On the road to optimum total system solutions
While there are significant differences in the mobility needs around the world, vehicle transmissions have a decisive role to play in terms of the energy efficiency and environmental sustainability of mobility in all regions of the world. The development of energy efficient transmission concepts will therefore become increasingly important in the future. Continuous increases in efficiency and high levels of electrification will define the technological path of the drive architecture. Transmissions will therefore have an important part to play in the future of the engine and the overall efficiency of the drivetrain.
Interdisciplinary developmental work is the key to success
Finding the optimum combination of the individual components is a critical factor in reducing consumption. In this respect, Schaeffler offers the automotive industry benefits that are not available from any other supplier. A key to Schaeffler’s success is its interdisciplinary developmental work where expertise from different specialist areas is brought together. The internal combustion engine, the transmission and the electrical components are regarded as a single unit in order to produce joint solutions.
“One example is the close coordination of the development work involved in cylinder deactivation strategies in the internal combustion engine, the effects on the timing drive and the required control of the modified torsional vibration excitations using optimized damper systems in the transmission,” states Klaus Cierocki, Vice President, Engine Systems at Schaeffler.
The comprehensive product portfolio of solutions in and around the engine, transmission and chassis leads to synergistic development of customer-oriented products.
Optimizing the internal combustion engine
Measures to optimize the combustion engine are a particular point of focus. Apart from reducing friction – through a highly efficient coating process in the valve train or by replacing plain bearings with rolling bearings or through efficient tensioning and decoupling systems in the auxiliary drive assembly – Schaeffler is also working on the introduction of turbochargers supported by rolling bearings, increasing thermodynamic efficiency and a diverse range of technical solutions. For example:
Thermal management: An important element is the Thermal Management Module (TMM) which accurately controls the temperature balance in the engine in an energy efficient way, and allows the ideal temperature window for the engine and the transmission to be reached rapidly. This unit can also provide parallel control of the temperature balance in hybrid components and batteries. The cold running phase can be shortened considerably by blocking off the engine’s cooling jacket while individual components can be run hotter than would otherwise be possible with thermostatic control. The module therefore also has a positive effect on the operating life of drivetrain components. A further benefit is being able to reduce the engine temperature while under full load, thus reducing the tendency towards knocking and full load enrichment.
All of this makes this module, which can be adapted to suit customer requirements, a key element in the reduction of fuel consumption and CO2 emissions. This technology has been successfully introduced in the European and Asian markets and will be used in volume production in the North American market in 2017. The most recent generation of the TMM is a modular design and is more compact and has additional functions, such as intelligent smart actuator technology. Integrating control into the module takes some of the strain off the engine control system and leads to optimum coordination of all operating points. As part of the company’s “In the Region, for the Region” strategy, Schaeffler will also manufacture the TMM in continental America in the future.
Variable valve train: From phasing units and switchable finger followers through to the fully-variable valve train system UniAir, Schaeffler offers a comprehensive range of products for variability in the valve train. Tailor-made operating strategies, such as cylinder deactivation or special valve stroke curves, can be produced to suit customer requirements. The start of volume production of the UniAir technology in 2009 marked the beginning of a new era in valve control systems. At the same time, Schaeffler set a new technological standard for environmentally-friendly and dynamic engines. To date, over one million UniAir systems have been produced in North America and this will exceed to two million globally in 2016. The fully-variable electrohydraulic valve train system UniAir controls the engine valves and allows almost any valve stroke to be realized. It is possible to achieve considerable reductions in consumption and emissions through this technology, as well as a significant improvement in torque curves.
Partially and fully-variable valve train systems also allow individual cylinders to be deactivated while driving. So, for example, the fuel consumption of an eight-cylinder vehicle could be reduced by temporarily running on four cylinders. Hydraulically switchable valve train components are usually used to deactivate specific cylinders. UniAir provides an extended range of options for matching engine operation to specific situations or requirements, such as rolling cylinder deactivation where each cylinder can be switched off in turn. A key advantage is that the deactivated cylinder does not cool down, allowing the system to reactivate more quickly after a cold start.
Electromechanical camshaft phasing unit: Another approach is replacing hydraulic systems with electromechanical systems. Schaeffler’s electromechanical camshaft phasing unit adjusts the camshaft more quickly and accurately to the engine’s current operating conditions. Electromechanics make it possible to phase the camshaft at speeds of up to 600 crank angle degrees per second. Modern, highly efficient combustion processes can be achieved due to the considerably extended adjustment range compared to hydraulic systems resulting in a simultaneous reduction in consumption and emissions. Another advantage is that the timing is freely selectable when the engine is started. This makes it possible to adjust the effective compression of the engine as needed and, therefore, to have a soft onset of combustion when starting the engine. This is an important option for the increasing number of engines with stop-start systems and hybrid drives, where the internal combustion engine is repeatedly switched on and off during driving.
Modern transmission technologies from Schaeffler
Schaeffler’s comprehensive range of transmission technologies has a decisive role to play on the road to optimum total systems solutions. One thing is obvious – transmissions are key in reducing consumption and emissions. For example, modern transmissions allow an engine’s operation to be maintained at an optimum point in terms of consumption by means of an increasing number of gears. Innovative damping concepts, such as the torque converter with centrifugal pendulum-type absorbers, reduce vibrations and lower speeds to a point of optimum consumption.
Matthias Zink, President of the Transmissions Systems Business Division at Schaeffler, sees new damping technologies providing a significant contribution and effective support for new engine trends, such as downspeeding, downsizing and cylinder deactivation. Mr. Zink is confident transmissions will have a substantial part to play in the overall efficiency of the drivetrain and also emphasizes the benefit of interdisciplinary development work.
According to Mr. Zink, “We develop solutions together with our colleagues from the engine systems and e-mobility divisions, and regard the internal combustion engine, the electrical components and the transmission as one unit. This collaborative use of expertise from the various specialist divisions is one of Schaeffler’s great strengths. This allows us to provide automotive developers with optimum total system solutions.”
A number of new transmissions have been developed and brought onto the market in recent years. Schaeffler is driving the development of all designs and concepts through its innovative components and systems. This provides increased driving comfort, lower consumption and more space for use with hybrid modules. This new generation of integrated hybrid transmissions is providing the transmissions specialists at Schaeffler with an interesting set of challenges.
“The clutch will have a vital role in the hybridization of an extremely diverse range of transmissions in future years. Integrating clutch and actuator technology into the rotor in the electric motor, controllability, minimum losses and good heat dissipation from the rotor are just a few of the relevant functional requirements,” says Mr. Zink.
Schaeffler has supplied the essential components for electric drive systems in P2 hybrids since 2010. The whole system, which is integrated into the transmission housing between the internal combustion engine and the transmission, consists of a dual mass flywheel, an automatic disconnect clutch with an actuator integrated into the rotor and an electric motor. The hybrid module from Schaeffler is a modular solution with low adaptation costs which can be configured to customers’ specific requirements. The module can be easily matched to all current types of transmission, irrespective of whether it is a planetary automatic transmission, double clutch transmission (wet or dry), continuously variable transmission or automated manual transmission. Furthermore, it offers complete hybrid functionality for electric driving, boosting, sailing, recuperation and quick engine start. The module is suitable for mild, full and plug-in hybrids, as well as for longitudinal or transverse configurations.
