Two Main Causes Of Crankshaft Journal Wear Of Diesel Generator

After the diesel generator crankshaft has been used for a long time, uneven wear occurs due to the periodic change of the magnitude and direction of the force acting on the connecting rod journal and crankshaft journal, which is an inevitable result of natural wear and is a normal phenomenon. However, due to improper use, poor lubrication, excessive or small bearing clearance, the wear of journal and the unevenness of journal wear will be accelerated. The main performance after wear is that the journal is not round (out of round) and not cylindrical (conical).

The wear of crankshaft journal (also known as main journal) and connecting rod journal is caused by uneven wear, resulting in non-circular shaft diameter along the circumference and non-cylindrical wear along the length. The wear of connecting rod journal is usually 1~2 times greater than that of crankshaft journal. The wear of the crankshaft journal is generally less than that of the connecting rod journal due to the interaction of the piston and connecting rod groups at both ends. Therefore, its wear is also less than that of the connecting rod journal.

(1) Out of round: The wear of connecting rod journal is out of round, mainly due to the combined force formed by the gas pressure during the operation of the internal combustion engine, the inertia force of the piston and connecting rod group movement and the centrifugal force at the large end of the connecting rod, acting on the inner side of the journal. Therefore, the maximum wear of connecting rod journal occurs on the inner side of each journal (that is, the side near the center of the crankshaft).

The out-of-roundness of the crankshaft journal is smaller than that of the connecting rod journal, which is also caused by the non-uniformity of the load at each point and the difference of the continuous time under the restriction of the centrifugal force of the connecting rod journal. The largest part is the side near the connecting rod journal.

(2) Non-cylindrical: Non-cylindrical (oblique cutting) wear of the connecting rod journal is mainly caused by the accumulation of mechanical impurities in the oil passage. Because the oil passage to the connecting rod journal is inclined, the mechanical impurities in the lubricating oil will flow into one side of the connecting rod journal along the upper slope of the oil passage under the action of the centrifugal force of the crankshaft rotation. Due to the accumulation of impurities, the uneven wear of the same journal is caused. The largest part of wear is the side of the accumulation of impurities. In addition, in order to shorten the length of the connecting rod, some internal combustion engines make the large end of the connecting rod asymmetrical, resulting in uneven load distribution on the connecting rod journal along the axis direction, resulting in uneven wear of the connecting rod journal along the axis direction.

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