A piston ring is a split ring that is found in reciprocating engines such as an internal combustion engine. This ring is typically found fit into a groove that is present on the outer diameter of the piston in a reciprocating engine.
Functions of a Piston Ring
The piston rings perform a number of functions in the engine.
- The ring seals the combustion chamber in order to minimize the loss of gases to the crankcase.
- It increases the efficiency of the transfer of heat from the piston to the cylinder walls.
- It works to maintain the required quantity of oil between the piston and the walls of the cylinder.
- It also regulates the use of engine oil by scraping the oil off from the walls and back to the sump.
Different Types of Piston Rings
In a typical reciprocating engine, there are usually two compression rings present at the two ends and one oil control ring. However, sometimes there is a third kind called the Wiper ring which is used in addition to the first two kinds of rings.
Compression rings or pressure rings
The compression rings work to seal both the sides of the combustion chamber in order to prevent the leakage of gases from inside it. In a typical design, the compression rings are present in the first grooves of the piston but this may change if there are any changes in the designs of the engine. Their primary function is to transfer heat from the piston to the piston walls and to prevent the leakage of gases.
These function as the backup combustion rings and are usually present below the combustion rings. Their main purpose is to act as a back and stop the leaking of gases and to clean any excess oil from the liner surface. Most wiper rings have a tapered angle face that allows it to wipe off the excess oil as the piston moves towards the crankshaft.
Oil Control Rings
The oil control rings control the amount of oil that passes up and down the cylinder walls. They also work to spread the oil evenly over the circumference of the liner. They are also called scraper rings because they scrape the oil that is splashed into the cylinder, off the walls and back into the crankshaft. These prevent the oil from passing in between the space between the ring and the cylinder wall.
How To Maintain Different Types of Piston Rings
The inspection of the rings on a timely basis is an important part of the maintenance of the rings. While inspecting the following things must be looked for:
- In routine checks, the rings should be pressed up with the help of a screwdriver. This is done in order to check the spring action of the rings. This also is a way to tell if the ring is broken or not because if the spring is broken there will be no spring action.
- The rings are checked for freeness in their grooves to see if any carbon deposits that could get the rings stuck and finally break, damaging the cylinder. The ring is also checked for any scuffing marks, other damages and wear and its quality is also assessed.
- In any major overhauls, the piston may be changed completely for a new set. This is done if the ring is found stuck in the groove, if the axial height of the ring has reduced and there is too much gap between the rings and the groove and if the chrome layer has peeled off or has been damaged.
The quality of the piston rings and the engine is subject to the regular checkups that are conducted on it.