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Pumping fluid back to the oil side
240 hours leak-free at 20,130 rpm
A clean-sheet development approach

Trelleborg Sealing Solutions has launched Stefa® HiSpin® EV40, an elastomer radial shaft seal developed with proprietary technology and engineering to meet the requirements of modern electric vehicle (EV) motors. Designed for high surface speeds, the seal offers low-friction sealing and a long service life.

In the fast-evolving automotive sector, electric vehicles are pushing the limits of engineering, with traction motor speeds reaching up to 20,000 rpm. As efficiency and power density increase, so does the need for reliable sealing solutions.

Pumping fluid back to the oil side

At the heart of Stefa HiSpin EV40 is Trelleborg’s patented Phase-Shifted-Wave (PSW) technology. By actively pumping fluid back to the oil side as the shaft rotates, this solution provides superior sealing even under heavy lubrication conditions. The design reduces radial force, lowering friction and increasing drivetrain efficiency.

“This patented hydrodynamic feature consists of multiple single-sided wavy grooves separated by static bands. The shifted undulation between neighbouring grooves enables a progressive back-pumping from the air side to the oil side. The design is the result of finite element analyses carried out at different sizes,” says Nino Dakov, Technology Engineering Manager at Trelleborg Sealing Solutions.

The seal’s symmetrical design simplifies customer validation, as no additional testing is required for a lower-performing direction of rotation. Operating with the same efficiency in both directions, the seal can be used in different EV applications.

240 hours leak-free at 20,130 rpm

The seal has undergone extensive testing. In a high-speed endurance test, it ran flawlessly at 20,130 rpm (40 m/s) for 240 hours without any sign of leakage or wear. An additional 1,000-hour endurance test also confirmed that the seal withstands extreme speeds and temperatures without losing its integrity.

The specially formulated fluorocarbon (FKM) material used in the seal has proven compatibility with a range of e-axle oils, and its design is suitable for high-volume production. Designed to tolerate shaft runout, the seal delivers high sealing efficiency and long-lasting, reliable performance under different lubrication conditions.

A clean-sheet development approach

“In the past, automotive development was an evolutionary process focused on incremental improvements. The shift to electric vehicles, however, requires a complete rethink of components and performance criteria,” says Guillaume Carron, Business Development Engineer at Trelleborg Sealing Solutions.

Carron emphasises the importance of developing solutions from scratch with the new product, rather than relying on traditional approaches: “We conducted in-depth research to analyse market needs and define the development scope for EV traction motor radial shaft seals. In this process, we filtered out niche requirements that could lead to unnecessary over-engineering. Stefa HiSpin EV40 is an example of our clean-sheet engineering strategy to optimise performance while minimising complexity and cost.”