SPOOL AND METHOD FOR MANUFACTURING SPOOL

摘要

To provide a spool considering a tribo coating.SOLUTION: A spool 2 made of aluminum includes an area where an oxide film is formed (Alumite area Rc) and an area where the oxide film is not formed (Aluminum area Rn) on a surface thereof. The spool 2 is used for a pressure regulator 1 for regulating oil OL (hydraulic oil) used in an automatic transmission for vehicle. The oil OL includes an S-based addition agent with high affinity for alumite area Rc, and a P-based addition agent with high affinity for Aluminum area Rn. A ratio or the alumite area and the aluminum area Rn on the surface of large diameter portions 21 and 23 of the spool 2 based on coefficient of dynamic friction of a tribo coating in which the S-based addition agent forms on the alumite area Rc and dynamic friction of a tribo coating in which the P-based addition agent forms on the aluminum area Rn.SELECTED DRAWING: Figure 1