Method for manufacturing curved resin tube, and curved resin tube

Abstract

The invention provides a method for manufacturing a bent resin pipe and the bent resin pipe, wherein the thickness deviation of a pipe wall on the whole length of the pipe is inhibited even if the pipe length is relatively long. When manufacturing a curved resin tube (1) having a tube length of 350 mm or more, a molten resin (R1) is injected by an injection machine (7) from one end (13a) to the other end (13b) of a cavity (13) extending with a curved portion (13c) in a mold (12), then a gas as an auxiliary material (As) is injected from the other end (13b) of the cavity (13) to the one end (13a) at a predetermined injection pressure, and the excess molten resin (R1) is discharged from the cavity (13). Thus, a curved resin tube (1) comprising a cured resin (R2) obtained by curing the cylindrical molten resin (R1) remaining in the cavity (13) is manufactured.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a curved resin tube and a curved resin tube, and more specifically, to a method for manufacturing a curved resin tube and a curved resin tube thereof capable of suppressing wall thickness deviations along the entire length of a long tube. Background Technology

[0002] To manufacture curved resin tubes, the industry has proposed the following method: after filling a cavity that is curved and extended in a mold with molten resin, a core is passed through the cavity to form a hollow body made of molten resin, which is then cured (see, for example, Patent Documents 1 and 2). In the methods proposed in these documents, a solid core such as metal or resin is used.

[0003] During the process of the core passing through a cavity filled with molten resin, the temperature of the molten resin in contact with the core (especially a metal core) tends to drop rapidly. Furthermore, if the core is made of resin, the molten resin tends to adhere tightly to the core surface. Therefore, when the core is passed through a cavity filled with molten resin and having a long tube with bends, the difference in wall thickness between the hollow tube formed in the region corresponding to the core's inlet and outlet becomes larger, and this difference increases with the length of the tube. The difference in wall thickness in the bends also increases with the degree of curvature of the bends. As a result, in the manufactured curved resin tubes, the wall thickness deviation along the entire length of the tube becomes larger. Therefore, there is room for improvement in suppressing wall thickness deviation when manufacturing long curved resin tubes.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-49644

[0007] Patent Document 2: Japanese Patent Application Publication No. 2021-88088 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] The purpose of this invention is to provide a method for manufacturing a curved resin tube that can suppress wall thickness deviations along the entire length of a long tube, and a curved resin tube thereof.

[0010] Solution for solving the problem

[0011] To achieve the above objectives, in the method for manufacturing a curved resin tube according to the present invention, after injecting molten resin from one end of a cavity that is curved and extended in a mold toward the other end using an injection molding machine, an auxiliary material is injected into the cavity to discharge excess molten resin from the cavity, thereby solidifying the cylindrical molten resin remaining in the cavity to manufacture a curved resin tube. The method for manufacturing a curved resin tube is characterized in that the length of the curved resin tube is 350 mm or more, and gas is used as the auxiliary material.

[0012] The curved resin tube of the present invention is a curved resin tube with a length of 350 mm or more, and has the following specifications: it has a connecting base for connecting auxiliary equipment at the midpoint of its length, the connecting base protruding from the outer surface of the tube and having a connecting hole communicating with the pipeline; the curved resin tube is characterized in that the curved resin tube and the connecting base are integral structures formed of the same resin, the average wall thickness of the curved resin tube is 1.5 mm or more and 1.75 mm or less, and the wall thickness deviation along the entire length of the tube is within 0.25 mm.

[0013] Invention Effects

[0014] According to the method for manufacturing a curved resin tube of the present invention, when manufacturing a curved resin tube with a length of 350 mm or more, a gas is used as the auxiliary material. When a gas is used as the auxiliary material, compared to using a solid core, the temperature drop of the molten resin in contact with the auxiliary material is suppressed during the passage of the auxiliary material through the cavity filled with the molten resin, and the molten resin does not adhere tightly to the auxiliary material. As a result, even for curved resin tubes with a length of 350 mm or more, it is beneficial to suppress wall thickness deviations along the entire length of the tube.

[0015] By using this method for manufacturing a bent resin tube, it is possible to create an integral structure in which the bent resin tube and the connecting base are formed from the same resin. The bent resin tube has the following specifications: a length of 350 mm or more, a connecting base for connecting auxiliary equipment at a midpoint along its length, the connecting base protruding from the outer surface of the tube, and a connecting hole communicating with a conduit. Furthermore, it is possible to make the average wall thickness of the bent resin tube 1.5 mm to 1.75 mm, and to keep the wall thickness deviation along the entire length of the tube within 0.25 mm. Attached Figure Description

[0016] Figure 1 This is an explanatory diagram illustrating an embodiment of a curved resin tube from a top-down perspective.

[0017] Figure 2 It is from a frontal perspective (arrow A perspective) Figure 1 An illustrative diagram illustrating a curved resin tube.

[0018] Figure 3 It is from a side view (arrow B view) Figure 1 An illustrative diagram illustrating a curved resin tube.

[0019] Figure 4 It is from the perspective of cross-section (CC section perspective) Figure 1 An illustrative diagram illustrating a curved resin tube.

[0020] Figure 5 From the perspective of longitudinal section Figure 1 An illustrative diagram illustrating a curved resin tube.

[0021] Figure 6 Yes Figure 1 An explanatory diagram illustrating an apparatus for manufacturing curved resin tubes.

[0022] Figure 7 It is Figure 6 An explanatory diagram showing a partial enlargement of a (lower) mold, illustrated from a top-down perspective.

[0023] Figure 8 In relation to Figure 7 An explanatory diagram illustrating the state in which the molding part connected to the cavity is equipped with metal components.

[0024] Figure 9 From the perspective of cross-section Figure 8 This is an illustrative diagram illustrating the state of the mold after it is closed.

[0025] Figure 10 opposite Figure 9 An illustrative diagram illustrating the state of the cavity after molten resin has been injected and filled.

[0026] Figure 11 opposite Figure 10 An illustrative diagram illustrating the state of an auxiliary material injected into a cavity filled with molten resin.

[0027] Figure 12 Yes Figure 11 An illustrative diagram illustrating the state of the molten resin remaining in the cavity after solidification. Detailed Implementation

[0028] The following describes the manufacturing method of the curved resin tube and the curved resin tube of the present invention based on the embodiments shown in the figures.

[0029] Figures 1-5The illustrated curved resin tube 1 (hereinafter referred to as resin tube 1) is a cylindrical body having a tube wall 2 formed of cured resin R2, with the tube 3 extending along its length. The resin tube 1 has bends 4 at one or more locations, and its length is 350 mm or more. In this embodiment, the resin tube 1 is curved in both a top view and a frontal view (side view), thus exhibiting a three-dimensional curved shape.

[0030] The length of resin tube 1 is, for example, 750 mm or more, or 1000 mm or more. The upper limit of the length of resin tube 1 is, for example, 2500 mm or 2000 mm. The inner diameter of resin tube 1 is, for example, 4 mm or more, and 16 mm or less, and is substantially set to a constant value along its entire length. The single-dotted line CL in the figure represents the centerline passing through the center of the cross-section of resin tube 1 (pipe 3). The length of resin tube 1 refers to the length from one end of pipe 3 along the centerline CL to the other end.

[0031] This resin tube 1 is used, for example, as piping for air conditioners installed in vehicles such as automobiles. The resin tube 1, located within such a confined space, has a complex three-dimensional curved shape.

[0032] A connecting base 5 for connecting auxiliary equipment such as sensor valves is provided at a midpoint along the length of the resin tube 1. The connecting base 5 protrudes from the outer surface of the resin tube 1. The resin tube 1 may have the connecting base 5 at multiple points, not just one midpoint along its length. The connecting base 5 has a connecting hole 5a that communicates with the conduit 3. The resin tube 1 and the connecting base 5 are integral structures formed from the same resin.

[0033] The resin used to form the resin tube 1 is selected from a variety of injectable, known thermoplastic resins based on the required properties of the resin tube 1. For example, when manufacturing the resin tube 1 for use in an air conditioner for automobiles, polyamide, polypropylene, ABS resin, etc., are used, and nylon resins (6 nylon, 66 nylon, 12 nylon, 11 nylon), polyethylene, polycarbonate, polystyrene, polyoxymethylene, polymethyl methacrylate, polybutylene terephthalate, acrylic acid, polyetheretherketone, thermoplastic polyurethane, polyethylene terephthalate, and polyvinyl chloride are preferred.

[0034] The resin tube 1 may also be formed solely from thermoplastic resin, and may be configured such that it contains various fibers (e.g., glass fiber or carbon fiber, which can be short or long fibers) mixed in a specified proportion (e.g., 30% to 40% by weight relative to 100 parts by weight of the resin) as reinforcing fibers. When the reinforcing fibers f are short fibers, their dimensions are, 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.

[0035] The average wall thickness Ta of the pipe wall 2 of the resin pipe 1 is more than 1.5 mm and less than 1.75 mm. In addition, the deviation V of the wall thickness t of the pipe wall 2 along the entire length of the pipe is within 0.25 mm.

[0036] The average wall thickness Ta of pipe wall 2 is defined as follows. For example... Figure 5 As illustrated, the resin tube 1 is divided into five equal parts along its length. In each of the five regions P1, P2, P3, P4, and P5, the wall thickness t of the tube wall 2 at the cross-section at the center position along the length is measured. In regions P1 to P5, the wall thickness t is measured at positions with the same inner diameter, excluding portions belonging to the connecting base 5. If the connecting base 5 is present at the center position along the length of a region, the wall thickness t is measured at the cross-section at the position closest to the center position along the length of the region, excluding portions belonging to the connecting base 5. The maximum value t of the wall thickness t at this cross-section is determined. max and minimum value t min Calculate the maximum value t obtained in each region P. max With minimum value t min The simple average value is set as the wall thickness T of pipe wall 2 in its region P (T = (t max +t min ( ) / 2). For example, the maximum value of the wall thickness t at the cross-section at the center of the longitudinal direction of region P1. max With minimum value t min The simple average value is taken as the wall thickness T1 in region P1. The wall thicknesses T2, T3, T4, and T5 in each region P2, P3, P4, and P5 are calculated in the same way. Then, the simple average value of the wall thicknesses T1 to T5 in regions P1 to P5 is calculated, and this simple average value is taken as the average wall thickness Ta of resin tube 1 (Ta = (T1 + T2 + T3 + T4 + T5) / 5).

[0037] The deviation V of the wall thickness t of the pipe wall 2 along the entire length of the pipe is defined as follows. The maximum value t for each region P1 to P5 is selected. max The maximum value Tmax is selected, and the minimum value t is chosen for each region P1 to P5. min The minimum value Tmin is then calculated. The difference between the maximum value Tmax and the minimum value Tmin is then taken as the deviation V (V = Tmax - Tmin).

[0038] Hereinafter, an example of the steps in manufacturing resin tube 1 using the bending resin tube manufacturing method of the present invention will be described.

[0039] Resin tube 1 is used Figures 6-9It is manufactured using the illustrated manufacturing apparatus 6. The manufacturing apparatus 6 includes an injection molding machine 7, an auxiliary material injection machine 10, and a mold 12. In this embodiment, a pair of upper and lower molds 12 are used.

[0040] The injection molding machine 7 includes a cylinder 8 and a screw 9 internally disposed within the cylinder 8. The injection molding machine 7 is not limited to the type shown in the figure; various known resin injection molding machines, such as pre-molding machines, can be used. An injection path 14a is connected to the injection port 8a at the front end of the cylinder 8. The injection path 14a is connected to the mold 12. The resin used is heated inside the cylinder 8 to become molten resin R1, and the rotating screw 9 injects the molten resin R1 from the injection port 8a toward the interior of the mold 12.

[0041] The auxiliary material injection machine 10 has a housing section 11 that contains a gas used as the auxiliary material As. Various known injection machines can be used as the auxiliary material injection machine 10. The auxiliary material As is nitrogen, air, or other gases.

[0042] An injection path 14b is connected to the injection port 11a at the front end of the receiving section 11. The injection path 14b is connected to the mold 12. Gas As is injected into the mold 12 from the injection port 11a at a specified pressure. Gas As at room temperature (20℃±15℃) is usually injected.

[0043] Mold 12 consists of an assembled mold 12A and another mold 12B. Molds 12A and 12B are joined and separated from each other by the parting line PL. Mold 12 is not limited to a two-part mold 12, and can also be any other known type of mold 12.

[0044] A cavity 13, serving as a hollow space, is formed inside the mold 12. The cavity 13 extends from one end 13a to the other end 13b, and has a bend 13c in the middle. The shape of the cavity 13 is the same as that of the manufactured resin tube 1. One end 13a, the other end 13b, and the bend 13c of the cavity 13 correspond to one end 1a, the other end 1b, and the bend 4 of the resin tube 1, respectively.

[0045] Furthermore, a molding section 15 is connected at a midpoint along the length of the cavity 13. The molding section 15 is a cavity that forms the outline of the connecting base 5, constituting part of the cavity 13, and is formed at a position corresponding to the connecting base 5. A metal component 16, which is mounted to the connecting base 5, is provided in the molding section 15. Figure 8 As illustrated, a gap (cylindrical gap) is formed between the molded part 15 and the metal part 16.

[0046] Metal components 16 include, for example, valves such as sensor valves and inflation valves, but are not limited to these; they are various components installed on the resin tube 1 (connecting base 5). Figure 7 , Figure 8 The document describes one of a pair of molds 12 (lower side) 12B, but the other (upper side) mold 12A also has a cavity 13 and a molding part 15 with the same shape as mold 12B.

[0047] Injection port 8a is connected to one end 13a of cavity 13 via injection path 14a, and injection port 11a is connected to the other end 13b of cavity 13 via injection path 14b. Injection port 8a can be connected to one end 13a of cavity 13 indirectly or directly, and injection port 11a can be connected to the other end 13b of cavity 13 indirectly or directly.

[0048] When manufacturing resin tube 1, with mold 12 in the open state, such as Figure 8 As illustrated, it becomes a state in which the metal part 16 is disposed in the molding section 15. Next, as... Figure 9 As illustrated, molds 12A and 12B are assembled together to perform mold closing.

[0049] Next, as Figure 10 As illustrated, molten resin R1 is injected into the cavity 13 of the mold 12 after mold closing via injection molding machine 7. In this embodiment, molten resin R1 mixed with reinforcing fibers f is injected from injection molding machine 7. The injected molten resin R1 is injected from injection port 8a through injection path 14a into the interior of cavity 13.

[0050] In detail, molten resin R1 is ejected from one end 13a of the cavity 13 toward the other end 13b, thereby filling the cavity 13 with molten resin R1. In the molding section 15, molten resin R1 fills the cylindrical gap between the molding section 15 and the metal component 16. It should be noted that... Figures 10-12 In the figure, the reinforcing fiber f mixed in the molten resin R1 is omitted.

[0051] Next, as Figure 11 As illustrated, auxiliary material (gas) As is injected into the interior of mold 12 by auxiliary material injection machine 10. That is, gas As is injected at a specified pressure from one end 13b of cavity 13 filled with molten resin R1 toward one end 13a. The injected gas As passes through the interior of cavity 13 along the extending direction of cavity 13.

[0052] By allowing gas As to pass through the interior of cavity 13, excess molten resin R1 is discharged from one end 13a of cavity 13, where it remains in a cylindrical shape. A discharge path (not shown) is connected to one end 13a of cavity 13, through which excess molten resin R1 is discharged. Figure 12As illustrated, the molten resin R1 remaining inside the cavity 13 solidifies into cured resin R2, thereby forming the resin tube 1. That is, the cured resin 2 portion becomes the tube wall 2, and the cavity portion becomes the tube 3. At this stage, the unused portions of the cured resin R2 (the portions that do not form the resin tube 1) extend from both ends of the resin tube 1 and become integral.

[0053] In the molding section 15, the molten resin R1 that fills the gap (cylindrical gap) between the molding section 15 and the metal component 16 remains and becomes cured resin R2. Therefore, in the molding section 15, a cylindrical connecting base 5 is formed from the cured resin R2. As a result, the resin tube 1 and the connecting base 15 become an integral structure formed from the same cured resin R2.

[0054] In the molding section 15, the portion containing the metal component 16 becomes a connecting hole 5a that communicates with the pipe 3. Therefore, in this embodiment, the lower end of the metal component 16 is embedded in the connecting hole 5a of the connecting base 5, and the metal component 16 is fixed to the connecting base 5. It should be noted that a core of the same shape as the metal component 16 can also be used in the molding section 15 to replace the metal component 16 in order to mold the resin tube 1. In this case, after the core is removed from the connecting base 5 of the molded resin tube 1, the portion after the core is removed becomes the connecting hole 5a. Therefore, by inserting and embedding the lower end of the metal component 16 into the connecting hole 5a, the metal component 16 is fixed to the connecting base 5 in a post-installation manner.

[0055] Next, molds 12A and 12B are separated at the parting line PL to open mold 12, and the molded resin tube 1 and the unused portion of cured resin R2 are removed together. A product is manufactured by cutting off the unused portion of cured resin R2 from the removed resin tube 1. Figures 1-5 The resin tube 1 is shown in the example.

[0056] like Figure 10As illustrated, the molten resin R1 injected into cavity 13 contacts the surface of cavity 13, causing a temperature decrease. Therefore, the molten resin R1 essentially decreases in temperature (increases in viscosity) from the side closest to the surface of cavity 13 toward the center of the cross-section. Furthermore, if the viscosity of the molten resin R1 filling cavity 13 is high, the injection pressure of gas As needs to be increased to allow gas As to pass from one end 13b to one end 13a of cavity 13. However, since gas As passes through a relatively soft portion (low viscosity portion) of the molten resin R1, if the injection pressure is too high, the gas will locally pass through the molten resin R1 near the center of the cross-section of cavity 13, resulting in an excessively large wall thickness t in the manufactured resin tube 1. Therefore, to ensure that the wall thickness t of tube 2 is within the desired range along the entire length of the tube, the injection pressure of gas As into cavity 13 must be appropriately set based on the predetermined inner diameter of resin tube 1 and the viscosity of the molten resin R1 in cavity 13.

[0057] Furthermore, if the resin tube 1 (cavity 13) is relatively long, the injection pressure needs to be increased to allow gas As to pass from one end 13b to the other end 13a of the cavity 13. Therefore, the injection pressure of gas As into the cavity 13 must be appropriately set based on the length of the resin tube 1. Thus, while taking into account the predetermined inner diameter and length of the resin tube 1, the viscosity of the molten resin R1 in the cavity 13 is controlled within a desired range, and gas As is injected into the cavity 13 at an injection pressure suitable for the viscosity within this specified range.

[0058] In order to control the viscosity of the molten resin R1 in the cavity 13 within a desired range, the temperature of the molten resin R1 is adjusted. As a method for adjusting the temperature of the molten resin R1, at least one of the temperature of the molten resin R1 injected into the cavity 13 and the temperature of the mold 12 (cavity 13) is adjusted. More preferably, the temperature of the molten resin R1 injected into the cavity 13 and the temperature of the mold 12 (cavity 13) are both adjusted.

[0059] From the perspective of the melting temperature and firing process of each resin, the temperature of the molten resin R1 injected into the cavity 13 is limited to a certain extent depending on the type of resin. The injection temperature of the molten resin R1 is typically set within a range of, for example, 150°C to 350°C. Furthermore, the temperature of the mold 12 (cavity 13) is also similarly limited to a certain extent. The temperature of the mold 12 (cavity 13) is typically set within a range of, for example, 30°C to 120°C. Therefore, by appropriately determining the injection temperature of the molten resin R1 and the temperature of the mold 12 (cavity 13) within such ranges, the viscosity of the molten resin R1 in the cavity 13 is controlled within a desired range. In other words, to achieve an appropriate viscosity for the molten resin R1 in the cavity 13, the temperature of the molten resin R1 injected into the cavity 13 and the temperature of the mold 12 (cavity 13) are controlled and set within a desired range.

[0060] The appropriate injection pressure of gas As varies depending on the length and shape of the resin tube 1 (cavity 13), the viscosity of the molten resin R1 in the cavity 13, etc., and therefore cannot be uniformly set. Therefore, to ensure that the molten resin R1 in the cavity 13 is within a desired range, as described above, the temperature of the molten resin R1 injected into the cavity 13 and the temperature of the mold 12 (cavity 13) are controlled and set within a desired range. Then, under these set temperature conditions, test molding is performed using various different injection pressures of gas As to produce samples of the resin tube 1. The average wall thickness Ta of the tube wall 2 and the deviation V of the wall thickness t along the entire length of the tube in the resin tube 1 samples produced through each test molding are determined. Then, the injection pressure used when the average wall thickness Ta is between 1.5 mm and 1.75 mm, and the deviation V is within 0.25 mm, is set as the appropriate injection pressure of gas As. Subsequently, in the formal production of resin tube 1, the temperature (viscosity) of molten resin R1 is set to the conditions set in the experimental molding, and gas As is injected into cavity 13 at the appropriate injection pressure set therein to manufacture resin tube 1.

[0061] As in this embodiment, since a gas is used as the auxiliary material As to form the resin tube 1, even if the tube length is long, it is superior to the case where a solid core is used as the auxiliary material As in terms of reducing the deviation of the wall thickness t of the tube wall 2 along the entire length. That is, when the gas as the auxiliary material As passes through the cavity 13 filled with molten resin R1, the temperature of the molten resin R1 in contact with the gas can be prevented from dropping rapidly compared to the case where a solid auxiliary material As is used. Furthermore, when the auxiliary material As is a gas, the molten resin R1 does not adhere tightly to the auxiliary material As as it does when the auxiliary material As is a solid.

[0062] Therefore, even when the cavity 13, which has a long tube length and a bend 13c, is filled with molten resin R1, passing gas As through it is beneficial to suppress the deviation of the wall thickness t of the tube wall 2 formed in the region corresponding to the gas As injection port side (the other end 1b side) and the region corresponding to the outlet side (the one end 1a side). This embodiment is also effective when the tube length of the resin tube 1 is 750 mm or more, and further 1000 mm or more, or 1500 mm or more, and it is also beneficial to suppress the deviation of the wall thickness t of the tube wall 2 at the bend 13c. As a result, the deviation V of the wall thickness t of the tube wall 2 can be reduced in the manufactured resin tube 1. Furthermore, since gas is used as the auxiliary material As, the resin tube 1 can be manufactured relatively easily even when the tube length is long and has a three-dimensional curved shape.

[0063] Example

[0064] A three-dimensional curved resin tube with a length of 1500 mm and an outer diameter of 7 mm throughout its entire length is manufactured by injecting molten resin from one end of a cavity that is bent and extended in a mold towards the other end using an injection molding machine, and then injecting auxiliary material from the other end of the cavity towards one end.

[0065] 30 parts by weight of glass fiber (short fiber) are mixed into 100 parts by weight of nylon 6 resin and used as a molten resin. The outer diameter of the glass fiber is 0.001 mm to 0.05 mm and the length is 0.01 mm to 0.1 mm.

[0066] Then, five different specifications of the auxiliary materials were set as shown in Table 1 (Examples, Comparative Examples 1-4), and resin tubes were manufactured. The injection temperature and injection speed of the molten resin, and the mold temperature were set to be the same. As auxiliary materials, room temperature nitrogen was used in the examples, and spherical cores made of nylon 6 resin were used in Comparative Examples 1-4. In Comparative Examples 1-4, only the outer diameter of the auxiliary material (core) was different, and the injection pressure of the auxiliary material was set to be the same. In addition, the injection pressure of the auxiliary material (nitrogen) in the examples was approximately the same as the injection pressure of the auxiliary material (core) in Comparative Examples 1-4. The difference between the examples and Comparative Examples 1-4 was essentially only the specifications of the auxiliary materials. The wall thickness t of each manufactured resin tube was measured according to the above definition, the average wall thickness Ta was calculated, and the deviation V of the wall thickness t along the entire length of the tube was calculated according to the above definition. The results are shown in Table 1.

[0067] [Table 1]

[0068]

[0069] As can be seen from the results in Table 1, the embodiment can suppress the deviation V of the pipe wall thickness along the entire length of the pipe.

[0070] Explanation of reference numerals in the attached figures

[0071] 1: Bending resin tube

[0072] 1a: One end

[0073] 1b: The other end

[0074] 2: Pipe wall

[0075] 3: Piping

[0076] 4: Bending section

[0077] 5: Connecting base

[0078] 5a: Connecting hole

[0079] 6: Manufacturing apparatus for bent resin tubes

[0080] 7: Injection molding machine

[0081] 8: Cylinder

[0082] 8a: Injection port

[0083] 9: Screw

[0084] 10: Auxiliary material injection machine

[0085] 11: Containment Department

[0086] 11a: Injection port

[0087] 12 (12A, 12B): Mold

[0088] 13: Cavity

[0089] 13a: One end

[0090] 13b: The other end

[0091] 13c: Bend

[0092] 14a: Injection route

[0093] 14b: Injection Path

[0094] 15: Molding section

[0095] 16: Metal components (core)

[0096] PL: Parting line

[0097] R1: Molten resin

[0098] R2: Cured resin

[0099] As: Auxiliary material (gas)

[0100] f: Reinforcing fiber

Claims

1. A method for manufacturing a curved resin tube, wherein the method comprises injecting molten resin from one end of a cavity that is curved and extended in a mold toward the other end using an injection molding machine, injecting auxiliary material into the cavity to discharge excess molten resin from the cavity, thereby solidifying the cylindrical molten resin remaining in the cavity to manufacture the curved resin tube. in, The length of the bent resin tube is 350 mm or more, and gas is used as the auxiliary material.

2. The method for manufacturing a curved resin tube according to claim 1, wherein the method for manufacturing a curved resin tube sets the injection pressure of the gas into the cavity based on a pre-set inner diameter of the curved resin tube and the viscosity of the molten resin in the cavity.

3. The method for manufacturing a curved resin tube according to claim 2, wherein the method for manufacturing a curved resin tube further sets the injection pressure based on the tube length.

4. The method for manufacturing a curved resin tube according to claim 3 or 4, wherein the viscosity is controlled within a desired range by adjusting the temperature of the molten resin.

5. The method for manufacturing a bent resin tube according to any one of claims 1 to 4, wherein, The curved resin tube has the following specifications: it has a connecting base for connecting auxiliary equipment at the midpoint of its length direction. The connecting base protrudes from the outer surface of the tube and has a connecting hole communicating with the pipeline. The connecting base is manufactured by connecting a molding part that has the connecting base pre-formed to the cavity, and filling the molding part with molten resin and allowing it to solidify, thereby making the connecting base and the curved resin tube an integral part.

6. The method for manufacturing a curved resin tube according to claim 5, wherein the method for manufacturing a curved resin tube involves filling the molding part with molten resin and solidifying it while the metal part is disposed in the molding part, thereby embedding and fixing the metal part in the communicating hole of the connecting base.

7. A curved resin tube, wherein the curved resin tube has a length of 350 mm or more, and has the following specifications: a connecting base for connecting auxiliary equipment is provided at a midpoint along its length, the connecting base protruding from the outer surface of the tube, and having a connecting hole communicating with a pipeline. in, The curved resin tube and the connecting base are integral structures formed of the same resin. The average wall thickness of the curved resin tube is more than 1.5 mm and less than 1.75 mm, and the wall thickness deviation along the entire length of the tube is within 0.25 mm.

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