| 摘要 |
PROBLEM TO BE SOLVED: To prevent a spacer expander main body, especially a waveform corner part, from being nitraded in a nitrading process by exposition of a base material accompanying plating film chip of the wave form corner part, exfoliation and plating thickness insufficiency and the like when molding a gear of the spacer expander. SOLUTION: As illustrated in Fig. 1, the spacer expander 1 is formed at a piston axial direction waveforms 3, 4 with a flat plate wire material 2, extends in a circumference direction and has a pressing piece part 7, formed at an inner peripheral part by shearing the base material to protrude in a piston axial direction for pressing a side rail to outside of a radial direction. A nitraded layer is formed on a sheared surface 5 of the base material 2 of the pressing piece part 7. Surfaces other than the sheared surface 5 are coated by a Ni plating film having an Ni plating film or an Ni diffusion layer. COPYRIGHT: (C)2007,JPO&INPIT
|
