求翻译：由于活塞的位置不同，工作条件不同，气缸套各部位的磨损也不同。气缸套的磨损以第一道活塞环和气缸壁接触部分最严重，由上往下，磨损量显著减少。这种上大下小的磨损，使气缸成为锥形。如果机油中有杂质而未被滤清器过滤，机油中的杂质和金属屑被带到气缸壁表面，就产生了磨料磨损，磨损后气缸套变为腰鼓形。是什么意思？

As the piston position, working conditions, the various parts of the cylinder liner wear. Cylinder liner wear contact part of the first piston ring and cylinder walls from top to bottom, significantly reduce the amount of wear. Under small wear this on to make the cylinder to become cone. If the oil