Manufacturing method and manufacturing device for hollow part with branching portion

An apparatus for manufacturing a hollow part with a branch, the apparatus including:

• a mold having a main cavity in which a hollowing piece is, placed and a branch cavity (i) that is formed so as to communicate with the main cavity, (ii) in which a slide shaft is inserted so as to advance and withdraw, and (iii) that forms a branch pipe portion in an annular space between the branch cavity and the slide shaft,
• a fluid injection apparatus that injects pressurized fluid into the main cavity through a pressurizing port formed at a first end of the main cavity that is an opposite end of the main cavity from an outlet port formed at a second end of the main cavity, in order to form a hollow main pipe portion by moving the hollowing piece to force excess resin out of the main cavity through the outlet port and thus form a main hollow portion in the resin in the main cavity, and
• a slide shaft moving apparatus that withdraws the slide shaft located in the branch cavity to form a branch hollow portion in the branch pipe portion, the slide shaft moving apparatus including a lead screw mechanism including a lead screw and an electric motor that is configured to rotate the lead screw to linearly reciprocate the slide shaft,
• the hollow part with the branch being made of a resin and having the branch pipe portion integrally connected to the main pipe portion such that the main hollow portion and the branch hollow portion communicate with each other,
• the slide shaft moving apparatus being configured to advance and withdraw the slide shaft so that a communication hole is formed through a portion of a resin wall of the main pipe portion, at which the branch pipe portion is connected, by advancing the slide shaft toward the main cavity so that an entire outer peripheral edge of a tip end of the slide shaft projects into the main hollow portion of the main pipe portion, and
• a tip end face of the slide shaft having a concave shape curved inward in a middle, and an outer peripheral edge of the tip end face having a plurality of protruding portions that protrude toward a tip end side and that are separated from each other in a circumferential direction,
• wherein the apparatus is configured to manufacture the hollow part with the branch by performing an injection molding in the mold.