Resin pipe, assembly product of resin pipe and hose, and manufacturing method for resin pipe

Abstract

To provide a resin pipe capable of improving durability and sealability of a nipple onto which a hose is externally fitted and caulked, and enabling weight saving, and an assembly product of the resin pipe and the hose, and a manufacturing method for the resin pipe.SOLUTION: A metal core pipe 5 is internally fitted into a predetermined range X including the entire length of a caulking range CA where a hose 7 is caulked in a longitudinal direction of a resin nipple 4 at a tip part of a resin pipe 1; a fitting recess 4a and a fitting protrusion 4b formed on the nipple 4 and a cutout part 6a and a recessed part 6b formed on the core pipe 5 restrict axial and circumferential movement of the core pipe 5 relative to the nipple 4 to integrate the nipple 4 and the core pipe 5; and with the hose 7 externally fitted onto the nipple 4, a hose fitting 8 is extrapolated, and the hose fitting 8 is caulked to fix the hose 7 to the nipple 4.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a plastic pipe, an assembly of this plastic pipe and a hose, and a method for manufacturing this plastic pipe, and more specifically, to a plastic pipe that can be made lighter while suppressing deformation of a nipple onto which a hose is fitted and crimped, thereby improving durability and sealing performance, and an assembly of this plastic pipe and a hose, and a method for manufacturing this plastic pipe. [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 plastic pipe that can be made lighter while suppressing deformation of the nipple onto which the hose is fitted and crimped, thereby improving durability and sealing performance, and an assembly of this plastic pipe and hose, as well as a method for manufacturing this plastic pipe. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the plastic pipe of the present invention is a plastic pipe having a cylindrical nipple onto which a hose is crimped, the plastic pipe having a metal core tube fitted into the nipple and positioned in a predetermined range in the longitudinal direction of the nipple that includes the entire length of the crimping range in which the hose is crimped, and the core tube and the nipple have regulating portions that regulate the axial and circumferential movement of the core tube relative to the nipple.

[0007] The plastic pipe and hose assembly of the present invention is an assembly of the above-mentioned plastic pipe and a hose that is fitted onto the nipple of the plastic pipe and crimped, 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, a part of the resin forming the nipple penetrates into the notch, and the resin that has penetrated into the notch and the notch constitute the regulating portion.

[0008] The method for manufacturing a plastic pipe of the present invention is characterized in that, in the above-mentioned method for manufacturing a plastic pipe, the core tube is placed in a nipple molding section that forms the nipple of a cavity for forming the plastic pipe extending into a mold, and while the mold is closed, molten resin is injected from one end of the cavity to the other end by an injector, and then an assist material is injected into the cavity to discharge excess molten resin from the cavity, thereby hardening the cylindrical molten resin remaining in the cavity to form the plastic pipe, and the core tube is fitted into the nipple while restricting the axial and circumferential movement of the core tube relative to the nipple. Effect of the Invention

[0009] According to the resin pipe of the present invention, a metal core tube is fitted in a predetermined range including the entire length of the crimping range where the hose is crimped in the longitudinal direction of the nipple, improving the rigidity of this crimping range. Therefore, even if the hose is crimped to the nipple, the nipple is prevented from deforming, improving the durability of the nipple and the sealing between the hose and the nipple. 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 even more advantageous in improving the durability and sealing of the nipple. Furthermore, since the core tube is integrated into the predetermined range in the longitudinal direction of the resin nipple, the weight of the nipple can be reduced compared to when the entire nipple is made of metal.

[0010] According to the assembly of the present invention, the durability of the plastic pipe is improved, and therefore a strong and stable connection between the nipple and the hose can be ensured, which is advantageous in maintaining an excellent seal between them for a long period of time. In addition, the weight of the plastic pipe is reduced, and therefore the assembly is also reduced in weight. Furthermore, the method of manufacturing the plastic pipe of the present invention allows the manufacture of the plastic pipe in which the core tube is fitted into the nipple and integrated with it. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is an explanatory diagram illustrating an embodiment of a resin pipe in a vertical cross-sectional view. [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] 10A to 10C are explanatory diagrams illustrating a process of crimping a hose to a nipple. [Figure 12] FIG. 2 is an explanatory diagram illustrating a manufacturing apparatus for a resin pipe. [Figure 13] 13 is an explanatory diagram illustrating a part of one of the molds in FIG. 12 together with a core tube and a support pipe as viewed from the front. FIG. [Figure 14] 14 is an explanatory diagram illustrating a state in which a core tube is disposed in the nipple molding portion of FIG. 13. [Figure 15] 15 is an explanatory diagram illustrating a schematic example of the inside of a cavity filled with injected molten resin after the mold in FIG. 14 is clamped. FIG. [Figure 16] 16 is an explanatory diagram illustrating a schematic example of a state in which an assist material is injected into the cavity in FIG. 15. FIG. [Figure 17] 17 is an explanatory diagram illustrating a schematic example of a state in which the molten resin remaining in the cavity in FIG. 16 has hardened. FIG. [Figure 18] 18 is an explanatory view illustrating a state in which the mold in FIG. 17 is opened and the support pipes are removed. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plastic pipe, an assembly of the plastic pipe and a hose, and a method for manufacturing the plastic pipe according to the present invention will be described below with reference to the embodiments shown in the drawings.

[0013] The embodiment of the resin pipe 1 illustrated in Figs. 1 to 4 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. The dashed-dotted line CL in the figures indicates an axis passing through the center of the cross section of the pipe line 3 of the resin pipe 1 and the core tube 5. The extension direction of this axis CL is the axial direction (longitudinal direction) of the resin pipe 1 and the core tube 5.

[0014] 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 length of the pipe. The inner diameter of the resin pipe 1 and the inner diameter of the core pipe 5 are substantially the same, and the inner peripheral surface of the resin pipe 1 and the inner peripheral surface of the core pipe 5 are smoothly continuous in the axial direction to form the pipe line 3. The wall thickness of the pipe wall 2 of the resin pipe 1 is, for example, 1 mm or more and 3 mm or less. This resin 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 resin 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 on the nipple 4 is crimped and connected and fixed, as shown in Figs. 9 and 10.

[0015] 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.

[0016] A locking portion 2a is formed on the outer circumferential surface of the resin pipe 1. The locking portion 2a is an annular groove that is continuous 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.

[0017] 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.

[0018] The resin pipe 1 can be made of only thermoplastic resin, but can also be made to have a specification in which various types of fibers (for example, glass fibers or carbon fibers, which can be short or long fibers) are mixed as reinforcing fibers f in a predetermined ratio (for example, 30% to 40% by mass relative to 100 parts by mass of resin). When the reinforcing fibers f are short fibers, their 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 reinforcing fibers f are mixed into the cured resin R2.

[0019] 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.

[0020] The core tube 5 has a notch 6a at its tip. In this embodiment, 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 circumferential direction. The recess 6b consisting of this circumferential groove is formed at multiple locations (3 locations) spaced apart in the axial direction. The depth of the recess 6b is very small, for example about 0.1 mm.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] The recess 6b made of a circumferential groove as illustrated in Fig. 5 may be formed in only one place, or may be formed in multiple places spaced apart in the axial direction. As illustrated 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 as in this embodiment. When multiple straight groove recesses 6b are formed, they should be arranged at equal intervals in the circumferential direction.

[0026] 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.

[0027] 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 on the outer peripheral surface of the core tube 5 and the resin in?tted into the recesses 6b function as the above-mentioned restricting portion.

[0028] 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.

[0029] 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.

[0030] In this embodiment, 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 about 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.

[0031] The notch 6a is disposed outside the crimping range CA. In this embodiment, 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 approximately 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.

[0032] In an embodiment of an assembly 9 of a plastic pipe 1 and a hose 7 shown in Figures 9 and 10, the hose 7 is fitted onto the nipple 4 of the above-mentioned plastic pipe 1 and crimped. 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.

[0033] 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.

[0034] To manufacture the assembly 9, as illustrated in Fig. 11, 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 pushed 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. Any of various known types of hose fittings 8 and crimping jigs may be used.

[0035] 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.

[0036] 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.

[0037] In this embodiment, the notch 6a is formed at the tip of the core tube 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 tube 5 can be reduced and the core tube 5 can be prevented from falling off from the nipple 4 without compromising the effect of suppressing deformation of the nipple 4.

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

[0046] 13, the other end 17b of the cavity 17 is a nipple forming portion 19. 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.

[0047] 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 of the same shape as the base 20b.

[0048] As shown in FIG. 14, 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.

[0049] Next, after the molds 16A and 16B are assembled together and closed, the molten resin R1 is injected into the cavity 17 of the closed mold 16 by the injector 11, as illustrated in Fig. 15. In this embodiment, the molten resin R1 mixed with the reinforcing fibers f is injected from the injector 11. The injected molten resin R1 is injected into the cavity 17 from the injection port 12a via the injection path 18a.

[0050] More specifically, the molten resin R1 is injected from one end 17a to the other end 17b of the cavity 17, and the cavity 17 is filled with the molten resin R1. In the nipple forming portion 19, the molten resin R1 fills a cylindrical gap between the inner peripheral surface of the nipple forming portion 19 and the outer peripheral surface of the core tube 5. The molten resin R1 penetrates into the notch portion 6a and the recessed portion 6b and fills them. Note that in Figs. 15 to 18, the reinforcing fibers f mixed with the molten resin R1 are omitted from illustration.

[0051] 16, the assist material (gas) As is injected into the mold 16 by the assist material injector 14. That is, the assist material As is injected at a predetermined pressure from the opening 20a toward the other end 17b of the cavity 17 filled with the molten resin R1 toward one end 17a. The injected assist material As passes through the interior of the cavity 17 along the extension direction of the cavity 17.

[0052] As the assist material As passes through the cavity 17, excess molten resin R1 is discharged from one end 17a of the cavity 17, and the molten resin R1 remains in a cylindrical shape in the cavity 17. In the nipple molding part 19, the molten resin R1 that filled the gap (cylindrical gap) between the inner peripheral surface of the nipple molding part 19 and the outer peripheral surface of the core tube 5 remains. The molten resin R1 that entered and filled the notched part 6a and the recessed part 6b also remains. Since an exhaust path (not shown) is connected to one end 17a of the cavity 17, the excess molten resin R1 is discharged to this exhaust path.

[0053] As shown in FIG. 17, the remaining molten resin R1 in the cavity 17 hardens and becomes the hardened resin R2, forming the resin pipe 1. That is, the hardened resin R2 becomes the pipe wall 2, and the hollow becomes the pipe line 3. The molten resin R1 filled in the gap (cylindrical gap) between the inner peripheral surface of the nipple forming part 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 part 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 part of the hardened resin R2 (the resin discharged from the cavity 17) extends and is integrated with one end of the resin pipe 1.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] Various known molding methods that do not use the assist material As can also be used to mold the resin pipe 1. For example, the resin pipe 1 can be molded by injecting molten resin R1 into the cavity 17 with a core placed in the cavity 17, and then removing the core to form the pipe line 3. EXAMPLES

[0061] Analytical models were created for four types of samples (Examples 1 to 4) of resin pipes with the same structure as the resin pipes shown in Figures 1 to 4, but differing only in the material of the core pipe and the thickness of the wall of the core pipe, and for a simple resin pipe (Comparative Example) sample in which the core pipe portion of Examples 1 to 4 was replaced with resin. For these five types of samples, the same hose was crimped under the same conditions to manufacture the assembly shown in Figures 9 and 10, and the maximum stress generated in each nipple by the crimping force was calculated. The results are shown in Table 1.

[0062] The resin tube was made of 6 nylon resin, the nipple had an inner diameter of 11.0 mm and an outer diameter of 15.0 mm, and the core tube was placed in a range of 35 mm from the tip of the nipple near the locking part of the resin tube. In Examples 1 to 4, the thickness of the resin part of the nipple's tube wall was "outer diameter of nipple x 0.5 - thickness of tube wall of core tube". The crimping force of each sample was set to a practically applicable value based on actual data. In Table 1, the maximum stress was evaluated by an index, and a practically acceptable level was set to 100 as the standard. The smaller the index value, the smaller the maximum stress and the better the durability.

[0063] [Table 1]

[0064] From the results in Table 1, it can be seen that the nipples of Examples 1 to 4 have sufficient durability. Moreover, the nipple of the comparative example was not able to be evaluated because the deformation due to the crimping force was too large compared to the nipples of Examples 1 to 4, and the result was that the durability was inferior to Examples 1 to 4. [Explanation of symbols]

[0065] 1 Plastic pipe 2 Pipe wall 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 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. In a resin pipe having a cylindrical nipple to which a hose is fitted and crimped, A plastic pipe having a metal core tube that is fitted into the nipple and is positioned within a predetermined range that includes the entire length of the crimping range in which the hose is crimped in the longitudinal direction of the nipple, and the core tube and the nipple have regulating portions that regulate the axial and circumferential movement of the core tube relative to the nipple.

2. 2. The resin pipe 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, a portion of the resin forming the nipple penetrates into the notch, and the resin that has penetrated into the notch and the notch constitute the regulating portion.

3. 3. A resin pipe as described in claim 1 or 2, wherein an unevenness is formed on the outer peripheral surface of the core tube, a part of the resin forming the nipple penetrates into a recess of the unevenness, and the resin that has penetrated into the recess and the recess constitute the regulating portion.

4. 2. The assembly of claim 1, comprising a resin pipe and a hose fitted around the nipple of the resin pipe and crimped, An assembly of a resin pipe and a hose, 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, a part of the resin forming the nipple penetrates into the notch, and the resin that has penetrated into the notch and the notch constitute the regulating portion.

5. The method for producing a resin pipe according to claim 1, A method for manufacturing a resin tube, comprising: placing the core tube in a nipple molding section which forms the nipple of a cavity for forming the resin tube extending into a mold; injecting molten resin from one end of the cavity to the other end with the mold closed; injecting an assist material into the cavity and discharging excess molten resin from the cavity to harden the cylindrical molten resin remaining in the cavity to form the resin tube; and fitting the core tube into the nipple while restricting its axial and circumferential movement relative to the nipple.

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