Engine cylinder liners and piston rings are a pair of friction pairs that work under high temperature, high pressure, alternating loads and corrosion. Working under complex and changeable conditions for a long time will result in cylinder liner wear and deformation, affecting the engine's power, economy and service life. Carefully analyzing the causes of cylinder liner wear and deformation is of great significance for improving the economy of engine use.
Analysis of the causes of cylinder liner wear
The working environment of the cylinder liner is very harsh, and there are many reasons for wear. Normal wear and tear is usually allowed due to structural reasons, but improper use and maintenance will cause abnormal wear and tear.
1. Wear due to structural reasons
Poor lubrication conditions cause serious wear on the upper part of the cylinder liner. The upper part of the cylinder liner is adjacent to the combustion chamber, where the temperature is very high and the lubrication conditions are poor. The flushing and dilution of fresh air and unevaporated fuel aggravates the deterioration of the upper condition, leaving the cylinder in a state of dry friction or semi-dry friction, which is the cause of serious wear on the upper part of the cylinder.
The upper part bears large pressure, causing the cylinder to wear heavier at the top and lighter at the bottom. The piston ring is pressed against the cylinder wall under its own elasticity and back pressure. The greater the positive pressure, the more difficult it is to form and maintain a lubricating oil film, and mechanical wear increases.
Mineral and organic acids corrode and peel the cylinder surface. After the combustible mixture in the cylinder is burned, water vapor and acidic oxides are produced. They dissolve in water to form mineral acids, which corrode the cylinder surface. The corrosives are gradually scraped off by the piston rings during friction, causing cylinder liner deformation.
Mechanical impurities enter, causing increased wear in the middle part of the cylinder. Dust in the air, impurities in the lubricating oil, etc. enter between the piston and the cylinder wall, causing abrasive wear. When dust or impurities reciprocate with the piston in the cylinder, the wear in the middle of the cylinder is aggravated because the movement speed is maximum at the middle position of the cylinder.
2. Wear and tear caused by improper use
The lubricating oil filter has poor filtration effect. If the lubricating oil filter does not work properly, the lubricating oil cannot be effectively filtered, and the lubricating oil containing a large number of hard particles will inevitably increase the wear of the inner wall of the cylinder liner.
The air filter has low filtration efficiency. The function of the air filter is to remove dust and sand contained in the air entering the cylinder to reduce wear on parts such as cylinders, pistons, and piston rings.
Long-term low-temperature operation. Long-term low-temperature operation will firstly cause poor combustion, and carbon deposits will spread from the upper part of the cylinder liner, causing severe abrasive wear on the upper part of the cylinder liner; secondly, it will cause electrochemical corrosion.
Low-quality lubricants are often used. In order to save trouble and money, some car owners often buy inferior lubricating oil from roadside shops or unscrupulous oil dealers. As a result, the upper part of the cylinder liner is severely corroded, and the wear amount is 1-2 times greater than the normal value.
3. Wear and tear caused by improper maintenance
The cylinder liner is installed in an improper position. When installing the cylinder liner, if there is an installation error and the cylinder center line and the crankshaft axis are not vertical, it will cause abnormal wear of the cylinder liner.
The copper sleeve hole of the connecting rod is deflected. During repairs, when reaming the connecting rod small end copper sleeve, the reamer is tilted, causing the connecting rod copper sleeve hole to be deflected. The center line of the piston pin and the connecting rod small end center line are not parallel, forcing the piston to tilt to a certain side of the cylinder liner, which will also cause abnormal wear of the cylinder liner.
The connecting rod is bent and deformed. Due to a speeding accident or other reasons, the impacted connecting rod will bend and deform. If it is not corrected in time and continues to be used, it will also accelerate the wear of the cylinder liner.
The crankshaft connecting rod journal and main journal are not parallel. The engine's crankshaft will be deformed due to severe impact due to reasons such as burning tiles. If it is not corrected in time and continues to be used, it will also accelerate the wear of the cylinder liner.
Measures to reduce cylinder liner wear
1. Correct start and start
When an engine is started cold, low temperature makes the engine oil more viscous and less fluid, resulting in insufficient oil supply from the oil pump. In addition, oil on the cylinder walls drains downward after shutdown, so lubrication at the moment of starting is less effective than during normal operation, greatly increasing cylinder-wall wear. Before the initial start, therefore, turn the engine over for several revolutions so that the friction surfaces are lubricated before it fires. After starting, let it idle to warm up and never rev it sharply. Move off only after the oil temperature reaches 40°C. Start in a low gear and travel some distance in each successive gear until the oil temperature is normal, then switch to normal driving.
2.Choose the correct lubricant
Lubricating oil with the best viscosity value must be selected strictly according to the season and engine performance requirements. Low-quality lubricating oil must not be purchased at will, and the quantity and quality of lubricating oil must be checked and maintained frequently.
3. Strengthen filter maintenance
Keeping the air filter, oil filter and fuel filter in good working order is crucial to reducing cylinder liner wear. Strengthening the maintenance of the "three filters" is an important measure to prevent mechanical impurities from entering the cylinder, reduce cylinder wear, and extend the service life of the engine. It is especially important in rural areas and windy and sandy areas. It is absolutely wrong for some drivers not to install an air filter in order to save fuel.
4. Maintain normal engine operating temperature
Maintain normal engine operating temperature. The engine's normal operating temperature should be 80–90°C. If the temperature is too low, adequate lubrication cannot be maintained and cylinder-wall wear increases. Water vapor inside the cylinder readily condenses into droplets, which dissolve acidic gas molecules from the exhaust to form acidic substances that cause corrosive wear of the cylinder walls. Tests show that when the cylinder-wall temperature falls from 90°C to 50°C, cylinder wear is 4 times that at 90°C. Excessively high temperature reduces cylinder strength and increases wear, and can even cause excessive piston expansion and cylinder seizure.
5.Improve warranty quality
During use, problems should be discovered and eliminated promptly, and damaged and deformed accessories should be replaced or repaired at any time. When installing the cylinder liner, it must be inspected and assembled strictly according to the technical requirements. During the maintenance ring replacement operation, piston rings with appropriate elasticity should be selected. If the elasticity is too small, the gas will escape into the crankcase and blow off the oil on the cylinder wall, increasing the wear of the cylinder wall. If the elasticity is too large, the wear of the cylinder wall will be directly increased, or the oil film on the cylinder wall will be damaged and the wear will be aggravated.
Source: Internet
(Copyright belongs to the original author or institution)