The function of the cylinder liner
1. Together with the cylinder head and piston, it forms the cylinder working space;
2. The cylinder liner of the cylindrical piston diesel engine Bear the side thrust of the piston and become the lead of the piston’s reciprocating motion;
3. Transfer the heat of the piston assembly and itself to the cooling water to make the working temperature appropriate;
4. 2. The cylinder liner of the stroke diesel engine is equipped with air ports, which are opened and closed by the piston to realize air distribution.
What material is the cylinder liner made of?
The materials of the cylinder liner include ductile iron and alloy cast iron. The material of the cylinder liner must have sufficient mechanical strength and heat resistance, as well as good wear resistance, corrosion resistance, oil retention and lubricity.
What two types of cylinder liners are there
Cylinder liners are divided into dry cylinder liners and wet cylinder liners. The difference between the two is mainly judged based on whether it is in contact with coolant.
1. Dry cylinder liner
The characteristic of dry cylinder liner is that the outer surface of the cylinder liner does not come into contact with the coolant. In order to obtain sufficient actual contact area with the cylinder block and ensure the heat dissipation effect and positioning of the cylinder liner, the outer surface of the dry cylinder liner and the matching inner surface of the cylinder block socket have high machining accuracy, and are generally used Interference fit. The wall of dry cylinder liner is thin, generally only 1~3mm. Dry cylinder liners are commonly used in gasoline engines, and some small-horsepower diesel engines also use dry cylinder liners.
Advantages: high body rigidity, small cylinder center distance, small body mass, and simple processing technology.
Disadvantages: poor heat dissipation, uneven temperature distribution, inconvenient repair, and prone to local deformation.
2. Wet cylinder liner
The characteristic of the wet cylinder liner is that its outer surface is in direct contact with the coolant. In addition, it has a thicker wall than a dry cylinder liner. The radial positioning of the wet cylinder liner generally relies on two protruding annular belts on the upper and lower sides that are clearance-fitted with the cylinder block. The axial positioning uses the lower plane of the upper flange. The lower part of the cylinder liner is sealed by 1 to 3 heat-resistant and oil-resistant rubber sealing rings. There are two types of sealing: expansion sealing and pressure sealing.
Advantages: There is no sealed water jacket on the body, it is easy to cast, has good heat transfer, relatively uniform temperature distribution, and the wall thickness is generally 5~8mm. The most important thing is that the cylinder liner can be replaced without removing the engine from the car during maintenance, making maintenance convenient. Wet cylinder liners are generally used in diesel engines.
Disadvantages: The body has poor rigidity and is prone to water leakage.
The cause of excessive wear of cylinder linerDue to the different positions of the piston and different working conditions, the wear of various parts of the cylinder liner is also different. The wear of the cylinder liner is most severe at the contact part between the first piston ring and the cylinder wall. From top to bottom, the wear amount is significantly reduced. This kind of wear on the top and bottom makes the cylinder tapered. If there are impurities in the engine oil that are not filtered by the filter, the impurities and metal shavings in the engine oil will be brought to the surface of the cylinder wall, causing abrasive wear. After the wear, the cylinder liner becomes a waist-drum shape.
Serious wear of the cylinder liner in the engine is caused by the following reasons:
1. Filter failure. In particular, the air filter is broken and the air is short-circuited into the cylinder without filtering. As dust and impurities in the air enter the cylinder, the wear of the cylinder liner increases.
2. The engine oil grade is incorrect, resulting in poor lubrication and severe cylinder liner wear.
3. The use of inferior diesel fuel causes severe coking after combustion, causing severe wear of the cylinder liner.
4. Operational issues. During cold start, especially in winter, due to the high viscosity and poor fluidity of the oil, the oil pump will not supply enough oil; at the same time, the oil on the original cylinder wall will flow down along the cylinder wall after stopping, and will not work at the moment of starting. Such lubrication will increase the wear of the cylinder wall.
5. Driving at low temperatures. Because the temperature is too low, good lubrication cannot be maintained, which increases the wear of the cylinder.
(6) Quality and assembly issues of cylinder liner.
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