Scalable electric powertrain targets utility vehicles

Scalable electric powertrain targets utility vehicles

Technology News |
By eeNews Europe

Within the ESKAM project, eleven research partners led by Fraunhofer Institute for Tool Machines and Forming Technology (IWU) developed an axle module for commercial vehicles. Motor, power electronics and transmission are integrated in a single compact casing. The casing can be incorporated into the target vehicle by means of a frame design, which also has been developed in this context.

The module offers numerous advantages. Besides high power density it offers very high torque which translates into good acceleration. While most motors for electric vehicles offer a rotation speed of 10.000, or 15.000 rpm at the utmost, the ESKAM motor can be driven up to 20.000 rpm. "When we started development some three years ago, we were the only ones that dared to implement such high rotational speeds", remembers IWU project manager Hans Bräunlich.

The most striking advantage of the ESKAM design however is a different one: The consortium did not only develop the axle module but also the technology necessary for series production. "Due to our innovative approach, the modules can be manufactured flexibly", Bräunlich says. "Low quantities are feasible at economic conditions just as good as large quantities".

The project manager claims production cost savings up to 20% compared to the conventional approach. For example, the integrated transmission consists of shafts and gearwheels. Usually such shafts are made either of tubes (expensive) or through deep hole drilling (complex, time-consuming, ineffective with regard to material). The IWU researchers instead established novel processes that make efficient use of time and material. They developed a new processing technology, a combination of drilling and pressing which reduces material and labour cost by about 30%; on top of that, it yields lightweight products.

The ESKAM module with integrated electric motor, power electronics and transmission is very versatile. As the image shows, it can be used as front axle in light to medium-sized vehicles, as rear axle in trucks and also as rear axle in sports cars.

In addition, the module is scalable – it can be manufactured in different sizes to fit small transporters and large buses or trucks equally. This feature is not possible with wheel hub drives.

At this opportunity the Fraunhofer researchers discussed assets and drawbacks of wheel hub drives and their own approach. While wheel hub drives enable a higher steering angle and offer a more direct response to driver’s actions, wheel hub drives are not suited for commercial vehicles, since they cannot exceed a rotation speed of much more than 2000 rpm. In addition, wheel hub drives are more expensive since they require a separated power electronics unit for each wheel while the ESKAM approach does it with one central power electronics unit per axle.

The next step will be integrating the axle into a demonstrator. By end of the year they plan to install the axle module into a real-world car and test it.

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