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Publisher: LuK GmbH & Co.Industriestrasse 3 • D -77815 Bühl/Baden

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Print: Konkordia GmbH, BühlDas Medienunternehmen

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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

WESTEV

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

173LuK SYMPOSIUM 2002

Electro-Mechanical ActuatorsShifting Transmissions Into Gear

Burkhard PollakMarkus KneißlerNorbert EslyViggo Norum, Kongsberg DevoTekGunter Hirt, Kongsberg DevoTek

15

15 Electro-Mechanical Actuators

174 LuK SYMPOSIUM 2002

IntroductionWith the introduction of Electronic ClutchManagement (ECM) as in the Mercedes A-Class, the demand for the automation of thegearbox itself soon followed. The LuK ASG isthe first Automated Shift Gearbox with electro-mechanical gear shifting as an add-on design.The system was originally installed in the OpelCorsa Easytronic® [1], with Opel and Boschinvolved in the development.

The actuator modules were fitted to existinggearboxes on the first generation. The inter-faces to the release system, including the hy-draulic lines, were carried over. This conceptsupports the demand for modularity, enablingthe function of existing components to be ex-tended simply.

Fig. 1: Add-on Actuator of Opel Corsa

Figure 1 shows both actuator modules. Theclutch actuator is integrated with the controlunit. A hydraulic concentric slave cylinder isused. Engagement of gears is achieved usingan actuator with two motors. To change gear,select is performed by translation movementand shifting by rotation.

Greater integration is possible when a newgearbox is developed, since automation canbe taken into consideration from the start.

Clutch Actuator

Requirements and Operating PrinciplesThe basic functional requirements for theclutch actuator are derived from the manualtransmission. These are the take up from rest,gear shifting and stopping processes.

Take up from rest, particularly when manoeu-vring, requires precise clutch control. Thismust be done differently depending on the re-spective operating conditions; for example, ahill start differs considerably from starting upon a level road.

During gear shifts the clutch must be dis-engaged and re-engaged. This

must be a highly precise and ac-curate process to ensure com-

fortable gear shifting. How-ever, it must also have theappropriate dynamics to

ensure gear shifting isexecuted swiftly.

Stopping under nor-mal conditions typi-cally requires lessprecision. However,

in the event of emer-gency braking or a rapid

stop, there are extreme dy-namic demands on the clutch

actuator that must be fulfilled.



The demands on accuracy, dynamics andservice life are also influenced by other addi-tional functions. These additional functionsparticularly increase the comfort of the XSGfamily members, and only become possibledue to the automation of the clutch.

� Adaptation routines accurately monitor theoperating condition of the drive train.

� Creeping of the vehicle for easy and com-fortable manoeuvring

� Slip control for vibration damping of vehicleswithout DMFW [4]

The clutch actuator currently successfullyused, shown in figure 1, is designed for a max-imum engine torque of 300 Nm depending onclutch size. However, the future design of theXSG family will support even larger engines.

The limiting element in this is the worm gear.It has therefore been replaced in the next gen-eration by a new drive element. The gearboxwear rates and strength of the gear set mustbe suitable for higher clutch release forces –especially for the Parallel Shift Gearbox(PSG) [2], [3].

The acknowledged safety design of the XSGfamily [3] demands self-locking features. Ex-amples of two design solutions are presentedbelow:

� a lead screw and nut having surface contact,

� the spring band principle, which was pre-sented in [5] in connection with the electricalconcentric actuator (ECA).

Both solutions work without a hydraulic line.The forces can be transferred to the releasebearing via a lever or concentrically to the in-put shaft with ramps. This results in the fol-lowing combinations:

Examples of RCA and a variant of an externalrelease system are presented below.

Automation with Mechanical Concentric Release System

The mechanical concentric release system(MCR) replaces the hydraulic release system.Ramps or ball ramps convert a rotationalmovement around the input shaft of the gear-box into the axial release movement. Figure 2shows a diagram of such a release system, asit was presented in [6].

The combination of the MCR with a lead screwdrive and a cable, results in a clutch actuatorfor the XSG family, the Robotized Clutch Ac-tuator (RCA), shown in figure 3. The rotarymotion of the electric motor is transferred di-rectly to a lead screw. A nut, which is rotation-ally fixed and connected to a cable, runs onthis lead screw pulling on the MCR to producethe release motion.

Fig. 2: Mechanical Concentric ReleaseSystem

lead screw spring band

concentric RCA ECA

lever external release system



With a brushless motor [2] such a system canalso be installed in the compact packagingspace of the clutch bell housing. Figure 4 il-lustrates an example of this.

The RCA increases the maximum releaseforce capacity and improves the dynamicsconsiderably compared to the clutch actuatorshown in figure 1. Increased potential isachieved by using a compensation spring.

Fig. 3: Clutch Actuator with Lead Screw Drive

Fig. 4: Example of an RCA Installation

Clutch Actuation with Levers

Fig. 5: External Spring Band Release System

Clutch actuation with a lever has been aroundconsiderably longer than the hydraulic con-centric slave cylinder [7]. An actuator with aspring band gear set or a lead screw takes onthe function of the clutch master cylinder forthe XSG family.

Fig. 6: PSG Actuation with Levers

Figure 5 shows an illustration of an externalspring band release system. A spring band iswound and unwound by the rotation of abrushless motor. This results in axial move-ment analogous to the electrical concentricactuator (ECA) shown in [5].



A lever mechanism transfers this movementdirectly to the release system. Figure 6 showsa layout for a PSG system [2], [3] where twoclutches are actuated by two levers. The lay-out of both levers opposite one another reduc-es the required axial space.

Torque of up to approximately 900 Nm can beactuated by optimising the entire release sys-tem from the brushless motor to the SAC.

Gear ActuatorThe starting point for the gear actuator is theproduction solution shown in figure 1. The cur-rent development objectives are reduction ofpackaging space, modularity, and integration.

Shift Drum Concepts for Gear Actuation

One of the concepts being investigated is theuse of shift drums for integration of the actu-ator into the gearbox. A single electric motoris used to drive this type of actuator. The effortis reduced compared to that of the shift-selectactuator shown in figure 1. However, such so-lutions have two critical disadvantages:

� The great effort of gearbox redesign is onlyjustified by total automation (e.g. as in theSmart car).

� If a shift drum is used, arbitrary gear selec-tion is not available. Gear changes are inev-itably sequential.

The latter can be avoided to a large extent byusing two shift drums. For example, figure 7shows a solution with an external drive to theshift drums. The ratio is achieved with two spurgear stages.

Integrating the motors inside the shift drumsreduces the packaging space required (seefigure 8). The smaller design of the brushlessmotors [2] supports this. The ratio is achievedwith integrated planetary steps.

Fig. 7: Double Shift Drum with External Drive

Fig. 8: Double Shift Drum with Internal Drive

The entire shift drum unit with the integratedmotors can be tested prior to installation. It isfitted directly into the gearbox between thecasing walls.

However, two motors are necessary with thistwin shift drum just as with the normal shift-se-lect actuator, but in the twin shift drum bothmotors must be sized to apply the shift forces.The use of an expensive twin shift drum ar-rangement would therefore appear to makemore sense on a PSG than on the ASG. Thetwo gear groups of the PSG gearbox can beactuated independently of each other with ei-ther of the two shift drums.

This is also possible with the newly developedconcept presented below, but with even moreadvantages.



Active Interlock

The demand for modularity is not sufficientlysatisfied by existing concepts. The vision is toactuate both a manual transmission and themembers of the XSG family with one and thesame concept.

Analysis and Breakdown of ShiftMovements

A totally new solution emerged when the shiftprocess of a known gearbox mechanism wasbroken down and analysed.

On a manual transmission or an ASG with ashift-select actuator three actions run in a fixedsequence.

� Disengage the current gear

� Select

� Engage the new gear

In the sequence disengage – select – en-gage it is mandatory that disengagement oc-curs prior to engagement. On the other hand,the select movement could occur prior to thedisengagement movement.

To make this happen a ‘trick’ is used, throughan additional disengagement cam on the cen-tral selector shaft and a modified slot in theshift rail. They take on the disengagementfunction with the shift finger still responsible forgear engagement. Details of this are de-scribed in paragraph Geometry and Modular-ity.

The disengagement cams work in all gateswhere the shift finger is not active. The fixedrelationship between shift finger and disen-gagement cams simultaneously representsan active gear lock. For this reason, this de-sign approach is called Active Interlock.

Basic Principle

The advantage with Active Interlock is that theshift finger can be moved back to the centreposition when a gear is engaged, without dis-engaging that gear. A select movement istherefore possible before the gear is disen-gaged.

Disengagement cams act in all gates wherethe shift finger is not positioned. The cams dis-engage the old gear immediately prior to thenew gear being engaged by the shift finger inthe same motion.

Figure 9 shows a gear shift sequence wherethe old and new gears are on different rails.In the first picture 2nd gear has been engagedby the shift finger. The finger is moved backto the central position, without the 1st/2nd railbeing moved. Then the 3rd/4th rail is selected.2nd gear remains engaged as previously.

Now the selector shaft is rotated to make thegear shift. Initially the cam disengages2nd gear. When disengagement is completethe rotation continues and the finger engages3rd gear.

A 4th� 2nd downshift follows a similar se-

quence, but the shift rail direction is the samefor both gears in this case.

Figure 10 shows the sequence. The 4th gearis engaged by the shift finger. The central se-lector shaft rotates back into its centre posi-tion. Then a select movement into the1st/2nd gate can occur. This select action andthe opening of the clutch can happen simul-taneously. Next the selector shaft is rotated,which disengages 4th and then engages 2nd,in one rapid movement.



Fig. 9: 2nd� 3rd Gear Shift

with Active InterlockFig. 10: 4th

� 2nd Gear Shift with Active Interlock



Fig. 11: Comparison of Shift Times

A sequence with a double shift gate changeis the same in principle (e.g. 5th

� 2nd). Thesedouble shift gate changes are more frequenton the auto shift gearboxes of the XSG family,than on a manual transmission, due to shiftstrategies being optimised for fuel consump-tion. As high a gear as possible is used duringpart load driving, then these kinds of down-shifts are demanded when the driver pressesthe accelerator pedal. Systems with a shiftdrum have distinct disadvantages here.

Figure 11 shows examplesof tractive force characteris-tics of downshifts with thevarious systems.

It compares the torque pat-tern of a 5th

� 2nd shift withan ASG with conventionalshift-select actuator. On thesystem with a single shiftdrum the traction interrup-tion is significantly longer. Inthis case it relates to a5th

� 3rd shift.

With the Active Interlock thegear shift is noticeablyshorter compared to theconventional system due tothe elimination of selecttime. The reduction of trac-tion interruption time isachieved without increasingthe synchronisation forces.

Active Interlock forPSG Application

Active Interlock is the simplest solution for op-erating a PSG. Due to the active locking mech-anism and the possibility of selecting with agear engaged, then both gearbox units of aPSG can be operated by one Active Interlockactuator. Disengagement cams and shift fin-gers are arranged together, so that they act forone gearbox unit.

The central selector shaft shown in figure 12has two disengagement cams and a shift fin-ger in the middle. The distance between thecams and finger matches the distance be-tween the shift rails. The shift rails shown inthe same colour are from the same group. Theodd gears are arranged in one group, the evengears in another. Whenever the shift finger isaligned to a rail, a disengagement cam isaligned to the other shift rail of that group.

Fig. 12: Active Interlock for PSG



This ensures that only one gear in a group canbe engaged. However, a gear from each group(an odd and an even gear) can be engagedsimultaneously. If a gear from a group is en-gaged or disengaged, everything remains un-changed in the other group.

The layout in figure 12 shows the simplest ar-rangement. If there are larger distances be-tween the shift rails, a second shift finger isused (as in all variants in figure 17).

Fig. 13: Active Interlock for Inline-Gearbox with Parking Lock Actuation

Figure 13 shows an Active Interlock actuatorfor application on vehicles with rear-wheeldrive. The module is flange-mounted at theside. In this particular application the centralselector shaft possesses a shift finger and twodisengagement cams. These are positionedso that during select they can slide along therectangular selector shaft. This makes the ac-tuator very compact.

A brushless motor rotates the selector shaftvia a double planetary gear step and a toothsegment. A second motor drives a lead screw,which slides the shift finger and disengage-ment cams up and down the selector shaft.

It was shown with Active Interlock that twogearbox units could be shifted independentlyfrom one another on a PSG. This raises thequestion whether further operation taskscould be conducted with the actuator. It is ac-tually conceivable that the parking lock oftenrequired for a PSG system could also be ac-tuated with the Active Interlock gear actuator.

To do this, a further shift rail is required be-tween the two upper and two lower rails shownin figure 12. This actuates a parking lock, anexample of which is found in [3].

Geometry and ModularityActive Interlock provides a system which can beused in both ASG and PSG systems. The dif-ference is merely one of size, quantity, and lay-out of shift fingers or disengagement cams. Thenew shift slots are the same for ASG and PSG.

The basic shapes are shown in figure 14. Thered shift finger is responsible for the engage-ment of gears. The green geometry takes overdisengagement of gears. Depending on thedirection of actuation, different sections act tomove the shift rails into the Neutral position.The circular surfaces ultimately form the lock-ing cylinder – as known for solutions in manualtransmissions.

Fig. 14: Active Interlock Geometry



Figure 15 shows a detailed example of an Active Interlock gear actuator.

Fig. 15: Detailed Example of a TransverseActive Interlock

The interfaces for assembly are identical onthe manual and automated gearbox. Thethrust bearing for the central selector shafts isalso used by the gear actuator if necessary.The actuators are very compact due to thebrushless motors shown in [2]. As a rule, thegear actuator has no greater packaging spacerequirement than the manual transmissionmodule (see also figure 17).

By using the incremental travel measurementfor the electronic commutation of the motorsand determining the position of the gear actu-ator, additional sensors or redesign of thegearbox are unnecessary.

In the case of a manually operated gearbox,the new shift slot geometry from figure 14 iscombined with a wide shift finger, as illustratedin figure 16.

Fig. 16: Shift Finger and Shift Slot for Manual Transmission

Hence the manual transmission variant is apart of the modular system. The individual var-iants are illustrated alongside each other infigure 17:

� Left: Manual Transmission Version,

� Centre: ASG Version,

� Right: PSG Design.

Both variants shown to the left in figure 17 canbe used in the same transmission. By usingthe same interfaces for the manual transmis-sion and members of the XSG family, the con-cepts offer the greatest flexibility for planningmanufacturing equipment.



Fig. 17: Actuation Modules for Manual Transmission, ASG and PSG

SummaryWith RCA, the external lever release system,and the ECA presented in [5], customisedclutch actuation is available for various gear-boxes. These actuators can operate clutcheswith higher torques with low packaging spacerequirements and high dynamics. Just as withthe gear actuator, an essential feature is theuse of brushless motors [2].

Active Interlock is a compact and universalgearbox actuation for the XSG family. The in-itial ASG prototype impressively demon-strates the advantages of the operating prin-ciple. This is reflected in the positive feedbackfrom numerous test drives. Active Interlock iscurrently being implemented in its first produc-tion projects.

References[1] Fischer, R.; Berger, R.; Bührle, P.;

Ehrlich, M.: Vorteile des elektromotor-ischen LuK ASG am Beispiel derEasytronic im Opel Corsa, VDI.

[2] Fischer, R.; Schneider, G.: The XSGFamily – Dry Clutches and Electric Mo-tors as Core Elements of the Future Au-tomated Gearbox, 7th LuK Symposium2002.

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

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

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

[6] Kooy, A.: The Mechanical Central Re-lease System for the SAC, an Alterna-tive? 5th LuK Symposium 1994.

[7] Zink, M.; Welter, R.; Shead, R.: ClutchRelease Systems, 7th LuK Symposium2002.

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