) P i ä h 5) 10) Di h b 14) Rill k ll i 21) S

AN INTRODUCTION TOAUTOMOTIVE CLUTCHT E C H N O L O G Y

AS AUTOTEILE SERVICE GMBH & CO.A M E M B E R O F T H E L U K G R O U P

LuK CLUTCH COURSE

A W A R D E D

When it comes to setting the pace in Clutch Technology and Product Quality, LuK leads the way worldwide.Numerous awards from the major vehicle manufacturers are a clear indication of excellence, e.g.:

three times GM Supplier of the Year; four times Audi Supplier of the Year and 1994 winner of the Gold Award;awards from Toyota and Nissan, as well as the VW Group’s ”Value of the Customer Award”,

presented for the first time in 1993, are the latest examples of LuK’s success.The LuK Group consists of 16 subsidiaries with manufacturing plants in Germany, Brazil, Mexico,

the US, Great Britain and South Africa. LuK supply original equipment to 1 in 4 vehicles worldwide, makes such as Audi, Autolatina, BMW, Chrysler, Citroën, Fiat, Ford, GM, Jaguar, Mazda, Mercedes-Benz, Nissan, Opel, Peugeot, Porsche,

Seat, Toyota, Vauxhall and VW. That’s a total of 13 million clutches a year.

The original equipment choice.

3

Introduction ContentsKnowledge is power …

... as the saying goes, and these words acquirenew meaning in an age of changing technolo-gies and increasing standards of convenienceand engineering. It is no longer a matter ofgaining mastery over others, but of masteringtechnologies and the problems they pose.

This assumes appropriate training and aconstant flow of information about changesand about experience gathered. As a maker ofclutches for almost every automotive manufac-turer in the world, LuK knows that its productscan only display their qualities to the full whenthey are properly installed and professionallymaintained.

This brochure is intended to give all readers anoverview of the basic principles and designs ofmodern clutch technology. An important aim isto make clear that clutches have becomeprecision parts which need careful handlingand must be installed and removed exactly asper the assembly instructions.

Supplementary training documents, such asthe NOK brochure, flashcards (also availableas overheads) are likewise available forpurchase. AS/LuK has also developed an inter-active teaching programme.

The European Training Concept

This deals with the basic principles of clutchtechnology, correct diagnosis of damage andessential service tips. This training programme,which works with the aid of video, can bepurchased as a self-tutoring unit (for privatestudy) or as a trainer guide (for trainers).

AS can provide you with more information ifyou need it – please call +49 6103 753251.

LuK hopes that you enjoy working with thisbooklet and wishes you every success bothlearning and subsequently working“on the spot”.

AS Autoteile-Service GmbH & Co.LuK Aftermarket-Service Ltd

Thomas PetriSiegfried Kronmüller Customer Service/Managing Director Engineering Manager

A history of clutch technology 4–9

Chart 1: Functional Schematic with components 10

Chart 2: Clutch disc- detail parts, torsion damper and cushion deflection 12

Chart 3: Clutch disc – designs, torsion damper graphs 14

Chart 4: Clutch pressure plate assembly – designs and graphs 16

Chart 5: Clutch pressure plate assembly – designs and installation principles 18

Chart 13: SAC clutch cover assembly – designs types and characteristics 20

Chart 11: Dual-mass flywheel (DMF) – design and function 22

Chart 12: DFC – Damped Flywheel Clutch (Compact DMF) – Layout and function 24

Index 26

4

A history of clutch technologyIn the course of over 100 years of automotivehistory, nearly all components have undergoneenormous technological developments. Relia-bility, production costs and service-friend-liness as well as, more recently, environmentalsafety, have been and continue to be the crite-ria demanding new and better solutions fromautomotive engineers. The basic designs areusually known early on, but only the availabilityof new materials and processing proceduresmakes their realisation feasible.

It was not until the end of the first decade ofthis century that the internal combustionengine surpassed the competing steam andelectricity-based automotive drive conceptson a large scale. In 1902, a petrol-enginedvehicle for the first time broke the overallspeed record; up to then, electric and steam-powered vehicles had set the standards, andproponents of the three drive concepts con-tinued to compete for the absolute speedrecord throughout the first decade.

Steam and electric drives have a decisiveadvantage over “motorised vehicles with liquidfuels”, as they used to be called. Thanks to thealmost ideal torque band, they required neitherclutches nor transmissions, and thus wereeasier to operate, had fewer malfunctions andwere easier to service. As an internal combus-tion engine only delivers its output at enginespeed, there must be a division betweenengine and transmission. The speed-depend-ent drive principle of the petrol engine necessi-tates a mechanical aid for starting, as suffi-cient output (torque) is only available aftercertain engine speeds have been attained.Besides the function of a starting clutch, how-ever, that of a dividing clutch is equally import-ant, for it allows load-free gear changing whiledriving. Because of the complexity of therelated problems, many smaller vehicles in theearly years of automotive design did not have astarting clutch; the motor car had to be pushedinto motion.

The operating principles of the first clutchesoriginated in the mechanised factories of earlymodern industry. By analogy with the trans-mission belts used there, flat leather belts werenow introduced into motor cars. When ten-sioned by a roller, the belt transmitted the driveoutput of the engine’s belt pulley to the drivegears, and when loosened, it slipped through –i. e. disengaged. As this procedure caused theleather belts to wear out fast, a new tactic wasadopted of installing an idler pulley of the samesize beside the drive belt pulley. By moving alever, the transmission belt could be guidedfrom the idler pulley on to the drive pulley.The motor car patented by Benz in 1886, whichBertha Benz used to make the first long-dis-tance journey in the history of motor vehicles –from Mannheim to Pforzheim – already oper-ated according to this clutch concept.

The disadvantages of a belt drive, such as lowefficiency, high susceptibility to wear and inad-equate running characteristics especially

under rainy conditions, on one hand and thenecessity of variable-speed transmissions forthe gradually increasing engine outputs on theother hand, induced engineers to seek betteralternatives to transmission clutches.

The results were a wide variety of clutch types– including the forerunners of our present-dayclutches – all based on the principle of the fric-tion clutch. Here the disc is located on the endof the crankshaft and is joined by a second,stationary disc. When the two make contact,friction is produced and the secondary disc isset in motion. As the clamping load isincreased, the driving disc carries along thedriven disc with increasing speed until powertransmission is reached, and both discs havethe same rotational speed. In the period up tofull engagement, the main driving energy isconverted into heat as the discs slide acrossone another. This arrangement meets the twochief demands – on the one hand gradual andgentle engagement, so that, when driving off,the engine is not cut off and does not jerk withthe drive train, and on the other hand loss-freepower transmission with the clutch engaged.

The clutch is actuated via the foot pedal, whichpulls back the cone carrier via a release leveragainst the spring force and thus disengagesthe clutch.

The basic form of this design principle wasalready used in 1889, in the steel wheel cars

from Daimler, which had a cone/bevel frictionclutch. Here a freely moving frictional conelocated on the engine shaft and firmlyconnected to the clutch shaft via the clutchhousing engages in the conically machined outflywheel. A spring presses the cone into the fly-wheel recess so that pressure on the foot

pedal will pull the cone back against the springpressure via the freely movable clutch releasesleeve, thereby interrupting the power trans-mission. Camel hair belts originally functionedas friction linings on the cone surface, butwere soon replaced by leather belts. The latterwere soaked in castor oil as a protectivemeasure against moisture, grease and oil.

The advantages – self-adjusting, no strain onthe drive or transmission shaft – were, how-ever, out-weighed by the disadvantages: on theone hand, the friction lining wore out fast andreplacement was complicated; hence oneswitched to designs with spring-loaded pins orleaf springs under the leather lining. Secondly,the flywheel and clutch cone were very large,so that, owing to its high moment of inertia, the

Transmission belt clutch from the Benz patented motor car of 1886.

The basic principle of the friction clutch:The driven disc is pressed onto the driving disc until thefrictional connection is made.

Design of the cone/bevel friction clutch dominant through-out the 1920s.

Motorschwungrad mit Hohlkegel vom Motor Anpreßfeder zum Getriebe Mitnehmerkegel mit Lederbelag

engine flywheel with hollow conefrom enginecoil springto transmissiondriver cone with leather lining

5

clutch part came to rest much more slowlythan was required after the release for gearchanging (transmissions were not yet synchro-nised). To remedy this problem, around 1910 anadditional clutch brake or transmission brakewas installed which had to be actuated via asecond foot pedal – usually in conjunction withthe clutch pedal and located together with thelatter on a common pedal shaft.

The habit of many drivers of allowing the clutchto slip instead of changing gears when regulat-ing the vehicle speed, heated the flywheelmore than it did the friction cone, which wasthermally insulated by the leather lining. After aspell of rugged driving, the cone could engagemore deeply in the flywheel as it had beenexpanded by the heat – leaving it jammed tightwhen it cooled down.

By the end of the First World War, metallicfriction linings were becoming increasinglypopular. Previously, one had experimentedwith other solutions: For example, the “NeueAutomobil-Gesellschaft (NAG)” constructed aclutch containing a camel-hair lined cone,stamped from sheet metal and equipped withfan-like blades for cooling, which engaged ina two-part, leather-lined ring screwed into theflywheel. The two-part construction allowedthe ring to be easily removed, simplifyingmaintenance and reducing the frequency ofjamming.

The Daimler engine corporation developed anopen friction clutch with a bare aluminiumcone. For a soft release, oil had to be drippedonto the frictional surfaces at regular intervals.

Cone clutches continued to dominate through-out the 1920s thanks to their simplicity. Metallic

clutches with cylindrical friction surfaces didnot win acceptance because of their pooroperational characteristics. Only the springband clutch, a derivative of the cylindricalclutch that had been installed in Mercedescars by Daimler since the turn of the century,

was able to persevere until the First World Warthanks to an ingenious design.

In the spring band clutch, a sturdy, spiral-shaped spring band, which received the drum-shaped end of the transmission shaft, wasfitted in a recess of the flywheel. One end of thecoil spring was connected to the flywheel,while the other was fastened to the cover ofthe spring housing. The actuation of the clutch

Cross section of a cone clutch showing the typicalcomponents: clutch cone and correspondingly turned-outflywheel.

View of a chassis with a cone clutch. During disengagement, the clutch brake ensured quick speed reduction of the largemass with a cone clutch.

Cone clutch with spring-compressed leather lining.

Schwungrad KurbelwellenflanschKupplungsfußhebelAusrückmuffe Ausrückhebel Kupplungswelle KupplungsgehäuseKupplungsfeder KupplungskegelKupplungsbelag

crankshaft flangeflywheelrelease sleeveclutch pedalrelease leverclutch shaftclutch housingclutch springclutch coneclutch lining

Motor KupplungKupplungsfußhebelWechselgetriebeKreuzgelenk Gelenkwelle Linkes Hinterrad GelenkwellenrohrTellerrad FederLinke HinterachswelleHinterachsbrückeSchubkugel zur Aufnahme desHinterachsschubes und Übertragungauf den FahrgestellrahmenHinterachsgehäuse Antriebskegelrad Rechte Hinterachswelle Ausgleichgetriebe Fahrgestellrahmen Rechtes Hinterrad

engineclutchclutch pedalvariable-speed transmission universal jointpropshaftrear left wheelpropshaft tubedifferential ring gear springleft rear axle shaftrear-axle housingtorque ball for absorbing rear-axle thrust and transferring it to chassis framedifferential housingdifferential bevel pinion right rear axle shaftdifferentialchassis framerear right wheel

6

A history of clutch technology

pedal tensioned the spring band, which thencoiled itself (self-reinforcing) more and morefirmly around the drum, driving the trans-mission shaft – and engaging the clutch. Thecompression of the springs required onlyslight force and effected a gentle engagementof the clutch.

At about the same time that the Daimlercorporation were developing their spring bandclutch, Professor Hele-Shaw from Englandwas already experimenting with a multi-plateclutch that can be regarded as the forerunnerof today’s conventional single-disc dryclutch. Multi-plate clutches, named “Weston

clutches” after the first large-scale producer,had a decisive advantage over the cone fric-tion clutch: much greater friction surface areawith a lower space requirement and constantengagement.

In the case of the multi-plate clutch, the fly-wheel is connected to a drum-shaped housingthat has grooves on the inside correspondingto the shape of the outer edge of the plate,allowing it to turn with the crankshaft orflywheel and at the same time to move longitu-dinally. An identical number of discs withmatching inner recesses are centred on a hubconnected to the clutch shaft. The discs canmove longitudinally along the clutch shaft onthe hub. During installation, inner and outerclutch plates are alternately combined to forma plate packet, so that a driving and a drivendisc always follow one another.

The plate pairs formed in this fashion, originallywith a bronze disc always turning against asteel one, were pressed together by a pressureplate under the force of a clutch spring. In thisway, all clutch plates were constantlyengaged.

This gradual increase of frictional effectenabled the multi-plate clutch to engage verygently.

As the spring pressure eased off, the platesdisengaged again, in part supported by thespring-loaded strips bent out from the plane ofthe plate. By varying the number of plate pairs,a basic clutch type could be adjusted to eachengine output.

Multi-plate clutches operated either immersedin oil/petroleum or dry, in which case, however,special, riveted friction linings were used.

The greatest drawback of the multi-plateclutch was certainly the drag effect, especiallyin the oil bath, causing only partial disengage-ment, and thus making gear changing difficult.

By 1904, De Dion & Bouton had introduced thesingle-plate clutch principle, which because ofthe initially inadequate materials only cameinto widespread use in the US during the 1920s– largely on demand from the supply industry,

6

Cone clutch of the Daimler Engine Corporation, withaluminium cone.

The Daimler spring band clutch, which, owing to itsingeniously simple design, was produced up to the FirstWorld War.

Professor Hele-Shaw from England was the first to experi-ment with multi-plate clutches.

Multi-plate dry clutch with riveted lining.

Oil-immersed multi-plate clutch.

Plate pair from a multi-plate clutch: left, the inner clutchplate, right the outer plate.

NAG clutch with two-part hollow cone ring, which greatlysimplified maintenance.

Schwungrad KurbelwellenflanschKupplungsfußhebelKupplungsgehäuse Kupplungsnabe Kupplungsscheiben KupplungsfederDruckscheibeGelenkaugeKupplungswelle Ausrückmuffe

flywheelcrankshaft flangeclutch housingclutch hubclutch pedalclutch platesclutch springpressure platepropshaft flangeclutch shaftrelease sleeve

Führungsbolzen Mitnehmscheibe zur KupplungswelleDruckteller mit AusrückmuffeKupplungsfeder Innere Kupplungsscheiben Äußere Kupplungsscheiben mitKupplungsbelag Kupplungswelle Ausrückmuffe

guide pindrive disc for clutch shaft

thrust plate with release sleeveclutch springinner clutch platesouter clutch plates with clutchliningclutch shaftrelease sleeve

7

who towards the end of that decade grantedlicences to European manufacturers. Within afew years, the single-plate had supersededcone and multi-plate clutches.While De Dion & Bouton still lubricated thefriction surfaces of their multi-plate clutcheswith graphite, clutch technology greatlyadvanced with the advent of Ferodo-asbestoslinings, which were used from about 1920 tothe present day, when they were replaced byasbestos-free linings. The advantages of thesingle-plate dry clutch were clear: the low

mass of the clutch plate allowed it to come torest more quickly when released, making shift-ing much easier – farewell to transmissionbrakes. The initial design of the single-plate dry clutch

was relatively complicated. The clutch housingwas flanged onto the flywheel, and the clutchcover screwed into the housing. This coverheld lug levers which were pressed inwards bysprings and which transmitted pressure froman intermediate disc via the friction plate andhence the power transmission from the fly-wheel. The friction disc was connected to theconnecting or transmission shaft by a driver.The clutch was engaged and disengaged by aslip-ring disc that moved a cone back and forth.

The sides of the cone accordingly actuated thespring-pressured lug levers, which stressed orreleased, i. e. engaged/disengaged, the inter-mediate disc. As the cone rotated about theslip-ring disc at rest, lubrication was requiredat regular intervals.

The coil spring clutch, in which the clampingload is produced by coil springs, was able togain acceptance. At first, experiments weremade with centrally arranged springs, but onlythe version with several smaller coil or clutchsprings distributed along the outer edge of theclutch housing entered large-scale production.The levers compress the coil springs via arelease bearing that moves freely on the clutchshaft, releasing the pressure plate and thusdisengaging. The clamping load could bevaried by using different spring packages buthad the crucial disadvantage that, as theengine speed increased, the coil springslocated outside on the pressure plate werepressed further outwards against the springhousings by centrifugal force. The frictionarising between the spring and the housingthen caused the clamp load characteristics tochange. As the engine speed increased, the

clutch became progressively heavier. In addi-tion to this, the bearings for the release leverswere constantly under strain, making themsusceptible to wear, and the spring housings,especially when gear changing at high enginespeeds, quickly wore through.

To overcome these systematic drawbacks, thediaphragm spring clutch was developed, cre-ated in the research laboratories of GeneralMotors in 1936 and entering volume productionin the US in the late 1930s. In Europe, it becameespecially familiar from the American GMCmilitary trucks used after the Second WorldWar, and starting in the mid-1950s it was usedon an individual basis by European manufac-turers. The Porsche 356, the Goggomobil, theBMW 700 and DKW Munga were the firstGerman-made vehicles to be so equipped. Theclutch entered volume production in 1965with the Opel Rekord.As the diaphragm spring is rotationally sym-metric and therefore speed-insensitive, its

hour of triumph occurred in the 1960s, whenhigh-speed engines with overhead camshafts(Glas, BMW, Alfa Romeo) largely supersededthe push-rod designs. By the end of the 1960s,nearly all manufacturers had shifted to dia-phragm spring clutches. Here LuK played apivotal role in making the diaphragm springclutch ready for mass production. The replace-ment of the complete lever – coil spring systemby a diaphragm spring that assumed bothfunctions brought many advantages: Simplemechanical construction, constant clamploads, less space required for relatively highclamp loads (very important with transversely

De Dion & Bouton were the first to recognise that single-plate clutches would be the way of the future.

This form of coil spring clutch, with the clutch springsarranged parallel to the central axis, predominated throughthe 1960s.

In Britain and the US, the Borg & Beck model with springslocated under the clutch cover was the most popular …

Initial design of the coil spring clutch with clutch springsperpendicular to the central axis.

Schwungrad KupplungsgehäuseKupplungsdeckelFederNasenhebel Kegela: ausgerückt / b: eingerücktSchleifringscheibeFedergelenkVerbindungswelle Lederbelag Mitnehmer ReibscheibeZwischenscheibe

flywheelclutch housingclutch coverspringlug leverconea: disengaged / b: engagedslip ring discspring jointconnection shaftleather liningdrive discfriction discintermediate disc

Schwungrad KupplungsbelagKupplungsscheibeKurbelwelle Druckscheibe 6 Kupplungsfedern AusrückmuffeKupplungswelleKupplungsdeckel3 Abzughebel

flywheelclutch liningclutch platecrankshaftpressure plate6 clutch springsrelease sleeveclutch shaftclutch coveroperating levers x3

Kupplungsgehäuse Kupplungskorb (Kupplungsdeckel)KupplungsdruckfederAusrücklager (dauergeschmiert) KupplungsgabelAusrückhebel EinstellmutterDruckplatte (Anpreßplatte)Mitnehmerscheibe (gefedert und stoßgedämpft)Schwungrad

Bellhousingclutch coverclutch compression springrelease bearing(permanently lubricated)release leverclutch forkadjusting nutpressure platedriven plate (spring-loaded and damped)flywheel

8

installed engines) and speed-insensitivity.Thanks to these features, the diaphragm springclutch is today nearly the only type used, itis also finding increasing applications in utilityvehicles – long a domain of coil springclutches.

Parallel to this development, the clutch platewas optimised. The continually changingspeed and fluctuating torque of an internalcombustion engine produce vibrations that aretransmitted from the crankshaft, clutch andtransmission shaft to the transmission. Noiseand severe tooth profile wear are the result.Lower flywheel mass and light construction inmodern vehicles amplify these effects, so thatclutch plates were provided with torsiondampers and spring-loaded facings.

While clutch operation for a long time requiredstrong legs, as pedal loads had to be trans-mitted via the linkage and shafts, comfort wasimproved in the 1930s with the use of controlcables, and in the 1950s with the use ofhydraulic actuation.

Easy operation was also promoted by variousattempts to automate the clutch process: in1918 Wolseley had the first idea of an electro-magnetic clutch. In the early 1930s the Frenchfirm Cotal built a pre-selector gearbox with anelectromagnetic clutch, which was used inluxury cars. Best known were the centrifugalclutch, which regulated its clamping load bythe centrifugal force, and automatic clutchessuch as Saxomat (Fichtel & Sachs), LuKomat(LuK), Manumatik (Borg & Beck) and Ferlec(Ferodo).

None of these was able to prevail; the com-petition from manual and automatic trans-missions with torque converters was too great.

Reprinted with permission from “MARKT”magazine for classic cars and motorcycles.

With the multi-plate clutch developed by Chevrolet, also known as the Chevrolet or Inboard clutch, the coil springs were replaced by a diaphragm spring.

Vorderes Führungslager der KupplungswelleHaltefeder mit SchraubeTeller- oder Membranfeder mit den fingerförmigen AusrücklamellenAusrückerHaltefeder Kugelbolzen zur Lagerung der KupplungsgebelSchwungradMitnehmerscheibeDruckplatteInnerer FührungsringÄußerer Führungsring Kupplungskorb KupplungsgabelRückzugsfeder der Kupplungsgabel

spigot bearingretaining spring with screwdiaphragm spring with pre-formed fingersrelease ringretaining springball pin for clutch forkflywheeldrive discpressure plateinner fulcrum ringouter fulcrum ringclutch coverrelease forkreturn spring of release fork

Schwungrad DruckplatteEinstellmutterAusrückhebelAusrückringKupplungswelleAusrücker mit GraphitringMitnehmerscheibeKupplungsdruckfederKupplungsdeckel

flywheelpressure plateadjusting nutrelease leverthrust plateclutch shaftrelease bearing with graphite ringdriven plateclutch compression springclutch cover

… while on the European continent the versionwith springs externally located above the clutch coverprevailed.

A history of clutch technology

9

Functional Schematic with components Chart 1

Internal combustion engines provide usefuloutput only over a certain speed range. To beable to use this range for various driving con-ditions, vehicles must have a gearbox or trans-mission. Today, the transmission is generallyconnected to the engine via a “single-plate dryclutch”. Only in special cases are dual-disc dryclutches found, such as sports cars and heavylorries. Unlike “dry” clutches (i.e. clutchesoperating in air as the medium), wet clutchesoperate immersed in oil or oil mist. They aregenerally used as multi-plate clutches in auto-matic transmissions, building machinery,special vehicles and predominantly in motor-cycles.

Diaphragm spring clutches, as displayed inchart 1, are also being increasingly used inutility vehicles. They have the following advan-tages over the coil spring clutches previouslyused:

• less space• insensitivity to engine speeds• lower release loads• longer life

The diagram on the right, shows a typicalclutch installation and highlights its basic useas a connection/separation element betweenthe engine and transmission.

Besides the main function of connecting orseparating the crankshaft (14) and the trans-mission input shaft (17), a modern clutch hasseveral further tasks.

It must:• enable gentle and jerk-free starting • ensure fast gear changing of the transmission• keep engine torsional vibrations as far away

from the transmission and thereby decreas-ing noise and wear

• serve as an overload protection for the entiredrive train (e. g. in case of faulty gearchang-ing)

• be durable and easily replaceable

LuK Clutch Course Chart 1

10

The main components of a complete clutchunit are:

The clutch cover assembly (1) with individualparts consisting of the clutch cover pressing(2) clutch pressure plate (3) as the frictionalcounterpart on the clutch side for the clutchplate, the diaphragm spring (4) for generatingthe clamp load, the tangential leaf spring (5) asa spring-loaded connection between the coverpressing and pressure plate for providingpressure plate lift, the fulcrum ring (6) and thediaphragm rivet (7) for positioning and provid-ing a mounting for the diaphragm spring.

The clutch driven plate (8) with individual partsconsisting of the hub (12), torsion damper (9)with friction device (10) and stop pin (23), thesegment cushion spring (22) and the facingsriveted to them (11). The flywheel (13) with thespigot (pilot) bearing (15).

The release mechanism with release bearingguide tube (gearbox quill) (18), release bearing(19) and release fork (20).

How the clutch works.

The two diagrams on the left show how asingle-plate dry clutch with diaphragm springoperates.

With the clutch engaged (left), the drive fromthe crankshaft (14) is transmitted via the fly-wheel (13) to the clutch cover assembly. Theclutch driven plate, (8) which is positivelyengaged to the flywheel and clutch pressureplate through the action of the diaphragmspring (4) transmits the drive via the hubassembly (12) to the transmission inputshaft.(17).

Thus the engine – transmission connection ismade.

To disconnect the drive between engine andtransmission requires the clutch pedal to bedepressed, and via the release mechanism(cable or hydraulic) the release fork (20) andthe release bearing (19) connected to it movestowards the clutch cover assembly (2), therelease bearing acts against the fingers of thediaphragm spring and depresses the dia-phragm spring fingers. As further pressure isapplied, diaphragm spring load is relieved, andwith the aid of the leaf springs (5) the clutchpressure plate moves away from the drivenplate. the clutch driven plate is now able torotate freely.

Engine and transmission are now discon-nected

The facing segment cushion spring (22) can beseen on the cutaway diagram. By applying theload uniformly across the facing it ensures asmooth and gentle clutch engagement

Although not a requirement for the basic oper-ational function of a clutch, the importance ofthe torsion damper (9) cannot be understated.Through a combination of coil springs andfriction washers tailored to suit specificvehicle applications it can dampen out unevencrankshaft rotation, reducing noise levels, andavoiding premature wear on transmissionassemblies. (illustrations 2 and 3 deal withtorsion dampers in detail).

The spigot (pilot) bearing (15) serves as a guideand bearing for the transmission input shaft(17).

The guide sleeve (gearbox quill) (18) guides therelease bearing (19) centrally to the clutch.

The shaft seals at the engine (16) and trans-mission (21) are designed to keep the clutchbell-housing free of oil. Even the slightestamount of grease or oil on the clutch facingscan considerably impair the friction coef-ficient.

The transmittable torque of a single-plateclutch is calculated as follows:

where:rm = mean radius of facingsn = number of facingsm = coefficient of friction of facingsFa = clamp loadMd = transmittable torque

An example:Inner diameter of facing: 134 mmOutside diameter of facing: 190 mmClamp load F: 3500 N

Coefficient of friction µ

0.27 – 0.32 (for organic facings)0.36 – 0.40 (for inorganic facings)

Md (81 x 10–3 m) x 2 x O,27 x 3.500N.Md: = 153 Nm

The transmittable torque of a clutch mustalways be greater than the maximum enginetorque.

= 81 x 10–3m mean facing radius

= = 81mm162mm2

dm2

rm =

= 162mm mean facing diameter

= 134mm+190mm2

di+da2

dm =

Md = rm x n x µ x Fa

Functional Schematic with components

11

Chart 1

Coil spring clutch

For the purpose of showing a complete picture,we have included the design of a coil springclutch. The clutch housing (1) contains metalhousings (2) for retaining the coil springs (3).These springs press the pressure plate (4)towards the flywheel (5) and thereby clamp theclutch plate (6). The torque can thus be trans-mitted via the flywheel (5), the clutch housing(1) and pressure plate (4) to the clutch plate (6),located on the transmission input shaft (8).

Whereas in the case of a diaphragm springclutch the clamping element and lever form asingle part, the coil spring clutch requires arelease lever as well as clamp load springs.The pressure plate is moved through the entirelifting stroke against the increasing springpressure. This is responsible for the com-paratively higher actuating force in a coilspring clutch for the same clamp load. Furtherdisadvantages are the relatively low speed-resistance as well as the greater spacerequirement for coil spring clutches.

12

The clutch plate is the central connectingelement of the clutch. It forms a friction systembetween the engine flywheel and the clutchpressure plate. With the clutch engaged, it ispressed between the flywheel and clutchpressure plate and actuated by friction. Ittransmits the drive torque to the transmissioninput shaft through the hub splines.

In modern vehicles, only clutch plates withtorsion dampers and spring-loaded facings areused. Organic friction facings are used almostwithout exception in car construction. Metal-ceramic sintered facings are used primarilyfor special vehicles and tractors.

The diagram on the left shows a typical carclutch plate with a two-stage torsion damper,integrated idle damper and a variable frictioncontrol assembly.

Its components are: The clutch facings (1),which are riveted to the spring segments (3)with the facing rivets (2). These spring seg-ments are fastened to the retainer plate (17)with rivets. The retainer plate (17) is alignedto rotate on the hub by means of the pivotbush (22).

The torsion damper is composed of the idledamper (with springs 10 and 11), the maindamper (with springs 12 and 13) and the frictioncontrol assembly (friction washer 8, and fric-tion control plate 20, spring washer 7, andsupport washer 9).

Torsion damper

Torsion dampers have the task of dampingvibrations between the engine and trans-mission.

Unlike electrical motors and turbines, internalcombustion engines do not deliver a constanttorque. The constantly changing angularspeeds of the crankshaft produce vibrationsthat are transmitted via the clutch and trans-mission input shaft to the transmission, whereunpleasant rattling noises are the result.Torsion dampers are designed to minimisethese vibrations between engine and trans-mission.

The constant reduction in flywheel mass andthe lighter construction of modern vehiclesincrease these undesirable effects. Accord-ingly, every vehicle today must be subjected tospecial tuning, which has led to a wide varietyof dampers and designs. Illustration 2 thereforeshows only a few typical designs.On the right of the illustration, three types oftorsion damper are displayed.

They operate according to the following basicprinciple:The hub (15), supported on bushes between thedrive disc (17) and the retainer plate (18), isspring-loaded via the hub flange (19) and thedamper springs (10-13) against the drive discand the retainer plate, so that under loadlarge or small angular motion is achieved. The

spring compression is dampened by a frictionassembly (7, 8, 9, 20). The transfer torque ofthe damper must always be greater than theengine torque, to prevent the hub flange (19)from striking against the stop pin (6).

In modern vehicle construction, two- andmultiple-stage characteristic curves are oftenrequired. The stages are produced by springswith various spring rates and variously sizedwindows. The friction assemblies also differlargely due to different friction and springwashers. The characteristic curves are usuallynot symmetrical, but display in the direction ofdrive a steeper line with a higher stop torquethan in the ‘coast’or ‘overrun’ direction (forfurther details, see “Designs and TorsionDamping Diagrams” in the commentary tochart 3).

The upper torsion damper has a simple frictiondevice with a friction washer producing con-stant friction and a two-stage characteristiccurve. The hub flange (19) runs between thedrive disc (17) and retainer plate (18), and issupported by the main damper springs of the1st stage (12) and 2nd stage (13). The hubflange (19) can be turned up to 16 degreesagainst the drive disc (17) and retainer plate(18) before striking the stop pin (6). In thisway the coil springs lying in the windows ofthe clutch and retainer plates, which havedifferent spring rates, are tensioned. Vibrationis converted to friction through the springwasher (7).

Clutch plate – Designs, torsion damper and

LuK Clutch Course Chart 2

13

cushion deflection Chart 2The middle torsion damper is designed simi-larly to the upper one, but is additionally pro-vided with two friction washers (8). They aremade of either organic material or plastic.Organic friction washers offer higher frictionalcoefficients, while plastic friction washersprovide less friction, but excellent wear resis-tance.

The lower torsion damper has a 3-stage frictionassembly dependent on the torsion angle, atwo-stage main damper and a separate two-stage idle damper. The separate idle damper,consisting of an idle damper flange (24) andidle damper retainer plate (25) with idle damp-ing springs of the 1st stage (10) and 2nd stage(11), is primarily used in cars with dieselengines. It acts at lower engine torque’s anddampens during idling. The three frictionwashers (8) of the 3-stage friction assemblybegin to act at different torsion angles. The 2-stage main damper (12) and (13) operates simi-larly to the above-described systems.

The facing cushion springs (segments)

The lower part of the illustration shows the fourmost common types of facing springs. Thefacing springs lie between the clutch facings.They ensure gentle clutch engagement andhence smooth take up of drive. The pressureplate of the clutch must at first press the clutchplate against the flywheel, acting against thespring load of the facing springs. As this loadbuilds up slowly and draws out the engage-ment process, the transmission speed can beadjusted to the engine speed with a delayby the flexing of the plates. Besides smoothtake off, good wear resistance, a better wearpattern and, a more uniform heat distributionare further advantages of the facing springs.We basically distinguish between four types offacing cushion spring systems (from left toright):

Single segment cushion spring, in which thefacings on both sides are riveted to thin, bowedsegments that in turn are riveted to the drivedisc. The advantages are the small flywheeleffect of the disc and the easier operation ofthe cushioning

With a dual segment cushion spring, thefacings are riveted to two segments lying ontop of one another and acting in opposite direc-tions. As with single segment cushion spring,the segments are riveted at the drive disc. Theadvantage of better cushioning and better utili-sation of the available cushion space is offsetby the disadvantages of a greater flywheeleffect and a higher price.

Multi-plate cushion spring is the most com-mon version. The carrier plate of the facings isslotted and corrugated at the outer edge,where the facing lies. It functions in essentiallythe same way as the single segment cushionspring and is primarily used where there is noroom for riveting the single segments to thecarrier plate. With more heavily stressedclutch plates, the comparatively thin carrierplate in the area of the torsion damper must bereinforced by a second counterplate.

Intermediate cushion plate spring is generallyused for heavy commercial vehicles. The seg-ment-like, corrugated panels are riveted onone side of the carrier plate that is extended tothe outer edge. They therefore act only alongone direction. A disadvantage is the largeflywheel effect of the disc.

Tasks:

As the friction ‘mate’ between the flywheel andthe pressure plate, the clutch plate has theprimary task of transmitting the engine torqueto the transmission input shaft.

The main components are:

• drive disc (15)• clutch facings riveted in pairs (1)• splined hub

As already shown in chart 2, it also has severalother tasks, which we briefly mention hereagain:

It must allow smooth take up and fast gear-changing, keep engine vibrations away fromthe transmission and thus prevent trans-mission noise generated by gear rattle.

The fulfilment of these tasks – an absolute“must” for the modern vehicles of today –requires a few additional components:

• segments (3)• torsion damper (7–13)

14

Clutch plate – Designs, torsion damper graphs

Designs:

The designs are selected according to vehicletype and requirements. The mode of operationcan be displayed by “torsion damping graphs”,as shown in chart 3, below the clutch discs.The torsion angle of the torsion damper isplotted as a function of the given torque. Thedashed/dotted line represents the theoreticaltorsional characteristic curve, while theshaded band shows the torsional character-istic curve when friction is taken into account(hysteresis).

Two-stage torsion damper

The left hand illustration shows a two-stagetorsion damper. The four tangential windowscontain coil springs (12, 13) with two differentspring rates for the two stages. The springslying opposite each other are identical.

The hub flange (17) lying between the drivedisc (15) and retainer plate (16) can be turnedagainst spring pressure. The drive disc (15) andretainer plate (16) are firmly connected to thestop pin (6).

Torque introduced via the drive disc (15) andretainer plate (16) is transmitted via the torsionsprings to the hub flange (17) and thus to theinput shaft.

As the springs alone cannot absorb vibrations,an additional friction assembly is required fordamping. It is composed of the friction washers(8) lying to the right and left of the hub flange,the support washer (9) and the spring washer(7). The spring washer presses via a supportwasher (9) on to the right hand friction washerand also, via the fixed connection between thecover plate (16) and the retainer plate (15), onto the left hand friction washer lying betweenthe retainer plate (15) and hub flange (17).

When the engine provides the torque, thetwo springs (12) are first compressed at thelower spring rate, i.e. damping stage 1 up to atorsion angle of 4 degrees. In this position, inthe example shown, they receive a torque of20 Nm.

From this point on, the two springs (13) ofdamping stage 2 are also engaged. They causethe torsional characteristic curve to climbmore steeply up to the stop, at a torsion angleof 8 degrees and 140 Nm.

The torsion dampers are designed so that themaximum torque is well above the enginetorque.

If the vehicle is decelerating, the 1st dampingstage (12) acts up to an angle of 7 degrees anda torque of 40 Nm. From this point on, the 2nddamper stage (13) acts up to a torsion angle of8 degrees, corresponding to a torque of 65 Nm.

LuK Clutch Course Chart 3

15

Chart 3 Two-stage torsion damper, separateidle damper.

The principles previously described also applyto the design of two-stage torsion damperswith separate idle dampers, as shown in thecentre of the illustration. Added is the separateidle damper (10, 11). It was previously usedprimarily for diesel vehicles. Thanks to thelighter construction and the resulting high levelof vibration elimination, this design is alsoincreasingly being used for petrol engines.

The torsion damper diagram is clearly differentfrom the preceding one. The torsional charac-teristic curve stays flat around the zero posi-tion, to prevent the transmission gears from“rattling” especially with diesel engines at idlespeeds. The 1st main stage (12) is applied atbarely 10 degrees torsional angle and very lowtorque.

With this type of clutch plate, the idle damper(10, 11), which produce the flat characteristiccurve at zero, is separately inserted in theretainer plate and the idle damper cover plate(20) riveted to it. The idle damper flange (18) isconnected to the hub. The idle damper stagemust therefore always be turned to the maxi-mum, until the mechanism of the main damperstages (12, 13) described above is applied.

This clutch plate has a friction washer (8)between the hub flange (17) and the coverplate (16). The frictional force is produced bytwo spring washers located between the huband retainer plate and between the hub flange(17) and the retainer plate (15).

Two-stage torsion damper, integratedidle damper, variable friction control.

In the version illustrated on the right, the idledamper springs (10, 11) are located not in theclutch plate, but in the spring windows.

Whereas the friction was constant in thepreceding versions, here it is made variable bythe two separate friction washers (8), with twocorresponding spring washers (7). One oper-ates in the first main damper stage and theother in the 2nd main damper stage. They takeeffect only after the corresponding torsionangle is achieved (5 degrees and 8.5 degrees,respectively, on the ‘drive’ side and 1 degreeand 7 degrees, respectively, on the ‘coast’side).

The torsional characteristic curve and frictiondamping cannot be predetermined for avehicle type. Extensive tuning, together withvibration computations for the vehicle areindispensable for optimising the torsionalcharacteristic curves and friction damping.

16

Tasks

The clutch cover assembly forms a frictionalsystem together with the flywheel and theclutch plate. It is secured to the flywheel viathe bolts of the cover pressing and acts totransmit the engine torque via the clutch plateto the transmission input shaft. One of the mostimportant components of modern vehicleclutches is the diaphragm spring (3). It hasalmost completely replaced the previouslyconventional coil springs in car clutches.

Other important components: The clutch cover(1) serves as a carrier for the diaphragm spring(3), which is supported by fulcrum rivets (5)and/or fulcrum rings (4) on the cover. The dia-phragm spring (3) presses the pressure plate(2) against the clutch facing. Tangential leafsprings (7) or triangular leaf springs (8) form aconnection between the cover (1) and thepressure plate (2).

The balance hole (9) is made to compensate forthe imbalance of the pressure plate (2). Dowelholes (10) assist in aligning the cover (1) to theflywheel.

The diaphragm spring

A central component of all these designs is thediaphragm spring. It is made flatter and lighterthan the coil springs. Especially important isthe characteristic curve of the diaphragmspring, which clearly differs from the linearcurve of a coil spring.

Precise design of the diaphragm inside andoutside diameters, thickness, opening angleand material hardness allow a characteristiccurve to be produced as represented by thecontinuous curve in the left-hand diagram inchart 4.

While the clamp load with a coil spring clutchlinearly decreases with decreasing facingthickness due to wear, here it initiallyincreases and then drops again. The design isselected so that the clutch begins to slip beforethe wear limit of the facing is reached. Thenecessity of a clutch change is thus signalledin due time, so that further damage, e.g. by aningress of the facing rivets, is avoided. More-over, because of the diaphragm spring char-acteristic curve the requisite pedal force isless than with coil spring clutches.

Designs

Diaphragm spring clutch, standard design.

The left-hand diagram in illustration 4 showsthe standard version of a diaphragm springclutch. The clutch cover (1) encloses the dia-phragm spring (3) and pressure plate (2). Thepressure plate (2) is connected to the clutchcover via tangential leaf springs (7). They areriveted to the pressure plate (2) at three lugs.The tangential leaf springs (7) perform threebasic functions:

• lifting the pressure plate during disengage-ment

• transmitting the engine torque from the coverto the pressure plate

• aligning the pressure plate

The diaphragm spring is clamped between thepressure plate (2) and the clutch cover (1) soas to produce the load required to clamp theclutch plate between the flywheel and press-ure plate (1). In doing so, it is supported by a ribin the clutch cover (1) and by a fulcrum ring (4).The outside diameter of the diaphragm sits onthe pressure plate (2). If the clutch is actuated,the release bearing presses on the ends of thediaphragm spring fingers (3) – the pressureplate (2) is lifted and the clutch plate is dis-engaged

Clutch cover assembly – Designs and graphs

LuK Clutch Course Chart 4

17

Diaphragm spring clutch with a triangular leafspring design.

First, observe the version presented on theright in illustration 4. It essentially differs fromthe standard design by having a different typeof connection between the clutch cover (1) andthe pressure plate (2). As the design doesnot allow lugs to be attached to the pressureplate (2), because of a pot or recessed fly-wheel, a triangular leaf spring arrangementwas chosen.

The leaf springs are riveted at both ends tothe clutch cover (1), with the pressure platefastened to the centre of each leaf spring.

Instead of the cover rib as a support andfulcrum ring for the diaphragm spring (3), anadditional steel fulcrum ring (4) is used here.

Diaphragm spring clutch with a keyhole coverdesign.

The latest design is the diaphragm springclutch with keyhole tabs shown in the centre ofillustration 4. The keyhole tabs are formed soas to pull the rivets (5) outwards. As a result,the diaphragm spring (3) is constantly held inposition despite wear which will occur at thediaphragm spring seats. The advantage; uni-form lift throughout the entire life of the clutch.

Clutch characteristic curves and load dia-grams.

The lower part of illustration 4 shows someexamples of clutch characteristic curves andload diagrams. They do not directly refer to thedesigns pictured above them, but apply gen-erally.

The load is specified along the y-axis on theleft, while the abscissa represents the releasetravel – in the diagram on the left shows therelease bearing travel as well – and the y-axison the right gives the lift of the pressure plate.

The continuous curve in the diagram on the leftrepresents the development of clamp load.With a newly installed clutch plate. (operatingpoint: new pressure plate assy).As the facingbegins to wear the clamp load increases to it’soptimum level.

The clutch plate thickness decreases by about1.5 to 2 mm during its lifetime. The clamp load iscalculated so that the clutch begins to slipshortly before the rivets of the clutch facing runagainst the pressure plate or the flywheel andthereby avoiding additional damage.

The dashed/dotted line shows the develop-ment of the release load, i.e. the load requiredto actuate the new clutch and (compare thedotted line) that load after facing wear. Therelease load initially increases until the operat-ing point is reached, and then slowly dropsagain. The curve for the release load withfacing wear has been moved to the left forbetter representation of the ratio of clamp loadto release load. The larger the clamp load atthe operating point the greater the releaseload.

The dashed line shows the lifting of the press-ure plate above the release bearing travel. Inthis case the lever ratio in the clutch is clear: 8mm release travel corresponds to 2 mm lift, i.e.to a ratio of 4:1 (not considering the elasticity ofthe clutch). This also applies to the ratiobetween clamp load and release load.

In the centre and right-hand diagrams, themeasurements are contrasted for clutcheswith and without considering the spring com-pression of the clutch plate cushion springs.The commentary to illustration 2 already notedthe advantages of cushion springs, such asgentle clutch engagement and more favour-able wear characteristics. Without the cushionsprings, the effective clamp load (solid line)falls off linearly and relatively sharply duringdisengagement. Conversely, it increases justas steeply and suddenly during clutch engage-ment.

In the diagram on the right, however, we seethat the available release load, along which theclamp load diminishes, is about twice as great.On the other hand, with the clutch engaged, theclamp load slowly increases along a curve, asthe cushion spring must first be compressed.Thanks to the relatively gentle climb of theclamp load curve (solid line), the pronouncedload peak at the required release load isreduced. As long as the pressure plate (2) stillmakes contact with the clutch plate, the clampload and cushion spring correspond to oneanother.

Chart 4

Clutch cover assembly – Designs and installation

18

Diaphragm spring clutches are used almostexclusively in automotive construction today.The coil spring clutches used so frequently inthe past have practically disappeared, owingto a number of disadvantages, but especiallybecause of their considerably larger instal-lation space requirement and greater weight.

The most important advantages of the dia-phragm spring clutch compared to the coilspring version are:

• insensitivity to high engine speeds• despite the small space, clamp loads are

achieved at low release loads• the diaphragm spring fingers also function as

release levers• fewer wearing parts

The diaphragm spring also makes a big differ-ence for the driver, as the lower release loadmeans that only low pedal efforts need beapplied.

Depending on the design and type of clutchactuation, we distinguish between:

• pulled diaphragm spring clutch• spring loaded diaphragm spring clutch

Pulled diaphragm spring clutch.

The left clutch in chart 5 was speciallydesigned for the VW Golf and Jetta. Withrespect to the support position of the dia-phragm springs, one speaks of a pulled clutch;of course, because of the reversed installationcompared with the usual design, actuation isonly through pressing. Usually the drive pro-ceeds from the crankshaft to the flywheel andthen to the clutch and transmission. Here, how-ever, the clutch is initially bolted to the crank-shaft. The flywheel is attached after the clutchplate is fixed and then connected to the clutch.

This construction constrains the design of theclutch in the following way: the outer edge ofthe diaphragm spring (3) is supported by theclutch cover (1) and the inner edge by thepressure plate.

A reversal of the diaphragm springs, as withstandard clutches, does not occur during dis-engagement. The diaphragm spring (3) issimply lifted via the thrust plate (11), which isinserted in the diaphragm spring points. Thethrust plate is actuated via a push rod sup-ported by bearings in the hollow transmissioninput shaft and extending to the rear of thetransmission end, where the release bearingand release arm are located.

LuK Clutch Course Chart 5

19

Diaphragm spring clutch LuK TS.

The diaphragm spring clutch LuK TS is apressed steel clutch. It is recognised by theintegration of clutch and flywheel. The poly-gonal hub (15) of the clutch is bolted togetherwith the V-belt pulley to the crankshaft, whichhas the corresponding matching taper.

The drive line is through the clutch cover (1) tothe flywheel fastened to it. The pressure plate(2) is seated between the clutch cover (1) andclutch plate (14). It is connected via tangentialleaf springs (7) to the clutch pressure plate (2).

The seats of the pressure plate (2) protrudethrough the openings in the clutch housing (1).The outer diaphragm spring is supported bythese seats, and is mounted at the housing bythe fulcrum rivets (5) and fulcrum rings (4). Therelease bearing is mounted so as to slide on theoutside diameter of the polygonal hub. Thetorque is transmitted via the clutch plate (14)to the transmission input shaft, formed as ahollow shaft and positioned on the crankshaftend – between the clutch and the engine. Inthis way, the transmission could be integratedinto the lower half of the engine.

Spring loaded diaphragm spring clutch

The diaphragm spring clutch with second steelpressing is a special version. Here the fulcrumrings have been completely replaced by a rib inthe clutch cover (1) and by a sprung secondsteel pressing (16) formed as a further fulcrum.In this way, any wear can be compensated forand automatic re-adjustment is achieved.Otherwise this design does not differ fromthose shown in illustration 4.

principles Chart 5

20

As has already been mentioned on page 18, thediaphragm spring clutch is almost exclusive tomodern vehicle construction.

Further technological development on thiscomponent has been pushed ahead vigorouslyin the past few years (e.g. diaphragm springkey hole cover; for description, see pages 17and 18), and has now evolved into the currentnew development, the SAC clutch.

The abbreviation SAC stands for Self-AdjustingClutch.

Higher performance engines of the type gain-ing ground nowadays also need clutches withhigher-transmission moments, this means thatpedal force has also increased. It may havebeen possible to keep this increase within cer-tain limits by means of various measures (suchas improved release systems), but, despite this,the demands are steadily growing for clutcheswith reduced actuation force.

The most important advantages of thistype of design in relation to previousformats are:

• Low disengagement forces, which remainconstant throughout the entire service life,

• Resulting in high levels of driving comfortthroughout the entire service life,

• Increased wear reserves, and thereforelonger service life thanks to automatic wearadjustment,

• The over-travel of the release bearing islimited by the diaphragm spring stop.

This in turn results in a whole range ofsecondary advantages:

• No further need for servo systems (on utilityvehicles)

• Simpler release systems• Shorter pedal travel• Uniform pedal forces across the entire range

of engines• New possibilities for reducing clutch dia-

meters (torque transfer)• Shorter release bearing travel throughout

the service life

Figure 2: self adjusting clutch (SAC)

8

7

1

2

6

11

10

4

3

5

9

SAC clutch cover assembly – design types and

1) cover pressing2) adjustment wedge3) coil spring4) main diphragm spring

5) sensor diaphragm spring6) stop rivet7) strap rivet8) drive strap

9) pressure plate10) stop plate11) driven plate

21

characteristics Chart 13

Principle of the self adjusting clutch(SAC):

The LuK wear adjustment feature works on the following principle: the load sensor deter-mines the increased release load due to wearand correctly compensates for the reduction infacing thickness.Figure 1 shows a schematic representation ofthe SAC. As opposed to the conventionalclutch, the (main) diaphragm spring is sup-ported by a sensor diaphragm spring insteadof being riveted to the cover.In contrast to the strongly regressive main dia-phragm spring, the sensor diaphragm springprovides a sufficiently wide range of almostconstant load.The constant load range of the sensor dia-phragm spring is designed to be slightly higherthan the targeted release load. The pivot pointof the main diaphragm spring remains station-ary as long as the release load is smaller thanthe load of the sensor spring. When facing wear increases the release loadincreases, the opposing load of the sensorspring is overcome and the pivot point movestowards the flywheel to a position where therelease load again falls below the sensor load.Graphically, this means that the intersectionpoint between the two curves has returned toits original location. When the sensor springdeflects, a gap develops between pivot pointand cover, which can be compensated for byintroducing a wedge-shaped component.

Design of a wear-sdjusting clutch witha load sensor.

The load sensor with the thickness adjustmentwedge can be realized in a simple and elegantmanner. Figure 2 shows such a design. In com-parison to the conventional clutch, the onlyadditional parts required by this design are asensor diaphragm spring (red) and a ramp ring (yellow).The sensor diaphragm spring is suspended inthe cover. Its inside fingers position the maindiaphragm spring. Because of centrifugalforces, the wedges that provide the actualadjustment are positioned circularly instead ofradially. A plastic ring with twelve rampsmoves on opposing ramps in the cover. The plastic ring (adjustment or ramp ring) iscircularly preloaded with three small coilsprings which force the ring to fill the gapbetween the diaphragm spring and the coverwhen the sensor spring moves.Figure 3 shows the release load curves for aconventional clutch in new and worn facingcondition. In contrast, compare the lowerrelease load of the SAC, which has a characte-ristic curve that remains virtually unchangedover its service life.

An additional advantage is the higher wearcapacity, which no longer depends on thelength of the diaphragm spring curve (as in conventional clutches), but rather on theramp height, which can easily be increased to4 mm for small and up to 10 mm for very largeclutches. This represents a decisive steptowards the development of clutches with highdurability.

Figure 1: principle of the self adjusting clutch (SAC)

sensor diaphragm spring

pivot point of themain diaphragm spring

adjustment wedge

main diaphragm spring

load

sen

sor

rele

ase

load

new worn worn

new

22

The increase in noise sources owing to inad-equate natural damping is a noticeable fea-ture of modern automotive construction. Thecauses lie in the reduced weight of thevehicles and in the wind-tunnel optimisedbodies, whose low wind noise now makesother noise sources perceptible. But also sleekbody designs and extremely low-revvingengines, as well as 5-speed transmissions andthin oils, contribute to this phenomenon.

The periodical combustion process of thereciprocating engine induces torsionalvibrations in the drive train, which as trans-mission rattle and body noise interfere withdriving comfort.

Design:

The division of the conventional flywheel intotwo parts results in a primary flywheel mass (1)with starter ring gear (21) on the engine side,and a secondary flywheel mass (2) with ventslots (22) for heat transfer, which increases theangular momentum on the transmission side.

The two masses are connected to one anothervia a spring/damping system and supported bya radial ball bearing (11) to allow free rotation.Sealing is provided by the O-ring (12) and theseal (13).

Two moulded sheet metal parts (1, 3) laser-welded to the outer edge (25) form the ring-shaped grease cavity (8), in which the curvedcompression springs (5) with spring guides (6)are located. Sealing is provided by the dia-phragm (9).

The flange (7) in the form of a diaphragm springengages with its lugs between the curved com-pression springs (5). It lies frictionally engagedbetween the friction and support rings (10)riveted on the secondary side. The diaphragmspring load is designed so that the frictiontorque is greater than the maximum enginetorque.

An additional friction device (15, 16), bearing-floated on the hub (4), is carried by one of theretaining plates.

As the spring/damping system is integrated inthe dual-mass flywheel, a rigid version of theclutch plate (B) is used without a torsiondamper.

Usually a diaphragm spring clutch with a key-hole cover positioned via dowel pins (20) isused as a clutch cover (A).

Dual-mass flywheel (DMF) – Design and function

LuK Clutch Course Chart 11

23

Chart 11Function:

Physical study of drive trains has revealed thatthe resonance speed range can be shifted bychanging the allocation of angular moments.As the transmission angular momentumincreases, the resonance speed, which gener-ates loud noise, drops below the idle speed andthus falls outside the engine’s rev range.

Using the dual-mass flywheel (DMF), LuK wasable to develop a large-scale product thatembodies this principle and thereby keepsresonance amplitude extremely low.

As shown in the “function” diagram, with theDMF the angular moment is decreased in frontof the torsion damper and increased behind it.The angular moment of the engine is nowassigned to the primary mass of the DMF, whilethat of the transmission is assigned to thesecondary mass including the clutch drivenplate and the clutch pressure plate. In this way,the resonance speed is shifted from approx.1300 rpm to about 300 rpm and can no longer

interfere with driving comfort, as the engine isnot operated in this speed range.

An added positive effect is provided by thereduced angular momentum on the engineside: Gear changing is improved thanks to thelower mass to be synchronised, and the syn-chromesh units are subject to less wear.The effects on torsional vibrations can be seenfrom the diagram With previous conventionalflywheels and torsion-damped clutch plates,the torsional vibrations in the idle speed rangewere transmitted to the transmission with theleast possible filtering, causing the teeth of thetransmission gears to strike against oneanother (transmission rattle).

The use of a dual-mass flywheel however,filters out the torsional vibrations of the engineby the complex construction of the torsiondamper, preventing vibration from affecting thetransmission components – rattling does notoccur, and driver comfort is fully ensured.

The advantages of the LuK dual-massflywheel at a glance:

• first-class driving comfort• absorption of vibrations• noise insulation • fuel saving due to lower engine speeds• increased gearchanging comfort• less synchronisation wear• overload protection for the drive train

24

Layout and function

The dual-mass flywheel provides a highly effi-cient system for the damping of torsionalvibrations in the drive train. It has proved itsworth in the prestige vehicle sector.

The middle range sector and those referred toas compact vehicles, with transverse enginesare steadily growing in demand. The demandsfor used engines and those with reduced pollu-tant emissions is also growing, but at the sametime this is leading to increased irregularities inengine performance, especially in the direct-injection Diesel engine sector. LuK has nowdeveloped the DFC, to provide top-of-the-rangedriving comfort for the middle range sector.

There were two basic problems whichneeded to be overcome in this context:

1. The installation space in front transverseengine vehicles is very restricted.

2. The price structure on which this class ofvehicle is based makes cost-optimisedsolutions essential.

The DFC is already effectively cutting outengine vibrations when idling; in other words,there is no more gearbox rattle, and theunpleasant drumming of the bodywork at cer-tain engine speed ranges has become a thingof the past.

With regard to environmental protec-tion positive results are also becomingapparent.

• Thanks to the excellent noise reduction atlow engine speeds, there are fewer gearchanges, as well as the average operatingspeeds of the engine dropping.

• The degree of efficiency of the system as awhole is boosted, and the fuel consumptionand emissions of pollutants usually associ-ated with this are reduced.

The DFC is an integrated assembly of dual-mass flywheel, cover assembly, and drivenplate.

It is supplied complete to the vehicle manufac-turer, including the crankshaft bolts, and canthen be fitted as a unit in one operation on thevehicle assembly line. The crankshaft bolts canbe tightened through drillholes in the drivenplate and the cover assembly.

Other advantages in relation toconventional systems:

• Lower weight• Less imbalance of the system as a whole• Reduced set up height tolerances for the

diaphragm spring.

3

11

34

39

12

38

37

30

31

36

27

32

24

33

25

29

28

26

20

10

42

23

6

9

4

12

21

1

2

8

13

17

18

19

15

41

40

14

43

16

5

35

22

7

DFC – Damped Flywheel Clutch – (Compact-DMF)

1) primary flywheelmassand damper housing

2) secondary flywheelmasswith friction surface

3) cover (primary flywheelmass)

4) arc coil spring5,10) gland seal6) arc spring guide race7) cover ring and flange8,13,26) ventilation slot9) starter ring gear

11) support plate12) balance weight14) deep grooved ball bearing15) socket head cap screw16,19,27,35) diaphragm spring17) load friction plate

18) retainer plate20) dowel21) dowel pin22) grease cavity23) laser welding24,32) access opening for removal/ installation tool

25) pressure plate with friction surface28) fulcrum ring29) stretch bolt30) leaf spring31,40,43) rivet33) hub

36) segment rivet37) driven plate segment38) lining rivet39) linings42) inertia ring

Layout and function Chart 12

25

Total technologyClutch cover:

The pot-shaped clutch cover (30) and the cover(1) which forms the damper housing for the arcsprings (4) are deep-drawn from one singleblank. The flywheel is made of grey cast ironGG 25, which has extremely good thermal con-ductivity properties. The carefully designedventilation and air-cooling system providesexcellent cooling effects for the flywheel andthe pressure plate.

Damper springs:

The arc spring damper, already in use in thedual-mass flywheel, is integrated in the DFCunit. The spring damping system is required tofulfil two contradictory requirements.

1. Under normal operating conditions, theirregular shape of the engine vibration curvemeans that there are only low workingangles in the damper. In this operatingrange, low spring rates associated with lowdamping are required for the optimum fly-wheel damping effect.

2. With the typical load changes (e. g. fullacceleration), the engine vibration curvethen changes, which to a considerable

degree leads to the creation of noise. Thiseffect can only be offset by a torsion damper,which has an extremely low spring rate and,at the same time, a high damping effect.

The arc spring resolves this contradiction; inother words, at high operating angles it pro-vides a high damping effect at very low springrates. At the same time providing perfect iso-lation of vibration due to low damping and suit-able spring rates under normal driving con-ditions.

Bearings:

A special design of bearing makes it possiblefor it to be arranged inside the crankshaft bolthousing. The bearing (14) is subjected con-stantly to the rotational vibrations of theengine, with no further relative motion occur-ring between the inner and outer ring. It mustalso withstand peak operating temperatures.These operating conditions impose an extra-ordinarily high burden on the bearing.

The solution is an integrated bearing conceptwith special seals, which guarantees lubri-cation throughout the entire service life. Athermal insulation cap (14) also resists eventhe most extreme operating temperatures.

Installation and logistics:

The DFC drastically reduces the effort andexpenditure needed for installation duringvehicle manufacture, as well as in the work-shop.

The cover assembly can be removed from theunit, in order to replace the driven plate ifnecessary (oil contamination etc.).

A further advantage is the arrangement of thecomponents: All the parts are matched to oneanother, and are, as a rule, delivered andreplaced complete.

The number and variety of types can bereduced dramatically, which accordingly cutsdown on logistics and overall expenditure(parts stocks, catalogue applications, etc.).

400

300

200

100

00 10 20 30 40

Vibration curve in thenormal drive conditionwith low damping

Large damping onload change

Torsion angle [°]

Engi

ne [N

m]

CalculatedMeasured

Index of termsTable Page

Adjuster ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Air gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24Applied force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 14 18Arc spring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24, 25

Balance hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16, 18

Centrifugal clutch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Clutch brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Clutch facing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 3, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10 12, 14, 24Clutch housing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 4, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 11, 16, 17, 18, 19Clutch plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 5, 11, 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 11, 12, 18, 19, 20, 22Clutch pressure plate. . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10Cone clutch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5, 6Cover. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20, 22, 24, 25Cover plate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13, 14, 15Crank shaft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10Cushion spring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 12, 13, 14

Damped flywheel clutch . . . . . . . . . . . . . . . . . . . . . . 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Diaphragm spring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 3, 4, 5, 11, 12, 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 12, 14, 15, 16, 17, 18, 20, 22, 24Diaphragm spring clutch . . . . . . . . . . . . . . . . . . . . . . . 4, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 11, 16, 17, 18, 19Diaphragm spring clutch bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7,11Dowel hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Dual cushion spring . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13Dual mass flywheel . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Dual segment cushion . . . . . . . . . . . . . . . . . . . . . . . . . 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12,13

Flywheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 11, 18Friction device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Friction material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 12, 15, 22Friction plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 15Friction washer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10 ,12, 15, 22

Gearbox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 11, 14Gearbox snout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9,10

Hub . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 3, 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 12, 14, 22, 24Hub flange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13, 14, 15

Idle damper. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 14, 15Idle damper flange . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13, 14, 15Idle damper stop plate . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13, 14, 15

Laser welding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24Leaf spring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 20, 24Lift. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 11, 16, 17Lifting stroke. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Load sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

26

Index of terms

27

Table Page

Laser welding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24Leaf spring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 20, 24Lift. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 11, 16, 17Lifting stroke. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Load sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Main damper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13, 14Metal housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Overload protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 23

Polygon hub . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18,19Pressure plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Pressure plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 4, 5, 12, 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 11, 16, 17, 18, 19, 20, 24, 25Primary flywheel mass. . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24, 25

Release bearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10Release fork. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10Release lever . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Release system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Resonance frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Retainer plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 12, 13, 15Return spring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

SAC clutch plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Starter ring gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24Secondary flywheel . . . . . . . . . . . . . . . . . . . . . . . . . . . 11, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 24, 25Segment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10Sensor – diaphragm spring. . . . . . . . . . . . . . . . . . . . . 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Shaft seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10Single segment cushion . . . . . . . . . . . . . . . . . . . . . . . 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 13Spacer bolt. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10Spigot bearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9,10Spring band clutch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Spring segment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 14, 24Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Stop bolt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 12, 13, 14Stop plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 14, 22Stop ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10Stop spring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18, 19

Tangential strap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 4, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 16, 18, 19Torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10, 11, 14, 16Torsion damper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 10, 12, 14, 15Triangular straps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Twin plate clutch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

AS AUTOTEILE SERVICE GMBH & CO.A M E M B E R O F T H E L U K G R O U P

World-wide presence

LuK Group Headquarters andMain Plant in Bühl/Baden

WORLD-WIDE PRESENCELuK can now supply clutches from productionplants in six countries to vehicle manufacturers allover th world. The LuK subsidiary, AS, has beenmarketing LuK clutches for years on a world widelevel for the spare parts sector, supported by itsown subsidiaries in England, Spain, and the USA.

AS Autoteile-Service GmbH & CoP.O. Box 1105 · D-63201 LangenPaul-Ehrlich-Strasse 21 · D-63225 LangenPhone ++49 61 03/753-0Fax ++49 61 03/753-295