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Anonymous users2024-02-11The wear clearance of the shaft or hole at the bearing installation is less than and can be repaired directly with adhesive. Here's how to fix it:
With acetone. Wipe the fit, degreasing and drying - evenly apply a layer of adhesive at the journal or bore, at the inner diameter of the bearing or the outer diameter of the bearing (generally using anaerobic adhesive or epoxy cavity) - install the bearing - the adhesive layer can be used after curing.
When the wear clearance of the shaft or hole at the bearing installation place is larger, it can be repaired by turning a small journal or expanding the bore diameter, and preparing a shaft sleeve or hole bushing, and then bonding with cavity adhesive. The fix is:
Turn a small axle sleeve or file a large hole diameter, prepare the corresponding axle sleeve or hole bushing, bond the bearing or hole bushing with the shaft or hole with adhesive (generally use inorganic adhesive), a glue layer is completely cured, and the original size and accuracy are restored by mechanical processing.
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Anonymous users2024-02-10Causes of crankshaft journal wear During the working process of automobile engine, high friction occurs between the crankshaft journal and the bearing, especially when the engine is running or starting at low speed, dry friction occurs due to the difficulty of establishing the lubricating oil film, resulting in bearing wear. The reason for the damage of the crankshaft journal and the bearing is that the radial clearance between the crankshaft journal and the bearing is very small, which can make the crankshaft rotate freely without opening and radial runout. If the radial clearance between the journal and the bearing changes, it will often cause early wear and damage to the crankshaft journal and shaft, which will increase the working vibration of the engine, increase the noise, increase the fuel consumption and increase the number of accidents.
Damage to the crankshaft journal and bearing can take the form of scratches, wear, fatigue peeling, corrosion, and burning. 1.The fatigue spalling crankshaft is constantly subjected to periodic gas force, alternating inertia force and rotational centrifugal force, which act on different parts of the crankshaft and accelerate the wear of the crankshaft. Under the action of long-term sudden load and impact load, the bearing causes fatigue of the alloy, and then cracks, and expands to the depth, causing the alloy to peel off.
2.Corrosion If the oil fails and its acid number is too high, it will corrode the crankshaft and bearing. Especially when the bearing is exposed to copper, it will corrode faster due to the lack of a corrosion-resistant surface layer and a nickel protective layer.
The honeycomb structure produced by corrosion will greatly reduce the strength of the bearing. 3.When the oil between the crankshaft journal and the bearing is too low, the oil channel is blocked, and the oil viscosity is reduced, the severe friction between the journal and the bearing occurs, which causes the temperature of the journal and the bearing to rise rapidly, burns the surface of the journal, and in severe cases, causes the bearing metal to melt and adhere to the journal, causing the crankshaft to jam or even break.
4.Scratching metal abrasive debris, poor lubricating oil filtration or foreign granular impurities enter between the journal and the bearing surface with the flow of oil, these hard particles will scratch the alloy surface, and in severe cases, many annular grooves can be scraped on the alloy surface and the journal surface. 5.
Defects in the geometry of the connecting rod, such as saddle, drum, different shafts and non-straightness, will cause the normal clearance between the journal and the bearing to change. Excessive clearance will lead to a smaller contact arc between the journal and the bearing, which will increase the pressure load of the oil film and aggravate the fatigue of the bearing. Too small a gap will restrict the flow of oil, make it difficult to form an oil film, and cannot take away the frictional heat generated, increasing the tendency of overheating deformation and "tile holding". 6.
Improper connecting rod assembly Improper torque of connecting rod bolts, wrong assembly of connecting rod bearing covers, and wrong assembly of connecting rod bearings will cause different degrees and different forms of damage to the crankshaft. Crankshaft machining error When the crankshaft geometry appears such as the journal is stepped, tapered, drum and saddle, etc., the gap between the crankshaft journal and the bearing will change, reduce the thickness of the oil film or prevent the formation of the oil film, resulting in direct metal contact and abnormal wear of the bearing.
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