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Common gasoline engine bearing failure analysis

The formation of oil film is not easy, so prone to bush-burning failure. Common gasoline engine oil deterioration is caused mainly produced Burnt failure. 4. Oil in the engine lubrication system, a serious shortage. Oil in the engine running during the main lubrication, cleaning, cooling and anti-corrosion. If the engine lubrication system in a serious shortage of oil, the crankshaft journal and bearing of the two friction surfaces are poor lubrication and cooling, so that the surface temperature of both the rapid increase in friction occurs Burnt failure. Cause the engine lubrication system is mainly due to a serious shortage of oil: oil filter seriously blocked, damaged oil pump,[link widoczny dla zalogowanych], oil pipeline blockage, a serious oil spill oil pipeline, pipeline joints are not broken and the time to add oil and so on. 5. Crankshaft journal and bearing clearance does not meet the standards. The Space of lubricant film formation. If the gap is too small then the oil is not easy access to the crankshaft journal and bearing between two friction surfaces so that the friction surface between the two is not easy in the formation of lubricant film, and the friction surface of friction heat is not well taken, increasing the occurrence of bush-burning failure possibilities. If the gap is too large, the lubricant film thickness decreases, which can not be completely separated the two friction surfaces, the results of the two direct contact friction surface temperature, the occurrence of bush-burning also increases the possibility of failure. And the gap is too large will increase the crankshaft journal and bearing vibration between the impact, leading to lubricant film breakdown, and further increase the likelihood of occurrence of bush-burning failure. 6. Repair damage to the crankshaft of the crankshaft journal wear resistant surface layer and the fatigue level. Because of a car engine crankshaft journal is the result of good treatment, so it has a high wear-resistant layer (usually a thickness of 0.1-0.2mm) and fatigue level (in the high wear-resistant layer, the thickness of 0.8mm) . Burnt in the event of failure will be if the engine crankshaft in any method of grinding repair repair, the crankshaft will lose their high wear-resistant layer and the fatigue level,[link widoczny dla zalogowanych], resulting in equipped bush bush-burning occurs soon after failure,[link widoczny dla zalogowanych], or even cylinder crankshaft fracture and broke a serious accident. In addition, if the crankshaft and the bearing assembly process, the maintenance staff without the required tightening torque of the order and tighten the bolts fastening the bearing cap, or fitted with the connecting rod bolts have been removed (some vehicle engine connecting rod bolt is a one-time, and must be replaced in removed),[link widoczny dla zalogowanych], the bush-burning is also prone to failure. Second, the bearing failure usually scratch scratch bearing crankshaft bearing and the lack of oil or lubricant between the instantaneous rupture of membranes occurs under transient, characterized by bearing and journal surface abrasion of the mark. Have the following main reasons bearing scratches: 1. Improper use. Mainly in the engine immediately after cold start the engine at high speed operation. After cold start the engine, oil engine oil path is full of time required is generally 15-40s, leaving the engine speed to maximum speed only 3 ~ 8s. Thus, the engine will run short of oil under high above 7s, so it is possible bearing abrasion failure. 2. Oil too dirty. If the oil be replaced without using too long, or the engine load and often at high operating temperatures, the impurities within the oil would be too much, these impurities will scratch bearing. 3. The engine oil level does not meet the requirements. Dongfeng Cummins Engine, such as a naturally aspirated car, supercharged and intercooled supercharger types. Should pay attention in the choice of oil for supercharged diesel engines can not use ordinary engine oil, use a clean distributed, oxidation security, better resistance to corrosion and abrasion resistance engine oil, because a larger load of diesel engines. Third, the bearing alloy used crack and fall off when the engine is not the time, and the crankshaft journal bearing surface of the two would be more frequent friction and direct contact, the micro-bumps in the interaction will produce fatigue crack, while the oil into the crack after the produce hydraulic role in accelerating crack growth, the alloy particles quickly fall off from the bearing surface; and the two friction surfaces has led to friction and direct contact with the surface temperature, so that the fatigue strength of bearing alloy lower, which further accelerate the bearing alloy cracks and fall off. Bearing alloys gradually fall off, will lead to the crankshaft journal and bearing with the gap increases, oil pressure drops and the emergence of sound (percussion). Fourth, severe wear bushing bearing severe wear is generally the case of repeated occurrence of transient short of oil. In the starvation period, and the crankshaft journal bearing surface of the two direct contact with the friction, resulting in severe bearing wear. Result is mainly due to bearing wear dramatic: the engine oil level is too low in the case of oil under the continuous operation (no time to add oil), immediately after the engine starts running at high speed, serious obstruction oil filter, engine oil temperature is too or the use of high-grade oil does not meet the requirements. (02)
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