Double-pipe heat exchanger and its manufacturing method

Abstract

To provide a double-tube type heat exchanger which is simple in a structure, and high in the assembling performance of an inner tube and an outer tube, and a manufacturing method therefor.SOLUTION: A double-tube type heat exchanger 1 comprises an outer tube 2 and an inner tube 3 which is inserted into the outer tube 2. An inside flow passage 4 is formed in the inner tube 3, an outside flow passage 5 is formed between the inner tube 3 and the outer tube 2, and heat is exchanged between fluid flowing in the inside flow passage 4 and fluid flowing in the outside flow passage 5. The inner tube 3 has an irregular part 32 having irregularities at an external peripheral face. A large-diameter seal part S1 is interposed between one end part 20 of the outer tube 2 in an axial direction and the inner tube 3. A small-diameter seal part S2 which is smaller than the large-diameter seal part S1 in a diameter is interposed between the other end part 21 of the outer tube 2 in the axial direction and the inner tube 3. The outside flow passage 5 and the irregular part 32 are arranged by using a difference of axial positions of the large-diameter seal part S1 and the small-diameter seal part S2, and a diameter difference between the seal parts.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a double-pipe heat exchanger used in, for example, an air conditioner, and a method for manufacturing the same. [Background technology]

[0002] Patent Documents 1 to 4 disclose double-pipe heat exchangers. The double-pipe heat exchangers include an outer pipe and an inner pipe. The inner pipe is disposed radially inside the outer pipe. An inner flow path is formed inside the inner pipe. An outer flow path is formed between the inner pipe and the outer pipe. A spiral portion is disposed on the pipe wall of the inner pipe.

[0003] Double-pipe heat exchangers are used, for example, in the refrigeration cycle of vehicle air conditioners. In this refrigeration cycle, the inner flow path of the double-pipe heat exchanger is located between the evaporator and the compressor. The outer flow path is located between the condenser and the expansion valve. Heat is exchanged between a low-pressure refrigerant flowing through the inner flow path and a high-pressure refrigerant flowing through the outer flow path via the spiral portion of the inner pipe. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-162238 [Patent Document 2] Japanese Patent Application Publication No. 2018-025374 [Patent Document 3] Japanese Patent Application Publication No. 2020-109329 [Patent Document 4] Japanese Patent Application Laid-Open No. 2002-318015 Summary of the Invention [Problem to be solved by the invention]

[0005] Both axial ends of the outer flow passage of a double-pipe heat exchanger are fluid-tightly sealed by seal portions (connections between the outer and inner pipes). In the double-pipe heat exchangers of Patent Documents 1 to 4, the diameters of both seal portions are the same. Therefore, it is difficult to arrange the outer flow passage and the spiral portion by utilizing the difference in diameter between the two seal portions. This tends to result in a complex structure. Furthermore, in the double-pipe heat exchangers of Patent Documents 1 to 4, the diameters of both seal portions are the same, so the inner pipe is likely to interfere with the outer pipe when inserting the inner pipe into the outer pipe. This results in poor assembly of the inner pipe and the outer pipe. Therefore, an object of the present disclosure is to provide a double-pipe heat exchanger having a simple structure and high assembly ease between the inner pipe and the outer pipe, and a method for manufacturing the same. [Means for solving the problem]

[0006] In order to solve the above problems, the double-pipe heat exchanger of the present disclosure is a double-pipe heat exchanger comprising an outer pipe and an inner pipe inserted into the outer pipe, an inner flow path formed inside the inner pipe, an outer flow path formed between the inner pipe and the outer pipe, and performing heat exchange between a fluid flowing through the inner flow path and a fluid flowing through the outer flow path, wherein the inner pipe has an uneven portion with unevenness on its outer peripheral surface, a large-diameter seal portion is interposed between one axial end of the outer pipe and the inner pipe, and a small-diameter seal portion having a diameter smaller than that of the large-diameter seal portion is interposed between the other axial end of the outer pipe and the inner pipe, and the outer flow path and the uneven portion are positioned by utilizing the difference in axial position and diameter between the large-diameter seal portion and the small-diameter seal portion.

[0007] In order to solve the above-mentioned problems, the present disclosure provides a method for manufacturing a double-pipe heat exchanger, which includes an outer pipe and an inner pipe inserted into the outer pipe, an inner flow path formed inside the inner pipe, an outer flow path formed between the inner pipe and the outer pipe, and heat exchange between a fluid flowing in the inner flow path and a fluid flowing in the outer flow path, wherein the front side in an insertion direction when the inner pipe is inserted into the outer pipe is defined as the front side, and the rear side in the insertion direction is defined as the rear side, and the inner pipe has an uneven portion with unevenness on its outer peripheral surface, and a large-diameter pipe is provided between the rear end of the outer pipe and the inner pipe. a seal portion interposed between the front end of the outer pipe and the inner pipe, and a small-diameter seal portion having a diameter smaller than the large-diameter seal portion interposed between the front end of the inner pipe and the inner pipe, and the method comprises: an insertion step of inserting the front end of the inner pipe into the rear end of the outer pipe; a positioning step of advancing the inserted inner pipe relative to the outer pipe to position the inner pipe and the outer pipe; and a sealing step of connecting the rear end of the positioned outer pipe to the inner pipe to form the large-diameter seal portion, and connecting the front end of the positioned outer pipe to the inner pipe to form the small-diameter seal portion.

[0008] Here, "connection" in the "sealing process" includes a form in which the outer tube (rear end, front end) and the inner tube are directly connected (for example, a form in which the outer tube and the inner tube are connected by crimping, bonding, welding, brazing, etc.), and a form in which the outer tube and the inner tube are indirectly connected (for example, a form in which the outer tube and the inner tube are connected via a sealing member). [Effects of the Invention]

[0009] In the double-pipe heat exchanger of the present disclosure, a space is provided due to the difference in axial position between the large-diameter seal portion and the small-diameter seal portion and the difference in diameter between the large-diameter seal portion and the small-diameter seal portion. According to the double-pipe heat exchanger of the present disclosure, this space can be used to arrange at least a part of the outer flow path and at least a part of the concave-convex portion. This simplifies the structure of the double-pipe heat exchanger.

[0010] Furthermore, according to the manufacturing method of the double-pipe heat exchanger of the present disclosure, the front end of the inner pipe can be easily inserted into the rear end of the outer pipe by utilizing the diameter difference between the large-diameter seal portion and the small-diameter seal portion, thereby improving the ease of assembly of the inner pipe and the outer pipe. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a heat pump cycle of a vehicle air conditioner in which a double-pipe heat exchanger according to the first embodiment is arranged. [Figure 2] FIG. 2 is a perspective view of the double-pipe heat exchanger. [Figure 3] FIG. 3 is an exploded perspective view of the double-pipe heat exchanger. [Figure 4] FIG. 4 is a cross-sectional view of the double-pipe heat exchanger taken in the front-rear direction. [Figure 5] FIG. 5 is a cross-sectional view taken along the VV direction of FIG. [Figure 6] 6A and 6B are cross-sectional views of the mold in the front-rear direction at an inner pipe forming step (initial stage) of the manufacturing method of the double-pipe heat exchanger, respectively, and are cross-sectional views of the mold in the front-rear direction at the same step (final stage). [Figure 7] 7(A) and 7(B) are cross-sectional views of the mold in the front-rear direction at the outer tube molding step (initial stage) of the manufacturing method, respectively. [Figure 8] 8A is a cross-sectional view of the inner and outer tubes in the insertion step (initial stage) of the manufacturing method, and FIG. 8B is a cross-sectional view of the inner and outer tubes in the positioning step (initial stage) of the same step (final stage). [Figure 9] 9(A) is a cross-sectional view of the inner and outer pipes in the positioning step (final stage) and sealing step of the manufacturing method, and FIG. 9(B) is a cross-sectional view of the inner and outer pipes in the piping connection step of the manufacturing method. [Figure 10] FIG. 10 is a cross-sectional view of the double-pipe heat exchanger of the second embodiment taken along the front-rear direction. [Figure 11] FIG. 11 is a cross-sectional view of the double-pipe heat exchanger of the third embodiment taken along the front-rear direction. [Figure 12]Fig. 12(A) is a cross-sectional view in the front-rear direction of the double-pipe heat exchanger of the fourth embodiment, and Fig. 12(B) is a cross-sectional view in the direction XIIB-XIIB of Fig. 12(A). [Figure 13] Figure 13(A) is a radial cross-sectional view of a double-pipe heat exchanger according to another embodiment (part 1), and Figure 13(B) is a radial cross-sectional view of a double-pipe heat exchanger according to another embodiment (part 2). DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the double-pipe heat exchanger and the manufacturing method thereof according to the present disclosure will be described.

[0013] First Embodiment [Heat pump cycle configuration] First, the configuration of the heat pump cycle of the vehicle air conditioner in which the double-pipe heat exchanger of this embodiment is disposed will be described. Fig. 1 shows a schematic diagram of the heat pump cycle of the vehicle air conditioner in which the double-pipe heat exchanger of this embodiment is disposed.

[0014] The heat pump cycle 9 includes a compressor 90, a condenser (exterior heat exchanger) 91, an expansion valve (expander) 92, and an evaporator (interior heat exchanger) 93. During cooling, a refrigerant (heat medium) circulates through the heat pump cycle 9 in the order of the compressor 90 → the condenser 91 → the expansion valve 92 → the evaporator 93 → and back to the compressor 90. The refrigerant is included in the concept of "fluid" in this disclosure.

[0015] The compressor 90 compresses the refrigerant to a high temperature and high pressure using driving force from the vehicle's driving source (engine, battery, etc.). The condenser 91 condenses and liquefies the refrigerant through heat exchange with outside air. The expansion valve 92 isenthalpically reduces the pressure and expands the refrigerant. The evaporator 93 evaporates the refrigerant through heat exchange with the vehicle interior. During this process, the air inside the vehicle interior is cooled by the latent heat of evaporation of the refrigerant, etc. In this way, during cooling, the heat pump cycle 9 absorbs heat from the vehicle interior via the refrigerant and discharges the heat to the outside of the vehicle. The double-pipe heat exchanger 1 of this embodiment forms part of the piping of the heat pump cycle 9.

[0016] As will be described later, the double-pipe heat exchanger 1 includes an inner flow path 4 and an outer flow path 5. The inner flow path 4 is disposed between the downstream end of the evaporator 93 and the upstream end of the compressor 90. The outer flow path 5 is disposed between the downstream end of the condenser 91 and the upstream end of the expansion valve 92. Heat exchange occurs between the low-pressure refrigerant flowing through the inner flow path 4 and the high-pressure refrigerant flowing through the outer flow path 5.

[0017] [Configuration of double-pipe heat exchanger] Next, the configuration of the double-pipe heat exchanger of this embodiment will be described. In the following figures, the front-rear direction corresponds to the "axial direction" in this disclosure. The rear side corresponds to the "one axial end side" and "rear side in the insertion direction" in this disclosure. The front side corresponds to the "other axial end side" and "front side in the insertion direction" in this disclosure.

[0018] Fig. 2 shows a perspective view of the double-pipe heat exchanger of this embodiment. Fig. 3 shows an exploded perspective view of the double-pipe heat exchanger. Fig. 4 shows a cross-sectional view of the double-pipe heat exchanger in the front-to-rear direction. Fig. 5 shows a cross-sectional view of Fig. 4 in the VV direction. As shown in Figs. 2 to 5, the double-pipe heat exchanger 1 of this embodiment includes an outer pipe 2 and an inner pipe 3.

[0019] (outer tube) The outer pipe 2 has an overall cylindrical shape. The outer pipe 2 is integrally formed from the same material (metal). The outer pipe 2 includes an outer pipe first medium diameter portion (one axial end, rear end) 20, an outer pipe small diameter portion (the other axial end, front end) 21, an outer pipe large diameter portion 23, and an outer pipe second medium diameter portion 24.

[0020] The outer pipe first medium diameter section 20 has a circular tubular shape. The outer pipe first medium diameter section 20 has an opening 200. The opening 200 is the rear end of the outer pipe 2. The outer pipe small diameter section 21 is disposed on the front side of the outer pipe first medium diameter section 20. The outer pipe small diameter section 21 has a circular tubular shape. The outer pipe small diameter section 21 has an opening 210. The opening 210 is the front end of the outer pipe 2. The outer pipe large diameter section 23 is connected to the front side of the outer pipe first medium diameter section 20 via a tapered pipe section 29a whose diameter increases from the rear side to the front side. The outer pipe large diameter section 23 has a larger inner diameter (hereinafter, "inner diameter" and "outer diameter" mean diameter unless otherwise specified) than the outer pipe first medium diameter section 20. A first opening 230 is formed in the pipe wall of the outer pipe large diameter section 23. The first opening 230 is connected to the first expansion section 51 of the outer flow path 5. The first pipe 94 is inserted into the first opening 230. The first pipe 94 is connected to the upstream end of the expansion valve 92 shown in FIG.

[0021] The outer pipe second medium diameter section 24 is connected to the front side of the outer pipe large diameter section 23 via a tapered pipe section 29b whose diameter decreases from the rear side to the front side. The outer pipe second medium diameter section 24 is connected to the rear side of the outer pipe small diameter section 21 via a tapered pipe section 29c whose diameter decreases from the rear side to the front side. The outer pipe second medium diameter section 24 has a circular pipe shape. The outer pipe second medium diameter section 24 has the same inner diameter as the outer pipe first medium diameter section 20. A second opening 240 is formed in the pipe wall of the outer pipe second medium diameter section 24. The second opening 240 is connected to the second expansion section 52 of the outer flow path 5. A second pipe 95 is inserted into the second opening 240. The second pipe 95 is connected to the downstream end of the condenser 91 shown in FIG. 1 .

[0022] (inner tube) The inner pipe 3 has an overall cylindrical shape. The inner pipe 3 is integrally formed from the same material (metal). The inner pipe 3 is disposed radially inside the outer pipe 2. The inner pipe 3 includes an inner pipe large diameter portion 30, an inner pipe first small diameter portion 31, a spiral portion 32, and an inner pipe second small diameter portion 33.

[0023] The inner pipe large diameter section 30 is disposed radially inside the outer pipe first medium diameter section 20. The inner pipe large diameter section 30 has a circular tubular shape. A large diameter seal section S1 is disposed between the outer peripheral surface of the inner pipe large diameter section 30 and the inner peripheral surface of the outer pipe first medium diameter section 20. The large diameter seal section S1 fluid-tightly seals the rear end of the outer flow passage 5 (to prevent refrigerant from leaking from the outer flow passage 5 to the outside).

[0024] The inner pipe first small diameter portion 31 is disposed radially inward of the outer pipe small diameter portion 21. The inner pipe first small diameter portion 31 has a circular tubular shape. A small diameter seal portion S2 is disposed between the outer peripheral surface of the inner pipe first small diameter portion 31 and the inner peripheral surface of the outer pipe small diameter portion 21. The small diameter seal portion S2 fluid-tightly seals the front end of the outer flow path 5. The small diameter seal portion S2 has a smaller diameter than the large diameter seal portion S1. The small diameter seal portion S2 is disposed forward of the large diameter seal portion S1. The inner pipe first small diameter portion 31 has an opening 310. The opening 310 is the front end of the inner pipe 3. The opening 310 is disposed forward of the opening 210. In other words, the front end of the inner pipe 3 protrudes forward from the front end of the outer pipe 2. The opening 310 is continuous with the downstream end of the inner flow path 4. Opening 310 communicates with the upstream end of compressor 90 shown in FIG.

[0025] The spiral portion 32 is disposed between the inner pipe large diameter portion 30 and the inner pipe first small diameter portion 31. The spiral portion 32 is disposed by utilizing the difference in front-to-rear position and diameter between the large diameter seal portion S1 and the small diameter seal portion S2. The spiral portion 32 has a spiral tubular shape. The spiral portion 32 has spirally shaped irregularities that run along the pipe wall of the inner pipe 3. Specifically, the spiral portion 32 has three spirally extending recesses 32a and three spirally extending protrusions 32b. The protrusions 32b protrude radially outward relative to the recesses 32a. Conversely, the recesses 32a recede radially inward relative to the protrusions 32b.

[0026] The rear end of the spiral portion 32 is connected to the inner pipe large diameter portion 30 by a convex portion 32b. Therefore, no tapered pipe portion for adjusting the diameter difference is interposed between the spiral portion 32 and the inner pipe large diameter portion 30. The front end of the spiral portion 32 is connected to the inner pipe first small diameter portion 31 by a concave portion 32a. Therefore, no tapered pipe portion for adjusting the diameter difference is interposed between the spiral portion 32 and the inner pipe first small diameter portion 31. The rear end of the spiral portion 32 is located forward of the rear end of the outer pipe large diameter portion 23. On the other hand, the front end of the spiral portion 32 is located rearward of the rear end of the second opening 240.

[0027] The inner pipe second small diameter section 33 is connected to the rear side of the inner pipe large diameter section 30 via a tapered pipe section 39a whose diameter increases from the rear side to the front side. The inner pipe second small diameter section 33 has a circular pipe shape. The inner pipe second small diameter section 33 has the same outer diameter and inner diameter as the inner pipe first small diameter section 31. The inner pipe second small diameter section 33 has an opening 330. The opening 330 is the rear end of the inner pipe 3. The opening 330 is located rearward of the opening 200. In other words, the rear end of the inner pipe 3 protrudes rearward from the rear end of the outer pipe 2. The opening 330 is connected to the upstream end of the inner flow path 4. The opening 330 is connected to the downstream end of the evaporator 93 shown in FIG. 1.

[0028] (inner flow path, outer flow path) An inner flow path 4 is formed inside the inner pipe 3. The inner flow path 4 is arranged between the downstream end of the evaporator 93 and the upstream end of the compressor 90. An outer flow path 5 is formed between the inner pipe 3 and the outer pipe 2. The outer flow path 5 is arranged between the downstream end of the condenser 91 and the upstream end of the expansion valve 92. The outer flow path 5 includes a spiral flow path section 50, a first expansion section 51, and a second expansion section 52. The outer flow path 5 is arranged by utilizing the difference in front-to-rear position, or diameter, between the large diameter seal section S1 and the small diameter seal section S2.

[0029] The spiral flow path section 50 is disposed radially outside the spiral section 32 and radially inside the outer pipe second medium diameter section 24. The refrigerant flows spirally through the spiral flow path section 50 from the front side (upstream side) to the rear side (downstream side).

[0030] The first expansion section 51 is disposed rearward of the spiral flow path section 50. The first expansion section 51 has a larger flow path cross-sectional area than the spiral flow path section 50. The first expansion section 51 is disposed radially outward of the spiral section 32 and the inner pipe large diameter section 30, and radially inward of the outer pipe large diameter section 23. The first expansion section 51 is connected to the first piping 94.

[0031] The second expansion section 52 is disposed forward of the spiral flow path section 50. The second expansion section 52 has a larger flow path cross-sectional area than the spiral flow path section 50. The second expansion section 52 is disposed radially outward of the inner pipe first small diameter section 31 and radially inward of the outer pipe second medium diameter section 24. In other words, the rear end of the outer pipe small diameter section 21 is disposed shifted forward relative to the rear end of the inner pipe first small diameter section 31. Corresponding to this positional shift, a space is defined between the inner pipe first small diameter section 31 and the outer pipe second medium diameter section 24. The second expansion section 52 corresponds to this space. The second expansion section 52 is connected to the second piping 95.

[0032] [Manufacturing method for double-pipe heat exchangers] Next, a method for manufacturing the double-pipe heat exchanger of this embodiment will be described. The method for manufacturing the double-pipe heat exchanger 1 includes an inner pipe molding step, an outer pipe molding step, an opening forming step, an insertion step, a positioning step, a sealing step, and a piping connection step.

[0033] (Inner tube forming process) Fig. 6(A) shows a cross-sectional view of the mold in the front-rear direction at the inner pipe molding step (initial stage) of the manufacturing method of the double-pipe heat exchanger of this embodiment, and Fig. 6(B) shows a cross-sectional view of the mold in the front-rear direction at the same step (final stage).

[0034] In this process, the inner tube 3 is produced from a tubular inner tube blank 3a by so-called hydroforming. As shown in FIGS. 6(A) and 6(B), the mold 7 includes a first die 70, a second die 71, a first punch 72, and a second punch 73. A substantially cylindrical cavity C1 is defined between a die surface 700 of the first die 70 and a die surface 710 of the second die 71. The die surface 700 of the first die 70 and the die surface 710 of the second die 71 are each provided with the shape of the outer peripheral surface of the inner tube 3 (a concave-convex inverted shape). The first punch 72 is located at the rear end of the cavity C1. An opening 720 is formed in the first punch 72. The second punch 73 is located at the front end of the cavity C1. An opening 730 is formed in the second punch 73.

[0035] In this process, first, the inner tube blank 3a is placed in the cavity C1 of the mold 7, which is in an open state (a state in which the first mold 70 and the second mold 71 are separated). Next, the mold 7 is switched from the open state to a closed state (a state in which the first mold 70 and the second mold 71 are in contact). Next, the rear end of the inner tube blank 3a is sealed and pressed by the first punch 72. At the same time, the front end of the inner tube blank 3a is sealed and pressed by the second punch 73. Then, high-pressure water (pressure medium) is injected into the inner tube blank 3a from the outside through the openings 720 and 730. The water pressure causes the inner tube blank 3a (more specifically, the portions of the inner tube blank 3a corresponding to the convex portion 32b of the helical portion 32, the inner tube large-diameter portion 30, and the tapered tube portion 39a of the inner tube 3 shown in FIG. 4) to undergo diametric expansion and deformation. Due to this deformation, the shapes of the die surfaces 700, 710 are transferred to the outer peripheral surface of the inner tube material 3a. In this manner, the inner tube 3 is formed.

[0036] (Outer tube forming process, opening opening process) Fig. 7(A) shows a cross-sectional view of the mold in the front-rear direction during the outer tube molding step (initial stage) of the manufacturing method of the double-pipe heat exchanger of this embodiment, and Fig. 7(B) shows a cross-sectional view of the mold in the front-rear direction during the same step (final stage).

[0037] In the outer tube forming step, the outer tube 2 is produced from a tubular outer tube blank 2a by so-called hydroforming. As shown in Figures 7(A) and 7(B), the configuration of the mold 8 is the same as that of the mold 7. That is, the mold 8 includes a first die 80, a second die 81, a first punch 82, and a second punch 83. A substantially cylindrical cavity C2 is defined between the mold surfaces 800 and 810. The mold surfaces 800 and 810 are each given the shape of the outer peripheral surface of the outer tube 2 (a concave-convex inverted shape).

[0038] As with the inner tube molding process described above, in the outer tube molding process, first, the outer tube blank 2a is placed in the cavity C2 of the mold 8 in the mold open state (a state in which the first mold 80 and the second mold 81 are separated). Next, the mold 8 is switched from the mold open state to the mold closed state (a state in which the first mold 80 and the second mold 81 are in contact). Next, the front and rear ends of the outer tube blank 2a are sealed and pressed by the first punch 82 and the second punch 83. Then, high-pressure water (pressure medium) is injected into the outer tube blank 2a from the outside through the openings 820 and 830. Due to the water pressure, the outer tube blank 2a (more specifically, the portions of the outer tube blank 2a other than the outer tube small diameter portion 21 of the outer tube 2 shown in FIG. 4 (the outer tube first medium diameter portion 20, the outer tube large diameter portion 23, the outer tube second medium diameter portion 24, and the tapered tube portions 29a-29c)) undergoes diameter expansion deformation. As a result of this deformation, the shapes of the die surfaces 800, 810 are transferred to the outer peripheral surface of the outer tube blank 2a. In this manner, the outer tube 2 is formed.

[0039] In the opening forming step, a first opening 230 shown in Fig. 4 is formed in the outer pipe large diameter portion 23 shown in Fig. 7(B), and a second opening 240 shown in Fig. 4 is formed in the outer pipe second medium diameter portion 24.

[0040] (Insertion process, positioning process, joining process, pipe joining process) Fig. 8(A) shows a cross-sectional view of the inner and outer pipes in the insertion step (initial stage) of the manufacturing method for the double-pipe heat exchanger of this embodiment. Fig. 8(B) shows a cross-sectional view of the inner and outer pipes in the insertion step (final stage) and the positioning step (initial stage). Fig. 9(A) shows a cross-sectional view of the inner and outer pipes in the positioning step (final stage) and the sealing step of the manufacturing method. Fig. 9(B) shows a cross-sectional view of the inner and outer pipes in the piping connection step of the manufacturing method.

[0041] As shown in FIGS. 8(A) and 8(B), in the insertion step, the front end of the inner pipe 3 (inner pipe first small diameter section 31) is inserted into the rear end of the outer pipe 2 (outer pipe first medium diameter section 20). As shown in FIG. 9(A), in the positioning step, the inner pipe 3 is advanced relative to the outer pipe 2. Then, the inner pipe large diameter section 30 is positioned radially inside the outer pipe first medium diameter section 20. Also, the inner pipe first small diameter section 31 is positioned radially inside the outer pipe small diameter section 21. In the sealing step, the positioned outer pipe first medium diameter section 20 and the inner pipe large diameter section 30 are connected. Also, the positioned outer pipe small diameter section 21 and the inner pipe first small diameter section 31 are connected. In other words, the outer flow path 5 is fluid-tightly sealed. As shown in FIG. 9(B), in the piping connection step, the first piping 94 is connected to the first opening 230. Also, the second piping 95 is connected to the second opening 240. Thereafter, at least a portion of the double-pipe heat exchanger 1 is curved appropriately according to the path of the heat pump cycle 9 shown in FIG.

[0042] [Double-pipe heat exchanger in action] Next, the operation of the double-pipe heat exchanger of this embodiment will be described. As shown in FIG. 1, the inner flow path 4 is disposed between the downstream end of the evaporator 93 and the upstream end of the compressor 90. The outer flow path 5 is disposed between the downstream end of the condenser 91 and the upstream end of the expansion valve 92. As shown in FIG. 4, heat exchange occurs between a low-pressure refrigerant flowing through the inner flow path 4 and a high-pressure refrigerant flowing through the outer flow path 5 via the wall of the inner pipe 3. Specifically, a spiral portion 32 is disposed in the inner pipe 3. The outer and inner surfaces of the spiral portion 32 are formed with spiral irregularities. The refrigerant in the inner flow path 4 and the refrigerant in the outer flow path 5 flow along the irregularities. That is, the refrigerant in the inner flow path 4 and the refrigerant in the outer flow path 5 flow in opposite directions via the spiral portion 32. At this time, heat exchange occurs between the refrigerant in the inner flow path 4 and the refrigerant in the outer flow path 5. Specifically, heat is transferred from the refrigerant in the outer flow path 5 to the refrigerant in the inner flow path 4 via the spiral portion 32. The refrigerant in the outer flow passage 5 is cooled, and the refrigerant in the inner flow passage 4 is heated.

[0043] [Action and effect] Next, the effects of the double-pipe heat exchanger of this embodiment and its manufacturing method will be described. In the double-pipe heat exchanger 1 of this embodiment, a space is provided due to the difference in axial position between the large-diameter seal portion S1 and the small-diameter seal portion S2 and the difference in diameter between the large-diameter seal portion S1 and the small-diameter seal portion S2. With the double-pipe heat exchanger 1 of this embodiment, this space can be used to arrange at least a part of the outer flow path 5 and at least a part of the spiral portion 32. This simplifies the structure of the double-pipe heat exchanger 1.

[0044] Furthermore, according to the manufacturing method of the double-pipe heat exchanger 1 of this embodiment, the difference in diameter between the large-diameter seal portion S1 and the small-diameter seal portion S2 can be utilized to easily insert the front end of the inner pipe 3 into the rear end of the outer pipe 2. This improves the ease of assembling the inner pipe 3 and the outer pipe 2.

[0045] As shown in FIG. 4, according to the double-pipe heat exchanger 1 and the manufacturing method thereof of this embodiment, the following formulas (1) and (2) are established. D1>D2 (1) d1≧d3>d2 (2) D1: inner diameter of the outer pipe first medium diameter portion 20 D2: inner diameter of outer tube small diameter portion 21 d1: outer diameter of the large diameter portion 30 of the inner pipe d2: outer diameter of the first small diameter portion 31 of the inner pipe d3: maximum outer diameter of the spiral portion 32 (as shown in FIG. 5, the maximum outer diameter d3 is the diameter of an imaginary circle A1 formed by connecting the radially outer ends of the outer peripheral surfaces of the convex portions 32b of the spiral portion 32 in the circumferential direction)

[0046] That is, the inner diameter D1 of the outer pipe first medium diameter portion 20 is larger than the inner diameter D2 of the outer pipe small diameter portion 21. Furthermore, the outer diameter d1 of the inner pipe large diameter portion 30 is equal to or larger than the maximum outer diameter d3 of the helical portion 32. Furthermore, the maximum outer diameter d3 of the helical portion 32 is larger than the outer diameter d2 of the inner pipe first small diameter portion 31.

[0047] Since formulas (1) and (2) are established, as shown in FIG. 8(A), when inserting the inner tube 3 into the outer tube 2 in the insertion step, the insertion direction of the inner tube 3 relative to the outer tube 2 is easy to understand.

[0048] Furthermore, since formula (2) is established, compared to when the outer diameter d1 of the inner pipe large diameter portion 30 is the same as the outer diameter d2 of the inner pipe first small diameter portion 31, in the positioning step, after the inner pipe 3 and the outer pipe 2 are positioned, the outer pipe first medium diameter portion 20 and the inner pipe large diameter portion 30 can be arranged close to each other, as shown in Fig. 9(A). Therefore, in the sealing step, the operation of connecting the outer pipe first medium diameter portion 20 and the inner pipe large diameter portion 30 can be easily performed.

[0049] As shown in FIG. 4, according to the double-pipe heat exchanger 1 and the manufacturing method thereof of this embodiment, the following formula (3) is established. D1>d2 (3)

[0050] That is, the inner diameter D1 of the outer pipe first medium diameter section 20, which has the rear end (opening 200) of the outer pipe 2, is larger than the outer diameter d2 of the inner pipe first small diameter section 31, which has the front end (opening 310) of the inner pipe 3. Specifically, the inner diameter D1 of the outer pipe first medium diameter section 20 is larger than the outer diameter d2 of the inner pipe first small diameter section 31 by the difference between the maximum outer diameter d3 of the spiral section 32 and the minimum outer diameter d4, which will be described later. Therefore, as shown in FIG. 8(A), when the inner pipe 3 is inserted into the outer pipe 2 in the insertion step, it is possible to prevent the front end of the inner pipe 3 from interfering with the rear end of the outer pipe 2.

[0051] As shown in FIG. 4, according to the double-pipe heat exchanger 1 and the manufacturing method thereof of this embodiment, the following formula (4) is established. D3>D1=D4 (4) D3: inner diameter of the outer pipe large diameter part 23 D4: inner diameter of the outer tube second medium diameter portion 24

[0052] That is, the inner diameter D3 of the outer pipe large diameter portion 23 is larger than the inner diameter D1 of the outer pipe first medium diameter portion 20. Furthermore, the inner diameter D1 of the outer pipe first medium diameter portion 20 is the same as the inner diameter of the outer pipe second medium diameter portion 24. Therefore, as shown in FIG. 8(A), when the inner pipe 3 is inserted into the outer pipe 2 in the insertion step, interference of the inner pipe 3 with the outer pipe large diameter portion 23 (first opening 230) can be suppressed.

[0053] As shown in FIG. 4, according to the double-pipe heat exchanger 1 and the manufacturing method thereof of this embodiment, the following formulas (5) and (6) are established. d2=d4 (5) d1=d3 (6) d4: minimum outer diameter of the spiral portion 32 (as shown in FIG. 5, the minimum outer diameter d4 is the diameter of an imaginary circle A2 formed by connecting the radially inner ends of the outer peripheral surfaces of the recesses 32a in the circumferential direction)

[0054] That is, the front end of the spiral portion 32 is connected to the inner pipe first small diameter portion 31, which has the same diameter as the recessed portion 32a. On the other hand, the rear end of the spiral portion 32 is connected to the inner pipe large diameter portion 30, which has the same diameter as the protruding portion 32b. Therefore, even though there is a diameter difference (d1>d2) between the inner pipe first small diameter portion 31 (outer diameter d2) and the inner pipe large diameter portion 30 (outer diameter d1), there is no need to provide a tapered pipe portion or the like for adjusting the diameter difference. Therefore, the length of the spiral portion 32 in the front-to-rear direction can be increased. In other words, the heat transfer area can be increased.

[0055] As shown in FIG. 4, according to the double-pipe heat exchanger 1 and the manufacturing method thereof of this embodiment, the following formulas (7) and (8) are established. D1>d1 (7) D2>d2 (8)

[0056] In formula (7), there is a small difference in diameter between the inner diameter D1 of the outer pipe first medium diameter section 20 and the outer diameter d1 of the inner pipe large diameter section 30. Therefore, as shown in Fig. 9(A), the connection work (welding, brazing, bonding, crimping, etc.) between the outer pipe first medium diameter section 20 and the inner pipe large diameter section 30 can be easily performed in the sealing process.

[0057] Similarly, in formula (8), there is a small difference in diameter between the inner diameter D2 of the outer pipe small diameter portion 21 and the outer diameter d2 of the inner pipe first small diameter portion 31. Therefore, as shown in Fig. 9(A), the connection work (welding, brazing, bonding, crimping, etc.) between the outer pipe small diameter portion 21 and the inner pipe first small diameter portion 31 can be easily performed in the sealing process.

[0058] As shown in FIG. 4, according to the double-pipe heat exchanger 1 and the manufacturing method thereof of this embodiment, the following formula (9) is established. d3>D2 (9)

[0059] That is, the maximum outer diameter d3 of the helical portion 32 is larger than the inner diameter D2 of the outer pipe small diameter portion 21. Therefore, as shown in Figure 9(A), there is no risk that the helical portion 32 will fall off forward from the outer pipe small diameter portion 21 during the positioning step. This makes it easy to position the inner pipe 3 relative to the outer pipe 2.

[0060] As shown in FIG. 4, according to the double-pipe heat exchanger 1 and the manufacturing method thereof of this embodiment, the following formula (10) is established. d5≦d6 (10) d5: inner diameter of the first small diameter portion 31 of the inner pipe d6: minimum inner diameter of the spiral portion 32 (as shown in FIG. 5, the minimum inner diameter d6 is the diameter of an imaginary circle A3 formed by connecting the radially inner ends of the inner peripheral surfaces of the recesses 32a in the circumferential direction)

[0061] That is, the inner diameter d5 of the inner pipe first small diameter portion 31 (the same applies to the inner diameter of the inner pipe second small diameter portion 33) is equal to or smaller than the minimum inner diameter d6 of the spiral portion 32. This prevents the spiral portion 32 from protruding radially inward of the inner pipe first small diameter portion 31 and the inner pipe second small diameter portion 33. This reduces the flow path resistance of the inner flow path 4.

[0062] As shown in FIGS. 2 to 4, the inner pipe 3 has a helical portion 32. The outer peripheral surface of the helical portion 32 is formed with helical irregularities. Therefore, the heat transfer area of ​​the outer peripheral surface of the helical portion 32 can be increased compared to when the inner pipe 3 does not have the helical portion 32. Furthermore, the refrigerant can flow in a helical manner in the outer flow path 5. Therefore, the contact time between the refrigerant and the outer peripheral surface of the helical portion 32 can be increased. Similarly, the inner peripheral surface of the helical portion 32 has helical irregularities. Therefore, the heat transfer area of ​​the inner peripheral surface of the helical portion 32 can be increased compared to when the inner pipe 3 does not have the helical portion 32. Furthermore, the refrigerant (at least a part of the refrigerant) can flow in a helical manner in the inner flow path 4. Therefore, the contact time between the refrigerant and the inner peripheral surface of the helical portion 32 can be increased.

[0063] 4, the rear end of the outer pipe small diameter portion 21 is shifted forward relative to the rear end of the inner pipe first small diameter portion 31. Therefore, a second expanded portion 52 can be provided between the inner pipe first small diameter portion 31 and the outer pipe small diameter portion 21. In other words, the second expanded portion 52 can be provided by utilizing the positional shift between the rear end of the inner pipe first small diameter portion 31 and the rear end of the outer pipe small diameter portion 21 and the diameter difference between the inner pipe first small diameter portion 31 and the outer pipe small diameter portion 21, without intentionally forming an expanded diameter portion in the outer pipe 2 or forming a reduced diameter portion in the inner pipe 3 (however, this disclosure does not exclude these embodiments).

[0064] 4, the first expansion section 51 has a larger flow path cross-sectional area than the spiral flow path section 50. Therefore, the refrigerant flowing from the spiral flow path section 50 into the first expansion section 51 can be stably joined together, thereby reducing pressure loss. Similarly, the second expansion section 52 has a larger flow path cross-sectional area than the second opening 240 (second piping 95). Therefore, the refrigerant flowing from the second piping 95 into the second expansion section 52 can be stably diffused, thereby reducing pressure loss.

[0065] 4, 7(A), and 7(B), the outer pipe large diameter section 23 (first expanded section 51) and the outer pipe second medium diameter section 24 (second expanded section 52) are formed by expanding the outer pipe blank 2a in the outer pipe forming process. Therefore, compared to forming the first expanded section 51 and the second expanded section 52 by contracting the inner pipe 3 (however, this disclosure does not exclude this embodiment), the inner pipe 3 can be produced only by the inner pipe forming process (hydroforming) shown in FIGS.

[0066] 4, the rear end of the spiral portion 32 is located forward of the rear end of the outer pipe large diameter portion 23. This prevents the spiral portion 32 from entering the outer pipe first medium diameter portion 20. This prevents the sealing performance of the large diameter seal portion S1 from deteriorating.

[0067] 4, the front end of the spiral portion 32 is disposed rearward of the rear end of the second opening 240. Therefore, compared to when the front end of the spiral portion 32 is disposed forward of the rear end of the second opening 240 (however, the present disclosure does not exclude this embodiment), a second extension portion 52 with a larger volume can be secured below the second opening 240.

[0068] 4, the second pipe 95, which opens into the outer flow path 5, is inserted into the second opening 240. The lower end (insertion end) of the second pipe 95 protrudes downward (radially inward) from the inner circumferential surface of the outer pipe second medium diameter section 24. The front end of the spiral section 32 is located rearward of the rear end of the second opening 240. This prevents the spiral section 32 from interfering with the lower end of the second pipe 95.

[0069] The outer pipe 2 is made of metal and is integrally formed. Therefore, it is easier to ensure the sealing of the outer flow path 5 compared to when the outer pipe 2 is not integrally formed (when the outer pipe 2 has a seam). Similarly, the inner pipe 3 is made of metal and is integrally formed. Therefore, it is easier to ensure the sealing of the inner flow path 4 and the outer flow path 5 compared to when the inner pipe 3 is not integrally formed (when the inner pipe 3 has a seam).

[0070] As shown in Fig. 9(B), the piping connection step is performed after the sealing step, which improves the handleability of the outer pipe 2 in the insertion step shown in Fig. 8(A) and Fig. 8(B), the positioning step shown in Fig. 9(A), and the sealing step.

[0071] Second Embodiment The double-pipe heat exchanger and manufacturing method thereof of this embodiment differ from the double-pipe heat exchanger and manufacturing method thereof of the first embodiment in that the outer pipe has two outer-pipe large-diameter portions. This difference will be mainly described here. Figure 10 shows a cross-sectional view of the double-pipe heat exchanger of this embodiment taken from the front-rear direction. Note that parts corresponding to those in Figure 4 are designated by the same reference numerals.

[0072] As shown in Fig. 10, the outer pipe 2 includes an outer pipe first large diameter portion 23a (corresponding to the outer pipe large diameter portion 23 in Fig. 4) and an outer pipe second large diameter portion 23b. The outer pipe second large diameter portion 23b is disposed between the outer pipe second medium diameter portion 24 and the outer pipe small diameter portion 21. The rear end of the spiral portion 32 is disposed in the center of the outer pipe first large diameter portion 23a in the front-rear direction. In addition, the front end of the spiral portion 32 is disposed in the center of the outer pipe second large diameter portion 23b in the front-rear direction.

[0073] The double-pipe heat exchanger and its manufacturing method of this embodiment and the double-pipe heat exchanger and its manufacturing method of the first embodiment have the same effects as those of the first embodiment with respect to the common configuration. As in the double-pipe heat exchanger 1 of this embodiment, a second expansion section 52 having a volume equivalent to that of the first expansion section 51 may be provided.

[0074] When the rear end of the spiral portion 32 enters the outer pipe first medium diameter portion 20, the sealing performance of the large diameter seal portion S1 may be reduced. On the other hand, when the rear end of the spiral portion 32 enters the outer pipe second medium diameter portion 24, the length of the spiral flow path portion 50 in the front-to-rear direction is shortened. As a result, the heat transfer area is reduced. In this regard, the rear end of the spiral portion 32 is positioned in the center of the outer pipe first large diameter portion 23a in the front-to-rear direction. As a result, the sealing performance of the large diameter seal portion S1 can be prevented from being reduced. In addition, the length of the spiral flow path portion 50 in the front-to-rear direction can be prevented from being shortened.

[0075] 9(A), the target position of the inner pipe 3 relative to the outer pipe 2 may be set to "the position where the rear end of the spiral portion 32 is at the center of the outer pipe first large diameter portion 23a in the front-to-rear direction." In this way, even if the actual position is slightly deviated from the target position, it is possible to prevent the sealing performance of the large diameter seal portion S1 from being reduced. Also, it is possible to prevent the length of the spiral flow path portion 50 in the front-to-rear direction from being shortened.

[0076] Similarly, when the front end of the spiral portion 32 enters the outer pipe small diameter portion 21, the sealing performance of the small diameter seal portion S2 may be reduced. On the other hand, when the front end of the spiral portion 32 enters the outer pipe second medium diameter portion 24, the length of the spiral flow path portion 50 in the front-to-rear direction is shortened. As a result, the heat transfer area is reduced. In this regard, the front end of the spiral portion 32 is positioned at the center of the outer pipe second large diameter portion 23b in the front-to-rear direction. As a result, the sealing performance of the small diameter seal portion S2 can be prevented from being reduced. In addition, the length of the spiral flow path portion 50 in the front-to-rear direction can be prevented from being shortened.

[0077] 9(A), the target position of the inner pipe 3 relative to the outer pipe 2 may be set to "the position where the front end of the spiral portion 32 is at the center of the outer pipe second large diameter portion 23b in the front-to-rear direction." In this way, even if the actual position is slightly deviated from the target position, it is possible to prevent the sealing performance of the small diameter seal portion S2 from being reduced. Also, it is possible to prevent the length of the spiral flow path portion 50 in the front-to-rear direction from being shortened.

[0078] Third Embodiment The double-pipe heat exchanger and manufacturing method thereof of this embodiment differ from the double-pipe heat exchanger and manufacturing method thereof of the first embodiment in that the double-pipe heat exchanger does not have a first expansion section and a second expansion section. Also, the inner pipe has a positioning section. Here, the differences will be mainly described. Figure 11 shows a cross-sectional view of the double-pipe heat exchanger of this embodiment taken from the front-rear direction. Note that parts corresponding to those in Figure 4 are designated by the same reference numerals.

[0079] 11, from the front to the rear, the inner pipe 3 comprises an inner pipe first small diameter portion 31, a spiral portion 32, an inner pipe large diameter portion 30, a positioning portion 34, a tapered pipe portion 39a, and an inner pipe second small diameter portion 33. From the front to the rear, the outer pipe 2 comprises an outer pipe small diameter portion 21, a tapered pipe portion 29d, and an outer pipe medium diameter portion 20a.

[0080] A first opening 200a and a second opening 201a are formed in the pipe wall of the outer pipe medium diameter section 20a. A first pipe 94 is connected to the first opening 200a. A first expansion section 51 (see FIG. 4) is not arranged below (radially inward from) the first opening 200a. A spiral flow path section 50 (spiral section 32) is arranged below the first opening 200a. A second pipe 95 is connected to the second opening 201a. A second expansion section 52 (see FIG. 4) is not arranged below (radially inward from) the second opening 201a. A spiral flow path section 50 (spiral section 32) is arranged below the second opening 201a.

[0081] The positioning portion 34 protrudes radially outward from the rear end of the inner pipe large diameter portion 30. In the positioning step shown in Figure 9(A), the inner pipe 3 and the outer pipe 2 are positioned so that the positioning portion 34 abuts against the rear end of the outer pipe 2.

[0082] The double-pipe heat exchanger of this embodiment and its manufacturing method and the double-pipe heat exchanger of the first embodiment and its manufacturing method have similar effects with respect to the parts that share a common configuration. The double-pipe heat exchanger 1 of this embodiment does not have a first expansion section 51 or a second expansion section 52 (see FIG. 4). This simplifies the structure of the outer pipe 2. This improves the productivity of the outer pipe 2 and, in turn, the double-pipe heat exchanger 1. The double-pipe heat exchanger 1 of this embodiment has a positioning section 34. This allows for easy positioning of the inner pipe 3 and the outer pipe 2 in the positioning step shown in FIG. 9(A).

[0083] <Fourth embodiment> The double-pipe heat exchanger and manufacturing method thereof of this embodiment differ from the double-pipe heat exchanger and manufacturing method thereof of the first embodiment in that the inner pipe is provided with an uneven portion with heat transfer fins. Here, the difference will be mainly described. Fig. 12(A) shows a cross-sectional view of the double-pipe heat exchanger of this embodiment in the front-rear direction. Note that parts corresponding to those in Fig. 4 are designated by the same reference numerals. Fig. 12(B) shows a cross-sectional view taken along the line XIIB-XIIB of Fig. 12(A). Note that parts corresponding to those in Fig. 5 are designated by the same reference numerals.

[0084] As shown in Figures 12(A) and 12(B), from the front to the rear, the inner pipe 3 includes an inner pipe first small diameter section 31, an uneven section 35, a tapered pipe section 39b, an inner pipe large diameter section 30, a tapered pipe section 39a, and an inner pipe second small diameter section 33. The uneven section 35 includes a base pipe section 35a and multiple heat transfer fins 35b. The base pipe section 35a has the same inner and outer diameters as the inner pipe first small diameter section 31. The heat transfer fins 35b protrude from the outer peripheral surface of the base pipe section 35a. The heat transfer fins 35b are shaped like thin plates extending in the front-rear direction. The multiple heat transfer fins 35b are arranged circumferentially spaced apart by a predetermined angle. A straight flow path section 53 extending in the front-rear direction is formed between adjacent pairs of heat transfer fins 35b.

[0085] The double-pipe heat exchanger and manufacturing method thereof of this embodiment and the double-pipe heat exchanger and manufacturing method thereof of the first embodiment have the same effects as those of the first embodiment, with respect to the common configuration. The inner pipe 3 has an uneven portion 35. The uneven portion 35 has a plurality of heat transfer fins 35b. Therefore, the heat transfer area can be increased compared to when the heat transfer fins 35b are not provided.

[0086] <Other> The above describes the embodiments of the double-pipe heat exchanger and the manufacturing method thereof according to the present disclosure. However, the embodiments are not particularly limited to the above-described embodiments. Various modifications and improvements that can be made by those skilled in the art are also possible.

[0087] Figure 13(A) shows a radial cross-sectional view of a double-pipe heat exchanger according to another embodiment (part 1). Figure 13(B) shows a radial cross-sectional view of a double-pipe heat exchanger according to another embodiment (part 2). Note that parts corresponding to those in Figure 5 are designated by the same reference numerals.

[0088] As shown in FIG. 13(A), there may be a gap E between the outer pipe second medium diameter portion 24 and the convex portion 32b of the helical portion 32. Of course, as shown in FIG. 5 above, there may be no gap between the outer pipe second medium diameter portion 24 and the convex portion 32b of the helical portion 32. As shown in FIG. 13(B), the helical portion 32 may have four concave portions 32a extending in a spiral shape and four convex portions 32b extending in a spiral shape. That is, the number of concave portions 32a and convex portions 32b (number of threads) is not particularly limited. Furthermore, the pitch of the convex portions 32b in the front-rear direction is not particularly limited. It may be constant or not constant.

[0089] The shape, extension direction, position, number, and material of the heat transfer fins 35b of the uneven portion 35 shown in FIGS. 12(A) and 12(B) are not particularly limited. Similar to the gap E shown in FIG. 13(A), a gap may exist between the outer pipe second medium diameter portion 24 and the radially outer end of the heat transfer fin 35b. Furthermore, multiple heat transfer fins 35b may be continuously arranged at predetermined intervals in the axial direction. Furthermore, the heat transfer fins 35b may extend in a spiral shape, as in the convex portion 32b shown in FIG. 2. Furthermore, the base pipe portion 35a and the heat transfer fins 35b may be formed of the same material or different materials. Furthermore, the base pipe portion 35a and the heat transfer fins 35b may be integrally formed or not.

[0090] The configurations of the double-pipe heat exchangers 1 of the above-described embodiments may be combined as appropriate. For example, the rear end of the spiral portion 32 of the double-pipe heat exchanger 1 shown in Fig. 4 may be disposed at the center of the outer pipe large-diameter portion 23 in the front-rear direction, as in the double-pipe heat exchanger 1 shown in Fig. 10. Furthermore, a positioning portion 34 shown in Fig. 11 may be disposed on the inner pipe 3 of the double-pipe heat exchanger 1 shown in Fig. 4.

[0091] It is not necessary for the entire outer flow path 5 to be arranged by taking advantage of the difference in axial position or diameter between the large diameter seal portion S1 and the small diameter seal portion S2. It is sufficient that at least a portion of the outer flow path 5 (for example, at least one of the spiral flow path portion 50, the first expansion portion 51, and the second expansion portion 52) is arranged by taking advantage of the difference in axial position or diameter between the large diameter seal portion S1 and the small diameter seal portion S2. Similarly, it is not necessary for the entire spiral portion 32 to be arranged by taking advantage of the difference in axial position or diameter between the large diameter seal portion S1 and the small diameter seal portion S2. It is sufficient that at least a portion of the spiral portion 32 is arranged by taking advantage of the difference in axial position or diameter between the large diameter seal portion S1 and the small diameter seal portion S2.

[0092] As shown in Figures 4 and 10, the volumes of the first expansion section 51 and the second expansion section 52 are not particularly limited. The volumes of both sections may be the same or different. Also, as shown in Figure 11, the first expansion section 51 and the second expansion section 52 do not have to be provided.

[0093] The shape of the uneven portion (such as the spiral portion 32 shown in Figures 4, 13(A), and 13(B) and the uneven portion 35 shown in Figures 12(A) and 12(B)) is not particularly limited. The outer peripheral surface of the base pipe portion 35a shown in Figures 12(A) and 12(B) may be provided with an uneven shape such as a striped pattern, a piqué pattern, or a polka dot pattern. The position of the uneven portion is not particularly limited. It is sufficient that the uneven portion is provided in at least a part of the longitudinal section between the front end of the first opening 230 and the rear end of the second opening 240 shown in Figure 4. The uneven portion may also be provided on the outer pipe 2. That is, the inner peripheral surface of the outer pipe 2 may be provided with an uneven shape. The uneven portion may also be provided on the outer pipe 2 and the inner pipe 3.

[0094] The materials of the outer tube 2 and the inner tube 3 are not particularly limited. They may be aluminum, aluminum alloy, copper, stainless steel, titanium, etc. The outer tube 2 and the inner tube 3 may be formed of the same material or different materials. The outer tube 2 and the inner tube 3 may be integrally formed or may be a joint of multiple tubes. The shapes of the outer tube 2 and the inner tube 3 are not particularly limited. They may be circular (circular, elliptical), rectangular (triangular, square, etc.), etc. The double-pipe heat exchanger 1 may be straight, curved, etc. When the double-pipe heat exchanger 1 is straight, the axial direction of the double-pipe heat exchanger 1 may be oriented horizontally, vertically, or in a direction inclined relative to the vertical or horizontal direction. The double-pipe heat exchanger 1 may also have a shape that appropriately combines straight and curved tubes. In other words, the double-pipe heat exchanger 1 may have at least one curved portion. In this case, the axial direction of the double-pipe heat exchanger 1 may be curved according to the extension shape of the double-pipe heat exchanger 1.

[0095] The difference between the inner diameter D1 of the outer pipe first medium diameter section 20 and the outer diameter d2 of the inner pipe first small diameter section 31 shown in Figure 4 is not particularly limited. As shown in Figures 8(A) and 8(B), the greater the difference in diameter, the easier it is to carry out the insertion process. Preferably, the following formula (11) is established. 0.1<{(D1-d2) / D1}×100<5 (11)

[0096] In the manufacturing method of the double-pipe heat exchanger 1, the order of the inner pipe molding step shown in Figures 6(A) and 6(B) and the outer pipe molding step shown in Figures 7(A) and 7(B) is not particularly limited. The outer pipe molding step may be performed before the inner pipe molding step. Furthermore, other steps (one or more) may be performed between the two steps.

[0097] The opening forming step may be performed after the outer pipe molding step and before the piping connecting step. For example, the opening forming step may be performed between the inserting step shown in Figures 8(A) and 8(B) and the positioning step shown in Figure 9(A). The opening forming step may also be performed between the positioning step and the sealing step shown in Figure 9(A). The opening forming step may also be performed between the sealing step shown in Figure 9(A) and the piping connecting step shown in Figure 9(B).

[0098] 8(A) and 8(B), a pipe connecting process shown in FIG. 9(B) may be performed. In this case, as shown in FIG. 4, the lower end (insertion end) of the first pipe 94 protrudes downward (radially inward) from the inner circumferential surface of the outer pipe large diameter portion 23. However, the lower end of the first pipe 94 is positioned above (radially outward) the inner circumferential surface of the outer pipe first medium diameter portion 20. This prevents the front end of the inner pipe 3 from interfering with the lower end of the first pipe 94 during the insertion process and positioning process. Similarly, the lower end (insertion end) of the second pipe 95 protrudes radially inward from the inner circumferential surface of the outer pipe second medium diameter portion 24. However, the lower end of the second pipe 95 is positioned radially outward from the inner circumferential surface of the outer pipe first medium diameter portion 20. This prevents the front end of the inner pipe 3 from interfering with the lower end of the second pipe 95 during the insertion process and positioning process.

[0099] The manufacturing method of the outer pipe 2 and the inner pipe 3 is not limited to hydroforming. The outer pipe 2 and the inner pipe 3 may be manufactured by other methods. For example, the helical portion 32 may be formed in the inner pipe 3 by recessing a helical groove (recess 32a) in the outer circumferential surface of the inner pipe blank 3a. In this case, the portion where the helical groove is not recessed corresponds to the protrusion 32b.

[0100] 9(A), the method of connecting the outer pipe first medium diameter portion 20 and the inner pipe large diameter portion 30 is not particularly limited. For example, a seal member may be interposed between the outer pipe first medium diameter portion 20 and the inner pipe large diameter portion 30. Furthermore, after the positioning step, the outer pipe first medium diameter portion 20 may be reduced in diameter and joined to the inner pipe large diameter portion 30. In these cases, the diameter of the large diameter seal portion S1 refers to the average diameter of the inner diameter D1 of the outer pipe first medium diameter portion 20 and the outer diameter d1 of the inner pipe large diameter portion 30. The same applies to the method of connecting the outer pipe small diameter portion 21 and the inner pipe first small diameter portion 31 and the diameter of the small diameter seal portion S2.

[0101] The flow direction of the refrigerant in the double-pipe heat exchanger 1 is not particularly limited. In the inner flow path 4, the refrigerant may flow from the opening 330 toward the opening 310 shown in FIG. 4. Of course, the refrigerant may flow in the opposite direction. In the outer flow path 5, the refrigerant may flow from the second pipe 95 toward the first pipe 94 shown in FIG. 4. Of course, the refrigerant may flow in the opposite direction. In the spiral section 32, the flow direction of the refrigerant in the inner flow path 4 and the flow direction of the refrigerant in the outer flow path 5 are not particularly limited. The flow directions of the two refrigerants may be the same (parallel flow) or opposite (counterflow). The fluid flowing in the inner flow path 4 and the fluid flowing in the outer flow path 5 may be the same or different. Furthermore, the phase state of the fluid flowing in the inner flow path 4 and the outer flow path 5 is not particularly limited. It may be gas phase, liquid phase, or two-phase gas-liquid phase.

[0102] The double-pipe heat exchanger 1 is not particularly limited in its application. It can be used for heat pump cycles (refrigeration cycles (cooling cycles) and heating cycles), EGR (Exhaust Gas Recirculation) coolers, oil coolers, condensers, etc. It can also be used for binary power generation. It can also be used to cool and warm the batteries of electric vehicles (including hybrid vehicles, plug-in hybrid vehicles, and fuel cell vehicles). [Explanation of symbols]

[0103] 1: Double tube heat exchanger, 2: Outer tube, 2a: Outer tube material, 20: Outer tube first middle diameter section, 20a: Outer tube middle diameter section, 200: Opening, 200a: First opening, 201a: Second Opening, 21: Outer tube small diameter section, 210: Opening section, 23: Outer tube large diameter section, 23a: Outer tube first large diameter section, 23b: Outer tube second large diameter section, 230: First opening, 24: Outer tube second middle diameter portion, 240: second opening, 29a to 29d: tapered pipe portion, 3: inner pipe, 3a: inner pipe material, 30: inner pipe large diameter portion, 31: inner pipe first small diameter portion, 310: opening, 32: spiral portion, 32a: recess, 32b: protrusion, 33: inner pipe second small diameter portion, 330: opening, 34: positioning portion, 35: uneven portion, 35a: base pipe portion, 35b: heat transfer fin, 39 a to 39b: tapered pipe portion, 4: inner flow path, 5: outer flow path, 50: spiral flow path portion, 51: first expansion portion, 52: second expansion portion, 53: straight flow path portion, 7: mold, 70: first mold, 700: mold surface, 71: second mold, 710: mold surface, 72: first punch, 720: opening, 73: second punch, 730: opening, 8: mold, 80: first mold, 800: mold surface, 81: second mold, 810: mold surface, 82: first punch, 820: opening, 83: second punch, 9: heat pump cycle, 90: compressor, 91: condenser, 92: expansion valve, 93: evaporator, 94: first piping, 95: second piping, C1: cavity, C2: cavity, E: gap, S1: large diameter seal portion, S2: small diameter seal portion

Claims

1. A double-pipe heat exchanger comprising an outer pipe and an inner pipe inserted into the outer pipe, an inner flow path formed inside the inner pipe, an outer flow path formed between the inner pipe and the outer pipe, and performing heat exchange between a fluid flowing through the inner flow path and a fluid flowing through the outer flow path, the inner tube has an uneven portion having unevenness on an outer peripheral surface, a large-diameter seal portion is interposed between one axial end portion of the outer pipe and the inner pipe; a small-diameter seal portion having a smaller diameter than the large-diameter seal portion is interposed between the other axial end of the outer pipe and the inner pipe; the outer flow path and the uneven portion are arranged by utilizing a difference in axial position and a difference in diameter between the large diameter seal portion and the small diameter seal portion, the outer tube does not have a concave-convex portion that engages with the concave-convex portion, the inner pipe has an inner pipe large diameter portion and an inner pipe small diameter portion that is located closer to the other end in the axial direction than the inner pipe large diameter portion, the concave-convex portion is disposed between the inner pipe large diameter portion and the inner pipe small diameter portion, and has a concave portion and a convex portion; one axial end of the concave-convex portion is connected to the inner pipe large diameter portion by the convex portion, the other axial end of the concave-convex portion is connected to the inner pipe small diameter portion by the concave portion; A double-pipe heat exchanger characterized by:

2. the outer pipe has an outer pipe medium diameter portion which is one end portion of the outer pipe in the axial direction, and an outer pipe small diameter portion which is the other end portion of the outer pipe in the axial direction, the inner pipe large diameter portion is disposed radially inside the outer pipe medium diameter portion, the inner pipe small diameter portion has the other axial end of the inner pipe and is disposed radially inside the outer pipe small diameter portion, the large-diameter seal portion is interposed between the outer pipe medium-diameter portion and the inner pipe large-diameter portion and fluid-tightly seals one axial end of the outer flow path; the small diameter seal portion is interposed between the outer pipe small diameter portion and the inner pipe small diameter portion and fluid-tightly seals the other axial end of the outer flow path; The double-pipe heat exchanger according to claim 1, wherein the inner diameter of the outer pipe medium diameter portion is D1, the inner diameter of the outer pipe small diameter portion is D2, the outer diameter of the inner pipe large diameter portion is d1, the outer diameter of the inner pipe small diameter portion is d2, and the maximum outer diameter of the uneven portion is d3, and the following formulas (1) to (3) all hold: D1>D2...(1) d1≧d3>d2 (2) D1>d2...(3)

3. the outer pipe medium diameter portion is an outer pipe first medium diameter portion, the outer pipe has, between the outer pipe first medium diameter portion and the outer pipe small diameter portion, an outer pipe large diameter portion having an inner diameter larger than that of the outer pipe first medium diameter portion and an outer pipe second medium diameter portion having the same inner diameter as that of the outer pipe first medium diameter portion, from one axial end side to the other axial end side; a first opening portion communicating with the outer flow path is formed in the outer pipe large diameter portion; The double-pipe heat exchanger according to claim 2 , wherein the second medium diameter portion of the outer pipe is provided with a second opening communicating with the outer flow passage.

4. The double-pipe heat exchanger according to claim 3 , wherein one axial end of the uneven portion is located closer to the other axial end than one axial end of the outer pipe large-diameter portion.

5. 5. The double-pipe heat exchanger according to claim 3, wherein the other axial end of the uneven portion is located closer to one axial end than one axial end of the second opening.

6. the outer tube is integrally formed from the same material, the inner tube is integrally formed from the same material, the inner pipe small diameter portion is an inner pipe first small diameter portion, 6. The double-pipe heat exchanger according to claim 2, wherein the inner pipe has an inner pipe second small diameter portion having the same outer diameter as the inner pipe first small diameter portion at one axial end side of the inner pipe large diameter portion.

7. 7. The double-pipe heat exchanger according to claim 1, wherein the uneven portion is a spiral portion having a spiral unevenness that runs around the outer circumferential surface of the inner pipe.

8. A method for manufacturing a double-pipe heat exchanger comprising: an outer pipe; and an inner pipe inserted into the outer pipe, wherein an inner flow path is formed inside the inner pipe; an outer flow path is formed between the inner pipe and the outer pipe; and wherein heat is exchanged between a fluid flowing through the inner flow path and a fluid flowing through the outer flow path, The front side in the insertion direction when the inner tube is inserted into the outer tube is defined as the front side, and the rear side in the insertion direction is defined as the rear side. the inner tube has an uneven portion having unevenness on an outer peripheral surface, a large-diameter seal portion is interposed between a rear end portion of the outer pipe and the inner pipe; a small-diameter seal portion having a smaller diameter than the large-diameter seal portion is interposed between a front end portion of the outer pipe and the inner pipe; the outer tube does not have a concave-convex portion that engages with the concave-convex portion, the inner pipe has an inner pipe large diameter portion and an inner pipe small diameter portion disposed forward of the inner pipe large diameter portion, the concave-convex portion is disposed between the inner pipe large diameter portion and the inner pipe small diameter portion, and has a concave portion and a convex portion; a rear end of the concave-convex portion is connected to the inner pipe large diameter portion by the convex portion, a front end of the concave / convex portion is connected to the inner pipe small diameter portion by the concave portion; an inserting step of inserting a front end of the inner tube into a rear end of the outer tube; a positioning step of advancing the inserted inner tube relative to the outer tube to position the inner tube and the outer tube; a sealing step of connecting the rear end of the outer pipe and the inner pipe after positioning to form the large diameter seal portion, and connecting the front end of the outer pipe and the inner pipe after positioning to form the small diameter seal portion; A method for manufacturing a double-pipe heat exchanger, comprising the steps of:

9. the outer pipe has an outer pipe medium diameter portion which is the rear end portion of the outer pipe, and an outer pipe small diameter portion which is the front end portion of the outer pipe, the inner pipe large diameter portion is disposed radially inside the outer pipe medium diameter portion, the inner pipe small diameter portion has a front end of the inner pipe and is disposed radially inside the outer pipe small diameter portion, the large-diameter seal portion is interposed between the outer pipe medium-diameter portion and the inner pipe large-diameter portion and fluid-tightly seals the rear end of the outer flow path; the small diameter seal portion is interposed between the outer pipe small diameter portion and the inner pipe small diameter portion and fluid-tightly seals a front end of the outer flow path; 9. The method for manufacturing a double-pipe heat exchanger according to claim 8, wherein the inner diameter of the outer pipe medium diameter portion is D1, the inner diameter of the outer pipe small diameter portion is D2, the outer diameter of the inner pipe large diameter portion is d1, the outer diameter of the inner pipe small diameter portion is d2, and the maximum outer diameter of the uneven portion is d3, and the following formulas (1) to (3) all hold. D1>D2...(1) d1≧d3>d2 (2) D1>d2...(3)

10. Before the inserting step, 10. A method for manufacturing a double-pipe heat exchanger according to claim 9, further comprising an inner pipe molding step of: setting a tubular inner pipe material in a mold; supplying a fluid into the inner pipe material; and expanding and deforming the inner pipe material along the mold surface by the pressure of the fluid, thereby expanding and deforming the inner pipe large diameter portion and the uneven portion relative to the inner pipe small diameter portion, which has the same outer diameter as the inner pipe material, to form the inner pipe.

11. the outer pipe medium diameter portion is an outer pipe first medium diameter portion, the outer pipe has, between the outer pipe first medium diameter portion and the outer pipe small diameter portion, an outer pipe large diameter portion having an inner diameter larger than that of the outer pipe first medium diameter portion, and an outer pipe second medium diameter portion having the same inner diameter as that of the outer pipe first medium diameter portion, from the rear side to the front side; Before the inserting step, an outer tube forming step of forming the outer tube by deforming a tubular outer tube material; an opening forming step of forming a first opening in the outer pipe large diameter portion after molding, the first opening communicating with the outer flow path, and forming a second opening in the outer pipe second medium diameter portion after molding, the second opening communicating with the outer flow path; The method for manufacturing a double-pipe heat exchanger according to claim 9 or 10, comprising:

12. Before the inserting step or after the sealing step, The method for manufacturing a double-pipe heat exchanger according to claim 11, further comprising a pipe connecting step of connecting a first pipe to the first opening and connecting a second pipe to the second opening.

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