An automobile is generally composed of four basic parts: engine, chassis, body and electrical equipment.
Automobile engine: The engine is the power device of the automobile. It consists of engine body, crank-connecting rod mechanism, valve train, cooling system, lubrication system, fuel system and ignition system (diesel engine without ignition system). According to fuel, there are two kinds of engines: gasoline engine and diesel engine. There are two working modes: two-stroke and four-stroke. The general engine is a four-stroke engine.
Working process of the four-stroke engine: The four-stroke engine is that the piston reciprocates for four strokes to complete a working cycle, including intake, compression, work and exhaust. Four-stroke diesel engines, like gasoline engines, have to go through the processes of intake, compression, work and exhaust. But unlike gasoline engines, gasoline engines are ignition-type and diesel engines are compression-ignition type.
Cooling system: generally composed of water tank, water pump, radiator, fan, thermostat, water thermometer and drain switch. There are two cooling methods for automobile engines, namely air cooling and water cooling. Generally, automobile engines are mostly water-cooled.
Lubrication system: the engine lubrication system consists of oil pump, filter screen, oil filter, oil circuit, pressure limiting valve, oil gauge, pressure sensitive plug and dipstick.
Fuel system: The fuel system of a gasoline engine consists of fuel tank, gasoline meter, gasoline pipe, gasoline filter, gasoline pump, carburetor, air filter, intake and exhaust manifold, etc.
Carburetor: it is a device that mixes gasoline and air into atomized gas according to a certain proportion. This atomized gas is called combustible mixture, which is supplied to the cylinder in a timely and proper amount.
Automobile chassis:
Transmission system: mainly composed of clutch, transmission, universal joint, transmission shaft and drive axle.
Clutch: Its function is to make the power of the engine smoothly engage or temporarily separate from the transmission device, so as to facilitate the driver to start, stop and shift gears.
Transmission: It consists of transmission housing, transmission cover, first shaft, second shaft, intermediate shaft, reverse shaft, gears, bearings, control mechanism and other parts, and is used to change the speed and output torque of the automobile.
Drive system: consists of frame, axle, suspension and wheels. Its basic function is to support the quality of the whole vehicle and ensure the running of the vehicle.
Leaf spring and shock absorber: The role of leaf spring is to keep the elastic connection between the frame and the body, wheel or axle. The function of shock absorber is to reduce the vibration when the car is impacted by vibration. The shock absorber is used in parallel with the leaf spring.
Steering system: It consists of steering wheel, steering gear, steering knuckle, steering knuckle arm, tie rod and straight tie rod, and its function is steering.
Front wheel alignment: In order to keep the car running smoothly in a straight line, turn conveniently and reduce the wear of tires and steering parts, the front wheel, steering kingpin and front axle have a certain relative position, which is called "front wheel alignment". It includes kingpin backward inclination, production and marketing inward inclination and front wheel toe-in. Toe value refers to the difference between the front edge distance and the rear edge distance of two front wheels. ? Braking system: the braking performance of motor vehicles refers to the efficiency of forced parking in the shortest time. ?
Function of the hand brake: The hand brake is a device to prevent the car from slipping when parking, and it is used in conjunction with the foot brake under special circumstances.
Hydraulic braking structure: The hydraulic braking device consists of brake pedal, master brake cylinder, sub-brake cylinder, drum (wheel) brake and oil pipe.
Pneumatic braking device: it consists of brake pedal, air compressor, barometer, brake valve, brake air chamber, drum (wheel) brake and air pipe.
Electrical equipment:
Automobile electrical equipment is mainly composed of battery, generator, regulator, starter, ignition system, instrument, lighting device, audio device, wiper and so on.
Battery: The function of the battery is to supply power to the starter, and supply power to the engine ignition system and other electrical equipment when the engine starts or runs at low speed. When the engine is running at high speed, the generator generates enough electricity, and the battery can store excess electricity. Each battery cell has a positive electrode and a negative electrode. Its identification method is: the positive electrode is engraved with a "+"sign, which is dark brown; The negative electrode is engraved with "-",which is light gray.
Starter: Its function is to convert electric energy into mechanical energy, drive the crankshaft to rotate and start the engine. When using the starter, it should be noted that the starting time should not exceed 5 seconds each time, the interval between each use should not be less than 10- 15 seconds, and it should be used continuously for no more than 3 times. If the continuous starting time is too long, it will cause a lot of discharge of the battery and overheating and smoking of the starting coil, which will easily damage the parts.
1. Vehicle equipment quality (kg): the fully equipped quality of the vehicle, including the quality of all equipment, such as lubricating oil, fuel, vehicle tools and spare tires.
2. Maximum total mass? Kg: the total mass of the car when it is fully loaded.
3. What is the maximum loading mass? Kg: the maximum loading mass of a car when driving on the road.
4. Maximum axle load mass (kg): the maximum total mass of a single bearing load of an automobile. Related to road capacity.
5. conductor? Mm: the distance between two longitudinal bars of a car.
6. How wide is this car? Mm: the distance between two poles in the width direction of the car.
7. How high is this car? Mm: the distance from the highest point of the car to the ground.
8. wheelbase? Mm: the distance from the center of the front axle to the center of the rear axle.
9. Tracking? Mm: the distance between the center lines of the left and right tire treads on the same axle.
10. Front suspension? Mm: the distance from the front end of the car to the center of the front axle.
1 1. Rear suspension? The distance from the rear end of the car to the center of the rear axle.
12. Minimum ground clearance? Mm: the distance from the lowest point to the ground when the car is fully loaded.
Basic structure of automobile
Abstract: An automobile is generally composed of four basic parts: engine, chassis, body and electrical equipment. Automobile engine: The engine is the power device of the automobile. It consists of engine body, crank-connecting rod mechanism, valve train, cooling system, lubrication system, fuel system and ignition system (diesel engine without ignition system). According to fuel, there are two kinds of engines: gasoline engine and diesel engine. There are two working modes: two-stroke and four-stroke. The general engine is a four-stroke engine.
Key words: working, sealing, engine, cooling system, lubricating system, fuel system, ignition system, compression ratio, clutch, transmission, carburetor.
The engine is the heart of a car. To understand a car, you must first have a general understanding of the engine.
First, let's look at one of the most common engine parameters-engine displacement. Engine displacement is the sum of the working volumes of each cylinder of the engine, which is generally expressed in liters (L). The working volume of cylinder refers to the volume of gas swept by piston from top dead center to bottom dead center, also known as single cylinder displacement, which depends on cylinder diameter and piston stroke. Engine displacement is a very important engine parameter, which can represent the size of the engine better than cylinder diameter and cylinder number, and many indexes of the engine are closely related to displacement. Generally speaking, the greater the displacement, the greater the output power of the engine.
Knowing the displacement, let's look at other commonly used parameters of the engine. Many junior riders report that they often see the words "L4", "V6", "V8" and "W 12" in the engine column of automobile data, trying to find out what they mean. These all indicate the arrangement and number of cylinders of the engine. The number of cylinders commonly used in automobile engines is 3, 4, 6, 8, 10, 12, etc.
Generally speaking, engines with displacement less than 1 liter are generally three cylinders, such as 0.8-liter Alto and Fuller. 1 displacement up to 2.5 liters is generally a 4-cylinder engine, and the engines of common economy cars and mid-range cars are basically 4 cylinders. An engine of about 3 liters is generally 6 cylinders, such as Regal and the new Accord with a displacement of 3.0 liters.
Engines with a displacement of about 4 liters are generally 8 cylinders, such as the Beijing Jeep JEEP4700 with a displacement of 4.7 liters. Engines with a displacement of more than 5.5 liters generally use 12 cylinder engines. For example, the 6-liter BMW 760Li uses a V 12 engine. With the same cylinder diameter, the more cylinders, the greater the displacement and the higher the power. Under the condition of the same engine displacement, the more cylinders, the smaller the cylinder diameter, which can increase the engine speed and thus obtain greater lifting power.
The above is the knowledge about the number of engine cylinders. Let's continue to understand the important parameter "cylinder arrangement". Generally, the cylinders of engines with less than 5 cylinders are arranged in line, and the most common middle and low-grade cars are L4 engines, that is, in-line 4 cylinders. In addition, there are a few 6-cylinder engines arranged in a straight line.
The cylinder block of an in-line engine is arranged in a straight line. Cylinder block, cylinder head and crankshaft are simple in structure, low in manufacturing cost, good in low-speed torque characteristics, low in oil consumption, small in size and wide in use, with the disadvantage of low power. Generally, gasoline engines below 1 liter mostly use inline 3 cylinders, gasoline engines with 1 to 2.5 liters mostly use inline 4 cylinders, and some four-wheel drive models use inline 6 cylinders. Because of the small width, facilities such as supercharger can be arranged beside it. For example, the JEEP4000 of Beijing Jeep uses in-line 6 cylinders.
According to professionals, the in-line 6-cylinder engine has good dynamic balance and relatively small vibration, so it is also adopted by some middle and high-end cars. Engines with cylinders 6 to 12 are generally arranged in a V-shape, in which V 10 engines are mainly installed in racing cars. The length and height of the V-type engine are very small, so it is very convenient to arrange. It is generally believed that V-type engine is a relatively advanced engine, so it has become one of the symbols of automobile class.
V8 engine is rarely used because of its complicated structure and high manufacturing cost. The V 12 engine is too big and heavy, and there are only a few advanced vehicles, such as the BMW 760Li mentioned above. Recently, Volkswagen also has a newly developed W-type engine, including W8 and W 12, that is, four rows of cylinders are staggered and compact. Phaeton, Volkswagen's top car, has an engine W 12 and a displacement of 6.0 liters.
The engine block is the skeleton of the engine and the installation foundation of various mechanisms and systems of the engine. The main parts of the engine are all installed inside and outside and bear various loads. Therefore, the car body must have sufficient strength and rigidity. Engine cylinder block is mainly composed of cylinder block, crankcase, cylinder head and cylinder gasket.
I. Cylinder block
The cylinder block and upper crankcase of water-cooled engine are often cast into a whole, which is called cylinder block-crankcase or cylinder block. The cylinder block is usually made of gray cast iron. The cylindrical cavity in the upper part of the cylinder block is called the cylinder, the lower part is the crankcase supporting the crankshaft, and its inner cavity is the space for the crankshaft to move. Many reinforcing ribs, cooling water jackets and lubricating oil passages are cast in the cylinder block.
The cylinder block should have sufficient strength and rigidity. According to the different installation plane positions of the cylinder block and the oil pan, the cylinder block is usually divided into the following three forms.
(1) The general cylinder block is characterized in that the installation plane of the oil pan is at the same height as the rotation center of the crankshaft. The advantages of this cylinder block are small height, light weight, compact structure, convenient processing and convenient disassembly and assembly of crankshaft; But its disadvantages are poor rigidity and strength.
(2) The gantry cylinder block is characterized in that the installation plane of the oil pan is lower than the rotation center of the crankshaft. Its advantages are good strength and rigidity, and it can bear large mechanical load. But its disadvantages are poor manufacturability, heavy structure and difficult processing.
(3) Tunnel cylinder block The crankshaft main bearing hole of this cylinder block is integral with rolling bearings. The main bearing hole is large, and the crankshaft is loaded from the back of the cylinder block. Its advantages are compact structure, good rigidity and strength, but its disadvantages are high machining accuracy, poor manufacturability and inconvenient disassembly and assembly of crankshaft.
In order to make the inner surface of the cylinder work normally at high temperature, it is necessary to properly cool the cylinder and cylinder head. There are two cooling methods, one is water cooling and the other is air cooling. Cooling water jackets are processed around the cylinder and cylinder head of water-cooled engine, and the cylinder block and cylinder head are communicated with each other. The cooling water continuously circulates in the water jacket, taking away some heat and cooling the cylinder and cylinder head.
Modern cars basically use water-cooled multi-cylinder engines. For a multi-cylinder engine, the arrangement of cylinders determines the overall size and structural characteristics of the engine, and also affects the stiffness and strength of the engine block, which is related to the overall layout of the automobile. According to the different arrangement of cylinders, the cylinder block can also be divided into three types: single row, V-shaped and opposite.
(1) embedded type
The cylinders of an engine are usually arranged vertically in a row. The single exhaust cylinder block is simple in structure and easy to process, but the length and height of the engine are large. Generally, engines with less than six cylinders are mostly single-row engines. For example, Jetta, Fukang and Hongqi cars all use this kind of in-line cylinder block. Some cars tilt the engine at an angle to reduce the height of the engine.
(2) V type
The cylinders are arranged in two rows, and the included angle between the center lines of the left and right rows of cylinders is γ < 180, which is called a V-type engine. Compared with the in-line engine, the V-type engine shortens the length and height of the engine block, increases the rigidity of the engine block and reduces the weight of the engine, but increases the width of the engine, which is complicated in shape and difficult to process. Generally used for engines with more than 8 cylinders, this type of cylinder block is also used for engines with 6 cylinders.
(3) objection
Cylinders are arranged in two rows, and the left and right cylinders are on the same horizontal plane, that is, the included angle between the center lines of the left and right cylinders is γ = 180, which is called opposition. It is characterized by small height and convenient overall layout, which is beneficial to air cooling. This kind of cylinder is seldom used.
A cylinder that directly drills holes in the cylinder block is called an integral cylinder. The integral cylinder has good strength and rigidity and can bear a large load. This kind of cylinder requires high materials and costs. If the cylinder is manufactured as a separate cylindrical part (i.e., cylinder liner) and then installed in the cylinder block. In this way, the cylinder liner is made of wear-resistant high-quality materials, and the cylinder block can be made of low-priced general materials, thus reducing the manufacturing cost. At the same time, the cylinder liner can be taken out of the cylinder block, which is convenient for maintenance and replacement and can greatly prolong the service life of the cylinder block. There are two kinds of cylinder liners: dry cylinder liners and wet cylinder liners.
The characteristic of dry cylinder liner is that after the cylinder liner is put into the cylinder block, its outer wall is not in direct contact with cooling water, but in direct contact with the cylinder block wall. The wall thickness is relatively thin, generally 1 ~ 3 mm, which has the advantages of integral cylinder block, good strength and rigidity, but complicated processing, inconvenient disassembly and assembly, and poor heat dissipation.
The characteristic of wet cylinder liner is that after the cylinder liner is put into the cylinder block, its outer wall is in direct contact with cooling water, and the cylinder liner is only in contact with the cylinder block up and down, and the wall thickness is generally 5 ~ 9mm. Good heat dissipation, uniform cooling and easy processing. Usually, only the inner surface needs to be finished, and the outer surface in contact with water does not need to be processed, so it is convenient to disassemble and assemble. However, its strength and stiffness are not as good as dry cylinder liner, which is easy to cause water leakage. Some measures should be taken to prevent leakage.
The lower part of the cylinder used to install the crankshaft is called crankcase, which is divided into upper crankcase and lower crankcase. The upper crankcase is integrated with the cylinder block, and the lower crankcase is used to store lubricating oil and seal the upper crankcase, so it is also called the oil pan diagram (Figure 2-6). The oil pan bears little force and is generally stamped from thin steel plate. Its shape depends on the overall layout of the engine and the oil capacity. An oil stabilizing baffle is installed in the oil pan to prevent the oil level from fluctuating too much when the car bumps. There is also an oil drain plug at the bottom of the oil pan. A permanent magnet is usually installed on the oil drain plug to absorb the metal chips in the lubricating oil and reduce the wear of the engine. The gasket is installed between the joint surfaces of the upper crankcase and the lower crankcase to prevent the lubricating oil from leaking.
Three. cylinder head
The cylinder head is installed on the cylinder block to seal the cylinder from the upper part to form a combustion chamber. It is often in contact with high temperature and high pressure gas, so it bears great thermal load and mechanical load. A cooling water jacket is arranged in the cylinder head of the water-cooled engine, and the cooling water hole at the lower end face of the cylinder head is communicated with the cooling water hole of the cylinder block. Circulating water is used to cool high-temperature components such as combustion chambers.
The cylinder head is also equipped with intake and exhaust valve seats, valve guide holes for installing intake and exhaust valves, and intake and exhaust passages. The cylinder head of gasoline engine has holes for installing spark plugs, and the cylinder head of diesel engine has holes for installing fuel injectors. There are also camshaft bearing holes on the cylinder head of overhead camshaft engines for installing camshafts.
Generally, the cylinder head is made of gray cast iron or alloy cast iron, and the aluminum alloy has good thermal conductivity, which is conducive to improving the compression ratio, so the use of aluminum alloy cylinder heads is increasing in recent years.
The cylinder head is an integral part of the combustion chamber, and the shape of the combustion chamber has a great influence on the work of the engine. Because of the different combustion modes of gasoline engine and diesel engine, the parts of cylinder head that make up the combustion chamber are also very different. The combustion chamber of gasoline engine is mainly on the cylinder head, and the combustion chamber of diesel engine is mainly in the pit at the top of piston. Only the combustion chamber of gasoline engine is introduced here, and the combustion chamber of diesel engine is introduced in the diesel supply system.
Three common types of combustion chambers in gasoline engines.
(1) hemispherical combustion chamber
The hemispherical combustion chamber is compact in structure, and the spark plug is arranged in the center of the combustion chamber, which has short flame stroke, high combustion rate, low heat dissipation and high thermal efficiency. The structure of this combustion chamber also allows the valves to be arranged in two rows, and the diameter of the air inlet is larger, so the charging efficiency is higher. Although the valve train has become more complicated, it is beneficial to exhaust purification and is widely used in automobile engines.
(2) Wedge combustion chamber
The wedge-shaped combustion chamber has simple and compact structure, small heat dissipation area and small heat loss, which can ensure the mixture to form a good vortex motion in the compression stroke, which is beneficial to improve the mixing quality of the mixture, with small intake resistance and improved charging efficiency. The valves are arranged in a row, which makes the valve train simple, but the spark plug is placed at the height of the wedge-shaped combustion chamber, and the flame propagation distance is longer. This type of combustion chamber is used in Cherokee automobile engines.
(3) Basin combustion chamber
The pot-shaped combustion chamber has good cylinder head manufacturability and low manufacturing cost, but the intake and exhaust effect is worse than that of the hemispherical combustion chamber because the valve diameter is easily limited. Jetta engine and Audi engine use basin combustion chamber.
Four. cylinder gasket
The cylinder gasket is installed between the cylinder head and the cylinder block, and its function is to ensure the sealing of the contact surface between the cylinder head and the cylinder block and prevent air leakage, water leakage and oil leakage.
The material of the cylinder gasket should have certain elasticity, which can compensate the unevenness of the joint surface and ensure sealing. At the same time, it should have good heat resistance and pressure resistance, and it will not burn or deform under high temperature and high pressure. At present, the cylinder gasket with copper cotton structure is widely used. Because there are three layers of copper skin at the flanging of copper skin-cotton cylinder pad, it is not easy to deform when pressed compared with asbestos. Some engines also use cylinder pads made of asbestos with woven steel mesh or perforated steel plate as the skeleton and asbestos and rubber adhesive pressed on both sides.
When installing the cylinder gasket, first check the quality and integrity of the cylinder gasket, and all the holes in the cylinder gasket should be aligned with the holes in the cylinder block. Secondly, the cylinder head bolts should be installed in strict accordance with the requirements of the manual. When tightening the cylinder head bolts, they must be expanded symmetrically from the center to the periphery for 2 ~ 3 times, and finally tightened to the specified torque.
Working process of the four-stroke engine: The four-stroke engine is that the piston reciprocates for four strokes to complete a working cycle, including intake, compression, work and exhaust. Four-stroke diesel engines, like gasoline engines, have to go through the processes of intake, compression, work and exhaust. But unlike gasoline engines, gasoline engines are ignition-type and diesel engines are compression-ignition type.
Cooling system: generally composed of water tank, water pump, radiator, fan, thermostat, water thermometer and drain switch. There are two cooling methods for automobile engines, namely air cooling and water cooling. Generally, automobile engines are mostly water-cooled.
Lubrication system: the engine lubrication system consists of oil pump, filter screen, oil filter, oil circuit, pressure limiting valve, oil gauge, pressure sensitive plug and dipstick.
Fuel system: The fuel system of a gasoline engine consists of fuel tank, gasoline meter, gasoline pipe, gasoline filter, gasoline pump, carburetor, air filter, intake and exhaust manifold, etc.
Carburetor: it is a device that mixes gasoline and air into atomized gas according to a certain proportion. This atomized gas is called combustible mixture, which is supplied to the cylinder in a timely and proper amount.
Automobile chassis:
Transmission system: mainly composed of clutch, transmission, universal joint, transmission shaft and drive axle.
Clutch: Its function is to make the power of the engine smoothly engage or temporarily separate from the transmission device, so as to facilitate the driver to start, stop and shift gears.
Transmission: It consists of transmission housing, transmission cover, first shaft, second shaft, intermediate shaft, reverse shaft, gears, bearings, control mechanism and other parts, and is used to change the speed and output torque of the automobile.
Drive system: consists of frame, axle, suspension and wheels. Its basic function is to support the quality of the whole vehicle and ensure the running of the vehicle.
Leaf spring and shock absorber: The role of leaf spring is to keep the elastic connection between the frame and the body, wheel or axle. The function of shock absorber is to reduce the vibration when the car is impacted by vibration. The shock absorber is used in parallel with the leaf spring.
Steering system: It consists of steering wheel, steering gear, steering knuckle, steering knuckle arm, tie rod and straight tie rod, and its function is steering.
Front wheel alignment: In order to keep the car running smoothly in a straight line, turn conveniently and reduce the wear of tires and steering parts, the front wheel, steering kingpin and front axle have a certain relative position, which is called "front wheel alignment". It includes kingpin backward inclination, production and marketing inward inclination and front wheel toe-in. Toe value refers to the difference between the front edge distance and the rear edge distance of two front wheels. ? Braking system: the braking performance of motor vehicles refers to the efficiency of forced parking in the shortest time. ?
Function of the hand brake: The hand brake is a device to prevent the car from slipping when parking, and it is used in conjunction with the foot brake under special circumstances.
Hydraulic braking structure: The hydraulic braking device consists of brake pedal, master brake cylinder, sub-brake cylinder, drum (wheel) brake and oil pipe.
Pneumatic braking device: it consists of brake pedal, air compressor, barometer, brake valve, brake air chamber, drum (wheel) brake and air pipe.
Electrical equipment:
Automobile electrical equipment is mainly composed of battery, generator, regulator, starter, ignition system, instrument, lighting device, audio device, wiper and so on.
Battery: The function of the battery is to supply power to the starter, and supply power to the engine ignition system and other electrical equipment when the engine starts or runs at low speed. When the engine is running at high speed, the generator generates enough electricity, and the battery can store excess electricity. Each battery cell has a positive electrode and a negative electrode. Its identification method is: the positive electrode is engraved with a "+"sign, which is dark brown; The negative electrode is engraved with "-",which is light gray. Starter: Its function is to convert electric energy into mechanical energy, drive the crankshaft to rotate and start the engine. When using the starter, it should be noted that the starting time should not exceed 5 seconds each time, the interval between each use should not be less than 10- 15 seconds, and it should be used continuously for no more than 3 times. If the continuous starting time is too long, it will cause a lot of discharge of the battery and overheating and smoking of the starting coil, which will easily damage the parts.
On the seal maintenance of automobile engine
In automobile engine maintenance, the phenomenon of "three leaks" (water leakage, oil leakage and air leakage) is the most headache for maintenance personnel. The "three leaks" seem ordinary and insignificant, but they directly affect the normal use of the car and the appearance cleanliness of the car engine. Whether the "three leaks" in important parts of the engine can be strictly controlled is an important issue that maintenance personnel must consider.
1 Types and Selection of Engine Seals
The quality of engine sealing material and its correct selection directly affect the sealing performance of engine.
1. 1 cork gasket
Cork gasket is made of granular cork and pressed with appropriate adhesive. Commonly used in oil pan, water jacket side cover, water outlet, thermostat housing, water pump and valve cover. In use, because the cork board is easy to break and inconvenient to install, this gasket is no longer the first choice for modern cars, but it can still be used as a substitute.
1.2 gasket asbestos plate gasket
Gasket asbestos board is a plate-like material made of asbestos fiber and adhesive material, which has the characteristics of heat resistance, pressure resistance, oil resistance and no deformation. Commonly used in carburetor, gasoline pump, oil filter, timing gear housing, etc.
1.3 Oil-resistant rubber pad
Oil-resistant rubber pad is mainly made of nitrile rubber and natural rubber, and asbestos fiber is added as additive. It is often used as a molding pad for automobile engine seal, mainly used in oil pan, valve cover, timing gear housing and air filter.
1.4 special washer
A. Crankshaft front and rear oil seals are usually special standard parts. Most of them use skeleton rubber oil seals. Pay attention to its directionality when installing. If not indicated, the oil seal lip with smaller inner diameter should be installed in the engine.
Cylinder liners are usually made of steel plates or copper sheets wrapped with asbestos. At present, automobile engine cylinder gasket mostly adopts composite gasket, that is, a metal inner layer is added in the middle of asbestos layer to improve its rigidity, and at the same time, 4 -5 layers of steel sheets are embossed near the edge of cylinder hole, thus improving the "washing" resistance of cylinder gasket. The installation of cylinder gasket should pay attention to its directionality, and if there is an assembly mark "top", it should face upwards; If there is no assembly mark, the cylinder pad smooth surface of cast iron cylinder block should face the cylinder block, while the cylinder pad smooth surface of aluminum alloy cylinder block should face the cylinder head.
C The intake and exhaust manifold gaskets are made of steel or copper asbestos. During installation, pay attention to make the curled surface (that is, the matte surface) face the cylinder block.
D the sealing of the side of the last main bearing cover of the crankshaft usually adopts soft technology or bamboo pieces. But in the absence of this piece, asbestos rope soaked in lubricating oil can also be used instead, but the asbestos rope should be compacted with a special shovel to prevent oil leakage.
E. The interface pads of spark plug and exhaust pipe should be replaced with new interface pads after disassembly and assembly once; Double gaskets should not be used to prevent air leakage. Experience has proved that the sealing performance of double gaskets is worse.
1.5 sealant
Sealant is a new type of sealing material in modern automobile engine maintenance. Its appearance and development provide good conditions for improving the sealing technology and solving the "three leaks" of the engine. There are many kinds of sealants, which can be applied to different parts of automobiles. Non-stick sealant (commonly known as liquid gasket) is usually used in automobile engines. It is a viscous liquid substance based on polymer compounds. After coating, a uniform, stable and continuous adhesive thin layer or peelable film is formed on the joint surface of the parts, which can fully fill the depressions and gaps in the joint surface. Sealants can be used alone or in combination with gaskets in engine valve cover, oil pan, valve lifter cover, etc. It can also be used alone under the last bearing cover, oil hole plug and oil plug of crankshaft.