Gear box

Gear Box

1. Ch-3 Gear Box
By, Deep Shah
Sub: ATM (3330202)

2. Introduction of Powertrains
ATransmissionsystemusesaclutch,gearbox,propellershaftanda
differentialgeartotransmitpowerfromenginetotheroadwheels
Thepowermaybetransmittedtorearorfrontorallfourwheels
dependingonthedriveused
Theclutchandgearboxvariestheratiooftorqueoutputtotorque
input
Thepropellershafttransmitsfinaltorquetotherearaxlefromgear
box
Adifferentialgearequallydistributesthefinaltorquebetweenthe
roadwheels.

3. Functions of Transmission System
Itdisconnectsenginefromdrivingwheelswhen
required
Theengineisconnectedtodrivingwheelswhen
required
Itchangesratiooftorqueoutputtotorqueinput,as
desired
Itturnsthedrivethrougharightangle

4. What is Gear Box….???

5. Gear Box
Thegearboxisnecessaryinthetransmissionsystemto
maintainenginespeed(ortorque)atthemosteconomical
valueunderallconditionsofvehiclemovement.
Anidealgearboxwouldprovideaninfiniterangeof
gearratios,sothattheenginespeedshouldbekeptator
nearthatthemaximumpowerisdevelopedwhateverthe
speedofthevehicle.

6. Purpose of Gear Box
Providesspeedandtorqueconversionsbecauseofthelimitationsofinternal
combustionengines.
Alsofacilitateschangeofdirectionofoutputshaftforreversing.
Automotivegearboxesareusedtoreduceloadontheenginebymanipulating
torqueandspeed.
Theyhavetheoptiontoselectoneofseveraldifferentgearratios.
Oncetheenginehasreachedanumberofrevolutionsperminute,itisadvisableto
increasethegeartoreducetheenginerpmtoreducewearontheengine,allow
morecontrol,andgreaterspeeds,betteracceleration,andbetterfueleconomy.
Mostgearboxesareusedtoincreasetorque&reducethespeedofaoutputshaft.
Thisproducesamechanicaladvantage
Automotivegearboxalsohavetheprovisiontodotheoppositei.e.providean
increaseinoutputshaftspeedwithareductionoftorque(overdrive).

7. Types of Gear Box
SlidingMeshtypegearbox
ConstantMeshtypegearbox
SynchroMeshtypegearbox
Planetarytypegearbox

8. Types of Gear Box
ManuallyOperatedSelectivetype
SlidingMeshtypegearbox
ConstantMeshtypegearbox
SynchroMeshtypegearbox
Planetarytypegearbox
Over-Drive
Semi-Automatic
AutomaticTransmission

9. Sliding Mesh type Gear Box
Thepowercomesfromtheenginetotheclutchshaftandthen
totheclutchgearwhichisalwaysinmeshwithgearonthelay
shaft.
Allthegearsonthelayshaftarefixedtoitandassuchtheyare
allthetimerotatingwhentheengineisrunningandtheclutchis
engaged.
Threedirectandonereversespeedsareattainedonsuitably
movingthegearonthemainshaftbymeansofselector
mechanism.

10. Sliding Mesh type Gear Box

11. Constant Mesh type Gear Box
Inthistypeofgearbox,allthegearsareinconstantmeshwiththe
correspondinggearsonthelayshaft.Thegearsonthemainshaft
whichissplinedarefree.
Thedogclutchareprovidedwhicharefreetoslideonthemainshaft.
Thegearsonthelayshaftare,however,fixed.
Whentheleftdogclutchisslidetotheleftbymeansoftheselector
mechanism,itsteethareengagedwiththoseontheclutchgearandwe
getthedirectgear.
Thesamedogclutch,however,whentheslidetorightmakescontact
withthesecondgear.
Similarlymovementoftherightdogclutchtotheleftresultinlow
gearandtowardsrightinreversegear.

12. Constant Mesh type Gear Box

13. Synchro-Mesh type Gear Box
Thistypeofgearboxissimilartotheconstantmeshtypeinthatall
thegearsonthemainshaftareinconstantmeshwiththe
correspondinggearsonthelayshaft.
Thegearsonthelayshaftarefixedtoitwhilethoseonthemain
shaftarefreetorotateonthesame.
Itsworkingisalsosimilartotheconstantmeshtype,butinthe
formerthereisonedefiniteimprovementoverthelatter.
Thisistheprovisionofsynchromeshdevicewhichavoidsthe
necessityofdoubledeclutching.Thepartswhichultimatelyaretobe
engagedarefirstbroughtintofrictionalcontactwhichequalizestheir
speed,afterwhichthesemaybeengagedsmoothly.

14. Synchro-Mesh type Gear Box

15. Synchronizers
Adeviceusedtobringtwoadjacentmemberstothesamespeed
beforeallowingthesleevetoengagethem.
Thetwoelementsarefrictionclutchandtoothedclutch.
LockthepositiveengagementuntilspeedsareSynchronized.
Establishthepositiveengagementandpowerflow.
SynchronizerissplinedontheshaftConeonthegear(blue)fitsinto
cone-shapedareainthecollar.
Frictionbetweentheconeandcollarsynchronizethecollar&gear.
Theouterportionofthecollar(sleeve)thenslidessothatthedogteeth
engagethegear.

16. Synchronizers

17. Epicyclic/Planetary Gear Box
Itconsistsoftwo,threeorevenfourepicyclicorplanetarygear
sets.Asimplegearsethasasungear,aboutwhichplanetsturn
around.Theseplanetgeararecarriedbyacarrierandashaft
andarealsoinmeshinternallywitharinggear,whichisalso
calledannulusorinternalgearsometimes.
Differenttorqueratiosi.e.speedratiosareobtainedbymaking
ofthepartstationary.Similarlybylockingtwopartswitheach
other,asoliddrivei.e.directgearobtain.

18. Epicyclic/Planetary Gear Box

19. Epicyclic/Planetary Gear Box
Driving MemberDriven MemberStationary
Forward Very Slow Sun Planetary Ring
Forward Slow Ring Planetary Sun
Forward Fast Planetary Ring Sun
Forward Very FastPlanetary Sun Ring
Reverse Slow Sun Ring Planetary
Reverse Fast Ring Sun Planetary

20. Different Types of Gears (Spur Gear)
Advantages
SimpleandRigid
Spacerisnotrequiredattheend
ofshaft
Canjointwoparallelshafts
Disadvantages
Producenoiseduringworking
Wornoutfast/quickly

21. Different Types of Gears (Helical Gear)
Advantages
Loadcanbedividedonmorethen
oneteeth.
Lightinweight
Canrotatewithoutvibrationat
highspeed
Workseasilyandnoiseless
Doesn’twearoutfast
Disadvantages
Duetoinclinedtooth,spaceris
requiredatshaftend
Possiblethatgearmaycomeout
ofmeshing

22. Different Types of Gears (Double Helical Gear)
Advantages
Spacerisnotnecessarytoprovide
atshaftenddueitsdoubleform
Gearsisn’tcomingoutofthe
meshing
Canrotateathighspeedwithout
vibration
Functionissimple
Servicelifeismore
Disadvantages
Producelittlenoiseduring
working
Constructioniscomplex
Productioncostismore

23. Gear Shifting (Selector) Mechanism
Thegearshiftlevercanbelocatedeitheronsteeringoronthe
steeringcolumn,forusingitforshiftingthegears.
Thesteeringcolumngearshiftmechanismisusedoncars
whilefootboardtypeisusedincommercialvehicles,jeeps,
mediumvehiclesandvans.
Thegearshiftingmechanismisusedforchanginggearseasily
andselectingrequiredgeartrainandbringingtheselected
gearsintooperation.

24. Gear Shifting (Selector) Mechanism
Forengagingtheslotsonthegearboxitisconsistingoffork
onthegearbox.
Intoaslotatthetopofthebossoftheselectorfork,thetipof
thegearshiftleverisfitted.
Inneutralpositionitisprovidedwithfreesidewaymovement
ineitherway.Incaseofsteeringcolumngearchanges
arrangement,thefreemovementisintheupanddown
direction.
Thefloortypeshiftingmechanismislesscostlyasitrequires
lessmaintenance.

25. Gear Shifting (Selector) Mechanism
Thesteeringcolumntypeshiftingmechanismcanbeoperated
easily,asdriverhastomovehishandthroughashortdistance
andthefrontcompartmentspaceofthevehicleismore.
Itisdifficulttolearntooperatethesteeringcolumnshifting
mechanism,itiscomplex,needmoremaintenanceandis
costly.

26. Gear Shifting (Selector) Mechanism

27. Gear Shifting (Selector) Mechanism

28. Gear Inter-locking Device

29. Torque Converter
Internalcombustionenginescreatepowerbyburningfuelthatforcesthe
pistonstoturnthecrankshaftlocatedatthebottomoftheengine.This
rotationalforceistransferredtothetransmissionbythefluidpressure
insidethetorqueconverter.
Insideofthetorqueconvertercoverlivesaseriesofpropeller-likeblades
calledthepump.Thisassemblyspinsinunisonwiththeengine
crankshaft,forcingtransmissionfluidontoanotherbladeassemblycalled
theimpeller.Thissecondsetofbladesisconnectedtothetransmission
inputshaft.Theamountofhydraulicpressurethatitcreatesinsidethe
transmissiondictatesthegearandultimately,thespeedofthevehicle.

30. Torque Converter
Theimpeller’sspeedisregulatedbytheenginesideofthis
hydrodynamiccircuit(i.e.speedofthepumpblades).Whenthevehicleis
stationary,orthedriverappliesthebrakes,theimpellerwillslow
considerably,whilethepumpcontinuestospin.Thisallowsthetorque
convertertoactliketheclutchinamanualtransmission–itallowsthe
enginetocontinuerunningwhilethevehicleisatacompletestop.
Oncethetransmissionfluidhasbeenhurledontotheimpellerblades,it
hastoreturntothepumpinordertokeepthecyclegoing.Sincethefluid
isnowflowinginadifferentdirectionthanthepump,ithastobe
reversedtoavoidslowingdown(andstalling)theengine.

31. Torque Converter
Todothis,athirdfinnedwheelcalledthestatorislocatedbetweenthe
twoturbinesonthetransmissionpumpshaft.Itsbladesareprecisely
angledsothatwhenthetransmissionfluidhitsthem,itreversesdirection
andgetschanneledbacktothepump.Whenthevehiclestops,itsbuilt-in
one-wayclutchcausesittostopspinning,breakingthehydrodynamic
circuit.

32. Torque Converter

33. Torque Converter

34. Advantages of Torque Converter
Itmultipliesthetorquebythemovementofoil.
Allpartsareremainsinkedinoilhencetheirwearisless.
Ittransmitspowerwithoutnoise&shocksatdifferentspeedandtorque
ratio.
Operationiscompletelyautomatic&reliable.
Generallyservicingoftorqueconverterisnotnecessary.
Constructionoftorqueconverterissimple,wearislessduetolesseffect
ofslip.

35. Disadvantages of Torque Converter
Thetorqueavailabletostartthevehiclefromrestinfirstgearisreduces
withtheincreaseinspeedofthevehicle.
Itbecomesfluidcouplingonincreasingspeedofvehicle,hencethe
torquemultiplicationstopsthereafter.
Thereisnotorquemultiplicationinthirdandfourthgear.
Reversegeararrangementofmechanicaltypeistobeusedwithit.
Topreventtorqueconverterfromoverrunning,afreewheeldeviceis
required.

36. Over Drive
Overdriveisadevicetostepupthegearratiointhecar.Itisfittedinbetween
transmissionandthepropellershaft.Itenablesahighcruisingspeedtobeattainedwith
acomparativelylowenginespeed(upto20–25%)onlongjourneys.
Thisresultsinlesswearoftheengineanddecreasesvibrationandnoise.Asthefriction
lowsatlowerspeedsisless,thereisasavingoffuelalsowiththeoverdrive.
Overdriveisgenerallyfittedontopgearonly.Butinsomesportcars,overdrivesare
alsofittedongearsotherthanthetopgearwhichincreasesthetorqueratiosavailable.
Forexamples,whenoverdriveisfatedontop,thirdandsecondgear,sevenforward
speedsortorqueratiosareavailable.
Theoverdrivemaybeoperatedeithermanuallyorautomaticallyatapredetermined
speed.

37. Over Drive

38. Over Drive
Itconsistsofanepicyclicgeartraininwhichthesungearisfreetorotateonthe
inputshaft,whilethecarriercanmoveonsplines,ontheinputshaft.Afreewheel
clutchisalsofittedontheinputshaftsplines.Theoutputshaftisconnectedtothe
ring.Whenthesungearislockedwiththecasingi.e.,itbecomesstationary,ofthe
outputshaftisincreasedi.e.,overdriveisengaged.
Whenthesungearislockedtothecarrierortothering,soliddrivethroughnis
obtained.Thusdependingonthelockingofthesungearwithringgearorwith
carriertheoverdriveorthenormaldirectdriveisobtained.Thereisanother
possiblecontrolofthemechanismi.e.,whenthesunwheeliskeptfreetorotateon
theinputshaft.Inthiscasethereisdirectdrivethroughthefreewheelclutchwhen
theenginedevelopspower.

39. Advantages of Over Drive
Whencarismovingaheadatconstantspeed,thenisdoesn’trequiremorepowerto
maintainthatspeed.Hencetomaintainthespeedofthecar,enginespeedcanbereduced
usingtheoverdrive.
Highspeedrunningofvehicleatlowenginespeedcanbeobtain.
Fuelconsumptiondecrease.
Thewearofengine&auxiliaryunitsdecreases.
DuetoreductioninengineRPMconsiderablesavingoffuelisachieved.
Forrequiredvehiclespeed,engineissunningslowlyhenceitsservicelifeincrease.
Theoverdrivecanbecontrolledelectricallyorhydraulicallyfromdash-boardoraswitch
providedonsteeringcolumn.