An Electrically Driven Chassis System Concept for Sub-Compact Vehicles with Integrated Close-to-Wheel Motors
Currently in the automotive sector both hybrid and completely electric drives are being discussed and developed. The comparatively compact design of electric motors permits considerably more flexible installation in the vehicle than is the case with conventional internal combustion engines. Thus, depending on the category of vehicle, in addition to classic placement in the conventional engine or differential installation space (conversion design), configurations with the motor positioned close to the wheel or integrated into the chassis are conceivable, permitting selective wheel drive, with elimination of the classic differential and driveshaft. On the one hand, close-to-wheel configurations involve increased system complexity, since they require more than an electric motor and a transmission, for instance. However, on the other hand they are particularly attractive with respect to space requirements, because they permit integration into the installation package that is required in any case for the chassis. The space thus saved in the middle of the vehicle can then be used for a comparatively large energy storage system or for additional electronic/electrical components. At the IAA 2011 in Frankfurt, in an early concept study, ZF presented a driven chassis system for the minicar and sub-compact segment, where the electric motors and the transmission are integrated close to the wheel in the chassis. In contrast to familiar close-to-wheel drives, in the concept presented, the unsprung mass is only slightly increased. The total system weight continues to be attractive, since the comparatively heavy side shafts and the differential are eliminated. The chassis system can be integrated into the floor assembly of a global sub-compact vehicle platform with no significant changes in the vehicle body, and has the additional advantage that both standard-size wheel rims and conventional brakes can be used.