JP7143745B2 - Method for manufacturing resin pipe - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a resin pipe, and more particularly, to manufacture a resin pipe having a multi-layer structure having an inner layer and an outer layer with a desired layer thickness by resin injection molding using an assisting material such as a gas-assisted molding method. The present invention relates to a method for manufacturing a resin pipe that can be

A gas-assisted molding method is known in which, when molding a resin pipe by resin injection molding, a high-pressure gas such as nitrogen gas is injected into the mold after injecting molten resin into the mold (see, for example, Patent Document 1). . Instead of high-pressure gas, water, metal balls, or resin balls may be used as an assist material and injected into the mold at high pressure.

A method of manufacturing a resin pipe having a two-layer structure having an inner layer and an outer layer by resin injection molding using a floating core (assist material) has been proposed (see Patent Document 2). In this proposed method, the main cavity is filled with resins for the inner layer and the outer layer, respectively, and then the floating core is passed through the resin for the inner layer. As a result, a predetermined amount of the resin that forms the inner layer is extruded from the main cavity by the floating core to form a resin pipe having a two-layer structure.

This proposed method is based on the premise that only the resin that forms the inner layer is pushed out of the main cavity by the moving floating core, so there is little freedom in setting the thickness of the inner and outer layers to desired thicknesses. Therefore, there is room for improvement in manufacturing a multi-layer resin pipe having inner and outer layers of desired thickness.

Japanese Patent Application Laid-Open No. 2003-181868 JP-A-9-123212

An object of the present invention is to provide a method for manufacturing a resin pipe, which is capable of manufacturing a resin pipe having a multi-layered structure having an inner layer and an outer layer with a desired layer thickness by resin injection molding using an assisting material such as a gas-assisted molding method. to do.

In order to achieve the above object, the method of manufacturing a resin pipe according to the present invention is to inject two types of melted resins in the extending direction of a cavity formed in a mold, respectively, so that a A columnar filling portion and a single cylindrical filling portion arranged coaxially with the columnar filling portion on the outer peripheral side of the columnar filling portion to form a laminated state are formed. Adjacent filling portions are made of different types of resin, and an assisting material is injected into the cavity in the direction in which the cavity extends, and the injected resin is cured to achieve the A resin pipe for manufacturing a resin pipe having a two -layer structure having an inner layer of a predetermined inner layer thickness formed of a resin of a cylindrical filling portion and an outer layer of a predetermined outer layer thickness formed of a resin of the cylindrical filling portion. In the manufacturing method, when the inner layer thickness is equal to or greater than a predetermined reference value, the layer thickness of the cylindrical filling portion is set to the same size as the outer layer thickness, and the circular The outer diameter of the columnar filling portion is set to be larger than the thickness of the inner layer, and the specifications for injecting the assisting material are such that the cylindrical filling portion is formed into the inner layer without changing the layer thickness of the cylindrical filling portion. When the specification is set to deform into a thick cylindrical shape, and the inner layer thickness is less than a predetermined reference value, the outer diameter of the cylindrical filling portion and the layer thickness of the cylindrical filling portion are respectively equal to the inner layer thickness , the injection specification of the assisting material is set to be larger than the thickness of the outer layer, and the injection specifications of the assist material are such that the cylindrical filling portion is deformed into a cylindrical shape having the thickness of the inner layer, and the thickness of the cylindrical filling portion is set to the thickness of the outer layer. It is characterized by being set to specifications that reduce to
Another method of manufacturing a resin pipe according to the present invention is to inject a plurality of types of molten resins in the extending direction of a cavity formed in a mold to form a cylindrical filling in the center of the cross section of the cavity. and two cylindrical filling portions arranged coaxially with the columnar filling portion on the outer peripheral side of the columnar filling portion so as to be in a laminated state, and radially adjacent to each other. The filling portions are formed of different kinds of resins among the plurality of kinds of resins, and an assisting material is injected into the cavity in the extending direction of the cavity to cure each of the injected resins. As a result, an inner layer having a predetermined inner layer thickness formed of the resin of the cylindrical filling portion, an intermediate layer having a predetermined layer thickness formed of the resin of the cylindrical filling portion on the inner peripheral side, and the above-mentioned A resin pipe manufacturing method for manufacturing a resin pipe having a three-layer structure having an outer layer with a predetermined outer layer thickness formed from a resin of a cylindrical filling portion, wherein the inner layer thickness is a predetermined reference value. In the above case, the layer thickness of the cylindrical filling portion on the inner peripheral side and the layer thickness of the cylindrical filling portion on the outer peripheral side are set to be the same as the thickness of the intermediate layer and the thickness of the outer layer, respectively. Further, the outer diameter of the cylindrical filling portion is set larger than the thickness of the inner layer, and the injection specifications of the assisting material change the layer thickness of the cylindrical filling portion on the inner peripheral side and the outer peripheral side. The specification is set so that the columnar filling portion is deformed into a cylindrical shape having the inner layer thickness without being deformed, and when the inner layer thickness is less than a predetermined reference value, the outer diameter and the inner circumference of the columnar filling portion The layer thickness of the cylindrical filling portion on the side and the layer thickness of the cylindrical filling portion on the outer peripheral side are set larger than the inner layer thickness, the intermediate layer thickness, and the outer layer thickness, respectively, and the assist material The injection specification of deforms the cylindrical filling part into a cylindrical shape with the inner layer thickness, and the layer thickness of the cylindrical filling part on the inner peripheral side and the layer thickness of the cylindrical filling part on the outer peripheral side are respectively set to the thickness of the intermediate layer and the thickness of the outer layer.

According to the present invention, the outer diameter of the cylindrical filling portion made of resin formed in the center of the cross section of the cavity and the injection specification of the assisting material are determined based on the inner layer thickness of the inner layer in the resin pipe to be manufactured. By appropriately setting, it becomes possible to make each of the inner layer and the outer layer of the manufactured resin pipe have desired layer thicknesses.

1(A) is a longitudinal sectional view, and FIG. 1(B) is a transverse sectional view, illustrating a resin pipe manufactured according to the present invention. It is an explanatory view showing an example of a forming device for manufacturing a resin pipe. FIG. 3 is an explanatory view illustrating the mold of FIG. 2 as viewed in longitudinal section; FIG. 4 is an explanatory diagram illustrating a state in which the cavity in FIG. 3 is filled with two types of resin; FIG. 5 is an explanatory diagram illustrating a state in which an assist material is being injected into the cavity of FIG. 4; FIG. 6 is an explanatory diagram illustrating a resin pipe molded in the cavity of FIG. 5; Fig. 7(A) is a vertical cross-sectional view and Fig. 7(B) is a cross-sectional view illustrating another resin pipe manufactured according to the present invention. It is explanatory drawing which illustrates the state which filled the cavity with two types of resin by the longitudinal cross-sectional view of the mold. FIG. 9 is an explanatory diagram illustrating a state in which an assist material is being injected into the cavity of FIG. 8; FIG. 10 is an explanatory diagram illustrating a resin pipe molded in the cavity of FIG. 9; Fig. 11(A) is a vertical cross-sectional view and Fig. 11(B) is a cross-sectional view illustrating yet another resin pipe manufactured according to the present invention. It is explanatory drawing which illustrates the state which filled the cavity with three types of resin. FIG. 13 is an explanatory diagram illustrating a resin pipe molded in the cavity of FIG. 12;

Hereinafter, a method for manufacturing a resin pipe according to the present invention will be described based on embodiments shown in the drawings.

As illustrated in FIGS. 1 and 2, a resin pipe 6 manufactured according to the present invention has an inner layer 7 and an outer layer 8 in which a cylindrical inner layer 7 and a cylindrical outer layer 8 are integrally joined. It has a two-layer structure. More specifically, in this resin pipe 6 (inner diameter D1, outer diameter D2), an outer layer 8 having a desired outer layer thickness t2 is laminated on the outer peripheral surface of an inner layer 7 having a desired inner layer thickness t1.

Since the shape of the resin pipe 6 is determined by space constraints such as the installation location, it is not limited to a straight pipe shape as in this embodiment, but may be a curved pipe. A dashed-dotted line CL in the drawing indicates a center line passing through the cross-sectional center of the pipeline 10 .

Different types of resin are used for the inner layer 7 and the outer layer 8 in order to satisfy the performance required for the resin pipe 6 . Here, different types of resins do not only mean that the types of resins themselves are different, but even if the types of resins themselves are the same, the amounts or types of additives mixed are different also means

For example, the inner layer 7 is made of a resin that is highly resistant to the fluid flowing through the pipeline 10, and the outer layer 8 is made of a resin that is highly resistant to external impact, abrasion, ultraviolet rays, and the like. In this embodiment, the inner layer 7 is made of a resin that is highly resistant to the fluid flowing through the pipeline 10, and the outer layer 8 is made of the same type of resin as the resin used for the inner layer 7, with reinforcing fibers (for example, glass fiber, carbon fiber, etc.) are mixed at a predetermined ratio. That is, the inner layer 7 and the outer layer 8 differ only in whether or not reinforcing fibers are contained in the resin.

This resin pipe 6 is manufactured using the molding apparatus 1 illustrated in FIG. The molding apparatus 1 includes a cylinder 1a for injecting molten resin 4 (two kinds of resins 4a and 4b) into molds 2 (2a and 2b) and an assisting material injection section 1b for injecting assisting material 5 into the molds 2. ing.

The inner layer 7 is formed from one resin 4a, and the outer layer 8 is formed from the other resin 4b. The cylinder 1a employs a known mechanism capable of so-called two-color molding that can inject the respective resins 4a and 4b in a molten state.

The assist material 5 may be a known one, and an appropriate material is selected from gases such as nitrogen gas, liquids such as water, metal balls, resin balls, bullet-shaped metal lumps, resin lumps, and other solids. For the assist material injection part 1b, a known appropriate mechanism is adopted according to the type of the assist material 5. As shown in FIG.

As exemplified in FIG. 3, the mold 2 is a so-called split type, and is composed of one mold 2a and the other mold 2b to be assembled. Mutual molds 2a and 2b are joined and separated with a parting line PL as a boundary.

A cavity 3 that is hollow is formed in the mold 2 . This cavity 3 has the same outer shape as the resin pipe 6 to be manufactured, and in this embodiment is a columnar shape with an outer diameter D2. The cavity 3 is connected to the injection nozzle of the molding device 1 via a runner or the like formed in the mold 2 . The mold 2 is also provided with a discharge portion for discharging excess resin 4 (4a, 4b) from the cavity 3 and a discharge portion for the assist material 5 injected into the cavity 3. FIG.

Next, an example of the procedure of the method for manufacturing the resin pipe 6 illustrated in FIG. 1 will be described.

First, as shown in FIG. 3, the molds 2a and 2b are assembled together and closed. In this state, two types of melted resins 4a and 4b are injected into the cavity 3 by injecting them from the cylinder 1a in the extending direction of the cavity 3 respectively.

By injecting the resins 4a and 4b, as shown in FIG. 4, one resin 4a is filled in the central portion of the cross section of the cavity 3 to form a columnar filling portion 4A having an outer diameter T1. In addition, the cavity 3 is filled with the other resin 4b, and a cylindrical filling portion having a layer thickness of T2 is arranged coaxially with the cylindrical filling portion 4A on the outer peripheral side of the cylindrical filling portion 4A so as to be in a laminated state. 4B is formed. Therefore, the filling portions 4A and 4B adjacent to each other in the radial direction are formed of different types of melted resins 4a and 4b.

When manufacturing a resin pipe 6 having an inner diameter D1, an outer diameter D2, an inner layer 7 having an inner layer thickness t1, and an outer layer 8 having an outer layer thickness t2, the cylindrical shape in the cavity 3 is determined based on the size of the inner layer thickness t1. An outer diameter T1 of the filling portion 4A and injection specifications of the assist material 5 are set. The injection specifications are the injection pressure, injection speed, passage outer diameter W, resin 4 (4a, 4b) are working conditions including temperature.

When the inner layer thickness t1 is thicker than the predetermined reference value C, the layer thickness T2 of the cylindrical filling portion 4B is set to the same size as the outer layer thickness t2 (T2=t2). Since the outer diameter D2 of the cavity 3 is determined, the outer diameter T1 of the cylindrical filling portion 4A is automatically set by setting the layer thickness T2. The outer diameter T1 is set larger than the inner layer thickness t1 (T1>t1).

The injection specification of the assisting material 5 is set so as to transform the cylindrical filling portion 4A into a cylindrical shape having an inner layer thickness t1 without changing the layer thickness T2 of the cylindrical filling portion 4B in the cavity 3 . Specifically, the passing outer diameter W of the assist material 5 is set substantially equal to the inner diameter D1 of the resin pipe 6 to be manufactured. When the solid assist material 5 is used, the outer diameter of the assist material 5 is made the same as the passage outer diameter W (outer diameter D1). The injection pressure and injection speed of the assist material 5 and the temperature of the resin 4 (4a, 4b) are set to values within an appropriate allowable range based on the data obtained during the molding test of the resin pipe 6 and the like. In order to suppress the fluidity of the cylindrical filling portion 4B (resin 4b), the temperature should be lower than that of the cylindrical filling portion 4A (resin 4a). When gas or liquid assisting material 5 is used, the injection pressure, injection speed, etc. of assisting material 5 are adjusted so that the passing outer diameter W (outer diameter D1) is obtained.

Immediately after filling the cavity 3 with the resin 4 (4a, 4b), the assisting material 5 is injected into the mold 2 from the assisting material injection part 1b at a predetermined high pressure according to the set injection specifications as shown in FIG. do. The injected assisting material 5 passes through the interior of the uncured columnar filling portion 4A along the extending direction of the cavity 3 at high pressure. As the assist material 5 passes through, part of the resin 4a of the columnar filling portion 4A that is not yet completely cured is discharged to the outside of the cavity 3, and the columnar filling portion 4A has a desired layer thickness (inner layer It is molded into a cylindrical shape with a thickness t1). The passing outer diameter W of the assist material 5 is set smaller than the outer diameter T1 of the cylindrical filling portion 4A. Therefore, even if the assist material 5 is injected, the layer thickness T2 of the cylindrical filling portion 4B does not substantially change.

Thereafter, as illustrated in FIG. 6, the respective resins 4a and 4b are cured to form an inner layer 7 having an inner layer thickness t1 and an outer layer 8 having an outer layer thickness t2, and the resins 4a and 4b are joined together. . Thereby, a resin pipe 6 having a desired shape along the cavity 3 is formed. That is, when the injection molding process of the resin 4 is completed, the resin pipe 6 having a two-layer structure having the inner layer 7 and the outer layer 8 is manufactured.

As described above, when the inner layer thickness t1 is greater than or equal to the predetermined reference value C, only the cylindrical filling portion 4A formed in the cavity 3 is deformed by the injected assist material 5 to Part of the resin 4 a is discharged from the cavity 3 . When molding is performed in this way, it is easy to secure the desired inner layer thickness t1 and outer layer thickness t2.

Next, as illustrated in FIG. 7, the procedure for manufacturing the resin pipe 6 when the inner layer thickness t1 is less than a predetermined reference value C will be described.

In this case, as illustrated in FIG. 8, the outer diameter T1 of the cylindrical filling portion 4A in the cavity 3 and the layer thickness T2 of the cylindrical filling portion 4B are larger than the inner layer thickness t1 and the outer layer thickness t2, respectively. are set (T1>t1, T2>t2).

The injection specification of the assist material 5 is such that the columnar filling portion 4A in the cavity 3 is deformed into a cylindrical shape with an inner layer thickness t1, and the layer thickness T2 of the cylindrical filling portion 4B is reduced to an outer layer thickness t2. set. Specifically, the passing outer diameter W of the assist material 5 is set substantially equal to the inner diameter D1 of the resin pipe 6 to be manufactured. When the solid assist material 5 is used, the outer diameter of the assist material 5 is made the same as the passage outer diameter W (outer diameter D1). The injection pressure and injection speed of the assist material 5 and the temperature of the resin 4 (4a, 4b) are set to values within an appropriate allowable range based on the data obtained during the molding test of the resin pipe 6 and the like. The cylindrical filling portion 4A (resin 4a) and the cylindrical filling portion 4B (resin 4b) are maintained at a high temperature corresponding to the injection temperature of the respective resins 4a and 4b in order to ensure high fluidity. do it. When gas or liquid assisting material 5 is used, the injection pressure, injection speed, etc. of assisting material 5 are adjusted so that the passing outer diameter W (outer diameter D1) is obtained.

Immediately after filling the cavity 3 with the resin 4 (4a, 4b), the assisting material 5 is injected into the mold 2 from the assisting material injection part 1b at a predetermined high pressure according to the set injection specifications as shown in FIG. do. The injected assisting material 5 passes through the interior of the uncured columnar filling portion 4A along the extending direction of the cavity 3 at high pressure. As the assist material 5 passes through, part of the resin 4a of the columnar filling portion 4A that is not yet completely cured is discharged to the outside of the cavity 3, and the columnar filling portion 4A has a desired layer thickness (inner layer It is molded to a thickness t1).

The passing outer diameter W of the assist material 5 is set larger than the outer diameter T1 of the cylindrical filling portion 4A. Therefore, when the assist material 5 is injected, the columnar filling portion 4A expands in diameter and deforms into a cylindrical shape. The filling portion 4B is formed to have a desired layer thickness (outer layer thickness t2).

Thereafter, as illustrated in FIG. 10, the respective resins 4a and 4b are cured to form an inner layer 7 having an inner layer thickness t1 and an outer layer 8 having an outer layer thickness t2, and the resins 4a and 4b are joined together. . Thereby, a resin pipe 6 having a desired shape along the cavity 3 is formed. That is, when the injection molding process of the resin 4 is completed, the resin pipe 6 having a two-layer structure having the inner layer 7 and the outer layer 8 is manufactured.

As described above, when the inner layer thickness t1 is thin and less than the predetermined reference value C, the cylindrical filling portion 4A and the cylindrical filling portion 4B in the cavity 3 are deformed by the injected assist material 5. , part of each resin 4a, 4b is discharged from the cavity 3. As shown in FIG. When molding is performed in this way, it is easy to secure the desired inner layer thickness t1 and outer layer thickness t2.

The predetermined reference value C for the thickness t1 of the inner layer 7 differs depending on the type (specification) of the resin 4 . Therefore, for example, a molding test of the resin pipe 6 is repeatedly performed under various conditions in which the dimensions T1 and T2 of the filling portions 4A and 4B in the cavity 3 are varied for each type (specification) of the resin 4. FIG. Data of the layer thicknesses of the inner layer 7 and the outer layer 8 of the resin pipe 6 formed by such a molding test can be obtained, and the predetermined reference value C can be determined based on the obtained data. In the case of the resin pipe 6 having an inner diameter D1 of about 10 mm to 20 mm, the predetermined reference value C is about 1 mm, for example.

Thus, based on the preset inner layer thickness t1 of the inner layer 7 in the resin pipe 6, the outer diameter T1 of the cylindrical filling portion 4A in the cavity 3 and the injection specification of the assisting material 5 are appropriately set. do. By performing injection molding based on these set conditions, it is possible to manufacture the resin pipe 6 having the inner layer 7 with the desired inner layer thickness t1 and the outer layer 8 with the desired outer layer thickness t2.

The resin pipe 6 is not limited to a two-layer structure as in each of the above-described embodiments, and as illustrated in FIG. , an inner layer 7, an intermediate layer 9, and an outer layer 8 may be integrally joined to form a multi-layer structure. The resin pipe 6 illustrated in FIG. 11 has a three-layer structure in which one intermediate layer 9 (layer thickness t3) is interposed between an inner layer 7 having an inner layer thickness t1 and an outer layer 8 having an outer layer thickness t2. Although it is possible to manufacture a resin pipe 6 having a four-layer structure or a five-layer structure by using two or three intermediate layers 9, it becomes more difficult to manufacture the resin pipe 6 as the number of layers of the intermediate layers 9 increases. .

In order to manufacture the resin pipe 6 having a three-layer structure, as shown in FIG. A cylindrical filling portion 4A having a diameter T1, and two cylindrical filling portions 4B and 4C arranged coaxially with the cylindrical filling portion 4a on the outer peripheral side of the cylindrical filling portion 4A to form a stacked state. Form. The layer thicknesses of the cylindrical filling portions 4B and 4C are T2 and T3, respectively. Filling portions 4A, 4B, and 4C are formed of resins 4a, 4b, and 4c, respectively. Filling portions 4A, 4B, and 4C adjacent to each other in the radial direction are made of resins 4 of different types.

Next, as in the previous embodiment, the assist material 5 is injected into the cavity 3 in the extending direction of the cavity 3 . Here, when the inner layer thickness t1 is thicker than the predetermined reference value C, the layer thickness T2 of the outermost cylindrical filling portion 4B is The outer diameter T1 of the cylindrical filling portion 4A, which is set to the same size as the outer layer thickness t2, is set larger than the inner layer thickness t1. Furthermore, the layer thickness T3 of the cylindrical filling portion 4C is set substantially equal to the layer thickness t3 of the intermediate layer 9 .

The injection specification of the assisting material 5 is set so as to transform the cylindrical filling portion 4A into a cylindrical shape having an inner layer thickness t1 without changing the layer thickness T2 of the outermost cylindrical filling portion 4B. Furthermore, the thickness T3 of the cylindrical filling portion 4C is also set to a specification that does not change.

When the inner layer thickness t1 is thin and less than the predetermined reference value C, as in the embodiment illustrated in FIGS. The layer thickness T2 of 4B is set larger than the inner layer thickness t1 and the outer layer thickness t2, respectively. Furthermore, the layer thickness T3 of the cylindrical filling portion 4C is set larger than the layer thickness t3 of the intermediate layer 9 .

The specifications for injecting the assisting material are set such that the cylindrical filling portion 4A is deformed into a cylindrical shape with an inner layer thickness t1, and the layer thickness T2 of the outermost cylindrical filling portion 4B is reduced to the outer layer thickness t2. be. Furthermore, the specification is set such that the layer thickness T3 of the cylindrical filling portion 4C is reduced to the layer thickness t3 of the intermediate layer 9 .

Then, by curing each injected resin 4, as illustrated in FIG. 13, the inner layer 7 having a predetermined inner layer thickness t1 and the cylindrical filling portion are formed by the resin 4a forming the cylindrical filling portion 4A. The resin 4b forming 4B forms an outer layer 8 having a predetermined outer layer thickness t2, and the resin 4c forming the cylindrical filling portion 4C forms an intermediate layer 9 having a predetermined layer thickness t3.

Thereafter, the respective resins 4a, 4b, and 4c are cured to form an inner layer 7 having an inner layer thickness t1, an outer layer 8 having an outer layer thickness t2, and an intermediate layer 9 having a layer thickness t3. 4b and 4c are joined together. Thereby, a resin pipe 6 having a desired shape along the cavity 3 is formed. That is, when the injection molding process of the resin 4 is completed, the three-layer structure resin pipe 6 having the inner layer 7, the outer layer 8 and the intermediate layer 9 is manufactured.

1 molding device 1a cylinder 1b assist material injection part 2 (2a, 2b) mold 3 cavity 4 (4a, 4b, 4c) resin 4A cylindrical filling part 4B, 4C cylindrical filling part 5 assist material 6 resin pipe 7 inner layer 8 outer layer 9 intermediate layer 10 pipeline

Claims (4)

Two kinds of melted resins are injected in the extending direction of the cavity formed in the mold, respectively, to form a cylindrical filling portion in the center of the cross section of the cavity and the outer peripheral side of the cylindrical filling portion. Then, one cylindrical filling portion is arranged coaxially with the columnar filling portion to form a layered state, and the filling portions adjacent to each other in the radial direction are formed of different types of resin. Then, by injecting an assisting material into the cavity in the extending direction of the cavity and curing each of the injected resins, a predetermined inner layer thickness formed by the resin of the cylindrical filling portion is obtained. A resin pipe manufacturing method for manufacturing a resin pipe having a two -layer structure having an inner layer and an outer layer having a predetermined outer layer thickness formed of the resin of the cylindrical filling portion,
When the inner layer thickness is equal to or greater than a predetermined reference value, the layer thickness of the cylindrical filling portion is set to the same size as the outer layer thickness, and the outer layer thickness of the cylindrical filling portion The diameter is set larger than the thickness of the inner layer, and the injection specification of the assisting material is such that the cylindrical filling portion is deformed into a cylindrical shape having the thickness of the inner layer without changing the layer thickness of the cylindrical filling portion. It is set to specifications that allow
When the inner layer thickness is less than a predetermined reference value, the outer diameter of the cylindrical filling portion and the layer thickness of the cylindrical filling portion are set larger than the inner layer thickness and the outer layer thickness, respectively, and the assist The material injection specification is set to a specification that deforms the cylindrical filling part into a cylindrical shape with the inner layer thickness and reduces the layer thickness of the cylindrical filling part to the outer layer thickness. A method for manufacturing a resin pipe. 2. The method of manufacturing a resin pipe according to claim 1 , wherein the resin of the cylindrical filling portion is a fiber-reinforced resin in which reinforcing fibers are mixed with the same type of resin as the resin of the cylindrical filling portion. A plurality of types of melted resins are injected in the extending direction of the cavity formed in the mold to form a cylindrical filling portion in the center of the cross section of the cavity and the outer peripheral side of the cylindrical filling portion. Then, two cylindrical filling portions are arranged coaxially with the cylindrical filling portion to form a layered state, and the filling portions adjacent to each other in the radial direction are filled with the plurality of kinds of resins. By injecting an assisting material into the cavity in the extending direction of the cavity and curing each of the injected resins, the resin of the columnar filling portion is An inner layer with a predetermined inner layer thickness formed by, an intermediate layer with a predetermined layer thickness formed from the resin of the cylindrical filling portion on the inner peripheral side, and the resin of the cylindrical filling portion on the outer peripheral side A resin pipe manufacturing method for manufacturing a resin pipe having a three -layer structure having an outer layer with a predetermined outer layer thickness, comprising:
When the inner layer thickness is equal to or greater than a predetermined reference value, the layer thickness of the cylindrical filling portion on the inner peripheral side and the layer thickness of the cylindrical filling portion on the outer peripheral side are respectively the intermediate layer and the thickness of the outer layer is set to be the same as the thickness of the outer layer, and the outer diameter of the cylindrical filling portion is set to be larger than the thickness of the inner layer. It is set to a specification that deforms the cylindrical filling part into a cylindrical shape with the inner layer thickness without changing the layer thickness of the cylindrical filling part on the side,
When the inner layer thickness is less than a predetermined reference value, the outer diameter of the cylindrical filling portion, the layer thickness of the cylindrical filling portion on the inner peripheral side, and the layer thickness of the cylindrical filling portion on the outer peripheral side are The thickness of the inner layer, the thickness of the intermediate layer, and the thickness of the outer layer are set to be larger than the thickness of the inner layer, and the thickness of the outer layer is set to be larger than the thickness of the outer layer. The thickness of the cylindrical filling portion on the peripheral side and the thickness of the cylindrical filling portion on the outer peripheral side are set to be reduced to the thickness of the intermediate layer and the thickness of the outer layer, respectively. A method for manufacturing a resin pipe . 4. The method of manufacturing a resin pipe according to claim 3 , wherein the resin of the cylindrical filling portion on the inner peripheral side is a fiber-reinforced resin in which reinforcing fibers are mixed with the same type of resin as the resin of the cylindrical filling portion. .

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