Crank mechanism in simple words. Crank mechanism of an internal combustion engine: device, purpose, how it works. Checking the condition of the crank mechanism
It's no secret that the main mechanism that sets a car in motion is the engine. Those. we can say that the power unit is the heart of any car. But without a crank mechanism, the operation of an internal combustion engine is impossible. It turns out that the crankshaft is nothing more than the heart of the engine. And it is this mechanism that Auto-Gurman.ru will talk about below.Crank mechanism. What it is?
KShM is a mechanism that converts one movement into another. That is, for example, it can transform rotation into rocking, translational-pushing and other movements.The crank mechanism can be found not only in piston internal combustion engines, but also in various compressors, pumps and other mechanical devices.
Today, the KShM is the most popular mechanism for converting one movement into another. Therefore, now it is worth considering its device.
KShM device
The main elements of the mechanism are divided into two groups:1. Movable;
2. Fixed.
The moving elements are pistons, piston rings, pins, crankshaft with flywheel and connecting rod. All piston elements are a piston group.
The fixed elements are the connecting parts, the cylinder block and its head, as well as the pan and crankcase with crankshaft bearings.
Let's look at each element in more detail.
Piston
The piston is an element of the crankshaft that changes the gas pressure. Such changes are carried out by its reciprocating movement.
Externally, the piston is made in the form of a cylinder made of aluminum alloy. The main parts of the piston are the bottom, skirt and head. Each detail performs its function. The bottom has a combustion chamber. The head contains special threaded grooves in which the piston rings are located. The main purpose of the rings is to protect the engine crankcase from gases and remove excess oil from the cylinder walls. The skirt inside has a piston pin, which is placed in this element of the mechanism due to special bosses.
The skirt contains two bosses to accommodate the piston with the connecting rod of the pin.
connecting rod
The connecting rod is the main element of the crank mechanism for transmitting piston force to the crankshaft. This part can be forged from steel or titanium.
By design, the connecting rod consists of a rod with an I-section, as well as heads (upper and lower). The upper head, like the skirt, has bosses in which the piston pin is located, and the lower collapsible head ensures high accuracy of joining parts.
Block and cylinder head
The cylinder block has special cooling jackets, mounting points for the main components and instruments, as well as a bed for the crankshaft and camshaft bearings.
The block itself and the head are cast from cast iron or aluminum. Well, the main purpose of the block is to direct the pistons.
As for the cylinder head, it has inside it special holes for spark plugs, intake and exhaust channels, bushings, as well as a combustion chamber and pressed seats.
Crankshaft
The crankshaft is an element for receiving forces from the connecting rod, which further converts these forces into torque. Most often it is made of cast iron or steel. It consists of root and connecting rod journals. The necks are connected by special cheeks. Their main working process takes place directly in the plain bearings. The cheeks and necks have special holes designed to supply oil.
Flywheel
The flywheel is located at the end of the crankshaft. It plays one of the main roles in the operation of the engine - it participates in starting the internal combustion engine through the starter.
Here are the main elements of the crank mechanism. Now Auto-Gurman.ru wants to introduce you to the operating principle of the KShM.
Crank mechanism: operating principle
And so, the piston is at the maximum distance from the crankshaft. The crank and connecting rod line up in one line. At this moment, fuel enters the cylinder and it begins to burn. Combustion products, namely expanding gases, move the piston towards the crankshaft. At the same time, the connecting rod also moves, the lower head of which rotates the crankshaft 180°. After this, the connecting rod and its head move and rotate in the opposite direction, returning to its original position. The piston also returns back to its original place. And this process of work goes in circles.As you can see, the crank mechanism is the main mechanism of the engine, on the operation of which the health of the car depends. Therefore, you should always monitor this unit and, if there are any signs of a malfunction, fix it as quickly as possible, since the result of a crankshaft failure can be a complete failure of the engine, the repair of which will greatly affect your personal budget.
The crank mechanism (CPM) perceives gas pressure during the working stroke and converts the reciprocating movement of the piston into rotational movement of the crankshaft. The crankshaft consists of a cylinder block with a head, pistons with rings, piston pins, connecting rods, a crankshaft, a flywheel and an oil pan.
KShM device
Cylinder block is the main part of the engine to which all mechanisms and parts are attached. Cylinder blocks are cast from cast iron or aluminum alloy. The same casting is used to make the crankcase and the walls of the cooling jacket surrounding the engine cylinders. Insert liners are installed into the cylinder block. The sleeves are either “wet” (cooled by liquid) or “dry”. Many modern engines use linerless blocks. The inner surface of the liner (cylinder) serves as a guide for the pistons.
The cylinder block is closed from above by one or two (in V-shaped engines) cylinder heads made of aluminum alloy. The cylinder head (cylinder head) contains combustion chambers, in which there are threaded holes for spark plugs (in diesel engines, for glow plugs). ICE heads with direct injection also have an opening for injectors. To cool the combustion chambers, a special jacket is made around them. The parts of the gas distribution mechanism are fixed to the cylinder head. The cylinder head has inlet and outlet channels and installed insert seats and valve guides. To create a seal, a gasket is installed between the block and the cylinder head, and the head is secured to the cylinder block with studs and nuts. The cylinder head is closed from above with a cover. An oil-resistant gasket is installed between them.
Piston perceives gas pressure during the power stroke and transmits it through the piston pin and connecting rod to the crankshaft. The piston is an inverted cylindrical glass cast from an aluminum alloy. At the top of the piston there is a head with grooves into which the piston rings are inserted. Below the head there is a skirt that guides the movement of the piston. The piston skirt has bosses with holes for the piston pin.
When the engine is running, the piston, heating up, will expand and, if there is no necessary clearance between it and the cylinder wall, it will jam in the cylinder. If the gap is too large, then some of the exhaust gases will break into the crankcase. This will lead to a drop in cylinder pressure and a decrease in engine power. Therefore, the piston head is made of a smaller diameter than the skirt, and the skirt itself in cross section is not made in a cylindrical shape, but in the form of an ellipse with a larger axis in a plane perpendicular to the piston pin. There is a cut on the piston skirt. Due to the oval shape and cut of the skirt, jamming of the piston during operation of a warm engine is prevented. The general design of the pistons is fundamentally the same, but their designs may differ depending on the characteristics of a particular engine.
Piston rings are divided into compression and oil scraper. Compression rings seal the piston in the cylinder and serve to reduce the breakthrough of gases from the cylinders into the crankcase, and oil scraper rings remove excess oil from the cylinder walls and prevent oil from penetrating into the combustion chamber. Rings made of cast iron or steel have a cut (lock). The number of rings in different engines may vary.
Piston pin pivotally connects the piston to the upper head of the connecting rod. The finger is made in the form of a hollow cylindrical rod, the outer surface of which is hardened by high-frequency currents. The axial movement of the pin in the piston bosses is limited by split steel rings.
connecting rod serves to connect the crankshaft to the piston. The connecting rod consists of an I-section steel rod, an upper one-piece head and a lower split head. The upper head has a piston pin, and the lower head is mounted on the crankpin of the crankshaft. To reduce friction, a bushing is pressed into the upper head of the connecting rod, and thin-walled liners are installed into the lower, consisting of two parts. Both parts of the lower head are fastened with two bolts and nuts. Oil is supplied to the connecting rod heads when the engine is running. In V-shaped engines, two connecting rods are attached to one crankpin of the crankshaft.
Crankshaft made of steel or high-strength cast iron. It consists of connecting rod and main ground journals, cheeks and counterweights. The rear part of the shaft is made in the form of a flange to which the flywheel is bolted. A belt pulley and a camshaft drive sprocket are attached to the front end of the crankshaft. A torsional vibration damper can be integrated into the pulley. The most common design consists of two metal rings connected through an elastic medium (rubber-elastomer, viscous oil).
The number and location of connecting rod journals depend on the number of cylinders and their location. The connecting rod journals of the crankshaft of a multi-cylinder engine are made in different planes, which is necessary for uniform alternation of power strokes in different cylinders. The main and connecting rod journals are connected to each other by cheeks. To reduce the centrifugal forces created by the cranks, counterweights are made on the crankshaft, and the connecting rod journals are made hollow. The surface of the main and connecting rod journals is hardened with high frequency currents. There are channels in the necks and cheeks for supplying oil. Each crankpin has a cavity that serves as a dirt trap. Oil enters the dirt traps from the main journals and when the shaft rotates, dirt particles in the oil are separated from the oil under the influence of centrifugal forces and settle on the walls. Cleaning of dirt traps is carried out through screw plugs wrapped in their ends only when disassembling the engine. The movement of the shaft in the longitudinal direction is limited by thrust washers. Where the crankshaft exits the engine crankcase there are oil seals and gaskets that prevent oil leakage.
When the engine is running, the loads on the connecting rods and main journals of the crankshaft are very high. To reduce friction, the shaft journals are located in sliding bearings, which are made in the form of metal liners coated with an antifriction layer. Earbuds consist of two halves. The connecting rod bearings are installed in the lower split head of the connecting rod, and the main bearings are installed in the block and bearing cap. The main bearing caps are bolted to the cylinder block and locked to prevent self-unscrewing. To prevent the liners from turning, protrusions are made in them, and corresponding ledges are made in the covers, saddles and connecting rod heads.
Flywheel reduces uneven engine operation, makes it easier to start and promotes smooth starting of the car. The flywheel is made in the form of a massive cast-iron disk and is attached to the crankshaft flange with bolts and nuts. During manufacture, the flywheel is balanced together with the crankshaft. To ensure that the balancing is not disturbed when disassembling the engine, the flywheel is installed on asymmetrically located pins or bolts. This prevents it from being installed incorrectly. In some engines, to reduce torsional vibrations transmitted to the gearbox, dual-mass flywheels are used, which are two disks elastically connected to each other. The disks can move relative to each other in the radial direction. Marks are placed on the flywheel rim, along which the piston of the first cylinder is installed in the top line. when installing the ignition or when the fuel supply starts (for diesel engines). A ring gear is also attached to the rim, designed to engage with the starter bendix.
To reduce vibration in in-line engines, they use balance shafts located under the crankshaft in the oil pan.
Crankcase cast integrally with the cylinder block. Parts of the crank and gas distribution mechanisms are attached to it. To increase rigidity, ribs are made inside the crankcase, into which the seats of the crankshaft main bearings are bored. The bottom of the crankcase is closed with a pan stamped from a thin steel sheet. The pan is used as an oil reservoir and protects engine parts from contamination. There is a plug at the bottom of the pan for draining engine oil. The pan is attached to the crankcase with bolts. To prevent oil leakage, a gasket is installed between them.
KShM malfunctions
Signs of a crankshaft malfunction include: the appearance of extraneous knocks and noises, a drop in engine power, increased oil consumption, excessive fuel consumption, and the appearance of smoke in the exhaust gases.
Knocks and noises in the engine arise as a result of wear of its main parts and the appearance of increased gaps between mating parts. When the piston and cylinder wear out, as well as when the gap between them increases, a loud metallic knock occurs, which can be clearly heard when the engine is running cold. A sharp metallic knock in all engine operating modes indicates an increase in the gap between the piston pin and the bushing of the upper connecting rod head. An increase in knocking noise with a sharp increase in the number of revolutions of the crankshaft indicates wear of the main or connecting rod bearing shells, and a knock of a duller tone indicates wear of the main bearing shells. If the liners are worn too much, the oil pressure may drop sharply. In this case, the engine cannot be operated.
Power drop engine failure occurs when piston rings are worn out or stuck in the grooves, pistons and cylinders are worn out, and the cylinder head is not properly tightened. These faults cause a drop in compression in the cylinder. Compression is checked using a compression gauge on a warm engine. To do this, unscrew all the spark plugs and install the tip of a compression gauge in place of one of them. With the throttle fully open, crank the engine with the starter for 2-3 seconds. In this way, all cylinders are checked sequentially. The compression value must be within the limits specified in the engine technical data. The difference in compression between individual cylinders should not exceed 1 kg/cm2.
Increased oil consumption, excessive fuel consumption, the appearance of smoke in the exhaust gases (at a normal oil level in the crankcase) usually appear when the piston rings are stuck or the rings and cylinders are worn out. A stuck ring can be eliminated without disassembling the engine by pouring special fluid into the cylinder through the spark plug hole.
Carbon deposits on the bottoms of the pistons and combustion chambers reduces thermal conductivity, which causes engine overheating, a drop in power and increased fuel consumption.
Cracks in the walls of the cooling jacket of the block and cylinder head can appear as a result of freezing of the coolant, filling the cooling system of a hot engine with cold coolant, or as a result of engine overheating. Cracks in the cylinder block can allow coolant to enter the cylinders. In this case, the color of the exhaust gases becomes white.
Crankpin (Fig. 32) is a link in the crank mechanism that can make a full revolution around a fixed axis. The crank (I) has a cylindrical projection - spike 1, the axis of which is offset relative to the axis of rotation of the crank by a distance r, which can be constant or adjustable. A more complex rotating part of the crank mechanism is the crankshaft. Eccentric (III) - a disk mounted on a shaft with eccentricity, that is, with a displacement of the axis of the disk relative to the axis of the shaft. The eccentric can be considered as a design variation of the crank with a small radius.
Rice. 32
Crank mechanism- a mechanism that converts one type of movement into another. For example, uniform rotation - into translational, rocking, uneven rotation, etc. The rotating link of the crank mechanism, made in the form of a crank or crankshaft, is connected to the rack and the other link by rotational kinematic pairs (hinges). It is customary to distinguish such mechanisms into crank-rod, crank-rocker, crank-rocker, etc., depending on the nature of the movement and the name of the link with which the crank works.
Crank mechanisms are used in piston engines, pumps, compressors, presses, in driving movement of metal-cutting machines and other machines.
crank mechanism- one of the most common motion transformation mechanisms. It is used both to convert rotary motion into reciprocating motion (for example, piston pumps), and to convert reciprocating motion into rotational motion (for example, internal combustion engines).
connecting rod- a part of the crank-rod (slider) mechanism that transmits the movement of the piston or slider to the crankshaft crank. The part of the connecting rod that connects to the crankshaft is called the crank head, and the opposite part is called the piston (or slide) head.
The mechanism consists of a rack 1 (Fig. 33), a crank 2, a connecting rod 3 and a slider 4. The crank performs continuous rotation, the slider performs a reciprocating movement, and the connecting rod performs a complex, plane-parallel movement. , The full stroke of the slider is equal to twice the length of the crank. Considering the movement of the slider from one position to another, it is easy to see that when the crank is turned at equal angles, the slider travels different distances: when moving from the extreme position to the middle, the sections of the slider’s path increase, and when moving from the middle position to the extreme, they decrease. This indicates that with uniform movement of the crank, the slider moves unevenly. Thus, the speed of movement of the slider changes from zero at the beginning of its movement and reaches its greatest value when the crank and connecting rod form a right angle with each other, then decreases again to zero at the other extreme position.
Rice. 33
The uneven movement of the slide causes inertial forces to appear, which have a negative impact on the entire mechanism. This is the main disadvantage of the crank-slider mechanism.
In some crank mechanisms, there is a need to ensure the straightness of movement of the piston rod 4 (Fig. 34). To do this, between the crank 1, connecting rod 2 and slider 5, a so-called crosshead 3 is used, which absorbs the rocking movements of the connecting rod (4 is the intermediate rod).
Rice. 34
The crank mechanism is designed to convert the reciprocating motion of the piston in the cylinder into the rotational motion of the engine crankshaft.
For a four-cylinder engine, the crank mechanism consists of:
Cylinder block with crankcase, - cylinder heads, - engine oil pan, - pistons with rings and pins, - connecting rods, - crankshaft, - flywheel.
The crank mechanism of the engine crank mechanism includes two groups of parts: stationary and moving.
Fixed parts include the engine block, which serves as the basis of the engine, the cylinder, the cylinder heads or heads, and the oil pan.
The moving parts are pistons with rings and piston pins, connecting rod, crankshaft, flywheel.
The crank mechanism senses gas pressure during the combustion-expansion stroke and converts the linear, reciprocating motion of the piston into rotational motion of the crankshaft.
Material and design of the main parts of the crankshaft. The crank mechanism consists of: a cylinder block with a crankcase, a cylinder head, pistons with rings, piston pins, connecting rods, a crankshaft, a flywheel and an oil pan.
Cylinder block. The cylinder block is the main part of the engine to which all mechanisms and parts are attached.
The cylinders in the blocks of the engines under study are arranged Y-shaped in two rows at an angle of 90° (Fig. 1).
Cylinder blocks are cast from cast iron (ZIL-130) or aluminum alloy. The same casting is used to make the crankcase and the walls of the cooling cavity surrounding the engine cylinders.
Insert sleeves are installed in the engine block, washed with coolant. The inner surface of the liner serves as a guide for the pistons. The sleeve is bored to the required size and ground. Sleeves washed by coolant are called wet liners. They have sealing rings made of special rubber or copper at the bottom. At the top, sealing of the liners is achieved by the cylinder head gasket.
An increase in the service life of cylinder liners is achieved by pressing short thin-walled liners made of acid-resistant cast iron into the most wearable (upper) part of them. The use of such an insert reduces wear on the upper part of the liner by 2-4 times.
The cylinder block of the ZIL-130 U-shaped engine is closed from above with two aluminum alloy heads. The cylinder head of the ZIL-130 engine contains combustion chambers in which there are threaded holes for spark plugs. To cool the combustion chambers in the head, a special cavity is made around them.
The parts of the gas distribution mechanism are fixed to the cylinder head. The cylinder head has inlet and exhaust ports and installed insert seats and valve guides. To create a seal, a gasket is installed between the block and the cylinder head, and the head is secured to the cylinder block with studs and nuts. The gasket must be durable, heat-resistant and elastic. In the ZIL-130 engine it is steel-asbestos. To seal the steel gasket, a steel ring with a sharp protrusion is pressed into the bore on the lower plane of the cylinder head.
The bottom of the engine crankcase is covered with a pan stamped from sheet steel. The pan protects the crankcase from dust and dirt and is used as an oil reservoir. The pallet is attached to the parting plane with bolts, and to ensure the tightness of the connection, gaskets made of cardboard or glued cork chips are used.
While the engine is running, gases enter the crankcase, which can lead to an increase in pressure, rupture of gaskets and leakage of oil. Therefore, the crankcase communicates with the atmosphere through a special tube (breather).
Piston perceives gas pressure during the power stroke and transmits it through the piston pin and connecting rod to the crankshaft. The piston is an inverted cylindrical glass cast from an aluminum alloy (Fig. 2). At the top of the piston there is a head with grooves into which the piston rings are inserted. Below the head there is a skirt that guides the movement of the piston. The piston skirt has bosses with holes for the piston pin.
When the engine is running, the piston, heating up, will expand and, if there is no required clearance between it and the mirror (the inner surface of the cylinder or its liner is called a mirror) of the cylinder, it will jam in the cylinder and the engine will stop working. However, a large gap between the piston and the cylinder mirror is also undesirable, since this leads to the breakthrough of some gases into the engine crankcase, a drop in pressure in the cylinder and a decrease in engine power. To prevent the piston from jamming when the engine is warm, the piston head is made of a smaller diameter than the skirt, and the cross-section of the skirt itself is not made of a cylindrical shape, but in the form of an ellipse with its larger axis in a plane perpendicular to the piston pin. There may be a cut on the piston skirt. Thanks to the oval shape and cut of the skirt, jamming of the piston is prevented when the engine is warm.
The general design of the pistons of all engines is fundamentally the same, but each of them differs in diameter and a number of features unique to this engine. For example, in the piston head of the ZIL-130 engine there is a cast iron ring, in which a groove is made for the upper compression ring. This design helps reduce wear on the piston ring groove.
After machining, the pistons of the ZIL-130 engine are coated with tin, which promotes better break-in and reduced wear during the initial period of engine operation.
Piston rings, used in the engine, are divided into compression and oil scraper. Compression rings seal the gap between the piston and the cylinder and serve to reduce the breakthrough of gases from the cylinders into the crankcase, while oil scraper rings remove excess oil from the cylinder surface and prevent oil from entering the combustion chamber. Rings made of cast iron or steel have a cut (lock) (see Fig. 2).
When installing the piston into the cylinder, the piston ring is pre-compressed, resulting in its tight fit to the cylinder mirror when decompressed. There are chamfers on the rings, due to which the ring is slightly warped and rubs against the cylinder mirror faster, and the pumping effect of the rings is reduced. The number of rings installed on engine pistons is not the same. The pistons of ZIL-130 engines have three compression rings, the top two are chrome-plated on the surface in contact with the liner. The oil scraper ring is assembled from four separate elements - two thin steel split rings and two corrugated steel expanders (axial and radial).
Piston pin pivotally connects the piston to the upper head of the connecting rod. The finger is made in the form of a hollow cylindrical rod, the outer surface of which is hardened by heating with high frequency current.
The ZIL-130 engine uses “floating” pins, i.e., those that can rotate freely both in the upper head of the connecting rod and in the piston bosses, which contributes to uniform wear of the pin. To avoid scuffing of the cylinders when the pin leaves the bosses, its axial movement is limited by two split steel rings installed in recesses in the piston bosses.
connecting rod serves to connect the crankshaft to the piston. Through the connecting rod, the pressure on the piston during the working stroke is transmitted to the crankshaft. During auxiliary strokes (intake, compression and exhaust), the piston is driven through the connecting rod by the crankshaft. The connecting rod (Fig. 3) consists of an I-section steel rod, an upper one-piece head and a lower split head. The top one has a piston pin, and the bottom one is fixed to the crankpin of the crankshaft. To reduce friction, a bronze or bimetallic bushing with a bronze layer is pressed into the upper head of the connecting rod, and thin-walled liners are installed into the lower head, consisting of two parts, which are a steel strip, the inner surface of which is coated with a thin layer of anti-friction alloy (ZIL-130 - high-tin aluminum). Both parts of the lower head of the connecting rod are fastened with two bolts, the nuts of which are fixed to prevent self-loosening. In the ZIL-130 engine, special washers are placed under the nuts, the tightening torque of the nuts is 80...90.Nm, and special stamped lock nuts prevent self-loosening. The lock nut must be tightened by rotating it 1.5 ... 2 edges from the position of contact with the main nut.
There is a part number stamped on the connecting rod rod and a mark on the cap. The number on the connecting rod and the mark on its cover should always face the same direction. Oil is supplied to the upper and lower heads of the connecting rod: to the lower head through a channel in the crankshaft, and to the upper head through a slot. From the bottom head of the connecting rod, oil is sprayed through the hole onto the cylinder walls.
In engines, two connecting rods are attached to one crankpin of the crankshaft. To assemble them correctly with the pistons, you need to remember that the connecting rods of the right row of cylinders are assembled with the pistons so that the number on the connecting rod faces backward in the direction of the car (see Fig. 3), and the connecting rods of the left row face forward, i.e. it coincides with the inscription on the piston.
The crankshaft receives the forces transmitted from the pistons by the connecting rods and converts them into torque, which is then transmitted to the transmission units through the flywheel.
The ZIL-130 engine has a steel crankshaft. The crankshaft (Fig. 4) consists of connecting rods and main ground journals, cheeks and counterweights. At the front end of the shaft of the ZMZ-53-12 and ZIL-130 engines there is a recess for the timing gear key and the fan drive pulley, as well as a threaded hole for attaching the ratchet; the rear part of the shaft is made in the form of a flange to which the flywheel is bolted. The gearbox drive shaft bearing is located in the recess at the rear end of the crankshaft.
The number and location of the crankpins of the crankshaft depends on the number of cylinders. In a V-shaped engine, the number of connecting rod journals is half the number of cylinders, since two connecting rods are installed per crankpin of the shaft - one for the left and the other for the right row of cylinders.
The connecting rod journals of the crankshaft of multi-cylinder engines are made in different planes, which is necessary for uniform alternation of power strokes in different cylinders.
In eight-cylinder V-engines, the crankshafts have four crankpins located at an angle of 90°.
In an engine, the number of crankshaft main journals is one more than the connecting rod journals, i.e., each connecting rod journal has a main journal on both sides. Such a crankshaft is called full-support.
The main and connecting rod journals of the crankshaft are connected to each other by cheeks.
To reduce the centrifugal forces created by the cranks, counterweights are made on the crankshaft, and the connecting rod journals are made hollow. To increase hardness and increase service life, the surface of the main and connecting rod journals of steel shafts is hardened by heating with high frequency currents.
The main and connecting rod journals of the shaft are connected by channels (drillings) in the cheeks of the shaft. These channels are designed to supply oil from the main bearings to the connecting rod bearings.
Each crankpin of the shaft has a cavity that acts as a dirt trap. This is where the oil comes from the main journals. When the shaft rotates, dirt particles in the oil are separated from the oil under the influence of centrifugal forces and settle on the wall of the dirt trap, and purified oil flows to the connecting rod journals. Cleaning of dirt traps is carried out through screw plugs screwed into their ends only when disassembling the engine.
The movement of the shaft in the longitudinal direction is limited by thrust steel-babbit washers, which are located on both sides of the first main bearing or by four steel-aluminum half-rings installed in the recess of the rear main bearing. Where the crankshaft exits the engine crankcase there are oil seals and gaskets that prevent oil leakage.
A rubber self-clamping oil seal is installed at the front end of the shaft, and an oil drain thread or oil deflector collar is made at the rear end.
Oil catch channels are made in the rear main bearing, into which oil is discharged from the oil drain thread or oil deflector collar, and an oil seal consisting of two pieces of asbestos cord is installed.
Connecting rod and main bearings. When the engine is running, the loads on the connecting rods and main journals of the crankshaft are very high. To reduce friction, the main journals, like the connecting rod journals, are located in plain bearings, which are made in the form of liners similar to the connecting rod journals. The shells of each main or connecting rod bearing consist of two halves installed in the lower split head of the connecting rod and in the block socket and main bearing cap. The liners are kept from turning by a protrusion that fits into the groove of the connecting rod or main bearing. The main bearing caps are secured with bolts and nuts, which are cottered with wire or locked with locking plates to prevent self-loosening.
Flywheel reduces uneven engine operation, removes pistons from dead spots, facilitates engine starting and promotes smooth starting of the car. The flywheel is made in the form of a massive cast-iron disk and is attached to the crankshaft flange with bolts and nuts. During manufacture, the flywheel is balanced together with the crankshaft. To prevent imbalance when disassembling the engine, the flywheel is mounted on asymmetrically located pins or bolts.
Crankcase, cast integrally with the cylinder block, is the basic (main) part. Parts of the crank and gas distribution mechanisms are attached to the crankcase. To increase rigidity, ribs are made inside the crankcase, into which the seats of the crankshaft main bearings and camshaft journals are bored.
The bottom of the crankcase is covered with a pan stamped from a thin steel sheet.
Pallet serves as a reservoir for oil and at the same time protects engine parts from dust and dirt. At the bottom of the pan there is a hole for releasing oil, closed with a screw plug. The pan is bolted to the crankcase. To prevent oil leakage, gaskets and rubber seals are installed between the pan and the crankcase.
Malfunctions and ways to eliminate them. In case of significant wear and damage, the crankshaft parts are restored or replaced. These works are usually performed by sending them to centralized repairs.
Coking of the piston rings in the grooves can be eliminated without disassembling the engine. To do this, at the end of the working day, until the engine has cooled down, 20 g of a mixture of equal parts of denatured alcohol and kerosene is poured into each cylinder through the spark plug hole. In the morning, start the engine and after running it for 10-15 minutes at cold speed, stop it and change the oil.
Diagnosis of the crank mechanism is carried out at post D-2. When identifying reduced traction qualities, measured in all cylinders of the car at the traction-economic qualities stand.
Engine compression is determined with the spark plugs turned out, a warm engine at t = 70-80°C and the air and throttle valves fully open. Having installed the rubber tip of the compression gauge into the spark plug hole of the cylinder being tested, turn the crankshaft with the starter 10-15 turns and record the pressure gauge readings. Compression should be 0.75 - 0.80 MPa for a working car. The difference in performance between the cylinders should not be more than 0.07 - 0.1 mPa.
As a result of wear of the cylinder, piston and piston rings, compression (compression end pressure) and power drop, the crankshaft speed decreases, fuel and lubricating oil consumption increases, and smoke appears in the engine crankcase. The same phenomena can also be observed as a result of coking of the piston rings. A drop in compression in diesel engines makes them very difficult to start, especially at low temperatures.
Detonation knocks when running a carburetor engine on gasoline of the appropriate brand and with the correct ignition setting occur when there are increased carbon deposits in the combustion chamber and overheating of parts. Premature fuel combustion also occurs as a result of overheating of parts and deposits of carbon deposits.
Knocks of pistons, pins, as well as knocks in connecting rod and main bearings occur when the gaps in the interfaces of these parts greatly increase during their wear.
A drop in oil pressure in the lubrication system occurs due to an increase in clearances in the connecting rod and main bearings.
Types and types of CVM
a) An undisplaced (central) crankshaft, in which the cylinder axis intersects with the axis of the crankshaft.
b) Offset crankshaft, in which the cylinder axis is offset relative to the axis of the crankshaft by an amount a;
c) V-shaped crankshaft (including with a trailed connecting rod), in which two connecting rods working on the left and right cylinders are placed on one crankshaft.
Information model of the harrowing technological process. Types of working parts of harrows. Structural layouts of disc and tooth harrows. Graphic and analytical methods for calculating the main design parameters of disk and tooth harrows.
Nowadays, there are harrows manufactured in two main types of working tools: disc harrows (similar to disk discs) and tine harrows (in the form of teeth). The teeth are special metal rods 100 millimeters long. They are located on the frame in such a way that when working with their help, none of them will follow the trail of the other. Mesh harrows that do not have a rigid frame are also used. And on rocky soils, harrows that have teeth similar to leaf springs often work.
crank mechanism(hereinafter abbreviated as KShM) – engine mechanism. The main purpose of the crankshaft is to convert the reciprocating movements of a cylindrical piston into rotational movements of the crankshaft and vice versa.
KShM device
Piston
The piston has the form of a cylinder made of aluminum alloys. The main function of this part is to convert changes in gas pressure into mechanical work, or vice versa - to increase pressure due to reciprocating motion.
The piston consists of a bottom, head and skirt put together, which perform completely different functions. The piston bottom, which is flat, concave or convex, contains a combustion chamber. The head has cut grooves where the piston rings (compression and oil scraper) are placed. Compression rings eliminate gas breakthrough into the engine crankcase, and piston oil scraper rings help remove excess oil on the inner walls of the cylinder. There are two bosses in the skirt that provide placement of the piston pin connecting the piston to the connecting rod.
connecting rod
A stamped or forged steel (less commonly titanium) connecting rod has hinged joints. The main role of the connecting rod is to transmit piston force to the crankshaft. The design of the connecting rod assumes the presence of an upper and lower head, as well as a rod with an I-section. The upper head and bosses contain a rotating (“floating”) piston pin, and the lower head is dismountable, thereby allowing for a close connection with the shaft journal. Modern technology of controlled splitting of the lower head allows for high precision in joining its parts.
Crankshaft
Made of high-strength steel or cast iron, the crankshaft consists of connecting rods and main journals, connected by cheeks and rotating in plain bearings. The cheeks create a counterweight to the connecting rod journals. The main function of the crankshaft is to receive force from the connecting rod and convert it into torque. Inside the cheeks and necks of the shaft there are holes for supplying oil under pressure.
Flywheel
The flywheel is installed at the end of the crankshaft. Today, dual-mass flywheels, which have the form of two elastically connected disks, are widely used. The flywheel ring gear is directly involved in starting the engine through.
Block and cylinder head
Cylinder block and cylinder head cast from cast iron (less commonly, aluminum alloys). The cylinder block contains beds for the crankshaft and camshaft bearings, as well as mounting points for instruments and components. The cylinder itself acts as a guide for the pistons. The cylinder head contains a combustion chamber, intake and exhaust ports, special threaded holes for spark plugs, bushings and pressed seats. The tightness of the connection between the cylinder block and the head is ensured by the gasket. In addition, the cylinder head is closed with a stamped cover, and between them, as a rule, a gasket made of oil-resistant rubber is installed.
In general, the piston, cylinder liner and connecting rod form a cylinder or cylinder-piston group crank mechanism. Modern engines can have up to 16 or more cylinders.