Oil carbon on the piston—simply gone
Stuttgart, September 2008—Cast iron anti-polishing rings in the cylinder liner remove dangerous oil carbon from pistons, and have been the standard in large engines for years. Commercial vehicle engines, however, have much less space. MAHLE has now applied for a patent on a scraper ring made of sheet metal that solves the space problem very simply.
Oil carbon is produced, under operating conditions that cannot be precisely defined, as combustion residue from oil, and builds up as a hard film on the piston. There it can attack the cylinder running surface and cause piston seizure and capital engine damage.
In large engines, there is enough space in the cylinder liners for cast iron anti-polishing rings. For commercial vehicle cylinder liners with diameters of less than 160 mm, however, the liner flange that provides contact between the liner and the block is relatively narrow. A cast iron ring would need so much space that the flange would become too thin and could break off.
A thin sheet metal ring solves the problem. It is slit like a piston ring, and is simply inserted at the top in the cylinder liner. A fold in the ring prevents it from sliding down in the cylinder liner. The sheet metal anti-polishing ring is less that 1 mm thick. It protrudes somewhat into the combustion chamber, scrapes along the piston, and thus reliably removes any oil carbon that may build up on the uppermost land of the piston.
Meanwhile, MAHLE has successfully tested sheet metal anti-polishing rings in endurance tests. The manufacturing process is currently being optimized.
The MAHLE Group is one of the 30 largest companies in the automotive supply industry worldwide. As a leading manufacturer of components and systems for the combustion engine and related products, MAHLE ranks among the top 3 systems suppliers for piston systems, cylinder components, valve train systems, air management systems, and liquid management systems. MAHLE employs around 48,000 people at 110 production plants and eight research and development centers. In 2007, MAHLE achieved sales of over EUR 5 billion (USD 7.5 billion).