New options contribute to improved reliability and longer range of electric vehicles

NSK now offers a greater range of options in anti-electrical-erosion technologies for bearings used in eAxles in EV and hybrid vehicles and has completed performance evaluations.

New options for eAxle bearings include insulating polymer coatings and conductive brushes, enhancing NSK's ability to respond to diverse customer requirements for electrical erosion and contributing to improved reliability and extended range of EV.

NSK aims to achieve 7.5 billion yen in sales by 2030 of electrical-erosion-resistant bearings for eAxles.

Background

Against the background of environmental issues such as climate change, societal efforts toward carbon neutrality are increasing in importance and there is a shift towards EV that can reduce the environmental impact of transportation. A key issue in ensuring long-life operation of EV is preventing the electrical erosion of eAxle components.

Preventing electrical erosion is becoming increasingly difficult due to the higher output of electric motors and higher drive voltages. Insulating ceramic-ball rolling bearings are commonly used to prevent electrical erosion but they are very expensive.

Details

1. Insulating Polymer Coated Bearings

A polymer is sprayed onto the outer ring (outer raceway and end faces) of the bearing and sintered to form a thin insulating coating a few dozen micrometers thick. This can provide the electrical insulation required for eAxle bearings at a lower cost than ceramic-ball bearings.

The extremely thin polymer coating also makes it possible to install these NSK bearings in existing eAxle designs without changing the housing dimensions.

2. Overmolded bearings

Plastic overmolded bearings have been developed to provide the electrical insulation required for eAxles, but at a lower cost than ceramic-ball bearings.

Overmolded bearings for railway applications are complex designs using special materials, but for eAxle applications, conventional polymers can be used to achieve both high performance and cost efficiency.

3. Conductive brushes

Trends in eAxle motors is towards the use of highly efficient oil-cooled systems. Conventional conductive brushes cannot be used in environments with oil, but NSK's new brushes feature sufficient conductivity even in cooling oil-lubricated environments. The brush can be incorporated directly into the shaft to save space.

Benefits

NSK has already completed basic durability evaluations and can promptly provide customers with proposals including evaluation result data for practical applications.

NSK's anti-electrical-erosion options cover both insulating and conductive methods to meet a diverse range of design requirements, including configurations at a lower price than ceramic-ball bearings.

These technologies improve the reliability of eAxles and include space saving measures that enable reducing overall eAxle unit size. They further contribute to reduced electricity consumption and longer vehicle range on a single charge.