Injection molding method and injection molding device for resin molded products

Abstract

To provide a method and apparatus for injection molding resin molded products in which the formation of a mold break line along the axial direction is prevented by injection molding.SOLUTION: The method of injection molding a resin molded product 12 comprises: a first molding process in which an intermediate molded product is formed by means of first and second main molds 44, 46 and a first slide mold that is mold-closed axially to the first and second main molds 44, 46, a release process in which the first slide molds 48a, 48b are released from the intermediate molded product 40; a second forming process in which a second annular wall portion 18 is formed on the intermediate compact by means of the second slide molds 64a, 64b, which are mold-closed along the axial direction to tube end faces 14a, 14b of the intermediate molded product, and the first and second core molds 66, 68, which are mold-closed orthogonally to the axial center to the intermediate compact.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for injection molding a resin molded product. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing an airtight member to be attached to the outer periphery of a pipe. The airtight member is formed into a circular ring shape by injection molding, with resin material filling the interior of closed upper and lower dies. An annular groove is formed on the outer periphery of the airtight member. The airtight member is attached to a hole in the dashboard, thereby maintaining airtightness between the inside and outside of the dashboard. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 1-209113 Summary of the Invention [Problem to be solved by the invention]

[0004] In an airtight member molded by injection molding, a parting line is formed at the parting point between the upper and lower dies. The parting line is formed linearly along the axial direction on the outer peripheral surface of the airtight member. Such a parting line is also formed in the annular groove. When the airtight member is fitted to a hole in a dashboard, the parting line formed in the annular groove along the axial direction creates a gap between the dashboard and the outer peripheral surface of the airtight member, raising concerns about a decrease in airtightness. While it is conceivable to remove the parting line from the outer peripheral surface by additional processing such as grinding in order to maintain airtightness, this approach involves complex processing work and increases manufacturing costs.

[0005] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0006] An aspect of the present invention is a method for injection molding a tubular resin molded product by injection molding, wherein the resin molded product comprises: a cylindrical portion extending along an axial direction of the resin molded product and having a tube end surface that is an end surface on at least one end side in the axial direction; a first annular wall portion protruding radially outward from an outer circumferential surface of the cylindrical portion at least on the one end side of the cylindrical portion and having a side wall surface facing outward in the axial direction; a second annular wall portion protruding radially outward from the outer circumferential surface of the cylindrical portion at least on the one end side of the cylindrical portion and disposed spaced apart 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, wherein the cylindrical portion comprises a tube main body that constitutes from the side wall surface of the first annular wall portion to at least a central portion of the cylindrical portion in the axial direction; and a second annular wall portion that extends from the side wall surface to the tube end surface of the cylindrical portion and has an outer circumferential surface and a pipe end portion which forms a part of the annular groove portion, and the injection molding method includes: a first molding step of molding an intermediate molded body having the pipe main body and the first annular wall portion in the resin molded product using first and second main dies which are molded in a direction perpendicular to the axial center of the cylindrical portion, and a first slide die which is molded against at least one end face of the first and second main dies along the axial direction of the cylindrical portion; a detaching step of detaching the first slide die from the intermediate molded body along the axial direction of the cylindrical portion after molding the intermediate molded body; and a second molding step of molding the second annular wall portion on the outer peripheral surface of the cylindrical portion using a second slide die which is molded against the pipe end face of the cylindrical portion of the intermediate molded body along the axial direction, and first and second core dies which are molded in a direction perpendicular to the axial center of the cylindrical portion and are disposed adjacent to the side wall surface. [Effects of the Invention]

[0007] According to the present invention, in a first molding step of injection molding a resin molded product, an intermediate molded body having a cylindrical pipe main body and a first annular wall is molded, and then in a second molding step, a second slide mold is closed axially onto the intermediate molded body to mold the second annular wall onto the outer peripheral surface of the cylindrical portion, thereby preventing the formation of a parting line along the axial direction by injection molding on the outer peripheral surface of the annular groove between the first and second annular wall. This eliminates the need to remove the parting line of the annular groove by additional processing after molding the resin molded product, making it possible to reduce manufacturing steps and costs. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an injection molding apparatus for injection-molding a resin molded product according to an embodiment of the present invention. [Figure 2] FIG. 2 is an external plan view of a resin molded product obtained by the injection molding apparatus of FIG. [Figure 3] FIG. 3 is a schematic diagram showing the primary molding die of the injection molding apparatus of FIG. [Figure 4] FIG. 4 is a configuration diagram showing a first molding step in which a resin material is filled into the first cavity of the injection molding device of FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a configuration diagram showing a removing step of removing the first slide mold after the intermediate molded body is molded in the first molding step. [Figure 7] FIG. 7 is a configuration diagram showing a preparation state for the second molding step in which the first and second core dies are attached to the first and second main dies. [Figure 8] FIG. 8 is a structural diagram showing the injection molding apparatus of FIG. 7 in a closed state of the secondary molding die to which the second slide die is attached. [Figure 9] FIG. 9 is a diagram showing the state after the second molding step is completed, the mold is opened, and the resin molded product is removed. DETAILED DESCRIPTION OF THE INVENTION

[0009] As shown in FIG. 1, an injection molding apparatus 10 according to this embodiment molds a tubular resin molded product 12 by injection molding.

[0010] First, a resin molded product 12 injection molded by the injection molding apparatus 10 will be described with reference to FIGS.

[0011] The resin molded product 12 is a tubular body formed linearly along the axial direction (the direction of arrow A). The resin molded product 12 includes a cylindrical portion 14, a first annular wall portion 16, a second annular wall portion 18, and an annular groove portion 20.

[0012] The cylindrical portion 14 is formed in an annular shape with a constant diameter along the axial direction. One end and the other end of the cylindrical portion 14 in the axial direction have tube end faces 14a and 14b, respectively. The tube end faces 14a and 14b are the end faces on the one end and the other end of the cylindrical portion 14. The interior of the cylindrical portion 14 is provided with a through hole 22 that runs along the axial direction (direction of arrow A). The through hole 22 opens to the tube end faces 14a and 14b of the cylindrical portion 14, respectively.

[0013] The cylindrical portion 14 has a pipe main body 24 and a pair of pipe end portions 26a, 26b. The pipe main body 24 extends from the axial center of the cylindrical portion 14 to a side wall surface 16a of a first annular wall portion 16, which will be described later. The pipe end portion 26a is disposed closer to the pipe end surface 14a with respect to the pipe main body 24. The pipe end portion 26a extends from the side wall surface 16a of the first annular wall portion 16 to the pipe end surface 14a of the pipe main body 24. The pipe end portion 26b is disposed closer to the pipe end surface 14b with respect to the pipe main body 24. The pipe end portion 26b extends from the side wall surface 16a of the first annular wall portion 16 to the pipe end surface 14b of the pipe main body 24. An outer peripheral surface 28 of the pipe end portions 26a, 26b forms a part of the annular groove portion 20.

[0014] The first and second annular wall portions 16, 18 are respectively disposed on one end side and the other end side in the axial direction of the cylindrical portion 14. The first and second annular wall portions 16, 18 are annular and protrude radially outward from the outer peripheral surfaces 24a, 28 of the cylindrical portion 14. The first annular wall portion 16 and the second annular wall portion 18 are spaced apart from each other in the axial direction of the cylindrical portion 14 (direction of arrow A) and face each other.

[0015] The first annular wall portion 16 is disposed closer to the axial center from the pipe end faces 14a, 14b of the cylindrical portion 14. The first annular wall portion 16 is disposed on the outer peripheral surface 24a of the pipe main body 24 of the cylindrical portion 14.

[0016] The first annular wall portion 16 has a side wall surface 16a that faces outward in the axial direction of the cylindrical portion 14. The side wall surface 16a is a plane that is approximately perpendicular to the axis of the cylindrical portion 14. The side wall surface 16a faces the second annular wall portion 18. The first annular wall portion 16 has a wall surface 16b that faces the center of the cylindrical portion 14 in the axial direction. The side wall surface 16a and the wall surface 16b are approximately parallel and spaced apart in the axial direction of the cylindrical portion 14 (direction of arrow A).

[0017] The second annular wall portion 18 is disposed on the outer peripheral surfaces 28 of the tube ends 26a, 26b of the cylindrical portion 14. The second annular wall portion 18 is disposed axially outwardly and spaced apart from the first annular wall portion 16. The second annular wall portion 18 has an inner wall surface 18a. The inner wall surface 18a faces the side wall surface 16a of the first annular wall portion 16. The first annular wall portion 16 and the second annular wall portion 18 are parallel. The height of the first annular wall portion 16 and the height of the second annular wall portion 18 relative to the outer peripheral surfaces 24a, 28 of the cylindrical portion 14 are approximately the same. The second annular wall portion 18 has an axial end surface 18b facing outward in the axial direction of the cylindrical portion 14. The axial end surface 18b and the inner wall surface 18a are approximately parallel.

[0018] The annular groove 20 is disposed between the first annular wall 16 and the second annular wall 18. The annular groove 20 is a space surrounded by the outer peripheral surfaces 28 of the pipe ends 26a, 26b, the side wall surface 16a of the first annular wall 16, and the inner wall surface 18a of the second annular wall 18. For example, an annular seal member 30 (see FIG. 2) can be attached to the annular groove 20. The seal member 30 contacts the bottom surface of the annular groove 20 (the outer peripheral surfaces 28 of the pipe ends 26a, 26b).

[0019] Next, the injection molding apparatus 10 for injection molding the resin molded product 12 will be described.

[0020] As shown in Fig. 1, the injection molding apparatus 10 includes a primary molding die 34 (see Fig. 3) having a first cavity C1 therein, a secondary molding die 36 having a second cavity C2 therein, and a resin material supply device 38. The injection molding apparatus 10 forms an intermediate molded body 40 that serves as the base of a resin molded product 12 through primary molding (first molding step) using the primary molding die 34. The injection molding apparatus 10 forms a resin molded product 12 (see Fig. 1) based on the intermediate molded body 40 (see Fig. 4) through secondary molding (second molding step) using the secondary molding die 36.

[0021] As shown in Fig. 3, the primary molding die 34 and the resin material supply device 38 are connected to each other via a pipe 42. The resin material supply device 38 is capable of supplying heated and melted resin material R to the primary molding die 34 via the pipe 42 (see Fig. 4). As shown in Fig. 1, the secondary molding die 36 and the resin material supply device 38 are connected to each other via the pipe 42. The resin material supply device 38 is capable of supplying heated and melted resin material R to the secondary molding die 36 via the pipe 42. The resin material supply device 38 can selectively supply resin material R to either the primary molding die 34 or the secondary molding die 36.

[0022] As shown in FIGS. 3 and 4, the primary molding die 34 includes first and second main dies 44, 46 and a pair of first slide dies 48a, 48b.

[0023] The first and second main dies 44, 46 extend along the axial direction (the direction of arrow A). When viewed from the axial direction of the first and second main dies 44, 46 shown in Fig. 5, the cross sections of the first and second main dies 44, 46 are semicircular. The first and second main dies 44, 46 have approximately symmetrical shapes, facing each other across the axial centers of the intermediate molded body 40 and the resin molded article 12. The first main dies 44 and the second main dies 46 are arranged symmetrically across the axial centers of the intermediate molded body 40 and the resin molded article 12.

[0024] A displacement mechanism (not shown) positions the first main mold 44 and the second main mold 46 so that they can move toward and away from each other, sandwiching the intermediate molded body 40 and the resin molded article 12. The movement direction of the first and second main molds 44, 46 is a direction (arrow B direction) perpendicular to the axes of the first and second main molds 44, 46. The movement direction of the first and second main molds 44, 46 may also be a direction perpendicular to the arrow A direction and the arrow B direction.

[0025] The first main mold 44 has mold end portions 44a, 44b at both ends along the axial direction. The mold end portions 44a, 44b have surfaces perpendicular to the axial direction of the first main mold 44. The second main mold 46 has mold end portions 46a, 46b at both ends along the axial direction. The mold end portions 46a, 46b have surfaces perpendicular to the axial direction of the second main mold 46. The inner peripheral surfaces of the first and second main molds 44, 46 form part of the first cavity C1.

[0026] The inner peripheral surfaces of the first and second main dies 44, 46 have a cylindrical body molding portion 50 and a pair of first wall portion molding portions 52.

[0027] The cylindrical body forming portion 50 extends along the axial direction of the first and second main dies 44, 46. The cylindrical body forming portion 50 forms the outer peripheral surface 24a of the pipe main body 24 of the cylindrical portion 14.

[0028] The first wall molding portions 52 are disposed at both axial ends of the cylindrical body molding portion 50. The first wall molding portions 52 are recessed radially outward relative to the cylindrical body molding portion 50. The first wall molding portions 52 open to the mold ends 44a, 44b of the first main mold 44 and the mold ends 46a, 46b of the second main mold 46, respectively. The inner peripheral surface of the first wall molding portion 52 is disposed radially outward relative to the cylindrical body molding portion 50. The inner peripheral surface of the first wall molding portion 52 is an inclined surface that slopes radially outward toward the tube end faces 14a, 14b of the first and second main molds 44, 46. The first wall molding portions 52 form the outer peripheral surface of the first annular wall portion 16 and a wall surface 16b of the first annular wall portion 16 that connects the outer peripheral surface 24a of the tube main body 24 to the outer peripheral surface of the first annular wall portion 16.

[0029] The first main mold 44 has a first runner 54 to which molten resin material R is supplied. The first runner 54 is disposed at the axial center of the first main mold 44 and is connected to the resin material supply device 38 via piping 42. The molten resin material R is supplied from the resin material supply device 38 to the first runner 54, whereby the resin material R is filled into the inside of the first cavity C1 including the first main mold 44 (see FIG. 4). The first runner 54 may be disposed in the second main mold 46, or the first runners 54 may be disposed in each of the first and second main molds 44, 46.

[0030] The first slide die 48a faces one die end portions 44a, 46a of the first and second main dies 44, 46. The first slide die 48a is clamped against the die end portions 44a, 46a of the first and second main dies 44, 46 along the axial direction of the cylindrical portion 14 of the intermediate molded body 40. The first slide die 48b faces the other die end portions 44b, 46b of the first and second main dies 44, 46. The first slide die 48b is clamped against the die end portions 44b, 46b of the first and second main dies 44, 46 along the axial direction of the cylindrical portion 14 of the intermediate molded body 40. The first slide dies 48a, 48b mold the pipe ends 26a, 26b of the cylindrical portion 14 of the intermediate molded body 40, the inner circumferential surface of the pipe body 24, and the side wall surface 16a of the first annular wall portion 16.

[0031] The first slide dies 48a, 48b include a first cover portion 56 and a first shaft portion 58 protruding from the first cover portion 56. The first cover portion 56 is disk-shaped. The first cover portion 56 is disposed so as to cover the die ends 44a, 46a and die ends 44b, 46b of the first and second main dies 44, 46. The diameter of the first cover portion 56 is approximately the same as the diameter of the first and second main dies 44, 46 aligned in the radial direction.

[0032] The first cover portion 56 has a first cover end portion 60 that faces the die ends 44a, 46a and die ends 44b, 46b of the first and second main dies 44, 46. The first cover end portion 60 is annular and forms the outer edge of the first cover portion 56. The first cover end portion 60 has a flat surface that is perpendicular to the axis of the first cover portion 56. When the first and second main dies 44, 46 and the first slide dies 48a, 48b are closed, the first annular wall portion 16 is formed between the first cover end portion 60 and the die ends 44a, 46a of the first and second main dies 44, 46, and between the first cover end portion 60 and the die ends 44b, 46b, respectively. The first cover end portion 60 forms the side wall surface 16a of the first annular wall portion 16.

[0033] The first shaft portion 58 is disposed at the axial center of the first cover portion 56. The first shaft portion 58 protrudes from the first cover end portion 60 along the axial direction. When viewed from the axial direction of the first slide dies 48a, 48b, the cross-sectional shape of the first shaft portion 58 is circular (see FIG. 5). The diameter of the first shaft portion 58 corresponds to the diameter of the through-hole 22 of the resin molded product 12. The first shaft portion 58 forms the inner circumferential surface of the cylindrical portion 14 in the intermediate molded body 40.

[0034] An annular first recess 62 is formed between the inner peripheral surface of the first cover end portion 60 and the first shaft portion 58. The first recess 62 is recessed in the axial direction from the end face of the first cover end portion 60. When primary molding is performed by the primary molding die 34, the first recess 62 forms the pipe ends 26a, 26b of the cylindrical portion 14.

[0035] 3, when primary molding is performed using the primary molding die 34, one first slide die 48a is assembled to one die end portion 44a, 46a of the first and second main dies 44, 46, and the other first slide die 48b is assembled to the other die end portions 44b, 46b of the first and second main dies 44, 46, thereby closing the primary molding die 34. At this time, the first shaft portions 58 of the first slide dies 48a, 48b are inserted up to the axial center of the intermediate molded body 40 and face each other.

[0036] 1, the secondary molding die 36 includes first and second main dies 44, 46, a pair of second slide dies 64a, 64b, and a pair of first and second core dies 66, 68. The first and second main dies 44, 46 of the secondary molding die 36 are common to the first and second main dies 44, 46 of the primary molding die 34.

[0037] The second slide dies 64a, 64b are respectively clamped against the tube end surfaces 14a, 14b of the cylindrical portion 14 of the intermediate molded body 40. The second slide dies 64a, 64b mold the second annular wall portion 18 on the intermediate molded body 40. The second slide dies 64a face one die end portions 44a, 46a of the first and second main dies 44, 46, respectively. The second slide dies 64b face the other die end portions 44b, 46b of the first and second main dies 44, 46.

[0038] The second sliding dies 64a, 64b include a second cover portion 70, a second shaft portion 72 protruding from the second cover portion 70, and a second recess 74. The second cover portion 70 is disk-shaped. The second cover portion 70 is disposed so as to cover the die ends 44a, 46a and die ends 44b, 46b of the first and second main dies 44, 46. The diameter of the second cover portion 70 is approximately the same as the diameter of the first cover portion 56 of the first sliding dies 48a, 48b.

[0039] The second cover portion 70 has a second cover end portion 76 that faces the die ends 44a, 44b of the first main mold 44 and the die ends 46a, 46b of the second main mold 46. The second cover end portion 76 is annular and forms the outer edge of the second cover portion 70. The second cover end portion 76 has a flat surface that is perpendicular to the axis of the second cover portion 70. During secondary molding, when the first and second main molds 44, 46 and the second slide molds 64a, 64b are closed, the second cover end portion 76 and the die ends 44a, 46a of the first and second main molds 44, 46 are spaced apart in the axial direction, and the second cover end portion 76 and the die ends 44b, 46b are also spaced apart in the axial direction. The side surfaces of the second cover end portion 76 abut against the first and second core molds 66, 68, which will be described later.

[0040] Each second cover portion 70 has a second runner 78 to which molten resin material R is supplied. The second runner 78 axially penetrates the second cover portion 70. The second runner 78 and the resin material supply device 38 are connected via piping 42. The molten resin material R is supplied from the resin material supply device 38 to the second runner 78, and thereby the resin material R is supplied into the second recess 74 that constitutes the second cavity C2.

[0041] The second shaft portion 72 is disposed at the axial center of the second cover portion 70. The second shaft portion 72 protrudes from the second cover end portion 76 along the axial direction. The cross-sectional shape of the second shaft portion 72 is circular. The diameter of the second shaft portion 72 is approximately the same as the diameter of the first shaft portion 58 of the first slide dies 48a, 48b. During secondary molding, when the first and second main dies 44, 46 and the second slide dies 64a, 64b are closed, the second shaft portion 72 is inserted into the through-hole 22 of the intermediate molded body 40. At this time, the second shaft portion 72 is inserted up to the axial center of the intermediate molded body 40.

[0042] The second recess 74 is annular and is located between the inner circumferential surface of the second cover end 76 and the second shaft portion 72. The second recess 74 is recessed in the axial direction from the end face of the second cover end 76. The second recess 74 has an end insertion portion 80 and a second wall portion molding portion 82. The end insertion portion 80 is annular and is located radially outward of the second shaft portion 72. When secondary molding is performed by the secondary molding die 36, the pipe ends 26a, 26b of the intermediate molded body 40 are inserted into the end insertion portion 80.

[0043] The second wall molding portion 82 is annular and disposed radially outward of the end insertion portion 80. The inner circumferential surface of the second wall molding portion 82 is an inclined surface that slopes radially inward in a direction away from the side wall surface 16a of the second cover end portion 76. The second wall molding portion 82 forms the second annular wall portion 18.

[0044] The first and second core dies 66, 68 have approximately symmetrical shapes with respect to the axial center of the intermediate molded body 40 and the resin molded article 12. The first core dies 66 and the second core dies 68 are arranged symmetrically with respect to the axial center of the intermediate molded body 40. The first core dies 66 are arranged adjacent to the first main die 44. The second core dies 68 are arranged adjacent to the second main die 46.

[0045] A displacement mechanism (not shown) positions the first and second core dies 66 and 68 so that they can move toward and away from each other in a direction (direction of arrow B) perpendicular to the axes of the first and second main dies 44 and 46 (cylindrical portion 14). The first and second core dies 66 and 68 are positioned so that they can move toward and away from each other, sandwiching the intermediate molded body 40 therebetween. The movement direction of the first and second core dies 66 and 68 is a direction perpendicular to the axes of the first and second main dies 44 and 46 and the intermediate molded body 40.

[0046] The first and second core dies 66, 68 each have a pair of core bodies 84a, 84b. The core bodies 84a, 84b are halves of a torus. One core body 84a and the other core body 84b are spaced apart in the axial direction of the first and second core dies 66, 68 (the direction of arrow A). The pair of core bodies 84a, 84b are parallel to each other and perpendicular to the axes of the first and second core dies 66, 68. The one core body 84a and the other core body 84b are connected to each other by a frame 86.

[0047] When secondary molding is performed using the secondary molding die 36, the first core die 66 is attached to the outer periphery of the first main die 44, and the second core die 68 is attached to the outer periphery of the second main die 46. The core bodies 84a, 84b of the first core die 66 are inserted between the die ends 44a, 44b of the first main die 44 and the second cover ends 76 of the second slide dies 64a, 64b. The core bodies 84a, 84b of the first core die 66 are disposed adjacent to the side wall surface 16a of the first annular wall portion 16 of the intermediate molded body 40.

[0048] The core bodies 84a, 84b of the second core die 68 are inserted between the die ends 46a, 46b of the second main die 46 and the second cover ends 76 of the second slide dies 64a, 64b. The core bodies 84a, 84b of the second core die 68 are disposed adjacent to and facing the side wall surface 16a of the first annular wall portion 16 of the intermediate molded body 40.

[0049] Next, the case where the resin molded product 12 is injection molded by the injection molding device 10 will be described.

[0050] First, primary molding (first molding step) is performed to mold an intermediate molded body 40, which will serve as the base for the resin molded product 12, using the primary molding die 34. In the first molding step shown in FIG. 3, the first and second main dies 44, 46 constituting the primary molding die 34 are closed in a direction perpendicular to the axial center (the direction of arrow B) by a displacement mechanism (not shown). The pair of first slide dies 48a, 48b are closed in a direction that brings them closer to each other along the axial direction of the first and second main dies 44, 46. The pair of first slide dies 48a, 48b cover the die ends 44a, 44b of the first main die 44 and the die ends 46a, 46b of the second main die 46. A first cavity C1 covered by the first and second main dies 44, 46 and the first slide dies 48a, 48b is formed inside the primary molding die 34.

[0051] As shown in Fig. 4, molten resin material R is supplied from resin material supply device 38 to first runner 54 through piping 42. The resin material R flows from first runner 54 through the inside of first main mold 44 and is filled into first cavity C1. The resin material R is cooled and solidified in first cavity C1, thereby forming an intermediate molded body 40 in first cavity C1. The intermediate molded body 40 has a cylindrical portion 14 having a pipe main body 24 and pipe end portions 26a, 26b, and a first annular wall portion 16 formed on the outer circumferential surface 24a of the cylindrical portion 14.

[0052] In detail, the pipe main body 24 of the cylindrical portion 14 of the intermediate molded body 40 is molded between the first wall portion molding portions 52 of the first and second main dies 44, 46 and the first shaft portions 58 of the first slide dies 48a, 48b. The outer peripheral surface and wall surface 16b of the first annular wall portion 16 of the intermediate molded body 40 are molded between the first wall portion molding portions 52 of the first and second main dies 44, 46 and the first cover end portions 60 of the first slide dies 48a, 48b. The pipe end portions 26a, 26b of the intermediate molded body 40 are molded between the first cover end portions 60, the first recess 62, and the first shaft portions 58. The side wall surface 16a of the first annular wall portion 16 of the intermediate molded body 40 is molded by the first cover end portions 60 of the first slide dies 48a, 48b.

[0053] After the molding of the intermediate molded body 40 is completed in the first molding step shown in FIG. 4, a separating step is carried out in which the first slide dies 48a, 48b are opened and separated as shown in FIG.

[0054] Specifically, the pair of first slide dies 48a, 48b are moved in a direction away from the first and second main dies 44, 46. The first cover portions 56 of the first slide dies 48a, 48b are moved away from the first and second main dies 44, 46, respectively. The first shaft portions 58 of the first slide dies 48a, 48b are removed from the through-holes 22 of the intermediate molded body 40. At this time, the first and second main dies 44, 46 form part of the secondary molding die 36 used in the next second molding step, so the first and second main dies 44, 46 remain attached radially outward of the pipe body 24 and first annular wall portion 16 of the intermediate molded body 40.

[0055] When the pair of first slide dies 48a, 48b are separated in the axial direction, the pipe end parts 26a, 26b of the intermediate formed body 40 and the side wall surface 16a of the first annular wall portion 16 are exposed to the outside. At this time, a first parting line L1 is formed on the inner circumferential surface of the through hole 22 between the first axial portion 58 of one first slide die 48a and the first axial portion 58 of the other first slide die 48b in the first molding step. The first parting line L1 is annular and follows the inner circumferential surface of the through hole 22.

[0056] A second parting line L2 is formed on the outer periphery of the first annular wall portion 16. The second parting line L2 is formed at the boundary between the outer periphery of the first annular wall portion 16 and the side wall surface 16a. The second parting line L2 is a line formed in the first molding step at the boundary between the mold end portion 44a of the first main mold 44 and the mold end portion 46a of the second main mold 46 and the first cover end portion 60 of the first slide mold 48a. The second parting line L2 is a line formed in the first molding step at the boundary between the mold end portion 44b of the first main mold 44 and the mold end portion 46b of the second main mold 46 and the first cover end portion 60 of the first slide mold 48b. The second parting line L2 is annular along the outer periphery of the first annular wall portion 16.

[0057] Next, secondary molding (second molding step) is performed, in which the resin molded product 12 is molded from the intermediate molded body 40 using the secondary molding die 36. In a preparation step for the second molding step shown in FIG. 7, the first and second core dies 66, 68 are attached to the first and second main dies 44, 46 and then closed. From a state in which the first core dies 66 and the second core dies 68 are opened, the first core dies 66 and the second core dies 68 are moved toward the intermediate molded body 40 by a displacement mechanism (not shown) so that they approach each other. The movement direction of the first and second core dies 66, 68 is a direction perpendicular to the axial center of the intermediate molded body 40 (the direction of arrow B). The core bodies 84a, 84b of the first and second core dies 66, 68 are inserted from the radially outer side into the axial outside of the first annular wall portion 16 of the intermediate molded body 40. Each of the core bodies 84 a, 84 b is disposed adjacent to the side wall surface 16 a of the first annular wall portion 16 .

[0058] 8, the second slide mold 64a is attached to the mold end portion 44a of the first main mold 44 and the mold end portion 46a of the second main mold 46, and the second slide mold 64b is attached to the mold end portion 44b of the first main mold 44 and the mold end portion 46b of the second main mold 46, and the molds are closed. At this time, the second shaft portions 72 of the second slide molds 64a, 64b are inserted into and held in the through-holes 22 of the intermediate molded body 40. As a result, the second slide molds 64a, 64b are positioned coaxially with the intermediate molded body 40.

[0059] The second slide dies 64a, 64b abut against the tube end parts 26a, 26b of the intermediate compact 40, thereby positioning the second slide dies 64a, 64b in the axial direction relative to the intermediate compact 40. At this time, the second cover end part 76 abuts against and faces the core bodies 84a, 84b of the first and second core dies 66, 68. The die end parts 44a, 44b, 46a, 46b of the first and second main dies 44, 46 and the second cover end part 76 are spaced apart in the axial direction of the intermediate compact 40, with the core bodies 84a, 84b between them. The second recess 74 faces the side wall surface 16a of the first annular wall part 16 of the intermediate compact 40. The tube end parts 26a, 26b of the intermediate compact 40 are inserted into the end part insertion parts 80 of the second recess 74.

[0060] As a result, an annular second cavity C2 is formed from the second wall molding portion 82 of the second recess 74 between the second cover end portions 76 of the second slide dies 64a, 64b and the core bodies 84a, 84b of the first and second core dies 66, 68. The second cavity C2 is disposed radially outward from the pipe end portions 26a, 26b of the intermediate molded body 40.

[0061] As shown in FIG. 1, molten resin material R is supplied from the resin material supply device 38 to the second runners 78 of each second slide mold 64a, 64b through the piping 42. The resin material R is then filled from the second runners 78 into the second wall molding portion 82 of the second recess 74, which is the second cavity C2. As the resin material R cools and solidifies in the second cavity C2, a second annular wall portion 18 is molded around the outer peripheries of the pipe ends 26a, 26b in the second cavity C2. The second annular wall portion 18 is connected to and integrated with the outer peripheral surfaces 28 of the pipe ends 26a, 26b. The second annular wall portion 18 is formed in an annular shape that protrudes radially outward from the outer peripheral surfaces 28 of the pipe ends 26a, 26b. The second annular wall portion 18 is molded by the core bodies 84a, 84b at a position spaced axially outward (in the direction of arrow A) from the side wall surface 16a of the first annular wall portion 16.

[0062] As a result, annular grooves 20 are formed radially outward from the outer circumferential surfaces 28 of the pipe ends 26a, 26b between the first annular wall 16 and the second annular wall 18. In the second molding step, the pair of second annular walls 18 are molded onto the pipe ends 26a, 26b of the intermediate molded body 40, thereby forming the resin molded product 12.

[0063] As shown in FIG. 9, the secondary molding die 36 is opened to remove the resin molded product 12.

[0064] The first and second main dies 44, 46 are each moved in a direction away from the resin molded article 12. The pair of second slide dies 64a, 64b are released from the first and second main dies 44, 46. The second cover portions 70 of the second slide dies 64a, 64b are released from the first and second main dies 44, 46. The second shaft portions 72 of the second slide dies 64a, 64b are removed from the through-holes 22 of the resin molded article 12.

[0065] The first core die 66 and the second core die 68 are moved in a direction perpendicular to the axial center of the resin molded article 12, in a direction separating them from each other. The core bodies 84a, 84b of the first and second core dies 66, 68 are released radially outward from the annular groove portion 20. The first main die 44 and the second main die 46 are moved in a direction perpendicular to the axial center of the resin molded article 12, in a direction separating them from each other. The first and second main dies 44, 46 are released radially outward from the cylindrical portion 14 and the first annular wall portion 16 of the resin molded article 12. As a result, the resin molded article 12 is removed from the secondary molding die 36.

[0066] 2, a third parting line L3 is formed in the resin molded article 12 at the parting portion between the first main mold 44 and the second main mold 46. The third parting line L3 extends linearly on the outer peripheral surface along the axial direction to the pipe main body 24 in the cylindrical portion 14 and the side wall surface 16a of the first annular wall portion 16. Two third parting lines L3 are formed at symmetrical positions with respect to the axial center of the resin molded article 12.

[0067] A fourth parting line L4 is formed on the outer periphery of the second annular wall portion 18. The fourth parting line L4 is formed at the boundary between the outer periphery of the second annular wall portion 18 and the wall surface of the second annular wall portion 18 that faces the pipe main body 24. The fourth parting line L4 is a line formed in the second molding step at the boundary between the core bodies 84a, 84b and the second cover end portions 76 of the second slide dies 64a, 64b. The fourth parting line L4 is annular and follows the outer periphery of the second annular wall portion 18.

[0068] A fifth parting line L5 is formed on the inner periphery of the second annular wall portion 18. The fifth parting line L5 is formed at the boundary between the inner wall surface 18a of the second annular wall portion 18 facing the first annular wall portion 16 and the outer periphery 28 of the pipe end portions 26a, 26b. The fifth parting line L5 is an annular line formed in the second molding step at the boundary between the inner periphery of the core bodies 84a, 84b of the first and second core dies 66, 68 and the second wall portion molding portion 82 of the second slide dies 64a, 64b.

[0069] A sixth parting line L6 is formed on the axial end surface 18b of the second annular wall portion 18. The sixth parting line L6 is formed at the boundary between the outer peripheral surfaces 28 of the pipe end portions 26a, 26b and the second wall portion molding portion 82 of the second slide dies 64a, 64b. The sixth parting line L6 is an annular line formed at the boundary between the outer peripheral surfaces 28 of the pipe end portions 26a, 26b and the second annular wall portion 18.

[0070] No parting line extending in the axial direction is formed in the annular groove 20 of the resin molded product 12. In the first molding step for molding the intermediate molded body 40, because the first cover end 60 of the first slide dies 48a, 48b is annular, no parting line extending in the axial direction is formed in the outer peripheral surface 28 of the pipe ends 26a, 26b that form the annular groove 20. In the second molding step for molding the resin molded product 12, because the core bodies 84a, 84b of the first and second core dies 66, 68 are arranged adjacent to the side wall surface 16a of the first annular wall 16, the inflow of the resin material R is prevented, and no parting line extending in the axial direction is formed in the annular groove 20. Although a fifth parting line L5 is formed in the annular groove 20, the fifth parting line L5 is annular and does not extend in the axial direction of the annular groove 20. The fifth parting line L5 is formed at a corner of the annular groove 20 adjacent to the inner wall surface 18a of the second annular wall 18. In other words, the resin molded product 12 has the annular groove 20 surrounded by the first and second annular walls 16, 18, and no parting line is formed along the axial direction on the outer peripheral surfaces 28 of the pipe ends 26a, 26b, which form the bottom surfaces of the annular groove 20.

[0071] The resin molded product 12 is not limited to the case where the first and second annular wall portions 16, 18 (annular groove portion 20) are provided at one end side and the other end side along the axial direction of the cylindrical portion 14, respectively. The resin molded product 12 may also have the first and second annular wall portions 16, 18 (annular groove portion 20) provided at only one end side or the other end side of the cylindrical portion 14. In this case, in the primary molding, one first slide die 48a (48b) may be closed at one end side or the other end side of the first and second main dies 44, 46 to mold the intermediate molded body 40 having one first and second annular wall portion 16, 18, and in the secondary molding, one second slide die 64a (64b) may be closed at one end side or the other end side of the first and second main dies 44, 46 to mold one annular groove portion 20, thereby molding the resin molded product 12 having one each of the first and second annular wall portions 16, 18 (annular groove portion 20).

[0072] As described above, in an embodiment of the present invention, when injection molding a tubular resin molded product 12, the intermediate molded body 40 having the pipe main body 24 of the cylindrical portion 14 and the first annular wall portion 16 is molded in a first molding step, and then, in a second molding step, the second slide dies 64a, 64b are closed axially against the intermediate molded body 40 to mold the second annular wall portion 18 against the outer circumferential surface 28 of the cylindrical portion 14. This prevents the formation of a parting line extending in the axial direction due to molding in the annular groove portion 20 between the first annular wall portion 16 and the second annular wall portion 18 in the resin molded product 12. This eliminates the need to remove the parting line of the annular groove portion 20 by additional processing after molding the resin molded product 12, thereby reducing the number of manufacturing steps and manufacturing costs.

[0073] In the first molding process for molding the intermediate molded body 40, the resin material R is supplied into the first cavity C1 from the first runner 54 of the first main mold 44 of the first and second main molds 44, 46, thereby filling the first cavity C1 with the resin material R and molding the intermediate molded body 40.

[0074] In an injection molding apparatus 10 for molding a resin molded product 12, when an intermediate molded body 40 having a pipe main body 24 of a cylindrical portion 14 and a first annular wall portion 16 is molded using a primary molding die 34, the second slide dies 64a, 64b are opened in the axial direction relative to the intermediate molded body 40, and the second slide dies 64a, 64b of the secondary molding die 36 are used to mold the second annular wall portion 18 in the cylindrical portion 14. This prevents the annular groove portion 20 (the outer peripheral surfaces 28 of the pipe ends 26a, 26b) between the first annular wall portion 16 and the second annular wall portion 18 from being parted in the radial direction, and further prevents the first and second core dies 66, 68 from supplying resin material R to the annular groove portion 20. This prevents a parting line from being formed on the outer peripheral surface of the annular groove portion 20 of the resin molded product 12.

[0075] The above embodiment can be summarized as follows.

[0076] The above embodiment is a method for injection molding a tubular resin molded product (12) by injection molding, The resin molded product is a cylindrical portion (14) extending along the axial direction of the resin molded product and having pipe end faces (14a, 14b) which are end faces on at least one end side in the axial direction; a first annular wall portion (16) that protrudes radially outward from an outer circumferential surface (24a) of the cylindrical portion at least on the one end side thereof and has a side wall surface (16a) that faces outward in the axial direction; a second annular wall portion (18) that protrudes radially outward from the outer circumferential surface of the cylindrical portion at least on the one end side of the cylindrical portion and is disposed spaced apart from the first annular wall portion on the outer side in the axial direction; an annular groove (20) formed between the first annular wall portion and the second annular wall portion; and the cylindrical portion has a pipe main body (24) that forms from the side wall surface of the first annular wall portion to at least a central portion of the cylindrical portion in the axial direction, and pipe end portions (26a, 26b) that extend from the side wall surface to the pipe end surface of the cylindrical portion and whose outer circumferential surfaces form a part of the annular groove portion, The injection molding method includes: a first molding step of molding an intermediate molded body (40) including the pipe main body and the first annular wall portion of the resin molded product by using first and second main molds (44, 46) that are clamped together in a direction perpendicular to the axial center of the cylindrical portion, and first slide molds (48a, 48b) that are clamped against at least one end surface of the first and second main molds along the axial direction of the cylindrical portion; a detaching step of detaching the first slide die from the intermediate molded body along the axial direction of the cylindrical portion after molding the intermediate molded body; a second molding step of molding the second annular wall portion on the outer peripheral surface of the cylindrical portion by using second slide dies (64a, 64b) that are molded along the axial direction against the tube end surface of the cylindrical portion of the intermediate molded body, and first and second core dies (66, 68) that are molded in a direction perpendicular to the axial center of the cylindrical portion and are arranged adjacent to the side wall surface; It has.

[0077] In the first molding step, molten resin material (R) is injected from at least one of the first main mold and the second main mold into a first cavity (C1) formed by the first main mold, the second main mold, and the first slide mold.

[0078] the resin molded product has the first annular wall portion, the second annular wall portion, and the annular groove portion at each of the one end side and the other end side in the axial direction of the cylindrical portion, In the first molding step, the intermediate molded body having the two first annular wall portions is molded by the first and second main molds and the two first slide molds arranged on both sides of the first and second main molds in the axial direction, In the second molding process, the two second annular wall portions are molded on the outer surface of the cylindrical portion using the first and second main molds, the two second slide molds arranged on both sides of the cylindrical portion in the axial direction, and the first and second core molds arranged on both sides of the cylindrical portion in the axial direction.

[0079] An injection molding apparatus for molding a tubular resin molded product by injection molding, The resin molded product is a cylindrical portion extending along an axial direction of the resin molded product and having a tube end surface that is an end surface on 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 least on the one end side of the cylindrical portion and has a side wall surface that faces outward in the axial direction; a second annular wall portion that protrudes radially outward from the outer circumferential surface of the cylindrical portion at least on the one end side of the cylindrical portion and is spaced apart from the first annular wall portion outward in the axial direction; an annular groove formed between the first annular wall and the second annular wall; and the cylindrical portion has a pipe main body that forms from the side wall surface of the first annular wall portion to at least a central portion of the cylindrical portion in the axial direction, and a pipe end portion that extends from the side wall surface to the pipe end surface of the cylindrical portion and whose outer peripheral surface forms a part of the annular groove portion, The injection molding apparatus a primary molding die (34) having a first cavity therein and configured to mold an intermediate molded body having the cylindrical portion and the first annular wall portion of the resin molded product; a secondary molding die (36) having a second cavity (C2) therein and configured to mold the second annular wall portion on the outer circumferential surface of the cylindrical portion of the intermediate molded body; Equipped with The primary molding mold is first and second main dies that are closed together in a direction perpendicular to the axial center of the cylindrical portion and that mold an outer peripheral surface of the pipe body, an outer peripheral surface of the first annular wall portion, and a wall surface (16b) of the first annular wall portion that connects the outer peripheral surface of the pipe body and the outer peripheral surface of the first annular wall portion; a first slide mold that is clamped against at least one end surface of the first and second main molds along the axial direction of the cylindrical portion and that forms the side wall surface of the first annular wall portion and the tube end portion; Equipped with The secondary molding mold is a second slide mold that is closed against the tube end surface of the cylindrical portion of the intermediate molded body and that forms the second annular wall portion; first and second core dies that are clamped onto the outer peripheral surface of the pipe end of the intermediate formed body in a direction perpendicular to the axial center of the cylindrical portion and are disposed adjacent to the side wall surface of the first annular wall portion; Equipped with.

[0080] At least one of the first main mold and the second main mold is provided with a runner (54) that injects a molten resin material into a first cavity formed by the first main mold, the second main mold, and the first slide mold.

[0081] the resin molded product has the first annular wall portion, the second annular wall portion, and the annular groove portion at each of the one end side and the other end side in the axial direction of the cylindrical portion, the primary molding die molds the intermediate molded body having the two first annular wall portions by using the first and second main dies and the two first slide dies arranged on both sides of the first and second main dies in the axial direction, The secondary molding die molds two second annular wall portions on the outer surface of the cylindrical portion using the first and second main dies, the two second slide dies arranged on both sides of the cylindrical portion in the axial direction, and the first and second core dies arranged on both sides of the cylindrical portion in the axial direction.

[0082] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention. [Explanation of symbols]

[0083] 10...Injection molding equipment 12...Resin molded products 14... Cylindrical portion 14a, 14b... Pipe end surfaces 16...first annular wall portion 16a...side wall surface 18... Second annular wall portion 20... Annular groove portion 24...Pipe body 26a, 26b...Pipe end 40... intermediate molded body 44... first main mold 46...Second main mold 48a, 48b...First slide mold 64a, 64b... Second slide mold 66... ​​First core mold 68…Second core mold

Claims

1. A method for injection molding a tubular resin molded product, comprising: The resin molded product is a cylindrical portion extending along an axial direction of the resin molded product and having a tube end surface that is an end surface on 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 least on the one end side of the cylindrical portion and has a side wall surface that faces outward in the axial direction; a second annular wall portion that protrudes radially outward from the outer circumferential surface of the cylindrical portion at least on the one end side of the cylindrical portion and is disposed spaced apart from the first annular wall portion outward in the axial direction; an annular groove formed between the first annular wall and the second annular wall; and the cylindrical portion has a pipe main body that forms from the side wall surface of the first annular wall portion to at least a central portion of the cylindrical portion in the axial direction, and a pipe end portion that extends from the side wall surface to the pipe end surface of the cylindrical portion and whose outer peripheral surface forms a part of the annular groove portion, The injection molding method includes: a first molding step of molding an intermediate molded body including the pipe main body and the first annular wall portion of the resin molded product using first and second main molds that are clamped together in a direction perpendicular to the axial center of the cylindrical portion and a first slide mold that is clamped against at least one end surface of the first and second main molds along the axial direction of the cylindrical portion; a detaching step of detaching the first slide die from the intermediate molded body along the axial direction of the cylindrical portion after molding the intermediate molded body; a second molding step of molding the second annular wall portion on the outer peripheral surface of the cylindrical portion by using a second slide mold that is mold-closed along the axial direction against the tube end surface of the cylindrical portion of the intermediate molded body, and first and second core dies that are mold-closed in a direction perpendicular to the axial center of the cylindrical portion and arranged adjacent to the side wall surface; A method for injection molding a resin molded product, comprising:

2. 2. The method for injection molding a resin molded product according to claim 1, A method for injection molding a resin molded product, wherein in the first molding step, molten resin material is injected from at least one of the first main mold and the second main mold into a first cavity formed by the first main mold, the second main mold, and the first slide mold.

3. 3. The method for injection molding a resin molded product according to claim 1 or 2, the resin molded product has the first annular wall portion, the second annular wall portion, and the annular groove portion at each of the one end side and the other end side in the axial direction of the cylindrical portion, In the first molding step, the intermediate molded body having the two first annular wall portions is molded by the first and second main molds and the two first slide molds arranged on both sides of the first and second main molds in the axial direction, In the second molding step, the two second annular wall portions are molded on the outer peripheral surface of the cylindrical portion using the first and second main dies, the two second slide dies arranged on both sides of the cylindrical portion in the axial direction, and the first and second core dies arranged on both sides of the cylindrical portion in the axial direction, in this injection molding method for a resin molded product.

4. An injection molding apparatus for molding a tubular resin molded product by injection molding, The resin molded product is a cylindrical portion extending along an axial direction of the resin molded product and having a tube end surface that is an end surface on 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 least on the one end side of the cylindrical portion and has a side wall surface that faces outward in the axial direction; a second annular wall portion that protrudes radially outward from the outer circumferential surface of the cylindrical portion at least on the one end side of the cylindrical portion and is disposed spaced apart from the first annular wall portion outward in the axial direction; an annular groove formed between the first annular wall and the second annular wall; and the cylindrical portion has a pipe main body that forms from the side wall surface of the first annular wall portion to at least a central portion of the cylindrical portion in the axial direction, and a pipe end portion that extends from the side wall surface to the pipe end surface of the cylindrical portion and whose outer peripheral surface forms a part of the annular groove portion, The injection molding apparatus a primary molding die having a first cavity therein and configured to mold an intermediate molded body having the cylindrical portion and the first annular wall portion of the resin molded product; a secondary molding die having a second cavity therein and configured to mold the second annular wall portion on the outer circumferential surface of the cylindrical portion of the intermediate molded body; Equipped with The primary molding mold is first and second main dies that are closed together in a direction perpendicular to the axial center of the cylindrical portion and that mold an outer peripheral surface of the pipe body, an outer peripheral surface of the first annular wall portion, and a wall surface of the first annular wall portion that connects the outer peripheral surface of the pipe body and the outer peripheral surface of the first annular wall portion; a first slide mold that is closed against at least one end surface of the first and second main molds along the axial direction of the cylindrical portion and that forms the side wall surface of the first annular wall portion and the tube end portion; Equipped with The secondary molding mold is a second slide mold that is closed against the tube end surface of the cylindrical portion of the intermediate molded body and that forms the second annular wall portion; first and second core dies that are clamped onto the outer peripheral surface of the pipe end of the intermediate formed body in a direction perpendicular to the axial center of the cylindrical portion and are disposed adjacent to the side wall surface of the first annular wall portion; An injection molding apparatus comprising:

5. 5. The injection molding apparatus according to claim 4, an injection molding apparatus, wherein at least one of the first main mold and the second main mold is provided with a runner that injects molten resin material into a first cavity formed by the first main mold, the second main mold, and the first slide mold.

6. 6. The injection molding apparatus according to claim 4 or 5, the resin molded product has the first annular wall portion, the second annular wall portion, and the annular groove portion at each of the one end side and the other end side in the axial direction of the cylindrical portion, the primary molding die molds the intermediate molded body having the two first annular wall portions by using the first and second main dies and the two first slide dies arranged on both sides of the first and second main dies in the axial direction, the secondary molding die molds the two second annular wall portions on the outer peripheral surface of the cylindrical portion using the first and second main dies, the two second slide dies arranged on both sides of the cylindrical portion in the axial direction, and the first and second core dies arranged on both sides of the cylindrical portion in the axial direction, an injection molding apparatus.

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