Indoor unit of air conditioner

Abstract

An indoor unit 102 of an air conditioner according to the present invention comprises: an interposed gas pipe 30c (first pipe) which is located downstream of an indoor heat exchanger 3 during cooling operation, is formed from aluminum or an aluminum alloy (first material), and inside which refrigerant flows; and a connecting gas pipe 30b (second pipe) which is located downstream of the interposed gas pipe 30c (first pipe) during cooling operation, is formed from copper or a copper alloy (second material) different from the aluminum or aluminum alloy (first material), and inside which refrigerant flows, wherein the difference (Δ1 = D1 - D2) between the outer diameter D1 of the interposed gas pipe 30c (first pipe) and the outer diameter D2 of the connecting gas pipe 30b (second pipe) is greater than the difference (Δ2 = D3 - D4) between the inner diameter D3 of the interposed gas pipe 30c (first pipe) and the inner diameter D4 of the connecting gas pipe 30b (second pipe).

Description

Air conditioner indoor unit

[0001] The present invention relates to an indoor unit of an air conditioner.

[0002] Conventionally, copper pipes have been primarily used in the refrigerant circuits of air conditioners. However, in recent years, aluminum pipes have sometimes been used as part of the refrigerant circuits. The copper pipes and aluminum pipes in such refrigerant circuits are bonded with an adhesive or metallically joined. For example, Patent Document 1 discloses a bonded pipe for use in a refrigerant circuit in which a copper pipe and an aluminum pipe are eutectic-bonded. This bonded pipe prevents waste materials generated during the joining process from being discharged into the pipes, improving the reliability of the bonded pipe.

[0003] JP 2009-72820 A

[0004] However, conventional connecting pipes (see, for example, Patent Document 1) can generate so-called refrigerant noise due to the flowing refrigerant. Therefore, when such connecting pipes are used in the indoor unit of an air conditioner, the generated refrigerant noise disrupts the quietness of the room.

[0005] An object of the present invention is to provide an indoor unit for an air conditioner that can suppress the generation of refrigerant noise.

[0006] The indoor unit of the air conditioner of the present invention comprises a first pipe that is arranged downstream of the indoor heat exchanger during cooling operation, is made of a first material, and has a refrigerant flowing through it, and a second pipe that is arranged downstream of the first pipe during cooling operation, is made of a second material different from the first material, and has a refrigerant flowing through it, wherein the difference between the outer diameter of the first pipe and the outer diameter of the second pipe is greater than the difference between the inner diameter of the first pipe and the inner diameter of the second pipe.

[0007] According to the indoor unit of the air conditioner of the present invention, the generation of refrigerant noise can be suppressed.

[0008] Fig. 3A is a structural explanatory diagram of an air conditioner having an indoor unit according to an embodiment of the present invention. Fig. 3B is a partially enlarged perspective view of the internal structure of the indoor unit shown in Fig. 1. Fig. 3C is a partially enlarged perspective view of gas piping that constitutes the indoor unit according to an embodiment of the present invention. Fig. 3D is a cross-sectional view of Fig. 3A taken along IIIB-IIIB in Fig. 3A.

[0009] Below, a detailed description will be given of a form (embodiment) for carrying out an indoor unit of an air conditioner of the present invention, with appropriate reference to the drawings. Here, the overall configuration of the air conditioner will be described, followed by a more detailed description of the indoor unit. <Air Conditioner> FIG. 1 is a structural explanatory diagram of an air conditioner 100 having an indoor unit 102 according to an embodiment of the present invention. FIG. 2 is a partially enlarged perspective view of the internal structure of the indoor unit 102 shown in FIG. 1. As shown in FIG. 1, the air conditioner 100 comprises an outdoor unit 101 and an indoor unit 102. The outdoor unit 101, which is installed outdoors, exchanges heat between a refrigerant and outdoor air. The indoor unit 102, which is installed on a wall 104 inside a room, exchanges heat between a refrigerant and indoor air.

[0010] 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 to flow through the heat transfer tubes 8 of the indoor heat exchanger 3 in the indoor unit 102. At this time, the indoor heat exchanger 3 functions as an evaporator to cool the surrounding air. The gas refrigerant vaporized in the heat transfer tubes 8 of the indoor heat exchanger 3 is then sent to the outdoor unit 101 via the gas piping 30. The gas refrigerant sent to the outdoor unit 101 becomes liquid refrigerant (including gas-liquid two-phase refrigerant) via a compressor (not shown) and an outdoor heat exchanger (functioning as a condenser) of the outdoor unit 101. This liquid refrigerant is sent again to the indoor unit 102 via the liquid piping 20.

[0011] Furthermore, during heating operation, the air conditioner 100 sends high-temperature, high-pressure gas refrigerant from the compressor to the indoor unit 102 via the gas piping 30 by switching the refrigerant flow path using a four-way valve (not shown) in the outdoor unit 101. At this time, the indoor heat exchanger 3 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 8 of the indoor heat exchanger 3 is sent to the outdoor unit 101 via the liquid piping 20. The liquid refrigerant sent to the outdoor unit 101 passes through an outdoor heat exchanger (not shown) functioning as a condenser in the outdoor unit 101 and a compressor, and becomes high-temperature, high-pressure gas refrigerant again, and is sent to the indoor unit 102.

[0012] The indoor heat exchanger 3 in this embodiment includes fins 7 stacked at predetermined intervals and heat transfer tubes 8. The indoor heat exchanger 3 is a so-called fin-tube heat exchanger having heat transfer tubes 8 formed by connecting a plurality of tubes that penetrate the plurality of fins 7 in the stacking direction in a serpentine manner. The indoor heat exchanger 3 is an all-aluminum heat exchanger in which the fins 7 and heat transfer tubes 8 are made of aluminum or an aluminum alloy.

[0013] In this embodiment, the indoor heat exchanger 3 is formed in a roughly 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. The indoor air drawn into the housing 1 by the driven cross-flow fan 2 through an inlet 4 formed at the top of the housing 1 passes through the indoor heat exchanger 3 and is blown out into the room from an outlet 5 formed at the front of the housing 1. At this time, the indoor air is cooled or heated by the indoor heat exchanger 3 depending on whether it is heating or cooling. The indoor unit 102 blows out such conditioned air from the outlet 5.

[0014] In this air conditioner 100, the liquid piping 20 connecting the outdoor unit 101 and the indoor unit 102 includes an extension liquid piping 20a extending from the outdoor unit 101 side via the flare nut connection part 11, and a connection liquid piping 20b extending from the tip of the extension liquid piping 20a to the indoor unit 102 side via the flare nut connection part 11. In addition, as will be described later, the liquid piping 20 further includes an intervening liquid piping 20c (see FIG. 2) interposed between the tip of the connection liquid piping 20b and the indoor unit 102.

[0015] 1, the gas piping 30 includes an extension gas piping 30a extending from the outdoor unit 101 side via the flare nut connection portion 11, and a connection gas piping 30b extending from the tip of the extension gas piping 30a to the indoor unit 102 side via the flare nut connection portion 11. In addition, the gas piping 30 further includes an intermediate gas piping 30c (see FIG. 2) interposed between the tip of the connection gas piping 30b and the indoor unit 102, as will be described later.

[0016] The connecting liquid pipe 20b (see FIG. 1), the intervening liquid pipe 20c (see FIG. 2), the connecting gas pipe 30b (see FIG. 1), and the intervening gas pipe 30c (see FIG. 2) are drawn into the room through a hole 105 (see FIG. 1) formed in a wall 104 (see FIG. 1). As shown in FIG. 2, the intervening liquid pipe 20c connected to the connecting liquid pipe 20b inside the indoor unit 102 is connected to one end of a heat transfer pipe 8. The intervening gas pipe 30c connected to the connecting gas pipe 30b inside the indoor unit 102 is connected to the other end of the heat transfer pipe 8. In FIG. 2, only a portion of the heat transfer pipe 8 is shown by hidden lines for convenience of drawing.

[0017] The liquid pipe 20 (see Figures 1 and 2) consisting of the extension liquid pipe 20a (see Figure 1), the connecting liquid pipe 20b (see Figure 1), and the intervening liquid pipe 20c (see Figure 2) as described above, and the gas pipe 30 (see Figures 1 and 2) consisting of the extension gas pipe 30a (see Figure 1), the connecting gas pipe 30b (see Figure 1), and the intervening gas pipe 30c (see Figure 2) are formed partly from aluminum pipes and the remaining parts except for that part are formed from copper pipes, as described below.

[0018] <Indoor unit> Next, the indoor unit 102 of this embodiment will be described in more detail. Of the pipes that make up the liquid pipe 20 shown in Figures 1 and 2, the extension liquid pipe 20a (see Figure 1) and the connection liquid pipe 20b (see Figure 1) are made of copper pipes. In contrast, the intervening liquid pipe 20c (see Figure 2) is made of aluminum pipes.

[0019] 1 and 2, the extension gas pipe 30a (see FIG. 1) and the connecting gas pipe 30b (see FIG. 1) are made of copper pipes. In contrast, the intervening gas pipe 30c (see FIG. 2) is made of aluminum pipe. As described above, the gas pipe 30 having the intervening gas pipe 30c and the connecting gas pipe 30b is disposed downstream of the indoor heat exchanger 3 during cooling operation. As described above, the connecting gas pipe 30b is disposed downstream of the intervening gas pipe 30c during cooling operation.

[0020] That is, in this indoor unit 102, the intervening gas pipe 30c (see FIG. 2) made of aluminum or an aluminum alloy (first material) corresponds to the "first pipe." Also, the connecting gas pipe 30b (see FIG. 1) made of copper or a copper alloy (second material) constitutes the "second pipe." In this embodiment, the extension gas pipe 30a (see FIG. 1) and the connecting gas pipe 30b (see FIG. 1) are made of copper pipes having the same inner diameter, outer diameter, and wall thickness.

[0021] Fig. 3A is a partially enlarged perspective view of the gas piping 30 constituting the indoor unit 102 (see Fig. 2) according to this embodiment. Fig. 3B is a cross-sectional view taken along IIIB-IIIB in Fig. 3A. For convenience of illustration, Fig. 3A omits the extension gas piping 30a (see Fig. 1), which constitutes the gas piping 30 together with the connection gas piping 30b. As shown in Fig. 3A, the gas piping 30 has an intermediate gas piping 30c (first pipe) made of an aluminum pipe and a connection gas piping 30b (second pipe) made of a copper pipe.

[0022] 3B, in this gas pipe 30, the joint end 30b2 of the connecting gas pipe 30b (second pipe) is inserted inside the joint end 30c2 of the intermediate gas pipe 30c (first pipe). The joint end 30c2 of the intermediate gas pipe 30c (first pipe) and the joint end 30b2 of the connecting gas pipe 30b (second pipe) are connected by eutectic bonding.

[0023] The joint end 30b2 of the connecting gas pipe 30b (second pipe) has the same outer diameter as the general section 30b1 of the connecting gas pipe 30b (second pipe). Also, in this gas pipe 30, as shown in FIG. 3B , the difference (Δ1 = D1 - D2) between the outer diameter D1 of the general section 30c1 of the intervening gas pipe 30c (first pipe) and the outer diameter D2 of the general section 30b1 of the connecting gas pipe 30b (second pipe) is set to be larger than the difference (Δ2 = D3 - D4) between the inner diameter D3 of the general section 30c1 of the intervening gas pipe 30c (first pipe) and the inner diameter D4 of the general section 30b1 of the connecting gas pipe 30b (second pipe) (Δ1 > Δ2).

[0024] As will be described later with reference to specific examples, the outer diameter D1 of the general portion 30c1 of the intermediate gas pipe 30c (first pipe) is set to be larger than the outer diameter D2 of the general portion 30b1 of the connecting gas pipe 30b (second pipe). Also, the wall thickness T1 of the general portion 30c1 of the intermediate gas pipe 30c (first pipe) is set to be thicker than the wall thickness T2 of the general portion 30b1 of the connecting gas pipe 30b (second pipe) (T1 > T2).

[0025] In such a gas pipe 30, it is desirable that the inner diameter D3 of the intermediate gas pipe 30c (first pipe) is equal to or larger than the inner diameter D4 of the connecting gas pipe 30b (second pipe) (D3≧D4).

[0026] The comparison of the pipe diameters and wall thicknesses of the intermediate gas pipe 30c (first pipe) and the connecting gas pipe 30b (second pipe) as described above does not include the pipe diameters and wall thicknesses of the joints between the intermediate gas pipe 30c (first pipe) and the connecting gas pipe 30b (second pipe). Also, although not shown, in the indoor unit 102 where the intermediate gas pipe 30c (first pipe) branches on the indoor heat exchanger 3 side and is connected to the heat transfer pipe 8, only the intermediate gas pipe 30c (first pipe) that merges downstream of the branch pipe to form one path is subject to comparison of the pipe diameter and wall thickness.

[0027] Returning to Figure 2, in the relationship between the heat transfer tube 8 and the intervening gas pipe 30c (first pipe), if the outer diameter of the general part of the heat transfer tube 8 is D5 and the inner diameter of the general part of the heat transfer tube 8 is D6, it is desirable that the difference between the outer diameter D5 of the heat transfer tube 8 and the outer diameter D1 of the intervening gas pipe 30c (first pipe) (Δ3 = D1 - D5) be larger than the difference between the inner diameter D6 of the heat transfer tube 8 and the inner diameter D3 of the intervening gas pipe 30c (first pipe) (Δ4 = D6 - D3) (Δ3 > Δ4).

[0028] Furthermore, if the thickness of the general portion of the heat transfer tube 8 is T3, it is desirable that the outer diameter D1 of the intermediate gas pipe 30c (first pipe) is larger than the outer diameter D5 of the heat transfer tube 8 (D1>D5), and that the thickness T1 of the intermediate gas pipe 30c (first pipe) is thicker than the thickness T3 of the heat transfer tube 8 (T1>T3). It is also desirable that the inner diameter D3 of the intermediate gas pipe 30c (first pipe) is equal to or smaller than the inner diameter D6 of the heat transfer tube 8 (D3≦D6).

[0029] The comparison of the pipe diameters and wall thicknesses of the intermediate gas pipe 30c (first pipe) and the heat transfer pipe 8 as described above does not include the pipe diameters and wall thicknesses at the joints between the intermediate gas pipe 30c (first pipe) and the heat transfer pipe 8. Furthermore, if the heat transfer pipe 8 (see FIG. 1) that turns back and forth while penetrating the fin 7 (see FIG. 1) is configured by connecting multiple heat transfer pipe 8 sections whose inner diameters are not uniform, the pipe diameters and wall thicknesses are compared on the condition that the heat transfer pipe 8 and the intermediate gas pipe 30c (first pipe) are connected by a single path. Furthermore, if there are irregularities on the inside of the heat transfer pipe 8 near the intermediate gas pipe 30c (first pipe), the wall thickness T1 of the intermediate gas pipe 30c (first pipe) is compared with the wall thickness T3 of the thin-walled portion (recess) of the heat transfer pipe 8.

[0030] The gas piping 30 and heat transfer pipe 8 used in the refrigerant circuit of the air conditioner 100 (see Figure 1) are selected from pipe sizes with outer diameters of, for example, approximately 6.35 mm to 12.7 mm, such that the intervening gas piping 30c (first pipe), connecting gas piping 30b (second pipe), extension gas piping 30a, and heat transfer pipe 8 satisfy the above correlation.

[0031] In this case, the intervening liquid pipe 20c and the intervening gas pipe 30c (first pipe) shown in Fig. 2 may be aluminum pipes having the same inner and outer diameters, or different aluminum pipes may be selected. Also, the connecting liquid pipe 20b and the extension liquid pipe 20a, and the connecting gas pipe 30b (second pipe) and the extension gas pipe 30a shown in Fig. 1 may be copper pipes having the same inner and outer diameters, or different copper pipes may be selected.

[0032] Specific examples of the intervening liquid pipe 20c, the intervening gas pipe 30c (first pipe), the connecting liquid pipe 20b, the extension liquid pipe 20a, and the connecting gas pipe 30b (second pipe) shown in Figures 1 and 2 are described below, but are not limited to these. The intervening liquid pipe 20c may be an aluminum pipe with an outer diameter of 7.00 mm, an inner diameter of 5.20 mm, and a wall thickness of 0.90 mm. The connecting liquid pipe 20b and the extension liquid pipe 20a may be a copper pipe with an outer diameter of 6.35 mm, an inner diameter of 5.15 mm, and a wall thickness of 0.60 mm.

[0033] The intermediate gas pipe 30c (first pipe) may be an aluminum pipe having an outer diameter D1 of 8.00 mm, an inner diameter D3 of 6.00 mm, and a wall thickness T1 of 1.00 mm. The connecting gas pipe 30b (second pipe) may be a copper pipe having an outer diameter D2 of 7.00 mm, an inner diameter D4 of 5.60 mm, and a wall thickness T2 of 0.70 mm. The heat transfer pipe 8 may be an aluminum pipe having an outer diameter D5 of 7.37 mm, an inner diameter D6 of 6.25 mm, and a wall thickness T3 of 0.56 mm.

[0034] The difference Δ1 between the outer diameter D1 of the intermediate gas pipe 30c (first pipe) and the outer diameter D2 of the connecting gas pipe 30b (second pipe) in this indoor unit 102 is 1.00 mm. Also, the difference Δ2 between the inner diameter D3 of the intermediate gas pipe 30c (first pipe) and the inner diameter D4 of the connecting gas pipe 30b (second pipe) in this indoor unit 102 is 0.40 mm. In other words, the difference Δ1 in the outer diameters is greater than the difference Δ2 in the inner diameters (Δ1 > Δ2).

[0035] Furthermore, in this indoor unit 102, the difference (Δ3 = D1 - D5) between the outer diameter D5 of the heat transfer tube 8 and the outer diameter D1 of the intermediate gas pipe 30c (first pipe) is 0.63 mm. The difference (Δ4 = D6 - D3) between the inner diameter D6 of the heat transfer tube 8 and the inner diameter D3 of the intermediate gas pipe 30c (first pipe) is 0.25 mm. In other words, the difference in outer diameter Δ3 is greater than the difference in inner diameter Δ4 (Δ3 > Δ4).

[0036] Furthermore, in such an indoor unit 102, the inner diameter D3 (6.00 mm) of the intervening gas pipe 30c (first pipe) is larger than the inner diameter D4 (5.60 mm) of the connecting gas pipe 30b (second pipe) (D3>D4).

[0037] In this indoor unit 102, the thickness T1 (1.00 mm) of the intermediate gas pipe 30c (first pipe) is thicker than the thickness T2 (0.70 mm) of the connecting gas pipe 30b (second pipe) (T1 > T2). Also, the outer diameter D1 (8.00 mm) of the intermediate gas pipe 30c (first pipe) is larger than the outer diameter D2 (7.00 mm) of the connecting gas pipe 30b (second pipe) (D1 > D2).

[0038] In addition, in this indoor unit 102, the outer diameter D1 (8.00 mm) of the intermediate gas pipe 30c (first pipe) is larger than the outer diameter D5 (7.37 mm) of the heat transfer pipe 8 (D1 > D5). Also, the wall thickness T1 (1.00 mm) of the intermediate gas pipe 30c (first pipe) is thicker than the wall thickness T3 (0.56 mm) of the heat transfer pipe 8 (T1 > T3).

[0039] <Effects> Next, the effects of the indoor unit 102 of this embodiment will be described. Generally, in a joint pipe (see, for example, Patent Document 1) between dissimilar material pipes, such as copper pipes and aluminum pipes, used in a refrigerant circuit, the outer and inner diameters of the dissimilar material pipes differ depending on, for example, their thermal conductivity and bending strength. In particular, in a joint pipe between a copper pipe and an aluminum pipe (see, for example, Patent Document 1), butt-joining the pipes is difficult. The connecting end of the copper pipe is inserted into the connecting end of the aluminum pipe, which has a relatively thick wall. However, in such a joint pipe, a gap occurs between the inner diameters of the dissimilar material pipes at the joint between the dissimilar material pipes. Therefore, an indoor unit of an air conditioner using a conventional joint pipe may generate so-called refrigerant noise due to the flowing refrigerant.

[0040] In contrast, the indoor unit 102 of the air conditioner 100 of this embodiment is equipped with an intermediate gas pipe 30c (first pipe) that is arranged downstream of the indoor heat exchanger 3 during cooling operation, is made of aluminum or an aluminum alloy (first material), and has a refrigerant flowing through it, and a connecting gas pipe 30b (second pipe) that is arranged downstream of the intermediate gas pipe 30c (first pipe) during cooling operation, is made of copper or a copper alloy (second material) different from aluminum or an aluminum alloy (first material), and has a refrigerant flowing through it, and the difference (Δ1 = D1 - D2) between the outer diameter D1 of the intermediate gas pipe 30c (first pipe) and the outer diameter D2 of the connecting gas pipe 30b (second pipe) is greater than the difference (Δ2 = D3 - D4) between the inner diameter D3 of the intermediate gas pipe 30c (first pipe) and the inner diameter D4 of the connecting gas pipe 30b (second pipe) (Δ1 > Δ2). With this indoor unit 102, the inner diameter of the intermediate gas pipe 30c (first pipe) and the inner diameter of the connecting gas pipe 30b (second pipe) can be made closer to each other. The indoor unit 102 can reduce pressure loss of the refrigerant flowing through it compared to conventional indoor units. As a result, the indoor unit 102 of this embodiment can suppress the generation of refrigerant noise.

[0041] Furthermore, in this indoor unit 102, the difference (Δ3 = D5 - D1) between the outer diameter D5 of the heat transfer tube 8 and the outer diameter D1 of the intermediate gas pipe 30c (first pipe) can be set to be greater than the difference (Δ4 = D6 - D3) between the inner diameter D6 of the heat transfer tube 8 and the inner diameter D3 of the intermediate gas pipe 30c (first pipe) (Δ3 > Δ4). With this indoor unit 102, the inner diameter D6 of the heat transfer tube 8 and the inner diameter D3 of the intermediate gas pipe 30c (first pipe) can be made closer to each other. The indoor unit 102 can reduce pressure loss of the refrigerant flowing through it compared to conventional units. As a result, the indoor unit 102 of this embodiment can suppress the generation of refrigerant noise.

[0042] Furthermore, in this type of indoor unit 102, the first material is aluminum or an aluminum alloy, and the second material is copper or a copper alloy. With this type of indoor unit 102, it is possible to construct an indoor heat exchanger 3 that is cheaper than conventional ones and has excellent thermal conductivity, while using copper or a copper alloy that has traditionally been used in the main refrigerant circuit of the air conditioner 100.

[0043] Furthermore, in this indoor unit 102, the intervening gas pipe 30c (first pipe) and the connecting gas pipe 30b (second pipe) are eutectic-bonded. According to this indoor unit 102, the intervening gas pipe 30c (first pipe) and the connecting gas pipe 30b (second pipe) can be bonded together by an intermetallic compound between the metal components of the intervening gas pipe 30c (first pipe) and the connecting gas pipe 30b (second pipe), without using a bonding method that involves brazing.

[0044] In addition, in this indoor unit 102, the inner diameter D3 of the intervening gas pipe 30c (first pipe) can be set to be equal to or larger than the inner diameter D4 of the connecting gas pipe 30b (second pipe) (D3 ≥ D4). With this indoor unit 102, the generation of refrigerant noise is further suppressed.

[0045] In addition, in this indoor unit 102, the thickness T1 of the intermediate gas pipe 30c (first pipe) is set to be thicker than the thickness T2 of the general section 30b1 of the connecting gas pipe 30b (second pipe) (T1 > T2). In addition, in this indoor unit 102, the outer diameter D1 of the intermediate gas pipe 30c (first pipe) is set to be larger than the outer diameter D2 of the connecting gas pipe 30b (second pipe) (D1 > D2). This indoor unit 102 more reliably brings the inner diameter D3 of the intermediate gas pipe 30c (first pipe) and the inner diameter D4 of the connecting gas pipe 30b (second pipe) closer to each other. This allows the indoor unit 102 of this embodiment to more reliably suppress the generation of refrigerant noise.

[0046] Furthermore, in this indoor unit 102, the outer diameter D1 of the intermediate gas pipe 30c (first pipe) can be set to be larger than the outer diameter D5 of the heat transfer pipe 8 (D1 > D5), and the wall thickness T1 of the intermediate gas pipe 30c (first pipe) can be set to be thicker than the wall thickness T3 of the heat transfer pipe 8 (T1 > T3). According to this indoor unit 102, the inner diameter D6 of the heat transfer pipe 8 and the inner diameter D3 of the intermediate gas pipe 30c (first pipe) can be more reliably brought closer to each other. As a result, the indoor unit 102 of this embodiment can more reliably suppress the generation of refrigerant noise.

[0047] Although the present invention has been described above as an embodiment, it is not limited to the above embodiment and can be embodied in various forms. The indoor unit 102 in the above embodiment has been described as having a first pipe made of aluminum or an aluminum alloy and a second pipe made of copper or a copper alloy. However, the indoor unit 102 of the present invention is not limited to this and can also be applied to an indoor unit having a first pipe and a second pipe made of another metal.

[0048] 30 Gas pipe 30a Extension gas pipe 30b Connecting gas pipe (second pipe) 30c Intervening gas pipe (first pipe) 100 Air conditioner 102 Indoor unit

Claims

1. An indoor unit for an air conditioner comprising: a first pipe that is arranged downstream of an indoor heat exchanger during cooling operation, made of a first material, and through which a refrigerant flows; and a second pipe that is arranged downstream of the first pipe during cooling operation, made of a second material different from the first material, and through which a refrigerant flows, wherein the difference between the outer diameter of the first pipe and the outer diameter of the second pipe is greater than the difference between the inner diameter of the first pipe and the inner diameter of the second pipe.

2. An indoor unit of an air conditioner as described in claim 1, characterized in that the difference between the outer diameter of the heat transfer tube of the indoor heat exchanger and the outer diameter of the first tube is greater than the difference between the inner diameter of the heat transfer tube and the inner diameter of the first tube.

3. The indoor unit of an air conditioner according to claim 1, wherein the first material is aluminum or an aluminum alloy, and the second material is copper or a copper alloy.

4. The indoor unit of an air conditioner according to claim 1, wherein the first pipe and the second pipe are joined by eutectic bonding.

5. An indoor unit for an air conditioner according to claim 1, characterized in that the inner diameter of the first pipe is equal to or greater than the inner diameter of the second pipe.

6. An indoor unit for an air conditioner according to claim 2, characterized in that the inner diameter of the first pipe is equal to or smaller than the inner diameter of the heat transfer pipe.

7. An indoor unit for an air conditioner as described in claim 1, characterized in that the outer diameter of the first pipe is larger than the outer diameter of the second pipe, and the wall thickness of the first pipe is thicker than the wall thickness of the second pipe.

8. An indoor unit for an air conditioner as described in claim 2, characterized in that the outer diameter of the first pipe is larger than the outer diameter of the heat transfer pipe, and the wall thickness of the first pipe is thicker than the wall thickness of the heat transfer pipe.

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