Clutch

clutch assembly, clutch exploded view, sub parts functions

1. Clutch

4. Components of an Automobile
Automobile
Power Unit
Transmission System
Basic Structure
Controls
Auxiliaries
Superstructure
Power
Plant
Running
Gear
Framework
Or
Automobile
Chassis

5. Components of an Automobile
Automobile
Power Unit
Transmission System
Basic Structure
Controls
Auxiliaries
Superstructure
Transmission System
Clutch
Manual Transmission & Transaxles
Automatic transmission
Propeller shafts and drive shafts
Differential
Power
Plant
Gearbox

6. Some New Terms
•Transmissionrefersto
–rear-wheeldrivevehicles
–Aseparatedifferentialisusedwithatransmission.
•Transaxleusuallyrefers
–tofront-wheel-drivevehicles
–thathaveadifferentialbuiltintotheunit.

7. The Chassis
•Transmissionisthemechanismwhichisusedtotransfer
thepowerdevelopedbyenginetothewheelsofan
automobile.
•Oftentransmissionreferssimplytothegearboxthatuses
gearsandgeartrainstoprovidespeedandtorque
conversionsfromarotatingpowersourcetoanotherdevice.
Transmission System

8. Typical drive train components for a
rearwheel-drive car.

9. The Clutch
•Aclutchisadevicefordisconnectingandconnectingrotating
shafts.
•Inavehiclewithamanualgearbox,thedriverpushesdownthe
clutchwhenchanginggear,thusdisconnectingtheenginefrom
thegearbox.
•Itallowsatemporaryneutralpositionforgearchangesandalsoa
gradualwayoftakingupdrivefromrest.
•Theclutchassemblyislocatedbetweentheengineandthe
transmission/transaxle.

10. The Clutch
•Mostclutchesusedinthemodernmotorcararecalledfriction
clutches.
•Thismeansthattheyrelyonthefrictioncreatedbetweentwo
surfacestotransmitthedrivefromtheenginetothegearbox.
•Theclutchfulfilsanumberofdifferenttasks.

11. The Clutch
•Thefourmainonesare:
–Toconnect&transmitenginetorquetothetransmission/
transaxle/gearbox;
–Toprovideasmoothengagement&disengagementbetween
theengineandthetransmission/transaxle;
–Todampen&absorbengineimpulsesanddrivetrain
vibrations
–Toprovidethevehiclewithatemporaryneutral.

12. The Clutch
•Ifthevehiclehadnoclutchandtheengine
wasalwaysconnectedtothetransmission,then
–theenginewouldstopeverytimethevehiclewasbroughtto
astop.
•Theclutchengagesthetransmissiongraduallybyallowinga
certainamountofslippagebetweenthetransmission’sinput
shaftandtheflywheel.

13. What happens when the clutch is
engaged

14. Requirements of a clutch
•Aclutchmusttransmitdrivesmoothlywithnodrag.
–Dragiswheretheclutchisnotfullydisengagedandrubs
together,stilltransmittingsomedrive.
•Aclutchmusttransmitdrivesmoothlywithnoslip
onceitisfullyengaged.
–Slipiswheredriveisnotfullytransmittedandthefriction
surfacesslideovereachother,producingalossofturning
effort.
•Africtionclutchmustbeabletotransmitalloftheengine
torquetotherestofthetransmissionsystemwithoutslip.

15. Three methods that increase the torque
transmitting ability of a friction clutch

16. Parts of a Clutch
•Themaincomponentpartsofaclutchare:
–drivenplate,sometimesreferredtoastheclutch,centreor
frictionplate;
–pressureplatewhichcomescompletewiththeclutchcover,
springsordiaphragmtoprovidetheforcetopressthe
surfacestogether;
–releasebearingwhichprovidesthebearingsurfacewhich,
whenthedriveroperatestheclutchpedal,disconnectsthe
drivebetweentheengineandthegearbox;
–flywheel,themaindrivingmemberoftheclutch.

17. Parts of a Clutch

18. Parts of a Clutch
(1) Flywheel

19. Parts of a Clutch
•Theflywheel,animportantpartoftheengine,isalsothemaindriving
memberoftheclutch.
•Itisheavy,orhasalargemass,whichcreatesinertia.
•Itisnormallymadeofnodularorgraycastiron,whichhasahigh
graphitecontent(about3%)tolubricatetheengagementoftheclutch.
•Onarunningengine,thecrankshaftspeedsupasacylinderfires,then
slowsduetointernalenginefrictionuntilthenextcylinderfires.
(1) Flywheel

20. Parts of a Clutch
•Theinertiaprovidedbytheflywheelmasstendstokeep
crankshaftspeedmoreconstant.
•Wheneverfrictionexistsbetweentwomovingparts,heatis
generated.
•Theflywheelabsorbssomeoftheheatcreatedbyclutch
operationbyactingasaheatsinkfortheclutchfrictiondisc.
•Theflywheelhastwosetsofboltholesdrilledintoit.
(1) Flywheel

21. Parts of a Clutch
•Theinnersetisusedtofastentheflywheeltothecrankshaft,and
theoutersetprovidesamountingplateforthepressureplate
assembly.
•Anexternalringgearispressedorweldedontotheflywheel
alongitsoutercircumference.
•Whenthestartermotorisengaged,thestarter-drivegear
mesheswiththeflywheelringgear.
(1) Flywheel

22. Parts of a Clutch
•Throughgearreduction,theflywheeltransfersstartermotor
rotationtothecrankshafttocranktheengine.
•Thefaceonthetransmissionsideoftheflywheelhasasmooth,
machinedareathatcreatestheapplicationsurfacefortheclutch
frictiondisc.
•Thissurfacemustbeproperlyfinishedtoallowadequateslippage
astheclutchengagesanddisengages,andtopreventslippage
whentheclutchisengaged.
(1) Flywheel

23. Parts of a Clutch
Engaged Disengaged

24. Parts of a Clutch

25. Multi Plate Clutch

26. Parts of a Clutch
(2) Clutch Disc

27. Parts of a Clutch
(2) Clutch Disc

28. Parts of a Clutch
(2) Clutch Disc

29. Parts of a Clutch
(2) Clutch Disc
•Theclutchdiscisalsocalledadrivencenterplateorafriction
disc.
•Theclutchdiscprovidesthefrictionmaterialneededtotransmit
enginetorquefromtheflywheelandpressureplatetotheinput
shaftofthetransmission.
•Thecentralalloy-steel—splinedhubisseparatefromthesteel
disc(CentralPlate).Driveistransmittedfromthesteeldisctothe
hubthroughheavytorsionalcoilsprings.

30. Parts of a Clutch
(2) Clutch Disc
•Thisspringhubarrangementdampenstorsionalvibrationsfrom
theengine.
•Italsoabsorbsshockloadsimposedonthedrivelinebysudden
orviolentclutchengagement.
•Wavedspringsteelsegmentslocatedbetweenthefriction
facingscausethefacingstospreadapartslightlywhentheclutch
isdisengagedandtocompressasitisengaged.

31. Parts of a Clutch
(2) Clutch Disc

32. Parts of a Clutch
(2) Clutch Disc
•This gives a cushioning effect during clamping of the clutch disc in the
pressure plate.
•These waved springs allow a progressive application of the pressure
plate clamping force as the waved springs are being compressed when
the pedal is being released.
•The result is smoother engagement of the clutch when starting from a
stop.
•These springs reduce chatter when the clutch is engaged and also
reduce the chance of the clutch disc sticking to the flywheel and
pressure plate surfaces when the clutch is disengaged.

33. Parts of a Clutch
(2) Clutch Disc
•Theclutchdiscissplinedtothetransmission’sinputshaftand
receivesthedrivingmotionfromtheflywheelandpressureplate
assemblyandtransmitsthatmotiontothetransmissioninput
shaft.
•Frictionmaterialisrivetedtobothsidesoftheclutchdisc—one
sidetouchestheflywheeloftheengineandtheotherside
touchesthefrictionsurfaceofthepressureplate.

34. Parts of a Clutch
(2) Clutch Disc
•Therearetwotypesoffrictionfacings:-Molded&Woven
•Moldedfrictionfacingsarepreferredbecausetheywithstand
greaterpressureplateloadingforcewithoutdamage.
•Wovenfrictionfacingsareusedwhenadditionalcushioning
actionisneededforclutchengagement.Wovenmaterialsare
softer,buttheymaynotlastaslongasmoldedmaterials.

35. Parts of a Clutch
(2) Clutch Disc
•Frictionmaterialsoperateinhighheatandpressure.
•Formanyyears,asbestoswasthemostcommonmaterialusedin
bothclutchandbrakelinings.
•However,itisnolongerusedbecauseinhalingtinyparticlesof
asbestoscauseslungdamage.
•Today,clutchfrictionmaterialmaycontainsparticlesofcotton,
brass,rope,andwiretoprolongthelifeoftheclutchdiscandto
providetorsionalstrength.

36. Parts of a Clutch
(2) Clutch Disc
•Groovesarecutacrossthefaceofthefrictionfacings.
•Thispromotescleandisengagementofthedrivendiscfromthe
flywheelandpressureplate;italsopromotesbettercooling.

37. Parts of a Clutch
(3) Pressure Plate Assembly
•Thepurposeofthepressureplateassemblyistwofold.
•First,itmustsqueezetheclutchdiscontotheflywheelwith
sufficientforcetotransmitenginetorqueefficiently.
•Second,itmustmoveawayfromtheclutchdiscsotheclutchdisc
canstoprotating,eventhoughtheflywheelandpressureplate
continuetorotate.

38. Parts of a Clutch
(3) Pressure Plate Assembly
•Basically,therearetwotypesofpressureplateassemblies:
–thosewithcoilspringsand
–thosewithadiaphragmspring.
•Bothtypeshaveastampedsteelcoverthatboltstotheflywheel
andactsasahousingtoholdthepartstogether.Inboth,thereis
alsothepressureplate,whichisaheavy,flatringmadeof
nodularorgraycastiron.

39. Parts of a Clutch
(3) Pressure Plate Assembly
•Acoilspringpressureplateassemblyusescoilspringsandrelease
leverstomovethepressureplatebackandforth.
•Thespringsexertpressuretoholdthepressureplatetightly
againsttheclutchdiscandflywheel.
•Thisforcestheclutchdiscagainsttheflywheel.
•Thereleaseleversreleasetheholdingforceofthesprings.There
areusuallythreeofthem.
Coil Spring Pressure Plate Assembly

40. Parts of a Clutch
(3) Pressure Plate Assembly
•Todisengagetheclutch,thereleasebearingpushestheinner
endsofthereleaseleversforwardtowardtheflywheel.
•Eachendofthelevermovesintheoppositedirection.When
forcepushesoneendoftheleverdown,theotherendmovesup.
•Inacoilspringpressureplate,thereleaseleveryokesactas
fulcrumsforthelevers,andtheouterendsofthereleaselevers
movebackward,pullingthepressureplateawayfromtheclutch
disc.
Coil Spring Pressure Plate Assembly

41. Parts of a Clutch
(3) Pressure Plate Assembly
•Thiscompressesthespringsandreleasestheclampingofthe
clutchdiscbetweenthepressureplateandflywheel.
•Whentheclutchisengaged,thereleasebearingmovesaway
fromthepressureplate.
•Thisallowsthepressureplatespringstopushthepressureplate
andclutchdiscagainsttheflywheel,allowingpowertransfer
fromtheenginetothetransmission.
Coil Spring Pressure Plate Assembly

42. Parts of a Clutch
(3) Pressure Plate Assembly
Coil Spring Pressure Plate Assembly

43. Parts of a Clutch
(3) Pressure Plate Assembly
Diaphragm Spring Pressure Plate Assembly

44. Parts of a Clutch
(3) Pressure Plate Assembly
Engaged Disengaged

45. Parts of a Clutch
4. Clutch Release Bearing

46. Parts of a Clutch
4. Clutch Release Bearing
•The clutch release bearing is also called a throwoutbearing.
•Its function is to smoothly and quietly move the pressure plate
release levers or diaphragm spring through the engagement and
disengagement process.
•When the driver depresses the clutch pedal, the movement is
passed to the release bearing by either hydraulics or cable and
the release bearing then pushes or pulls the diaphragm spring
(depending on whether the clutch is a ‘push’ or ‘pull’ design)

47. Parts of a Clutch
4. Clutch Release Bearing
•The outer part of the release bearing is held (by the release lever)
so it does not rotate, and the inner race of the bearing rotates
with the diaphragm spring and clutch cover.

48. Coil Spring vs. Diaphragm spring
•Anumberofearlyclutchesusedcoilspringstoprovidethe
clampingeffort.Overaperiodoftime,coilspringtensionand
lengthwouldchangeduetowearandtear.Whenthishappened,
anunevenclampingforcecouldbeproducedatthepressure
plate.Thisunevenclampingforcemightleadtoclutchdrag,slip
orvibrations.
•Toovercometheseproblemsaspringmechanismcalled‘a
diaphragm’wasdeveloped.Thisdiaphragmspringisasingle
metalplate,madeintoaseriesofsprungsteelfingers.Itis
slightlydishedinshape.

49. Coil Spring vs. Diaphragm spring
•Whenoneendofthefingersispressedbytheclutchrelease
bearing,thefingerspivotaboutafulcrum(likeaseesaw).This
movestheoppositeendofthediaphragmfingersintheother
direction.Whenthishappens,thepressureplateismovedaway
fromthefrictionplateanddisengagestheclutch.
•Whenthedriverliftshisfootofftheclutchpedal,theendsofthe
fingersofthediaphragmspringarereleased.Becausethesteel
fingersaresprung,theyreturntotheiroriginalpositionand
reapplypressuretothefrictionplate.Thisthenreconnectsthe
drive.Becausethespringdiaphragmfingersaremadefroma
singlepieceofmetal,anevenclampingforcecanbeproduced.
Thisovercomesmanyoftheproblemscreatedwhenusingcoil
springmechanisms.

50. Freeplay
•Whentheclutchisengaged,noforceshouldbeplacedonthe
releasebearingwhereittouchesthediaphragmspringsofthe
pressureplate.
•Asmallclearanceorgapisnormallyneededatthepedalend.
Thisiscalled‘clutchpedalfreeplay’.
•Clutchpedalfreeplayisneededfortworeasons:
–Itmakessurethatthereleasebearingisnotcontinuouslypressedagainst
therotatingfingersofthediaphragmspring.Thiswillhelpreducewearon
boththediaphragmspringfingersandtheclutchreleasebearingitself.
–Itensuresthattheclutchmechanismisfullyengaged.

51. Freeplay
•Iffreeplaydidn’texist,thenthebearingmightbepushingonthe
clutchreleasesprings.Thiswouldpartlydisengagetheclutch
frictionplate.Thiswouldthencausethedriveplatetoslipandto
wearoutearly.
•Iftoomuchfreeplayexists,thenwhentheclutchpedalispressed
bythedriver,theclutchmightnotfullydisengage.Thiswould
meanthatthefrictionplateisstillbeinggrippedslightlybetween
thepressureplateandTheflywheel.Ifthishappens,theengine
couldnotbefullydisconnectedfromthegearbox.Thiscanmake
changinggeardifficult.Iftheclutchfrictionplatedoesnotfully
disengage,thisisreferredtoasclutchdrag.