Joint structure and method for manufacturing joint structure

Abstract

To provide a joint structure with which a pressure loss inside a pipe is reduced.SOLUTION: A joint structure comprises: a stepped joint that is formed of a thermoplastic resin to have a hollow with a predetermined inner diameter, and has a base and a fitting portion whose outer diameter is smaller than the outer diameter of the base; and a tubular body that is formed of a thermoplastic resin into a tubular shape and has a general portion with an inner diameter equal to the inner diameter of the stepped joint, in which a portion on an opening end side is set as a fitted portion having an inner diameter larger than that of the general portion, the tubular body is fitted with the fitting portion, and the fitted portion is heat welded to the stepped joint in the state that an inner step at the boundary between the general portion and the fitted portion abuts against the end face of the fitting portion in the stepped joint.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a joint structure and a method for manufacturing the joint structure.

Background Art

[0002] The heat fusion joint described in Patent Document 1 has an insertion hole into which a pipe to be joined is inserted, and at least the inner peripheral surface on the inlet side of the insertion hole is composed of an inner peripheral surface layer made of a resin material that melts at a lower temperature than the other heat fusion joint main body part.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a joint structure including a stepped joint and a tubular body, when the tubular body in a state where a part thereof is fitted inside the fitting portion of the joint is heat-welded, a step is generated between the joint and the tubular body, and a pressure loss inside the pipe occurs.

[0005] An object of the present disclosure is to provide a joint structure in which the pressure loss inside the pipe is reduced as compared with a configuration in which a tubular body in a state where a part thereof is fitted inside the fitting portion of the joint is heat-welded.

Means for Solving the Problems

[0006] The joint structure according to the first aspect is a stepped joint formed of a thermoplastic resin and hollow with a predetermined inner diameter, the stepped joint having a base portion and a fitting portion with an outer diameter smaller than the outer diameter of the base portion, and a tubular body formed of a thermoplastic resin and having a general portion with an inner diameter equivalent to the inner diameter of the stepped joint, and a fitted portion on a part of the open end side having an inner diameter larger than that of the general portion, the fitted portion being heat-welded to the stepped joint in a state where it is fitted to the fitting portion and abuts against an inner step at the boundary between the general portion and the fitted portion.

[0007] According to the joint structure according to the first aspect, in the fitting portion between the stepped joint and the tubular body, compared with a configuration in which the stepped joint and the tubular body are separated in the tube axis direction or a configuration in which the inner diameter of the stepped joint and the inner diameter of the tubular body are different, the inside of the tube is formed of a smooth surface, so that the pressure loss inside the tube is reduced.

[0008] The joint structure according to the second aspect is the joint structure according to the first aspect, wherein the stepped joint has an outer step at the boundary between the base portion and the fitting portion, the tubular body has an outer diameter equivalent to the outer diameter of the base portion, and the end face of the fitted portion abuts against the outer step.

[0009] According to the joint structure according to the second aspect, the fitting portion having an outer diameter smaller than the outer diameter of the base portion in the stepped joint and the fitted portion of the tubular body having an outer diameter equivalent to the outer diameter of the base portion are fitted and the fitted portion in a state of abutting against the outer step is heat-welded to the stepped joint. As a result, in this joint structure, there is no step at the connection portion between the base portion of the stepped joint and the tubular body, so that it looks better than a configuration in which the tubular body is heat-welded inside the fitting portion of the joint.

[0010] The joint structure according to the third aspect is the joint structure according to the first aspect or the second aspect, wherein the stepped joint has a diameter-expanded portion formed on the outer periphery of the fitting portion and in contact with the inner surface of the fitted portion.

[0011] According to the joint structure according to the third aspect, in a state where the tubular body is fitted until the fitted portion abuts against the outer step of the stepped joint, since the diameter-expanded portion contacts the inner surface of the fitted portion, it serves as a retaining means in the fitting direction of the tubular body with respect to the stepped joint before welding.

[0012] The joint structure according to the fourth aspect is the joint structure according to the third aspect, wherein the diameter-expanded portion is formed in a tapered shape that continuously expands in diameter as it moves away from the first step.

[0013] According to the joint structure according to the fourth aspect, since the diameter-expanded portion continuously expands the outer periphery of the fitting portion, processing becomes easier compared to a configuration in which protrusions are provided on the outer periphery of the fitting portion.

[0014] The joint structure according to the fifth aspect is the joint structure according to any one of the first to fourth aspects, wherein the fitted portion is formed with a through hole that opens to the inner and outer circumferences and is filled with the thermoplastic resin.

[0015] According to the joint structure according to the fifth aspect, since the through hole is filled with the melted thermoplastic resin from the fitting portion side of the stepped joint, it is confirmed that the fitting of the tubular body to the stepped joint is completed.

[0016] A method for manufacturing a joint structure according to the sixth aspect is a stepped joint formed hollow with a thermoplastic resin, having a base portion and a fitting portion having an outer diameter smaller than the outer diameter of the base portion, and preparing a stepped joint having an outer step at the boundary between the base portion and the fitting portion, processing a part of the open end side of a tubular body formed with a thermoplastic resin to form a fitted portion having an inner diameter larger than the general portion of the tubular body, abutting the fitted portion against the first step of the fitting portion and fitting it with the fitting portion, and heating the fitting portion and the fitted portion to thermally weld the tubular body to the stepped joint.

[0017] According to the method for manufacturing a joint structure according to the sixth aspect, since a fitting portion having an outer diameter smaller than the outer diameter of the base portion in the stepped joint and a fitted portion of the tubular body having the same outer diameter as the outer diameter of the base portion are thermally welded, the appearance of the joint structure is better compared to a configuration in which the tubular body is thermally welded inside the fitting portion of the joint.

Effect of the Invention

[0018] According to the present disclosure, the pressure loss inside the pipe is reduced as compared with a configuration in which a tubular body in a state where a part thereof is fitted inside the fitting portion of the joint is thermally welded.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0020] An example of a joint structure 10 according to an embodiment of the present disclosure will be described in detail with reference to FIGS. 1 to 3. In the figures, the arrow W indicates the width direction (longitudinal direction) of the joint structure 10, and the arrow H indicates the vertical direction (height direction) of the joint structure 10. Also, a direction orthogonal to the arrows W and H and going from the front to the back is shown as the depth direction. The width direction, the vertical direction, and the depth direction are orthogonal to each other. In this specification, the above directions are used for the description, but the posture of the joint structure 10 is not limited to these directions.

[0021] <Joint Structure> (Overall Configuration) As shown in FIG. 1, the joint structure 10 according to the present embodiment is, as an example, a connection between a stepped joint 20 for water supply and hot water supply and a pipe 30. Hereinafter, in the present embodiment, the stepped joint 20 is simply referred to as the joint 20. The joint structure 10 is a hollow cheese (tees, tee) pipe extending in the longitudinal direction and the vertical direction, respectively. The joint structure 10 has a joint 20 and a pipe 30. In the joint structure 10 according to the present embodiment, one pipe 30 is fitted into the joint 20 from the longitudinal direction.

[0022] (Joint) As shown in FIGS. 1 and 2, the joint 20 is a T-shaped hollow member along the center line c1 in the longitudinal direction and along the vertical direction orthogonal to the center line c2 at the center in the longitudinal direction, and both ends in the longitudinal direction and the upper end in the vertical direction are open. The joint 20 can fit the pipe 30 to both ends in the longitudinal direction and the upper end in the vertical direction, respectively. The joint 20 is formed of a thermoplastic resin. The thermoplastic resin is, for example, polybutene, polyethylene, polypropylene, an elastomer compounded polyolefin resin, PET (polyethylene terephthalate), PPS (polyphenylene sulfide). The joint 20 has a base 22, a first fitting portion 23, a second fitting portion 24, and a third fitting portion 25. The first fitting portion 23, the second fitting portion 24, and the third fitting portion 25 are examples of fitting portions. In the joint 20, the first fitting portion 23 is arranged along the vertical direction, and the second fitting portion 24 and the third fitting portion 25 are arranged along the longitudinal direction, respectively.

[0023] In the present embodiment, the fitting and connection between the joint 20 and the second fitting portion 24 will be described. However, since the fitting and connection are also applicable to the fitting and connection between the joint 20 and the first fitting portion 23 and the third fitting portion 25, the description of the fitting and connection between the joint 20 and the first fitting portion 23 and the third fitting portion 25 will be omitted.

[0024] ((Base)) The base 22 is a T-shaped hollow part that extends vertically in the center of a cylindrical body extending in the longitudinal direction and has a shape in which a cylindrical body common to the cylindrical body is connected. The base 22 has an outer diameter d22 and an inner diameter d21. That is, the base 22 has a uniform outer diameter d22 and an inner diameter d21 in the longitudinal direction and the vertical direction, respectively, except for the connection part between the cylindrical bodies.

[0025] ((Fitting part)) The second fitting part 24 is a cylindrical body that extends longitudinally from the end of the base 22 and is along the center line c1. The second fitting part 24 fits with a fitting part 34 of a pipe 30 described later. The second fitting part 24 has an inner diameter d21 common to the inner diameter of the base 22 and an outer diameter d23 smaller than the outer diameter d22 of the base 22. That is, there is a step 26 at the boundary between the second fitting part 24 and the base 22.

[0026] An end surface 24A along the vertical direction is formed at the end of the second fitting part 24 on the opening side (opposite side to the connection end with the base 22). Also, the outer cylindrical surface of the second fitting part 24 is an outer peripheral surface 24B. The longitudinal length of the second fitting part 24 is, for example, shorter than the longitudinal length of the base 22.

[0027] The step 26 is a flat surface with an annular shape when viewed from the longitudinal direction and is a step surface at the boundary between the outer peripheral surface of the base 22 and the outer peripheral surface 24B of the second fitting part 24. That is, the step 26 can be said to be the longitudinal end surface of the base 22. The step 26 extends along the vertical direction and is in surface contact with the end of the fitting part 34 of the pipe 30 described later. The step 26 is an example of an outer step.

[0028] As described above, the joint 20 has the base 22 and the second fitting part 24, and is a stepped joint with a step 26 formed at this boundary.

[0029] (Pipe) As shown in FIG. 2, the pipe 30 is a cylindrical body that extends in the longitudinal direction and has a uniform outer diameter d32. The pipe 30 is an example of a tubular body. The pipe 30 is fitted with the second fitting part 24 of the joint 20 on the one end 30A side. The pipe 30 has a general part 32 and a fitting part 34 with different inner diameters from each other.

[0030] ((General part)) The general part 32 is a cylindrical part that extends in the longitudinal direction and has an inner diameter d31. The wall thickness of the general part 32 (the difference between the outer diameter d32 and the inner diameter d31) is made equal to the wall thickness of the base 22 of the joint 20 (the difference between the outer diameter d22 and the inner diameter d21).

[0031] ((Fitted part)) The fitted part 34 is a cylindrical part that extends in the longitudinal direction and has an inner diameter d33. The inner diameter d33 of the fitted part 34 is formed larger than the inner diameter d31 of the general part 32. That is, there is a step 36 at the boundary between the fitted part 34 and the general part 32. The step 36 is an example of an inner step. The longitudinal length of the fitted part 34 is, for example, shorter than the longitudinal length of the general part 32. The fitted part 34 has an inner peripheral surface 34A.

[0032] The step 36 is a flat surface inside the annular pipe 30 as viewed from the longitudinal direction, and is a step surface at the boundary between the inner peripheral surface 34A of the fitted part 34 and the inner peripheral surface of the general part 32. That is, the step 36 can be said to be one end surface in the longitudinal direction of the general part 32.

[0033] The step 36 extends along the vertical direction and is in surface contact with the end surface 24A of the second fitting part 24 of the joint 20. That is, the pipe 30 is in a state where the step 36 abuts against the end surface 24A of the second fitting part 24 in the joint 20, and the fitted part 34 of the pipe 30 is fitted with the second fitting part 24 of the joint 20. When the joint 20 and the pipe 30 are heated under predetermined conditions in a state where the fitted part 34 and the second fitting part 24 are fitted, the contact surface between the pipe 30 and the joint 20 is welded by heat (heat welding), and the pipe 30 is connected to the joint 20.

[0034] As described above, the pipe 30 has the general part 32 and the fitted part 34, and is a pipe in which the step 36 is formed at this boundary.

[0035] Therefore, the joint structure 10 is heat welded in a state where arc-shaped surfaces without longitudinal gaps or vertical steps are continuous on the inner and outer circumferences of the connection portion between the joint 20 and the pipe 30.

[0036] <Manufacturing method of joint structure> Next, a manufacturing method of the joint structure 10 in the present embodiment will be described with reference to FIG. 3.

[0037] In FIG. 3(A), in the present embodiment, a joint 20 having a base portion 22 and at least a second fitting portion 24 and having a step 26 is prepared such that the center of the second fitting portion 24 is along the longitudinal direction.

[0038] Next, in FIG. 3(B), a base material that will become a pipe 30 formed of a thermoplastic resin and having an inner diameter d31 is prepared such that the center of the base material is along the longitudinal direction.

[0039] Next, in FIG. 3(C), from one end 30A side which is the open end of the base material that will become the pipe 30, along the longitudinal direction by a predetermined distance, the inner peripheral surface 34A is peeled with a jig until the inner diameter becomes d33. Here, peeling is an example of processing, and peeling means cutting a part of the processing target, shaving it off, etc. The jig is a well-known cutting tool, for example, a scraper, a grinder, a sander, a plane, a plane, etc. As a result of peeling, the base material becomes the pipe 30, and the pipe 30 forms a fitted portion 34 on the one end 30A side with the step 36 as a boundary.

[0040] In FIG. 3(D), the fitted portion 34 of the pipe 30 is abutted against the step 26 of the joint 20 and fitted with the second fitting portion 24. Then, at least the second fitting portion of the joint 20 and the fitted portion 34 of the pipe 30 are heated using a heater (not shown) to thermally weld the pipe 30 to the joint 20.

[0041] <Function and effect> The joint structure 10 according to this embodiment is a joint 20 formed hollow with an inner diameter d21 from a thermoplastic resin, the joint 20 having a base portion 22 and a second fitting portion 24 with an outer diameter d23 smaller than the outer diameter d22 of the base portion 22, and a pipe 30 formed tubular from a thermoplastic resin, the pipe 30 having a general portion with an inner diameter d31 equivalent to the inner diameter d21 of the joint 20, a part on the one end 30A side being a fitted portion 34 with an inner diameter d33 larger than the inner diameter d31 of the general portion 32, and the fitted portion 34 being heat-welded to the joint 20 in a state where the second fitting portion 24 is fitted and a step 36 abuts against the end face 24A of the second fitting portion 24. According to the joint structure 10 according to this embodiment, in the fitting portion between the joint 20 and the pipe 30, compared with a configuration where the end face 24A of the second fitting portion 24 and the step 36 are separated in the longitudinal direction, or a configuration where the inner diameter d21 of the joint 20 and the inner diameter d31 of the pipe 30 are different, since the inside of the pipe is formed with a smooth surface, the pressure loss inside the pipe 30 is reduced. That is, by heat-welding the inner surface of the pipe 30, since the inner diameter of the joint 20 is the same as the inner diameter of the pipe 30, a flow rate is ensured.

[0042] Moreover, the manufacturing method of the joint structure 10 according to this embodiment is to prepare a joint 20 formed hollow from a thermoplastic resin, the joint 20 having a base portion 22 and a second fitting portion 24 with an outer diameter d23 smaller than the outer diameter d22 of the base portion 22, and having a step 26 at the boundary between the base portion 22 and the second fitting portion 24, peel a part on the one end 30A side of a pipe 30 formed from a thermoplastic resin to form a fitted portion 34 with an inner diameter d33 larger than the inner diameter d31 of the general portion 32 of the pipe 30, abut the fitted portion 34 against the step 36 of the second fitting portion 24 to fit it with the second fitting portion 24, heat the second fitting portion 24 and the fitted portion 34, and heat-weld the pipe 30 to the joint 20.

[0043] According to the manufacturing method of the joint structure 10 according to the present embodiment, a second fitting portion 24 having an outer diameter d23 smaller than the outer diameter d22 of the base portion 22 in the joint 20 and a fitting portion 34 of the pipe 30 having an outer diameter d32 equal to the outer diameter d22 of the base portion 22 are fitted, and the fitting portion 34 in a state of abutting against the step 26 is heat-welded to the joint 20. As a result, in this joint structure, there is no step at the connection portion between the base portion 22 of the joint 20 and the pipe 30, so it looks better than a configuration in which the pipe in a state where a part is fitted inside the fitting portion of the joint is heat-welded. That is, when a step is generated between the outer surface of the joint and the outer peripheral surface of the pipe, it is necessary to separately prepare a protective material. By adopting an inner surface water stop structure, the outer diameter of the joint 20 becomes equal to the outer diameter of the pipe 30, improving the design and leading to simplification of the protective material due to the generation of a step. Further, by heat-welding the inner surface of the pipe 30, the melting amount of the thermoplastic resin is reduced compared to the outer surface water stop structure, so the melting time and the cooling time are shortened.

[0044] Further, in the joint structure 10 according to the present embodiment, the joint 20 has a step 26, the pipe 30 has an outer diameter d32 equal to the outer diameter d22 of the base portion 22, and one end 30A of the fitting portion 34 abuts against the step 26.

[0045] According to the joint structure 10 according to the present embodiment, a second fitting portion 24 having an outer diameter d23 smaller than the outer diameter d22 of the base portion 22 in the joint 20 and a fitting portion 34 of the pipe 30 having an outer diameter d32 equal to the outer diameter d22 of the base portion 22 are fitted, and the fitting portion 34 in a state of abutting against the step 26 is heat-welded to the joint 20. As a result, in this joint structure, there is no step at the connection portion between the base portion 22 of the joint 20 and the pipe 30, so it looks better than a configuration in which the pipe in a state where a part is fitted inside the fitting portion of the joint is heat-welded.

[0046] <Modification example> Although the present disclosure has been described in detail with respect to specific embodiments, it is obvious to those skilled in the art that the present disclosure is not limited to the specific embodiments and that the present disclosure can take various other embodiments within the scope of the present disclosure.

[0047] For example, the following modification examples can be cited. In the descriptions of the first modification example, the second modification example, and the third modification example, descriptions of the configurations common to the joint structure 10 according to the above embodiment will be omitted.

[0048] (First Modification Example) As shown in FIG. 4, in the joint 20 of the joint structure 10 according to the first modification example, a diameter-expanded portion 28 is formed on the outer peripheral surface 24B of the second fitting portion 24. In this modification example, when viewed from the front, the cross section is triangular, and the first diameter-expanded portion 28A and the second diameter-expanded portion 28B are formed at a predetermined distance from each other in the longitudinal direction. The diameter-expanded portion 28 has an outer diameter d24. That is, the diameter-expanded portion 28 is a circular ring-shaped surface with a diameter d24 when viewed from the longitudinal direction. The outer diameter d24 of the diameter-expanded portion 28 in this modification example is formed smaller than the outer diameter d22 of the base portion 22. The diameter-expanded portion 28 is formed on the base portion 22 side rather than the end surface 24A, and the second diameter-expanded portion 28B is formed closer to the base portion 22 than the first diameter-expanded portion 28A.

[0049] The fitted portion of the pipe into which the second fitting portion 24 is fitted has the same shape as in the above embodiment, but a shape corresponding to the diameter-expanded portion 28, for example, a groove with a triangular cross section may be formed on the inner peripheral surface of the fitted portion.

[0050] In this modification example, in a state where the pipe 30 is fitted until the fitted portion 34 abuts against the step 26 of the joint 20, the diameter-expanded portion 28 contacts the inner surface of the fitted portion 34, so that it serves as a retaining means in the fitting direction (longitudinal direction) of the pipe 30 with respect to the joint 20 before welding.

[0051] (Second Modification Example) Also, as shown in FIG. 5, the joint 20 of the joint structure 10 according to the second modification example has a diameter-expanded portion 28 formed in a tapered shape on the outer peripheral surface 24B of the second fitting portion 24. Specifically, the diameter-expanded portion 28 in this modification example is formed in a tapered shape that continuously expands as it moves away from the step of the base portion 22. The outer diameter d24 at the end surface 24A of the diameter-expanded portion 28 is formed smaller than the outer diameter d22 of the base portion 22.

[0052] In this modified example, since the diameter-expanded portion 28 continuously expands the outer peripheral surface 24B of the second fitting portion 24, the processing becomes easier compared to the configuration in which protrusions are provided on the outer periphery of the second fitting portion 24.

[0053] (Third Modified Example) Also, as shown in FIG. 6, in the pipe 30 of the joint structure 10 according to the third modified example, a through hole 34B is formed in the fitting portion 34. The through hole 34B opens to the inner and outer circumferences along the vertical direction.

[0054] In this modified example, when the pipe 30 is heat-welded to the joint 20, the through hole 34B is filled with the melted thermoplastic resin from the second fitting portion 24 side of the joint 20, so that the completion of the connection of the pipe 30 to the joint 20 can be confirmed, for example, by visual inspection or touch.

[0055] (Other Modified Examples) The joint structure 10 is used for water supply and hot water supply, but is not limited thereto. For example, the joint structure 10 may be used for drainage containing foreign substances or oil, and the substance flowing inside is not limited to a fluid, and may be powder, granule, or gas.

[0056] The joint 20 extends in the longitudinal direction and the vertical direction, respectively, but is not limited thereto. For example, the joint 20 may extend in the longitudinal direction and a direction intersecting the longitudinal direction, respectively, and may extend only in the longitudinal direction or only in the vertical direction. Also, the joint 20 is not limited to a tee, and may be an elbow, a straight pipe joint, a reducing tee, or the like. Also, the joint 20 may not have an inner diameter equivalent to the inner diameter d31 of the general portion 32 of the pipe 30. Also, the joint 20 may not have a diameter-expanded portion 28. When the joint 20 has a diameter-expanded portion 28, the shape of the diameter-expanded portion 28 does not have to be tapered or triangular.

[0057] The pipe 30 is a cylindrical body, but is not limited thereto. The cross section of the pipe 30 is not limited to a circle, and may be an ellipse. Also, regarding the peel of the base material related to the pipe 30, the direction and method of peeling are not limited. Also, a through hole 34B may not be formed in the fitting portion 34 of the pipe 30.

[0058] Also, regarding the third modification example, the joint 20 may be configured such that the color changes according to the thickness when melted. Specifically, when a joint 20 formed by sequentially laminating thermoplastic resins mixed with different dyes for each specific thickness in the pipe diameter direction is used for the joint structure 10, the melting amount can be determined by the dye, so that the melting amount can be saved and the melting amount becomes clear.

[0059] (Contribution to the Sustainable Development Goals (SDGs) led by the United Nations) The SDGs have been proposed towards the realization of a sustainable society. One embodiment of the present disclosure can be a technology that contributes to "No. 6 - Safe water and toilets around the world" and the like.

[0060] (Supplementary Note) (((1))) A stepped joint formed hollow with a thermoplastic resin, having a base portion and a fitting portion with an outer diameter smaller than the outer diameter of the base portion, and a stepped joint having an outer step at the boundary between the base portion and the fitting portion, A tubular body formed of a thermoplastic resin into a tubular shape having an outer diameter equal to the outer diameter of the base portion, with a fitting portion on the opening end side having an inner diameter larger than that of the general portion, and the fitting portion fitting and the fitting portion in a state of abutting against the outer step being heat - welded to the stepped joint, A joint structure comprising the above. (((2))) The stepped joint has an inner diameter equal to the inner diameter of the general portion of the tubular body, In the tubular body, an inner step at the boundary between the general portion and the fitting portion abuts against the end face of the fitting portion in the stepped joint. The joint structure according to ((2)). According to ((1)), a fitting portion having an outer diameter smaller than the outer diameter of the base portion in the stepped joint and a fitted portion of the tubular body having the same outer diameter as the outer diameter of the base portion are fitted, and the fitted portion in a state of abutting against the outer step is heat-welded to the stepped joint. Thereby, in this joint structure, since there is no step at the connection portion between the base portion of the stepped joint and the tubular body, the appearance is better than the configuration in which the tubular body is heat-welded inside the fitting portion of the joint. According to ((2)), in the fitting portion between the stepped joint and the tubular body, compared with a configuration in which the stepped joint and the tubular body are separated in the tube axis direction or a configuration in which the inner diameter of the stepped joint and the inner diameter of the tubular body are different, the inside of the tube is formed of a smooth surface, so that the pressure loss inside the tube is reduced. As long as the configuration of the above ((1)) exhibits the effects, the configuration of the above ((2)) is not an essential requirement.

Explanation of Reference Numerals

[0061] 10 Joint structure, 20 Joint, 22 Base portion, 23 Second fitting portion (an example of the fitting portion), 24A End face, 24B Outer peripheral surface, 26 Step (an example of the outer step), 28 Diameter-expanded portion, 30 Pipe (an example of the tubular body), 32 General portion, 34 Fitted portion, 34A Inner peripheral surface, 34B Through hole, 36 Step (an example of the inner step), c1 Center line, c2 Center line, d21 Inner diameter, d22 Outer diameter, d23 Inner diameter, d23 Outer diameter, d24 Outer diameter, d24 Diameter, d31 Inner diameter, d32 Outer diameter, d3 Inner diameter

Claims

1. A stepped joint formed hollow with a predetermined inner diameter from a thermoplastic resin, the stepped joint having a base portion and a fitting portion with an outer diameter smaller than the outer diameter of the base portion, A tubular body formed tubular from a thermoplastic resin, having a general portion with an inner diameter equivalent to the inner diameter of the stepped joint, with a part on the open end side being a fitted portion having an inner diameter larger than that of the general portion, and the fitted portion being heat welded to the stepped joint in a state where an inner step at the boundary between the general portion and the fitted portion abuts against the end face of the fitting portion in the stepped joint, A joint structure comprising the above.

2. The stepped joint has an outer step at the boundary between the base portion and the fitting portion, The tubular body has an outer diameter equivalent to the outer diameter of the base portion, and the end face of the fitted portion abuts against the outer step, The joint structure according to Claim 1.

3. The stepped joint has a diameter-expanded portion formed on the outer periphery of the fitting portion and in contact with the inner surface of the fitted portion The joint structure according to Claim 2.

4. The diameter-expanded portion is formed in a tapered shape that continuously expands in diameter as it moves away from the outer step, The joint structure according to Claim 3.

5. In the fitted portion, through holes that open on the inner and outer circumferences and are filled with the thermoplastic resin are formed, The joint structure according to any one of Claims 1 to 4.

6. A stepped joint formed hollow from a thermoplastic resin, having a base portion and a fitting portion with an outer diameter smaller than the outer diameter of the base portion, and preparing a stepped joint having an outer step at the boundary between the base portion and the fitting portion, Processing a part on the open end side of a tubular body formed from a thermoplastic resin to form a fitted portion having an inner diameter larger than that of the general portion of the tubular body, Bringing the fitted portion into contact with the outer step of the fitting portion and fitting it with the fitting portion, Heating the fitting portion and the fitted portion to heat weld the tubular body to the stepped joint, A method for manufacturing a joint structure.

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