Drivetrain Lubricants with High Cooling and Efficiency-Boosting Properties for Electric Vehicles

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Drivetrain Lubricants with High Cooling and Efficiency-Boosting Properties for Electric Vehicles

Tada, Akira / Masuda, Kohei / Iino, Mari / Matsuki, Shingo / Onumata PhD, Yasushi

In electric vehicles (EVs), drivetrain lubricants (EV fluids) are often relied upon to aid in cooling the motors. In such cases, the lubricants must provide high cooling performance. They should also improve the efficiency of the transmissions and reduction gearboxes in EV drivetrains. Both requirements can be met by lowering the viscosity of the fluid. This effectively improves the heat transfer coefficient and also helps increase efficiency by reducing churning loss. However, a viscosity that is too low can negatively affect the fatigue life of mechanical parts such as gears and bearings. To solve the issues associated with lower viscosities, we optimized the anti-wear agents, dispersants, and other additives to develop formulations specially designed for EV drivetrains. The result are lubricants that provide excellent extreme pressure properties and protection for drivetrain components despite their lower viscosities. We evaluated performance of the developed lubricants, and it was confirmed that lower viscosity contributes to better cooling effect and improved helical gear efficiency as expected. In addition, these lubricants have much improved electrical insulation properties and Cu compatibility compared to conventional automatic transmission fluids (ATFs). In summary, we showed it was possible to lower viscosity without sacrificing protection and developed EV fluids that provide excellent motor cooling performance and help increase the range of the vehicle.