| 摘要 |
PURPOSE:To ensure sealing of the surroundings of a pin during oxidation treatment of an anode, by a method wherein a locking pin is mounted in a ring groove, which is adapted to contain a piston ring, in a partially exposed state, and a mask for a pin with which the locking pin is covered is formed separately, and a slip-off is prevented from occurring by means of an outwardly engaged spring. CONSTITUTION:In a piston 10 for a 2-cycle engine for a motor bicycle, the surrounding of a locking pin 16 of a piston ring is covered with a cap type mask 20 in a state that a top ring groove 13 in which a part of the locking pin is placed in an exposed state is left uncovered. A mask 30 for a pin having a groove 33 for densely containing the exposed heat part of the pin 16 is engaged with the top ring groove 13, and slip-off is prevented from occurring by means of an outwardly engaged spring 40. With this state, an anode oxidation treatment 18 is formed along the top ring groove 13, and a nickel-plated layer 17 is formed on a top part 11 of the piston 10 in a state to mask a portion below the layer 18. Further, a tin-plated layer 19 is formed to a skirt part 12 of the piston 10 in a state to mask the layers 17 and 18. |
