The vision of frictionless drive systems – Coating technology cuts energy loss in half
Dr.-Ing. Patrick Izquierdo (Spokesperson)
Dipl.-Ing. Manuel Michel
Dipl.-Ing. (FH) Bernd Zapf* Daimler AG, Ulm
*Gebrüder Heller Maschinenfabrik GmbH, Nürtingen
Although the number of electric cars is increasing, vehicles powered by internal combustion engines still rule the roads. An important starting point to making IC engines more fuel efficient and thus more environmentally friendly is the friction losses in the engine. How can they be avoided?
In their search for a solution, Dr. Patrick Izquierdo, engineer Manuel Michel and Bernd Zapf set their sights on the piston and cylinder liner system. This part of the engine accounts for almost 50 percent of the friction losses in the drive unit. Izquierdo and Michel, both Daimler researchers, developed a novel process for coating the cylinder walls of aluminum crankcases. This eliminates the need for special cylinder liners in the cases - and friction is dramatically reduced. Working with Bernd Zapf from the company Gebrüder Heller Maschinenfabrik GmbH they refined the technology for use in series production.
Patrick Izquierdo is head of Lightweight Construction, Casting/Forging Structures at Daimler AG in Ulm. Manuel Michel is the Daimler project manager for NANOSLIDE. Bernd Zapf heads the New Business and Technology division at Gebrüder Heller Maschinenfabrik GmbH in Nürtingen.
Without friction losses, a combustion engine would use twenty-five percent less fuel. Emissions harmful to the climate, like carbon dioxide (CO2), would also be lower. Friction can never be entirely eliminated, but with the NANOSLIDE® process developed by the three researchers, a significant step has been made in the right direction. The process picks up a trend in automobile manufacturing that uses lightweight aluminum for the crankcase of combustion engines. In the past, these had to have a heavy sleeve or liner made of grey cast iron or used an aluminum-silicium alloy as the bore for the cylinder. In this configuration, a lot of energy was lost when the piston moved. NANOSLIDE® makes the additional sleeve unnecessary.
This technology uses a thin sliding layer just a tenth of a millimeter thick and applied to the inner wall of the aluminum cylinder. To apply the layer, two wires made of an iron-carbon alloy produce an electric arc in which liquid metal drops form. A stream of nitrogen gas atomizes the drops and directs them onto the cylinder wall where they solidify and form a thin coating of nanometer size pores. These pores are oil reservoirs which are exposed during subsequent machining. The layer then forms a mirror-like surface with very little frictional resistance - and virtually no wear. The researchers succeeded in improving the process to such a degree that it uses 96 percent less energy and water use was reduced to zero.
The friction losses in the piston and cylinder bore system are half that of conventional manufacturing methods. This reduces fuel consumption in vehicles with gasoline or diesel engines by at least 3 percent. According to an independent study, CO2 emissions can be lowered by up to 50 million tons per year by using the NANOSLIDE® technology. Another advantage of the process is that the thick-walled grey-cast iron liner is no longer needed which means that the engine design can be more compact and lighter - an ideal requirement for combining it with an electric motor in a hybrid vehicle.
NANOSLIDE® is patented and is offered for series production by Gebrüder Heller Maschinenfabrik GmbH. Using the process, any size of cylinder inner diameter can be coated in a wide range of crankcase types. The coatings can also be configured with specific properties. Numerous car manufacturers and suppliers are already using the technology which is developing into a global standard. This will secure or create several thousand jobs in Germany. At Heller, NANOSLIDE® opened up a new business segment. Daimler established the subsidiary MDC Technology GmbH in Arnstadt in 2013 to design the manufacturing process for large series production and is now using it at several production sites.