Air conditioner

Abstract

An air conditioner (A) according to the present invention comprises: a heat exchanger (15) having heat exchanger tubes (r1) formed from aluminum or an aluminum alloy; and connecting tubes (r0) which are formed, at least in part, from aluminum pipes made of aluminum or an aluminum alloy and through which passes a refrigerant flowing out of the heat exchanger tubes (r1) or a refrigerant flowing into the heat exchanger tubes (r1), wherein the aluminum pipe of at least one of the connecting tubes (r0) connected to each of two refrigerant in-outlets provided in the heat exchanger tubes (r1) is covered, at least in part, with a soundproofing material, a sound-absorbing material, or a sound-insulating material (19a, 19b).

Description

air conditioner

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

[0002] Copper pipes are the mainstream for heat exchangers in air conditioners (room air conditioners), but in recent years, aluminum pipes have increasingly been used for heat exchangers in outdoor units.

[0003] Japanese Patent Application Laid-Open No. 2023-013765

[0004] When aluminum or aluminum alloy pipes were used for the heat exchanger and connecting pipes, a problem occurred in which the sound of the refrigerant flowing leaked out.

[0005] Patent Document 1 describes a manufacturing method that does not increase costs when brazing a heat transfer tube made of aluminum to a connecting pipe, but does not describe how to reduce the noise generated by the refrigerant flowing through the heat transfer tube and the connecting pipe.

[0006] Therefore, an object of the present invention is to provide an air conditioner that can suppress refrigerant noise even when aluminum pipes or aluminum alloy pipes are used for at least a portion of the heat exchanger and connecting piping.

[0007] In order to solve the above-mentioned problems, the air conditioner of the present invention comprises a heat exchanger having heat transfer tubes made of aluminum or an aluminum alloy, and connecting pipes through which refrigerant flowing out of or into the heat transfer tube passes, and at least a portion of the connecting pipes is made of aluminum piping made of aluminum or an aluminum alloy, and at least a portion of at least one of the connecting pipes connected to two refrigerant inlets and outlets provided on the heat transfer tube is covered with soundproofing material, sound-absorbing material, or sound-blocking material.

[0008] According to the present invention, it is possible to provide an air conditioner that can suppress refrigerant noise even when aluminum pipes or aluminum alloy pipes are used for at least a part of the heat exchanger and connecting piping.

[0009] 1 is a perspective view of an indoor unit of an air conditioner according to a first embodiment of the present invention, as seen from the front right; 2 is a perspective view of the indoor unit of the air conditioner, as seen from the lower right front; 3 is a configuration diagram including the indoor unit and outdoor unit of the air conditioner; 4 is a schematic view of an indoor heat exchanger; 5 is an enlarged cross-sectional view of part I in FIG. 4; 6 is a schematic view of the flow in a sudden contraction pipe; 7 is a schematic view of the indoor heat exchanger after soundproofing material or the like has been attached; 8 is a schematic view of the flow in a sudden expansion pipe of a second embodiment; 9 is an enlarged cross-sectional view equivalent to part I in FIG. 4 of the second embodiment; 10 is a schematic view of the indoor heat exchanger after soundproofing material, sound-absorbing material, or sound-insulating material has been attached of the second embodiment;

[0010] First Embodiment Configuration of Air Conditioner A FIG. 1 shows a perspective view of an indoor unit 1 of an air conditioner A according to a first embodiment of the present invention, as viewed from the front right-hand corner.

[0011] Figure 2 shows a perspective view of the indoor unit 1 of air conditioner A as seen from the right front bottom. Air conditioner A is a device that performs air conditioning, such as indoor cooling and heating operations. Air conditioner A is equipped with an indoor unit 10 (see Figure 1) that is installed indoors and an outdoor unit 20 (see Figure 3) that is installed outdoors. Figure 3 shows a configuration diagram of air conditioner A, including the indoor unit 1 and outdoor unit 20.

[0012] The indoor unit 10 shown in FIG. 1 has an indoor unit 1 that performs air conditioning operation.

[0013] The indoor unit 1 shown in Fig. 3 is connected to the outdoor unit 20 via a connecting pipe r0 through which a refrigerant circulates. The connecting pipe r0 refers to a pipe that connects the indoor heat exchanger 15 in the indoor unit 1 to the refrigerant pipe r20 of the outdoor unit 20. The indoor unit 1 is also connected to the outdoor unit 20 via a power line and a communication line.

[0014] The indoor unit 1 shown in Figure 1 includes a panel 11 that forms an outer shell and a filter 12 that removes dust from the indoor air. The panel 11 is a resin box that houses an indoor heat exchanger 15 (see Figure 3), an indoor fan 16 (see Figure 3), etc. The filter 12 (see Figure 1) collects dust from the air flowing toward the indoor heat exchanger 15 (see Figure 3). The filter 12 is provided on the upper and front sides of the indoor unit 1 (see Figure 1) on the upstream side of the air flow toward the indoor heat exchanger 15.

[0015] The indoor unit 1 also includes an indicator lamp 13 (see FIG. 2), an upper and lower airflow direction vane 14 (see FIG. 2), an indoor heat exchanger 15 (see FIG. 3), and an indoor fan 16 (see FIG. 3). The indicator lamp 13 shown in FIG. 2 displays the air conditioning operation status of the indoor unit 1, etc.

[0016] The vertical air deflectors 14 are plate-shaped members that adjust the vertical direction of the air blown out from the indoor unit 1. The rotation angle of the vertical air deflectors 14 changes when an air deflector motor (not shown) is driven. In addition, left-right air deflectors (not shown) that adjust the left-right direction of the air blown out from the indoor unit 1 may be provided.

[0017] The solid arrows in Fig. 3 indicate the flow of refrigerant in the heating cycle. The dashed arrows in Fig. 3 indicate the flow of refrigerant in the cooling cycle. The air conditioner A is provided with components in the outdoor unit 20, including a compressor 21, an outdoor heat exchanger 22, an outdoor fan 23, an expansion valve 24, and a four-way valve 25. The air conditioner A is also provided with components in the indoor unit 1, including an indoor heat exchanger 15 and an indoor fan 16.

[0018] The compressor 21 is a device that compresses a low-temperature, low-pressure gas refrigerant and discharges it as a high-temperature, high-pressure gas refrigerant. Although not shown in Figure 3, an accumulator that separates the refrigerant into gas and liquid is provided on the suction side of the compressor 21.

[0019] The outdoor heat exchanger 22 is a heat exchanger in which heat is exchanged between the refrigerant flowing through its heat transfer tubes (not shown) and outdoor air. The outdoor fan 23 shown in FIG. 3 is a fan that sends outdoor air to the outdoor heat exchanger 22. The outdoor fan 23 is driven by an outdoor fan motor 23a and is installed near the outdoor heat exchanger 22. The expansion valve 24 is a valve that reduces the pressure of the refrigerant condensed in the "condenser" (one of the outdoor heat exchanger 22 and the indoor heat exchanger 15). The refrigerant reduced in pressure by the expansion valve 24 is sent to the "evaporator" (the other of the outdoor heat exchanger 22 and the indoor heat exchanger 15). The refrigerant at the outlet of the evaporator has a high proportion of gas or vapor, resulting in a high flow rate. For example, when the indoor heat exchanger 15 serves as an evaporator, the refrigerant at the outlet of the indoor heat exchanger 15 has a high proportion of gas or vapor, resulting in a high flow rate at the outlet of the indoor heat exchanger 15.

[0020] 4 shows a schematic diagram of the indoor heat exchanger 15. The indoor heat exchanger 15 is a device in which heat exchange occurs between the refrigerant flowing through its heat transfer tube r1 and the indoor air. The indoor fan 16 is a fan that sends indoor air into the indoor heat exchanger 15. The indoor fan 16 is driven by an indoor fan motor 16a and is installed near the indoor heat exchanger 15.

[0021] The four-way valve 25 switches the refrigerant flow path depending on the operation mode of the air conditioner A. For example, during cooling operation indicated by the dashed arrow in Fig. 3, the refrigerant circulates in the refrigerant circuit Q1 sequentially through the compressor 21, the outdoor heat exchanger 22 (condenser), the expansion valve 24, and the indoor heat exchanger 15 (evaporator). Furthermore, during heating operation indicated by the solid arrow in Fig. 3, the refrigerant circulates in the refrigerant circuit Q1 sequentially through the compressor 21, the indoor heat exchanger 15 (condenser), the expansion valve 24, and the outdoor heat exchanger 22 (evaporator).

[0022] <Indoor Heat Exchanger 15> Figure 5 shows an enlarged cross-sectional view of section I in Figure 4. The indoor heat exchanger 15 includes a heat transfer tube r1 and fins 27 (see Figure 5) formed on the heat transfer tube r1. The heat transfer tube r1 is made of aluminum or an aluminum alloy. A refrigerant undergoing heat exchange flows through the heat transfer tube r1. The fins 27 are components that increase the heat exchange area. When connecting a connecting pipe r0 to the heat transfer tube r1, which is responsible for heat exchange, it is possible to reduce the diameter of the connecting pipe r0 and insert the reduced section r01 into the heat transfer tube r1. Because aluminum pipes (aluminum alloy pipes) have lower strength than copper pipes, it is possible to make the wall thickness larger than that of copper pipes. When aluminum pipes are used in the indoor heat exchanger 15 of the indoor unit 10, the inner diameter ratio s2 / s1, which is the ratio between the inner diameter s1 of the heat transfer tube r1 and the inner diameter s2 of the reduced section of the connecting pipe, is likely to be larger than that of copper pipes. This increases pressure loss and refrigerant noise. The indoor unit 10 is used in a quiet space such as a living space. Therefore, if an aluminum pipe is used for the indoor heat exchanger 15 of the indoor unit 10, there is a risk that the sound of the refrigerant will leak into the living space.

[0023] A plate 28, which is a strength member, is provided adjacent to the heat transfer tube r1. The heat transfer tube r1 is supported by the plate 28. A connection pipe r0, which allows the refrigerant to move through the refrigerant circuit Q1 (see FIG. 3), is connected to the heat transfer tube r1 of the indoor heat exchanger 15.

[0024] As shown in FIG. 5 , the connection pipe r0 has a contracted portion r01. The connection pipe r0 is inserted all the way into the heat transfer tube r1 at the back of the plate 28 to prevent the connection pipe r0 from breaking. That is, the outer surface r0a of the connection pipe r0 contacts the inner surface r1a of the heat transfer tube r1. The connection pipe r0 has the contracted portion r01, and the outer surface r0a of the connection pipe r0 contacts the inner surface r1a of the heat transfer tube r1. This allows the connection pipe r0 to be inserted all the way into the heat transfer tube r1 at the back of the plate 28 and be securely fixed, thereby preventing the connection pipe r0 from breaking. Here, assuming an inner diameter s1 of the heat transfer tube r1 (see FIG. 5 ) and an inner diameter s2 of the connection pipe r01, the aluminum connection pipe r0 has a thicker wall thickness than a copper pipe because of its low strength.

[0025] Therefore, when the heat transfer tube r1 and the connecting pipe r0 are both made of aluminum pipes, the difference s9 between the inner diameter s1 of the heat transfer tube r1 and the inner diameter s2 of the connecting pipe r01 is larger than when both the heat transfer tube r1 and the connecting pipe r0 are made of copper pipes. In other words, s1 / s2=s9 is larger.

[0026] <Sudden Contraction Pipe K1> The flow in the sudden contraction pipe K1 shown in Fig. 6 will now be described. Fig. 6 shows a schematic diagram of the flow in the sudden contraction pipe K1. Note that Fig. 6 exaggerates the flow phenomenon in the sudden contraction pipe K1. The flow path changes from a thick pipe k11 with a cross-sectional area A11 to a thin pipe k12 with a cross-sectional area A12. In detail, the flow suddenly changes from the flow in the thick pipe k11 (arrow α11 in Fig. 6) to the flow in the thin pipe k12 (arrow α13 in Fig. 6).

[0027] In the process of the flow suddenly changing from the flow in the thick pipe k11 (arrow α11 in Figure 6) to the flow in the thin pipe k12 (arrow α13 in Figure 6), a vortex is generated (arrow α12 in Figure 6), causing a loss of energy, in other words, a loss of pressure.

[0028] As mentioned above, when replacing copper pipes with aluminum or aluminum alloy pipes, the thickness of the aluminum pipe is increased due to its low strength. Therefore, the cross-sectional area ratio A12 / A11 increases. This increases the occurrence of vortices. In other words, changing to aluminum pipes increases pressure loss. Therefore, the vibration of the aluminum or aluminum alloy connecting pipe r0 caused by the energy lost through pressure loss is greater than that of copper pipes, resulting in increased noise, i.e., refrigerant noise.

[0029] <Soundproofing material, sound absorbing material, or sound insulating material 19a, 19b, 19c and indoor heat exchanger 15>

[0030] FIG. 7 shows a schematic diagram of the indoor heat exchanger 15 after applying soundproofing, sound-absorbing, or sound-insulating materials 19a, 19b, and 19c. Hereinafter, the soundproofing, sound-absorbing, or sound-insulating materials 19a, 19b, and 19c are referred to as soundproofing materials, etc. 19a, 19b, and 19c. Therefore, to reduce noise generated by vortices in the aluminum or aluminum alloy connecting pipe r0, the following configuration is adopted. Specifically, soundproofing materials 19a and 19b are applied to the noise-generating portions r01 and r02 of the contracted connecting pipe r0. As mentioned above, the refrigerant at the outlet of the indoor heat exchanger 15, which serves as an evaporator, is gas or has a high gas content, resulting in a high flow rate. Therefore, noise also occurs from the connecting pipe r0, which is located away from the contracted portion r01 (see FIG. 5) at the outlet of the indoor heat exchanger 15, which serves as an evaporator. Therefore, the length of the aluminum piping of the connecting pipe r0, which connects to the refrigerant outlet when the indoor heat exchanger 15 functions as an evaporator, and which is covered with soundproofing, sound-absorbing, or sound-insulating material (19a or 19b), is longer than the length of the aluminum piping of the connecting pipe r0, which connects to the refrigerant inlet when the indoor heat exchanger 15 functions as an evaporator, and which is covered with soundproofing, sound-absorbing, or sound-insulating material (19a or 19b). This reduces noise from the connecting pipe r0, which connects to the refrigerant outlet when the indoor heat exchanger 15 functions as an evaporator. Additionally, vibrations are transmitted from the bent pipe at point r03, which is closest to the refrigerant inlet / outlet of the heat transfer tube r1 of the indoor heat exchanger 15 shown in FIG. 7 (the connection point between the heat transfer tube r1 and the connecting pipe r0 shown in FIG. 5), and generates noise. Therefore, soundproofing material 19c is also attached to point r03, which is close to the vortex generation location and where vibrations are transmitted and noise is generated. The soundproofing material 19c reduces noise at the location r0 where vibrations are transmitted and sound is generated. That is, of the connecting pipes r0 connected to the two refrigerant inlets and outlets (r01, r02) provided on the heat transfer tube r1 shown in Fig. 7, at least one of the aluminum pipes is covered with a soundproofing material, sound absorbing material, or sound insulating material 19c, and the bent pipe (r03) closest to the refrigerant inlet and outlet is the connecting pipe r0.

[0031] The soundproofing materials 19a, 19b, and 19c are made of rubber, such as butyl rubber. For example, the butyl rubber (soundproofing materials 19a, 19b, and 19c) has a wall thickness of 3 mm, while the aluminum pipe forming the connecting pipe r0 has a wall thickness of 1 mm. The soundproofing effect is enhanced when the butyl rubber (soundproofing materials 19a, 19b, and 19c) is thicker than the aluminum pipe. Note that materials other than butyl rubber may be used for the soundproofing materials 19a, 19b, and 19c. The soundproofing materials 19a, 19b, and 19c are made of a material softer than aluminum or an aluminum alloy. This is because the soundproofing materials 19a, 19b, and 19c must be soft enough to cover the connecting pipe r0. By attaching the soundproofing materials 19a, 19b, and 19c, the sound generated by the refrigerant is insulated. For example, at least a portion of the contracted portions r01 and r02 of the connecting pipe r0 is covered with soundproofing materials 19a, 19b, and 19c. "At least a portion of the contracted portions r01 and r02 of the connecting pipe r0" means that only the contracted portions r01 and r02, which are the primary sound sources, are covered with soundproofing materials 19a, 19b, and 19c.

[0032] By covering the connection pipe r0 with soundproofing materials 19a, 19b, and 19c, sound generated by the vibration of the connection pipe r0 is blocked. In addition, by increasing the weight of the connection pipe r0 and suppressing the vibration of the connection pipe, sound reverberating in the room can be suppressed. In addition, by increasing the weight of the connection pipe r0 with the soundproofing materials 19a, 19b, and 19c, the vibration of the connection pipe r0 can be suppressed. This suppresses sound reverberating in the room. For example, the soundproofing materials 19a, 19b, and 19c are configured with weights attached so that the total weight of the connection pipe r0 and the soundproofing materials 19a, 19b, and 19c made of aluminum or an aluminum alloy is equal to or heavier than the weight of the connection pipe r0 made of copper.

[0033] <Condensation> Furthermore, the soundproofing materials 19a, 19b, and 19c attached to the tube-reducing sections r01 and r02 and the bent pipe section r03 have a low insulating effect, and the temperature difference between the tube-reducing sections r01 and r02 and the bent pipe section r03 and the ambient temperature is large, causing condensation to occur on the soundproofing materials 19a, 19b, and 19c. For this reason, as shown in Figure 7, a dew tray 30 for receiving condensation is provided in a position below the soundproofing materials 19a, 19b, and 19c so that all of them can be accommodated. In other words, the soundproofing materials 19a, 19b, and 19c are located within a range vertically above the dew tray 30 for receiving condensation. This allows the dew tray 30 to receive condensation that occurs on the soundproofing materials 19a, 19b, and 19c.

[0034] Second Embodiment Fig. 8 shows a schematic diagram of the flow in the sudden expansion pipe K2 of the second embodiment. Note that Fig. 8 exaggerates the flow phenomenon in the sudden expansion pipe K2. In the first embodiment, the case where the connecting pipe r0 is the sudden contraction pipe K1 (see Fig. 6) has been described, but in the second embodiment, the case where the connecting pipe r2 (see Fig. 10) is the sudden expansion pipe K2 (see Fig. 8) will be described.

[0035] <Sudden Expansion Pipe K2> In the sudden expansion pipe K2, the flow path changes from a narrow pipe k21 with a cross-sectional area A21 to a wide pipe k22 with a cross-sectional area A22. More specifically, the flow suddenly changes from the flow in the narrow pipe k21 (arrow α21 in FIG. 8 ) to the flow in the wide pipe k22 (arrow α23 in FIG. 8 ). During the process of the flow suddenly changing from the flow in the narrow pipe k21 (arrow α21 in FIG. 8 ) to the flow in the wide pipe k22 (arrow α23 in FIG. 8 ), a vortex is generated (arrow α22 in FIG. 8 ), causing a loss.

[0036] As in the first embodiment, if the heat transfer tube r1 and the connecting pipe r2 are changed from copper pipes to aluminum pipes, the thickness of the aluminum pipes must be increased because of their low strength. A thicker pipe increases the cross-sectional area ratio A22 / A21, which increases the generation of vortices and the resulting noise. In other words, changing the heat transfer tube r1 and the connecting pipe r2 to aluminum or aluminum alloy pipes increases pressure loss.

[0037] FIG. 9 shows an enlarged cross-sectional view of the second embodiment, corresponding to the portion I in FIG. 4 . In the second embodiment, the connecting pipe r2 has an expanded portion r2a instead of the contracted portion r01 of the connecting pipe r0 (see FIG. 5 ) of the first embodiment. The connecting pipe r2, through which the refrigerant flows, is connected to the heat transfer pipe r1 of the indoor heat exchanger 15. The connecting pipe r2 has an expanded portion r2a. The connecting pipe r2 is inserted deep into the heat transfer pipe r1 to prevent bending of the connecting pipe r2. That is, the connecting pipe r2 has an expanded portion r2a in which the inner surface r2b of the connecting pipe r2 contacts the outer surface r1b of the heat transfer pipe r1. The connecting pipe r2 has the expanded portion r2a, and the inner surface r2b of the connecting pipe r2 contacts the outer surface r1b of the heat transfer pipe r1, so that the connecting pipe r2 can be securely fixed to the heat transfer pipe r1.

[0038] Here, if the inner diameter of the aluminum heat transfer tube r1 is s1 and the inner diameter of the aluminum connecting pipe r2 is s3, the aluminum heat transfer tube r1 has a thick wall because of its low strength. Therefore, the difference s10 between the inner diameter s3 of the aluminum connecting pipe r2 and the inner diameter s1 of the aluminum heat transfer tube r1 is larger than in the case of copper tubes for both the heat transfer tube r1 and the connecting pipe r2. In other words, s3 / s1 = s10 is large.

[0039] Therefore, the cross-sectional ratio A32 / A31 is large. This results in a large amount of vortex generation, and the resulting noise is louder. Figure 10 shows a schematic diagram of the indoor heat exchanger 15 after applying soundproofing materials (soundproofing, sound-absorbing, or sound-insulating materials) 29a, 29b, and 29c according to the second embodiment. In the second embodiment, in order to reduce the noise caused by the vortex, the soundproofing materials 29a and 29b are applied to the expanded connection pipe r2 at locations r21 and r22 where noise is generated. For example, at least a portion of the expanded portion r2a of the connection pipe r2 is covered with the soundproofing materials 29a and 29b.

[0040] In addition, soundproofing material 29c is also attached to area r23, which is close to the vortex generation location and where vibrations are transmitted and noise is generated. By attaching soundproofing materials 29a, 29b, and 29c, noise caused by the refrigerant is blocked. As in the first embodiment, soundproofing materials 29a, 29b, and 29c are formed of rubber, such as butyl rubber. Soundproofing materials 29a, 29b, and 29c are made of a material softer than aluminum or aluminum alloy. Furthermore, soundproofing materials 29a, 29b, and 29c shown in FIG. 10 have a low insulating effect, and areas r21, r22, and r23 have a large temperature difference from the ambient temperature, resulting in condensation on soundproofing materials 29a, 29b, and 29c.

[0041] For this reason, a dew tray 31 for receiving condensed water is provided in a position below where all of the soundproofing materials 29a, 29b, and 29c are accommodated. In other words, the soundproofing materials 29a, 29b, and 29c are positioned within a range vertically above the dew tray 31 for receiving condensed water. This allows condensed water generated on the soundproofing materials 29a, 29b, and 29c to be received by the dew tray 31. Note that while the first and second embodiments describe cases where the present invention is applied to the indoor heat exchanger 15 of the indoor unit 1, the present invention may also be applied to the outdoor heat exchanger 22 of the outdoor unit 20 (see FIG. 3). In this case, the refrigerant pipe r20 connected to the outdoor heat exchanger 22 corresponds to the connecting pipe.

[0042] Furthermore, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. Furthermore, the above-described mechanisms and configurations are those considered necessary for explanation, and do not necessarily represent all mechanisms and configurations of the product.

[0043] 15 Indoor heat exchanger 19a to 19c, 29a to 29c Soundproofing material, sound absorbing material, or sound insulating material 30, 31 Dew tray A Air conditioner r0, r2 Connecting pipe r01, r02 Contracted section (refrigerant inlet / outlet) r0a Outer surface of connecting pipe r1 Heat transfer pipe r1a Inner surface of heat transfer pipe r1b Outer surface of heat transfer pipe r2a Expanded section r2b Inner surface of connecting pipe

Claims

1. An air conditioner comprising: a heat exchanger having heat transfer tubes made of aluminum or an aluminum alloy; and connecting pipes through which a refrigerant flowing out of said heat transfer tube or a refrigerant flowing into said heat transfer tube passes, the connecting pipes being at least partially made of aluminum piping made of aluminum or an aluminum alloy, wherein at least one of the connecting pipes connected to two refrigerant inlets and outlets provided on said heat transfer tube is at least partially covered with a soundproofing material, a sound absorbing material, or a sound insulating material.

2. An air conditioner as claimed in claim 1, characterized in that the total weight including the aluminum piping and the soundproofing, sound absorbing or sound insulating material is configured to be heavier than the weight of the aluminum piping if it were made of copper.

3. An air conditioner as claimed in claim 1 or 2, characterized in that the connecting pipe has a connection part whose outer surface contacts the inner surface of the heat transfer tube or whose inner surface contacts the outer surface of the heat transfer tube, and at least a portion of the connection part of the aluminum pipe is covered with the soundproofing material, sound-absorbing material or sound-blocking material.

4. An air conditioner as claimed in claim 1 or 2, characterized in that at least a portion of the aluminum pipes of both of the connecting pipes connected to each of the two refrigerant inlets and outlets provided on the heat transfer tube are covered with soundproofing material, sound absorbing material or sound insulating material.

5. An air conditioner as claimed in claim 4, characterized in that the length of the aluminum piping of the connecting piping that connects to the refrigerant outlet when the heat exchanger becomes an evaporator and that is covered with the soundproofing material, sound absorbing material or sound insulating material is longer than the length of the aluminum piping of the connecting piping that connects to the refrigerant inlet when the heat exchanger becomes an evaporator and that is covered with the soundproofing material, sound absorbing material or sound insulating material.

6. An air conditioner as claimed in claim 1 or 2, characterized in that the bent pipe closest to the refrigerant inlet / outlet of at least one of the aluminum pipes among the connecting pipes connected to each of the two refrigerant inlets / outlets provided on the heat transfer tube is covered with the soundproofing material, sound absorbing material or sound insulating material.

7. An air conditioner according to claim 1 or 2, characterized in that the soundproofing material, the sound absorbing material or the sound insulating material is made of a material softer than aluminum or an aluminum alloy.

8. An air conditioner as claimed in claim 1 or claim 2, characterized in that the connection portion is a contracted portion whose outer surface contacts the inner surface of the heat transfer tube, or an expanded portion whose inner surface contacts the outer surface of the heat transfer tube.

9. An air conditioner according to claim 1 or 2, characterized in that the thickness of the soundproofing material, sound absorbing material or sound insulating material is thicker than the wall thickness of the aluminum piping.

10. An air conditioner as claimed in claim 1 or 2, characterized in that a dew tray for receiving condensed water is provided below the soundproofing material, the sound absorbing material or the sound insulating material.

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