Optimal rings for the heart of the engine
Stuttgart, September 2014 – With the power cell unit, MAHLE offers a completely and perfectly matched system consisting of the piston, rings, pin, cylinder liner, and conrod with bearing bushings for original equipment. This complete package provides many advantages—not least due to optimal tuning of the piston rings for a particular field of application.
Combustion engines are highly complex systems. Their individual components fulfil specific tasks, often under very difficult environmental conditions. The core is the piston system, which converts the energy released in combustion into a rotary motion of the crankshaft. MAHLE develops pistons made of aluminium or steel in a variety of styles—for example, for commercial vehicle engines. They withstand ignition pressures of over 220 bar and allow commercial vehicle engines to achieve mileages of well over one million kilometres.
This tremendous performance is only possible, however, because of the interaction of all components in an optimally tuned piston system. This requires thinking in terms of systems and integral concepts. MAHLE therefore designs its piston rings, piston pins, conrods, cylinder liners, and bearings and bushings with great care to suit the particular application, and coordinates them precisely with the other components. Only the entire package—the power cell unit—mobilises additional power reserves and provides the best possible performance. When all components are optimally tuned, a CO2 reduction of up to 5% can be achieved.
The right ring for every task
A system of several matched piston rings doesn’t just seal off the combustion chamber. Its other tasks include transferring combustion heat from the piston into the cylinder surfaces, and controlling the oil supply.
New generations of engines, however, are characterised by rising temperatures, pressures, and speeds. In addition, less and less oil is available for lubrication in order to keep engine emissions as low as possible. This leads to the first piston ring, for example, being subjected to greater loads than ever before. Before now, it has withstood these loads thanks to a coating applied by physical vapour deposition (PVD). In the future, however, the greater thermal loads may heighten the risk that conventional coatings will flake off and wear will increase.
MAHLE has therefore developed a new, multilayer system that is also applied by means of PVD. It consists of alternating microlayers of niobium nitride and chromium nitride. NanoBium MIP290 decisively increases the durability and thermomechanical strength of the first piston ring. First piston rings with the new, patented coating are thus extremely well equipped to meet the requirements of future generations of engines.
However, for the third ring of a modern piston, the oil control ring, the emphasis is on controlling the oil film at the cylinder wall. Its performance has a substantial effect on the oil supply and thus on wear in the piston system. Too much oil must not enter the combustion chamber, however, so that the engine emissions do not increase. To meet these conflicting objectives, MAHLE has developed a two-piece oil control ring with a V-shape design in recent years. This special outer contour of the ring reduces the tangential stresses that press the ring against the cylinder wall by up to 50 per cent. In addition, MAHLE coats the running surface of the oil control ring with a new type of PVD coating based on chromium nitride. This ensures that friction is minimised and service life is increased. Additional technical measures, such as lower ring widths or reduced tangential forces on the rings, can also increase their performance.
Such optimised piston ring packages from MAHLE are already in widespread use as original equipment. They are therefore used by MAHLE Aftermarket as well—because what is used as original equipment is also the first choice for repairs. MAHLE piston rings meet the strict requirements of original equipment for all applications—with high-quality materials and precision machining. For normal to high stresses, materials with laminar graphite inclusions are used, while ultra-high requirements call for grey cast iron materials with embedded nodular graphite or steel materials. A special coating can be applied to the running surfaces of the piston rings to increase resistance to wear and scuffing.
The MAHLE piston ring product range offers the optimal piston ring or piston ring set for every engine—whether in original equipment quality or especially for high-mileage engines, to reduce compression losses and lower oil consumption. MAHLE provides piston ring sets for nearly all passenger car petrol and diesel engines, as well as commercial vehicle diesel engines, with piston diameters from 60 to 160 millimetres.
MAHLE is the globally leading manufacturer of components and systems for the internal combustion engine and its peripherals as well as vehicle air conditioning and engine cooling. In 2014, some 64,000 employees at 140 production locations and ten major research and development centres are expected to generate sales of around ten billion euros.
About MAHLE Aftermarket
MAHLE Aftermarket, the business unit specialising in spare parts, uses the expertise from the series production of original equipment in its automotive aftermarket product range, and supplies trade, repair shop, and engine repair partners. MAHLE Aftermarket is represented at 23 locations and other sales offices worldwide, with 1,670 employees. In 2013, the business unit achieved a global sales volume of EUR 805 million.
Find out more about MAHLE Aftermarket GmbH at www.mahle-aftermarket.com