Cause analysis of cylinder sleeve wear
The working environment of cylinder liner is very bad, and there are many reasons for wear. Under normal circumstances, due to construction reasons, normal wear is allowed, but improper use and maintenance will lead to abnormal wear.
Structural reasons
(1)The upper part of the cylinder liner is severely worn due to poor lubrication conditions. The upper part of the cylinder liner is close to the combustion chamber, with high temperature and poor lubrication conditions. The cleaning and dilution of fresh air and un-evaporated fuel aggravate the deterioration of the upper conditions, making the upper part of the cylinder in a dry or semi-dry friction state, which is the reason for the severe wear of the upper part of the cylinder.
(2)The upper pressure is large, which makes the cylinder wear less. The piston ring is tightly pressed on the cylinder wall under its own elastic force and back pressure. The greater the positive pressure, the more difficult it is to form and maintain the lubricating oil film, and the greater the mechanical wear. During the working stroke, as the piston decreases, the positive pressure gradually decreases, so the wear of the cylinder is heavier and lighter.
(3)Mineral and organic acids can cause corrosion and peeling of the cylinder surface. After the combustible mixture is burned in the cylinder, it will produce water vapor and acid oxide. They will dissolve in water to form inorganic acids. In addition, the organic acid produced during combustion will cause corrosion to the cylinder surface. During the friction process, the piston ring will gradually scrape away the corrosion, resulting in the deformation of the cylinder liner.
(4)Mechanical impurities enter the cylinder, which aggravates the wear in the middle of the cylinder. Dust in the air and impurities in the lubricating oil enter the piston and cylinder wall, resulting in wear. When dust or impurities move back and forth with the piston in the cylinder, the wear in the middle of the cylinder increases due to the maximum moving speed in the middle of the cylinder.
Improper use
(1)The filtering effect of lubricating oil filter is poor. 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 aggravate the wear of the inner wall of the cylinder liner.
(2)The filtration efficiency of air filter is low. The function of the air filter is to remove the dust and sand contained in the air entering the cylinder, thus reducing the wear of the cylinder, piston, piston ring and other components. The experiment shows that if the engine is not equipped with air filter, the cylinder wear will increase 6-8 times. The air filter cannot be cleaned and maintained for a long time, and the filtering effect is poor, which will accelerate the wear of the cylinder liner.
(3)Long-term low-temperature operation. Long-term low temperature operation leads to poor combustion, and carbon deposits diffuse from the upper part of the cylinder liner, resulting in serious wear of the upper part of the cylinder liner; Second, it causes electrochemical corrosion.
(4)Always use inferior lubricating oil. In order to save time and money, some car owners often buy inferior lubricating oil from roadside stores or illegal oil vendors for use. Therefore, the upper part of the cylinder liner is severely corroded, and its wear is 1-2 times greater than the normal value.
Improper maintenance
(1)Improper installation position of cylinder sleeve. When installing the cylinder liner, if there is an installation error, the cylinder centerline and crankshaft axis are not vertical, which will lead to abnormal wear of the cylinder liner.
(2)The connecting rod copper sleeve hole is skewed. During the maintenance process, when the copper sleeve is reamed at the small end of the connecting rod, the reamer is inclined, resulting in the deviation of the copper sleeve hole of the connecting rod. The centerline of the piston pin is not parallel to the centerline of the small end of the connecting rod, forcing the piston to tilt to the side of the cylinder liner, which will also cause abnormal wear of the cylinder liner.
(3)The connecting rod is bent and deformed. The impacted connecting rod will bend and deform due to flight accidents or other reasons. 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 wear
1.Start and start correctly
When the engine is cold started, the oil supply of the oil pump is insufficient due to low temperature, high oil viscosity and poor fluidity. At the same time, the oil on the cylinder wall of the feed gas flows downward along the cylinder wall after stopping, so it cannot be lubricated as it is during normal operation during startup, resulting in a significant increase in the wear of the cylinder wall during startup. Therefore, when starting the engine for the first time, it is necessary to idle the engine for several cycles, and then start it after lubricating the friction surface. After starting, the engine should run at idle speed to increase the temperature. It is forbidden to knock the oil port and restart when the oil temperature reaches 40 ℃; When starting, stick to the low gear and drive a certain mileage in each gear until the oil temperature is normal.
2.Correct selection of lubricating oil
The lubricant with the best viscosity should be selected strictly according to the season and engine performance requirements. Do not purchase and use inferior lubricating oil at will, and regularly check and maintain the quantity and quality of lubricating oil.
3.Strengthen the maintenance of filter
Keep the air filter, oil filter and fuel filter in good working condition to reduce the wear of cylinder liner. Strengthening the "three filters" maintenance is an important measure to prevent mechanical impurities from entering the cylinder, reduce cylinder wear and prolong the service life of the engine, especially in rural areas and sandstorm areas. For some drivers, it is absolutely wrong not to install air filter in order to save fuel.
4.Maintain the normal operating temperature of the engine
The normal operating temperature of the engine shall be 80-90 ℃. If the temperature is too low to maintain good lubrication, it will increase the wear of the cylinder wall. The water vapor in the cylinder is easy to condense into water droplets, dissolve the acid gas molecules in the exhaust gas, generate acid substances, and cause corrosion and wear of the cylinder wall. The test shows that when the cylinder wall temperature drops from 90 ℃ to 50 ℃, the cylinder wear is four times as high as that at 90 ℃. If the temperature is too high, the strength of the cylinder will be reduced, the wear will be intensified, and the piston may even expand excessively, leading to the "cylinder expansion" accident.
5.Improve warranty quality
In the process of use, timely find and eliminate problems, and replace or repair damaged and deformed parts at any time. The cylinder liner shall be inspected and assembled in strict accordance with the technical requirements. During the warranty ring replacement operation, piston rings with proper elasticity should be selected. If the elasticity is too small, the gas will flow into the crankcase and drain the oil on the cylinder wall, which will increase the wear of the cylinder wall; Excessive elasticity will directly aggravate the wear of the cylinder wall, or the damage of the oil film on the cylinder wall will aggravate the wear of the cylinder wall. The crankshaft connecting rod journal and the main journal are not parallel. The crankshaft will be deformed due to severe impact due to the combustion of the engine pad and other reasons. If it is not corrected in time and continues to be used, it will also accelerate the wear of the cylinder liner.
