5.3.2. Krivoshipno-shatunny mechanism
Pistons are cast from high-siliceous aluminum alloy and thermally processed. Piston head cylindrical. The piston bottom — flat, with four tsekovka under valves which prevent a contact (blows) about the bottom of the piston of plates of valves at the violation of phases of gas distribution caused, for example, by break of a chain of the drive of camshafts.
In the top part of a cylindrical surface of pistons three flutes are pierced: in two top compression rings, and in lower — oil scraper are established.
In the top part of a skirt of the piston about two openings on both sides with an exit in a flute under an oil scraper ring which serve for removal of the oil accumulating under an oil scraper ring are 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 0,514 — 0,554 mm. The largest diameter of a skirt of the piston in longitudinal section settles down below an axis of a piston finger on 8 mm.
Diameter of a skirt in longitudinal section 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 0,047 — 0,056 mm. On the lower edge of the directing part of a skirt the maximum reduction of diameter makes 0,009 — 0,018 mm.
In a piston body between the lower flute and an opening under a piston finger the steel temperature-controlled insert serving for reduction of deformation of the piston when heating to working temperature and reduction of initial assembly gaps at assembly is filled in. Pistons are installed in cylinders of the same dimensional group with a gap of 0,036 — 0,060 mm. For providing the required gap pistons and cylinders of the block are divided (on diameter) into five groups designated by the corresponding letter (And, B, In, E) which is beaten out on the bottom of the piston and is put with paint on an external surface in the top part of the block, on the right side.
For improvement extra earnings the working surface of pistons has a special microrelief.
That pistons worked correctly, they have to be installed in cylinders in strictly certain situation. For this purpose on a sidewall one of lugs under a piston finger has a cast inscription "BEFORE". According to this inscription the piston the specified party has to be turned to a forward part of the engine.
Fig. 4.114. Piston rings: 1 — the top compression ring; 2 — the lower compression ring; 3 — a ring disk; 4 — a dilator
Compression rings are cast from cast iron. The top ring of 1 (fig. 4.114) has a barrel-shaped working surface for improvement extra earnings and is covered with a layer of porous chrome; the working surface of the lower ring 2 is covered with a layer of tin 0,006 — 0,012 mm thick or has a phosphatic covering which is applied on all surface, 0,002 — 0,006 mm thick. On an internal surface of the lower compression ring there is a bore. This ring has to be installed on the piston by bore up, to the piston bottom. Violation of this condition causes sharp increase of a consumption of oil and smoking of the engine.
The oil scraper ring — assembly, three-element, consists of two steel ring disks 3 and one two-functional dilator 4 performing functions of radial and axial dilators. The working surface of ring disks is covered with a chrome layer.
Piston fingers — floating type (they are not fixed neither in the piston, nor in a rod), are made of the low-alloyed chromonickel steel, the external surface of a finger is subjected to an uglerodonasyshcheniye on depth of 1,0 — 1,5 mm and tempered by heating of TVCh to NRSE 59 — 66 hardness. Outer diameter of a finger — 22 mm.
Axial movement of a finger is limited to the lock rings established in flutes of lugs of the piston. Lock rings are made of a round spring wire with a diameter of 1,6 mm.
To prevent knock of fingers, they are selected to pistons with the minimum gap, admissible under the terms of lubricant.
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. 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 a nut of conrod bolts are made of the alloyed steel and thermally processed. Nuts of conrod bolts have the self-stopped carving and therefore in addition are not stopped.
Covers of rods 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, grooves for the fixing ledges of inserts also have to be in a rod and a cover on the one hand.
For cooling of the bottom of the piston with oil in a rod openings are executed: in a core — with a diameter of 5 mm, in the top head — 3,5 mm.
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 10 g that is provided with selection of details of the corresponding weight.
The bent shaft is cast from high-strength cast iron, five-basic, has eight counterbalances for the best unloading of support. The shaft is dynamically balanced: an admissible imbalance — no more than 18 g · cm on each end of a shaft. Diameter of radical necks — 62 mm, conrod — 56 mm. Radical and conrod necks are tied by openings in shaft cheeks. Cavities in conrod necks are closed by carving traffic jams and intended for additional purification of the oil arriving on conrod necks.
Oil to radical necks is carried out on channels in block partitions from the oil highway, to cavities of conrod necks — on openings in shaft cheeks from flutes in the top inserts of radical necks of a bent shaft.
Fig. 4.115. Average (persistent) radical bearing of a bent shaft: 1 — the block of cylinders; 2 — bearing inserts; 3 — persistent semi-washers; 4 — a bearing cover; 5 — a bent shaft
Axial movement of a bent shaft is limited to the persistent steel-aluminum semi-washers of 3 (fig. 4.115) located on both sides of the average (persistent) radical bearing.
Semi-washers are turned by an antifrictional layer to cheeks of a bent shaft 5. Semi-washers refrain from rotation at the expense of ledges on the lower semi-washers entering grooves at cover end faces 4 radical bearings. The size of an axial gap makes 0,06 — 0,162 mm.
Fig. 4.116. Forward end of a bent shaft: 1 — a bolt (or a ratchet); 2 — a pulley damper with a synchronization disk; 3 — an epiploon; 4 — a chain cover; 5 — the plug; 6 — an asterisk; 7 — the block of cylinders; 8 — bearing inserts; 9 — a bent shaft; 10 — a bearing cover; 11 — an oil case; 12 — a rubber sealing ring; 13 — a lock washer
On the forward end of a bent shaft on splines are established the leading asterisk 6 (fig. 4.116.) drive of camshafts, plug 5 and pulley damper 2. All these details are pulled together with the bolt 1 screwed in a forward end face of a bent shaft. Between an asterisk and the plug it is established rubber sealing by a ring of roundish section.
On a cylindrical surface of a pulley damper of a bent shaft it is executed risk for definition of VMT of the first cylinder at installation of the drive of camshafts. At combination of a tag on a pulley damper with an edge index on a chain cover the piston of the first cylinder is in VMT. Besides, on a pulley damper the special gear disk (a synchronization disk) with number of teeths 60 minus 2 teeth which ensures functioning of the sensor of provision of a bent shaft is executed. The forward end of a bent shaft is condensed with the rubber epiploon 3 pressed in a chain cover. Reliable functioning of an epiploon is ensured by centering of a cover of a chain on two pins plugs pressed in a forward end face of the block of cylinders.
Fig. 4.117. Back end of a bent shaft: 1 — a bent shaft; 2 — bearing inserts; 3 — the block of cylinders; 4 — a cover; 5 — an epiploon; 6 — a flywheel; 7 — a bolt of fastening of a flywheel; 8 — the bearing; 9 — the expansion plug; 10 — a washer of bolts of a flywheel; 11 — an oil case; 12 — a bearing cover
The back end of a bent shaft is also condensed with the rubber epiploon of 5 (fig. 4.117) pressed in a cover 4 which fastens to a back end face of the block of cylinders.
The flywheel is cast from gray cast iron, established on a landing ledge and a pin of a flange of a bent shaft and fastens to it six bolts of M8 having самоконтрящуюся a carving. For reliability of fastening of a head of bolts nestle on the steel thermoprocessed washer. On a flywheel напрессован a gear rim for launch of the engine a starter. To a back end face of a flywheel six bolts of M8 attached coupling. In the central opening of a flywheel the expansion plug 9 and the bearing 8 of a main shaft of the transmission are installed.
Radical and conrod bearings of a bent shaft consist of the thin-walled inserts made of the low-carbonaceous steel tape which is filled in with a thin layer of antifrictional vysokoolovyanisty aluminum alloy. Thickness of a radical insert — 2,5 — 2,508 mm, conrod — 2,0 — 2,008 mm. About two inserts are installed in each bearing. Axial movement and a provorachivaniye of inserts in beds of the block and in rods are interfered by the fixing ledges on the inserts entering the corresponding grooves in beds of the block or in rods.
The top inserts of radical bearings with flutes and openings, lower — without flutes and openings. Through an opening of the top insert oil comes to bearings from the channel to block beds, and through openings in cranked to a shaft — to conrod bearings. The opening in connecting rods coincides with an opening in a rod. Width of radical inserts is 28,0 mm, conrod — 20,5 mm. The diametrical gap between a neck and inserts makes 0,019 — 0,073 mm for radical and 0,009 — 0,063 mm for conrod bearings.