Scheme of operation 6 cylinder engine. The order of the cylinders of the internal engine engine

System components

System Overview

Mechanical nodes and details of diesel first are described by the following engines are divided into three large parts.

• Crankcase
• crank mechanism
• Gas distribution mechanism

These three parts are in constant interaction. Relationships that have a significant impact on engine properties:
• the interval between ignitions;
• the order of the cylinders;
• balanting the masses.

Interval between ignition
Mechanical elements of the engine are mainly divided into three groups: engine crankcase, crank-connecting mechanism and valve drive. These three groups are closely interconnected and must be interconnected. The interval between ignitions is an angle of rotation of the crankshaft between two next to each other inflammation.
For one working cycle in each cylinder, the fuel-air mixture is ignited once. The operating cycle (suction, compression, work move, release) at the four-stroke engine occupies two full turns of the crankshaft, i.e. the angle of rotation is 720 °.
The same interval between ignitions provides uniform engine operation at all rotation frequencies. This interval between ignitions is obtained as follows:
the interval between ignitions \u003d 720 °: the number of cylinders

Examples:

• four-cylinder engine: 180 ° crankshaft (KB)
• sixi Cylinder Engine: 120 ° Kb
• eight-cylinder engine: 90 ° square.

The greater the number of cylinders, the less the interval between ignitions. The less the interval between ignitions, the most evenly the engine works.
At least, theoretically, t. To this is still added to the balancing of masses, which depends on the design of the engine and the order of operation of the cylinders. In order for the cylinder to be inflammation, the corresponding piston should be in the "NTC of the end of the compression tact", i.e. the corresponding intake and exhaust valves should be closed. It may only take place when the crankshaft and the camshaft are correctly located relative to each friend. The interval between ignitions is determined by the mutual arrangement of connecting rods (angular distance between the knee) of the crankshaft, i.e. the angle between the necks of the following cylinders (the order of the cylinders). In V-shaped engines, the corner of the collapse should be equal to the interval between ignitions To achieve uniform work.
Therefore, the eight-cylinder BMW engines have an angle between the rows of cylinders of 90 °.

The order of the cylinders
The operation of the cylinders is a sequence in which ignition is ignited in the engine cylinders.
The order of cylinders is directly responsible for smooth work Engine. It is determined depending on the design of the engine, the number of cylinders and the interval between ignitions.
The operation of the cylinders is always indicated from the first cylinder.

Balancing masses
As described earlier, the smoothness of the engine depends on the engine design, the number of cylinders, the order of operation of the cylinders and the interval between ignitions.
Their influence can be shown on the example of a six cylinder engine, which BMW manufactures in the form of an inline engine, although it takes more space and more workflows in the manufacture. The difference can be understood if we compare the balancing of mass of inline and V-shaped six-cylinder engines.
The following figure shows the inertia momentum curves of the inline sixi-cell-carbon engine BMW, the V-shaped six-cylinder engine with an angle between the rows of 60 ° and the V-shaped six-cylinder engine with an angle of 90 °.
The difference is obvious. In the case of a row six-cylinder engine, the mass movement is equalized so much that the entire engine is almost immobile. V-shaped six-cylinder engines, on the contrary, have an explicit tendency to move, which manifests itself in uneven operation.

Cabinet parts
Engine cabinet parts take on isolation from ambient and perceive various forces which occur during the engine operation.

The enclosure parts of the engine consist of the main details shown in the following figure. To perform the crankcase of its tasks, sealing gaskets and bolts are also necessary.

Main goals:

• perception of the energy occurring during the operation;
• sealing combustion chambers, oil pallet and cooling shirt;
• placing a crank-connecting rod mechanism and drive valve, as well as other nodes.

Cracked-connecting mechanism
The crank-connecting mechanism is responsible for converting the fuel-air mixture of pressure occurring during combustion into a useful movement. In this case, the piston receives a straight rate acceleration. The connecting rod transmits this movement on the crankshaft, which turns it into a rotational movement.

The crank-connecting mechanism is a functional group that converts pressure in the combustion chamber into kinetic energy. At the same time, the return-translational movement of the piston passes into the rotational motion of the crankshaft. Cracked-connecting mechanism is the optimal solution in terms of work output, coefficient useful action and technical realizability.

Of course, there are the following technical limitations and constructive requirements:

• restriction of rotational speed due to inertia forces;
• impermanence forces during the working cycle;
• the occurrence of the vibrations, which create loads on the transmission and on the crankshaft;
• the interaction of various friction surfaces.

Valve drive
Valve drive controls the charge shift. In modern diesels bMW engines Finds the use of exclusively Done valves drive with four valves per cylinder. The transfer of movement to the valve is carried out through the pusher lever.

In the engine must be periodically served outer airWhile the exhaust gas that it produces must be discharged. In the case of a four-stroke engine, the suction of the outer air and the release of the exhaust gas is called a change of charge or gas exchange. In the process of changing the charge, intake and outlet channels are opened and closed using intake and exhaust valves.
Lifting valves are used as intake and exhaust valves. Duration and sequence of valve movements are provided switchgear.

Design
Valve drive consists of the following details:

• distribution shafts;
• transmission elements (roller levers of pushers);
• valves (whole group);
• hydraulic valve gap compensation system (HVA) if available;
• valve guide sleeves with valve springs.

The following figure shows the design of the cylinder head with four valves (M47 engine) with roller levers of the pushers and the hydraulic valve gap compensation system.

Designs
Valve drive can have different executions. They are distinguished by the following signs:

• the number and location of the valves;
• the number and location of the camshafts;
• method of transmitting motion on valves;
• the method of adjusting the gaps in the valves.

BMW diesel engines today have only four valves on the cylinder and two arranged camshafts for each row of cylinders (DOHC). BMW M21 / M41 / M51 engines had only two valves per cylinder and one distribution shaft for each row of cylinders (OHC).
Transfer the movement of camshaft camshafts on valves in diesel engines BMW is carried out by roller levers of pushers. At the same time, the desired gap between the camshaft cam and the so-called cam repeater (for example, a roller lever of the pusher) is ensured by mechanical or hydraulic system Cleaner compensation (HVA).
The following figure shows the Details of the M57 engine valve valves.

Block Carter

Block Carter, also called the cylinder block, includes cylinders, cooling shirt and crankcase drive mechanism. Requirements and tasks that are presented to block boards, highly due to the complexity of today's HighTech engines. However, the improvement of the block Carter occurs in the same pace, especially since many new or advanced systems interact with the block cartridge.

Below are the main tasks.

• Perception of forces and moments
• Placing a crank-connecting mechanism
• Accommodation and connection of cylinders
• Placing the crankshaft support
• Placing the cooling fluid and lubrication channels
• Integration of the ventilation system
• Fixing various auxiliary and hinged equipment
• Sealing cavity Carter

Based on these tasks, various and overlapping requirements for tensile strength and compression, bending and twisting are arise. In particular:

• gas impact forces that are perceived by the threaded compounds of the head of the cylinder block and the crankshaft supports;
• internal inertia (bending forces), which are the result of inertia for rotation and oscillations;
• internal forces of twist (twisting forces) between individual cylinders;
• the torque of the crankshaft and, as a result, the reaction force of the engine support;
• free forces and moments of inertia, as the result of inertia forces with oscillations that are perceived by the engine supports.

Design
The main form of the block Carter did not change too much from the beginning of the engine. Changes in the design touched in private, for example, from what amount of parts a block carter is made or how individual parts are performed. Designs can be classified depending on the version:

• top plate;
• area bed of the indigenous bearing;
• cylinders.

Top plate
The upper plate can be performed in two different design versions: closed and open. Constructive execution affects both the casting process and the stiffener of the block.
With the closed execution, the upper stove of the block crankcase is completely closed around the cylinder.
There are holes and channels for supplying oil under pressure, flow of oil, coolant, crankcase ventilation and threaded joints of the cylinder block.
The coolant holes are connected by a water shirt that surrounds the cylinder, with a water jacket in the head of the cylinder block.
Such a design has drawbacks in terms of cooling cylinders in the VMT zone. The advantage of closed execution compared to the open is the higher rigidity of the top plate and, thereby, a smaller deformation of the plate, a smaller shift of cylinders and better acoustics.
With open execution, the water shirt surrounding the cylinder is open at the top. This improves the cooling of cylinders at the top. Less rigidity is currently compensated by the use of a metal laying of the block head.

Fig.2 - Closed version of the top engine plate M57TU2 BMW diesel engine cartridges are made of gray cast iron. Starting with M57TU2 and U67TU engines, the crankcase is made of high-grade aluminum alloy.

In diesel engines, BMW uses closed plates. Area bed of indigenous bearing
Performance of the area The bed of the indigenous bearing is of particular importance, since the forces acting on the crankshaft bearing are perceived in this place.
Performances are distinguished by the plane of the block of cartridge and oil pan and the design of the covers of the indigenous bearings.
Connector Plane Performance:

• oil pallet flange in the center of the crankshaft;
• oil pallet flange below the crankshaft center.

Constructions of indigenous bearings:
• separate indigenous bearing caps;
• integration into one frame design.

Bed of indigenous bearing
Bearing bed is the top of the crankshaft support in the block cartridge. Bearing bed are always integrated into the Carter Casting.
The number of bearings bed depends on the engine design, first of all, on the number of cylinders and their location. Today, the maximum number of native crankshaft bearings is used for reasons of fluctuations. The maximum number means that there is a native bearing near each knee shaft.
With the engine running, the gas in the cavity of the crankcase is constantly in motion. Movement of pistons act on gas like pumps. To reduce losses for this work, many engines today have holes in bearings. This makes it easier to align the pressure throughout the block crankcase.

Carter connector plane

The plane of the block cartridge and oil pallet connector forms an oil pallet flange. Distinguish two constructive performance. In the first case, the plane of the connector lies in the center of the crankshaft. T. K. This is a constructive design in economically in the manufacture, but has significant disadvantages of rigidity and acoustics, it is not used in BMW diesel engines.
With the second constructive execution (IN) The oil pallet flange is located below the crankshaft center. At the same time distinguish a block cartridge with lowered walls and a block carter
with upper and lower parts, the latter is called a design with bedplate (FROM). BMW diesel engines have a carcard with lowered walls.

The engine M67 also uses a design with lowered walls. It provides high dynamic rigidity and good acoustics. The jumper from steel reduces the load on the mounting bolts of the bearing cover and additionally enhances the area of \u200b\u200bthe bed of the indigenous bearing.

Fig.6 - Supporting Beam Concept

Concept of supporting beam
To achieve high dynamic rigidity, BMW diesel engines block cartridges are designed according to the supporting beam. With such a design in the walls of the block, the horizontal and vertical elements of a box cross section are cast. In addition, the block Carter has lowered walls that reach 60 mm reach below the crankshaft center and end with the plane for the installation of the oil pan.

The cover of the root bearing
The covers of the indigenous bearings are the bottom of the crankshaft support. In the manufacture of a block-cartera bed and covers of indigenous bearings are processed together. Therefore, their fixed position is necessary relative to each other. This is usually done using centering sleeves or made on sides in surface beds. If the block cartridge and indigenous bearing caps are made of one material, the covers can be made according to the method of fault.
When separating the indigenous bearing cover, the exact fault surface is formed by the fault. Such a surface structure accurately center the indigenous bearing cover when installed on the bed. Additional surface treatment is not required.

Another possibility of accurate positioning is to send the surfaces of the bed and the cover of the indigenous bearing.
This fixation provides a completely smooth transition between the bed and the lid in the hole for the indigenous bearing after re-assembly.

Fig.8 - Fulling the surface of the M67TU engine roof bearing
1 The cover of the root bearing
2 Employment of the surface of the indigenous bearing cover
3 Surface Surface Shape Bed of Indigen Bearing
4 Bed of indigenous bearing

When climbing the surface, the indigenous bearing cover receives a specific profile. With the first tightening of the fastening bolts of the indigenous bearing cover, this profile is imprinted on the surface of bed and provides no movements in transverse and longitudinal directions.
The covers of the indigenous bearings are almost always made of gray cast iron. Total processing with an aluminum block carter, although there is special requirements, is today usual for large-scale production. The combination of aluminum block ceter with indigenous bearing caps made of gray cast iron gives certain advantages. The low heat expansion coefficient of gray cast iron limits the working gaps of the crankshaft. Along with the high rigidity of gray cast iron, this leads to a decrease in noise in the area of \u200b\u200bthe bed of the indigenous bearing.

The cylinder and piston form a combustion chamber. The piston is inserted into the cylinder sleeve. The smoothly treated surface of the cylinder sleeve, along with piston rings, provides an efficient seal. In addition, the cylinder gives the heat of a block videoer or directly coolant. The designs of the cylinders differ by the material used:

• monometallic design (cylinder sleeve and block carder are made of one material);
• insert technology (cylinder sleeve and block carder are made of various materials connected physically);
• compound technology (cylinder sleeve and block carcard are made of various materials connected metallic).

Monometallic design
With a monometallic design, the cylinder is made from the same material as a block carder. First of all, according to the principle of the monometallic design, a gray cast iron canter and AISI-block Carter are manufactured. The required surface quality is achieved by repeated processing. BMW diesel engines have a monometallic design block cartridge only from gray cast iron, since the maximum pressure during ignition reaches 180 bar.

Technology insert
Not always the material of the block Carter satisfies the requirements for the cylinder. Therefore, often the cylinder is made from another material, usually in combination with an aluminum block carter. Cylinder sleeves distinguish:

1. By the method of connecting a block cartridge with a sleeve

• integrated in casting
• passed
• crimped
• insert.

2. On the principle of work in the block Carter

• wet I.
• dry

3. By material

• from gray cast iron or
• aluminum

Wet cylinder sleeves have direct contact with a water jacket, that is, cylinder sleeves and cast block cartridge form a water shirt. The water shirt with dry cylinder sleeves is completely in the cast block carter - similar to the monometallic design. The cylinder sleeve does not have direct contact with a water jacket.

Fig.9 - Dry and wet cylinder sleeve
BUT Cylinder with dry sleeve
IN Cylinder with wet sleeve
1 Block Carter
2 Cylinder liner
3 Water jacket

Wet cylinder sleeves have an advantage in terms of heat transfer, while the advantage of dry sleeves in production and processing possibilities. As a rule, the cost of production of cylinder sleeves decreases with large quantities. Gray cast iron sleeves for both M57TU2 and M67TU engines are thermal processing.

Compound technology
Another possibility of making the cylinder mirror, with an aluminum block crankcase, is the connection technology. And in this case, the cylinder sleeves are inserted when casting. Of course, this is carried out using a special process (for example, under high pressure), the so-called intermetallic connection with a block cartridge. Thus, the mirror of the cylinder and the block Carter is inseparable. This technology limits the use of casting processes and, thereby, the design of the block Carter. In Diesel engines BMW, this technology is currently not used.

Treatment of cylinders mirrors
The cylinder mirror is a sliding surface and a piston seal and piston rings. The quality of the surface of the cylinder mirror is decisive for the formation and distribution of the oil film between the contacting items. Therefore, the roughness of the cylinder mirror is largely responsible for the oil consumption and engine wear. The final processing of the cylinder mirror is carried out by honing. Honing - polishing the surface with the help of combined rotational and reciprocating movements of the cutting tool. Thus, it turns out an extremely small deviation of the cylinder shape and a uniform low surface roughness. Processing should be relaxing with respect to the material to eliminate chips, irregularities in the fields of transitions and the formation of burrs.

Materials

Even now Block Carter is one of the most severe parts of the entire car. And it takes the most critical place for the dynamics of movement: place above the front axle. Therefore, it is here that attempts are made to fully use the potential to reduce the mass. Gray cast iron, which for decades was used as a material for a block of crankcase, more and more replaced in Diesel engines BMW aluminum alloys. This allows you to obtain a significant reduction in mass. In the engine M57TU it is 22 kg.
But the advantage of mass is not the only difference, which takes place when processing and using another material. Acoustics, anti-corrosion properties, processing requirements and maintenance volumes are also varied.

Gray cast iron
Cast iron is an aloy of iron with a carbon content of more than 2% and silicon more than 1.5%. In the gray cast iron, excess carbon is contained in the form of graphite
For BMW diesel engines block cartridges, cast iron with lamellar graphite has been used, which received its name in the arrangement of graphite in it. Other components of the alloy are a manganese, sulfur and phosphorus in very small quantities.
The cast iron was offered from the very beginning as a material for blocking cartridges of serial engines, since this material is not expensive, simply processed and has the necessary properties. Light alloys could not satisfy these requirements for a long time. BMW uses cast-iron for its plastic graphite engines due to its particularly favorable properties.
Namely:

• good thermal conductivity;
• good strength properties;
• simple mechanworking;
• good foundry properties;
• very good damping.

Outstanding damping is one of the distinguishing properties of cast iron with lamellar graphite. It means the ability to perceive oscillations and extinguish them due to internal friction. This is significantly improved by the vibration and acoustic characteristics of the engine.
Good properties, strength and simple processing make a gray cast iron box and today competitive. Due to high strength, gasoline engines M and diesel engines and today are made with gray cast iron cartridge. Increasing requirements for the mass of the engine on light car In the future, only light alloys will be able to satisfy.

Aluminum alloys
Aluminum alloy block cartridges are still relative to the new BMW diesel engines. The first representatives of the new generation are M57TU2 and M67TU engines.
The density of aluminum alloys is about a third in comparison with the gray cast iron. However, this does not mean that the advantage of the mass has the same relation, since, due to lower strength, such a block Carter has to make a massive.

Other properties of aluminum alloys:

• good thermal conductivity;
• good chemical resistance;
• good strength properties;
• simple machining.

Pure aluminum is not suitable for casting a block Carter, since there is not enough good strength properties. Unlike gray cast iron, the main alloying components are added herein in relatively large quantities.

Alloys are divided into four groups, depending on the prevailing alloying additive.
These additives:

• silicon (Si);
• copper (SI);
• magnesium (MD);
• zinc (Zn).

For Aluminum BMW Diesel Engine Carter Motors, Alsi alloys are used. They are improved by small additions of copper or magnesium.
Silicon has a positive effect on alloy strength. If a component is more than 12%, then a special surface hardness can be obtained by special treatment, although the cutting will be complicated. In the region of 12% outstanding casting properties.
The addition of copper (2-4%) can improve the foundry properties of the alloy if the silicon content is less than 12%.
A small magnesium additive (0.2-0.5%) significantly increases the strength values.
For both Diesel engines BMW uses aluminum alloy AISI7MGCUO, 5. The material has already been used by BMW for diesel engines cylinder heads.
As can be seen from the designation of AISL7MGCUO, 5, this alloy contains 7% silicon and 0.5% copper.
It is characterized by high dynamic strength. Other positive properties are good casting properties and plasticity. True, it does not allow to achieve a sufficiently wear-resistant surface, which is necessary for the cylinder mirror. Therefore, block cards from AISI7MGCUO, 5 have to be performed with cylinder sleeves (see the chapter "Cylinders").

Table Review

general information
The collected head of the cylinder block, like no other functional group of the engine, determines the operational properties, such as power output, torque and emission harmful substances, Fuel consumption and acoustics. The head of the cylinder block is almost the entire gas distribution mechanism.
Accordingly, extensive and tasks that the cylinder head must be solved:

• perception of forces;
• placing the valve drive;
• placement of channels for changing charge;
• placing glow candles;
• placing nozzles;
• placing the cooling fluid channels and lubrication systems;
• cylinder limitation from above;
• heat removal to coolant;
• fastening the auxiliary and attachment equipment and sensors.

The following loads flow from the tasks:
• the impact forces of gases that are perceived by the threaded compounds of the head of the cylinder block;
• torque of distributional shafts;
• forces arising in the supports of the camshafts.

Injection processes
In diesel engines, depending on the design and layout, the combustion chamber distinguishes immediate and indirect injection. Moreover, in the case of an indirect injection, in turn, the dramatic and ancestor-dimensional mixture is distinguished.

Pre-commercial mixture

The pre-boat is located in the center relative to the main combustion chamber. This pre-unit is injected with fuel for pre-commercial combustion. The main combustion occurs with the known delay in self-ignition in the main chamber. The pre-boat is connected to the main chamber of several holes.
The fuel is injected with a nozzle, providing a stepped fuel injection, under a pressure of about 300 bar. The reflective surface in the center of the chamber breaks the fuel stream and mixing with air. The reflective surface contributes to the rapid mixture formation and streamlining of air movement.

The disadvantage of this technology is a large surface of the cooling of the pre-boam. Compressed air is cooled relatively quickly. Therefore, such engines are launched without the help of incandescent candles, as a rule, only at a coolant temperature of at least 50 ° C.
Thanks to two-stage combustion (first in the pre-commerce, and then in the main chamber), the combustion occurs softly and almost completely with relatively level engine operation. Such an engine reduces the emission of harmful substances, but it develops less power compared to the direct injection engine.

Drying mixing
Difforine injection, like ancestor, is an indirect injection option.
The vortex chamber is designed in the shape of a ball and is located separately on the edge of the main combustion chamber. The main combustion chamber and the vortex chamber are connected by a direct tangential channel. Tangential directed direct channel when compressed creates a strong air twist. Diesel fuel Fixed through a nozzle providing stepwise injection. The opening pressure of the nozzle, providing a stepped fuel injection, is 100-150 bar. When injected with a finely sprayed fuel cloud, the mixture is partially flammable and develops its full power in the main combustion chamber. The design of the vortex chamber, as well as the location of the nozzle and the incandescent candles, are factors that determine the combustion quality.
This means that the combustion begins in a spherical vortex chamber and ends in the main combustion chamber. To start the engine, the incandescent candles are needed, since there is a large surface between the combustion chamber and the vortex chamber, which contributes to the rapid cooling of the suction air.
The first serial diesel engine of the BMW M21D24 works on the principle of dry-forming mixing.

Direct injection
This technology allows you to refuse to separate the combustion chamber. This means that with the direct injection there is no preparation of the working mixture in the next chamber. The fuel is injected with the help of the nozzle right into the combustion chamber above the piston.
Unlike indirect injection, multi-line nozzles use. Their jets must be optimized and adapted to the combustion chamber design. Due to the large pressure of the injected jets, instant combustion occurs, which in earlier models led to the loud operation of the engine. However, such a combustion exempts more energy, which can then be more efficient. Fuel consumption is reduced. Direct injection requires a higher injection pressure and, accordingly, a more complex injection system.
At temperatures below about ° C, as a rule, preheating is not required, since the heat loss through the walls due to a single combustion chamber is noticeably less than that of engines with adjacent combustion chambers.

Design
The design of the heads of the cylinder blocks has changed a lot in the process of improving engines. The shape of the head of the cylinder block strongly depends on the parts it turns on.

Basically, the following factors affect the shape of the head of the cylinder block:

• the number and location of the valves;
• the number and location of the camshafts;
• position of incandescent candles;
• position of nozzles;
• channel shape for charging.

Another requirement for the head of the cylinder block is, the perhaps, compact form.
The shape of the head of the cylinder block primarily defines the valve drive concept. To ensure high engine power, low emissions of harmful substances and a small fuel consumption are necessary, the cause, efficient and flexible charge shift and high degree of cylinder filling. In the past, the following was done to optimize these properties:

• top Layout of Valves;
• the upper arrangement of the camshaft;
• 4-valves on the cylinder.

The special shape of intake and exhaust channels improves charge shift. Basically head blocks of cylinders are distinguished by the following criteria:

• number of details;
• valve number;
• cooling concept.

In this place, we should once again mention that only the head of the cylinder block is considered here as a separate item. Due to its complexity and severe dependence on these parts, it is often described as a single functional group. Other topics can be found in the relevant chapters.

Number of details
The head of the cylinder block is called one-room when it consists of only one of the only large casting. Such small details, like the lids of the bearings of the camshaft, are not considered here. Many heads of cylinder blocks are collected from several separate parts. A frequent example of this is the heads of the blocks of cylinders with configured support straps for distributional shafts. However, in diesel engines BMW, only one-piece heads of cylinder blocks are currently being used.

Fig.15 - Comparison of heads with two and four valves
BUT Cylinder head with two valves
IN Four Valve Cylinder Head
1- Cover of the Camera Combustion
2- Valves
3- Direct Channel (Dyed Valve District Education)
4- Position Candle of Incandescent (4 Valves)
5- Nozzle position ( direct injection with four valves)

Number of valves
Initially, four-stroke diesel engines had two valves per cylinder. One graduation and one intake valve. Thanks to the installation of the turbocharger, good filling of cylinders was obtained and at 2 valves. But for several years now, all diesel engines have four valves per cylinder. Compared to two valves, it gives a large total area of \u200b\u200bthe valves and, thereby, the best passage section. Four valves per cylinder, moreover, allow you to place a nozzle in the center. Such a combination is necessary in order to ensure high power at low outflow indicators.
Fig.16 - Vortex Channel and M57 engine filling channel
1- Graduation channel
2- Exhaust valves
3- Vortex Canal
4- Nozzle
5- Inlet valves
6- Filling Channel
7- Swirl valve
8- Candle of incandescent

In the vortex channel, the incoming air is driven into rotation for good mixing at low frequencies of rotation of the engine crankshaft.
Through the tangential channel, the air can act freely in a straight line into the combustion chamber. This improves the filling of cylinders, especially at high rotational frequencies. To control the filling of cylinders, a vortex valve is sometimes installed. It closes the tangential channel at low rotational frequencies (strong twist) and smoothly opens it when increasing the speed of rotation (good filling).
The cylinder head in modern BMW diesel engines includes a vortex channel and a filling channel, as well as a centrally located nozzle.

• Combination of both types

When cooled by the transverse flow, the coolant proceeds from the hot side of the release to the cold side of the intake. This gives the advantage that in the entire head of the cylinder block there is a uniform distribution of heat. In contrast to this, when cooled by the longitudinal flow, the coolant flows along the axis of the cylinder head of the cylinder head, that is, from the front side to the power take-off side or vice versa. The coolant is heated more and more when moving from the cylinder to the cylinder, which means a very uneven heat distribution. In addition, it means a drop in the pressure in the cooling circuit.
The combination of both types cannot eliminate cooling flaws with a longitudinal flow. Therefore, in diesel engines, BMW uses exceptionally cooling the transverse flow.

• condenses the head of the cylinder block from above;
• weakens the sound of the engine operation;
• wares cuttern gases from the Carter unit;
• placement of the oil waste system

• placement of valve adjustment of the potter ventilation pressure;
• placement of sensors;
• placing pipelines.

Sealing cylinder head head gasket
Sealing cylinder block head gasket (ZKD) in any internal combustion engine, whether it is gasoline or diesel, is a very important detail. It is exposed to extreme thermal and mechanical loads.

The functions of ZKD refers to isolated four substances from each other:

• combusting fuel in combustion chamber
• atmospheric air
• oil in oil canals
• coolant

Sealing gaskets are mainly divided into soft and metal.

Soft sealing pads
Sealing gaskets of this type are made of soft materials, but have a metal frame or carriage plate. On this plate, soft linings hold on both sides. Plastic coating is often applied on soft linings. This design allows you to withstand the loads that are usually subjected to sealing gaskets of the cylinder block. The holes in the ZKD, which goes into the combustion chamber, as a result of the loads have a metal edging. Elastomeric coatings are often used to stabilize coolant and oil passes.

Metal sealing pads
Metal sealing gaskets are used in engines working with large loads. Such sealing gaskets include several steel plates. The main feature of the metal pads is that the seal is carried out mainly due to the corrugated plates and stoppers between the plates from the springs. The properties of the ZKD deformation allow it, firstly, optimally lie down in the head of the cylinder block and, to a large extent, to largely compensate for the deformation due to elastic recovery. Such elastic recovery takes place due to thermal and mechanical loads.

The thickness of the necessary ZKD is determined by the appearance of the bottom of the piston relative to the cylinder. Decisive is the greatest value from the measured on all cylinders. There are three options for laying the cylinder head of the cylinder head.
The difference in the thickness of the gasket is determined by the thickness of the intermediate laying. Details To determine the protrusion of the bottom of the piston, see Tis.

Oil pallet

Oil pallet serves as a collection for engine oil. It is made by casting aluminum under pressure or from a double steel sheet.

General remarks
Oil pallet closes the engine crankcase from below. Diesel engines BMW Oil pallet flange is always below the crankshaft center. Oil pallet performs the following tasks:

• serves as a tank for engine oil and
• collects flowing engine oil;
• closes the bottom of the block Carter;
• is an element of engine gain and sometimes gearboxes;
• serves as the location of the sensors and
• the guide tube oil-veneered probe;
• here is a plug of oil-drain hole;
• weakens engine work noise.

A steel sealing gasket is installed as a compaction. Cork sealing pads that were installed in the past had a shrinkage that could lead to the weakening of the threaded fastening.
To ensure the operation of steel gasket when it is installed, oil should not fall on rubber surfaces. Under certain circumstances, the sealing gasket can slip with a sealing surface. Therefore, the flange surface must be cleaned immediately before installation. In addition, it is necessary to ensure that the oil does not drop from the engine and does not fall on the surface of the flange and gasket.

Ventilation Carter

When working in the crankcase cavity, the partare gases are formed to be discharged to prevent seeping of oil in places of sealing surfaces under the action of overpressure. A compound with a pure air pipe in which there is a lower giving singing, waging ventilation. In modern engines, the ventilation system is adjusted using a pressure adjustment valve. The oil separator cleans the crankcase gases from the oil, and it returns through the removal pipeline into the oil pan.

General remarks
When the engine works, the crankcase gases fall from the cylinder into the cavity of the crankcase due to the pressure difference.
Cartrenic gases contain unburned fuel and all the components of the exhaust gases. In the cavity of the crankcase they are mixed with motor Oilwhich is present there in the form of an oil fog.
The number of crankcase gases depends on the load. In the cavity of the crankcase, an excessive pressure arises, which depends on the movement of the piston and on the rotational speed of the crankshaft. This excessive pressure is established in all cavity-related crankcase of hidden cavities (for example, a drain oil pipeline, a gas-distribution mechanism drive crankcase, etc.) and can lead to sealing oil in places of seal.
To prevent this, a crankcase ventilation system was developed. First, the crankcase gases in the mixture with engine oil were simply thrown into the atmosphere. For considerations of environmental protection, crankcase ventilation systems have long been used.
The crankcase ventilation system removes crankcase gases separated from the engine oil in the intake manifold, and droplets of engine oil - through the oil pipe into the oil pan. In addition, the crankcase ventilation system takes care that the crankcase does not arise overpressure.

Unregulated ventilation Carter
In the case of unregulated ventilation, the crankcase mixed with oil crankcase gases are discharged by pouring at the highest rotation frequencies of the engine crankshaft. This vacuum is created when connected to the intake channel. From here the mixture gets into the oil separator. There is a separation of crankcase gases and engine oil.
In Diesel engines of BMW with irregular ventilation, the separation is carried out using a wire mesh. "Purified" Carter gases are discharged into the intake manifold of the engine, while the engine oil returns to the oil pan. The level of the vacuum in the block Carter is limited using a calibrated hole in the clean air channel. Too large vacuum in the block crankcase leads to a breakdown of the engine seals (crankshaft seals. Sealing gasket of the oil pallet flange, etc.). At the same time, the engine comes into the engine, and, as a result, the oil and the formation of the sludge occurs.

Adjustable ventilation Carter
The M51TU engine became the first BMW diesel engine with an adjustable crankcase ventilation system.
BMW diesel engines with an adjustable crankcase ventilation system for oil separation can be equipped with a cyclone, labyrinth or grid oil separator.
In the case of adjustable ventilation of the crankcase, the cavity of the crankcase is connected to the pure air pipe after air filter through the following components:

• ventilation channel;
• soothing chamber;
• carter gases channel;
• oil separator;
• pressure adjustment valve.

Fig.23 - Malotid lazy engine M47
1- Crude crankcase gases
2- Cyclone oil separator
3- Grid oil separator
4- Pressure adjustment valve
5- Air filter
6- Channel to the pure air pipeline
7- Hose to Clean Air Channel
8- Pure air pipeline

In the pure air pipeline, there is a permit due to the operation of the turbocharger O.
Under the action of the pressure difference relative to the block-carter, the crankcase gases fall into the head of the cylinder block and first reach a sedative chamber there.
The sedative chamber is used to splash oil, for example, distributive treals Fit to the crankcase ventilation system. If the oil is carried out with a labyrinth, the task of the sedative chamber is the elimination of crankcase oscillations. This will eliminate the excitation of the membrane in the pressure adjustment valve. In engines with cyclone oil separator, these oscillations are quite valid, because the efficiency of oil waste increases. The gas is then calmed in the cyclone oil separator. Therefore, here the sedative chamber has a different design than in the case of labyrinth oil.
Through the feed pipe cutter gases fall into the oil separator, in which the engine oil separation occurs. The separated engine oil flows back into the oil pan. Purified crankcase gases through the pressure adjustment valve are constantly fed into the clean air pipe in front of the BMW turbocharger in modern diesel engines, 2-component oil separators are installed. First, the preliminary oil is made using a cyclone oil separator, and then the final networkotel in the following mesh separator. Almost all modern Diesel engines BMW both oil separators are placed in one case. An exception is the engine M67. Here, the oil waste is also carried out by cyclone and grid oil separators, but they are not combined into one node. Pre-oil flow occurs in the head of the cylinder block (aluminum), and the final oil separation with the help of a mesh oil separator is in a separate plastic case.

Process adjustment
When the engine is not working, the pressure adjustment valve is open (condition BUT). On both sides of the membrane, the ambient pressure is valid, i.e. the membrane is fully opened under the action of the spring.
When the engine is started, the vacuum increases intake manifold and pressure adjustment valve closes (condition IN). This condition is always preserved at idle or when driving, since the crankcase gases are absent. On the inner side of the membrane, thus, there is a large relative vacuum (relative to the environmental pressure). At the same time, the pressure of the environment, which acts on the outer side of the membrane, closes the valve against the spring force. When loading and rotating crankshaft, crankcase gases appear. Carter gases ( 8 ) Reduce the relative vacuum that acts on the membrane. As a result, the spring can open the valve, and the crankcase gases go. The valve remains open until the equilibrium is established between the pressure of the environment and the crank ravery plus plus the spring force (condition FROM). The larger the crankcase gases, the less the relative vacuum acting on the inner side of the membrane becomes, and the more the pressure adjustment valve opens. Thus, a certain vaccine is maintained in the crankcase (approx. 15 mbar).

Oil waste

To release crankcase gases from engine oil, various oil separators are used depending on the type of engine.

• Cyclone oil separator
• Labyrinth oil separator
• Grid oil separator

When cyclone oil separatorcarter gases are sent to the cylindrical chamber in such a way that they rotate there. Under the action of centrifugal force, heavy oil is pressed out of gas out to the walls of the cylinder. From there through the oil tube, it can flock into the oil pan. Cyclone oil separator is very effective. But it requires a lot of space.
IN labyrinth oil separator Carter gases are passed through a labyrinth of plastic partitions. Such an oil separator is placed in the housing in the cover of the head of the cylinder block. The oil remains on the partitions and can flip into the head of the cylinder block through special holes and from there back into the oil pan.
Grid oil separator In a state, even the smallest drops are filtering. The core of the mesh filter is a fibrous material. However, thin nonwoven fibers with high soot content are prone to rapid pore contamination. Therefore, the grid oil separator has a limited service life and it must be replaced within the framework of maintenance.

Crankshaft with bearings

The crankshaft converts the straight line of the piston in the rotational movement. Loads that act on the crankshaft are very large and extremely complex. The crankshafts are unscrewed or go for use at elevated loads. Crankshafts are installed sliding bearings in which oil is served. In this case, one bearing is a guide in the axial direction.

general information
The crankshaft converts straight (reciprocating) piston movements into the rotational motion. Efforts are transmitted through rods on the crankshaft and are converted to the torque. In this case, the crankshaft relies on the indigenous bearings.

Additionally, the crankshaft assumes the following tasks:

• driver auxiliary and attachment with belts;
• valve drive;
• often the car pump;
• in some cases, the drive of Balan-siren shafts.

Under the action of time-changing and in the direction of force, torque and bending moments, as well as excited oscillations arise. Such complex loads impose very high requirements for the crankshaft.
The lifetime of the crankshaft depends on the following factors:

• bending strength ( weak places are transitions between landing places bearings and shaft cheeks);
• twisting strength (it usually reduces lubricating holes);
• resistance to twisted oscillations (this affects not only rigidity, but also in need);
• wear strength (in places of support);
• wear salts (loss of engine oil with a leakage).

Design
The crankshaft consists of one detail, cast or forged, which is divided into a large number of different sections. The neck of the native bearings fall into the bearings in the block cartridge.
Through the so-called cheeks (or sometimes earrings), connecting rod cervies are connected to the crankshaft. This part with rod cervical and cheeks is called knee. BMW diesel engines are near each rod crankshaft roof bearing. In row engines with each rod cervical through the bearing, one rod is associated, in V-shaped engines - two. This means that the crankshaft of a 6-cylinder-cargo row engine has seven native bearings. The indigenous bearings are numbered in front of the front.
The distance between the connecting rod cervical and the axis of the crankshaft determines the stroke of the piston. The angle between connecting rod cervix determines the interval between ignitions in individual cylinders. For two full turns of the crankshaft or 720 ° in each cylinder, one ignition occurs.
This angle, which is called the distance between connecting cakes or an angle between the knee, is calculated depending on the number of cylinders, the design (V-shaped or inline engine) and the order of the cylinder. At the same time, the goal is a smooth and smooth move of the engine. For example, in the case of a 6-cylinder engine we obtain the following calculation. The angle of 720 °, divided by 6 cylinders, results in the distance between connecting cakes or the interval between the ignitions of 120 ° of the crankshaft.
In the crankshaft there are lubricating holes. They supply rocker bearings with oil. They pass from the necks of the indigenous bearings to connecting rod cervix and through the bed of bearings are connected to the oil circuit of the engine.
The counterweights form symmetrical relative to the axis of the crankshaft mass and, thus, contribute to the uniform operation of the engine. They are made so that along with the power of the inertia of rotation compensate and part of the inertia of the reciprocating movement.
Without counterweight, the crankshaft would be strongly deformed that it would be to the imbalance and deflection of the stroke, as well as to high stresses in the dangerous sections of the crankshaft.
The number of counterweights is different. Historically, most crankshafts had two counterweights, symmetrically on the left and right from the rod cervical. V-shaped eight-cylinder engines, such as M67, have six identical counterweights.
To reduce the mass of crankshafts can be performed by hollow in the middle indigenous bearings. In the case of forged crankshafts, this is achieved by drilling.

Manufacture and properties
Crankshafts are cast or forged. In engines with a large torque, wrought crankshafts are installed.

Advantages of cast crankshafts before writing:

• cast crankshaft shafts are significantly cheaper;
• foundry materials are very well amenable to surface processing to increase the vibrational;
• completed crankshafts in the same performance have a lot of less approx. on 10 %;
• cast crankshafts are better processed;
• crankshaft cheeks usually can not be processed.

Advantages of forged crankshafts in front of cast:

• forged crankshafts tougher and have better vibration.
• in combination with an aluminum block carter, the transmission must be as tough as possible, since the block Carter itself has low rigidity;
• forged crankshafts have low wear of supporting necks.

The advantages of forged crankshafts can be compensated for street shafts with:

• larger diameter in the bearing area;
• expensive systems damping of oscillations;
• very rigid design block carder.

Bearings

As already mentioned, the crankshaft in the BMW diesel engine is installed in the bearings on both sides of the rod cervical neck. These indigenous bearings hold the crankshaft in the block cartridge. The loaded side is in the bearing lid. The force arising during the combustion process is perceived here.
For reliable engine operation, poorly wanted indigenous bearings are required. Therefore, bearings inserts are used, the slide surface of which is covered with special bearings. The sliding surface is inside, that is, the liners of the bearings do not rotate together with the shaft, but are fixed in the block crankcase.
Small wear is ensured if the sliding surface is separated by a thin oil film. It means that there should be sufficient oil supply. It is ideal with an unloaded side, that is, in this case, on the part of the bed of the indigenous bearing. Motor oil lubricant occurs through a lubricant. The circular groove (in the radial direction) improves oil distribution. However, it reduces the sliding surface and, thus, increases the current pressure. More precisely, the bearing is divided into two halves with a smaller bearing capacity. Therefore, oil grooves are usually located only in the unloaded zone. Engine oil, in addition, cools the bearing.

Bearings with three-layer insert
The native crankshaft bearings to which high requirements are presented are often performed as bearings with a three-layer liner. On the metal coating of bearings (for example, swine or aluminum bronze) on steel liner is additionally galvanically applied by a layer of babbit. This gives an improvement in dynamic properties. The strength of such a layer is higher than the thinner layer. Babbit thickness is approx. 0.02 mm, the thickness of the metal base of the bearing - between 0.4 and 1 mm.

Bearings with spraying
Another type of crankshaft bearings is a spray bearing. At the same time, we are talking about a bearing with a three-layer liner with a layer sputted on the sliding surface withsting very high loads. Such bearings are used in high-loaded engines.
Bearings with a spraying of material properties are very solid. Therefore, such bearings are usually used in places in which the largest loads have. This means that the bearings with spraying are installed only on the one hand (from the pressure side). From the opposite side, a softer bearing is always installed, namely the bearing with a three-layer liner. The softer material of such a bearing is able to choose from the detail of the dirt particles. It is extremely important to prevent damage.
When evacuated, the smallest particles are separated. With the help of electromagnetic fields, these particles are applied to the sliding surface with a three-layer liner. Such a process is called spraying. The sprayed sliding layer is characterized by the optimal distribution of individual components.
Bearings with a spraying area in the area of \u200b\u200bthe crankshaft are installed in the BMW diesel engines with maximum power and in the toroids.

Careful treatment of bearings liners is of great importance, since very thin metal layer of bearing is not able to compensate for plastic deformation.
Bearings with spraying can be distinguished by the letter "s" on the back of the bearing cover.
Thrust bearings
The crankshaft has only one thrust bearing, which is often called a centering or stubborn bearing. The bearing holds the crankshaft in the axial direction and should perceive the forces acting in the longitudinal direction. These forces arise under the action:

• gears with oblique teeth for the oil pump drive;
• adhesion control drive;
• acceleration of the car.

The stubborn bearing may have a bearing shape with a border or compound bearing with stubborn semirings.
The stubborn bearing with a collar has 2 grinded support surfaces for the crankshaft and relies on the bed of the root bearing in the block crankcase. Bearing bearing is a single bearing half of the bearing, with a flat surface, perpendicular or parallel to the axis. Only one half of the bearing with a collar was installed on earlier engines. The crankshaft had an axial support of only 180 °.
Composite bearings consist of several parts. With such technology, on both sides, it is established by one stubborn semiring. They provide a stable, free connection with the crankshaft. Due to this, stubborn semiring is movable and fit evenly, which reduces wear. In modern diesel engines, two halves of the composite bearing are installed for the direction of the crankshaft. Due to this, the crankshaft has a 360 ° support, which provides very good resistance to axial movement.
It is important that engine oil lubricant is provided. The reason for refractive bearing failure is usually overheating.
Wirelessly stubborn bearing begins to make noise, first of all, in the area of \u200b\u200bthe damper vibrations. Another symptom may be a malfunction of the crankshaft sensor that automatic box The gear is manifested through hard shoes when switching gear.

Runners with bearings General information
The connecting rod in the crank-connecting mechanism connects the piston with the crankshaft. It converts the straight line of piston into the rotational motion of the crankshaft. In addition, it transfers the forces arising from the combustion of fuel and acting on the piston, from the piston on the crankshaft. T. K. It is a detail that experiences very large accelerations, its mass is directly affected by the power and smoothness of the engine. Therefore, when creating the most comfortable engines, great importance is attached to the optimization of the mass of rods. The connecting rod is experiencing loads of the impact of gases in the combustion chamber and inertial masses (including its own). On the connecting rod, there are variable loads of compression and stretching. In high-speed gasoline engines Stretch loads are determining. In addition, due to side deviations, the connecting rod arises centrifugal forcewhich causes bending.

The features of the connectors are:

• m47 / M57 / M67 engines: parts of bearings on the rod rod are performed in the form of bearing with spraying;
• engine M57: The rod is the same as the engine M47, material C45 V85;
• m67 engine: a trapezoid connecting rod with a lower head, made by the method of fault, material C70;
• M67TU: The wall thickness of the rolled bearings inserts is increased to 2 mm. Batched bolts are first installed with sealant.

The connecting rod transmits the effort and the bottom of the piston on the crankshaft. The connecting rods today are made of forged steel, and the connector on the big head is made by the method of fault. The relatives, among other things, have the advantages that the plane of the sample does not require additional processing and both part are precisely positioned relative to each other.

Design
The connecting rod has two heads. Through a small head, the connecting rod connects with the piston with the help of a piston finger. Due to the side deviations of the connecting rod during the rotation of the crankshaft, it should be able to rotate in the piston. This is carried out using a sliding bearing. To do this, the sleeve is pressed into the small head of the rod.
Through the hole at this end of the connecting rod (from the side of the piston), the oil is supplied to the bearing. From the side of the crankshaft there is a large slotted head of the rod. A large rod head is divided into that the connecting rod can be combined with a crankshaft. The work of this node is provided by the sliding bearing. The sliding bearing consists of two inserts. Lubricant in the crankshaft shaft provides motor oil bearing.
The following figures show the geometry of rods of rods with direct and oblique connectors. The connecting rods with the oblique connector are used mainly in V-shaped engines.
V-shaped engines as a result of large loads have a large diameter of connecting skeins. The oblique connector allows you to make a block-Carter more compact, because when rotating the crankshaft, it describes a smaller curve at the bottom.

Schitun trapezoidal shape
In the case of a trapezoid rod, a small head in cross section has a trapezoid form. This means that the connecting rod becomes thinner from the base adjacent to the rod rod, by the end of the small head of the rod. This allows you to further reduce the mass, since the material is saved with the "unloaded" side, while the full bearing width is saved on the loaded side. In addition, it allows you to reduce the distance between the bins, which, in turn, reduces the deflection of the piston finger . Another advantage is the lack of a lubricating hole in the small head of the connecting head, since the oil rolls the sliding bearing. Due to the absence of the opening, its negative effect on strength is eliminated, which allows you to make a rod in this place. Thus, not only the mass But it turns out the winnings in the space of the piston.

Manufacture and properties
The rooting of the connecting rod can be performed in various ways.

Hot stamping
The source material for the manufacture of the rod blank is a steel rod that heats up approx. Up to 1250-1300 "S. Rolling is performed by the redistribution of masses towards the connecting rod. When the main form is formed during the stamping, due to the extra material, there is a breakdown, which is then removed. At the same time, the holes of the connecting rod heads are also sold. Depending on the doping steel after Stamping properties are improved using heat treatment.

Casting
When casting rods, a plastic or metal model is used. This model consists of two halves, which together form the connecting rod. Each half is molded in the sand, so that there are reverse halves. If they are now connecting, it turns out a shape for casting rod. For greater efficiency in one foundry, many connecting rods are cast next to each other. The form is filled with liquid cast iron, which then slowly cools.

Treatment
Regardless of how the billets were made, they are processed by cutting to final sizes.
To ensure uniform operation of the engine, the connecting rod must have a given mass in the narrow limits of tolerance. Previously, additional sizes for processing were asked for this, which, if necessary, milled during modern methods of manufacture, technological parameters are controlled so accurately that it makes it possible to produce rods in permissible mass limits.
Only the end surfaces of the big and low heads and the heads of the connecting rod are processed. If the connecting rod head connector is cut, then the surface of the connector must be processed additionally. The inner surface of the big head of the rod is drilled and honing.

Perform connector by the method of fault
In this case, the big head is divided as a result of fault. At the same time, the specified fault location is caused by a cernation with a stretcher or with a laser. Then the connecting rod head is clamped on a special mandrel of two parts and is separated by the pressing of the wedge.
To do this, we need a material that breaks without pulling around before it is too much (deformation when the connecting rod cover is failed, both in the case of a steel connecting rod and in the case of a rod of powder materials, the surface of the fault is formed. Such a surface structure is formed accurately centers the indigenous bearing cover when installed On the rod rod.
The result is the advantage that no additional processing of the connector surface is required. Both halves exactly coincide with each other. Positioning with the help of centering sleeves or bolts is not required. If the connecting rod cover is confused or installed on another rod rod, the structure of the fault of both parts is destroyed, and the cover is not centered. In this case, it is necessary to replace the entire rod to the new one.

Threaded fastening

The threaded mount of the connecting rod requires a special approach, since it is subjected to very high loads.
Threaded mounting rods are subjected when rotating the crankshaft very quickly changing loads. T. K. The connecting rod and bolts of its attachments belong to the movable parts of the engine, their mass must be minimal. In addition, the boundedness of the place requires a compact threaded mount. From here, a very high load on the threaded mount of the rod, which requires particularly cautious circulation.
Detailed data on threaded mounting rods such as thread, tightening order, etc. See Tis and ETC.
When installed new set of rods:
batched bolts can be tightened when the connecting rod is installed only once to check the bearing gap and then with the final installation. T. K. The connecting rod bolts have been tightened three times during the roller processing, they have already achieved their maximum tensile strength.
If the connecting rods are used again, but only connecting connecting bolts are replaced: the connecting rod bolts must be tightened again after checking the bearing gaps, weaken again and tightening to the third time to bring to maximum tensile strength.
If the connecting rod bolts have been tightened at least three times or more than five times, it leads to engine damage.

Piston with rings and piston finger

Pistons convert the gas pressure arising during combustion, the shape of the bottom of the piston is determined for the mixture formation. Piston rings provide a thorough compaction of the combustion chamber and adjust the thickness of the oil film on the cylinder wall.
general information
Piston is the first link in the parts chain transmitting the power of the engine. The task of the piston is to perceive the pressure of pressure arising from the combustion and transfer them through the piston finger and the rod to the crankshaft. That is, it converts thermal energy of combustion into mechanical energy. In addition, the piston must lead the top head of the connecting rod. The piston, along with piston rings, should prevent the release from the combustion chamber of gases and the oil consumption, and it is securely and to do it and with all engine operation modes. Available on the surfaces of contact oil helps sealing. BMW diesel engines pistons are made exclusively from aluminum-silicon alloys. The so-called autothermal pistons with a solid skirt are established, in which steel strips are included in the casting are used to reduce the installation gaps and regulating the amount of heat generated by the engine. For the selection of the material in a pair to the walls of the cylinders from the gray cast iron on the surface of the piston skirt, a layer of graphite is applied (by the method of semi-vacation friction), due to which the friction decreases and acoustic characteristics are improved.

As part of the crank-connecting mechanism, the piston is experiencing loads:

• gas pressure forces formed during combustion;
• moving inertial parts;
• forces of the lateral injection;
• the moment in the center of gravity of the piston, which is caused by the location of the piston finger with the displacement relative to the center.

The inertia forces of moving returnable parts arise as a result of the movement of the piston itself, piston rings, piston fingers and the part of the connecting rod. Inertia forces are increasing in quadratic dependence on the speed of rotation. Therefore, in high-speed engines, a small mass of pistons together with rings and piston fingers is very important. In diesel engines, the bottoms of the pistons are subject to a particularly heavy load due to the pressure of the ignition reaching 180 bar.
The deflection of the connecting rod creates the side load of the piston perpendicular to the axis of the cylinder. It acts so that the piston, respectively, after the bottom or top dead point pressed on one side of the cylinder wall to another. Such behavior is called the change of adjustment or shift. To reduce noise in pistons and wear, the piston finger is often located with a displacement from the center of approx. 1-2 mm (dezaxically), due to this, the moment occurs that optimizes the behavior of the piston when the fit is changed.

Design

The piston distinguishes the following main areas:

• piston bottom;
• piston rings belt with cooling channel;
• piston skirt;
• piston Bush.

In Diesel engines BMW in the bottom of the piston there is a combustion chamber cavity. The form of the cavity is determined by the combustion process and the location of the valves. The area of \u200b\u200bthe piston rings belt is the bottom of the so-called fire belt, between the bottom of the piston and the first piston Ring, as well as the jumper between the 2nd piston ring and the oilmaging ring.