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

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

As a supplier to the automotive industry, 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 the 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 storm and stress period of the auto industry around 100 years ago, the competition between designers from the various manufacturers and suppliers is currently creating a colorful bouquet of previously unseen technical solutions – more ideas than can remain at the end of this heyday. However, the one from Schaeffler could be one of them. For the modern electric car, it follows a step that has already been taken for cars with combustion engines: the integration of various components into a larger unit. However, the objective was different.

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

This is how the draftsman represents the installation position in the car. Exactly how the drives have already been placed in the widespread front/transverse cars.
(Image: Schaeffler)

With electric cars, the drive can of course be arranged much more easily either at the front and/or at the rear. It does not require such a large cooler, nor is it as bulky as the cylinder bank, which is usually arranged vertically. In addition, it does not require nearly as good noise insulation as a thermodynamic drive. Almost every major electric car manufacturer already has it in one way or another.

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

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

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

What can actually be called an “axle” is a special type of electric drive. The design as a rigid axle eliminates the need for drive shaft joints, as the entire unit is flexibly suspended. Instead of the differential, the e-machines are housed in the middle, with drive shafts in the hubs. Gears and power electronics are also integrated into the axle here. In commercial vehicles, it can be used directly instead of a driven rigid axle, as is already the case with Bergischeachsen BPW. It is installed in 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 is actually only the case with loaded commercial vehicles. In light passenger cars, such a design would neither meet the requirements for driving comfort nor for driving dynamics and ultimately safety. 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 drive for another car and then suddenly a transporter gets a rear independent 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 conventionally motorized Transit and the comparatively almost exquisite comfort, this is likely to remain rare in the future.

Schaeffler reports that they are working on the electrification of medium-duty pick-up trucks, especially for the North American market, and have already secured “the first orders for electric rigid axles from automobile manufacturers”. The supplier is currently expanding its capacities at the Wooster site in North America.


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