Gas distribution mechanism:
In engines internal combustion the timely admission of a fresh charge of the combustible mixture into the cylinders and the release of exhaust gases is ensured by the gas distribution mechanism.
The ZIL-130 engine is equipped with a gas distribution mechanism with an overhead valve arrangement.
The gas distribution mechanism consists of camshafts, a camshaft, pushers, rods, rocker arms with fastening parts, valves, springs with fastening parts and valve guides.
The camshaft is located between the right and left cylinder banks.
When the camshaft rotates, the cam runs onto the pushers and raises it together with the rod. The upper end of the rod presses the adjusting screw in the inner arm of the rocker arm, which, turning on its axis, presses the valve stem with the outer arm and opens the inlet or outlet port in the cylinder head. In the engines under consideration, the camshaft acts on the pushers of the right and left cylinder banks.
The gas distribution mechanism with the overhead valve arrangement makes it possible to improve the shape of the combustion chamber, the filling of the cylinders and the conditions of combustion of the working mixture. The better shape of the combustion chamber also allows for increased compression ratio, power and efficiency of the engine.
Rice. 1 - Gas distribution mechanism with the upper arrangement of valves
The camshaft is used to open the valves in a certain sequence in accordance with the order of the engine.
The camshafts are cast from special cast iron or forged from steel. Install it in the holes in the walls and ribs of the crankcase. For this purpose, the shaft has cylindrical ground support collars. To reduce friction between the shaft journals and the supports, bushings are pressed into the holes, the inner surface of which is covered with an anti-friction layer.
On the shaft, in addition to the bearing journals, there are cams - two for each cylinder, a gear for driving the oil pump and a breaker-distributor and an eccentric for the drive fuel pump.
From the front end camshafts of the ZIL-130 engine, the sensor of the pneumatic centrifugal speed limiter is activated crankshaft engine. The rubbing surfaces of the camshaft are hardened by heating with a high frequency current to reduce wear.
The camshaft is driven from the crankshaft using a gear transmission. For this purpose, a steel gear is mounted on the front end of the crankshaft, and a cast iron gear on the front end of the camshaft. The timing gear from turning on the shaft is held by a key and secured with a washer and a bolt wrapped in the end of the shaft. Both camshaft gears have oblique teeth, which cause axial displacement of the shaft when the shaft rotates.
To prevent axial displacement of the shaft during engine operation, a flange is installed between the gear and the front bearing journal of the shaft, which is fixed with two bolts to the front wall of the cylinder block.
Rice. 2 - Device for limiting the axial displacement of the camshaft
Inside the flange, on the toe of the shaft, there is a spacer ring, the thickness of which is slightly greater than the thickness of the flange, as a result of which a slight axial displacement of the camshaft is achieved. In four-stroke engines, the working process takes place in four piston strokes or two revolutions of the crankshaft, i.e., during this time, the intake and exhaust valves of each cylinder must open sequentially, and this is possible if the number of camshaft revolutions is 2 times less than the number of revolutions of the crankshaft, therefore the diameter of the gear, installed on the camshaft, make 2 times larger than the diameter of the crankshaft gear.
The valves in the engine cylinders must open and close depending on the direction of movement and the position of the pistons in the cylinder. Strike the intake as the piston moves from to. m. t. to n. m., the inlet valve must be open, and closed during the compression, expansion (stroke) and exhaust strokes. To ensure such dependence, marks are made on the gears of the gas distribution mechanism: on the tooth of the crankshaft gear and between the two teeth of the camshaft gear. When assembling the engine, these marks must match.
Rice. 3 - Alignment of labels of distribution gears
Pushers are designed to transfer force from the camshaft cams to the rods.
The rods transmit the force from the pushers to the rocker arms and are made in the form of steel rods with hardened tips (ZIL-130) or duralumin tubes with spherical steel tips pressed on both sides. On the one hand, the tips abut against the recess of the pusher, and on the other, against the spherical surface of the rocker arm adjusting bolt.
The rocker arms transmit force from the rod to the valve. They are made of steel in the form of a two-armed lever, planted on an axle. A bronze bushing is pressed into the hole of the rocker arm to reduce friction. The hollow axle is mounted in struts on the cylinder head. A spherical spring holds the link against longitudinal movement. On the ZIL-130 engines, the koromysla are not equal arms. An adjusting screw with a lock nut is wrapped in a short arm, abutting against the spherical surface of the rod tip.
The valves are used to periodically open and close the openings of the inlet and outlet channels, depending on the position of the pistons in the cylinder and the order of engine operation.
In the ZIL-130 engine, the inlet and outlet channels are made in the cylinder heads and end with plug-in sockets made of high-temperature cast iron.
Rice. 4 - the Valve and fastening details
The valve consists of a head and a stem. The head has a narrow, 45 or 30 ° beveled edge (working surface) called a chamfer. The chamfer of the valve must fit snugly against the chamfer of the seat, for which these surfaces are rubbed against each other. Intake and exhaust valve heads have different diameters. For better filling of the cylinders with fresh fuel mixture, the diameter of the intake valve head is made larger than the diameter of the exhaust valve. Due to the fact that the valves heat up unevenly during engine operation (the exhaust valve is washed by hot exhaust gases, heats up more), they are made of different materials: inlet valves - from chromium, exhaust - from silchrome heat-resistant steel. To increase the service life of the exhaust valves of the ZIL-130 engine, a heat-resistant alloy is deposited on their working surface, the rods are made hollow and have sodium filling, which contributes to better heat removal from the valve head to its rod.
The valve stem of cylindrical shape in the upper part has a recess for the valve spring fastening parts. Valve stems are housed in cast iron or sintered metal guide bushings. The bushings are pressed into the cylinder heads and secured with locking rings.
The valve is pressed against the seat of a cylindrical steel spring, which has a variable pitch of turns, which is necessary to eliminate its vibration. The spring rests on one side against the washer located on the cylinder head, and on the other against the support washer. The support washer is held on the valve stem by two tapered beads, the inner flange of which fits into the recess of the valve stem.
To reduce the penetration of oil along the valve stems into the engine combustion chamber, rubber rings are installed in the support washers or rubber caps are put on the valve stems. For uniform heating and wear of the valve, it is desirable that when the engine is running, it turns.
Rice. 5 - Device for turning the exhaust valve of the ZIL-130 engine
In the ZIL-130 engine, the exhaust valves have a swing mechanism. It consists of a stationary body, in the inclined grooves of which there are balls with return springs, a disk spring and a support washer with a locking ring. The mechanism is installed on the valve guide bush in the recess of the cylinder head.
The valve spring bears against the support washer. When the valve is closed and the pressure of the valve spring is low, the disc spring is bent with the outer edge up and with the inner edge against the shoulder of the body.
In this case, the balls are squeezed out in the grooves to the extreme position by means of springs.
When the valve is opened, the pressure of the valve spring increases, straightening the disc spring through the support washer. In this case, the inner edge of the spring moves away from the shoulder of the body and the valve spring, resting on the balls, transfers all the pressure to them, as a result of which the balls move into the groove of the body grooves, causing the disc spring and with it the support washer of the valve spring and valve to rotate. When the valve is closed, all parts return to their original position.
Advancement of opening and delay of closing of valves. When describing the working process of a four-stroke engine, it was indicated that the opening and closing of the valves occurs at the moments when the piston reaches the dead center. However, due to the high speed of the crankshaft, the period of time allotted for the inlet of the combustible mixture and the release of the exhaust gases is short, filling and cleaning the cylinders is difficult.
To obtain the highest power, it is necessary to fill the cylinders with a combustible mixture as best as possible and clean them from combustion products. For this purpose, the inlet valve opens before the piston enters the TDC. at the end of the release cycle, i.e. with an advance within 10 ... 31º of crankshaft rotation, and it closes after the piston arrives at nominal point. at the beginning of the compression cycle, i.e. with a delay of 46 ... 83º.
The duration of the intake valve opening is 236 ... 294º of crankshaft rotation, which significantly increases the amount of combustible mixture or air supplied to the cylinders. The intake of the mixture or air before the piston arrives at the TDC. at the end of the release cycle and after n.m.t. The start of the compression stroke occurs due to the inertial pressure in the intake manifold due to frequently repeated strokes in the cylinders.
The outlet valve opens 50 ... 67º before the piston reaches the nominal pressure. at the end of the stroke, combustion - expansion and closes after the arrival of the piston in the TDC. the cycle of release by 10 ... 47º. The duration of the exhaust valve opening is 240 ... 294º of crankshaft rotation. The exhaust valve opens earlier because the pressure at the end of the expansion stroke is low and is used to clean the cylinders.
After the piston has passed through the VMT. the exhaust gases will continue to flow out by inertia.
The moments of opening and closing of valves of relative dead spots, expressed in degrees of rotation of the crankshaft, are called valve timing.
Rice. 6 - the gas distribution phase
The figure shows a diagram of the valve timing, which shows that there are moments in the engine (at the end of the exhaust stroke and the beginning of the intake stroke) when both valves are open. At this time, the cylinders are purged with a fresh charge of a combustible mixture or air to better clean them from combustion products. This period is called valve overlap.
rice. 7
Camshaft and timing parts for engines 3M3-53 and ZIL-130 - part 1
Camshaft. In fig. 40 shows the camshaft of the ZIL-130 engine and the parts included in its group. The camshafts of 3M3-53 engines are distinguished by the fact that the fuel pump drive eccentric is manufactured as a separate part and a counterweight is provided; the last two parts are slipped onto the front end of the camshaft.
The camshafts of the ZIL-130 and 3M3-53 engines are forged, steel. Bearing journals and cams are hardened i.e. hardened. hours to a depth of 2.5-6 mm to a hardness of HRC 54-62. In 3M3-53 engines, the shaft cams are ground on a cone, which, as mentioned above, causes the pusher to rotate during operation and reduce its wear.
Rice. 40. The camshaft of the ZIL-130 engine:
1 - retaining ring; 2- drive roller washer; 3- centrifugal sensor drive roller; 4 - roller spring; 5 - gear mounting nut; 6-lock washer; 7 - distribution gear; 8 - spacer ring; 9 - thrust flange; 10- fuel pump drive rod; 11- end of the fuel pump lever; 12 - a camshaft
To drive the fuel pump to the camshaft ZMZ engines an eccentric is inserted. For the same purpose, a cam is provided on the shaft of the ZIL-IZO engine, located next to the front support neck, which acts on the fuel pump lever through the rod. Helical gears are provided at the rear end of the shafts to drive the oil pump and ignition distributor.
The camshaft must be repaired and restored in the presence of the following defects:
Chipping at the ends at the tops of the cams is not more than 3.0 mm along the width of the cam;
Shaft bending (runout along the middle bearing journal is more than 0.05 mm);
Risks, seizure and wear of the bearing journals;
The wear of the intake and exhaust cams in height, when the difference between the largest and smallest cams does not exceed: for all cams of ZIL-IZO engines - 5.80 mm, for 3M3-53 engines, intake valve cams 5.7 mm, and for exhaust cams - 5 , 1 mm;
Wear of the journal for the timing gear to a size of less than 30.0 mm for ZIL-IZO engines and less than 28.0 mm for 3M3-53;
Wear of the keyway in width up to 6.02 mm for ZIL-IZO and 5.1 mm for 3M3-53;
The eccentric of the fuel pump drive is worn down to a size of less than 42.50 mm;
Worn and broken threads of more than two threads.
Camshafts with cracks of any nature and location, the cylindrical part of the cams less than 34.0 mm (ZIL-IZO) and 29.0 mm (3M3-53) cannot be restored.
Risks and nicks on the surfaces of the camshaft center holes are cleaned with a triangular scraper. If it is impossible to eliminate the defects in this way, they are eliminated on a 1K62 screw-cutting lathe with a boring cutter or centering countersink.
Shaft dressing. To determine the need to straighten the shaft, check its bending against the beating of the middle bearing journal. For this purpose, the shaft is mounted on a prism of a device with a dial indicator (measurement range 0-10 mm), mounted on a universal tripod (Fig. 41). The concave side is marked with chalk or paint. When the runout of the middle bearing journal is more than 0.1 mm, the shaft must be straightened.
The shaft is driven on the press with a force of up to 5 T. The camshaft is installed with the extreme support journals on the prisms installed on the press table so that the convex side
was directed upwards and the middle support neck was against the press rod. The shaft is ruled by giving it a 10-15 fold deflection (3-5 repetitions). To avoid excessive shaft deflection, a check stop is placed under the middle bearing journal. The distance between the journal surface and the control stop is established empirically (equal to approximately 10-15 times the shaft deflection).
To protect the surfaces of the bearing journals from damage, copper or brass gaskets are installed between these surfaces, the prisms and the press rod.
The camshaft can also be straightened by peening the surface of the shaft from the side of the depression from deflection with light hammering blows using a pneumatic hammer.
When the keyway for attaching the distribution gear is worn out, it is milled to a repair size of 6.445- 6.490 mm (ZIL-130) and 5.545-5.584 mm (3M3-53). At the same time, the distribution gear is also installed with a groove increased in width. The displacement of the keyway in the diametral plane is not more than ± 0.075 mm.
In some cases, the keyway is repaired by welding using D.C. reverse polarity with extremely short arc (current 170-210 A, voltage 30-35 V and electrode 03H-250 with a diameter of 4 mm). Then the keyway is machined. Shaft neck
under the camshaft gear is restored to the nominal size by chromium plating.
The bearing journals of the camshaft and journals for the camshaft gear can also be restored by stopping using a technology similar to restoring the landing belts of cylinder liners.
Constructive and technological characteristics of the part
Camshaft car engine is one of the crucial parts. The operation of the engine as a whole is determined from the state of the main working surfaces of the shaft. The main defects of the engine camshafts are:
1. Wear of the camshaft bearing journals;
2. Wear of the cams in height;
3. Changing the cam profile;
4. Shaft bending.
All of the above camshaft defects cause knocking in the valve mechanism, a decrease in engine power, and an increase in bearing clearances, in addition, causes a drop in oil pressure in the lubrication system. The operation of the valve-distributor mechanism is theoretically estimated by a parameter called "cut time" and is characterized by the area limited by the curve of the change in valve lift over time.
Figure 5 shows the curves of changes in the area of the valve-distribution mechanism. Shaded areas: the lower one characterizes the reduction in area as a result of cam wear along the profile.
A decrease in the "section time" of the valve as a result of wear of these mating parts leads to a decrease in the filling time of the cylinders and a drop in engine power.
Rice. 5. Change in area "time-section" with wear
valve and distribution mechanism
Restoration of the valve lift to normal dimensions is carried out by resurfacing the cam along the entire profile and is justified by the fact that if you remove the same (with respect to the unworn cam) layer of metal from the cam, the amount of valve lift and the moments of opening and closing the valve do not change. You just need to bring the clearance between the valve and the tappet to normal value (Fig. 6).
Rice. 6. Camshaft cam, ground to oversize
with saving the profile
The design dimensions and technical conditions for the manufacture and repair of the camshaft of the ZIL-130 car are given in Appendix. 3.
Purpose of work:
1. To study the possible types of defects in the camshaft for those. conditions for control-sorting and establish the existing defects on the controlled shaft;
2. To study the nature and magnitude of wear of the camshaft cams;
3. Acquire skills in using special fixtures and tools for measuring the shaft cams.
1. External inspection of the camshaft;
2. Measurement of all cams in 2 zones with the determination of the wear of the cams in height;
3. Determination of camshaft deflection;
4. Measurement of the camshaft bearing journals;
5. Building the profile of one cam.
Equipment, devices, tools:
1. Workbench for camshaft installation;
2. Device for measuring cam elements;
3. Tools:
a) micrometers 25-50, 50-75 mm;
b) indicator with a stand with an accuracy of 0.01 mm;
c) triangular scraper.
4.Technical conditions for control and sorting of parts during overhaul.
Research objects
Engine camshafts: GAZ-51, ZIL-130, M-21, YaMZ-236 (YaMZ-238), etc.
Work order:
1. Carry out an external inspection of the camshaft and record the results of the inspection in the report form.
2. An external examination reveals the following shaft defects:
a) spalls on the journals, gears and cams;
b) cracks different sizes and location;
c) local wear, tears and risks;
d) thread breakdown and clogging, wear, damage to the keyway, etc.
Measurements are established:
a) wear of the bearing journals;
b) wear of the cams in height;
c) shaft deflection.
3. Adjust the measuring tool.
4. Take measurements to the extent specified in this manual.
5. According to the results of external inspection and measurements of the camshaft in accordance with those. the conditions for control-sorting belong to one of 3 categories: a) are suitable, b) are not suitable, c) require repair.
6. Enter the measurement results into the report form and build the pusher lift curve for the new and changed cam.
7. Prepare a report, making a conclusion on the work.
8. Hand over the workplace to the laboratory assistant.
Determination of the repair size of the camshaft journals
Repair size: D p = D z - Z,
where D p is the closest required repair size of the shaft journal, mm;
D z - measured diameter of the shaft journal, mm;
Z - machining allowance (per diameter).
Grinding allowance
where Z - allowance, taking into account the uneven wear of the journals, Z = 0.06 mm;
f - shaft deflection that cannot be straightened (permissible according to TU, f = 0.05 mm;
Z h - allowance, taking into account the depth of the notches on the necks (depth of the damaged layer Z h = 0.08 mm);
в - error of locating and fixing the shaft during grinding ( в = 0.02 mm).
Work instructions:
1. Determination of the wear of the bearing journals.
To determine the wear of the bearing journals of the shaft, it is necessary to measure each journal of the shaft in 2 planes 1 - 1 (1st chord) and 2 - 2 (2nd chord), spaced 5 mm from the edges of the bearing journals (Fig. 2.7).
In each chord, the bearing journals are measured in 2 mutually perpendicular planes A - A, parallel to the plane of the keyway and plane B - B, perpendicular to the plane passing through the keyway.
When measuring journal journals, the camshaft must be mounted on prisms or at centers.
2. Determination of cam height wear.
To determine cam height wear:
a) measure each cam in 2 planes (fig. 7);
b) compare the obtained results of measurements of the height with the nominal height of the new cam and determine the amount of wear of the cams in height.
c) give an opinion on the possibility of further operation of the camshaft cams without repair, based on the permissible amount of wear for those. conditions or designate a method for restoring the cams to the nominal value.
Rice. 7. Camshaft cams measurement scheme
Determination of shaft deflection.
To determine the deflection of the shaft, the camshaft is installed in the center:
a) alternately bring the measuring rod of the indicator head to the middle neck (with a symmetrical shaft arrangement);
b) set the rod of the indicator head to the position at which the small arrow gives a deviation of 1 - 2 mm and bring the zero of the movable scale to the large arrow,
c) orient the camshaft along the cam to be measured relative to the measuring device,
d) set the cam to the maximum lift position, which is determined by a small arrow reading when turning the camshaft,
e) turn the shaft 90 in any direction and set the indicator arrow to zero,
f) rotating the shaft, fix the cam lift according to the indicator readings, every 10 of the rotation angle. The maximum cam lift should correspond to an angle of rotation of 90 from the origin,
g) according to the measurements and tabular data (for a new cam, see the poster), construct the cam lift curves (new and modified).
Reference data are presented in Appendix 2.
Control questions
List the main structural elements of the camshaft and its defects?
What parameters characterize the condition of the bearing journals and camshaft cams?
How to determine the largest neck size for which the repair size category is assigned?
How to check the camshaft for deflection?
In what sequence is the micrometer set to "0"?
How to check the cam profile of the camshaft?
ZIL-130 engine
The Likhachev plant produces truck ZIL-130 and on its base different modifications... The car is equipped with a multi-cylinder carburetor ZIL-130 engine power of 150 l / s, provides vehicle movement at a speed of 90 km / h. O design features I'll tell you about the engine.
The engine has 8 cylinders arranged in a V-shape in 2 rows at an angle of 90 degrees, reducing its length and making it possible to conveniently and easily place its external equipment on the engine. On the right side of the engine there is an oil pump and a generator. On the left side of the reservoir, the power steering pump, oil gauge and starter.
In the camber between the cylinders there is a carburetor, a fuel pump, an air filter, an oil filter, a distributor breaker and an intake manifold. In front, the engine is equipped with a water pump, air compressor, air filter, pulleys V-belt transmission and a fan. The engine is based on crank mechanism... It consists of a knee shaft, a crank, which is connected to the pistons of the cylinders by means of connecting rods.
Distribution mechanism
The crankshaft and camshafts are connected by gears, so they work in strict harmony. From the camshaft cams, through the pushers and rods, the movement is transmitted by the rocker arms, which open the valves, and the valves are pressed against their seats by a spring.
In the process of operation, all parts of the mechanism must be lubricated, cooled, and the working process must provide power to the combustible mixture. All shown mechanisms and systems form a single power unit ZIL-130 engine
Consider the details of the crank mechanism.
The crankshaft, together with the connecting rod-piston groups, moves, and the cylinder block with heads is stationary body parts. The cylinder block is reinforced with partitions, cooling jacket walls and transverse arches, so the block body is solid, rigid and durable.
Wet cylinder liners are installed in the hole in the upper part of the block. At the top, the liners are sealed with a collar clamp between the cylinder heads and the block, and at the bottom with two rubber rings. To increase wear resistance, annular inserts made of anticorrosive cast iron are pressed into the sleeves.
Block head
Each cylinder head is a complex cast of aluminum alloy. The head has side walls with cooling jackets and a bottom plate. On the one hand, inlet channels are made in the head, and on the other, outlet channels. Seats are pressed into the bottom plate and valve guides are pressed on top. The reliability of the tight connection of the cylinder head to the block is achieved by a gasket made of asbestos steel sheet.
Pistons
The pistons are made from a special aluminum alloy. During operation, the piston experiences large mechanical loads and significant heat, therefore, the flat piston crown is massive. From the inside, it is reinforced with ribs connecting it to the bosses.
The piston skirt is a guide. The piston has grooves for installation in them piston rings... Resilient cast iron compression rings are installed in the top three grooves. The piston is connected to the connecting rod by a piston pin.
Knee shaft
The peculiarity of the design of the shaft elbows is that there are 2 connecting rods on each neck of its crank. The crankshaft is steel fully supported. Its 5 main journals are evenly distributed after each crank. The main journals are enlarged in diameter but insignificant in length, and the connecting rod journals are vice versa. The main journals of the shaft, like the connecting rod journals, rotate in bearings with thin-walled three-layer liners consisting of 2 interchangeable half rings.
During engine operation, the pistons make a forward-reverse, rectilinear motion, and the crank rods turn this motion into a rotary motion, while the mass of the cranks together with the lower connecting rod heads create centrifugal forces on the shaft that unevenly load the main bearings, the engine crankcase and cause vibration. therefore the crankshaft is made with six counterweights.
These counterweights balance the centrifugal force of the crank and connecting rods. Grooves are drilled in the main journals of the shaft elbows to lubricate the connecting rod bearings. The channels pass through the crank cheeks to the connecting rod journals, and cavities for the dirt trap are made in the journals.
From axial movement in the crankshaft block, the shaft is held by 2 steel thrust washers located on both sides of the first main bearing. At the front end of the shaft, a spacer - thrust washer, a shaft knee gear, an oil deflector, a ratchet, and a belt pulley are installed.
The rear end of the shaft has a slinger ridge and an oil drainage thread. The shaft end is sealed with a gland. A flywheel with a gear ring is installed on the flange of the shaft elbows to start the engine from the starter. The flywheel is attached to the flange with six bolts.
Pallet
The engine crankcase is closed by a sump. It becomes an oil reservoir and protects parts from contamination. A cork gasket is placed between the crankcase and the sump. The distribution mechanism of the ZIL-130 engine of the valve type. The intake and exhaust valves for each cylinder are located directly above the cylinder cavity.
The valve poppets are pressed against their seats by springs. The camshaft is connected with a gear crankshaft and works with it synchronously. The cams of the shaft through pushers and rods transmit the movement to the rocker arms. The rocker arms, turning on the axle, overcome the force of the springs and lower the valve, opening the holes in the cylinders.
At the same time, under the action of a spring, the pushers are pressed against the shaft cam and provide the required duration of the valve opening, this is how this mechanism works.
Camshaft
Steel camshaft. There are 16 cams on the shaft to control the valves, the fuel pump eccentric, the gear pump, the ignition distributor drive gear and the oil pump. The shaft has 5 bearing journals, which rotate in bearings consisting of bimetallic alloy bushings.
The shaft is held against axial movement by a locking flange, and the gap between the gear hub and the end of the bearing journal of the shaft is fixed by a spacer ring, the thickness of which is slightly larger than the thrust flange. The camshaft is driven by the crankshaft through a pair of gears.
The gears are closed with a cover. Synchronous operation of the 2 shafts is achieved by the correct connection according to the marks. The pushers are hollow steel cups. The rods consist of steel tubes with hardened tips pressed at the ends.
Rocker
8 steel rocker arms are installed on the axes of the block head. The axis of the rocker arms is fixed on 4 racks. The rocker arm is an unequal arm, with a short arm below the stem and a long arm above the valve stem, which contributes to greater opening.
The short arm of the rocker arm has a screw with a counter nut. Valve stems run in guide sleeves. They ensure that the valves fit into the seats without distortion. The valve seats are insertable. Springs help seat the valves.
The lower end of the spring rests against thrust washer, and the upper one, into a plate, which is held on the valve stem by 2 crackers. The valve opening times in relation to the dead center is called the valve timing, which is expressed in degrees of rotation of the knees of the shaft.
Valve
The inlet valve begins to open before the piston reaches TDC for 21 degrees of rotation of the crank of the knees of the shaft. This is necessary for greater valve opening and better filling of the cylinders with the mixture. The intake valve closes after the piston passes at TDC by 75 degrees of rotation of the crank shaft.
The exhaust valve is open until the piston reaches TDC after 57 degrees of rotation of the crank shaft. The exhaust closes after the piston passes at TDC by 39 degrees of crank rotation. This achieves better cleaning of the combustion chamber. The period of simultaneous opening of valves near TDC is called overlap.
On the ZIL-130 engine, the numbering of the cylinders goes like this 12345678 from the right left row, and the sequence of operation of the cylinders is as follows 15426378. The engine is attached to the frame at 3 points. The front point is the attachment of the front gear distributor cover.
The paws rest on the frame cross member with two rear supports; the clutch housing paws are fixed on 2 frame brackets. Each attachment point is elastic with rubber pads. The complex engine unit ZIL-130 is easy to maintain, reliable and durable in operation.
WATCH THE VIDEO
In almost all four-stroke piston internal combustion engines, there is a gas distribution mechanism based on a camshaft. All about the camshafts, their existing types, design and features of work, as well as about the right choice and replacement of shafts, read the proposed article.
vigator (motors with a lower shaft arrangement); Installation in the head of the block (motors with an upper shaft arrangement). Usually, there are no additional elements in the lower shafts; they are lubricated by oil mist in the crankcase and supplying oil under pressure to the bearing journals through bushings. The upper shafts often have a longitudinal channel and cross-drilled holes in the bearing journals - this is how the journals are lubricated by supplying oil under pressure. The engine can have one or two RVs, in the first case one shaft drives all the valves, in the second case one shaft drives only the intake valves, the second only the exhaust valves. Accordingly, the number of cams on the common PB corresponds to the number of all valves, and on each of the separate PB the number of cams is half the total number of valves. The RV drive can be carried out using a belt, chain or gear directly connected to the crankshaft gear. Today, the most commonly usedThe device and principle of operation of the camshaft
The car engine is a complex mechanism, one of the essential elements which is the camshaft that is part of the timing. From accurate and smooth operation the camshaft is largely dependent on the normal operation of the engine.
On the engine device, the gas distribution mechanism can have a lower or upper valve arrangement. Today, timing belts with overhead valves are more common. This design allows for faster and easier maintenance, which includes adjusting and repairing the camshaft, which will require camshaft parts. Camshaft arrangement From a structural point of view, the engine camshaft is connected to the crankshaft, which is ensured by the presence of a chain and a belt. The camshaft chain or belt slides over the crankshaft sprocket or camshaft pulley. A camshaft pulley such as a split gear is considered the most practical and effective option, therefore it is often used to tune engines in order to increase their power. The bearings, inside of which the camshaft bearing journals rotate, are located on the cylinder head. If the neck mounts come out of
