Wheel hub drives are considered the Egg of Columbus: They save an enormous amount of space in the vehicle because dedicated engine compartments are no longer required. As a result, they enable innovative vehicle designs. They also make it possible to implement new steering concepts – the vehicles can drive sideways or turn on the spot. The disadvantage is that it is not easy to get the required high amounts of energy into the wheel. At the same time, heat dissipation presents designers with major challenges.
Now automotive supplier Schaeffler has succeeded in reconciling these conflicting requirements and turning them into a series product. “Schaeffler is bringing a new approach to the drive of small, light, electric commercial vehicles in our inner cities,” says Matthias Zink, Schaeffler’s Executive Board member responsible for Automotive Technologies. What is special about the innovative wheel hub drive is that all the components required for the drive and brake are installed directly in the wheel – not in the center of the vehicle or on the drive axles. This saves space and makes the vehicles significantly more agile and easier to maneuver in city traffic. The low-noise electric drive system ensures that they can do their work quietly in pedestrian zones, on roads and in residential areas, and even during extended operating hours, as they cause much less disturbance to residents. Hummer Wheel Bearing Units
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One of the first companies to launch a multifunction vehicle with a wheel hub drive from Schaeffler this year is the Swiss manufacturer, Jungo. Schaeffler and Jungo have jointly adapted the drive to the special everyday requirements of commercial use. “Thanks to the electric individual wheel drive, our machines gain significantly in performance. This includes higher efficiency, less weight, more safety, better driving characteristics and a safe electric brake,” says Nicolas Jungo, founder and CEO of Jungo.
Schäffler sees great demand for the use of wheel hub drives in mobile work machines for inner cities. The company plans to tap into a new and growing market with this drive technology. In the future, the automotive supplier envisions that more work vehicles for cities and municipalities, in factory and logistics yards, at ports, in large parking lots and airports could be equipped with wheel hub drives. Since such vehicles usually have a fixed route schedule, they are particularly suitable for e-drives with fixed ranges and predictable charging times. Operators also benefit from the fact that the wheel bearings and gearbox of the drive unit are designed for a particularly long service life.
The electric motor (stator and rotor), together with the gearbox and mechanical friction brake, is housed around the wheel bearing inside the rim to save space. This creates free space in the vehicle – for the battery, for example, or as additional storage space for transport. Vehicle manufacturers also have more scope for developing a wide range of mobility concepts, including rolling chassis solutions.
Thanks to its compact design, Schaeffler’s wheel hub drive including gearbox can fit in a 14-inch rim. The inverter, on the other hand, can be flexibly placed in the vehicle and controls one or two wheel hub motors. The drive power of the motor can be scaled – depending on the application. The company’s range extends from 7 to 26 kilowatts (nominal) and reaches a peak of 60 kilowatts. The torque generated is transmitted directly to the wheel via the gearbox. This direct power transmission means particularly high drive efficiency. Since torque and direction of rotation can be controlled individually for each wheel, the vehicles are four-wheel drive. Hill climbs are therefore no problem, even in wintry road conditions. Schaeffler is developing wheel hub motors for voltages of 48 volts and 400 volts. In the future, the company says, higher voltages are also possible.
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