Method of manufacturing resin pipe

Abstract

To provide a method of manufacturing a resin pipe that enables enhancement of durability and sealability and weight reduction of a nipple with a hose fit over it and swaged.SOLUTION: Between one end 17a of a cavity 17 and a one-end side exhaust cavity 17d is blocked, and molten resin R1 injected from the one end 17a is filled in the cavity 17. After that, a communication channel between the one end 17a and an injection machine 11 is blocked, and the one end 17a and the one-end side exhaust cavity 17d are made to communicate with each other. An assist material As is injected from the other end 17b, to allow a surplus molten resin R1 to be exhausted from the cavity 17 to the one-end side exhaust cavity 17d. Then, the cylindrical molten resin R1 remaining in the cavity 17 is hardened to form a resin pipe 1. At the same time, a fitting protrusion 4b that fits a cutout 6a of a core pipe 5 is formed on a nipple 4 to restrict movement in an axial direction and a circumferential direction of the core pipe 5 fit inside the nipple 4.SELECTED DRAWING: Figure 15

Description

[Technical field]

[0001] The present invention relates to a manufacturing method for a plastic pipe, and more specifically, to a manufacturing method for a plastic pipe that can reduce weight while suppressing deformation of a nipple onto which a hose is fitted and crimped, thereby improving durability and sealing performance. [Background technology]

[0002] Various structures are known in which a pipe body is fitted and fixed to a nipple (see, for example, Patent Documents 1 and 2). Patent Document 1 discloses a structure in which a resin first low-pressure pipe is fitted and fixed to a resin first cylindrical portion (corresponding to a nipple) (paragraphs 0020-0023, Fig. 2, etc.). Patent Document 2 discloses a structure in which a resin tube is fitted and fixed to a press-fit mounting portion (corresponding to a nipple) of a quick connector (paragraph 0013, Fig. 1, etc.).

[0003] In recent years, various studies have been conducted on the use of plastic pipes instead of metal pipes for piping used in vehicles such as automobiles in order to reduce weight. In a plastic pipe having a nipple at the tip, a hose is fitted onto the nipple and crimped. In more detail, after the hose is fitted onto the nipple, the hose fitting fitted onto the tip of the hose is crimped to firmly fix the hose to the nipple. Compared to the metallic nipple of a metal pipe, the plastic nipple of a plastic pipe has low rigidity. Therefore, in a simple plastic pipe, the plastic nipple is easily deformed when the hose is crimped and fixed, and there is a problem that the durability and the sealing property between the hose and the nipple are reduced compared to the nipple of a metal pipe. Therefore, there is room for improvement in reducing the weight while suppressing the deformation of the nipple when the hose is fitted onto the nipple and crimped, thereby improving durability and sealing property. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6714784 [Patent Document 2] JP 2004-263729 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for manufacturing a plastic pipe that can reduce weight while suppressing deformation of a nipple onto which a hose is fitted and crimped, thereby improving durability and sealing performance. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a method for manufacturing a plastic pipe comprising: a cylindrical nipple onto which a hose fitted thereon is crimped; and a metal core tube fitted into the nipple, the metal core tube being disposed in a predetermined range in the longitudinal direction of the nipple including the entire length of the crimping range in which the hose is crimped, the core tube and the nipple being provided with restricting portions for restricting axial and circumferential movement of the core tube relative to the nipple, the nipple and the core tube being integrated at a longitudinal tip, the mold being provided with a cavity having one end and the other end and extending between the one end and the other end to form the plastic pipe, a nipple forming portion set at the other end, and a one-end side discharge cavity extending outside the cavity and capable of communicating with the one end, the nipple forming portion being provided with a cavity for discharging the core tube, and in a state where the communication between the one end and the cavity for discharge on the one end side is blocked and the mold is clamped, molten resin is injected from the one end toward the other end by an injector to fill the cavity with the molten resin, and then the communication path between the one end and the injector is blocked to connect the one end to the cavity for discharge on the one end side, and an assist material is injected from the other end toward the one end to discharge excess molten resin from the cavity into the cavity for discharge on the one end side, thereby hardening the cylindrical molten resin remaining in the cavity to form the resin tube with the hardened resin, and the regulating portion of the nipple is formed to regulate axial and circumferential movement of the core tube relative to the nipple and fit the core tube into the nipple. Effect of the Invention

[0007] According to the present invention, the resin pipe can be manufactured in which the metal core tube is fitted and integrated with the nipple. In the resin pipe, the core tube is fitted in a predetermined range including the entire length of the crimping range in which the hose is crimped in the longitudinal direction of the nipple, so that the rigidity of this crimping range is improved. Therefore, even if the hose is crimped to the nipple, the nipple is suppressed from deforming, so that the durability of the nipple and the sealing performance between the hose and the nipple are improved. The axial and circumferential movements of the core tube relative to the nipple are restricted by the restricting portion, so that the core tube is stably fixed to the nipple, which is more advantageous for improving the durability and sealing performance of the nipple. In addition, since the core tube is integrated in the predetermined range in the longitudinal direction of the resin nipple, the weight of the resin pipe can be reduced compared to the case where the entire nipple is made of metal. [Brief description of the drawings]

[0008] [Figure 1] 1 is an explanatory diagram illustrating a vertical cross-sectional view of a resin pipe manufactured according to the present invention. [Diagram 2] 2 is an explanatory diagram illustrating a state in which the resin pipe in FIG. 1 is rotated 45° around its axis. FIG. [Diagram 3] 2 is an explanatory view illustrating the resin pipe of FIG. 1 as viewed from an arrow A. [Figure 4] 2 is an explanatory diagram illustrating the resin pipe of FIG. 1 in a BB cross-sectional view. FIG. [Diagram 5] FIG. 2 is a perspective view of the core tube of FIG. [Figure 6] 2 is an explanatory view illustrating a state in which the resin tube and the core tube in FIG. 1 are separated. FIG. [Figure 7] FIG. 13 is a perspective view showing a modified example of the core tube. [Figure 8] FIG. 11 is a perspective view showing another modified example of the core tube. [Figure 9] FIG. 2 is an explanatory diagram illustrating an assembly of a resin pipe and a hose in a vertical cross-sectional view. [Figure 10] 10 is an explanatory diagram illustrating the assembly of FIG. 9 as viewed along CC. [Figure 11]FIG. 2 is an explanatory diagram illustrating a manufacturing apparatus for a resin pipe. [Figure 12] 12 is an explanatory diagram illustrating a part of one of the molds in FIG. 11 as viewed from the front together with a core tube and a support pipe. FIG. [Figure 13] 13 is an explanatory diagram illustrating a state in which a core tube is disposed in the nipple molding portion of FIG. 12. FIG. [Figure 14] 14 is an explanatory diagram illustrating a schematic example of the inside of a cavity filled with injected molten resin after the mold in FIG. 13 is clamped. FIG. [Figure 15] 15 is an explanatory diagram illustrating a state in which an assist material is injected into the cavity in FIG. 14. FIG. [Figure 16] 16 is an explanatory diagram illustrating a schematic example of a state in which the molten resin remaining in the cavity in FIG. 15 has hardened. FIG. [Figure 17] 17 is an explanatory view illustrating a state in which the mold in FIG. 16 is opened and the support pipes are removed. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a method for manufacturing a resin pipe according to the present invention will be described based on an embodiment shown in the drawings.

[0010] A resin pipe 1 illustrated in Figures 1 to 4 is manufactured according to the present invention. This resin pipe 1 has a resin nipple 4 at its longitudinal tip. A metal core tube 5 is fitted into this nipple 4, and the core tube 5 is integrated with the resin pipe 1. The resin pipe 1 is a cylinder having a pipe wall 2 formed from a cured resin R2, and a pipe line 3 extends in the longitudinal direction.

[0011] The pipe wall 2 of this resin pipe 1 has a two-layer structure in which a cylindrical inner pipe portion 2N and a cylindrical outer pipe portion 2T are laminated coaxially. The inner pipe portion 2N and the outer pipe portion 2T are formed from cured resins R2 of different specifications. Cured resins R2 of different specifications mean that the types of resins are different, or that the materials mixed into the resins are different. The dashed dotted line CL in the figure indicates the axis passing through the center of the cross section of the pipe passage 3 of the resin pipe 1 and the core pipe 5. The extension direction of this axis CL becomes the axial direction (longitudinal direction) of the resin pipe 1 and the core pipe 5.

[0012] The inner diameter of the resin pipe 1 is, for example, 4 mm or more and 16 mm or less, and is set to a substantially constant value over the entire pipe length. The inner diameter of the resin pipe 1 and the inner diameter of the core tube 5 are substantially the same, and the inner peripheral surfaces of the resin pipe 1 and the core tube 5 are smoothly continuous in the axial direction to form the pipe line 3. The thickness of the pipe wall 2 of the resin pipe 1 is, for example, 1 mm or more and 3 mm or less. The thickness of the outer pipe portion 2T is smaller than the thickness of the inner pipe portion 2N, for example, 0.5 mm or more and 2.0 mm or less.

[0013] This plastic pipe 1 is used as piping for various devices, for example, as piping for an air conditioner mounted on a vehicle such as an automobile. The plastic pipe 1 may be a straight pipe or a bent pipe depending on the application (place of use). As will be described in detail later, a hose 7 fitted onto the nipple 4 is crimped and connected and fixed, as shown in Figs. 9 and 10.

[0014] The nipple 4 is a tapered cylinder that tapers slightly toward the longitudinal tip. That is, the outer peripheral surface of the nipple 4 is inclined so that it tapers slightly toward the longitudinal tip. The tapered outer peripheral surface of the nipple 4 has anti-dislodgement protrusions formed at intervals in the axial direction.

[0015] A locking portion 2a is formed on the outer circumferential surface of the resin pipe 1. This locking portion 2a is an annular groove that continues around the entire circumference. The locking portion 2a is located axially rearward of the core pipe 5. In other words, the core pipe 5 does not extend to the position of the locking portion 2a.

[0016] The resin for forming the resin pipe 1 is selected from various known injectable thermoplastic resins, and an appropriate type is selected depending on the performance required for the resin pipe 1. For example, when manufacturing a resin pipe 1 for an air conditioner mounted on an automobile, polyamide, polypropylene, ABS resin, etc. are used, and nylon resin (nylon 6, nylon 66, nylon 12, nylon 11), polyethylene, polycarbonate, polystyrene, polyoxymethylene, polymethyl methacrylate, polybutylene terephthalate, acrylic, polyether ether keto, thermoplastic polyurethane, polyethylene terephthalate, and polyvinyl chloride are preferred.

[0017] The resin pipe 1 can be made of only thermoplastic resin, but can also be made to have a specification in which various fibers (e.g., glass fiber or carbon fiber, which can be short or long) are mixed as reinforcing fibers f in a predetermined ratio (e.g., 30% to 40% by mass relative to 100 parts by mass of resin). When the reinforcing fibers f are short fibers, the size is, for example, an outer diameter of 0.001 mm to 1.0 mm, and a length of 0.01 mm to 10 mm. In this embodiment, the inner pipe portion 2N and the outer pipe portion 2T are made of the same cured resin R2, but the cured resin R2 forming the outer pipe portion 2T is mixed with reinforcing fibers f, and the cured resin R2 forming the inner pipe portion 2N is not mixed with reinforcing fibers f.

[0018] The core tube 5 illustrated in Fig. 5 is made of carbon steel, stainless steel, or the like. The inner and outer diameters of the core tube 5 are set to be substantially constant over the entire length of the tube. The wall thickness of the core tube 5 is, for example, 0.3 mm or more and 1.0 mm or less, and is substantially constant over the entire length of the tube (excluding the recess 6b). The length of the core tube 5 is, for example, 10 mm or more and 80 mm or less. Since it is difficult to ensure sufficient rigidity with an aluminum core tube 5, it is preferable to form the core tube 5 from a material having a tensile strength equal to or greater than that of SS400, for example.

[0019] The core tube 5 has a notch 6a at its tip. In this resin tube 1, four rectangular notches 6a are arranged at equal intervals in the circumferential direction. A recess 6b is formed on the outer circumferential surface of the core tube 5. In this embodiment, the recess 6b is a groove with a semicircular cross section that extends around the entire circumference in the circumferential direction. The recess 6b consisting of this circumferential groove is formed in multiple places (3 places) spaced apart in the axial direction. The depth of the recess 6b is very small, for example about 0.1 mm.

[0020] As shown in FIG. 6, when the resin tube 1 and the core tube 5 are separated, the inner peripheral surface of the nipple 4 has a mating recess 4a of the same shape as the outer peripheral surface of the core tube 5. That is, the inner peripheral surface of the nipple 4 has a mating recess 4a of a shape transferred by pressing the outer peripheral surface of the core tube 5. In detail, the inner peripheral surface of the nipple 4 has an engagement protrusion 4b that fits into the notch 6a of the core tube 5 at a position corresponding to the notch 6a, and an annular small protrusion that fits into the recess 6b at a position corresponding to the recess 6b. The depth of the mating recess 4a is substantially the same as the wall thickness of the core tube 5. The core tube 5 is integrated with the resin tube 1 in a state where it is fitted inside the mating recess 4a.

[0021] Since the core tube 5 is fitted into the fitting recess 4a, the axial movement of the core tube 5 relative to the nipple 4 is restricted. Also, since the engagement protrusion 4b enters and fits into the notch portion 6a, the axial and circumferential movement of the core tube 5 relative to the nipple 4 is restricted. Also, since the small protrusions on the inner peripheral surface of the nipple 4 enter and fit into the recess 6b, the axial movement of the core tube 5 relative to the nipple 4 is restricted. In this way, the fitting recess 4a, the engagement protrusion 4b, the small protrusions on the inner peripheral surface, the notch portion 6a, and the recess 6b of the core tube 5 of the nipple 4 function as a restricting portion that restricts the axial and circumferential movement of the core tube 5 relative to the nipple 4. Due to this restricting portion, the core tube 5 is stably fixed at a predetermined position of the nipple 4 while being prevented from shifting relative to the nipple 4, so that the core tube 5 is prevented from falling off the resin tube 1.

[0022] Furthermore, forming the recess 6b increases the contact area between the outer circumferential surface of the core tube 5 and the inner circumferential surface of the nipple 4. As a result, this is advantageous for stably fixing the core tube 5 to the nipple 4 at a predetermined position.

[0023] The portion functioning as the above-mentioned restricting portion can be of various specifications. The notch portion 6a formed in the core tube 5 is not limited to a rectangular shape, and various shapes such as a triangular shape, a semicircular shape, and a semi-elliptical shape can be adopted. As shown in FIG. 7, the notch portion 6a may have a trapezoid shape that narrows toward the tip of the core tube 5, and as shown in FIG. 8, the notch portion 6a may have a trapezoid shape that widens toward the tip of the core tube 5. The number of the notch portion 6a is at least one, and may be any number of notches. When there are multiple notches 6a, they may be arranged at equal intervals in the circumferential direction. In addition, multiple types of notches 6a with different shapes and sizes may be mixed. The fitting protrusion 4b has a shape according to the shape of the notch portion 6a.

[0024] The recess 6b made of a circumferential groove as exemplified in Fig. 5 may be formed in only one place, or may be formed in multiple places spaced apart in the axial direction. As exemplified in Fig. 7, a recess 6b made of a straight groove extending parallel to the axial direction of the core tube 5 may also be used. This straight groove recess 6b may be formed in only one place, or may be formed in multiple places (four places) spaced apart in the circumferential direction. When forming a plurality of straight groove recesses 6b, they should be disposed at equal intervals in the circumferential direction.

[0025] As shown in Fig. 8, a recess 6b consisting of a spiral groove extending in a spiral shape around the axis CL may be used. The recess 6b shown in Figs. 7 and 8 may be formed over the entire length of the core tube 5 in the longitudinal direction, or may be formed only within a specific range in the longitudinal direction. The minute protrusions on the inner peripheral surface of the nipple 4 that fit into the recess 6b have a shape that corresponds to the shape of the recess 6b.

[0026] The recesses 6b are not limited to extending grooves and may be dot-like recesses, and the outer peripheral surface of the core tube 5 may be speci?ed with recesses 6b scattered thereon. Instead of or in addition to the recesses 6b, protrusions (extending protrusions or dot-like protrusions) may be used. That is, it is only necessary that the outer peripheral surface of the core tube 5 can be formed uneven by the recesses 6b or protrusions. The inner peripheral surface of the nipple 4 has a shape corresponding to the unevenness of the outer peripheral surface of the core tube 5, so that the resin on the inner peripheral surface of the nipple 4 is in?tted into the recesses 6b. Therefore, the recesses 6b and the resin in?tted into the recesses 6b function as the above-mentioned restricting portion.

[0027] A plurality of types of recesses 6b and protrusions having different shapes and sizes may be mixed, and the recesses 6b and protrusions can be formed in combination with the desired notch 6a. The recesses 6b and protrusions can be provided arbitrarily, and the outer peripheral surface of the core tube 5 can be made smooth without minute irregularities, and only the fitting protrusions 4b and the notch 6a can function as the above-mentioned restricting portion.

[0028] The core tube 5 is disposed in a predetermined range X including the entire length of the crimping range CA in which the hose 7 is crimped in the longitudinal direction of the nipple 4. That is, the core tube 5 is disposed so as to cover at least the crimping range CA. The crimping range CA is a range in which the crimping force actually acts when the hose 7 is crimped to the nipple 4. By comparing the outer diameters of the nipple 4 before and after the hose 7 is crimped, the position (range) where there is a difference between the two can be determined as the crimping range CA, and the position (range) where there is no difference between the two can be determined as outside the crimping range CA. Generally, the crimping force does not act in the range from the tip position of the nipple 4 (plastic pipe 1) to about 5 mm to 20 mm in the axial direction, so this range is outside the crimping range CA.

[0029] In this plastic pipe 1, the tip position of the core tube 5 coincides with the tip position of the plastic pipe 1, and the rear end position of the core tube 5 is located approximately 5 mm behind the rear end position of the crimping range CA. The tip position of the core tube 5 can be set slightly back from the tip position of the plastic pipe 1, but by making the tip positions of both pipes coincident, it becomes easier to manufacture the plastic pipe 1. The rear end position of the core tube 5 can also be made to substantially coincide with the rear end position of the crimping range CA to reduce weight.

[0030] The notch 6a is located outside the crimping range CA. In this plastic pipe 1, the leading end position of the notch 6a coincides with the leading end position of the plastic pipe 1, and the rear end position of the notch 6a is located about 5 mm forward of the leading end position of the crimping range CA. The rear end position of the notch 6a can also be made to substantially coincide with the leading end position of the crimping range CA to reduce weight.

[0031] 9 and 10, an assembly 9 of a plastic pipe 1 and a hose 7 is formed by fitting the hose 7 onto the nipple 4 of the plastic pipe 1 and crimping it. The core tube 5 has a notch 6a at its tip, which is positioned outside the crimping range CA in the longitudinal direction of the nipple 4. The hose 7 may be a rubber hose or a plastic hose in which a reinforcing layer 7c made of a reinforcing wire is coaxially laminated between an inner layer 7a and an outer layer 7b.

[0032] Describing the structure of the assembly product 9 in detail, the hose 7 fitted onto the nipple 4 is covered by a cylindrical hose fitting 8. At one end of the hose fitting 8, a circular locking portion 8a protrudes toward the inner circumference, and this locking portion 8a is locked to a locking portion 2a formed on the outer circumference of the plastic pipe 1. When the outer circumference of the hose fitting 8 (pressing portion 8b) is pressed strongly by a crimping jig, the hose 7 together with the hose fitting 8 deforms toward the nipple 4 (axis center CL), and the hose 7 is crimped to the nipple 4.

[0033] To manufacture the assembly 9, the locking portion 8a of the hose fitting 8 is locked to the locking portion 2a of the resin pipe 1, and the hose fitting 8 is attached so as to cover the outer peripheral surface of the nipple 4 with a gap therebetween. Then, the nipple 4 is inserted into one end of the hose 7, and the one end of the hose 7 is pressed into the gap between the nipple 4 and the hose fitting 8. Next, the outer peripheral surface of the hose fitting 8 is strongly pressed toward the axis CL by a crimping jig. This causes the hose 7 together with the hose fitting 8 to deform toward the nipple 4 (axis center CL), and the hose 7 is crimped and connected to the nipple 4. Various known types of hose fittings 8 and crimping jigs may be used.

[0034] The crimping force acts on the nipple 4 when the hose 7 is crimped. The core tube 5 is fitted into the nipple 4 in a predetermined range X including the entire length of the crimping range CA, so the rigidity of the crimping range CA of the nipple 4 is improved. Therefore, compared to a resin nipple, the deformation of the nipple 4 to which the hose 7 is crimped is suppressed. Therefore, damage to the nipple 4 when the hose 7 is crimped is avoided, and it is also advantageous for suppressing deformation and damage over time, so the durability of the nipple 4 is improved. In other words, compared to a resin nipple, the hose 7 can be fixed to the nipple 4 with a stronger crimping force, so the sealing between the hose 7 and the nipple 4 can be improved. As a result, the hose 7 is stably fixed to the nipple 4 over a long period of time, which is advantageous for maintaining good sealing between the hose 7 and the nipple 4.

[0035] The axial and circumferential movement of the core tube 5 relative to the nipple 4 is restricted by the restricting portion, so that the core tube 5 is stably fixed to the nipple 4. This is all the more advantageous in improving the durability and sealing performance of the nipple 4. Furthermore, because the core tube 5 is integrated into the resin nipple 4 within a predetermined range X in the longitudinal direction, the nipple 4 can be made lighter than if it were entirely made of metal.

[0036] In the above-described resin pipe 1, the notch 6a is formed at the tip of the core pipe 5 and is located outside the crimping range CA. In other words, the range in which the notch 6a is formed is not a portion necessary for suppressing deformation of the nipple 4 due to the crimping force, so the weight of the core pipe 5 can be reduced and the core pipe 5 can be prevented from falling off from the nipple 4 without compromising the effect of suppressing deformation of the nipple 4.

[0037] Furthermore, since the pipe wall 2 of this resin pipe 1 has a two-layer structure consisting of an inner pipe portion 2N and an outer pipe portion 2T, the inner pipe portion 2N can be made to specifications more suitable for the fluid flowing through the pipeline 3, while the outer pipe portion 2T can be made to specifications with improved weather resistance, impact resistance, etc. In this embodiment, impact resistance is improved by mixing reinforcing fibers f only into the outer pipe portion 2T. Also, since reinforcing fibers f are not mixed into the inner pipe portion 2N, it is possible to prevent the reinforcing fibers f from falling off for some reason and becoming mixed into the fluid flowing through the pipeline 3.

[0038] An example of a procedure for manufacturing the resin pipe 1 will now be described.

[0039] The resin pipe 1 is manufactured using a manufacturing apparatus 10 illustrated in Fig. 11. This manufacturing apparatus 10 includes an injector 11, an assist material injector 14, and a mold 16. In this embodiment, a pair of left and right molds 16 are used.

[0040] The injection machine 11 has a cylinder 12 and a screw 13 disposed inside the cylinder 12. The injection machine 11 is not limited to the type shown in the figure, and various known resin injection molding machines such as pre-plastication type can be used. An injection path 18a is connected to an injection port 12a at the tip of the cylinder 12. The injection path 18a is connected to a mold 16. The resin used is heated inside the cylinder 12 to become molten resin R1, and the rotating screw 13 injects the molten resin R1 from the injection port 12a through the injection path 18a toward the inside of the mold 16.

[0041] The assist material injector 14 has a storage section 15 that stores a gas used as the assist material As. Various known injectors can be used as the assist material injector 14. As the assist material As, a gas (vapor) such as nitrogen gas or air is used.

[0042] An injection path 18b is connected to the injection port 15a at the tip of the accommodation portion 15. The injection path 18b is connected to the mold 16. The assist material As is injected at a predetermined pressure from the injection port 15a through the injection path 18b toward the inside of the mold 16. For example, gas at room temperature (20°C ± 15°C) is injected as the assist material As.

[0043] The mold 16 is composed of one mold 16A and the other mold 16B that are assembled together. The molds 16A and 16B come into contact with and are separated from each other at a parting line PL. In this embodiment, the mold 16 is not limited to a two-piece mold, and various other types of molds 16 known in the art can be used.

[0044] A hollow cavity 17 is formed inside the mold 16. The cavity 17 extends from one end 17a to the other end 17b. The outer shape of the cavity 17 is the same as that of the resin pipe 1 to be manufactured. In this embodiment, the cavity 17 extends vertically between the upper end 17a and the lower end 17b, and a pair of left and right molds 16A, 16B are used.

[0045] An injection port 12a is connected to one end 17a of the cavity 17 via an injection path 18a, and an injection port 15a is connected to the other end 17b of the cavity 17 via an injection path 18b. The injection port 12a may be indirectly connected to one end 17a of the cavity 17, and the injection port 15a may be indirectly connected to the other end 17b of the cavity 17.

[0046] Furthermore, the mold 16 is formed with a one-end discharge cavity 17d that extends outside the cavity 17 and can communicate with one end 17a of the cavity 17, and an other-end discharge cavity 17e that extends outside the cavity 17 and communicates with the other end 17b of the cavity 17. A switching unit 17c is provided in a communication path (injection path 18a) between the one end 17a and the injector 11. The one-end discharge cavity 17d is connected to the switching unit 17c. By operating the switching unit 17c, it is possible to switch between a mode in which one end 17a is connected to the injection path 18a and the communication between one end 17a and the one-end side discharge cavity 17d is blocked, and a mode in which the communication between one end 17a and the injection path 18a is blocked and the one end 17a is connected to the one-end side discharge cavity 17d.

[0047] 12, a nipple forming portion 19 is provided at the other end 17b of the cavity 17. A pipe fixing portion 19a is connected to this nipple forming portion 19. A support pipe 20 is used to position the core tube 5 in the nipple forming portion 19.

[0048] The support pipe 20 has a cylindrical body with an opening 20a at the tip and a larger-diameter base 20b connected to the lower end of the cylinder. The core tube 5 is inserted into this cylinder, and the outer diameter of the cylinder is set to be almost the same as the inner diameter of the core tube 5, but only slightly smaller, so that the core tube 5 is inserted into the cylinder with virtually no gap. A flow path that is continuous with the injection path 18b penetrates the support pipe 20, and the tip of this flow path becomes the opening 20a. Therefore, the opening 20a becomes the outlet of the injection path 18b. The pipe fixing part 19a is formed as a recess into which the base 20b fits.

[0049] As shown in FIG. 13, when manufacturing the resin pipe 1, the mold 16 is opened and the core tube 5 is placed in the nipple forming portion 19. That is, the base 20b of the support pipe 20 on which the core tube 5 is inserted is fitted to the pipe fixing portion 19a, leaving a gap between the outer peripheral surface of the core tube 5 and the inner peripheral surface of the nipple forming portion 19. The core tube 5 is placed on the base 20b with its lower end, on which the notch 6a is formed, abutting against the base 20b. In this embodiment, the opening 20a protrudes upward from the upper end of the core tube 5, but it can be located at the same position as this upper end or slightly lower than this upper end.

[0050] Next, the molds 16A, 16B are assembled together and closed, and then, as illustrated in Fig. 14, the molten resin R1 is injected by the injector 11 into the cavity 17 of the closed mold 16. In this embodiment, the molten resin R1 mixed with the reinforcing fibers f (the outer tube molten resin R1 forming the outer tube portion 2T) and the molten resin R1 not mixed with the reinforcing fibers f (the inner tube molten resin R1 forming the inner tube portion 2N) are injected from the injector 11. Each of the injected molten resins R1 is injected into the cavity 17 from the injection port 12a via the injection path 18a.

[0051] In detail, the switching unit 17c is operated to connect the one end 17a to the injection path 18a, and to block the connection between the one end 17a and the one end side discharge cavity 17d. In this state, the outer tube molten resin R1 is injected from the one end 17a toward the other end 17b to fill the cavity 17 in a cylindrical shape, and the inner tube molten resin R1 is injected from the one end 17a toward the other end 17b of the cavity 17 to fill the inner periphery of the cylindrical outer tube molten resin in a cylindrical shape. In the nipple forming unit 19, the outer tube molten resin R1 and the inner tube molten resin R1 are stacked and filled in the cylindrical gap between the inner periphery of the nipple forming unit 19 and the outer periphery of the core tube 5. The inner tube molten resin R1 enters the notch 6a and the recess 6b to fill them. Excess molten resin R1 is discharged into the other end side discharge cavity 17e. 14 to 17, the reinforcing fibers f mixed in the outer tube molten resin R1 are omitted.

[0052] Next, as shown in FIG. 15, the assist material (gas) As is injected into the mold 16 by the assist material injector 14. More specifically, the switching unit 17c is operated to block communication between the one end 17a and the injection path 18a, and to connect the one end 17a to the one end side discharge cavity 17d. In this state, the assist material As is injected at a predetermined pressure from the other end 17b of the cavity 17 filled with the molten resin R1 toward the one end 17a through the opening 20a. The injected assist material As passes through the inside of the cavity 17 along the extension direction of the cavity 17.

[0053] As the assist material As passes through the cavity 17, excess molten resin R1 (mainly inner tube molten resin R1) is discharged from one end 17a of the cavity 17 to one end side discharge cavity 17d, and the inner tube molten resin R1 is formed into a cylindrical shape and remains in the cavity 17. The outer tube molten resin R1 remains cylindrical in the cavity 17. In the nipple forming portion 19, the outer tube molten resin R1 and the inner tube molten resin R1 that have filled the gap (cylindrical gap) between the inner peripheral surface of the nipple forming portion 19 and the outer peripheral surface of the core tube 5 remain in a layered state. The inner tube molten resin R1 that has entered and filled the cutout portion 6a and the recessed portion 6b also remains.

[0054] As shown in Fig. 16, the remaining molten resin R1 in the cavity 17 hardens to become the hardened resin R2, forming the resin pipe 1. That is, the inner pipe molten resin R1 hardens to form the inner pipe section 2N, and the outer pipe molten resin R1 hardens to form the outer pipe section 2T, which becomes the pipe wall 2, and the hollow section becomes the pipe line 3. The molten resin R1 filled in the gap (cylindrical gap) between the inner peripheral surface of the nipple forming section 19 and the outer peripheral surface of the core tube 5 becomes the hardened resin R2, forming the nipple 4 and the mating recess 4a. The molten resin R1 filled in the cutout section 6a becomes the hardened resin R2, forming the mating protrusion 4b, and the molten resin R1 filled in the recess 6b becomes the hardened resin R2, forming the annular minute protrusion. At this stage, the waste portions of the hardened resin R2 (resin discharged into the one-end discharge cavity 17d and the other-end discharge cavity 17e) extend and are integrated at both ends of the resin pipe 1.

[0055] Next, the molds 16A and 16B are separated at the parting line PL to open the mold 16, and the support pipe 20 is removed from the mold 16 as shown in Fig. 18. The molded resin pipe 1 is then removed together with the unnecessary portion of the cured resin R2. The unnecessary portion of the cured resin R2 is cut away from the removed resin pipe 1 to produce the resin pipe 1 in which the core tube 5 is integrated with the nipple 4 as shown in Figs. 1 to 4.

[0056] In this embodiment, excess molten resin R1 is discharged to one end side discharge cavity 17d and other end side discharge cavity 17e connected to cavity 17. As a result, at one end 17a and the other end 17b of cavity 17, molten resin R1 (inner pipe molten resin R1 and outer pipe molten resin R1) is stably laminated without shortage, which is advantageous for manufacturing a resin pipe 1 with the wall thicknesses of the inner pipe portion 2N and the outer pipe portion 2T within a standard range.

[0057] According to this assembly product 9, as the durability of the plastic pipe 1 is improved, a strong and stable connection between the nipple 4 and the hose 7 can be ensured, which is advantageous for maintaining an excellent seal between them for a long period of time. In addition, as the plastic pipe 1 is made lighter, the assembly product 9 is also made lighter.

[0058] The injection temperature of the molten resin R1 is generally set within a range of, for example, 150° C. or more and 350° C. or less. The temperature of the mold 16 (cavity 17) is generally set within a range of, for example, 30° C. or more and 120° C. or less. Therefore, the injection temperature of the molten resin R1 and the temperature of the mold 16 (cavity 17) are appropriately determined within such ranges to control the viscosity of the molten resin R1 in the cavity 17 within a desired range. In other words, in order to make the molten resin R1 in the cavity 17 have an appropriate viscosity, the temperature of the molten resin R1 injected into the cavity 17 and the temperature of the mold 16 (cavity 17) are set within a desired range.

[0059] The appropriate injection pressure of the assist material (gas) As varies depending on the length and shape of the resin pipe 1 (cavity 17), the viscosity of the molten resin R1 in the cavity 17, and the like, and therefore cannot be set uniformly and comprehensively. Therefore, in order to set the viscosity of the molten resin R1 in the cavity 17 to a desired range, the temperature of the molten resin R1 injected into the cavity 17 and the temperature of the mold 16 (cavity 17) are set to a desired range within the above-mentioned range. Then, under the temperature conditions set in this way, test molding is performed with a plurality of different injection pressures of the assist material As to manufacture samples of the resin pipe 1. The injection pressure at which the wall thickness of the pipe wall 2 of the sample of the resin pipe 1 manufactured by each test molding falls within a standard range (for example, 1.5 mm or more and 1.75 mm or less) is grasped, and the grasped injection pressure may be set as the appropriate injection pressure of the assist material As. In the actual production of the resin pipe 1, the temperature of the molten resin R1 is set to the conditions set in the test molding, and the assist material As is injected into the cavity 17 at the appropriate injection pressure set, to manufacture the resin pipe 1.

[0060] In this embodiment, gas is used as the assist material As, but liquid such as water or solid such as metal balls or resin balls can also be used as the assist material As. The assist gas injector 14 employs a known appropriate mechanism depending on the type of assist material As.

[0061] In the process in which the gas assist material As passes through the cavity 17 filled with the molten resin R1, the temperature of the molten resin R1 that comes into contact with this gas can be prevented from dropping rapidly, compared to when a solid or liquid assist material As is used. In addition, the gas assist material As does not allow the molten resin R1 to adhere closely to the assist material As, as occurs with a solid assist material As. Therefore, molding the resin pipe 1 using a gas as the assist material As is advantageous in reducing the variation in the wall thickness of the pipe wall 2 over the entire pipe length, even if the pipe length is long.

[0062] In the above embodiment, the pipe wall 2 has a two-layer structure of an inner pipe portion 2N and an outer pipe portion 2T, but the present invention can also be applied to the manufacture of a plastic pipe 1 having a single-layer pipe wall 2. When manufacturing such a plastic pipe 1, the above-mentioned procedure can be applied assuming that the inner pipe portion 2N and the outer pipe portion 2T are made of the same resin. When the pipe wall 2 has a single-layer structure, the other end side discharge cavity 17e can be omitted.

[0063] The present disclosure encompasses the following inventions: Invention 1: A cylindrical nipple to which the fitted hose is tightened; a metal core tube disposed in a predetermined range including the entire length of a crimping range in the longitudinal direction of the nipple and fitted into the nipple; a core tube and a nipple each having a restricting portion that restricts axial and circumferential movement of the core tube relative to the nipple, the nipple and the core tube being integrated at a longitudinal tip end of the resin tube, The mold is provided with a cavity having one end and the other end and extending between the one end and the other end for forming the resin pipe, a nipple forming portion set at the other end, and a one-end side discharge cavity extending outside the cavity and capable of communicating with the one end, The core tube is placed in the nipple molding portion, and in a state where the communication between the one end and the one end side discharge cavity is blocked and the mold is closed, molten resin is injected from the one end toward the other end by an injector to fill the cavity with the molten resin, and then the communication path between the one end and the injector is blocked and the one end is made to communicate with the one end side discharge cavity, A method for manufacturing a resin tube, in which an assist material is injected from the other end toward the one end, and the excess molten resin is discharged from the cavity into the one end side discharge cavity to harden the cylindrical molten resin remaining in the cavity, thereby forming the resin tube with the hardened resin, and forming the regulating portion of the nipple to regulate the axial and circumferential movement of the core tube relative to the nipple and fit the core tube into the nipple. Invention 2: The method for manufacturing a resin tube described in Invention 1, wherein the core tube has a notch at its tip, the notch being positioned outside the crimping range in the longitudinal direction of the nipple, and the regulating portion is formed by filling a portion of the molten resin into the notch and hardening the resin, together with the notch. Invention 3: A method for manufacturing a resin tube as described in Invention 1 or 2, in which an unevenness is formed on the outer peripheral surface of the core tube, and a portion of the molten resin is caused to enter into a recess of the unevenness, and the regulating portion is formed by the hardened resin that has entered into the recess and hardened and the recess. Invention 4: The resin tube has a two-layer structure in which an inner tube portion and an outer tube portion made of cured resins with different specifications are stacked coaxially, the mold is provided with an other end side discharge cavity extending outside the cavity and communicating with the other end, an outer pipe molten resin forming the outer pipe portion and an inner pipe molten resin forming the inner pipe portion are injected into the cavity as the molten resin, the outer pipe molten resin is filled in a cylindrical shape into the cavity, and the inner pipe molten resin is filled in a columnar shape on the inner peripheral side of the cylindrical outer pipe molten resin, and excess molten resin is discharged into the other end side discharge cavity; A method for manufacturing a resin pipe according to any one of Inventions 1 to 3, comprising the steps of injecting an assist material from the other end toward the one end, discharging the excess molten resin from the cavity into the one end side discharge cavity, and hardening the cylindrical molten resin remaining in the cavity to form the resin pipe. Invention 5: 5. The method for producing a resin pipe according to claim 4, wherein only the outer tube molten resin contains reinforcing short fibers among the molten resins. Invention 6: 6. The method for producing a resin pipe according to any one of Inventions 1 to 5, wherein a gas is used as the assist material. [Explanation of symbols]

[0064] 1 Plastic pipe 2 Pipe wall 2N inner tube 2T outer tube part 2a Locking part 3 conduit 4 Nipples 4a Fitting recess (regulating part) 4b Fitting protrusion (regulating part) 5 core tube 6a Notch (restriction part) 6b Recess (regulating portion) 7 Hose 7a Inner layer 7b Outer layer 7c reinforcement layer 8 Hose fittings 8a Locking part 8b Pressing part 9 Assembly 10. Plastic pipe manufacturing equipment 11 Injection machine 12 cylinders 12a Injection port 13 Screw 14 Assist material injection machine 15 Storage section 15a Inlet 16(16A, 16B) Mold 17 Cavity 17a One end 17b Other end 17c Switching section 17d Discharge cavity on one end 17e Discharge cavity on the other end 18a injection path 18b Injection path 19 Nipple molding part 19a Pipe fixing part 20 Support pipe 20a opening 20b base PL parting line R1 Molten resin R2 cured resin As Assist Material f Reinforcing fiber

Claims

1. A cylindrical nipple to which the fitted hose is tightened; a metal core tube disposed in a predetermined range including the entire length of a crimping range in the longitudinal direction of the nipple and fitted into the nipple; a core tube and a nipple each having a restricting portion that restricts axial and circumferential movement of the core tube relative to the nipple, the nipple and the core tube being integrated at a longitudinal tip end of the resin tube, The mold is provided with a cavity having one end and the other end and extending between the one end and the other end for forming the resin pipe, a nipple forming portion set at the other end, and a one-end side discharge cavity extending outside the cavity and capable of communicating with the one end, The core tube is placed in the nipple molding portion, and in a state where the communication between the one end and the one end side discharge cavity is blocked and the mold is closed, molten resin is injected from the one end toward the other end by an injector to fill the cavity with the molten resin, and then the communication path between the one end and the injector is blocked and the one end is made to communicate with the one end side discharge cavity, A method for manufacturing a resin tube, in which an assist material is injected from the other end toward the one end, and the excess molten resin is discharged from the cavity into the one end side discharge cavity to harden the cylindrical molten resin remaining in the cavity, thereby forming the resin tube with the hardened resin, and forming the regulating portion of the nipple to regulate the axial and circumferential movement of the core tube relative to the nipple and fit the core tube into the nipple.

2. 2. The method for manufacturing a resin tube according to claim 1, wherein the core tube has a notch at its tip, the notch is positioned outside the crimping range in the longitudinal direction of the nipple, and the regulating portion is formed by hardening a portion of the molten resin by filling the notch and hardening the hardened resin together with the notch.

3. 3. A method for manufacturing a resin tube as described in claim 1 or 2, wherein an unevenness is formed on the outer peripheral surface of the core tube, and a portion of the molten resin is caused to enter into a recess of the unevenness, and the cured resin that has entered the recess and hardened therein and the recess form the regulating portion.

4. The resin tube has a two-layer structure in which an inner tube portion and an outer tube portion made of cured resins with different specifications are stacked coaxially, the mold is provided with an other end side discharge cavity extending outside the cavity and communicating with the other end, an outer pipe molten resin forming the outer pipe portion and an inner pipe molten resin forming the inner pipe portion are injected into the cavity as the molten resin, the outer pipe molten resin is filled in a cylindrical shape into the cavity, and the inner pipe molten resin is filled in a columnar shape on the inner peripheral side of the cylindrical outer pipe molten resin, and excess molten resin is discharged into the other end side discharge cavity; 3. A method for manufacturing a resin pipe as described in claim 1 or 2, in which an assist material is injected from the other end toward the one end, and excess molten resin is discharged from the cavity into the one end side discharge cavity, thereby hardening the cylindrical molten resin remaining in the cavity to form the resin pipe.

5. 5. The method for producing a resin pipe according to claim 4, wherein only the outer tube molten resin contains short reinforcing fibers among the molten resins.

6. 3. The method for manufacturing a resin pipe according to claim 1, wherein the assist material is a gas.

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