The Parallel Shift Gearbox PSG

Publisher: LuK GmbH & Co. Industriestrasse 3 • D -77815 Bühl/Baden Telephon +49 (0) 7223 / 941 - 0 • Fax +49 (0) 7223 / 2 69 50 Internet: www.LuK.de Editorial: Ralf Stopp, Christa Siefert Layout: Vera Westermann Layout support: Heike Pinther Print: Konkordia GmbH, Bühl Das Medienunternehmen Printed in Germany Reprint, also in extracts, without authorisation of the publisher forbidden. Foreword Innovations are shaping our future. Experts predict that there will be more changes in the fields of transmission, electronics and safety of vehicles over the next 15 years than there have been throughout the past 50 years. This drive for innovation is continually providing manufacturers and sup- pliers with new challenges and is set to significantly alter our world of mobility. LuK is embracing these challenges. With a wealth of vision and engineering performance, our engineers are once again proving their innovative power. Bühl, in April 2002 This volume comprises papers from the 7th LuK Symposium and illustrates our view of technical developments. Helmut Beier We look forward to some intere- President sting discussions with you. of the LuK Group Content 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 LuK SYMPOSIUM 2002 The Parallel Shift Gearbox PSG Twin Clutch Gearbox with Dry Clutches Reinhard Berger Rolf Meinhard Carsten Bünder 17 LuK SYMPOSIUM 2002 197 17 The Parallel Shift Gearbox PSG Introduction As a member of the XSG family [2] the PSG has the following features: The Parallel Shift Gearbox (PSG) is a variant ; of the twin clutch gearbox. Dry clutches and electro-mechanical clutch actuators, Such gearboxes have been around for a long time. For example, at the end of the 1980s a ; Parallel shaft design and constant mesh Porsche twin clutch gearbox (PDK) was being gears used in motor racing [1]. However, it never reached production. Thanks to the search for ; synchronised dog clutches with electro-me- transmission systems which minimise fuel chanical actuator and Active Interlock [4], consumption, twin clutch gearboxes are now experiencing a renaissance. ; system strategy elements in common with the ASG. It is this combination of features that makes the PSG stand out from other twin clutch gearboxes. In terms of functionality and comfort, the requirements of a PSG and its components correspond to those also placed on the automatic transmission designs of today. The logical integration of the PSG in the XSG family is therefore particularly important, since a whole string of gearbox manufacturers are working on modular gearbox families, where, in addition to the manual gearbox, various automated ver- sions are also produced using the same manufacturing equipment. LuK extends this modular approach to its components, clutches and actuators. Hence, for example, the same gear actuator can be used for an ASG or a PSG in conjunction with the Active Interlock. This paper shows the opportunities avail- able if dry clutches are used in a twin clutch gearbox, but also highlights the issues still to be resolved. It further dem- Fig. 1: PSG - Principle onstrates the integration of the individual components presented in other papers [2], [3], [4], [5] into the entire system. The subject of vibration isolation using slip control also plays an important part here. 198 LuK SYMPOSIUM 2002 17 The Parallel Shift Gearbox PSG Opportunities and Key dry clutch wet clutch Issues for the Dry Clutch in the PSG consumption overload capacity Overview hill take-up LuK manufactures about 12 million dry clutch- option for es and about 3 million lock-up clutches for modular families torque converters annually. Hence it possess- es a wealth of know-how of both variants – dry packing space/ and wet. This also applies to automation, weight since, in addition to ASG applications with dry clutches, LuK also played quite a crucial part fail safe in the development of the wet starting clutch behaviour for Audi’s multitronic®. shift quality controllability The following explains why the use of a dry twin clutch is preferred in the PSG: Fig. 2: Dry or Wet Clutch ; Lower fuel consumption, ; Option for modular gearbox families (MT, ASG, PSG), Gearbox Power Loss and Fuel Consumption ; More frequently used as start-up element. This has raised various concerns which crop With more than 96%, the manual gearbox up repeatedly whenever there is talk of replac- (MT) has an outstanding full-load efficiency. ing conventional automatic transmissions However, in actual driving cycles with a high with gearboxes with dry clutches. More spe- part-load content, friction losses in gears and cifically, these are: bearings as well as lubrication losses, have al- ; Lining wear, ready reached double figures [6]. Figure 3 illustrates the additional losses that occur in the ; Thermal capacity and robustness against misuse clutches and for the gearbox control (whilst the base loss figures mentioned above are con- ; Controllability, sidered equal across all variants and conse- ; Behaviour in the event of a system failure. quently not shown). LuK will today demonstrate that all these is- These values describe the rates of power loss sues can be satisfactorily resolved. In some in relation to the energy induced in the com- cases, there are even advantages of using the dry clutch in comparison to the wet clutch -see bustion engine. Convertion into consumption figure 2. The most important criteria are now values can result in slight discrepancies due to covered in detail. the engine consumption mapping. LuK SYMPOSIUM 2002 199 17 The Parallel Shift Gearbox PSG downforce on the clutch(es) during driving, an electrical oil pump would not improve the sit- uation. Given the automotive industry‘s voluntary commitment to reduce fleet consumption by 2008 to 140 g CO2 per kilometre, the alterna- tive concept with the dry clutches is the best possible solution. Service Life of Dry Clutches Since the introduction of asbestos-free clutch linings and self-adjusting clutches with increased wear life, the replacement of the Fig. 3: Clutch Losses and Control Auxiliary Energy clutch within the normal life of a car is practi- cally never wear-related. With an automated Friction losses occur in the clutches when clutch the average service life is even further starting up and changing gear. This only af- increased. This is not only due to the greater fects the gear shifts for automatic transmis- consistency in clutch actuation, but also to the sions, since start up is via the torque converter strategies implemented against misuse. and not the clutches (start-up energy AT is in- In contrast to that, one question is justifiably cluded in the orange bar). As a result of the raised regarding the PSG: how does a dry power shifts on the PSG and wet twin clutch clutch sustain the additional energy input fol- gearbox (hereafter, ‘DKG’), the clutch losses lowing the power shifts? After all, a clutch must prove to be approximately 0.6% higher com- firstly take over the full engine torque and then pared with the manual gearbox in the NEDC reduce the speed difference. This creates cycle. three times more fictional energy than in ASG Further losses occur as a result of drag torque gearshifts. in the non-active clutches. This represents a A mixed driving cycle has been developed at distinct advantage for the dry clutch. The larg- LuK to estimate the service life of dry clutches, est slip losses occur in the automatic trans- which has gained approval from our custom- mission (AT) of conventional design, since ers with field results and endurance tests. This three or more load-free clutches or brakes with cycle contains 50% urban driving, 30% rural several discs are dragged along constantly driving, 18% motorway driving and 2% hill [7]. On the PSG and wet DKG the load-free driving. In total, this cycle includes 240 000 clutch runs without drag losses during driving, journeys and 1.5 million gear shifts at a re- if no gear is preselected. quired vehicle endurance of 240 000 km. A dry clutch system with an electro-mechan- Figure 4 shows the results of the wear extrap- ical actuator is also the optimum solution when olation for a standard-size vehicle. It is clear auxiliary power is required for the actuation of from the figure that part of the start-up energy clutches and gear shifting. The average elec- is also absorbed in the clutch of the second trical power requirement is estimated at gear. Depending on the ratio configuration, it 20 watts; on the current ASG in production it is possible on the one hand to start up directly is 12 watts. The oil pump, which runs perma- in second gear (e.g. part-load operation) or to nently, the leakage of pressurised oil, the oil apply both clutches during start-up. flow through the radiator and the filter all cause considerably greater losses on the AT or wet The results shown in figure 4 are based on an DKG. Since there is a constant engagement average wear rate that is 30% higher than to- 200 LuK SYMPOSIUM 2002 17 The Parallel Shift Gearbox PSG day‘s manual gearbox.

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