs.Thebrake bandtakesverylittlespaceinthecavityofthetransmissionhousing andhasalargesurfaceareatocreatestrongholdingforce.One-way clutchesaresmallinsizeandreleaseandapplyquickly,givinggood responseforupshiftsanddownshifts. Multiplate Clutch The multiplate clutch connects two rotating components of the planetary gear set. Themultiplateclutchconnectstworotatingcomponentsofthe planetarygearset.TheSimpsonplanetarygearunitusestwo multiplateclutches,theforwardclutch(C1)andthedirectandreverse clutch(C2).Eachismadeupofaclutchdrumwhichissplinedto accepttheinputshaftandturningtorquefromtheengine.Thedrum alsoprovidestheborefortheclutchpiston.Becausethisassembly rotateswhilethevehicleisinmotion,itpresentsauniquechallengeto ensurefluidunderpressurereachestheclutchandholdstheclutch engagedforthousandsofmilesofservice. Holding Devices For Planetary Gear Set Multiplate ClutchSIMPSON PLANETARY GEAR UNIT Automatic Transmissions - Course 262 Thepistonhousesasealonitsinnerdiameterandonitsouter diameterwhichsealstheflui
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