Cylindrical article made of fiber-reinforced resin material, injection molding mold thereof, and injection molding method

An injection molding method for a cylindrical article that injects a molten resin containing reinforcing fibers from a gate into a cavity to join the molten resins containing the reinforcing fibers together in the cavity to form a weld line, the injection molding method for the cylindrical article comprising:

• installing a center pin shaping an inner peripheral surface side of the cylindrical article and an external piece shaping an outer peripheral surface side of the cylindrical article;
• forming the cavity between the center pin and the external piece;
• and
• moving the external piece with respect to the center pin to change an interval with the center pin, to forcibly cause the molten resin containing the reinforcing fibers in the cavity to flow, and to disturb directions of the reinforcing fibers at the weld line.

A cylindrical article made of a fiber-reinforced resin material where a molten resin containing reinforcing fibers is injected from a gate into a cavity to join the molten resins containing the reinforcing fibers together in the cavity to form a weld line, the cylindrical article made of the fiber-reinforced resin material comprising:

• a center pin shaping an inner peripheral surface side of the cylindrical article;
• and
• an external piece shaping an outer peripheral surface side of the cylindrical article, wherein:
• the cavity is formed between the center pin and the external piece, and
• the external piece is moved with respect to the center pin to change an interval with the center pin, to forcibly cause the molten resin containing the reinforcing fibers in the cavity to flow, and to disturb directions of the reinforcing fibers at the weld line.