Heat transfer tube, heat exchanger, tube expanding tool, tube expanding device, method for connecting heat transfer

Abstract

The heat transfer tube (1A) is provided with a flared section (30) having a ball band shape in which the inner diameter of the distal end is larger than the inner diameter of the proximal end. A pipe to be connected passes through the flared portion (30). The flared portion (30) is connected to the pipe by a brazing material filled in a gap between the pipe and an inner wall of the flared portion itself.

Description

Technical Field

[0001] The present invention 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 Art

[0002] Among heat exchangers having a plurality of heat transfer tubes, there is a heat exchanger in which an elbow is connected to the tube end portion of the heat transfer tube in order to connect the heat transfer tubes to each other, and the elbow is brazed to the tube end portion. In such a heat exchanger, in order to suppress the brazing material from dripping onto the heat transfer tube during brazing, a structure for receiving the brazing material, called a flared portion, is sometimes provided at the tube end portion of the heat transfer tube into which the elbow is inserted to receive the brazing material.

[0003] For example, Patent Document 1 discloses a heat exchanger in which a flared portion is provided at the end of a heat transfer tube, and the flared portion has a bottom formed in a funnel shape and a cylindrical wall portion surrounding the bottom. In the heat exchanger described in Patent Document 1, an annular brazing material is placed between a curved tube inserted into the end of the heat transfer tube and the cylindrical wall portion of the flared portion, and brazing is performed by melting the annular brazing material. In the heat exchanger described in Patent Document 1, the annular brazing material is surrounded by the cylindrical wall portion and received by the bottom portion, so that the brazing material is difficult to drip.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2017 / 168747 Summary of the invention

[0007] Problems to be solved by the invention

[0008] Generally, the expanded portion is formed by expanding the end portion of the heat transfer tube. On the other hand, in the heat exchanger described in Patent Document 1, the expanded portion is sized to accommodate the annular brazing material. Therefore, if the expanded portion described in Patent Document 1 is formed by expanding the tube, the expansion rate increases, and as a result, the thickness of the expanded portion becomes thinner. As a result, the expanded portion may break during forming.

[0009] The present disclosure is completed to solve the above-mentioned problems, and its purpose is to provide a heat transfer tube, a heat exchanger, a tube expansion tool, a tube expansion device, a method for connecting heat transfer tubes and a method for manufacturing a heat exchanger that is not easy to break during the expansion part molding and suppresses the dripping of the brazing material.

[0010] Means for solving problems

[0011] In order to achieve the above-mentioned object, the heat transfer tube of the present invention has a flared portion, the flared portion has a spherical shape with an inner diameter at the end larger than the inner diameter at the base end, and the tube to be connected passes through the flared portion. Moreover, the flared portion is connected to the tube by a brazing material filled in a gap between the tube and the inner wall of the flared portion itself.

[0012] Effects of the Invention

[0013] According to the structure disclosed in the present invention, the flared portion has a spherical band shape in which the inner diameter of the end is larger than the inner diameter of the base end, so that damage caused by molding is not easily concentrated at the end. As a result, the flared portion is not easily broken during molding. In addition, since the flared portion has the above-mentioned spherical band shape, the gap between the flared portion and the pipe to be connected becomes wider as it moves toward the end. As a result, the flared portion is easy to receive the solder. As a result, dripping of the solder is suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1A This is a perspective view of a heat exchanger including the heat transfer tube according to Embodiment 1 of the present disclosure.

[0015] Figure 1B This is a cross-sectional view of a heat exchanger including the heat transfer tube according to Embodiment 1 of the present disclosure.

[0016] Figure 1C This is a right side view of the heat exchanger including the heat transfer tube according to Embodiment 1 of the present disclosure.

[0017] Figure 2 This is a perspective view of the heat transfer tube according to Embodiment 1 of the present disclosure.

[0018] Figure 3 yes Figure 2 A cross-sectional view taken along the III-III cutting line is shown.

[0019] Figure 4 yes Figure 3 A magnified view of region IV is shown

[0020] Figure 5 This is a flowchart showing a method for manufacturing a heat exchanger including the heat transfer tube according to Embodiment 1 of the present disclosure.

[0021] Figure 6 This is a side view of a tube expansion tool used in the method for manufacturing a heat exchanger including the heat transfer tube according to Embodiment 1 of the present disclosure.

[0022] Figure 7 This is an enlarged view of the tip portion of a tube expansion tool used in the method for manufacturing a heat exchanger including the heat transfer tube according to Embodiment 1 of the present disclosure.

[0023] Figure 8This is a simulation diagram showing the distribution of damage values ​​in the heat transfer tube when the expanded portion of the heat transfer tube according to Embodiment 1 of the present disclosure is formed.

[0024] Fig. 9 This is a graph showing the relationship between the outer diameter of the heat transfer tube and the damage value when the expanded portion is formed.

[0025] Fig.10 This is a graph showing the relationship between the outer diameter of the heat transfer tube and the equivalent strain increment when the expanded portion is formed.

[0026] Fig.11 This is a simulation diagram showing the distribution of damage values ​​in a heat transfer tube when the tube is expanded using a truncated cone-shaped tube expansion tool.

[0027] Fig.12 This is a front view of a heat transfer tube of a reference example in which the tube is expanded using a truncated cone-shaped tube expansion tool.

[0028] Fig.13 This is a simulation diagram showing the distribution of damage values ​​in the heat transfer tube when the tube is expanded using the tube expansion tool having a spherical table portion according to the first embodiment of the present disclosure.

[0029] Fig.14 This is a front view of a heat transfer tube expanded by the tube expansion tool having a spherical base portion according to the first embodiment of the present disclosure.

[0030] Fig.15 This is a graph showing the relationship between pipe expansion and equivalent stress when the expanded portion is formed.

[0031] Fig.16 This is a front view of the heat transfer tube when the tube expansion tool including the spherical base portion according to the first embodiment of the present disclosure is pressed in to a value exceeding a target value.

[0032] Fig.17 This is a cross-sectional view showing a heat transfer tube in which a brazing material is placed in a brazing step of a method for manufacturing a heat exchanger including the heat transfer tube according to Embodiment 1 of the present disclosure.

[0033] Fig.18 This is a cross-sectional view showing a heat transfer tube having fillets formed therein in a brazing step of a method for manufacturing a heat exchanger including the heat transfer tube according to Embodiment 1 of the present disclosure.

[0034] Fig.19 This is a side view of a tube expansion tool used in the method for manufacturing a heat exchanger including a heat transfer tube according to Embodiment 2 of the present disclosure.

[0035] Fig. 20 This is an enlarged view of a tip portion of a tube expansion tool used in a method for manufacturing a heat exchanger including a heat transfer tube according to a second embodiment of the present disclosure.

[0036] Fig.21 It is a perspective view of a modified example of the heat transfer tube according to Embodiment 1 of the present disclosure.

[0037] Fig. 22 This is a side view of a modification of the tube expansion tool used in the method for manufacturing a heat exchanger including the heat transfer tube according to Embodiment 1 of the present disclosure. DETAILED DESCRIPTION

[0038] Hereinafter, the heat transfer tube, heat exchanger, expansion tool, expansion device, connection method of heat transfer tube and tube, and manufacturing method of heat exchanger of the embodiment of the present disclosure are described in detail with reference to the accompanying drawings. In addition, in the drawings, the same reference numerals are marked for the same or equivalent parts. In the orthogonal coordinate system XYZ shown in the figure, the vertical direction when the tube axis direction of the heat transfer tube is toward the vertical direction is the Z axis, and the horizontal plane is the XY plane. Hereinafter, the coordinate system is appropriately cited for explanation.

[0039] (Implementation Method 1)

[0040] The heat transfer tube of the first embodiment is a heat transfer tube having an arm-shaped flared portion. In order to suppress cracking during molding, the flared portion is formed by expanding the tube end portion of the heat transfer tube using a spherical table-shaped tube expansion tool. Figure 1A-Figure 1C , the structure of a heat exchanger having the heat transfer tube is described.

[0041] Figure 1A It is a perspective view of the heat exchanger 100 provided with the heat transfer tube 1A of Embodiment 1. Figure 1B is a cross-sectional view of the heat exchanger 100 . Figure 1C is a right side view of the heat exchanger 100. Figure 1A-1B For easy understanding, only a portion of the heat exchanger 100 is shown instead of the entirety.

[0042] like Figure 1A-Figure 1C As shown, the 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.

[0043] The heat transfer tube 1A is formed into a circular tube shape in order to allow a fluid, such as a refrigerant, to flow through the heat exchange object. Figure 1A-Figure 1C Although not shown in the figure, the heat transfer tube 1A has a spiral groove extending along the inner wall, that is, a spiral groove. Thus, the heat transfer tube 1A stirs the refrigerant when the refrigerant flows therein.

[0044] Furthermore, in order to circulate the refrigerant in the heat exchanger 100, Figure 1BAs shown, the round tube of the heat transfer tube 1A is in the form of a pair of straight portions 11, 12 extending in a straight line and a U-shaped bent portion 13 connecting the ends of one side of these straight portions 11, 12 to each other. In short, the heat transfer tube 1A is a so-called hairpin tube. And, the direction in which these straight portions 11, 12 of the heat transfer tube 1A extend is oriented in the up and down direction. And, in the heat transfer tube 1A, the upper end portions of the straight portion 11 and the straight portion 12 are connected by a U-shaped bent pipe 3. Thus, the heat transfer tubes 1A are connected to each other. As a result, the refrigerant flows between the heat transfer tubes 1A.

[0045] 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 heat transfer of the refrigerant flowing therein. A plurality of fins 2 are mounted on the heat transfer tube 1A to exchange the heat transferred thereto.

[0046] In order to improve the heat dissipation, the fins 2 are formed of a metal with high thermal conductivity, similar to the heat transfer tube 1A. Figure 1A-Figure 1C As shown, the fin 2 is plate-shaped. Moreover, the plate surface of the fin 2 is oriented in the up-down direction, that is, in the direction perpendicular to the tube axis of the heat transfer tube 1A. Moreover, the fin 2 is joined to the heat transfer tube 1A. As a result, the heat of the heat transfer tube 1A is transferred to the fin 2, and the fin 2 releases the heat to the surrounding air.

[0047] In addition, the fins 2 are arranged at a certain interval in the vertical direction. Thus, the fins 2 are in a state where air flows through the gaps between them, thereby improving the heat exchange efficiency.

[0048] As described above, the heat transfer tubes 1A are connected to each other through the elbow 3. The elbow 3 and the heat transfer tube 1A are joined by brazing. During the brazing, the brazing material may drip onto the heat transfer tube 1A or the fin 2. In order to suppress the dripping of the brazing material, the heat exchanger 100 is provided with a flared portion 30 at the upper end of the heat transfer tube 1A. Figure 2-Figure 4 , the structure of the heat transfer tube 1A including the expanded portion 30 will be described.

[0049] Figure 2 It is a perspective view of the heat transfer tube 1A according to the first embodiment. Figure 3 yes Figure 2 A cross-sectional view taken along the III-III cutting line is shown. Figure 4 yes Figure 3 The enlarged view of region IV is shown. Figure 2 and Figure 3 In order to facilitate understanding, only Figure 1A-Figure 1C The upper end portion of the heat transfer tube 1A is shown in an enlarged manner.

[0050] like Figure 2-Figure 4As shown, the heat transfer tube 1A is provided with a tube holding portion 20 and a flared portion 30 at the upper end portion in order to connect the above-mentioned bent tube 3 .

[0051] The tube holding portion 20 is Figure 1A-Figure 1C Specifically, the tube holding portion 20 has a greater diameter than the main body portion 10 of the heat transfer tube 1A. Figure 3 The inner diameter D1 shown is larger than the inner diameter D3. Figure 1C The outer diameter D2 of the curved pipe 3 shown is large. In the pipe holding portion 20, since such a curved pipe 3 having an outer diameter D2 can be inserted, the inner diameter D3 is larger than the outer diameter D2 of the curved pipe 3 by a tolerance amount. For example, the inner diameter D3 is larger than the outer diameter D2 of the curved pipe 3 by an amount of deviation such as the bend of the curved pipe 3 and the outer diameter D2. Thus, the pipe holding portion 20 can insert the pipe end portion of the curved pipe 3 and hold the pipe end portion of the curved pipe 3 when the pipe end portion of the curved pipe 3 is inserted.

[0052] Although not shown, when the end portion of the elbow 3 is inserted, the tube holding portion 20 and the tube end portion are welded. Specifically, they are brazed. As a result, the tube holding portion 20 fixes the inserted elbow 3. Figure 2-Figure 4 As shown, a flared portion 30 is continuously formed on the end side, that is, the upper end side, of the tube holding portion 20 .

[0053] In order to prevent the brazing material from dripping during the brazing, the flared portion 30 has an arm-like shape. Specifically, the flared portion 30 has a spherical shape with an inner diameter at one end larger than that at the other end. In addition, since the flared portion 30 collects the molten brazing material during brazing, the other end side with a smaller inner diameter faces the tube holding portion 20. As a result, Figure 3 As shown, the flared portion 30 is in a spherical zone shape in which the inner diameter D4 at the upper end is larger than the inner diameter D5 at the lower end. As a result, the flared portion 30 is in a shape that becomes larger as it inclines toward the upper end.

[0054] Here, in this specification, a spherical zone refers to a portion of a spherical surface sandwiched by two parallel planes when the spherical surface is cut. Furthermore, the spherical surface mentioned here includes not only the spherical surface of a sphere but also the spherical surface of an ellipsoid, such as the spherical surface of a prolate sphere and the spherical surface of an oblate sphere. As a result, not only the spherical zone having a circular shape when viewed from a direction perpendicular to the two parallel planes cutting the spherical surface, but also the spherical zone having an elliptical, oblong, flat, etc. shape.

[0055] In addition, the inner diameter D5 of the lower end of the flared portion 30 is the same as the inner diameter D3 of the tube holding portion 20. Thus, when the tube end portion of the bent tube 3 is partially inserted into the tube holding portion 20, the bent tube 3 passes through the flared portion 30. Also, 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 it is easy to receive the molten brazing material when brazing the tube holding portion 20 and the bent tube 3. As a result, dripping of the brazing material is suppressed.

[0056] Thus, the expanded 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 the dripping of the brazing material during brazing. On the other hand, the expanded portion 30 has a spherical shape, thereby suppressing its own cracking during manufacturing. Figure 5-Figure 18 The method for manufacturing the heat exchanger 100 will be described together with the method for suppressing the flared portion 30 from breaking during the molding.

[0057] Figure 5 This is a flowchart showing a method for manufacturing the heat exchanger 100 including the heat transfer tube 1A according to the first embodiment. Figure 6 It is a side view of the tube expansion tool 4A used in the manufacturing method of the heat exchanger 100. Figure 7 It is an enlarged view of the tip portion of the pipe expansion tool 4A.

[0058] In the manufacturing method of the heat exchanger 100, although not shown in the figure, first, a plurality of semi-finished heat transfer tubes formed into the above-mentioned hairpin shape and having an inner diameter smaller than the inner diameter D1 of the main body 10 of the above-mentioned heat transfer tube 1A are prepared. In addition, a plurality of fins 2 of the above-mentioned shape and size are prepared. Then, they are arranged in the above-mentioned positional relationship, and the fins are attached to the semi-finished heat transfer tubes. In this way, a heat exchanger core is manufactured.

[0059] Then, if Figure 5 As shown, a primary expansion is performed (step S1). The primary expansion process is described in detail. In this primary expansion process, a spherical tool having a diameter equal to the inner diameter D1 of the main body 10 is inserted into the semi-finished heat transfer tube forming the heat exchanger core. As described above, the heat transfer tube 1A is formed of a metal with high thermal conductivity. The semi-finished heat transfer tube is also the same. As a result, when the spherical tool is inserted into the semi-finished heat transfer tube, the heat transfer tube undergoes plastic deformation. As a result, the inner diameter and outer diameter of the semi-finished heat transfer tube are enlarged.

[0060] Although not shown in the figure, in the heat exchanger core, the fin 2 is provided with a fin sleeve, and the semi-finished heat transfer tube passes through the fin sleeve. When the tube is expanded once, the outer periphery of the semi-finished heat transfer tube is expanded, and the semi-finished heat transfer tube and the fin sleeve are closely attached. As a result, the fin 2 is fixed to the semi-finished heat transfer tube.

[0061] Next, proceed Figure 5 The secondary expansion (step S2) is shown. In the secondary expansion step, a cylindrical tool having an outer diameter equal to the inner diameter D3 of the tube holder 20 is inserted into the tube end portion of the semi-finished heat transfer tube expanded in step S1. Then, the cylindrical tool is pressed into the tube end portion equal to the length of the tube holder 20. Thus, the tube holder 20 is formed at the tube end portion of the semi-finished heat transfer tube.

[0062] When the secondary expansion is completed, the expanded portion 30 is formed (step S3). In the forming process of the expanded portion 30, the expanded portion 30 is formed using Figure 6 The illustrated tube expanding tool 4A expands the end portion of the tube holding portion 20 formed in step S2 , thereby forming the expanded portion 30 .

[0063] First, the structure of the pipe expansion tool 4A is described. Figure 6 and Figure 7 As shown, the pipe expansion tool 4A includes a guide portion 42 and a spherical base portion 43 at the distal end portion of the rod portion 41, that is, at the -Z end portion of the rod portion 41. The guide portion 42 and the spherical base portion 43 are provided in this order from the -Z side.

[0064] also, Figure 6 The base end portion 44 shown is adjacent to the +Z end of the rod portion 41 and is a portion provided with an external thread for attaching the pipe expansion tool 4A to a driving mechanism of a pipe expansion device (not shown).

[0065] The guide portion 42 is 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 .

[0066] Describing the structure in detail, the guide portion 42 is formed in a cylindrical shape with its axis facing the Z direction. In addition, in the guide portion 42, the corner at the -Z end is chamfered to facilitate insertion into the tube holding portion 20.

[0067] in addition, Figure 7 The outer diameter D6 of the guide portion 42 shown is larger than that of the tube holding portion 20. Figure 3 The inner diameter D3 shown is small enough to allow clearance fit. As a result, the guide portion 42 can move along the inner wall of the tube holding portion 20 when it is inserted into the tube holding portion 20 and pressed into the inside of the tube holding portion 20. In addition, the outer peripheral surface of the guide portion 42 abuts against the inner wall of the tube holding portion 20, thereby determining the position of the spherical table portion 43 adjacent to the guide portion 42 relative to the tube holding portion 20. As a result, the guide portion 42 guides the spherical table portion 43 to the correct position when the tube expansion tool 4A is inserted into the tube holding portion 20.

[0068] On the other hand, the spherical base portion 43 is a portion provided for molding the expanded portion 30 of the heat transfer tube 1A.

[0069] Specifically, as described above, the flared portion 30 is formed in a spherical zone shape. In order to form the spherical zone shape, the spherical base portion 43 is formed in a spherical base shape that can fit with the spherical zone of the flared portion 30 .

[0070] Here, in this specification, a sphere table refers to a part of a sphere sandwiched by two parallel planes when the sphere is cut by these planes. As in the case of the spherical surface defining the above-mentioned spherical zone, the sphere includes ellipsoids, such as prolate spheres and oblate spheres. As a result, the sphere table includes not only a sphere table whose outer shape is circular when viewed from a direction perpendicular to the two parallel planes cutting the sphere, but also a sphere table with an elliptical, oblong, flat, etc. shape.

[0071] If the shape of the ball table portion 43 is further described in detail, Figure 6 as well as Figure 7 As shown, the spherical table portion 43 is a spherical table shape in which the outer diameter of the -Z end is smaller than the outer diameter of the +Z side. In this spherical table shape, the outer diameter of the -Z end is equal to Figure 7 The outer diameter of the spherical base portion 43 gradually increases from the outer diameter of the same size as the outer diameter D6 toward the +Z side. The outer diameter of the spherical base portion 43 decreases by a certain amount after reaching the maximum outer diameter D7 on the +Z side.

[0072] In addition, the outer diameter of the -Z end of the spherical table portion 43 is the same as the inner diameter D5 of the -Z end of the flared portion 30 formed by the spherical table portion 43, and the outer diameter D7 of the maximum diameter portion located at the +Z end of the spherical table portion 43 is the same as the inner diameter D4 of the +Z end of the flared portion 30. Here, the same diameter means substantially the same diameter including tolerance.

[0073] In addition, the spherical table portion 43 is larger than the guide portion 42 at the maximum diameter portion that becomes the outer diameter D7. If the difference between the radius of the maximum diameter portion and the radius of the guide portion 42 is set as the distance D0, the distance D0 is preferably a distance that can form a rounded corner so that the rounded corner can be formed in the expanded portion 30 in the brazing process described later. For example, the distance D0 is preferably less than 1 mm. In addition, the distance D0 is preferably a size that can place the brazing material in the expanded portion 30 formed by the spherical table portion 43 in the brazing process described later. However, in order to reduce the expansion rate and prevent the heat transfer tube 1A from rupturing, the distance D0 is preferably a distance that does not allow the brazing material to enter the expanded portion 30.

[0074] Since the spherical base part 43 has such a shape, when the guide part 42 is inserted into the tube holding part 20, the spherical base part 43 enters the tube holding part 20 along with the guide part 42. Then, the spherical base part 43 expands the tube holding part 20 to form the above-mentioned expanded part 30.

[0075] At this time, the spherical base portion 43 reduces the damage value applied to the expanded tube end portion of the tube holding portion 20 and suppresses the occurrence of cracks.

[0076] Here, the damage value is derived from the Cockcroft-Latham equation shown in the following equation 1, which is known as an evaluation equation for extension failure. When the damage value reaches the limit damage value, it can be evaluated that the expansion tube has cracked, so the higher the value, the easier it is for the heat transfer tube 1A to crack.

[0077] [Mathematical formula 1]

[0078]

[0079] D f : Damage value σ max : Maximum principal stress Equivalent stress dε: Equivalent strain increment

[0080] Next, the effect of suppressing the occurrence of cracks in the pipe expansion tool 4A will be described. Figure 8-Figure 10 The simulation result is shown when simulating the damage value of the heat transfer tube 1A when the expanded portion 30 is formed using the tube expansion tool 4A.

[0081] Figure 8 This is a simulation diagram showing the distribution of damage values ​​in the heat transfer tube 1A when the expanded portion 30 of the heat transfer tube 1A according to the first embodiment is formed. Fig. 9 It is a graph showing the relationship between the outer diameter of the heat transfer tube 1A and the damage value when the expanded portion 30 is formed. Fig.10 It is a graph showing the relationship between the outer diameter of the heat transfer tube 1A and the equivalent strain when the expanded portion 30 is formed.

[0082] In addition, Figure 8 In FIG. 1 , the damage value of each part of the heat transfer tube 1A is indicated by shades. Figure 8 In order to facilitate understanding, only three portions of the heat transfer tube 1A with large damage values ​​are shown, but the portions with large damage values ​​are arranged along the opening of the tube end portion. Figure 8 The open-ended inclined linear object shown is caused by the spiral groove 14 mentioned above.

[0083] in addition, Fig. 9 as well as Fig.10 The so-called spherical table type graph shown is a graph when the tube holding portion 20 is expanded using the tube expansion tool 4A having a spherical table portion 43. The so-called truncated cone type graph is a graph when the tube holding portion 20 is expanded using a tube expansion tool having a truncated cone portion with a truncated cone side surface curved inward instead of the spherical table portion 43.

[0084] Reference Figure 8 It can be seen that the damage value is high at the tube end portion on the upper end side of the expanded tube when the expanded portion 30 is formed. The graph showing the relationship between the maximum value of the damage value and the outer diameter of the heat transfer tube 1A when the tube is expanded is Fig. 9 . Reference Fig. 9 It can be seen that in the curve of the spherical table type, if the pipe is expanded from the outer diameter at the start of the pipe expansion, the damage value becomes high sharply, but the damage value gradually becomes low. On the other hand, in the curve of the truncated cone type, it can be seen that the damage value becomes high as the pipe is expanded from the outer diameter at the start of the pipe expansion. According to these curves, when the pipe holding portion 20 is expanded using the spherical table type, that is, the pipe expansion tool 4A, even if the pipe expansion rate is high, cracks are not easy to occur.

[0085] In addition, refer to Fig.10 It can be seen that the change in the equivalent strain during pipe expansion has the same tendency as the change in the damage value. As can be seen from Mathematical Formula 1, the damage value is the integral value of the equivalent strain increment. Fig.10 It is also understood that the pipe expansion using the pipe expansion tool 4A is less likely to cause cracks even if the pipe expansion rate is higher than the pipe expansion using the truncated cone-shaped pipe expansion tool.

[0086] The reason why the tube expansion tool 4A is less likely to break during tube expansion than a truncated cone-shaped tube expansion tool is believed to be that a portion with a high damage value is generated on the inner side of the tube end portion of the heat transfer tube 1A. Figure 11-Figure 14 , explain the reasons.

[0087] Fig.11 It is a simulation diagram showing the distribution of damage values ​​in the heat transfer tube 200 when the tube is expanded using the truncated cone-shaped tube expansion tool 40 . Fig.12 It is a front view of a heat transfer tube 200 of a reference example which is expanded by a truncated cone-shaped tube expanding tool 40 . Fig.13 It is a simulation diagram showing the distribution of damage values ​​in the heat transfer tube 1A when the tube is expanded using the tube expansion tool 4A having the spherical base portion 43 . Fig.14 This is a front view of a heat transfer tube 1A which is expanded by a tube expansion tool 4A having a spherical base portion 43 .

[0088] In addition, Fig.11 In the figure, only a part of the tube end portion of the heat transfer tube 200 of the reference example is enlarged and shown for easy understanding. Fig.13 Similarly, only a portion of the tube end portion of the heat transfer tube 1A is enlarged and shown. Fig.12 and Fig.14 In the embodiment, the portion where the expansion tool 40 contacts the heat transfer tube 200 and the portion where the expansion tool 4A contacts the heat transfer tube 1A exist throughout the entire circumference, but Fig.12 and Fig.14In FIG. 1 , only the portions P1 and P2 located on the side surfaces of the portions abutting over the entire circumference are shown.

[0089] Reference Fig.11 and Fig.13 It is known that in using Fig.13 When the pipe is expanded by the pipe expansion tool 4A shown in the figure, Fig.11 Compared with the case where the pipe is expanded by the truncated cone type pipe expansion tool 40 shown in FIG. 1 , the range R indicating the portion with the damage value being medium or above is larger. This is because, when the pipe is expanded by the truncated cone type pipe expansion tool 40, the pipe expansion tool 40 and the pipe expansion tool 40 are in contact with each other during the pipe expansion process. Fig.12 The portion P1 near the open end of the heat transfer tube 200 shown in the figure continues to abut, and as a result, stress is concentrated near the open end of the heat transfer tube 200. In contrast, when the tube is expanded using the tube expansion tool 4A, the tube expansion tool 4A and the heat transfer tube 200 are not in contact. Fig.14 The portion P2 of the heat transfer tube 1A which is away from the opening end and is inside the heat transfer tube 1A shown in the figure abuts against the heat transfer tube 1A. As a result, the stress is dispersed in the range from the vicinity of the opening end of the heat transfer tube 1A to the inside.

[0090] Thus, the tube expansion tool 4A includes the spherical portion 43, so that stress is less likely to concentrate near the open end of the heat transfer tube 1A, and damage is less likely to be applied to the heat transfer tube 1A. As a result, when the tube is expanded using the tube expansion tool 4A, the occurrence of cracks in the heat transfer tube 1A is suppressed.

[0091] In the pipe expansion tool 4A, the spherical portion 43 has an outer diameter that increases from the guide portion 42, and as a result, a step is formed between the guide portion 42 and the spherical portion 43. Fig.14 As shown by arrow A1, compressive stress is applied to the tube end of the heat transfer tube 1A during the tube expansion process. And, as shown by arrow A2, the tube expansion is performed in a state where compressive stress is applied.

[0092] It is known that by applying a compressive force in a direction different from the direction in which the deformation is intended to be caused by the tensile force, the amount of deformation until the tube breaks increases. In the tube expansion using the tube expansion tool 4A, the compressive force is applied in the tube axial direction of the heat transfer tube 1A, while the tensile force is applied in the circumferential direction of the heat transfer tube 1A. Therefore, the above-mentioned relationship between the tensile force and the compressive force holds. As a result, the equivalent stress increases.

[0093] Fig.15 30 is a graph showing the relationship between pipe expansion and equivalent stress when the expanded portion 30 is formed. Fig.15 The curves of the spherical table and truncated table are shown in Figure 1. Fig. 9 and Fig.10 The curves of the spherical table type and the truncated table type are the curves when the tube is expanded using the same tool.

[0094] The above relationship between tensile force and compressive force is valid as a result, if Fig.15 As shown in FIG. 1 , the equivalent stress when the pipe is expanded using the spherical table type, that is, the pipe expansion tool 4A is larger than the equivalent stress when the pipe is expanded using the truncated cone type pipe expansion tool 40. The equivalent stress is a parameter that becomes the denominator of mathematical formula 1. Therefore, when the pipe is expanded using the pipe expansion tool 4A, the damage value represented by mathematical formula 1 is smaller than when the pipe is expanded using the truncated cone type pipe expansion tool 40.

[0095] As described above, the tube expansion tool 4A includes a step between the guide portion 42 and the spherical base portion 43 , thereby reducing the damage value and suppressing the occurrence of cracks in the heat transfer tube 1A during tube expansion by the tube expansion tool 4A.

[0096] Furthermore, as described above, the outer diameter of the spherical portion 43 of the pipe expansion tool 4A once reaches the maximum outer diameter D7 from the tool tip toward the opposite base end and then decreases by a certain amount. As a result, even if the amount of insertion of the pipe expansion tool 4A deviates from the target value, the damage value is not accumulated.

[0097] Fig.16 FIG. 4 is a front view of the heat transfer tube 1A when the tube expansion tool 4A having the spherical base portion 43 is pressed in to a value exceeding the target value. Fig.16 In the figure, only the tube end portion of the heat transfer tube 1A is shown in an enlarged manner.

[0098] like Fig.16 As shown, as a result of pressing the expansion tool 4A to a value above the target value, the heat transfer tube 1A is deformed to the desired inner diameter. Here, the target value refers to the distance value from the end of the guide portion 42 of the expansion tool 4A to the portion of the spherical table portion 43 that becomes the maximum outer diameter D7. When the expansion tool 4A is pressed to a value above the target value, the portion of the expansion tool 4A that is above the portion that becomes the maximum outer diameter D7, that is, the portion P3 on the base end side, enters the interior of the heat transfer tube 1A. However, in the expansion tool 4A, at the portion P3 on the base end side, the outer diameter gradually decreases as it moves toward the base end. As a result, even if the expansion tool 4A is pressed to a value above the target value and the amount of pressing is deviated, the damage value will not be accumulated.

[0099] Thus, the spherical base portion 43 has a shape in which the outer diameter gradually decreases at the portion P3 closer to the base end than the portion having the maximum outer diameter D7. Therefore, even if the amount of press-in varies in the pipe expansion tool 4A, the damage value does not accumulate, and the occurrence of cracks in the heat transfer tube 1A during the pipe expansion by the pipe expansion tool 4A is suppressed. In addition, the pipe expansion tool 4A is not easy to get caught on the inner wall of the heat transfer tube 1A when being pulled out from the heat transfer tube 1A, and as a result, it is easy to be pulled out from the heat transfer tube 1A.

[0100] return Figure 5In the process of forming the expanded portion 30 in step S3, the expansion tool 4A of the above structure is used to expand the end of the tube holding portion 20 formed on the semi-finished heat transfer tube. At this time, the expansion tool 4A is pressed in until the portion with the maximum outer diameter D7 enters the tube holding portion 20. Thus, the expanded portion 30 having a spherical zone shape is formed. As a result, a spherical zone shape having a thickness in the direction of the expansion tool 4A is formed. Figure 4 The expanded portion 30 is formed in a shape where the end is reduced in size and the inner side of the end surface of the end is chamfered. Then, the heat transfer tube 1A of the above shape is formed. Thus, the forming process of the expanded portion 30 is completed.

[0101] In addition, the step of forming the expanded portion 30 is the third tube expansion in the process of the method for manufacturing the heat exchanger 100 , and is therefore also referred to as a third tube expansion step.

[0102] Then, if Figure 5 As shown, the elbow 3 is assembled with respect to the heat transfer tube 1A (step S4). To explain in detail, in the assembly process of the elbow 3, the tube end portion of the elbow 3 is inserted into the flared portion 30 formed in step S3, so that the tube end portion of the elbow 3 is held in the tube holding portion 20 further inward than the flared portion 30. This process is performed for all the heat transfer tubes 1A provided in the heat exchanger core. Thus, the assembly of the elbow 3 is completed.

[0103] When the assembly of the elbow 3 is completed, brazing is performed (step S5). In this brazing process, a brazing material is placed adjacent to the flared portion 30. Then, the brazing material is melted to form a fillet. Fig.17 and Fig.18 , which is described in detail. In addition, hereinafter, for easy understanding, the brazing material obtained by melting the brazing material is referred to as a brazing material.

[0104] Fig.17 It is a cross-sectional view showing a heat transfer tube 1A in which a brazing material 5 is placed in a brazing step of a method of manufacturing a heat exchanger. Fig.18 It is a cross-sectional view showing a heat transfer tube 1A in which a fillet 6 is formed in a brazing step in a method of manufacturing a heat exchanger.

[0105] In the brazing process, Fig.17 As shown in FIG. 1 , in order to facilitate the brazing material to enter the expanded portion 30 when the brazing material 5 is melted, the brazing material 5 is placed adjacent to the opening of the expanded portion 30. Then, the brazing material 5 is melted in this state. Fig.18 As shown, the gap between the tube holding portion 20 of the heat transfer tube 1A and the elbow 3, and the gap between the flared portion 30 of the heat transfer tube 1A and the elbow 3 are filled with brazing material. In addition, a fillet 6 is formed in the section from the upper end of the flared portion 30 to the outer peripheral surface of the elbow 3, that is, in the section from the open end of the flared portion 30 to the outer peripheral surface of the elbow 3.

[0106] At this time, the width W1 of the opening of the expanded portion 30 is preferably a distance that can form a rounded corner, for example, less than 1 mm. This can improve the bonding strength between the expanded portion 30 and the bent pipe 3. In addition, the width W1 of the opening is preferably greater than Fig.17 The size of the brazing filler metal 5 in the radial direction of the heat transfer tube 1A, i.e., the width W2, is small. This is because, with such a size, the expansion rate in the forming process of the flared portion 30 can be reduced as much as possible to suppress the rupture of the heat transfer tube 1A. In this case, the width W1 of the opening of the flared portion 30 can be more than half of the width W2 of the brazing filler metal 5 and less than the width W2 of the brazing filler metal 5 by the thickness T of the flared portion 30, for example, in order to place the brazing filler metal 5.

[0107] Furthermore, when the brazing material is filled into the gap between the heat transfer tube 1A and the elbow 3 in the brazing process, the expanded portion 30 surrounds the brazing material, thereby suppressing the brazing material from dripping.

[0108] When the brazing material solidifies, the elbow 3 is fixed to the heat transfer tube 1A. Thus, the brazing step is completed. Through the above steps, the method for manufacturing the heat exchanger 100 is completed, and the heat exchanger 100 is completed.

[0109] In addition, the upper end portion of the heat transfer tube 1A is an example of the tube end portion mentioned in the present disclosure. The upper end and the lower end of the flared portion 30 are examples of the terminal end and the base end of the flared portion 30 mentioned in the present disclosure. In addition, the assembly process of the bent tube 3 is an example of the process of inserting the insertion tube mentioned in the present disclosure.

[0110] As described above, in the heat transfer tube 1A of Embodiment 1, the flared portion 30 has a spherical zone shape in which the inner diameter of the distal end is larger than the inner diameter of the proximal end. As a result, the flared portion 30 is less likely to be broken during molding.

[0111] In addition, since the flared portion 30 is in the above-mentioned spherical zone shape, the gap between the flared portion 30 and the bent pipe 3 to be connected becomes wider toward the end of the flared portion 30. Therefore, the flared portion 30 can easily receive the brazing material located at the end side. As a result, the flared portion 30 can suppress the dripping of the brazing material.

[0112] In the tube expansion tool 4A, the spherical table portion 43 has a spherical table shape in which the outer diameter of the distal end is smaller than the outer diameter of the proximal end. Therefore, when the heat transfer tube 1A is manufactured by tube expansion, stress is less likely to be concentrated near the open end of the heat transfer tube 1A, and damage caused by tube expansion is less likely to be applied to the heat transfer tube 1A. As a result, the heat transfer tube 1A is less likely to break.

[0113] In addition, the outer diameter of the spherical portion 43 increases from the distal end toward the proximal end to reach a maximum value, and then decreases by a certain amount. Therefore, even if the expansion tool 4A is pressed into the heat transfer tube 1A for a length greater than the length from the distal end of the spherical portion 43 to the portion where the outer diameter reaches a maximum value, the damage to the heat transfer tube 1A caused by the expansion does not change. As a result, the heat transfer tube 1A is less likely to break.

[0114] In addition, in the tube expansion tool 4A, a step is provided between the guide portion 42 and the spherical base portion 43. Therefore, damage to the heat transfer tube 1A caused by tube expansion is reduced, and the heat transfer tube 1A is less likely to be broken during tube expansion.

[0115] (Example)

[0116] A tube expansion tool 4A of the above-mentioned shape was produced, and an experiment was conducted to expand a circular copper tube with a wall thickness of 0.17 mm using the tube expansion tool 4A. In this experiment, (1) the tube expansion was conducted with the tube expansion tool 4A pressing at a speed of 0.1 mm / sec and the tube expansion amount of 3.5 mm. Also, (2) the tube expansion was conducted with the tube expansion tool 4A pressing at a speed of 20 mm / sec and the tube expansion amount of 3.5 mm. In addition, reference was used. Fig.12 The described truncated cone type pipe expansion tool 40 was used to expand the pipe under the same conditions as a comparative example. Then, after the pipe expansion, the copper pipe after the pipe expansion was checked for cracks. Furthermore, for the copper pipe that did not crack, the copper pipe was checked for buckling. The results are shown in Table 1. In addition, in Table 1, the pipe expansion tool 4A is recorded as "spherical cone type" and the pipe expansion tool 40 is recorded as "truncated cone type".

[0117] [Table 1]

[0118]

[0119] Referring to Table 1, it can be seen that when the tube is expanded using the spherical tube expansion tool, i.e., the tube expansion tool 4A, it is less likely to cause the copper tube to break, and it is also less likely to cause buckling, which is the main cause of the copper tube break, compared to the case where the tube is expanded using the truncated tube expansion tool, i.e., the tube expansion tool 40. In addition, it can be seen that even if the pressing speed of the tube expansion tool 4A is increased, the copper tube is not likely to break, and the efficiency of the tube expansion is high. In this way, if the tube is expanded using the tube expansion tool 4A, it is less likely to cause the copper tube to break. In addition, the efficiency of the tube expansion is high.

[0120] (Implementation Method 2)

[0121] In the first embodiment, the pipe expanding tool 4A includes the guide portion 42 and the spherical base portion 43 , and the guide portion 42 and the spherical base portion 43 are arranged in this order from the distal end side.

[0122] However, the pipe expansion tool 4A is not limited thereto. The pipe expansion tool 4A only needs to include a spherical portion 43, the outer diameter of the distal end of which is smaller than the outer diameter of the proximal end, and the distal end is sized to be inserted into the pipe end portion of the heat transfer pipe 1A. Furthermore, the flared portion 30 can be formed by inserting the spherical portion 43 from the distal end to the proximal end into the pipe end portion of the heat transfer pipe 1A. Therefore, the pipe expansion tool 4A may also include a structure other than the spherical portion 43.

[0123] In the second embodiment, the pipe expansion tool 4B includes a truncated cone portion 45 in addition to the guide portion 42 and the spherical cone portion 43. Figure 19-20 Next, a pipe expansion tool 4B according to Embodiment 2 will be described. In Embodiment 2, the description will be centered on the structure that is different from Embodiment 1.

[0124] Fig.19 It is a side view of the pipe expansion tool 4B. Fig. 20 This is an enlarged view of the tip portion of the pipe expansion tool 4B.

[0125] like Fig.19 and Fig. 20 As shown, the pipe expansion tool 4B includes a truncated cone portion 45 disposed between the guide portion 42 and the spherical cone portion 43 .

[0126] The truncated cone portion 45 is formed in a truncated cone shape with the upper base facing the guide portion 42 and the lower base facing the spherical cone portion 43. Fig. 20 As shown, the outer diameter of the truncated cone portion 45 increases from the outer diameter D6 of the guide portion 42 to the outer diameter D8 of the minimum outer diameter of the -Z end of the spherical cone portion 43 from the guide portion 42 toward the spherical cone portion 43, that is, toward the +Z direction. As a result, the truncated cone portion 45 has an inclined surface 46 inclined relative to the central axis L. In the first embodiment, it is explained that when the tube is expanded by the tube expansion tool 4A, a compressive force is applied in the tube 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 the equivalent stress, but the inclined surface 46 changes the direction and magnitude of the compressive force. As a result, the inclined surface 46 can reduce the damage to the heat transfer tube of the second embodiment during the tube expansion by the tube expansion tool 4B.

[0127] The angle θ of the inclined surface 46 relative to the central axis L is preferably 40° or more and less than 60°. The angle θ is, for example, 45°. This is because such an angle θ can suppress buckling and reduce the damage value described in the first embodiment.

[0128] In addition, the truncated cone portion 45 is an example of a frustum portion referred to in the present disclosure.

[0129] As described above, in Embodiment 2, the tube expansion tool 4B includes a truncated cone portion 45 that tapers toward the distal end on the -Z side, i.e., the distal end side, of the spherical cone portion 43. Therefore, the tube expansion tool 4B can direct the direction of the compressive force applied to the heat transfer tube of Embodiment 2 in a specific direction during tube expansion, and adjust the magnitude of the compressive force applied in the direction, thereby reducing damage to the heat transfer tube of Embodiment 2. As a result, the tube expansion tool 4B can suppress the rupture of the heat transfer tube of Embodiment 2.

[0130] The heat transfer tube 1A, the heat exchanger 100, the tube expansion tools 4A, 4B, the tube expansion device, the method for connecting the heat transfer tube 1A and the tube, and the method for manufacturing the heat exchanger 100 according to the embodiment of the present disclosure are described above, but the heat transfer tube 1A, the heat exchanger 100, the tube expansion tools 4A, 4B, the tube expansion device, the method for connecting the heat transfer tube 1A and the tube, and the method for manufacturing the heat exchanger 100 are not limited to these.

[0131] For example, in Embodiment 1, the connection object connected to the heat transfer tube 1A is the elbow 3, but the connection object connected to the heat transfer tube 1A is not limited thereto. The connection object connected to the heat transfer tube 1A may be a tube. For example, the connection object may also be a connecting tube or a refrigerant tube for connecting the heat exchanger 100 to an external device. In addition, the connection object may be a tube, so the shape of the tube is not limited, and the tube may be a tube other than a round tube.

[0132] In embodiments 1 and 2, the heat transfer tube 1A is a round 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 only needs to have a spherical band shape with an inner diameter at the end larger than the inner diameter at the base end and a flared portion 30 for the tube of the connection object to pass through. In addition, the flared portion 30 can be connected to the tube by filling the brazing material in the gap between the tube and the inner wall of the flared portion 30 itself. As long as this condition is met, the shape of the heat transfer tube 1A is arbitrary. Therefore, the tube cross section of the heat transfer tube 1A can also be flat.

[0133] Fig.21 It is a perspective view of a modified example of the heat transfer tube 1A according to the first embodiment.

[0134] like Fig.21 As shown, the heat transfer tube 1A may also be a flat tube with an oblong cross section. In this case, the expanded portion 30 may be a spherical band shape obtained by cutting the spherical surface of a long sphere in the long radius direction with two parallel planes. Furthermore, in order to form such an expanded portion 30, the spherical table portion 43 of the expansion tools 4A and 4B may be a spherical table shape obtained by cutting the spherical body of the long sphere in the long radius direction with the same two parallel planes.

[0135] In the first and second embodiments, the heat transfer tube 1A has a spiral groove 14 inside. However, the heat transfer tube 1A is not limited thereto. As described above, the heat transfer tube 1A only needs to have a spherical shape with an inner diameter at the end larger than that at the base end, and a flared portion 30 through which a tube to be connected passes. Furthermore, the flared portion 30 only needs to be connected to the tube by a brazing material filled in a gap between the tube and the inner wall of the flared portion 30 itself. Therefore, the internal structure of the heat transfer tube 1A, that is, the flow path shape, is arbitrary.

[0136] For example, the heat transfer tube 1A may have a plurality of parallel grooves extending parallel to the tube axis direction on the inner wall. When there are grooves such as the spiral groove 14 and the parallel grooves, the heat transfer tube 1A is easily broken during the tube expansion, but the heat transfer tube 1A has the above-mentioned flared portion 30, thereby suppressing the heat transfer tube 1A from breaking during the tube expansion. In addition, the heat transfer tube 1A may have no grooves and have a smooth inner wall.

[0137] In Embodiments 1 and 2, the flared portion 30 is provided at the upper end of the heat transfer tube 1A. However, as long as the above conditions are met, the flared portion 30 may be provided at any end of the heat transfer tube 1A. For example, when 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.

[0138] In the first and second embodiments, the expansion tools 4A and 4B have a guide portion 42. However, the expansion tools 4A and 4B are not limited thereto. The expansion tools 4A and 4B only need to have a spherical portion 43 whose outer diameter at the distal end is smaller than that at the proximal end and whose distal end is sized to be inserted into the tube end portion of the heat transfer tube 1A. Furthermore, the expanded portion 30 can be formed by inserting the spherical portion 43 from the distal end to the proximal end into the tube end portion of the heat transfer tube 1A. The expansion tools 4A and 4B only need to satisfy this condition, so the presence or absence of the guide portion 42 is optional.

[0139] Fig. 22 4A is a side view of a modified example of the expansion tool 4A. Fig. 22 , only the tip portion of a modified example of the pipe expanding tool 4A is shown.

[0140] like Fig. 22 As shown, the tube expansion tool 4A may include only the spherical portion 43 at the distal end of the rod portion 41. This is because even in such a form, the expanded portion 30 of the above-mentioned shape can be formed. Furthermore, the heat transfer tube 1A can be prevented from being broken during the forming process.

[0141] In addition, in embodiments 1 and 2, the outer diameter of the spherical table portion 43 of the expansion tool 4A decreases by a certain amount after reaching the maximum outer diameter D7 toward the base end on the opposite side of the terminal. However, the spherical table portion 43 is not limited to this. The spherical table portion 43 only needs to have an outer diameter at the terminal that is smaller than the outer diameter at the base end and the terminal is a size that can be inserted into the tube end portion of the heat transfer tube 1A. Therefore, the outer diameter of the spherical table portion 43 does not need to decrease by a certain amount after reaching the maximum value on the base end side. The outer diameter of the spherical table portion 43 may also be the maximum at the base end. In this case, the expansion tool 4A is not easy to be pulled out of the heat transfer tube 1A after expansion, compared with the method in which the outer diameter of the spherical table portion 43 once reaches the maximum value on the base end side and then decreases by a certain amount, but it is still possible to suppress the rupture of the heat transfer tube 1A during expansion.

[0142] The pipe expanding tools 4A and 4B may also be referred to as punches. Furthermore, the pipe expanding tools 4A and 4B may be attached to a pipe expanding device including a driving unit capable of holding the rod 41 and moving the rod 41 in the axial direction thereof.

[0143] 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 of connecting the heat transfer tube 1A and the tube, and the method of manufacturing the heat exchanger 100 are not limited to the above-mentioned embodiments, and various modifications and substitutions can be made.

[0144] (Note 1)

[0145] A heat transfer pipe having 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 a pipe to be connected is passed through the flared portion.

[0146] The flared portion is connected to the tube via a brazing material filled in a gap between the tube and an inner wall of the flared portion itself.

[0147] (Note 2)

[0148] The heat transfer tube according to Supplement 1, wherein:

[0149] The flared portion has a fillet formed by the brazing material on the inner side at the tip end side.

[0150] (Note 3)

[0151] The heat transfer tube according to Supplement 1 or 2, wherein:

[0152] The flared portion has an end surface having an inner wall side chamfered at the distal end.

[0153] (Note 4)

[0154] The heat transfer tube according to Supplementary Note 3, wherein:

[0155] The flared portion has a thickness that decreases from the base end toward the tip end.

[0156] (Note 5)

[0157] A heat transfer tube according to any one of Supplementary Notes 1 to 4, wherein:

[0158] The flared portion has a spiral groove on the inner wall.

[0159] (Note 6)

[0160] A heat exchanger comprising:

[0161] A plurality of heat transfer tubes as described in any one of Supplementary Notes 1 to 5;

[0162] a fin mounted on the heat transfer tube; and

[0163] The tube.

[0164] (Note 7)

[0165] A tube expansion tool is used to form an expanded portion at the tube end of a heat transfer tube for a tube to be connected to pass through, wherein:

[0166] The pipe expansion tool includes a spherical table portion, the outer diameter of the distal end of the spherical table portion is smaller than the outer diameter of the proximal end, and the distal end is sized to be inserted into the pipe end portion.

[0167] The flared portion is formed by inserting the spherical table portion into the pipe end portion from the distal end to the base end.

[0168] (Note 8)

[0169] The pipe expansion tool according to Supplementary Note 7, wherein:

[0170] The outer diameter of a portion of the spherical base portion located between the tip and the base end is larger than the outer diameter of the base end.

[0171] (Note 9)

[0172] The pipe expansion tool according to Supplement 7 or 8, wherein:

[0173] A frustum portion is provided on the distal end side of the spherical table portion, and the frustum portion becomes thinner toward the distal end.

[0174] (Note 10)

[0175] A pipe expansion tool according to any one of Supplementary Notes 7 to 9, wherein:

[0176] A guide portion that can be fitted with the inner peripheral surface of the pipe end portion is provided on the distal end side of the spherical base portion.

[0177] (Note 11)

[0178] A pipe expansion tool according to any one of Supplementary Notes 7 to 10, wherein:

[0179] The outer diameter of the spherical table portion and the inner diameter of the flared portion are the same diameter.

[0180] (Note 12)

[0181] A pipe expansion device, comprising:

[0182] The pipe expansion tool as described in any one of Notes 7 to 11; and

[0183] The driving mechanism presses the spherical base portion of the tube expansion tool into the heat transfer tube.

[0184] (Note 13)

[0185] A method for connecting a heat transfer tube to another tube, wherein a tube to be connected is connected to an end portion of the heat transfer tube. The method for connecting a heat transfer tube to another tube comprises the following steps:

[0186] Inserting the spherical table portion provided in any one of the pipe expansion tools of Supplementary Notes 7 to 11 into the pipe end portion from the distal end to the base end of the spherical table portion, thereby forming a flared portion at the pipe end portion;

[0187] inserting the tube into the flared portion; and

[0188] The heat transfer tube and the tube are connected by filling a brazing material in a gap between the inner wall of the expanded portion and the tube.

[0189] (Note 14)

[0190] The method for connecting heat transfer tubes according to Appendix 13, wherein:

[0191] In the step of connecting the heat transfer tube to the tube, a brazing material larger than the gap between the inner wall of the flared portion and the tube is placed at the end of the flared portion, and the brazing material is melted to fill the gap.

[0192] (Note 15)

[0193] A method for manufacturing a heat exchanger, comprising the method for connecting heat transfer tubes as described in Note 13 or 14.

[0194] The present disclosure is capable of various embodiments and modifications without departing from the broad spirit and scope of the present disclosure. In addition, the above-mentioned embodiments are used to illustrate the present disclosure and do not limit the scope of the present disclosure. That is, the scope of the present disclosure is not shown by the embodiments, but by the claims. Moreover, various modifications implemented within the scope of the claims and the equivalent public meanings are considered to be within the scope of the present disclosure.

[0195] This application is based on Japanese Patent Application No. 2022-80337 filed on May 16, 2022. In this specification, the specification, claims, and drawings of Japanese Patent Application No. 2022-80337 are incorporated herein by reference in their entirety.

[0196] Description of symbols

[0197] 1A: heat transfer tube; 2: fin; 3: elbow; 4A, 4B: expansion tool; 5: brazing material; 6: fillet; 10: main body; 11, 12: straight part; 13: curved part; 14: spiral groove; 20: tube holding part; 30: flaring part; 40: expansion tool; 41: rod; 42: guide part; 43: spherical table part; 44: base end part; 45: frustum part; 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: center axis; P1-P3: part; R: range; T: thickness; W1, W2: width; θ: angle.

Claims

1. A heat transfer pipe, comprising a flared portion, wherein the flared portion has a spherical shape in which the inner diameter of the distal end is larger than the inner diameter of the proximal end, and a pipe to be connected is passed through the flared portion. The flared portion is connected to the tube via a brazing material filled in a gap between the tube and an inner wall of the flared portion itself.

2. The heat transfer tube according to claim 1, wherein: The flared portion has a fillet formed by the brazing material on the inner side at the tip end side.

3. The heat transfer tube according to claim 1 or 2, wherein: The flared portion has an end surface having a shape in which the inner wall side is chamfered at the distal end.

4. The heat transfer tube according to claim 3, wherein: The flared portion has a thickness that decreases from the base end toward the tip end.

5. The heat transfer tube according to any one of claims 1 to 4, wherein: The flared portion has a spiral groove on the inner wall.

6. A heat exchanger comprising: A plurality of heat transfer tubes according to any one of claims 1 to 5; a fin mounted on the heat transfer tube; and The tube.

7. A tube expansion tool for forming an expanded portion at the end of a heat transfer tube for a tube to be connected to pass through, wherein: The pipe expansion tool includes a spherical table portion, the outer diameter of the distal end of the spherical table portion is smaller than the outer diameter of the proximal end, and the distal end is sized to be inserted into the pipe end portion. The flared portion is formed by inserting the spherical table portion into the pipe end portion from the distal end to the base end.

8. The pipe expansion tool according to claim 7, wherein: The outer diameter of a portion of the spherical base portion located between the tip and the base end is larger than the outer diameter of the base end.

9. The pipe expansion tool according to claim 7 or 8, wherein: A frustum portion is provided on the distal end side of the spherical table portion, the frustum portion becomes thinner toward the distal end, and a base portion has the same thickness as the distal end of the spherical table portion.

10. The pipe expansion tool according to any one of claims 7 to 9, wherein: A guide portion that can be fitted with the inner peripheral surface of the pipe end portion is provided on the distal end side of the spherical base portion.

11. The pipe expansion tool according to any one of claims 7 to 10, wherein: The outer diameter of the spherical table portion and the inner diameter of the flared portion are the same diameter.

12. A pipe expansion device comprising: The pipe expansion tool according to any one of claims 7 to 11; and The driving mechanism presses the spherical base portion of the tube expansion tool into the heat transfer tube.

13. A method for connecting a heat transfer tube to another tube, wherein a tube to be connected is connected to an end portion of the heat transfer tube, the method comprising the following steps: Inserting the spherical table portion provided in the pipe expansion tool according to any one of claims 7 to 11 into the pipe end portion from the distal end to the proximal end, thereby forming a flared portion in the pipe end portion; inserting the tube into the flared portion; as well as The heat transfer tube and the tube are connected by filling a brazing material in a gap between the inner wall of the expanded portion and the tube.

14. The method for connecting heat transfer tubes according to claim 13, wherein: In the step of connecting the heat transfer tube to the tube, a brazing material larger than the gap between the inner wall of the flared portion and the tube is placed at the end of the flared portion, and the brazing material is melted to fill the gap.

15. A method for manufacturing a heat exchanger, comprising the method for connecting heat transfer tubes according to claim 13 or 14.

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