| 摘要 |
PROBLEM TO BE SOLVED: To facilitate a proper oil lubrication so as to reduce wear of a ceramic piston pin and a mating pin boss part by forming a proper recess serving as a lubricant sump at the outer circumferential part of the piston pin. SOLUTION: This piston pin has a cylindrical double-layer structure of an inner layer pin and an outer layer pin made of ceramics. A plurality of recesses 7 are formed on an outer circumferential surface 2a. The difference between the recess 7 and a projection 6 is called as the roundness which corresponds to the depth of the recess 7 in this case. When the depth of the recess 7 (roundness) is in a range of 0.7-5μm, a suitable lubrication state for a piston pin is attained. Since the number of the recesses 7 is two (2) an unstable rotation occurs, three or more of the recesses 7 are required. The work on the surface 2a of the pin is made by the centerless work method in consideration of mass production.
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