Stacked oil scraper rings. What types of piston rings are there? The oil scraper ring serves for uniform
There are two types of piston rings in a power plant: compression and oil scraper.
Compression rings serve as a seal between the piston body and the cylinder bore, creating compression as they work. In this case, the upper ring on the piston is purely compression, and the second is compression and oil scraper, due to a recess in the form of a scraper. The lowest ring on the piston is only an oil scraper ring.
MSK - Oil scraper ring
Oil scrapers are necessary to remove heat from the piston body. This occurs due to the fact that during operation the rings are pressed against the cylinder mirror and transfer heat from the heated piston to the cylinder. The cylinder, in turn, gives off heat to the coolant circulating in the cooling jacket outside the cylinders. They are also necessary to protect the combustion chambers from excess oil by removing it from the cylinder surface.
Piston, compression and oil rings
Design
By design, oil scraper rings can be solid or stacked, that is, consisting of several parts.
Solid rings consist of two parts: the ring itself and a spiral spring, which creates additional elasticity for the ring.
A) One-piece oil scraper ring B) set ring
Stacked rings are made of three elements; these are two thin rings with a radial expander between them. The ring locks are separated from each other. Due to the fact that each of the rings can work independently, that is, changing the elastic force at different points, for example, when the piston passes at the bottom dead center, when the piston tries to turn, the set ring removes excess oil from the cylinder more thoroughly than a solid ring.
Therefore, mechanics, when performing scheduled repairs to replace rings or engine repairs, give preference to stacked oil scraper rings.
Differences between oil scraper rings and caps
Inexperienced car owners often confuse oil scraper rings with valve stem seals. In fact, these two elements perform the same important job in the engine - they protect the combustion chamber from excess oil.
Reduced dynamics and power;
Increased fuel consumption.
Signs of malfunctioning oil scraper rings:
Oiling of spark plugs;
The connection to the exhaust pipe is given;
The cylinder head and engine sump are removed;
Cylinder head, pistons covered in carbon deposits. Photo — drive2.ru
The connecting rod caps and piston caps (preliminarily marked by cylinder number) with connecting rods are removed from the power unit block one by one;
Old piston rings are removed from the pistons and the pistons are cleaned and washed, especially paying attention to the ring tracks, where carbon deposits must be removed;
New rings are installed on the pistons, locks are opened;
New rings
Oil is spilled over the rings and the pistons, using a mandrel, are installed in the order of removal into the cylinders of the block;
New rings on the pistons
The connecting rod caps are installed and tightened to the prescribed torque;
The cylinder head and engine sump with new gaskets are installed;
All timing elements are installed, the engine is turned two turns and the factory marks are checked;
All removed attachments are mounted;
Engine oil and coolant are added;
The engine is started.
Cost of replacing rings and caps
The cost of replacing piston rings varies at bus stations and averages from 8,000 to 10,000 rubles or more, depending on the design of the engine and the complexity of the work, as well as the make of the car.
To replace the caps, the cost of work starts at an average of 3,000 rubles.
Piston rings installed in the piston group simultaneously perform several important functions for the engine.
Purpose of the rings
Gas seal of the combustion chamber (space above the piston)
Removal of part of the heat from the piston surface of the cylinder
"oil control", i.e. removing excess oil from the cylinder walls and simultaneously ensuring lubrication of the rings and cylinder themselves.
Most modern engines, both gasoline and diesel, are equipped with a set of three rings. The two upper rings are compression and the lower oil ring.
Although the middle ring is often assigned a dual role, where it not only serves to maintain compression, but also partially serves to remove oil, but this will be a separate article.
Oil scraper rings of modern engines are installed in two types:
Box ring with expander type spring
Set ring consisting of a dual-function expander and two steel discs
The box ring is essentially an oil control ring, while the set ring is purely an oil control ring.
The box ring provides slightly higher oil consumption due to the passage of part of it near dead spots, but it provides lubrication of the piston and cylinder. This occurs due to the separation of the “ridge” of the ring from the cylinder wall at the moment of “shifting” the piston.
There is no such drawback oil scraper ring, since its disks are not rigidly connected to each other and the contact of the disk with the cylinder mirror always remains constant.
This is achieved due to the fact that the disks has a small thickness, about 0.50-0.63 mm, which allows them to “adapt” well to the surface of the cylinder, compared to a box-shaped oil scraper ring.
This design oil scraper ring allows him to remove almost all the oil from the cylinder walls, sometimes even leading to starvation of the piston-cylinder pair.
For this purpose, the design of the middle compression ring has been specially modified, which is capable of holding part of the oil to lubricate the rings, piston and cylinder above the oil scraper ring.
In diesel engines, where the operating conditions of the piston group are much more stringent and the requirements for lubrication are increased, box-shaped oil scraper rings are mainly installed.
Japanese and American gasoline engines are mostly equipped from the factory stacked oil scraper rings, and European manufacturers give preference to box-shaped oil scraper rings.
When the box ring wears heavily, the height of the scallops becomes minimal, and sometimes they wear out completely, which leads to an increase in the gap in the ring lock and high oil consumption.
Oil scraper ring is not subject to this, since the increased gap in the lock overlaps another disk, moved apart by the ring lock in the opposite direction.
When replacing rings, without performing any grinding operations, the option with stacked oil scraper rings will be more reliable. Typically these rings are more expensive than box type oil rings, but the price is justified and will pay off handsomely.
For novice car enthusiasts, this is just some kind of set of words: piston compression rings. To make it clearer, let’s first understand what this mechanism is.
Purpose of a compression ring in a car piston assembly
This simple product is an open circle that has a small gap (it can reach several hundredths of a millimeter in size). The ring is seated in a piston engine, be it internal combustion or steam. Regardless of where it is used, it performs three main functions. Firstly, it perfectly seals the combustion chambers. Secondly, it is a heat transmitter through the cylinder walls - it filters heat from the piston and prevents overheating. Thirdly, it would seem such a simple element, but it also perfectly reduces the consumption of engine oil, if, of course, one is used.
As you can see, the functions are important, so at this point in time it is impossible to imagine an engine without a piston ring. Let's take a closer look at the structure of our element. Regardless of the type, all have a lock, it is the joint between the end of our ring, which compresses to a few hundredths of a millimeter when the piston enters the cylinder. Compression rings serve to seal the chamber to create the desired... Most often, their cross-section is rectangular in shape, and at the very edge it has a cylindrical profile. During operation, it can twist slightly, thereby making running-in easier.
Compression and oil scraper rings - what's the difference?
Piston rings are divided into compression and oil scraper rings. Oil scraper rings are not used everywhere. For example, in gasoline two-stroke engines, this part does not make sense, since the oil burns out along with the fuel. After all, the main function of the oil scraper ring is to remove excess oil. These small parts come in two different types: cast iron (cast with a slot) and steel (composite using expansion springs).
The compression ring should prevent excess fluid and air from entering the combustion chamber.
We smoothly move on to the principle of operation of compression types of rings. To create a reliable piston that will be of high quality and efficient operation, it is necessary to use narrow piston rings. It is worth noting that when free, the ring has a larger diameter and slopes outward from the lock. It is this design that allows, after the ring is installed, to be pressed more tightly against the walls. This increases the efficiency of our part.
The ring is also actively pressed by the force of the working gas and liquid during engine operation. They penetrate into the piston grooves gradually with pressure, which in turn is many times greater than the tension of the ring. They push it out of the groove and thereby, accordingly, minimize any attempts by the working gases to fill the crank chamber.
How can a piston compression ring fail?
For stable operation of the engine, one ring is enough. For example, scooters or motorcycles with weak engines have a single ring piston. But if you do not take into account the scooter engine, then some devices have pistons with a loaded working part, where 5 rings or even more can be used on the piston.
Like any part of a car, piston rings can break or be damaged in some way during an accident or other physical impact on the car. Most often, pistons break due to a large number of high loads during operation.
During a fracture test, you will be able to observe raster lines on the surface of the affected area, which can help identify damage and assess the overall condition of the piston. When the piston wears, thermal stress cracks may also be observed. As a rule, they are located at the bottom of the piston and, of course, seeing them will be much more difficult.
Many car enthusiasts are interested in how to promptly identify a problem with piston rings and what are the main signs of malfunction of these parts. In order to understand this issue, it is necessary to clearly understand the purpose of engine compression and oil scraper rings, the features of their design and operating conditions.
Design features and purpose of engine piston rings.
The piston rings of a car engine perform 3 main tasks:
- Preventing the breakthrough of gases from the combustion chamber into the crankcase.
- Removal of heat from the piston heated by exhaust gases into the cylinder walls.
- Ensuring lubrication of parts of the cylinder-piston group and preventing (or at least minimizing) oil from entering the combustion chamber from the crankcase and, as a result, increased oil consumption.
In most modern engines, these functions are performed by three piston rings:
The upper compression ring is responsible for sealing the combustion chamber and experiences very heavy loads, as it absorbs most of the exhaust gas pressure during combustion. In addition, the rings operate at elevated temperatures, which affects their lubrication and wear conditions, which ultimately leads to increased oil consumption. To ensure resistance to high temperature and power loads, the upper rings are made of high-strength cast iron alloyed with molybdenum, nickel and chromium.
In addition to the sealing function, the middle compression oil scraper ring also controls the lubrication of parts and prevents increased oil consumption. As the piston moves from top dead center to bottom, the ring removes oil from the cylinder walls. To ensure this function, the middle rings have a special shape that allows oil to be removed from the walls during the downward stroke of the piston and to pass it during the upward stroke, which prevents oil from entering the combustion chamber. Since these rings are less loaded than compression rings, they are usually made of less durable material - gray alloy cast iron with flake graphite. 
As you can guess from the name itself, the main task of the lower oil scraper ring is to remove oil from the surface of the cylinder and dump it into the crankcase through holes or grooves in the piston groove. Since the functions of this ring are different from those performed by compression rings, its design is also significantly different.
Currently, 2 types of oil scraper rings are most widespread:
- box-shaped with expander spring;
- set, which consists of two disks and a dual-function expander.
The main requirements for these rings are good running-in to the cylinder walls and high pressure on them, which ensures effective removal of lubricant and prevents increased oil consumption. Depending on the type, oil scraper rings are made of gray alloy cast iron or carbon steel. To work effectively in tandem with a cast iron sleeve, their surface is chrome-plated.
Main signs of piston ring wear
When the upper compression rings wear out, as a rule, the compression in the engine decreases, which manifests itself in a deterioration in the acceleration dynamics of the car, and if the rings are not worn out on all cylinders, then such an engine runs unevenly. In order to determine in which cylinder the rings are worn out, it is necessary to measure the compression. In a working gasoline engine it should be 11 - 13 bar, in a diesel engine - from 23 to 40 bar.
When worn oil rings
Wear or malfunction of the oil scraper rings results in increased oil consumption under normal operating conditions. Also, a sign of ring wear is the presence of black smoke from the exhaust system and crankcase ventilation system (breather). The reason for this is the burnout of the engine oil that has entered the combustion chamber.
One of the possible signs that may indicate wear of the oil scraper rings is contamination of the spark plugs with oil, but this also happens if the oil valve caps are worn out. To accurately determine the cause of the malfunction, disassembling the engine will be required.
In most cases, in modern internal combustion engines, the service life of oil scraper rings is 150-200 thousand kilometers, and in some engines even from 300 to 500 thousand. However, if the car is operated in difficult conditions or its owner does not change the oil in a timely manner, then they will be replaced necessary after 50 thousand kilometers. In this regard, when deciding to replace compression and oil scraper rings, you should not rely only on the mileage of the car.
What to do if the rings wear out?
In order to choose a way to solve a problem, you need to find out why it arose. The occurrence of the above symptoms may be caused by wear or breakage of the compression and oil rings, or if they are coked and stuck.
In the first case, it will be necessary to disassemble the engine and install new parts instead of damaged ones. In this case, you should carefully inspect all mating parts, since if the rings break, scoring may occur, which can only be eliminated by carrying out a major overhaul.
If there is an assumption that the piston and oil scraper rings are stuck, then you can add a special additive to the oil. But this method is used, as a rule, for preventive purposes.
Malfunctions related to piston rings arise in practice quite often. Therefore, in order to prevent serious consequences and, as a result, high repair costs, it is necessary to recognize their first symptoms in time and take appropriate measures.
Evgeniy Shuba, Ph.D., lecturer at the Department of Engines and Heat Engineering of the National Transport University
Oil scraper rings prevent oil from entering the combustion chamber from the crankcase, removing excess oil from the cylinder wall. They are installed below the compression ones. Unlike compression rings, they have through slots or consist of two scraper-type rings. On the pistons of some engines, composite oil scraper rings are installed, made of two steel disks and two spring expanders - axial and radial. The axial expander located between the discs presses them tightly against the walls of the piston groove. The radial expander presses the discs tightly against the cylinder. The prefabricated rings adhere well to the cylinder surface and provide low crankcase oil consumption.
Main functions and types
Oil scraper rings are installed at a level lower than the compression rings. Unlike the one-piece structure of compression ones, they are produced with through slots (made of cast iron) or composite ones with expansion springs (made of steel). Composite rings consist of one thin upper ring, one lower ring and two expanders (axial and radial). Depending on the type of piston and engine, a pair of oil scraper rings can be installed. This type of rings is available in three types:
- chrome plated,
- non-chromed,
- steel.
Sealing the expansion or combustion chamber; increasing compression so the engine can run and start. Reducing the overall engine oil consumption of the machine (for all four-stroke and diesel two-stroke engines); At the same time, sufficient lubrication of all sliding elements must be ensured. Keeping exhaust gases from entering the crankcase. Removal of excess heat from the working piston, which prevents it from overheating and normalizes heat transfer through the cylinder walls.
Ring design
Before considering malfunctions and finding out when replacement or decarbonization of oil scraper rings is required, you need to know their design features. One-piece parts are no longer produced today, as they are no longer popular. Such parts have increased rigidity, which is why they do not adhere well to the surface and do not remove oil well. Today, parts are produced that consist of two or three parts. Such parts are called “stacked oil scraper rings”.
The first option consists of the oil scraper ring itself and a spiral spring. The advantages of such a product: it is quite flexible, which is why it fits tightly to the walls of the cylinder. The spring is pressed against the ring so tightly that the part looks solid. Three-piece rings consist of the following elements: a spacer spring and two steel plates. They are usually used in cars with gasoline engines. The advantage of this design is that it fits as tightly as possible to the cylinder.
Signs of ring wear and their diagnosis
You can find out when oil scraper rings need repair or replacement based on several factors: engine oil consumption has become much higher; at the beginning of movement or after a short stop - the appearance of bluish smoke; leakage and evaporation of oil in caps, sealing gaskets, etc.; The color of the leaking liquid also matters: if it is dark, then the seals need to be replaced; The next step is to check the spark plugs; if they are dirty, then you need to contact a car service or carry out repairs yourself. If any signs of wear are detected, the first thing you need to pay attention to is the oil scraper rings. Checking the caps is quite easy. You need to remove the ventilation hose; if the pressure in the crankcase is high, then the caps are out of order.
What to do if the rings wear out?
In order to choose a way to solve a problem, you need to find out why it arose. The occurrence of the above symptoms may be caused by wear or breakage of the compression and oil rings, or if they are coked and stuck.
In the first case, it will be necessary to disassemble the engine and install new parts instead of damaged ones. In this case, you should carefully inspect all mating parts, since if the rings break, scoring may occur, which can only be eliminated by carrying out a major overhaul.
If there is an assumption that the piston and oil scraper rings are stuck, then you can add a special additive to the oil. But this method is used, as a rule, for preventive purposes.
Malfunctions related to piston rings arise in practice quite often. Therefore, in order to prevent serious consequences and, as a result, high repair costs, it is necessary to recognize their first symptoms in time and take appropriate measures.
FEATURES OF OIL RING INSTALLATION
I would like to draw your attention to the installation of oil scraper rings. There should be no problems with compression if you follow simple rules, install them with the inscriptions facing up (inscriptions, dot) and use a special tool.
When installing oil scraper valves, difficulties may arise if there are no inscriptions, or if the expander lock is installed correctly. Let's look at this in more detail. If there are no inscriptions, then it does not matter which side you put the ring on and which one will be on top and which one will be on the bottom (inlaid).
Often errors occur when installing the piston into the cylinder, even if a special clamp is used to tighten the rings on the piston. The peculiarity is as follows. When assembling the oil scraper ring, you should pay attention to the expander lock and the correctness of its docking. For clarity, see the image below. 
During compression of the rings on the piston, the lock of the oil scraper ring expander can jump out of the correct position and overlap, gathering in a spiral, so the plates fall through the expander and this will lead to scuffing of the cylinder walls and piston grooves. To avoid this, the tightening clamp should be positioned as shown in the image.
Differences between oil scraper rings and caps
Inexperienced car owners often confuse oil scraper rings with valve stem seals. In fact, these two elements perform the same important job in the engine - they protect the combustion chamber from excess oil. The oil seals themselves, or valve seals as they are also called, are located in the cylinder head and mounted on the valve bushings. Their job is to remove oil from the valve stems from the top of the cylinder head. Oil scraper seals Oil scraper rings are part of the piston rings and are installed on the pistons located in the engine cylinder block. Malfunctions When both oil scraper rings and valve seals wear out, increased waste of engine oil begins, the temperature rises and interruptions in the operation of the power plant occur. This is expressed in such malfunctions as: unstable engine starting; interruptions in cylinder operation; increase in engine temperature; decreased dynamics and power; increasing fuel consumption.
What to do if the oil scraper rings are stuck?
The occurrence of piston rings leads to loss of their mobility. This happens due to the accumulation of soot from burnt oil, which heavily clogs the grooves in the piston, which leads to sticking of the rings inside the “sockets”. In this case, the seals between the piston and cylinder are necessarily deteriorated. The engine loses compression without developing the required power, because the working mixture is not sufficiently compressed. By the way, it is for this same reason that the engine will not start adequately in cold weather, since the rings are clogged with coke.
What comes next? The first thing that will indicate problems with the engine is increased oil consumption. Oil scraper rings suffer from carbon deposits because they work like a scraper. Often, stuck piston rings occur during short trips within the city, when the engine does not have time to warm up.
Another reason for ring sticking is low-grade (fake) oil. The quality of the oil is a very important aspect, since whether there will be carbon deposits or not depends on the quality of the product. So, for example, if you use questionable oil, it will burn like margarine in a frying pan. Therefore, buy the oil that is recommended for your car by the manufacturer.
Cost of replacing rings and caps
The cost of replacing piston rings varies at bus stations and averages from 8,000 to 10,000 rubles or more, depending on the design of the engine and the complexity of the work, as well as the make of the car.
To replace the caps, the cost of work starts at an average of 3,000 rubles.