Coated engine bearings for boundary lubrication conditions
Stuttgart, September 2011—Vehicles with stop-start systems or hybrid drives place new and more severe demands on the bearing points in the engine, due to the high number of additional starts. MAHLE has addressed this problem, and developed new polymer-coated bearings for the main crankshaft bearing and the connecting rod's big end bearing.
The polymer coating is made of a very low friction polyamide-imide material with additives, and is sprayed onto the high-quality aluminum, two-component bearings from MAHLE. Due to the spraying method, the coating has an extremely durable bond to the bearing material and is very wear-resistant. Thanks to the solid lubricant it contains, the composite material reduces the otherwise typical indications of wear. Boundary lubrication conditions, wherein the lack of an oil film causes frequent contact between the two members of a friction pair, are mitigated by solid lubricants. Excellent resistance is thus provided during the numerous engine starts that unavoidably occur in stop-start systems. Metal particles distributed in the polymer matrix also increase the strength and ensure improved dissipation of frictional heat.
Polyamide-imides are polymers that present excellent mechanical and chemical resistance. Their long-term temperature resistance can exceed 220 degrees Celsius. This makes them one of the most temperature-resistant polymers currently used in technical applications.
Initial tests with polymer-coated plain bearings under stop-start conditions and boundary lubrication conditions have shown very promising results. Wear and abrasion are significantly lower compared with typical bearing journals—particularly under boundary lubrication conditions.
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, among others, the areas of large engines, industrial filtration, as well as cooling and air conditioning systems. The Aftermarket business unit serves the independent parts market, supplying MAHLE products in original equipment quality. In 2010, the MAHLE Group generated sales of approximately EUR 5.3 billion; around 47,000 employees work at over 100 production plants and eight research and development centers.