Cover Story FUTURE POWERTRAIN STRATEGIES POWERTRAIN INCLUDING AUTOMATIC FOR THE A-SEGMENT

The A-segment is very versatile. In this article, FEV describes the requirements for this vehicle class, focusing on the conventional powertrain. Worldwide conventional powertrain trends are indicated and the article offers a prac- tically-oriented proposal with regard to a small, compact , explicitly for these vehicles.

© FEV

26 www.autotechreview.com Authors MARKET A-segment vehicles are primarily used in or near towns and cities. On an The A-segment achieved a worldwide annual basis, the average mileage is sales volume of 5.2 mn vehicles in 2014, around 10,000 km. Results from an FEV representing approximately six per cent of endurance fleet testing programme indic- the total worldwide market volume for ate that driving distances exceeding 40 passenger . The majority of these km/day are rare. On most days, the max- DR.-ING. INGO STEINBERG is Group Vice President of Business vehicles are equipped with conventional imum distance driven was on the order Unit Transmission Systems at FEV powertrains consisting of a gasoline of 20 km. The average distance was 17.7 GmbH in Aachen (Germany). engine and a five-speed manual transmis- km/day and the average vehicle speed sion. However, the Japanese market rep- was 36 km/h. resents an exception, where, in this So-called “stop phases” occupy a large vehicle class, the continuously variable fraction of the time within the typical transmission (CVT) is also strongly rep- driving profile for A-class vehicles. As resented. The gasoline engine is also oper- determined by a test vehicle that was ated with alternative fuels in many mar- operated over the entire test period with a DR.-ING. MARC DANIEL kets; for example, in South America. In large number of start-off events, the is Team Leader Thermodynamic Gasoline Engines at FEV GmbH in India, in particular, an automated five- vehicle was stopped for over 15 % of the Munich (Germany). speed is preferen- time. Examinations carried-out in Asian tially offered in new applications. conurbations show stop phases of up to An annual growth of around two per 25 % of the total driving duration. In the cent is forecasted for this A-class vehicle discussion below, the corresponding segment until 2022. 1 shows the global vehicle requirements are discussed. volume distribution for the A-segment across individual markets. Western DIPL.-ING. PATRICK GLUSK Europe, Japan and India represent the VEHICLE REQUIREMENTS is Senior Consultant at strongest markets, accounting for over FEV Consulting GmbH in Aachen (Germany) 60 % of the total number of vehicles Upcoming vehicles in the A-segment are sold. Sales growth in India will probably expected to change noticeably. New compensate for the decreasing sales requirements will be gradually introduced volumes in the Japanese market. depending on the market, starting with Slightly decreasing numbers are also the upper vehicle classes: forecast for China. However, increased :: Additional comfort and safety func- sales in the other markets make the tions, such as Brake Assist or Lane overall, global growth possible. Assist; :: Additional networking, such as - to-X communication (“Connected Vehicles”); :: More extensive requirements for active and passive safety; :: Provision of a “Battery ” variant; :: Coasting operation and, in the final development stage, autonomous driv- ing; and :: Extension of the warranty period to at least five years beginning with the registration of the vehicle. The A-segment is typified by high cost pressure and strong competition. The cus- tomer expects these additional vehicle features, but is not willing to pay a higher price for them. Existing vehicle compon- ents must be manufactured more econom- ically or must provide a significant advantage to the customer in order to sur- vive the competitive market for the com- 1 A-segment global volume and sales growth until 2022 (© FEV, LMC, 2015) plete vehicle. autotechreview October 2016 Volume 5 | Issue 10 27 Cover Story FUTURE POWERTRAIN STRATEGIES

Many vehicle functions require an class, this means a transition away from WLTP. In particular, the low part-load automatic transmission, when using a today’s strategy of building with several range, which has a dominant influence conventional powertrain. Beyond this, drive shafts as short as possible, but in the NEDC on the cycle consumption, an automatic transmission is well suited wider instead. The A-segment demands is becoming less important. to the urban driving profile, because it slender powertrains. The proposal for a Therefore, a substantial reduction of increases comfort with regard to the small automatic transmission considers CO2 must be achieved in the future in the large number of gear shifts and start- this central spatial requirement. central load range of the map. In CO2 stop events. sensitive markets, naturally aspirated The spatial requirement of the passen- engines will increasingly be replaced by ger compartment also represents a tech- INTERNAL COMBUSTION ENGINE small-volume turbocharged engines. Tur- nical challenge. 2 shows the development (ICE) DEVELOPMENT TRENDS bocharging is the main technology used of the track of the driving of to achieve, on one hand, a reduction in three vehicles in this small vehicle class. Due to the high cost pressure in the A-seg- fuel consumption through a reduction in Within two successive vehicle genera- ment, naturally aspirated engines with displacement (downsizing) and the adap- tions, the wheel track of the driving axle port fuel injection are predominantly ted longer gearbox ratio (downspeeding) was widened by at least 40 mm. The used. The increasing CO2 requirements and, on the other hand, to meet customer cause of this is the larger vehicle width at worldwide are forcing manufacturers to demands with regard to driving perform- shoulder height as a means of offering the significantly improve fuel consumption. ance. Turbocharging goes hand in hand customer greater comfort. It is to be With the limitation of the number of par- with a conversion from port fuel injection expected that this width will increase by ticulate emission, an additional emission to direct injection. Full potential of a tur- at least a further 40 mm in the coming component has been added that requires bocharged engine concept can only be vehicle generations. special attention during an engine devel- realised with direct injection. The situation is different when opment process. At the same time, cus- A further trend is becoming apparent it comes to the vehicle length. The tomer requirements for driving perform- in the gas exchange strategy. In the past, spatial requirements for the powertrain ance are increasing, requiring further the event lengths for the intake and are becoming more complex. The increases in the power and torque output exhaust valve stroke were, above all, customer expects more usable space. engines in the A-segment. filling-optimised. In contrast, the Miller For reasons of comfort, the passenger In Europe, the test procedure is chan- cycle for a turbocharged engine in con- compartment requires a greater length. ging from NEDC to WLTP. A similar junction with a short intake event length Battery electric vehicles require space, development is expected in China, from according to the early intake valve closing especially for placement of the battery NEDC to FTP-75. The common goal of (EIVC) strategy represents a between both . these changes is to adapt the certification non-filling-optimised gas exchange The powertrain will have to be to the real driving cycles and to further strategy. The advantage of this, apart from restricted in the direction of vehicle tighten the boundary conditions. This improving the pumping losses, is that the travel, but will be given additional development has a considerable influ- effective compression ratio is lowered. design options transverse to the direc- ence on engine manufacturers. Techno- As a result, the geometrical compres- tion of travel due to the use of three-cyl- logy potentials must be re-evaluated. 3 sion ratio can be increased by up to two inder engines and a larger vehicle wheel clearly illustrates the change of the load units. This improves the thermodynamic track. For transmissions in this vehicle spectrum in the NEDC compared to the efficiency of the ICE. In particular, there is a significant improvement in fuel con- sumption in the central map area. At present, variable cam phasing units are mainly used to individually optimise the gas exchange with respect to the operat- ing point. This variability will be exten- ded in future so that it will also be pos- sible to optimise the event length of the intake valve lift curve to the operating point. In the cost-sensitive A-segment, sliding cam systems in particular will be used to implement the switchover of the valve lift curve. Fully variable systems will also be used in isolated cases. Their market share is, however, limited by the higher system costs.

Above all, in order to fulfil the CO2 fleet consumptions after 2021, cooled 2 Increase of driving axle wheel track (© FEV)

28 www.autotechreview.com are and will remain significantly lower. 4

shows the CO2 requirements in India for the period from 2016 to 2021 and for the period after 2021. The average vehicle weight in Europe is 1,377.4 kg. The agreed and binding

CO2 target for that weight is 95 g/km in NEDC for 2021. In India, for the same

vehicle weight, the CO2 target is 124.6 g/km, this means 31 % lower than the

European value. The CO2 target level in India for 2021 is therefore comparable to values reached in Europe today. Due to this environment, the naturally aspir- 3 Fuel share comparison in NEDC versus WLTP (© FEV) ated engine with port fuel injection will continue to play an important role in the future.

AUTOMATIC TRANSMISSION RECOMMENDED

Each market has specific customer requirements that mainly result from traffic conditions and the respective his- tory (example given, widespread use of manual transmissions or the early intro- duction of automatic transmissions with ). For the comparatively simple use of demand-based actuators, however, the automated manual transmissions (AMT) and modern dual transmissions

4 Fuel consumption targets in India in comparison to Europe (© FEV, Bureau of energy efficiency, (DCT) have a decisive advantage with

REGD. NO. D. L.-33004/99) regard to efficiency and, thus, low CO2 emissions at the vehicle level. Demand- based actuators will gain importance with exhaust gas recirculation (cooled EGR) the use of hybridisation. 48 V hybrid sys- the introduction of functions such as represents a technology for realising fur- tems, in conjunction with a belt-driven coasting operation, including the integra- ther potential in the gasoline engine. With starter-generator, can realise significant tion of GPS data. the introduction of cooled EGR, the tend- fuel consumption benefits in the A-seg- From the point of view of manufactur- ency to knock is reduced by the additional ment. Depending on the battery size, it is ing cost, the AMT has a clear advantage inert gas in the cylinder and the thermo- no longer necessary to improve the ICE over the DCT, but it also has a concept-re- dynamic efficiency is increased. If EGR is with all mentioned technologies. The mix lated disadvantage with respect to the also used up to full load, the compression between ICE, hybrid and battery electric harsh shifting that occurs as a result of ratio can additionally be increased and, in powertrain is decisive for achieving the the interruption in the vehicle tractive this way, fuel consumption benefits fleet consumptions targets. However, only force. The task is to combine the cost tapped in the entire map. The challenge the future will tell which strategy, further advantage of the AMT with the advantage here is the dynamic control of the EGR development of the ICE or hybridisation, of the softer shifting of the DCT. The DCT rate under all boundary conditions. The and in addition, purely battery electric can only compensate this cost disadvant- expenditure for cooling and application powertrains, will ultimately dominate the age through the increased reuse of com- significantly increases. In addition, cost market. This will be influenced by cus- ponents already present in high numbers disadvantages due to the additional com- tomer acceptance regarding electric range in the series. This approach reduces not ponents of the EGR system are unavoid- and cost, but also by national subsidies of only material cost and investment, but able. This will limit widespread use in the electric mobility. also development costs. The 5DCT130 cost-sensitive A-segment. The Indian market is becoming dual clutch transmission currently under In general terms, further improvement increasingly important for the A-segment. development at FEV precisely follows this of the combustion engine competes with There, compared to Europe, CO2 targets approach, and especially where expensive autotechreview October 2016 Volume 5 | Issue 10 29 Cover Story FUTURE POWERTRAIN STRATEGIES

taken over is maximised. Apart from the gear actuator from LuK, series synchron- isers from Hoerbiger Antriebstechnik, a standard dual clutch from BorgWarner, a standard differential from GKN Driveline and exclusive catalogue roller bearings are used. In order to further increase the effi- ciency, all shafts including the differential, are executed with a fixed and floating bearing arrangement. The first picture of the article shows the 5DCT130. The filter system containing combined suction/ pressure filters is sup- plied by IBS Filtran. For economic reas- ons, a separate control unit is used instead of an integrated traction control unit (TCU). The solution is provided by United Automotive Electronic Systems (UAES)/ Bosch. The plug connectors are 5 Dual clutch and mechanical sub-system (© FEV) all series components as well.

components are concerned, falls back on The disadvantage of multiple energy SUMMARY “off-the-shelf” components. transformations in the case of motor- driven pump usage cannot be overcom- FEV will continue the development of pensated in this particular vehicle 5DCT130, focusing on the usage of avail- 5DCT130 TRANSMISSION segment. able components from mass production. The capacity of the pump in support- The main target is to offer an affordable The 5DCT130 transmission meets the ing the start-stop function must be alternative solution in comparison to the A-segment requirements of a slender observed. In parallel with restarting the automated manual transmissions. At the transmission with only one output shaft, internal combustion engine, the pump same time, the conceptual disadvantage along with an advantage for the efficiency must fill the cylinder of the setting piston of AMTs (interruption of traction) is maps and low cost. The transmission fea- of the starting clutch in order to enable avoided. The company is also initiating tures five forward speeds and one reverse fast start-up of the vehicle. Dual clutch the development of a cost efficient trans- speed. Detailed examinations show that a transmissions that currently exist in the mission variant for hybrid powertrains, double bearing on the output shaft is suf- market show that this is reproducibly pos- again based on 5DCT130. ficient. A third support bearing is not sible, if the launch gear is pre-selected. required despite the long design. The The volumetric oil flow produced during rated torque in each speed is 130 Nm. the restart phase of the internal combus- The shortest first speed is 16.1 and the tion engine exclusively benefits the con- longest fifth speed is 2.8. The maximum trol and the cooling of the starting clutch. ratio spread is 5.8. The centre distance The gear actuator of a dual clutch between crank shaft axis and differential transmission is driven sporadically. A axis can be varied between 170 mm and power-on-demand based actuator makes 183 mm. The wet clutch comes in a nes- sense for this function and an elec- ted arrangement with the advantage of a tromechanical system supplied by LuK small mass moment of inertia. The has been used. This system has a further BorgWarner dual clutch requires hydraulic advantage for the inexpensive introduc- actuation. The required pump is driven by tion of the park-by-wire function. Three Thanks the internal combustion engine for the fol- shift forks actuate the sliding sleeves of lowing reasons: the six speeds. The parking lock is actu- The authors wish to express their thanks to :: A-segment vehicles operated mostly at ated via a fourth shift fork. Park-by-wire BorgWarner, GKN, Hoerbiger Antriebstechnik, IBS high torques in comparison to the enables higher flexibility in the passenger Filtran, LuK and UAES/ Bosch for their co-operation maximum torque of the combustion compartment design. The actuator is in the development of the 5DCT130 transmission. engine; already in use in mass production. :: Permanent energy supply required due 5 shows the individual assemblies of to “normally open” clutch; and the 5DCT130 transmission. The number Read this article on :: Cost reduction. of mass-produced sub-systems that are www.autotechreview.com

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