Piston rings are an important element of piston cylinders tibology systems. They fulfil numerous important tasks:
- gas seal of the combustion chamber
- regulation of the oil film at the cylinder surface
- heat removal from the piston to the cylinder
- minimisation of wear and tear of piston, cylinder and piston rings
In the process of continuous development of the combustion engine the thermic and mechanical stress on the parts grow while the dimensions shrink. The resulting demanding requirements have to be met with innovative technologies.
The development led from simple cast iron rings via steel rings on to coatings which reduce wear and tear.
Ring sets for petrol engines
Over the last few years great efforts have been made to reduce CO2 emissions by reducing fuel consumption in petrol engines. The following developments have taken place:
- reduced friction through the use of the ideal combination of piston rings
- axially thin compression and oil rings
- surface treatment (increased lifespan)
- optimisation of cross sections
Ring sets for diesel engines
In this area high speeds and a long lifespan are the most important factors.
For the first ring as well as for the two-piece oil control ring steel is being used and nitridation and PVD can be applied.
Medium-sized and larger engines (3- or 4-piece ring sets)
Higher performance with controlled emissions are the main criteria for these types of engine. For the first (and possibly the second) ring trapeze rings are being used which prevent the ring from getting stuck. In addition PVD coatings are also being applied.
The use of steel rings leads to a width and weight reduction.
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