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01/10/2007
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Diesel engine design has taken a further step forward with a new generation of aluminium-based piston materials combined with a laser technology for configuring the piston bowl lip, accoring to Kolbenschmidt Pierburg.
New materials and processes for diesel engine pistons have been engineered to work in high-stress environments. The components exhibit significant strength and durability gains at temperatures above 300ºC, achieved through the specially developed blend of alloys along with a process-controlled microstructure design adapted to the specific piston loads.
To meet high local thermal and mechanical stresses at the bowl lip of the pistons, the zone is remelted using controlled laser technology. This results in a flawless finely homogeneous microstructure which improves thermal fatigue in the area by up to 60%. Further advantages are improved corrosion protection and higher process robustness.
Group member KS Gleitlager, meanwhile, has made some advances in plain bearing systems. One of these is a crankshaft bearing that takes over the indirect lubricant supply to the connecting rod bearings, allowing a smaller oil pump to be used.
The bearing features integrated ‘sealing lips’ which reduce axial oil dissipation. Two flexible plastic elements are embedded in the sliding surface. These seal off the bearing gap, widening on the non-load side caused by the crankshaft’s offset track and by system deformation. As a result the oil, rather than running off, remains largely within the bearing and more efficiently supplies the connecting-rod bearings.
Gleitlager has also come up with an innovative unleaded sputter bearing ready for the time when lead has to removed from systems (July 2008). However, it also copes with higher loads and can be produced at a lower cost than its predecessor.
Today’s sputter bearings have an extremely thin aluminum-tin coating (AlSn20) deposited onto the bearing’s lead-bronze coating. With the new, unleaded bearings, the leaded bronze has been replaced by an unleaded brass coating. This is not only more resilient but also more corrosion resistant to engine oil.
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Author
Roger Bishop
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