357217bd 357217bd

5.1.3. Six-cylinder diesel engines

Fig. 4.5. A motor compartment with the diesel engine 300 D: 1 – the cooled box from plastic for electronic regulators and relay blocks; 2 – lattice of an air inlet of ventilation of salon; 3 – case of valves of adjustment of pressure; 4 – cover of office of nozzles and spark plugs; 5 – screen wiper drive; 6 – oil filter; 7 – inlet collector; 8 – a tank for brake fluid with the main brake cylinder and the amplifier of brakes; 9 – block of safety locks and relay; 10 – broad tank; 11 – air filter; 12 – perepuskny valve of final system; 13 – masloizmeritelny probe; 14 – cover of an oil-filling mouth; 15 – petrol filter; 16 – spare capacity of hydraulic oil for a servoupravleniye; 17 – a washer reservoir (in front — for headlights, behind — for a screen wiper); 18 – brake unit

Along with 5-cylinder Mercedes turbo engines offers the 6-cylinder diesel engine with a volume of cylinders of 3 l (OHM 606) (fig. 4.5). Technically the OHM 606 almost completely corresponds to the OHMS models 604 and OHM 605 with smaller number of cylinders (2,5 l, 5 tsit.). It is equipped with a head of the block of cylinders with forkamery and four valves on the cylinder, electronic control, line TNVD, a two-mass flywheel (at models with the mechanical transmission). The bent shaft of the 6-cylinder engine is established on seven basic bearings. Exclusive feature of OHMS 606 is the inlet collector regulated on length in the form of the three-stage resonant soaking-up branch pipe with gates.

Fig. 4.6. A motor compartment with the diesel engine 320 CDI: 1 – broad tank; 2 – air filter; 3 – channel of air supply of a turbocompressor; 4 – the cooled box for electronic regulators and relay blocks; 5 – cover of an oil-filling mouth; 6 – lattice of an air inlet of ventilation of salon; 7 – engine cover; 8 – cover of an inlet collector; 9 – a tank for brake fluid with the main brake cylinder and the amplifier of brakes; 10 – masloizmeritelny probe; 11 – sound signal; 12 – protective front grille; 13 – radiator hose; 14 – cover of the petrol filter; 15 – a washer reservoir (in front — for headlights, behind — for a windshield screen wiper); 16 – control unit of the brake system; 17 – spare capacity of hydraulic oil with a servoregulyator; 18 – block of safety locks and relay

Since August, 1999 began to install the engine 320 CDI (fig. 4.6) with the Common Rail system which replaced E 300 of D on the Mercedes cars.
All engines CDI are carried out on modular system, they have identical distance between cylinders (97 mm) both identical diameters and the working course (88 x 88,34 mm). At the same time engines CDI received a new head of cylinders with four valves, tsentralnoraspolozhenny nozzles and an aluminum design.

Fig. 4.7. Distribution of fuel in the combustion chamber

Fig. 4.8. Multivalvate system

Fig. 4.9. The piston with a rod: 1 – the piston with three piston rings; 2 – rod; 3 – cover of the basic bearing

Fig. 4.10. Two-mass flywheel: 1 – bent shaft; 2 – forward part of a flywheel; 3 – quencher of tortional fluctuations; 4 – back part of a flywheel

Fig. 4.11. A longitudinal section of the 4-cylinder diesel engine with forkamerny injection (OHM 604): 1 – the fan from viskomufty; 2 – oil probe; 3 – chain of the drive of camshafts; 4 – oil-filling mouth; 5 – inlet collector; 6 – a branch pipe from the case of the operating valve; 7 – oil filter; 8 – starter; 9 – two-mass flywheel; 10 – a rod with the piston; 11 – bent shaft; 12 – reception funnel of the oil pump; 13 – oil pump; 14 – chain of the drive of the oil pump

Fig. 4.12. A cross-section of the 4-cylinder diesel engine with forkamerny injection (OHM 604): 1 – reception highway of inlet system; 2 – inlet collector; 3 – glow plugs; 4 – TNVD drive gear wheel; 5 – conrod shaft of a bent shaft; 6 – gear wheel of the drive of the oil pump; 7 – oil level sensor; 8 – cooling system thermostat; 9 – final branch pipe; 10 – the channel of recirculation of the fulfilled gases; 11 – the valve of recirculation of the fulfilled gases; 12 – the case of the operating valve

Fig. 4.13. Five-cylinder diesel engine CDI (OHM 612)

Fig. 4.14. Six-cylinder diesel engine CDI (OHM 613)

Fig. 4.15. Collaboration of the camshaft and valves: 1 – cover of a head of cylinders; 2 – casing of a head of cylinders; 3 – camshaft of final valves; 4 – pushers with hydraulic adjustment of a gap; 5 – injection nozzle; 6 – final valve; 7 – a forkamer with the inlet channel to the combustion chamber; 8 – inlet channel; 9 – nozzle; 10 – camshaft of inlet valves

Fig. 4.16. Provisions of the piston: 1 – top dead point; 2 – working course; 3 – lower dead point; 4 – combustion chamber; 5 – head of the block of cylinders

   Multivalvate system
Four-valve head of the cylinder. Power of the motor depends not only on the volume of cylinders and speed, but also on the speed of intake of fuel-air mix in the combustion chamber and speeds of production of the fulfilled gases. Therefore in comparison with 2-valvate system 4-valvate promotes more intensive filling of the combustion chamber (fig. 4.7). Besides, four valves of smaller diameter have much more the big area of opening, than two — the bigger diameter (fig. 4.8). Combustion of fuel in engines happens to 4-valvate system "more softly", than in engines with 2-valvate as inertia of valves is less. It promotes lowering of the level of noise during the work.
   Engine details
Block of cylinders. In this biggest and heavy knot the krivoshipno-conrod mechanism settles down. The block of cylinders is manufactured of gray cast iron. In the block there are channels for water cooling. From below the block — a pillow for basic bearings of a bent shaft. Blocks for new 5-and 6-cylinder engines CDI are made of gray cast iron. Because of the increased mechanical loadings (direct injection) blocks have additional stiffening ribs and thicker walls.
Head of the block of cylinders. Closes the block from above. It is made of light alloy. In comparison with a head from gray cast iron the probability of a distortion because of insufficient cooling, the wrong installation or dismantle of not cooled down engine is higher here, but it is easier on weight and at it the thermolysis in the cooling system is higher. In a head of the block there are channels for cooling, lubricants, inlet system and final system. Also in it seats for candles of an incandescence, nozzles, valves and pushers are mounted. Camshafts settle down from above heads of cylinders. Branch pipes are mounted outside on a head of cylinders. At the left various sensors, switches and valves are located. Saddles of valves are made of solid metal. The head of cylinders from aluminum for engines of models CDI differs except other in existence of two spiral inlet channels. One of them serves for a turbulence, another — for filling. Both channels correspond to symmetrically executed combustion chambers and serve for a strong turbulence of air in front of cylinders which helps to create optimum mix of fuel with the forced air. For uniform distribution of fuel in combustion chambers the nozzles of a new design located in the middle of cylinders serve.
Cylinders. Cylinders are built in the block and together with combustion chambers of a head of cylinders form the volume of cylinders. Internal walls of cylinders honingutsya by a so-called method of mesh grinding. Diameters of cylinders are carried out 0,02 mm more, than the corresponding pistons. At capital repairs of the engine it is possible to grind cylinders in addition to 3 times, providing the corresponding repair size.
Pistons. They assume pressure of the burning-down mix and transmit effort to a bent shaft through a rod. Are made of light metal. In the top third of the piston piston rings are located. Two top rings (compression) interfere with penetration of gases during the work in an engine case. The lower (oil scraper) ring removes oil from cylinder walls.
Rods. Connect pistons to a bent shaft (fig. 4.9). The rod head with a bronze insert connects by means of freely put finger to the piston. The basis of a rod is fixed by means of a cover of the basic bearing on cranked to a shaft.
Bent shaft. Will transform back and forth motion of pistons to rotary. In order to avoid vibration during the work of a knee of a shaft have counterbalances. For prevention of uncontrollable fluctuations or a deflection during the work basic necks of a shaft fasten bearings on the engine block. Behind (in the direction of the movement) at an end face of a bent shaft the basic ring with a gear wreath for elimination of an axial beating of a shaft is established. On the forward end of a bent shaft gear wheels for the drive of the camshaft and the oil pump, and also a pulley for a belt of the drive of auxiliary units are mounted.

 Engine details
Two-mass flywheel. The two-mass flywheel (fig. 4.10) is installed in cars with the mechanical transmission. It smoothes the tortional fluctuations of a bent shaft arising during the operation of the engine. A forward part of a flywheel is densely fastened by bolts to a bent shaft 1. On it the quencher of tortional fluctuations 3 consisting of system of springs and dampers is established. A back part of a flywheel is strengthened on a quencher of tortional fluctuations and has no rigid connection with a forward part and a bent shaft.
Appearance, cuts and details of engines are shown in fig. 4.11, fig. 4.12, fig. 4.13, fig. 4.14.
Valves. Through them the injection of gas mixture and production of the fulfilled gases is made.
Camshaft. At four valves on the cylinder both camshafts are installed in the special case.
The camshaft serves for the drive of valves in a certain order. The moment of closing and opening is set by installation of a bent shaft in a certain situation (fig. 4.15).
The drive of camshafts is carried out by a chain from a bent shaft. Both camshafts have gear gearing with each other. The gear wheel on distributive to a shaft has twice more teeth, than a gear wheel on cranked to a shaft. According to number of cylinders camshafts have different length. For economy of weight shaft hollow.

   The basic concepts about operation of engines
Four-cycle principle of work.
Admission (1st step): the piston goes down to the lower dead point; the inlet valve opens, the forced air moves in the cylinder.
Compression (2nd step): the piston goes from the lower dead point to top; the inlet valve is closed; under pressure of the piston air compresses.
Combustion (3rd step): from compression temperature fuel ignites, fuel mix at combustion pushes the piston to the lower dead point, and the rod turns a bent shaft.
Release (4th step): the piston goes again upward, the final valve is open, and the fulfilled gases go to system of release.
Working volume of the cylinder. The volume of the cylinder at which the piston passes from the lower dead point to top is called working volume. On reaching the piston of the top dead point there is still a small space of the combustion chamber. The combustion chamber and working volume are shown in fig. 4.16.
Extent of compression. It is the characteristic of a ratio between the working volume of the cylinder and volume of the combustion chamber. It shows, in how many time gas mixture before ignition is condensed.

Repair of knots and details on engines demands high qualification and the special tool. All works need to be carried out only on specialized STOA.