Polymeric engine bearings for stop-start

Gaining momentum on passenger vehicles, hybrid and stop-start technologies are expected to find more application in commercial vehicles. Mahle has developed a proprietary lead-free polymer overlay for bearings that's suitable for this aggressive operating environment.

The challenge of designing internal-combustion-engine (ICE) components has become more complex and challenging as OEMs are driven to comply with stricter government legislation. For example, the European Directive on End of Life Vehicles has banned the use of “heavy metals” in automotive and light commercial vehicle applications. In respect to bearings, this translates into the use of lead as an alloying element. This subsection of the Directive was brought into force in 2008; however, for commercial heavy-duty applications it is not yet enforced.

Although some OEMs are reluctant, there is a positive trend that they are starting to move away from established leaded to lead-free materials for their new engine platforms. Commercial vehicles are often expected to operate for a prolonged durability over the life of the application; therefore, the robustness of the bearing system is considered paramount. Lead-based substrates and overlays have been used for many years as lead was an excellent bearing material with very good lubricious tribological properties, so the challenges for bearing suppliers were to develop lead-free materials with comparable and improved characteristics as alternative solutions.