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Foreword

Innovations are shaping ourfuture. Experts predict that therewill be more changes in the fieldsof transmission, electronics andsafety of vehicles over the next15 years than there have beenthroughout the past 50 years. Thisdrive for innovation is continuallyproviding manufacturers and sup-pliers with new challenges and isset to significantly alter our worldof mobility.

LuK is embracing these challen-ges. With a wealth of vision andengineering performance, ourengineers are once again provingtheir innovative power.

This volume comprises papersfrom the 7th LuK Symposium andillustrates our view of technicaldevelopments.

We look forward to some intere-sting discussions with you.

Bühl, in April 2002

Helmut Beier

Presidentof the LuK Group

Content

LuK SYMPOSIUM 2002

1 DMFW – Nothing New? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 Torque Converter Evolution at LuK . . . . . . . . . . . . . . . . . . . . . . . 15

3 Clutch Release Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4 Internal Crankshaft Damper (ICD). . . . . . . . . . . . . . . . . . . . . . . . . 41

5 Latest Results in the CVT Development. . . . . . . . . . . . . . . . . . . . 51

6 Efficiency-Optimised CVT Clamping System . . . . . . . . . . . . . . . 61

7 500 Nm CVT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

8 The Crank-CVT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

9 Demand Based Controllable Pumps. . . . . . . . . . . . . . . . . . . . . . . 99

10 Temperature-controlled Lubricating Oil Pumps Save Fuel . . . 113

11 CO2 Compressors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

12 Components and Assemblies for Transmission Shift Systems135

13 The XSG Family . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

14 New Opportunities for the Clutch?. . . . . . . . . . . . . . . . . . . . . . . 161

15 Electro-Mechanical Actuators. . . . . . . . . . . . . . . . . . . . . . . . . . . 173

16 Think Systems - Software by LuK. . . . . . . . . . . . . . . . . . . . . . . . 185

17 The Parallel Shift Gearbox PSG . . . . . . . . . . . . . . . . . . . . . . . . . 197

18 Small Starter Generator – Big Impact . . . . . . . . . . . . . . . . . . . . . 211

19 Code Generation for Manufacturing. . . . . . . . . . . . . . . . . . . . . . 225

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The XSG FamilyDry Clutches and Electric Motors as Core Elements of the Future Automated Gearbox

Robert FischerGeorg Schneider

13

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IntroductionWithin the XSG family, LuK has brought to-gether automated gearboxes that are basedon the Manual Transmission (MT, in German‘Handschaltgetriebe’) and use essentiallysimilar technology. They include ElectronicClutch Management (ECM), the Auto ShiftGearbox (ASG), the Uninterrupted Shift Gear-box (USG), the Parallel Shift Gearbox (PSG)and the Electrical Shift Gearbox (ESG). Thefirst part of this paper presents an overview ofthe family members and how they relate toeach other. In the second section, some of thefamily members are presented in more detail,in particular the ASG and USG. The ECM hasalready been adequately covered in earlierpapers [1], [2] and the PSG and ESG will becovered elsewhere in this book [3], [4]. Thethird part of the paper introduces the commoncomponents of the XSG family whilst thefourth part contains a system comparison.

Presentation of Family MembersAs previously mentioned, the XSG family isbased on the Manual Transmission (MT,

figure 1). The diagram has been simplified forthe purposes of this paper; parts which inter-act are shown in the same colour, where nec-essary with a different shade. A transversegearbox has been used as the example here.

Manual transmissions have the advantage ofbeing very efficient and relatively low inweight; they are low-cost and there are nu-merous manufacturing plants.

The first step in automation of the manualtransmission is Electronic Clutch Manage-ment (ECM). This dispenses with the clutchpedal. The clutch is controlled by an actuator,which can be either electrical, hydraulic orpneumatic. The diagrams show the electro-motoric variant preferred by LuK, see figure 2.

Automating the clutch itself brings significantbenefits in comfort, which are particularly ad-vantageous, especially in urban traffic, whichis becoming increasingly heavier. ECM is alsoa fundamental requirement for all subsequentmembers of the XSG family.

With an Auto Shift Gearbox (ASG) the actualgear shifting is also automated. Two electricmotors take over the task of selecting andshifting gears from the driver, see figure 3.

This also brings about an additionalincrease in comfort. Fuel consump-tion can be reduced through the au-tomatical and optimally configuredshift point selection - that‘s one rea-son why an auto shift gearbox isused on practically all energy-sav-ing vehicles. A further advantage isthe flexible interior design, sincewith shift-by-wire, the mechanicalconnection between gearbox andthe driver’s control element is omit-ted. This can extend as far as thegear lever being completely omittedand being replaced by tip switchesor a lever on the steering wheel. Theinterior acoustics are also improvedby shift-by-wire, since the noisebridge is removed.

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Fig. 2: From MT to ECM

Fig. 3: From ECM to ASG

On an Uninterrupted Shift Gearbox (USG,figure 4) a partial filling of the torque interrup-tion during a gear shift is achieved with an ad-ditional clutch.

As a result the shift comfort is further im-proved. The extra cost compared with an ASGis minimal; as explained in [5], only one clutchactuator is necessary for both clutches on the

USG. However, this gearbox can only be usedup to a certain level of engine torque.

The Parallel Shift Gearbox (PSG) belongs tothe twin clutch gearbox group. LuK has giventhe PSG (figure 5) its own name, as it is rathera special design. Dry clutches and electromo-toric actuators are used. An additional feature isthat only one actuator similar to the ASG is usedfor the gear shifting of both gearbox sections.

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Fig. 4: From ASG to the USG

Fig. 5: From USG to PSG

With PSG, an additional increase in comfortover ASG and PSG is achieved, since it is pos-sible to have a fully torque filled power shift.In contrast to the USG, LuK sees no limit to the

options for high engine torque. The benefit forfuel consumption is almost as great as with theASG.

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Fig. 6: From PSG to ESG

The next step is to combine the starter gen-erator with the gearbox. A PSG can be easilyextended into an Electrical Shift Gearbox(ESG, figure 6), in which a starter generator iscoupled in parallel to one of the two inputshafts.

If this option is considered when designing thePSG, only minor modifications to convert to anESG are necessary. The advantages of theESG are a further reduction in fuel consump-tion and an additional increase in comfort.

That completes the XSG family - at least forthe time being, who knows what the futureholds.

Common features of the XSG family are there-fore:

� similar manufacturing technology (such asspur gears)

� the use of dry clutches [6]

� the use of similar actuators

� the use of electric motors

� common software strategies [7]

Fig. 7: The XSG Family

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Two XSG Family Members in Detail (ASG and USG)

The Auto Shift GearboxThe ASG was presented in detail in [2]. Thissystem has already been in production for ayear in the form of the Opel Easytronic®

(figure 8).

Fig. 8: Easytronic®(Source: Opel), [9]

The LuK-ASG is the first and, until now, theonly electromotoric auto shift gearbox

� that offers free gear selection,

� that is designed as an add-on concept,

� that makes it possible to have engine torqueof over 200 Nm.

Each of these properties is a unique featurein its own right.

Not for much longer though – the launch ofLuK ASG components into production by an-other car manufacturer isn’t far away.

LuK also has production experience with hy-draulically operated ASGs (figure 9), which,although technologically sound, are more ex-pensive and heavier. After the successfullaunch of the Corsa Easytronic®, LuK decidedto focus on pursuing the electromotoric route.This path also supports the trend for substi-tuting hydraulically driven functions with elec-tromotoric ones.

The LuK ASG is in this version an add-on sys-tem (figure 10). The manual shift mechanismwith shift cables or shift rods and shift lever isreplaced with the gearbox actuator (two mo-tors). The clutch actuator, which is fixed to thegearbox, replaces the clutch pedal and hous-es the control and power electronics, includingsoftware, for the entire system. In the Corsait actuates the same hydraulic concentricslave cylinder which is used on the manuallyoperated gearbox. A self-adjusting clutch(SAC) is used, ensuring low release forces. Ason the ECM in the A-Class, system operationis achieved without a clutch travel sensor onthe release system and without a speed sen-sor on the gearbox input shaft. This not onlysaves on the cost of the sensors themselves,but also on associated gearbox modificationsand wiring.

With the LuK ASG, the Corsa Easytronic® hasan extra weight of less than 4 kg when com-pared with the manual version. The extracosts for the end customer are only approxi-mately 50% of that of the automatic transmis-sion. Responsiveness and driving pleasureare distinctly greater than with an automatictransmission, whilst fuel consumption is con-siderably lower than on an automatic. It iseven lower than on a manual transmission. Onthe 1.2 l engine, a reduction in fuel consump-tion of 2% was achieved without any specialtuning being optimised for fuel consumption.On the Corsa Eco 1.0 l a substantial propor-tion of the more than 10% of fuel consumptionreduction has been achieved through eco-nomic shift point selection.

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Fig. 9: LuK´s Route to the Corsa Easytronic®

Fig. 10: ASG as Add-On System

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The Uninterrupted Shift Gearbox USG

Fig. 11: The Uninterrupted SG - USG

The USG was presented in [5]. In the mean-time, an initial prototype for a vehicle withfront-wheel drive transverse gearbox and amore well-proven prototype for a vehicle withrear-wheel drive were built. The section of anUSG, built in co-operation with BMW and Ge-trag (figure 11), shows that the USG is wellsuited for rear-wheel drive. Synchronisationunits could also be dispensed with to a largeextent.

The measurement in figure 12 shows an ex-ample of the effect of the torque filling. De-pending on gear and accelerator position, thisfilling amounts to between 40% and 100%. In-terestingly, even with partial filling, it is sub-jectively hardly possible to detect any torque

interruption. The importantpoint here seems to be thatthe vehicle accelerationdoesn’t become negative,as occurs during gear shift-ing on the ASG.

The power shift is achievedby the fact that the powershift clutch linked with thehighest or second highestgear not only allows syn-chronisation, but also trans-fers the necessary torque forthis to the output. The clutchis loaded the entire time witha relatively high differentialspeed, especially duringgear shifts into lower gears.The power shift torque de-

pends on the desired level of fill. This high loadduring every gear shift means that this clutchis significantly more heavily loaded than thestart-up clutch. That’s why in figure 11 the larg-er clutch is the power shift clutch. A connectioncan be made between the engine torque andthe necessary external diameter of the clutchdisc (figure 13). The packaging conditionsmean that the USG is restricted to engine tor-ques of max. 200 to 250 Nm. For a gearboxgeneration which does not exceed this torquelevel, the USG is a solution which provides ahigh degree of comfort at sensible costs. Thedevelopment of new high-performance fric-tion linings could still increase the uppertorque limit of USG.

Fig. 12: USG – Increase in Comfort Fig. 13: USG – Torque Limit

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The Common Components of the XSG Family

New Electric MotorsLuK uses electric mo-tors for automatingmanual transmissions.The reasons for thishave already beenpartly explained: thesystem does not usehydraulic fluid - whichalso follows to thetrend - it is low cost,low in weight and ro-bust etc.

Fig. 14: Comparison of Electric Motors

The motors used on the Easytronic® arebased on window lifter motors (DC-motors).However, the load on the ASG is far higherthan on the window lifter. The motors are ex-posed to relatively high temperatures, heavyvibrations and salt water etc. Brush motors ca-pable of high performance were developedwith Bosch for this application (figure 14 photobottom).

Just how these motors have become complexas a result of the environmental conditions canbe seen, for example, by the incorporation ofthe large bearing that is necessary due to vi-brations.

LuK has sought ways to further reduce thepackaging space and costs, whilst increasingeven the performance. Brushless motorshave therefore been adopted (figure 14 top).

These electronically commutated motors(EC-motors) use rare earth magnets to helpmake the motor very compact with a high pow-er density.

Fig. 15: Dynamics of New Electric Motors(Example: Clutch Actuation)

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Fig. 16: Characteristic Parameters of New Motors

Admittedly, the rare earth motors are expen-sive and additional electronic components inthe control unit have to be considered for elec-tric commutation. These additional costs aremore than compensated by the simple designof the motor, however. As no brushes areused, no costly measures are necessary tomake the brush-holders vibration and temper-ature resistant. Since the rotor mass is verylow, no costly bearing support is required. Asshown in the next section, savings can also bemade in the actuator design, since the load onthe actuator is less due to the lower mass ofthe motors.

This factor also improves the dynamic re-sponse as the nominal operating speed isachieved substantially faster due to the lowerrotor inertia. This results in an even shorter ac-tuation time during a step response. Thespeed characteristics are compared infigure 15 at the bottom, the resulting actuationtravels are shown in figure 15 at the top. Thisdiagram also illustrates the characteristics ofexisting motors (DC), the clutch motor and thealready optimised shift motor.

The advantages of the new electric motors aresummarised again in the table (figure 16).

New Development of Clutch Actuation [8]

The small size of the new motors opens upnew design possibilities. For example, the mo-tor can be fitted directly to the clutch bell hous-ing - actuation can then be performed via alead screw on a MCR (mechanical concentricrelease system), figure 17 left.

A further benefit is the potential for highertorque. The motors currently used cannot befurther extended (due to shaft deflection) andneither can they be thicker (due to packagingspace, dynamics). With EC motors, extendingthe motors presents no problem.

In addition, LuK can offer one further innova-tion - to be precise, the electric concentricclutch actuator (ECA), which fits in the pack-aging space of the traditional hydraulic con-centric slave cylinder [6].

These new clutch actuators can be used forautomating the clutch of all XSG family mem-bers.

present clutch motor (DC)

present shift motor(DC)

new motor(EC)

power density 101 W/kg 163 W/kg 267 W/kg

100% 162% 266%

inertia 30.4 � 10-6 kgm2 25.0 � 10-6 kgm2 6.5 � 10-6 kgm2

100% 82% 21%

mechanical time constant

27.75 ms 7.46 ms 1.88 ms

100% 27% 6.8%

weight 693 g 813 g 438 g

100% 117% 63%

volume 166 cm2 162 cm2 62 cm2

100% 98% 37%

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New Development of Gearbox actuation [8]

With the new EC motors it is possible to con-siderably reduce the volume of the gearboxactuator compared with the current - alreadycompact - design. In most cases it is even pos-sible that the complete gearbox actuator willfit into the space otherwise filled by the manualtransmission shift module. The vibrationalload of the actuator housing is reduced due tothe low mass of the motors - as a result ofwhich, weight and volume are significantly re-duced.

This actuator is used throughout the entireXSG family for automating the gear shiftmechanism.

On twin clutch gearboxes, two gearbox sec-tions have to be automated. Two ASG actua-tors would therefore normally have to be used,but as a result of an innovative LuK develop-ment called Active Interlock, the gear shiftingof both gearbox sections is possible with oneactuator, as on the ASG. This is one of the fun-damental features of the PSG (figure 18).

A design example of an Active Interlock gear-box actuator for an Inline-PSG is shown on theright in figure 17.

The Active Interlock technology also acceler-ates gear shifting on the ASG, due to the elim-ination of the select times. The Active Interlockcan thus be used for gearbox shifting on allXSG family members and is highly modular indesign (figure 19).

Fig. 17: New Development XSG Actuators

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Fig. 18: PSG with Only One Gearbox Actuator

Fig. 19: Active Interlock

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System ComparisonAn important part of the argument in favour ofautomation of manual transmissions, andhence for the XSG family, is the good fuel con-sumption. If the manual transmission is takenas a basis, automatic transmissions sufferfrom greater fuel consumption at the sameshift point selection due to hydraulic powerloss – see figure 20 top, red arrow, marked ‘H’.This increased fuel consumption amounts toseveral percent. Automatic transmissions(and automated gearboxes) can use thechoice of more favourable operating points inthe engine map for shift point selection to theiradvantage. This can result in a reduced fuelconsumption in legally defined cycles – seefigure 20 top, green arrow, marked ‘S’. More-over, this reduction in fuel consumptionthrough automatic shift point selection is alsorealized in practice, since the average driverusing a manual transmission generally avoidsdriving at economic low engine speeds.

The first member of the XSG family, the ECM,has the same fuel consumption as the manual

transmission. The power consumption of theactuator is under 10 W, which is not detectablein fuel consumption. The automated gearbox-es ASG, USG and PSG can achieve the samefuel consumption benefits with the samespread of ratios as the automatic transmis-sion, due to automatic shift points. The differ-ence between these automated manual gear-boxes and the conventional automatic trans-mission is the increased fuel consumption as-sociated with the latter caused by hydraulicpower losses. This applies, even if the fuelconsumption of the AT is below that of the MTin the legal fuel consumption cycle. In thatcase, the reduction achieved throuh the auto-matic selection of the shift points outweighsthe hydraulic power losses. The automatedmanual transmissions will still remain aheadby the amount of these hydraulic losses.

A significant additional fuel consumption re-duction can again be achieved through regen-eration - see figure 20 bottom, marked ‘R’. TheESG therefore has the lowest fuel consump-tion.

Fig. 20: Fuel Consumption

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Does an increase in comfort and a reductionin fuel consumption have to be incompatible?Figure 21 shows that this doesn’t have to bethe case.

Fig. 21: Comparison of Fuel Consumption and Comfort

Despite increased comfort and functionality,fuel consumption is reduced. Implementationof power shifting on USG and PSG slightly re-duces fuel consumption improvements whencompared with ASG, power shift losses beingsmaller in case of the PSG (these losses arenot taken into account in the simplified illus-tration in figure 20, neither for the automatictransmission; compare also [3]). The ESG isby far and away the best.

These fuel consumption values are roughguide values; they depend on many variables,in particular engine torque. There are two fun-damental effects here. The first effect is thata non-torque-dependent base value exists inthe absolute amount of power loss. The othereffect is that the potential for reduction in fuelconsumption through shift point selection isless with a small engine than with a large one.

The qualities of the first effect are illustratedin figure 22.

The power losses associated with oil pumpand oil cooler, drag losses from the multi-discclutches, splashing and torque converter loss-es are substantially constant and do not re-duce in proportion to with decreasing enginesize - to be precise, with decreasing enginetorque. The relative increased fuel consump-tion with the automatic transmission therefore

increases significantly with a decreasing en-gine torque.

An electrically driven oil pump scarcely reduc-es these losses. And the reason: as an esti-mate, for 100% mechanical power of the oilpump, the electric motor needs 200% electri-cal power. In order to supply this, the gener-ator needs 400% mechanical power. Thismeans that only if the mechanical energy con-sumption of the oil pump is reduced to a quar-ter by controlling its duty cycle, will its use notdegrade fuel consumption.

The other effect is illustrated in figure 23.

The driver requires a certain driving perform-ance which can be achieved by different en-gine torque - engine speed combinations andappropriate gear ratio. This means that the op-erating point in the engine map is moved alongthe line of the same power through the gearratio. The reduction in fuel consumption isbased on the fact that normally the specificfuel consumption is lower with high load andlow speed. There is substantially more poten-tial with a high-performance engine, than witha small engine.

Fig. 22: AT- Increased Fuel Consumption as a Result of Hydraulic Losses

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Fig. 23: Reduction of Fuel Consumption with Optimum Engine Operating Point

Furthermore, as can be seen in figure 23, agreater gearbox ratio spread makes sense,particularly with high-performance engines.

However, modern designed engines have alarger range of lower specific fuel consump-tion as a result of dethrottling; that means thatthe potential for reducing fuel consumptionthrough overdrive and gear selection is lessand the efficiency of the gearbox is, as such,increasingly more important.

This information is summarised in figure 24. Itis recognised that modern automatic trans-missions can even drop below the fuel con-sumption of manual transmissions. However,the family members ASG, USG and PSG areclearly superior, since they do not have the hy-draulic losses of the automatic transmission(compare again figures 20 and 22). Infigure 24, three auto shift gearboxes alreadyin operation, using LuK components, are alsoshown.

Fig. 24: Consumption of Automated Transmissions compared to MT

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Summary

Fig. 25: Summary - XSG Family

The XSG family is:

� low in cost and weight

� unsurpassed in terms of its efficiency

� and thus has the best fuel consumption

LuK therefore predicts a great future for thisfamily.

References[1] Kremmling, B.; Fischer, R.: The Auto-

mated Clutch – The New LuK ECM,5th LuK Symposium 1994.

[2] Fischer, R.; Berger, R.: Automation ofManual Transmission, 6th LuK Sympo-sium 1998.

[3] Berger, R.; Meinhard, R.; Bünder, C.:The Parallel Shift Gearbox PSG – TwinClutch Gearbox with Dry Clutches,7th LuK Symposium 2002.

[4] Pels, T.; Vestgård, B.; Mán, L.;Reitz, D.: Small Starter Generator – BigImpact, 7th LuK Symposium 2002.

[5] Fischer, R.; Hirt, G.: Integration autom-atisierter Schaltgetriebe mit E-Maschine, Fachtagung 1999.

[6] Reik, W.; Kimmig, K.-L.; Meinhard, R.;Elison, H.-D.; Raber, C.: New Opportu-nities for the Clutch? 7th LuK Symposi-um 2002.

[7] Küpper, K.; Werner, O.; Seebacher, R.:Think Systems – LuK Software, 7th LuKSymposium 2002.

[8] Pollak, B.; Kneißler, M.; Esly, N.;Norum, V.; Hirt, G.: Electro-MechanicalActuators – Setting Gearboxes in Mo-tion, 7th LuK Symposium 2002.

[9] An Opel brand