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Schaeffler has developed a transmission for plug-in hybrid vehicles that is optimized for the design envelope. The dedicated hybrid transmission combines the advantages of automatic manual transmissions with those of electrified powertrains. At the same time, driving dynamics and comfort are increased while emissions are reduced.
2018-04-16 | Sutton Coldfield
The newly-established E-Mobility business division will be presenting innovative solutions for future electric and hybrid drives at the 11th Schaeffler Symposium. These include particularly compact hybrid modules with an integrated triple clutch, as well as a new generation of electric axle drives and complete “dedicated hybrid transmissions”. The electric and electronic components for the different powertrains are based on a shared development platform, which the technology company will be presenting to the public for the first time. In doing so, Schaeffler aims to help electric mobility quickly establish itself on the market.
BADEN-BADEN, April 16, 2018. CO2 limit values on important automotive markets will be tightened even further over the next decade. The European Union, for example, is planning to reduce the 2021 fleet target of 95 grams of CO2 per kilometre by another 30 per cent by 2030. At the same time, several markets, such as China and California, have fixed regulations in place for vehicles with alternative drives. Given that not only legal requirements but also customer preferences vary from country to country, Schaeffler’s new E-Mobility business division focuses on a variety of different drive solutions. In order to be able to design cost-effective electric and hybrid vehicles in spite of this, the electric and electronic drive components are based on a shared development platform. This platform comprises both hardware components such as electric motors and power electronics, as well as essential software modules that are required for regulating the drive.
Schaeffler is already achieving great market success with double clutches and hybrid modules for hybrid vehicles today, in which the electric drive is positioned between the internal combustion engine and the transmission – a solution that engineers refer to as a “P2 arrangement”. In the current second-generation hybrid module, one success has already been achieved: it was possible to fit the disconnect clutch that decouples the hybrid module from the internal combustion engine during electric driving inside the electric motor. In the third generation, which will be presented for the first time at the Schaeffler Symposium, the complete double clutch is fitted inside the electric motor – more precisely, inside the hollow space of the rotor. In order to ensure the necessary force-locking, multi-disk clutches of the kind fitted as standard in high-performance sports cars are used. Combined with a highly-integrated actuator for activating the three clutches, an extremely compact hybrid module is thus developed that makes the powertrain only slightly longer than in variants that are based purely on an internal combustion engine.
With market shares for plug-in hybrid vehicles increasing, car makers are reviewing their transmission designs. Instead of positioning the electric motor in front of and behind the transmission, it is becoming conceivable to couple the electric drive and the transmission in such a way that they merge into one component and functional unit. Schaeffler will be presenting a revolutionary concept for one such “dedicated hybrid-shift transmission” for the first time at the Symposium. The “DH-ST 6+2” (dedicated hybrid-shift transmission) is based on an automated manual transmission and offers two electric and six mechanical gears. The electric motor that operates parallel to the internal combustion engine is integrated into the transmission structure in such a way that it has two ratios available. The advantage: the electric motor can be operated very efficiently even at high driving speeds. Two transmission stages are also exclusively available for the internal combustion engine. A type of multiplier transmission between the two sub-transmissions ensures that the internal combustion engine also uses the sub-transmission of the electrical path, which means it has four additional gears available. As one wheel plane is being used twice, only five wheel planes are required for the six gears. Simulations carried out by Schaeffler show that not only sporty driving performance is possible with the “DH-ST 6+2” and a system performance of 220 kilowatts – a very low WLTC fuel consumption of around 4.5l/100km can also be achieved.
Schaeffler presented a concept vehicle with two electric axle drives on the front and rear axle back in 2011, which additionally allowed the active distribution of torque between the wheels of an axle. Since then, Schaeffler has not only put key components for such drives into volume production, but has also developed a complete modular system for electric axles. This system comprises both axially parallel and coaxial drive variants including optional components for differential, switchable dual-speed transmissions, and active torque distribution. Using a configurator that the company will be presenting for the first time at the Symposium, electric axle drives for electric and hybrid vehicles can in future be defined according to space requirements, driving performance, and functions.
When comparing the 2011 axle drive with the current version, the progress that has been achieved in the field of electric drives becomes apparent. While the maximum performance of a 90-kg axle drive was 60kW at the beginning of the decade, the latest generation achieves 145kW with a weight reduction of 10kg. “Results like these can only be achieved because we develop the electrical, mechanical, and electronic components of our drives with a system-based approach”, explains Matthias Zink, CEO Automotive at Schaeffler. “We consider ourselves a development partner for all forms of electrification. Schaeffler offers a broad and well-stocked technology portfolio today that can be used to electrify the powertrain. For the P2 position alone, we offer hybrid modules in combination with torque converters, CVT transmissions, and double clutches, for example. In this field, the profound mechanical expertise of our technology company represents another strength from which our customers can benefit”, adds Mr. Zink. “This way, we provide the right products for our customers’ various requirements and for different mobility needs.”