Patent ID: 8247048

Claim:
A cylindrical molded article formed by injection molding, comprising: a cylindrical portion; at least three cam grooves formed on either the inner peripheral surface or the outer peripheral surface of the cylindrical portion; three first gate portions formed at an end of the cylindrical portion as vestiges of gates in injection molding; and three second gate portions formed at an end of the cylindrical portion as vestiges of gates in injection molding, wherein: the first and second gate portions are alternately disposed in the circumferential direction, the first gate portions are disposed at a location corresponding to three high-density regions, respectively, in which there is the highest proportion of the axis direction dimension accounted for by the portion corresponding to the cam grooves with respect to the axial direction dimension of a cavity, or closer to the high-density regions than the second gate portions, the residual stress in areas around the first gate portions is greater than the residual stress in areas around the second gate portions, and the cylindrical portion has recesses depressed in an axial direction at a part where the first and second gate portions are formed.