Heat exchanger, indoor unit for air conditioning device, air conditioning device, and heat exchanger manufacturing method

Abstract

Provided is a heat exchanger (500), wherein header single-pass heat transfer tubes (222) and two-pass heat transfer tubes (223) are inserted into fins. A header (100) constitutes a common internal flow path (125) that communicates with a plurality of header single-pass heat transfer tubes (222). A two-pass flow path (300) connects an extension end part (221a) of one of a pair of two-pass heat transfer tubes (223) and an extension end part (221a) of the other of the pair of two-pass heat transfer tubes (223). A header projection region obtained by vertically projecting the header (100) onto a virtual plane parallel to an end plate (212) and a two-pass flow path projection region obtained by vertically projecting the two-pass flow path (300) onto the virtual plane overlap each other. A back surface (100d) of the header (100) facing the end plate (212) is disposed at a position closer to the end plate (212) than a top part (310) of the two-pass flow path (300), the top part being located farthest from the end plate (212).

Description

Heat exchanger, indoor unit for air conditioner, air conditioner, and method for manufacturing heat exchanger

[0001] The present disclosure relates to a heat exchanger, an indoor unit for an air conditioner, an air conditioner, and a method for manufacturing a heat exchanger.

[0002] As disclosed in Patent Document 1, a heat exchanger including a heat exchanger main body and a plate laminate as a header attached to the heat exchanger main body is known. The heat exchanger main body has a structure in which a heat transfer tube group is inserted into fins. At the end of the fins, a tube plate as an end plate is arranged. A header is arranged at a position facing the end plate.

[0003] Each heat transfer tube constituting the heat transfer tube group has an extending end portion extending from the end plate. The heat transfer tube group includes a pair of heat transfer tubes for folding in which the extending end portions of each other are connected, and a plurality of heat transfer tubes for direct connection to the header in which each extending end portion is connected to the header. The header constitutes a second flow path as a common internal flow path communicating with a plurality of heat transfer tubes for direct connection to the header.

[0004] On the other hand, a folding flow path is provided in the pair of heat transfer tubes for folding. The folding flow path connects the extending end portion on one side of the pair of heat transfer tubes for folding and the extending end portion on the other side. In Patent Document 1, the folding flow path is constituted by a U-bend tube.

[0005] Japanese Unexamined Patent Application Publication No. 2024-52597

[0006] In the heat exchanger according to Patent Document 1, the projection area (hereinafter referred to as the header projection area) obtained by vertically projecting the header onto a virtual plane parallel to the end plate and the projection area (hereinafter referred to as the folding flow path projection area) obtained by vertically projecting the folding flow path onto the virtual plane do not overlap. Specifically, the U-bend tube is arranged on the side of the header.

[0007] When such an arrangement of the header and the U-bend tube is adopted, the shape of the header (hereinafter referred to as the planar shape of the header) as viewed in the direction perpendicular to the end plate (hereinafter referred to as the header thickness direction) must be made to avoid the U-bend tube. For this reason, there arises a problem that the planar shape of the header becomes complicated.

[0008] These problems can be avoided by arranging the header projection area and the return channel projection area to overlap. However, in that case, the header needs to be positioned further from the end plate than the U-bend pipe in the header thickness direction. As a result, there is a concern that the dimension in the header thickness direction (hereinafter referred to as the header protrusion dimension), from the end plate to the upper surface of the header furthest from the end plate in the header thickness direction, will increase.

[0009] The purpose of this disclosure is to provide a heat exchanger that can suppress the header protrusion dimension despite adopting an arrangement in which the header projection area and the return flow channel projection area overlap, an indoor unit for an air conditioning system equipped with the heat exchanger, an air conditioning system equipped with the indoor unit for an air conditioning system, and a heat exchanger manufacturing method for manufacturing the heat exchanger.

[0010] The heat exchanger according to this disclosure comprises a fin structure, a group of heat transfer tubes, a header, and a return channel. The fin structure has fins and end plates positioned at the ends of the fins. The group of heat transfer tubes consists of a plurality of heat transfer tubes, each inserted into a fin. Each heat transfer tube has an extended end that extends outward from the end plate to the fin structure. The plurality of heat transfer tubes include a pair of return heat transfer tubes whose extended ends are connected to each other, and a plurality of header-direct heat transfer tubes other than the return heat transfer tubes. The header is positioned opposite the end plates and is connected to the extended ends of each header-direct heat transfer tube. The header constitutes a common internal channel communicating with the plurality of header-direct heat transfer tubes. The return channel connects the extended end of one of the pair of return heat transfer tubes to the extended end of the other. The header projection region, obtained by projecting the header perpendicularly onto a virtual plane parallel to the end plate, and the return channel projection region, obtained by projecting the return channel perpendicularly onto the virtual plane, overlap. The back surface of the header facing the end plate is positioned closer to the end plate than the top of the return channel furthest from the end plate.

[0011] With the above configuration, since the back of the header is positioned closer to the end plate than the top of the return channel, the header protrusion can be reduced even though the header projection area and the return channel projection area overlap.

[0012] Conceptual diagram showing the configuration of the air conditioning system according to Embodiment 1 Perspective view of the indoor heat exchanger according to Embodiment 1 Perspective view of the header according to Embodiment 1 Plan view of the header according to Embodiment 1 Cross-sectional view of the header according to Embodiment 1 at the position of line V-V in Figure 4 Perspective view of the back plate according to Embodiment 1 Perspective view of the header body according to Embodiment 1 Flowchart of the heat exchanger manufacturing method according to Embodiment 1 Conceptual diagram for explaining the heat exchanger manufacturing method according to Embodiment 1 Plan view of the back plate according to Embodiment 2 Flowchart of the heat exchanger manufacturing method according to Embodiment 2 Conceptual diagram for explaining the heat exchanger manufacturing method according to Embodiment 2 Related to Embodiment 3 Plan view of the back plate Cross-sectional view showing the main part of the indoor heat exchanger according to Embodiment 4 Flowchart of the heat exchanger manufacturing method according to Embodiment 4 Conceptual diagram for explaining the heat exchanger manufacturing method according to Embodiment 4 Cross-sectional view of the heat transfer tube for direct connection to the header according to Embodiment 5 Cross-sectional view of the portion of the indoor heat exchanger including the header according to Embodiment 5 Conceptual diagram for explaining the heat exchanger manufacturing method according to Embodiment 5 Cross-sectional view of the heat transfer tube for direct connection to the header according to Embodiment 6 Conceptual diagram for explaining the heat exchanger manufacturing method according to Embodiment 6 Conceptual diagram for explaining the heat exchanger manufacturing method according to Embodiment 7 Conceptual diagram for explaining the heat exchanger manufacturing method according to Embodiment 8

[0013] The following description of the air conditioning system according to the embodiment will be given with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

[0014] [Embodiment 1] As shown in Figure 1, the air conditioning system 600 according to this embodiment includes a refrigerant closed circuit 610 through which the refrigerant circulates. The refrigerant closed circuit 610 constitutes a refrigeration cycle using the refrigerant.

[0015] Specifically, the refrigerant closed circuit 610 includes a compressor 611 that compresses the refrigerant, an outdoor heat exchanger 612 that functions as a condenser to condense the compressed refrigerant, an expander 613 that expands the condensed refrigerant, a relay heat exchanger 614 that functions as an evaporator to evaporate the expanded refrigerant, and a gas-liquid separator 615 that allows the evaporated refrigerant to return to the compressor 611 while capturing any liquid refrigerant that has not evaporated completely.

[0016] Furthermore, the refrigerant closed circuit 610 also includes a four-way valve 616 that reverses the direction of the refrigerant flow in the refrigeration cycle. Figure 1 illustrates a state in which the outdoor heat exchanger 612 functions as a condenser and the intermediate heat exchanger 614 functions as an evaporator. Because the direction of the refrigerant flow can be reversed by the four-way valve 616, the outdoor heat exchanger 612 also functions as an evaporator, and the intermediate heat exchanger 614 also functions as a condenser.

[0017] Furthermore, the air conditioning unit 600 also includes a heat transfer medium closed circuit 620 independent of the refrigerant closed circuit 610. A heat transfer medium circulates through the heat transfer medium closed circuit 620. The heat transfer medium is a different fluid from the refrigerant circulating in the refrigerant closed circuit 610. In this embodiment, water is used as the heat transfer medium.

[0018] The heat transfer medium closed circuit 620 has a temperature control unit 621 that passes inside the intermediate heat exchanger 614 described above. In other words, the intermediate heat exchanger 614 is shared by the refrigerant closed circuit 610 and the heat transfer medium closed circuit 620.

[0019] Furthermore, the heat transfer medium closed circuit 620 includes an indoor heat exchanger 500 that performs heat exchange with the air in the space to be air-conditioned (hereinafter referred to as indoor air), a relay pipe 622 which is a flow path connecting the indoor heat exchanger 500 to the temperature control unit 621, and a pump 623 that circulates the heat transfer medium between the indoor heat exchanger 500 and the temperature control unit 621 through the relay pipe 622.

[0020] Furthermore, the air conditioning unit 600 has an outdoor fan 630 that promotes heat exchange between the refrigerant in the outdoor heat exchanger 612 and the outside air (hereinafter referred to as outside air). The outdoor fan 630 forms an airflow of outside air that passes through the outdoor heat exchanger 612.

[0021] Furthermore, the air conditioning unit 600 has an indoor fan 640 that promotes heat exchange between the heat transfer medium in the indoor heat exchanger 500 and the indoor air. The indoor fan 640 forms an airflow of indoor air that passes through the indoor heat exchanger 500.

[0022] The intermediate heat exchanger 614 causes heat exchange to occur between the refrigerant circulating in the refrigerant closed circuit 610 and the heat transfer medium circulating in the heat transfer medium closed circuit 620.

[0023] Specifically, when the intermediate heat exchanger 614 functions as an evaporator in the refrigerant closed circuit 610, the heat transfer medium circulating in the heat transfer medium closed circuit 620 is cooled in the temperature control unit 621. As a result, the cooled heat transfer medium flows through the indoor heat exchanger 500, and the space to be air-conditioned is cooled.

[0024] On the other hand, when the intermediate heat exchanger 614 functions as a condenser in the refrigerant closed circuit 610, the heat transfer medium circulating in the heat transfer medium closed circuit 620 is heated in the temperature control unit 621. As a result, the heated heat transfer medium flows through the indoor heat exchanger 500, and the space to be air-conditioned is heated.

[0025] In this way, the refrigerant closed circuit 610 plays the role of a cooperative device that adjusts the temperature of the heat transfer medium flowing through the indoor heat exchanger 500 using the refrigeration cycle.

[0026] Of the components of the air conditioning system 600 described above, the indoor heat exchanger 500 and the indoor fan 640 constitute the indoor unit 600a for the air conditioning system, which is located indoors, in the space that is to be air-conditioned.

[0027] Furthermore, the compressor 611, outdoor heat exchanger 612, gas-liquid separator 615, outdoor fan 630, and four-way valve 616 constitute an outdoor unit 600b for an air conditioning system, which is located outdoors.

[0028] Furthermore, the expander 613, the intermediate heat exchanger 614 including the temperature control unit 621, and the pump 623 constitute an air conditioning system repeater 600c. The air conditioning system repeater 600c is installed indoors in a location isolated from the space to be air-conditioned.

[0029] The air conditioning system 600 according to this embodiment is most distinctive in the configuration and manufacturing method of the indoor heat exchanger 500. Therefore, the indoor heat exchanger 500 will be described below. Note that the indoor heat exchanger 500 is an example of a heat exchanger according to this disclosure.

[0030] Figure 2 shows the external appearance of the indoor heat exchanger 500. The indoor heat exchanger 500 includes a fin structure 210. The fin structure 210 has metal fins 211 through which the previously described indoor air passes.

[0031] Furthermore, the indoor heat exchanger 500 includes a heat transfer tube group 220 composed of a plurality of heat transfer tubes 221. Each heat transfer tube 221 is made of metal, specifically copper or a copper-containing alloy. Each heat transfer tube 221 is inserted through a fin 211. Each heat transfer tube 221 is thermally coupled to the fin 211.

[0032] The heat transfer medium described above flows through each of the heat transfer tubes 221. Heat exchange takes place between the internal air passing through the fins 211 and the heat transfer medium flowing through the heat transfer tubes 221 via the fins 211 and the heat transfer tubes 221.

[0033] In this specification, "fin 211" refers to a component through which the heat transfer tube group 220 is inserted, and which is an assembly of components that promotes heat exchange between the heat transfer medium flowing through the heat transfer tube group 220 and the aforementioned internal air. Specifically, the fin 211 according to this embodiment is composed of an assembly of metal fin plates. That is, a plurality of fin plates are arranged parallel to each other to form the fin 211. Each heat transfer tube 221 passes through the plurality of fin plates that make up the fin 211. The aforementioned internal air then passes between the fin plates. The fin 211 may be composed of one or more corrugated fins.

[0034] Furthermore, the indoor heat exchanger 500 includes a header 100 located outside the fin structure 210. The header 100 is connected to a plurality of heat transfer tubes 221 extending from the fins 211. Hereinafter, each of the plurality of heat transfer tubes 221 connected to the header 100 among the heat transfer tube group 220 will be referred to as a "direct connection heat transfer tube 222 for the header".

[0035] The header 100 is also connected to the inlet pipe 500a and the outlet pipe 500b, which are located outside the fin structure 210. The relay pipe 622 shown in Figure 1 is connected to each of the inlet pipe 500a and the outlet pipe 500b.

[0036] Specifically, the heat transfer medium, whose temperature has been adjusted by the temperature control unit 621 shown in Figure 1, flows into the inside of the header 100 through the introduction pipe 500a. In addition, the heat transfer medium that has exchanged heat with the internal air as described above (hereinafter referred to as the heat-exchanged heat transfer medium) flows out from the discharge pipe 500b through the header 100 towards the temperature control unit 621 shown in Figure 1.

[0037] As shown in Figure 3, the header 100 has an inlet 100a and an outlet 100b. The inlet pipe 500a shown in Figure 2 is connected to the inlet 100a. The outlet pipe 500b shown in Figure 2 is connected to the outlet 100b.

[0038] The header 100 has a distribution function that (i) distributes the heat transfer medium that has flowed in through the introduction pipe 500a and the inlet 100a to a plurality of direct heat transfer tubes 222 for the header, and a merging function that merges the heat-exchanged heat transfer medium that has flowed in from each of the plurality of direct heat transfer tubes 222 for the header and discharges it from the outlet 100b in order to guide it to the discharge pipe 500b.

[0039] Furthermore, among the heat transfer tube group 220, the multiple direct-connection heat transfer tubes 222 described above also serve to hold the header 100. As a result, the header 100 is fixed to the fin structure 210 through the multiple direct-connection heat transfer tubes 222.

[0040] Specifically, the fin structure 210 has plate-shaped end plates 212 positioned at the ends of the fins 211, and the header 100 is held in a position opposite the end plates 212 by a plurality of heat transfer tubes 222 that connect directly to the header. The end plates 212 extend perpendicularly to the portion of the heat transfer tubes 221 that is inserted through the fins 211. In this embodiment, the heat transfer tubes 221 penetrate the fin plates constituting the fins 211 at a right angle, and the end plates 212 are positioned parallel to the fin plates at the ends in the direction of the fin plate arrangement.

[0041] Hereinafter, a direction parallel to the direction in which the header 100 and the end plate 212 face each other and representing the thickness of the header 100 is referred to as the "header thickness direction". The header thickness direction is perpendicular to the end plate 212.

[0042] Further, among the plurality of heat transfer tubes 221 constituting the heat transfer tube group 220, there are a plurality of pairs of return heat transfer tubes 223 that are not directly connected to the header 100, separate from the plurality of header-direct heat transfer tubes 222 connected to the header 100.

[0043] Both the header-direct heat transfer tubes 222 and the return heat transfer tubes 223 have an extending end portion 221a that extends outward from the end plate 212 to the outside of the fin structure 210. Each extending end portion 221a extends straight in the header thickness direction.

[0044] The extending end portion 221a of each header-direct heat transfer tube 222 is connected to the header 100. The extending end portion 221a of the header-direct heat transfer tube 222 holds the header 100 at a position facing the end plate 212.

[0045] On the other hand, the extending end portions 221a of the pair of return heat transfer tubes 223 are not in communication with the header 100 and are connected to each other. Hereinafter, the manner of connecting the pair of extending end portions 221a will be specifically described.

[0046] FIG. 4 is a plan view of the header 100 viewed with a line of sight parallel to the header thickness direction. As shown in FIG. 4, the header 100 has a shape with one direction as the longitudinal direction when viewed with a line of sight parallel to the header thickness direction. In FIG. 4, the upper surface 100c of the header 100, which is the farthest from the end plate 212 in the header thickness direction, is shown. The header-direct heat transfer tubes 222 and the return heat transfer tubes 223 shown in FIG. 3 are indicated by broken lines as hidden lines.

[0047] In FIG. 4, for the purpose of clearly showing the header-direct heat transfer tubes 222 and the return heat transfer tubes 223, the illustration of the inlet 100a and the outlet 100b shown in FIG. 3 is omitted. Actually, on the upper surface 100c of the header 100, as shown in FIG. 3, the inlet 100a and the outlet 100b are open.

[0048] As shown in FIG. 4, a folding tube joint 300 is provided for each pair of the folding heat transfer tubes 223. The folding tube joint 300 forms a folding flow path that connects the extending end portion 221a on one side of the pair of folding heat transfer tubes 223 and the extending end portion 221a on the other side.

[0049] The folding tube joint 300 is a tubular body bent in a U-shape convex in a direction away from the end plate 212 in the header thickness direction. Specifically, the folding tube joint 300 is constituted by a so-called U-bend tube.

[0050] In each pair of the folding heat transfer tubes 223, the heat medium flowing out from the extending end portion 221a of one folding heat transfer tube 223 is introduced into the extending end portion 221a of the other folding heat transfer tube 223 through the folding tube joint 300. In this way, the flow of the heat medium is turned back.

[0051] The heat transfer tube group 220 of the indoor heat exchanger 500 according to the present embodiment includes a plurality of pairs, specifically three pairs, of folding heat transfer tubes 223 whose extending end portions 221a are connected by the folding tube joints 300 and whose positions in a plane parallel to the end plate 212 overlap with the header 100.

[0052] Hereinafter, attention will be paid only to the pair of folding heat transfer tubes 223 and the set of folding tube joints 300 connecting the pair, whose positions in a plane parallel to the end plate 212 overlap with the header 100.

[0053] Next, the problems to be solved in the present embodiment will be described. As described above, the header-direct heat transfer tube 222 is connected to the header 100. Therefore, the position of the header-direct heat transfer tube 222 needs to overlap with the position of the header 100 in the header thickness direction.

[0054] On the other hand, the folding tube joint 300 is not directly connected to the header 100. That is, the heat medium does not flow directly from one of the folding tube joint 300 and the header 100 to the other. Therefore, originally, it is not necessary to overlap the position of the header 100 with the position of the folding tube joint 300 in the header thickness direction.

[0055] However, designing the shape of the header 100 as viewed in the header thickness direction, that is, the planar shape of the header 100, to avoid the folded pipe joint 300 may lead to increased complexity of the planar shape of the header 100.

[0056] In particular, as shown in Figure 4, if a folding pipe joint 300 is positioned between one direct-connection heat transfer tube 222 and another direct-connection heat transfer tube 222 in a plane parallel to the end plate 212, there is a concern that the planar shape of the header 100 will become significantly more complex if an attempt is made to avoid the folding pipe joint 300 by the planar shape of the header 100.

[0057] Therefore, the indoor heat exchanger 500 according to this embodiment adopts a configuration in which the header 100 avoids the folding pipe joint 300 in the header thickness direction. In this case, as shown in Figure 4, it is possible to create an overlap between the header projection region RH, which is obtained by vertically projecting the header 100 onto a virtual plane VP parallel to the end plate 212 and perpendicular to the header thickness direction, and the folding channel projection region RU, which is obtained by vertically projecting the folding channel formed by the folding pipe joint 300 onto the virtual plane VP. This avoids complicating the planar shape of the header 100.

[0058] On the other hand, if the header projection area RH and the return channel projection area RU overlap, the header 100 must be positioned further from the end plate 212 than the return pipe joint 300 in the header thickness direction. As a result, a problem arises in which the distance from the end plate 212 to the upper surface 100c of the header 100 in the header thickness direction, i.e., the header protrusion dimension, increases.

[0059] The following describes a configuration for solving these problems, referring to Figure 5.

[0060] Figure 5 is a cross-sectional view of the indoor heat exchanger 500 according to this embodiment at the position of line V-V in Figure 4. As shown in Figure 5, in this embodiment, in order to solve the above problem, a recessed portion 101 is formed in the surface of the back surface 100d of the header 100 that faces the end plate 212, in a direction away from the end plate 212 with respect to the thickness direction of the header, and a folding pipe joint 300 is inserted into the recessed portion 101.

[0061] If this configuration is not adopted, the back surface 100d of the header 100 must be positioned further from the end plate 212 than the top 310 of the return flow path formed by the return pipe joint 300, which is furthest from the end plate 212. As a result, the header projection dimension H, which is the distance in the header thickness direction from the end plate 212 to the upper surface 100c of the header 100, will increase.

[0062] In contrast, in this embodiment, at least a portion of the folding pipe joint 300, including the top portion 310, is inserted into the recessed portion 101. This makes it possible to position the back surface 100d of the header 100 closer to the end plate 212 than the top portion 310.

[0063] Therefore, as shown in Figure 4, even though the header projection area RH and the return channel projection area RU are arranged to overlap, the header protrusion dimension H shown in Figure 5 can be kept down. This contributes to making the indoor heat exchanger 500 more compact.

[0064] As shown in Figure 4, the indoor heat exchanger 500 according to this embodiment is equipped with a plurality of, specifically three, folded pipe joints 300 whose positions in a plane parallel to the end plate 212 overlap with the header 100. These three folded pipe joints 300 are adjacent to each other in a direction parallel to the end plate 212.

[0065] As shown in Figure 5, at least a portion of each of the three folded pipe joints 300, including the top portion 310, fits into a common recess 101. That is, although not shown, the projection area obtained by perpendicularly projecting the bottom surface of the recess 101, which faces the end plate 212, onto the virtual plane VP shown in Figure 4, encompasses the three folded flow channel projection areas RU described above.

[0066] The configuration of header 100 will be explained in detail below.

[0067] As shown in Figure 5, the header 100 has a metal back plate 110 that constitutes the back surface 100d facing the end plate 212, a resin header body portion 120 laminated on the back plate 110 in the header thickness direction perpendicular to the back plate 110, and a metal reinforcing plate 130 that constitutes the upper surface 100c described above. The header body portion 120 is sandwiched in the header thickness direction by the back plate 110 and the reinforcing plate 130. The back plate 110 extends parallel to the end plate 212.

[0068] The recessed portion 101 described above is composed of an opening 111 formed in the back plate 110 and a recess 121 formed in the header body portion 120 at the position of the opening 111. The recess 121 is recessed in the direction away from the end plate 212 with respect to the header thickness direction. The opening 111 exposes the recess 121.

[0069] In the following, a hairpin-shaped tubular body composed of a folding pipe joint 300 and a pair of extended ends 221a connected by the folding pipe joint 300 will be referred to as a "folded section 400". A folded section 400 is formed for each pair of folding heat transfer tubes 223. That is, in this embodiment, three folded sections 400 are formed.

[0070] Figure 5 illustrates a configuration in which only a portion of each folded pipe joint 300, including its top portion 310, is fitted into the recess 101. The entire folded pipe joint 300 may be fitted into the recess 101, or not only the folded pipe joint 300 but also a portion of the extended end portion 221a connected by the folded pipe joint 300 may be fitted into the recess 101. In short, it is sufficient that at least a portion of the folded portion 400, including its top portion 310, is fitted into the recess 101.

[0071] Figure 6 is a perspective view showing the back plate 110. In Figure 6, in order to clearly show the opening 111 of the back plate 110, the parts of the header 100 other than the back plate 110 are omitted from the illustration. As shown in Figure 6, three folded portions 400 are inserted through the opening 111. In this embodiment, a portion of each folded portion 400, including the top portion 310, protrudes from the opening 111.

[0072] As also shown in Figure 5, in this embodiment, a gap GP is secured between each folded portion 400 and the edge of the opening 111 of the back plate 110. In other words, in this embodiment, none of the folded portions 400 are in contact with the edge of the opening 111 of the back plate 110.

[0073] Figure 7 shows a recess 121 formed in the header body 120. The recess 121 is formed within the contact surface 122 of the header body 120, which is in close contact with the back plate 110 shown in Figure 6. The portions of the three folded-over parts 400 shown in Figure 6 that protrude from the opening 111 of the back plate 110 are accommodated in the recess 121.

[0074] The header body 120 has a rear portion 120a that constitutes the aforementioned contact surface 122, and a front portion 120b that is laminated on the rear portion 120a in the header thickness direction. The header body 120 is formed by joining the rear portion 120a and the front portion 120b in the header thickness direction. The rear portion 120a is in close contact with the back plate 110 shown in Figure 6 on the contact surface 122. The front portion 120b is in close contact with the reinforcing plate 130 shown in Figure 3.

[0075] As shown in Figure 5, the recess 121 is formed only in the rear portion 120a of the rear portion 120a and the front portion 120b.

[0076] The front portion 120b has an internal flow channel recess 124 that is recessed in the direction away from the end plate 212 with respect to the header thickness direction. The upper surface 123 of the rear portion 120a, which is opposite to the aforementioned contact surface 122 with respect to the header thickness direction, faces the bottom of the internal flow channel recess 124.

[0077] Furthermore, an internal flow path 125 for distribution is defined by the internal flow path recess 124 of the front section 120b and the upper surface 123 of the rear section 120a. The internal flow path 125 for distribution is for realizing the distribution function (i) described above and is in communication with the inlet 100a described above and the multiple direct-connection heat transfer tubes 222 of the header.

[0078] In addition, although not shown in the diagram, a second internal channel for merging, which realizes the (ii) merging function described above, is defined by a front section 120b and a rear section 120a, in the same manner as the internal channel for distribution 125.

[0079] In other words, a merging internal flow path (not shown) is defined by a second internal flow path recess (not shown) formed in the front section 120b and the upper surface 123 of the rear section 120a. This merging internal flow path (not shown) is connected to a plurality of direct-connection heat transfer tubes 222 for the header, which are separate from the direct-connection heat transfer tubes 222 that flow through the distribution internal flow path 125, and to the aforementioned outlet 100b.

[0080] The distribution internal channel 125 and the merging internal channel (not shown) described above are examples of internal channels related to this disclosure. Hereinafter, the projection area obtained by vertically projecting the distribution internal channel 125 onto the virtual plane VP shown in Figure 4 will be referred to as the "distribution internal channel projection area." Similarly, the projection area obtained by vertically projecting the merging internal channel (not shown) onto the virtual plane VP shown in Figure 4 will be referred to as the "merging internal channel projection area." The distribution internal channel projection area and the merging internal channel projection area are examples of internal channel projection areas related to this disclosure.

[0081] In this embodiment, the recessed portion 101 and the internal flow channel are adjacent to each other in the header thickness direction, and the recessed portion projection region, which is the projection region obtained by perpendicularly projecting the recessed portion 101 onto the virtual plane VP shown in Figure 4, overlaps with the internal flow channel projection region.

[0082] Specifically, the recessed projection region overlaps with both the distribution internal channel projection region and the merging internal channel projection region. The distribution internal channel projection region overlaps with at least one of the return channel projection regions RU shown in Figure 4. The merging internal channel projection region also overlaps with at least one of the return channel projection regions RU shown in Figure 4. However, a configuration in which the recessed projection region overlaps with only one of the distribution internal channel projection region and the merging internal channel projection region is also possible.

[0083] Despite the complex structure of the header body 120, the header body 120 can be easily manufactured by joining the front portion 120b, which has internal flow channel recesses 124 and a second internal flow channel for merging (not shown), and the rear portion 120a, which has recesses 121, in the header thickness direction.

[0084] Furthermore, in the header body 120, the positions of the area occupied by the internal flow path and the area occupied by the recess 101 are different in the header thickness direction, so that the area that can be used as an internal flow path in the header body 120 is not easily limited by the presence of the recess 101.

[0085] Next, the configuration of the part of the header 100 that is connected to the heat transfer tube 222 for direct connection to the header will be described.

[0086] As shown in Figure 7, a plurality of insertion holes 126 are opened in the plane of the aforementioned contact surface 122 in the rear portion 120a. The plurality of insertion holes 126 are distributed on the sides of the aforementioned recess 121 within the plane of the contact surface 122. Specifically, the plurality of insertion holes 126 are distributed on both sides of the recess 121 in the longitudinal direction of the header 100.

[0087] An insertion hole 126 is formed for each of the aforementioned heat transfer tubes 222 that connect directly to the header, and there is a one-to-one correspondence between the insertion hole 126 and the heat transfer tube 222. In this embodiment, as shown in Figures 3 and 4, six heat transfer tubes 222 that connect directly to the header are connected to the header 100. Correspondingly, as shown in Figure 7, six insertion holes 126 open in the rear portion 120a.

[0088] Furthermore, as shown in Figure 6, through holes 112 are formed at the positions of each insertion hole 126 in the back plate 110 shown in Figure 3, which is in close contact with the contact surface 122. The through holes 112 communicate with the insertion holes 126.

[0089] As shown in Figure 5, the extended end 221a of the header direct heat transfer tube 222 is connected to the insertion hole 126 and the through hole 112 which communicates with the insertion hole 126. Each header direct heat transfer tube 222 communicates with the distribution internal flow path 125 or the merging internal flow path (not shown) through the through hole 112 and the insertion hole 126.

[0090] Furthermore, elastic sealing members 140 are provided between the rear plate 110 and the rear portion 120a, with each extended end 221a of the header direct heat transfer tube 222 being provided. The elastic sealing members 140 are formed from an elastic body, specifically a rubber O-ring.

[0091] The back plate 110 is pressed against the rear portion 120a of the header body 120 by screws 150. The elastic sealing member 140 is elastically compressed in the header thickness direction by the back plate 110 and the rear portion 120a, surrounding the extended end 221a of the header direct heat transfer tube 222 or the pipe joint connected to the extended end 221a.

[0092] As described above, a seal is applied to the interface where the back plate 110 and the rear portion 120a are in pressure contact, specifically around the extended end 221a of the header direct heat transfer tube 222, to prevent leakage of the heat transfer medium. Each elastic sealing member 140 plays a role in this sealing.

[0093] Therefore, it is not necessarily required to apply a seal to the portion of the interface where the rear plate 110 and the rear portion 120a are in pressure contact, specifically the portion surrounding the aforementioned recess 101. In other words, the irregularly shaped O-ring that can surround the edge of the recess 121 shown in Figure 7 is not necessarily required.

[0094] Referring to Figures 8 and 9, the heat exchanger manufacturing method according to this embodiment will be described below.

[0095] First, the heat exchanger body 510, which constitutes the main part of the indoor heat exchanger 500 other than the header 100, is prepared (step S10). The heat exchanger body 510 consists of a fin structure 210 and the portions of each heat transfer tube 221 that constitute the heat transfer tube group 220, which are inserted into the fins 211 and the extended ends 221a. Note that the concept of the heat exchanger body 510 does not include the end pipe joints 160 which will be described later. Step S10 is an example of the heat exchanger body preparation process according to this disclosure.

[0096] Next, the indoor heat exchanger 500 is obtained by assembling the header 100 and the folding pipe joint 300 to the heat exchanger body 510 (step S50). Step S50 is an example of the assembly process according to the present disclosure. The contents of step S50 will be described below.

[0097] First, a folding pipe joint 300 is joined to each pair of folding heat transfer tubes 223 in the heat exchanger body 510 (step S11A). As previously described, the folding pipe joint 300 connects the extended end 221a of one pair of folding heat transfer tubes 223 to the extended end 221a of the other pair. The joining of these extended ends 221a to the folding pipe joint 300 can be achieved by brazing. Step S11A is an example of a folding pipe joint joining process according to the present disclosure.

[0098] Meanwhile, a back plate 110 having the aforementioned opening 111 and through hole 112 is prepared (step S20A). As previously described, the back plate 110, like the heat transfer tube 221, is made of metal, specifically copper or a copper-containing alloy. Step S20A is an example of a back plate preparation step according to the present disclosure.

[0099] Next, end pipe fittings 160 are joined to each of the through holes 112 in the back plate 110 (step S21A). Each end pipe fitting 160 is a component that will constitute the end of the header direct connection heat transfer tube 222. Specifically, each end pipe fitting 160 is an example of a pipe fitting that is joined to the extended end 221a of the header direct connection heat transfer tube 222. That is, an end pipe fitting 160 is prepared for each header direct connection heat transfer tube 222, and there is a one-to-one correspondence between the end pipe fitting 160 and the header direct connection heat transfer tube 222.

[0100] Each end pipe fitting 160 is composed of a straight, extending tubular body. The end pipe fittings 160 are inserted through each of the through holes 112 in the back plate 110 and joined to the portion of the back plate 110 that includes the edge of the through hole 112.

[0101] The end pipe fitting 160, like the back plate 110, is made of metal, specifically copper or a copper-containing alloy. Therefore, the end pipe fitting 160 and the back plate 110 can be joined by brazing.

[0102] Step S21A is an example of a pre-joining process in which necessary components are joined to the back plate 110 prior to joining the back plate 110 to the heat exchanger body 510.

[0103] Next, the back plate 110, which has gone through step S21A, is joined to the extended ends 221a of each direct-connection heat transfer tube 222 in the heat exchanger body 510, which has gone through step S11A (step S30A). Step S30A is an example of the back plate joining process according to the present disclosure.

[0104] Specifically, each end pipe fitting 160 joined to the back plate 110 is joined to the extended end 221a of the header direct connection heat transfer tube 222 corresponding to the end pipe fitting 160. The joining of the end pipe fitting 160 and the extended end 221a of the header direct connection heat transfer tube 222 can be achieved by brazing. In this way, the back plate 110 is joined to the heat exchanger body 510 via the end pipe fittings 160.

[0105] In step S30A, with the folding pipe joint 300 inserted through the opening 111 of the back plate 110, the back plate 110 is joined to the extended ends 221a of each header-direct heat transfer tube 222 in the heat exchanger body 510.

[0106] Next, the header body portion 120 is attached to the back plate 110 via the elastic sealing member 140 (step S31A). Step S31A is an example of the header body portion attachment process according to the present disclosure.

[0107] Specifically, as shown in Figure 3, the header body 120 is attached to the back plate 110 through the reinforcing plate 130 and a screw 150. The head of the screw 150 is in contact with the back plate 110, and the shaft of the screw 150 is inserted through the reinforcing plate 130 and the header body 120. The header body 120 is fixed to the back plate 110 by screwing the shaft of the screw 150 into the back plate 110.

[0108] By screwing the screw 150 into the back plate 110, the header body 120 is pressed against the back plate 110. As a result, each elastic sealing member 140 is elastically compressed in the header thickness direction by the header body 120 and the back plate 110. In this manner, the header 100 is assembled to the heat exchanger body 510.

[0109] Furthermore, after step S30A and before step S31A, the portion of each folded pipe fitting 300, including the top portion 310, protrudes from the opening 111 of the back plate 110. In step S31A, the portion of each folded pipe fitting 300 that protrudes from the opening 111 fits into the recess 121 of the header body portion 120. As a result, as shown in Figure 5, an indoor heat exchanger 500 is obtained in which at least the portion constituting the top portion 310 of each folded pipe fitting 300 fits into the recess 101.

[0110] [Embodiment 2] Figure 5 illustrates a configuration in which a gap GP is secured between each folded portion 400 and the edge of the opening 111 of the back plate 110, that is, a configuration in which each folded portion 400 and the edge of the opening 111 of the back plate 110 are not in contact. The folded portion 400 may be joined to the edge of the opening 111 of the back plate 110. Specific examples are described below.

[0111] As shown in Figure 10, the following description will exemplify the case where there is one folded portion 400 that fits into the opening 111 of the back plate 110.

[0112] The opening 111 in this embodiment is of a size necessary and sufficient to accommodate the portion of the folding pipe joint 300, including the top portion 310, within one folding portion 400. In this embodiment, the portion of the folding pipe joint 300, including the top portion 310, is joined to the edge of the opening 111 of the back plate 110.

[0113] The folding pipe joint 300, like the back plate 110, is made of metal, specifically copper or a copper-containing alloy. Therefore, the joining of the folding pipe joint 300 and the edge of the opening 111 of the back plate 110 can be achieved by brazing. The brazing material BR that joins the folding pipe joint 300 and the edge of the opening 111 is placed at least between the portion of the folding pipe joint 300 facing the edge of the opening 111 and the edge of the opening 111. The brazing material BR may also be placed around the entire circumference of the edge of the opening 111.

[0114] The configuration of the indoor heat exchanger 500 according to this embodiment, other than the configuration shown in Figure 10, is the same as in Embodiment 1. Although not shown, the header body portion 120 according to this embodiment has a recess 121 formed together with the opening 111 shown in Figure 10 to form a recessed portion 101. The shape and size of the recess 121 according to this embodiment, as viewed in the header thickness direction, are the same as the shape and size of the opening 111 shown in Figure 10, as viewed in the header thickness direction.

[0115] Referring to Figures 11 and 12, the heat exchanger manufacturing method according to this embodiment will be described below. The following will mainly describe the differences from the heat exchanger manufacturing method shown in Figures 8 and 9.

[0116] In step S21B, which is a pre-joining process according to this embodiment, not only the multiple end pipe fittings 160 but also the folded pipe fitting 300 are joined to the back plate 110. The folded pipe fitting 300 is inserted through the opening 111 of the back plate 110 and joined to the edge of the opening 111 in the back plate 110. This joining can be achieved by brazing, as described above.

[0117] As described above, in this embodiment, the folding pipe joint 300 is joined to the back plate 110 in advance, so step S11A shown in Figures 8 and 9 is omitted.

[0118] Furthermore, in step S30B, which is the back plate joining process according to this embodiment, in addition to joining each end pipe joint 160 joined to the back plate 110 to the extended end 221a of the header direct heat transfer tube 222, the folded pipe joint 300 joined to the back plate 110 to the extended end 221a of one of the pair of folded heat transfer tubes 223 and the extended end 221a of the other.

[0119] The joining of the end pipe joint 160 to the extended end 221a of the heat transfer tube 222 for direct connection to the header, and the joining of the folded pipe joint 300 to the extended end 221a of the heat transfer tube 223 can be achieved by brazing. In this way, in the back plate joining process according to this embodiment, the back plate 110 is joined to the heat exchanger body 510 via the end pipe joint 160 and the folded pipe joint 300.

[0120] Other steps are the same as in Embodiment 1. The same effects as in Embodiment 1 can be obtained with this embodiment as well. Furthermore, in the indoor heat exchanger 500 according to this embodiment, the folded portion 400 and the edge of the opening 111 of the back plate 110 are joined together, so even if vibration is applied to the indoor heat exchanger 500, the generation of abnormal noise due to contact between the folded portion 400 and the edge of the opening 111 can be avoided.

[0121] [Embodiment 3] Figure 13 shows a back plate 110 according to Embodiment 3. As shown in Figure 13, a plurality of openings 111 are formed in the back plate 110, and one or more folded portions 400 may be fitted into each opening 111. The number of folded portions 400 fitted into each opening 111 may differ for each opening 111.

[0122] The configuration of the indoor heat exchanger 500 according to this embodiment, other than the configuration shown in Figure 13, is the same as in Embodiment 1. Although not shown, the header body portion 120 according to this embodiment has recesses 121 formed together with the openings 111 shown in Figure 13 to form a recessed portion 101, with each recess 111 having a recess 121. The shape and size of the openings 111 and the recesses 121 that form the recessed portion 101 together with the openings 111 are the same when viewed in the header thickness direction.

[0123] In any of the multiple openings 111, a gap GP as shown in Figures 5 and 6 may be secured between the edge of the opening 111 and all the folded portions 400 fitted into the opening 111. In that case, the indoor heat exchanger 500 according to this embodiment can be obtained using the manufacturing method shown in Figures 8 and 9.

[0124] Furthermore, in any of the multiple openings 111, the edge of the opening 111 and all the folded portions 400 fitted into the opening 111 may be joined together. In that case, the indoor heat exchanger 500 according to this embodiment can be obtained using the manufacturing method shown in Figures 11 and 12.

[0125] Furthermore, in one opening 111, a gap GP is secured between the edge of the opening 111 and all the folded portions 400 fitted into the opening 111, while in another opening 111, the edge of the opening 111 and all the folded portions 400 fitted into the opening 111 may be joined together.

[0126] In that case, the indoor heat exchanger 500 according to this embodiment can be obtained by using in combination the manufacturing methods shown in Figures 8 and 9 and the manufacturing methods shown in Figures 11 and 12. That is, the folded pipe joint 300 that does not contact the edge of the opening 111 is joined to the heat exchanger body 510 in step S11A shown in Figures 8 and 9. On the other hand, the folded pipe joint 300 that is joined to the edge of the opening 111 is joined to the edge of the opening 111 in step S21B shown in Figures 11 and 12.

[0127] [Embodiment 4] In Embodiments 1-3 described above, a tubular body, i.e., a folded pipe joint 300, was shown as a specific example of a folded flow path connecting pairs of folded heat transfer tubes 223. The folded flow path may be formed by a cavity (hereinafter referred to as an internal cavity) formed inside the header 100. A specific example thereof will be described below.

[0128] Figure 14 shows the main parts of the indoor heat exchanger 500 according to this embodiment. In Figure 14, in order to clearly show only the main parts of the header 100, the configurations related to the inlet 100a and outlet 100b shown in Figure 5, the reinforcing plate 130, etc. are omitted from the illustration.

[0129] As shown in Figure 14, the header 100 according to this embodiment has a pair of insertion openings 113 and an internal cavity 129.

[0130] A pair of insertion openings 113 is formed for each pair of folded heat transfer tubes 223. Each insertion opening 113 opens into the back surface 100d of the header 100. Each insertion opening 113 is composed of a hole that penetrates the back plate 110, similar to the previously described through-holes 112 formed in the back plate 110.

[0131] An internal cavity 129 is formed in the header body portion 120 for each pair of insertion openings 113. The internal cavity 129 connects one insertion opening 113 to the other insertion opening 113.

[0132] Specifically, the internal cavity 129 has a pair of rising cavity portions 127 that extend in the direction of the header thickness, and a communicating cavity portion 128 that extends in a direction perpendicular to the direction of the header thickness, that is, in a direction parallel to the back plate 110. One of the pair of rising cavity portions 127 (hereinafter referred to as the first rising cavity portion 1271) rises from one insertion opening 113 in the direction of the header thickness. The other of the pair of rising cavity portions 127 (hereinafter referred to as the second rising cavity portion 1272) rises from the other insertion opening 113 in the direction of the header thickness. The communicating cavity portion 128 connects the first rising cavity portion 1271 and the second rising cavity portion 1272.

[0133] The communicating cavity 128 connects the upper end of the first rising cavity 1271, which is furthest from the back surface 100d, with the upper end of the second rising cavity 1272, which is furthest from the back surface 100d. For this reason, the communicating cavity 128 is positioned further from the back plate 110 in the header thickness direction than the contact surface 122 of the header body 120, which is in close contact with the back plate 110.

[0134] In this embodiment, the aforementioned folding channel is formed by the pair of insertion openings 113 and the internal cavity 129. Therefore, in this embodiment, the projection region obtained by perpendicularly projecting the pair of insertion openings 113 and the internal cavity 129 onto a virtual plane VP extending perpendicularly in the header thickness direction is the folding channel projection region. The fact that this folding channel projection region overlaps with the header projection region obtained by perpendicularly projecting the header 100 onto the virtual plane VP is the same as in Embodiments 1-3.

[0135] In the configuration according to this embodiment, as in the configuration according to Embodiments 1-3, the back surface 100d of the header 100 is positioned closer to the end plate 212 than the top portion 129a of the return channel. Therefore, even though the header projection area and the return channel projection area overlap, the header protrusion dimension H described above can be suppressed.

[0136] Furthermore, in this embodiment, the internal cavity 129 is formed only in the rear portion 120a of the header body portion 120, which consists of a rear portion 120a and a front portion 120b. The front portion 120b, together with the rear portion 120a, defines the internal distribution channel 125 and the internal merging channel (not shown), which is the same as in Embodiment 1-3.

[0137] In this way, it is achieved that the areas occupied by the internal flow channels and the areas occupied by the internal cavities 129 in the header body 120 are located at different positions in the header thickness direction. Therefore, the area in the header body 120 that can be used as an internal flow channel is not easily limited by the presence of the internal cavities 129.

[0138] Furthermore, the projection region of the return channel in this embodiment overlaps with the projection region of the internal channel obtained by perpendicularly projecting the internal channel onto the virtual plane VP, which is the same as in Embodiments 1-3. Specifically, the “internal channel projection region” here refers to the projection region obtained by perpendicularly projecting the distribution internal channel 125 onto the virtual plane VP and the projection region obtained by perpendicularly projecting a merging internal channel (not shown) onto the virtual plane VP.

[0139] In this embodiment, the flow of the heat transfer medium is folded back in the header thickness direction within the internal cavity 129. Accordingly, the extended end 221a of one pair of folded heat transfer tubes 223 is connected to one insertion opening 113, and the extended end 221a of the other pair of folded heat transfer tubes 223 is connected to the other insertion opening 113.

[0140] Specifically, each pair of extended ends 221a in a pair of folded heat transfer tubes 223 is connected to the insertion opening 113 via the end pipe joint 160 described above.

[0141] Furthermore, the header 100 according to this embodiment further includes elastic sealing members 170 provided at each extended end 221a of the folded heat transfer tube 223. The elastic sealing members 170 surround the end pipe joint 160, which serves as a pipe joint connected to the extended end 221a of the folded heat transfer tube 223, while being elastically compressed in the header thickness direction by the back plate 110 and the rear portion 120a of the header body 120.

[0142] The significance of the first rising cavity 1271 and the second rising cavity 1272 will be described below.

[0143] As a comparative example, consider the case where the internal cavity 129 does not have a first rising cavity portion 1271 and a second rising cavity portion 1272, but is composed of a recess (hereinafter referred to as a "communicating recess") that is recessed from the close contact surface 122 and connects one insertion opening 113 to the other insertion opening 113.

[0144] In that case, an O-ring with a shape and size that can surround the communication recess is required to prevent leakage of the heat transfer medium from the communication recess. Such an O-ring must be non-circular when viewed from a line parallel to the header thickness direction and have a long circumference. Such an O-ring is prone to falling off the header body 120 during the manufacturing process of the indoor heat exchanger 500, which can reduce manufacturing efficiency.

[0145] In contrast, in this embodiment, the internal cavity 129 has a first rising cavity portion 1271 and a second rising cavity portion 1272. This makes it possible to position the communicating cavity portion 128 away from the close contact surface 122 in the header thickness direction.

[0146] Therefore, in order to prevent leakage of the heat transfer medium from the internal cavity 129, it is sufficient to seal only the boundary between the first rising cavity 1271 and the insertion opening 113, and the boundary between the second rising cavity 1272 and the insertion opening 113. Such sealing can be achieved using the same material as the material used to seal the boundary between the insertion hole 126 and the through hole 112 as described above.

[0147] In other words, according to this embodiment, the elastic sealing member 170 for sealing the boundary between the first rising cavity 1271 and the insertion opening 113, and the elastic sealing member 170 for sealing the boundary between the second rising cavity 1272 and the insertion opening 113, can be the same as the elastic sealing member 140 described above. Specifically, the elastic sealing members 140 and 170 are composed of circular O-rings when viewed from a line parallel to the header thickness direction. The irregularly shaped O-rings required in the above comparative embodiment are unnecessary.

[0148] Referring to Figures 15 and 16, the heat exchanger manufacturing method according to this embodiment will be described below. The following will mainly describe the differences from the heat exchanger manufacturing method shown in Figures 11 and 12.

[0149] First, in step S20C, which is the back plate preparation step according to this embodiment, a back plate 110 is prepared in which not only through holes 112 but also a pair of insertion openings 113 are formed.

[0150] Next, in step S21C, which is a pre-joining process according to this embodiment, the end pipe fittings 160 are joined not only to each of the through holes 112 in the back plate 110, but also to each of the insertion openings 113. Each end pipe fitting 160 is joined to the edge of the through hole 112 or insertion opening 113 in the back plate 110 while passing through the through hole 112 or insertion opening 113 in the back plate 110. This joining can be achieved by brazing.

[0151] The end pipe joint 160 joined to the through hole 112 is a component that will constitute the end of the heat transfer tube 222 for direct connection to the header, specifically an example of a pipe joint that will be connected to the extended end 221a of the heat transfer tube 222 for direct connection to the header. The end pipe joint 160 joined to the insertion opening 113 is a component that will constitute the end of the folded heat transfer tube 223, specifically an example of a pipe joint that will be connected to the extended end 221a of the folded heat transfer tube 223.

[0152] Next, in step S30C, which is the back plate joining process according to this embodiment, a portion of the multiple end pipe fittings 160 joined to the back plate 110 is joined to the extended end 221a of the direct-connection heat transfer tube 222 of the header. The remaining portion of the multiple end pipe fittings 160 joined to the back plate 110 is joined to the extended end 221a of the folded heat transfer tube 223. As a result, the back plate 110 is joined to the heat exchanger body 510 via the multiple end pipe fittings 160.

[0153] Furthermore, the joining of the end pipe joint 160 to the extended end 221a of the direct-connection heat transfer tube 222 to the header, and the joining of the end pipe joint 160 to the extended end 221a of the folded-back heat transfer tube 223, can be achieved by brazing.

[0154] Next, in step S31C, which is the header body mounting process according to this embodiment, the header body 120, in which the internal cavity 129 is formed, is attached to the back plate 110 via the elastic sealing members 140 and 170.

[0155] In step S31C, the header body 120 is positioned relative to the back plate 110 to which the end pipe fittings 160 are joined, such that (a) the end pipe fitting 160 joined to the extended end 221a of the header direct heat transfer tube 222 communicates with the distribution internal flow path 125 or the merging internal flow path (not shown), and (b) the end pipe fitting 160 joined to the extended end 221a of the return heat transfer tube 223 communicates with the internal cavity 129.

[0156] Then, with the header positioned in this manner, the screw 150 is screwed into the back plate 110, causing the header body 120 to be pressed against the back plate 110. As a result, the elastic sealing members 140 and 170 are elastically compressed in the header thickness direction by the header body 120 and the back plate 110. In this way, the header 100 is assembled to the heat exchanger body 510. The other steps are the same as in Embodiment 1 or 2.

[0157] [Embodiment 5] Figures 5 and 9 show one configuration of the arrangement of the elastic sealing member 140, which is responsible for sealing to prevent leakage of the heat transfer medium from the header 100. In this configuration, the ring-shaped elastic sealing member 140 surrounding the end pipe joint 160 is arranged in a state in which it is elastically compressed in the header thickness direction by the back plate 110 and the header body portion 120.

[0158] However, if the above sealing is achieved, the direction in which the elastic sealing member 140 is compressed is not particularly limited. Below, as a modified example applicable to any of the embodiments 1-4 described above, we will describe a configuration in which the ring-shaped elastic sealing member 140 is arranged in a compressed state in a direction perpendicular to the header thickness direction, that is, in a direction parallel to the virtual plane VP shown in Figure 4 (hereinafter referred to as the in-plane direction).

[0159] Figure 17 shows a cross-sectional view of the end portion of the heat transfer tube 222 for direct connection to the header according to this embodiment, including the insertion portion 230. The configuration of the insertion portion 230 of the heat transfer tube 222 for direct connection to the header according to this embodiment will be described below with reference to Figure 17.

[0160] Here, "insertion portion 230" refers to the portion of the heat transfer tube 222 for direct connection to the header that is inserted into the header 100. In other words, as shown in Figure 7, the header 100 has a plurality of insertion holes 126, and each insertion hole 126 receives the corresponding insertion portion 230. Each insertion hole 126 is connected to the internal flow path described above.

[0161] As shown in Figure 17, in this embodiment, similar to the configurations shown in Figures 5 and 9, the insertion portion 230 of the heat transfer tube 222 for direct connection to the header is formed by an end pipe joint 160, which serves as a pipe joint connected to the extended end 221a. However, as will be shown in a specific example in Embodiment 6 later, if the end pipe joint 160 is not used, the insertion portion 230 may be formed by the extended end 221a.

[0162] In this embodiment, the insertion portion 230 of each header-direct heat transfer tube 222 has an elastic seal member holding portion 240 that holds an elastic seal member 140. The elastic seal member 140 used in this embodiment is also ring-shaped when viewed in the header thickness direction, similar to the elastic seal member 140 shown in Figures 5 and 9. The ring-shaped elastic seal member 140 that surrounds the insertion portion 230 while in contact with the insertion portion 230 is held by the elastic seal member holding portion 240.

[0163] The elastic seal member holding portion 240 is composed of a pair of flange portions 240a and 240b. Each of the flange portions 240a and 240b protrudes in a flange shape from the cylindrical tubular body (hereinafter referred to as the straight-bore main body portion) that constitutes the main body of the insertion portion 230. One flange portion 240a and the other flange portion 240b face each other in the longitudinal direction of the end of the direct-connection heat transfer tube 222 for the header, that is, in the header thickness direction.

[0164] A ring-shaped elastic sealing member 140 is positioned between one flange portion 240a and the other flange portion 240b. The ring-shaped elastic sealing member 140 can be attached to the insertion portion 230 while being sandwiched in the header thickness direction by the pair of flange portions 240a and 240b.

[0165] Figure 18 shows the state in which the insertion portion 230 of the heat transfer tube 222 for direct connection to the header is inserted into the insertion hole 126 of the header 100. As shown in Figure 18, in the indoor heat exchanger 500 according to this embodiment, the elastic sealing member 140 surrounds the insertion portion 230 in a state in which it is elastically compressed in an in-plane direction perpendicular to the header thickness direction by the insertion portion 230 and the inner circumferential surface of the insertion hole 126.

[0166] In this way, the elastic sealing member 140 closes the gap between the insertion portion 230 and the inner surface of the insertion hole 126 all around. As a result, the elastic sealing member 140 provides sealing to prevent leakage of the heat transfer medium from the header 100.

[0167] Referring to Figure 19, the heat exchanger manufacturing method according to this embodiment will be described below. In Figure 19, steps S10, S11A, and S20A are the same as steps S10, S11A, and S20A in Figure 9, respectively. Below, the differences between steps S21A, S30A, and S31A in Figure 19 and the manufacturing method shown in Figure 9 will be described.

[0168] In this embodiment, an end pipe joint 160 having an elastic seal member holding portion 240 as shown in Figure 17 is prepared in advance. As an example, each of the flange portions 240a and 240b constituting the elastic seal member holding portion 240 can be obtained by applying a plastic deformation process to the straight cylindrical main body portion constituting the main body of the insertion portion 230 to locally expand the pipe diameter.

[0169] Then, in step S21A, which is a pre-joining process according to this embodiment, the end pipe joints 160, on which the elastic seal member holding portion 240 is formed, are joined to each of the through holes 112 in the back plate 110. After step S21A, the insertion portion 230 of each end pipe joint 160 protrudes from the back plate 110.

[0170] In step S21A, it is preferable to join the end pipe fitting 160 and the back plate 110 by crimping. Specifically, the portion of the end pipe fitting 160 that fits into the through hole 112 of the back plate 110 is subjected to plastic deformation to expand the pipe diameter of the end pipe fitting 160. As a result, the outer surface of the end pipe fitting 160 comes into close contact with the inner surface of the through hole 112. Consequently, the end pipe fitting 160 is fixed to the back plate 110.

[0171] Next, in step S30A, which is the back plate joining process according to this embodiment, each end pipe joint 160 joined to the back plate 110 is joined to the extended end 221a of the header direct heat transfer tube 222. In this way, the back plate 110 is joined to the heat exchanger body 510 via a plurality of end pipe joints 160.

[0172] In step S30A, the elastic sealing member 140 is attached to the elastic sealing member holding portion 240 of the insertion portion 230 that protrudes from the back plate 110 of each header direct heat transfer tube 222.

[0173] However, the timing of attaching the elastic seal member 140 to the elastic seal member holding portion 240 is not particularly limited as long as it is before step S31A, which is the header body mounting process. In this way, the elastic seal member 140 is held in the elastic seal member holding portion 240 of each insertion portion 230 before step S31A, which is the header body mounting process.

[0174] Next, in step S31A, which is the header body mounting process according to this embodiment, the header body 120 is attached to the back plate 110. In step S31A, the insertion portion 230 holding the elastic sealing member 140 is inserted into the header body 120 in the header thickness direction.

[0175] As shown in Figure 17, the elastic sealing member 140 is positioned between a pair of flanges 240a and 240b that are aligned in the header thickness direction. Therefore, during the process of inserting the insertion portion 230 into the insertion hole 126, the position of the elastic sealing member 140 relative to the insertion portion 230 is less likely to shift in the header thickness direction.

[0176] When the insertion portion 230 into the header body portion 120 is completed, as shown in Figure 18, the elastic sealing member 140 is elastically compressed in a plane perpendicular to the header thickness direction between the insertion portion 230 and the inner circumferential surface of the insertion hole 126. This provides sealing to prevent leakage of the heat transfer medium from the header 100.

[0177] [Embodiment 6] Figure 17 illustrates a configuration in which the elastic seal member holding portion 240 is integrally formed with the straight-bodied main body portion, which is the part of the insertion portion 230 other than the elastic seal member holding portion 240. However, the elastic seal member holding portion 240 may be a separate component from the straight-bodied main body portion, and may be composed of a component attached to the straight-bodied main body portion. Specific examples are described below.

[0178] As shown in Figure 20, the elastic seal member holding portion 240 according to this embodiment is composed of a pair of ring members 240x and 240y. The ring members 240x and 240y are separate components from the straight cylindrical main body portion of the insertion portion 230. Each of the ring members 240x and 240y is ring-shaped when viewed from a line parallel to the header thickness direction, similar to the elastic seal member 140.

[0179] Each of the ring members 240x and 240y is fixed to the straight cylindrical main body of the insertion portion 230 while fitted into the straight cylindrical main body. Each of the ring members 240x and 240y protrudes from the straight cylindrical main body in a flange-like manner, with one ring member 240x and the other ring member 240y facing each other in the header thickness direction.

[0180] A ring-shaped elastic sealing member 140 is positioned between one ring member 240x and the other ring member 240y. The ring-shaped elastic sealing member 140 can be attached to the insertion portion 230 while being sandwiched in the header thickness direction by the pair of ring members 240x and 240y.

[0181] In this embodiment, the insertion portion 230 having the elastic seal member holding portion 240 is formed by the extended end portion 221a. In other words, in this embodiment, the end pipe joint 160 shown in Figure 17 is not used.

[0182] Referring to Figure 21, the heat exchanger manufacturing method according to this embodiment will be described below. In Figure 21, step S20A is the same as step S20A in Figure 9. Below, the differences between steps S30A, S40, and S31A in Figure 21 and the manufacturing method shown in Figure 9 will be described.

[0183] In step S30A, which is the back plate joining process according to this embodiment, the back plate 110 is directly joined to the extended ends 221a of each direct-connection heat transfer tube 222 in the heat exchanger body 510. Here, "directly joined" means that the extended ends 221a are joined to the back plate 110 without using the end pipe joint 160 shown in Figure 9.

[0184] Next, in this embodiment, an elastic seal member holding portion 240 is formed on the insertion portion 230 of each header direct heat transfer tube 222 that protrudes from the back plate 110 (step S40). Step S40 is an example of an elastic seal member holding portion formation process in which an elastic seal member holding portion 240 is formed on the insertion portion 230.

[0185] Specifically, in step S40, first, the ring members 240x and 240y shown in Figure 20 are prepared. The inner diameters of these ring members 240x and 240y are larger than the outer diameter of the insertion portion 230 of each header direct heat transfer tube 222.

[0186] Next, the ring members 240x and 240y are fitted into the insertion portions 230 of the respective header direct heat transfer tubes 222. Then, the fitted ring members 240x and 240y are fixed to the insertion portions 230 by crimping.

[0187] Specifically, the portion of the insertion portion 230 into which the ring members 240x and 240y are fitted is subjected to plastic deformation to expand the diameter of the insertion portion 230. As a result, the outer surface of the insertion portion 230 comes into close contact with the inner surface of the ring members 240x and 240y. Consequently, the ring members 240x and 240y are fixed to the insertion portion 230. This completes the elastic seal member holding portion 240.

[0188] Furthermore, it is preferable to join the back plate 110 and the extended end 221a in step S30A by crimping. Therefore, the joining of the back plate 110 and the extended end 221a by crimping in step S30A and the joining of the ring members 240x and 240y and the extended end 221a by crimping in step S40 may be performed together using a common tool for expanding the pipe diameter.

[0189] Next, the elastic sealing members 140 are attached to the elastic sealing member holding portions 240 of each insertion portion 230, and then in step S31A, which is the header body mounting process, the header body portion 120 is attached to the back plate 110. In this step S31A, the insertion portion 230 holding the elastic sealing member 140 is inserted into the header body portion 120 in the header thickness direction.

[0190] As shown in Figure 20, the elastic sealing member 140 is positioned between a pair of ring members 240x and 240y that are aligned in the header thickness direction. Therefore, during the process of inserting the insertion portion 230 into the insertion hole 126, the position of the elastic sealing member 140 relative to the insertion portion 230 is less likely to shift in the header thickness direction.

[0191] When the insertion portion 230 into the header body portion 120 is completed, the elastic sealing member 140 is elastically compressed in a plane perpendicular to the header thickness direction between the insertion portion 230 and the inner circumferential surface of the insertion hole 126. This provides sealing to prevent leakage of the heat transfer medium from the header 100.

[0192] [Embodiment 7] Embodiments 5-6 show a configuration in which an elastic seal member holding portion 240 is provided on the heat transfer tube 222 for direct connection to the header. The elastic seal member holding portion 240 can be provided not only on the heat transfer tube 222 for direct connection to the header, but also on the folded heat transfer tube 223 according to Embodiment 4.

[0193] Referring to Figure 22, a method for manufacturing a heat exchanger will be described in which the elastic seal member holding portion 240 according to Embodiment 5 is provided not only for the direct-connection heat transfer tube 222 of the header, but also for the folded heat transfer tube 223 according to Embodiment 4.

[0194] In Figure 22, steps S10 and S20C are the same as steps S10 and S20C in Figure 16, respectively. Below, we will describe the differences between steps S21C, S30C, and S31C in Figure 22 and the manufacturing methods shown in Figures 16 and 19.

[0195] In step S21C, which is a pre-joining process according to this embodiment, the end pipe joint 160, on which the elastic seal member holding portion 240 is formed, is joined not only to each of the through holes 112 of the back plate 110, but also to the insertion opening 113. In this step S21C, it is preferable to join the end pipe joint 160 and the back plate 110 by the crimping process described above. The inner diameter of the insertion opening 113 is the same as the inner diameter of the through hole 112.

[0196] Next, in step S30C, which is the back plate joining process according to this embodiment, a portion of the multiple end pipe joints 160 joined to the back plate 110 is joined to the extended end 221a of the header direct heat transfer tube 222, and the remaining portion is joined to the extended end 221a of the folded heat transfer tube 223. In this way, the back plate 110 is joined to the heat exchanger body 510 via the multiple end pipe joints 160.

[0197] Furthermore, in step S30C, the elastic seal member 140 is attached to the elastic seal member holding portion 240 of the heat transfer tube 222 for direct connection to the header, and the elastic seal member 170 is attached to the elastic seal member holding portion 240 of the heat transfer tube 223 for folding back. Note that the same elastic seal member 170 as the elastic seal member 140 can be used.

[0198] However, the timing of attaching the elastic seal member 140 or 170 to the elastic seal member holding portion 240 is not particularly limited as long as it is before step S31C, which is the header body mounting process. In this way, the elastic seal member 140 or 170 is held in the elastic seal member holding portion 240 of each insertion portion 230 before step S31C, which is the header body mounting process.

[0199] Next, in step S31C, which is the header body mounting process according to this embodiment, the header body 120 is attached to the back plate 110. In this step S31C, the insertion portion 230 holding the elastic sealing member 140 or 170 is inserted into the header body 120 in the header thickness direction.

[0200] The elastic sealing member 140 or 170 is positioned between a pair of flange portions 240a and 240b that are aligned in the header thickness direction. Therefore, during the process of inserting the insertion portion 230 into the insertion hole 126, the position of the elastic sealing member 140 relative to the insertion portion 230 is less likely to shift in the header thickness direction. Also, during the process of inserting the insertion portion 230 into the rising cavity 127, the position of the elastic sealing member 170 relative to the insertion portion 230 is less likely to shift in the header thickness direction.

[0201] When the insertion portion 230 into the header body portion 120 is completed, the elastic sealing member 140 is elastically compressed in a plane perpendicular to the header thickness direction by the insertion portion 230 and the inner circumferential surface of the insertion hole 126. Similarly, the elastic sealing member 170 is elastically compressed in a plane perpendicular to the header thickness direction by the insertion portion 230 and the inner circumferential surface of the rising cavity portion 127. This achieves sealing to prevent leakage of the heat transfer medium from the header 100.

[0202] [Embodiment 8] The above describes a configuration in which the elastic seal member holding portion 240 according to Embodiment 5 is applied to the folded heat transfer tube 223 according to Embodiment 4. The elastic seal member holding portion 240 according to Embodiment 6 may also be applied to the folded heat transfer tube 223 according to Embodiment 4.

[0203] Referring to Figure 23, a method for manufacturing a heat exchanger will be described in which the elastic seal member holding portion 240 according to Embodiment 6 is provided not only for the direct-connection heat transfer tube 222 of the header, but also for the folded heat transfer tube 223 according to Embodiment 4.

[0204] In Figure 23, step S20C is the same as step S20C in Figure 22. Below, we will describe the differences between steps S30C, S40, and S31C in Figure 23 and the manufacturing methods shown in Figures 21 and 22.

[0205] In step S30C, which is a back plate joining process according to this embodiment, the back plate 110 is directly joined to the extended ends 221a of each header direct heat transfer tube 222 and each folded heat transfer tube 223 in the heat exchanger body 510.

[0206] Next, in step S40, which is the process for forming the elastic seal member holding portion according to this embodiment, the elastic seal member holding portion 240 is formed not only on the insertion portion 230 protruding from the back plate 110 of each direct-connection heat transfer tube 222 of the header, but also on the insertion portion 230 protruding from the back plate 110 of each folded-back heat transfer tube 223.

[0207] In this embodiment, the elastic seal member holding portion 240 is composed of the ring members 240x and 240y shown in Figure 20. As described in Embodiment 5, the crimping of the back plate 110 and the extended end portion 221a in step S30A and the crimping of the ring members 240x and 240y and the extended end portion 221a in step S40 may be performed together using a common tool for expanding the pipe diameter.

[0208] Next, the elastic sealing members 140 or 170 are attached to the elastic sealing member holding portion 240 of each insertion portion 230, and then in step S31A, which is the header body mounting process, the header body portion 120 is attached to the back plate 110. In this step S31C, the insertion portion 230 holding the elastic sealing member 140 or 170 is inserted into the header body portion 120 in the header thickness direction.

[0209] The elastic sealing member 140 or 170 is positioned between a pair of ring members 240x and 240y aligned in the header thickness direction. Therefore, during the process of inserting the insertion portion 230 into the insertion hole 126, the position of the elastic sealing member 140 relative to the insertion portion 230 is less likely to shift in the header thickness direction. Also, during the process of inserting the insertion portion 230 into the rising cavity 127, the position of the elastic sealing member 170 relative to the insertion portion 230 is less likely to shift in the header thickness direction.

[0210] When the insertion portion 230 into the header body portion 120 is completed, the elastic sealing member 140 is elastically compressed in a plane perpendicular to the header thickness direction by the insertion portion 230 and the inner circumferential surface of the insertion hole 126. Similarly, the elastic sealing member 170 is elastically compressed in a plane perpendicular to the header thickness direction by the insertion portion 230 and the inner circumferential surface of the rising cavity portion 127. This achieves sealing to prevent leakage of the heat transfer medium from the header 100.

[0211] Embodiments 1-8 have been described above. The following modifications are also possible.

[0212] (1) In Embodiment 1, Figures 5 and 6 illustrate a gap GP between the folded portion 400 and the edge of the opening 111, but the folded portion 400 may be in contact with the edge of the opening 111. Even in that case, if the folded portion 400 is not joined to the edge of the opening 111, the manufacturing method shown in Figure 9 can be adopted.

[0213] However, by ensuring a gap GP between the folded portion 400 and the edge of the opening 111, contact between the folded portion 400 and the edge of the opening 111 is less likely to occur even when vibrations are applied to the indoor heat exchanger 500. Therefore, the generation of abnormal noises and damage to the folded portion 400 caused by such contact can be avoided.

[0214] Furthermore, by securing a gap GP between the folded portion 400 and the edge of the opening 111, the degree of freedom in the in-plane position of the back plate 110 relative to the folded portion 400 in the direction perpendicular to the header thickness direction is increased. Therefore, the positioning of the back plate 110 relative to the heat exchanger body 510 in step S30 of Figure 9 can be easily performed.

[0215] (2) In the explanation of step S21B in Figure 12, brazing was given as an example of a joining means for joining the folded pipe joint 300 to the back plate 110, but the joining means is not limited to brazing. The folded pipe joint 300 may be joined to the back plate 110 by adhesive. Similarly, the joining means for joining the end pipe joint 160 or the extension end 221a to the back plate 110 is not limited to brazing. The end pipe joint 160 or the extension end 221a may be joined to the back plate 110 by adhesive. Also, as previously described, the end pipe joint 160 or the extension end 221a may be joined to the back plate 110 by crimping. The same applies to other joining locations.

[0216] (3) In addition, while embodiments 1-4, 5, and 7 illustrate a manufacturing method using end pipe fittings 160, as described in embodiments 6 and 8, the indoor heat exchanger 500 can also be manufactured without using end pipe fittings 160. In other words, end pipe fittings 160 are not essential as a component of the indoor heat exchanger 500.

[0217] As an example, in the manufacturing method shown in Figure 9, step S21A may be omitted. In that case, in step S30A, the extended end 221a of the heat transfer tube 222 for direct connection to the header may be brazed directly to the inner edge of the through hole 112 of the back plate 110 without using the end pipe joint 160.

[0218] Furthermore, in the manufacturing method shown in Figure 12, the brazing of the end pipe joint 160 to the back plate 110 in step S21B may be omitted. In that case, in step S30B, the extended end 221a of the direct-connection heat transfer tube 222 to the header can be brazed directly to the inner edge of the through hole 112 in the back plate 110 without using the end pipe joint 160.

[0219] Furthermore, in the manufacturing method shown in Figure 16, step S21C may be omitted. In that case, in step S30C, the extended end 221a of the direct-connection heat transfer tube 222 for the header may be brazed directly to the inner edge of the through-hole 112 of the back plate 110 without using the end pipe joint 160. Similarly, the extended end 221a of the folded heat transfer tube 223 may be brazed directly to the inner edge of the insertion opening 113 of the back plate 110 without using the end pipe joint 160.

[0220] This disclosure allows for various embodiments and modifications without departing from the broad spirit and scope of this disclosure. The embodiments described above are for illustrative purposes only and do not limit the scope of this disclosure. The scope of this disclosure is indicated by the claims, not by the embodiments. Various modifications made within the scope of the claims and the equivalent significance of the disclosure are deemed to be within the scope of this disclosure.

[0221] This application is based on Japanese Patent Application No. 2024-205792, filed on 26 November 2024. The entire specification, claims, and drawings of Japanese Patent Application No. 2024-205792 are incorporated herein by reference.

[0222] 100 Header, 100a Inlet, 100b Outlet, 100c Top surface, 100d Back surface, 101 Recessed section, 110 Back plate, 111 Opening, 112 Through hole, 113 Insertion opening (folding channel), 120 Header body section, 120a Rear section, 120b Front section, 121 Recess, 122 Close contact surface, 123 Upper surface, 124 Recess for internal channel, 125 Internal channel for distribution (internal channel), 126 Insertion hole, 127 Rising cavity section, 1271 First rising cavity section, 1272 Second rising cavity section, 128 Connecting cavity section, 129 Internal cavity (folding channel), 129a Top section, 130 Reinforcement plate, 140 Elastic sealing member, 150 Screw, 160 End pipe fitting (pipe fitting), 170 Elastic sealing member, 210 Fin structure, 211 Fin, 212 End plate, 220 Heat transfer tube group, 221 Heat transfer tube, 221a Extended end, 222 Heat transfer tube for direct connection to header, 223 Heat transfer tube for folding, 230 Insertion part, 240 Elastic sealing member holding part, 240a, 240b Flange part, 240x, 240y Ring member, 300 Folding pipe fitting (folding flow path), 310 Top part, 400 Folding part, 500 Indoor heat exchanger (heat exchanger), 500a Inlet piping, 500b Outlet piping, 510 Heat exchanger body, 600 Air conditioning system, 600a Indoor unit for air conditioning system, 600b Outdoor unit for air conditioning system, 600c Air conditioning relay unit, 610 refrigerant closed circuit (cooperative equipment), 611 compressor, 612 outdoor heat exchanger, 613 expander, 614 relay heat exchanger, 615 gas-liquid separator, 616 four-way valve, 620 heat transfer medium closed circuit, 621 temperature control unit, 622 relay piping, 623 pump, 630 outdoor fan, 640 indoor fan, BR brazing material, GP gap, VP virtual plane, RH header projection area, RU return flow path projection area.

Claims

1. A fin structure having fins and end plates positioned at the ends of the fins; a group of heat transfer tubes comprising a plurality of heat transfer tubes inserted through each fin, wherein each heat transfer tube has an extended end extending outward from the end plate to the fin structure, and the plurality of heat transfer tubes include a pair of folded heat transfer tubes whose extended ends are connected to each other, and a plurality of heat transfer tubes other than the folded heat transfer tubes that connect directly to the header; a header positioned opposite the end plate and connected to the extended end of each of the direct-connection heat transfer tubes that connect directly to the header, forming a common internal flow path that communicates with the plurality of direct-connection heat transfer tubes; and a folded flow path connecting the extended end of one of the pair of folded heat transfer tubes to the extended end of the other pair. A heat exchanger wherein the header projection region obtained by projecting the header perpendicularly onto a virtual plane parallel to the end plate and the return channel projection region obtained by projecting the return channel perpendicularly onto the virtual plane overlap, and the back surface of the header facing the end plate is positioned closer to the end plate than the top of the return channel furthest from the end plate.

2. The heat exchanger according to claim 1, wherein the folded flow path is composed of a folded pipe joint, which is a tubular body connecting the extended end of one of the pair of folded heat transfer tubes to the extended end of the other, and a recess is formed in the back surface of the header, in a direction away from the end plate, and at least the portion constituting the top of the folded pipe joint fits into the recess.

3. The heat exchanger according to claim 2, wherein the header comprises a metal back plate constituting the back surface, and a resin header body laminated on the back plate in the header thickness direction perpendicular to the back plate, and the recess is composed of an opening formed in the back plate and a recess formed in the header body at the position of the opening.

4. A folded portion, comprising a folding pipe fitting and a pair of extended ends connected by the folding pipe fitting, is inserted through the opening of the back plate, and a gap is secured between the edge of the opening of the back plate and the folded portion, according to claim 3.

5. A folded portion, comprising the folded pipe fitting and the pair of extended ends connected by the folded pipe fitting, is inserted through the opening of the back plate, and the edge of the opening of the back plate and the folded portion are joined together, the heat exchanger according to claim 3.

6. The heat exchanger according to any one of claims 3 to 5, wherein the header body has a rear portion that is in close contact with the back plate and a front portion that is stacked on the rear portion in the direction of the header thickness, the recess is formed only in the rear portion of the rear portion and the front portion, and the internal flow path is formed in the front portion.

7. The heat exchanger according to any one of claims 3 to 6, wherein each of the heat transfer tubes for direct connection to the header has an insertion portion inserted into the header, the insertion portion being composed of the extension end or a pipe joint joined to the extension end, and the header further comprises an elastic sealing member provided for each insertion portion, surrounding the insertion portion in a state where it is elastically compressed in the thickness direction of the header by the back plate and the header body.

8. The heat exchanger according to any one of claims 3 to 6, wherein each of the heat transfer tubes for direct connection to the header has an insertion portion inserted into the header, the insertion portion being composed of the extension end or a pipe joint joined to the extension end, and the header further comprises an elastic sealing member provided for each insertion portion, surrounding the insertion portion in a state where it is elastically compressed in a direction perpendicular to the thickness direction of the header by the insertion portion and the header body.

9. The heat exchanger according to any one of claims 2 to 8, wherein the heat transfer tube group includes a plurality of pairs of folded heat transfer tubes, and for each pair of folded heat transfer tubes, the extended end of one of the folded heat transfer tubes in the pair is connected to the extended end of the other folded heat transfer tube by a folded tube joint, and at least the portion of the top of each folded tube joint fits into a common recess.

10. The heat exchanger according to claim 1, wherein the header has a pair of insertion openings each opening on the back surface, and an internal cavity that, together with the pair of insertion openings, constitutes the return flow path, and the internal cavity connects one of the insertion openings to the other insertion opening, the extended end of one of the pair of return heat transfer tubes is connected to one of the insertion openings, and the extended end of the other of the pair of return heat transfer tubes is connected to the other insertion opening.

11. The heat exchanger according to claim 10, wherein each of the heat transfer tubes for direct connection to the header and each of the heat transfer tubes for folding back have an insertion portion inserted into the header, the insertion portion being composed of the extended end or a pipe joint joined to the extended end, the header having a pair of insertion openings formed thereon and a metal back plate constituting the back surface, a resin header body portion laminated on the back plate in the header thickness direction perpendicular to the back plate and having the internal cavity formed thereon, and an elastic sealing member provided for each insertion portion, surrounding the insertion portion in a state elastically compressed in the header thickness direction by the back plate and the header body portion.

12. The heat exchanger according to claim 10, wherein each of the heat transfer tubes for direct connection to the header and each of the heat transfer tubes for return connection have an insertion portion inserted into the header, the insertion portion being composed of the extended end or a pipe joint joined to the extended end, the header having a pair of insertion openings formed thereon and a metal back plate constituting the back surface, a resin header body portion laminated on the back plate in the header thickness direction perpendicular to the back plate and having the internal cavity formed thereon, and an elastic sealing member provided for each insertion portion, surrounding the insertion portion in a state where it is elastically compressed in a direction perpendicular to the header thickness direction by the insertion portion and the header body portion.

13. The heat exchanger according to any one of claims 1 to 12, wherein the internal flow path projection region obtained by perpendicularly projecting the internal flow path onto the virtual plane and the return flow path projection region overlap.

14. An indoor unit for an air conditioning system comprising: an indoor heat exchanger comprising a heat exchanger according to any one of claims 1 to 13, wherein a heat transfer medium flows through each of the heat transfer tubes in the heat exchanger; and an indoor fan that passes air of a space to be air-conditioned through the indoor heat exchanger.

15. An air conditioning system comprising: an indoor unit for an air conditioning system as described in claim 14; and a cooperative device for adjusting the temperature of the heat transfer medium using a refrigeration cycle.

16. A fin structure having fins and end plates positioned at the ends of the fins; a group of heat transfer tubes comprising a plurality of heat transfer tubes inserted through each fin, wherein each heat transfer tube has an extended end extending outward from the end plate to the fin structure, and the plurality of heat transfer tubes include a pair of folded heat transfer tubes whose extended ends are connected to each other, and a plurality of heat transfer tubes other than the folded heat transfer tubes that connect directly to the header; a header positioned opposite the end plate and connected to the extended end of each of the direct-connection heat transfer tubes that connect directly to the header, and constituting a common internal flow path that communicates with the plurality of direct-connection heat transfer tubes that connect directly to the header; and a folded flow path connecting the extended end of one of the pair of folded heat transfer tubes to the extended end of the other pair. A heat exchanger manufacturing method for manufacturing a heat exchanger in which a header projection region obtained by perpendicularly projecting the header onto a virtual plane parallel to the end plate and a return channel projection region obtained by perpendicularly projecting the return channel onto the virtual plane overlap, comprising: a heat exchanger body preparation step of preparing a heat exchanger body composed of the fin structure and the portion of each of the heat transfer tubes constituting the heat transfer tube group that is inserted into the fin and the extended end; and an assembly step of assembling the header onto the heat exchanger body, wherein in the heat exchanger obtained through the assembly step, the back surface of the header facing the end plate is positioned closer to the end plate than the top of the return channel furthest from the end plate.

17. The method for manufacturing a heat exchanger according to claim 16, wherein the folded flow path is composed of a folded pipe joint, which is a tubular body connecting the extended end of one of the pair of folded heat transfer tubes to the extended end of the other, in which the assembly step involves assembling not only the header but also the folded pipe joint to the heat exchanger body, and a recess is formed in the back surface of the header assembled to the heat exchanger body in the assembly step, which faces the end plate, and in the heat exchanger obtained through the assembly step, at least the portion of the folded pipe joint that constitutes the top is recessed into the recess.

18. The method for manufacturing a heat exchanger according to claim 17, wherein the header comprises a metal back plate constituting the back surface and a resin header body laminated on the back plate, the recess is composed of an opening formed in the back plate and a recess formed in the header body at the position of the opening, the assembly step includes a back plate joining step of joining the back plate to the extended ends of each of the direct-connection heat transfer tubes of the header in the heat exchanger body, and a header body mounting step of attaching the header body to the back plate, wherein after the back plate joining step and before the header body mounting step, at least the portion constituting the top of the folded pipe joint protrudes from the opening in the back plate, and in the header body mounting step, the portion of the folded pipe joint protruding from the opening fits into the recess in the header body.

19. The method for manufacturing a heat exchanger according to claim 18, wherein the assembly step includes, before the back plate joining step, a folding pipe joint joining step in which the folding pipe joint is joined to the extended end of one of the pair of folding heat transfer tubes in the heat exchanger body and to the extended end of the other, and in the back plate joining step, the back plate is joined to the extended ends of each of the direct-connection heat transfer tubes for the header in the heat exchanger body with the folding pipe joint inserted through the opening of the back plate.

20. The method for manufacturing a heat exchanger according to claim 18, wherein the assembly step includes, before the back plate joining step, a pre-joining step of joining the folded pipe joint, which is inserted through the opening of the back plate, to the edge of the opening, and in the back plate joining step, the folded pipe joint joined to the back plate is joined to the extended end of one of the pair of folded heat transfer tubes in the heat exchanger body and to the extended end of the other.

21. Each of the direct-connection heat transfer tubes for the header has an insertion portion that protrudes from the back plate after the back plate joining process and before the header body mounting process, and which is to be inserted into the header body during the header body mounting process, and each of the insertion portions has an elastic seal member holding portion that holds an elastic seal member surrounding the insertion portion, and in the header body mounting process, each of the insertion portions that is holding the elastic seal member in the elastic seal member holding portion is inserted into the header body, the heat exchanger manufacturing method according to any one of claims 18 to 20.

22. The method for manufacturing a heat exchanger according to claim 16, wherein the header assembled to the heat exchanger body in the assembly step has a pair of insertion openings opening on the back surface, and an internal cavity which together with the pair of insertion openings constitutes the return flow path, and which connects one of the insertion openings to the other insertion opening, and in the assembly step, the extended end of one of the pair of return heat transfer tubes is connected to one of the insertion openings, and the extended end of the other of the pair of return heat transfer tubes is connected to the other insertion opening.

23. The method for manufacturing a heat exchanger according to claim 22, wherein the header comprises a metal back plate having a pair of insertion openings formed thereon and constituting the back surface, and a resin header body portion laminated on the back plate in the header thickness direction perpendicular to the back plate and having the internal cavity formed thereon, and the assembly step comprises a back plate joining step of joining the back plate to the extended ends of each of the direct heat transfer tubes and each of the folded heat transfer tubes in the heat exchanger body portion, and a header body portion attachment step of attaching the header body portion to the back plate.

24. Each of the heat transfer tubes for direct connection to the header and each of the heat transfer tubes for folding back has an insertion portion that protrudes from the back plate after the back plate joining process and before the header body mounting process, and which is to be inserted into the header body during the header body mounting process, and each of the insertion portions has an elastic seal member holding portion that holds an elastic seal member surrounding the insertion portion, and in the header body mounting process, each of the insertion portions that is holding the elastic seal member in the elastic seal member holding portion is inserted into the header body, the heat exchanger manufacturing method according to claim 23.

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