Tuesday 18 October 2016

Schaeffler launches all-electric concept vehicle

Schaeffler regards its electric wheel-hub drive, as in its STEP² concept vehicle, as an enabler for future space-efficient vehicle concepts.

“Our innovative solutions from the E-Clutch to the electric axle, from our STEP² concept vehicle to the electric wheel-hub drive clearly show that Schaeffler is able to make decisive contributions towards the development of mobility for tomorrow – from basic components all the way up to the complete system,” claims Prof. Dr.-Ing. Peter Gutzmer, deputy chief executive officer and chief technology officer.
The STEP² Concept Vehicle with a Two-speed Electric Drive represents an entirely electric vehicle with a two-speed powershift transmission.
“By shifting between two gears – a short gear ratio for a high traction force and a long gear ratio for good overall efficiency levels even at higher driving speeds – it is possible to improve dynamics and electric range at the same time,” explains Uwe Wagner, vice president R&D Automotive.
Compared to a similar vehicle with only one speed, Schaeffler claims the STEP² attains a “clear consumption advantage” of around six per cent.
STEP² is based on a large series compact class vehicle. The concept comprises an IDAM electric motor while the transmission consists of a planetary gear set, a wet multi-disk clutch, a band brake, and a lightweight differential.
Power shifting is used to change gears, with the “coming shift element” (e.g. the clutch) taking over the initial torque from the “going shift element” (e.g. the brake). It is only afterwards that the speed is adjusted. The upshot of this is that the drive torque supplied is constant even during the shifting process, resulting in a gear change that is comfortable and without an interruption to the traction force.
With its E-Wheel Drive electric wheel-hub drive, Schaeffler claims it is setting its sights on completely new vehicle concepts of the future and offering a promising approach for the mobility of tomorrow.
“For us, the E-Wheel Drive is an enabler for new space-efficient concepts for future vehicles and thus a key to fulfilling the needs of urban mobility,” explains Gutzmer. This also goes along with the increasingly important topic of highly-automated driving.Integrating the electric motor, power electronics, and the control unit directly into the wheel provides new degrees of functional freedom and significant installation space advantages over conventional drive concepts. 
The design is based on a permanently-excited synchronous motor without a transmission unit, making high power density possible in an extremely compact package. Naturally, the recuperation of deceleration energy is also part of the performance range of this electrical drive system. In addition to efficiency, the drive system also offers advantages with respect to driving dynamics.
The torque that is constantly available to the complete system is 500 Nm, with a peak torque of 810 Nm for each drive system. An integrated drum brake corresponds to current production standards – just like the link to conventional axle architectures and wheel rims, which also makes it possible to replace the tires without difficulty, the same as for any other production vehicle. 

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