Polymer on bronze—bearings for future requirements
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The new lead-free MAHLE bearing with polymer coating (above) after engine testing, compared with conventional lead-based bearings (below).
Hanover, September 2012 – The operating environment for engine components is radically changing as a result of measures to reduce fuel consumption and emissions in modern engines. The main task of bearings is to support moving parts and to absorb and transfer the forces acting on them. With the introduction of new technologies such as stop-start or hybrid systems, downsizing, and low-viscosity oils, these components need to withstand considerably greater loads. MAHLE has consequently developed a new polymer coating.
During engine operation, an oil film builds up between the bearing and the rotating shaft. At higher specific engine outputs, and thus higher peak cylinder pressures, greater forces act on the engine components, which increases the pressure and leads to a thinner oil film. This effect is accentuated by lower-viscosity oils. Stop-start and hybrid systems intensify the operating conditions of bearings even further. Every time the engine is started, the bearing passes through the wear-intensive mixed friction regime. A considerable increase in the number of starts therefore poses a significant challenge in terms of the wear resistance of bearings.
In order to deal with this increasingly aggressive operating environment, MAHLE has developed a new lead-free polymer coating on bronze bearings. A polymer matrix with additional solid lubricant and aluminum flakes ensures high strength as well as thermal and chemical resistance. Engine test results demonstrate excellent wear and fatigue resistance compared with established lead-based products. The tests have indicated a load capacity of up to 95 MPa, which highlights the coating's suitability for heavy-duty truck applications. The functionally relevant layer is preserved throughout the service life of the bearing.
Thanks to their special properties, the new MAHLE bearings can be used directly in existing engines, but are also able to withstand the additional loads associated with future technology trends in commercial vehicle engines, such as stop-start systems.
The MAHLE Group is one of the 30 largest companies in the automotive supply industry worldwide. With its two business units Engine Systems and Components and Filtration and Engine Peripherals, MAHLE ranks among the top three systems suppliers worldwide for piston systems, cylinder components, as well as valve train, air management, and liquid management systems. MAHLE’s industrial activities are combined in the Industry business unit. These include the areas of large engines, industrial filtration, as well as cooling and air conditioning systems. The Aftermarket business unit serves the independent spare parts market with MAHLE products in OE quality. In 2011, the MAHLE Group generated sales of approximately EUR 6 billion; around 49,000 employees work at over 100 production plants and eight research and development centers.
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