NSK Corporation (NSK) has developed a low-friction hub bearing unit. The newly developed product contributes to the extension of the vehicle's cruising range by reducing friction by 40% compared to conventional bearings, and by using new technology to achieve both low friction and slurry resistance of the bearings (it is expected to increase the annual range of an electric vehicle by about 1,000 km for 365 days on a full charge*1). NSK aims to achieve JPY 20 billion in sales by 2026 in the global market, mainly electric vehicles.
1. Development Background
The hub bearing unit is installed at the rim of the tire and is exposed to harsh conditions such as mud and during operation, thus requiring high resistance to mud and water. Meanwhile, as the world strictly controls carbon emissions and sets decarbonization goals, various industries are seeking to reduce energy consumption and lower their carbon footprint. Bearings, as key components in mechanical equipment, have their friction torque directly affecting the energy efficiency of the equipment., low-friction bearings, with their potential to reduce energy loss and improve energy efficiency, have become one of the key technologies for achieving these goals, and the for them is increasing day by day.
2. Technology of the Developed Product
To meet this real-world need, NSK developed a new grease in 2020 and the "Low Friction Hub Unit for EVs," which reduces friction. This time, NSK has developed three new sealing technologies that achieve both low friction and resistance mud and water. Compared to conventional products, these new technologies maintain resistance to mud and water while further reducing friction losses. 1) Development of the Seal Shape NSK's tribology and analysis technologies, we have designed a seal shape that maintains resistance to mud and water while reducing friction. The developed seal is at the top in terms of both low friction and resistance to mud and water*2.
・ Reduction in the number of sealing lips: The number of sealing lips is reduced from three to one, achieving low friction.
・ aling lip tip folding: The sealing lip is folded to reduce the contact width with the metal slip ring.
・ Change in the shape of the metal slip ring Based on NSK's analysis technology, a U-shaped metal slip ring with excellent drainage has been developed.
2) New Technology "Development of Seal Grease"
Based on NSK's tribology technology, friction is reduced by lowering the viscosity of the base*3 in the seal grease. The developed seal is the world's first product that uses a polymer as a thickener in seal grease, forming an oil film the grease.
*3Base oil: The main component of grease, it bears the lubrication role.
3) Development of new technology "Seal sliding * surface"
Using NSK tribology technology, the seal sliding surface is processed by laser. By uniformizing the concave and convex shapes of the sliding surface, friction reduced. The developed seal is the world's first to use laser processing as a method for processing the sliding surface.
*4 sliding: Refers to the movement that produces frictional force due to the friction between objects. In bearing seals, the surfaces where the lip and the metal sliding ring rub against each other are called sliding surfaces.
