Pipe connection structure and water heater

Abstract

A pipe connection structure (1) comprises: a first pipe; and a joint (10) including a first joint part having a tubular shape, inserted from an end part of the first pipe, and press-fitted into the first pipe, and a second joint part communicating with an internal space of the first joint part and connectable to a second pipe. The first joint part has protrusions (16, 17) that are provided on the outer peripheral part thereof, extend in the circumferential direction, and are press-fitted into the first pipe so as to be located inward of the end part of the first pipe. The outer diameter of each of the protrusions (16, 17) is larger than the inner diameter of the end part of the first pipe.

Description

Pipe connection structure and water heater

[0001] The present disclosure relates to a pipe connection structure and a water heater.

[0002] Some pipe connection structures have a joint connected to the end of a pipe for connecting another pipe.

[0003] For example, Patent Document 1 discloses a pipe connection structure including a joint inserted into an expanded end of a pipe, and a cylindrical fitting that tightens the end of the pipe to bring the end into close contact with the joint.

[0004] Japanese Unexamined Patent Application Publication No. 2023-174243

[0005] In the pipe connection structure described in Patent Document 1, if the tightening of the cylindrical fitting is insufficient, the joint may come off from the pipe. In addition, this pipe connection structure has a large number of components as a result of being provided with the fitting for tightening the pipe.

[0006] The present disclosure has been made to solve the above problems, and an object of the present disclosure is to provide a pipe connection structure and a water heater in which the pipe is less likely to come off from the joint and which has a small number of components.

[0007] To achieve the above object, a pipe connection structure according to the present disclosure includes a first pipe and a joint. The joint has a tubular shape, and includes a first joint portion that is inserted from an end of the first pipe and press-fitted into the first pipe, and a second joint portion that communicates with an internal space of the first joint portion and to which a second pipe can be connected. The first joint portion has a protruding portion that is provided on an outer peripheral portion, extends in a circumferential direction, is press-fitted into the first pipe, and is located further inside the first pipe than the end of the first pipe. An outer diameter of the protruding portion is larger than an inner diameter of the end of the first pipe.

[0008] According to the configuration of the present disclosure, since the outer diameter of the protruding portion is larger than the inner diameter of the end of the first pipe, the protruding portion cannot pass through the end of the first pipe. As a result, the first joint portion of the joint is less likely to come off from the first pipe. In addition, the pipe connection structure according to the present disclosure can prevent the joint from coming off with such a configuration, so new components for fixing the joint or the first pipe are not required. According to the configuration of the present disclosure, it is possible to prevent the joint from coming off from the first pipe with a small number of components.

[0009] Front view of the pipe connection structure according to Embodiment 1 of this disclosure Perspective view of the pipe connection structure according to Embodiment 1 of this disclosure Cross-sectional view of the pipe connection structure according to Embodiment 1 of this disclosure Enlarged view of area IV shown in Figure 3 Enlarged view of area V shown in Figure 3 Cross-sectional view of a modified circular pipe provided in the pipe connection structure according to Embodiment 1 of this disclosure Circuit diagram of a water heater according to Embodiment 2 of this disclosure Cross-sectional view of the pipe connection structure according to Embodiment 3 of this disclosure Cross-sectional view of a modified pipe connection structure according to Embodiment 3 of this disclosure Enlarged view of a modified projection provided in the pipe connection structure according to Embodiment 1 of this disclosure Cross-sectional view of a first modified pipe connection structure according to Embodiment 1 of this disclosure Cross-sectional view of a second modified pipe connection structure according to Embodiment 1 of this disclosure

[0010] Hereinafter, the pipe connection structure and water heater according to the embodiments of this disclosure will be described in detail with reference to the drawings. In the drawings, the same or equivalent parts are denoted by the same reference numerals. In the Cartesian coordinate system XYZ shown in the drawings, when the cylindrical axis of the cylindrical press-fit portion of the joint of the pipe connection structure is oriented vertically, and the plate surface of the flange portion of the joint is horizontal, the vertical direction is the Z-axis and the horizontal plane is the XY-plane. Hereafter, this coordinate system will be referenced as appropriate in the explanation.

[0011] (Embodiment 1) The pipe connection structure according to Embodiment 1 has a structure in which a joint is provided at the end of a specific pipe in order to connect another pipe to that specific pipe. Furthermore, in order to prevent the joint from falling out of the end of the specific pipe, this pipe connection structure has a joint portion in which the joint is press-fitted, in other words, a press-fit portion. The configuration of the pipe connection structure will be described below with reference to Figures 1 to 5, using the case in which the specific pipe and the other pipe are circular pipes of different diameters as an example. In the following description, the positional relationship of the configuration of the pipe connection structure will be described using the case in which pipes with their pipe axes oriented in the vertical direction are connected as an example. Note that the pipe connection structure is also simply called the connection structure.

[0012] Figure 1 is a front view of the pipe connection structure 1A according to Embodiment 1. Figure 2 is a perspective view of the connection structure 1A. Figure 3 is a cross-sectional view of the connection structure 1A. Figure 4 is an enlarged view of area IV shown in Figure 3. Figure 5 is an enlarged view of area V shown in Figure 3. For ease of understanding, Figure 1 schematically shows the entire pipe connection structure 1A. Figures 3-5 show the cross-section of the connection structure 1A shown in Figure 1 when cut by a plane extending in the direction of extension of the cylinder and in the radial direction of the cylinder at the upper end of the circular pipe 2, specifically the cross-section when cut by a plane parallel to the XZ plane.

[0013] As shown in Figures 1 and 2, the pipe connection structure 1A is a structure for connecting a circular pipe 3 to a circular pipe 2. The connection structure 1A comprises a joint 10 to which the circular pipe 3 can be connected, and a circular pipe 2 connected to the joint 10.

[0014] The joint 10 is a component for connecting the circular pipes 2 and 3, and is a so-called male-type joint. To connect the circular pipes 2 and 3, the joint 10 has a joint portion 11 for connecting the circular pipe 3 and a press-fit portion 12 that is press-fitted into the circular pipe 2, as shown in Figure 3. In this specification, the press-fit portion 12 is also referred to as the joint portion, in which case the press-fit portion 12 is referred to as the first joint portion and the joint portion 11 as the second joint portion.

[0015] The joint portion 11 is formed in a cylindrical shape to connect with the circular pipe 3. A joint 4 is provided at the end of the circular pipe 3, specifically at the lower end of the circular pipe 3. The joint 4 is a so-called female type joint and has a cylindrical shape with the upper cylindrical end closed. A through hole 41 is formed at the upper cylindrical end of the joint 4, and the lower end of the circular pipe 3 passes through this through hole 41. In order to connect with the joint 4 with this configuration, the outer diameter R1 of the joint portion 11 is the same as the inner diameter of the joint 4 to the extent that the joint portion 11 can be inserted into and removed from the joint 4. As a result, the joint portion 11 can be inserted into the joint 4 and connected by insertion into the joint 4. Furthermore, the inner diameter R2 of the joint portion 11 is the same as the outer diameter of the circular pipe 3 to the extent that the circular pipe 3 can be inserted into and removed from the joint 4. As a result, when the joint portion 11 is connected to the joint 4, it can hold the lower end of the circular pipe 3 that has passed through the joint 4.

[0016] Furthermore, the joint portion 11 has a groove 14 for inserting an O-ring 13 to ensure watertightness when connected to the joint 4. The groove 14 extends circumferentially around the outer circumference of the joint portion 11. As a result, the groove 14 is formed around the entire circumference of the joint portion 11. This makes it possible to fit the O-ring 13 into the groove 14. The joint portion 11 ensures watertightness when the O-ring 13 is fitted into the groove 14 and the O-ring 13 adheres tightly to the inner wall of the joint 4. The joint portion 11 also holds the joint 4 due to this adhesion force. A flange 15 is provided below the groove 14.

[0017] As shown in Figure 2, the flange 15 is formed in the shape of an annular plate. The annular shape of the flange 15 is concentric with the cylinder of the joint portion 11, as shown in Figure 3. The flange 15 is also provided at the lower end of the joint portion 11. With this configuration, the flange 15 protrudes radially and outward from the lower end of the joint portion 11. As shown in Figure 2, the flange 15 is fixed to the location where the clamping device 5 is installed by being clamped by the clamping device 5, which has a slit into which the flange 15 is inserted.

[0018] Returning to Figure 3, further below the flange 15, there is a press-fit portion 12 which has an internal space that communicates with the internal space of the circular pipe 3 held by the joint portion 11.

[0019] The press-fit portion 12 is the part that connects the circular pipe 2 to the joint portion 11 that holds the circular pipe 3 by being pressed into the circular pipe 2. The press-fit portion 12 has a cylindrical shape. The inner diameter R3 of the press-fit portion 12 is the same as the inner diameter R4 of the circular pipe 3 in order to reduce the pressure loss of the fluid when fluid flows in the internal space of the circular pipe 3. Furthermore, the outer diameter R5 of the press-fit portion 12 is smaller than the outer diameter R1 of the joint portion 11, but larger than the inner diameter R6 of the circular pipe 2 in order to be pressed into the circular pipe 2. As a result, the press-fit portion 12 can be pressed into the circular pipe 2. When the press-fit portion 12 is inserted into the circular pipe 2, there is a clearance between it and the circular pipe 2, resulting in it being firmly held in the circular pipe 2.

[0020] On the other hand, the cylindrical tube 2 is formed from a plastic material, such as a resin material. For example, the cylindrical tube 2 is formed from polyphenylene sulfide (PPS) resin. As a result, when the press-fit portion 12 is pressed in, the cylindrical tube 2 is molded and expanded by the press-fit portion 12. The press-fit portion 12 may be pressed in by a method of heating the cylindrical tube 2, such as shrink-fitting, but in Embodiment 1, it is done by cold press-fitting. As a result of this press-fitting, the cylindrical tube 2 and the press-fit portion 12 are firmly fixed together. However, if the press-fit portion 12 is simply cylindrical in shape, there is a possibility that the press-fit portion 12 may come out of the cylindrical tube 2 if a large force is applied to the cylindrical tube 2 or the press-fit portion 12. Therefore, in order to make it more difficult for the press-fit portion 12 to come out of the cylindrical tube 2, projections 16 and 17 are provided on the press-fit portion 12.

[0021] The protrusions 16 and 17 are formed on the outer circumference of the press-fit portion 12. The protrusions 16 and 17 have a cross-sectional shape that extends from the outer circumference of the press-fit portion 12. In detail, the shape of the protrusions 16 and 17 is a triangular shape in cross-section, with one side aligned along the outer circumference of the press-fit portion 12.

[0022] Here, a cross-sectional view refers to a view of the cross-section obtained by cutting the press-fit portion 12 with a plane that extends in the direction of extension of the cylinder and in the radial direction of the cylinder. For example, the cross-sectional view is the view obtained by cutting with the XZ plane as shown in Figure 3. Furthermore, in the triangular cross-sectional shape of the projections 16 and 17, it is desirable that the interior angle A1 on the +Z side, as shown in Figure 4, is 90° or less. This is because if the interior angle A1 exceeds 90°, it becomes difficult to manufacture the projections 16 and 17. In other words, if the interior angle A1 is such that the manufacturing of the projections 16 and 17 is easy.

[0023] Due to the triangular shape of the projections 16 and 17, as shown in Figures 3 and 4, in a cross-sectional view, the amount of radial and outward protrusion of the press-fit portion 12 increases from the tip to the base, i.e., from the -Z end to the +Z end, until it reaches the protrusions 161 and 171, and then the amount of protrusion decreases as it moves towards the +Z end. As a result, when the press-fit portion 12 is pressed into the circular pipe 2, the projections 16 and 17 gradually expand the circular pipe 2 from the -Z side, thus facilitating press-fitting into the circular pipe 2. Furthermore, when the press-fit portion 12 is pressed into the circular pipe 2, the projections 16 and 17 shape the cylindrical surface portion of the circular pipe 2 to conform to the shape of the projections 16 and 17, preventing the press-fit portion 12 from coming out of the circular pipe 2 after press-fitting.

[0024] In detail, when the press-fit portion 12 is press-fitted into the circular pipe 2, the projections 16 and 17 expand the portion of the cylindrical surface of the circular pipe 2 that contacts the projections 16 and 17, forming a corrugated shape in cross-section. In the corrugated portion of the circular pipe 2 in cross-section, the points where they contact the protrusions 161 and 171 form the peaks of the waves. By shaping the circular pipe 2 in this way, the projections 16 and 17 prevent the press-fit portion 12 from coming out of the circular pipe 2 after press-fitting. Furthermore, the projections 16 and 17 are positioned inside the circular pipe 2 after press-fitting. As a result, the projections 16 and 17 are located deeper inside the circular pipe 2 than at the ends of the circular pipe 2. That is, they are located lower than at the upper end of the circular pipe 2. This makes it difficult for the projections 16 and 17 to come out of the formed circular pipe 2.

[0025] When the press-fit portion 12 is pressed into the cylindrical pipe 2 and the cylindrical pipe 2 is formed into a corrugated shape in cross-section, a gap may form around the protrusions 16 and 17 between the cylindrical pipe 2 and the protrusions 16 and 17, or between the cylindrical pipe 2 and the outer circumference of the press-fit portion 12. In that case, the gap reduces the heat transfer from the press-fit portion 12 to the cylindrical pipe 2, thereby improving the heat insulation of the connection structure 1A.

[0026] The projections 16 and 17 have this cross-sectional shape and extend in the circumferential direction of the press-fit portion 12. As a result, the projections 16 and 17 surround the entire circumference of the press-fit portion 12. Furthermore, the projections 16 and 17 are located inside the end of the press-fit portion 12, that is, on the +Z side of the -Z end of the press-fit portion 12, and are aligned in the Z direction. As a result, when the press-fit portion 12 is pressed into the circular pipe 2, the projections 16 and 17 shape the cylindrical surface portion inside the end of the circular pipe 2, that is, the cylindrical surface portion below the upper end of the circular pipe 2, into the aforementioned corrugated cross-sectional shape. As a result, the press-fit portion 12 is less likely to come out of the circular pipe 2 after press-fitting. In addition, the position of the press-fit portion 12 relative to the circular pipe 2 is prevented from shifting after press-fitting.

[0027] Furthermore, when the press-fit portion 12 is press-fitted into the cylindrical pipe 2, the projections 16 and 17 are formed so that the inner diameter R7 of the upper end of the cylindrical pipe 2 is smaller than the outer diameter R8 of the portion where the protruding ends 161 and 171 of the projections 16 and 17 are located. As a result, the cylindrical pipe 2 is less likely to come off the press-fit portion 12 after press-fitting. Thus, in the connection structure 1A, the press-fit portion 12 is less likely to come off the cylindrical pipe 2 even without providing a device to prevent the press-fit portion 12 from falling off by tightening the cylindrical pipe 2.

[0028] Furthermore, to facilitate press-fitting, the press-fitting portion 12 is provided with a tapered portion 18 at its tip, i.e., its lower end.

[0029] The lower end of the cylinder of the press-fit portion 12 is thicker than the rest of the cylinder of the press-fit portion 12, and as a result protrudes outward. The tapered portion 18 has a chamfered shape on the outer circumference of the lower end of the press-fit portion 12. In detail, as shown in Figure 5, the tapered portion 18 has an inclined surface S that extends upward in the radial direction of the cylinder of the press-fit portion 12 and outward. The inclination angle A2 of the inclined surface S with respect to the cylindrical axis of the press-fit portion 12 is acute with respect to the cylindrical axis of the press-fit portion 12, and is preferably 45° or less. This is because such an inclination angle A2 makes it easier to press-fit the press-fit portion 12. The tapered portion 18 has a thickened portion 181 adjacent to the inclined surface S where the thickness of the cylinder of the press-fit portion 12 is increased, and a groove 182 for inserting an O-ring (not shown) is provided in the thickened portion 181. In the tapered section 18, an O-ring is fitted into the groove 182, and the O-ring 13 adheres tightly to the inner wall of the cylindrical pipe 2, thereby ensuring watertightness.

[0030] Furthermore, the thickened portion 181 is adjacent to the cylindrical portion of the press-fit portion 12 of normal thickness on its upper side. As a result, a step is formed on the upper side of the thickened portion 181. Due to this configuration, the tapered portion 18 has a trapezoidal shape in cross-section, with its lower base facing inward, that is, facing in the cylindrical axis direction of the press-fit portion 12. For this reason, the tapered portion 18 performs the same function as the protrusions 16 and 17. That is, when the press-fit portion 12 is press-fitted into the circular pipe 2, the tapered portion 18 shapes the cylindrical surface portion of the circular pipe 2 to follow the shape of the tapered portion 18, preventing the press-fit portion 12 from coming out of the circular pipe 2 after press-fitting.

[0031] Returning to Figure 3, the press-fit portion 12, having the aforementioned projections 16, 17 and tapered portion 18, shapes the circular pipe 2 to conform to the projections 16, 17 and tapered portion 18 when press-fitted into the circular pipe 2. As a result, each portion of the cylindrical surface of the circular pipe 2 is expanded to an outer and inner diameter corresponding to the outer diameter of each portion of the projections 16, 17 and tapered portion 18, and the circular pipe 2 develops irregularities that interlock with each portion of the projections 16, 17 and tapered portion 18. If the circular pipe 2 and the press-fit portion 12, which have such irregularities, expand or contract due to the temperature of the operating environment, the press-fit portion 12 may shift from the desired position on the circular pipe 2. Therefore, the entire joint 10, including the press-fit portion 12, is made of the same resin material as the circular pipe 2.

[0032] More specifically, the entire joint 10 is formed from a material whose main component is the same resin as that of the cylindrical pipe 2. For example, the joint 10 is formed from a material whose main component is the same polyphenylene sulfide (PPS) resin as that of the cylindrical pipe 2, with glass filler added. In short, the joint 10 and the cylindrical pipe 2 are formed from grades of material whose main component is the same resin, but with different additives and their amounts. As a result, the coefficient of linear expansion of the material forming the joint 10 is the same as, or approximates, that of the material forming the cylindrical pipe 2. Consequently, the position of the press-fit portion 12 is prevented from shifting relative to the cylindrical pipe 2 due to temperature changes in the operating environment. For example, if the operating environment of the connection structure 1A is such that hot and cold water at 0 to 100°C flows through the cylindrical pipe 2, resulting in a temperature of 0 to 100°C, the position of the press-fit portion 12 is prevented from shifting relative to the cylindrical pipe 2 in that temperature environment.

[0033] The circular pipe 2 described above is an example of the first pipe as referred to in this disclosure. The circular pipe 3 is an example of the second pipe as referred to in this disclosure. The press-fit portion 12 and the joint portion 11 are examples of the first joint portion and the second joint portion as referred to in this disclosure. The lower end and upper end of the press-fit portion 12, i.e., the -Z end and the +Z end, are examples of the tip and base end of the first joint portion as referred to in this disclosure. The press-fit portion 12 is also referred to as the press-fitted portion.

[0034] As described above, in the connection structure 1A according to Embodiment 1, the press-fit portion 12 has projections 16 and 17 on its outer circumference that extend in the circumferential direction. The projections 16 and 17 surround the entire circumference of the press-fit portion 12. The projections 16 and 17 are press-fitted into the cylindrical pipe 2 and are located below the upper end of the cylindrical pipe 2. That is, the projections 16 and 17 are located inside the cylindrical pipe 2, below the end of the cylindrical pipe 2. Furthermore, the outer diameter of the projections 16 and 17 is larger than the inner diameter of the end of the cylindrical pipe 2. For this reason, the projections 16 and 17 cannot pass through the end of the cylindrical pipe 2. As a result, the press-fit portion 12 is difficult to remove from the cylindrical pipe 2.

[0035] The connection structure 1A, with the above configuration, can prevent the press-fit portion 12 from coming out of the cylindrical pipe 2. Therefore, the connection structure 1A does not require any new parts to fix the cylindrical pipe 2 to the press-fit portion 12. As a result, the connection structure 1A can prevent the press-fit portion 12, i.e., the joint 10, from coming out of the cylindrical pipe 2 with a small number of parts.

[0036] Furthermore, the joint 10 and the cylindrical pipe 2 are made of the same resin material. Therefore, even if there are temperature changes in the operating environment, the position of the joint 10 relative to the cylindrical pipe 2 is less likely to shift. As a result, the joint 10 is also prevented from coming loose from the cylindrical pipe 2 due to temperature changes. Note that resin material refers to materials whose main component is the same resin.

[0037] (Modification) In Embodiment 1, the circular pipe 2 is expanded by press-fitting the press-fit portion 12. The expansion ratio of the circular pipe 2 is preferably 143% or less at the point where the protrusions 16 and 17, which are considered to be the most expanded portion, make contact. Table 1 shows the results of the circular pipe 2 expansion experiment. In the circular pipe 2 expansion experiment, a circular pipe 2 with a wall thickness of 1.4 mm was used.

[0038]

[0039] As shown in Table 1, up to a pipe expansion ratio of 143%, there was no problem in the pipe expansion of the circular pipe 2, and favorable pipe expansion was achieved. However, at a pipe expansion ratio of 150%, a problem occurred in that the circular pipe 2 cracked. From these experimental results, the pipe expansion ratio of the circular pipe 2 is desirably 143% or less. Note that in the experiments of Table 1, since the wall thickness of the circular pipe 2 was 1.4 mm, more reliably, the pipe expansion ratio of the circular pipe 2 is desirably 140% or less when the wall thickness of the circular pipe 2 is 1.4 mm or more.

[0040] Here, the pipe expansion ratio refers to a ratio obtained by dividing the inner diameter R6 of the circular pipe 2 by the outer diameter R8 of the portions where the protruding ends 161 and 171 of the press-fitting portion 12 are located.

[0041] Further, in the first embodiment, the circular pipe 2 is a cylinder with a uniform wall thickness. The same applies to the circular pipe 3 (not shown). However, the circular pipes 2 and 3 are not limited thereto. Since the circular pipes 2 and 3 only need to be pipes, their cross-sectional shape is arbitrary.

[0042] FIG. 6 is a cross-sectional view of a modified example of the circular pipe 2 included in the pipe connection structure 1A according to the first embodiment.

[0043] As shown in FIG. 6, the circular pipe 2 may be a so-called double pipe. In that case, the circular pipe 2 may have an outer pipe 21, an inner pipe 22 passed through the outer pipe 21, and a plurality of column portions 23 and 24 that connect the inner pipe 22 to the outer pipe 21. The total number of the plurality of column portions 23 and 24 is two in FIG. 6, but the total number may be three or more. Similarly, the circular pipe 3 (not shown) may also be a double pipe.

[0044] Note that the circular pipe 2 may desirably be bent two or more times. For example, as shown in FIG. 1, the circular pipe 2 may be bent twice. In such a case, the circular pipe 2 preferably has a length of 300 mm or more.

[0045] (Embodiment 2) The pipe connection structure 1A according to the first embodiment is applicable to connection between pipes through which a fluid flows. For example, the pipe connection structure 1A can be applied to piping of a hot water storage type water heater.

[0046] In the second embodiment, the pipe connection structure 1A is used for connecting components of the water heater 100. Hereinafter, the water heater 100 according to the second embodiment will be described with reference to FIG. 7. The second embodiment will be described focusing on configurations different from those of the first embodiment.

[0047] FIG. 7 is a circuit diagram of the water heater 100 according to the second embodiment.

[0048] The water heater 100 shown in FIG. 7 includes 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 causing the hot water in the hot water storage tank 101 to flow to the heat exchanger 102, and pipes 104 for connecting these components.

[0049] The connection structure 1A according to the first embodiment is used for connection between the pipe 104 and a component of the water heater 100, for example, connection between the pipe 104 extending from the heat exchanger 102 and the pump 103. For example, the pipe 104 is used as the circular pipe 2 described in the first embodiment, and the pipe extending from the pump 103 is used as the circular pipe 3. By applying the connection structure 1A to such a pipe 104 and the pump 103, the connection strength between the pipe 104 and the pump 103 can be increased. As a result, in the water heater 100, the pipe 104 can be prevented from coming off.

[0050] Further, the connection structure 1A according to the first embodiment is used for connection between the hot water storage tank 101 and the heat exchanger 102. For example, it is used for connection between the pipe 104 extending from the lower portion of the hot water storage tank 101 shown in FIG. 7 and the pipe 104 extending from the heat exchanger 102. In this case, the pipe 104 extending from the lower portion of the hot water storage tank 101 is used as the circular pipe 2 described in the first embodiment, and the pipe 104 extending from the heat exchanger 102 is used as the circular pipe 3. By applying the connection structure 1A to the hot water storage tank 101 and the heat exchanger 102 in this manner, the connection strength of the pipes between the hot water storage tank 101 and the heat exchanger 102 can be increased. Even in such a case, the water heater 100 can prevent the pipe 104 from coming off.

[0051] As described above, in the water heater 100 according to Embodiment 2, the pipe connection structure 1A according to Embodiment 1 is applied to the connection of the pipes 104 together. As a result, in the water heater 100, the connection of the pipes 104 is strong and difficult to detach, similar to Embodiment 1.

[0052] (Embodiment 3) The pipe connection structure 1A according to Embodiment 1 has a groove 182 between the tapered portion 18 and the projection 17 into which an O-ring is fitted. However, the presence or absence of the groove 182 is optional in the pipe connection structure 1A. Also, if the pipe connection structure 1A has a groove 182, it is optional whether or not an O-ring is fitted into the groove 182.

[0053] In Embodiment 3, the groove 19 provided between the tapered portion 18 and the projection 17 is not a groove for arranging an O-ring, but is provided to improve heat insulation. The pipe connection structure 1B according to Embodiment 3 will be described below with reference to Figures 8 and 9. Embodiment 3 will be described mainly for its configuration which differs from Embodiments 1 and 2.

[0054] Figure 8 is a cross-sectional view of the pipe connection structure 1B according to Embodiment 3. Figure 9 is a cross-sectional view of a modified example of the pipe connection structure 1B.

[0055] As shown in Figure 8, the groove 19 is provided between the tapered portion 18 and the projection 17 of the press-fit portion 12. The groove 19 extends in the circumferential direction of the press-fit portion 12. As a result, the groove 19 is formed around the entire circumference of the press-fit portion 12.

[0056] As described in Embodiment 1, the press-fit portion 12 is press-fitted into the circular pipe 2. As a result, the groove 19 is covered by the cylindrical surface portion of the circular pipe 2. As described in Embodiment 1, the circular pipe 2 is made of a flexible material, and as a result of the press-fit portion 12 being press-fitted, it expands. As a result, the cylindrical surface portion of the circular pipe 2 that covers the tapered portion 18 to the projection portion 17 is deformed into a gentle wave shape. And, as a result of the groove 19 being sufficiently deep, a space 9 is formed between the bottom of the groove 19 and the cylindrical surface portion of the circular pipe 2. This space 9 is filled with air.

[0057] When the pipe connection structure 1B is used to explain the piping of the water heater 100 as described in Embodiment 2, hot water flows through it. In this case, if the circular pipe 2 and the press-fit portion 12 are in complete contact, the heat from the hot water may be transferred from the press-fit portion 12 to the circular pipe 2 and dissipated to the outside.

[0058] Conventionally, in order to suppress such heat dissipation, if the cylindrical pipe 2 is a metal pipe such as copper or stainless steel, the metal pipe is covered with an insulating tube made of foamed resin, such as urethane resin, and the tube is fixed to the metal pipe with fasteners.

[0059] In contrast, the pipe connection structure 1B, as described above, has an air-filled space 9 between the bottom of the groove 19 and the cylindrical surface portion of the circular pipe 2. The entire joint 10 having the press-fit portion 12 and the circular pipe 2 are made of resin material, as explained in Embodiment 1. As a result, the resin material of the joint 10 and the circular pipe 2 and the air in the space 9 function as insulating materials. Therefore, when hot water flows through the circular pipe 2, the pipe connection structure 1B can suppress the dissipation of heat from the hot water to the outside, unlike the case of the metal pipe described above. Furthermore, since the pipe connection structure 1B does not require the installation of insulating tubes, fasteners, etc., the installation cost is lower compared to conventional metal pipes.

[0060] The width, depth, and number of grooves 19 are arbitrary, as long as a space 9 is formed. As shown in Figure 9, the press-fit portion 12 may have multiple grooves 19 formed between the tapered portion 18 and the projection portion 17. In that case, it is preferable to provide projections, i.e., support portions 20, between the grooves 19, which protrude outward from the bottom of the grooves 19 and support the cylindrical surface portion of the circular pipe 2. In that case, it is preferable that the support portions 20 extend in the circumferential direction of the press-fit portion 12 and surround the entire circumference of the press-fit portion 12. This is because if such support portions 20 are provided between the grooves 19, a space 9 can be reliably formed.

[0061] As described above, in the pipe connection structure 1B according to Embodiment 3, the press-fit portion 12 is provided between the tapered portion 18 and the projection portion 17 and has one or more grooves 19 extending in the circumferential direction. The grooves 19 are filled with air. For this reason, the pipe connection structure 1B has high heat insulation properties. When the pipe connection structure 1B is used, for example, in a water heater 100, it does not easily dissipate the heat of the hot water.

[0062] The cylindrical surface portion of the circular pipe 2 described in Embodiment 3 is an example of the cylindrical surface portion of the first pipe as referred to in this disclosure.

[0063] The pipe connection structure 1A and the water heater 100 according to the embodiments of this disclosure have been described above, but the pipe connection structure 1A and the water heater 100 are not limited thereto.

[0064] For example, in embodiments 1A and 1B, the cylindrical pipes 2 and 3 have their cylindrical axes oriented vertically. However, the pipe connection structures 1A and 1B and the water heater 100 are not limited to this. The orientation of the cylindrical axes of the cylindrical pipes 2 and 3 is merely described as vertical for the sake of explanation. The orientation is arbitrary as long as the positional relationship of each component of the pipe connection structures 1A and 1B and the water heater 100 is maintained.

[0065] In Embodiment 1, the press-fit portion 12 is provided with protrusions 16 and 17, but the number of protrusions 16 and 17 is not limited to this. It is sufficient to have at least one protrusion 16 or 17 on the press-fit portion 12, and to more reliably prevent the press-fit portion 12 from coming out of the cylindrical pipe 2, it is preferable to provide multiple protrusions 16 and 17 on the press-fit portion 12. When multiple protrusions 16 and 17 are provided on the press-fit portion 12, the shape of the press-fit portion 12 may be called a bamboo shoot shape.

[0066] In Embodiment 1, the projections 16 and 17 are triangular in cross-section, but the projections 16 and 17 are not limited to this. The projections 16 and 17 are provided on the outer circumference of the press-fit portion 12, extend in the circumferential direction, and are press-fitted into the circular pipe 2 so that they are located inside the circular pipe 2 beyond the end of the circular pipe 2. Furthermore, the outer diameter of the projections 16 and 17 is larger than the inner diameter of the end of the circular pipe 2. Therefore, as long as these conditions are met, the cross-sectional shape of the projections 16 and 17 is arbitrary.

[0067] Figure 10 is an enlarged view of a modified example of the projection 17 provided in the pipe connection structure 1A according to Embodiment 1.

[0068] As shown in Figure 10, the projection 17 may have a cross-sectional wave shape. Although not shown, the projection 16 may also have a cross-sectional wave shape. Furthermore, the projections 16 and 17 do not have to have the same shape in cross-section; for example, the projection 16 may be triangular in cross-section, and the projection 17 may have a cross-sectional wave shape. Furthermore, the projections 16 and 17 do not have to be the same size in cross-section, for example, they do not have to have the same protrusion amount. For example, the projection 16 on the base side of the press-fit portion 12 may be larger in cross-section and have a larger protrusion amount.

[0069] Furthermore, the projections 16 and 17 may be trapezoidal in cross-section, similar to the tapered portion 18. In addition, although difficult to manufacture, the projections 16 and 17 may have an obtuse angle greater than 90° in interior angle A1 as shown in Figure 4, resulting in the formation of a so-called "return."

[0070] Furthermore, in Embodiment 1, a flange 15 is provided on the joint portion 11. However, the joint portion 11 is not limited to this. Whether or not the joint portion 11 has a flange 15 is optional.

[0071] Figure 11 is a cross-sectional view of a first modified example of the pipe connection structure 1A according to Embodiment 1.

[0072] As shown in Figure 11, the joint portion 11 may not have a flange 15 and may be cylindrical in shape.

[0073] Furthermore, in Embodiment 1, the joint portion 11 and the press-fit portion 12 are coaxial, and as a result, their axes are aligned vertically. However, the position of the press-fit portion 12 relative to the joint portion 11 is not limited to this.

[0074] Figure 12 is a cross-sectional view of a second modified example of the pipe connection structure 1A according to Embodiment 1.

[0075] As shown in Figure 12, the connection structure 1A may have a bent portion between the joint portion 11 and the press-fit portion 12. Furthermore, the connection structure 1A may have a branching portion between the joint portion 11 and the press-fit portion 12.

[0076] In Embodiment 1, the press-fit portion 12 has a tapered portion 18, but the tapered portion 18 has an arbitrary configuration. Therefore, the press-fit portion 12 does not have to have a tapered portion 18. Also, the groove 182 of the tapered portion 18 has an arbitrary configuration, and the groove 182 is unnecessary if watertightness can be ensured. Furthermore, if the press-fit portion 12 does not have a tapered portion 18, the resulting straight pipe portion may be omitted.

[0077] Furthermore, in Embodiment 1, the circular pipes 2 and 3 are pipes with a circular cross-section. However, the circular pipes 2 and 3 are not limited to this. The circular pipes 2 and 3 can be any pipe, for example, they may be rectangular pipes.

[0078] In Embodiment 1, the inner diameter R3 of the press-fit portion 12 is the same as the inner diameter R4 of the circular pipe 3. That is, the press-fit portion 12 has the same diameter as the circular pipe 3. However, the press-fit portion 12 and the circular pipe 3 are not limited to this. The press-fit portion 12 and the circular pipe 3 may have different diameters. Also, in Embodiment 1, the inner diameter R6 of the circular pipe 2 and the inner diameter R4 of the circular pipe 3 are the same diameter. That is, the inner diameter R6 of the circular pipe 2 and the inner diameter R4 of the circular pipe 3 are the same diameter. However, the circular pipes 2 and 3 are not limited to this. The circular pipes 2 and 3 may have different diameters.

[0079] Furthermore, in Embodiment 1, the fitting 10 is a male fitting, but the fitting 10 only needs to be capable of connecting to the circular pipe 3, or in other words, the second pipe as referred to in this disclosure. For this reason, whether the fitting 10 is a male fitting or a female fitting is arbitrary. For example, the fitting 10 may be a female fitting.

[0080] This disclosure allows for various embodiments and modifications without departing from the broad spirit and scope of this disclosure. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of this disclosure. In other words, the scope of this disclosure is indicated by the claims, not by the embodiments. Various modifications made within the scope of the claims and the equivalent significance of the disclosure are considered to be within the scope of this disclosure.

[0081] This application is based on Japanese Patent Application No. 2025-069147, filed on 18 April 2025. The entire specification, claims, and drawings of Japanese Patent Application No. 2025-069147 are incorporated herein by reference.

[0082] 1A, 1B Pipe connection structure, 2, 3 Circular pipe, 4 Fitting, 5 Clamping device, 9 Space, 10 Fitting, 11 Fitting section, 12 Press-fit section, 13 O-ring, 14 Groove, 15 Flange, 16, 17 Projection, 18 Tapered section, 19 Groove, 20 Support section, 21 Outer pipe, 22 Inner pipe, 23, 24 Column section, 41 Through hole, 100 Water heater, 101 Hot water storage tank, 102 Heat exchanger, 103 Pump, 104 Piping, 161, 171 Protrusion, 181 Thick-walled section, 182 Groove, A1 Inner angle, A2 Inclination angle, R1 Outer diameter, R2 Inner diameter, R3 Inner diameter, R4 Inner diameter, R5 Outer diameter, R6 Inner diameter, R7 Inner diameter, R8 Outer diameter, S Slope.

Claims

1. A pipe connection structure comprising: a first pipe; a joint having a cylindrical shape, a first joint portion inserted from the end of the first pipe and press-fitted into the first pipe; and a second joint portion communicating with the internal space of the first joint portion and to which a second pipe can be connected, wherein the first joint portion has a projection provided on its outer circumference, extending in the circumferential direction, and press-fitted into the first pipe, and located inside the first pipe beyond the end of the first pipe, and the outer diameter of the projection is larger than the inner diameter of the end of the first pipe.

2. The pipe connection structure according to claim 1, wherein the first pipe is widened in the portion that the projection abuts from the inside, and the inner diameter of the end of the first pipe is smaller than the inner diameter of the portion that the projection abuts from the inside.

3. The pipe connection structure according to claim 1 or 2, wherein the first pipe and the first joint are formed of the same resin.

4. The pipe connection structure according to any one of claims 1 to 3, wherein the projection increases in protrusion from the tip of the first joint inserted into the first pipe toward the base end of the first joint, and then decreases toward the base end of the first joint.

5. The pipe connection structure according to claim 4, wherein the shape of the projection when cut by a plane extending in the extending direction and radial direction of the cylinder of the first joint is a triangular shape with one side aligned with the outer circumference of the first joint.

6. The pipe connection structure according to claim 5, wherein the triangular shape of the projection has an interior angle of 90° or less on the base end side of the first joint.

7. The shape of the projection when cut by a plane extending in the extending direction and radial direction of the cylinder of the first joint is wave-shaped, as described in claim 4.

8. The pipe connection structure according to any one of claims 1 to 7, wherein the first pipe is expanded by 143% or less at the portion where the tip of the projection abuts.

9. The pipe connection structure according to any one of claims 1 to 8, wherein a plurality of projections are provided on the outer circumference of the first joint portion, extending from the tip of the first joint portion inserted into the first pipe toward the base end of the first joint portion.

10. The pipe connection structure according to any one of claims 1 to 9, wherein the first joint is provided at the tip inserted into the first pipe and has a tapered portion in which a radially and outwardly inclined surface is formed toward the base end of the first joint.

11. The pipe connection structure according to claim 10, wherein the inclined surface of the tapered portion is inclined at an angle of 45° or less with respect to the cylindrical axis of the first joint portion.

12. The pipe connection structure according to claim 10 or 11, wherein the first joint portion is provided between the tapered portion and the projection portion of the outer circumference and has at least one groove extending in the circumferential direction.

13. The pipe connection structure according to claim 12, wherein the groove is covered by the cylindrical surface portion of the first pipe when the first joint is press-fitted into the first pipe, and has an air-filled space between the cylindrical surface portion and the bottom of the groove.

14. The pipe connection structure according to claim 13, wherein the first joint portion has a plurality of grooves and a support portion provided between the grooves for supporting the cylindrical surface portion of the first pipe.

15. The pipe connection structure according to any one of claims 1 to 14, wherein the first pipe comprises an outer pipe, an inner pipe passed through the outer pipe, and a plurality of columnar portions connecting the inner pipe to the outer pipe.

16. The pipe connection structure according to any one of claims 1 to 15, wherein the first pipe has a length of 300 mm or more and is bent two or more times.

17. A water heater comprising: a first pipe comprising a pipe connection structure according to any one of claims 1 to 16; a joint comprising the connection structure; and a second pipe connected to the second joint.

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