Low-torque, low-friction ball bearings for hybrid vehicles

In recent years, demand for hybrid vehicles has been rising rapidly thanks to the low fuel consumption and low emissions realised through a more efficient integration of the engine and electric motor. In order to improve fuel efficiency further there is a growing need to reduce torque losses in the bearings used in the transmissions (drivetrains) of hybrid cars. NSK has met this need with its new low-torque bearings that dramatically reduce frictional loss. Going forward, NSK expects growing sales to automobile manufacturers of hybrid vehicles inside and outside Japan. The new product will be featured first in the latest Toyota Prius.

Product features

To date, most observers considered it too difficult to achieve further reductions in the torque loss of ball bearings. Despite this, NSK has found a way to cut torque by 50-65 per cent compared to existing products by implementing the measures described below.

1 - Optimisation of internal design. The number of balls has been dramatically reduced, and ball diameters, race dimensions, and clearances have been optimised so that rolling friction losses can be minimised. Another key factor in this success was NSK's development of new manufacturing processes that overcame conventional hurdles to significantly decrease the number of balls.

2 - Low-torque cages. Losses have been reduced by agitating lubrication oils during operation via the introduction of specially shaped resin cages.

NSK has achieved compactness, lightness and low torque via its four core technologies (tribology, materials, analysis and mechatronics), which it has cultivated for 90 years.