Principle of operation of the OI. What is the engine of the car and how it works from which parts the engine consists

(Internal combustion engine) is a heat machine and works on the basis of burning fuel and air mixture in the combustion chamber. The main task of such a device is the conversion of fuel charge combustion energy into mechanical useful operation.

In spite of general principle Actions, today there are a large number of aggregates that differ significantly from each other thanks to a number of individual design features. In this article we will talk about what is internal combustion engines, as well as consist of their main features and differences.

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Types of internal combustion engines

Let's start with the fact that the engine can be a two-stroke and four-stroke. As for automotive engines, the specified four-stroke units. Engine work clocks are:

• inlet of fuel mixture or air (which depends on type of DVS);
• compression mixture of fuel and air;
• combustion of fuel charge and workforce;
• release from the combustion chamber of exhaust gases;

According to this principle, both gasoline and diesel piston motors, which have been widely used in cars and on other techniques. It is also worth mentioning and, in which gas fuel is burned similarly to diesel fuel or gasoline.

Gasoline power units

Such a power system, especially distributed injection, allows you to increase the power of the motor, while achieving fuel efficiency and a decrease in the toxicity of the exhaust gases is reached. This became possible due to the accurate dosage of fuel supplied under control (electronic engine control system).

Further development of fuel feed systems led to the emergence of motors with direct (immediate) injection. Their main difference from the predecessors is that air and fuel are fed to the combustion chamber separately. In other words, the nozzle is not installed on the inlet valves, but is mounted directly into the cylinder.

A similar solution allows the supply of fuel directly, and the feed itself is divided into several stages (sidewalls). As a result, it is possible to achieve the most efficient and complete combustion of the fuel charge, the engine is able to work on a poor mixture (for example, Motors of the GDI family), fuel consumption drops, exhaust toxicity decreases, etc.

Diesel motors

Works on a dieselopliva, as well as largely different from gasoline. The main difference lies in the absence of a spark ignition system. The ignition of the mixture of fuel and air in the diesel is derived from compression.

If simply, first the air is compressed in the cylinders, which is very heated. At the last moment there is injection directly into the combustion chamber, after which the heated and strongly compressed mixture flames itself.

If you compare diesel and gasoline вс, diesel is characterized by a higher efficiency, the best efficiency and maximum, which is available on low revs. Given that diesel engines develop more traction with smaller crankshaft turnover, in practice such a motor does not need to be "twist" at the start, and you can also count on confident pickup from the very "bottoms".

However, the list of minuses of such aggregates can be distinguished, as well as greater weight and lower speeds in the mode of maximum revolutions. The fact is that diesel originally "slow" and has a smaller speed of rotation compared to gasoline engine.

Diesels are also distinguished by a greater mass, since the features of ignition from compression involve more serious loads on all elements of such an aggregate. In other words, the details in the diesel engine are stronger and heavy. Also diesel motors are more noisy, due to the process of ignition and combustion of diesel fuel.

Rotary engine

Vankel engine ( rotary-piston engine) is fundamentally different power installation. In such an economy, the usual pistons, which make reciprocating movements in the cylinder, are simply missing. The main element of the rotor motor is the rotor.

The specified rotor rotates on a given trajectory. Rotary DVS gasoline, as a similar design is not able to provide a high degree of compression of the working mixture.

The advantages include compactness, greater power with a minor working volume, as well as the ability to quickly unwind up to high revolutions. As a result, cars with such an engine have outstanding acceleration characteristics.

If we talk about minuses, it is worth highlighting a noticeable reduced resource compared with piston units, as well as high flow Fuel. Also rotary engine It is distinguished by increased toxicity, that is, it does not quite fit into modern environmental standards.

Hybrid engine

On one-time engine, it is used to obtain the necessary power in a complex with turbocharged, whereas there are no such solutions on others with exactly the same working volume and layout.

For this reason, for an objective assessment of the performance of a different engine on different revs, not on the crankshaft, but on wheels, it is necessary to carry out special complex measurements on a dynamometer stand.

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DVS - This is an engine operating on the basis of burning various fuels directly within the aggregate itself. Unlike other types of engines, the internal combustion engine is deprived: any elements of transmitting heat for further conversion into mechanical energy, the transformation comes directly from fuel combustion; significantly more compact; have low weight relative to the units of another type with comparable power; require the use of certain fuel with the rigid characteristics of the combustion temperature, degree of evaporation, octane number etc.

Four-stroke engines are used in the automotive:

1. Inlet;

2. Compression;

3. Workforce;

4. Release.
But there are two-stroke versions of internal combustion engines, but in modern worldThey have limited use.

This article will consider only the motors that are installed on cars.

Varieties of engines for used fuel

Gasoline motorsAs it is clear from the name is used as fuel for work - gasoline with different octane numbers, and have a forced ignition system fuel mixes With the help of an electrical spark.

Can be divided by the type of intake on carburetor and injection. Carburetor motors are already disappearing from production due to the complexity in the exact setting, high consumption of gasoline, ineffectiveness of mixing the fuel mixture and inconsistencies with modern rigid environmental requirements. In such motors, mixing combustible mixture Starts in the chambers of the carburetor and ends on the way in the intake manifold.

Injector aggregates are developing in large pace, and the fuel injection system is improving each generation. The first injectors had "MonovPronsk" with a single nozzle. In fact, it was the modernization of carburetor motors. Over time, on most aggregates, systems with separate nozzles for each cylinder began to be used. The use of nozzles in the inlet system made it possible to more accurately control the proportions of fuel and air in different modes of the unit operation, reduce fuel consumption, increase the quality of the fuel mixture, increase the power and environmental friendliness of power units.

Modern nozzles installed on power units with system direct injection Fuel into cylinders, capable of producing several separate fuel injections for one tact. This allows you to still improve the quality of the fuel mixture and seek the maximum return of energy from the amount of gasoline used. That is, the savings and productivity of motors increased even more.

Diesel units - use the principle of ignition of a mixture of diesel fuel and air when heated from strong compression. At the same time, the forced ignition systems are not used in diesel units. These motors have a number of advantages over the gasoline, primarily this is the economy of fuel (up to 20%), with comparative power. The fuel is less consumed due to a greater degree of compression in the cylinders, which improves the combustion characteristics and the rate of energy of the fuel mixture, and therefore, the fuel needs less to achieve the same results. In addition, diesel units do not use throttle valvesthat improves air intake in the power unit, which still reduces fuel consumption. Diesels develop a greater torque, and at lower revs crankshaft.

Not without flaws. Due to the increased load on the walls of the cylinders, the designers had to use more reliable materials, and increase the size of the design (weight gain and the rise in price). In addition, the work of diesel power aggregate - Loud due to the features of fuel ignition. And the increased weight of the parts does not allow the motor to develop high revs at the same speed as gasoline, and the maximum value of the crankshaft revolutions is lower than that of gasoline units.

DVS variation in design

Hybrid power aggregate

This type of car began to gain popularity in recent years. Due to its efficiency of fuel economy and an increase in the total capacity of the car due to the combination of two types of aggregates. In fact, this design is two separate aggregates - small internal combustion engine (most often diesel) and electric motor (or several electric motors) with rechargeable battery Large tank.

The advantages of combination are expressed in the ability to combine the energy of two aggregates during acceleration, or the use of each type of engine separately, depending on the need. For example, when moving in a city traffic jam - only an electric motor, saving diesel fuel. When driving around the country roads, an internal engine works, like a more hardy, powerful and with a large stock of the aggregate.

At the same time, a special battery for electric motors can be recharged from the generator, or using the recovery system when braking, which allows you to save not only fuel, but also electricity required to charge the battery.

Rotary-piston motor

The rotary-piston motor is constructed by a unique pattern of the movement of the piston-rotor, which moves inside the cylinder not by the reciprocating trajectory, but around its axis. This is carried out due to the special triangular piston design and the special location of intake and outlet holes in the cylinder.

Thanks to such a design, the engine quickly gains momentum, which increases the dynamic characteristics of the car. But with the development of the classic DVS design, the Vankel engine began to lose their relevance due to constructive limitations. The principle of the movement of the piston does not allow to achieve a large degree of compression of the fuel mixture, which eliminates the use of diesel fuel. And the small resource, the complexity of service and repair, as well as weak environmental indicators do not allow automakers to develop this direction.

Varieties of strength assemblies on the layout

Due to the need to reduce weight and dimensions, as well as, the placement of a larger number of pistons in one unit led to the appearance of models for the layout.

Row motors

An inline engine is the most classic version of the power unit. In which all pistons and cylinders are located in one row. Wherein, modern motors With row layout, contain no more than six cylinders. But it is six-cylinder row engines that have the best indicators for balancing vibration during operation. The only minus is a significant engine length, relative to other layouts.

V-shaped motors

These motors appeared due to the desires of the designers to reduce the dimensions of the engines, and the need to place more than six pistons in one block. In these motors, cylinders are in different planes. Visually, the location of the cylinders forms the letter "V", from where and the name went. The angle between the two rows is called the corner of the collapse, and varies in a wide range, dividing this type of motors to the subgroups.

Opposite motors

Opposite engines, obtained the maximum corner of the collapse of 180 degrees. What allowed the designers to reduce the height of the unit to the minimum sizes, and distribute the load on the crankshaft, increasing its resource.

VR Motors

This is a combination of the properties of inline and V-shaped aggregates. The angle of collapse in such engines reaches 15 degrees, which allows you to use one head block cylinders with a single gas distribution mechanism.

W-shaped motors

Some of the most powerful and "extreme" KBS designs. There may be three rows of cylinders with a large collapse angle, or two combined VR blocks. To date, the spreads received motors for eight and twelve cylinders, but the design allows you to use more cylinders.

Internal combustion engine characteristics

Viewing a lot of information about various cars, any interested person will see certain basic motor parameters:

Power of the power unit measured in hp (or kw * h);

Maximum torque developed by a power unit measured in n / m;

Most car enthusiasts are separated by power units, only in power. But this separation is not quite correct. Of course, the aggregate in 200 "horses", preferred engine In 100 "horses" on a heavy crossover. And for easy urban hatchback, there is enough 100 strong motor. But there are some nuances.

The maximum power specified in the technical documentation is achieved with certain circulation of crankshaft. But using a car in urban environments, the driver rarely spins the motor above 2,500 revolutions per minute. Therefore, larger operation of the machine, only part of potential power is involved.

But often, there are cases on the road. When it is necessary to dramatically increase the speed for overtaking, or to care from the emergency. It is the maximum torque that affects the unit's ability to quickly dial the required turnover and power. If you say easier, the torque affects the car dynamics.

It is worth noting a small difference between gasoline and diesel engines. The engine operating on gasoline - gives the maximum torque when turnover of the crankshaft from 3,500 to 6,000 per minute, and diesel engines can reach maximum parameters at lower revs. Therefore, it seems to many. That diesel units are more powerful and better "pull". But, most of the most powerful aggregates use gasoline fuel, as they are able to develop a larger number of revolutions per minute.

And for a detailed understanding of the term, the torque, you should look at the units of it: Newtons multiplied by meters. In other words, the torque determines the force with which the piston presses on the crankshaft, and in turn transmits power to the gearbox, and ultimately - on the wheels.

Also, it is possible to mention a powerful technique, which has a maximum torque can be achieved when turnover of 1,500 per minute. Basically, these are tractors, powerful dump trucks, and some diesel all-terrain vehicles. Naturally, such machines do not need to spin the motor to maximum revolutions.

Based on the information given, it can be concluded that the torque depends on the volume of the power unit, its dimensions, the size of the parts and their weight. The harder all these elements, the more prevailing the torque at low revs. Diesel units have a larger torque and smaller crankshaft revolutions (the large inertness of heavy crankshaft and other elements do not allow the development of large revolutions).

Motor power

It is worth recognizing that power and torque are interconnected parameters that depend on each other. Power is a certain amount of work produced by the engine during the time. In turn, the operation of the motor is torque. Therefore, power is characterized as the amount of torque per unit of time.

There is a known formula that characterizes the ratio of power and torque:

Power \u003d torque * Turns per minute / 9549

As a result, we obtain the value of the power in kilowatts. But naturally, looking through the characteristics of cars, we are familiar to see the indicators in "LS". For the translation of Kilowatt in L.S. You must multiply the resulting value by 1.36.

Output

As it became clear from this article, automotive internal combustion engines may have many differences from each other. And choosing a car for permanent use - it is necessary to study all the nuances of the structure, characteristics, economy, environmental friendliness, power and reliability of the power unit. Also, it will be useful to explore the information on engine maintainability. Since many modern aggregates use complex gas distribution systems, fuel injection and exhaust, which may complicate their repair.

Machine components Machine engine:

Cylinder and Carter, protected by a bottom of the pallet;

Piston with compression rings, located inside the cylinder;

The crankshaft, which moves in the root bearings of the crankcase.

The elements of the crankshaft: native cervices, cheeks and rod cervicals. With the help of a cylinder, piston, connecting rod and crankshaft, a crank-connecting mechanism leads to the movement of the pistons, as a result of which the crankshaft rotation occurs.

On top of the cylinders installed a block of the head with valves. Their opening and closing is technically coordinated with the rotation of the crankshaft, which leads to a consistent movement of the piston.

The piston moves to the upper end point (NTT) and the lower end point (NMT).

With the engine running engine, the piston moves without stopping from NTC to NMT due to the flywheel in the form of a disc and a tightly press-tightly metal crown with teeth of the rim.

Why does the engine work?

The operation of the engine is based on the fact that when the fuel is supplied to the combustion chamber in the VMT position, the spark is fed from the candle and a mini-explosion of fuel is fed. At the same time, the pressure of explosive gases pushes the piston to the NMT. In this process, all the pistons of the engine are used alternately, which lead the crankshaft crankshaft mechanism in motion, which allows the car to move.

For constant and correct operation of the engine, it is necessary to inlet valve Periodically received new portions of air and fuel through the nozzles. Exhaust gases, after their combustion, pushed out of the combustion chamber through the exhaust valve. For this corresponds to the mechanism of car distribution and fuel injection system.

Purpose of systems and automotive engine mechanisms

crank mechanism - leads to the reciprocating movement of the pistons, which entails the rotation of the crankshaft.

Fuel supply system - Serves for the dosed injection fuel in the car engine.

Gas distribution mechanism - responsible for the timely inlet and the release of exhaust gases in the engine.

Ignition system - It serves to supply an intermittent electrotock signal over high voltage circuits for spark plugs, as a result of which the spark is formed in the engine combustion chamber and flammable combustible mixture.

Cooling system - Protects the engine from overheating by means of a mechanical (oncoming air flow) or static inclusion of the forced blowing engine with an impeller located in close proximity to the radiator.

Lubrication system - Provides oil supply over maslochanals to moving and rubbing mechanisms in order to reduce their wear. The oil system includes a pallet with butter, pump, fine and coarse cleaning filters, and oil valves and oil valves.

Also, the car is equipped with a starting device consisting of a battery, starter, ignition lock and other instruments of control, control and supply of the vehicle.

You can ask your questions on the topic of the submitted article, leaving your comment at the bottom of the page. Deputy General Director Driving School "Mustang" on Academic Work Teacher of Higher School, Candidate of Technical Sciences Kuznetsov Yuri Aleksandrovich

Part 1. Engine and its mechanisms

The engine is a source of mechanical energy.

On the overwhelming majority of cars, an internal combustion engine is used.

Internal combustion engine is a device in which the chemical energy of fuel turns into useful mechanical work.

Automotive internal combustion engines are classified:

By the nature of the fuel used:

Light liquid (gas, gasoline),

Heavy liquid (diesel fuel).

Gasoline engines

Gasoline carburetor.Fuel mixture with air Preparing B.carburetor or in the intake manifold with the help of spraying nozzles (mechanical or electrical), then the mixture is supplied to the cylinder, compressing, and then sets up with a spark that skipping between the electrodescandles .

Injector gasoline Mixing formation occurs by the injection of gasoline in the intake manifold or directly into the cylinder with sprayinginjectors ( injector s). There are systems of single-point and distributed injection of various mechanical and electronic systems. IN mechanical systems The injection of fuel delivery is carried out by a plunger-lever mechanism with the possibility of electron adjustment of the composition of the mixture. In the electronic systems, the mixing formation is carried out under control electronic block Control (ECU) injection controlling electric gasoline valves.

Gas engines

The engine burns as a fuel hydrocarbons in a gaseous state. Most often gas engines I work on propane, but there are other working on associated (petroleum), liquefied, domain, generator and other types of gaseous fuels.

The fundamental difference between gas engines from gasoline and diesel in a higher compression. The use of gas avoids excessive wear of parts, since the combustion processes of the fuel-air mixture occur more correctly due to the initial (gaseous) fuel condition. Also gas engines are more economical, as gas costs cheaper oil and is easier to produce.

The undoubted advantages of gas engines should include the safety and smokelessness of the exhaust.

By themselves, gas engines are rarely produced serially, most often they appear after the alteration of traditional DVS, by equipment by their special gas equipment.

Diesel engines

Special diesel fuel is injected at a certain point (not reaching the top point) into a high pressure cylinder through the nozzle. The combustible mixture is formed directly in the cylinder as the fuel injection. The movement of the piston inside the cylinder causes heating and subsequent ignition of the fuel and air mixture. Diesel engines are low-speed and characterized by a high torque on the motor shaft. An additional advantage of the diesel engine is that, unlike the engines with forced ignition, it does not need electricity to work (in car diesel engines electrical system Used only to start), and, as a result, less afraid of water.

By way of ignition:

From spark (gasoline),

From compression (diesel).

By the number and location of cylinders:

Row

Opposite

V - shaped,

VR - shaped,

W - shaped.

Row Engine

This engine is known from the very beginning of the automotive engine. Cylinders are located in one row perpendicular to the crankshaft.

Dignity: Easy design

Failure: With a large number of cylinders, a very long unit is obtained, which cannot be placed transversely relative to the longitudinal axis of the car.

Opposite Engine

Horizontal opposite engines are distinguished by a smaller overall height than engines with row or V-shaped cylinders, which reduces the center of gravity of the entire car. Lightweight, design compactness and layout symmetry reduces the torque of the car.

V-engine

To reduce the length of the engines, in this engine cylinders are located at an angle from 60 to 120 degrees, while the longitudinal axes of cylinders pass through the longitudinal axis of the crankshaft.

Dignity: Relatively short engine

Disadvantages: The engine is relatively wide, has two separate block heads, an increased cost of manufacture, too large working volume.

VR engines

In search of a compromise engine performance solution for passenger cars The middle class came to the creation of VR engines. Six cylinders at an angle of 150 degrees form relatively narrow and overall short engine. In addition, such an engine has only one block head.

W-engines

In the w-family engines in one engine, two rows of cylinders in VR-executing are connected.

The cylinders of each row are placed at an angle of 150 one to another, and the rows of cylinders themselves are located at an angle of 720.

The standard automotive engine consists of two mechanisms and five systems.

Engine mechanisms

Crank mechanism,

Gas distribution mechanism.

Engine systems

Cooling system,

Lubrication system,

Supply system,

Ignition system

Exhaust gas production system.

crank mechanism

The crank-connecting mechanism is designed to transform the reciprocating movement of the piston in the cylinder to the rotational motion of the crankshaft of the engine.

The crank-connecting mechanism consists of:

Cylinder block with crankcase,

Cylinder heads,

Engine Carter Pallet,

Pistons with rings and fingers,

Rods

Crankshaft,

Flywheel.

Cylinder block

It is a solid detail that combines the engine cylinders. On the cylinder block, there are reference surfaces to install the crankshaft, to the top of the block, as a rule, the cylinder head is fastened, the lower part is part of the crankcase. Thus, the cylinder block is the basis of the engine on which the remaining parts are hung.

Mounted as a rule - from cast iron, less often - aluminum.

Blocks made of these materials are by no means equal in their properties.

Thus, the cast iron block is the most hard, and therefore - with other things being equal, it can withstand the highest degree of forsing and the least sensitive to overheating. The heat capacity of the cast iron is approximately twice as well as aluminum, which means the engine with the cast-iron block is heated faster to the operating temperature. However, the cast iron is very heavy (2.7 times heavier than aluminum) is inclined to corrosion, and its thermal conductivity is approximately 4 times lower than that of aluminum, therefore the engine with a cast-iron crankcase operates the cooling system in a more voltage mode.

Aluminum blocks of cylinders are light and better cooled, but in this case there is a problem with the material from which the cylinder walls are directly made. If the pistons of the engine with such a block are made of cast iron or steel, they very quickly wear aluminum walls of cylinders. If you make pistons made of soft aluminum, then they simply "grab" with the walls, and the engine instantly commits.

The cylinders in the cylinder block can be both part of the casting of the cylinder block, and to be separate interchangeable sleeves that can be "wet" or "dry". In addition to the generator part of the engine, the cylinder block is increasing additional functions, such as the base of the lubrication system - along the holes in the cylinder block, the oil under pressure is supplied to the lubrication places, and in the liquid cooling engines, the base of the cooling system - by similar holes, the liquid circulates through the cylinder block.

The walls of the inner cavity of the cylinder serve also guides for the piston during its movements between the extreme pollinium. Therefore, the length of the forming cylinder is predetermined by the magnitude of the piston stroke.

The cylinder works under conditions of pressure variables in the oily cavity. The inner walls of it come into contact with flames and hot gases, hot gases to a temperature of 1500-2500 ° C. In addition average speed Slides of the piston kit along the walls of the cylinder in car motors reaches 12-15 m / s with insufficient lubrication. Therefore, the material used for the manufacture of cylinders should have a large mechanical strength, and the design of the walls with increased rigidity itself. The walls of the cylinders should be well to resist abrasion with limited lubrication and have a total high resistance against other possible types of wear

In accordance with these requirements, pearly gray cast iron with non-large additives of alloying elements (nickel, chromium, etc.) are used as the main material for cylinders. Also high-alloyed cast iron, steel, magnesium and aluminum alloys are used.

Head block cylinder

It is the second most important and magnitude of an integral part of the engine. The head of combustion chambers, valves and cylinder candles are located in the bearings, a camshaft with cams are rotated on the bearings. Just as in the cylinder block, there are water and oil canals in its head and cavities. The head is attached to the cylinder block and, when the engine is running, is a single whole with a block.

Engine crankcase pallet

It closes the engine at the bottom (it is molded as a whole with a cylinder block) and is used as an oil tank and protects engine parts from contamination. At the bottom of the pallet there is a plug plug motor oil. The pallet is attached to the Carter bolts. To prevent oil leakage between them, a gasket is installed.

Piston

The piston is a detail of a cylindrical shape that performs a reciprocating movement inside the cylinder and serving to convert gas pressure, steam or liquid into mechanical work, or vice versa - reciprocating movement into pressure change.

The piston is divided into three parts performing various functions:

Bottom,

Sealing

Guide part (skirt).

The bottom form depends on the function performed by the piston. For example, in internal combustion engines, the form depends on the arrangement of candles, nozzles, valves, engine designs and other factors. With a concave form of the bottom, the most rational combustion chamber is formed, but in it more intensively, the Nagar deposition occurs. With a convex bottom form, the strength of the piston increases, but the form of combustion chamber is worse.

The bottom and sealing part form the head of the piston. In the sealing part of the piston there are compression and oil-changing rings.

The distance from the bottom of the piston to the groove of the first compression ring is called the firing belt of the piston. Depending on the material from which the piston is made, the fire belt has a minimally permissible height, the decrease in which can lead to a piston deflection along the outer wall, as well as destruction landing Upper compression ring.

The seal functions performed by the piston group are of great importance for normal work Piston engines. ABOUT technical condition The engine is judged by the sealing ability of the piston group. For example, in automotive engines it is not allowed so that the consumption of oil due to the ugon is due to excessive penetration (supply) into the combustion chamber exceeded 3% of the fuel consumption.

Piston skirt (Trond) is its guide part when moving in the cylinder and has two tides (bolsters) to install the piston finger. To reduce the temperature stresses of the piston from both sides, where the bins are located, from the surface of the skirt, remove the metal to a depth of 0.5-1.5 mm. These recesses that improve the lubrication of the piston in the cylinder and preventing the formation of jackets from temperature deformations are called "refrigerators". In the lower part of the skirt can also be located an oil surcharge ring.

Gray cast iron and aluminum alloys are used for the manufacture of pistons.

Cast iron

Advantages: Pistons made of cast iron are durable and wear-resistant.

Due to the small linear extension coefficient, they can work with relatively small gaps, providing good cylinder seal.

Disadvantages: Cast iron has a rather large proportion. In this regard, the area of \u200b\u200bapplication of pig-iron pistons is limited by relatively low-intensive engines, in which the inertia's strengths return moving masses do not exceed one sixth of the pressure of gases on the bottom of the piston.

The cast iron has a low thermal conductivity, so the heating of the bottom in cast iron pistons reaches 350-400 ° C. Such heating is undesirable especially in carburetor enginesSince it is the cause of the occurrence of a caliling ignition.

Aluminum

The overwhelming majority of modern automotive engines have aluminum pistons.

Advantages:

Low mass (at least 30% less compared to cast iron);

High thermal conductivity (3-4 times higher than the thermal conductivity of the cast iron), providing the heating of the piston bottom of no more than 250 ° C, which contributes to better filling of cylinders and allows you to increase the degree of compression in gasoline engines;

Good antifriction properties.

Shatun.

Schitun - Detail connectingpiston (throughpiston finger) and connecting rod cervicalcrankshaft. It serves to transfer reciprocating movements from the piston on the crankshaft. For smaller wear of connecting rod crankshaft necks between them and rods are placedspecial liners that have antifriction coating.

Crankshaft

Crankshaft - detail shape having cervix for fasteningshatunov from which effort perceives and transforms them intotorque .

The crankshafts are made of carbon, chromanganese, chromonicelmolybdenum, and other steels, as well as from special high-strength cast iron.

Basic elements of the crankshaft

Non-cervical - True support, lying in a radicalbearing placed incarter Engine.

Rolling cervical - Support, with which the shaft is associated withshatuns (For lubrication of connecting connecting rod bearings there are oil channels).

Cheeks - Bind the root and connecting rod cervix.

Front output of the shaft (sock) - part of the shaft on which attachedgear orpulley Power take-off for drivegas distribution mechanism (timing) and various auxiliary nodes, systems and aggregates.

Rear output of the shaft (shank) - part of the shaft connecting withflywheel or massive gear selection of the main power part.

Counterweight - Provide unloading of native bearings from centrifugal inertia forces of the first order of unbalanced masses of the crank and the bottom of the connecting rod.

Flywheel

Massive disc with a gear crown. The gear is needed to start the engine (the starter gear enters the gear of the flywheel and spins the motor shaft). Also, the flywheel serves to reduce the uneven rotation of the crankshaft.

Gas distribution mechanism

It is intended for a timely intake to cylinders of a combustible mixture and exhaust exhaust gases.

The main parts of the gas distribution mechanism are:

Camshaft,

Inlet and exhaust valve.

Camshaft

By location distribution Vala Engines highlight:

With camshaft located incylinders block (CAM-IN-BLOCK);

With a camshaft located in the head of the cylinder block (CAM-IN-HEAD).

In modern car engines, as a rule, is located at the top of the block headcylinders and connected by S.pulley or toothed starscrankshaft The timing or chain of timber, respectively and rotates with twice as smaller frequency than the last (on 4-stroke engines).

Part of the camshaft are itskulachka , the number of which corresponds to the number of intake and graduationvalves Engine. Thus, each valve corresponds to an individual cam, which opens the valve, riding on the valve pusher lever. When the cam "runs out" from the lever, the valve closes under the action of a powerful return spring.

Engines with row configuration of cylinders and one pair of valves on the cylinder usually have one camshaft (in the case of four valves per cylinder, two), and V-shaped and opposite - either one in the collapse of the block, or two, one for each semi-block ( In each block of the block). Engines having 3 valves per cylinder (most often two intake and one graduation), usually have one camshaft on the block head, and having 4 valves per cylinder (two intake and 2 graduation) have 2 camshafts in each block head.

Modern engines Sometimes there are systems for adjusting the phases of gas distribution, that is, mechanisms that allow to turn the camshaft relative to the drive sprocket, thereby changing the opening and closing and closing (phase) of the valves, which makes it possible to more effectively fill the cylinder with a working mixture on different revs.

Valve

The valve consists of a flat head and a rod interconnected by a smooth transition. For better filling cylinders of a combustible mixture, the diameter of the intake valve head is much larger than the degree diameter. Since the valves operate in high temperatures, they are made of high quality steels. The intake valves are made of chromium steel, graduation from the heat-resistant, since the latter are in contact with combustible exhaust gases and heat up to 600 - 800 0 C. The high temperature of the valve heating causes the need to be installed in the cylinder head of special inserts from heat-resistant cast iron, which are called saddles.

Principle of engine operation

Basic concepts

Top dead point - Extremely upper position of the piston in the cylinder.

Lower dead point - The extreme lower position of the piston in the cylinder.

Piston move - The distance that the piston passes from one dead point to the other.

The combustion chamber - the source of the cylinder block and the piston when it is in the upper dead point.

Cylinder work volume - The space released by the piston when it moves from the top of the dead point to the lower dead point.

Engine work - The sum of the working volumes of all engine cylinders. It is expressed in liters, therefore it is often called the engine litter.

Full volume of cylinder - The sum of the combustion chamber volume and the working volume of the cylinder.

Compression ratio - shows how many times the total volume of the cylinder is greater than the volume of the combustion chamber.

Compression - Cylinder at the end of the compression tact.

Tact - process (part of the working cycle), which occurs in the cylinder in one stroke of the piston.

Engine working cycle

1st tact - inlet. When the piston moves down in the cylinder, a vacuum is formed, under the action of which a combustible mixture is added to the cylinder through the open intake valve (a mixture of fuel with air).

2nd tact - compression . The piston under the action of the crankshaft and the connecting rod moves up. Both valves are closed and the combustible mixture is compressed.

3rd tact - workforce . At the end of the tact of compression, the combustible mixture is ignited (from compression in diesel engine, from spark candles in gasoline engine). Under the pressure of expanding gases, the piston moves down and through the connecting rod leads to the rotation of the crankshaft.

4th tact - release . The piston moves upwards and through the opened exhaust valve the exhaust gases come out.

The internal combustion engine (DVS) is to date the most common type of engine. Scroll vehicle, in which it is installed just huge. DVS can be detected on cars, helicopters, tanks, tractors, boats, etc.

The internal combustion engine is a thermal engine, in which the transformation of a portion of the chemical energy of the combusting fuel into mechanical energy occurs. A significant separation of engines in the category this division on the working cycle for 2 and 4-stroke; according to the method of preparing a combustible mixture - with an external (in particular carburetor) and internal (for example, diesel) mixture formation; According to the energy converter, the engine is divided into piston, turbine, jet and combined.

The efficiency coefficient of the internal combustion engine is 0.4-0.5. The first internal combustion engine is designed by E. Lenoar in 1860. We will look at the most frequently used four-stroke engine internal combustion in the automotive industry.

For the first time, the four-stroke engine was represented by Nicholas Otto in 1876 and therefore it also carries the engine name with Otto cycle. A more competent name of such a cycle is a four-stroke cycle. Currently, this is the most common type of engine for cars.

Principle of operation of internal combustion engine (DVS)

The effect of the piston internal combustion engine is based on the use of pressure of thermal expansion of heated gases during the movement of the piston. Gas heating occurs as a result of combustion in the cylinder of the fuel-air mixture. To repeat the cycle, the spent gas mixture must be released at the end of the movement of the piston and fill in a new portion of fuel and air. In the extreme position there is a fuel tag from the spark of the candle. The intake and release of fuel and combustion products occur through the valves controlled by the gas distribution mechanism and the fuel supply system.

Thus, the engine cycle is divided into the following steps:

• Tact intake.
• Compression tact.
• Extension tact, or work move.
• Tact release.

The force from the moving piston of the cylinder through the crankshaft is converted into the rotational motion of the motor shaft. A part of the rotation energy is spent on the return of the pistons to its original state, to make a new cycle. The shaft design determines the different position of the pistons in different cylinders at each time. Thus, the larger in the engine of the cylinders, in general, is evenly rotating its shaft.

By the location of the cylinders, engines are divided into several types:

a) engines with a vertical or inclined location of cylinders in one row

B) V-shaped with a mutual arrangement of cylinders at an angle in the form of a Latin letter V:

D) engines with opposite cylinders. It is called "Opposite", the cylinders in it are located at an angle of 180 degrees:

The mechanism of engine gas distribution on the output tact ensures cleaning of cylinders from combustion products (exhaust gases) and filling the cylinders with a new portion of the fuel and air mixture on the intake tact.

The ignition system produces a high-voltage discharge and transfers its cylinder candle through the high voltage wire. The voltage control performs a rubber, the wires from which are suitable for each candle. The rubber arranged in such a way that the discharge arose in that cylinder, where the piston is currently going through the point of the greatest compression of the fuel mixture. If the mixture flashes earlier, the gas pressure will work against its stroke, if later, the power is not fully secreted by the expansion of gases.

To start the engine, it needs to give the initial movement. To do this, use the start system (see the article "How Starter Works") from electric engine - Starter.

Advantages of gasoline engines

• More low level noise and vibrations compared to diesel;
• High power with an equal volume of the engine;
• Ability to work on high revolutions, without serious consequences for the engine.

Disadvantages of gasoline engines

• Larger than diesel fuel consumption, and higher requirements for its quality;
• The need for the presence and permanent operation of the fuel ignition system;
• Most power gasoline DVS It is achieved in a narrow range of revolutions.