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Electric car: Schaeffler integrates drive into the “4in1 electric axle”

As an automotive industry supplier, Schaeffler is also repositioning itself for a future core business involving electromobility. The company’s most recent development is an integrated drive, which now also includes power electronics. To be more precise, the so-called “4in1-E-Axle” is equipped not only with the electric motor and its transmission, but also with the associated power electronics and thermal management. There are obviously good reasons for this.

Similar to the time of storm and stress in the automotive industry some 100 years ago, competition between designers from various manufacturers and suppliers is currently creating a colorful bouquet of unprecedented technical solutions – more ideas than can remain at the end of this period. gold. However, Schaeffler’s could be one of them. For the modern electric car follows a step already taken for cars with a combustion engine: the integration of various components into a larger unit. However, the goal was different.

But first, be careful with the terminology. What Schaeffler casually calls an “axle” is a power unit permanently mounted in the vehicle, each with a driveshaft for each wheel. In a classic car, this would correspond to the most common transmission configuration with a transversely installed motor-transmission unit. This is now known from the smallest car to the upper middle class, almost always installed in the front, apart from the Smart / Twingo with its exotic rear engine.


This is how the designer represents the installation position in the car, exactly as the drives have already been positioned in the popular front / transverse cars.
(Image: Schaeffler)

With electric cars, of course, driving can be organized much more easily both in the front and / or in the back. It does not need such a large chiller, nor is it as bulky as the cylinder bank, which is usually arranged vertically. It also doesn’t require good sound insulation like a thermodynamic drive. This or something similar is already the case with almost every major electric car manufacturer.

According to Schaeffler, the main benefit is the integration of heat management. The waste heat from the power electronics should now also be able to contribute to the heating of the battery. This means that charging processes are more efficient in cold weather because the battery uses less electricity to maintain its comfortable temperature.

Thanks to the more compact design without individual housing and additional hoses, the total surface area through which heat is dissipated is reduced. According to Schaeffler, the battery should be able to benefit from so much heat that efficiency can be increased by up to 14%. Thanks to carbon dioxide as a refrigerant, air conditioning efficiency should also increase, both with a direct effect on autonomy.

A side effect of the design is a drivetrain that can be integrated more quickly and cost-effectively for car designers because fewer parts need to be housed in the bodywork and, according to Schaeffler, fewer cables and hoses are required. This also applies to the use of the 4in1 electric axle in fuel cell vehicles.

What can actually be called an “axis” is a special type of electric drive. The rigid axle design eliminates the need for driveshaft couplings, as the entire unit is suspended flexibly. Instead of the differential, the electric cars are housed in the center, with drive shafts in the hubs. The gears and power electronics are also integrated into the axle here. In commercial vehicles it can be used directly instead of a rigid drive axle, as is already the case with the Bergischeachsen BPW. It is installed on an Isuzu N in joint production with Paul Nutzfahrzeugtechnik, in which it replaces the conventional rear axle.

Such solutions only make sense if the vehicle weight generally significantly exceeds the unsprung mass of the axle, which in reality is only the case with loaded commercial vehicles. In light passenger cars, such a design would satisfy neither driving comfort nor driving dynamics and, ultimately, safety requirements. For commercial vehicles, on the other hand, it is the most obvious design from the point of view of flexibility and costs.

However, there is also the case that a manufacturer has already developed a complete transmission for another car and then suddenly a van gets independent rear wheel suspension instead of a rigid axle. Ford is currently doing this with the Transit, which weighs up to 4.25 tons. Despite the high driving dynamics compared to the conventional powered Transit and the relatively almost exquisite comfort, this is likely to remain rare in the future.

Schaeffler reports that he is working on electrification of medium-duty pickup trucks, particularly for the North American market, and that he has already secured “the first orders of electric rigid axles from automakers.” The supplier is currently expanding its capabilities at the Wooster headquarters in North America.


(fpi)

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