NSK supplies high-performance bearings for electric vehicle

NSK is supplying the rotor shaft bearings for the front and rear axle drives of an electric SUV (sports utility vehicle) being built by a European car manufacturer. Although this is the first project of its type for NSK in Europe, the company is able to draw on its long experience of electric powertrain technology in Japanese vehicles.

Developing the optimum bearings for the drive motor or motors is recognised as a major challenge in the electric vehicle segment. Very tough requirements are placed on the bearings because electric motors run at significantly higher speeds than internal combustion engines. In addition, the bearing operating locations often find themselves in a dry environment, so lifetime lubricated bearings have to be used.
 

Several European manufacturers are launching electric SUVs with up to 300 kW power and ranges extending to 400 km. To obtain the required combination of power and compact dimensions, special design solutions are employed, such as electric motors which have the axle running through the motor. This concept can reduce the overall drive unit size, but requires relatively large rotor shaft bearings, which consequently reach high peripheral speeds at 13,000 rpm. Speed reduction is then implemented using compact planetary gears.

This demanding application used ball bearings – a relatively simple bearing design – and with good reason. In contrast to angular contact ball bearings, ball bearings do not need specific pre-tensioning. The cage design of the bearings for the European electric SUV has also been adapted to the specific application conditions, while the contactless and yet extremely efficient seals help to reduce friction and thus contribute to the vehicle’s long range.

Success in the European electric SUV project was aided by NSK’s previous experiences in Japan. As early as 2005, the company began the volume production of high-speed bearings for the hybrid version of the Toyota Harrier/Lexus RX.