Links or piston rings represent one of the most important elements of cylinder or piston assemblies of engines or compressors.
Two functions of the rings are disputed:
• cylinder sealing and
• lubrication between piston and cylinder.
Based on this, two types of rings are derived: compression and oil rings.
Engine compression itself, which is the basis of power, actually implies a tolerant relationship between the piston or pistons and the cylinders. It is an important part of the engine as a whole, but insufficient when it comes to power. In addition to the above-mentioned tolerant ratio of pistons and cylinders, the most important power factor is the piston rings. They keep the compression of the engine within the appropriate limits, so that the output degree of compression is maximal for as long as possible.
The compression ring participates in the formation of the combustion space, so it heats up intensively. That is why oil contact with the compression ring is not desirable. However, the rings are not efficient enough in the direct transition from the sealing function to the lubrication function. The oil ring can effectively lubricate the oil in the piston movement towards SMT, but it is not effective enough in removing oil from under the compression ring in the piston movement towards UMT.
The compression ring is not efficient enough in sealing during expansion. Therefore, between the compression and oil rings there is usually one ring that has two functions – a combined ring.
The combined ring on the upper side seals the compression space together with the compression ring, and on the lower side it removes the oil from the cylinder wall, working as an oil “scraper”. However, the sealing is never complete (100%), nor is the prevention of oil entering the combustion space complete (100%).