Fluid-assisted molding mold

Abstract

To facilitate mold modification and reduce cost and work period required for mold modification.SOLUTION: A mold (10) for gas-assisted molding includes, as a cavity (C), a discard cavity part (Cd) from which excess resin (R) is discharged by injection of pressurized gas (GS) from a molding cavity part (Cm). The discard cavity part includes: a first discard cavity part (Cd1) that connects to one end of the molding cavity part in a longitudinal direction; and a second discard cavity part (Cd2) that is linearly connected to the molding cavity part through the first discard cavity part. A diameter (D1) of the second discard cavity part is larger than a diameter (D2) of the first discard cavity part. An extent of the molding cavity part that includes a portion that connects to the first discard cavity part and the first discard cavity part is constituted by a replaceable nested mold (40).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a mold for fluid-assisted molding. [Background technology]

[0002] Fluid-assisted molding has long been known as a technique for producing hollow resin molded products. In fluid-assisted molding, molten resin is injected into a mold cavity, and then a pressurized fluid such as gas is injected into the resin, forming the resin into a hollow shape and forcing it against the molding surface of the mold to solidify.

[0003] A mold used in fluid-assisted molding has a molding cavity and a sacrificial cavity. The molding cavity is a space in which a tube is molded. The sacrificial cavity is connected to one end of the molding cavity. A method for manufacturing a tube by fluid-assisted molding using such a mold is disclosed in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-53954 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, design requirements for tubes manufactured using fluid-assisted molding have increased, resulting in the creation of longitudinally curved sections and increasingly longer overall tube lengths. This has led to tubes becoming more susceptible to deformation after molding. For this reason, product dimensions must be managed. Tube dimensions are managed by controlling the position of the second open end, which is the other end of the tube, relative to the first open end, which is the end on the resin inflow side during molding. If the second open end deviates from its designated position due to tube deformation, the mold must be adjusted to account for the tube deformation.

[0006] Mold modifications are made by hollowing out a portion of the mold that will mold the second open end of the tube and then fitting a nested mold for modification into the hollowed-out portion. However, a void cavity is provided on the mold on the extension side of the second open end of the molding cavity. Therefore, the cavity of the nested mold must be connected to the void cavity smoothly and with high precision without any steps. This increases the cost and time required for mold modifications.

[0007] An object of the present invention is to facilitate the modification of a mold and reduce the cost and work time required for modifying the mold. [Means for solving the problem]

[0008] In order to achieve the above object, in the present invention, a part of the molding cavity portion where the mold is modified is made to have a nested structure including a part of the discarded cavity portion, and the nested cavity portion of the nested mold and the discarded cavity portion of the mother mold that form the nested structure are devised so that they can be connected appropriately even if the nested mold is replaced.

[0009] Specifically, the first invention relates to a fluid-assisted molding die for molding a hollow resin molded article having a longitudinal direction by fluid-assisted molding. The fluid-assisted molding die of the first invention has a cavity formed therein when the die is closed, a gate for injecting molten resin into the cavity, and a fluid supply path for injecting pressurized fluid into the resin injected into the cavity. The cavity includes a molding cavity portion for molding the hollow molded article and a sacrificial cavity portion from which excess resin is discharged by injecting the pressurized fluid from the molding cavity portion. The sacrificial cavity portion includes a first sacrificial cavity portion connected to one longitudinal end of the molding cavity portion and a second sacrificial cavity portion linearly communicating with the molding cavity portion via the first sacrificial cavity portion. In a width direction perpendicular to the center line of the sacrificial cavity portion, the dimension of at least the portion of the second sacrificial cavity portion that connects to the first sacrificial cavity portion is larger than the dimension of at least the portion of the first sacrificial cavity portion that connects to the second sacrificial cavity portion. An area including the part of the molding cavity portion that connects to the first sacrificial cavity portion and the first sacrificial cavity portion is formed by a nesting mold that is replaceable with a mother mold that forms the other part of the molding cavity portion.

[0010] A second invention is a fluid-assisted molding mold according to the first invention, wherein the first sacrificial cavity portion and the second sacrificial cavity portion are each cylindrical spaces. In the fluid-assisted molding mold of the second invention, the diameter of the second sacrificial cavity portion is larger than the diameter of the first sacrificial cavity portion.

[0011] The third invention is a mold for fluid-assisted molding according to the second invention, wherein the center line of the first sacrificial cavity portion and the center line of the second sacrificial cavity portion coincide with each other.

[0012] A fourth invention is a mold for fluid-assisted molding according to any one of the first to third inventions, wherein the molding cavity portion includes a curved cavity portion that is curved in the longitudinal direction. [Effects of the Invention]

[0013] In the first invention, a portion of the molding cavity portion connected to the first sacrificial cavity portion and a range including the first sacrificial cavity portion are pre-formed using a nesting mold. The nesting mold is replaceable with a master mold that forms the other portion of the molding cavity portion. Furthermore, the dimension of at least the portion of the second sacrificial cavity portion that connects to the first sacrificial cavity portion in the width direction of the sacrificial cavity portion is larger than the dimension of at least the portion of the first sacrificial cavity portion that connects to the second sacrificial cavity portion. This ensures a margin in the width direction of the sacrificial cavity portion for displacement of the connecting position of the first sacrificial cavity portion relative to the second sacrificial cavity portion. This allows for a smooth, high-precision connection of the first sacrificial cavity portion of the replacement nesting mold to the second sacrificial cavity portion, even if the connecting position of the first sacrificial cavity portion of the replacement nesting mold displaces in the width direction of the sacrificial cavity portion. Therefore, when modifying the mold, the displacement can be tolerated, and the first sacrificial cavity portion can be connected to the second sacrificial cavity portion smoothly and without steps with high precision. Therefore, mold modifications can be easily performed by replacing the nesting mold. As a result, the cost and time required for modifying the mold can be reduced.

[0014] In the second invention, the first sacrificial cavity portion and the second sacrificial cavity portion are each cylindrical spaces. This is advantageous for smoothly flowing the resin discharged from the molding cavity portion into the sacrificial cavity portion. The diameter of the second sacrificial cavity portion is larger than the diameter of the first sacrificial cavity portion. This ensures the margin for displacement of the connecting position of the first sacrificial cavity portion in all directions perpendicular to the center line of the sacrificial cavity portion. Therefore, even if the connecting position of the first sacrificial cavity portion is displaced in any width direction of the sacrificial cavity portion due to mold correction, the first sacrificial cavity portion and the second sacrificial cavity portion can be connected smoothly and with high precision without any steps.

[0015] In the third aspect of the present invention, the center line of the first sacrificial cavity portion and the center line of the second sacrificial cavity portion coincide with each other. This ensures a similar margin for displacement of the joining position of the first sacrificial cavity portion relative to the second sacrificial cavity portion in all directions perpendicular to the center line of the sacrificial cavity portion. This is advantageous for joining the first sacrificial cavity portion and the second sacrificial cavity portion smoothly and with high precision without any steps.

[0016] In a fourth aspect of the present invention, the molding cavity includes a curved cavity that is curved in the longitudinal direction. A hollow molded product molded using such a molding cavity has a curved portion molded in the curved cavity. A tube having a curved portion is prone to deformation after molding. Therefore, the present invention is effective in a mold for fluid-assisted molding that includes a curved cavity as the molding cavity. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a gas-assisted molding apparatus according to an embodiment. [Figure 2] FIG. 2 is an exploded perspective view illustrating a schematic configuration of a mold for gas-assisted molding according to an embodiment. [Figure 3] 3 is a plan view illustrating a schematic configuration of a mold according to an embodiment, in which the cavity and the insert mold are shown in a see-through manner. [Figure 4] FIG. 4 is a diagram illustrating a connecting position of the first sacrificial cavity portion of the initial nesting mold to the second sacrificial cavity portion of the mold according to the embodiment. [Figure 5A] FIG. 6A is a view equivalent to FIG. 3, conceptually illustrating a state in which a resin is injected and filled into a cavity of a mold in the manufacturing method of a tube body according to the embodiment. [Figure 5B] FIG. 6B is a view equivalent to FIG. 3, conceptually illustrating a state in which pressurized gas is injected into the resin in the manufacturing method of the tubular body according to the embodiment. [Figure 5C]FIG. 6C is a view corresponding to FIG. 3, conceptually illustrating a state in which a hollow portion is formed in the resin in the cavity in the manufacturing method of the tubular body according to the embodiment. [Figure 6] FIG. 6 is a perspective view illustrating a state in which the tube is demolded in the tube manufacturing method according to the embodiment. [Figure 7] FIG. 7 is a plan view illustrating a schematic configuration of a tube formed by the mold of the embodiment. [Figure 8] FIG. 8 is a plan view illustrating a main part of the mold according to the embodiment after modification. [Figure 9] FIG. 9 is a diagram illustrating a connecting position of the first sacrificial cavity portion relative to the second sacrificial cavity portion when the mold of the embodiment is corrected. [Figure 10] FIG. 10 is a plan view illustrating an example of a state in which the pipe body is deformed after molding. [Figure 11] FIG. 11 is a conceptual diagram illustrating a state in which the second open end is displaced due to deformation of the tube body and the molding position of the second open end after the mold is corrected. DETAILED DESCRIPTION OF THE INVENTION

[0018] Exemplary embodiments will be described in detail below with reference to the drawings. In the following embodiments, a mold according to the present invention will be described using a mold for gas-assisted molding as an example. The drawings are intended to conceptually explain the present invention. Therefore, in the drawings, dimensions, ratios, or numbers may be exaggerated or simplified to facilitate understanding of the present invention. Furthermore, the terms "first," "second," "third," etc. described below are used to distinguish between terms to which these terms are attached, and do not limit the number or order of the terms.

[0019] The mold 10 of this embodiment is a mold for molding a tubular body 100 by gas-assist molding. Gas-assist molding is an example of fluid-assist molding, also known as gas injection molding. In gas-assist molding, gas is used as the pressurized fluid. The tubular body 100 is a hollow molded product made of resin and has a longitudinal direction. The tubular body 100 is, for example, a water pipe through which engine cooling water flows.

[0020] -Tube structure- As shown in FIG. 7, the pipe 100 is a cylindrical pipe having a hollow portion 102 for circulating cooling water. The pipe 100 is made of, for example, a thermoplastic resin. Examples of thermoplastic resins used for the pipe 100 include polyamide resins (PA) such as nylon 6 and nylon 66, polyphenylene sulfide (PPS), and polypropylene (PP). Openings at both ends of the pipe 100 face in opposite directions. Center lines CL1 and CL2 of the openings at both ends of the pipe 100 are not aligned in a straight line.

[0021] The tubular body 100 includes a first straight pipe section 104, a first bent pipe section 106, a second straight pipe section 108, a second bent pipe section 110, and a third straight pipe section 112. The first straight pipe section 104, the first bent pipe section 106, the second straight pipe section 108, the second bent pipe section 110, and the third straight pipe section 112 are integrally molded. The hollow section 102 is provided continuous with the first straight pipe section 104, the first bent pipe section 106, the second straight pipe section 108, the second bent pipe section 110, and the third straight pipe section 112.

[0022] The first straight pipe section 104 extends linearly in the first direction X. One end of the first straight pipe section 104 forms a first open end 105 of the pipe body 100. One end of the first bent pipe section 106 is connected to the other end of the first straight pipe section 104. One end of the first bent pipe section 106 curves from the other end of the first straight pipe section 104 in a second direction Y that is perpendicular to the first direction X. One end of the second straight pipe section 108 is connected to the other end of the first bent pipe section 106. The second straight pipe section 108 extends linearly in the second direction Y.

[0023] One end of the second curved pipe section 110 is connected to the other end of the second straight pipe section 108. The second curved pipe section 110 bends in the first direction X from the other end of the second straight pipe section 108. The second curved pipe section 110 forms a convex surface on the side opposite to the first curved pipe section 106. One end of the third straight pipe section 112 is connected to the other end of the second curved pipe section 110. The third straight pipe section 112 extends linearly in the first direction X. The other end of the third straight pipe section 112 forms a second open end 113 of the pipe body 100.

[0024] - Mold for gas-assisted molding - The tubular body 100 having the above configuration is manufactured using a mold 10 for gas-assist molding. Gas-assist molding is a method that can improve quality by reducing defective products and reduce costs by cutting material costs. The mold 10 in this example constitutes a gas-assist molding apparatus 1 as shown in FIG. 1. The gas-assist molding apparatus 1 includes a resin injector 3, a gas supplier 5, and a mold 10.

[0025] The resin injector 3 heats and melts the resin R, which is the molding material. The resin injector 3 injects the molten resin R into the cavity C in the mold 10 via the sprue 12, runner 14, and gate 16. The gas supplier 5 injects pressurized gas GS, which serves as a pressurized fluid, into the cavity C in the mold 10 at a predetermined pressure via the gas supply path 18. In the gas-assisted molding apparatus 1 of this example, an inert gas such as nitrogen gas is used as the pressurized gas GS. As also shown in FIG. 2, the mold 10 includes a fixed mold 20 and a movable mold 30.

[0026] The mold 10 forms a cavity C between the fixed mold 20 and the movable mold 30 by closing the mold 10 and the cavity C between the two molds 20, 30. That is, the mold 10 has the cavity C formed therein when the mold is closed. In addition to the cavity C, the mold 10 also has a sprue 12, a runner 14, a gate 16, and a gas supply path 18. The gas supply path 18 is formed in the movable mold 30. The gas supply path 18 is a passage for injecting pressurized gas GS into the resin R injected into the cavity C. The gas supply path 18 is an example of a fluid supply path. The gas supply path 18 opens into the cavity C (strictly speaking, into the introduction cavity portion Ci) (see Figure 3).

[0027] A sprue 12 is formed in the fixed mold 20. The sprue 12 opens on the outer surface of the fixed mold 20. A nozzle of the resin injection machine 3 is connected to the outer surface opening of the sprue 12. The runner 14 is connected to the sprue 12. The gate 16 is connected to the runner 14 and opens to the cavity C (strictly speaking, the introduction cavity portion Ci) (see Figure 3). The gate 16 injects molten resin R into the cavity C. The fixed mold 20 has a first molding surface 22. The first molding surface 22 molds one radial surface of the tube body 100, for example, one half of the outer peripheral surface.

[0028] The movable mold 30 has a second molding surface 32. The second molding surface 32 molds the other mold surface in the radial direction of the tube 100, for example, one half of the outer peripheral surface. The movable mold 30 moves toward and away from the fixed mold 20 by a movement mechanism (not shown). The mold 10 is closed by moving the movable mold 30 toward the fixed mold 20. The mold 10 is opened by moving the movable mold 30 away from the fixed mold 20. The movable mold 30 is provided with a plurality of ejector pins (not shown).

[0029] As shown in FIG. 3, the mold 10 in the closed state includes a cavity C consisting of a molding cavity portion Cm, an introduction cavity portion Ci, and a waste cavity portion Cd.

[0030] The molding cavity Cm is a hollow for molding the tube 100. The molding cavity Cm is formed in a crank-shaped space with an extent corresponding to the outer shape of the tube 100. The molding cavity Cm is defined by the first molding surface 22 of the fixed mold 20 and the second molding surface 32 of the movable mold 30. The molding cavity Cm includes a first straight portion Cm1, a first curved portion Cm2, a second straight portion Cm3, a second curved portion Cm4, and a third straight portion Cm5.

[0031] The first straight portion Cm1 is a cavity that forms the first straight pipe portion 104 of the pipe 100. The first straight portion Cm1 consists of a cylindrical space that extends linearly in the first direction X. The first curved portion Cm2 is a cavity that forms the first curved pipe portion 106 of the pipe 100. The first curved portion Cm2 consists of a cylindrical space that is curved in the longitudinal direction of the molding cavity portion Cm. The second straight portion Cm3 is a cavity that forms the second straight pipe portion 108 of the pipe 100. The second straight portion Cm3 consists of a cylindrical space that extends linearly in the second direction Y.

[0032] The second curved portion Cm4 is a cavity that forms the second curved pipe portion 110 of the pipe 100. The second curved portion Cm4 is a cylindrical space that is curved on the opposite side to the first curved portion Cm2 in the longitudinal direction of the molding cavity portion Cm. The third straight portion Cm5 is a cavity that forms the third straight pipe portion 112 of the pipe 100. The third straight portion Cm5 is a cylindrical space that extends linearly in the first direction X. The first curved portion Cm2 and the second curved portion Cm4 are each an example of a curved cavity portion.

[0033] The introduction cavity Ci is a hollow cavity that serves as a path for introducing the molten resin R and pressurized gas GS into the molding cavity Cm. The introduction cavity Ci is connected to one longitudinal end of the molding cavity Cm. The part of the molding cavity Cm where the introduction cavity Ci is connected is the first straight section Cm1. The introduction cavity Ci is linearly connected to the first straight section Cm1. A gate 16 and a gas supply path 18 open into the introduction cavity Ci. The opening of the gate 16 is located on the outer circumferential surface of the wall defining the introduction cavity Ci.

[0034] As shown in FIG. 2, the movable mold 30 is provided with a block-shaped protrusion 34 that protrudes toward the fixed mold 20. The protrusion 34 constitutes the portion of the wall surface that defines the introduction cavity portion Ci on the opposite side from the molding cavity portion Cm. The gas supply path 18 is provided in the protrusion 34. The opening of the gas supply path 18 is located at a position on the wall surface of the protrusion 34 that faces the introduction cavity portion Ci, corresponding to the opening of the first straight pipe portion 104. The fixed mold 20 is provided with a recess 24 in a portion that corresponds to the protrusion 34. The recess 24 fits into the protrusion 34 when the mold 10 is closed.

[0035] The sacrificial cavity portion Cd is a hollow into which excess resin R is discharged by injecting pressurized gas GS from the molding cavity portion Cm. The sacrificial cavity portion Cd in this example is made up of a combination of cylindrical spaces with different diameters.

[0036] Specifically, as shown in FIG. 3, the sacrificial cavity portion Cd includes a first sacrificial cavity portion Cd1 and a second sacrificial cavity portion Cd2. The first sacrificial cavity portion Cd1 is connected to one longitudinal end of the molding cavity portion Cm. The portion of the molding cavity portion Cm that is connected to the first sacrificial cavity portion Cd1 is a third straight portion Cm5. The first sacrificial cavity portion Cd1 is linearly connected to the third straight portion Cm5. The second sacrificial cavity portion Cd2 is linearly connected to the third straight portion Cm5 via the first sacrificial cavity portion Cd1.

[0037] In this example, the first sacrificial cavity portion Cd1 and the second sacrificial cavity portion Cd2 are each a cylindrical space. The first sacrificial cavity portion Cd1 and the second sacrificial cavity portion Cd2 are each formed to have the same diameter throughout. As shown in Figure 4, the diameter D2 of the second sacrificial cavity portion Cd2 is larger than the diameter D1 of the first sacrificial cavity portion Cd1. For example, the diameter D2 of the second sacrificial cavity portion Cd2 is set to be 1.3 to 1.8 times the diameter D1 of the first sacrificial cavity portion Cd1.

[0038] Thus, in the width direction perpendicular to the center line CL3 of the sacrificial cavity portion Cd, the dimension of the portion of the second sacrificial cavity portion Cd2 that connects to the first sacrificial cavity portion Cd1 is larger than the dimension of the portion of the first sacrificial cavity portion Cd1 that connects to the second sacrificial cavity portion Cd2. The diameter D2 of the second sacrificial cavity portion Cd2 is preferably larger than the diameter D1 of the first sacrificial cavity portion Cd1 by 6 mm or more and 20 mm or less. In this case, the step between the first sacrificial cavity portion Cd1 and the second sacrificial cavity portion Cd2 is 3 mm or more and 10 mm or less.

[0039] The first sacrificial cavity portion Cd1 and the second sacrificial cavity portion Cd2 extend linearly so that the center lines CL4, CL5, and CL6 coincide with the third straight portion Cm5. The center line CL4 of the first sacrificial cavity portion Cd1 and the center line CL5 of the second sacrificial cavity portion Cd2 coincide with each other. The initial joining position of the first sacrificial cavity portion Cd1 to the second sacrificial cavity portion Cd2 is set to the center position of the second sacrificial cavity portion Cd2 (see FIG. 4). In the mold 10 of this example, a margin is provided in the radial direction of the sacrificial cavity portion Cd to allow for displacement of the joining position of the first sacrificial cavity portion Cd2 to the second sacrificial cavity portion Cd2.

[0040] The mold 10 has a nesting structure that is used to correct a predetermined target portion of the molding cavity portion Cm. In this example, the target portion of the mold 10 to be corrected is a portion including the third straight portion Cm5. Specifically, in the mold 10, a portion of the molding cavity portion Cm that connects to the first sacrificial cavity portion Cd1 and an area including the first sacrificial cavity portion Cd1 are formed by a nesting mold 40. The nesting mold 40 is replaceable with a mother mold 50 that forms the other portion of the molding cavity portion Cm.

[0041] As shown in FIG. 2, a nesting mold 40 is provided in each of the fixed mold 20 and the movable mold 30. Corresponding portions of the fixed mold 20 and the movable mold 30 are constituted by the nesting mold 40. That is, the mold 10 has a pair of nesting molds 40. The nesting molds 40 are made of split blocks. Each of the nesting molds 40 of the fixed mold 20 and the movable mold 30 constitutes a range that includes the third straight portion Cm5, the second curved portion Cm4, and part of the second straight portion Cm3 of the molding cavity portion Cm, as well as the first sacrificial cavity portion Cd1.

[0042] Each of the mother dies 50 of the fixed die 20 and the movable die 30 forms the first straight portion Cm1, the first curved portion Cm2, the second straight portion Cm3, and the remaining portion of the molding cavity portion Cm, as well as the introduction cavity portion Ci. In each of the mother dies 50, a fitting recess 52 is provided in the range where the nesting die 40 forms the cavity C. The nesting die 40 is fitted into the fitting recess 52. The nesting die 40 is fixed to the mother die 50 using fasteners such as bolts.

[0043] -Tube body manufacturing method- The manufacturing method of the tube 100 includes a preparation step, a resin injection step, a fluid assist step, and a demolding step.

[0044] First, a preparation step is performed. In the preparation step, the gas-assisted molding apparatus 1 described above is prepared. Then, the mold 10 is closed to form the cavity C. Furthermore, pressure is applied to the closed mold 10 to clamp it.

[0045] Next, a resin injection step is performed. In the resin injection step, the resin injector 3 is driven to inject molten resin R into the cavity C of the mold 10 through the gate 16. At this time, the resin R is injected into the introduction cavity portion Ci. The injected resin R flows from the introduction cavity portion Ci through the first straight portion Cm1, the first curved portion Cm2, the second straight portion Cm3, and the second curved portion Cm4, and then into the third straight portion Cm5. Then, as shown in FIG. 5A, the resin R is spread throughout the entire molding cavity portion Cm, filling a portion of the cavity C with the resin R. The filling speed of the resin R is set to reduce variations in the appearance, function, shape, and weight of the tube 100.

[0046] Next, a fluid assist step is performed. In the fluid assist step, the gas supplier 5 is driven to inject pressurized gas GS (inert gas) into the resin R in the molding cavity portion Cm. As a result, as shown in FIG. 5B, the resin R is pressurized on the first molding surface 22 and the second molding surface 32, while the excess resin R is extruded into the waste cavity portion Cd, forming a hollow portion 102 in the resin R in the molding cavity portion Cm. In this example, the fluid assist step is performed after the completion of the injection and filling of the resin R into the molding cavity portion Cm in the resin injection step. The fluid assist step may also be performed while the injection and filling of the resin R into the molding cavity portion Cm is in progress.

[0047] At this time, the pressurized gas GS is injected into the introduction cavity portion Ci. The injected pressurized gas GS flows from the introduction cavity portion Ci through the first straight portion Cm1, the first curved portion Cm2, the second straight portion Cm3, and the second curved portion Cm4, and then into the third straight portion Cm5. In the fluid assist step, as shown in FIG. 5C, the pressurized gas GS is injected so as to reach a portion of the sacrificial cavity portion Cd. After the pressurized gas GS is injected, the pressure applied to the resin R by the pressurized gas GS is maintained for a predetermined time. The resin R with the hollow portion 102 formed therein is solidified by cooling within the cavity C of the mold 10. This results in the molding of a molded product 200 including a tubular body 100.

[0048] Thereafter, a demolding step is performed. In the demolding step, the mold 10 is opened and the movable mold 30 is separated from the fixed mold 20. When the mold 10 is opened, the molded article 200 remains on the second molding surface 32 of the movable mold 30. In the demolding step, an ejector pin is protruded from the movable mold 30 to lift the molded article 200 from the second molding surface 32. Then, as shown in FIG. 6, the molded article 200 is removed from the mold 10. Thereafter, the excess solid material 202 and the gate residue 204 in the introduction cavity portion Ci and the waste cavity portion Cd of the molded article 200 are cut away.

[0049] In this manner, the tube 100 can be manufactured as a hollow molded product.

[0050] -Mold Modification- The tube 100 undergoes deformation after molding. The dimensions of the tube 100 are controlled so that the dimensions (dimensions in each direction, including length L and width W) after deformation fall within tolerances. The dimensions of the tube 100 are controlled by inspecting and controlling the position Pi of the second open end 113 of the tube 100, with the first open end 105 of the tube 100 set as the reference position Pr (see FIG. 7). If the dimensions of the tube 100 do not fall within the tolerances as a result of the dimensional inspection of the tube 100, the mold 10 must be modified to adjust the dimensions of the tube 100.

[0051] For example, as shown in Fig. 10, if deformation occurs in the tube 100 such that the second opening end 113 is displaced in a direction toward the first curved tube section 106, the position Pi of the second opening end 113 will deviate from the designed normal position Pd in ​​the first direction X and the second direction Y. Furthermore, as shown by the solid line in Fig. 11, the position Pi of the second opening end 113 will also deviate from the normal position Pd in ​​a third direction Z that is perpendicular to the first direction X and the second direction Y. In this case, the mold 10 is modified to take into account the deformation of the tube 100.

[0052] The mold 10 is corrected by replacing the nesting dies 40 of the fixed die 20 and the movable die 30. Specifically, the target nesting dies 40 (nesting dies 40 having molding surfaces 42 shown by two-dot chain lines in FIG. 8) attached to the fixed die 20 and the movable die 30 are removed from the matrix 50, and a correcting nesting die 40 (nesting dies 40 having molding surfaces 42 shown by solid lines in FIG. 8) is attached to the matrix 50 in place of the target nesting dies 40. As shown in FIG. 8, the correcting nesting die 40 has a molding surface 42 (first molding surface 22 or second molding surface 32) that molds the second opening end 113 of the tube 100 so that the position Pi of the second opening end 113 is displaced to a correction position Pc (position shown by two-dot chain lines in FIG. 11) opposite to the direction of deformation.

[0053] When the mold 10 is modified in this manner, the connecting portion of the first sacrificial cavity portion Cd1 is displaced relative to the connecting portion of the second sacrificial cavity portion Cd2, as shown in Figure 9. However, because the diameter D2 of the second sacrificial cavity portion Cd2 is larger than the diameter D1 of the first sacrificial cavity portion Cd1, the displacement of the connecting portion of the first sacrificial cavity portion Cd1 can be tolerated, and the first sacrificial cavity portion Cd1 and the second sacrificial cavity portion Cd2 can be easily connected without forming a step between them. Then, by molding the tube 100 using the modified mold 10, the tube 100 can be molded so that the dimensions after deformation fall within the tolerances.

[0054] -Features of the embodiment- In the mold 10 of this embodiment, a portion of the molding cavity portion Cm that is connected to the first sacrificial cavity portion Cd1 and an area that includes the first sacrificial cavity portion Cd1 are pre-configured using a nesting mold 40. The nesting mold 40 is replaceable with a master mold 50 that configures the other portion of the molding cavity portion Cm. In addition, in the width direction of the sacrificial cavity portion Cd, the dimension of the portion of the second sacrificial cavity portion Cd2 that is connected to the first sacrificial cavity portion Cd1 is larger than the dimension of the portion of the first sacrificial cavity portion Cd1 that is connected to the second sacrificial cavity portion Cd2. This ensures a margin in the width direction of the sacrificial cavity portion Cd for displacement of the connecting position of the first sacrificial cavity portion Cd1 relative to the second sacrificial cavity portion Cd2. As a result, even if the connecting position of the first sacrificial cavity portion Cd1 of the replacement nesting die 40 is displaced in the width direction of the sacrificial cavity portion Cd when correcting the mold 10, the displacement can be tolerated and the first sacrificial cavity portion Cd1 can be connected to the second sacrificial cavity portion Cd2 smoothly and with high precision without any steps. Therefore, the mold 10 can be easily corrected by replacing the nesting die 40. As a result, the cost and work time required for correcting the mold 10 can be reduced.

[0055] In the mold 10 of this embodiment, the first sacrificial cavity portion Cd1 and the second sacrificial cavity portion Cd2 are each cylindrical. This is advantageous for smoothly flowing the resin R discharged from the molding cavity portion Cm into the sacrificial cavity portion Cd. The diameter D2 of the second sacrificial cavity portion Cd2 is larger than the diameter D1 of the first sacrificial cavity portion Cd1. This ensures the margin for displacement of the connecting position of the first sacrificial cavity portion Cd1 in all directions perpendicular to the center line CL3 of the sacrificial cavity portion Cd. Therefore, even if the connecting position of the first sacrificial cavity portion Cd1 is displaced in any width direction of the sacrificial cavity portion Cd due to correction of the mold 10, the first sacrificial cavity portion Cd1 and the second sacrificial cavity portion Cd2 can be connected smoothly and with high precision without any steps.

[0056] In the mold 10 of this embodiment, the center line CL4 of the first sacrificial cavity portion Cd1 and the center line CL5 of the second sacrificial cavity portion Cd2 are aligned with each other. This ensures a similar margin for displacement of the joining position of the first sacrificial cavity portion Cd1 relative to the second sacrificial cavity portion Cd2 in all directions perpendicular to the center line CL3 of the sacrificial cavity portions Cd. This is advantageous for joining the first sacrificial cavity portion Cd1 and the second sacrificial cavity portion Cd2 smoothly and with high precision without any steps.

[0057] In the mold 10 of this embodiment, the molding cavity Cm includes a first curved portion Cm2 and a second curved portion Cm4 that are curved in the longitudinal direction. A tube 100 molded with such a molding cavity Cm is provided with a first curved pipe portion 106 formed at the first curved portion Cm2 and a second curved pipe portion 110 formed at the second curved portion Cm4. A tube 100 having the first curved pipe portion 106 and the second curved pipe portion 110 is prone to deformation after molding. Therefore, the mold 10 of this embodiment is effective as a mold 10 for gas-assisted molding in which the molding cavity Cm includes the first curved portion Cm2 and the second curved portion Cm4.

[0058] As described above, preferred embodiments have been described as examples of the present invention. However, the present invention is not limited to these, and can be applied to embodiments in which appropriate modifications, substitutions, additions, omissions, etc. are made. It will be understood by those skilled in the art that the above-described embodiments are examples, and that various modifications are possible in the combinations of the respective components and processing processes, and that such modifications also fall within the scope of the present invention.

[0059] For example, in the above embodiment, each nesting mold 40 of the fixed mold 20 and the movable mold 30 defines a range that includes the third straight portion Cm5 to a portion of the second straight portion Cm3 of the molding cavity portion Cm and the first sacrificial cavity portion Cd1, but this is not limited to this. Each nesting mold 40 may define a range that includes only a portion or all of the third straight portion Cm5 and the first sacrificial cavity portion Cd1. The range defined by each nesting mold 40 in the mold can be set arbitrarily as long as it includes the first sacrificial cavity portion Cd1 and a portion of the molding cavity portion Cm that is connected to the first sacrificial cavity portion Cd1.

[0060] In the above embodiment, the first sacrificial cavity portion Cd1 and the second sacrificial cavity portion Cd2 are formed with the same diameter throughout, but this is not limited to this. The diameters D1, D2 of the first sacrificial cavity portion Cd1 and the second sacrificial cavity portion Cd2 may vary in the longitudinal direction of the sacrificial cavity portion Cd. The first sacrificial cavity portion Cd1 and the second sacrificial cavity portion Cd2 may be spaces having other expanding shapes, such as a rectangular column. In short, it is sufficient that the dimension of at least the portion of the second sacrificial cavity portion Cd2 connected to the first sacrificial cavity portion Cd1 in the width direction perpendicular to the center line CL3 of the sacrificial cavity portion Cd is larger than the dimension of at least the portion of the first sacrificial cavity portion Cd1 connected to the second sacrificial cavity portion Cd2.

[0061] In the above embodiment, the mold according to the present invention has been described using the mold 10 for gas-assisted molding as an example, but the present invention is not limited to this. The mold 10 for gas-assisted molding is merely one example of a specific embodiment of the mold according to the present invention, and the present invention is also applicable to molds used in other fluid-assisted molding processes that use a pressurized fluid other than gas, such as water-assisted molding, which uses a liquid such as water as the pressurized fluid.

[0062] In the above embodiment, the pipe body 100 is used as a water pipe, but the present invention is not limited to this. The mold according to the present invention can be used to mold any part, such as a pipe for carrying blow-by gas or EGR (Exhaust Gas Recirculation) gas, as long as it is a hollow resin molded product having a longitudinal direction. [Industrial Applicability]

[0063] As described above, the present invention is useful for a mold for fluid-assisted molding. [Explanation of symbols]

[0064] C cavity Cd void cavity Cd1 First sacrificial cavity Cd2 Second sacrificial cavity Cm Molding cavity GS Pressurized gas (pressurized fluid) R resin 10. Mold 16 Gates 18 Gas supply path (fluid supply path) 40 Nested 50 matrix 100 Tube body (hollow molded product)

Claims

1. A fluid-assisted molding die for molding a hollow resin molded product (100) having a longitudinal direction by fluid-assisted molding, A cavity (C) is formed inside the mold when it is closed. a gate (16) for injecting molten resin (R) into the cavity (C); a fluid supply path (18) for injecting a pressurized fluid (GS) into the resin (R) injected into the cavity (C), The cavity (C) includes a molding cavity portion (Cm) for molding the hollow molded product (100) and a waste cavity portion (Cd) from which an excess of the resin (R) is discharged by injecting the pressurized fluid (GS) from the molding cavity portion (Cm), the sacrificial cavity portion (Cd) includes a first sacrificial cavity portion (Cd1) connected to one end of the molding cavity portion (Cm) in the longitudinal direction, and a second sacrificial cavity portion (Cd2) linearly communicating with the molding cavity portion (Cm) via the first sacrificial cavity portion (Cd1), In a width direction perpendicular to a center line (CL3) of the sacrificial cavity portion (Cd), a dimension of at least a portion of the second sacrificial cavity portion (Cd2) that is connected to the first sacrificial cavity portion (Cd1) is larger than a dimension of at least a portion of the first sacrificial cavity portion (Cd1) that is connected to the second sacrificial cavity portion (Cd2); A part of the molding cavity portion (Cm) that is connected to the first sacrificial cavity portion (Cd1) and a range including the first sacrificial cavity portion (Cd1) are constituted by a nesting mold (40) that is replaceable with a mother mold (50) that constitutes the other part of the molding cavity portion (Cm). A mold for fluid-assisted molding.

2. The fluid-assisted molding die according to claim 1, the first sacrificial cavity portion (Cd1) and the second sacrificial cavity portion (Cd2) are each a cylindrical space, The diameter (D2) of the second sacrificial cavity portion (Cd2) is larger than the diameter (D1) of the first sacrificial cavity portion (Cd1). A mold for fluid-assisted molding.

3. The fluid-assisted molding die according to claim 2, The center line (CL4) of the first sacrificial cavity portion (Cd1) and the center line (CL5) of the second sacrificial cavity portion (Cd2) coincide with each other. A mold for fluid-assisted molding.

4. The mold for fluid-assisted molding according to any one of claims 1 to 3, The molding cavity portion (Cm) includes curved cavity portions (Cm2, Cm4) curved in the longitudinal direction. A mold for fluid-assisted molding.

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