| 摘要 |
PURPOSE:To provide high endurability against scuffing, and high resistivity against wear for a friction face of a piston of Mg alloy and to make the piston lightweight, by subjecting the top land thereof to anodic oxidization. CONSTITUTION:The external peripheral face 2 in contact with a cylinder liner 2, the interal peripheral face of a boss hole 3 of a piston pin and entire upper and lower faces of each of piston ring grooves 4 are subjected to anodic oxidization. Alternatively, a top land part 5 only, namely, the upper part of the piston ring grooves 4 among them may be subjected to same. Since a piston made of Mg alloy, if having a ridigity of Hv 70 or less, has poor scuff endurability and poor wear resistance, anodic oxidization may be needed to the executed throughout the friction face thereof. However, if the Mg alloy has a rigidity of Hv 70 or more, the piston proceeds improved wear resistance and therefore may be allowed to be subjected to anodic oxidization at the top land 5 only which is placed under extremely hard wear condition. |
