Piston ring
The piston ring is a sealing element on the plunger, for example an internal combustion engine or a reciprocating compressor.
General Description
Piston rings have several tasks:
- Sealing of the working space
- Extraction of the combustion heat from the piston to the cooled cylinder wall
- Dosage of the lubricating oil between the running surface of the ring and the cylinder wall
Piston rings are not closed rings, but also in the installed state on the periphery of an opening, the so-called ring joint. In the free, that is, not installed condition piston rings not circular, but have a defined non-circular shape and an opening - the mouth width. Only in the installed state, the rings are pressed into circular shape. Depending on the requirements for modulus of elasticity, mechanical strength and wear resistance Piston rings made of cast iron or steel materials are manufactured. To improve the wear behavior of coatings are sometimes necessary on the rings. This electrochemical methods are such as Chrome plating, or thermal spray coatings and ceramic coatings are used. On steel rings, the outer layer lying on the cylinder surface is often hardened by nitriding.
In today's car or truck engines, three piston rings per cylinder are usually used. The design of the piston rings differs according to the mounting position on the piston, since the task of the ring depends on the position on the piston. The top ring - the combustion chamber closest to - is the so-called compression ring and has to seal in the first place and dissipate heat. The lowermost ring scraper ring, clips lubricating oil on the cylinder wall and metered while the oil film on the slide, the upper piston rings during the stroke. The second or middle ring seals against the combustion gases and, by interaction with the movement of the first ring substantially affect the blow of the engine. But this second piston ring is also a thing a significant role in the control of the oil balance of the engine. The oil film must both provide sufficiently good tribological conditions than be thin to keep the oil losses attributed to evaporation. In the region of the upper piston ring, the oil film thickness is to some extent less than one thousandth of a millimeter and is therefore less than the surface roughness of the piston and cylinder.
Compression rings / compression rings
The main task of the KV- rings is to seal the combustion chamber against the piston housing and to channel the heat from piston to cylinder. Moreover, they are also there to regulate the lubrication household of great importance.
Compression rings are one-piece rings, which mainly involve their pressure against the cylinder wall from the gas pressure. To secure the seal at the start and prevent a ring flutter at high speeds, the rings being mechanically biased by the bending stress between the fine and integrated form. The height of the contact pressure is usually specified in terms of the tangential force of the ring.
Oil control ring
The main task of the rings in the piston groove bottom is the stripping of the oil from the cylinder wall, ie, the oil control ring has a significant effect on the oil supply of an internal combustion engine. To influence the consumption of lubricating oil is most effective, there are several mono-, di - or three-piece designs for selection.