Air conditioner

Abstract

To provide an air conditioner capable of suppressing generation of white rust in an indoor unit more than conventional ones.SOLUTION: In an air conditioner 100, a second liquid pipe 20b (refrigeration cycle pipe) and a second gas pipe 30b (refrigeration cycle pipe) formed of aluminum or an aluminum alloy are connected to one end side and the other end side of an indoor heat exchanger 4 and an outdoor heat exchanger 3, and of the refrigeration cycle pipes, a sacrificial anticorrosive layer is formed on outer surfaces of the second liquid pipe 20b (refrigeration cycle pipe) and the second gas pipe 30b (refrigeration cycle pipe) arranged inside an outdoor unit 101 and connected to the outdoor heat exchanger 3, and the sacrificial anticorrosive layer is not formed on outer surfaces of the second liquid pipe 20b (refrigeration cycle pipe) and the second gas pipe 30b (refrigeration cycle pipe) arranged inside an indoor unit 102 and connected to the indoor heat exchanger 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an air conditioner. [Background technology]

[0002] Conventionally, air conditioners have been known that have a heat exchanger in which a sacrificial corrosion protection layer is formed over the entire surface of heat transfer tubes made of aluminum or an aluminum alloy (see, for example, Patent Document 1). In such air conditioners, the sacrificial corrosion protection layer prevents corrosion of the aluminum that forms the base of the heat transfer tubes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-051137 Summary of the Invention [Problem to be solved by the invention]

[0004] The sacrificial anticorrosion layer is generally made up of a metal such as zinc, which has a lower potential than the metal forming the base, and therefore is prone to white rust. However, when white rust forms inside the indoor unit of an air conditioner, it scatters into the room as air is blown in. Furthermore, this white rust may clog the drain hole that drains condensation from the indoor heat exchanger.

[0005] An object of the present invention is to provide an air conditioner in which the occurrence of white rust inside the indoor unit is suppressed more than ever before. [Means for solving the problem]

[0006] The air conditioner of the present invention is an air conditioner comprising an indoor unit having an indoor heat exchanger that exchanges heat between indoor air and a refrigerant, and an outdoor unit having an outdoor heat exchanger that exchanges heat between outdoor air and a refrigerant, wherein refrigeration cycle piping made of aluminum or an aluminum alloy is connected to one end and the other end of the indoor heat exchanger and the outdoor heat exchanger, and a sacrificial corrosion protection layer is formed on the outer surface of the refrigeration cycle piping that is located inside the outdoor unit and connected to the outdoor heat exchanger, and no sacrificial corrosion protection layer is formed on the outer surface of the refrigeration cycle piping that is located inside the indoor unit and connected to the indoor heat exchanger.

[0007] The air conditioner of the present invention is an air conditioner comprising an indoor heat exchanger that exchanges heat between indoor air and a refrigerant, and an outdoor heat exchanger that exchanges heat between outdoor air and a refrigerant, wherein the indoor heat exchanger and the outdoor heat exchanger each have a heat transfer tube that forms a serpentine pipeline with a plurality of plate-shaped fins stacked at a predetermined interval in the plate thickness direction, a straight pipe section that passes through the plurality of fins in the stacking direction, and return bend sections that are located on both outer sides of the stacked fins, and the heat transfer tubes in the indoor heat exchanger and the outdoor heat exchanger are made of aluminum or an aluminum alloy, and a sacrificial corrosion protection layer is formed on the outer surface of at least one of the return bend sections that are located on the outer sides of the heat transfer tube of the outdoor heat exchanger, and the sacrificial corrosion protection layer is not formed on the outer surface of at least one of the return bend sections that are located on the outer sides of the heat transfer tube of the indoor heat exchanger. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an air conditioner in which the occurrence of white rust inside the indoor unit is suppressed more than conventionally. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a configuration explanatory diagram of an air conditioner according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram illustrating the configuration of an outdoor heat exchanger in the air conditioner shown in FIG. [Figure 3] 3 is a cross-sectional view of a heat transfer tube that constitutes the outdoor heat exchanger shown in FIG. 2. [Figure 4] FIG. 2 is a diagram illustrating the configuration of an indoor heat exchanger in the air conditioner shown in FIG. [Figure 5A] 5 is a cross-sectional view of a straight pipe portion of the U-shaped pipe shown in FIG. 4. [Figure 5B] 5 is a cross-sectional view of a return bend in the U-shaped tube shown in FIG. 4. [Figure 5C] FIG. 5 is a cross-sectional view of the connecting pipe shown in FIG. [Figure 6] FIG. 2 is a cross-sectional view of the dissimilar metal joint shown in FIG. [Figure 7] FIG. 2 is a diagram illustrating the configuration of the drain pan shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a mode (embodiment) for carrying out an air conditioner of the present invention will be described in detail with reference to the drawings as appropriate. First, the overall configuration of the air conditioner will be described, and then the indoor heat exchanger and the outdoor heat exchanger will be described in more detail.

[0011] <Air conditioner> FIG. 1 is a configuration diagram of an air conditioner 100 according to this embodiment. In FIG. 1, the flow of refrigerant in the heating cycle is indicated by solid arrows, and the flow of refrigerant in the cooling cycle is indicated by dashed arrows. As shown in FIG. 1, the air conditioner 100 includes an outdoor unit 101 installed outdoors and an indoor unit 102 installed indoors.

[0012] During cooling operation, the air conditioner 100 takes in liquid refrigerant (including gas-liquid two-phase refrigerant) from the outdoor unit 101 via the liquid piping 20, which has an expansion valve 6 midway along its length, to flow through heat transfer pipes 22 (see FIG. 4 ) of the indoor heat exchanger 4 in the indoor unit 102. At this time, the indoor heat exchanger 4 functions as an evaporator to cool the surrounding air. The gas refrigerant vaporized in the indoor heat exchanger 4 is then sent to the outdoor unit 101 via the gas piping 30.

[0013] The gas refrigerant sent to the outdoor unit 101 becomes liquid refrigerant (including gas-liquid two-phase refrigerant) after passing through the compressor 7 of the outdoor unit 101 and the outdoor heat exchanger 3 that functions as a condenser. This liquid refrigerant is sent again to the indoor unit 102 via the liquid piping 20.

[0014] Furthermore, during heating operation, the air conditioner 100 sends high-temperature, high-pressure gas refrigerant from the compressor 7 to the indoor unit 102 via the gas piping 30 by switching the refrigerant flow path with the four-way valve 8 of the outdoor unit 101. At this time, the indoor heat exchanger 4 functions as a condenser to heat the surrounding air. Then, the liquid refrigerant (including gas-liquid two-phase refrigerant) condensed in the heat transfer tube 22 (see FIG. 4) of the indoor heat exchanger 4 is sent to the outdoor unit 101 via the liquid piping 20. The liquid refrigerant sent to the outdoor unit 101 passes through the outdoor heat exchanger 3, which functions as an evaporator of the outdoor unit 101, and the compressor 7, and becomes high-temperature, high-pressure gas refrigerant again, and is sent to the indoor unit 102.

[0015] The liquid pipe 20 is composed of a first liquid pipe 20a made of copper and second liquid pipes 20b made of aluminum or an aluminum alloy and arranged on both ends of the first liquid pipe 20a. The gas pipe 30 is composed of a first gas pipe 30a made of copper and second gas pipes 30b made of aluminum or an aluminum alloy and arranged on both ends of the first gas pipe 30a.

[0016] <Outdoor heat exchanger and indoor heat exchanger> As shown in Fig. 1, the outdoor heat exchanger 3 exchanges heat between outdoor air drawn into the outdoor unit 101 by the outdoor fan 9 and a refrigerant flowing in a heat transfer tube 12 (see Fig. 2) described later. The outdoor air after heat exchange is discharged outside the outdoor unit 101.

[0017] Fig. 2 is a diagram illustrating the configuration of the outdoor heat exchanger 3. For convenience of drawing, Fig. 2 omits the middle of the outdoor heat exchanger 3 in the longitudinal direction (the direction in which fins 11, which will be described later, are stacked). Fig. 2 is also a partial view of the outdoor heat exchanger 3 on the connection side with the second gas pipe 30b shown in Fig. 1. As shown in FIG. 2, the outdoor heat exchanger 3 includes plate-shaped fins 11 and heat transfer tubes 12. A plurality of plate-like fins 11 are stacked at predetermined intervals in the plate thickness direction. In this embodiment, the fins 11 are made of aluminum or an aluminum alloy.

[0018] As shown in Figure 2, the heat transfer tube 12 has a straight tube section 13a that passes through the multiple fins 11 in the stacking direction, and return bend sections 13b that are arranged on both outsides of the stacked fins 11, sandwiching them on the inside, forming a meandering pipe path 10a. Specifically, the heat transfer tube 12 has a plurality of U-shaped tubes 13, each consisting of a pair of straight tube sections 13a and one return bend section 13b connecting them, and a plurality of connecting tubes 14, which form only the return bend section 13b of the pipe line 10a. The U-shaped pipe 13 in this embodiment is assumed to be a straight pipe bent into a U-shape. At the other end of the straight pipe portion 13a that passes through the plurality of fins 11, an expanded diameter portion 13a2 is formed, the inner diameter of which is larger than that of a general portion 13a1 that occupies most of the straight pipe portion 13a.

[0019] The connecting pipe 14 has an arc shape bent with the same curvature as the return bend portion 13b of the U-shaped pipe 13. The end of the connecting pipe 14 is press-fitted into the expanded diameter portion 13a2 of the U-shaped pipe 13 and is connected to the expanded diameter portion 13a2 by brazing.

[0020] 2, the second gas pipe 30b is press-fitted into the expanded diameter portion 13a2 of the U-tube 13 that forms one end of the heat transfer tube 12, and is connected to the expanded diameter portion 13a2 by brazing. Although not shown, the second liquid pipe 20b (see FIG. 1) is connected to the other end of the heat transfer tube 12 by brazing. The second gas pipe 30b (see FIG. 2) and the second liquid pipe 20b (see FIG. 1) connected to one end and the other end of the heat transfer tube 12, respectively, correspond to "refrigeration cycle pipes." In this embodiment, the heat transfer tube 12 (see FIG. 2), the second gas pipe 30b (see FIG. 2), and the second liquid pipe 20b (see FIG. 1) are made of aluminum or an aluminum alloy.

[0021] FIG. 3 is a cross-sectional view of the heat transfer tube 12. As shown in FIG. 3, the heat transfer tube 12 is configured to include a base tube 15 made of aluminum or an aluminum alloy, and a sacrificial corrosion protection layer 16 formed on the outer surface of the base tube 15 . In this embodiment, the sacrificial protection layer 16 is formed by zinc spraying. However, the sacrificial protection layer 16 is not limited to this, and can be formed of a metal layer containing a metal that exhibits a potential that is less noble than the potential of the metal that constitutes the base tube 15. Specifically, the sacrificial protection layer 16 can also be formed of a clad layer that contains, for example, a zinc-aluminum alloy or a magnesium alloy.

[0022] Such a sacrificial corrosion protection layer 16 is formed over the entire heat transfer tube 12, as indicated by thin dots in Fig. 2, and is also formed over the entire outer surface of the second gas pipe 30b. Although not shown, the sacrificial corrosion protection layer 16 is also formed over the entire outer surface of the second liquid pipe 20b (see Fig. 1) connected to the other end of the heat transfer tube 12.

[0023] Next, the indoor heat exchanger 4 (see FIG. 1) will be described. As shown in FIG. 1, the indoor heat exchanger 4 is formed in a substantially U-shape in cross section so as to cover the front and top surfaces of the cross-flow fan 2 which serves as a blower. Incidentally, the cross-flow fan 2 has a cylindrical shape that is long in the axial direction (the direction perpendicular to the paper surface of Figure 1), and the indoor heat exchanger 4 is formed longer than the cross-flow fan 2 along the axial direction of the cross-flow fan 2.

[0024] The driven cross-flow fan 2 draws indoor air from an inlet (not shown) formed at the top of the housing 1 of the indoor unit 102, passes the air through the indoor heat exchanger 4, and blows it out into the room from the outlet 5 of the housing 1. At this time, the indoor air is cooled or heated by the indoor heat exchanger 4 depending on whether it is heating or cooling. The indoor unit 102 blows out such conditioned air from the outlet 5.

[0025] Fig. 4 is a diagram illustrating the configuration of the indoor heat exchanger 4. For convenience of drawing, Fig. 4 omits the middle part in the longitudinal direction of the indoor heat exchanger 4. Fig. 4 is also a partial view of the indoor heat exchanger 4 on the connection side with the second liquid piping 20b shown in Fig. 1. As shown in FIG. 4, the indoor heat exchanger 4 includes plate-shaped fins 21 and heat transfer tubes 22. A plurality of plate-like fins 21 are stacked at predetermined intervals in the thickness direction of the fins 21. The thickness direction of the fins 21 corresponds to the axial direction (direction perpendicular to the plane of the paper in FIG. 1) of the cross-flow fan 2 (see FIG. 1). In this embodiment, the fins 21 are made of aluminum or an aluminum alloy.

[0026] As shown in FIG. 4, the heat transfer tube 22 has a straight tube section 23a that penetrates the multiple fins 21 in the stacking direction, and return bend sections 23b that are arranged on both outsides of the stacked fins 21, sandwiching them on the inside, forming a meandering pipe path 10b.

[0027] Specifically, the heat transfer tube 22 has a plurality of U-shaped tubes 23 each consisting of a pair of straight tube sections 23a and one return bend section 23b connecting them, and a plurality of connecting tubes 24 that form only the return bend section 23b of the pipeline 10b. The U-shaped pipe 23 in this embodiment is assumed to be a straight pipe bent into a U-shape. At the other end of the straight pipe portion 23a that passes through the plurality of fins 21, an expanded diameter portion 23a2 is formed, the inner diameter of which is larger than that of a general portion 23a1 that occupies most of the straight pipe portion 23a.

[0028] The connecting pipe 24 has an arc shape that is bent with the same curvature as the return bend portion 23b of the U-shaped pipe 23. The end of the connecting pipe 24 is press-fitted into the expanded diameter portion 23a2 of the U-shaped pipe 23, and is connected to the expanded diameter portion 23a2 by brazing.

[0029] 4, the second liquid pipe 20b is press-fitted into the expanded diameter portion 23a2 of the U-shaped tube 23 that forms one end side of the heat transfer tube 22, and is connected to the expanded diameter portion 23a2 by brazing. Although not shown, the second gas pipe 30b (see FIG. 1) is connected to the other end side of the heat transfer tube 22 by brazing. The second liquid pipe 20b (see FIG. 4) and the second gas pipe 30b (see FIG. 1) connected to one end and the other end of the heat transfer pipe 22, respectively, correspond to "refrigeration cycle pipes." In this embodiment, the heat transfer tube 22 (see FIG. 4), the second liquid pipe 20b (see FIG. 4), and the second gas pipe 30b (see FIG. 1) are made of aluminum or an aluminum alloy.

[0030] FIG. 5A is a cross-sectional view of the straight pipe portion 23a of the U-shaped pipe 23. FIG. As shown in FIG. 5A, a sacrificial anticorrosion layer 16 is formed on the outer surface of the straight pipe portion 23a. This sacrificial corrosion protection layer 16 is formed by zinc spraying on the outer surface of the base pipe 25 made of aluminum or an aluminum alloy. However, the sacrificial corrosion protection layer 16 is not limited to this, and can be formed of a metal layer containing a metal that exhibits a potential that is less noble than the potential of the metal that constitutes the base pipe 25. Specifically, the sacrificial corrosion protection layer 16 can also be formed of a clad layer containing, for example, a zinc-aluminum alloy or a magnesium alloy. As shown by thin dotted shading in FIG. 4, the sacrificial anticorrosion layer 16 is formed over the entire U-tube 23, including the outer surface of the return bend portion 23b.

[0031] FIG. 5B is a cross-sectional view of the return bend portion 23b of the U-tube 23. As shown in FIG. 5B, a coating layer 27 is formed on the return bend portion 23b. The covering layer 27 is made of heat-resistant synthetic rubber or synthetic resin. Examples of heat-resistant synthetic rubbers include butyl rubber, chlorinated butyl rubber, brominated butyl rubber, and ethylene-propylene-diene copolymer rubber. Of these, butyl rubber is preferred. Examples of heat-resistant synthetic resins include polytetrafluoroethylene, polyethersulfone, polyetheretherketone, polyamideimide, and polyimide. Of these, polytetrafluoroethylene is preferred. As shown in FIG. 4 with a portion of the coating layer 27 cut away, the coating layer 27 is formed so as to cover the sacrificial anticorrosion layer 16 over the entire return bend portion 23b of the U-shaped pipe 23.

[0032] FIG. 5C is a cross-sectional view of the connecting pipe 24. As shown in Fig. 5C, the connecting pipe 24 differs from the connecting pipe 14 of the outdoor heat exchanger 3 shown in Fig. 2 in that it does not have a sacrificial anticorrosion layer 16 (see Fig. 3) on the outer surface of the base pipe 25 made of aluminum or an aluminum alloy. In other words, the connecting pipe 24 corresponds to "the return bend portion 23b arranged on at least one outer side." Furthermore, as shown in FIG. 4, the connecting pipe 24, unlike the return bend portion 23b of the U-shaped pipe 23, does not have a coating layer 27 (see FIG. 5B). The wall thickness of the connecting pipe 24 (base pipe 25) indicated by reference symbol T1 in FIG. 5C is thicker than the wall thickness of the base pipe 25 of the U-shaped pipe 23 indicated by reference symbol T2 in FIG. 5A (T1>T2).

[0033] Furthermore, the connecting pipe 24 (see FIG. 5C) is preferably made of an aluminum alloy, which has better corrosion resistance than the connecting pipe 14 having the sacrificial anticorrosion layer 16 of the outdoor heat exchanger 3 shown in FIG. 2. Specifically, the connecting pipe 24 shown in FIG. 5C preferably has a corrosion resistance of 35 days or more in the SWAAT test (Sea Water Acidified Test) in accordance with ASTM-G85-A3.

[0034] In addition, the second liquid pipe 20b connected to one end of the heat transfer pipe 22 shown in Fig. 4 does not have the sacrificial corrosion protection layer 16 or the coating layer 27. In addition, the second gas pipe 30b (see Fig. 1), which is connected to the other end of the heat transfer pipe 22 and is not shown in Fig. 2, does not have the sacrificial corrosion protection layer 16 (see Fig. 4) or the coating layer 27 (see Fig. 4).

[0035] The second liquid pipe 20b and the first liquid pipe 20a joined to the indoor heat exchanger 4 shown in Fig. 1 form a dissimilar metal joint 28 between a pipe made of aluminum or an aluminum alloy and a pipe made of copper. Similarly, the second gas pipe 30b and the first gas pipe 30a joined to the indoor heat exchanger 4 shown in Fig. 1 also form a dissimilar metal joint 28 between a pipe made of aluminum or an aluminum alloy and a pipe made of copper.

[0036] FIG. 6 is a vertical cross-sectional view of the dissimilar metal joint 28 shown in FIG. 6, dissimilar metal joint 28 has copper pipe 28a inserted inside aluminum or aluminum alloy pipe 28b. Pipe 28a and pipe 28b are joined to each other by brazing or the like. The joint between pipe 28a and pipe 28b is covered with sealing member 28c, such as heat-shrink tubing. Such dissimilar metal joint 28 can prevent water from entering the contact area between aluminum or aluminum alloy and copper, thereby preventing galvanic corrosion.

[0037] As shown in FIG. 1, a drain pan 17 is provided below the indoor heat exchanger 4. The drain pan 17 forms a long, narrow tray that extends along the longitudinal direction (the direction perpendicular to the plane of the paper in FIG. 1) of the indoor heat exchanger 4. The drain pan 17 receives, below the indoor heat exchanger 4, condensation water that occurs when the indoor heat exchanger 4 cools the surrounding air.

[0038] Fig. 7 is an explanatory diagram of the configuration of the drain pan 17. Fig. 7 is a partial perspective view showing the internal structure at the right end (the end on the far side of the paper surface of Fig. 1) of the drain pan 17. Note that the front-rear and up-down directions indicated by arrows in Fig. 7 coincide with the front-rear and up-down directions of the indoor heat exchanger 4. As shown in Fig. 7, the bottom 17a of the drain pan 17 is inclined so that it gradually displaces downward toward the rear. A drain pipe 19 is provided at the rear of the bottom 17a and faces downward via a drain hole (not shown). A drain tube (not shown) is connected to this drain pipe 19. In Fig. 7, the symbol CW indicates the direction in which condensed water flows along the downward slope of the bottom 17a.

[0039] Although not shown, drain pipe 19 is also provided at the left end (the end on the near side of the paper in FIG. 1) of drain pan 17. In addition, although drain pipe 19 in this embodiment is formed so as to incline downward, it may also be formed so as to point vertically downward.

[0040] <Action and effect> Next, the effects and advantages achieved by the air conditioner 100 of this embodiment will be described. Conventionally, air conditioners have been known in which a sacrificial anticorrosion layer is formed over the entire surface of the heat transfer tubes in the indoor heat exchanger (see, for example, Patent Document 1). However, when such heat transfer tubes are exposed to air, white rust may form on the surface of the heat transfer tubes. This tendency is particularly pronounced in indoor heat exchangers used in environments exposed to chloride ions contained in concrete or salt damage near the coast. As mentioned above, if this white rust occurs on the heat transfer tubes of the indoor heat exchanger, the white rust may contaminate the room and may also clog the drain hole of the indoor unit.

[0041] The inventors have come to the realization that, among the heat transfer tubes 22 in the indoor heat exchanger 4, it is necessary to apply a sacrificial corrosion protection layer 16 to at least the straight pipe section 23a that passes through the fins 21 that is directly exposed to the flow of indoor air by the cross-flow fan 2, but that there is little need to apply a sacrificial corrosion protection layer 16 to the connecting tube 24 that is arranged outside the fins 21 and is less likely to be directly exposed to the flow of indoor air. The present inventors have also verified that indoor air is about one-tenth the corrosive environment of outdoor air (outdoor air).

[0042] The present invention, which was made based on this finding, is an air conditioner 100 comprising an indoor unit 102 having an indoor heat exchanger 4 that exchanges heat between indoor air and a refrigerant, and an outdoor unit 101 having an outdoor heat exchanger 3 that exchanges heat between outdoor air and a refrigerant, wherein second liquid piping 20b (refrigeration cycle piping) and second gas piping 30b (refrigeration cycle piping) made of aluminum or an aluminum alloy are connected to one end and the other end of the indoor heat exchanger 4 and the outdoor heat exchanger 3, and of the refrigeration cycle piping, the second liquid piping 20b (refrigeration cycle piping) and second gas piping 30b (refrigeration cycle piping) that are arranged inside the outdoor unit 101 and connected to the outdoor heat exchanger 3 have a sacrificial corrosion protection layer 16 formed on their outer surfaces, and the second liquid piping 20b (refrigeration cycle piping) and second gas piping 30b (refrigeration cycle piping) that are arranged inside the indoor unit 102 and connected to the indoor heat exchanger 4 do not have a sacrificial corrosion protection layer 16 formed on their outer surfaces.

[0043] According to such an air conditioner 100, a sacrificial corrosion protection layer 16 is not formed on the outer surfaces of the second liquid piping 20b (refrigeration cycle piping) and the second gas piping 30b (refrigeration cycle piping) connected to the indoor heat exchanger 4, so the occurrence of white rust can be suppressed more effectively than in the past. Furthermore, with this air conditioner 100, the occurrence of white rust in the indoor heat exchanger 4 can be suppressed more effectively than in the past, and therefore clogging of the drain hole can also be prevented. Furthermore, according to this air conditioner 100, a sacrificial anticorrosion layer 16 is formed on the outer surfaces of the second liquid piping 20b (refrigeration cycle piping) and the second gas piping 30b (refrigeration cycle piping) connected to the outdoor heat exchanger 3, so that corrosion of the second liquid piping 20b (refrigeration cycle piping) and the second gas piping 30b (refrigeration cycle piping) can be prevented even in the outdoor heat exchanger 3, which is more susceptible to salt damage and the like than the indoor heat exchanger 4. Furthermore, according to this air conditioner 100, even if a sacrificial corrosion protection layer 16 is not formed on the outer surfaces of the second liquid piping 20b (refrigeration cycle piping) and the second gas piping 30b (refrigeration cycle piping) connected to the indoor heat exchanger 4, these second liquid piping 20b (refrigeration cycle piping) and the second gas piping 30b (refrigeration cycle piping) are arranged outside the fins 21, which are unlikely to be directly exposed to the indoor air, and therefore these second liquid piping 20b (refrigeration cycle piping) and the second gas piping 30b (refrigeration cycle piping) can exhibit predetermined corrosion resistance performance. Furthermore, with such an air conditioner 100, it is not necessary to form a sacrificial corrosion protection layer 16 on the second liquid piping 20b (refrigeration cycle piping) and the second gas piping 30b (refrigeration cycle piping) connected to the indoor heat exchanger 4, which simplifies the manufacturing process and reduces manufacturing costs.

[0044] The present invention also provides an air conditioner 100 including an indoor heat exchanger 4 for exchanging heat between indoor air and a refrigerant, and an outdoor heat exchanger 3 for exchanging heat between outdoor air and a refrigerant, wherein the indoor heat exchanger 4 and the outdoor heat exchanger 3 each include plate-like fins 11, 21 stacked at predetermined intervals in the plate thickness direction, and heat transfer pipes 12, 22 that form meandering pipe paths 10a, 10b with straight pipe portions 13a, 23a penetrating the plurality of fins 11, 21 in the stacking direction, and return bend portions 13b, 23b arranged on both outsides with the stacked fins 11, 21 sandwiched between them. The heat transfer tubes 12, 22 in the indoor heat exchanger 4 and the outdoor heat exchanger 3 are made of aluminum or an aluminum alloy, and a sacrificial corrosion protection layer 16 is formed on the outer surface of at least one of the return bend sections 13b located on the outside of the heat transfer tube 12 of the outdoor heat exchanger 3, and a sacrificial corrosion protection layer 16 is not formed on the outer surface of at least one of the return bend sections 23b located on the outside of the heat transfer tube 22 of the indoor heat exchanger 4.

[0045] According to this air conditioner 100, the return bend sections 23b located on the outside of at least one of the return bend sections 23b located on both outsides of the heat transfer tube 22 of the indoor heat exchanger 4, i.e., the outer surface of the connecting tube 14, do not have a sacrificial corrosion protection layer 16 formed thereon, thereby making it possible to suppress the occurrence of white rust more effectively than in the past. Furthermore, with this air conditioner 100, the occurrence of white rust in the indoor heat exchanger 4 can be suppressed more effectively than in the past, and therefore clogging of the drain hole can also be prevented. Furthermore, according to this air conditioner 100, a sacrificial anticorrosion layer 16 is formed on the outer surface of at least one of the return bend sections 13b located on the outside of the heat transfer tubes 12 of the outdoor heat exchanger 3, so that corrosion of the heat transfer tubes 12 can be prevented even in the outdoor heat exchanger 3, which is more susceptible to salt damage and the like than the indoor heat exchanger 4. Furthermore, with this air conditioner 100, even if a sacrificial anticorrosion layer 16 is not formed on the outer surface of at least one of the return bend sections 23b located on both outer sides of the heat transfer tube 22 of the indoor heat exchanger 4, the return bend section 23b is located on the outside of the fin 21, which is unlikely to be directly exposed to the indoor air, and therefore can exhibit predetermined corrosion resistance performance. Furthermore, with this type of air conditioner 100, it is not necessary to form a sacrificial corrosion protection layer 16 on the return bend portion 23b located on at least one of the outer sides, which simplifies the manufacturing process and reduces manufacturing costs.

[0046] Furthermore, in this air conditioner 100, a sacrificial corrosion protection layer 16 can be formed on the outer surfaces of the straight pipe section 23a of the heat transfer pipe 22 in the indoor heat exchanger 4 and the return bend section 23b arranged on the other outside. In this air conditioner 100, the straight pipe section 23a having the sacrificial corrosion protection layer 16 is surrounded by the fins 21. This prevents the air conditioner 100 from scattering white rust that has formed on the sacrificial corrosion protection layer 16 when air is blown.

[0047] In this type of air conditioner 100, the return bend portion 23b of the U-shaped pipe 23 of the indoor heat exchanger 4 is disposed outside the fins 21, which is less likely to be directly exposed to the flow of indoor air from the cross-flow fan 2, and the sacrificial protection layer 16 can be omitted. However, considering the complexity of the manufacturing process for forming the sacrificial protection layer 16 only on the straight pipe portion 23a of the U-shaped pipe 23, a configuration of the air conditioner 100 in which the sacrificial protection layer 16 is provided on all of the U-shaped pipes 23 is preferable.

[0048] In addition, in this air conditioner 100, a coating layer 27 made of synthetic rubber or synthetic resin is formed on the surface of the sacrificial anticorrosion layer 16 of the return bend portion 23b arranged on the other outer side. According to this air conditioner 100, the coating layer 27 can more reliably prevent the occurrence of white rust in the return bend portion 23b.

[0049] In addition, in this air conditioner 100, a drain pan 17 that receives condensed water is arranged below the indoor heat exchanger 4, and a drain pipe 19 that discharges the condensed water from the drain pan 17 extends downward from the bottom 17a of the drain pan 17. According to this air conditioner 100, it is possible to promote the discharge of condensed water from the drain pan 17, and therefore it is possible to prevent the drain hole from becoming clogged with white rust.

[0050] Furthermore, in this air conditioner 100, the wall thickness T1 of the connecting pipe 24 of the indoor heat exchanger 4 is thicker than the wall thickness T2 of the U-shaped pipe 23 (straight pipe section 23a) of the indoor heat exchanger 4 excluding the thickness of the sacrificial corrosion protection layer 16. According to such an air conditioner 100, even the connecting pipe 24 that does not have the sacrificial anticorrosion layer 16 can have improved pitting corrosion resistance compared to the U-shaped pipe 23 (straight pipe portion 23a).

[0051] In addition, in this air conditioner 100, the connecting pipe 24 of the indoor heat exchanger 4, which does not have a sacrificial corrosion protection layer 16, is formed of an aluminum alloy that is more corrosion-resistant than the connecting pipe 14 of the outdoor heat exchanger 3, which has a sacrificial corrosion protection layer 16. According to such an air conditioner 100, even a connecting pipe 24 that does not have a sacrificial corrosion protection layer 16 can have improved pitting corrosion resistance compared to the connecting pipe 14 of the outdoor heat exchanger 3, and can suppress the occurrence of white rust.

[0052] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be embodied in various forms. In this embodiment, the air conditioner 100 is described as having a wall-mounted indoor unit 102, but the present invention can also be applied to an air conditioner having an indoor unit other than a wall-mounted type that is attached to a ceiling surface, for example. [Explanation of symbols]

[0053] 3 Outdoor heat exchanger 4 Indoor heat exchanger 10a conduit 10b conduit 11 Finn, 12 Heat transfer tube 13 U-shaped tube 13a Straight pipe section 13b Return bend 14 Connecting pipe 16 Sacrificial corrosion protection layer 17 Drain pan 17a bottom 19 Drain pipe 20b Second liquid piping (refrigeration cycle piping) 21 Finn 22 Heat transfer tube 23 U-shaped tube 23a Straight pipe section 23b Return bend 24 Connecting pipe 27 Covering layer 30b Second gas piping (refrigeration cycle piping) 100 Air conditioner 101 Outdoor unit 102 Indoor unit T1 wall thickness T2 wall thickness

Claims

1. an indoor unit having an indoor heat exchanger that exchanges heat between indoor air and a refrigerant; An air conditioner comprising an outdoor unit having an outdoor heat exchanger that exchanges heat between outdoor air and a refrigerant, a refrigeration cycle pipe made of aluminum or an aluminum alloy is connected to one end side and the other end side of the indoor heat exchanger and the outdoor heat exchanger, a sacrificial corrosion protection layer is formed on an outer surface of the refrigeration cycle piping that is disposed inside the outdoor unit and connected to the outdoor heat exchanger, An air conditioner in which a sacrificial anticorrosion layer is not formed on the outer surface of the refrigeration cycle piping that is arranged inside the indoor unit and connected to the indoor heat exchanger.

2. an indoor heat exchanger that exchanges heat between indoor air and a refrigerant; An air conditioner comprising an outdoor heat exchanger that exchanges heat between outdoor air and a refrigerant, The indoor heat exchanger and the outdoor heat exchanger each have a plurality of plate-shaped fins stacked at predetermined intervals in a plate thickness direction; a heat transfer tube having a meandering pipe path formed by a straight pipe portion passing through the plurality of fins in the stacking direction and return bend portions disposed on both outer sides of the stacked fins, with the stacked fins sandwiched between them; and the heat transfer tubes in the indoor heat exchanger and the outdoor heat exchanger are formed of aluminum or an aluminum alloy, a sacrificial corrosion protection layer is formed on an outer surface of the return bend portion arranged on at least one of the return bend portions arranged on the both outer sides of the heat transfer tube of the outdoor heat exchanger, An air conditioner in which a sacrificial corrosion protection layer is not formed on the outer surface of at least one of the return bend sections located on the outside of the heat transfer tubes of the indoor heat exchanger.

3. The air conditioner according to claim 2, characterized in that a sacrificial corrosion protection layer is formed on the outer surfaces of the straight pipe portion of the heat transfer pipe in the indoor heat exchanger and the return bend portion arranged outside the other.

4. 4. The air conditioner according to claim 3, wherein a coating layer made of synthetic rubber or synthetic resin is formed on the surface of the sacrificial anticorrosion layer of the return bend portion arranged on the other outer side.

5. An air conditioner as described in claim 1 or claim 2, characterized in that a drain pan for receiving condensation water is arranged below the indoor heat exchanger, and a drain pipe for discharging condensation water from the drain pan extends downward from the bottom of the drain pan.

6. The air conditioner according to claim 3, characterized in that the thickness of the return bend section, which is arranged on one outer side of the indoor heat exchanger and does not have a sacrificial corrosion protection layer formed thereon, is thicker than the thickness of the straight pipe section of the indoor heat exchanger excluding the thickness of the sacrificial corrosion protection layer.

7. 3. The air conditioner according to claim 2, wherein the return bend portion, which is disposed on one outer side of the indoor heat exchanger and does not have a sacrificial corrosion protection layer, is formed of an aluminum alloy that is more corrosion resistant than the return bend portion of the outdoor heat exchanger, which has a sacrificial corrosion protection layer.

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