Injection molding method for resin molded product and injection molding apparatus

An injection molding apparatus for forming a tubular resin molded product by injection molding, wherein:

• the resin molded product includes:
• a cylindrical portion that extends along an axial direction of the resin molded product and includes a tube end surface that is an end surface at at least one end side in the axial direction;
• a first annular wall portion that protrudes radially outward from an outer circumferential surface of the cylindrical portion at at least the one end side of the cylindrical portion, and includes a side wall surface facing outward in the axial direction;
• a second annular wall portion that protrudes radially outward from the outer circumferential surface of the cylindrical portion at at least the one end side of the cylindrical portion, and is arranged distanced outward in the axial direction from the first annular wall portion;
• and
• an annular groove portion formed between the first annular wall portion and the second annular wall portion;
• the cylindrical portion includes a tube body forming part of the cylindrical portion that extends from the side wall surface of the first annular wall portion to at least a center of the cylindrical portion in the axial direction, and a tube end portion that extends from the side wall surface to the tube end surface of the cylindrical portion and whose outer circumferential surface forms part of the annular groove portion,
• the injection molding apparatus comprising:
• a primary mold that includes therein a first cavity and is configured to mold an intermediate molded body including the cylindrical portion and the first annular wall portion of the resin molded product;
• and
• a secondary mold that includes therein a second cavity and is configured to mold the second annular wall portion on the outer circumferential surface of the cylindrical portion of the intermediate molded body,
• wherein
• the primary mold includes:
• first and second main molds configured to be closed together in a direction orthogonal to an axis of the cylindrical portion and to mold an outer circumferential surface of the tube body, an outer circumferential surface of the first annular wall portion, and a wall surface of the first annular wall portion that connects the outer circumferential surface of the tube body and the outer circumferential surface of the first annular wall portion;
• and
• a first slide mold configured to be closed against at least one end surface of the first and second main molds along an axial direction of the cylindrical portion and to mold the side wall surface of the first annular wall portion and the tube end portion, and
• the secondary mold includes:
• a second slide mold including a protrusion and configured to be closed against the tube end surface of the cylindrical portion of the intermediate molded body and to mold the second annular wall portion;
• first and second core molds configured to be closed, in a direction orthogonal to an axis of the cylindrical portion, against the outer circumferential surface of the tube end portion of the intermediate molded body and to be disposed adjacent to the side wall surface of the first annular wall portion, and
• in a closed state of the second slide mold, the protrusion of the second slide mold is brought into contact with the first and second core molds, and the first and second core molds and the second slide mold define a recessed portion configured to mold the second annular wall portion.