Working with 11 partners on the ESKAM (Electric, Scalable Axle Module) project (sponsored by the German government) the team says its new axles – which include the motor, gearbox and power electronics – are powerful, lightweight, compact and cost-effective.
According to project manager Dr Hans Bräunlich, the new module delivers high power density and very high torque, with motor speeds at 20,000 rpm. It fits into a frame also developed by the project scientists.
However, he also points to the series production technologies, which, he says, lead to "great flexibility" when manufacturing the modules, including for small batches – leading to a claimed 20% reduction in production costs.
Bräunlich gives the example of a gearbox, which consists of shafts and toothed wheels. Usually, these are manufactured from expensive cylinders or by deep-hole drilling. But the Frauhofer researchers have developed new, short process chains and methods that allow greater material efficiency.
One such is spin extrusion, which, although it also uses a block of material, starts with a shorter blank than the finished shaft, using an approach similar to that used by potters with clay.
"Because the module is scalable, we can use it in everything from small vans and municipal vehicles to buses and trucks," states Bräunlich.
He accepts that this won't work with wheel hub motors, but says that while these have advantages, such as wider steering angle and greater responsiveness.
However, those are not suitable for commercial vehicles, as they scarcely deliver more than 2,000 rpm. Also, since each wheel requires its own power electronics, costs are higher.
"Both our developed versions have their own clear raison d'être and should be chosen specifically for a planned vehicle type," says Bräunlich.
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