I. Analysis of the causes of cylinder liner wear
The working environment of the cylinder liner is very bad, and there are many reasons for the wear. Normal wear is usually allowed for structural reasons, but improper use and repair can cause abnormal wear.
1 Wear caused by structural reasons
1) The lubrication condition is not good, causing serious wear on the upper part of the cylinder liner. The upper part of the cylinder liner is adjacent to the combustion chamber, the temperature is high, and the lubrication condition is very poor. The flushing and dilution of fresh air and unvaporized fuel exacerbate the deterioration of the upper condition, causing the cylinder to be in a dry or semi-dry friction state, which is the cause of severe wear on the upper part of the cylinder.
2) The upper part is subjected to high pressure, so that the cylinder wear is heavy and light. The piston ring is pressed against the cylinder wall under the action of 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 mechanical wear is intensified. In the power stroke, as the piston descends, the positive pressure gradually decreases, and the cylinder wear is lighter and lighter.
3) Mineral acid and organic acid cause corrosion of the cylinder surface. After combustion of the combustible mixture in the cylinder, water vapor and acid oxide are generated. They are dissolved in water to form mineral acid, and the organic acid formed in the combustion causes corrosion on the cylinder surface. The corrosive material is gradually scraped by the piston ring during friction. Dropped, causing deformation of the cylinder liner.
4) Entering mechanical impurities, causing increased wear in the middle of the cylinder. Dust in the air, impurities in the lubricating oil, etc., enter the piston and the cylinder wall to cause abrasive wear. Dust or impurities as the piston reciprocates in the cylinder, the wear of the middle portion of the cylinder is exacerbated by the maximum speed of movement in the middle of the cylinder.
2Wear caused by improper use
1) Lubricating oil filter has poor filtering effect. If the lubricating oil filter is not working properly and the lubricating oil is not effectively filtered, the lubricating oil containing a large amount of hard particles will inevitably increase the wear of the inner cylinder liner.
2) Air filter filtration efficiency is low. The function of the air filter is to remove dust and sand contained in the air entering the cylinder to reduce wear on components such as cylinders, pistons and piston rings. Experiments have shown that if the engine is not equipped with an air filter, the cylinder wear will increase by 6-8 times. The air filter has not been cleaned and maintained for a long time, and the filtration effect is poor, which will accelerate the wear of the cylinder liner.
3) Low temperature operation for a long time. Long-term low-temperature operation, first, causing poor combustion, carbon deposition from the upper part of the cylinder liner, causing serious abrasive wear on the upper part of the cylinder liner; second, causing electrochemical corrosion.
4) Inferior lubricants are often used. Some car owners save money by saving money. They often use inferior lubricants in roadside shops or in the case of unscrupulous oil sellers. As a result, the upper part of the cylinder liner is strongly corroded, and its wear is 1-2 times larger than the normal value.
3 Wear caused by improper maintenance 1) The cylinder sleeve is not installed properly. When installing the cylinder liner, if there is installation error, the cylinder center line and the crankshaft axis are not perpendicular, which will cause abnormal wear of the cylinder liner.
2) The copper sleeve hole of the connecting rod is deflected. During the repair, when the copper sleeve of the connecting rod small head is reamed, the reamer is tilted to cause the copper sleeve hole of the connecting rod to be skewed, and the center line of the piston pin is not parallel with the center line of the connecting rod small head, forcing the piston to tilt to one side of the cylinder sleeve. It will also cause abnormal wear of the cylinder liner.
3) The connecting rod is bent and deformed. Due to a flying accident or other reasons, the impacted connecting rod will be bent and deformed. If it is not corrected in time, it will accelerate the wear of the cylinder liner.
4) The crankshaft connecting rod journal and main journal are not parallel. If the engine is burnt due to burning, etc., the crankshaft will be deformed by severe impact. If it is not corrected in time, it will accelerate the wear of the cylinder liner.
Second measures to reduce the wear of the cylinder liner
1.Starting and starting correctly
When the engine is cold, the temperature is low, the viscosity of the oil is large, and the fluidity is poor. The oil pump is not adequately supplied with oil. At the same time, the oil on the original cylinder wall flows down the cylinder wall after stopping, so that the lubrication is not as good as in the normal operation at the moment of starting, so that the cylinder bore wear is greatly increased at the time of starting. Therefore, when starting the first time, the engine should be idling a few turns, and then the friction surface should be lubricated before starting. After starting, it should be idling and warming up. It is forbidden to slam the oil port. When the standby oil temperature reaches 40 °C, start again. Start at the low speed and start a mileage for each gear until the oil temperature is normal. travel.
2. Correctly use lubricating oil
It is necessary to select the lubricating oil with the best viscosity value strictly according to the season and engine performance requirements. It is not allowed to purchase inferior lubricating oil at will, and often check and maintain lubricating oil. Quantity and quality.
3. Strengthening the maintenance of the filter
Keeping the air filter, oil filter and fuel filter in good working condition is essential to reduce the wear of the cylinder liner. . Strengthening the maintenance of “three filters” is an important measure to prevent mechanical impurities from entering the cylinder, reducing cylinder wear and prolonging the service life of the engine. It is especially important in rural areas and in windy areas. It is absolutely wrong for some drivers to install air filters in order to save fuel.
4. Maintaining the normal operating temperature of the engine The normal operating temperature of the engine should be at 80-90 °C. If the temperature is too low, it will not maintain good lubrication, which will increase the wear of the cylinder wall. The water vapor in the cylinder will easily condense into water droplets, dissolve the acid gas molecules in the exhaust gas, and generate acidic substances, causing the cylinder bore to be corroded and worn. Tests have shown that when the cylinder bore temperature is reduced from 90 ° C to 50 ° C, the cylinder wear amount is 4 times that of 90 ° C. If the temperature is too high, the strength of the cylinder will be reduced and the wear will be aggravated, and the piston may be over-expanded to cause an “expansion” accident.
5. Improve the quality of warranty
In the process of use, find problems in time to eliminate them, and replace or repair damaged and deformed parts at any time. When installing the cylinder liner, it must be inspected and assembled according to the technical requirements. In the warranty replacement operation, the piston ring with appropriate elastic force should be selected, the elastic force is too small, so that the gas is blown into the crankcase to blow off the oil on the cylinder wall, and the cylinder wall wear is increased; the elastic force is too large, which directly aggravates the wear of the cylinder wall. Or it is aggravated by the destruction of the oil film on the cylinder wall.