What is a piston and what does the piston group of an engine consist of? How does an internal combustion engine piston work? Operation of pistons in an engine.

The engine piston serves to convert chemical reaction fuel into the mechanical operation of the crankshaft. It operates under conditions of high temperature and pressure, therefore it is made of especially durable materials that can withstand such aggressive influences for a long time without changing its characteristics.

How does a piston work?

Externally, the piston is a cylinder consisting of elements such as:

Sealing belt;

Lugs;

Steel thermostatic insert.

Bottom

This part of the piston takes on the main thermal load and therefore has a fairly large thickness. The thicker the bottom, the lower its temperature heating, but the greater the mass of the piston itself. Typically, the thickness of the bottom is about 7-9 mm, for supercharged engines 11 mm, diesel 10-16 mm. Although, for example, on Honda models the thickness of the piston bottoms is 5.5-6 mm.

On some types of pistons, the bottom and the first groove for the compression ring are covered with a layer of cast iron for wear resistance, and hard anodizing is also used - converting a thin layer of aluminum into ceramic (0.008-0.012 mm). The coating strengthens the piston crown, reducing the risk of overheating and burnout.

Sealing belt

The part of the piston where the grooves for the piston rings are made.

Lugs

Serve to install the piston pin into the piston. On a number of pistons, the bosses may have ribs resulting from their cutting to the middle of the piston, so-called “coolers”, for uniform distribution of heat flow. Pistons with “refrigerators” have increased strength and rigidity, which is important for high-speed engines, especially supercharged ones.

Skirt

The guiding part of the piston, which serves to equalize the lateral forces when moving the piston at the top and bottom dead center. In modern pistons, the skirt has a slight narrowing towards the bottom, as does the sealing belt; such pistons have a barrel shape.

Thermostatic insert

It is located inside the skirt and, when heated, acts as a bimetal based on the difference in the expansion coefficients of steel and aluminum, preventing large expansion of the piston skirt.

Piston material

The pistons of all modern production car engines are made of aluminum alloy. Previously, cast iron pistons (gray and ductile iron) were installed on engines, which were subsequently replaced by pistons made of an alloy of aluminum and silicon, the share of which was about 12% -13%. The pistons were cast in a special mold - a chill mold.

The presence of silicon in the alloy made it possible to reduce piston wear, as well as reduce linear expansion, which made it possible to reduce the thermal gap of the piston in the cylinder.

As engines became more powerful, the requirements for piston reliability increased noticeably, and the proportion of silicon in the aluminum alloy was increased and rose to 18% and higher, this became especially important for diesel engines and supercharged engines. Such pistons are made by stamping.

To reduce the grinding time to the cylinder, tinning of low-melting metals such as tin, lead or tin-lead alloy (thickness 0.005-0.002 mm) is applied to the piston body.

Recently, pistons made of heat-resistant steels have also appeared, at the level of development and partial application. Steel pistons have less weight, but the structure itself is strong. Less weight is achieved by a thinner skirt thickness and a lower height from the bottom to the pin axis.

Due to the lower piston height at a normal block height, it becomes possible to install extended connecting rods, which reduces lateral loads in the piston-connecting rod friction pair.
However, such pistons have a number of disadvantages. This means higher processing costs and increased wear on the cylinder bore.

Principle of operation

When the mixture flashes in the combustion chamber, heat about 1800-2000 degrees, the energy released creates a lot of pressure on the piston head, forcing it to move down the cylinder body.

The piston through the connecting rod, in a reciprocating motion, transmits force to the crankshaft journal, causing the latter to rotate.

Piston malfunctions

Melting or burnout of the bottom;

Cracks in partitions between grooves;

Wear of grooves (large gap between groove and ring);

Cracks or deformation in the piston body;

Resource

This figure depends on various factors and can be 200-250-300 thousand km for domestic engines and 500-600 thousand kilometers or more for foreign cars.

Thus, failure to change the oil and filter in a timely manner causes the rings to lodge in the grooves of the piston, sharply worsening its cooling, as a result of overheating of the piston and the appearance of scuffs on its body.

The life of the piston is reduced by such faults as the development of a hole in the bosses for the connecting rod pin, as well as worn-out ones, when their height decreases and they begin to break the piston grooves.

Most often, problems with pistons are caused by the engine due to a failure of the thermostat, pump or depressurization of the cooling system, as well as a malfunction of the radiator cooling fan, the radiator itself or its sensor.

How to extend the life of pistons

In order for the pistons to reach their service life, it is recommended to use only the oil prescribed by the manufacturer and replace it strictly according to the regulations. If possible, do not reach the prescribed mileage of one two thousand and change the oil. Use fuel recommended by the manufacturer. engine before driving, especially in winter time. Monitor engine operating conditions to prevent overheating.

Rotary piston engine(RPD), or Wankel engine. Engine internal combustion, developed by Felix Wankel in 1957 in collaboration with Walter Freude. In a RPD, the function of a piston is performed by a three-vertex (triangular) rotor, which performs rotational movements inside a cavity of complex shape. After a wave of experimental automobiles and motorcycles in the 1960s and 1970s, interest in RPDs has waned, although a number of companies are still working to improve the Wankel engine design. Currently, Mazda passenger cars are equipped with RPD. The rotary piston engine is used in modeling.

Principle of operation

The force of gas pressure from the burnt fuel-air mixture drives a rotor mounted through bearings on an eccentric shaft. The movement of the rotor relative to the engine housing (stator) is carried out through a pair of gears, one of which, larger, is fixed on the inner surface of the rotor, the second, supporting, smaller, is rigidly attached to the inner surface of the side cover of the engine. The interaction of the gears leads to the fact that the rotor makes circular eccentric movements, touching the edges with the inner surface of the combustion chamber. As a result, three isolated chambers of variable volume are formed between the rotor and the engine body, in which the processes of compression of the fuel-air mixture, its combustion, expansion of gases that exert pressure on the working surface of the rotor, and purification of the combustion chamber from exhaust gases occur. The rotational movement of the rotor is transmitted to an eccentric shaft mounted on bearings and transmitting torque to the transmission mechanisms. Thus, two mechanical pairs operate simultaneously in the RPD: the first one regulates the movement of the rotor and consists of a pair of gears; and the second is transformative Roundabout Circulation rotor into rotation of the eccentric shaft. The gear ratio of the rotor and stator gears is 2:3, so in one full revolution of the eccentric shaft the rotor manages to rotate 120 degrees. In turn, for one full revolution of the rotor in each of the three chambers formed by its faces, a full four-stroke cycle of the internal combustion engine is performed.
RPD diagram
1 - inlet window; 2 outlet window; 3 - body; 4 - combustion chamber; 5 – fixed gear; 6 - rotor; 7 – gear; 8 - shaft; 9 – spark plug

Advantages of RPD

The main advantage of a rotary piston engine is its simplicity of design. The RPD has 35-40 percent fewer parts than a four-stroke piston engine. The RPD does not have pistons, connecting rods, crankshaft. In the “classic” version of the RPD there is no gas distribution mechanism. The fuel-air mixture enters the working cavity of the engine through the inlet window, which opens the edge of the rotor. Exhaust gases are ejected through an exhaust port, which again intersects the edge of the rotor (this resembles the gas distribution device of a two-stroke piston engine).
The lubrication system deserves special mention, which is practically absent in the simplest version of the RPD. Oil is added to the fuel - as when operating two-stroke motorcycle engines. Lubrication of friction pairs (primarily the rotor and the working surface of the combustion chamber) is carried out by the fuel-air mixture itself.
Since the mass of the rotor is small and is easily balanced by the mass of the counterweights of the eccentric shaft, the RPD is characterized by a low level of vibration and good uniformity of operation. In cars with RPD, it is easier to balance the engine, achieving a minimum level of vibration, which has a good effect on the comfort of the car as a whole. Twin-rotor engines are particularly smooth, in which the rotors themselves act as vibration-reducing balancers.
Another attractive quality of the RPD is its high power density at high speeds of the eccentric shaft. This makes it possible to achieve excellent speed characteristics from a vehicle with RPD with relatively low fuel consumption. Low rotor inertia and increased specific power compared to piston internal combustion engines make it possible to improve vehicle dynamics.
Finally, an important advantage of the RPD is its small size. A rotary engine is approximately half the size of a four-stroke piston engine of the same power. And this allows you to more rationally use the space of the engine compartment, more accurately calculate the location of transmission components and the load on the front and rear axles.

Disadvantages of RPD

The main disadvantage of a rotary piston engine is the low efficiency of sealing the gap between the rotor and the combustion chamber. The RPD rotor, which has a complex shape, requires reliable seals not only along the faces (and there are four of them for each surface - two on the apical faces, two on the side faces), but also on the side surface in contact with the engine covers. In this case, the seals are made in the form of spring-loaded strips of high-alloy steel with particularly precise processing of both working surfaces and ends. The tolerances built into the design of the seals for metal expansion from heating worsen their characteristics - it is almost impossible to avoid gas breakthrough at the end sections of the sealing plates (in piston engines they use a labyrinth effect, installing sealing rings with gaps in different directions).
In recent years, seal reliability has increased dramatically. Designers have found new materials for seals. However, there is no need to talk about any breakthrough yet. Seals still remain the bottleneck of RPD.
The complex rotor seal system requires effective lubrication of the rubbing surfaces. RPM consumes more oil than a four-stroke piston engine (from 400 grams to 1 kilogram per 1000 kilometers). In this case, the oil burns along with the fuel, which has a bad effect on the environmental friendliness of the engines. There are more substances hazardous to human health in the exhaust gases of RPDs than in the exhaust gases of piston engines.
Special requirements are also imposed on the quality of oils used in RPD. This is due, firstly, to a tendency to increased wear (due to the large area of ​​contacting parts - the rotor and the internal chamber of the engine), and secondly, to overheating (again due to increased friction and due to the small size of the engine itself ). Irregular oil changes are deadly for RPDs - since abrasive particles in old oil dramatically increase engine wear and engine overcooling. Starting a cold engine and insufficiently warming it up lead to the fact that there is little lubrication in the contact area of ​​the rotor seals with the surface of the combustion chamber and side covers. If a piston engine jams when overheated, then the RPD most often occurs when starting a cold engine (or when driving in cold weather when cooling is excessive).
Generally working temperature ROP is higher than that of piston engines. The most thermally stressed area is the combustion chamber, which has a small volume and, accordingly, an increased temperature, which makes it difficult to ignite the fuel-air mixture (RPDs, due to the extended shape of the combustion chamber, are prone to detonation, which can also be attributed to the disadvantages of this type of engine). Hence the RPD’s demands on the quality of candles. They are usually installed in these engines in pairs.
Rotary piston engines, despite their excellent power and speed characteristics, turn out to be less flexible (or less elastic) than piston engines. They produce optimal power only at fairly high speeds, which forces designers to use RPDs in conjunction with multi-stage gearboxes and complicates the design automatic boxes transmission Ultimately, RPDs turn out to be not as economical as they should be in theory.

Practical application in the automotive industry

RPDs became most widespread in the late 60s and early 70s of the last century, when the patent for the Wankel engine was purchased by 11 leading automakers in the world.
In 1967, the German company NSU released a serial a car business class NSU Ro 80. This model was produced for 10 years and sold around the world in the amount of 37,204 copies. The car was popular, but the shortcomings of the RPD installed in it ultimately ruined the reputation of this wonderful car. Compared to long-lasting competitors, the NSU Ro 80 model looked “pale” - mileage up to overhaul engine with a declared 100 thousand kilometers did not exceed 50 thousand.
Citroen, Mazda, and VAZ have experimented with RPD. Best of luck achieved by Mazda, which released its passenger car with RPD back in 1963, four years earlier than the appearance of the NSU Ro 80. Today, the Mazda concern equips RX series sports cars with RPD. Modern cars The Mazda RX-8 is spared many of the shortcomings of the Felix Wankel RPD. They are quite environmentally friendly and reliable, although they are considered “capricious” among car owners and repair specialists.

Practical application in the motorcycle industry

In the 70s and 80s, some motorcycle manufacturers experimented with RPD - Hercules, Suzuki and others. Currently, small-scale production of “rotary” motorcycles is established only in the Norton company, which produces the NRV588 model and is preparing the NRV700 motorcycle for serial production.
Norton NRV588 is a sports bike equipped with a twin-rotor engine with a total volume of 588 cubic centimeters and developing a power of 170 Horse power. With a dry motorcycle weight of 130 kg, the power supply of a sportbike looks literally prohibitive. The engine of this car is equipped with variable intake tract and electronic fuel injection systems. All that is known about the NRV700 model is that the RPM power of this sportbike will reach 210 hp.

In the cylinder-piston group (CPG), one of the main processes occurs, due to which the internal combustion engine functions: the release of energy as a result of combustion of the air-fuel mixture, which is subsequently converted into a mechanical action - rotation of the crankshaft. The main working component of the CPG is the piston. Thanks to it, the conditions necessary for combustion of the mixture are created. The piston is the first component involved in converting the energy received.

The engine piston is cylindrical in shape. It is located in the engine cylinder liner, it is a moving element - during operation it performs reciprocating movements, due to which the piston performs two functions.

1. During translational movement, the piston reduces the volume of the combustion chamber, compressing the fuel mixture, which is necessary for the combustion process (in diesel engines, ignition of the mixture occurs due to its strong compression).
2. After the air-fuel mixture is ignited, the pressure in the combustion chamber increases sharply. In an effort to increase volume, it pushes the piston back, and it makes a return movement that is transmitted through the connecting rod to the crankshaft.

DESIGN

The design of the part includes three components:

1. Bottom.
2. Sealing part.
3. Skirt.

These components are available both in solid-cast pistons (the most common option) and in composite parts.

BOTTOM

Bottom - main working surface, since it, the walls of the liner and the head of the block form the combustion chamber in which the combustion of the fuel mixture occurs.

The main parameter of the bottom is the shape, which depends on the type of internal combustion engine (ICE) and its design features.

Two-stroke engines use pistons with a spherical bottom - a protrusion of the bottom, this increases the efficiency of filling the combustion chamber with the mixture and removing exhaust gases.

In four-stroke gasoline engines the bottom is flat or concave. Additionally, technical recesses are made on the surface - recesses for valve plates (eliminate the likelihood of a piston colliding with the valve), recesses to improve mixture formation.

In diesel engines, the recesses in the bottom are the largest and have different shapes. These recesses are called the piston combustion chamber and are designed to create turbulence as air and fuel enter the cylinder to ensure better mixing.

The sealing part is designed to install special rings (compression and oil scraper), the task of which is to eliminate the gap between the piston and the liner wall, preventing the breakthrough of working gases into the sub-piston space and lubricants into the combustion chamber (these factors reduce the efficiency of the motor). This ensures heat transfer from the piston to the liner.

SEALING PART

The sealing part includes grooves in the cylindrical surface of the piston - grooves located behind the bottom, and bridges between the grooves. In two-stroke engines, special inserts are additionally placed in the grooves, into which the ring locks rest. These inserts are necessary to eliminate the possibility of the rings turning and their locks getting into the intake and exhaust windows, which can cause their destruction.


The bridge from the edge of the bottom to the first ring is called the fire belt. This belt takes on the greatest temperature impact, so its height is selected based on the operating conditions created inside the combustion chamber and the material used to make the piston.

The number of grooves made on the sealing part corresponds to the number of piston rings (and 2 to 6 of them can be used). The most common design is with three rings - two compression and one oil scraper.

In the groove under the oil scraper ring, holes are made to allow oil to drain, which is removed by the ring from the liner wall.

Together with the bottom, the sealing part forms the piston head.

SKIRT

The skirt acts as a guide for the piston, preventing it from changing position relative to the cylinder and providing only reciprocating movement of the part. Thanks to this component, a movable connection is made between the piston and the connecting rod.

For connection, holes are made in the skirt to install the piston pin. To increase strength at the finger contact point, with inside The skirts are made of special massive extensions called bosses.

To fix the piston pin in the piston, grooves for retaining rings are provided in the mounting holes for it.

TYPES OF PISTONS

In internal combustion engines, two types of pistons are used, differing in design - solid and composite.

Solid parts are manufactured by casting followed by machining. The metal casting process creates a blank that is given the overall shape of the part. Next, on metalworking machines, the working surfaces in the resulting workpiece are processed, grooves are cut for rings, technological holes and recesses are made.

In the component parts, the head and skirt are separated, and they are assembled into a single structure during installation on the engine. Moreover, assembly into one part is carried out by connecting the piston to the connecting rod. For this purpose, in addition to the holes for the piston pin in the skirt, there are special eyes on the head.

The advantage of composite pistons is the ability to combine manufacturing materials, which improves the performance of the part.

MATERIALS OF MANUFACTURE

Aluminum alloys are used as manufacturing materials for solid-cast pistons. Parts made from such alloys are characterized by low weight and good thermal conductivity. But at the same time, aluminum is not a high-strength and heat-resistant material, which limits the use of pistons made from it.

Cast pistons are also made from cast iron. This material is durable and resistant to high temperatures. Their disadvantage is their significant mass and poor thermal conductivity, which leads to strong heating of the pistons during engine operation. Because of this, they are not used on gasoline engines, since high temperatures cause glow ignition (the fuel-air mixture ignites from contact with heated surfaces, and not from a spark plug).

The design of composite pistons allows the above materials to be combined with each other. In such elements, the skirt is made of aluminum alloys, which ensures good thermal conductivity, and the head is made of heat-resistant steel or cast iron.

But elements of the composite type also have disadvantages, including:

• Can only be used in diesel engines;
• greater weight compared to cast aluminum;
• the need to use piston rings made of heat-resistant materials;
• higher price;

Due to these features, the scope of use of composite pistons is limited; they are used only on large-sized diesel engines.

VIDEO: PISTON. PRINCIPLE OF OPERATION OF THE ENGINE PISTON. DEVICE

In the cylinder-piston group (CPG), one of the main processes occurs, due to which the internal combustion engine functions: the release of energy as a result of combustion of the air-fuel mixture, which is subsequently converted into a mechanical action - rotation of the crankshaft. The main working component of the CPG is the piston. Thanks to it, the conditions necessary for combustion of the mixture are created. The piston is the first component involved in converting the resulting energy.

The engine piston is cylindrical in shape. It is located in the engine cylinder liner, it is a moving element - during operation it performs reciprocating movements and performs two functions.

1. During translational movement, the piston reduces the volume of the combustion chamber, compressing the fuel mixture, which is necessary for the combustion process (in diesel engines, ignition of the mixture occurs due to its strong compression).
2. After the air-fuel mixture is ignited, the pressure in the combustion chamber increases sharply. In an effort to increase volume, it pushes the piston back, and it makes a return movement that is transmitted through the connecting rod to the crankshaft.

What is a piston in an internal combustion engine?

The design of the part includes three components:

1. Bottom.
2. Sealing part.
3. Skirt.

These components are available both in solid-cast pistons (the most common option) and in composite parts.

Bottom

The bottom is the main working surface, since it, the walls of the liner and the head of the block form the combustion chamber in which the fuel mixture is burned.

The main parameter of the bottom is the shape, which depends on the type of internal combustion engine (ICE) and its design features.

Two-stroke engines use pistons with a spherical bottom - a protrusion of the bottom, this increases the efficiency of filling the combustion chamber with the mixture and removing exhaust gases.

In four-stroke gasoline engines, the bottom is flat or concave. Additionally, technical recesses are made on the surface - recesses for valve plates (eliminate the likelihood of a piston colliding with the valve), recesses to improve mixture formation.

In diesel engines, the recesses in the bottom are the largest and have different shapes. These recesses are called the piston combustion chamber and are designed to create turbulence as air and fuel enter the cylinder to ensure better mixing.

The sealing part is designed to install special rings (compression and oil scraper), the task of which is to eliminate the gap between the piston and the liner wall, preventing the breakthrough of working gases into the sub-piston space and lubricants into the combustion chamber (these factors reduce the efficiency of the motor). This ensures heat transfer from the piston to the liner.

Sealing part

The sealing part includes grooves in the cylindrical surface of the piston - grooves located behind the bottom, and bridges between the grooves. In two-stroke engines, special inserts are additionally placed in the grooves, into which the ring locks rest. These inserts are necessary to eliminate the possibility of the rings turning and their locks getting into the intake and exhaust windows, which can cause their destruction.


The bridge from the edge of the bottom to the first ring is called the fire belt. This belt takes on the greatest temperature impact, so its height is selected based on the operating conditions created inside the combustion chamber and the material used to make the piston.

The number of grooves made on the sealing part corresponds to the number of piston rings (and 2 - 6 of them can be used). The most common design is with three rings - two compression and one oil scraper.

In the groove under the oil scraper ring, holes are made to allow oil to drain, which is removed by the ring from the liner wall.

Together with the bottom, the sealing part forms the piston head.

You will also be interested in:

Skirt

The skirt acts as a guide for the piston, preventing it from changing position relative to the cylinder and providing only reciprocating movement of the part. Thanks to this component, a movable connection is made between the piston and the connecting rod.

For connection, holes are made in the skirt to install the piston pin. To increase the strength at the point of contact of the finger, special massive bulges called bosses are made on the inside of the skirt.

To fix the pin in the piston, grooves for retaining rings are provided in the mounting holes for it.

Piston types

In internal combustion engines, two types of pistons are used, differing in design - solid and composite.

Solid parts are manufactured by casting followed by machining. The metal casting process creates a blank that is given the overall shape of the part. Next, on metalworking machines, the working surfaces in the resulting workpiece are processed, grooves are cut for rings, technological holes and recesses are made.

In the component parts, the head and skirt are separated, and they are assembled into a single structure during installation on the engine. Moreover, assembly into one part is carried out by connecting the piston to the connecting rod. For this purpose, in addition to the finger holes in the skirt, there are special eyes on the head.

The advantage of composite pistons is the ability to combine manufacturing materials, which improves the performance of the part.

Manufacturing materials

Aluminum alloys are used as manufacturing materials for solid-cast pistons. Parts made from such alloys are characterized by low weight and good thermal conductivity. But at the same time, aluminum is not a high-strength and heat-resistant material, which limits the use of pistons made from it.

Cast pistons are also made from cast iron. This material is durable and resistant to high temperatures. Their disadvantage is their significant mass and poor thermal conductivity, which leads to strong heating of the pistons during engine operation. Because of this, they are not used on gasoline engines, since high temperatures cause glow ignition (the fuel-air mixture ignites from contact with heated surfaces, and not from a spark plug).

The design of composite pistons allows the above materials to be combined with each other. In such elements, the skirt is made of aluminum alloys, which ensures good thermal conductivity, and the head is made of heat-resistant steel or cast iron.

But elements of the composite type also have disadvantages, including:

• Can only be used in diesel engines;
• greater weight compared to cast aluminum;
• the need to use piston rings made of heat-resistant materials;
• higher price;

Due to these features, the scope of use of composite pistons is limited; they are used only on large-sized diesel engines.

Video: The principle of operation of the engine piston. Device

Piston is one of the parts of the engine crank mechanism and is an integral element conventionally divided into a head and a skirt. It is the basis of the process of converting fuel combustion energy into thermal energy, and then into mechanical energy. The performance of the engine, as well as its reliability and durability, directly depends on the quality of this part.

Purpose and types of pistons

In an engine, the engine piston performs a number of functions, in particular:

1. transformation of gas pressure into force transmitted to the connecting rod;
2. ensuring the tightness of the combustion chamber;
3. heat sink

The piston operates in extreme conditions under consistently high mechanical loads. Therefore, for modern engines they are made from special aluminum alloys, which are lightweight and durable with sufficient heat resistance. Steel pistons are somewhat less common. Previously, they were mainly made from cast iron. The piston markings that are necessarily present on each product will tell you what it is made of. These parts are made by two methods - casting and stamping. Forged pistons, common in tuning, are made by stamping rather than hand-forged.

Piston design

The piston design is not complicated. This is a solid part, which, for ease of definition, is conventionally divided into a skirt and a head. Specific form and design features The pistons are determined by the engine type and model. In common types of gasoline internal combustion engines, you can only see pistons with flat heads or heads that are extremely close to this shape. They often have grooves designed to allow the valves to open as fully as possible. In engines with direct fuel injection, the pistons are made in a slightly more complex form. Piston diesel engine has a head with a specific configuration to ensure optimal swirling for high-quality mixture formation.

Engine piston diagram.

Under the head there are grooves on the piston into which the piston rings are installed. The skirts of different pistons are also different: with a shape similar to a cone or barrel. This configuration makes it possible to compensate for the expansion of the piston that occurs when it heats up during operation. It should be noted that the piston acquires its full working volume only after the engine has warmed up to normal temperature.

To minimize the effect of constant lateral friction of the piston on the cylinder, a special anti-friction material is applied to its side surface, the type of which also depends on the type of engine. Also in the piston skirt there are special holes with bosses intended for mounting the piston pin.

The operation of the piston involves intense heating. It is cooled, and in different motors in different ways. Here are the most common ones:

• by supplying oil mist into the cylinder;
• through oil splashing through a connecting rod or a special nozzle;
• through oil injection through an annular channel;
• using constant circulation of oil through a coil located directly in the piston head.

It is not the piston itself that comes into close contact with the cylinder walls, but its rings. To ensure the highest wear resistance, they are made from a special type of cast iron. The number and exact location of these rings depends on the type of motor. Most often, the piston has a pair of compression rings and another oil scraper ring.

Compression rings are designed to prevent gases from the combustion chamber from breaking into the crankcase. The first ring bears the heaviest load, therefore, in all diesel and powerful gasoline engines, a steel insert is additionally present in the groove of the first ring, which increases the strength of the structure. There are many types of compression rings, which are unique to almost every independent manufacturer.

Oil scraper rings- to remove excess oil from the cylinder and prevent it from entering the combustion chamber. Such rings are made with a large number of drainage holes, as well as with spring expanders, although not in all engine models.

Piston device

The engine piston is connected to the connecting rod through a piston pin, a tubular steel part. The most common method of attaching a pin is a floating one, thanks to which the part can be rotated during operation. Special locking rings prevent the pin from moving to the sides. Hard finger hooking is practically not common at the moment due to the obvious greater vulnerability of such structures.

Breakage of the piston and related parts

During intensive or simply prolonged use, the piston may fail due to the presence of a foreign body in the cylinder, which the piston constantly bumps into during movement. Such an object could be a particle of a connecting rod, or something else flying away from the part. The surfaces of such a fracture are gray in color and are not characterized by abrasion, cracks or other visual signs. The piston disintegrates quickly and suddenly.

A fracture caused by metal fatigue is characterized by the formation of raster lines in the problem area. This allows you to determine in advance whether there is a breakdown and replace the piston. In addition to aging, the cause of such a fracture can be detonation ignition, increased piston shaking due to the collision of its head with the cylinder head, or excessive skirt clearance. In any case, cracks form on the part, indicating its imminent failure.

After ring wear, damage to the piston head is the most common.

In addition to wear and tear of the metal, piston-related failures can occur for a variety of reasons, including:

• violation of the combustion mode, for example due to ignition delay;
• improper organization of starting a cold engine;
• filling the cylinder with oil or water with the engine off, which is called;
• unreasonable increase in power as a result of electronics reconfiguration;
• use of unsuitable parts;
• other reasons.

Most often, repairs are carried out by replacing the piston, rings or the entire piston group.

Related terms