Heat transfer tube, heat exchanger, tube expansion tool, tube expansion device, method for connecting heat transfer tubes and tubes, and method for manufacturing heat exchanger

Abstract

A heat transfer pipe (1A) is provided with a flared portion (30) which has a spherical-zone shape and in which an inner diameter of a leading end is larger than that of a base end. A pipe as a connection target is passed through the flared portion (30). Further, the flared portion (30) is connected to the pipe by a brazing material with which a gap between the pipe and the inner wall of the flared portion (30) is filled.

Description

[Technical Field]

[0001] The present disclosure relates to a heat transfer tube, a heat exchanger, a tube expansion tool, a tube expansion device, a method for connecting a heat transfer tube to a tube, and a method for manufacturing a heat exchanger. [Background technology]

[0002] In some heat exchangers equipped with multiple heat transfer tubes, vent pipes are connected to the end portions of the heat transfer tubes and brazed to the end portions to connect the heat transfer tubes together. In such heat exchangers, a structure called a flare that receives the brazing filler metal is sometimes provided at the end portion of the heat transfer tube where the vent pipe is inserted to prevent the brazing filler metal from dripping onto the heat transfer tubes during brazing.

[0003] For example, Patent Document 1 discloses a heat exchanger in which a flared portion having a funnel-shaped bottom and a cylindrical wall portion surrounding the bottom is provided at the tube end portion of a heat transfer tube. In the heat exchanger described in Patent Document 1, a ring-shaped brazing filler metal is placed between a vent pipe inserted into the tube end portion of the heat transfer tube and the cylindrical wall portion of the flared portion, and the ring-shaped brazing filler metal is melted to perform brazing. In the heat exchanger described in Patent Document 1, the ring-shaped brazing filler metal is surrounded by the cylindrical wall portion and is received at the bottom, so the brazing filler metal is less likely to drip. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 168747 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, a flared portion is formed by expanding the end portion of a heat transfer tube. On the other hand, in the heat exchanger described in Patent Document 1, the flared portion is large enough to accommodate a ring-shaped brazing filler metal. Therefore, if the flared portion described in Patent Document 1 is formed by expanding the tube, the expansion ratio becomes large, resulting in a thin flared portion. This raises the risk of the flared portion cracking during forming.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a heat transfer tube, a heat exchanger, a tube expansion tool, a tube expansion device, a method for connecting heat transfer tubes to other tubes, and a method for manufacturing a heat exchanger, in which the flared portion is less likely to crack and in which dripping of wax is suppressed during molding. [Means for solving the problem]

[0007] In order to achieve the above object, the heat transfer tube according to the present disclosure has an inner diameter at the tip end that is larger than the inner diameter at the base end. The inner diameter increases toward the tip. A flared section with a spherical shape through which the pipe to be connected is passed. a tube holding portion provided at a base end of the flared portion and into which an end of the tube is inserted; The flare section and the inner wall of the tube holder teeth ,reactor It is connected to the pipe by means of a brazing compound. [Effects of the Invention]

[0008] According to the configuration of the present disclosure, the flared portion has a spherical shape in which the inner diameter of the tip is larger than the inner diameter of the base end, so that damage caused by molding is less likely to concentrate at the tip. As a result, the flared portion is less likely to crack during molding. Furthermore, because the flared portion has the spherical shape described above, the gap between the flared portion and the pipe to be connected becomes wider toward the tip. This makes it easier for the flared portion to receive the brazing filler metal. As a result, dripping of the brazing filler metal is suppressed. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 1 is a perspective view of a heat exchanger including a heat transfer tube according to a first embodiment of the present disclosure; [Figure 1B] 1 is a cross-sectional view of a heat exchanger including a heat transfer tube according to a first embodiment of the present disclosure; [Figure 1C]1 is a right side view of a heat exchanger including a heat transfer tube according to a first embodiment of the present disclosure; [Figure 2] FIG. 1 is a perspective view of a heat transfer tube according to a first embodiment of the present disclosure. [Figure 3] Cross-sectional view taken along the line III-III in Figure 2 [Figure 4] An enlarged view of region IV shown in Figure 3 [Figure 5] 1 is a flowchart illustrating a method for manufacturing a heat exchanger including a heat transfer tube according to a first embodiment of the present disclosure. [Figure 6] FIG. 1 is a side view of a tube expanding tool used in a method for manufacturing a heat exchanger including a heat transfer tube according to a first embodiment of the present disclosure. [Figure 7] FIG. 10 is an enlarged view of a tip portion of a tube expanding tool used in a manufacturing method of a heat exchanger including a heat transfer tube according to the first embodiment of the present disclosure. [Figure 8] FIG. 10 is a simulation diagram showing the distribution of damage values ​​in a heat transfer tube when forming a flared portion of the heat transfer tube according to the first embodiment of the present disclosure. [Figure 9] Graph showing the relationship between the outer diameter of the heat transfer tube and the damage value when forming the flare section [Figure 10] Graph showing the relationship between the outer diameter of the heat transfer tube and the equivalent strain increment when forming the flare section [Figure 11] Simulation diagram showing the distribution of damage values ​​in a heat transfer tube when expanding with a truncated cone-shaped tube expansion tool [Figure 12] FIG. 1 is a front view of a heat transfer tube according to a reference example, which is expanded by a truncated cone-shaped tube expanding tool. [Figure 13] FIG. 10 is a simulation diagram showing the distribution of damage values ​​in a heat transfer tube when expanding the tube using a tube expanding tool having a ball base portion according to the first embodiment of the present disclosure. [Figure 14] FIG. 1 is a front view of a heat transfer tube expanded by a tube expanding tool including a ball base portion according to a first embodiment of the present disclosure; [Figure 15] Graph showing the relationship between pipe expansion and equivalent stress when forming a flare section [Figure 16] FIG. 10 is a front view of a heat transfer tube when a tube expanding tool including a ball base portion according to the first embodiment of the present disclosure is pushed in beyond a target value; [Figure 17]FIG. 1 is a cross-sectional view showing a heat transfer tube on which a brazing material is placed during a brazing step in a method for manufacturing a heat exchanger including the heat transfer tube according to a first embodiment of the present disclosure. [Figure 18] FIG. 1 is a cross-sectional view showing a heat transfer tube on which a fillet is formed in a brazing step in a method for manufacturing a heat exchanger including the heat transfer tube according to a first embodiment of the present disclosure. [Figure 19] FIG. 10 is a side view of a tube expanding tool used in a manufacturing method of a heat exchanger including a heat transfer tube according to a second embodiment of the present disclosure. [Figure 20] FIG. 10 is an enlarged view of a tip portion of a tube expanding tool used in a manufacturing method of a heat exchanger including a heat transfer tube according to a second embodiment of the present disclosure. [Figure 21] FIG. 10 is a perspective view of a modified example of the heat transfer tube according to the first embodiment of the present disclosure. [Figure 22] FIG. 10 is a side view of a modified example of a tube expanding tool used in the method for manufacturing a heat exchanger including a heat transfer tube according to the first embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a heat transfer tube, a heat exchanger, a tube expansion tool, a tube expansion device, a method for connecting a heat transfer tube to a tube, and a manufacturing method for a heat exchanger according to embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the same or equivalent parts in the drawings are designated by the same reference numerals. In the Cartesian coordinate system XYZ shown in the drawings, when the axial direction of the heat transfer tube is oriented vertically, the vertical direction is the Z axis and the horizontal plane is the XY plane. Below, this coordinate system will be referred to as appropriate in the description.

[0011] (Embodiment 1) The heat transfer tube according to the first embodiment has an arm-shaped flared portion. The flared portion is formed by expanding the end portion of the heat transfer tube with a spherical expanding tool to prevent cracks during the forming process. First, the configuration of a heat exchanger including this heat transfer tube will be described with reference to FIGS. 1A to 1C.

[0012] Fig. 1A is a perspective view of a heat exchanger 100 including a heat transfer tube 1A according to embodiment 1. Fig. 1B is a cross-sectional view of the heat exchanger 100. Fig. 1C is a right side view of the heat exchanger 100. For ease of understanding, Figs. 1A and 1B show only a portion of the heat exchanger 100, rather than the entire heat exchanger 100.

[0013] As shown in FIGS. 1A to 1C, a heat exchanger 100 includes a plurality of heat transfer tubes 1A and a plurality of fins 2 attached to the plurality of heat transfer tubes 1A.

[0014] The heat transfer tube 1A is formed in the shape of a circular pipe to carry a fluid to be heat exchanged, such as a refrigerant. Although not shown in Figures 1A to 1C, the heat transfer tube 1A has a spiral groove extending along the inner wall, i.e., a spiral groove. This allows the heat transfer tube 1A to agitate the refrigerant when it flows inside.

[0015] Furthermore, in order to circulate the refrigerant within the heat exchanger 100, the heat transfer tube 1A has a pair of straight sections 11, 12 extending linearly from a circular tube, and a U-shaped curved section 13 connecting one end of the straight sections 11, 12, as shown in FIG. 1B. In essence, the heat transfer tube 1A is a so-called hairpin tube. The straight sections 11, 12 of the heat transfer tube 1A extend in the vertical direction. Furthermore, the upper ends of the straight sections 11 and 12 of the heat transfer tube 1A are connected by a U-shaped vent pipe 3. This connects the heat transfer tubes 1A to each other. As a result, the refrigerant flows between the heat transfer tubes 1A.

[0016] The heat transfer tube 1A is made of a metal with high thermal conductivity, such as pure copper, copper alloy, pure aluminum, or aluminum alloy, to facilitate the transfer of heat from the refrigerant flowing through it. A plurality of fins 2 are attached to the heat transfer tube 1A to exchange the heat transferred thereto.

[0017] The fins 2 are made of a metal with high thermal conductivity, just like the heat transfer tube 1A, to enhance heat dissipation. Furthermore, the fins 2 are plate-shaped, as shown in FIGS. 1A-1C, to enhance heat dissipation. The fins 2 are oriented with their plate surfaces facing up and down, i.e., in a direction perpendicular to the axis of the heat transfer tube 1A. The fins 2 are joined to the heat transfer tube 1A. As a result, heat from the heat transfer tube 1A is transferred to the fins 2, which then release the heat into the surrounding air.

[0018] The fins 2 are arranged at regular intervals in the vertical direction, thereby allowing air to flow through the gaps between the fins 2 and improving heat exchange efficiency.

[0019] As described above, the heat transfer tubes 1A are connected to each other by the vent pipes 3. The vent pipes 3 and the heat transfer tubes 1A are joined by brazing. When brazing, the brazing filler metal may drip onto the heat transfer tubes 1A or the fins 2. To prevent the brazing filler metal from dripping, the heat exchanger 100 is provided with a flared portion 30 at the upper end of the heat transfer tube 1A. Next, the configuration of the heat transfer tube 1A, including the flared portion 30, will be described with reference to FIGS. 2 to 4.

[0020] Fig. 2 is a perspective view of a heat transfer tube 1A according to embodiment 1. Fig. 3 is a cross-sectional view taken along the III-III cutting line shown in Fig. 2. Fig. 4 is an enlarged view of region IV shown in Fig. 3. Note that, for ease of understanding, Figs. 2 and 3 show only the upper end portion of the heat transfer tube 1A shown in Figs. 1A-1C in an enlarged manner.

[0021] As shown in FIGS. 2 to 4, the heat transfer tube 1A has a tube holding portion 20 and a flared portion 30 at its upper end portion in order to connect the above-mentioned vent tube 3.

[0022] The pipe holding portion 20 is a portion that holds the inserted vent pipe 3 shown in FIGS. 1A to 1C. Specifically, the pipe holding portion 20 has an inner diameter D3 that is larger than the inner diameter D1 (shown in FIG. 3) of the main body 10 of the heat transfer tube 1A. The inner diameter D3 is also larger than the outer diameter D2 of the vent pipe 3 shown in FIG. 1C. To enable the insertion of a vent pipe 3 having such an outer diameter D2 into the pipe holding portion 20, the inner diameter D3 is larger than the outer diameter D2 of the vent pipe 3 by a tolerance. For example, the inner diameter D3 is larger by an amount that accounts for variations in the bending of the vent pipe 3, the outer diameter D2, etc. As a result, the pipe holding portion 20 allows the pipe end portion of the vent pipe 3 to be inserted and holds the pipe end portion of the vent pipe 3 when inserted.

[0023] Although not shown, when the pipe end portion of the vent pipe 3 is inserted, the pipe holding portion 20 is welded to the pipe end portion. More specifically, it is brazed. As a result, the pipe holding portion 20 fixes the inserted vent pipe 3. Meanwhile, a flared portion 30 is formed continuously on the end side, i.e., the upper end side, of the pipe holding portion 20, as shown in FIGS. 2 to 4.

[0024] The flared portion 30 has an arm-like shape to prevent dripping of the brazing filler metal during brazing. Specifically, the flared portion 30 has a spherical annular shape with one end having a larger inner diameter than the other end. The other end of the flared portion 30, which has a smaller inner diameter, faces the pipe holding portion 20 to collect the molten brazing filler metal during brazing. As a result, the flared portion 30 has a spherical annular shape with an inner diameter D4 at the upper end being larger than an inner diameter D5 at the lower end, as shown in FIG. 3 . As a result, the flared portion 30 has a shape that becomes increasingly inclined toward the upper end.

[0025] In this specification, the term "spherical zone" refers to a portion of a sphere that is sandwiched between two parallel planes when the sphere is cut by the planes. The term "spherical zone" as used herein includes not only a spherical spherical surface but also an ellipsoidal spherical surface, such as a prolate spherical surface or an oblate spherical surface. Consequently, the spherical zone includes not only a circular shape when viewed from a direction perpendicular to the two parallel planes that cut the sphere, but also an elliptical, oblong, flat, or other shape.

[0026] Furthermore, the inner diameter D5 of the lower end of the flared portion 30 is the same as the inner diameter D3 of the above-described pipe holding portion 20. As a result, when the pipe end portion of the vent pipe 3 is inserted into the pipe holding portion 20, the vent pipe 3 passes through the flared portion 30. As described above, the inner diameter D4 of the upper end of the flared portion 30 is larger than the inner diameter D5 of the lower end, so that the flared portion 30 can easily receive molten brazing filler metal when brazing the pipe holding portion 20 and the vent pipe 3. As a result, dripping of brazing filler metal is suppressed.

[0027] In this way, the flared portion 30 has a spherical shape in which the inner diameter D4 at the upper end is larger than the inner diameter D5 at the lower end, thereby suppressing dripping of brazing material during brazing. Meanwhile, the flared portion 30 has a spherical shape, which suppresses cracking of the flared portion 30 during manufacturing. Next, with reference to FIGS. 5-18, how the flared portion 30 suppresses cracking during molding will be described along with a manufacturing method for the heat exchanger 100.

[0028] Fig. 5 is a flowchart showing a method for manufacturing a heat exchanger 100 including a heat transfer tube 1A according to embodiment 1. Fig. 6 is a side view of a tube expanding tool 4A used in the method for manufacturing the heat exchanger 100. Fig. 7 is an enlarged view of the tip portion of the tube expanding tool 4A.

[0029] In the method for manufacturing the heat exchanger 100, although not shown, first, a plurality of semi-finished heat transfer tubes formed into the above-described hairpin shape and having an inner diameter smaller than the inner diameter D1 of the main body 10 of the above-described heat transfer tube 1A are prepared. A plurality of fins 2 having the above-described shape and size are also prepared. These are then arranged in the above-described positional relationship, and the fins are attached to the semi-finished heat transfer tubes. This completes the production of a heat exchanger core.

[0030] Next, as shown in FIG. 5, a primary tube expansion is performed (step S1). To explain the primary tube expansion process in detail, in this primary tube expansion process, a spherical tool having a diameter equal to the inner diameter D1 of the main body 10 described above is inserted into the semi-finished heat transfer tube that forms the heat exchanger core. As described above, the heat transfer tube 1A is made of a metal with high thermal conductivity. The same is true for semi-finished heat transfer tubes. As a result, when the spherical tool is inserted into the semi-finished heat transfer tube, the heat transfer tube undergoes plastic deformation. This expands the inner and outer diameters of the semi-finished heat transfer tube.

[0031] Although not shown, in the heat exchanger core, the fins 2 are equipped with fin collars, through which semi-finished heat transfer tubes are inserted. When the primary tube expansion is performed, the outer periphery of the semi-finished heat transfer tube expands, and the semi-finished heat transfer tube is brought into close contact with the fin collars. As a result, the fins 2 are fixed to the semi-finished heat transfer tube.

[0032] Next, secondary tube expansion is performed (step S2) as shown in Fig. 5. In the secondary tube expansion process, a cylindrical tool having an outer diameter equal to the inner diameter D3 of the above-mentioned tube holding portion 20 is inserted into the tube end portion of the semi-finished heat transfer tube expanded in step S1. The cylindrical tool is then pushed in a distance equal to the length of the above-mentioned tube holding portion 20. In this way, the tube holding portion 20 is formed at the tube end portion of the semi-finished heat transfer tube.

[0033] Once the secondary tube expansion is complete, the flared portion 30 is formed (step S3). In the process of forming the flared portion 30, the end of the tube holding portion 20 formed in step S2 is expanded using a tube expansion tool 4A shown in FIG. 6, thereby forming the flared portion 30.

[0034] First, the configuration of the tube expansion tool 4A will be described. As shown in Figures 6 and 7, the tube expansion tool 4A is provided with a guide portion 42 and a ball base portion 43 at the tip portion of a rod portion 41, i.e., at the -Z end portion of the rod portion 41. The guide portion 42 and the ball base portion 43 are provided in this order from the -Z side.

[0035] In addition, the +Z end of the rod portion 41 is adjacent to the base end portion 44 shown in Figure 6, and this base end portion 44 is the portion where a male thread is provided for attaching the expansion tool 4A to the drive mechanism of a tube expansion device not shown.

[0036] The guide portion 42 is a portion provided to guide the tube expanding tool 4A along the inner wall of the tube holding portion 20 when the tube expanding tool 4A is inserted from the +Z end of the tube holding portion 20.

[0037] To explain the configuration in detail, guide portion 42 is formed in the shape of a cylinder with its axis oriented in the Z direction. Furthermore, guide portion 42 has a chamfered corner at its -Z end to facilitate insertion into pipe holding portion 20.

[0038] 7 is smaller than the inner diameter D3 (shown in FIG. 3) of the pipe holding part 20 to the extent that a loose fit is possible. This allows the guide part 42 to move along the inner wall of the pipe holding part 20 when inserted into the pipe holding part 20 and pushed into the pipe holding part 20. The outer peripheral surface of the guide part 42 abuts against the inner wall of the pipe holding part 20, thereby determining the position of the ball base part 43 adjacent to the guide part 42 relative to the pipe holding part 20. As a result, the guide part 42 guides the ball base part 43 to the correct position when the pipe expansion tool 4A is inserted into the pipe holding part 20.

[0039] On the other hand, the sphere base portion 43 is a portion provided for forming the flared portion 30 of the heat transfer tube 1A described above.

[0040] In detail, as described above, flare portion 30 is formed in the shape of a spherical band. In order to mold the shape of this spherical band, spherical base portion 43 is formed in the shape of a spherical base that can be fitted into the spherical band of flare portion 30.

[0041] Here, in this specification, a spherical truncation refers to a portion of a sphere that is sandwiched between two parallel planes when the sphere is cut by the planes. As with the spherical surfaces that define the spherical zones described above, spheres include ellipsoids, such as prolate spheroids and oblate spheroids. As a result, spherical truncations include those that have a circular outer shape when viewed from a direction perpendicular to the two parallel planes that cut the sphere, as well as those that have an elliptical, oblong, or flattened shape.

[0042] To explain the shape of sphere pedestal portion 43 more specifically, sphere pedestal portion 43 has a sphere-frustum shape in which the outer diameter at the -Z end is smaller than the outer diameter at the +Z side, as shown in Figures 6 and 7. In this sphere-frustum shape, the outer diameter at the -Z end is the same as the outer diameter D6 of guide portion 42 shown in Figure 7. The outer diameter of sphere pedestal portion 43 gradually increases from the outer diameter D6 toward the +Z side. Furthermore, the outer diameter of sphere pedestal portion 43 reaches a maximum outer diameter D7 on the +Z side, and then decreases by a fixed amount.

[0043] The outer diameter of the -Z end of sphere pedestal portion 43 is the same as the inner diameter D5 of the -Z end of flared portion 30 formed by sphere pedestal portion 43, and the outer diameter D7 of the maximum diameter portion at the +Z end of sphere pedestal portion 43 is the same as the inner diameter D4 of the +Z end of flared portion 30. Here, "the same diameter" means that the diameters are substantially the same, including tolerances.

[0044] Furthermore, the sphere frustum portion 43 is larger than the guide portion 42 at its maximum diameter portion, which is the outer diameter D7. If the difference between the radius of the maximum diameter portion and the radius of the guide portion 42 is a distance D0, the distance D0 is desirably a distance that allows a fillet to be formed in the flared portion 30 in the brazing process described below. For example, the distance D0 is desirably 1 mm or less. The distance D0 is desirably a size that allows a brazing filler material to be placed on the flared portion 30 formed by the sphere frustum portion 43 in the brazing process described below. However, the distance D0 is desirably a distance that prevents the brazing filler material from entering the interior of the flared portion 30 in order to reduce the tube expansion ratio and prevent cracking of the heat transfer tube 1A.

[0045] Because of this shape, when guide portion 42 is inserted into tube holding portion 20, ball base portion 43 enters tube holding portion 20 following guide portion 42. Then, ball base portion 43 expands tube holding portion 20 to form the flared portion 30 described above.

[0046] At this time, the ball base portion 43 reduces the damage value applied to the expanded pipe end portion of the pipe holding portion 20, thereby suppressing the occurrence of cracks.

[0047] Here, the damage value is a value derived from the Cockcroft-Latham equation, which is known as an evaluation formula for extensional fracture and is expressed as the following formula 1. The damage value can be evaluated as indicating that cracking will occur during tube expansion when it reaches the critical damage value, so the higher the value, the more likely the heat transfer tube 1A is to crack.

[0048]

number

[0049] Next, the effect of suppressing cracking of the tube expansion tool 4A will be described. Figures 8 to 10 show the results of a simulation of damage to the heat transfer tube 1A when forming the flared portion 30 using the tube expansion tool 4A.

[0050] Fig. 8 is a simulation diagram showing the distribution of damage values ​​in the heat transfer tube 1A when forming the flared portion 30 of the heat transfer tube 1A according to embodiment 1. Fig. 9 is a graph showing the relationship between the outer diameter of the heat transfer tube 1A and the damage value when forming the flared portion 30. Fig. 10 is a graph showing the relationship between the outer diameter of the heat transfer tube 1A and the equivalent strain when forming the flared portion 30.

[0051] In Fig. 8, the magnitude of the damage value of each part of the heat transfer tube 1A is represented by shading. Also, for ease of understanding, Fig. 8 shows only three parts of the heat transfer tube 1A with large damage values, and these large damage value parts are lined up along the opening of the tube end portion. The linear object inclined with respect to the open end shown in Fig. 8 is caused by the spiral groove 14 described above.

[0052] 9 and 10, the graphs labeled "spherical truncation type" are graphs obtained when the pipe holding portion 20 is expanded using a pipe expansion tool 4A equipped with a spherical truncation portion 43. The graphs labeled "conical truncation type" are graphs obtained when the pipe holding portion 20 is expanded using a pipe expansion tool equipped with a conical truncation portion, in which the side surface of the cone is curved inward, instead of the spherical truncation portion 43.

[0053] Referring to Figure 8, it can be seen that the damage value is high at the upper tube end portion that is expanded when forming the flared portion 30. Figure 9 is a graph showing the relationship between the maximum damage value and the outer diameter of the heat transfer tube 1A during expansion. Referring to Figure 9, it can be seen that in the spherical truncated graph, the damage value suddenly increases as the tube is expanded from the outer diameter at the start of expansion, but then gradually decreases. On the other hand, in the conical truncated graph, it can be seen that the damage value increases as the tube is expanded from the outer diameter at the start of expansion. These graphs show that when the tube holding portion 20 is expanded using a spherical truncated tube, i.e., using the tube expansion tool 4A, cracks are less likely to occur even at a high expansion rate.

[0054] Furthermore, referring to Figure 10, it can be seen that the change in equivalent strain during expansion follows the same trend as the change in damage value. As is clear from Equation 1, the damage value is the integral value of the equivalent strain increment. For this reason, Figure 10 also shows that expansion using expansion tool 4A is less likely to cause cracks, even at higher expansion rates, than expansion using a truncated cone-shaped expansion tool.

[0055] The reason why the tube expansion tool 4A is less likely to cause cracks during expansion than the truncated cone type tube expansion tool is thought to be because the areas with high damage values ​​occur inside the tube end portion of the heat transfer tube 1A. The reason for this will be explained with reference to Figures 11 to 14.

[0056] Fig. 11 is a diagram of a simulation showing the distribution of damage values ​​in a heat transfer tube 200 when expanded using a truncated cone-shaped tube expansion tool 40. Fig. 12 is a front view of a heat transfer tube 200 according to a reference example that is expanded using a truncated cone-shaped tube expansion tool 40. Fig. 13 is a diagram of a simulation showing the distribution of damage values ​​in a heat transfer tube 1A when expanded using a tube expansion tool 4A that has a spherical frustum portion 43. Fig. 14 is a front view of a heat transfer tube 1A that is expanded using a tube expansion tool 4A that has a spherical frustum portion 43.

[0057] For ease of understanding, Fig. 11 shows an enlarged view of only a portion of the tube end portion of the heat transfer tube 200 according to the reference example. Similarly, Fig. 13 shows an enlarged view of only a portion of the tube end portion of the heat transfer tube 1A. In Figs. 12 and 14, the contact portion between the tube expansion tool 40 and the heat transfer tube 200 and the contact portion between the tube expansion tool 4A and the heat transfer tube 1A exist over the entire circumference, but Figs. 12 and 14 show only side portions P1 and P2 of the contact portion over the entire circumference.

[0058] 11 and 13, it can be seen that when tube expansion is performed using the tube expansion tool 4A shown in Fig. 13, the range R indicating the portions with medium or higher damage values ​​is wider than when tube expansion is performed using the truncated cone-shaped tube expansion tool 40 shown in Fig. 11. This is because when tube expansion is performed using the truncated cone-shaped tube expansion tool 40, the tube expansion tool 40 continues to hit the portion P1 near the open end of the heat transfer tube 200 shown in Fig. 12 during tube expansion, resulting in stress concentration near the open end of the heat transfer tube 200. In contrast, when tube expansion is performed using the tube expansion tool 4A, the tube expansion tool 4A hits the inner portion P2 away from the open end of the heat transfer tube 1A shown in Fig. 14, resulting in stress being dispersed over a range from the vicinity of the open end of the heat transfer tube 1A to its interior.

[0059] In this way, by providing the tube expansion tool 4A with the ball base portion 43, stress is less likely to concentrate near the open end of the heat transfer tube 1A, and damage is less likely to occur to the heat transfer tube 1A. As a result, when the tube is expanded with the tube expansion tool 4A, the occurrence of cracks in the heat transfer tube 1A is suppressed.

[0060] Furthermore, in the tube expansion tool 4A, the ball base portion 43 has a shape in which the outer diameter increases from the guide portion 42, resulting in a step being formed between the guide portion 42 and the ball base portion 43. As a result, compressive stress is applied to the tube end of the heat transfer tube 1A during tube expansion, as shown by arrow A1 in Fig. 14. Then, as shown by arrow A2, the tube is expanded while compressive stress is still applied.

[0061] It is known that applying a compressive force in a direction different from the desired direction of deformation by a tensile force increases the amount of deformation until fracture. When expanding the tube using the tube expansion tool 4A, a compressive force is applied in the axial direction of the heat transfer tube 1A, while a tensile force is applied in the circumferential direction of the heat transfer tube 1A. This results in the above-mentioned relationship between tensile force and compressive force. As a result, the equivalent stress increases.

[0062] Fig. 15 is a graph showing the relationship between tube expansion and equivalent stress when forming the flared portion 30. The graphs for the spherical and truncated cone shapes shown in Fig. 15 show graphs for tube expansion using the same tools as those used in the graphs for the spherical and truncated cone shapes in Figs. 9 and 10.

[0063] As a result of the above-mentioned relationship between tensile force and compressive force being established, as shown in Figure 15, the equivalent stress when expanding the tube using a spherical tube expansion tool 4A is greater than the equivalent stress when expanding the tube using a truncated cone tube expansion tool 40. This equivalent stress is the parameter that serves as the denominator in Equation 1. For this reason, the damage value expressed by Equation 1 is smaller when expanding the tube using the tube expansion tool 4A than when expanding the tube using the truncated cone tube expansion tool 40.

[0064] In this way, by providing the tube expansion tool 4A with a step between the guide portion 42 and the ball base portion 43, the damage value is reduced, and the occurrence of cracks in the heat transfer tube 1A during tube expansion with the tube expansion tool 4A is suppressed.

[0065] Furthermore, as described above, the outer diameter of the ball base portion 43 of the tube expansion tool 4A reaches a maximum outer diameter D7 from the tip of the tool toward the base end, and then decreases by a certain amount. As a result, even if the pushing amount of the tube expansion tool 4A varies from the target value, damage values ​​do not accumulate.

[0066] Fig. 16 is a front view of the heat transfer tube 1A when a tube expansion tool 4A having a ball base portion 43 is pressed in to a target value or more. Note that Fig. 16 shows an enlarged view of only the tube end portion of the heat transfer tube 1A.

[0067] As shown in FIG. 16, the tube expansion tool 4A is pushed in beyond the target value, resulting in the heat transfer tube 1A being deformed to the desired inner diameter. Here, the target value refers to the distance from the tip of the guide portion 42 of the tube expansion tool 4A to the point where the maximum outer diameter D7 of the ball-shaped portion 43 is reached. When the tube expansion tool 4A is pushed in beyond the target value, the portion of the tube expansion tool 4A above the maximum outer diameter D7, i.e., the base-side portion P3, penetrates into the heat transfer tube 1A. However, the outer diameter of the base-side portion P3 of the tube expansion tool 4A gradually decreases toward the base end. As a result, even if the tube expansion tool 4A is pushed in beyond the target value and the pushing amount varies, no damage value is accumulated.

[0068] In this way, the spherical base portion 43 has a shape in which the outer diameter gradually decreases at portion P3, which is closer to the base end than the portion with the maximum outer diameter D7. Therefore, even if the amount of pushing in of the tube expansion tool 4A varies, damage does not accumulate, and the occurrence of cracks in the heat transfer tube 1A during tube expansion with the tube expansion tool 4A is suppressed. Furthermore, the tube expansion tool 4A is less likely to get caught on the inner wall of the heat transfer tube 1A when pulled out from the heat transfer tube 1A, making it easy to remove from the heat transfer tube 1A.

[0069] Returning to FIG. 5, in the molding process of the flared portion 30 in step S3, the tube expansion tool 4A configured as described above is used to expand the end of the tube holding portion 20 formed on the semi-finished heat transfer tube. At this time, the tube expansion tool 4A is pushed in until the portion with the maximum outer diameter D7 enters the tube holding portion 20. This molds the flared portion 30 having a spherical band shape. As a result, the flared portion 30 is formed with a shape that decreases in thickness toward the tip as shown in FIG. 4 and has a shape in which the inside of the end face of the tip is chamfered. Then, the heat transfer tube 1A having the shape described above is formed. This completes the molding process of the flared portion 30.

[0070] The molding step of the flare portion 30 is also called a third tube expansion step because it is the third tube expansion step in the flow of the manufacturing method of the heat exchanger 100.

[0071] Next, as shown in Fig. 5, the vent pipe 3 is assembled to the heat transfer tube 1A (step S4). More specifically, in the vent pipe 3 assembly step, the end portion of the vent pipe 3 is inserted into the flared portion 30 formed in step S3, and the end portion of the vent pipe 3 is held by the tube holder 20 located deeper than the flared portion 30. This step is performed for all of the heat transfer tubes 1A included in the heat exchanger core. This completes the assembly of the vent pipe 3.

[0072] Once the assembly of the vent pipe 3 is complete, brazing is performed (step S5). In the brazing process, a brazing material is placed adjacent to the flared portion 30. The brazing material is then melted to form a fillet. This will be described in detail with reference to Figures 17 and 18. For ease of understanding, the brazing material obtained by melting the brazing material will hereinafter be referred to as the brazing material.

[0073] Fig. 17 is a cross-sectional view showing a heat transfer tube 1A on which a brazing material 5 is placed in a brazing step in a manufacturing method of a heat exchanger. Fig. 18 is a cross-sectional view showing a heat transfer tube 1A on which a fillet 6 is formed in a brazing step in a manufacturing method of a heat exchanger.

[0074] In the brazing process, as shown in FIG. 17 , the brazing material 5 is placed adjacent to the opening of the flare portion 30 so that the brazing material 5 can easily enter the flare portion 30 when melted. Furthermore, the brazing material 5 is melted in this state. Next, as shown in FIG. 18 , the gap between the tube holding portion 20 of the heat transfer tube 1A and the vent tube 3, and the gap between the flare portion 30 of the heat transfer tube 1A and the vent tube 3, are filled with brazing material. Then, a fillet 6 is formed between the upper end of the flare portion 30 and the outer peripheral surface of the vent tube 3, i.e., between the open end of the flare portion 30 and the outer peripheral surface of the vent tube 3.

[0075] In this case, the width W1 of the opening of the flared portion 30 is preferably a distance that allows a fillet to be formed, for example, 1 mm or less. This is because the bonding strength between the flared portion 30 and the vent pipe 3 can be increased. Furthermore, the width W1 of the opening is preferably smaller than the width W2 of the brazing filler metal 5 shown in FIG. 17 , which is the size of the brazing filler metal 5 in the radial direction of the heat transfer tube 1A. This size makes it possible to minimize the tube expansion rate during the molding process of the flared portion 30 and suppress cracking of the heat transfer tube 1A. In this case, the width W1 of the opening of the flared portion 30 is preferably at least half the width W2 of the brazing filler metal 5, for example, to accommodate the brazing filler metal 5, and is preferably equal to or smaller than the width W2 of the brazing filler metal 5 by the thickness T of the flared portion 30.

[0076] Furthermore, when the brazing material is filled into the gap between the heat transfer tube 1A and the vent pipe 3 in the brazing process, the flared portion 30 surrounds the brazing material, thereby preventing the brazing material from dripping.

[0077] When the brazing material solidifies, the vent pipe 3 is fixed to the heat transfer pipe 1A. This completes the brazing process. Through the above steps, the method for manufacturing the heat exchanger 100 is completed, and the heat exchanger 100 is completed.

[0078] The upper end portion of the heat transfer tube 1A described above is an example of a tube end portion as defined in the present disclosure. The upper and lower ends of the flared portion 30 are an example of a tip and a base end of the flared portion 30 as defined in the present disclosure. The assembling process of the vent pipe 3 is an example of a tube inserting process as defined in the present disclosure.

[0079] As described above, in the heat transfer tube 1A according to the first embodiment, the flared portion 30 has a spherical band shape in which the inner diameter at the tip is larger than the inner diameter at the base end, which makes the flared portion 30 less likely to crack during molding.

[0080] Furthermore, because the flared portion 30 has the spherical shape described above, the gap between the flared portion 30 and the vent pipe 3 to be connected becomes wider toward the tip of the flared portion 30. This makes it easier for the flared portion 30 to receive the brazing material near the tip. As a result, the flared portion 30 can prevent the brazing material from dripping.

[0081] In the tube expansion tool 4A, the ball base portion 43 has a ball base shape in which the outer diameter of the tip is smaller than the outer diameter of the base. Therefore, when manufacturing the heat transfer tube 1A by tube expansion, stress is less likely to concentrate near the open end of the heat transfer tube 1A, and the heat transfer tube 1A is less likely to be damaged by tube expansion. As a result, the heat transfer tube 1A is less likely to crack.

[0082] The outer diameter of the ball pedestal portion 43 increases from the tip to the base end, reaches a maximum value, and then decreases by a fixed amount. Therefore, even if the tube expansion tool 4A is inserted into the heat transfer tube 1A beyond the length from the tip of the ball pedestal portion 43 to the point where the outer diameter reaches its maximum value, the damage to the heat transfer tube 1A caused by tube expansion does not change. As a result, the heat transfer tube 1A is less likely to crack.

[0083] Furthermore, the tube expanding tool 4A has a step between the guide portion 42 and the ball base portion 43. This reduces damage to the heat transfer tube 1A caused by tube expansion, making the heat transfer tube 1A less likely to crack during tube expansion.

[0084] (Example) An experiment was conducted using the expansion tool 4A of the above-described shape to expand a 0.17 mm thick circular copper tube. In the experiment, (1) the expansion tool 4A was used at a thrust speed of 0.1 mm / sec and a thrust depth of 3.5 mm. (2) The expansion tool 4A was used at a thrust speed of 20 mm / sec and a thrust depth of 3.5 mm. A comparative example was also conducted using the truncated cone-shaped expansion tool 40 described with reference to FIG. 12 under the same conditions. After expansion, the expanded copper tube was inspected for cracks. Furthermore, the copper tubes without cracks were inspected for buckling. The results are shown in Table 1. In Table 1, the expansion tool 4A is referred to as the "frustum-shaped" expansion tool, and the expansion tool 40 is referred to as the "frustum-shaped" expansion tool.

[0085] [Table 1]

[0086] Referring to Table 1, it can be seen that when expanding a copper pipe using a spherical expansion tool, i.e., expansion tool 4A, cracks in the copper pipe are less likely to occur and buckling, which is a cause of cracks in the copper pipe, is less likely to occur than when expanding a copper pipe using a truncated cone expansion tool, i.e., expansion tool 40. It can also be seen that cracks in the copper pipe are less likely to occur even when the pushing speed of expansion tool 4A is increased, and the efficiency of expansion is high. Thus, when expanding a copper pipe using expansion tool 4A, cracks in the copper pipe are less likely to occur. In addition, the efficiency of expansion is high.

[0087] (Embodiment 2) In the first embodiment, the tube expanding tool 4A includes a guide portion 42 and a ball base portion 43, and the guide portion 42 and the ball base portion 43 are arranged in this order from the tip side.

[0088] However, the tube expansion tool 4A is not limited to this. The tube expansion tool 4A only needs to have a ball base portion 43 whose tip outer diameter is smaller than the base outer diameter and whose tip is large enough to be inserted into the tube end portion of the heat transfer tube 1A. The flared portion 30 can be formed by inserting the ball base portion 43 from the tip to the base end into the tube end portion of the heat transfer tube 1A. Therefore, the tube expansion tool 4A may have a configuration other than the ball base portion 43.

[0089] In the second embodiment, the tube expanding tool 4B includes a frustum cone portion 45 in addition to the guide portion 42 and the frustum spherical portion 43. The tube expanding tool 4B according to the second embodiment will be described below with reference to Figures 19 and 20. In the second embodiment, the configuration different from the first embodiment will be mainly described.

[0090] Fig. 19 is a side view of the tube expanding tool 4B, and Fig. 20 is an enlarged view of the tip portion of the tube expanding tool 4B.

[0091] As shown in FIGS. 19 and 20, the tube expanding tool 4B includes a truncated cone portion 45 disposed between the guide portion 42 and the truncated spherical portion 43.

[0092] The truncated cone portion 45 is formed in a truncated cone shape with its upper base facing the guide portion 42 and its lower base facing the frustum spherical portion 43. As shown in FIG. 20 , the truncated cone portion 45 expands in outer diameter from the outer diameter D6 of the guide portion 42 toward the frustum spherical portion 43, i.e., in the +Z direction, to the smallest outer diameter D8 at the -Z end of the frustum spherical portion 43. As a result, the truncated cone portion 45 has an inclined surface 46 inclined with respect to the central axis L. In the first embodiment, when expanding the heat transfer tube 1A using the tube expanding tool 4A, a compressive force is applied in the axial direction of the heat transfer tube 1A, and a tensile force is applied in the circumferential direction of the heat transfer tube 1A, resulting in an increase in equivalent stress. However, the inclined surface 46 changes the direction and magnitude of the compressive force. As a result, the inclined surface 46 can reduce damage to the heat transfer tube according to the second embodiment when expanding the tube using the tube expanding tool 4B.

[0093] Furthermore, it is desirable that the angle θ of the inclined surface 46 with respect to the central axis L be equal to or greater than 40° and less than 60°. The angle θ is, for example, 45°. This is because such an angle θ can reduce the damage value described in the first embodiment while suppressing buckling.

[0094] The above-described truncated cone portion 45 is an example of the truncated cone portion defined in the present disclosure.

[0095] As described above, in the second embodiment, the tube expansion tool 4B is provided with the truncated cone portion 45, which has a truncated cone shape that tapers toward the tip, on the -Z side of the frustum spherical portion 43, i.e., on the tip side. Therefore, during tube expansion, the tube expansion tool 4B can direct the direction of the compressive force applied to the heat transfer tube according to the second embodiment in a specific direction and adjust the magnitude of the compressive force applied in that direction, thereby reducing damage to the heat transfer tube according to the second embodiment. As a result, the tube expansion tool 4B can suppress cracking of the heat transfer tube according to the second embodiment.

[0096] The above describes the heat transfer tube 1A, heat exchanger 100, tube expansion tools 4A and 4B, tube expansion device, method for connecting heat transfer tube 1A to a tube, and method for manufacturing heat exchanger 100 according to the embodiments of the present disclosure, but the heat transfer tube 1A, heat exchanger 100, tube expansion tools 4A and 4B, tube expansion device, method for connecting heat transfer tube 1A to a tube, and method for manufacturing heat exchanger 100 are not limited to these.

[0097] For example, in the first embodiment, the object to be connected to the heat transfer tube 1A is the vent pipe 3, but the object to be connected to the heat transfer tube 1A is not limited to this. The object to be connected to the heat transfer tube 1A may be any pipe. For example, the object to be connected may be a connecting pipe for connecting the heat exchanger 100 to an external device or a refrigerant pipe. Furthermore, since the object to be connected may be a pipe, the shape of the pipe is not limited, and the pipe may be a pipe other than a circular pipe.

[0098] In the first and second embodiments, the heat transfer tube 1A is a circular tube. That is, the tube cross section is circular. However, the heat transfer tube 1A is not limited to this. The heat transfer tube 1A may have a spherical shape with the inner diameter at the tip end larger than the inner diameter at the base end, and may include a flared portion 30 through which a tube to be connected is inserted. Furthermore, the flared portion 30 may be connected to the tube by a brazing material filled in the gap between the inner wall of the flared portion 30 and the tube. The shape of the heat transfer tube 1A is arbitrary as long as it satisfies this condition. Therefore, the heat transfer tube 1A may have a flat tube cross section.

[0099] FIG. 21 is a perspective view of a modified example of the heat transfer tube 1A according to the first embodiment.

[0100] 21, the heat transfer tube 1A may be a flattened tube with an elliptical cross section. In this case, the flared portion 30 may have a spherical band shape obtained by cutting a prolate sphere along its major axis with two parallel planes. To form such a flared portion 30, the spherical truncated portion 43 of the tube expansion tools 4A, 4B may have a spherical truncated shape obtained by cutting the prolate sphere along its major axis with the same two parallel planes.

[0101] In the first and second embodiments, the heat transfer tube 1A has a spiral groove 14 therein. However, the heat transfer tube 1A is not limited to this. As described above, the heat transfer tube 1A may have a spherical shape with the inner diameter at the tip end larger than the inner diameter at the base end, and may include a flared portion 30 through which a tube to be connected is passed. Furthermore, the flared portion 30 may be connected to the tube by a brazing material filled in the gap between the tube and its own inner wall. Therefore, the internal structure of the heat transfer tube 1A, i.e., the shape of the flow passage, may be any desired shape.

[0102] For example, the heat transfer tube 1A may have a plurality of parallel grooves on its inner wall that extend parallel to the tube axis direction. If the heat transfer tube 1A has grooves such as spiral grooves 14 or parallel grooves, it is likely to crack when expanded, but by providing the heat transfer tube 1A with the above-mentioned flared portion 30, cracking of the heat transfer tube 1A during expansion can be suppressed. Alternatively, the heat transfer tube 1A may have a smooth inner wall without grooves.

[0103] In addition, in the first and second embodiments, the flared portion 30 is provided at the upper end of the heat transfer tube 1A, but the end of the heat transfer tube 1A where the flared portion 30 is provided is arbitrary as long as the above-mentioned conditions are satisfied. For example, if the heat transfer tube 1A extends in the left-right direction, the flared portion 30 may be provided at the right end or the left end of the heat transfer tube 1A.

[0104] In the first and second embodiments, the tube expansion tools 4A, 4B have a guide portion 42. However, the tube expansion tools 4A, 4B are not limited to this. The tube expansion tools 4A, 4B may be any tools that have a ball-shaped base portion 43 whose tip outer diameter is smaller than the base outer diameter and whose tip is large enough to be inserted into the tube end portion of the heat transfer tube 1A. Furthermore, the tube expansion tools 4A, 4B may be any tools that form the flared portion 30 by inserting the ball-shaped base portion 43 from its tip to its base end into the tube end portion of the heat transfer tube 1A. As long as the tube expansion tools 4A, 4B satisfy this condition, the presence or absence of the guide portion 42 is optional.

[0105] Fig. 22 is a side view of a modified example of the tube expanding tool 4A, and Fig. 22 shows only the tip portion of the modified example of the tube expanding tool 4A.

[0106] 22, the tube expanding tool 4A may have only a spherical base portion 43 at the tip of a rod portion 41. This is because even in this configuration, the flared portion 30 having the above-described shape can be formed. Furthermore, this is because cracking of the heat transfer tube 1A during the forming can be suppressed.

[0107] Furthermore, in the first and second embodiments, the ball frustum portion 43 of the tube expansion tool 4A has a maximum outer diameter D7 toward the base end opposite the tip, and then the outer diameter decreases by a certain amount. However, the ball frustum portion 43 is not limited to this. The ball frustum portion 43 only needs to have an outer diameter at the tip that is smaller than the outer diameter at the base end and be large enough to allow the tip to be inserted into the tube end portion of the heat transfer tube 1A. Therefore, the outer diameter of the ball frustum portion 43 does not need to decrease by a certain amount after reaching a maximum value at the base end. The outer diameter of the ball frustum portion 43 may be maximum at the base end. In this case, compared to a configuration in which the outer diameter of the ball frustum portion 43 reaches a maximum value at the base end and then decreases by a certain amount, the tube expansion tool 4A is more difficult to remove from the heat transfer tube 1A after tube expansion. However, the heat transfer tube 1A can still be prevented from cracking during tube expansion.

[0108] The tube expanding tools 4A and 4B may also be called punches. Furthermore, the tube expanding tools 4A and 4B may be attached to a tube expanding device that is capable of holding the rod portion 41 and has a drive unit that moves the rod portion 41 in its axial direction.

[0109] As described above, the heat transfer tube 1A, the heat exchanger 100, the tube expansion tools 4A and 4B, the tube expansion device, the method for connecting the heat transfer tube 1A to a tube, and the method for manufacturing the heat exchanger 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.

[0110] (Appendix 1) The inner diameter of the tip is larger than the inner diameter of the base The inner diameter increases toward the tip. A flared section with a spherical shape through which the pipe to be connected is passed. and, a tube holding portion provided at a base end of the flared portion and into which an end of the tube is inserted; Equipped with The flare portion and the inner wall of the tube holding portion teeth ,reactor connected to the pipe by a brazing material; Heat transfer tube. (Appendix 2) the inner diameter of the distal end is larger than the inner diameter of the proximal end, the inner diameter has a spherical shape that increases toward the distal end, the thickness at the distal end where the inner diameter is the largest is smaller than the thickness at the proximal end, and the flared portion is provided with a pipe to be connected thereto being passed therethrough, The flared portion is connected to the tube by a brazing material filled in a gap between the tube and an inner wall of the flared portion. Heat transfer tube. (Note 3 ) The flared portion has a fillet formed by the brazing material on the side of the tip and on the inside. Appendix 1 or 2 The heat transfer tube according to claim 1. (Note 4 ) The flare portion has an end face at the tip end that is chamfered on the inner wall side. Appendix 1 One of the three The heat transfer tube according to claim 1. (Note 5 ) The flared portion has a thickness that decreases from the base end to the tip end. Additional notes 4 The heat transfer tube according to claim 1. (Note 6 ) The flared portion has a spiral groove on an inner wall. From Appendix 1 5 10. The heat transfer tube according to claim 9, wherein (Note 7 ) Multiple, from Appendix 1 6 a heat transfer tube according to any one of the above items; fins attached to the heat transfer tube; the tube; Equipped with heat exchanger. (Note 8 ) A tube expansion tool for forming a flared portion at a tube end portion of a heat transfer tube through which a tube to be connected passes, a ball-shaped portion having an outer diameter of a tip end smaller than an outer diameter of a base end, the tip end being sized to be insertable into the tube end portion; the flared portion is formed by inserting the pedestal portion into the tube end portion from the distal end to the proximal end, A frustum portion, which becomes thinner toward the tip and has a base the same thickness as the tip of the frustum portion, is provided at the tip of the frustum portion. moreover Prepare 、 Tube expansion tool. (Note 9 ) A tube expansion tool for forming a flared portion at a tube end portion of a heat transfer tube through which a tube to be connected passes, a ball-shaped portion having an outer diameter of a tip end smaller than an outer diameter of a base end, the tip end being sized to be insertable into the tube end portion; the flared portion is formed by inserting the pedestal portion into the tube end portion from the distal end to the proximal end, A guide portion that can be fitted to the inner peripheral surface of the tube end portion is provided on the tip side of the ball base portion. moreoverPrepare 、 Tube expansion tool. (Note 10 ) The outer diameter of the frustum portion between the tip end and the base end is larger than the outer diameter of the base end. Additional notes 8 or 9 The tube expansion tool described in (Appendix 11) The outer diameter of the frustum portion is the same as the inner diameter of the flare portion. Additional notes 8 11. A tube expansion tool according to any one of claims 1 to 10. (Appendix 12) Additional notes 8 12. A tube expansion tool according to any one of claims 1 to 11, a drive mechanism that pushes the spherical base portion of the tube expanding tool into the heat transfer tube; A tube expansion device comprising: (Appendix 13) A method for connecting a heat transfer tube to a tube end portion of a heat transfer tube, the method comprising: Additional notes 8 12. A process of forming a flared portion at the tube end portion by inserting the ball base portion of the tube expansion tool according to any one of claims 1 to 11 into the tube end portion from the tip end to the base end of the ball base portion; inserting the tube into the flared portion; a step of filling a gap between an inner wall of the flared portion and the tube with a brazing material to connect the heat transfer tube to the tube; Equipped with How to connect heat transfer tubes. (Appendix 14) In the step of connecting the heat transfer tube and the tube, a brazing filler metal larger than the gap between the inner wall of the flare portion and the tube is placed at the tip of the flare portion, and the brazing filler metal is melted to fill the gap. 14. A method of connecting heat transfer tubes to tubes as described in Appendix 13. (Appendix 15) a width of the gap between the inner wall of the flared portion and the tube is smaller than a width of the brazing material in a radial direction of the tube; 15. A method of connecting heat transfer tubes to tubes as described in Appendix 14. (Appendix 1 6 ) Appendix 13 One of 15 The heat transfer tube and the tube connecting method according to claim 1, A method for manufacturing a heat exchanger.

[0111] 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.

[0112] This application is based on Japanese Patent Application No. 2022-80337, filed on May 16, 2022. The entire specification, claims, and drawings of Japanese Patent Application No. 2022-80337 are incorporated herein by reference. [Explanation of symbols]

[0113] 1A heat transfer tube, 2 fin, 3 bent tube, 4A, 4B tube expansion tool, 5 brazing material, 6 fillet, 10 main body portion, 11, 12 straight portion, 13 curved portion, 14 spiral groove, 20 tube holding portion, 30 flared portion, 40 tube expansion tool, 41 rod portion, 42 guide portion, 43 spherical truncated portion, 44 base end portion, 45 conical truncated portion, 46 inclined surface, 100 heat exchanger, 200 heat transfer tube, A1, A2 arrows, D0 distance, D1 inner diameter, D2 outer diameter, D3-D5 inner diameter, D6-D8 outer diameter, L central axis line, P1-P3 portion, R range, T thickness, W1, W2 width, θ angle.

Claims

1. a flared portion having a spherical shape in which the inner diameter of the distal end is larger than the inner diameter of the proximal end and the inner diameter increases toward the distal end, and through which a pipe to be connected is passed; a tube holding portion provided at a base end of the flared portion and into which an end of the tube is inserted; Equipped with The flared portion and the inner wall of the tube holding portion are connected to the tube by a brazing material. Heat transfer tube.

2. The inner diameter of the tip is larger than the inner diameter of the base end, and the inner diameter has a spherical shape that increases toward the tip, and the thickness at the tip where the inner diameter is the largest is smaller than the thickness at the base end, and the flared portion is provided with a pipe to be connected that is passed through, The flared portion is connected to the tube by a brazing material filled in a gap between the tube and an inner wall of the flared portion. Heat transfer tube.

3. The flared portion has a fillet formed by the brazing material on the side of the tip and on the inside. The heat transfer tube according to claim 1 or 2.

4. The flare portion has an end face at the tip end that is chamfered on the inner wall side. The heat transfer tube according to claim 1 or 2.

5. The flared portion has a thickness that decreases from the base end to the tip end. The heat transfer tube according to claim 4.

6. The flared portion has a spiral groove on an inner wall. The heat transfer tube according to claim 1 or 2.

7. A plurality of heat transfer tubes according to claim 1 or 2; fins attached to the heat transfer tube; the tube; Equipped with heat exchanger.

8. A tube expansion tool for forming a flare portion at the tube end portion of a heat transfer tube through which a tube to be connected can be passed, a ball-shaped portion having an outer diameter of a tip end smaller than an outer diameter of a base end, the tip end being sized to be insertable into the tube end portion; the flared portion is formed by inserting the pedestal portion into the tube end portion from the distal end to the proximal end, The tip of the frustum portion further includes a frustum portion that becomes thinner toward the tip and has a base that is the same thickness as the tip of the frustum portion. Tube expansion tool.

9. A tube expansion tool for forming a flare portion at a tube end portion of a heat transfer tube through which a tube to be connected can be passed, a ball-shaped portion having an outer diameter of a tip end smaller than an outer diameter of a base end, the tip end being sized to be insertable into the tube end portion; the flared portion is formed by inserting the pedestal portion into the tube end portion from the distal end to the proximal end, A guide portion that can be fitted to the inner peripheral surface of the tube end portion is further provided at the tip end side of the ball base portion. Tube expansion tool.

10. The outer diameter of the frustum portion between the tip end and the base end is larger than the outer diameter of the base end.

10. A tube expansion tool according to claim 8 or 9.

11. The outer diameter of the frustum portion is the same as the inner diameter of the flare portion.

10. A tube expansion tool according to claim 8 or 9.

12. The tube expanding tool according to claim 8 or 9; a drive mechanism that pushes the spherical base portion of the tube expanding tool into the heat transfer tube; A tube expansion device comprising:

13. A method for connecting a heat transfer tube to a tube end portion of a heat transfer tube, the method comprising: a step of inserting the ball base portion of the tube expanding tool according to claim 8 or 9 into the tube end portion from the tip end to the base end to form a flared portion at the tube end portion; inserting the tube into the flared portion; a step of filling a gap between an inner wall of the flared portion and the tube with a brazing material to connect the heat transfer tube to the tube; Equipped with How to connect heat transfer tubes.

14. In the step of connecting the heat transfer tube and the tube, a brazing filler metal larger than the gap between the inner wall of the flare portion and the tube is placed at the tip of the flare portion, and the brazing filler metal is melted to fill the gap. The method for connecting heat transfer tubes to tubes according to claim 13.

15. The width of the gap between the inner wall of the flare portion and the pipe is smaller than the radial width of the brazing material of the pipe. The method for connecting heat transfer tubes to tubes according to claim 14.

16. The method for connecting a heat transfer tube to a tube according to claim 13 is provided. A method for manufacturing a heat exchanger.

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