JP7792651B2 - Joint of copper pipe and aluminum pipe and air conditioner - Google Patents

Description

The present invention relates to a joint formed by joining a copper pipe and an aluminum pipe, and an air conditioner equipped with the joint.

Copper pipes have traditionally been used as refrigerant piping in refrigeration and air conditioning equipment. However, in recent years, they have been replaced with aluminum pipes due to their low material costs, ease of procurement, and light weight. There is also a trend toward replacing heat exchangers connected to refrigerant piping entirely with aluminum, including fins and heat transfer tubes. When manufacturing or installing refrigeration and air conditioning equipment equipped with copper and aluminum pipes, it is necessary to join the copper and aluminum pipes together.

Copper pipes and aluminum pipes are primarily joined using the eutectic bonding method. Eutectic bonding is a method of diffusion bonding materials at low temperature and low pressure using a eutectic reaction. When copper and aluminum are brought into contact and heated above the eutectic temperature of 548°C, a eutectic melt is formed at the contact surface. When heated under pressure and then rapidly cooled, a bonded product is obtained in which the copper and aluminum are diffusion bonded via the Cu-Al eutectic phase.

Patent Document 1 discloses a joint made of a copper pipe and an aluminum pipe using the eutectic bonding method. In this joint, one end of an aluminum pipe is fitted onto a tapered, reduced section formed on one end of the copper pipe. A small-diameter section with an outer diameter smaller than the inner diameter of the aluminum pipe extends from the tip of the reduced section of the copper pipe. A contact section is provided at the tip of the small-diameter section, where the copper pipe and the aluminum pipe are in contact around their entire circumference. An airtight space is formed between the eutectic bonded joint and the contact section, surrounded by the outer diameter surface of the copper pipe and the inner diameter surface of the aluminum pipe.

JP 2009-072820 A

When forming a joint between copper and aluminum pipes using the eutectic bonding method, it is necessary to generate sufficient eutectic liquid to reduce joint failure. It is also necessary to ensure the strength of the joint between the copper and aluminum pipes. Therefore, it is important to ensure a sufficient contact area between the copper and aluminum pipes. It is desirable to form a joint with a large contact area between the copper and aluminum pipes, where many atoms at the interface have diffused into each other.

However, conventional joints between copper and aluminum pipes, as described in Patent Document 1, have a structure in which an aluminum pipe is fitted onto the tip of a reduced-diameter copper pipe. Simply creating such a structure poses the problem of not ensuring a sufficient contact area between the copper and aluminum pipes. In particular, as described in Patent Document 1, if an enclosed space is formed between the eutectic-bonded joint and the contact area, it becomes difficult to ensure a sufficient contact area.

Furthermore, as described in Patent Document 1, conventional joints of copper and aluminum pipes have a structure in which the inner surface of the tip of the copper pipe tends to protrude toward the inside of the pipe. This structure increases flow resistance, which can lead to increased refrigerant noise when the refrigerant flows through. There is a demand for joints that can ensure sufficient contact area between the copper and aluminum pipes while suppressing abnormal refrigerant noise.

The present invention aims to provide a joint in which copper and aluminum pipes are joined together, which makes it easier to ensure a sufficient contact area between the copper and aluminum pipes, reduces poor joints between the copper and aluminum pipes, suppresses abnormal noise caused by fluid flow, and provides high joint strength, as well as an air conditioner equipped with the joint.

To solve the above problem, the present invention provides a joined assembly in which a copper tube and an aluminum tube are joined, wherein the copper tube and the aluminum tube each have an expanded diameter portion at their tip, the expanded diameter portion of the copper tube has a tapered portion that narrows in diameter toward the tip, the tapered portion of the copper tube and the tip side of the expanded diameter portion of the aluminum tube are joined to each other via a eutectic phase, and the outer diameter of the rear end of the tapered portion of the copper tube is equal to or greater than the outer diameter of the tip of the expanded diameter portion of the aluminum tube.

The air conditioner according to the present invention is an air conditioner equipped with a refrigerant circuit in which a compressor, a four-way valve, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are connected via refrigerant piping, and the refrigerant circuit includes a joint formed by joining a copper tube and an aluminum tube, and the copper tube and the aluminum tube each have an enlarged diameter portion at their tip, and the enlarged diameter portion of the copper tube has a tapered portion whose diameter decreases toward the tip, and the tapered portion of the copper tube and the tip of the enlarged diameter portion of the aluminum tube are joined to each other via a eutectic phase, and the outer diameter of the rear end of the tapered portion of the copper tube is equal to or greater than the outer diameter of the tip of the enlarged diameter portion of the aluminum tube.

This invention makes it possible to provide a joint in which copper and aluminum pipes are joined together, which makes it easier to ensure a sufficient contact area between the copper and aluminum pipes, reduces poor joints between the copper and aluminum pipes, suppresses abnormal noise caused by fluid flow, and provides high joint strength, as well as an air conditioner equipped with the joint.

1 is a cross-sectional view showing a joined body in which a copper pipe and an aluminum pipe are joined together according to an embodiment of the present invention. 1 is a cross-sectional view showing a copper pipe and an aluminum pipe forming a joined body in which a copper pipe and an aluminum pipe are joined together according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating dimensions of a joined body in which a copper pipe and an aluminum pipe are joined together according to an embodiment of the present invention. 1 is a cross-sectional view showing an embodiment of the present invention in which a joined body in which a copper pipe and an aluminum pipe are joined is covered with a heat-shrinkable tube. FIG. 2 is a diagram illustrating an example of a heat exchanger. 1 is a cross-sectional view illustrating a primary tube expansion process performed on a heat transfer tube of a heat exchanger. 1 is a cross-sectional view illustrating a secondary tube expansion process performed on a heat transfer tube of a heat exchanger. 1 is a diagram showing an example of the configuration of an air conditioner according to an embodiment of the present invention.

A joint formed by joining a copper pipe and an aluminum pipe according to one embodiment of the present invention, and an air conditioner equipped with the joint, will be described with reference to the drawings. Note that common components in the following figures will be assigned the same reference numerals, and duplicate explanations will be omitted.

In this specification, the term "front end" refers to the end or portion of a tube that is located on the side where the tubes are joined together. The term "rear end" refers to the end or portion of a tube that is located on the opposite side from the side where the tubes are joined together.

Figure 1 is a cross-sectional view showing a joined body in which a copper pipe and an aluminum pipe are joined together according to an embodiment of the present invention. Figure 1 shows the main structure of an example of a joined body in which a copper pipe and an aluminum pipe are joined together. As shown in Figure 1, the joined body 1 in which a copper pipe and an aluminum pipe are joined together according to this embodiment is formed by joining a copper pipe 10 whose tip end is expanded and an aluminum pipe 20 whose tip end is also expanded together via a Cu-Al eutectic phase 30.

The copper tube 10 is a tube such as a circular tube, and is made of phosphorus-deoxidized copper, oxygen-free copper, or the like. At the tip where the copper tube 10 is joined to the aluminum tube 20, it has an expanded diameter portion 11 whose inner and outer diameters are larger than those of the original tube used as the raw material. Further, rearward of the expanded diameter portion 11, it has a reduced diameter portion 12 whose inner and outer diameters are reduced from those of the expanded diameter portion 11. Further rearward of the reduced diameter portion 12, it has a non-expanded diameter portion 13 whose inner and outer diameters are not expanded from those of the original tube used as the raw material.

The expanded diameter portion 11 is formed by expanding the base pipe of the copper tube 10. The expanded diameter portion 11 has a larger inner diameter than the non-expanded diameter portion 13, and a larger outer diameter than the non-expanded diameter portion 13. The reduced diameter portion 12 is a portion formed in conjunction with the formation of the expanded diameter portion 11, where the inner and outer diameters transition between the non-expanded diameter portion 13 and the expanded diameter portion 11. The non-expanded diameter portion 13 is a portion of the base pipe of the copper tube 10 that has not been expanded.

The expanded diameter section 11 of the copper tube 10 has a tapered portion 11a with a tapered outer shape at the tip end where it is joined to the aluminum tube 20. The tapered portion 11a has a shape in which the inner and outer diameters decrease toward the tip end. The tapered portion 11a is formed by performing a diameter reduction process on the tip end of the expanded diameter section 11. From the tip to the rear end, the tapered portion 11a has a larger inner diameter than the non-expanded diameter section 13 and a larger outer diameter than the non-expanded diameter section 13.

Furthermore, the expanded diameter portion 11 of the copper tube 10 has a straight portion 11b with a straight outer shape at the rear end where it connects to the non-expanded diameter portion 13. The straight portion 11b has a straight shape with an outer diameter that does not change substantially along the longitudinal direction of the copper tube 10. The straight portion 11b has an inner diameter larger than the non-expanded diameter portion 13 and the tapered portion 11a, and an outer diameter larger than the non-expanded diameter portion 13 and the tapered portion 11a.

The aluminum tube 20 is a tubular body such as a circular tube, and is made of aluminum or an aluminum alloy such as an Al-Mn or Al-Mg-Si alloy. At the tip where the aluminum tube 10 is joined, the aluminum tube 20 has an expanded diameter portion 21 whose inner and outer diameters are larger than those of the base tube used as the raw material. Further, rearward of the expanded diameter portion 21, the aluminum tube 20 has a reduced diameter portion 22 whose inner and outer diameters are reduced from those of the expanded diameter portion 21. Further rearward of the reduced diameter portion 22, the aluminum tube 20 has a non-expanded diameter portion 23 whose inner and outer diameters are not expanded from those of the base tube used as the raw material.

The expanded diameter portion 21 is formed by expanding the base tube of the aluminum tube 20. The expanded diameter portion 21 has a larger inner diameter than the non-expanded diameter portion 23, and a larger outer diameter than the non-expanded diameter portion 23. The reduced diameter portion 22 is a portion formed in conjunction with the formation of the expanded diameter portion 21, and is a portion where the inner diameter and outer diameter transition between the non-expanded diameter portion 23 and the expanded diameter portion 21. The non-expanded diameter portion 23 is a portion of the base tube of the aluminum tube 20 that has not been expanded.

Figure 2 is a cross-sectional view showing a copper tube and an aluminum tube that form a joined assembly in accordance with an embodiment of the present invention. As shown in Figure 2, when joining a copper tube 10 and an aluminum tube 20 together, the copper tube 10 and the aluminum tube 20 are positioned so that the tip end of the expanded copper tube 10 faces the tip end of the expanded aluminum tube 20. Then, the tip end of the expanded copper tube 10 is inserted into the tip end of the expanded aluminum tube 20, and the tip end of the aluminum tube 20 is fitted over the tip end of the copper tube 10.

The copper tube 10 and aluminum tube 20 are joined using a eutectic bonding method that utilizes the eutectic reaction between Cu and Al. When the tip of the aluminum tube 20 is fitted onto the tip of the copper tube 10, the outer surface of the tapered portion 11a of the enlarged diameter portion 11 of the copper tube 10 and the inner surface of the tip of the enlarged diameter portion 21 of the aluminum tube 20 are easily brought into contact with each other. In this state, the copper tube 10 and aluminum tube 20 are compressed in a direction parallel to their longitudinal directions while the contact surfaces between the copper tube 10 and aluminum tube 20 are heated.

With the eutectic bonding method, the contact surfaces of the copper tube 10 and the aluminum tube 20 are pressed together at a lower pressure than with conventional pressure welding, allowing for bonding at a lower temperature. The contact surfaces of the copper tube 10 and the aluminum tube 20 are heated to a temperature above 548°C, the eutectic temperature of Cu-Al, but below the melting points of Cu and Al. To prevent thermal deformation, it is preferable to restrain at least the outer surface of the aluminum tube 20 using a mold.

Heating methods that can be used include resistance heating, which directly passes current through the copper tube 10 and aluminum tube 20 to heat the contact surfaces, contact-type high-frequency induction heating using electrodes, and non-contact-type high-frequency induction heating using coils. The heating electrodes can be a pair of mold-shaped electrodes with semicircular inner surfaces in cross section, positioned to sandwich the tubes and contact their outer surfaces, or clamp-type electrodes that can grip the tubes. Resistance heating, which directly passes current, can heat both materials at the contact surfaces to temperatures equal to or higher than the eutectic temperature in a short period of time. This improves the productivity of the joined body 1.

When the contact surface between the copper tube 10 and the aluminum tube 20 is heated to a temperature equal to or higher than the eutectic temperature, stable phases such as Al ₃ Cu and AlCu are generated, which melt to form a Cu-Al eutectic melt. When the copper tube 10 and the aluminum tube 20 with their heated contact surfaces are cooled by air cooling using compressed air, a joined body 1 is obtained in which the outer surface of the tapered portion 11a of the enlarged diameter portion 11 of the copper tube 10 and the inner surface of the tip side of the enlarged diameter portion 21 of the aluminum tube 20 are joined together through atomic diffusion.

The joined body 1, in which the copper tube 10 and the aluminum tube 20 are joined, is formed using the eutectic bonding method. As shown in Figure 1, the outer surface of the tapered portion 11a of the copper tube 10 and the inner surface of the tip of the expanded diameter portion 21 of the aluminum tube 20 are joined to each other via a Cu-Al eutectic phase 30. Diffusion bonding via the eutectic phase 30 bonds the outer surface of the tapered portion 11a and the inner surface of the tip of the expanded diameter portion 21 around the entire circumference without any gaps.

When joining is performed using the eutectic bonding method, a joint is formed between the outer surface of the tapered portion 11a of the copper pipe 10 and the inner surface of the tip of the expanded diameter portion 21 of the aluminum pipe 20, free of any aluminum oxide film or unnecessary intermetallic compounds. This results in a joint 1 with high joint strength between the copper pipe 10 and the aluminum pipe 20 and airtightness of the pipe. With the eutectic bonding method, the eutectic reaction occurs at a relatively low temperature, allowing for faster joining and increased productivity.

Figure 3 is a cross-sectional view illustrating the dimensions of a joint formed by joining a copper tube and an aluminum tube according to an embodiment of the present invention. In Figure 3, the symbol Lt indicates the length of the tapered portion 11a of the copper tube 10 along the longitudinal direction of the copper tube 10. The symbol Ls indicates the length of the straight portion 11b of the copper tube 10 along the longitudinal direction of the copper tube 10. The symbol La indicates the length of the expanded portion 21 of the aluminum tube 20 along the longitudinal direction of the aluminum tube 20, excluding the portion joined to the copper tube 10. The symbol D1 indicates the inner diameter of the expanded portion 11 of the copper tube 10. The symbol D2 indicates the inner diameter of the non-expanded portion 13 of the copper tube 10. The symbol D3 indicates the inner diameter of the expanded portion 21 of the aluminum tube 20. The symbol D4 indicates the inner diameter of the non-expanded portion 23 of the aluminum tube 20. The symbol Da indicates the outer diameter of the expanded portion 11 of the copper tube 10. The symbol Db indicates the outer diameter of the expanded diameter portion 21 of the aluminum tube 20.

As shown in Figure 3, when the copper tube 10 and the aluminum tube 20 are joined, the outer surface of the tapered portion 11a of the copper tube 10 contacts the inner surface of the tip of the expanded diameter portion 21 of the aluminum tube 20 at an angle. When this condition is created, high pressure can be applied to the contact surface between the copper tube 10 and the aluminum tube 20 from a direction parallel to the longitudinal direction of the copper tube 10 and the aluminum tube 20. Furthermore, when the copper tube 10 is compressed, a component force is generated in the tapered portion 11a of the copper tube 10 toward the center of the pipe, reducing shape abnormalities such as eccentricity between the tubes.

In the joined assembly 1, in which the copper tube 10 and the aluminum tube 20 are joined, the outer diameter of the rear end of the tapered portion 11a of the copper tube 10 is set to be equal to or larger than the outer diameter of the tip of the expanded diameter portion 21 of the aluminum tube 20. That is, in the shape shown in FIG. 3, the outer diameter Da of the expanded diameter portion 11 of the copper tube 10 is set to be equal to or larger than the outer diameter Db of the expanded diameter portion 21 of the aluminum tube 20. With such an outer diameter, when the tip end of the aluminum tube 20 is fitted onto the tip end of the copper tube 10, it is easy to ensure a sufficient contact area between the expanded diameter portion 11 of the copper tube 10 and the expanded diameter portion 21 of the aluminum tube 20. When the outer surface of the tapered portion 11a of the copper tube 10 is in oblique contact with the inner surface of the tip end of the expanded diameter portion 21 of the aluminum tube 20, the contact area between the copper tube 10 and the aluminum tube 20 can be increased for any Lt.

As a result, sufficient eutectic melt is generated during joining using the eutectic bonding method, reducing poor joining between the copper pipe 10 and the aluminum pipe 20. Furthermore, high joining strength can be achieved when joining the copper pipe 10 and the aluminum pipe 20. Furthermore, the change in flow path diameter along the longitudinal direction can be reduced for any given taper angle or thickness of the tapered portion 11a. Because the flow path resistance of the joined body 1 is reduced, abnormal noises associated with the flow of fluids, such as refrigerant noises associated with the flow of a refrigerant, can be suppressed. Furthermore, because it is a function of the outer diameter, the joining condition can be easily estimated by visual inspection from the outside.

The inner diameter D3 of the expanded diameter portion 21 of the aluminum tube 20 is preferably slightly larger than the outer diameter of the tip of the tapered portion 11a of the expanded diameter portion 11 of the copper tube 10. With such an inner diameter, the tapered portion 11a of the expanded diameter portion 11 of the copper tube 10 can be inserted into the inside of the expanded diameter portion 21 of the aluminum tube 20 with little force. Furthermore, while improving the insertability of the tapered portion 11a, a large contact area can be ensured between the outer surface of the tapered portion 11a of the expanded diameter portion 11 of the copper tube 10 and the inner surface of the tip side of the expanded diameter portion 21 of the aluminum tube 20 for a given Lt.

As shown in Figure 3, when joining a copper tube 10 and an aluminum tube 20, the expanded diameter portion 11 of the copper tube 10 is inserted into the expanded diameter portion 21 of the aluminum tube 20 up to a midpoint in the longitudinal direction of the aluminum tube 20. It is preferable that the expanded diameter portion 11 of the copper tube 10 be inserted to a position where the rear end of the tapered portion 11a coincides with or is close to the front end of the expanded diameter portion 21 of the aluminum tube 20. By inserting it in this manner, the outer surface of the tapered portion 11a can ensure a large contact area between the copper tube 10 and the aluminum tube 20.

The tip end of the expanded diameter portion 21 of the aluminum tube 20 forms the joint portion 21a, which is joined to the copper tube 10. The remaining portion of the expanded diameter portion 21 of the aluminum tube 20, excluding the joint portion 21a, forms the non-joint portion 21b, which is not joined to the copper tube 10. The inner diameter of the section of the expanded diameter portion 21 of the aluminum tube 20, including the non-joint portion 21b, is larger than that of the base tube used as the material. This structure reduces the flow resistance of the joined body 1, thereby suppressing abnormal noise associated with the flow of fluid, such as refrigerant noise associated with the flow of refrigerant.

The enlarged diameter portion 11 of the copper tube 10, excluding the tapered portion 11a, preferably has a straight shape with an outer diameter that does not change substantially along the longitudinal direction of the copper tube 10. In other words, the enlarged diameter portion 11 is preferably composed only of the tapered portion 11a and the straight portion 11b. This shape makes it easier for the heating electrode to come into contact with the outer surface of the enlarged diameter portion 11 when joining the copper tube 10 and the aluminum tube 20. This makes it easier for current to flow uniformly between the electrode and the copper tube 10, improving the efficiency of heating the contact surface and the uniformity of heating at the contact surface.

The expanded diameter portion 21 of the aluminum tube 20 preferably has a straight shape with an outer diameter that does not change substantially along the longitudinal direction of the aluminum tube 20. This shape makes it easier for the heating electrode to come into contact with the outer surface of the expanded diameter portion 21 when joining the copper tube 10 and the aluminum tube 20. This makes it easier for current to flow evenly between the electrode and the aluminum tube 20, improving the efficiency and uniformity of heating at the contact surface. In addition, gaps are less likely to form between the heating electrode or fixing jig such as a clamp and the aluminum tube 20. Because heat is less likely to penetrate around the aluminum tube 20, melting of the aluminum tube 20 can be prevented even when the copper tube 10 is heated sufficiently.

The length Ls of the expanded diameter portion 11 of the copper tube 10, excluding the tapered portion 11a, along the longitudinal direction of the copper tube 10, i.e., the length Ls of the straight portion 11b of the copper tube 10 along the longitudinal direction of the copper tube 10, is preferably longer than the length Lt of the tapered portion 11a of the copper tube 10 along the longitudinal direction of the copper tube 10. The tapered portion 11a forms a contact surface with high electrical resistance when the copper tube 10 and the aluminum tube 20 are joined, and is therefore a region where Joule heat is likely to concentrate. On the other hand, the straight portion 11b is the region where the heating electrode comes into contact. The electrode serves as a heat dissipation path for dissipating heat from the copper tube 10. With this length relationship, the straight portion 11b, which serves as a heat dissipation path, is longer than the tapered portion 11a, where heat is likely to concentrate, thereby suppressing excessive temperature rise at the contact surface, etc. Furthermore, heat can be efficiently dissipated from the joined body 1 after the eutectic reaction.

The length Ls of the expanded diameter portion 11 of the copper tube 10, excluding the tapered portion 11a, along the longitudinal direction of the copper tube 10, i.e., the length Ls of the straight portion 11b of the copper tube 10 along the longitudinal direction of the copper tube 10, is preferably longer than the length La of the expanded diameter portion 21 of the aluminum tube 20, excluding the portion joined to the copper tube 10, along the longitudinal direction of the aluminum tube 20, i.e., the length La of the non-jointed portion 21b of the aluminum tube 20 along the longitudinal direction of the aluminum tube 20. The expanded diameter portion 21 of the aluminum tube 20 is the portion that comes into contact with a heating electrode or a restraining fixture. The electrodes and fixtures provide a heat dissipation path for dissipating heat from the aluminum tube 20. On the other hand, the straight portion 11b of the copper tube 10 is the portion that comes into contact with a heating electrode. The electrodes provide a heat dissipation path for dissipating heat from the copper tube 10. However, unlike the aluminum tube 20, the straight portion 11b of the copper tube 10 is adjacent to a tapered portion 11a where heat is likely to concentrate. With this length relationship, the straight portion 11b adjacent to the tapered portion 11a where heat is likely to concentrate is longer than the non-jointed portion 21b, which serves as a heat dissipation path on the aluminum tube 20 side. Therefore, the heat dissipation path on the copper tube 10 side can suppress excessive temperature rise at the contact surface, etc. Furthermore, the heat dissipation path on the copper tube 10 side allows the joined body 1 to efficiently dissipate heat after the eutectic reaction.

Figure 4 is a cross-sectional view showing an embodiment of the present invention in which a copper pipe and an aluminum pipe are joined together and covered with a heat-shrinkable tube. As shown in Figure 4, the joined body 1, in which a copper pipe 10 and an aluminum pipe 20 are joined together, can be covered with a heat-shrinkable tube 40 after the copper pipe 10 and the aluminum pipe 20 are joined together. The joined body 1 can form a pipeline for transporting a fluid when the heat-shrinkable tube 40 is thermally shrunk.

The heat-shrinkable tube 40 is made of resin and is formed into a cylindrical shape. The heat-shrinkable tube 40 is a coating material that shrinks when heated, reducing its inner and outer diameters. After the heat-shrinkable tube 40 is placed over the outer surface of the copper pipe 10 or aluminum pipe 20, the heat-shrinkable tube 40 is heated, causing the heat-shrinkable tube 40 to thermally shrink and adhere tightly to the outer surface of the copper pipe 10 or aluminum pipe 20. This prevents the copper pipe 10 or aluminum pipe 20 from coming into contact with the outside air, thereby suppressing corrosion caused by moisture in the outside air, condensation, etc.

Materials for the heat-shrinkable tube 40 include polyvinyl chloride, silicone rubber, polyolefin, polystyrene, polyester, polycarbonate, polyamide, polyimide, polyamide-imide, polyether ketone, fluororesin, and acrylic resin. There are no particular limitations on the shrinkage ratio of the heat-shrinkable tube 40, but it is preferable that it be 2:1 (50%) or greater.

Examples of polyolefins include polyethylene and polypropylene. Examples of fluororesins include polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene/ethylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer. Examples of acrylic resins include ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl methacrylate copolymer.

The heat shrink tubing 40 may or may not contain additives. Examples of additives include antioxidants, thermal stabilizers, metal deactivators, flame retardants, UV absorbers, antistatic agents, and colorants. The heat shrink tubing 40 may or may not have an adhesive applied to its surface.

The copper tube 10 and aluminum tube 20 constituting the joint 1 are preferably covered with heat-shrinkable tubing 40 in a heat-shrunk state, respectively, at sections including the expanded diameter portion 11 of the copper tube 10 and at least a portion of the reduced diameter portion 12 and non-expanded diameter portion 13 located rearward of the expanded diameter portion 11, and at sections including the expanded diameter portion 21 of the aluminum tube 20 and at least a portion of the reduced diameter portion 22 and non-expanded diameter portion 23 located rearward of the expanded diameter portion 21. The copper tube 10 and aluminum tube 20 come into contact with heating electrodes and restraining fixtures during expansion and joining. Therefore, pressure marks from the electrodes and fixtures may remain on the outer surface. Pressure marks are prone to corrosion. Covering these areas prevents contact between the pressure marks and the outside air, effectively suppressing corrosion caused by moisture in the outside air, condensation, etc.

Figure 5 is a diagram showing an example of a heat exchanger. The structure of the joined body 1, in which a copper tube 10 and an aluminum tube 20 are joined, can be applied to joining heat transfer tubes in a heat exchanger. Figure 5 shows a plate-fin heat exchanger as an example of a heat exchanger. As shown in Figure 5, the heat exchanger 100 includes multiple fins 101 that dissipate heat from the working medium, side plates 102 that are arranged to sandwich the multiple fins 101, and heat transfer tubes 103 that are arranged to penetrate the multiple fins 101 and side plates 102 and through which the working medium flows.

The heat exchanger 100 is a device that exchanges heat between a working medium and air. In the heat exchanger 100, heat is exchanged between the working medium flowing inside the heat transfer tube 103 and the external air via the fins 101. The heat exchanger 100 can be used, for example, as a condenser that condenses the refrigerant in an air conditioner, or as an evaporator that evaporates the refrigerant.

The fins 101 are thin metal plates that ensure a large heat transfer area for dissipating heat from the working medium to the surrounding air, promoting heat exchange between the working medium and the air. Multiple fins 101 are stacked parallel to one another at a specified distance. Through holes for inserting heat transfer tubes 103 are formed in the fins 101 so that they run through the thickness. The through holes can be formed as burring holes with protruding collars using a burring process. The through holes are formed in concentric positions on the multiple fins 101. The fins 101 are made of aluminum, aluminum alloy, etc.

The side plates 102 are fixed to both ends of the stacked fins 101. Through holes for inserting heat transfer tubes 103 are formed in the side plates 102 so that they run through the thickness. The through holes in the side plates 102 are formed in positions that are concentric with the through holes in the fins 101. The side plates 102 are made of aluminum, aluminum alloy, stainless steel, etc.

The heat transfer tubes 103 form a conduit through which the working medium flows and mediate heat transfer between the working medium and the fins 101. The heat transfer tubes 103 are bent into a U-shape. The heat transfer tubes 103 are inserted into the through holes of the fins 101 and the through holes of the side plates 102 and joined by crimping or brazing. The heat transfer tubes 103 are made of copper, copper alloy, aluminum, aluminum alloy, etc.

In the heat exchanger 100, the working fluid flows into the heat transfer tubes 103 from one side of the stacked fins 101 and passes through the stacked fins 101 to the other side. It then turns around at the bend tube on the other side and flows back toward the opposite side, passing through the stacked fins 101. After repeating this round trip and exchanging heat with the outside air, the working fluid is discharged from the heat transfer tubes 103.

The fins 101, side plates 102, and heat transfer tubes 103 are preferably made of aluminum or an aluminum alloy. Aluminum is lightweight and has high corrosion resistance and workability, making it advantageous for reducing the weight of the heat exchanger 100, improving durability, and manufacturability. Furthermore, aluminum has lower material costs and is easier to procure than copper and other materials, making it advantageous for improving the productivity of the heat exchanger 100.

The heat exchanger 100 may include flat tubes with a flat cross section as the heat transfer tubes 103, instead of circular tubes with a circular cross section. The interior of the flat tubes may be divided into multiple pipe passages by partitions formed along the short side. The fins 101 may also be corrugated. The fins 101 and the heat transfer tubes 103 may be joined by crimping or brazing.

The heat exchanger 100 may also be of a parallel flow type. In the parallel flow type, tank-shaped headers are placed on both ends of the stacked fins 101. The working fluid is distributed to multiple heat transfer tubes arranged in parallel to each other, or to multiple pipes partitioned inside the heat transfer tubes. Heat exchange occurs when the multiple branches of working fluid flow parallel to each other. The parallel flow type allows the total flow rate of the working fluid to be increased, thereby reducing the volume occupied by the heat exchanger and the capacity of the working fluid.

Figure 6 is a cross-sectional view illustrating the primary tube expansion process performed on heat exchanger heat transfer tubes. Figure 7 is a cross-sectional view illustrating the secondary tube expansion process performed on heat exchanger heat transfer tubes. Figures 6 and 7 show cross-sectional views of the fins 101, side plates 102, and heat transfer tubes 103 provided on the heat exchanger 100 shown in Figure 5, as well as processing tools (110, 120, 130) provided on the tube expansion device, to explain the types of tube expansion processes used on heat transfer tubes.

In Figures 6 and 7, reference numeral 110 denotes a mandrel of the tube expansion device. Reference numeral 120 denotes a primary tube expansion head of the tube expansion device. Reference numeral 130 denotes a secondary tube expansion head of the tube expansion device. Reference numeral 101a denotes a through hole in the fin 101. Reference numeral 102a denotes a through hole in the side plate 102. Reference numeral d1 denotes the outer diameter of the heat transfer tube before primary tube expansion. Reference numeral d2 denotes the outer diameter of the heat transfer tube after primary tube expansion and before secondary tube expansion. Reference numeral d3 denotes the inner diameter of the heat transfer tube after primary tube expansion and before secondary tube expansion. Reference numeral d4 denotes the inner diameter of the heat transfer tube after secondary tube expansion.

As shown in Figure 6, when manufacturing the heat exchanger 100, the heat transfer tubes 103 inserted into the through holes 101a of the fins 101 and the through holes 102a of the side plates 102 are subjected to a primary tube expansion process. The primary tube expansion process fixes the heat transfer tubes 103 to the fins 101.

The fins 101 are made by pressing a plate material that has been surface-treated to make it hydrophilic. The outside of the fins 101 and the through holes 101a are punched out by pressing. Processing oil is applied to the fins 101. The heat transfer tubes 103 are made by cutting the tube material. The heat transfer tubes 103 are bent into a U-shape by bending.

The multiple fins 101 are stacked on top of each other so that the through holes 101a are concentric. Side plates 102 are attached to both ends of the stack of fins 101, sandwiching the multiple fins 101. The stack of fins 101 is fixed to the receiver plate of a tube expansion device that can support the U-shaped bent side, using side clamps that support the side, a work support table, etc. U-shaped bent heat transfer tubes 103 are inserted into the through holes 101a of the fins 101 and the through holes 102a of the side plates 102 so that they are facing the same direction.

Next, a primary tube expansion head 120 fixed to the tip of the mandrel 110 is inserted into the heat transfer tube 103. The tube expansion device is equipped with multiple mandrels 110 arranged in parallel so that they can be inserted from the ends of multiple heat transfer tubes 103 that are arranged in the same direction. The mandrels 110 are driven by a piston mechanism or the like to move forward and backward into the heat transfer tube 103.

The primary tube expansion head 120 has a tip surface that is hemispherical, semi-elliptical, or the like. The primary tube expansion head 120 is formed with an outer diameter that is larger than the inner diameter of the base tube of the heat transfer tube 103 and equal to the target inner diameter of the heat transfer tube 103 after the primary tube expansion process. The heat transfer tube 103 is plastically deformed by the pressure applied when the primary tube expansion head 120 is inserted, and its outer and inner diameters are expanded. As a result, the outer surface of the heat transfer tube 103 is brought into close contact with the inner surface of the through hole 101a of the fin 101, and the heat transfer tube 103 is crimped into the through hole 101a.

The primary tube expansion process is performed so that the outer diameter of the heat transfer tube 103 has a predetermined expansion ratio. The expansion ratio of the primary tube expansion is calculated by the following formula (1).
(Primary expansion ratio) [%] = [(outer diameter d2 after primary expansion) - (outer diameter d1 before primary expansion)] / (outer diameter d1 before primary expansion) × 100 (1)

As shown in Figure 7, after the primary expansion of the heat transfer tube 103, secondary expansion is performed on the ends of the heat transfer tube 103 inserted into the through-holes 101a of the fins 101 and the through-holes 102a of the side plates 102. This secondary expansion makes it possible to connect other tubes to the heat transfer tube 103, which has a smaller diameter.

After the primary expansion of the heat transfer tubes 103, a secondary expansion head 130 fixed to the middle of the mandrel 110 is inserted into the end of the heat transfer tube 103. By inserting the mandrel 110 deeply into multiple heat transfer tubes 103 arranged in parallel so that they are facing the same direction, the secondary expansion head 130 is inserted into the open end of the heat transfer tubes 103.

The secondary expansion head 130 has a tapered tip surface. The secondary expansion head 130 is set to an outer diameter larger than the inner diameter of the heat transfer tube 103 after the primary expansion process and equal to the target inner diameter of the heat transfer tube 103 after the secondary expansion process. The heat transfer tube 103 is plastically deformed by the pressure applied when the secondary expansion head 130 is inserted, expanding its outer and inner diameters. As a result, the heat transfer tube 103 can be connected to other tubes with larger diameters. The heat transfer tube 103 has a heat exchange section 103a, which is in contact with multiple fins 101, which are heat transfer plates that perform heat exchange, on its outer periphery, and a joint section 103b, which is located at the end of the heat exchange section 103a, has an inner diameter larger than the inner diameter of the heat exchange section 103a, and is used to join other piping.

The secondary tube expansion is performed so that the inner diameter of the end of the heat transfer tube 103 reaches a predetermined expansion ratio. The expansion ratio of the secondary tube expansion is calculated by the following formula (2). Note that the inner diameter of the joint portion 103b of the heat transfer tube 103 does not include the inner diameter of the expanded portion 21 of the aluminum tube 20.
(Expansion rate of secondary expansion) [%] = [(inner diameter d4 of joint after secondary expansion) - (inner diameter d3 of heat exchange section before secondary expansion)] / (inner diameter d3 of heat exchange section before secondary expansion) × 100 (2)

The mandrel 110 is then pulled out of the through-holes 101a of the fins 101 and the through-holes 102a of the side plates 102. The expanded heat transfer tubes 103 and fins 101 are subjected to a drying process to remove processing oil. After that, bend tubes are brazed to the ends of the heat transfer tubes 103 to connect the heat transfer tubes 103 together.

The joined body 1, in which a copper tube 10 and an aluminum tube 20 are joined, can be used to join the heat transfer tubes 103 of such a heat exchanger 100. The joined body 1, in which a copper tube 10 and an aluminum tube 20 are joined, can be connected directly or indirectly to the heat exchanger 100. For example, the structure of the joined body 1 can be used to join a copper tube 10 to an aluminum tube 20 that is the heat transfer tube 103 of the heat exchanger 100, or to join a copper tube 10 to an aluminum tube 20 that is the refrigerant pipe connected to the heat transfer tube 103 of the heat exchanger 100.

The difference between the maximum and minimum outer diameters of the expanded diameter portion 11 of the copper tube 10 and the difference between the maximum and minimum outer diameters of the expanded diameter portion 21 of the aluminum tube 20 are preferably smaller than the difference between the maximum and minimum outer diameters of the heat exchanger heat transfer tube connected to the rear end of the aluminum tube 20. Generally, the inner diameter of the heat exchanger heat transfer tube is primarily controlled for heat transfer calculations. On the other hand, for the copper tube 10 and aluminum tube 20 that make up the assembly 1, it is desirable to control the outer diameter in order to ensure the contact area between the copper tube 10 and the aluminum tube 20. This relationship between the outer diameter differences more reliably achieves the effect of limiting the outer diameter of the rear end of the tapered portion 11a of the copper tube 10.

The expansion ratio of the expanded portion 11 of the copper tube 10 and the expansion ratio of the expanded portion 21 of the aluminum tube 20 are preferably greater than the secondary expansion ratio applied to the end of the heat transfer tube of the heat exchanger connected to the rear end of the aluminum tube 20. Internally grooved tubes are typically used as heat transfer tubes for heat exchangers. Internally grooved tubes have longitudinal grooves or spiral grooves formed around the entire inner surface. The wall thickness of an internally grooved tube at the bottom of the groove is generally thinner than that of an ungrooved tube. Therefore, when comparing tubes with the same outer and inner diameters, the secondary expansion ratio of an internally grooved tube is smaller than that of an ungrooved tube. This expansion ratio relationship ensures that the flow resistance of the copper tube 10 or aluminum tube 20 is smaller than that of the internally grooved tube that constitutes the heat transfer tube, thereby more reliably suppressing abnormal noise associated with the flow of fluid, such as refrigerant noise.

The expansion ratio of the expanded diameter portion 11 of the copper pipe 10 is calculated by the following formula (3).
(Expansion ratio of the expanded portion of the copper pipe) [%] = [(inner diameter D1 of the expanded portion of the copper pipe) - (inner diameter D2 of the non-expanded portion of the copper pipe)] / (inner diameter D2 of the non-expanded portion of the copper pipe) × 100 (3)

The expansion ratio of the expanded diameter portion 21 of the aluminum tube 20 is calculated by the following formula (4).
(Expansion ratio of expanded diameter portion of aluminum pipe) [%] = [(inner diameter D3 of expanded diameter portion of aluminum pipe) - (inner diameter D4 of non-expanded diameter portion of aluminum pipe)] / (inner diameter D4 of non-expanded diameter portion of aluminum pipe) × 100 (4)

Figure 8 is a diagram showing an example of the configuration of an air conditioner according to an embodiment of the present invention. A joined assembly 1 in which a copper pipe 10 and an aluminum pipe 20 are joined can be provided as part of the refrigerant circuit of the air conditioner. As shown in Figure 8, the air conditioner 200 comprises an outdoor unit 210 that is installed outdoors, and an indoor unit 220 that is installed on a wall or the like inside the room. The outdoor unit 210 and the indoor unit 220 are connected to each other via connecting pipes through which refrigerant pipes and electrical wiring pass.

The air conditioner 200 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 210 and the indoor unit 220 through refrigerant piping. In the outdoor unit 210, heat exchange occurs between the refrigerant and outside air. In the indoor unit 220, heat exchange occurs between the refrigerant and indoor air. The indoor unit 220 exchanges heat between the air drawn in from the room and the refrigerant, then blows the air out into the room to adjust the temperature and humidity inside the room.

The air conditioner 200 is equipped with a refrigerant circuit 201 that constitutes a heat pump. The refrigerant circuit 201 executes a heat cycle for cooling operation, heating operation, etc. The refrigerant circuit 201 is composed of equipment such as a compressor 202, a four-way valve 203, an outdoor heat exchanger 204, an expansion valve 205, an indoor heat exchanger 206, and an accumulator 207, as well as refrigerant piping that circulates the refrigerant.

These devices are connected to each other via refrigerant piping. The devices and refrigerant piping form a refrigerant circuit 201, which is a closed circuit through which refrigerant circulates, between the outdoor unit 210 and the indoor unit 220. Refrigerant is sealed into the refrigerant circuit 201 when the air conditioner 200 is installed or during maintenance. The refrigerant circulates through the refrigerant circuit 201 and mediates heat exchange to perform cooling operation, heating operation, etc.

An outdoor blower fan 208 is installed near the outdoor heat exchanger 204. An indoor blower fan 209 is installed near the indoor heat exchanger 206. The compressor 202, four-way valve 203, outdoor heat exchanger 204, expansion valve 205, accumulator 207, and outdoor blower fan 208 are housed in the outdoor unit 210. The indoor heat exchanger 206 and indoor blower fan 209 are housed in the indoor unit 220.

Compressor 202 is a device that compresses refrigerant. It draws in low-pressure gas refrigerant, compresses it adiabatically, and discharges high-pressure gas refrigerant. Compressor 202 variably controls the amount of refrigerant circulated by inverter control. Compressor 202 can be of any suitable type, such as a scroll, piston, rotary, screw, or centrifugal type.

The four-way valve 203 has four ports and changes the flow path between the ports depending on the operating mode of the air conditioner 200, such as cooling operation or heating operation. The four-way valve 203 switches the circulation direction of the refrigerant discharged from the compressor 202 in the refrigerant circuit 201.

The outdoor heat exchanger 204 is a heat exchanger that exchanges heat between the refrigerant and outside air, and functions as a condenser during cooling operation and as an evaporator during heating operation. The outdoor blower fan 208 blows outside air into the outdoor heat exchanger 204 to promote heat exchange. The outdoor blower fan 208 is composed of a propeller fan. The expansion valve 205 is a valve with an adjustable opening, and functions as a pressure reducer during heating operation.

The indoor heat exchanger 206 is a heat exchanger that exchanges heat between the refrigerant and the indoor air, and functions as an evaporator during cooling operation and as a condenser during heating operation. The indoor blower fan 209 blows air into the indoor heat exchanger 206 to promote heat exchange, and also blows the air that has exchanged heat with the refrigerant into the room. The indoor blower fan 209 is composed of a cylindrical cross-flow fan.

The accumulator 207 is a tank-shaped device that separates the refrigerant gas from the liquid refrigerant, separating and storing the liquid refrigerant contained in the refrigerant gas. By removing any liquid refrigerant that has not yet evaporated from the refrigerant gas on the suction side of the compressor 202, liquid compression by the compressor 202, which can lead to abnormal noise and malfunction, is prevented.

The cooling operation of the air conditioner 200 is performed as follows. High-temperature, high-pressure gas refrigerant is adiabatically compressed in the compressor 202 and sent to the outdoor heat exchanger 204 through the four-way valve 203. The high-temperature, high-pressure gas refrigerant is condensed into liquid refrigerant through heat exchange with outside air in the outdoor heat exchanger 204, which functions as a condenser. The liquid refrigerant is decompressed and expanded in the expansion valve 205, becoming a low-temperature, low-pressure, two-phase gas-liquid refrigerant containing a small amount of gas refrigerant.

The low-temperature, low-pressure, two-phase gas-liquid refrigerant is sent to the indoor heat exchanger 206. The two-phase gas-liquid refrigerant evaporates through heat exchange with the indoor air in the indoor heat exchanger 206, which functions as an evaporator, and becomes low-temperature, low-pressure gas refrigerant. The low-temperature, low-pressure gas refrigerant passes through the four-way valve 203, and the liquid refrigerant is separated in the accumulator 207 before returning to the compressor 202. Heat is removed from the indoor air through heat exchange with the refrigerant in the indoor heat exchanger 206, which functions as an evaporator. This cycle is repeated to cool the room.

The heating operation of the air conditioner 200 is performed in the reverse cycle to the cooling operation. The high-temperature, high-pressure gas refrigerant is adiabatically compressed and discharged by the compressor 202 and sent to the indoor heat exchanger 206 by switching the four-way valve 203. The high-temperature, high-pressure gas refrigerant is cooled by heat exchange with the indoor air in the indoor heat exchanger 206, which functions as a condenser, and becomes liquid refrigerant. The liquid refrigerant is then decompressed by the expansion valve 205 to become low-temperature, low-pressure liquid refrigerant.

The low-temperature, low-pressure liquid refrigerant is sent to the outdoor heat exchanger 204. The low-temperature, low-pressure liquid refrigerant evaporates through heat exchange with outside air in the outdoor heat exchanger 204, which functions as an evaporator, and becomes low-temperature, low-pressure gas refrigerant. The low-temperature, low-pressure gas refrigerant passes through the four-way valve 203, and after the liquid refrigerant is separated in the accumulator 207, it returns to the compressor 202. The indoor air is given heat through heat exchange with the refrigerant in the indoor heat exchanger 206, which functions as a condenser. This cycle is repeated to heat the room.

The refrigerant piping is made of copper, such as phosphorus-deoxidized copper. The fins of the outdoor heat exchanger 204 and the indoor heat exchanger 206 are made of aluminum, aluminum alloy, etc. The side plates of the outdoor heat exchanger 204 and the indoor heat exchanger 206 are made of aluminum, aluminum alloy, stainless steel, etc. The heat transfer tubes of the outdoor heat exchanger 204 and the indoor heat exchanger 206 are made of copper, copper alloy, aluminum, aluminum alloy, etc.

It is preferable that the heat transfer tubes of at least one of the outdoor heat exchanger 204 and the indoor heat exchanger 206 be made of aluminum or an aluminum alloy, and it is even more preferable that the entire fins, heat transfer tubes, etc. be made of aluminum or an aluminum alloy. From the perspective of lightweight and size requirements, it is preferable that the entire construction be made of aluminum, at least for the indoor heat exchanger 206.

The structure of the joined assembly 1, in which the copper pipe 10 and the aluminum pipe 20 are joined, can be used to join the heat transfer pipes of the outdoor heat exchanger 204 or the indoor heat exchanger 206. The rear end of the aluminum pipe 20 that constitutes the joined assembly 1 can be connected directly or indirectly to the outdoor heat exchanger 204 or the indoor heat exchanger 206. For example, the copper pipe 10 can be joined to the aluminum pipe 20 that is the heat transfer pipe of the outdoor heat exchanger 204 or the indoor heat exchanger 206. Alternatively, the copper pipe 10 can be joined to the aluminum pipe 20 that is the refrigerant pipe connected to the heat transfer pipe of the outdoor heat exchanger 204 or the indoor heat exchanger 206.

When the rear end of the aluminum tube 20 constituting the assembly 1 is connected directly or indirectly to the outdoor heat exchanger 204 or the indoor heat exchanger 206, the difference between the maximum and minimum outer diameters of the expanded diameter portion 11 of the copper tube 10 constituting the assembly 1 is preferably smaller than the difference between the maximum and minimum outer diameters of the heat transfer tubes of the outdoor heat exchanger 204 connected to the rear end of the aluminum tube 20, or the difference between the maximum and minimum outer diameters of the heat transfer tubes of the indoor heat exchanger 206 connected to the rear end of the aluminum tube 20. Furthermore, the difference between the maximum and minimum outer diameters of the expanded diameter portion 21 of the aluminum tube 20 constituting the assembly 1 is preferably smaller than the difference between the maximum and minimum outer diameters of the heat transfer tubes of the outdoor heat exchanger 204 connected to the rear end of the aluminum tube 20, or the difference between the maximum and minimum outer diameters of the heat transfer tubes of the indoor heat exchanger 206 connected to the rear end of the aluminum tube 20. This relationship in outer diameter difference more reliably achieves the effect of limiting the outer diameter of the rear end of the tapered portion 11a of the copper tube 10.

When the rear end of the aluminum tube 20 constituting the joint 1 is connected directly or indirectly to the outdoor heat exchanger 204 or the indoor heat exchanger 206, it is preferable that the expansion ratio of the inner diameter of the expanded portion 11 relative to the inner diameter of the non-expanded portion 13 of the copper tube 10, as expressed by equation (3), is greater than the expansion ratio of the inner diameter of the joint portion 103b relative to the inner diameter of the heat exchange portion 103a of the heat transfer tube 103 of the outdoor heat exchanger 204 connected to the rear end side of the aluminum tube 20, or the expansion ratio of the inner diameter of the joint portion 103b relative to the inner diameter of the heat exchange portion 103a of the heat transfer tube 103 of the indoor heat exchanger 206 connected to the rear end side of the aluminum tube 20. Furthermore, the expansion ratio of the inner diameter of the expanded portion 21 to the inner diameter of the non-expanded portion 23 of the aluminum tube 20, as expressed by equation (4), is preferably greater than the expansion ratio of the inner diameter of the joint portion 103b to the inner diameter of the heat exchange section 103a of the heat transfer tube 103 of the outdoor heat exchanger 204 connected to the rear end of the aluminum tube 20, or the expansion ratio of the inner diameter of the joint portion 103b to the inner diameter of the heat exchange section 103a of the heat transfer tube 103 of the indoor heat exchanger 206 connected to the rear end of the aluminum tube 20. With such expansion ratios, the flow resistance of the copper tube 10 or aluminum tube 20 is smaller than the flow resistance of the internally grooved tube that constitutes the heat transfer tube, thereby more reliably suppressing abnormal noise associated with the flow of fluid, such as refrigerant noise.

The joined body 1, in which the copper pipe 10 and the aluminum pipe 20 are joined, is preferably formed in one or more of the following: the area belonging to the indoor heat exchanger 206, the section on the refrigerant circuit connecting the indoor heat exchanger 206 and the four-way valve 203, and the section on the refrigerant circuit connecting the indoor heat exchanger 206 and the expansion valve 205. On the other hand, the joined body 1, in which the copper pipe 10 and the aluminum pipe 20 are joined, is preferably not formed in the area belonging to the outdoor heat exchanger 204, the section on the refrigerant circuit connecting the outdoor heat exchanger 204 and the four-way valve 203, or the section on the refrigerant circuit connecting the outdoor heat exchanger 204 and the expansion valve 205.

The indoor heat exchanger 206 and the refrigerant piping around the indoor heat exchanger 206 are installed indoors or near the indoors, so ensuring the airtightness of the refrigerant circuit and suppressing refrigerant noise are required. On the other hand, there is a relatively low requirement for the outdoor heat exchanger 204 and the refrigerant piping around the outdoor heat exchanger 204 to be made of aluminum. Joining using the eutectic bonding method can be more time-consuming and costly than conventional brazing. Limiting the area where the bonded body 1 is formed to the area around the indoor heat exchanger 206 facilitates installation of the air conditioner 200 while ensuring bonding strength, airtightness, and suppressing refrigerant noise around the indoor heat exchanger 206.

When the joined body 1, in which the copper pipe 10 and the aluminum pipe 20 are joined, is formed around the indoor heat exchanger 206, it is preferably formed at least in the section of the refrigerant circuit connecting the indoor heat exchanger 206 and the four-way valve 203. The joined body 1 is preferably formed on the refrigerant piping located downstream of the indoor heat exchanger 206 during cooling operation, at least on the downstream refrigerant piping connected to the indoor heat exchanger 206. On the other hand, it is preferable that the joined body 1 is not formed in the section of the refrigerant circuit connecting the indoor heat exchanger 206 and the expansion valve 205. It is preferable that the joined body 1 is formed on the refrigerant piping located upstream of the indoor heat exchanger 206 during cooling operation, not on the upstream refrigerant piping connected to the indoor heat exchanger 206.

The section of the refrigerant circuit connecting the indoor heat exchanger 206 and the four-way valve 203 is located downstream of the indoor heat exchanger 206 during cooling operation. Low-temperature, low-pressure gas refrigerant flows through it during cooling operation, and high-temperature, high-pressure gas refrigerant flows through it during heating operation. In such a section, refrigerant noise becomes noticeable when flow resistance is high. On the other hand, the section of the refrigerant circuit connecting the indoor heat exchanger 206 and the expansion valve 205 is located upstream of the indoor heat exchanger 206 during cooling operation. Low-temperature, low-pressure two-phase gas-liquid refrigerant flows through it during cooling operation, and liquid refrigerant flows through it during heating operation. In such a section, refrigerant noise is less likely to reverberate. Limiting the location where the joint 1 is formed to the four-way valve 203 side of the indoor heat exchanger 206 facilitates installation around the indoor heat exchanger 206 while effectively suppressing refrigerant noise.

The joint 1, in which the copper pipe 10 and the aluminum pipe 20 are joined, is preferably formed at all locations in the indoor heat exchanger 206 where the copper pipe and the aluminum pipe are joined. Because the indoor heat exchanger 206 is installed indoors, it is necessary to ensure the airtightness of the refrigerant circuit and suppress refrigerant noise. By forming the joint 1 at all locations in the indoor heat exchanger 206, it is possible to more reliably ensure the joint strength, airtightness, and suppression of refrigerant noise in the indoor heat exchanger 206.

The above describes embodiments of the present invention, but the present invention is not limited to the above embodiments and includes various modifications within the technical scope. For example, the above embodiments are not necessarily limited to those including all of the configurations described. Furthermore, it is possible to replace part of the configuration of an embodiment with another configuration, or to add another configuration to the configuration of an embodiment. It is also possible to add other configurations to, delete configurations from, or replace part of the configuration of an embodiment.

For example, the copper pipe 10 and aluminum pipe 20 that make up the joint 1 have non-expanded portions 13, 23 that are not expanded relative to the base pipes. However, the non-expanded portions 13, 23 may be expanded in other ways, other than the expansion required to join the copper pipe 10 and aluminum pipe 20. The non-expanded portions 13, 23 are not limited to a linear shape, and may also be formed into a curved, bent, or other bent shape.

The air conditioner 200 may also be equipped with devices that make up the refrigerant circuit (not shown), such as a receiver, oil separator, dryer, etc., and sensors such as temperature sensors that measure the temperature at various locations. The air conditioner 200 may also be equipped with an injection circuit for injecting refrigerant at an intermediate pressure into the compressor 202. The injection circuit is connected to the compressor 202, bypassing the condenser and evaporator.

Furthermore, the air conditioner 200 can be any suitable air conditioner, such as a room air conditioner, a package air conditioner, a home multi-air conditioner, a commercial multi-air conditioner, or a building multi-air conditioner. In Figure 8, the outdoor unit 210 and the indoor unit 220 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.

1 Joint 10 Copper pipe 11 Expanded diameter portion 11a Tapered portion 11b Straight portion 12 Reduced diameter portion 13 Non-expanded diameter portion 20 Aluminum pipe 21 Expanded diameter portion 22 Reduced diameter portion 23 Non-expanded diameter portion 30 Eutectic phase 40 Heat shrinkable tube 100 Heat exchanger 101 Fin 102 Side plate 103 Heat transfer tube 110 Mandrel 120 Primary expansion head 130 Secondary expansion head 200 Air conditioner 201 Refrigerant circuit 202 Compressor 203 Four-way valve 204 Outdoor heat exchanger 205 Expansion valve 206 Indoor heat exchanger 207 Accumulator 208 Outdoor blower fan 209 Indoor blower fan 210 Outdoor unit 220 Indoor unit

Claims (12)

A joint in which a copper pipe and an aluminum pipe are joined,
The copper tube and the aluminum tube each have an expanded diameter portion at a tip thereof,
The enlarged diameter portion of the copper pipe has a tapered portion whose diameter decreases toward the tip side,
the tapered portion of the copper tube and the tip side of the expanded diameter portion of the aluminum tube are joined to each other via a eutectic phase,
A joined assembly in which the outer diameter of the rear end of the tapered portion of the copper pipe is equal to or larger than the outer diameter of the front end of the enlarged diameter portion of the aluminum pipe. The bonded body according to claim 1,
A joined body in which the outer diameter of the expanded diameter portion of the copper pipe, excluding the tapered portion, does not substantially change along the longitudinal direction of the copper pipe. The bonded body according to claim 1,
A joined assembly in which the expanded diameter portion of the aluminum pipe has an outer diameter that does not substantially change along the longitudinal direction of the aluminum pipe. The bonded body according to claim 1,
A joint body in which the length of the enlarged diameter portion of the copper pipe excluding the tapered portion is longer than the length of the tapered portion of the copper pipe. The bonded body according to claim 1,
A joint body in which the length of the expanded diameter portion of the copper pipe excluding the tapered portion is longer than the length of the expanded diameter portion of the aluminum pipe excluding the portion joined to the copper pipe. The bonded body according to claim 1,
The copper pipe and the aluminum pipe are joined together in such a manner that the enlarged diameter portion and a portion of the non-enlarged diameter portion located rearward of the enlarged diameter portion are covered with a heat-shrinkable tube. An air conditioner comprising a compressor, a four-way valve, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger,
The air conditioner includes a joint in which a copper pipe and an aluminum pipe are joined together,
The copper tube and the aluminum tube each have an expanded diameter portion at a tip thereof,
The enlarged diameter portion of the copper pipe has a tapered portion whose diameter decreases toward the tip side,
the tapered portion of the copper tube and the tip of the enlarged diameter portion of the aluminum tube are joined to each other via a eutectic phase,
An air conditioner in which the outer diameter of the rear end of the tapered portion of the copper pipe is equal to or larger than the outer diameter of the front end of the enlarged diameter portion of the aluminum pipe. The air conditioner according to claim 7,
The rear end of the aluminum pipe is directly or indirectly connected to the outdoor heat exchanger or the indoor heat exchanger,
An air conditioner in which the difference between the maximum outer diameter and the minimum outer diameter of the enlarged portion of the copper tube and the difference between the maximum outer diameter and the minimum outer diameter of the enlarged portion of the aluminum tube are smaller than the difference between the maximum outer diameter and the minimum outer diameter of the heat transfer tube of the outdoor heat exchanger or the indoor heat exchanger connected to the aluminum tube. The air conditioner according to claim 7,
The rear end of the aluminum pipe is directly or indirectly connected to the outdoor heat exchanger or the indoor heat exchanger,
The heat transfer tube of the outdoor heat exchanger or the indoor heat exchanger connected to the aluminum tube has a heat exchange section whose outer periphery is in contact with a plurality of heat transfer plates, and a joint section whose inner diameter is larger than the heat exchange section and into which the aluminum tube is inserted,
An air conditioner in which the expansion ratio of the inner diameter of the enlarged portion to the inner diameter of the non-enlarged portion of the copper tube and the expansion ratio of the inner diameter of the enlarged portion to the inner diameter of the non-enlarged portion of the aluminum tube are greater than the expansion ratio of the inner diameter of the joint to the inner diameter of the heat exchange section of the heat transfer tube of the outdoor heat exchanger or the indoor heat exchanger connected to the aluminum tube. The air conditioner according to claim 7,
The air conditioner wherein the joint is formed on at least one of the refrigerant pipes connected to the indoor heat exchanger, but is not formed on the refrigerant pipes connected to the outdoor heat exchanger. The air conditioner according to claim 7,
The air conditioner wherein the joint is located downstream of the indoor heat exchanger during cooling operation and is formed in a downstream refrigerant piping connected to the indoor heat exchanger, and is located upstream of the indoor heat exchanger during cooling operation and is not formed in an upstream refrigerant piping connected to the indoor heat exchanger. The air conditioner according to claim 7,
The air conditioner, wherein the joints are formed at all points where the copper pipes and the aluminum pipes are joined in the indoor heat exchanger.