5.1.2. Krivoshipno-shatunny mechanism

Pistons are cast from high-siliceous aluminum alloy and thermally processed. A piston head — cylindrical with the flat bottom. On a cylindrical surface of a head three flutes are pierced: in two top compression rings, and in lower — oil scraper are established. In a flute under an oil scraper ring cuts on both sides are executed in order that the rubbing piston skirt surfaces from heat going from the piston bottom did not overheat. On the same cuts the oil removed by an oil scraper ring is taken away in an engine case. Under a flute for an oil scraper ring the facet and on it — on two openings on both sides which serve for removal of the oil accumulating under an oil scraper ring too is executed.
Piston skirt oval in cross section and barrel-shaped in longitudinal. The big axis of an oval is located in the plane, a perpendicular axis of a piston finger. The size of ovality of the piston makes 0,39 — 0,43 mm. The largest diameter of a skirt of the piston settles down 8 mm below than an axis of a piston finger. Diameter of a skirt smoothly decreases also in the direction to the bottom and in an opposite direction: the maximum reduction of diameter on a facet edge under the lower flute makes 0,034 — 0,064 mm, on the lower edge of a basic part of a skirt — 0,050 — 0,080 mm. The opening axis under a piston finger is displaced from the average plane on 1,5 mm in right (on the car course) the party for reduction of noise from a piston rearrangement from one wall of a sleeve to another at change of the direction of the movement of the piston (up — down).
In a piston body between the lower flute and an opening under a piston finger the steel temperature-controlled insert serving for reduction of deformations of the piston when heating to working temperature and reduction of initial assembly gaps at assembly is filled in. Pistons are installed in sleeves of the same dimensional group with a gap of 0,024 — 0,048 mm.
For providing the required gap pistons and sleeves are divided (on diameter) into five groups designated by the corresponding letter which is beaten out on the bottom of the piston and is put on an external surface of the lower part of a sleeve (tab. 4.1).

Table 4.1. Dimensional groups of pistons and sleeves
Dimensional groups of pistons and sleeves
Designation of group
Diameter, mm
piston
piston
And
92,000-91,988
92,036-91,024
B
92,012-92,000
92,048-92,036
In
92,024-92,012
92,060-92,048
92,036-92,024
92,072-92,060
Д
92,048-92,036
92,084-92,072

For improvement extra earnings the surface of the piston is covered (an electrolytic way) with a layer of tin 0,001 — 0,002 mm thick.
That pistons worked correctly, they have to be installed in cylinders in strictly certain situation. For this purpose on one of lugs of the piston there is an inscription "BEFORE". According to this inscription the piston the specified party has to be turned to a forward part of the engine.
Piston rings. Compression rings are cast from cast iron: top — from the high-strength cast iron having high elasticity; lower — from gray cast iron. The top compression ring works in the most severe conditions (at a high temperature and pressure, and also at a lack of lubricant). For increase in wear resistance its external surface adjacent to the cylinder is covered with a chrome layer. The chrome layer considerably increases service life of the top ring. It promotes also increase in service life of the lower ring of the cylinder.

Fig. 4.4. Installation of piston rings on the piston: 1 — the top compression ring; 2 — the lower compression ring; 3 — a ring disk; 4 — an axial dilator; 5 — a radial dilator




The external cylindrical surface of the lower compression ring is covered with a layer of tin 0,006 — 0,012 mm thick (or all surface of a ring has a phosphatic covering) that improves it to extra earnings. On an internal cylindrical surface of the lower compression ring there is a bore (fig. 4.4) thanks to which the new rings installed in the cylinder are turned out and adjoin to the cylinder only an edge a little. It accelerates and improves to extra earnings of rings to a cylinder mirror. The ring has to be installed on the piston by bore up. Violation of this condition causes sharp increase of a consumption of oil and smoking of the engine. The top ring of bore has no.
Oil scraper ring — assembly, four - or three-element. The four-element ring consists of two steel ring disks 3 and two steel dilators: axial 4 and radial 5. The three-element oil scraper ring consists of two steel ring disks and one steel two-functional dilator. The working cylindrical surface (adjacent to the cylinder) ring disks is covered with a layer of chrome 0,080 — 0,130 mm thick.
Height of compression rings — 2 mm, oil scraper assembled — 4,9 mm. The lock of rings — a straight line.
Piston fingers of floating type (they are not fixed neither in the piston, nor in a rod) are made of the low-alloyed steel by method of cold disembarkation. The external surface of a finger is subjected to an uglerodonasyshcheniye on depth of 1 — 1,5 mm and tempered by heating of TVCh to HRC 59—66 hardness. Outer diameter of a finger — 25 mm.
To prevent knock of fingers, they are selected to pistons with the minimum gap, admissible under the terms of lubricant. As linear expansion of material of the piston is approximately twice more, than at a finger, at the room temperature the finger enters openings of lugs of the piston with a tightness.
The finger approaches a rod with a gap from 0,0045 to 0,0095 mm. For convenience of selection fingers, rods and pistons are divided into dimensional groups (tab. 4.2).

Table 4.2. Dimensional groups of fingers, pistons and rods
Dimensional groups of fingers, pistons and rods
Diameter, mm
Marking
finger
in a piston lug
in the rod plug
fingers and rods
piston
25,0000-24,9975
25,0000-24,9975
25,0070-25,0045
White
I
24,9975-24,9950
24,9975-24,9950
25,0045-25,0020
Green
II
24,9950-24,9925
24,9950-24,9925
25,0020-24,9995
Yellow
III
24,9925-24,9900
24,9925-24,9900
24,9995-24,9970
Red
IV


Fingers and rods are marked by paint: a finger — on an opening or at an end face, a rod — on a core of a piston head, the piston — the Roman figures (knockout) on the bottom or paint on a weight lug. It is necessary to select a piston finger to a rod and the piston as it is specified in the subsection "Repair of the Engine".
The exact size of mass of a finger is provided with keeping of admissions on the sizes at production.
In the piston the finger is kept by two lock rings made of a round spring wire with a diameter of 2 mm. Rings have the short mustache unbent aside. Lock rings establish by means of flat-nose pliers so that the short mustache was turned outside.
Rods — steel shod with a double-T section core. In a piston head of a rod the thin-walled plug from olovyanisty bronze is pressed. The Krivoshipny head of a rod — demountable. The cover of a krivoshipny head fastens to a rod two bolts with a polished landing part.
Bolts of fastening of covers and nut of conrod bolts are made of the alloyed steel and thermally processed.
Nuts of conrod bolts drag on the moment of 68 — 75 N · m (6,8 — 7,5 kgfs · l) also are stopped by Unigerm-9 sealant.
Covers of rods are processed assembled with a rod and therefore they cannot be rearranged from one rod on another. For prevention of a possible mistake on a rod and on a cover (on a lug under a bolt) serial numbers of cylinders are beaten out. They have to be located on the one hand. Besides, deepenings for the fixing ledges of inserts also have to be in a cover and a rod on the one hand.
In a rod core the krivoshipny head has an opening with a diameter of 1,5 mm through which cylinder mirror lubricant is produced. This opening has to be sent to the right side of the engine, i.e. aside, opposite to the camshaft. At the correct assembly number "24", vyshtampovanny on the average shelf of a core of a rod, and also a ledge on a cover of a rod have to be turned to the forward party of the engine.
For ensuring dynamic steadiness of the engine the total mass of the piston, the piston finger, rings and a rod installed in the engine can have a difference on cylinders no more than 12 g that is provided with selection of details of the corresponding weight. On details the difference in weight can be: pistons — 4 g, rods — 18 g, piston fingers — 2 g. For providing the above-stated difference in the mass of details in one engine (12 g) rods on weight break into four groups and no more than 5 g have to be selected for one engine with a difference.
The bent shaft - is cast from high-strength cast iron, has five support, assembled with a flywheel and coupling is dynamically balanced (an admissible imbalance — no more than 35 g · by cm). Diameter of radical necks — 64 mm, conrod — 58 mm. Conrod necks hollow. Cavities in conrod necks are closed by carving traffic jams and intended for additional purification of the oil arriving on conrod necks. Under the influence of the centrifugal forces arising at rotation of a bent shaft in cavities of conrod necks the metal particles of products of wear which are contained in oil are deposited.
Oil is brought to cavities of conrod necks on openings in shaft cheeks from a ring flute on inserts of radical necks of a bent shaft. To radical necks oil arrives from the oil highway on channels in block partitions.

Fig. 4.5. Forward end of a bent shaft: 1 and 2 — persistent washers; 3 — a bearing insert; 4 — a bearing cover; 5 — a pin; 6 — a washer persistent




Axial movement of a bent shaft is limited to two persistent steel-aluminum washers of 1 and 2 (fig. 4.5) located on both sides of the forward radical bearing. The forward washer is turned by 1 antifrictional layer to a steel persistent washer 6 on cranked to a shaft, a back washer 2 — to a cheek of a bent shaft. The forward washer refrains from rotation by two pins 5 pressed in the block and a cover of the radical bearing. The acting ends of pins enter washer grooves. The back washer refrains from rotation by the ledge entering a groove at a back end face of a cover of the radical bearing. The size of an axial gap makes 0,125 — 0,325 mm.
On the forward end of a bent shaft on splines the steel persistent washer, a camshaft drive gear wheel, a maslootrazhatel and a nave of a pulley of a bent shaft are established. All these details are pulled together with the bolt screwed in a forward end face of a bent shaft. The Shponochny groove in a nave of a pulley is condensed with a rubber stopper. To a nave six bolts the pulley of a bent shaft from which are given by two belts to rotation the fan, a krylchatka of the water pump and a pulley of the generator fastens. On a pulley the special device — the damper serving for clearing of tortional fluctuations of a bent shaft is mounted thanks to what noise decreases and operating conditions of gear wheels of the drive of the camshaft are facilitated. The damper consists of a pig-iron disk, napressovanny through elastic (rubber) laying on a cylindrical ledge of a pulley of a bent shaft.

Fig. 4.6. Definition of the top dead point




On a pulley of a bent shaft one tag, and on a damper disk — three tags (fig. 4.6) serving for definition of the top dead point (TDP) and installation of ignition is put.
Tag on a pulley and the third tag on a disk of a damper have to be against each other. Mutual mixture of tags indicates failure of a damper. At combination with an edge index on a cover of distributive gear wheels of the third tag (in the direction of rotation) on a damper disk pistons of the first and fourth cylinders are in VMT. The second tag corresponds to situation 5 ° to VMT and serves together with the third tag for installation of ignition on the idle engine.
The first tag corresponds to situation 12 ° to VMT and serves together with the second and third tags for control of correctness of installation of ignition on the working engine.
The forward end of a bent shaft is condensed with a rubber cuff with the maslootrazhatel pressed in a cover of distributive gear wheels. On a maslootrazhatel there is an otbortovka which is taking away the oil which is flowing down on a cover wall. For simplification of work of a cuff before it on cranked one more maslootrazhatel is established to a shaft.
Reliable functioning of a cuff after a partition is ensured by good centering of a cover of distributive gear wheels (see the subsection "Repair of the Engine").
The back end of a bent shaft is condensed with stuffing from the asbestos cord impregnated with antifrictional structure and covered with graphite.
Stuffing is put in flutes of the block of cylinders and the special holder who fastens two hairpins to the block. On a neck of a bent shaft under stuffing there is a microscrew, and before stuffing — the crest serving for rejection of oil from a consolidation zone. Joints of the holder are condensed with rubber laying of the G-shaped form. In a back end face of a bent shaft the nest for installation of the ball-bearing of a main shaft of the transmission is chiseled.
The flywheel is cast from gray cast iron. It fastens to a flange on the back end of a bent shaft four polished bolts.
The moment of an inhaling of nuts of bolts — 76 — 83 N · m (7,6 — 8,3 kgfs · м). Zakontrena nuts an otgibny plate. On a flywheel напрессован a gear rim for launch of the engine a starter. Before assembly with a bent shaft a flywheel statically balance (tab. 4.3).

Table 4.3. An imbalance of the rotating details, admissible at assembly of the engine
Imbalance of the rotating details, admissible at assembly of the engine
Detail
Balancing method
Admissible imbalance,   · cm, no more
Way of elimination of an imbalance
Bent shaft assembled with traffic jams
Dynamic
40 on each end
Drilling of metal in the radial direction from counterbalances on the 1,4, 5 and 8 cheeks a drill with a diameter of 8 mm on depth of 45 mm
Flywheel and gear wreath
Static
35
Drilling of metal from fastening of coupling on the radius of 146 mm a drill with a diameter of 12 mm on depth no more than 15 mm
Bent shaft, flywheel and coupling assembled
Dynamic
35 on the back end
Drilling of metal from fastening of coupling on the radius of 146 mm a drill with a diameter of 12 mm on depth no more than 15 mmvysverlivaniye of metal from a flywheel from coupling on the radius of 151 mm a drill with a diameter of 12 mm on depth no more than 12 mm; distance between centers openings - not less than 16 mm
Press a clutch plate with a casing assembled
Static
25
Drilling of metal from the lugs aligning springs, a drill with a diameter of 11 mm on depth no more than 25 mm taking into account a drill cone; at repeated installation of knot on the balancing machine the imbalance of 100 g · is allowed by cm
Pulley damper of a bent shaft with a nave assembled
Static
20
Drilling of metal from a forward end face of a pulley on the radius of 64 mm a drill with a diameter of 10 mm on depth no more than 9 mm

To a back end face of a flywheel six bolts attached a coupling casing. On a flange of a casing of coupling and a flywheel the tag is beaten out "About". At assembly of the engine both tags have to be combined not to break balancing of a bent shaft.
Inserts. Radical and conrod bearings of a bent shaft consist of the thin-walled interchangeable inserts made of a low-carbonaceous steel tape with a thin layer of antifrictional vysokoolovyanisty aluminum alloy. Thickness of a radical insert fluctuates within 2,233 — 2,240 mm, and conrod — 1,738 — 1,745 mm. About two inserts are installed in each bearing. Axial movement and a provorachivaniye of inserts in beds of the block or in rods are interfered by the fixing ledges on inserts entering the corresponding grooves in beds of the block or in rods.
All radical inserts have a ring flute for a continuous power oil of conrod necks of a bent shaft. In the middle of radical inserts there is an opening through which oil to bearings from the channel in a block bed moves. Openings in connecting rods coincide with openings in rods. For preservation of a vzamozamenyaemost and the prevention of mistakes at installation of new inserts on all radical and brass inserts openings are made. Width of radical inserts — 25,5 mm, conrod — 28,5 mm. The diametrical gap between a neck and inserts makes 0,020 — 0,073 mm for radical and 0,010 — 0,063 mm for conrod bearings.
For providing the specified gaps and an exception of deformation of details of a nut of conrod bolts, hairpins of fastening of covers of radical bearings tighten a dynamometer key with the moment stated above.