Air conditioner

Abstract

The present invention provides an air conditioner capable of suppressing, over a long period of time, galvanic corrosion of a connection part where an aluminum refrigerant pipe and a metal refrigerant pipe having a small ionization tendency are connected, while suppressing a manufacturing cost of a refrigerant circuit and securing the degree of freedom in the design of the refrigerant circuit. The air conditioner is provided with a connection part (13b) at which an aluminum refrigerant pipe (11b) formed from aluminum or an aluminum-containing metal is connected to a metal refrigerant pipe (12b) formed from a metal having a smaller ionization tendency than aluminum in a state of being positioned vertically below the metal refrigerant pipe. The outer surface of the connection part (13b) is coated with a cover (20), and a sacrificial anticorrosion layer is formed on the outer surface of the aluminum refrigerant pipe (11b).

Description

Air conditioner

[0001] The present invention relates to an air conditioner including a connection part where an aluminum refrigerant pipe and a metal refrigerant pipe formed of a metal having a lower ionization tendency than aluminum are connected.

[0002] An air conditioner includes a refrigerant circuit that circulates a refrigerant to execute a refrigeration cycle. The refrigerant circuit is formed by connecting devices such as a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger via refrigerant pipes. Conventionally, the refrigerant pipes and heat transfer pipes of heat exchangers in air conditioners are made of copper such as phosphor-deoxidized copper. However, in recent years, conversion of the devices and refrigerant pipes constituting the refrigerant circuit to aluminum has been considered.

[0003] When the devices and refrigerant pipes are converted to aluminum, it is possible to reduce material costs and weight of the devices. On the other hand, it is assumed that the conventionally used copper refrigerant pipes and aluminum refrigerant pipes coexist. Since the connection part connecting the aluminum refrigerant pipe and the copper refrigerant pipe is a joint between dissimilar metals, there is a problem that galvanic corrosion is likely to occur.

[0004] When water droplets adhere to the connection part due to dew condensation or the like, a local battery is formed between aluminum and copper. Further, when water droplets adhere to the copper refrigerant pipe, copper ions elute into the water droplets, and the water droplets containing copper ions adhere to the aluminum refrigerant pipe along the copper refrigerant pipe. When galvanic corrosion progresses due to these phenomena, gaps and through-holes occur in the connection part and the pipe wall, leading to refrigerant leakage.

[0005] Patent Document 1 describes a technique for preventing corrosion of an aluminum refrigerant pipe connected to a copper refrigerant pipe. In this technique, an inverted U-shaped part with the aluminum refrigerant pipe convex upward or a U-shaped part with the copper refrigerant pipe convex downward is provided near the connection point between the aluminum refrigerant pipe and the copper refrigerant pipe. The inverted U-shaped part and the U-shaped part suppress the movement of moisture adhering to the copper refrigerant pipe to the aluminum refrigerant pipe.

[0006] Japanese Patent No. 5853203

[0007] In refrigeration and air conditioning equipment such as air conditioners, aluminum refrigerant pipes, which are made of aluminum or an aluminum-containing metal, may be connected to metal refrigerant pipes made of metals with a lower ionization tendency than aluminum, such as copper refrigerant pipes or stainless steel refrigerant pipes. Therefore, more practical measures are needed to avoid galvanic corrosion at the connection points where aluminum refrigerant pipes are connected to metal refrigerant pipes with a lower ionization tendency.

[0008] As shown in Patent Document 1, arranging aluminum refrigerant pipes above and copper refrigerant pipes below can suppress the flow of water droplets onto the aluminum refrigerant pipes and the formation of local galvanic cells at the connection points. However, this method has the problem of limiting the arrangement and shape of the refrigerant pipes. The number of U-shaped return bends increases, making it difficult to secure space for arranging the refrigerant pipes. In addition, the manufacturing cost of the refrigerant circuit increases, and the refrigerant circuit becomes larger.

[0009] One way to avoid galvanic corrosion at the connection points between aluminum and metal refrigerant pipes, or in the aluminum refrigerant pipes themselves, is to cover the connection points and the aluminum refrigerant pipes. Covering the connection points and aluminum refrigerant pipes with covering materials such as tubes can prevent water droplets from accumulating due to condensation. However, if the length of the covering material increases, the covering work becomes more time-consuming, leading to increased manufacturing costs.

[0010] Therefore, the present invention aims to provide an air conditioner that can suppress galvanic corrosion at the connection point where an aluminum refrigerant pipe and a metal refrigerant pipe with a low ionization tendency are connected, over a long period of time, while suppressing the manufacturing cost of the refrigerant circuit and ensuring flexibility in the design of the refrigerant circuit.

[0011] To solve the aforementioned problems, the air conditioner according to the present invention includes a connection part in which an aluminum refrigerant pipe, made of aluminum or a metal containing aluminum, is connected such that it is positioned vertically below a metal refrigerant pipe, made of a metal having a lower ionization tendency than aluminum, the outer surface of the connection part is covered with a cover, and a sacrificial corrosion protection layer is formed on the outer surface of the aluminum refrigerant pipe.

[0012] According to the present invention, it is possible to provide an air conditioner that can suppress galvanic corrosion at the connection point where an aluminum refrigerant pipe and a metal refrigerant pipe with a low ionization tendency are connected, over a long period of time, while suppressing the manufacturing cost of the refrigerant circuit and ensuring flexibility in the design of the refrigerant circuit.

[0013] This is a diagram illustrating an example of the configuration of an air conditioner. This is a diagram illustrating an example of the refrigerant circuit provided by an air conditioner. This is a diagram illustrating the internal configuration of the outdoor unit of an air conditioner. This is a diagram illustrating the structure of the connection part in a conventional air conditioner. This is a diagram illustrating the structure of the connection part in an air conditioner according to an embodiment of the present invention. This is a diagram illustrating the structure of the refrigerant pipe connected between the outdoor heat exchanger and the expansion valve in an air conditioner according to an embodiment of the present invention. This is a diagram illustrating the structure of the refrigerant pipe connected between the expansion valve and the outdoor heat exchanger in an air conditioner according to an embodiment of the present invention. This is a diagram illustrating the structure of the refrigerant pipe connected between the outdoor heat exchanger and the liquid-side service valve in an air conditioner according to an embodiment of the present invention. This is a diagram illustrating the structure of the refrigerant pipe connected between the four-way valve and the outdoor heat exchanger in an air conditioner according to an embodiment of the present invention.

[0014] The following describes an air conditioner according to one embodiment of the present invention. In the following figures, common components are denoted by the same reference numerals, and redundant explanations are omitted. In the following description, a room air conditioner is used as an example to show the main components of the air conditioner and the components that suppress galvanic corrosion.

[0015] Figure 1 shows an example of the configuration of an air conditioner. As shown in Figure 1, the air conditioner 1 comprises an outdoor unit 100 installed outdoors and an indoor unit 200 installed on a wall or the like indoors. The outdoor unit 100 and the indoor unit 200 are connected to each other via connecting pipes 300. A remote control 400 is also provided separately. Refrigerant pipes and electrical wiring are routed through the connecting pipes 300. The remote control 400 is operated by the user and transmits operation signals to the indoor unit 200 for operation.

[0016] The air conditioner 1 is a device that adjusts the temperature and humidity of a space by blowing out heated air, cooled air, dehumidified air, etc. Refrigerant circulates between the outdoor unit 100 and the indoor unit 200 through refrigerant pipes. In the outdoor unit 100, heat exchange takes place between the refrigerant and the outside air. In the indoor unit 200, heat exchange takes place between the refrigerant and the indoor air. The indoor unit 200 blows out air drawn in from the room after heat exchange with the refrigerant, thereby adjusting the temperature and humidity of the room.

[0017] Figure 2 shows an example of a refrigerant circuit in an air conditioner. As shown in Figure 2, the air conditioner 1 is equipped with a refrigerant circuit 10 that constitutes a heat pump. The refrigerant circuit 10 performs a refrigeration cycle for cooling, heating, dehumidification, etc. The refrigerant circuit 10 is equipped with components such as a compressor 2, a four-way valve 3, an outdoor heat exchanger 4, an expansion valve 5, an indoor heat exchanger 6, and an accumulator 7.

[0018] These devices are connected to each other via refrigerant pipes through which the refrigerant flows. The outdoor unit 100 is connected to the indoor unit 200 via a liquid-side service valve 18, and a gas-side service valve 19, which is also a refrigerant pipe. These devices and refrigerant pipes form a closed refrigerant circuit 10 between the outdoor unit 100 and the indoor unit 200, through which the refrigerant circulates.

[0019] The refrigerant circuit 10 is filled with refrigerant during installation or maintenance of the air conditioner 1. The refrigerant circulates through the refrigerant circuit 10 and exchanges heat with indoor air or outside air for cooling, heating, dehumidifying, etc. The outdoor unit 100 houses the compressor 2, four-way valve 3, outdoor heat exchanger 4, expansion valve 5, accumulator 7, and outdoor blower fan 8. The indoor unit 200 houses the indoor heat exchanger 6 and indoor blower fan 9.

[0020] The compressor 2 is a device that compresses the refrigerant. It draws in low-pressure gaseous refrigerant, compresses it adiabatically, and discharges high-pressure gaseous refrigerant. The compressor 2 may be configured to variably control the amount of refrigerant circulated by inverter control. The compressor 2 can be a sealed electric compressor of an appropriate type, such as a scroll type, piston type, rotary type, screw type, or centrifugal type.

[0021] The four-way valve 3 has four ports and a valve body that switches the connection of the flow paths between the ports, and the connection of the flow paths between the ports is changed according to the operating mode, such as cooling operation or heating operation. The four-way valve 3 switches the circulation direction of the refrigerant discharged from the compressor 2 in the refrigerant circuit 10. In Figure 2, the solid arrows indicate the circulation direction of the refrigerant during cooling operation. The dashed arrows indicate the circulation direction of the refrigerant during heating operation.

[0022] The outdoor heat exchanger 4 is a heat exchanger that exchanges heat between the refrigerant and the outside air. It functions as a condenser during cooling operation and as an evaporator during heating operation. The outdoor blower fan 8 blows outside air to the outdoor heat exchanger 4 to promote heat exchange. The outdoor blower fan 8 is made up of a propeller fan. The expansion valve 5 is an electronically controlled valve with an adjustable opening and functions as a pressure reducer that expands the refrigerant.

[0023] In Figure 2, the outdoor heat exchanger 4 comprises a main unit 4a and a subcooler 4b. The heat transfer tubes of the main unit 4a and the heat transfer tubes of the subcooler 4b are connected via an expansion valve 5 and refrigerant pipes. The subcooler 4b cools the liquid refrigerant introduced into the expansion valve 5 during cooling operation. Cooling performance is improved by pre-cooling the liquid refrigerant. The subcooler 4b can also function as a hot pipe to prevent frost formation on the main unit 4a during heating operation.

[0024] The indoor heat exchanger 6 is a heat exchanger that exchanges heat between the refrigerant and the indoor air. During cooling operation, it functions as an evaporator, and during heating operation, it functions as a condenser. The indoor blower fan 9 blows air into the indoor heat exchanger 6 to promote heat exchange, and also blows the air that has exchanged heat with the refrigerant into the room. The indoor blower fan 9 is composed of a cylindrical through-fan.

[0025] The accumulator 7 is a tank-shaped device that separates gaseous refrigerant from liquid refrigerant, separating and storing the liquid refrigerant contained in the gaseous refrigerant. By removing any unevaporated liquid refrigerant from the gaseous refrigerant on the suction side of the compressor 2, liquid compression in the compressor 2, which can cause abnormal noise and malfunctions, is prevented.

[0026] The cooling operation of the air conditioner 1 is carried out as follows: The high-temperature, high-pressure gaseous refrigerant adiabatically compressed by the compressor 2 is sent to the outdoor heat exchanger 4 through the four-way valve 3. The high-temperature, high-pressure gaseous refrigerant is condensed into liquid refrigerant by heat exchange with the outside air in the outdoor heat exchanger 4, which acts as a condenser. The liquid refrigerant is pre-cooled by the subcooler 4b before being introduced to the expansion valve 5. The liquid refrigerant is depressurized and expanded in the expansion valve 5 to become a low-temperature, low-pressure gas-liquid two-phase refrigerant containing a small amount of gaseous refrigerant.

[0027] The low-temperature, low-pressure gaseous-liquid two-phase refrigerant is sent to the indoor heat exchanger 6. The gaseous-liquid two-phase refrigerant evaporates in the indoor heat exchanger 6, which acts as an evaporator, through heat exchange with the indoor air, becoming a low-temperature, low-pressure gaseous refrigerant. The low-temperature, low-pressure gaseous refrigerant passes through the four-way valve 3, and after the liquid refrigerant is separated in the accumulator 7, it returns to the compressor 2. The indoor air loses heat through heat exchange with the refrigerant in the indoor heat exchanger 6, which acts as an evaporator. This cycle is repeated, and the room is cooled.

[0028] The heating operation of the air conditioner 1 is performed in the reverse cycle of the cooling operation. The high-temperature, high-pressure gaseous refrigerant discharged by adiabatically compressed compressor 2 is sent to the indoor heat exchanger 6 by switching the four-way valve 3. The high-temperature, high-pressure gaseous refrigerant is cooled by heat exchange with the indoor air in the indoor heat exchanger 6, which acts as a condenser, and becomes liquid refrigerant. The liquid refrigerant is then depressurized by the expansion valve 5 to become low-temperature, low-pressure liquid refrigerant.

[0029] Low-temperature, low-pressure liquid refrigerant is sent to the outdoor heat exchanger 4. The low-temperature, low-pressure liquid refrigerant evaporates in the outdoor heat exchanger 4, which acts as an evaporator, through heat exchange with the outside air, becoming a low-temperature, low-pressure gaseous refrigerant. The low-temperature, low-pressure gaseous refrigerant passes through the four-way valve 3, and after the liquid refrigerant is separated in the accumulator 7, it returns to the compressor 2. The indoor air is heated in the indoor heat exchanger 6, which acts as a condenser, through heat exchange with the refrigerant. This cycle is repeated, heating the room.

[0030] In the air conditioner 1 according to this embodiment, the refrigerant circuit 10 may be filled with a single refrigerant consisting of a single refrigerant component, or with a mixed refrigerant consisting of multiple refrigerant components. As the mixed refrigerant, an azeotropic mixed refrigerant may be used, or a non-azeotropic mixed refrigerant may be used. Examples of refrigerants include hydrofluorocarbons (HFCs), hydrofluoroolefins (HFOs), and CO2. ２ One or more of hydrocarbons, ethers, fluoroethers, fluoroalkenes, etc., can be used. Additives such as stabilizers that suppress the decomposition of refrigerant components and polymerization inhibitors that suppress the polymerization of refrigerant components may be added to the refrigerant.

[0031] In the air conditioner 1 according to this embodiment, a predetermined refrigerant oil is injected into the compressor 2. The refrigerant oil is drawn from an oil reservoir during the operation of the compressor 2 and supplied to sliding parts such as the compression mechanism and bearings. The refrigerant oil lubricates, cools, and seals the sliding parts. A portion of the refrigerant oil is discharged from the compressor 2 together with the refrigerant and circulates in the refrigerant circuit 10. As the refrigerant oil, polyol ester oil, polyvinyl ether oil, polyalkylene glycol oil, etc., can be used. Additives such as acid scavengers, antioxidants, extreme pressure agents, stabilizers, defoamers, and metal deactivators may be added to the refrigerant oil.

[0032] Figure 3 is a diagram illustrating the internal configuration of the outdoor unit of an air conditioner. Figure 3 shows an example of the internal structure of the outdoor unit 100's casing and the main equipment installed inside. As shown in Figure 3, the outdoor unit 100 incorporates a compressor 2, a four-way valve 3, an outdoor heat exchanger 4, an expansion valve 5, an accumulator 7, and an outdoor fan 8 (not shown).

[0033] The outdoor unit 100 has a housing that is roughly rectangular in shape. The bottom surface of the housing is formed by a bottom base 101. The top surface of the housing is formed by a top plate (not shown). The front surface of the housing is formed by a front plate (not shown). The sides and rear surface of the housing are formed by side plates, rear plates, etc. (not shown). The housing is made of steel plate or the like that is painted for corrosion protection.

[0034] The interior of the outdoor unit 100's casing is divided by a partition plate 105 into a heat exchanger compartment 110 on one side and a machine compartment 120 on the other side. An electrical components box (not shown) is provided in the upper part of the interior of the casing, above the partition plate 105. The heat exchanger compartment 110 houses the outdoor heat exchanger 4, outdoor blower fan 8, etc. The machine compartment 120 houses the compressor 2, four-way valve 3, expansion valve 5, accumulator 7, etc. The electrical components box houses the control board and electrical components.

[0035] The heat exchanger chamber 110 is the compartment where heat exchange by the outdoor heat exchanger 4 takes place. The front panel of the heat exchanger chamber 110 is provided with an air outlet covered by a grid. The side and rear panels of the heat exchanger chamber 110 are provided with air intakes. When the outdoor fan 8 is driven to rotate by the fan motor, it draws outside air into the enclosure through the air intakes. The air drawn into the enclosure is heat-exchanged with the refrigerant by the outdoor heat exchanger 4. The heat-exchanged air is blown out of the enclosure through the air outlets.

[0036] The outdoor heat exchanger 4 is supported on a bottom base 101. The outdoor heat exchanger 4 is, for example, a cross-fin tube and includes heat transfer tubes through which the refrigerant flows, and a plurality of fins joined to the heat transfer tubes. The heat transfer tubes and fins can be made of, for example, an aluminum alloy. By switching the heat transfer tubes and fins to aluminum, material costs can be reduced and the weight of the heat exchanger can be reduced. The heat transfer tubes of the outdoor heat exchanger 4 are connected to the refrigerant tubes that constitute the refrigerant circuit 10 by brazing or eutectic bonding.

[0037] The machine room 120 is a compartment that houses equipment related to the operation of the outdoor unit 100. The machine room 120 houses equipment such as the compressor 2, four-way valve 3, expansion valve 5, accumulator 7, and refrigerant pipes that connect these devices. On the side of the outdoor unit 100 housing facing the machine room 120, a liquid-side service valve 18 to which the liquid pipe is connected and a gas-side service valve 19 to which the gas pipe is connected are installed.

[0038] One end of the heat transfer tube of the subcooler 4b of the outdoor heat exchanger 4 is connected to the internal port of the liquid-side service valve 18 via a refrigerant pipe or the like. One end of the heat transfer tube of the indoor heat exchanger 6 is connected to the external port of the liquid-side service valve 18 via a refrigerant pipe or the like. One port of the four-way valve 3 is connected to the internal port of the gas-side service valve 19 via a refrigerant pipe or the like. The other end of the heat transfer tube of the indoor heat exchanger 6 is connected to the external port of the gas-side service valve 19 via a refrigerant pipe or the like.

[0039] The inlet side of the accumulator 7 is connected to the other port of the four-way valve 3 via refrigerant pipes, etc. The suction side of the compressor 2 is connected to the outlet side of the accumulator 7 via refrigerant pipes, etc. One port of the four-way valve 3 is connected to the discharge side of the compressor 2 via refrigerant pipes, etc. One end of the heat transfer tube of the main body 4a of the outdoor heat exchanger 4 is connected to the other port of the four-way valve 3 via refrigerant pipes, etc. One port of the expansion valve 5 is connected to the other end of the heat transfer tube of the main body 4a of the outdoor heat exchanger 4 via refrigerant pipes, etc. The other end of the heat transfer tube of the subcooler 4b of the outdoor heat exchanger 4 is connected to the other port of the expansion valve 5 via refrigerant pipes, etc.

[0040] Next, we will explain the structure of the connection points where dissimilar metals are connected in the refrigerant circuit. In the following explanation, the refrigerant inlet and outlet of the equipment constituting the refrigerant circuit, and the upstream and downstream of the refrigerant flow in the refrigerant circuit, will be indicated based on the direction of refrigerant flow during cooling operation.

[0041] Figure 4 is a diagram illustrating the structure of a connection in a conventional air conditioner. Figure 4 shows the structure around the expansion valve 5 connected to the section between the main body 4a and the subcooler 4b of the outdoor heat exchanger 4 on the refrigerant circuit 10. The subcooler 4b is located in the lower part of the outdoor heat exchanger 4 and is formed below the main body 4a. The expansion valve 5 is connected to the heat transfer tubes of the main body 4a of the outdoor heat exchanger 4 and the heat transfer tubes of the subcooler 4b of the outdoor heat exchanger 4 via refrigerant pipes, etc.

[0042] In FIG. 4, the downstream end of the metal refrigerant pipe 12A is connected to the inlet of the expansion valve 5 via a strainer 16A. The metal refrigerant pipe 12A is generally made of copper. The downstream end of the aluminum refrigerant pipe 11A is connected to the upstream end of the metal refrigerant pipe 12A via a connection part 13A. The downstream end of the heat transfer pipe of the main body part 4a of the outdoor heat exchanger 4 is connected to the upstream end of the aluminum refrigerant pipe 11A.

[0043] Also, the upstream end of the metal refrigerant pipe 12B is connected to the outlet of the expansion valve 5 via a strainer 16B. The metal refrigerant pipe 12B is generally made of copper. The upstream end of the aluminum refrigerant pipe 11B is connected to the downstream end of the metal refrigerant pipe 12B via a connection part 13B. The upstream end of the heat transfer pipe of the sub-cooler 4b of the outdoor heat exchanger 4 is connected to the downstream end of the aluminum refrigerant pipe 11B.

[0044] When the outdoor heat exchanger 4 is converted to be made of aluminum, a part of the refrigerant pipe connecting between the heat transfer pipe of the main body part 4a of the outdoor heat exchanger 4 and the expansion valve 5, and a part of the refrigerant pipe connecting between the heat transfer pipe of the sub-cooler 4b of the outdoor heat exchanger 4 and the expansion valve 5 may also be converted to be made of aluminum. On the other hand, the conventionally used copper refrigerant pipe may be useful in terms of product assembly and component interchangeability, etc., and there is a possibility that the aluminum refrigerant pipe and the copper refrigerant pipe coexist.

[0045] Generally, a connection part where an aluminum refrigerant pipe formed of aluminum or a metal containing aluminum and a metal refrigerant pipe formed of a metal with a smaller ionization tendency than aluminum are connected becomes a joint between dissimilar metals, and thus is a location where galvanic corrosion is likely to occur.

[0046] Water droplets may adhere to the outer surface of the refrigerant pipe due to condensation or the like. When water droplets adhere to the connection part, a local battery is formed between aluminum and a metal such as copper with a smaller ionization tendency than aluminum through the water droplets. Also, when water droplets adhere to the outer surface of a metal refrigerant pipe such as a copper-made one, metal ions such as copper ions dissolve in the water droplets. The water droplets in which the metal ions are dissolved may flow down along the outer surface of the metal refrigerant pipe and adhere to the aluminum refrigerant pipe.

[0047] These phenomena are the causes of galvanic corrosion in the connection parts and aluminum refrigerant pipes. When galvanic corrosion progresses, gaps may occur in the connection parts, or through-holes due to pitting corrosion may occur in the connection parts or aluminum refrigerant pipes, which may lead to refrigerant leakage. Galvanic corrosion is likely to occur particularly when the aluminum refrigerant pipe is located below the metal refrigerant pipe in the vertical direction among the connection parts where the aluminum refrigerant pipe and the metal refrigerant pipe with a smaller ionization tendency are connected. This is because the water droplets adhering to the outer surface of the refrigerant pipe flow down along the outer surface following gravity.

[0048] In conventional air conditioners, as described in Patent Document 1, as a measure to prevent galvanic corrosion of the connection parts, measures are taken to limit the shape and arrangement of the refrigerant pipes.

[0049] As shown in FIG. 4, in a conventional air conditioner, the aluminum refrigerant pipes 11A and 11B are bent in a U shape so as to be convex upward. The copper-made metal refrigerant pipes 12A and 12B are bent in a U shape so as to be convex downward. The end sides of the aluminum refrigerant pipes 11A and 11B and the end sides of the metal refrigerant pipes 12A and 12B are connected such that the end sides of the aluminum refrigerant pipes 11A and 11B are located above the end sides of the metal refrigerant pipes 12A and 12B in the vertical direction.

[0050] With such a shape and arrangement of the refrigerant pipes, a situation where water droplets due to condensation or the like flow down from the metal refrigerant pipes 12A and 12B to the aluminum refrigerant pipes 11A and 11B is prevented.

[0051] However, with such a shape and arrangement, when extending the aluminum refrigerant pipe downward from the connection part with the metal refrigerant pipe, for example, the number of return bend parts bent in a U shape will increase. Since the total width of the refrigerant pipe increases due to the return bend parts, it becomes difficult to secure the space for arranging the refrigerant pipe. Also, since the number of return bend parts increases, the manufacturing cost of the refrigerant circuit increases or the refrigerant circuit becomes larger.

[0052] Therefore, in the air conditioner 1 according to this embodiment, at least a portion of the connection portion where the aluminum refrigerant pipe and the metal refrigerant pipe with a low ionization tendency are connected is structured such that the end of the aluminum refrigerant pipe is located vertically lower than the end of the metal refrigerant pipe. That is, at least a portion of the multiple connection portions provided on the refrigerant circuit 10 is formed by connecting the metal refrigerant pipe and the aluminum refrigerant pipe in this order from top to bottom.

[0053] Furthermore, in the air conditioner 1 according to this embodiment, among the connection parts where an aluminum refrigerant pipe and a metal refrigerant pipe with a low ionization tendency are connected, the connection part in which the aluminum refrigerant pipe and the metal refrigerant pipe are connected such that the end of the aluminum refrigerant pipe is located vertically lower than the end of the metal refrigerant pipe is covered with a cover. In addition, a sacrificial corrosion protection layer is formed on the outer surface of the aluminum refrigerant pipe that forms such a connection part.

[0054] This structure avoids constraints on the shape and arrangement of refrigerant pipes while suppressing galvanic corrosion of the connection points where aluminum refrigerant pipes are connected to metal refrigerant pipes with a lower ionization tendency, as well as the aluminum refrigerant pipes themselves, over a long period of time. By installing the connection points vertically, flexibility and space for refrigerant pipe installation are ensured, while galvanic corrosion caused by the flow of water droplets is suppressed by the cover and sacrificial corrosion protection layer.

[0055] Generally, the service life of an air conditioner is expected to be around 6 to 15 years if preventive maintenance is implemented. Considering the safety of the actual product, it is desirable that components such as heat exchangers, which are not subject to replacement, have a lifespan of 20 years or more. Under these premises, the inventors conducted an accelerated SWAT test based on the ASTM-compliant SWAT test for connection points where the end of an aluminum refrigerant pipe is located vertically lower than the end of a copper refrigerant pipe.

[0056] For the accelerated SWAAT test, test materials were provided that had a connection point where an aluminum refrigerant pipe with a sacrificial corrosion protection layer formed on its outer surface was connected to a copper refrigerant pipe. The accelerated SWAAT test was conducted under conditions in which water containing copper ions within a predetermined concentration range flowed down. As a result, it was confirmed that by using an aluminum refrigerant pipe with a sacrificial corrosion protection layer, no through-holes were formed in the connection point or the aluminum refrigerant pipe even after repeating a test cycle equivalent to 20 years, indicating that long-term use is possible.

[0057] The factors contributing to these test results are likely that the base aluminum material did not corrode until the sacrificial corrosion protection layer disappeared, and that it took time for corrosion to progress. Furthermore, at typical copper ion concentrations expected in contact with aluminum refrigerant pipes, it is possible that the corrosion rate required for through-hole formation would not be reached within a 20-year test cycle. The SWAAT test is more susceptible to the removal of the passive oxide film compared to the combined cycle corrosion test (CCT), which is known to simulate real-world conditions. Therefore, based on these test results, it can be said that sufficient corrosion protection is ensured in real-world environments.

[0058] The air conditioner 1 according to this embodiment includes, on the refrigerant circuit 10, an aluminum refrigerant pipe made of aluminum or a metal containing aluminum, a metal refrigerant pipe mainly composed of a metal having a lower ionization tendency than aluminum, and a connection part to which the aluminum refrigerant pipe and the metal refrigerant pipe are connected. Such a connection part may be provided at one location or at multiple locations on the refrigerant circuit 10. Covers and sacrificial corrosion protection layers may be provided on all of the connection parts and aluminum refrigerant pipes on the refrigerant circuit 10 or on some of them.

[0059] Examples of metals containing aluminum include aluminum-manganese alloys, aluminum-silicon alloys, and aluminum-silicon-magnesium alloys. Examples of metals with a lower ionization tendency than aluminum include iron, chromium, nickel, manganese, copper, and alloys containing these metals. Examples of metal refrigerant pipes include copper refrigerant pipes made of copper or copper-containing metals, and stainless steel refrigerant pipes made of stainless steel.

[0060] Using aluminum refrigerant pipes reduces the material cost of the refrigerant pipes compared to copper refrigerant pipes. It also allows for lighter products such as outdoor units. Using copper refrigerant pipes makes joining them by brazing easier compared to aluminum refrigerant pipes, thus facilitating the connection between the refrigerant pipes and equipment, as well as the replacement of refrigerant pipes and equipment. Using stainless steel refrigerant pipes reduces the material cost of the refrigerant pipes compared to copper refrigerant pipes. Furthermore, it offers excellent corrosion resistance.

[0061] Figure 5 is a diagram illustrating the structure of a connection in an air conditioner according to an embodiment of the present invention. The top of Figure 5 indicates the upward direction in the vertical direction. The bottom of Figure 5 indicates the downward direction in the vertical direction. As shown in Figure 5, in the air conditioner 1 according to this embodiment, an aluminum refrigerant pipe 11 made of aluminum or a metal containing aluminum and a metal refrigerant pipe 12 made of a metal having a lower ionization tendency than aluminum are joined to each other to form a connection 13.

[0062] In Figure 5, the end of the aluminum refrigerant pipe 11 is fitted and joined to the end of the metal refrigerant pipe 12. The inner surface of the end of the aluminum refrigerant pipe 11 and the outer surface of the end of the metal refrigerant pipe 12 are integrated via a joining metal 14. The connection portion 13 is formed as a region where dissimilar metals overlap radially in the refrigerant pipe via the joining metal 14. A sacrificial corrosion protection layer 15 is formed on the outer surface of the aluminum refrigerant pipe 11. The outer surface of the connection portion 13 is covered by a cover 20.

[0063] At the connection point 13, the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 are connected such that the end of the aluminum refrigerant pipe 11 is located vertically lower than the end of the metal refrigerant pipe 12. The aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 may be connected vertically, substantially parallel to the vertical direction, or they may be connected at an angle, inclined from the vertical direction. However, from the viewpoint of facilitating the connection between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 and the covering of the cover 20, it is preferable to connect them vertically.

[0064] The aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 forming the connection portion 13 may be arranged vertically substantially parallel to the vertical direction in the section near the end on the connection portion 13 side, or they may be arranged diagonally, inclined from the vertical direction. The section near the end opposite to the end on the connection portion 13 side may be arranged vertically substantially parallel to the vertical direction, diagonally, inclined from the vertical direction, or horizontally substantially parallel to the horizontal direction. However, from the viewpoint of securing space for installing the refrigerant pipes, etc., it is preferable to arrange them vertically.

[0065] The connection portion 13 can be formed by joining the end of the aluminum refrigerant pipe 11 and the end of the metal refrigerant pipe 12 by brazing or eutectic bonding. Eutectic bonding is a method of diffusion bonding materials at low temperature and low pressure by utilizing the eutectic reaction between aluminum and copper. Brazing and eutectic bonding can be performed using the inner surface of the end of the aluminum refrigerant pipe 11, on which the sacrificial corrosion protection layer 15 is formed, and the outer surface of the end of the metal refrigerant pipe 12 as the joining surfaces. When the expanded aluminum refrigerant pipe 11 is fitted onto the metal refrigerant pipe 12, the joining surface can be heated without excessively heating the aluminum refrigerant pipe 11 during joining, thus avoiding melting of the aluminum refrigerant pipe 11.

[0066] The sacrificial corrosion protection layer 15 protects against corrosion by lowering the electrode potential of aluminum to a low potential, which is the passivation region, and by sacrificial corrosion protection, in which metals that exhibit a higher corrosion potential than aluminum in aqueous solutions or seawater, or base metals that have a greater ionization tendency than aluminum, corrode sacrificially. Examples of materials for the sacrificial corrosion protection layer 15 include zinc, zinc alloys, and aluminum alloys to which metals that exhibit a higher corrosion potential than aluminum in aqueous solutions or seawater, or base metals that have a greater ionization tendency than aluminum, are added. Examples of zinc alloys include zinc-aluminum alloys and zinc-nickel alloys.

[0067] The sacrificial corrosion protection layer 15 can be formed by thermal spraying methods such as flame spraying, arc spraying, and laser spraying, or by cladding methods that pressurize and bond materials together, or by plating methods such as hot-dip galvanizing and displacement plating. When using thermal spraying, the formed sacrificial corrosion protection layer 15 may be subjected to sealing treatment, heat treatment, polishing, grinding, etc. When using cladding, it can be pressurized and bonded by rolling or drawing. Preferably, the sacrificial corrosion protection layer 15 is formed over substantially the entire outer surface of the aluminum refrigerant pipe 11 that constitutes the connection portion 13.

[0068] The thickness of the sacrificial corrosion protection layer 15 is preferably 75 μm or more, and more preferably 100 μm or more. The thickness of the sacrificial corrosion protection layer 15 can be, for example, 200 μm or less, 150 μm or less, or 125 μm or less. If the thickness is 75 μm or more, corrosion protection performance can be ensured for a long period of time, for example about 20 years, which exceeds the standard service life of equipment that is not subject to replacement.

[0069] The cover 20 covers the connection portion 13 and the outer surface of the aluminum refrigerant pipe 11 so that the joint portion 14 between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12, and the gap between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 are covered for a sufficient length along the longitudinal direction of the refrigerant pipe. The cover 20 may cover only the area around the connection portion 13, or it may cover both the connection portion 13 and the aluminum refrigerant pipe 11. The aluminum refrigerant pipe 11 can be covered from the end on the connection portion 13 side to the middle, or from the end on the connection portion 13 side to the end on the opposite side of the connection portion 13, etc.

[0070] The upper end of the cover 20 is preferably above the connection portion 13 between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12, and more preferably above the processed section on the end side of the metal refrigerant pipe 12. The upper end of the cover 20 may also be near the lower end of the enlarged diameter portion of the metal refrigerant pipe 12 or the equipment connected to the metal refrigerant pipe 12. The metal refrigerant pipe 12 and the equipment connected to the metal refrigerant pipe 12 may have an enlarged diameter portion in which the upper outer diameter is larger than the lower outer diameter. The enlarged diameter portion can be formed by processing the refrigerant pipe or by connecting fittings or refrigerant pipes.

[0071] The lower end of the cover 20 is preferably located below the connection portion 13 between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12, and is preferably located below the processed section on the end side of the aluminum refrigerant pipe 11, or on the end side opposite to the connection portion 13 side of the bend portion of the aluminum refrigerant pipe 11. The aluminum refrigerant pipe 11 can be bent into an elbow shape or an inclined elbow shape at the bend portion for connection with other refrigerant pipes or equipment.

[0072] The cover 20 is cylindrical in shape and covers the entire circumference of the connection portion 13. As the cover 20, a covering material such as a tube, sheet, or tape can be used. Preferably, the cover 20 is made of a resin or elastomer that exhibits electrical insulation and elasticity. Electrical insulation allows for more stable prevention of the formation of local galvanic cells via moisture, etc. Furthermore, elasticity ensures good adhesion to the outer surface of the connection portion 13, thereby suppressing the intrusion of water droplets and outside air into the joint and gaps between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12.

[0073] It is preferable to use a heat-shrinkable tube as the cover 20. A heat-shrinkable tube is a covering material that shrinks when heated, reducing its outer and inner diameters. After covering, the heat-shrinkable tube can be heated with a heat gun or the like to make it adhere tightly to the outer surface of the connection part 13 and the outer surface of the aluminum refrigerant pipe 11. Therefore, the intrusion of water droplets and outside air into the joint and gaps between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 can be suppressed more reliably.

[0074] Materials for heat-shrinkable tubing include polyvinyl chloride, silicone rubber, polyolefin, polystyrene, polyester, polycarbonate, polyamide, polyimide, polyamide-imide, fluororesin, and acrylic resin. Examples of polyolefins include polyethylene and polypropylene. Examples of fluororesins include polytetrafluoroethylene and polyvinylidene fluoride. Examples of acrylic resins include ethylene-methyl acrylate copolymer and ethylene-ethyl acrylate copolymer.

[0075] As shown in Figure 5, in the connection part 13 where the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 are connected such that the end of the aluminum refrigerant pipe 11 is located vertically lower than the end of the metal refrigerant pipe 12, if the connection part 13 is not covered by the cover 20, when water droplets due to condensation or the like adhere to the outer surface of the metal refrigerant pipe 12, the water droplets will flow down from the metal refrigerant pipe 12 and enter the joint or gap between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12, or adhere to the outer surface of the aluminum refrigerant pipe 11.

[0076] However, when the connection part 13 and the aluminum refrigerant pipe 11 are covered by the cover 20, it becomes difficult for water droplets and outside air to enter the joints and gaps between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12. Also, it becomes difficult for water droplets and outside air to come into contact with the outer surface of the connection part 13 and the outer surface of the aluminum refrigerant pipe 11. Furthermore, when a sacrificial corrosion protection layer 15 is formed on the outer surface of the aluminum refrigerant pipe 11, even if moisture comes into contact with it, it lowers the electrode potential of the aluminum to the passivation region and provides a sacrificial corrosion protection effect in which base metals corrode preferentially. Through these effects, galvanic corrosion of the connection part 13 and the aluminum refrigerant pipe 11 can be suppressed over a long period of time.

[0077] Therefore, with a structure that covers the connection point and aluminum refrigerant pipes with a sacrificial corrosion protection layer formed on them, when connecting aluminum refrigerant pipes and metal refrigerant pipes, it becomes possible to position the aluminum refrigerant pipe below the metal refrigerant pipe, unlike in conventional designs. Also, because galvanic corrosion is suppressed by the cover and sacrificial corrosion protection layer, there is no need to bend the aluminum or metal refrigerant pipes into a U-shape or other shapes to prevent water droplets from flowing down. It becomes possible to install aluminum or metal refrigerant pipes in any shape, such as straight pipes, elbows, or inclined elbows. Because it becomes easier to secure space for refrigerant pipes, the design of the refrigerant circuit can be made more flexible. In addition, the overall width of the refrigerant pipes is reduced, and the flexibility of refrigerant pipe placement is improved, thus avoiding the need to enlarge the refrigerant circuit. Furthermore, because there is no need to bend the refrigerant pipes into a U-shape or other shapes, the manufacturing cost of the refrigerant circuit can be reduced. Therefore, it becomes possible to suppress galvanic corrosion at the connection point where aluminum refrigerant pipes and metal refrigerant pipes are connected, over a period exceeding the standard service life, while keeping manufacturing costs of the refrigerant circuit down and ensuring design flexibility for the refrigerant circuit.

[0078] The connection portion 13, to which the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 are connected, is preferably provided in one or more of the following sections on the refrigerant circuit 10: the section between the outdoor heat exchanger 4 and the expansion valve 5, the section between the expansion valve 5 and the liquid-side service valve 18, the section between the four-way valve 3 and the outdoor heat exchanger 4, the section between the indoor exchanger 6 and the liquid-side service valve 18, and the section between the indoor exchanger 6 and the gas-side service valve 19. The connection portion 13 may be provided in the section between the main body 4a of the outdoor heat exchanger 4 and the expansion valve 5, in the section between the expansion valve 5 and the subcooler 4b of the outdoor heat exchanger 4, or in the section between the subcooler 4b of the outdoor heat exchanger 4 and the liquid-side service valve 18.

[0079] It is preferable that the aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed is connected to one or more of the following: the inlet / outlet on the expansion valve 5 side of the outdoor heat exchanger 4, the inlet / outlet on the liquid side service valve 18 side of the outdoor heat exchanger 4, the inlet / outlet on the four-way valve 3 side of the outdoor heat exchanger 4, the inlet / outlet on the liquid side service valve 18 side of the indoor heat exchanger 6, and the inlet / outlet on the gas side service valve 19 side of the indoor heat exchanger 6. By connecting to such locations, the refrigerant pipes and equipment of the outdoor heat exchanger 4, indoor heat exchanger 6 and their surroundings can be converted to aluminum, thereby reducing material costs and making the equipment lighter.

[0080] For example, an aluminum refrigerant pipe 11 on which a sacrificial corrosion protection layer 15 is formed can be connected to one or more of the following: the inlet / outlet on the expansion valve 5 side of the main body 4a of the outdoor heat exchanger 4; the inlet / outlet on the expansion valve 5 side of the subcooler 4b of the outdoor heat exchanger 4; the inlet / outlet on the liquid-side service valve 18 side of the subcooler 4b of the outdoor heat exchanger 4; the inlet / outlet on the four-way valve 3 side of the main body 4a of the outdoor heat exchanger 4; the inlet / outlet on the liquid-side service valve 18 side of the indoor heat exchanger 6; and the inlet / outlet on the gas-side service valve 19 side of the indoor heat exchanger 6. An aluminum refrigerant pipe 11 connected to such a location can be extended upward and connected to a metal refrigerant pipe 12 that is extended downward.

[0081] The structure in which the connection part 13 is covered with a cover 20, and the aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed, suppresses galvanic corrosion of the connection part 13 and the aluminum refrigerant pipe 11 even if the aluminum refrigerant pipe 11 is positioned lower than the metal refrigerant pipe 12. Therefore, the subcooler 4b can be positioned on the lower side of the outdoor heat exchanger 4, or the four-way valve 3 can be positioned on the upper side of the machine room 120, without being greatly restricted by the shape and arrangement of the refrigerant pipes.

[0082] Preferably, the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 connected to each other are arranged on the refrigerant circuit 10 such that the surface area or length along the centerline of the aluminum refrigerant pipe 11, i.e., the total length of the pipeline formed by the aluminum refrigerant pipe 11, is longer than the surface area or length along the centerline of the metal refrigerant pipe 12, i.e., the total length of the pipeline formed by the metal refrigerant pipe 12. This is because the larger the ratio of the surface area of ​​the aluminum refrigerant pipe 11 to that of the metal refrigerant pipe 12, the slower the progression of corrosion.

[0083] If the air conditioner 1 includes an outdoor heat exchanger having aluminum heat transfer tubes made of aluminum or an aluminum-containing metal and aluminum fins made of aluminum or an aluminum-containing metal, or an indoor heat exchanger having aluminum heat transfer tubes made of aluminum or an aluminum-containing metal and aluminum fins made of aluminum or an aluminum-containing metal, it is preferable that the aluminum refrigerant pipe 11 constituting the connection part 13 is connected to one or more of these aluminum heat transfer tubes.

[0084] In such cases, it is preferable that the sum of the surface areas of the aluminum refrigerant pipe 11, the aluminum heat transfer tube, and the aluminum fins constituting the connection section 13 is 10 times or more the surface area of ​​the metal refrigerant pipe 12 constituting the connection section 13. With such an area ratio, the acceleration rate of aluminum corrosion due to contact with copper or other materials that have a lower ionization tendency than aluminum can be suppressed to a smaller extent.

[0085] Furthermore, regarding the acceleration rate of corrosion due to contact between dissimilar metals, it has been reported that when the area ratio of aluminum to copper is 10 times, the acceleration rate of corrosion due to contact between aluminum and copper doubles in electrically conductive flowing seawater (see Teruaki Kawamoto, "Dissimilar Metal Contact Corrosion," Corrosion Prevention Technology, Japan Corrosion Protection Association, 1984, Vol. 33, No. 8, pp. 478-479: <https: / / www.jstage.jst.go.jp / article / jcorr1974 / 33 / 8 / 33_8_478 / _pdf>).

[0086] Figure 6 illustrates the structure of the refrigerant pipe connected between the outdoor heat exchanger and the expansion valve in an air conditioner according to an embodiment of the present invention. Figure 6 shows a structure that connects an aluminum refrigerant pipe connected to the outlet side of the outdoor heat exchanger during cooling operation with a metal refrigerant pipe connected to the inlet side of the expansion valve during cooling operation.

[0087] As shown in Figure 6, in the air conditioner 1 according to this embodiment, the connection portion 13 where the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 are connected is covered with a cover 20, and the aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed can be provided in the section between the outdoor heat exchanger 4 and the expansion valve 5, for example, in the section between the main body 4a of the outdoor heat exchanger 4 and the expansion valve 5. The aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed can be connected to the inlet and outlet on the expansion valve 5 side of the outdoor heat exchanger 4.

[0088] In Figure 6, the downstream ends of multiple heat transfer tubes 4c protrude from the side of the main body 4a of the outdoor heat exchanger 4. The upstream end of an aluminum refrigerant pipe 11n is connected to the downstream end of each heat transfer tube 4c. The downstream end of the aluminum refrigerant pipe 11n is connected to the inlet side of the distributor 21. The distributor 21 is a device that merges multiple flow paths into one flow path or divides one flow path into multiple flow paths, depending on the direction of refrigerant flow. Multiple thin-tube aluminum refrigerant pipes 11n are connected to the distributor 21 so that the diverted refrigerant flows can be merged.

[0089] The upstream end of the aluminum refrigerant pipe 11a is connected to the outlet side of the distributor 21. The upstream end of the metal refrigerant pipe 12a is connected to the downstream end of the aluminum refrigerant pipe 11a via a connection part 13a. The inlet side of the body of the expansion valve 5 is connected to the downstream end of the metal refrigerant pipe 12a via a strainer 16a and a metal refrigerant pipe connected to the body of the expansion valve 5. The upstream end of the metal refrigerant pipe 12b is connected to the outlet side of the body of the expansion valve 5 via a metal refrigerant pipe connected to the body of the expansion valve 5 and a strainer 16b. The upstream end of the heat transfer tube of the subcooler 4b of the outdoor heat exchanger 4 is connected to the downstream end of the metal refrigerant pipe 12b via a refrigerant pipe, etc.

[0090] The aluminum refrigerant pipe 11a and the metal refrigerant pipe 12a are formed only by straight sections, without being bent into a U-shape. The aluminum refrigerant pipe 11a and the metal refrigerant pipe 12a are connected such that the end of the aluminum refrigerant pipe 11a is located vertically lower than the end of the metal refrigerant pipe 12a. A sacrificial corrosion protection layer 15 is formed on the outer surface of the aluminum refrigerant pipe 11a. The connection part 13a and the aluminum refrigerant pipe 11a are covered by a cover 20.

[0091] In Figure 6, the aluminum refrigerant pipe 11a has only straight sections, but it may also have elbow-shaped sections or inclined elbow-shaped sections bent at less than 90 degrees. The aluminum refrigerant pipe 11a is not bent in a U-shape that folds back at 180 degrees. The metal refrigerant pipe 12d has only straight sections, but it may also have elbow-shaped sections or inclined elbow-shaped sections bent at less than 90 degrees, etc.

[0092] The cover 20 is positioned to cover the area around the connection portion 13a and the aluminum refrigerant pipe 11a, but it may also be positioned to cover only the area around the connection portion 13a. The upper end of the cover 20 may be above the connection portion 13a, or it may be near the lower end of the strainer 16a. The lower end of the cover 20 is preferably located near the middle of the aluminum refrigerant pipe 11a below the connection portion 13a, near the end of the aluminum refrigerant pipe 11a below the connection portion 13a, near the upper end of the distributor 21 below the connection portion 13a, or on the side of the distributor 21 closer to the outdoor heat exchanger 4.

[0093] With this arrangement, the intrusion of water droplets and outside air into the joints and gaps between the aluminum refrigerant pipe 11a and the metal refrigerant pipe 12a, and the contact of moisture with the connection part 13a and the aluminum refrigerant pipe 11a can be more reliably suppressed. The longer the cover 20, the more labor is required for the covering work, but it can suppress pitting corrosion of the aluminum refrigerant pipe 11a over a wider area. The distributor 21 can be made of, for example, aluminum or a metal containing aluminum.

[0094] In the section between the outdoor heat exchanger 4 and the expansion valve 5, the connection portion 13a may be located above the midpoint between the lowest and highest points in the vertical direction on the refrigerant circuit connecting the outlet of the distributor 21 and the inlet of the expansion valve 5, or it may be located below such a midpoint. If the connection portion 13a is located above, the section made of aluminum refrigerant pipe 11a becomes longer, which is advantageous for reducing material costs and making the equipment lighter. On the other hand, if the connection portion 13a is located below, the section made of aluminum refrigerant pipe 11a becomes shorter, which reduces the overall length of the cover 20 and the amount of work required for covering.

[0095] In this way, by providing the connection portion 13 covered by the cover 20 in the section between the outdoor heat exchanger 4 and the expansion valve 5, even if water droplets due to condensation adhere to the outer surface of the metal refrigerant pipe 12 when the refrigerant is depressurized by the expansion valve 5 and the refrigerant temperature drops, the cover 20 can suppress the intrusion of moisture into the joint between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12, the gap between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12, and the contact of moisture with the outer surface of the connection portion 13 and the outer surface of the aluminum refrigerant pipe 11. Furthermore, by providing the aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed in the section between the outdoor heat exchanger 4 and the expansion valve 5, even if moisture adheres to the inside of the cover 20 or the outer surface of the aluminum refrigerant pipe 11, the sacrificial corrosion protection layer 15 can protect the connection portion 13 and the aluminum refrigerant pipe 11 from corrosion. Therefore, in an air conditioner 1 in which the outdoor heat exchanger 4 is made of aluminum, galvanic corrosion of the connection part 13 and the aluminum refrigerant pipe 11 can be suppressed over a long period of time.

[0096] Figure 7 illustrates the structure of the refrigerant pipe connected between the expansion valve and the outdoor heat exchanger in an air conditioner according to an embodiment of the present invention. Figure 7 shows a structure that connects a metal refrigerant pipe connected to the outlet side of the expansion valve during cooling operation and an aluminum refrigerant pipe connected to the inlet side of the subcooler of the outdoor heat exchanger during cooling operation.

[0097] As shown in Figure 7, in the air conditioner 1 according to this embodiment, the connection portion 13 where the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 are connected is covered with a cover 20. The aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed can also be provided in the section between the expansion valve 5 and the outdoor heat exchanger 4, for example, in the section between the expansion valve 5 and the subcooler 4b of the outdoor heat exchanger 4. The aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed can be connected to the inlet and outlet on the expansion valve 5 side of the subcooler 4b of the outdoor heat exchanger 4.

[0098] In Figure 7, the upstream end of a metal refrigerant pipe 12b is connected to the outlet side of the expansion valve 5 via a strainer 16b. The upstream end of an aluminum refrigerant pipe 11b is connected to the downstream end of the metal refrigerant pipe 12b via a connector 13b. The upstream end of the heat transfer tube 4c of the subcooler 4b of the outdoor heat exchanger 4 is connected to the downstream end of the aluminum refrigerant pipe 11b. In Figure 7, the area indicated by the dashed line labeled 4b represents the area of ​​the subcooler 4b formed by the heat transfer tube 4c passing through the lower part of the outdoor heat exchanger 4. A liquid-side service valve 18 is connected to the downstream end of the heat transfer tube 4c of the subcooler 4b via a refrigerant pipe.

[0099] The aluminum refrigerant pipe 11b and the metal refrigerant pipe 12b are not bent into a U-shape, but are formed only by straight sections, elbow-shaped sections, and inclined elbow-shaped sections. The aluminum refrigerant pipe 11b and the metal refrigerant pipe 12b are connected such that the end of the aluminum refrigerant pipe 11b is located vertically lower than the end of the metal refrigerant pipe 12b. A sacrificial corrosion protection layer 15 is formed on the outer surface of the aluminum refrigerant pipe 11b. The connection part 13b and the aluminum refrigerant pipe 11b are covered by a cover 20.

[0100] In Figure 7, the aluminum refrigerant pipe 11b has straight sections, elbow-shaped sections, and inclined elbow-shaped sections, but it may also have only straight sections. The aluminum refrigerant pipe 11b is not bent in a U-shape that folds back 180 degrees. The metal refrigerant pipe 12b has straight sections and inclined elbow-shaped sections, but it may also have elbow-shaped sections, U-shaped return bend sections, etc.

[0101] The cover 20 is positioned to cover the area around the connection portion 13b and the aluminum refrigerant pipe 11b, but it may also be positioned to cover only the area around the connection portion 13b. The upper end of the cover 20 may be above the connection portion 13b, or it may be near the lower end of the strainer 16b. Preferably, the lower end of the cover 20 is positioned near the middle of the aluminum refrigerant pipe 11b below the connection portion 13b, near the end of the aluminum refrigerant pipe 11b below the connection portion 13b, or on the side of the outdoor heat exchanger 4 beyond the bend portion 17b of the aluminum refrigerant pipe 11b below the connection portion 13b.

[0102] With this arrangement, the intrusion of water droplets and outside air into the joints and gaps between the aluminum refrigerant pipe 11b and the metal refrigerant pipe 12b, and the contact of moisture with the connection part 13b and the aluminum refrigerant pipe 11b can be suppressed more reliably. The longer the cover 20, the more labor is required for the covering work, but it can suppress pitting corrosion of the aluminum refrigerant pipe 11b over a wider area. The bend section 17b is provided as a bent section for extending the aluminum refrigerant pipe 11b horizontally from the vertical direction toward the outdoor heat exchanger 4. The bend section 17b may be provided in multiple stages. Preferably, the lower end of the cover 20 is on the side of the outdoor heat exchanger 4 that is closer to the first stage bend section 17b than the connection part 13b side.

[0103] In the section between the expansion valve 5 and the outdoor heat exchanger 4, the connection portion 13b may be located above the midpoint between the lowest and highest points in the vertical direction on the refrigerant circuit connecting the outlet of the expansion valve 5 and the inlet of the subcooler 4b, or it may be located below such a midpoint. If the connection portion 13b is located above, the section made of aluminum refrigerant pipe 11b becomes longer, which is advantageous for reducing material costs and making the equipment lighter. On the other hand, if the connection portion 13b is located below, the section made of aluminum refrigerant pipe 11b becomes shorter, which reduces the overall length of the cover 20 and the amount of work required for covering.

[0104] In this way, by providing the connection portion 13 covered by the cover 20 in the section between the expansion valve 5 and the outdoor heat exchanger 4, even if water droplets due to condensation adhere to the outer surface of the metal refrigerant pipe 12 when the refrigerant is depressurized by the expansion valve 5 and the refrigerant temperature drops, the cover 20 can suppress the intrusion of moisture into the joint between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12, the gap between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12, and the contact of moisture with the outer surface of the connection portion 13 and the outer surface of the aluminum refrigerant pipe 11. Furthermore, by providing the aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed in the section between the expansion valve 5 and the outdoor heat exchanger 4, even if moisture adheres to the inside of the cover 20 or the outer surface of the aluminum refrigerant pipe 11, the sacrificial corrosion protection layer 15 can protect the connection portion 13 and the aluminum refrigerant pipe 11 from corrosion. Therefore, in an air conditioner 1 in which the outdoor heat exchanger 4 is made of aluminum, galvanic corrosion of the connection part 13 and the aluminum refrigerant pipe 11 can be suppressed over a long period of time.

[0105] Figure 8 illustrates the structure of the refrigerant pipe connected between the outdoor heat exchanger and the liquid-side service valve in an air conditioner according to an embodiment of the present invention. Figure 8 shows a structure that connects an aluminum refrigerant pipe connected to the outlet side of the subcooler of the outdoor heat exchanger during cooling operation with a metal refrigerant pipe connected to the inlet side of the liquid-side service valve during cooling operation.

[0106] As shown in Figure 8, in the air conditioner 1 according to this embodiment, the connection portion 13 where the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 are connected is covered with a cover 20. The aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed can also be provided in the section between the outdoor heat exchanger 4 and the liquid-side service valve 18, for example, in the section between the subcooler 4b of the outdoor heat exchanger 4 and the liquid-side service valve 18. The aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed can be connected to the inlet and outlet on the liquid-side service valve 18 side of the subcooler 4b of the outdoor heat exchanger 4.

[0107] In Figure 8, the area indicated by the dashed line labeled 4b represents the area of ​​the subcooler 4b formed by the heat transfer tubes 4c passing through the lower part of the outdoor heat exchanger 4. The upstream end of an aluminum refrigerant pipe 11c is connected to the downstream end of the heat transfer tubes 4c of the subcooler 4b of the outdoor heat exchanger 4. The upstream end of a metal refrigerant pipe 12c is connected to the downstream end of the aluminum refrigerant pipe 11c via a connection part 13c. The internal port of a liquid-side service valve 18 is connected to the downstream end of the metal refrigerant pipe 12c.

[0108] The aluminum refrigerant pipe 11c and the metal refrigerant pipe 12c are not bent in a U-shape, but are formed only by straight sections, elbow-shaped sections, and inclined elbow-shaped sections. The aluminum refrigerant pipe 11c and the metal refrigerant pipe 12c are connected such that the end of the aluminum refrigerant pipe 11c is located vertically lower than the end of the metal refrigerant pipe 12c. A sacrificial corrosion protection layer 15 is formed on the outer surface of the aluminum refrigerant pipe 11c. The connection part 13c and the aluminum refrigerant pipe 11c are covered by a cover 20.

[0109] In Figure 8, the aluminum refrigerant pipe 11c has straight sections, elbow sections, and inclined elbow sections, but it may also have only straight sections or elbow sections. The aluminum refrigerant pipe 11c is not bent in a U-shape that folds back 180 degrees. The metal refrigerant pipe 12c has straight sections, elbow sections, and inclined elbow sections, but it may also have a U-shaped return bend section, etc.

[0110] The cover 20 is positioned to cover the area around the connection portion 13c and the aluminum refrigerant pipe 11c, but it may also be positioned to cover only the area around the connection portion 13c. Preferably, the upper end of the cover 20 is above the connection portion 13c. Preferably, the lower end of the cover 20 is positioned near the middle of the aluminum refrigerant pipe 11c below the connection portion 13c, near the end of the aluminum refrigerant pipe 11c below the connection portion 13c, or on the side of the outdoor heat exchanger 4 above the bend portion 17c below the connection portion 13c.

[0111] This arrangement more reliably prevents water droplets and outside air from entering the joints and gaps between the aluminum refrigerant pipe 11c and the metal refrigerant pipe 12c, and also prevents moisture from coming into contact with the connection part 13c and the aluminum refrigerant pipe 11c. The longer the cover 20, the more work is required for the covering work, but it can suppress pitting corrosion of the aluminum refrigerant pipe 11c over a wider area. The bend section 17c is provided as a bent section for extending the aluminum refrigerant pipe 11c horizontally from the vertical direction toward the outdoor heat exchanger 4. The bend section 17c may be provided in multiple stages. Preferably, the lower end of the cover 20 is on the side of the outdoor heat exchanger 4 that is closer to the first stage bend section 17c than the connection part 13c side.

[0112] In the section between the outdoor heat exchanger 4 and the liquid-side service valve 18, the connection portion 13c may be located above the midpoint between the lowest and highest points in the vertical direction on the refrigerant circuit connecting the outlet of the subcooler 4b and the inlet of the liquid-side service valve 18, or it may be located below such a midpoint. If the connection portion 13c is located above, the section made of aluminum refrigerant pipe 11c becomes longer, which is advantageous for reducing material costs and making the equipment lighter. On the other hand, if the connection portion 13c is located below, the section made of aluminum refrigerant pipe 11c becomes shorter, which reduces the overall length of the cover 20 and the amount of work required for covering.

[0113] In this way, by providing the connection portion 13 covered by the cover 20 in the section between the outdoor heat exchanger 4 and the liquid-side service valve 18, even if water droplets due to condensation adhere to the outer surface of the metal refrigerant pipe 12, which has cooled down, in situations such as when the refrigerant is depressurized by the expansion valve 5 and its temperature drops, or when the refrigerant is cooled by the subcooler 4b, the cover 20 can suppress the intrusion of moisture into the joint between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12, the gap between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12, and the contact of moisture with the outer surface of the connection portion 13 and the outer surface of the aluminum refrigerant pipe 11. Furthermore, by providing the aluminum refrigerant pipe 11, on which the sacrificial corrosion protection layer 15 is formed, in the section between the outdoor heat exchanger 4 and the liquid-side service valve 18, even if moisture adheres to the inside of the cover 20 or the outer surface of the aluminum refrigerant pipe 11, the sacrificial corrosion protection layer 15 can protect the connection portion 13 and the aluminum refrigerant pipe 11 from corrosion. Therefore, in an air conditioner 1 in which the outdoor heat exchanger 4 is made of aluminum, galvanic corrosion of the connection part 13 and the aluminum refrigerant pipe 11 can be suppressed over a long period of time.

[0114] Figure 9 illustrates the structure of the refrigerant pipe connected between the four-way valve and the outdoor heat exchanger in an air conditioner according to an embodiment of the present invention. Figure 9 shows a structure that connects a metal refrigerant pipe connected to the outlet of the four-way valve on the outdoor heat exchanger side with an aluminum refrigerant pipe connected to the inlet side of the outdoor heat exchanger during cooling operation.

[0115] As shown in Figure 9, in the air conditioner 1 according to this embodiment, the connection part 13 where the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 are connected is covered with a cover 20, and the aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed can also be provided in the section between the four-way valve 3 and the outdoor heat exchanger 4. The aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed can be connected to the inlet and outlet on the four-way valve 3 side of the outdoor heat exchanger 4.

[0116] In Figure 9, the four-way valve 3 has a cylindrical body installed horizontally, with a valve body and other components housed inside. Three ports are formed at the bottom of the body. One port is formed at the top of the body. The body and ports of the four-way valve are made of, for example, copper or a copper alloy. The upstream end of the metal refrigerant pipe 12d is connected to the upper port. The metal refrigerant pipe 12d is bent into a U-shape so as to be convex upwards.

[0117] The downstream end of the metal refrigerant pipe 12d is connected to the upstream end of an aluminum refrigerant pipe 11d, which is a gas header pipe, via a connection part 13d. Downstream of the aluminum refrigerant pipe 11d, multiple thin aluminum refrigerant pipes 11m are connected, through which the diverted refrigerant can flow, so that the refrigerant flow path branches into multiple directions. The downstream end of each aluminum refrigerant pipe 11m is connected to the upstream end of a heat transfer tube 4c of the main body 4a of the outdoor heat exchanger 4. The upstream ends of multiple heat transfer tubes 4c protrude from the side of the main body 4a of the outdoor heat exchanger 4.

[0118] As shown in Figure 9, the aluminum refrigerant pipe 11d, which is a gas header pipe, is formed only by straight sections and elbow-shaped sections, without being bent in a U-shape. The aluminum refrigerant pipe 11d and the metal refrigerant pipe 12d are connected such that the end of the aluminum refrigerant pipe 11d is located vertically lower than the end of the metal refrigerant pipe 12d. A sacrificial corrosion protection layer 15 is formed on the outer surface of the aluminum refrigerant pipe 11d. The connection part 13d and the aluminum refrigerant pipe 11d are covered by a cover 20.

[0119] In Figure 9, the aluminum refrigerant pipe 11d, which is a gas header pipe, has straight sections and elbow-shaped sections, but it may also have only straight sections and inclined elbow-shaped sections bent at less than 90 degrees. The aluminum refrigerant pipe 11d is not bent in a U-shape that folds back at 180 degrees. The metal refrigerant pipe 12d may have straight sections, elbow-shaped sections, inclined elbow-shaped sections, U-shaped return bend sections, etc.

[0120] The cover 20 is positioned to cover the area around the connection portion 13d and the aluminum refrigerant pipe 11d, which is a gas header pipe, but it may also be positioned to cover only the area around the connection portion 13d. Preferably, the upper end of the cover 20 is above the connection portion 13d. Preferably, the lower end of the cover 20 is on the side of the outdoor heat exchanger 4 above the bend portion 17d below the connection portion 13d, and on the side of the four-way valve 3 above the branching point where the thin aluminum refrigerant pipe 11m of the aluminum refrigerant pipe 11d below the connection portion 13d is connected.

[0121] With this arrangement, the intrusion of water droplets and outside air into the joints and gaps between the aluminum refrigerant pipe 11d and the metal refrigerant pipe 12d, and the contact of moisture with the connection part 13d and the aluminum refrigerant pipe 11d can be more reliably suppressed. The longer the cover 20, the more labor is required for the covering work, but it can suppress pitting corrosion of the aluminum refrigerant pipe 11d over a wider area. The bend section 17d is provided as a bent section for extending the aluminum refrigerant pipe 11d horizontally from the vertical direction toward the outdoor heat exchanger 4. The bend section 17d may be provided in multiple stages. Preferably, the lower end of the cover 20 is on the side of the outdoor heat exchanger 4 that is closer to the first bend section 17d from the connection part 13d side, and on the side of the four-way valve 3 that is closer to the first branching point from the connection part 13d side.

[0122] In the section between the four-way valve 3 and the outdoor heat exchanger 4, the connection portion 13d may be located above the midpoint between the lowest and highest points in the vertical direction on the refrigerant circuit connecting the outlet of the four-way valve 3 and the heat transfer tubes 4c of the main body 4a of the outdoor heat exchanger 4, or it may be located below such a midpoint. If the connection portion 13d is located above, the section made of aluminum refrigerant pipe 11d becomes longer, which is advantageous for reducing material costs and making the equipment lighter. On the other hand, if the connection portion 13d is located below, the section made of aluminum refrigerant pipe 11d becomes shorter, which reduces the overall length of the cover 20 and the amount of work required for covering.

[0123] In this way, by providing the connection portion 13 covered by the cover 20 in the section between the four-way valve 3 and the outdoor heat exchanger 4, even if water droplets due to condensation adhere to the outer surface of the metal refrigerant pipe 12 during heating operation when the outdoor heat exchanger 4 acts as an evaporator or under high humidity conditions, the cover 20 can suppress the intrusion of moisture into the joint between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12, the gap between the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12, and the contact of moisture with the outer surface of the connection portion 13 and the outer surface of the aluminum refrigerant pipe 11. Furthermore, by providing the aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed in the section between the four-way valve 3 and the outdoor heat exchanger 4, even if moisture adheres to the inside of the cover 20 or the outer surface of the aluminum refrigerant pipe 11, the sacrificial corrosion protection layer 15 can protect the connection portion 13 and the aluminum refrigerant pipe 11 from corrosion. Therefore, in an air conditioner 1 in which the outdoor heat exchanger 4 is made of aluminum, galvanic corrosion of the connection part 13 and the aluminum refrigerant pipe 11 can be suppressed over a long period of time.

[0124] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications are included as long as they do not depart from the technical scope. For example, the embodiments described above are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace some of the configurations of one embodiment with other configurations, or to add other configurations to the configuration of one embodiment. It is also possible to add other configurations, delete configurations, or substitute configurations for some of the configurations of one embodiment.

[0125] For example, the air conditioner 1 may also be equipped with a receiver, oil separator, dryer, etc. on the refrigerant circuit 10. The air conditioner 1 may also be equipped with an injection circuit for injecting refrigerant at an intermediate pressure into the compressor 2. The injection circuit is connected to the compressor 2, bypassing the evaporator from the condenser. A structure in which the connection portion 13 where the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 are connected is covered with a cover 20, and the aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed can be provided in any section on the refrigerant circuit 10.

[0126] Furthermore, the air conditioner 1 can be replaced with a package air conditioner, a household multi-split air conditioner, a commercial air conditioner, a commercial multi-split air conditioner, a building multi-split air conditioner, etc., instead of the room air conditioner shown in Figure 1, etc. In Figure 2, the outdoor unit 100 and the indoor unit 200 are connected one-to-one, but multiple outdoor units may be connected to one indoor unit, multiple indoor units may be connected to one outdoor unit, or multiple indoor units may be connected to multiple outdoor units. The structure in which the connection part 13 where the aluminum refrigerant pipe 11 and the metal refrigerant pipe 12 are connected is covered with a cover 20, and the aluminum refrigerant pipe 11 on which the sacrificial corrosion protection layer 15 is formed can be provided in any section of the refrigerant circuit of these air conditioners.

[0127] 1. Air conditioner 2. Compressor 3. Four-way valve 4. Outdoor heat exchanger 4a. Main unit 4b. Subcooler 5. Expansion valve 6. Indoor heat exchanger 7. Accumulator 8. Outdoor fan 9. Indoor fan 10. Refrigerant circuit 11. Aluminum refrigerant pipe 12. Metal refrigerant pipe 13. Connection part 14. Joining metal 15. Sacrificial corrosion protection layer 16. Strainer 17. Bend part 18. Liquid side service valve 19. Gas side service valve 20. Cover 21. Distributor 100. Outdoor unit 101. Bottom base 105. Partition plate 110. Heat exchanger room 120. Machine room 200. Indoor unit 300. Connecting piping 400. Remote control

Claims

1. An air conditioner comprising a connection portion in which an aluminum refrigerant pipe, made of aluminum or an aluminum-containing metal, is connected such that it is positioned vertically below a metal refrigerant pipe made of a metal having a lower ionization tendency than aluminum, the outer surface of the connection portion is covered with a cover, and a sacrificial corrosion protection layer is formed on the outer surface of the aluminum refrigerant pipe.

2. An air conditioner according to claim 1, wherein the air conditioner comprises a refrigerant circuit in which a compressor, a four-way valve, an outdoor heat exchanger, an expansion valve, a service valve attached to an outdoor unit, and an indoor heat exchanger are connected via a refrigerant pipe, and the connection portion is provided in one or more of the following sections: the section between the outdoor heat exchanger and the expansion valve, the section between the expansion valve and the service valve, or the section between the four-way valve and the outdoor heat exchanger.

3. An air conditioner according to claim 2, wherein the aluminum refrigerant pipe is a refrigerant pipe connected to the heat transfer tube of the outdoor heat exchanger, and the aluminum refrigerant pipe and the metal refrigerant pipe are connected vertically substantially parallel to the vertical direction, or are connected diagonally at an angle from the vertical direction.

4. An air conditioner according to claim 1, wherein the metal refrigerant pipe is a copper refrigerant pipe made of copper or a metal containing copper, or a stainless steel refrigerant pipe made of stainless steel.

5. An air conditioner according to claim 1, wherein the surface area of ​​the aluminum refrigerant pipe is greater than the surface area of ​​the metal refrigerant pipe.

6. An air conditioner according to claim 1, comprising an outdoor heat exchanger having aluminum heat transfer tubes and aluminum fins, or an indoor heat exchanger having aluminum heat transfer tubes and aluminum fins, wherein the aluminum refrigerant pipe is a refrigerant pipe connected to the aluminum heat transfer tube, and the sum of the surface areas of the aluminum refrigerant pipe, the aluminum heat transfer tube and the aluminum fins is 10 times or more the surface area of ​​the metal refrigerant pipe.

7. An air conditioner according to claim 1, wherein the sacrificial corrosion protection layer is made of zinc or a zinc-aluminum alloy.

8. An air conditioner according to claim 1, wherein the thickness of the sacrificial corrosion protection layer is 75 μm or more.

9. An air conditioner according to claim 1, wherein the cover is a heat-shrinkable tube.

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