Piston rings are rings with a small gap, open. They are located in grooves on the outer walls of the pistons in all types of piston engines (for example, steam engines or internal combustion engines).
What are piston rings for?
1. To seal the combustion chamber. Compression rings significantly increase compression. With dead, broken, or worn rings, the engine may not start or lose power.
2. To improve heat transfer through the cylinder walls. The rings contribute to the removal of heat from the piston during the operation of the internal combustion engine, thereby preventing overheating.
3. To reduce oil consumption for the engine (in two-stroke diesel engines and in all four-stroke ICEs).
How are piston rings arranged?
The joint (aka lock) is located between the ends of the piston ring. When the piston is in the cylinder, the lock is slightly compressed - up to several fractions of a millimeter. It happens oblique (in four-stroke ICEs) and straight. The rings located in the grooves are positioned so that the angle between the joints is equal (2 rings - 180 degrees, 3 rings - 120 degrees). The result is a labyrinth that reduces the breakthrough of gases.
Rings are oil scraper and compression. Oil scraper protects the combustion chamber from oil from the crankcase. They remove excess engine oil from the cylinder. Oil
scraper rings are installed below the compression
rings . They have through slots. In two-stroke gasoline internal combustion engines, oil scraper is not used, as the oil for the engine burns together with the fuel. Now either
cast cast iron or composite steel rings with spreaders in the form of springs are available. Compounds are simpler and cheaper to manufacture, so they are much more common than cast ones.
Compression piston rings protect the crankcase from gas gusts from the combustion chamber. In the free state of the ring, the outer diameter is larger than the inner. For this reason, part of the product is cut out. The location of the cut is called a lock. Usually no more than three such rings are installed on one piston, for the reason that the degree of compaction of the piston increases slightly, and friction losses increase. As a rule, two rings are mounted on two-stroke ICEs. The cross section of most compression rings is rectangular. The edge has either a chamfer that narrows or a cylindrical profile. During the operation of the internal combustion engine, the rings are twisted to some extent (this provides a gap in the groove), which facilitates their running-in.
Piston Ring FabricationTechnologies and manufacturing methods should ensure the shape of the product, which in a free state would create the desired level of pressure in its working condition. A piston ring is usually made of high-strength gray cast iron, as it has good stable elasticity and strength, high wear resistance, and excellent anti-friction properties. Alloying additives are also used (special coating made of porous chromium, molybdenum surfacing, plasma spraying, ceramic coating, diamond particles), which contribute to a significant increase in the heat resistance of products.