Injection molding method and injection molding apparatus for resin molded parts

Abstract

An injection molding method and apparatus for resin molded parts are disclosed. The injection molding method for resin molded parts includes a first molding step in which an intermediate molded body is molded using a first main mold, a second main mold, and a first sliding mold, wherein the first sliding mold closes along the axial direction of the first and second main molds. The injection molding method for resin molded parts further includes a release step and a second molding step. In the release step, the first sliding mold is released from the intermediate molded body. In the second molding step, a second annular wall portion is molded on the intermediate molded body using a second sliding mold, a first core mold, and a second core mold. The second sliding mold closes axially relative to the tube end face of the intermediate molded body, and the first and second core molds close relative to the intermediate molded body in a direction orthogonal to the axis center. Accordingly, after molding the resin molded part, it is not necessary to remove the parting line of the annular groove portion through additional processing, thereby reducing manufacturing time and costs.

Description

Technical Field

[0001] This invention relates to an injection molding method and an injection molding apparatus for resin molded parts. Background Technology

[0002] Japanese Patent Publication No. 1-209113 discloses a method for manufacturing an airtight component installed on the outer periphery of a piping. The airtight component is formed into a ring shape by injection molding by filling resin material into the interior of a closed upper and lower mold. An annular groove is formed on the outer periphery of the airtight component. By installing the airtight component into the opening of the dashboard, airtightness between the inner and outer sides of the dashboard can be maintained. Summary of the Invention

[0003] In airtight components manufactured by injection molding, parting lines are formed at the parting points of the upper and lower molds. These parting lines are straight along the axial direction on the outer peripheral surface of the airtight component. Such parting lines are also formed in annular grooves. When an airtight component is installed in a bore in an instrument panel, the parting lines forming annular grooves along the axial direction create a gap between the instrument panel and the outer peripheral surface of the airtight component, potentially reducing airtightness. To maintain airtightness, it is considered to remove the parting lines from the outer peripheral surface through further processing such as grinding, but this process is complex and increases manufacturing costs.

[0004] The technical solution of the present invention is: an injection molding method for a resin molded part, wherein the method uses injection molding to form a tubular resin molded part, the resin molded part having a cylindrical portion, a first annular wall portion, a second annular wall portion, and an annular groove portion, wherein the cylindrical portion extends along the axial direction of the resin molded part and has a tube end face as at least one end face in the axial direction; the first annular wall portion protrudes radially outward from the outer peripheral surface of the cylindrical portion at at least one end face of the cylindrical portion and has a side wall surface facing outward in the axial direction; the second annular wall portion... At least one end of the cylindrical portion protrudes radially outward from the outer peripheral surface of the cylindrical portion and is separated from the first annular wall portion axially outward; the annular groove is formed between the first annular wall portion and the second annular wall portion; the cylindrical portion has a tube body and a tube end, wherein the tube body is configured to extend from the side wall surface of the first annular wall portion at least to the central portion of the cylindrical portion axially; the tube end extends from the side wall surface to the tube end face of the cylindrical portion and its outer peripheral surface forms part of the annular groove, the injection... The injection molding method includes a first molding step, a release step, and a second molding step. In the first molding step, an intermediate molded body is formed using a first main mold, a second main mold, and a first sliding mold. The first and second main molds close in a direction orthogonal to the axial center of the cylindrical portion, and the first sliding mold closes along the axial direction of the cylindrical portion relative to at least one end face of the first and second main molds. The intermediate molded body has the tube body of the resin molded part and the first annular wall portion. In the release step... After the intermediate molded body is formed, the first sliding mold is disengaged from the intermediate molded body along the axial direction of the cylindrical portion; in the second molding process, the second annular wall portion is formed on the outer peripheral surface of the cylindrical portion by the second sliding mold, the first core mold, and the second core mold, wherein the second sliding mold closes relative to the tube end face of the cylindrical portion of the intermediate molded body along the axial direction, and the first core mold and the second core mold close in a direction orthogonal to the axial center of the cylindrical portion and are arranged adjacent to the side wall surface.

[0005] According to the present invention, in the first molding step of injection molding of the resin molded part, after molding an intermediate molded body having a cylindrical portion and a first annular wall portion, in the second molding step, a second sliding mold is closed axially relative to the intermediate molded body, thereby molding the second annular wall portion relative to the outer peripheral surface of the cylindrical portion. This prevents the formation of an axial parting line on the outer peripheral surface of the annular groove portion between the first and second annular wall portions by injection molding. Consequently, after molding the resin molded part, it is not necessary to remove the parting line of the annular groove portion by additional processing, thereby reducing manufacturing time and costs.

[0006] The above-described objectives, features, and advantages should be readily understood from the following description of the embodiments with reference to the accompanying drawings. Attached Figure Description

[0007] Figure 1 This is a schematic structural diagram of an injection molding apparatus for injection molding resin molded parts according to embodiments of the present invention.

[0008] Figure 2 Through Figure 1 A top view of the appearance of a resin molded part obtained by an injection molding device.

[0009] Figure 3 It means Figure 1 A schematic structural diagram of the primary molding die of the injection molding device.

[0010] Figure 4 It means to Figure 3 The diagram shows the structure of the first molding process after the first cavity of the injection molding apparatus is filled with resin material.

[0011] Figure 5 It is along Figure 4 A cross-sectional view of the VV line.

[0012] Figure 6 This is a structural diagram showing the separation process after the intermediate molded body is formed in the first molding process, in which the first sliding mold is detached.

[0013] Figure 7 This is a structural diagram showing the preparation state of the second molding process, in which the first core mold and the second core mold are installed on the first main mold and the second main mold.

[0014] Figure 8 This indicates that the second sliding mold is installed on Figure 7 A structural diagram of the molded secondary molding die of the injection molding device in the closed state.

[0015] Figure 9 This is a structural diagram showing the state after the second molding process is completed, the mold is opened, and the resin molded part is removed. Detailed Implementation

[0016] like Figure 1 As shown, the injection molding apparatus 10 of this embodiment forms a tubular resin molded part 12 by injection molding.

[0017] First, refer to Figure 1 and Figure 2 The resin molded part 12, which is injection molded by the injection molding apparatus 10, will be described.

[0018] The resin molded part 12 is a tube formed in a straight line along the axial direction (arrow A direction). The resin molded part 12 has a cylindrical part 14, a first annular wall part 16, a second annular wall part 18, and an annular groove part 20.

[0019] The cylindrical portion 14 is formed into an annular shape with a certain diameter along the axial direction. One end face 14a and 14b are respectively provided on the other end face along the axial direction of the cylindrical portion 14. The cylindrical portion 14 has a through hole 22 along the axial direction (arrow A direction). The through hole 22 opens on the tube end faces 14a and 14b of the cylindrical portion 14.

[0020] The cylindrical portion 14 has a tube body 24 and a pair of tube ends 26a and 26b. The tube body 24 extends from the axial center of the cylindrical portion 14 to the side wall surface 16a of the first annular wall portion 16 (described later). The tube ends 26a are positioned relative to the tube body 24 near the tube end face 14a. The tube ends 26a extend from the side wall surface 16a of the first annular wall portion 16 to the tube end face 14a of the tube body 24. The tube ends 26b are positioned relative to the tube body 24 near the tube end face 14b. The tube ends 26b extend from the side wall surface 16a of the first annular wall portion 16 to the tube end face 14b of the tube body 24. The outer peripheral surfaces 28 of the tube ends 26a and 26b form part of the annular groove portion 20.

[0021] The first annular wall portion 16 and the second annular wall portion 18 are respectively disposed on one end side and the other end side of the cylindrical portion 14 in the axial direction. The first annular wall portion 16 and the second annular wall portion 18 are annular shapes that protrude radially outward from the outer peripheral surfaces 24a and 28 of the cylindrical portion 14. The first annular wall portion 16 and the second annular wall portion 18 are separated from each other and face each other in the axial direction (arrow A direction) of the cylindrical portion 14.

[0022] The first annular wall portion 16 is disposed on the cylindrical portion 14 near the axial center of the tube end faces 14a and 14b. The first annular wall portion 16 is disposed on the outer peripheral surface 24a of the tube body 24 in the cylindrical portion 14.

[0023] The first annular wall portion 16 has a side wall surface 16a facing the axially outer side of the cylindrical portion 14. The side wall surface 16a is a plane that is substantially orthogonal 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 facing the central side of the cylindrical portion 14 in the axial direction. The side wall surface 16a and the wall surface 16b are separated and substantially parallel in the axial direction (arrow A direction) of the cylindrical portion 14.

[0024] A second annular wall portion 18 is disposed on the outer peripheral surface 28 of the tube ends 26a and 26b in the cylindrical portion 14. The second annular wall portion 18 is disposed separately from the first annular wall portion 16, facing axially outward. 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 relative to the outer peripheral surfaces 24a and 28 of the cylindrical portion 14 is approximately the same as the height of the second annular wall portion 18 relative to the outer peripheral surfaces 24a and 28 of the cylindrical portion 14. The second annular wall portion 18 has an axial end face 18b facing axially outward of the cylindrical portion 14. The axial end face 18b is approximately parallel to the inner wall surface 18a.

[0025] An annular groove 20 is disposed between the first annular wall portion 16 and the second annular wall portion 18. The annular groove 20 is a space enclosed by the outer peripheral surfaces 28 of the tube ends 26a and 26b, the side wall surface 16a of the first annular wall portion 16, and the inner wall surface 18a of the second annular wall portion 18. An annular sealing member 30 (see reference) can be installed in the annular groove 20, for example. Figure 2 The sealing component 30 contacts the bottom surface of the annular groove 20 (the outer peripheral surface 28 of the tube ends 26a and 26b).

[0026] Next, the injection molding apparatus 10 for injection molding the resin molded part 12 will be described.

[0027] like Figure 1 As shown, the injection molding apparatus 10 has a one-piece molding die 34 (see reference). Figure 3 The injection molding apparatus 10 includes a primary molding die 34, a secondary molding die 36, and a resin material supply device 38. The primary molding die 34 has a first cavity C1, and the secondary molding die 36 has a second cavity C2. The injection molding apparatus 10 forms an intermediate molded body 40, which becomes the base of the resin molded part 12, through a primary molding process (first molding step) based on the primary molding die 34. The injection molding apparatus 10 further forms the intermediate molded body 40 (refer to...) through a secondary molding process (second molding step) based on the secondary molding die 36. Figure 4 ) as the matrix to form resin molded parts 12 (refer to) Figure 1 ).

[0028] like Figure 3 As shown, the primary molding die 34 and the resin material supply device 38 are connected to each other via piping 42. The resin material supply device 38 can supply heated and molten resin material R to the primary molding die 34 (see reference 34) via piping 42. Figure 4 Supply. For example... Figure 1As shown, the secondary molding die 36 and the resin material supply device 38 are connected to each other via piping 42. The resin material supply device 38 can supply heated and molten resin material R to the secondary molding die 36 via piping 42. The resin material R can be selectively supplied from the resin material supply device 38 to either the primary molding die 34 or the secondary molding die 36.

[0029] like Figure 3 and Figure 4 As shown, the one-piece molding die 34 includes a first main die 44 and a second main die 46, and a pair of first sliding dies 48a and 48b.

[0030] The first main mold 44 and the second main mold 46 extend axially (in the direction of arrow A). From Figure 5 Viewed axially, the first main mold 44 and the second main mold 46 have semi-circular cross-sections. They are approximately symmetrical in shape, facing each other across the axial centers of the intermediate molding body 40 and the resin molded part 12. The first main mold 44 and the second main mold 46 are symmetrically arranged across the axial centers of the intermediate molding body 40 and the resin molded part 12.

[0031] The first main mold 44 and the second main mold 46 are configured to approach and separate from each other via a displacement mechanism (not shown). The direction of movement of the first main mold 44 and the second main mold 46 is orthogonal to the axes of the first main mold 44 and the second main mold 46 (arrow B direction). The direction of movement of the first main mold 44 and the second main mold 46 can also be orthogonal to arrows A and B.

[0032] The first main mold 44 has mold ends 44a and 44b at both ends along the axial direction. Mold ends 44a and 44b have surfaces orthogonal to the axial direction of the first main mold 44. The second main mold 46 has mold ends 46a and 46b at both ends along the axial direction. Mold ends 46a and 46b have surfaces orthogonal to the axial direction of the second main mold 46. The inner circumferential surfaces of the first main mold 44 and the second main mold 46 form part of the first cavity C1.

[0033] The inner circumferential surfaces of the first main mold 44 and the second main mold 46 have a cylindrical forming part 50 and a pair of first wall forming parts 52.

[0034] The cylindrical forming section 50 extends axially along the first main mold 44 and the second main mold 46. The outer peripheral surface 24a of the tube body 24 of the cylindrical section 14 is formed by the cylindrical forming section 50.

[0035] The first wall forming portion 52 is respectively disposed at both ends of the cylindrical forming portion 50 along the axial direction. The first wall forming portion 52 is recessed radially outward relative to the cylindrical forming portion 50. The first wall forming portion 52 opens at the mold ends 44a and 44b of the first main mold 44 and the mold ends 46a and 46b of the second main mold 46. The inner circumferential surface of the first wall forming portion 52 is disposed radially outward of the cylindrical forming portion 50. The inner circumferential surface of the first wall forming portion 52 is an inclined surface that slopes radially outward toward the tube end faces 14a and 14b of the first main mold 44 and the second main mold 46. The outer circumferential surface of the first annular wall portion 16 and the wall surface 16b in the first annular wall portion 16 connecting the outer circumferential surface 24a of the tube body 24 to the outer circumferential surface of the first annular wall portion 16 are formed by the first wall forming portion 52.

[0036] The first main mold 44 has a first flow channel 54 for supplying molten resin material R. The first flow channel 54 is disposed at the axial center of the first main mold 44 and is connected to the resin material supply device 38 via a pipe 42. By supplying molten resin material R from the resin material supply device 38 to the first flow channel 54, the resin material R is filled into the interior of the first cavity C1 containing the first main mold 44 (see reference). Figure 4 The first runner 54 can be configured in the second main mold 46, or the first runner 54 can be configured in both the first main mold 44 and the second main mold 46.

[0037] The first sliding mold 48a faces the mold ends 44a and 46a of one of the first main mold 44 and the second main mold 46. The first sliding mold 48a closes with the mold ends 44a and 46a of the first main mold 44 and the second main mold 46 along the axial direction of the cylindrical portion 14 of the intermediate molded body 40. The first sliding mold 48b faces the mold ends 44b and 46b of the other of the first main mold 44 and the second main mold 46. The first sliding mold 48b closes with the mold ends 44b and 46b of the first main mold 44 and the second main mold 46 along the axial direction of the cylindrical portion 14 of the intermediate molded body 40. The first sliding molds 48a and 48b form the tube ends 26a and 26b of the cylindrical portion 14 in the intermediate molded body 40, the inner circumferential surface of the tube body 24, and the side wall surface 16a of the first annular wall portion 16.

[0038] The first sliding molds 48a and 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 in the shape of a circular plate. The first cover portion 56 is configured to cover the mold ends 44a, 46a, 44b, and 46b of the first main mold 44 and the second main mold 46. The diameter of the first cover portion 56 is approximately the same as the diameter that aligns the first main mold 44 and the second main mold 46 radially.

[0039] The first cover portion 56 has a first cover end portion 60 facing the mold ends 44a, 46a and 44b, 46b of the first main mold 44 and the second main mold 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 orthogonal to the axis of the first cover portion 56. When the first main mold 44 and the second main mold 46 are closed with the first sliding molds 48a, 48b, a first annular wall portion 16 is formed between the first cover end portion 60 and the mold ends 44a, 46a of the first main mold 44 and the second main mold 46, and between the first cover end portion 60 and the mold ends 44b, 46b. The first cover end portion 60 forms the side wall surface 16a of the first annular wall portion 16.

[0040] 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 end 60 of the first cover portion along the axial direction. Viewed axially from the first sliding molds 48a and 48b, the cross-sectional shape of the first shaft portion 58 is circular (see reference). Figure 5 The diameter of the first shaft portion 58 corresponds to the diameter of the through hole 22 of the resin molded part 12. The first shaft portion 58 molds the inner peripheral surface of the cylindrical portion 14 in the intermediate molded body 40.

[0041] An annular first recess 62 is formed between the inner circumferential surface of the first cover end 60 and the first shaft portion 58. The first recess 62 is recessed axially from the end face of the first cover end 60. When one-time molding is performed by the one-time molding die 34, the tube ends 26a and 26b of the cylindrical portion 14 are formed through the first recess 62.

[0042] When passing Figure 3 When the one-time molding die 34 is used for one-time molding, one of the first sliding dies 48a is assembled to the die ends 44a and 46a of one of the first main die 44 and the second main die 46, and the other of the first sliding dies 48b is assembled to the die ends 44b and 46b of the other of the first main die 44 and the second main die 46, thereby closing the one-time molding die 34. At this time, the first shaft portions 58 of each of the first sliding dies 48a and 48b are inserted into the axial center of the intermediate molding body 40 and face each other.

[0043] like Figure 1 As shown, the secondary molding mold 36 includes a first main mold 44 and a second main mold 46, a pair of second sliding molds 64a and 64b, and a pair of first core molds 66 and second core molds 68. The first main mold 44 and the second main mold 46 of the secondary molding mold 36 are shared with the first main mold 44 and the second main mold 46 of the primary molding mold 34.

[0044] The second sliding molds 64a and 64b are closed relative to the tube end faces 14a and 14b of the cylindrical portion 14 in the intermediate molded body 40, respectively. The second sliding molds 64a and 64b form the second annular wall portion 18 relative to the intermediate molded body 40. The second sliding mold 64a faces the mold ends 44a and 46a of one of the first main mold 44 and the second main mold 46, respectively. The second sliding mold 64b faces the mold ends 44b and 46b of the other of the first main mold 44 and the second main mold 46.

[0045] The second sliding molds 64a and 64b include a second cover portion 70, a second shaft portion 72 protruding from the second cover portion 70, and a second recess portion 74. The second cover portion 70 is in the shape of a circular plate. The second cover portion 70 is configured to cover the mold ends 44a, 46a, 44b, and 46b of the first main mold 44 and the second main mold 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 molds 48a and 48b.

[0046] The second cover portion 70 has a second cover end portion 76, which faces the mold ends 44a and 44b of the first main mold 44 and the mold ends 46a and 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 orthogonal to the axis of the second cover portion 70. In the secondary molding process, when the first main mold 44, the second main mold 46, and the second sliding molds 64a and 64b are closed, the second cover end portion 76 separates axially from the mold ends 44a and 46a of the first main mold 44 and the second main mold 46, and also separates axially from the mold ends 44b and 46b. The side surface of the second cover end portion 76 abuts against the first core mold 66 and the second core mold 68, which will be described later.

[0047] Each second cover portion 70 has a second flow channel 78 for supplying molten resin material R. The second flow channel 78 extends axially through the second cover portion 70. The second flow channel 78 is connected to the resin material supply device 38 via a pipe 42. By supplying molten resin material R from the resin material supply device 38 to the second flow channel 78, the resin material R is supplied into the second recess 74 constituting the second cavity C2.

[0048] 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 end 76 of the second cover portion 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 sliding molds 48a and 48b. During secondary molding, when the first main mold 44 and the second main mold 46 are closed with the second sliding molds 64a and 64b, 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 to the axial center of the intermediate molded body 40.

[0049] The second recess 74 is annular and disposed between the inner circumferential surface of the second cover end 76 and the second shaft portion 72. The second recess 74 is recessed axially from the end face of the second cover end 76. The second recess 74 has an end insertion portion 80 and a second wall forming portion 82. The end insertion portion 80 is annular and disposed radially outside the second shaft portion 72. During secondary forming by the secondary forming mold 36, the tube ends 26a and 26b of the intermediate molded body 40 are inserted into the end insertion portion 80.

[0050] The second wall forming portion 82 is annular and is disposed radially outside the end insertion portion 80. The inner peripheral surface of the second wall forming portion 82 is an inclined surface that slopes radially inward toward the side wall surface 16a away from the end of the second cover 76. The second annular wall portion 18 is formed by the second wall forming portion 82.

[0051] The first core mold 66 and the second core mold 68 are approximately symmetrical in shape, separated by the axis of the intermediate molding body 40 and the resin molded part 12. The first core mold 66 and the second core mold 68 are symmetrically arranged, separated by the axis of the intermediate molding body 40. The first core mold 66 is positioned close to the first main mold 44. The second core mold 68 is positioned close to the second main mold 46.

[0052] The first core mold 66 and the second core mold 68 are configured to approach and move away from the first main mold 44 and the second main mold 46 (cylindrical portion 14) in a direction orthogonal to the axes of the first main mold 44 and the second main mold 46 (arrow B direction) via a displacement mechanism (not shown). The first core mold 66 and the second core mold 68 are configured to approach and move away from each other with the intermediate molded body 40 in between. The direction of movement of the first core mold 66 and the second core mold 68 is orthogonal to the axes of the first main mold 44, the second main mold 46, and the intermediate molded body 40.

[0053] The first core mold 66 and the second core mold 68 each have a pair of core bodies 84a and 84b. Core bodies 84a and 84b are semi-divided bodies formed by splitting a circular ring in half. One core body 84a and the other core body 84b are separated along the axial direction (arrow A) of the first core mold 66 and the second core mold 68. The pair of core bodies 84a and 84b are orthogonal to and parallel to the axes of the first core mold 66 and the second core mold 68. One core body 84a and the other core body 84b are connected to each other by a frame 86.

[0054] During secondary molding using the secondary molding die 36, a first core die 66 is installed from the outer periphery of the first main die 44, and a second core die 68 is installed from the outer periphery of the second main die 46. The core bodies 84a and 84b of the first core die 66 are inserted between the die ends 44a and 44b of the first main die 44 and the second cover ends 76 of the second sliding dies 64a and 64b. The core bodies 84a and 84b of the first core die 66 are arranged adjacent to the side wall surface 16a of the first annular wall portion 16 of the intermediate molded body 40.

[0055] The core bodies 84a and 84b of the second core mold 68 are inserted between the mold ends 46a and 46b of the second main mold 46 and the second cover ends 76 of the second sliding molds 64a and 64b. The core bodies 84a and 84b of the second core mold 68 are arranged facing and adjacent to the side wall surface 16a of the first annular wall portion 16 in the intermediate molding body 40.

[0056] Next, the case of injection molding of resin molded part 12 by injection molding apparatus 10 will be described.

[0057] First, a primary molding process (first molding step) is performed using a primary molding die 34, that is, the intermediate molded body 40, which becomes the base of the resin molded part 12, is molded. Figure 3 In the first molding process shown, the first main mold 44 and the second main mold 46, which constitute the primary molding mold 34, are closed in a direction orthogonal to the axis center (arrow B direction) by a displacement mechanism (not shown). A pair of first sliding molds 48a and 48b are closed in a direction that approaches each other along the axial direction of the first main mold 44 and the second main mold 46. The mold ends 44a and 44b of the first main mold 44 and the mold ends 46a and 46b of the second main mold 46 are covered by the pair of first sliding molds 48a and 48b. A first cavity C1, covered by the first main mold 44, the second main mold 46, and the first sliding molds 48a and 48b, is formed inside the primary molding mold 34.

[0058] like Figure 4 As shown, molten resin material R is supplied from resin material supply device 38 to first flow channel 54 through pipe 42. The resin material R is filled from the first flow channel 54 into the first cavity C1 via the interior of the first main mold 44. An intermediate molded body 40 is formed within the first cavity C1 by cooling and solidifying the resin material R within the first cavity C1. The intermediate molded body 40 has: a cylindrical portion 14 having a tube body 24 and tube ends 26a, 26b; and a first annular wall portion 16 formed on the outer peripheral surface 24a of the cylindrical portion 14.

[0059] Specifically, a tube body 24 of the cylindrical portion 14 of the intermediate molded body 40 is formed between the first wall forming portion 52 of the first main mold 44 and the second main mold 46 and the first shaft portion 58 of the first sliding molds 48a and 48b. The outer peripheral surface and wall surface 16b of the first annular wall portion 16 of the intermediate molded body 40 are formed between the first wall forming portion 52 of the first main mold 44 and the second main mold 46 and the first cover end portion 60 of the first sliding molds 48a and 48b. The tube ends 26a and 26b of the intermediate molded body 40 are formed between the first cover end portion 60, the first recess 62, and the first shaft portion 58. The side wall surface 16a of the first annular wall portion 16 of the intermediate molded body 40 is formed by the first cover end portion 60 of the first sliding molds 48a and 48b.

[0060] exist Figure 4 In the first molding process shown, after the intermediate molded body 40 is molded, as follows: Figure 6 As shown, the process of opening and separating the first sliding molds 48a and 48b is carried out.

[0061] Specifically, the pair of first sliding molds 48a and 48b are moved away from the first main mold 44 and the second main mold 46. The first cover portion 56 of the first sliding molds 48a and 48b separates from the first main mold 44 and the second main mold 46, respectively. The first shaft portion 58 of the first sliding molds 48a and 48b disengages from the through hole 22 of the intermediate molded body 40. At this time, since the first main mold 44 and the second main mold 46 constitute part of the secondary molding mold 36 used in the subsequent second molding process, the first main mold 44 and the second main mold 46 are kept in a state where they are installed radially outside the tube body 24 and the first annular wall portion 16 of the intermediate molded body 40.

[0062] When the pair of first sliding molds 48a and 48b are axially disengaged, the tube ends 26a and 26b of the intermediate molded body 40 and the side wall surface 16a of the first annular wall portion 16 are exposed to the outside. At this time, on the inner circumferential surface of the through hole 22, between the first shaft portion 58 of one of the first sliding molds 48a and the first shaft portion 58 of the other first sliding mold 48b, a first parting line L1 is formed in conjunction with the first molding process. The first parting line L1 is annular along the inner circumferential surface of the through hole 22.

[0063] 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 peripheral surface of the first annular wall portion 16 and the side wall surface 16a. The second parting line L2 is formed during the first molding process at the boundary between the mold end 44a of the first main mold 44, the mold end 46a of the second main mold 46, and the first cover end 60 of the first sliding mold 48a. The second parting line L2 is also formed during the first molding process at the boundary between the mold end 44b of the first main mold 44, the mold end 46b of the second main mold 46, and the first cover end 60 of the first sliding mold 48b. The second parting line L2 is annular along the outer peripheral surface of the first annular wall portion 16.

[0064] Next, a secondary molding process (second molding step) is performed using the secondary molding mold 36, that is, the resin molded part 12 is molded using the intermediate molded body 40 as the base. Figure 7 In the preparation step of the second molding process shown, the first core mold 66 and the second core mold 68 are installed on the first main mold 44 and the second main mold 46 for mold closing. From the open state of the first core mold 66 and the second core mold 68, the first core mold 66 and the second core mold 68 are moved toward the intermediate molded body 40 in a manner that brings them closer to each other by a displacement mechanism (not shown). The moving direction of the first core mold 66 and the second core mold 68 is a direction orthogonal to the axial center of the intermediate molded body 40 (arrow B direction). The core bodies 84a and 84b of the first core mold 66 and the second core mold 68 are inserted radially outward into the axially outward side of the first annular wall portion 16 of the intermediate molded body 40. Each core body 84a and 84b is arranged adjacent to the side wall surface 16a of the first annular wall portion 16.

[0065] Next, as Figure 8 As shown, a second sliding mold 64a is installed on the mold end 44a of the first main mold 44 and the mold end 46a of the second main mold 46, and a second sliding mold 64b is installed on the mold end 44b of the first main mold 44 and the mold end 46b of the second main mold 46 for mold closing. At this time, the second shaft portion 72 of the second sliding molds 64a and 64b is inserted into the through hole 22 of the intermediate molded body 40 and held in the through hole 22. Accordingly, the second sliding molds 64a and 64b are coaxially positioned with the intermediate molded body 40.

[0066] The second sliding molds 64a and 64b are positioned axially relative to the intermediate molding body 40 by abutting against the tube ends 26a and 26b of the intermediate molding body 40. At this time, the second cover end 76 faces and abuts against the core bodies 84a and 84b of the first core mold 66 and the second core mold 68. The mold ends 44a, 44b, 46a, and 46b of the first main mold 44 and the second main mold 46 are separated from the second cover end 76 axially in the intermediate molding body 40 by a space between them and the core bodies 84a and 84b. The second recess 74 faces the side wall surface 16a of the first annular wall portion 16 of the intermediate molding body 40. The tube ends 26a and 26b of the intermediate molding body 40 are inserted into the end insertion portion 80 of the second recess 74.

[0067] Accordingly, an annular second cavity C2 is formed by the second wall forming portion 82 of the second recess 74 between the second cover end 76 of the second sliding molds 64a and 64b and the core bodies 84a and 84b of the first core mold 66 and the second core mold 68. The second cavity C2 is disposed radially outside the tube ends 26a and 26b of the intermediate molding body 40.

[0068] like Figure 1 As shown, molten resin material R is supplied from resin material supply device 38 through piping 42 to the second flow channels 78 of each of the second sliding molds 64a and 64b. The resin material R fills the second wall forming portion 82 of the second recess 74, which serves as the second cavity C2, from the second flow channels 78. By cooling and solidifying the resin material R within the second cavity C2, an annular second annular wall portion 18 is formed around the outer periphery of the tube ends 26a and 26b within the second cavity C2. The second annular wall portion 18 is integrally connected to the outer peripheral surface 28 of the tube ends 26a and 26b. The second annular wall portion 18 is formed as an annulus protruding radially outward from the outer peripheral surface 28 of the tube ends 26a and 26b. The second annular wall portion 18 is formed by the cores 84a and 84b at a position separating from the side wall surface 16a of the first annular wall portion 16 axially (in the direction of arrow A) outward.

[0069] Accordingly, an annular groove 20 is formed radially outward from the outer peripheral surface 28 of the tube ends 26a and 26b between the first annular wall portion 16 and the second annular wall portion 18. In the second molding process, a resin molded part 12 is formed by molding a pair of second annular wall portions 18 onto the tube ends 26a and 26b of the intermediate molded body 40.

[0070] like Figure 9 As shown, the mold is opened to remove the resin molded part 12 from the secondary molding mold 36.

[0071] The first main mold 44 and the second main mold 46 are moved toward the direction away from the resin molded part 12. The pair of second sliding molds 64a and 64b are disengaged relative to the first main mold 44 and the second main mold 46. The second cover portion 70 of the second sliding molds 64a and 64b separates from the first main mold 44 and the second main mold 46. The second shaft portion 72 of the second sliding molds 64a and 64b disengages from the through hole 22 of the resin molded part 12.

[0072] The first core mold 66 and the second core mold 68 are moved in a direction orthogonal to the axial center of the resin molded part 12, separating from each other. The core bodies 84a and 84b of the first core mold 66 and the second core mold 68 disengage radially outward from the annular groove portion 20. The first main mold 44 and the second main mold 46 are moved in a direction orthogonal to the axial center of the resin molded part 12, separating from each other. The first main mold 44 and the second main mold 46 disengage radially outward relative to the cylindrical portion 14 and the first annular wall portion 16 of the resin molded part 12. Accordingly, the resin molded part 12 is removed from the secondary molding mold 36.

[0073] like Figure 2 As shown, in the resin molded part 12, a third parting line L3 is formed at the parting point between the first main mold 44 and the second main mold 46. The third parting line L3 extends axially along the outer peripheral surface in a straight line to the tube body 24 in the cylindrical part 14 and the side wall surface 16a of the first annular wall part 16. Two third parting lines L3 are formed at symmetrical positions with respect to the axial center of the resin molded part 12.

[0074] A fourth parting line L4 is formed on the outer periphery of the second annular wall portion 18. The fourth parting line L4 forms the boundary between the outer peripheral surface of the second annular wall portion 18 and the wall surface of the second annular wall portion 18 facing the tube body 24. The fourth parting line L4 is formed during the second molding process at the boundary between the cores 84a and 84b and the second cover end 76 of the second sliding molds 64a and 64b. The fourth parting line L4 is annular along the outer peripheral surface of the second annular wall portion 18.

[0075] 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 peripheral surface 28 of the tube ends 26a, 26b. The fifth parting line L5 is an annular line formed in the second molding process at the boundary between the inner peripheral surface of the core bodies 84a, 84b of the first core mold 66 and the second core mold 68 and the second wall forming portion 82 of the second sliding mold 64a, 64b.

[0076] A sixth parting line L6 is formed on the axial end face 18b of the second annular wall portion 18. The sixth parting line L6 is formed at the boundary between the outer peripheral surface 28 of the tube ends 26a, 26b and the second wall forming portion 82 of the second sliding mold 64a, 64b. The sixth parting line L6 is an annular line formed at the boundary between the outer peripheral surface 28 of the tube ends 26a, 26b and the second annular wall portion 18.

[0077] No axially extending parting line is formed on the annular groove 20 of the resin molded part 12. In the first molding process of the intermediate molded body 40, since the first cover end 60 of the first sliding molds 48a and 48b is annular, no axially extending parting line is formed on the outer peripheral surface 28 of the tube ends 26a and 26b constituting the annular groove 20. In the second molding process of the resin molded part 12, since the cores 84a and 84b of the first core mold 66 and the second core mold 68 are arranged adjacent to the side wall surface 16a of the first annular wall 16, resin material R can be prevented from flowing in, and no axially extending parting line is formed in the annular groove 20. A fifth parting line L5 is formed on the annular groove 20, but the fifth parting line L5 is annular and does not extend axially along the annular groove 20. The fifth parting line L5 is formed at the corner of the annular groove 20 adjacent to the inner wall surface 18a of the second annular wall portion 18. That is, in the resin molded part 12, there is an annular groove 20 surrounded by the first annular wall portion 16 and the second annular wall portion 18, and no parting line along the axial direction is formed on the outer peripheral surface 28 of the tube ends 26a and 26b that form the bottom surface of the annular groove 20.

[0078] The resin molded part 12 is not limited to having a first annular wall portion 16 and a second annular wall portion 18 (annular groove portion 20) on one end side and the other end side along the axial direction of the cylindrical portion 14, respectively. It is also possible for the resin molded part 12 to have the first annular wall portion 16 and the second annular wall portion 18 (annular groove portion 20) only on one end side and the other end side of the cylindrical portion 14. At this time, in one molding process, a first sliding mold 48a (48b) can be closed on one end or the other end of the first main mold 44 and the second main mold 46 to form an intermediate molded body 40 having a first annular wall portion 16 and a second annular wall portion 18. In the second molding process, a second sliding mold 64a (64b) can be closed on one end or the other end of the first main mold 44 and the second main mold 46 to form an annular groove portion 20, thereby forming resin molded parts 12 each having a first annular wall portion 16 and a second annular wall portion 18 (annular groove portion 20).

[0079] As shown above, in the embodiment of the present invention, during the injection molding of the tubular resin molded part 12, after the intermediate molded body 40 having a cylindrical portion 14 and a first annular wall portion 16 is formed in the first molding step, in the second molding step, the second sliding molds 64a and 64b are closed axially relative to the intermediate molded body 40, thereby forming the second annular wall portion 18 relative to the outer peripheral surface 28 of the cylindrical portion 14. Accordingly, in the resin molded part 12, it is possible to prevent the annular groove portion 20 between the first annular wall portion 16 and the second annular wall portion 18 from forming an axially extending parting line due to molding. Accordingly, after molding the resin molded part 12, it is not necessary to remove the parting line of the annular groove portion 20 by additional processing, thereby reducing manufacturing time and manufacturing costs.

[0080] In the first molding process of molding the intermediate molded body 40, resin material R is supplied into the first cavity C1 from the first flow channel 54 of the first main mold 44 and the second main mold 46, so that the resin material R can fill the first cavity C1 and form the intermediate molded body 40.

[0081] In the injection molding apparatus 10 used for molding the resin molded part 12, when the intermediate molded body 40 having a cylindrical portion 14 and a first annular wall portion 16 is molded by the primary molding die 34, the second sliding dies 64a and 64b are opened axially relative to the intermediate molded body 40, and the second sliding dies 64a and 64b of the secondary molding die 36 are used to mold the second annular wall portion 18 in the cylindrical portion 14. Therefore, the annular groove portion 20 (outer peripheral surface 28 of the tube ends 26a and 26b) between the first annular wall portion 16 and the second annular wall portion 18 does not part radially, and the supply of resin material R to the annular groove portion 20 can be prevented by the first core die 66 and the second core die 68. Thus, parting lines can be prevented from forming on the outer peripheral surface of the annular groove portion 20 of the resin molded part 12.

[0082] The above implementation methods can be summarized as follows.

[0083] The above embodiment is: an injection molding method for molding a tubular resin molded part (12) by injection molding. In the injection molding method, the resin molded part has a cylindrical portion (14), a first annular wall portion (16), a second annular wall portion (18), and an annular groove portion (20). The cylindrical portion extends along the axial direction of the resin molded part and has a tube end face (14a, 14b) as an end face of at least one end side in the axial direction. The first annular wall portion protrudes radially outward from the outer peripheral surface (24a) of the cylindrical portion at at least one end side and has a tube end face (14a, 14b) facing the axial direction. The cylindrical portion has an outer sidewall surface (16a); the second annular wall portion protrudes radially outward from the outer peripheral surface of the cylindrical portion at least at one end of the cylindrical portion, and is separated from the first annular wall portion axially outward; the annular groove portion is formed between the first annular wall portion and the second annular wall portion, the cylindrical portion having a tube body (24) and tube ends (26a, 26b), wherein the tube body is configured to extend from the sidewall surface of the first annular wall portion at least to the central portion of the cylindrical portion axially; the tube ends extend from the sidewall surface to the tube end face of the cylindrical portion and the outer peripheral surface forms the annular groove. A portion of the cylindrical section, the injection molding method includes a first molding step, a release step, and a second molding step, wherein, in the first molding step, an intermediate molded body (40) is molded by a first main mold (44) and a second main mold (46), and a first sliding mold (48a, 48b), wherein the first main mold and the second main mold are closed in a direction orthogonal to the axial center of the cylindrical section, and the first sliding mold is closed along the axial direction of the cylindrical section relative to at least one end face of the first main mold and the second main mold; the intermediate molded body has the tube body and the first annular wall portion in the resin molded part; In the release process, after the intermediate molded body is formed, the first sliding mold is released from the intermediate molded body along the axial direction of the cylindrical portion; in the second molding process, the second annular wall portion is formed on the outer peripheral surface of the cylindrical portion by the second sliding mold (64a, 64b), the first core mold (66), and the second core mold (68), wherein the second sliding mold is closed relative to the tube end face of the cylindrical portion of the intermediate molded body along the axial direction, and the first core mold and the second core mold are closed in a direction orthogonal to the axial center of the cylindrical portion and are arranged adjacent to the side wall surface.

[0084] In the first molding process, molten resin material (R) is injected from at least one direction 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 sliding mold.

[0085] The resin molded part has a first annular wall portion, a second annular wall portion, and an annular groove portion on one end side and the other end side along the axial direction of the cylindrical portion, respectively. In the first molding process, the intermediate molded body having two first annular wall portions is formed by the first main mold and the second main mold, and two first sliding molds, wherein the two first sliding molds are arranged on both sides of the axial direction of the first main mold and the second main mold. In the second molding process, the two second annular wall portions are formed on the outer peripheral surface of the cylindrical portion by the first main mold and the second main mold, the two second sliding molds arranged on both sides of the axial direction of the cylindrical portion, and the first core mold and the second core mold arranged on both sides of the axial direction of the cylindrical portion.

[0086] An injection molding apparatus is disclosed for molding a tubular resin part by injection molding. In the injection molding apparatus, the resin part has a cylindrical portion, a first annular wall portion, a second annular wall portion, and an annular groove portion. The cylindrical portion extends axially along the resin part and has a tube end face as at least one end face in the axial direction. The first annular wall portion protrudes radially outward from the outer peripheral surface of the cylindrical portion at at least one end face and has a sidewall face facing outward in the axial direction. The second annular wall portion protrudes radially outward from the outer peripheral surface of the cylindrical portion at at least one end face and has a sidewall face facing outward in the axial direction. 1. An annular wall portion is separated from the outer side of the axial direction; an annular groove portion is formed between the first annular wall portion and the second annular wall portion; the cylindrical portion has a tube body and a tube end portion, wherein the tube body is configured to extend from the side wall surface of the first annular wall portion at least to the central portion of the cylindrical portion in the axial direction; the tube end portion extends from the side wall surface to the tube end face of the cylindrical portion and its outer peripheral surface forms part of the annular groove portion; the injection molding apparatus includes a primary molding die (34) and a secondary molding die (36), wherein the primary molding die has a first cavity inside for molding an intermediate molded body having The cylindrical portion and the first annular wall portion of the resin molded part; the secondary molding mold has a second cavity (C2) inside for forming the second annular wall portion on the outer peripheral surface of the cylindrical portion of the intermediate molded body; the primary molding mold has a first main mold and a second main mold, and a first sliding mold, wherein the first main mold and the second main mold are closed in a direction orthogonal to the axial center of the cylindrical portion to form the outer peripheral surface of the tube body, the outer peripheral surface of the first annular wall portion, and the wall surface (16b) in the first annular wall portion connecting the outer peripheral surface of the tube body and the outer peripheral surface of the first annular wall portion; the first A sliding mold is closed relative to at least one end face of the first main mold and the second main mold along the axial direction of the cylindrical portion to form the side wall surface of the first annular wall portion and the tube end. The secondary forming mold has a second sliding mold, a first core mold, and a second core mold. The second sliding mold is closed relative to the tube end face of the cylindrical portion of the intermediate forming body to form the second annular wall portion. The first core mold and the second core mold are closed on the outer peripheral surface of the tube end of the intermediate forming body in a direction orthogonal to the axial center of the cylindrical portion and are arranged adjacent to the side wall surface of the first annular wall portion.

[0087] At least one of the first main mold and the second main mold has a flow channel (54) for injecting molten resin material into a first cavity formed by the first main mold, the second main mold and the first sliding mold.

[0088] The resin molded part has a first annular wall portion, a second annular wall portion, and an annular groove portion on one end side and the other end side of the cylindrical portion along the axial direction, respectively. The primary molding die forms the intermediate molded body having two first annular wall portions by means of the first main mold and the second main mold, and two first sliding molds disposed on both sides of the first main mold and the second main mold along the axial direction. The secondary molding die forms two second annular wall portions on the outer peripheral surface of the cylindrical portion by means of the first main mold and the second main mold, two second sliding molds, and the first core mold and the second core mold, wherein the two second sliding molds are disposed on both sides of the cylindrical portion along the axial direction, and the first core mold and the second core mold are disposed on both sides of the cylindrical portion along the axial direction.

[0089] Furthermore, the present invention is not limited to the above description, and various structures may be adopted without departing from the spirit of the present invention.

Claims

1. A method for injection molding a resin molded part, wherein the method forms a tubular resin molded part (12) by injection molding, characterized in that, The resin molded part has a cylindrical portion (14), a first annular wall portion (16), a second annular wall portion (18), and an annular groove portion (20), wherein, The cylindrical portion extends along the axial direction of the resin molded part and has a tube end face (14a, 14b) as an end face of at least one end side in the axial direction. The first annular wall portion protrudes radially outward from the outer peripheral surface (24a) of the cylindrical portion at least at one end side, and has a side wall surface (16a) facing outward toward the axial direction; The second annular wall portion protrudes radially outward from the outer peripheral surface of the cylindrical portion at at least one end side of the cylindrical portion, and is separately disposed from the first annular wall portion outward in the axial direction; The annular groove is formed between the first annular wall portion and the second annular wall portion. The cylindrical portion has a tube body (24) and tube ends (26a, 26b), wherein the tube body is configured to extend from the side wall surface of the first annular wall portion to at least the central portion of the cylindrical portion along the axial direction; the tube ends extend from the side wall surface to the tube end face of the cylindrical portion and their outer peripheral surfaces form part of the annular groove portion. The injection molding method includes a first molding step, a release step, and a second molding step, wherein, In the first molding process, an intermediate molded body (40) is formed by a first main mold (44), a second main mold (46), and a first sliding mold (48a, 48b), wherein the first main mold and the second main mold are closed in a direction orthogonal to the axial center of the cylindrical portion, and the first sliding mold is closed along the axial direction of the cylindrical portion relative to at least one end face of the first main mold and the second main mold; the intermediate molded body has the tube body of the resin molded part and the first annular wall portion; In the separation process, after the intermediate molded body is formed, the first sliding mold is separated from the intermediate molded body along the axial direction of the cylindrical portion; In the second forming process, the second annular wall portion is formed on the outer peripheral surface of the cylindrical portion by the second sliding mold (64a, 64b), the first core mold (66), and the second core mold (68). The second sliding mold closes relative to the tube end face of the cylindrical portion of the intermediate molded body along the axial direction. The first core mold and the second core mold close in a direction orthogonal to the axial center of the cylindrical portion and are arranged adjacent to the side wall surface.

2. The injection molding method for resin molded parts according to claim 1, characterized in that, In the first molding process, molten resin material (R) is injected from at least one direction 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 sliding mold.

3. The injection molding method for resin molded parts according to claim 1, characterized in that, The resin molded part has a first annular wall portion, a second annular wall portion, and an annular groove portion on one end side and the other end side along the axial direction of the cylindrical portion, respectively. In the first molding process, the intermediate molded body having two first annular wall portions is formed by the first main mold, the second main mold, and the two first sliding molds, wherein the two first sliding molds are arranged on both sides of the first main mold and the second main mold. In the second forming process, two second annular wall portions are formed on the outer circumferential surface of the cylindrical portion by means of the first main mold and the second main mold, the two second sliding molds, and the first core mold and the second core mold. The two second sliding molds are arranged on both sides of the axial direction of the cylindrical portion, and the first core mold and the second core mold are arranged on both sides of the axial direction of the cylindrical portion.

4. An injection molding apparatus for molding tubular resin parts by injection molding, characterized in that, The resin molded part has a cylindrical portion, a first annular wall portion, a second annular wall portion, and an annular groove portion, wherein, The cylindrical portion extends along the axial direction of the resin molded part and has a tube end face as an end face of at least one end side in the axial direction. The first annular wall portion protrudes radially outward from the outer peripheral surface of the cylindrical portion at at least one end side of the cylindrical portion, and has a side wall surface facing outward toward the axial direction; The second annular wall portion protrudes radially outward from the outer peripheral surface of the cylindrical portion at at least one end side of the cylindrical portion, and is separately disposed from the first annular wall portion outward in the axial direction; The annular groove is formed between the first annular wall portion and the second annular wall portion. The cylindrical portion has a tube body and a tube end, wherein the tube body is configured to extend from the side wall surface of the first annular wall portion to at least the central portion along the axial direction of the cylindrical portion; the tube end extends from the side wall surface to the tube end face of the cylindrical portion and its outer peripheral surface forms part of the annular groove portion. The injection molding apparatus includes a primary molding die (34) and a secondary molding die (36), wherein, The primary molding die has a first cavity inside for molding an intermediate molded body, which has the cylindrical portion and the first annular wall portion of the resin molded part. The secondary molding die has a second cavity (C2) inside, used to form the second annular wall portion on the outer peripheral surface of the cylindrical portion of the intermediate molded body. The one-time forming mold has a first main mold and a second main mold, and a first sliding mold, wherein the first main mold and the second main mold are closed in a direction orthogonal to the axial center of the cylindrical part to form the outer peripheral surface of the tube body, the outer peripheral surface of the first annular wall part, and the wall surface (16b) in the first annular wall part that connects the outer peripheral surface of the tube body and the outer peripheral surface of the first annular wall part; The first sliding mold closes relative to at least one end face of the first main mold and the second main mold along the axial direction of the cylindrical portion to form the side wall surface of the first annular wall portion and the tube end. The secondary molding die includes a second sliding die, a first core die, and a second core die, wherein... The second sliding mold closes relative to the tube end face of the cylindrical portion of the intermediate molded body to form the second annular wall portion; The first core mold and the second core mold are closed on the outer peripheral surface of the tube end of the intermediate molded body in a direction orthogonal to the axial center of the cylindrical part, and are arranged adjacent to the side wall surface of the first annular wall part.

5. The injection molding apparatus according to claim 4, characterized in that, At least one of the first main mold and the second main mold has a flow channel (54) for injecting molten resin material into the first cavity formed by the first main mold, the second main mold and the first sliding mold.

6. The injection molding apparatus according to claim 4, characterized in that, The resin molded part has a first annular wall portion, a second annular wall portion, and an annular groove portion on one end side and the other end side along the axial direction of the cylindrical portion, respectively. The primary molding die forms the intermediate molded body having two first annular wall portions using the first main mold, the second main mold, and the two first sliding molds, wherein the two first sliding molds are disposed on opposite sides of the first main mold and the second main mold. The secondary forming mold forms two second annular wall portions on the outer circumferential surface of the cylindrical portion through the first main mold and the second main mold, the two second sliding molds, and the first core mold and the second core mold. The two second sliding molds are arranged on both axial sides of the cylindrical portion, and the first core mold and the second core mold are arranged on both axial sides of the cylindrical portion.

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