NTN Corporation (hereafter, NTN) has started the mass-production of the “Resin Mold Insulated Bearing”*1 suppressing the electrical pitting which is a specific issue to e-Axle, a driving source of EVs (electric vehicles).
*1Press release on May 23, 2024: NTN Develops “Resin Mold Insulated Bearing” for e-Axle
https://www.ntnglobal.com/en/news/new_products/news202400044.html
When electric current driving an e-Axle flows into a bearing, electrical pitting can occurred, causing damage of the bearing raceways. As the damage can lead to vibration and abnormal noise, bearings for e-Axles are required to have measures against electrical pitting.
The “Resin Mold Insulated Bearing” suppresses the electrical pitting by injection molding an insulating resin layer onto the bearing’s outer diameter and width surface. It has insulation resistance performance exceeding 1,000 V. The insulating resin layer features excellent durability achieved by the proprietary materials and molding techniques to withstand a wide range of temperature changes and be resistant to peeling during bearing assembly.
This product has been adopted by e-Axles manufactured by overseas automotive manufacturers. For the bearing usage conditions of the vehicle, we proposed this product as the optimum option from our product lineup of bearings resistant to electrical pitting. We received the mass-production order for this product, as the automotive manufacturer highly evaluated the insulation resistance performance and durability.
EV batteries are advancing towards higher voltages to extend cruising distance and decrease charging time. Batteries operating at approximately 800 V are anticipated to be widely used in the future. The increase in voltage could significantly intensify bearing damage due to the flow of electrical current. As this product achieves insulation resistance performance exceeding 1,000 V, it can be used with the 800 V batteries as well and we expect more adoption of this product in the future.
NTN will continue to propose optimal measures to meet customers’ needs for electric pitting which are expected to increase further in the future by enhancing our product lineup of bearings resistant to electrical pitting such as the conductive bearing*2 using rubber seals with excellent conductivity, and engaging in research to reveal mechanisms of damages due to the passage of electric current leading to vibration and noise, and to establish a predicting method for the operating life considering the electric pitting.
NTN will exhibit each bearing resistant to electrical pitting including this product at the “Automotive Engineering Exposition 2025 YOKOHAMA” to be held from May 21 to 23 at PACIFICO Yokohama in Japan.
*2Press release on May 23, 2024: NTN Enhances Product Lineup of Bearings Resistant to Electrical Pitting for EVs
https://www.ntnglobal.com/en/news/new_products/news202400043.html
1. Electrical pitting resistance
The bearing’s outer diameter and width surfaces are injection-molded with a resin with excellent insulation properties. This resin mold inhibits the flow of electric current into the bearing, thereby achieving an insulation resistance performance exceeding 1,000 V. This product is designed to endure battery voltages up to 800 V, a threshold anticipated to rise in the future.*3
*3The voltage applied to bearings for e-Axles is assumed to be less than 10% of the battery voltage
2. Durability
Differences in thermal expansion and shrinkage between resins and metals can lead to resin cracking due to temperature changes. For this reason, a resin material that can withstand the required strength across a wide temperature range was selected for this product. Subsequently, molding methods that provide sufficient strength for the entire insulating resin layer were adopted as well. This resulted in a product that offers durable performance over a wide range of temperature environments found in e-Axles.
Application
e-Axle for EVs and HEVs (motors and gearboxes)
SOURCE: NTN
