Electric vehicles (EVs) are here to stay, with an estimated two millions EVs on U.S. roads at the end of 2021. Some reports predict that number could jump to 18.7 millions EVs by 2030, when possibly half of all consumer passenger vehicles sold will be electric.

Advancements and development of the technology behind EVs will be one of the main factors that will attract new customers into the market and will lead to the cost of EV ownership dropping. The infrastructure, battery technology and charging times will all improve, contributing to the major shift toward renewable transport.

This also means eking out every bit of efficiency from the powertrain. This includes components that are oft-overlooked, but may in fact hurt the power transmission from electric motor to locomotive systems.

A new generation of extremely fast ball bearings has been developed for EV motors, which are capable of operation at over 1.8 million dmN -- dmN is a measurement of bearing rotational performance. It is the rotational speed N, by the bearing pitch diameter dm. In comparison, previous models are capable of around 1.4 million dmN.

This is the third generation of this type of ball bearing to be created and is known as the fastest deep groove grease-lubricated ball bearing made for the automotive industry. This new ball bearing technology will translate to a higher energy economy and longer EV range. It also facilitates the construction of a smaller motor and other components which will give manufacturers the option to optimize the interior space of the EVs.

This third generation of ultra-high-speed ball bearing will build on the improvements that the second generation saw, which were mainly in anti-seizure and cage advancements. The new ball-bearings will be able to withstand very high speeds for the new generation of EV motors.

How ball bearings fit into EVs

Electric vehicle powertrains are much simpler in mechanical terms than their internal combustion cousins. Since their inception, optimization of the EV motors has been one of the biggest pain points for manufacturers, along with battery technology. Through the improvement of EV motors, more and more stress has been placed on the ball bearings within the drivetrain. The additional friction created by the ball bearings, however negligible, also saps power transmission efficiency.

While e-axles feature the same amount of bearings as a traditional axle, there are more challenges to deal with in an EV. There are significantly higher centrifugal forces, and heat generation is also a problem due to the extremely high speed at which electric motors spin. To deal with this, special ball bearings that feature special cage designs, lubricant characteristics and internal geometry were developed. These ball bearings have to put up with these forces for the design life of the vehicle, which is typically 10 to 15 years or 185,000 miles. However, they are hoping that this design life can be extended to around 300,000 miles in the future.

Features of these new ball bearings

The topology of the cage was optimized by reducing as much weight as possible through the removal of any unnecessary parts while avoiding the removal of anything that would affect the rigidity and strength of the cage. The absolute best cage shape was also derived for high-speed rotation.

Source: NSK

The manufacturers were able to design this cage in a short timeframe by utilizing state-of-the-art simulation technology to confirm product considerations and performance.

The new bearings are also filled with a new specific type of grease that is proprietary to the manufacturer (NSK). This new grease was developed to reduce churning resistance and the heat that is generated from it. The lengthens the bearing and grease life, while also providing superior seizure protection.

A new resin material that provides high rigidity that is significantly better at decreasing deformation while subjected to high-speed rotation was used for the cage. Ceramic coatings can also be used for the same purpose. As mentioned previously, the combination of the proprietary grease and new cage material allows the bearing to operate at over 1.8 million dmN.

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Summary

This new ball bearing technology will enable EV manufacturers to construct and install motors that are able to run at significantly higher speeds than previously. Higher output from the EV motors results in greater efficiency (less power consumed over distance), more comfort for the users in the vehicle, and a significantly longer range. Higher speeds produced from electric motors mean that smaller motors can be used, therefore increasing the space within the cabin, more space for other components like batteries, and reducing the weight of the vehicle.