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How to prevent early damage of diesel engine sliding bearing

by:HMB     2021-01-24
Use on the engine of the sliding bearing is usually divided into two kinds: one kind is a thin-walled bearing bushing type, shape of tiles commonly known as bearing shell; The other is a liner, is also called copper sets, for hollow cylinder shape. Bushing type is mainly used for thin wall bearing retainer engine crankshaft and connecting rod; Bushing is mainly used for bearing CAM shaft neck and piston pins. This article main narration is bushing type thin wall bearing ( Bearing) 。 1, the early damage in the form of bearing in the process of normal use, due to the gradual wear and tear until the end of the last loss of working ability, its service life, the natural damage is difficult to avoid. But if an engine assembly improper adjustment, lubricating oil quality is bad or use conditions and other factors caused the bearing wear or prematurely appear all sorts of injury, early damage is man-made. Early damage not only greatly reduce the service life of bearing, at the same time also can affect the normal work of the engine. According to the maintenance experience of diesel engine is found for a long time, the common form of early damage of the sliding bearing has a mechanical damage, bearing hole corrosion, pitting corrosion fatigue, corrosion, etc. ( 1) Sliding bearing, mechanical damage mechanical damage refers to bearing alloy surface appear different degree of the trench, serious when in contact surface metal strip and a large area of scratches; Under normal circumstances, the contact surface damage and ablation phenomenon exist at the same time. Bearing mechanical damage is the main reason of the difficult to form the oil film bearing surface or oil film were severely damaged. ( 2) Cavitation, bearing sliding bearing in cylinder pressure impact load) Under the action of repeated, surface plastic deformation and cold work hardening, local loss of deformation ability, gradually formed and expanded, and then with the shedding of wear debris, formed in the surface layer loaded cavity. The cavitation, general bearing shell pits is first appeared, and then gradually expand the pits of the interface crack, and lead to an alloy layer along the interface crack parallel to the direction of extension, until it is peeling off. Sliding bearing is the main reason of the cavitation, due to structural elements such as oil groove and oil hole of the cross sectional sudden change flow caused by strong disturbance, in the vacuum area of the flow disorder form bubbles, then because of the pressure, generate cavitation bubble breaking. Cavitation occurs commonly in high load bearing, such as the crankshaft main bearing on the lower bearing. ( 3) , fatigue pitting bearing fatigue pitting refers to, because the engine to work overtime and make bearing overheating and bearing clearance is too large, central bearing fatigue damage and fatigue pitting or fall off. This kind of damage is mostly to overload, bearing clearance is too large, or lubricating oil is not clean, and mixed with caused by foreign bodies. Therefore, when using, should pay attention to avoid bearing overload work don't too low or too high speed operation; To adjust the engine to idle speed stable state; To ensure the normal bearing clearance, prevent engine speed too high or too low; Check, adjust the performance of the cooling system, to ensure that the engine working at a comfortable temperature. ( 4) , bearing alloy corrosion bearing alloy corrosion is generally area for the lubricating oil is not pure, lubricating oil in the chemical impurities ( Acidic oxides, etc. ) Make bearing alloy oxidation and acid generated, cause bearing alloy parts fall off, forms the rule of no small hiatal or small pits. Bearing alloy corrosion is the main reason of the improper selection, bearing lubricating oil material corrosion resistance is poor, or the engine work violent, the temperature too high. ( 5) Burning-out journal and bearing, bearing friction pair between have tiny bumps on metal surface, direct contact form local high temperature, in the case of insufficient lubrication, cooling, make or local burning-out bearing alloy were black. This failure is often caused by journal and bearing with tight; Insufficient pressure lubricating oil is easy to make the bearings burned. ( 6) , bearing cylindrical bearing walk outside the circle is bearing hole with relative rotation here. Cylindrical bearing go after, not only affect the heat dissipation of bearing, easy to make alloy bearing inner surface ablation, but also can make the bearings on the back of the injury, serious when burning bearing. The main reason is that the bearing are too short, tenon damage, processing or installation does not conform to the specifications, etc. 2, early prevention measures sliding bearing is more common than bearing to burn, so it is very important to early prevention of sliding bearing damage. The correct maintenance of the sliding bearing is an effective way to reduce early bearing damage, is also the reliable guarantee for extend bearing life. Therefore, in the daily maintenance and repair of the engine, must pay attention to the bearing surface of the alloy, the back end and the appearance of edge angles in shape, if there is any abnormal or half signs of wear and tear, to seriously investigate the cause, and take appropriate measures to improve the bearing of the working conditions, pay much attention to the prevention of early damage of the sliding bearing. ( 1) , improve the bearing design and manufacturing process design or choose bearing, want to consider the heat balance to control the temperature rise of bearing. Because the bearing under friction condition, oil liquid due to the internal friction ( The viscosity) Into power and heat caused by temperature rise, change, lubricating oil viscosity reduction, gap will soften the babbitt bearing, serious when produce tile burning accident holding shaft. Therefore, in the structure design, from on the bearing bush ( The bearing area) At the top of the oil into the hole, the lubricating oil from the bearing area introduction; Within the bearing surface of the oil hole centered along the longitudinal or transverse groove, conducive to uniform distribution of lubricating oil on the shaft neck to control the temperature. According to the requirements of the bearing working condition, bearing materials must have the following properties: small friction coefficient; Good thermal conductivity, thermal expansion coefficient; Wear-resisting, corrosion resistance and bonding ability; To have enough mechanical strength and plasticity.
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