The Clutch System of the Future More Than Disconnecti Ng and Connecti Ng

3 Clutch 3 Clutch Clutch 3

The clutch system of the future More than disconnecti ng and connecti ng

Jürgen Freitag Friedrich Gerhardt Markus Hausner Christoph Witt mann

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the number of cylinders or increase the efficien- 1000 Introducti on cy in the drive train bring about increased rotary Twinpla teclut ch and axial acceleration with reduced damping. At 900 Hybrid models, electric cars and hydrogen loco- the same time, the use of the components in moti on are only a few of the drive concepts on ever more complex systems, such as double 800 SAC which the automobile industry is betti ng for the clutches or hybrid applications, means that the 2010 3 700 future of personal transportati on. Nevertheless, requirements for the clutch with respect to com- the classic combusti on engine will, in the view of fort, durability and reduced installation space 600 many automoti ve experts [1 to 5], remain the pri- are constantly increasing in both the passenger mary drive form for passenger cars, commercial car and the commercial truck sector. Special 500 vehicles and farm equipment for the next 10 to NVH issues also create higher requirements in 2010 20 years. With new combusti on processes and the development of advanced, more powerful

Torque in Nm 400 other opti mizati ons, the engines are becoming systems. 1994 cleaner and more economical. And so the de- 300 Conv.Clut ch mand for manual transmissions, and the clutches and torsion dampers that go with them in the 200 drive train, remains strong for the foreseeable fu- Comfort ture. Compared to present-day applicati ons, the 100 requirements for these components are increas- LuK SAC 0 ing strongly, since engine technologies demand 220 230 240 250 260 270 280 290 greater isolati on potenti al for the downstream Always in tune with the Clutchsiz einmme in mm drive train. ti mes Figure 2 Development of torque and the clutch technologies adapted to it in 1994 and 2010 The LuK line of clutch products meanwhile covers the full range, from components for subcom- For years the trend in engine development has pact cars to component groups for tractors to been toward higher torques while keeping piston formance density of the clutch system. Torque Increased torque capacity with continued mod- modules for commercial trucks, of automobile displacement nearly constant [6]. Because the capacity has thus increased by about 50 % while erate release loads, or, alternatively, the ability and tractor applications (Figure 1). The engine space available has remained practi cally constant, clutch size has remained steady (Figure 2). The to reduce the difference between the maximum torques to be transmitted range from 60 to this development has led to a clear rise in the per- loads on the power train and thus also on the and minimum release load (drop-off) – these are 3500 Nm. clutch system have increased markedly. This trend the characteristics of the SAC2. This has been necessarily leads to higher release loads during implemented by means of the degressive leaf Numerous applicati on- clutch operati on. spring to connect the pressure plate with the specifi c opti mizati ons, cover [7] and the sensor fingers on the main dia- such as twin plate One of the fi rst responses to this development phragm spring. The sensor load of the degres- clutches for high- was the LuK SAC (self-adjusti ng clutch) with load- sive leaf springs is thus introduced via the pres- torque vehicles, double controlled wear adjustment. In the passenger car sure plate. At high axial excitation of the clutches, multi -stage segment, SUV applicati ons, off -road models and crankshaft – a common phenomenon in newer dampers for diesel ap- smaller vans in parti cular set high requirements engines – the system can, however, be dynami- plicati ons or dampers for wear resistance. The use of the SAC has prov- cally excited in connection with the mass of the for CVT transmissions, en itself in these vehicles because of the high pressure plate. make it clear how mar- torques and the high running performance ket-oriented compo- achieved in past several years. Despite rising In the development of the newest SAC generati on, nents have conti nu- torques, the SAC is also widely used in the area of these requirements have been taken on and the ously expanded the passenger cars because of the moderate release functi ons of degressive leaf spring and sensor fi n- product portf olio in the loads. ger replaced by functi onally new components to past to the benefi t of further opti mize the overtravel safety. The fi rst development goals of the SAC were [6]: the customer. The sensor diaphragm spring is now actuated with • To increase the wear range (longer service life) The modules do much each lift -off and introduces its load directly into the more today than just a • To reduce the operati ng load (comfort) main diaphragm spring. In this way, the pressure few years ago. Devel- plate mass exercises no infl uence on the sensor • Downsizing opments to reduce spring load. A support spring replaces the sensor CO2 output, such as • To reduce the bearing stroke (reducing space fi nger in order to raise the total eff ecti veness with downsizing, reduce Figure 1 LuK clutches for 60 and 3500 Nm engine torque and cost) three additi onal diaphragm spring fi ngers.

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Engaged Disangaged With this design there is a minimum available wear range of 6 mm. This makes the wear reserve nearly double that of other systems avail- Sensor diaphragm able on the market. spring Advanced SAC The positi vely actuated self-adjustment provides a 3

Release load SAC consistent adjustment quality over the enti re wear Load in N range. Depending on requirements, diﬀ erent release load characteristi cs can be drawn (Figure 5). Support In principle, the TAC adjustment principle can be Release travel spring Release travel in mm used for commercial vehicles, passenger cars, Figure 5 Possible release load curves for the TAC stamped and pressed clutch covers. The LuK TAC is a complement to the successful LuK SAC. With limited possibiliti es in selecti ng the release load these concepts, LuK oﬀ ers its customers nearly un- characteristi c and thus the pedal forces. In principle, the release SAC load level can be fur-

Load in N Advanced SAC ther reduced in all designs, even conventi onal clutches, by using a Release travel in mm servo spring between the cover and dia- Sensor load Release load phragm spring ﬁ nger.

New condition This approach was de- Figure 3 Further development of the LuK SAC scribed in [8].

During the release process, the sensor, support pends on the cast masses (flywheel and pres- Nut and leaf spring load combine to increase the sen- sure plate), the selected facing size and on the Vision sor load and thus expand the overtravel safety. Al- wear range of clutch disc and pressure plate. Es- New trails must be ternati vely, the maximum release load can be low- pecially in commercial vehicles, a variety of Spindle blazed in order to sig- ered with the same overtravel safety (Figure 3). start-up and maneuvering processes, such as in nificantly lower the construction traffic, result in a need for in- A constant sensor load in the wear of the clutch Adjuster ring operating loads. One creased wear resistance so that a reasonable disc is ensured by the tuning of the three spring approach is the use of service life can be achieved. components. Gear a booster clutch (Fig- The automated manual shift transmission with ure 6). This clutch sys- With this step, the LuK SAC is also equipped to pneumati c operati on frequently used in commer- tem consists of an ac- meet upcoming demands. cial vehicles also requires an ever-increasing re- tuation clutch and a Compared to the first-generation SAC, the release load characteristi c. This lack of ambiguity in main clutch. These lease load has been reduced by some 30 % at the the load-travel characteristi c curve is needed by two elements are con- same engine torque. Minimum and maximum the clutch control system. nected with one an- release load are now considerably closer to one other by a ramp sys- The LuK TAC (travel adjusted clutch) has been de- another. tem using roll bodies.

veloped for these applicati ons (Figure 4). Wear When the actuation LuK TAC The adjustment procedure is triggered in the clutch closes, the TAC by the travel measurement of the distance built-up torque ro- New roads for commercial between pressure plate and flywheel and the tates the ramps, thus vehicles axial travel change then by a gear with a spindle closing the main directly coupled with the adjuster ring. The trav- clutch. The energy re- In general, a clutch system is designed for a lifes- el compensation takes place between the pres- quired to operate the pan of about 200 000 km for passenger cars and sure plate and diaphragm spring with constant main clutch in this sys- between 600 000 km (local distribution) and finger height. Distortion or potting has no effect tem is provided by the >1 000 000 km (long-distance hauling) for com- on the adjustment quality because the complete combustion engine mercial vehicle applications. The lifespan de- adjustment unit is located on the pressure plate. Figure 4 LuK TAC (push-type clutch) with minimum wear reserve of 6 mm and the only external

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Bearing the torsion characteristi c with increasing engine 3000 speed. The comparison of the dynamic torsion Clamp load Main damper Ramp Release load characteristi cs of a standard damper and damp- 8000 2500 ers with opti mized spring guidance clearly shows 2000 6000 SAC Flanges the lower fricti on of the opti mized version (Fig- 1500 ure 7). 3 4000 1000 Side plates This system is also realized in a damper for com-

Clamp load in N 2000 Booster 500 Release load in N mercial vehicles (Figure 8). In connecti on with the Intermediate opti mized spring guidance, an additi onal interme- 0 0 hub diate hub, which defi nes the rotati on angle of the Main clutch Actuation clutch 0 1 2 3 4 5 6 7 8 9 10 Release travelinmm main damper by means of the external spline and Figure 6 Booster clutch that of the idle damper by means of the internal spline, is necessary to realize an idle stage. force that must be applied from is that needed The opti mized spring guidance is additi onally used to close the actuation clutch. The critical transi- Service life Idle damper for the standard design, depending on the coil tion from drive to coast is conquered with a suit- spring weight and engine speed. able friction control device. Initial tests in vehi- Reducing wear in the torsion cles are showing good results. The release loads Figure 8 Damper for commercial vehicles with damper opti mized spring guidance can be reduced by a factor of 2 or 3 compared to Development of clutch and present-day designs, thus offering great poten- Parti cularly in dampers with high coil spring mass, and the wear of the spring guidance are oft en the facing under one roof tial for the electrification of the clutch opera- such as in commercial vehicles, but also increas- limiti ng factor. With the new spring guidance sys- In cooperati on with Schaeffl er Fricti on, formerly tion, for example. ingly in hybrid and automati c applicati ons, the load tem developed at LuK, the wear on the coil springs Raybestos, LuK has access to high system compe- and guides in the damper can be reduced consider- tence with respect to development and manufac- Force flow Torsion characteristic under ably. turing of facings, which is also revealed in an opti - rotational speed 6000 1/min mized development process for fricti on facings With a standard spring guidance system, the posi- (Figure 9), which is characterized in that ti on of the coil springs changes between the fl ange Conventional and spring guide plates when transiti oning be- 1. the facing quality is defi ned with the fricti on

Nm spring guidance tween drive and coast. Geometric deviati ons in the development in the concept phase of the as- in spring windows of the ﬂ ange and spring guide sembly development

que in Nm plates caused by the producti on process, as well as 2. the requirements (wear, fricti on coeﬃ cient,

T displacement in the damper, cause slight radial Optimized gradient of the fricti on coeffi cient etc.) of the shift s in the coil springs under centrifugal load with spring guidance applicati on are transferred to the require- each change in the coil spring support, which ments of the fricti on pairing Flange1e 1 Flange2e 2 Rotation angle in ° causes fricti on and wear to the springs and guid- Spacer bolt ance. At high engine speeds, the coil spring can 3. existi ng test programs are either modifi ed or Hub even be impeded by the fricti on at the exact reset new programs developed, so that modifi ed re- Coil springs point. quirements can be taken in considerati on (e.g., conti nuous slip in double clutch applicati ons or In the new concept (Figure 7), the damper has short slip intervals with high specifi c compres- two fl anges which remain in constant contact sion in hybrid applicati ons) with the respecti ve coil spring ends. The transiti on between drive and coast torque occurs via 4. tests are performed fi rst on parti al facings, the positi on change from the fl ange to the spacer then in the assembly and fi nally in the vehicle bolt or to the external spline of the hub. The cir- – starti ng from the respecti ve system loads. In cumferenti al lash between the fl anges and the this way, the evaluati on of the fricti on facing hub also defi nes the total angle of rotati on of the material can be made swift ly and without out- damper. side infl uences from other components of the clutch or the vehicle. Due to the eliminati on of the positi on change in the spring guidance, less fricti on and wear occurs One result of this opti mized development process there and on the coil springs than in the standard is facings with improved burst behavior aft er ther- Figure 7 Damper for hybrid applicati on with opti mized spring guidance design. This also results in no essenti al change in mal damage. Experience shows that it is not

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Diaphragm spring NVH Friction washer of Friction Partialt est rig slipping clutch washer with ramps materialscr eening New ideas for well-known Damper mass with ramps 3 Coefficient Measured challenges of friction parameter Noise and vibrati on phenomena (NVH) are mostly Coefficient a problem of the enti re drive train, which means of friction Clutcht est rig that in the majority of cases, the cause cannot be materialt esting traced back to a single component. This can be 3St3 Steps standardtd tests Design Assumed parameters seen from the fact that a clutch assembly, for example, may cause problems in one vehicle and not Measured parameters in another. Two soluti on approaches are described Environmental below which contribute to reducing the likelihood conditions of problems occurring or compensate for possible Packaging Design faults. Coefficient Benefits Spring cages of friction Driver Vehicle Methodical product Diaphragm spring of Cover plate Application validation development Torsion damper to reduce slipping clutch Coil springs Drive train Engine Profoundma terial chatt er vibrati ons Transmission knowledge In all drive trains with fricti on lock-up transfer components, in the slip phase alternati ng torques are Counteractivete torque

Nm Figure 9 Development process of parti al facing, clutch and vehicle superimposed on the average torque, which can in Hysteresis lead to chatt er vibrati ons (Figure 11). However, this

que in Nm

enough just to consider the burst resistance of the Methods have been developed from test rig loads, is only problemati c when it means that vibrati ons or new fricti on facings that have not yet been sub- targeted thermal damage under laboratory condi- can be felt by the driver. How strong an eﬀ ect a T Rotation angle in ° jected to thermal load. Rather, the burst resistance ti ons and burst tests, which comparati vely describe of the components must also be tested aft er longer the mechanical strength of facings aft er thermal Withoutpr opsha ftdamper lasti ng thermal load – including considerati on of stress and serve as a development tool for the fric- 1000 thermal abuse. By using high grade facing materi- ti on facing and clutch developer. Figure 10 shows a 800 Figure 12 Torsion damper (chatt er damper) als and by opti mizing the design relati onship of fac- comparison of the results from diﬀ erent fricti on ing and steel plate, clear improvements in the facing materials. 600

burst resistance can be achieved. 1/min Engine given excitati on has depends on the engine drive

in 400 train and vehicle. Vehicles with high sensiti vity can, Transmission 200 under some circumstances, only be conquered Speed in 1/min with diﬃ culty at the state of the art. 0 4 6 In principle, a tuned mass damper oﬀ ers an ap- 15000 Timein s

min proach for reducing chatt er vibrati ons that occur / Friction layer 1/min Friction material by more than 50 %. LuK has already studied such in 10000 designs many ti mes in the past. The tuned mass 1000 Withpr opsha ftdamper damper then consisted of a mass arranged paral- speed 5000 t speed in 1 800 s lel to the clutch disc using springs and a fricti on control device. The fricti on had to be tuned to a Bur 0 Under layer Steel plate 600 A B deﬁ ned chatt er excitati on. C 1/min or A or B or C Engine in 400 tit tit tit CF1o As a result, the optimal damper performance B8080S R Transmission was only rarely achieved in real operation, since Compe Compe Compe 200 Speed in both excitation and friction can have great varia- Burstspeed a fterabuse t est 0 tion. If, for example, the friction is greater or the (300s tart-ups) 0 2 4 6 excitation lesser than assumed, the tuned mass Timein s Burstspeed a fter3 h @ 360 °C in o ven B8080S RCF1o damper tends to stick, in the opposite case, the Figure 10 Comparison of burst strength aft er abuse and thermal damage; conﬁ gurati on of facing and clutch disc Figure 11 Start-up with chatt er vibrati ons damping is too little for the previous natural fre-

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quency shifted by the Increasinge xcitation This can be achieved by significantly reducing tuned mass damper the mass of the clutch disc dominantly involved Opti mizati ons to the torsion and the new natural Tunedmass damper with c onstantfriction in the characteristic form. In design, this means, damper in the clutch disc frequency of the sys- 100% for example, that the facing mass is radially In additi on to the DMF as the currently most eﬀ ec- tem. A tuned mass decoupled from the hub of the clutch disc, for ti ve system for reducing torsional vibrati ons, con- damper with speed- 50% example. Through the now lower mass on the 3 venti onal systems with solid ﬂ ywheel and torsion- proportional damping input shaft, the natural bending frequency in-

Amplitude in % damped clutch disc are also sti ll used. is supposed to help. creases. Through the decoupling, a second natu- Tests, however, showed Tunedmass damper with v ariablefriction ral frequency arises, which is below the original For passenger cars with smaller engines and that the expense for 100% critical frequency. The advantage of the system light commercial vehicles whose requirements such a module would modified in this way is that the two new charac- for vibration damping in the power train are not be too great. 50% teristic forms are stable within the drivable so great, such as in medium class cars, the tor- range, and so do not start up in case of distur- sion damper in the clutch disc is the best com- In the new approach, 5 15 Amplitude in % bances. promise among space requirements, function the friction is made FrequencyinHz and cost. Systemwith Systemwithout Such a design is already in series producti on to- variable such that it tunedmass damper tunedmass damper day in misalignment compensati on discs, but a Depending on the applicati on, the torsion charac- increases with in- radial off set is only possible with low slip torques. teristi c can be designed with one to fi ve stages. In creasing relative rota- Figure 13 Principle of the tuned mass damper with fricti on dependent on rotati on angle For the noise problem, the relevant torque range principle, the LuK clutch discs have the fl att est tion angle and thus in which the problem can occur must be covered. possible main damper curve with a high-endur- with the moment of For example, the decoupling must work up to ance fricti on control device for stable fricti on excitement. The relationship of friction and ro- Clutch disc with decoupling about 60 Nm in a currently tested vehicle. damping/hysteresis. This is important because a tation angle is determined such that the opti- mum friction is always set for each excitation functi on amplitude. The friction tolerance is not elimi- Noise problems can also occur in the slip phase nated in this way; however the damper perfor- TTiltingilting stiffness of the clutch. A known phenomenon is the “eek mance only decreases perceptibly in extreme noise,” a whistling sound with a constant fre- Hub clutch disc situations. quency in the range of 300 - 500 Hz. The noise The friction control device is provided with frequency correlates, in a simplified view, with ramps that can rotate opposite one another, the natural bending frequency of the transmis- Input shaft which act on a diaphragm spring with a linear sion input shaft, which is calculated from the Facing characteristic curve (Figure 12). The clamp load mass of the clutch disc and the flexural strength in the friction control device and thus the of the input shaft. Theoretically there are two friction thus increase in exactly the required approaches to stabilizing the system with the Radial stiffness measure when the damper mass rotates with clutch disc, and thus of either significantly re- respect to the clutch disc (Figure 13). The damp- ducing or practically excluding the likelihood of er effect is thus independent of the excitation occurrence. torque. One possibility is to weaken the amplification In order to be able to cover common excitati on mechanism. This means that occurring distur- torques with a design-feasible vibrati on angle, bances are transmitted in weaker form to other the damper mass must be around 10 - 20 % of the elements so that a mutual build-up is weakened Tilting stiffness of various designs mass to be dampened. In case of defl ecti ons that or entirely suppressed. For this, the tilting stiff- 50 are nevertheless greater than the maximum vi- ness between the facing ring and hub is reduced 40 brati on angle, the enti re damper unit is fastened for the clutch disc. Thus flexural vibrations from Nm to the clutch disc with a slipping clutch. the input shaft are transferred to the friction in Nm 30 contact between pressure plate and friction fac- que 20 A general advantage of the torsion damper is or ing in weaker form. This can be realized in design T that chatter vibrations are reduced independent 10 by a segment foot configuration with reduced of the excitation mechanism as long as the exci- stiffness, for example (Figure 14). 0 tation frequency is close to the damper frequen- 0 0.5 1 1.5 2 cy. In this way, the torsion damper also prevents Another option for stabilizing the clutch disc is Angle in ° vibrations from starting up in case of friction-in- to detune the noise-determining natural bend- duced excitation (facing chatter). ing frequency of the input shaft considerably. Figure 14 Clutch disks with decoupling functi on

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The vibration simula- 150 Spacer bolt tion shows that the torsional irregularity 100 5th gear Input flange can be reduced by about 25 % by the 50

Spring set lower spring stiffness 1/min 3

in 0 of a double damper in Intermediate flange relevant range. In this tion in 150 way, it was possible Output flange 2nd gear

to achieve a similar fluctua 100 Intermediate hub vibration behavior us-

ing a supercharged Speed fluctua 50 3-cylinder engine in 150 combination with a 0 5thg ear Speed double damper as 4-Cylinder 12 Nm/° 1/min 100 with a 4-cylinder nat- in 3-Cylinder 12 Nm/° urally aspirated en- 3-Cylinder 6 Nm/°

tion in 50 gine and standard damper. Figure 16 Double damper

fluctua 0 Opti mizati ons in the clutch Speed fluctua Speed in 1/min Package 4-Cylinder 12 Nm/° 4-Cylinder 9 Nm/° To reduce the torsional vibrations in the drive train, it is also possible to integrate a centrifugal SlimDisc facing system Figure 15 Serial engagement of the coil springs in the damper pendulum-type absorber in the clutch cover (Figure 17), as is already used with the dual mass Especially with double clutch transmissions, due to flywheel [9, 10, 11]. the thermally relevant masses of the pressure noti ceable reducti on of the damper hysteresis The serial engagement of the springs lowers the plates and the central plate, which temporarily For this purpose, the areas between the strap over the service life can in criti cal applicati ons torsional sti ff ness by 25 %. When used with a store the thermal input, there is relati vely litt le pockets are used. The large effective radius in lead to failures of the synchro ring in the trans- 4-cylinder diesel engine, the speed fl uctuati ons at space available for the fricti on facing/cushion de- combination with large pendulum masses brings mission. the transmission input shaft can be reduced 10 - fl ecti on system of the clutch. Nevertheless, the about a high system effectiveness. In applica- 15 % compared to a standard damper. mileage (vehicle service life) requirements typical One way of reducing the torsional stiffness and tions with longitudinal engines, the system can for an automati c transmission of about 250 000 km thus the torsional irregularity in the drive train is The foreseeable replacement of 4-cylinder natu- normally be integrated in the available space, must be met. the serial engagement of the coil springs in the rally aspirated diesel engines with supercharged while additional space is required for front- damper. This causes a rise in the coil spring 3-cylinder engines provides new possibiliti es for transverse applications. In additi on, the parti al clutches, which are open weight and results – if appropriate counter-mea- the damper in the clutch disc. The relati vely nar- for a longer period – unlike use in manual trans- sures are not taken – in correspondingly higher row axial space in the front transverse drive with missions – experience dynamic loads due to vi- wear on springs and spring guides. The previ- 4-cylinder engine, which is available for the brati ons of the open parti al transmission. Burst ously mentioned new spring guidance system clutch, could, if one cylinder is eliminated, be damage to the clutch disc must be practi cally developed by LuK makes such serial engage- used in part for the clutch. Then clutch disc damp- eliminated for safety reasons. ments possible even at high torques and heavy ers could be designed with even less main damp- coil spring sets. er pitch. These special features result in new specifi c re- In additi on to the two described fl anges, an inter- A double damper, which actuates two parti al quirements for the fricti on facing/cushion defl ec- mediate fl ange is also used. The input fl ange dampers in sequence, makes it possible to halve ti on system of the clutch discs: guides the load to two spring sets located oppo- the spring sti ff ness. The mass moment of inerti a • large wear reserve designed to match the service site one another. These work by means of the in- of such a clutch disc (Figure 16) would normally life termediate fl ange on the nearest spring sets, increase by about 25 %, but could be compensat- which transfer the load to the output fl ange (Fig- ed for in part by measures to the facing, such as • least possible loaded thickness ure 15). The reciprocal control of input and out- thinner segments, opti mized rivet recess thick- • high dynamic connecti on strength put fl ange via spacer bolt or intermediate hub re- ness, etc. Figure 17 Centrifugal pendulum-type absorber in the places the spring transfer. clutch • increased burst resistance

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These requirements are met in the “SlimDisc facing With this system, whose possible applicati ons are segment cover. The system” (Figure 18) developed by LuK. naturally not limited just to double clutches, burst tuning of this tab load speeds > 13 000 1/min can be realized even aft er can be achieved in In this facing concept, the fricti on facing is fas- thermal damage. two different ways. In tened directly to a steel plate without a rivet re- one design, the select- cess (pressed or glued, depending on the facing ed tab load is always 3 material used). This driven plate increases the LuK FlexCompact higher than the maxi- burst resistance and transfers the torque directly For applicati ons of up to 150 Nm engine torque in mum occurring re- to the retainer plate. The foot area to join with which weight reducti on and/or reducing the axial lease load. The modu- the retainer plate is designed axially elasti c so space requirement is the main focus, the FlexCom- lation is by means of that it does not impede the axial movement of pact clutch (Figure 19) developed by LuK provides the cushion deflection the spring segments in the clutch. Spring seg- new possibiliti es. in this system. In the ments and shoulder rivets are no longer involved other case, the elastic in the torque transfer and are also decoupled This light constructi on clutch was the result of an -C- Cover assy with -Co- Cover assy with steel pressure plate tab is designed such from the dynamic circumferenti al loads occurring extensive functi on analysis. The clutch cover no castprt pressurepla te - Modulation spring in levers - Clutch disc with that the elasticity re- when the clutch is open. longer consists of one deep-drawn part, but of sev- - Clutch disc with idle damper, cushion deflection quired for start-up is eral similar components that exhibit a very high -St- Staked hub without idle damper The clutch disc with the SlimDisc facing system can without cushion deflection integrated in the actu- axial sti ff ness aft er being assembled in the com- be made 1.5 to 2 mm thinner with equal wear re- ating levers (modula- posite. serve than a standard facing concept. This space - Clutch disc without cushion deflection tion spring). In this advantage can be used as needed to enlarge the The functi on of the well-known diaphragm spring -St- Stamped hub without idle damper way, the cushion de- thermally relevant masses or to reduce the axial with fi ngers was divided into the actual dia- Figure 19 LuK FlexCompact flection can be elimi- space occupied by the clutch. phragm spring without fi ngers, which generates nated from the clutch the clamp load, and in- disc. This principle is dividual actuati on le- stamped steel pressure plate with correspondingly shown in comparison with cushion deflection in vers as a substi tute for high piece counts (Figure 20). Figure 21. Here the cushion deflection provides the fi ngers that pro- immediate movement of the pressure plate with The actuation levers are supported elastically by vide the lift -off of the the appropriate actuation. When the effect of means of an elastic tab on the outside of the pressure plate by this cushion deflection ends, the lift-off of the means of a boltless pressure plate begins. fastening to the cover. Castprt pressure plate With the elimination of the cushion deflection, a The sti ff actuati on le- retainer plate with a facing pressed onto both vers ensure an excel- sides can be used. This reduces the loaded thick- lent effi ciency. In addi- ness of the clutch disc by up to 3 mm, which ti on, the internal means additional space. The prerequisites for translati on of the pres- the elimination of the cushion deflection in the sure plate can be vari- clutch disc are a narrow pressure plate and nar- ably selected, since Standard row facing rings to keep the thermal distortion there is no direct cou- low. Otherwise, the drive train should be as un- pling between the ac-

X critical as possible as far as chatter. In this way, it tuati on levers and the is possible to reduce the mass and mass moment diaphragm spring load. Steel pressure plate of inertia of the clutch by up to 35 %, depending This is advantageous on the design. especially at small en- Shoulder rivets Shoulder rivets gine torques small re- The limitation on applications in the lower alternating unidirectional lease loads and thus torque range and the limited coil spring loads too small pedal forces and masses as a result mean that the flange can would result if with a

X - 1.5 mm be eliminated for spring guidance with the tor-

X - 1.9 mm S normal diaphragm sion damper. The spring guidance is designed so spring clutch. that the load transfer takes place from the re- The pressure plate can tainer plate via the coil springs under shear load S - 0.4 mm be made standard as a to the cover plate, which is directly staked with Figure 18 LuK SlimDisc facing system cast pressure plate or a Figure 20 Cast vs. steel pressure plate the hub.

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With cushion deflection With modulation spring Retainer plate

Cushion deflection Modulation spring Clutch cover Facings Pressure Plate 1 Damper Diaphragm 3 Lever spring 1 spring Cover-mounted Diaphragm spring release system

1 1 2

Figure 24 Damper with slipping clutch for safe torque F Release Figure 23 Clutch system for hybrid SUV limitati on 4 3 3 Dampers for hybrid applicati ons range from a Hybrid applicati on damper with clutch to torque limitati on by means of a damper with wear-free spring guidance on to Special hybrid applicati ons require a high degree of an arc spring damper based on the DMF. 3 2 system integrati on. The example shown (Figure 23) 1 2 3 4 was developed for a parallel hybrid for the stop- Without suitable counter-measures, the mass F Release Clamp load Clamp load start of the combusti on engine by means of the moment of inertia acting in a hybrid system can Lift-off Lift-off separati on coupling. In additi on to electrical opera- lead to excessively high torque peaks, which Release load Release load ti on, recuperati on and boost are also possible would quickly cause the destruction of whatever functi ons. Because of the space available, a clutch damper is used. For that reason, a clutch is ar- Figure 21 Functi on of cushion defl ecti on and modulati on spring design with the diaphragm spring att ached on the ranged before the damper to limit the torque in outside was selected. The clutch disc has an arc some applications. If the producti on numbers are high enough, the A clutch disc with a pre damper can also be realized spring damper based on the DMF. Cushion defl ec- Unlike other soluti ons, the concept for this clutch cover plate and hub can be economically manufac- according to this principle. Through a combinati on ti on can be eliminated due to the drag functi on of envisioned by LuK (Figure 24) enables easy mount- tured as a single stamped part (Figure 22). Depend- of the possible variants of clutch cover and clutch the engine by means of the E-machine (short ac- ing of the damper on the fl ywheel by the installer. ing on geometry and costs, a three-part division of disc it is possible to confi gure the LuK FlexCompact tuati on ti me with low energy input). The use of a the spring window patt ern is used instead of the clutch according to individual customer specifi ca- cover-mounted release system makes a compact For another hybrid system, LuK provides the fl y- usual four-part division. ti ons. design in the axial directi on possible. In this design, wheel, the dampened clutch disc with opti mized the release system is not supported on the trans- spring guidance and parts of the release system mission. The result is a reduced load on the crank- with a hydraulic line (Figure 25). The examples Possible characteristics shaft and a benefi t to the vibrati on behavior of the shown are similar in applicati on, but lead to diff er- Retainer plate with enti re system. ent designs due to customer requirements. pressed on facing material 125 Solid flywheel Clutch Damper Central release system Hydraulic line m 15 Nm/°

i 75 Stamped hub

orque

6 Nm/°

8.5 12.5

Rotation angle in ° Figure 22 FlexCompact clutch disc Figure 25 Hybrid system components

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[4] Into the Future with Octane, htt p://www. Summary spiegel.de/auto/aktuell/0,1518,661630,00. html, 2009-11-17 The concepts listed here show that there is sti ll [5] Automakers Losing Faith in Hydrogen potenti al for improvement in the clutch system, Power, htt p://www.handelsblatt .com/un- both in terms of performance and economy. In 3 ternehmen/industrie/autohersteller- combinati on with advanced technologies, espe- bmw-verliert-glauben-an-den-wasserstof- cially in the development of new combusti on fantrieb;2495118, 2009-12-07 methods and hybrid structures, new challenges are emerging, which LuK is taking on. What is [6] Reik, W.: The Self-Adjusti ng Clutch, 5th clear even today is that the variety of soluti ons LuK Symposium, 1994, pp. 43-63 employed will conti nue to expand. The right con- [7] Reik, W.; Kimmig, K.; Elison H.-D.; Meinhard, R.; cept, technically and economically, will be select- Raber, C.: New Opportuniti es for the Clutch?, ed, depending on the speciﬁ c customer require- 7th LuK Symposium, 2002, pp. 191-202 ments, and opti mized to the beneﬁ t of the customer. [8] Zink, M.; Hausner, M.; Welter, R.; Shead, R.: Clutch and Release System – Enjoyable Clutch Actuati on! 8th LuK Symposium, Literature 2006; pp. 27-45 [9] Fidlin, A. and Seebacher, R.: Simulati on [1] Mikulic, L.: What is the future of conven- Technology with the DMF Example – Find- ti onal combusti on engines? Video com- ing the Needle in the Haystack, 8th LuK mentary at htt p://www.handelsblatt .com, Symposium, 2006, pp. 55-71 2009-09-16 [10] Zink, M.; Hausner, M.: The Centrifugal Pen- [2] Ostmann, B.: E-Moti on, auto motor und dulum-Type Absorber – Applicati on, Perfor- sport, Issue 21/2009, 63rd volume, p. 3 mance and Limits of Speed-Adapti ve Damp- ers, ATZ, issue 07-08/2009, pp 546-553 [3] Alterna ti ve Drives – Concept Overview, http://www.auto-motor-und-sport.de/ [11] Kroll, J.; Kooy, A.; Seebacher, R.: Land ahoy? eco/alternati ve-antriebe-konzept-ueber- – Torsional dampers for engines of the fu- blick-938005.html, 2009-11-21 ture, 9th LuK Symposium, 2010, pp 28-39

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