The struggle for more efficiency in locomotion is certainly the greatest task of the automotive industry - from the customer's point of view, design, connectivity and image play an equally important role, of course, but it is precisely the political pressure, but also the public call for changes, that presents the industry not an easy problem to solve.
Because the possibilities are numerous, but the risk is also great: new developments are expensive and sometimes they are stray, which afterwards turn out to be not necessarily effective. This is where the suppliers' hour comes. As smaller and therefore more agile companies, they are the ones who specialize in intelligent solutions that can help familiar components to make significant leaps in efficiency. This is a great opportunity, especially in the medium term, as long as electrical traction, fuel cells and other future technologies are still struggling with technical, but above all infrastructure and acceptance problems.
We have now experienced one of these developments: Schaeffler's e-clutch concept.
The developers from Herzogenaurach see great potential for fuel savings in the automation of the clutch in conventional manual transmissions. This approach is particularly interesting in view of the fact that a good 50% of all vehicles produced annually are still delivered with manual transmissions - after all, that is 40 million cars. So far, fuel-saving functions such as sailing or hybridization with intelligent power flow distribution between the electric machine, transmission and internal combustion engine have only been inadequately or not at all integrated into manual transmissions.
In particular, the sailing function is considered very important at Schaeffler; in the short term, it can save three percent fuel in the new WLTP driving cycle; in the inner-city stop-and-go, the developers even expect realistic savings of over eight percent. The sailing function is already possible in the smallest configuration, the three offered e-clutch variants. They call it MT plus and behind it is a relatively simple mechanism: in addition to the well-known master cylinder, which transfers the hydraulic pressure built up by the clutch pedal to the slave cylinder on the clutch, Schaeffler installs a second, parallel master cylinder that can be supplied with pressure by an electric motor.
This system enables the vehicle to disengage automatically. The driver does not need to press the pedal or take the gear out. It is enough to take your foot off the accelerator pedal and the MT plus system already disengages and the engine either continues to idle or is switched off completely. When the engine is replayed, the engine switches on again immediately and the clutch is engaged again with a positive fit.
The second, somewhat more complex variant completely dispenses with a hydraulic connection from pedal to clutch: clutch-by-wire. A so-called force actuator sits on the clutch pedal, which in the first step only measures how hard the driver presses the pedal and passes this information on to a control unit. This then feeds an electric motor in a master cylinder mounted near the clutch, which builds up the hydraulic pressure required for the clutch. The main advantage for the increased component expenditure is the higher dynamics of the system. Unlike the MT plus, in which the automatic disengagement takes place only when sailing, the clutch-by-wire system couples in any situation without a direct connection to the driver. As a result, the components are significantly larger and stronger, which enables them to act more quickly, even in sudden braking and rapid acceleration, than the driver would be able to do with a conventional clutch system. In addition, the force actuator on the clutch pedal enables the pedal counterforce to be varied. This can be significantly reduced in traffic jams, for example, or artificially increased in a sport mode.
In both systems, however, the driver's request has priority: whenever he puts his foot on the clutch pedal, the mechanism is activated. Only in the last and technically most complex variant does this option become obsolete, because the system called EKM completely dispenses with the third pedal. The gearbox is still a conventional manual gearbox, but the information for changing gear comes from the gear lever alone. As soon as the driver operates the lever, the clutch is disengaged and the clutch is engaged again when another gear is engaged.
There are now many more types of play than just sailing and quicker clutch actuation. For example, hybridization through the integration of one or more electric motors. Since the driver no longer has a direct influence on the adhesion, the control units can optimally control the interaction between the electric and internal combustion engines. The EKM system also prevents the clutch from overheating due to excessive grinding.
The fact that these technologies are not all new shows that even Ferraro 1989 in the Mondial T installed a system corresponding to the EKM with electromechanical clutch actuation depending on the shift lever for an additional charge. Today, however, the signs are different: it's less about driving pleasure than about saving. Both in terms of fuel and total costs. Because not every customer is willing to pay the high surcharge for hybrid models. If clever coupling controls now enable the integration of an electric and combustion engine with a conventional - and therefore inexpensive - manual transmission, this should be very useful for the spread of hybrids even in the small vehicle classes.
Since not only Schaeffler is researching such solutions, but with Bosch, Valeo and Co also the other big players in the industry, we should soon be able to look forward to more comfort when shifting without having to completely do without manual work.