Highly-Integrated Wheel Hub Drives are a Key to New Vehicle Concepts
As part of the “auto, motor und sport” congress, Schaeffler will be presenting its E-Wheel Drive electric wheel hub drive. The innovative electric drive will be on display in a development vehicle created in cooperation with Ford and based on a Ford Fiesta. The compact vehicle is driven using two Schaeffler E-Wheel Drives that are installed in the rear wheel arches. All components required for drive, deceleration, and driving safety in the highly-integrated wheel hub drive – like the electric motor, power electronics, controller, brake, and cooling system – are installed inside the wheel rim.
They boast technical key data of 40 kW per drive, and a continuous output of 2 x 33 kW. When viewed as a traditional reading, this equates to 110 and 90 horsepower, respectively. The liquid-cooled wheel hub drive, which is in its second (Beta) stage of development, also delivers up to 700 Nm of torque. In comparison to the first-generation (Alpha) wheel hub drive, which was first exhibited in Schaeffler’s Opel Corsa-based Schaeffler Hybrid concept car in 2010, the E-Wheel Drive Beta thus features an output increase of one-third, as well as 75% more torque. The electrical voltage of the high-voltage drive is 360 – 420 V.
The highly-integrated wheel hub drive has a total weight of 53 kilograms, so the weight increase compared to a conventional wheel with a wheel bearing and brake is 45 kilograms. It has a 16-liter design envelope, which is housed inside a 16-inch wheel rim. The highly-integrated wheel hub drive outweighs its Alpha-generation predecessor, which still featured power electronics installed in the vehicle, by an additional six kilograms.
“Overall, we were able to reduce the vehicle weight once again”, explains Dr. Raphael Fischer, Director of the Wheel Hub Drives Product Group in Schaeffler’s eMobility Systems Division, “because, in addition to the liquid cooling, the power electronics and controller can now be integrated into the wheel, which means that the complex wiring in the vehicle can be omitted.”
“The B-segment vehicle serves as a pre-production model. However, wheel hub drives have to be integrated into new vehicle concepts in order to demonstrate their strengths to the full,” explains Prof. Peter Gutzmer, Member of the Executive Board and CTO at Schaeffler, in his assessment of the drive technology innovation during the “auto, motor und sport” congress: “Thanks to this highly-integrated wheel hub drive, we can now re-think the city car without restrictions. It will be a key factor in new vehicle concepts and automobile platforms in the future. For electric vehicles used in urban environments, which may become obligatory in many densely populated areas, the wheel hub drive makes previously unheard-of space savings possible. In these new vehicle concepts, all components that are relevant for propulsion, braking, and driving safety are housed inside the wheel. The vehicle platform therefore provides maximum space for passengers, luggage, and for the battery, electronics, and communication systems. And vehicle manufacturers can use this as a basis for a range of different body designs. Automobile manufacture originally started in just the same way.”
The premier of the Fiesta E-Wheel Drive development vehicle – designed in close cooperation with Ford Research & Advanced Engineering Europe – at the “auto, motor und sport” congress is a break from its otherwise tightly-packed testing schedule, which has recently included extensive test drives in the cold climate of Scandinavia. The winter testing is part of the comprehensive development, coordination, and testing program in which driving dynamics tests also play an essential part.
“Excellent driving dynamics are among the main attributes of Ford vehicles, and our expertise and experience in this area has also been used during this project. The test drives have shown clearly that the driving behavior of this test vehicle in terms of comfort and safety has remained at virtually the same level, despite the higher wheel-sprung masses compared to the conventional basic vehicle”, explains Roger Graaf, project manager at Ford Research & Advanced Engineering Europe. What is more, the Fiesta E-Wheel Drive displays extraordinary dynamics. In addition to regulating the stability of the driving dynamics, the two wheel hub drives also allow so-called torque vectoring, i.e. the selective distribution of the torque to the wheels.
“In this way, highly-integrated wheel hub drives also provide significant advantages in terms of maneuverability, driving dynamics, and active safety in addition to the perfect utilization of space. This will be able to play a significant role in the future, especially in combination with independent driving”, explains Prof. Gutzmer. “The electric wheel hub drive therefore has the potential to become one of the drives of tomorrow and a valuable addition to the range of drives that, from a global point of view, will continue to be governed by increasingly electrified drive trains based on internal combustion engines.”
Schaeffler’s E-Wheel Drive is now also part of a research project that is listed by the Federal Ministry of Economics and Technology – and is already being displayed in impressive fashion in the Fiesta E-Wheel Drive.
