There are many kinds of sliding bearings on an engine, both bushings and bushings are sliding bearings. In order to ensure the accuracy of the operation of the engine, the operating gap requirements of these sliding bearings is also very high. The cause of the engine slip bearing can be attributed to: lubrication of the critical state and cause damage to the operation of any interference and damage to the oil film of any material. Such as installation is not accurate, parts have bump damage and cleanliness is poor, the use of incorrect methods, harmful chemical reactions, etc., will lead to damage to the sliding bearing. According to the United States Cummins engine failure analysis of a book statistics, resulting in sliding bearing damage to the main reasons there are four aspects. The four percentages of these failures are as follows:
    
    1, due to clean damage caused by 45%;
    
    2, due to lubrication caused by damage to 25%;
    
    3, due to the use of the installation of the damage is 15%;
    
    4, due to surface reactions and other aspects of the damage caused by 15%.
    
    From this statistic ratio we can see that the cleanliness of the bearing damage caused by the main reason. Preventing damage caused by poor cleanliness is multifaceted: it ensures that the cleanliness of the part is only one aspect when the engine is assembled and on the other hand the engine is in use. Operators and maintenance personnel must be in accordance with the provisions of the correct use of timely maintenance checks, especially long-term dust and chemical raw materials in the environment of the engine, we must take measures to prevent the erosion of dust and chemical gases to ensure the use of the engine life. The main bearing in the engine, connecting rod surface alloy layer of the most soft, bear the largest load, but also the most vulnerable to damage, so the following to the main bearing and connecting rod tile surface damage phenomenon, analyze the reasons to avoid the repair after the failure of repeated The
    
    First, due to cleanliness problems caused by the failure:
    
    1, tiny particles of foreign body caused by the wear and tear of the bearing:
    
    When the oil filter and the engine oil pan oil drain plug, the first out of the tens of milliliters of oil, the naked eye can directly see and more alloy powder, the bearing has been worn. This is due to the small particles of impurities into the bearing surface of the bearing layer caused by the bearing, although the bearing does not cause serious damage, but such phenomena continue to develop, not only early damage to the pad, the shaft will be seriously damaged, it must According to the reasons for failure in a timely manner to exclude, to avoid damage to parts. After troubleshooting the life of the engine bushings can not be calculated according to the normal wear and tear time, because the occurrence of a small particle abnormal wear equivalent to the normal use of the engine 2500 hours of wear and tear.
    
    Micro-particles into the reasons: First, the air filter is poor or poor air intake system seal, to check the inlet system of the pipeline and the Department of the Department, with or without rupture and loosening, and check whether the filter loose, Whether the paper core rupture. Whether it is maintenance or maintenance of the entire intake system inspection is very important, must ensure reliability. Second, after the pollution of lubricating oil to join the engine or oil and filter the use of time is too long all the filter is blocked, then the lubricating surface of the oil without filtration directly into the filter. Third, the fuel oil supply is too large burning, nozzle leakage, resulting in fuel into the crankcase, while some impurities with the fuel into the crankcase and oil mixed together to reduce the lubrication effect. So the engine in use should pay attention to observe the engine exhaust and the operation of the situation, if any abnormalities to check the reasons for repair or replacement. Fourth, the engine assembly, the internal parts of the cleanliness is poor. In the maintenance and maintenance of the engine, be sure to pay attention to the cleaning parts, the installation should pay attention to prevent further pollution, to ensure that after the installation of internal cleanliness.
    
    For whatever reason, the engine oil and the filter element must be replaced after troubleshooting. After the maintenance of the engine to start the air run two hours to stop the operation to check the oil without alloy powder, can be put into half-load use, but in the first few days must pay attention to observation, after 60 to 120 hours to determine the operation of abnormal wear After the exclusion, and then replace the oil, the engine can be put into normal use. If abnormal wear continues to develop, it must stop using disintegration and repair.
    
    2, the larger particles of foreign matter and low-grade lubricants damage to the bearing:
    
    In the oil filter and the engine oil pan found in the larger particles of alloy pieces or sheets, the shaft and the bearing has been seriously damaged, and must immediately stop dismantling and repair, if you continue to use will cause more damage to parts.
    
    The reasons for the larger particles: the parts are not cleaned when installed, such as the processing of connecting rod bushing hole when the metal scraps remain in the rod oil, parts and oil within the sticky cutting or sediment, cleaning is not complete before installation Or with the moving surface of the processing of the processing of the burr is not removed, the installation of the bearing when the sticky large particles of foreign matter or the surface of the shaft was bruised. These phenomena are very serious damage to the bearing pad. So in the maintenance of the installation to carefully clean up the cleaning and inspection.
    
    Low-grade lubricating oil lubrication effect and cooling effect can not meet the requirements, so that bearing and shaft wear and tear intensified, the surface temperature is too high caused by alloy alloy melting and damage, while low-quality lubricants impurities more oil filter soon blocked, Impurities of the lubricating oil without filtering directly into the moving surface, further accelerating the shaft and bearing damage. So the purchase and replacement of lubricating oil must be in accordance with the provisions of strict control of the quality of lubricants, according to the provisions of the choice of lubricants.

    3, do not move the foreign body on the shaft and bearing damage:
    
    There is a large foreign body sandwiched between the bearing and the wall of the tile mounting hole between the bearing surface will produce a bump, when the shaft is running, the abnormal wear will start from the bumps, and extended to the surrounding, resulting in shaft and Bearing the early damage; if there is a large foreign body in the bearing surface between the bearing and the shaft, after installation will be embedded in the alloy layer of the bearing, the operation of the shaft at the same time damage the bearing; shaft and tile and mounting holes with its Related parts such as bump bumps will cause damage to the shaft and tile or damage.
    
    Cause and prevention: shaft, bearing, bearing hole (body, connecting rod) rust to produce oxide or sticky sediment, before installation to carefully check the cleaning, especially the oil and tubing lumen; installation site must be away from dust The use of tools to clean and take the necessary protective measures to avoid re-pollution, while the use of lubricating oil in the assembly to be clean to prevent dust mixed; shaft and bearing and bearing pad Storage and installation, to ensure that no contact with any metal objects and shall not have any knock knock operation.
    
    Second, the lubrication system caused by shaft and bearing damage and damage:
    
    1, the damage caused by poor lubrication and damage caused by the phenomenon:
    
    Shaft and bearing lubrication results can not meet the requirements, there will be a variety of fault characteristics. If the oil pressure is low, the part between the shaft and the bearing pad will be due to direct contact with dry friction caused by the movement of the surface damage and damage, then the surface of the shaft was blue. If the oil fails or the pressure can not be built, the moving surface will completely lose the protection of the oil film, direct contact with dry friction. The temperature rise of the alloy layer of the pad melting, timely shutdown to produce "hold tile" phenomenon, not timely downtime will cause more serious damage to parts.
    
    Causes: oil oil is too low or lubricating oil channel rupture; oil filter, oil, oil hole is blocked; oil pump wear or suction line leakage; pressure regulating valve, pressure limiting valve damage; engine idling time Too long; after the start of the engine without heating up the operation directly on the high-speed operation and full load operation; full load operation, the higher the temperature in the case of no empty load in the low-speed operation on the cooling down, the engine heat deposition, The temperature is increased; the standard oil is not selected and the oil is replaced regularly.
    
    2, there is water in the lubricating oil, resulting in shaft and bearing damage and damage:
    
    Lubricants in the water damage to the shaft and the bearing is more serious, because the water will make the oil deterioration damage oil film. The surface of the friction surface of the alloy surface of the bearing pad is grayed out on the edge of the friction surface, and a black corrosive material is formed on the alloy surface to cause irregular pits and local flaking of the friction surface of the bearing alloy.
    
    Cause: the cylinder seal seal is bad, the coolant infiltrates the crankcase; the engine oil radiator is damaged, the oil and water are mixed; when the oil is added, the water enters or the oil port and the oil seal is bad, the washing machine and the rain enter Crankcase; water in the fuel into the crankcase. So every time you start the engine, be sure to check the oil and oil oil, which must be done.
    
    3, lubricating oil in the shaft and bearing damage caused by:
    
    Fuel into the crankcase, the lubricating oil will become thinner, thinning film to reduce the lubrication effect, while the shaft and bearing corrosion. The surface of the bearing alloy is dark green with slight cavitation. In particular, the higher sulfur content of the fuel produced by the by-product, the fuel into the poor ventilation of the crankcase, the resulting sulfuric acid material on the surface of the shaft will cause serious cavitation.
    
    Reason: the fuel system fuel supply is too large, the fuel injected into the combustion chamber can not be completely burned; intake air intake is not enough, the fuel can not be fully burned; nozzle seal failure fuel into the crankcase; cylinder fuel tank There are stomatal trachoma or crack; idle time is too long, the engine temperature is low fuel can not be completely burned.
    
    To prevent the lubrication system caused by the shaft and bearing damage and damage must be done:
    
    A, in the absence of manual lubrication equipment, the installation of the engine in the axis and the bearing surface of the movement with the same label with the same cleaning oil, the engine installed, the first start before closing the fuel switch, with the starter to drive the engine Idle several times, when the engine oil pressure gauge is displayed, and then connected to open the fuel switch, the throttle in the low speed, start the engine to observe the operation.
    
    B, the engine long-term storage, the initial start also driven by the start-up after the idle, and then start.
    
    C, must be in accordance with the provisions of the time for the maintenance of the engine, check, replace the oil and filter.
    
    D, the engine oil level must be within the standard range, lubricants and fueling tools must be cleaned to prevent any dirt and water from entering, while ensuring that the engine parts of the sealing effect.
    
    E, to avoid the engine idle time is too long, idle operation can not be more than 5 minutes.
    
    F, the engine must start after the start-up temperature operation, when the water temperature rose to above 70 ℃ when put into use.
    
    G, the engine end of a long time after the full load of work, can not immediately stop, you must let the engine no load in the low speed to move after 15 minutes to stop, otherwise the internal heat to not come out.
    
    Third, the use of damage caused by improper damage and damage:
    
    1, the idle operation time caused by damage and damage phenomenon: bearing the surface of the alloy layer, was squeezed shift and flanging and flake off.
    
    The reason is: the engine idling time is too long, the engine is running below the normal operating temperature, the fuel injected into the combustion chamber can not be completely burned, part of the fuel can not burn the cylinder wall into the crankcase, destroyed the oil Of the oil film to reduce the lubrication effect. At the same time idle speed is low, the oil pump fuel supply is small, so it causes the bearing pad surface and the shaft of the slight dry friction, so that the alloy surface of the bearing pad is damaged, at the same time produce damage to the wear shaft and bearing wear And damaged. To prevent such problems will occur according to the operating procedures, each start the engine after the idle operation can not be more than 5 minutes, the engine no-load operation can not be less than 850 r / min.

    2, the engine after a long period of work on the shutdown (shutdown) caused by damage and damage phenomenon: bearing alloy surface was worn, there are uneven surface alloy from the middle to both sides of the shift.
    
    The reason is: the engine in a long time after the work of the larger load, the internal parts are in the highest working temperature state, especially the combustion chamber part of the high temperature, the engine stops running, the cooling system and lubrication system are stopped working, heat does not go out So that the relevant parts of the temperature rise, so that the lubrication of the surface of the oil film damage, when re-start, in the lubrication of the surface of the oil has not yet formed when the wear and tear of the bearing has occurred. Especially for the supercharger sliding bearing damage is more serious, while too high temperature will cause the shaft hole deformation, destruction of operating accuracy to speed up the damage to the engine. The occurrence of this phenomenon on the piston, cylinder liner and cylinder seal will cause serious damage. So the engine in a long time after the work of a larger load, let the engine no load in the low-speed operation for more than 10 minutes, the internal temperature is reduced and then stop.
    
    3, the engine starts directly into the high-speed operation and full load operation on the bearing damage or damage phenomenon: the engine seventh and sixth main bearing serious wear and tear, other bearing damage.
    
    The reason is: the engine is not started after the no-load heating operation, put into high-speed operation and full load operation. Because the engine does not meet the requirements of the working temperature, the Ministry of the force contact surface and the operating gap is not in the best condition, and the low temperature of the oil flow is poor, the movement of the surface heat can not be quickly taken away by lubricating oil and other reasons, Causing damage or damage to the bearing pad. The lower the outside temperature, the more serious damage to the bearing. To prevent such problems occur must be carried out according to the provisions of the heating operation, the engine starts after the low-speed air operation, when the engine water temperature rose to 70 ℃ or more to put into operation.
    
    4, due to adjustment and operation errors caused by bearing damage or damage to the phenomenon: crankshaft thrust bearing (thrust ring) serious wear or damage, the seventh main bearing damage.
    
    The reason is: crankshaft axial clearance is too large or too small, will cause the crankshaft thrust bearing damage. In the course of the use of large axial impact, the axial clearance of small temperature rise will produce abnormal wear and tear caused the damage of the seventh main bearing. To prevent the occurrence of such problems, to be installed in the engine must ensure that the axial clearance of the crankshaft in the standard range of 0.18 ~ 0.35mm.
    
    Fourth, the installation is not correct cause damage or damage to the bearing:
    
    1, individual bearing a single side of serious wear and tear, tile alloy surface abrasion.
    
    The reason is that the deformation of the connecting rod exceeds the allowable range of the connecting rod, the stamping force of the bearing cover is not uniform, and the side of the bearing on the back side of the bearing is bruised. The installation position of the bearing pad is not accurate and the center is not correct.
    
    2, seven bearing a single side of the wear and tear, the middle bearing than both ends of the bearing wear more serious.
    
    The reason is: the shaft hole deformation of the taper; crankshaft bending (resulting in crankshaft bending is due to: uneven operation gap, the relevant parts of the wear and tear.