US-12623381-B2 - Injection molding method for resin molded product and injection molding apparatus

US12623381B2US 12623381 B2US12623381 B2US 12623381B2US-12623381-B2

Abstract

An injection molding method for a resin molded product includes a first molding step of molding an intermediate molded body with first and second main molds and a first slide mold that is closed in an axial direction of the first and second main molds. The injection molding method for the resin molded product further includes a detachment step of detaching the first slide mold from the intermediate molder body and a second molding step of molding a second annular wall portion on the intermediate molded body using a second slide mold that is closed along the axial direction against a tube end surface of the intermediate molded body and first and second core molds that is closed against the intermediate molded body in a direction orthogonal to the axis.

Inventors

Yuhei HORIUCHI

Assignees

HONDA MOTOR CO., LTD.

Dates

Publication Date: 20260512
Application Date: 20230821
Priority Date: 20220825

Claims (3)

1 . 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.
2 . The injection molding apparatus according to claim 1 , wherein: at least one of the first main mold or the second main mold includes a runner through which melted resin is injected into the first cavity formed by the first main mold, the second main mold, and the first slide mold.
3 . The injection molding apparatus according to claim 1 , wherein: the resin molded product includes the first annular wall portion, the second annular wall portion, and the annular groove portion at each of the one end side and another end side in the axial direction of the cylindrical portion; the first slide mold comprises two first slide molds, and the primary mold is configured to mold the intermediate molded body including the two first annular wall portions, using the first and second main molds and the two first slide molds arranged at respective both sides of the first and second molds in the axial direction; and the second slide mold comprises two second slide molds, and the secondary mold is configured to mold the two second annular wall portions on the outer circumferential surface of the cylindrical portion, using the first and second main molds, the two second slide molds arranged at respective both sides of the cylindrical portion in the axial direction, and the first and second core molds arranged at respective both sides of the cylindrical portion in the axial direction.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-134063 filed on Aug. 25, 2022, the contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an injection molding method for a resin molded product and an injection molding apparatus. Description of the Related Art JP H01-209113 A discloses a manufacturing method for an air-tight member attached to an outer circumference of a pipe. The air-tight member is formed into an annular shape through injection molding by filling the inside of a closed upper mold and lower mold with resin material. An annular groove portion is formed in an outer circumferential portion of the air-tight member. By attaching the air-tight member to a hole portion of a dashboard, an air-tight state is maintained between the inside and outside of the dashboard. SUMMARY OF THE INVENTION In the air-tight member formed by injection molding, a parting line is formed at a parting location between the upper mold and the lower mold. The parting line is formed as a straight line along the axial direction on the outer circumferential surface of the air-tight member. Such a parting line is also formed in the annular groove portion. When the air-tight member is attached to the hole portion of the dashboard, there is a concern that a gap occurs between the dashboard and the outer circumferential surface of the air-tight member due to the parting line formed along the axial direction in the annular groove portion, thereby reducing the air-tight property. There is an idea to remove the parting line from the outer circumferential surface via additional machining such as grinding in order to maintain the air-tight property, but such a machining process is complicated and would increase the manufacturing cost. An aspect of the present invention is an injection molding method for a resin molded product, 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 method includes: a first molding step of molding an intermediate molded body that includes the tube body and the first annular wall portion of the resin molded product, using first and second main molds that are closed together along a direction orthogonal to an axis of the cylindrical portion and a first slide mold that is closed against at least one end surface of the first and second main molds along an axial direction of the cylindrical portion; a detachment step of, after the molding of the intermediate molded body, detaching the first slide mold from the intermediate molded body along the axial direction of the cylindrical portion; and a second molding step of molding the second annular wall portion on the outer circumferential surface of the cylindrical portion, using a second slide mold that is closed, along the axial direction, against the tube end surface of the cylindrical portion of the intermediate molded body and first and second core molds that are closed in a direction orthogonal to the axis of the cylindrical portion and disposed adjacent to the side wall surface. According to the present invention, after forming the intermediate molded body that has the first annular wall portion and the tube body of the cylindrical portion in the first molding step for injection molding of the resin molded product, the second slide molds are closed onto the intermediate molded body from the axial direction to form the second annular wall portion on the outer circumferential surface of the cylindrical portion in the second molding step. Due to this, the format