MonoXcomp®—Innovative pistons for modern commercial vehicles
Stuttgart, September 2008–Bolted pistons have been the state of the art for large engines since the ’60s. MAHLE is now using its decades of experience and has developed a steel piston for engines in commercial vehicles with this reliable bolting technology.
In coming years, the requirements for commercial vehicles and their components, such as pistons, will increase further, especially with regard to thermal load. That is why in 2005, MAHLE began the development of a new generation of pistons consisting of a crown and piston skirt bolted together. MAHLE engineers are looking back on 45 years of experience with this mature joining technology for large engines. The new MonoXcomp® pistons meet the highest requirements for peak cylinder pressure, temperature resistance, and oil consumption.
Since the compression height of pistons for commercial vehicles is significantly lower than those of large engines, the MonoXcomp® piston concept distributes the required elastic elongation between all the components. At the same time the number of components is reduced to three.
Stretch bolt and a screw thread are integrally formed on the piston crown. The thrust sleeve has the nut thread and an elastically deformable part with a contact zone to the piston skirt. The piston skirt has an integrally formed stretch collar, and can deform in its interior like a disc spring.
A specifically set elasticity within the bolt joint of the MonoXcomp® piston ensures that there is always sufficient bolt force, and that the contact surfaces are always closed, even at high speeds. This prevents wear at the contact surfaces.
The multi-piece design allows an inner and large outer cooling gallery to be formed, which has a positive effect on the cooling of the entire piston crown and especially the bowl rim, which is subject to high loads. The wall thicknesses can also be more precisely specified, especially between the cooling channels and the combustion chamber. Hence, the maximum piston temperature and the piston mass are subject to lower variations.
The different materials for the piston crown, piston skirt, and thrust sleeve allow the material potentials to be utilized optimally.
The MonoXcomp® piston has recently passed through internal release stages. For example, bowl rim temperatures were measured on MonoXcomp® pistons that were 50 to 70 degrees Celsius lower than for typical pistons—under the same boundary conditions. Many customers have already recognized this potential. For some customer projects, the series production development has already begun.
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).