Method and device for manufacturing bent resin pipe

Abstract

The present invention provides a method and apparatus for manufacturing a curved resin tube that can more reliably correct uneven thickness of a curved portion when manufacturing the curved resin tube by resin injection molding using an auxiliary material. At least one of a curved inner portion (14a) and a curved outer portion (14b) of a preselected curved portion (12) of a cavity (11) formed in a mold (10) is composed of a connecting plate portion (15) capable of adjusting temperature. After molten resin (R) is injected into the cavity (11) from an injection molding machine (8), the temperature of the connecting plate portion (15) is controlled by a control portion (17) so that the curved inner portion (14a) is at a lower temperature than the curved outer portion (14b). Auxiliary material (S) is injected from an auxiliary material injection portion (9) and passes through the cavity (11), thereby forming a pipe (1a), and the curved resin tube (1) is manufactured by hardening the resin (R) remaining in the cavity (11).

Description

Technical Field

[0001] The present invention relates to a method and apparatus for manufacturing a bent resin tube, and more particularly, to a method and apparatus for manufacturing a bent resin tube that can more reliably correct uneven thickness of a bent portion when the bent resin tube is manufactured by resin injection molding using an auxiliary material such as a gas-assisted molding method. Background Art

[0002] A gas-assisted molding method is known in which, when molding a resin tube by resin injection molding, a high-pressure gas such as nitrogen is injected into the mold after molten resin is injected into the mold (for example, see Patent Document 1). Sometimes, water, metal balls, or resin balls are used as auxiliary materials instead of high-pressure gas and injected into the mold at high pressure.

[0003] When a curved resin tube is manufactured by resin injection molding using an auxiliary material, the auxiliary material injected into the mold cavity has the characteristic of passing through the curved portion of the mold cavity in the shortest path. Therefore, the injected auxiliary material will pass through the curved portion of the mold cavity in a manner biased toward the inner side of the bend, so that the thickness of the resin in the inner part of the bend will become thinner than that in the outer part of the bend, resulting in uneven thickness. As a result, it is difficult for the manufactured curved resin tube to ensure the pressure resistance to withstand a preset target internal pressure. Therefore, a scheme is proposed in which a rib forming portion is provided in advance on the inner part of the bend of the mold cavity, and ribs are formed on the inner part of the bend of the manufactured curved resin tube for reinforcement, thereby ensuring pressure resistance (refer to patent document 2). However, in the proposed method, the inner part of the bend of the curved resin tube maintains a relatively thin wall thickness, so that the ribs that are not originally necessary become a protruding shape. Therefore, there is room for improvement in reliably correcting the uneven thickness of the curved portion.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2003-181868

[0007] Patent Document 2: Japanese Patent Application Publication No. 2020-82621 Summary of the invention

[0008] Problems to be solved by the invention

[0009] An object of the present invention is to provide a method and apparatus for manufacturing a bent resin tube that can more reliably correct uneven thickness of a bent portion when manufacturing the bent resin tube by resin injection molding using an auxiliary material such as a gas-assisted molding method.

[0010] Technical means of solving problems

[0011] In order to achieve the above-mentioned purpose, the manufacturing method of the bent resin tube of the present invention is characterized in that after injecting molten resin into a curved extended mold cavity formed in a mold, an auxiliary material is injected into the mold cavity, and the injected resin is hardened to manufacture the bent resin tube. The method is characterized in that when the auxiliary material is injected into the mold cavity, the inner side of the pre-selected curved portion of the mold cavity is made to have a lower temperature than the outer side of the curve.

[0012] The manufacturing device of the curved resin tube of the present invention comprises: a mold forming a cavity with a curved extension; an injection molding machine injecting molten resin into the cavity; and an auxiliary material injection portion injecting auxiliary material into the cavity injected with the resin, and is characterized in that it is constructed as follows: at least one of the curved inner part and the curved outer part of the pre-selected curved part of the cavity is composed of a connecting plate part capable of adjusting the temperature, and has a control part for controlling the temperature of the connecting plate part, and when the auxiliary material is injected into the cavity, the temperature of the connecting plate part is controlled by the control part, thereby making the temperature of the curved inner part lower than that of the curved outer part.

[0013] Effects of the Invention

[0014] According to the present invention, when the auxiliary material is injected into the mold cavity where the molten resin is injected, the temperature of the inner part of the bend of the pre-selected bend of the mold cavity is lower than that of the outer part of the bend. As a result, when the injected auxiliary material passes through, the injected molten resin is harder in the inner part of the bend than in the outer part of the bend. Therefore, even if the auxiliary material is inclined to the inner part of the bend when passing through the bend, the molten resin filled in the inner part of the bend is difficult to be removed (difficult to be cut off) by the auxiliary material passing through. As a result, it is possible to more reliably correct the uneven thickness of the bend. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is an explanatory diagram showing an embodiment of the manufacturing apparatus of the bendable resin pipe of the present invention by way of example.

[0016] Figure 2 This is an example from a bird's-eye view. Figure 1 An illustration of the mold.

[0017] Figure 3 Yes Figure 2 This is an explanatory diagram showing an example of the interior of a mold by partially enlarging it.

[0018] Figure 4 yes Figure 3 AA cross-section diagram.

[0019] Figure 5 This is an example to show Figure 3 An explanatory diagram of a state in which molten resin is injected into a mold cavity.

[0020] Figure 6 This is an example to show Figure 5 An illustration of a state where auxiliary material is injected into a mold cavity.

[0021] Figure 7 This is an explanatory diagram showing an example of a bent resin pipe manufactured according to the present invention in a top view.

[0022] Figure 8 Yes Figure 7 An explanatory diagram showing an example of the interior of a bent resin tube by partially enlarging the interior of the tube.

[0023] Fig. 9 yes Figure 8 BB cross-section diagram.

[0024] Fig.10 This is an explanatory diagram showing an example of a state where an auxiliary material is injected into a cavity filled with resin without controlling the temperature of a connecting plate portion.

[0025] Fig.11 This is an example of a bird's-eye view. Fig.10 An explanatory diagram of the interior of a bent portion of a bent resin tube manufactured by a process.

[0026] Fig.12 yes Fig.11 CC cross-section diagram.

[0027] Fig.13 This is an explanatory diagram showing an improved example of the connecting plate portion from a top view.

[0028] Fig.14 yes Fig.13 DD cross-section diagram. DETAILED DESCRIPTION

[0029] Hereinafter, a method and apparatus for manufacturing a bent resin pipe according to the present invention will be described based on the embodiments shown in the drawings.

[0030] Figures 1 to 4 The embodiment of the manufacturing device 7 of the curved resin tube shown in the example includes: a mold 10; an injection molding machine 8 for injecting molten resin R into a cavity 11 of the mold 10; and an auxiliary material injection unit 9 for injecting an auxiliary material S into the cavity 11. A part of the mold 10 is composed of a connection plate portion 15 whose temperature can be adjusted, and a control unit 17 for controlling the temperature of the connection plate portion 15 is provided.

[0031] Using the manufacturing device 7, manufacturing Figures 7 to 9The curved resin tube 1 is shown as an example. The curved resin tube 1 is a cylindrical body having a curved portion 4 (4A, 4B) with a smaller curvature radius and a curved portion 5 with a larger curvature radius and extending therefrom, and also has a straight portion 3. Both ends of the pipe 1a of the curved resin tube 1 in the longitudinal direction are openings 2. The single-point dashed line CL in the figure represents the center line passing through the center of the cross section of the pipe 1a. The curved resin tube 1 may not have a straight portion 3, and the number of curved portions 4 and 5 is not limited.

[0032] The injection molding machine 8 can use a known injection molding machine of various specifications for injecting thermoplastic resin R. The resin R used is selected in an appropriate type according to the performance required for the manufactured curved resin pipe 1. For example, when manufacturing the curved resin pipe 1 for an air conditioner mounted on a car, for example, polyamide, polyphenylene sulfide, etc. are used as the resin R.

[0033] The auxiliary material injection part 9 can use any known auxiliary material injection part of various specifications for injecting the auxiliary material S into the mold cavity 11. The auxiliary material S used can be any known material, and a suitable material can be selected from gases such as nitrogen, liquids such as water, and solids such as metal balls or resin balls according to the shape of the manufactured curved resin tube 1.

[0034] A cavity 11 extending in a curved shape is formed in the mold 10. In this embodiment, the mold 10 is composed of a pair of molds 10a and 10b that are assembled. The molds 10a and 10b are closed and opened with the parting line PL as a boundary.

[0035] A flow channel 18a connected to the cavity 11 through a gate 18b is formed in the mold 10. The flow channel 18a is connected to the injection molding machine 8 and the nozzle of the auxiliary material injection part 9 through a sprue formed in the mold 10. The mold 10 is also provided with a discharge part for the auxiliary material S injected into the cavity 11.

[0036] The cavity 11 forming the cavity is curved and extended in the same shape as the curved resin tube 1 to be manufactured. At least one of the curved inner portion 14a and the curved outer portion 14b of the pre-selected curved portion 12 (12A, 12B) of the cavity 11 is composed of a connection plate portion 15 capable of adjusting the temperature. That is, the mold 10 is composed of the connection plate portion 15 assembled in at least one of the curved inner portion 14a and the curved outer portion 14b of the pre-selected curved portion 12 (12A, 12B).

[0037] In this embodiment, only the curved inner portion 14a is composed of the connecting plate portion 15. The connecting plate portion 15 corresponds to the pair of molds 10a and 10b and is composed of a pair of connecting plate portions 15a and 15b. One connecting plate portion 15a is assembled in one mold 10a, and the other connecting plate portion 15b is assembled in the other mold 10b.

[0038] The specification may be such that only the curved outer portion 14b of the curved inner portion 14a and the curved outer portion 14b is composed of the connecting plate portion 15, or the specification may be such that both the curved inner portion 14a and the curved outer portion 14b are composed of the connecting plate portion 15. In addition, since the curved portions 12A and 12B have the same configuration, the curved portion 12A is described in detail in the drawings as a representative.

[0039] The curved portion 12 (12A, 12B) of the mold cavity 11 corresponds to the curved portion 4 (4A, 4B) having a smaller curvature radius of the curved resin tube 1, and the curved portion 13 of the mold cavity 11 corresponds to the curved portion 5 having a larger curvature radius of the curved resin tube 1. Therefore, a curved portion 12 having a relatively smaller curvature radius and a relatively smaller bending angle is selected, and at least a part of the selected curved portion 12 is constituted by the connecting plate portion 15.

[0040] The bending angle Ca of the inner curved portion 14a of the selected curved portion 12 is, for example, 90° or less, and more preferably 75° or less. The curvature radius Cr of the inner curved portion 14a is, for example, 20 mm or less, and more preferably 10 mm or less.

[0041] The connecting plate portion 15, for example, constitutes a range of about 15 mm or more and 20 mm or less in the front-to-back direction (the extension direction of the mold cavity 11) of the bending apex P of the curved inner portion 14a. If the range (length) constituted by the connecting plate portion 15 is too small, the uneven thickness of the bent resin tube 1 at the bent portion 4 cannot be corrected. On the other hand, if the range (length) constituted by the connecting plate portion 15 is too large, uneven thickness is likely to occur in portions other than the bent portion 4. The range constituted by the connecting plate portion 15 (the range in the extension direction of the mold cavity 11, etc.) is set to an appropriate value by conducting prior tests or computer simulations.

[0042] The connecting plate portion 15 is preferably formed of a metal having a higher thermal conductivity than the metal forming the portion of the mold 10 other than the connecting plate portion 15. The portion of the mold 10 other than the connecting plate portion 15 is formed of, for example, ordinary carbon steel, and the connecting plate portion 15 is formed of, for example, beryllium copper alloy.

[0043] A known computer is used as the control unit 17 for controlling the temperature of the connecting plate 15. A dedicated flow path for a medium such as water is formed on the connecting plate 15, and the temperature of the medium is adjusted by controlling the temperature regulator of the medium by the control unit 17, thereby controlling the connecting plate 15 within a desired temperature range. In this embodiment, water is used as the medium, and the cooling temperature of the water is adjusted by the control unit 17 to cool the connecting plate 15 within a desired temperature range.

[0044] Specifically, when the auxiliary material S is injected into the cavity 11, the control unit 17 controls the temperature of the connecting plate portion 15 so that the temperature of the inner curved portion 14a is lower than that of the outer curved portion 14b. By making the heat conductivity of the connecting plate portion 15 higher than that of other portions of the mold 10, it is advantageous to quickly increase the temperature difference between the connecting plate portion 15 and other portions (the outer curved portion 14b).

[0045] Next, an example of the steps of the method for manufacturing the curved resin pipe of the present invention will be described.

[0046] like Figure 1 , Figure 2 As shown in the example, in a state where a pair of molds 10a and 10b are assembled and clamped, molten resin R is injected from the injection molding machine 8 into the mold 10. Figure 5 As shown in FIG. 1 , the injected resin R passes through the sprue, runner 18a, and gate 18b formed in the mold 10 and is injected into the cavity 11. The cavity 11 is filled with the molten resin R.

[0047] Next, the auxiliary material S is injected into the mold 10 from the auxiliary material injection portion 9 at a predetermined high pressure. The injected auxiliary material S passes through the cavity 11 filled with the injected molten resin R at a high pressure along the extending direction of the cavity 11.

[0048] like Figure 6 As shown in the example, in the curved portions 12A and 12B of the cavity 11, the auxiliary material S injected at high pressure tends to pass through the shortest path in the cavity 11, that is, the inner side of the curve. Therefore, under normal circumstances, the resin R of the inner curved portion 14a of the curved portions 12A and 12B is cut off more by the auxiliary material S passing through under high pressure. As a result, the thickness of the resin R on the wall surface of the inner curved portion 14a becomes thinner than the thickness of the resin R on the outer curved portion 14b, resulting in uneven thickness. Therefore, in order to correct the uneven thickness, in this embodiment, the temperature of the connecting plate portion 15 is controlled.

[0049] In addition, the auxiliary material S is also passed through the curved portion 13 in the same manner as described above. However, since the curvature radius Cr of the curved portion 13 is relatively large, the resin R on the wall surface of the curved inner portion 14a is not easily cut by the auxiliary material S that passes through at high pressure. Therefore, the curved portion 13 is unlikely to have uneven thickness of the resin R, and the reference wall thickness can be ensured, so only the curved portions 12A and 12B are selected as the locations for assembling the connecting plate portion 15.

[0050] In this embodiment, when the auxiliary material S is injected into the cavity 11, the temperature of the connecting plate portion 15 is controlled by the control unit 17, so that the temperature of the inner curved portion 14a of the pre-selected curved portions 12A and 12B is lower than that of the outer curved portion 14b. The temperatures of all parts of the cavity 11 except the connecting plate portion 15 are substantially the same, and only the temperature of the inner curved portion 14a of the curved portions 12A and 12B in the cavity 11 is relatively low.

[0051] Thus, by controlling the temperature of the connecting plate portion 15, the molten resin R filled in the cavity 11 is harder in the curved inner portion 14a than in the curved outer portion 14b when the auxiliary material S passes through. Therefore, when the auxiliary material S passes through the curved portions 12A and 12B, even if the auxiliary material S is intended to be biased toward the curved inner portion 14a as described above, the molten resin R filled in the curved inner portion 14a is difficult to be cut (difficult to be removed) by the auxiliary material S that passes through.

[0052] In the mold 10, by passing the auxiliary material S through the entire length of the cavity 11, the resin R remaining in the cavity 11 forms a pipe 1a, and by hardening the resin R, a curved resin tube 1 along the shape of the cavity 11 is manufactured. In this embodiment, by making the resin R of the curved inner part 14a that is configured to be relatively easily cut by the passing auxiliary material S relatively hard, it is difficult to be cut. As a result, the uneven thickness of the resin R of the curved inner part 14a and the curved outer part 14b of the curved parts 12A and 12B can be corrected, and the uneven thickness of the curved inner part 6a and the curved outer part 6b of the curved parts 4A and 4B can be more reliably corrected. Figures 7 to 9 The bent resin tube 1 is shown as an example.

[0053] like Figures 10 to 12 As shown in the example, when the temperature of the connecting plate portion 15 is not controlled, after the temperature of the inner curved portion 14a and the outer curved portion 14b of the curved portions 12A and 12B becomes substantially the same, the passing auxiliary material S causes more resin R to be cut from the inner curved portion 14a than from the outer curved portion 14b. Therefore, although the curved portions 4A and 4B (12A and 12B) may have uneven thickness, the present invention can suppress the occurrence of such uneven thickness. Therefore, according to the present invention, the ribs for compensating for the insufficient wall thickness of the resin R of the inner curved portion 6a can be omitted.

[0054] In this embodiment, the inner curved part 14a of the curved parts 12A and 12B is cooled so that the temperature of the inner curved part 14a is lower than that of the outer curved part 14b when the auxiliary material S is injected into the cavity 11, but the method of temperature control of the cavity 11 is not limited to this. As long as the temperature is within the range that can produce a qualified curved resin tube 1, for example, the outer curved part 14b of the curved parts 12A and 12B can be additionally heated so that the temperature of the inner curved part 14a is lower than that of the outer curved part 14b when the auxiliary material S is injected into the cavity 11. Through this temperature control, the molten resin R filled in the cavity 11 will also be harder in the inner curved part 14a than in the outer curved part 14b. Therefore, the molten resin R filled in the inner curved part 14a is difficult to be cut (difficult to be removed) by the auxiliary material S that passes through.

[0055] According to the present invention, even if the shape of the curved resin tube 1 is complicated, it can be mass-produced. By using the manufactured curved resin tube 1, it is possible to achieve a lighter weight than a metal tube while ensuring the necessary pressure resistance. For example, it is also possible to manufacture and use a curved resin tube 1 having an internal pressure of 5 MPa or more and an inner diameter of about 10 mm or more and 20 mm or less. Since it can also be used as a low-pressure piping, by replacing a general-purpose curved metal tube with the curved resin tube 1, it is also possible to achieve a significant reduction in weight.

[0056] In the temperature control of the connecting plate portion 15, it is preferable to make the temperature difference between the curved inner portion 14a and the curved outer portion 14b not less than 20°C and not more than 40°C. If the temperature difference is less than 20°C, the difference in hardness of the molten resin R at the curved inner portion 14a and the curved outer portion 14b cannot be increased, so it is difficult to obtain the effect of correcting the uneven thickness at the curved portions 4A and 4B of the manufactured curved resin tube 1. On the other hand, if the temperature difference exceeds 40°C, there is a greater risk that the fluidity of the resin R filled in the curved inner portion 14a is too low, or the resin R filled in the curved outer portion 14b is overheated and burns occur, thereby adversely affecting the quality of the manufactured curved resin tube 1.

[0057] In order to ensure sufficient fluidity of the resin R filled in the inner curved portion 14a while correcting the uneven thickness at the curved portions 4A, 4B (12A, 12B), it is preferred to control the temperature of the inner curved portion 14a by controlling the temperature of the connecting plate portion 15 so that the temperature is above 30°C and below 70°C, and more preferably above 40°C and below 50°C.

[0058] You can also use Fig.13 , Fig.14The mold 10 of the specification shown as an example in FIG. In the mold 10, the heat insulating layer 16 is sandwiched between the connecting plate portion 15 and the portion of the mold 10 other than the connecting plate portion 15. The connecting plate portion 15 is assembled as a part of the mold 10 by sandwiching the heat insulating layer 16.

[0059] As the heat insulating layer 16, a material having a lower thermal conductivity than the portion of the mold 10 other than the connecting plate portion 15 is used. For example, if the mold 10 is formed of ordinary carbon steel (the thermal conductivity is about 49.81 W / m / C), a material lower than the thermal conductivity is used to form the heat insulating layer 16. For example, the heat insulating layer 16 is formed of a known ceramic (the thermal conductivity is about 0.61 W / m / C).

[0060] Thus, by interposing the heat insulating layer 16, the heat transfer between the connecting plate portion 15 and the portion of the mold 10 other than the connecting plate portion 15 can be cut off to a certain extent. This helps to suppress the connecting plate portion 15 from being affected by the temperature of the surrounding portion of the mold 10, and allows the connecting plate portion 15 to quickly reach the desired temperature, and also helps to stably maintain the desired temperature.

[0061] Description of Reference Numerals

[0062] 1: Bending resin tube

[0063] 1a: Pipeline

[0064] 2: Opening

[0065] 3: Straight line

[0066] 4 (4A, 4B): Bend

[0067] 5: Bending part

[0068] 6a: Bend the inner part

[0069] 6b: Bend the outer part

[0070] 7: Manufacturing device

[0071] 8: Injection molding machine

[0072] 9: Auxiliary material injection part

[0073] 10 (10a, 10b): Mold

[0074] 11: Cavity

[0075] 12 (12A, 12B): Bend

[0076] 13: Bending part

[0077] 14a: Bend the inner part

[0078] 14b: Bend the outer part

[0079] 15 (15a, 15b): Connecting plate portion

[0080] 16: Insulation layer

[0081] 17: Control Department

[0082] 18a: Runner

[0083] 18b: Gate

[0084] R: Resin

[0085] S: Supplementary materials

Claims

1. A method for manufacturing a curved resin tube, wherein after injecting molten resin into a curved and extended cavity formed in a mold, an auxiliary material is injected into the cavity to harden the injected resin to manufacture the curved resin tube, characterized in that: When the auxiliary material is injected into the mold cavity, the inner side of the curved portion of the preselected curved portion of the mold cavity is made to be at a lower temperature than the outer side of the curved portion, The temperature difference between the curved inner portion and the curved outer portion is set to 20° C. or more and 40° C. or less. 2 . The method for manufacturing a curved resin tube according to claim 1 , wherein the temperature of the curved inner portion is set to 30° C. or higher and 70° C. or lower.

3. The method for manufacturing a curved resin pipe according to claim 1 or 2, wherein: The bending angle of the curved inner portion of the curved portion is pre-selected to be 90° or less, and the curvature radius is 20 mm or less.

4. A device for manufacturing a curved resin tube, comprising: a mold having a cavity formed with a curved extension; an injection molding machine for injecting molten resin into the cavity; and an auxiliary material injection unit for injecting auxiliary material into the cavity where the resin is injected, characterized in that The mold cavity is constructed such that at least one of the inner curved portion and the outer curved portion of the preselected curved portion of the mold cavity is composed of a connecting plate portion capable of adjusting the temperature, and has a control portion for controlling the temperature of the connecting plate portion. When the auxiliary material is injected into the mold cavity, the temperature of the connecting plate portion is controlled by the control portion, thereby making the temperature of the inner curved portion lower than that of the outer curved portion, and making the temperature difference between the inner curved portion and the outer curved portion be greater than 20°C and less than 40°C.

5. The manufacturing device for a curved resin tube according to claim 4, wherein: The connecting plate portion is formed of a metal having a higher thermal conductivity than a metal forming a portion of the mold other than the connecting plate portion.

6. The manufacturing device for a curved resin tube according to claim 4 or 5, wherein: A heat insulating layer is interposed between the connection plate portion and a portion of the mold other than the connection plate portion, and the connection plate portion is assembled as a part of the mold.

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