ESKAM finishing electric drive axle module for commercial vehicles, new production technologies; vehicle testing this year
|Electric drive axle module with two motors and integrated power electronics. Groschopp AG. Click to enlarge.|
The ESKAM (Electric Scalable Axle Module, Elektrische SKalierbare AchsantriebsModule) consortium in Germany, sponsored by the German Federal Ministry of Education and Research (BMBF), is completing the development of an optimized electric drive axle module for commercial vehicles, consisting of two motors, transmissions and power electronics. All components fit neatly and compactly into a shared housing, which is fitted in the vehicle using a special frame construction also developed by the project engineers.
The individual modules developed by the various partners are complete, as are new manufacturing techniques developed by the partners. The consortium is now putting the individual parts together to make a demonstrator. After that, they want to fit the axle module into a real vehicle for testing by the end of 2015.
|The modules—with dual motors and integrated power electronics—are scalable for various vehicle types. © Fraunhofer IWU. Click to enlarge.|
Eleven partners are in the ESKAM consortium: Ebm Erich Büchele Maschinenbau GmbH; Technical University of Dusseldorf, Electrical Engineering and Electrical Machines; Groschopp AG; Hirschvogel Automotive Group GmbH; University of Applied Sciences Aalen, General Engineering; Metal foundry Wilhelm Funke GmbH & Co. KG; REFU Elektronik GmbH; Salzgitter Hydroforming GmbH & Co. KG; University of Stuttgart, Institute for Power Electronics and Electrical Drives (ILEA); Wilhelm Vogel GmbH Antriebstechnik; and Fraunhofer Institute for Machine Tools and Forming Technology (IWU).
The axle module presents numerous advantages, such as a high power density and a very high torque. For drivers, this means very fast acceleration. While the speed of most electric motors is approximately 10,000 to 15,000 rpm, the ESKAM motor (from Groschopp) achieves speeds of 20,000 rpm, with maximum torque of 45 N·m (33 lb-ft) and power of 32 kW (43 hp).
When we started on the project three years ago, we were the only ones who could obtain such high speeds. In the meantime, others have been attempting similarly high speeds. But our head-start in accumulating development experience has given us a technological edge, which we intend to further extend.—Dr. Hans Bräunlich, project manager at IWU
As well as designing the axle module, the project researchers and developers simultaneously developed the required series production technologies. IWU had the lead role in this work as well as being the technological lead for the overall project. Series production brings economic advantages, with reductions in production costs of up to 20 percent, according to Bräunlich.
Spin extrusion. As an example, gearbox shafts are usually manufactured from expensive cylinders or by means of deep-hole drilling. In both cases, the excess material is unused. By contrast, researchers at IWU have chosen new, short process chains together with methods that allow greater material efficiency. One such method is spin extrusion, which was developed by IWU.
Although it also uses a block of material, in this process the blank is shorter than the finished shaft.
To help visualize the process, think of pottery. The material is extruded during the shaping process, and pressed outward in a longitudinal direction. This allows us to use virtually all the material, cutting material costs by approximately 30% and reducing the overall weight of components.—Hans Bräunlich
Until now, there have been only initial ad-hoc approaches for this method. Now the scientists have made the technology fit for series production. The toothed gear wheels are also made using a different process. Instead of milling them from the material, they are now manufactured using a special forming process called gear-rolling, which was also developed at IWU. This method does not produce any metal chips, and effectively no material is lost.
All-purpose module. The flexibility of the axle module is not limited to batch sizes either, but also extends to geometry. Because the module is scalable, it be applied in vehicles ranging from small vans and municipal vehicles to buses and trucks, said Bräunlich.