Pipe joint, pipe joint structure, hot water supply machine, method for manufacturing pipe joint structure, and method for manufacturing hot water supply machine

Abstract

A pipe joint (1A) comprises: a ring (12) which has a ring shape capable of having an end surface part of a first pipe abut thereto from one direction side in the central axis direction, which is made of a material allowing a specific laser beam capable of melting the end surface part of the first pipe to transmit therethrough, and through which the laser beam transmits when the laser beam is emitted from the other direction side in the central axis direction; and a support (11) which is disposed in the radial direction of the ring 12, which is provided to the one-direction side of the ring (12), and which abuts against a cylindrical surface part of the first pipe to support the cylindrical surface part when the end surface part of the first pipe abuts against the ring (12).

Description

Pipe joint, pipe joint structure, water heater, method for manufacturing pipe joint structure, and method for manufacturing water heater

[0001] The present disclosure relates to a pipe joint, a pipe joint structure, a water heater, a method for manufacturing a pipe joint structure, and a method for manufacturing a water heater.

[0002] Some pipe joints are made of resin materials, and the parts of such resin materials are joined together by laser welding.

[0003] For example, Patent Document 1 discloses a joining method in which a lid for closing a cylindrical portion having an oval cross section and an open end surface is joined by laser welding. In Patent Document 1, the end surface of the cylindrical portion is formed of a resin material that absorbs specific laser light. The end surface of the cylindrical portion also includes a support portion, which is a cylindrical wall that surrounds the entire circumference of the cylindrical portion, to position and support the lid when the lid is fitted. The support portion is also formed of a resin material that absorbs the laser light. In contrast, the lid is formed of a resin material that transmits the laser light.

[0004] In the joining method described in Patent Document 1, a lid is fitted to a support part to close the end face of a cylindrical part, and the end face of the cylindrical part is irradiated with the above-mentioned specific laser light from the side where the lid is located, thereby melting the resin material on the end face of the cylindrical part. Then, the molten resin material solidifies, welding the lid to the end face of the cylindrical part. As a result, the end face of the cylindrical part and the lid are joined together.

[0005] JP 2016-117184 A

[0006] It is conceivable to use the joining method described in Patent Document 1 in manufacturing a pipe joint. In manufacturing a pipe joint structure in which a pipe joint is joined to an end face portion of a pipe, it is conceivable to use the joining method described in Patent Document 1 when joining the pipe and the pipe joint.

[0007] However, in the joining method described in Patent Document 1, a support portion is provided adjacent to the lid that transmits laser light and supports the lid. Furthermore, the support portion is formed of a material that absorbs laser light. Therefore, the laser light may hit the support portion adjacent to the lid, which may result in the support portion melting. This may result in the lid being misaligned, making it impossible to join the lid in the correct position.

[0008] If the joining method described in Patent Document 1 is applied to joining a pipe and a pipe joint, and the pipe joint has a support portion for supporting the pipe, it is expected that the support portion will melt and cause the pipe to shift position, making it impossible to weld the pipe to the pipe joint with high precision. As a result, it is thought that a joining failure will occur when joining the pipe and the pipe joint.

[0009] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a pipe joint, a pipe joint structure, a water heater, a method for manufacturing a pipe joint structure, and a method for manufacturing a water heater that can weld pipes with high precision.

[0010] To achieve the above object, a pipe fitting according to the present disclosure includes a ring portion and a support portion. The ring portion has a ring shape that can be contacted by an end surface portion of a first pipe from one side in the central axis direction, and is formed of a material that is transparent to a specific laser beam that can melt the end surface portion of the first pipe, and the laser beam passes through when irradiated with the laser beam from the other side in the central axis direction. The support portion is disposed radially of the ring portion and is provided on one side of the ring portion, and contacts and supports a cylindrical surface portion of the first pipe when the end surface portion of the first pipe contacts the ring portion. The pipe fitting is then intended to be laser welded to the first pipe.

[0011] According to the configuration of the present disclosure, the ring portion is formed of a material that is transmissive to a specific laser beam capable of melting the end surface of the first pipe, and when irradiated with laser beam from the other side of the central axis, the laser beam passes through. The support portion is disposed radially of the ring portion and is provided on one side of the ring portion in the central axis direction. Therefore, when the end surface of the first pipe abuts against the ring portion and laser beam is irradiated from the other side of the central axis, the laser beam passes through the ring portion and strikes the end surface of the first pipe. As a result, the end surface of the first pipe melts. Meanwhile, the support portion is less susceptible to laser beam irradiation and therefore less likely to melt. This allows the end surface of the first pipe to be welded to the ring portion while the support portion abuts against and supports the cylindrical surface of the first pipe. As a result, the configuration of the present disclosure allows the first pipe to be welded to the pipe fitting with high precision.

[0012] a cross-sectional view taken along the line II-II shown in FIG. 1; a cross-sectional view of the pipe fitting according to the first embodiment of the present disclosure and a circular pipe to which the pipe fitting is joined; a flowchart of a method for manufacturing a pipe fitting structure including a pipe fitting according to the first embodiment of the present disclosure; a cross-sectional view of a circular pipe and the pipe fitting in an assembly step of the pipe that is included in the method for manufacturing a pipe fitting structure including a pipe fitting according to the first embodiment of the present disclosure; a cross-sectional view of a circular pipe and the pipe fitting in a laser welding step that is included in the method for manufacturing a pipe fitting structure including a pipe fitting according to the first embodiment of the present disclosure; 9 is a top view showing the shape in top view of an irradiation area of ​​laser light irradiated onto a ring portion of a pipe fitting by a laser irradiation device in a laser welding step included in a manufacturing method of a pipe fitting structure including a pipe fitting according to embodiment 1 of the present disclosure; FIG. 10 is a top view showing the shape in top view of an irradiation area of ​​laser light irradiated onto a ring portion of a pipe fitting by a laser irradiation device of a modified example in a laser welding step included in a manufacturing method of a pipe fitting structure including a pipe fitting according to embodiment 1 of the present disclosure; FIG. 11 is a cross-sectional view of a pipe fitting structure including a pipe fitting according to embodiment 2 of the present disclosure, an enlarged cross-sectional view of region X shown in FIG. 9; FIG. 12 is a cross-sectional view of a pipe fitting showing a first modified example of a protrusion of a ring portion included in a pipe fitting according to embodiment 2 of the present disclosure; FIG. 13 is a cross-sectional view of a pipe fitting showing a second modified example of a protrusion of a ring portion included in a pipe fitting according to embodiment 2 of the present disclosure; Cross-sectional view of a pipe fitting and a circular pipe according to embodiment 3 of the present disclosure. Bottom view of the pipe fitting according to embodiment 3 of the present disclosure. Circuit diagram of a water heater according to embodiment 4 of the present disclosure. Cross-sectional view of a first modified example of the pipe fitting according to embodiment 1 of the present disclosure. Cross-sectional view of a second modified example of the pipe fitting according to embodiment 1 of the present disclosure. Cross-sectional view of a modified example of a circular pipe to be welded to the pipe fitting according to embodiment 1 of the present disclosure, cut parallel to the pipe axis. Cross-sectional view of a modified example of a circular pipe to be welded to the pipe fitting according to embodiment 1 of the present disclosure, cut perpendicular to the pipe axis.

[0013] A pipe fitting, a pipe fitting structure, a water heater, a method for manufacturing a pipe fitting structure, and a method for manufacturing a water heater according to embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that identical or equivalent parts in the drawings are designated by the same reference numerals. In addition, in the Cartesian coordinate system XYZ shown in the drawings, when the end face of a pipe to be joined to a pipe fitting in the pipe fitting structure is horizontal and the pipe axis of the pipe is oriented vertically, the left-right direction is the X-axis, the up-down direction is the Z-axis, and the direction perpendicular to the X-axis and Z-axis is the Y-axis. This coordinate system will be referenced as appropriate below in the following description.

[0014] (Embodiment 1) A pipe fitting according to Embodiment 1 is a component for joining an end of a pipe, such as a refrigerant pipe or a water supply pipe, to manufacture a pipe fitting structure for connecting the pipe to another pipe. This pipe fitting has a configuration suitable for laser welding to easily join the ends of the pipes with high precision. First, the pipe fitting structure, which is an application of this pipe fitting, will be described with reference to Figures 1 and 2.

[0015] Fig. 1 is a perspective view of a pipe joint structure 2A including a pipe joint 1A according to embodiment 1. Fig. 2 is a cross-sectional view taken along the line II-II shown in Fig. 1.

[0016] In devices such as water heaters and cooling systems, the piping extending from the components, specifically circular pipes, is sometimes connected to each other to allow fluids such as refrigerants and water to flow between the components. In this case, as shown in Figure 1, a pipe fitting 1A is joined to the end of one circular pipe 3, and a circular pipe 4 is connected to the pipe fitting 1A.

[0017] 2, a cylindrical pipe fitting 1A with a ring-shaped seal 5 attached to a groove on the outer periphery is provided at the end of the circular pipe 3. As a result, the end of the circular pipe 3 and the pipe fitting 1A form a pipe fitting structure 2A. The pipe fitting 1A is a so-called male socket pipe fitting.

[0018] Meanwhile, a cylindrical pipe fitting 6 that can be inserted into the pipe fitting 1A is provided at the tip of the circular pipe 4. The pipe fitting 6 is a so-called female socket pipe fitting. The circular pipe 4 is connected to the circular pipe 3 by inserting and attaching the pipe fitting 1A at the end of the circular pipe 3 into the pipe fitting 6. Furthermore, the flanges of the pipe fitting 6 and the pipe fitting 1A are clamped by a fixture 7, and the fixture 7 is fixed to the above-mentioned device, thereby fixing the circular pipe 4 to the device. The fixture 7 prevents the circular pipe 4 from coming off the circular pipe 3 due to the application of external force.

[0019] In this way, the end of the circular pipe 3 and the pipe joint 1A form a pipe joint structure 2A for connecting a circular pipe 4. The circular pipe 3 and the pipe joint 1A are made of a laser-weldable material to easily join them. Furthermore, to perform the laser welding with high precision, the pipe joint 1A is provided with a support portion for supporting the circular pipe 3. Next, the circular pipe 3 and the pipe joint 1A that form the pipe joint structure 2A will be described in detail with reference to Figure 3.

[0020] 3 is a cross-sectional view of the pipe joint 1A and the circular pipe 3 to which the pipe joint 1A is joined. Note that in FIG. 3, only the end of the circular pipe 3 is shown for ease of understanding.

[0021] The circular pipe 3 shown in FIG. 3 is made of a material that is opaque to laser light, i.e., a material that absorbs laser light, to enable laser welding. For example, when a red semiconductor laser is used as the laser irradiation device that emits the laser light, the circular pipe 3 is made of a resin primarily composed of black unreinforced, extrusion-grade polyphenylene sulfide (PPS). This allows the circular pipe 3 to absorb the laser light and melt due to the heat generated. Furthermore, the circular pipe 3 can be welded using the molten material. The circular pipe 3 is formed into a cylindrical shape, and its end portion is inserted into the pipe fitting 1A.

[0022] Pipe fitting 1A is provided at the end portion of circular pipe 3 and is a component for connecting that end portion to pipe fitting 6 at the tip of circular pipe 4 shown in Fig. 2. As shown in Fig. 3, pipe fitting 1A comprises a support portion 11 for supporting the end portion of circular pipe 3, a ring portion 12 to which the end portion of circular pipe 3 is welded, a flange portion 13 for holding pipe fitting 1A itself during welding, and a connection portion 14 for connecting to pipe fitting 6 of circular pipe 4.

[0023] The support part 11 is formed in a cylindrical shape. The inner diameter of the support part 11 is the same as the outer diameter D11 of the circular pipe 3, so that the circular pipe 3 is supported by the inner wall of the cylinder. More specifically, the inner diameter of the support part 11 is the same as the outer diameter D11 of the circular pipe 3 to such an extent that the circular pipe 3 can be inserted. The end portion of the circular pipe 3 is inserted into the support part 11. With this configuration of the support part 11, the inner wall of the cylinder of the support part 11 abuts against the outer peripheral surface portion of the circular pipe 3, i.e., the cylindrical surface portion, and supports the cylindrical surface portion.

[0024] Furthermore, the support portion 11 has its cylindrical axis A facing up and down, and its lower end, i.e., the -Z end, is open. The terminal portion of the circular pipe 3, i.e., the +Z end, is inserted from the -Z end of the support portion 11. A ring portion 12 is disposed on the +Z end of the support portion 11, which leaves only the central portion near the cylindrical axis A open and closes only the area near the inner circumferential surface around the central portion. The +Z end face of the circular pipe 3 abuts against the ring portion 12.

[0025] The ring portion 12 has a flat ring shape so that it can be contacted by the flat +Z end face of the circular pipe 3, which is perpendicular to the pipe axis. The ring portion 12 is concentric with the cylinder of the support portion 11. The inner diameter D21 of the ring portion 12 is the same as the inner diameter D22 of the +Z end portion of the circular pipe 3. The outer diameter D12 of the ring portion 12 is larger than the outer diameter D11 of the +Z end portion of the circular pipe 3. The -Z surface portion of the ring portion 12 has this configuration, and when the +Z end portion of the circular pipe 3 is pressed against it, it comes into contact with the entire +Z end face of the circular pipe 3.

[0026] The inner diameter D21 of ring portion 12 may be larger than the inner diameter D22 of the +Z end portion of circular pipe 3, to the extent that the joining strength with the +Z end portion of circular pipe 3 can be maintained. This is because such a size can reduce pressure loss when a fluid is flowed through circular pipe 3. Furthermore, the outer diameter D12 of ring portion 12 may be the same as the outer diameter D11 of the +Z end portion of circular pipe 3. This is because even with such a size, the +Z end surface of circular pipe 3 can abut against it.

[0027] Furthermore, the +Z end face of the circular pipe 3 not only abuts against the -Z surface of the ring portion 12, but is also joined to the +Z end face of the circular pipe 3. In detail, the +Z end face of the circular pipe 3 is laser welded to the -Z surface of the ring portion 12.

[0028] The ring portion 12 is formed of a material transparent to laser light to enable such laser welding during the manufacture of the pipe joint structure 2A. In other words, the ring portion 12 is formed of a material that can transmit laser light. For example, the ring portion 12 is desirably formed of a material that transmits 90 to 100% of laser light. In addition to such a high-transmittance material, the ring portion 12 may also be formed of a low-transmittance material, for example, a material that transmits 30 to 40% of laser light. In short, the ring portion 12 is preferably formed of a material that has a higher transmittance to laser light than the material of the circular pipe 3 described above, and therefore has a transmittance that is low enough to prevent the ring portion 12 from melting before the circular pipe 3 is melted by irradiation with laser light.

[0029] To explain the material of the ring portion 12 in more detail, for example, when a red semiconductor laser is used as the laser irradiation device that emits the laser light, the ring portion 12 is made of a resin material whose main component is polyphenylene sulfide (PPS) of a white laser light transmission grade. Furthermore, not only the ring portion 12 but also the pipe fitting 1A itself is made of such a material. This allows the ring portion 12 to transmit the laser light.

[0030] As described above, during the manufacturing of the pipe joint structure 2A, the +Z end face of the circular pipe 3 is brought into contact with the ring portion 12 from the -Z side. When laser light is irradiated from the +Z side while the ring portion 12 is in this contact state, the ring portion 12 transmits the laser light because it is made of the material described above. This allows the ring portion 12 to melt the +Z end face of the circular pipe 3 on the -Z side with the heat generated when the laser light is absorbed. By irradiating the laser light in this manner during the manufacturing of the pipe joint structure 2A, the +Z end face of the circular pipe 3 is laser-welded to the ring portion 12. As a result, the +Z end face of the circular pipe 3 is joined to the ring portion 12.

[0031] On the other hand, a flange portion 13 is provided radially outward of the ring portion 12 .

[0032] The flange portion 13 is provided to fix the pipe fitting 1A itself and press the circular pipe 3 against the ring portion 12 when laser welding the +Z end portion of the circular pipe 3 to the ring portion 12, or to move the pipe fitting 1A itself and press the ring portion 12 against the circular pipe 3.

[0033] More specifically, the flange portion 13 has an annular shape (not shown). As shown in FIG. 3, the flange portion 13 protrudes radially and outward beyond the support portion 11 and the connecting portion 14. This allows the flange portion 13 to easily hold the pipe fitting 1A. As a result, the flange portion 13 makes it easy to closely attach the circular pipe 3 to the ring portion 12 by laser welding during the manufacture of the pipe fitting structure 2A. Meanwhile, a connecting portion 14 is provided above the flange portion 13 to connect the pipe fitting 6 to the circular pipe 4 after the pipe fitting 1A is completed by welding the circular pipe 3 to the ring portion 12.

[0034] The connecting portion 14 is formed in a cylindrical shape to connect the pipe fitting 6 of the circular pipe 4 shown in Figures 1 and 2. As described above, the pipe fitting 6 is provided at the tip of the circular pipe 4. The pipe fitting 6 is a so-called female socket pipe fitting. In order to connect the female socket pipe fitting 6, the outer diameter D13 of the connecting portion 14 shown in Figure 3 is formed to be the same size as the inner diameter D23 of the pipe fitting 6 provided at the tip of the circular pipe 4 shown in Figure 2, so that the connecting portion 14 can be inserted. This allows the connecting portion 14 to function as a so-called male socket pipe fitting. As a result, the connecting portion 14 is connectable to the pipe fitting 6 of the circular pipe 4.

[0035] 3 , the inner diameter D24 of the connecting portion 14 is larger than the inner diameter D22 of the circular pipe 3 in order to facilitate the flow of fluid between the circular pipes 3 and 4 when the connecting portion 14 is connected to the pipe fitting 6 of the circular pipe 4. Furthermore, the cylindrical axis of the connecting portion 14 is located on an extension of the cylindrical axis A of the support portion 11. As a result, the connecting portion 14 is positioned coaxially with the circular pipe 3 when connected to the circular pipe 4. With this configuration, the connecting portion 14 facilitates the flow of fluid between the circular pipe 3 and the connecting portion 14 when connected to the circular pipe 4.

[0036] Furthermore, the inner diameter D24 of the connecting portion 14 is the same as the outer diameter D12 of the ring portion 12. As described above, the cylindrical axis of the connecting portion 14 is an extension of the cylindrical axis A of the support portion 11. That is, it is parallel to the Z axis. The +Z side of the connecting portion 14 is open. In the laser welding described above, focusing on this configuration, laser light parallel to the Z axis is irradiated from the +Z side of the connecting portion 14 toward the ring portion 12 inside the connecting portion 14. At this time, the inner diameter D24 of the connecting portion 14 is larger than the inner diameter of the support portion 11 so that the laser light hits the entire +Z end face of the circular pipe 3 to be welded. In other words, the inner diameter D24 of the connecting portion 14 is larger than the outer diameter D11 of the circular pipe 3. By forming the connecting portion 14 in this size, the entire +Z end face of the circular pipe 3 to be welded can be irradiated with laser light during laser welding. As a result, the connecting portion 14 suppresses welding defects and ensures sufficient joint strength.

[0037] The connection part 14 has a groove 141 on its outer circumferential surface that extends circumferentially and surrounds the entire outer periphery. The seal 5 shown in Fig. 2 is attached to the groove 141, thereby preventing a gap from forming between the connection part 14 and the circular pipe 4 when the connection part 14 is inserted into and attached to the circular pipe 4. This improves the watertightness or airtightness of the connection part 14.

[0038] 4 to 7, a method for joining the circular pipe 3 and the pipe fitting 1A, i.e., a method for manufacturing the pipe fitting structure 2A by joining the circular pipe 3 and the pipe fitting 1A, will be described. In the following description, since the cylindrical axis A of the support portion 11 is coaxial with the cylindrical axis of the connection portion 14 and the central axis of the ring portion 12, and is also coaxial with the pipe axis of the circular pipe 3, the cylindrical axis of the connection portion 14, the central axis of the ring portion 12, and the pipe axis of the circular pipe 3 will also be referred to as the cylindrical axis A.

[0039] Fig. 4 is a flowchart of a manufacturing method of the pipe joint structure 2A. Fig. 5 is a cross-sectional view of the circular pipe 3 and the pipe joint 1A in an assembly step of the circular pipe 3 included in the manufacturing method of the pipe joint structure 2A. Fig. 6 is a cross-sectional view of the circular pipe 3 and the pipe joint 1A in a laser welding step included in the same manufacturing method.

[0040] First, prepare the circular pipe 3 and pipe fitting 1A having the shape and material described above. For example, prepare the circular pipe 3 made of a material that absorbs light of the wavelength contained in the laser light emitted by the laser irradiation device used in the laser welding process described below. Also prepare the pipe fitting 1A, in which the support portion 11, ring portion 12, flange portion 13, and connecting portion 14 are all made of materials that transmit light of the above-mentioned laser light wavelength.

[0041] Next, as shown in FIG. 4, the circular pipe 3 is assembled to the pipe joint 1A (step S1).

[0042] More specifically, the end portion of the circular pipe 3 is inserted into the cylindrical interior of the above-mentioned support portion 11 provided in the pipe fitting 1A. For example, as shown in Figure 5, the support portion 11 of the pipe fitting 1A is faced downward, and the end portion of the circular pipe 3, i.e., the upper end portion of the circular pipe 3, is inserted into the cylindrical interior of the support portion 11 as indicated by arrow A1. In this way, the circular pipe 3 is assembled to the pipe fitting 1A.

[0043] Next, as shown in FIG. 4, the circular pipe 3 is laser welded to the pipe joint 1A (step S2).

[0044] First, before laser welding, to prevent welding defects, the end face of the upper end portion of the circular pipe 3 is brought into close contact with the ring portion 12 of the pipe fitting 1A. Specifically, as shown in FIG. 5 , a cylindrical holding jig 8 having a cylindrical wall that is hook-shaped in cross section is placed over the flange portion 13, and the hook-shaped portion 81 in cross section is hooked onto the upper surface of the flange portion 13. Then, as shown by arrow A2, the holding jig 8 is moved downward, thereby moving the entire pipe fitting 1A, including the flange portion 13, downward. This presses the ring portion 12 against the upper end portion of the circular pipe 3. As a result, the end face of the upper end portion of the circular pipe 3 is brought into close contact with the underside of the ring portion 12.

[0045] Next, as shown in Figure 6, the pipe fitting 1A is placed on the circular pipe 3, and further, with the cylindrical axes A of the circular pipe 3 and pipe fitting 1A facing vertically, a laser irradiation device 9 is positioned above the pipe fitting 1A. This positions the laser irradiation device 9 directly above the cylindrical opening of the connection portion 14. Then, while the pipe fitting 1A is pressed against the circular pipe 3 by the above-mentioned pressing jig 8, laser light L is irradiated. The shape of the irradiation area of ​​the laser light L at this time is shown in Figure 7.

[0046] 7 is a top view showing the shape of an irradiation area of ​​a laser beam L irradiated onto the ring portion 12 of the pipe joint 1A by a laser irradiation device 9 in a laser welding step included in the manufacturing method of the pipe joint structure 2A. Note that the holding jig 8 is omitted from FIG. 7 for ease of understanding.

[0047] As shown in FIG. 7 , the laser irradiation device 9 irradiates the ring portion 12 of the pipe fitting 1A with a laser beam L that is circular in top view. The laser beam L is collimated by a lens (not shown) provided in the laser irradiation device 9, parallel to the cylindrical axis A of the circular pipe 3 and the pipe fitting 1A. Furthermore, as described above, the ring portion 12 irradiated with the laser beam L is transparent to the laser beam L. As a result, as shown in FIG. 6 , the laser beam L passes through the ring portion 12 and reaches the end face of the upper end portion of the circular pipe 3 while remaining parallel to the cylindrical axis A. As described above, the circular pipe 3 is made of a material that absorbs the laser beam L. Therefore, the laser beam L is absorbed by the material, and the heat generated melts the end face of the upper end portion of the circular pipe 3. Furthermore, not only the end face of the upper end portion of the circular pipe 3 but also the ring portion 12 melts. The molten material penetrates between the end face of the upper end portion of the circular pipe 3 and the ring portion 12. The laser irradiation device 9 emits the laser light L for a certain period of time and then stops emitting the laser light L. Thereafter, the molten material is cooled and solidified, and the end face of the upper end portion of the circular tube 3 is welded to the ring portion 12.

[0048] In this welding, the support portion 11 of the pipe fitting 1A is located on the side of the ring portion 12 opposite to the side onto which the laser light L is irradiated. That is, the support portion 11 is located on the -Z surface side of the ring portion 12, while the laser light L is incident on the +Z surface side of the ring portion 12. As a result, the support portion 11 is less likely to melt. Also, the support portion 11 is located radially outward of the ring portion 12, and is less likely to be irradiated with the laser light L. Furthermore, the support portion 11 is formed of a material that is transparent to the laser light L. As a result of this configuration, the support portion 11 is less likely to melt. As a result, the position of the upper end portion of the circular pipe 3 is less likely to shift, and the upper end portion of the circular pipe 3 is welded to the ring portion 12 with high precision.

[0049] Through the above steps, the manufacturing method for the pipe joint structure 2A is completed, and the pipe joint structure 2A is completed, as shown in FIG.

[0050] The circular pipe 3 described above is an example of the "first pipe" defined in the present disclosure. The end face of the terminal portion of the circular pipe 3, i.e., the end face of the upper end portion and the cylindrical surface portion, are an example of the "first pipe" end face portion and cylindrical surface portion defined in the present disclosure. The cylindrical axis A is an example of the "center axis" defined in the present disclosure. The downward and upward directions of the cylindrical axis A are an example of one direction and the other direction of the center axis direction defined in the present disclosure.

[0051] As described above, in the pipe fitting 1A according to the first embodiment, the ring portion 12 is formed of a material that is transparent to the laser light L capable of melting the circular pipe 3, and when the laser light L is irradiated from above along the cylindrical axis A of the circular pipe 3 and the ring portion 12, the laser light L passes through the ring portion 12. Therefore, during the manufacture of the pipe fitting structure 2A, when the end face of the upper end portion of the circular pipe 3 abuts against the ring portion 12 and the laser light L is irradiated from above along the cylindrical axis A, the laser light L passes through the ring portion 12 and hits the end face of the distal end portion of the circular pipe 3. As a result, the end face of the circular pipe 3 melts. As a result, in the pipe fitting 1A, the end face of the upper end portion of the circular pipe 3 can be welded to the ring portion 12.

[0052] In contrast, the support portion 11 is disposed radially of the ring portion 12 and is provided below the ring portion 12. Therefore, the laser light L is less likely to hit the support portion 11, and the support portion 11 is less likely to melt. As a result, the end portion of the circular pipe 3 can be welded to the ring portion 12 with high precision while the support portion 11 remains in contact with and supports the cylindrical surface portion of the circular pipe 3. This allows the circular pipe 3 and the pipe fitting 1A to be welded with high precision.

[0053] (Modification) In the first embodiment, the laser irradiation device 9 used in the laser welding step is provided with a lens, and irradiates the laser light L that is circular in top view and parallel. However, the laser irradiation device 9 is not limited to this.

[0054] 8 is a top view showing the shape of the irradiation area of ​​the laser beam L irradiated onto the ring portion 12 of the pipe fitting 1A by the laser irradiation device 9 of the modified example. For ease of understanding, the holding jig 8 is omitted from FIG. 8, as in FIG. 7.

[0055] 8 , the laser irradiation device 9 may emit laser light L that irradiates a circular region having a diameter equal to the width W of the ring portion 12 in a top view. That is, the laser irradiation device 9 may irradiate spot light. In this case, the laser irradiation device 9 may move the irradiation destination of the laser light L along the outer circumferential direction of the ring portion 12 using an optical member, for example, a mirror.

[0056] (Embodiment 2) In the pipe fitting 1A according to embodiment 1, the lower surface of the ring portion 12 is flat. Furthermore, the end surface of the distal end portion of the circular pipe 3, i.e., the upper end surface, is also flat. As a result, the lower surface of the pipe fitting 1A and the upper end surface of the circular pipe 3 are welded together while maintaining a flat shape. However, the shape of the ring portion 12 is not limited to this. The ring portion 12 may have any ring shape that can be aligned along the cylindrical axis A and that allows the upper end surface of the circular pipe 3 to abut against it from below. Therefore, the shapes of the upper and lower surfaces of the ring portion 12 are arbitrary as long as they satisfy this condition. For example, the ring portion 12 may have irregularities formed on the entire lower surface.

[0057] In a pipe fitting 1B according to the second embodiment, a protrusion is provided over the entire lower surface of the ring portion 12. The configuration of the pipe fitting 1B will be described below with reference to Figures 9 and 10. The description of the second embodiment will focus on the configuration that differs from the first embodiment.

[0058] Fig. 9 is a cross-sectional view of a pipe joint structure 2B including a pipe joint 1B according to embodiment 2. Fig. 10 is an enlarged cross-sectional view of region X shown in Fig. 9. For ease of understanding, Fig. 10 shows the position of the laser light L when the laser light L is irradiated in the laser welding step during the manufacture of the pipe joint structure 2B.

[0059] As shown in FIG. 9, the ring portion 12 has a protrusion 121 on the lower surface that is triangular in cross section.

[0060] 9 and 10, the protrusion 121 is formed in the shape of an isosceles triangle with its apex pointing downward in cross section. Although not shown, the protrusion 121 extends along the inner peripheral surface of the ring portion 12 and is formed around the entire circumference of the ring portion 12. As a result, the protrusion 121 has a circular shape in top view. At least the tip of the protrusion 121 abuts against the upper end surface of the circular tube 3 fitted into the support portion 11.

[0061] The protrusion 121 is formed integrally with the ring portion 12. As a result, the protrusion 121 is formed of the same material as the other portions of the ring portion 12. In other words, the protrusion 121 is formed of a material that transmits the laser light L. As a result, even when the laser light L is irradiated during the laser welding process when manufacturing the pipe joint structure 2B, the laser light L is transmitted through the protrusion 121 with almost no absorption. As a result, the laser light L reaches the upper end surface of the circular pipe 3 during the laser welding process.

[0062] In the second embodiment, the circular pipe 3 has the same configuration as described in the first embodiment. Consequently, the circular pipe 3 is formed of a material that absorbs the laser light L. When the upper end surface of the circular pipe 3 is irradiated with the laser light L during the laser welding process for manufacturing the pipe joint structure 2B, the upper end surface absorbs the laser light L and melts due to the heat generated at that time. At this time, the heat also melts the surface of the protrusion 121 and the lower surface of the ring portion 12. As a result, although not shown, the upper end surface of the circular pipe 3 is welded to the lower surface of the ring portion 12 with the tip of the protrusion 121 inserted into the upper end surface of the circular pipe 3. The molten material not only closes the gap between the lower surface of the ring portion 12 and the upper end surface of the circular pipe 3, but also closes the gap between the protrusion 121 and the upper end surface of the circular pipe 3. In this state, the upper end surface of the circular pipe 3 is welded to the lower surface of the ring portion 12. With this configuration, the upper end surface of the circular pipe 3 and the lower surface of the ring portion 12 are welded over a larger area than in the first embodiment. In other words, the joining area between the upper end surface of the circular pipe 3 and the lower surface of the ring portion 12 is large, which results in an increased joining strength between the circular pipe 3 and the ring portion 12.

[0063] As described above, in the pipe fitting 1B according to the second embodiment, the ring portion 12 is provided on the side of the lower surface to which the circular pipe 3 is assembled, and has a protrusion 121 formed over the entire lower surface. Furthermore, the protrusion 121 abuts against the upper end surface of the circular pipe 3 when the circular pipe 3 is assembled. As a result, in the pipe fitting 1B, during the laser welding process in manufacturing the pipe fitting structure 2B, the material melted by the laser light L not only closes the gap between the lower surface of the ring portion 12 and the upper end surface of the circular pipe 3, but also closes the gap between the protrusion 121 and the upper end surface of the circular pipe 3. As a result, in the pipe fitting 1B, the joining area between the ring portion 12 and the circular pipe 3 is large, and the joining strength is high.

[0064] Furthermore, the protrusion 121 has an isosceles triangular shape with the apex pointing downward in cross section. Therefore, the material melted by the laser light L spreads evenly along the slope of the protrusion 121, which has equal sides in cross section. As a result, in the pipe fitting 1B, poor joining between the ring portion 12 and the circular pipe 3 is less likely to occur.

[0065] (Modification) In the second embodiment, the protrusion 121 has an isosceles triangle shape with the apex pointing downward in cross section. However, the protrusion 121 is not limited to this. The protrusion 121 is provided on the side of the ring portion 12 on which the circular pipe 3 is assembled, is formed around the entire circumference of the ring portion 12, and has a tip that abuts against the end face of the circular pipe 3 when the circular pipe 3 is assembled to the ring portion 12. Therefore, the cross-sectional shape of the protrusion 121 is arbitrary as long as it satisfies this condition.

[0066] Fig. 11 is a cross-sectional view of a pipe fitting 1B showing a first modified example of the protrusion 121 of the ring portion 12 provided in the pipe fitting 1B according to the second embodiment. Fig. 12 is a cross-sectional view of a pipe fitting 1B showing a second modified example of the protrusion 121. Fig. 13 is a cross-sectional view of a pipe fitting 1B showing a third modified example of the protrusion 121. Note that Figs. 11 to 13 show an enlarged view of the same region as region X shown in Fig. 9. Furthermore, for ease of understanding, Figs. 11 to 13, like Fig. 10, show the position of the laser light L when the laser light L is irradiated in the laser welding step of manufacturing the pipe fitting structure 2B.

[0067] As shown in Fig. 11 , the base of the isosceles triangle of the protrusion 121 in cross section may be larger than that in the second embodiment. Specifically, in the second embodiment, the base of the isosceles triangle of the protrusion 121 in cross section is smaller than the width W of the lower surface of the ring portion 12 in the radial direction. In contrast, as in a first modified example shown in Fig. 11 , the base of the isosceles triangle of the protrusion 121 in cross section may have the same length as the width W of the lower surface of the ring portion 12 in the radial direction. This is because, even in such a configuration, the joining area between the ring portion 12 and the circular pipe 3 can be increased, thereby increasing the joining strength.

[0068] 12, the protrusion 121 may have a triangular shape in cross section with the base pointing upward and the apex pointing downward, with the apex being offset inwardly in the radial direction of the ring portion 12 relative to the base. This configuration increases the joining strength between the ring portion 12 and the circular pipe 3, while making it difficult for the molten material to flow toward the inside of the ring portion 12 during the laser welding process in manufacturing the pipe joint structure 2B. As a result, the generation of burrs protruding inward from the inner wall of the ring portion 12 can be suppressed.

[0069] Furthermore, as shown in FIG. 13 , in addition to the protrusion 121, a protrusion 122 may be provided on the underside of the ring portion 12, positioned radially inward of the protrusion 121. In this case, the protrusion 122 may be formed along the entire underside of the ring portion 12 along the protrusion 121. In other words, the protrusion 122 may be circular, concentric with the circular shape of the protrusion 121 in a top view and smaller than the circular shape of the protrusion 121 in a top view. Furthermore, the protrusion 122 may have a smaller protrusion amount, i.e., a shorter vertical length, than the protrusion 121. As a result, while the tip of the protrusion 121 abuts the upper end surface of the circular pipe 3, the tip of the protrusion 122 does not abut the upper end surface of the circular pipe 3 but has a gap between it and the upper end surface of the circular pipe 3. This is because the protrusion 122 can prevent the molten material from flowing inside the ring portion 12 during the laser welding process in the manufacture of the pipe joint structure 2B. As a result, the generation of burrs can be suppressed.

[0070] (Embodiment 3) In the pipe fittings 1A and 1B according to Embodiments 1 and 2, the support portion 11 is cylindrical and has a smooth inner wall. However, the shape of the support portion 11 is not limited to this. The support portion 11 is arranged radially of the ring portion 12, and is provided on the side of the ring portion 12 that abuts against the circular pipe 3 when the circular pipe 3 is assembled to the pipe fittings 1A and 1B. When the end face of the circular pipe 3 abuts against the ring portion 12, the support portion 11 abuts against a cylindrical surface portion of the circular pipe 3 and supports the cylindrical surface portion. Therefore, the shape of the support portion 11 is arbitrary as long as it satisfies this requirement.

[0071] In a pipe fitting 1C according to embodiment 3, the support portion 11 has a guide portion on the cylindrical inner wall. The configuration of pipe fitting 1C will be described below with reference to Figures 14 and 15. The description of embodiment 3 will focus on the configuration that differs from embodiments 1 and 2.

[0072] Fig. 14 is a cross-sectional view of a pipe fitting 1C and a circular pipe 3 according to embodiment 3. Fig. 15 is a bottom view of the pipe fitting 1C. For ease of understanding, Fig. 14 shows the circular pipe 3 together with the pipe fitting 1C without the circular pipe 3 attached.

[0073] As shown in FIG. 14, the support portion 11 has a plurality of guide portions 111 on the cylindrical inner wall for guiding the circular pipe 3 when the circular pipe 3 is inserted.

[0074] As shown in Fig. 15, each guide portion 111 has an arc-shaped protrusion, more specifically a semicircular protrusion, when viewed from below from the cylindrical inner wall of the support portion 11. Each guide portion 111 extends in parallel with the cylindrical axis A of the pipe fitting 1C while maintaining its protruding shape, as shown in Fig. 14. In other words, each guide portion 111 extends in the vertical direction.

[0075] Furthermore, as shown in FIG. 15 , the guide portions 111 are arranged at equal angles around the cylindrical axis A in the inner circumferential direction of the support portion 11. Specifically, the guide portions 111 are provided every 45° around the cylindrical axis A in the inner circumferential direction of the support portion 11. As a result, a total of eight guide portions 111 are provided on the cylindrical inner wall of the support portion 11. The distance D between the apex of one guide portion 111 closest to the cylindrical axis A and the apex of the opposite guide portion 111 closest to the cylindrical axis A is the same as the outer diameter D11 of the circular pipe 3, as shown in FIG. 14 . As a result, the circular pipe 3 can be inserted between the guide portions 111.

[0076] When the circular pipe 3 is inserted into the internal space of the support part 11, only the top of each guide part 111 abuts against the outer circumferential surface of the circular pipe 3. As a result, friction between each guide part 111 and the circular pipe 3 is small. This makes it easier for each guide part 111 to insert the circular pipe 3 into the internal space of the support part 11. As a result, each guide part 111 makes it easier to assemble the circular pipe 3 into the pipe fitting 1C. This also improves the support part 11's ability to hold the circular pipe 3.

[0077] Furthermore, the guide portions 111 extend in the direction of the cylindrical axis A while maintaining the distance D between the opposing guide portions 111. Therefore, when the circular pipe 3 is inserted into the internal space of the support portion 11, the guide portions 111 guide the circular pipe 3 in the direction of the cylindrical axis A, making the insertion easier.

[0078] As described above, in the pipe fitting 1C according to the third embodiment, the support portion 11 has a plurality of guide portions 111 that protrude inward from the cylindrical inner wall, i.e., the inner peripheral surface portion, and extend in the direction of the cylindrical axis A to guide the circular pipe 3. The inner space formed by the tops of the guide portions 111 is a space into which the circular pipe 3 can be inserted, and when the circular pipe 3 is inserted, only the tops of the guide portions 111 support the outer peripheral surface portion of the circular pipe 3. This makes it easy to insert the circular pipe 3 into the pipe fitting 1C, and therefore easy to assemble the circular pipe 3 into the pipe fitting 1C.

[0079] (Embodiment 4) The pipe joints 1A-1C and pipe joint structures 2A and 2B according to Embodiments 1-3 are applicable to connecting pipes through which fluids flow. For example, the pipe joints 1A-1C and pipe joint structures 2A and 2B are applicable to water heaters.

[0080] FIG. 16 is a circuit diagram of a water heater 100 according to the fourth embodiment.

[0081] The water heater 100 shown in Figure 16 comprises a hot water storage tank 101, a heat exchanger 102 for heating the hot water in the hot water storage tank 101, a pump 103 for circulating the hot water in the hot water storage tank 101 to the heat exchanger 102, and piping 104 for connecting these components.

[0082] Pipe fitting 1A according to the first embodiment is used to connect pipe 104 to a component of water heater 100, such as pump 103. For example, pipe 104 is used as circular pipe 3 described in the first embodiment, and a pipe extending from pump 103 is used as circular pipe 4. Pipe fitting 1A and the end portion of pipe 104 form pipe fitting structure 2A. As a result, pipe 104 is connected to a pipe extending from pump 103, and water heater 100 is assembled.

[0083] Furthermore, the pipe fitting 1A according to the first embodiment is used to connect the hot water storage tank 101 and the heat exchanger 102. For example, the pipe extending from the hot water storage tank 101 is used as the circular pipe 3 described in the first embodiment, and the pipe extending from the heat exchanger 102 is used as the circular pipe 4. The pipe fitting 1A and the end portions of the pipes form the pipe fitting structure 2A. As a result, the pipes are connected to each other. In this way, the water heater 100 is assembled.

[0084] As described above, in the water heater 100 according to the fourth embodiment, the pipe joint 1A and the pipe joint structure 2A are used to connect the pipes together. In the pipe joint structure 2A, the pipes are welded to the pipe joint 1A with high precision, so that the pressure loss in the water heater 100 is small. In addition, the piping of the water heater 100 is easy.

[0085] The above describes the pipe fittings 1A-1C, pipe fitting structures 2A and 2B, water heater 100, methods for manufacturing pipe fitting structures 2A and 2B, and methods for manufacturing water heater 100 according to the embodiments of the present disclosure, but the pipe fittings 1A-1C, pipe fitting structures 2A and 2B, water heater 100, methods for manufacturing pipe fitting structures 2A and 2B, and methods for manufacturing water heater 100 are not limited to these.

[0086] In the embodiment 1-4, the pipe joints 1A-1C are so-called male socket pipe joints. However, the pipe joints 1A-1C are not limited to this. The pipe joints 1A-1C may also be so-called female socket pipe joints.

[0087] FIG. 17 is a cross-sectional view of a first modified example of the pipe fitting 1A according to the first embodiment.

[0088] As shown in Figure 17, the inner diameter D25 of the cylinder of the connecting portion 14 may be larger than the inner diameter D24 shown in Figure 3, so that the pipe fitting 1A can be fitted with a male pipe fitting. In this case, by having such a configuration, the pipe fitting 1A can be connected to a male pipe fitting (not shown) provided at the tip of the circular pipe 4. Furthermore, the flange portion 13 may be provided on the periphery of the opening of the connecting portion 14, as shown in Figure 17. Also, the groove 141 may be omitted.

[0089] Furthermore, in the embodiments 1-4, the pipe joints 1A-1C are provided with the flange portion 13, but in the pipe joints 1A-1C, the flange portion 13 has an optional configuration.

[0090] FIG. 18 is a cross-sectional view of a second modified example of the pipe fitting 1A according to the first embodiment.

[0091] 18 , the pipe fitting 1A does not have a flange portion 13, and as a result, the connecting portion 14 may have the same outer diameter in the direction of the cylindrical axis A. In this case, in the laser welding step for manufacturing the pipe fitting structure 2A, the pipe fitting 1A may be pressed against the circular pipe 3 by pressing the open end of the connecting portion 14, i.e., the upper end face, downward. Alternatively, the pipe fitting 1A may be pressed against the circular pipe 3 using a jig other than the holding jig 8 that can be hooked onto the open end of the connecting portion 14.

[0092] Furthermore, in the embodiments 1-4, the circular pipe 3 is cylindrical. However, in the pipe fittings 1A-1C, the shape of the circular pipe 3 is not limited to this. The circular pipe 3 welded to the pipe fittings 1A-1C may be any pipe. Therefore, the circular pipe 3 may have a more complex shape.

[0093] Fig. 19 is a cross-sectional view of a modified circular pipe 3 welded to the pipe fitting 1A according to embodiment 1, cut parallel to the pipe axis. Fig. 20 is a cross-sectional view of a modified circular pipe 3 cut perpendicular to the pipe axis. For ease of understanding, Fig. 19 shows the position of the laser light L when irradiated with the laser light L in the laser welding process.

[0094] As shown in Figures 19 and 20, the circular pipe 3 may have a cylindrical outer wall portion 31 and an inner wall portion 32 provided inside the outer wall portion 31 and having an outer diameter smaller than the inner diameter of the outer wall portion 31. Furthermore, to improve thermal insulation, a space may be provided between the outer wall portion 31 and the inner wall portion 32. In this case, as shown in Figure 20, the outer wall portion 31 and the inner wall portion 32 may be separated by a spacer portion 33. Even in this configuration, the circular pipe 3 can be welded to the ring portion 12 by irradiating at least the upper end surface of the inner wall portion 32 with laser light L through the ring portion 12, as shown in Figure 19. Furthermore, in this case, the support portion 11 is provided in a position where it is difficult to melt, so that the circular pipe 3 can be welded to the ring portion 12 with high precision.

[0095] Furthermore, in the first to fourth embodiments, the circular pipe 4 is also cylindrical, but the shape of the circular pipe 4 is not limited to this. The circular pipe 4 may be any pipe, and may have an outer wall portion 31 and an inner wall portion 32, similar to the modified example of the circular pipe 3 shown in Figures 19 and 20. The circular pipe 4 may also be a square pipe. The circular pipe 3 may also be a square pipe.

[0096] In the first embodiment, the laser light L from the laser irradiation device 9 is described as being red, but the laser light L is not limited to this. The laser light L may be any light that can melt the end face of a tube, for example, the end face of the circular tube 3. The laser light L may be emitted by various laser irradiation devices such as an yttrium aluminum garnet laser (YAG laser), a YVO4 laser, a glass laser, a ruby ​​laser, a helium-neon gas laser, or an argon laser. The laser irradiation device 9 may also be a so-called fiber laser that uses an optical fiber.

[0097] Furthermore, in the first embodiment, an example was shown in which the pipe fitting 1A including the ring portion 12 was made of polyphenylene sulfide, but at least the ring portion 12 of the pipe fitting 1A may be made of a material that is transparent to the laser light L, that is, made of a material that allows the laser light L to pass through, so that the laser light L passes through the ring portion 12. To that extent, at least the ring portion 12 may be made of a material other than polyphenylene sulfide, for example, a resin material such as acrylic or polycarbonate.

[0098] Furthermore, the circular tube 3 may be made of any material that provides such a characteristic as long as its end surface, for example, the end surface of the terminal portion, is meltable by the laser light L. Therefore, the circular tube 3 may be made of a material other than polyphenylene sulfide, such as an internally colored acrylic or an internally colored polycarbonate.

[0099] As described above, the pipe joints 1A-1C, the pipe joint structures 2A and 2B, the water heater 100, the manufacturing method of the pipe joint structures 2A and 2B, and the manufacturing method of the water heater 100 are not limited to the above-described embodiments, and various modifications and substitutions can be made. Various embodiments of the present disclosure are described below as appendices.

[0100] (Supplementary Note 1) A pipe fitting for laser welding to a first pipe, comprising: a ring portion having a ring shape against which an end surface portion of a first pipe can abut from one side in the central axis direction, and formed of a material that is transparent to a specific laser beam that can melt the end surface portion of the first pipe, so that the laser beam passes through when irradiated with the laser beam from the other side in the central axis direction; and a support portion that is arranged radially of the ring portion and is provided on the one side of the ring portion, so that when the end surface portion of the first pipe abuts against the ring portion, it abuts against a cylindrical surface portion of the first pipe to support the cylindrical surface portion. (Supplementary Note 2) The pipe fitting according to Supplementary Note 1, wherein the end surface portion of the first pipe is formed of a material that absorbs the laser beam, and abuts against the ring portion from the one side, and when the laser beam is irradiated on the ring portion from the other side, it melts together with the ring portion by the heat of the laser beam and is welded to the ring portion. (Appendix 3) The pipe fitting according to Appendix 1 or 2, further comprising a connection portion having a tubular shape into which a second pipe can be inserted, provided on the other side of the ring portion, and connecting to the second pipe when the second pipe is inserted. (Appendix 4) The pipe fitting according to any one of Appendixes 1 to 3, wherein the ring portion has a first protrusion provided on the one side and formed around the entire circumference, and a tip of the first protrusion abuts against the end face portion of the first pipe when the end face portion abuts against the ring portion. (Appendix 5) The pipe fitting according to Appendix 4, wherein the first protrusion has a triangular shape in cross section and extends in the circumferential direction of the ring portion. (Appendix 6) The pipe fitting according to Appendix 5, wherein the triangular shape of the first protrusion in cross section is an isosceles triangle with its base facing the ring portion or a triangle with its apex shifted toward the inner circumference of the ring portion relative to the base. (Appendix 7) The pipe fitting according to Appendix 4, wherein the ring portion has a second protrusion portion that is provided more inward than the first protrusion portion and is formed around the entire circumference of the ring portion along the first protrusion portion, and a tip of the second protrusion portion has a gap between it and the end face portion when the tip of the first protrusion portion abuts against the end face portion of the first pipe.(Appendix 8) The pipe fitting according to any one of Appendices 1 to 7, wherein the outer diameter of the ring portion is equal to or greater than the outer diameter of the first pipe. (Appendix 9) The pipe fitting according to any one of Appendices 1 to 8, wherein the support portion is provided radially outward of the ring portion and supports the cylindrical surface portion of the first pipe from the outside. (Appendix 10) The pipe fitting according to Appendices 9, wherein the support portion has an inner diameter that allows the first pipe to be inserted and is formed in a cylindrical shape extending in the direction of the central axis of the ring portion. (Appendix 11) The pipe fitting according to Appendices 10, wherein the support portion protrudes inward from the inner peripheral surface portion, extends in the direction of the central axis of the ring portion, and has a plurality of guide portions that guide the first pipe when inserted. (Appendix 12) The pipe fitting according to any one of Appendices 1 to 11, further comprising a flange portion protruding radially outward from the ring portion. (Supplementary Note 13) The pipe fitting according to Supplementary Note 1 or 2, wherein the ring portion is formed of a material that is transparent to the specific laser light. (Supplementary Note 14) A pipe fitting structure for connecting the second pipe to the first pipe, comprising: the pipe fitting according to any one of Supplements 1 to 13; and the first pipe, the end face portion of which abuts and is welded to the ring portion, wherein the pipe fitting has a cylindrical shape that surrounds the ring portion from the other side, and further has a connection portion for connecting a second pipe. (Supplementary Note 15) A water heater, comprising: the pipe fitting structure according to Supplementary Note 14; and the second pipe connected to the connection portion of the pipe fitting.(Supplementary Note 16) A method for manufacturing a pipe fitting structure by connecting a first pipe to a pipe fitting including: a ring portion having a ring shape against which an end surface portion of a first pipe can abut from one side in a central axis direction, and formed of a material transparent to a specific laser beam capable of melting the end surface portion of the first pipe; and a support portion disposed radially of the ring portion, provided on the one side of the ring portion, and abutting against a cylindrical surface portion of the first pipe to support the cylindrical surface portion when the end surface portion of the first pipe abuts against the ring portion, the method comprising the steps of: assembling the first pipe to the pipe fitting by abutting the end surface portion of the first pipe against the ring portion of the pipe fitting from the one side in the central axis direction, and supporting the cylindrical surface portion of the first pipe by the support portion of the pipe fitting; and a step of irradiating the ring portion of the pipe fitting to which the first pipe is assembled with the laser beam from the other side of the central axis direction to melt the end face portion of the first pipe to the ring portion. (Appendix 17) The pipe fitting further includes a flange portion protruding radially and outwardly from the ring portion, and in the step of welding the end face portion to the ring portion, the flange portion is pressed in the one direction to press the end face portion of the first pipe against the ring portion of the pipe fitting, and the end face portion of the first pipe is melted by the laser beam. (Supplementary Note 18) The method for manufacturing a pipe joint structure according to Supplementary Note 16 or 17, wherein in the step of welding the end face portion to the ring portion, the end face portion of the first pipe is melted along the entire circumference and simultaneously by irradiating the entire circumference with the laser light simultaneously. (Supplementary Note 19) A method for manufacturing a water heater, comprising: the method for manufacturing a pipe joint structure according to any one of Supplements 16 to 18; and the step of connecting a second pipe included in the water heater to the side of the ring portion in the other direction.

[0101] The present disclosure allows various embodiments and modifications without departing from the broad spirit and scope of the present disclosure. Furthermore, the above-described embodiments are intended to explain the present disclosure and do not limit the scope of the present disclosure. That is, the scope of the present disclosure is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and within the meaning of the disclosure equivalent thereto are considered to be within the scope of the present disclosure.

[0102] This application is based on Japanese Patent Application No. 2024-048216, filed on March 25, 2024. The entire specification, claims, and drawings of Japanese Patent Application No. 2024-048216 are incorporated herein by reference.

[0103] 1A-1C pipe fitting, 2A, 2B pipe fitting structure, 3, 4 circular pipe, 5 seal, 6 pipe fitting, 7 fixing tool, 8 holding jig, 9 laser irradiation device, 11 support portion, 12 ring portion, 13 flange portion, 14 connection portion, 31 outer wall portion, 32 inner wall portion, 33 spacer portion, 81 hook-shaped portion, 100 water heater, 101 hot water storage tank, 102 heat exchanger, 103 pump, 104 piping, 111 guide portion, 121, 122 protrusion, 141 groove, A cylinder axis, A1, A2 arrow, D distance, L laser light, D11, D12, D13 outer diameter, D21, D22, D23, D24, D25 inner diameter.

Claims

1. A pipe fitting for laser welding to a first pipe, comprising: a ring portion having a ring shape that can be brought into contact with an end surface portion of a first pipe from one side in the central axis direction, and formed of a material that can transmit a specific laser beam that can melt the end surface portion of the first pipe, so that the laser beam passes through when the laser beam is irradiated from the other side in the central axis direction; and a support portion that is arranged radially of the ring portion and is provided on the one side of the ring portion, so that when the end surface portion of the first pipe comes into contact with the ring portion, it comes into contact with a cylindrical surface portion of the first pipe and supports the cylindrical surface portion.

2. A pipe fitting as described in claim 1, wherein the end surface portion of the first pipe is formed from a material that absorbs the laser light, and when it abuts against the ring portion from the one side and the laser light is irradiated onto the ring portion from the other side, the heat of the laser light melts the end surface of the first pipe together with the ring portion and causes it to be welded to the ring portion.

3. A pipe fitting as set forth in claim 1 or 2, further comprising a connecting portion having a cylindrical shape into which a second pipe can be inserted, provided on the other side of the ring portion, and connecting with the second pipe when the second pipe is inserted.

4. A pipe fitting as set forth in claim 1 or 2, wherein the ring portion is provided on the one side and has a first protrusion formed around the entire circumference, and the tip of the first protrusion abuts against the end face portion of the first pipe when the end face portion abuts against the ring portion.

5. A pipe joint as set forth in claim 4, wherein the first protrusion has a triangular cross-sectional shape extending in the circumferential direction of the ring portion.

6. A pipe fitting as set forth in claim 5, wherein the triangular cross-sectional shape of the first protrusion is an isosceles triangle with its base facing the ring portion, or a triangle with its apex offset toward the inner periphery of the ring portion relative to its base.

7. A pipe fitting as set forth in claim 4, wherein the ring portion has a second protrusion that is provided more inward than the first protrusion and is formed along the entire circumference of the ring portion along the first protrusion, and when the tip of the first protrusion abuts against the end face portion of the first pipe, there is a gap between the tip of the second protrusion and the end face portion.

8. A pipe fitting according to claim 1 or 2, wherein the outer diameter of the ring portion is equal to or greater than the outer diameter of the first pipe.

9. A pipe joint according to claim 1 or 2, wherein the support portion is provided radially outward of the ring portion and supports the cylindrical surface portion of the first pipe from the outside.

10. A pipe joint as set forth in claim 9, wherein the support portion has an inner diameter that allows the first pipe to be inserted therein, and is formed in the shape of a tube that extends in the direction of the central axis of the ring portion.

11. A pipe fitting as set forth in claim 10, wherein the support portion has a plurality of guide portions that protrude inward from the inner peripheral surface portion, extend in the direction of the central axis of the ring portion, and guide the first pipe when the first pipe is inserted.

12. A pipe fitting according to claim 1 or 2, further comprising a flange portion that protrudes radially outward from said ring portion.

13. A pipe joint according to claim 1 or 2, wherein the ring portion is formed from a material that is transparent to the specific laser light.

14. A pipe fitting structure for connecting a second pipe to a first pipe, comprising: the pipe fitting according to claim 1 or 2; and the first pipe, the end face portion of which abuts and is welded to the ring portion, wherein the pipe fitting has a cylindrical shape that surrounds the ring portion from the other side and further has a connection portion for connecting a second pipe.

15. A water heater comprising: the pipe joint structure according to claim 14; and the second pipe connected to the connection part of the pipe joint.

16. A method for manufacturing a pipe joint structure by connecting a first pipe to a pipe joint comprising: a ring portion having a ring shape against which an end surface portion of a first pipe can abut from one side in the central axis direction, and formed of a material transparent to a specific laser beam capable of melting the end surface portion of the first pipe; and a support portion disposed radially of the ring portion, provided on the one side of the ring portion, for abutting against a cylindrical surface portion of the first pipe to support the cylindrical surface portion when the end surface portion of the first pipe abuts against the ring portion, the method comprising the steps of: assembling the first pipe to the pipe joint by abutting the end surface portion of the first pipe against the ring portion of the pipe joint from the one side in the central axis direction, and supporting the cylindrical surface portion of the first pipe against the support portion of the pipe joint; and applying the laser beam to the ring portion of the pipe joint to which the first pipe is assembled from the other side of the central axis direction to melt the end face portion of the first pipe, thereby welding the end face portion to the ring portion.

17. A method for manufacturing a pipe fitting structure as described in claim 16, wherein the pipe fitting further comprises a flange portion protruding radially and outwardly from the ring portion, and in the step of welding the end face portion to the ring portion, the flange portion is pushed in the one direction to press the end face portion of the first pipe against the ring portion of the pipe fitting, and the end face portion of the first pipe is melted by the laser light.

18. A method for manufacturing a pipe joint structure as set forth in claim 16 or 17, wherein in the step of welding the end face portion to the ring portion, the end face portion of the first pipe is melted along the entire circumference and simultaneously by irradiating the laser light along the entire circumference and simultaneously around the ring portion.

19. A method for manufacturing a water heater, comprising: a method for manufacturing a pipe joint structure as set forth in claim 16 or 17; and a step of connecting a second pipe provided in the water heater to the other side of the ring portion.

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