The percentages of these four aspects in the fault are as follows: Koyo bearing
There are many kinds of sliding Koyo bearings on an engine. Both bushing and bearing bush belong to sliding Koyo bearings. In order to ensure the running accuracy of the engine, the running clearance requirements of these sliding Koyo bearings are also very high. Technical analysis of engine sliding Koyo bearing
The fault causes of engine sliding Koyo bearings can be attributed to the critical state of lubrication, any interference causing damage to the running clearance and any substance damaging the oil film. For example, inaccurate installation and adjustment, collision damage and poor cleanliness of parts, incorrect use method, harmful chemical reaction, etc. will lead to the damage of sliding Koyo bearing. According to the statistics in Cummins engine fault analysis, there are four main causes of sliding Koyo bearing damage.
The damage caused by cleaning is 45%;
The damage caused by lubrication is 25%;
Damage due to use and installation is 15%;
The damage caused by surface reaction and other aspects is 15%.
From this statistical proportion, we can see that the damage caused by cleanliness to Koyo bearings is the main reason. The work of preventing damage caused by poor cleanliness is multifaceted: ensuring the cleanliness of parts during engine assembly is only one aspect, on the other hand, during the use of the engine. Technical analysis of engine sliding Koyo bearing
Operators and maintenance personnel must correctly use the timely maintenance and inspection according to the regulations, especially for the engine working in the environment of dust and chemical raw materials for a long time, and must take measures to prevent the erosion of dust and chemical gas and ensure the service life of the engine. Technical analysis of engine sliding Koyo bearing
The alloy layer on the surface of the main bearing bush and connecting rod bush in the engine is soft, bears large load and is easy to be damaged. Therefore, the following is to analyze the causes based on the surface damage of the main bearing bush and connecting rod bush, so as to avoid the recurrence of faults after repair.
Whether it is repair or maintenance, the inspection of the whole intake system is very important, and the reliability must be ensured. Second, after the lubricating oil is polluted, it is added to the engine or the oil and filter element are used for a long time. If all the filter elements of the machine are blocked, the oil on each lubricating surface will directly enter the filter element without filtering. Technical analysis of engine sliding Koyo bearing
Third, excessive fuel supply, incomplete combustion and nozzle leakage cause the fuel to penetrate into the crankcase. At the same time, some impurities enter the crankcase with the fuel and mix with the engine oil to reduce the lubrication effect. Therefore, during the use of the engine, pay attention to the smoke exhaust and operation of the engine.Technical analysis of engine sliding Koyo bearing
If there is any abnormality, find out the cause in time and repair or replace it. Fourth, the cleanliness of internal parts is poor during engine assembly. When repairing and maintaining the engine, be sure to pay attention to the cleaning of parts. During installation, pay attention to prevent re pollution and ensure the internal cleanliness after installation.Technical analysis of engine sliding Koyo bearing
Regardless of the cause, the engine oil and filter element must be replaced after troubleshooting. The repaired engine starts idling for two hours and stops running for inspection. If there is no alloy powder in the engine oil, it can be put into half load use. However, pay attention to observation in the first few days of use. Technical analysis of engine sliding Koyo bearing
After 60 ~ 120 hours of operation, it is determined that the abnormal wear is completely eliminated, and then change the engine oil, and the engine can be put into normal use. If abnormal wear continues to develop, it must be stopped for disassembly inspection and repair.Technical analysis of engine sliding Koyo bearing
Damage to inferior lubricating oil:Technical analysis of engine sliding Koyo bearing
When alloy blocks or flakes with large particles are found in the engine oil filter element and the engine oil pan, the shaft and bearing bush have been seriously damaged. It must be shut down immediately for disassembly and repair. If they continue to be used, more parts will be damaged.
Reasons for the entry of large particles: the parts are not cleaned during installation, such as the metal chips generated during the processing of the inner hole of the connecting rod bushing are left in the connecting rod oil passage, the cutting or sediment is stuck in the parts and oil passage, the cleaning is not thorough before installation, or the machining burr flanging of the machining parts related to the moving surface is not removed,
The foreign matters with large particles stuck during the installation of the bearing bush or the surface of the shaft is bruised. The damage caused by these phenomena to the bearing bush is very serious. Therefore, it is necessary to carefully clean, clean and check during maintenance and installation.Technical analysis of engine sliding Koyo bearing
The lubricating effect and heat dissipation effect of inferior lubricating oil can not meet the requirements, which aggravates the wear of bearing bush and shaft, and the high temperature of moving surface causes the alloy melting and damage of bearing bush. At the same time, there are many impurities in inferior lubricating oil, and the engine oil filter element is quickly blocked.Technical analysis of engine sliding Koyo bearing
The lubricating oil containing impurities directly enters the moving surface without filtering, further accelerating the damage of shaft and bearing bush. Therefore, when purchasing and replacing lubricating oil, we must strictly control the quality of lubricating oil and select lubricating oil according to regulations.
Damage matters not moving:Technical analysis of engine sliding Koyo bearing
There are large foreign matters sandwiched between the bearing bush and the inner wall of the Bush mounting hole, and the moving surface of the bearing bush will produce bumps. When the shaft is running, the abnormal wear will start from the bumps and expand to the periphery, resulting in early damage to the shaft and bearing bush; Technical analysis of engine sliding Koyo bearing
If there is a large foreign matter between the moving surface of the bearing bush and the shaft, it will be embedded in the alloy layer of the bearing bush after installation. During operation, it will damage the shaft and the bearing bush at the same time; If there are bumps and bumps on the shaft and pad, mounting hole and other related parts, the shaft and pad will be damaged or damaged.Technical analysis of engine sliding Koyo bearing
Causes and prevention: the shaft, bearing bush and bearing bush hole (body and connecting rod) are rusted, resulting in oxide or sediment. Carefully check and clean before installation, especially the inner cavity of oil duct and oil pipe; Technical analysis of engine sliding Koyo bearing
The installation site must be far away from the site with dust and debris splashing; The tools used for installation shall be clean, and necessary protective measures shall be taken to avoid re pollution. At the same time, the lubricating oil used in assembly shall be clean to prevent dust from mixing; The storage and installation of shaft, bearing bush and bearing bush hole shall ensure no contact with any metal object and no collision operation.
Damage and damage of shaft and bearing bush caused by lubrication system:
caused by poor lubrication effect:Technical analysis of engine sliding Koyo bearing
When the lubrication effect of shaft and bearing bush fails to meet the requirements, a variety of fault characteristics will appear. If the oil pressure is low, the local part between the shaft and the bearing bush will produce dry friction due to direct contact, resulting in damage and damage to the moving surface. At this time, the shaft surface is blue.Technical analysis of engine sliding Koyo bearing
Cleanliness problems :sliding Koyo bearing
Abrasion of bearing bush caused by small particles and foreign matters:
When there is more alloy powder that can be seen directly by the naked eye in the first tens of milliliters of oil flowing out of the oil filter element and the oil drain plug of the engine oil pan, the bearing bush has been abraded. This is caused by the impurities of small particles entering the moving surface of the bearing bush alloy layer.
Although there is no serious damage to the bearing bush, if this phenomenon continues to develop, not only the bearing bush will be damaged early, but also the shaft will be seriously damaged. Therefore, it must be eliminated in time according to the cause of the fault to avoid damage to the parts.
After troubleshooting, the service life of engine bearing bush cannot be calculated according to the service time of normal wear, because the abnormal wear amount of small particles once is equivalent to the wear amount of 2500 hours of normal use of the engine.Technical analysis of engine sliding Koyo bearing
Reasons for the entry of small particles: first, the filtration effect of the air filter is poor or the sealing of the air inlet system is not good. Check whether the pipelines and connections of each part of the air inlet system are broken and loose, and check whether the filter element is loose and the paper core is broken. Technical analysis of engine sliding Koyo bearing
Damage of fuel in lubricating oil:Technical analysis of engine sliding Koyo bearing
If the lubricating oil fails or the pressure cannot be built up, the moving surface will completely lose the protection of the oil film and directly contact for dry friction. When the temperature rises and the alloy layer of the bearing bush melts, the phenomenon of “bearing bush holding” will occur when the machine is shut down in time. If the machine is not shut down in time, it will cause more serious damage to the parts.Technical analysis of engine sliding Koyo bearing
Causes: the oil level of engine oil is too low or the lubricating oil passage is broken; The oil suction screen, oil passage and oil hole are blocked; Wear of oil pump or air leakage of oil suction pipeline; The pressure regulating valve and pressure limiting valve are damaged; The idle running time of the engine is too long;Technical analysis of engine sliding Koyo bearing
After the engine is started, high-speed operation and full load operation can be carried out directly without heating operation; After full load operation, when the temperature is high, the engine will be shut down without cooling during medium and low speed operation of no-load, so as to deposit heat in the engine and raise the temperature; The standard oil is not selected and replaced regularly according to the regulations.Technical analysis of engine sliding Koyo bearing
There is water in the lubricating oil, causing damage and damage to the shaft and bearing bush:Technical analysis of engine sliding Koyo bearing
The damage of water in the lubricating oil to the shaft and bearing bush is relatively serious, because water will deteriorate the lubricating oil and destroy the oil film. The edge of the friction surface of the alloy layer surface of the bearing bush appears hole like gray objects, and black corrosion objects are formed on the alloy surface, resulting in irregular pits and local flake spalling on the alloy friction surface of the bearing bush.Technical analysis of engine sliding Koyo bearing
Causes: poor sealing of cylinder liner sealing ring and coolant infiltration into crankcase; The engine oil radiator is damaged and the oil and water are mixed; When adding lubricating oil, water enters or the oil filler and dipstick are poorly sealed. When washing the car and raining, water enters the crankcase; Water in the fuel enters the crankcase. Therefore, before starting the engine every time, be sure to check the oil level and oil quality of the lubricating oil, which must be done.Technical analysis of engine sliding Koyo bearing
After the fuel enters the crankcase, the lubricating oil will become thinner, the oil film will become thinner, the lubrication effect will be reduced, and the shaft and bearing bush will be corroded at the same time. The alloy surface of bearing bush is black green with slight pitting corrosion. In particular, the by-products produced after the combustion of fuel with high sulfur content will cause serious pitting corrosion on the surface of the shaft after being brought into the poorly ventilated crankcase by the fuel.
Causes: the fuel supply of the fuel system is too large, and the fuel injected into the combustion chamber cannot be completely burned; The air intake is blocked, the air intake is insufficient, and the fuel cannot be fully burned; The nozzle seal fails and the fuel seeps into the crankcase; There are pores, sand holes or cracks in the fuel oil passage in the cylinder head; The idle running time is too long, the engine temperature is low, and the fuel cannot be completely burned.Technical analysis of engine sliding Koyo bearing
To prevent the damage and damage of shaft and bearing bush caused by lubrication system, the following must be done:Technical analysis of engine sliding Koyo bearing
When there is no manual lubrication equipment, the moving surface of each shaft and bearing bush shall be coated with clean lubricating oil with the same label when installing the engine. After the engine is installed, turn off the fuel switch before the initial start, drive the engine to idle for several times with the starter, turn on and turn on the fuel switch when the engine oil pressure gauge shows, set the throttle at medium and low speed, and start the engine for operation observation.Technical analysis of engine sliding Koyo bearing
After the engine is stored for a long time, it should be started after idling driven by the starter for the first time.
The engine must be maintained, inspected and replaced with lubricating oil and filter element at the specified time.
The lubricating oil level of the engine must be within the standard range, and the lubricating oil and refueling tools must be clean to prevent the entry of any dirt and water, and ensure the sealing effect of all parts of the engine.
Avoid idling the engine for too long, and the idling shall not exceed 5 minutes.Technical analysis of engine sliding Koyo bearing
After the engine is started, it must be heated at a medium speed and put into use when the water temperature rises to more than 70 ℃.Technical analysis of engine sliding Koyo bearing
The engine cannot be shut down immediately after long-time full load operation. The engine must be operated at no-load, medium and low speed for 15 minutes before it can be shut down, otherwise the internal heat cannot be dissipated.Technical analysis of engine sliding Koyo bearing
Damage Technical analysis of engine sliding Koyo bearing
Damage and damage caused by long idle running time: the surface alloy layer of bearing bush is extruded, displaced, flanging and flake peeling.
The reason is that the idle running time of the engine is too long, and the engine operates under the condition of lower than the normal working temperature. The fuel injected into the combustion chamber cannot be completely burned, and part of the unburned fuel flows into the crankcase along the cylinder wall, damaging the oil film of the lubricating oil and reducing the lubricating effect. Technical analysis of engine sliding Koyo bearing
The friction between the oil pump and the bearing bush at low idle speed will cause slight damage to the surface of the oil pump and the bearing bush at the same time. To prevent the occurrence of such problems, it is necessary to follow the operating procedures. After starting the engine each time, the idle operation shall not exceed 5 minutes, and the no-load operation of the engine shall not be less than 850 rpm.Technical analysis of engine sliding Koyo bearing
Damage and damage caused by engine shutdown after long-time operation: the alloy surface of bearing bush is abraded, and there are uneven surfaces. The alloy shifts from the middle to both sides.Technical analysis of engine sliding Koyo bearing
The reason is: after the engine works under heavy load for a long time, the internal parts are in the state of high working temperature, especially the combustion chamber is at high temperature. After the engine stops running, the cooling system and lubrication system stop working, and the heat cannot be dissipated, which increases the temperature of relevant parts and destroys the oil film on each lubrication surface.
When it is restarted, when the oil desert on each lubrication surface has not formed, Abnormal wear of bearing shells has occurred. Especially for the sliding Koyo bearing of the supercharger, the damage is more serious.
At the same time, too high temperature will cause the deformation of the shaft hole, damage the operation accuracy and accelerate the damage of the engine. The occurrence of this phenomenon will cause serious damage to the piston, cylinder liner and cylinder liner sealing ring. Therefore, after the engine works under heavy load for a long time, let the engine run at no-load, medium and low speed for more than 10 minutes, and then shut down after the internal temperature decreases.
Damage or damage to bearing bush caused by direct high-speed operation and full load operation after the engine is started: the seventh and sixth main bearing bushes of the engine are seriously worn, and other bearing bushes are damaged.
The reason is that after the engine is started, it is put into high-speed operation and full load operation without no-load temperature rise operation. When the engine fails to meet the working temperature requirements, the stress contact surface and running clearance of each part do not enter the state, and the low temperature lubricating oil has poor fluidity, and the heat of each moving surface cannot be quickly taken away by the lubricating oil, which will cause damage or damage to the bearing bush.Technical analysis of engine sliding Koyo bearing
The lower the external temperature, the more serious the damage to the bearing bush. To prevent the occurrence of such problems, temperature rise operation must be carried out according to the regulations. Technical analysis of engine sliding Koyo bearing
After the engine is started, medium and low speed idling shall be carried out. The operation can be put into operation only when the engine water temperature rises to more than 70 ℃.Technical analysis of engine sliding Koyo bearing