Joint of copper pipe and aluminum pipe and air conditioner

Abstract

To provide a joined body in which a copper pipe and an aluminum pipe are joined, which easily secures a contact area between the copper pipe and the aluminum pipe, reduces a joint failure between the copper pipe and the aluminum pipe, and obtains an effect of suppressing abnormal noise accompanying the flow of a fluid and high joint strength, and to provide an air conditioner including the same.SOLUTION: In a joined body 1, a copper pipe 10 and an aluminum pipe 20 are joined to each other, each of the copper pipe 10 and the aluminum pipe 20 has a diameter-enlarged portion enlarged at a tip end, a diameter-enlarged portion 11 of the copper pipe 10 has a tapered portion 11a reduced in size toward the tip end side, the tapered portion 11a of the copper pipe 10 and a tip end side of a diameter-enlarged portion 21 of the aluminum pipe 20 are joined to each other via a eutectic phase 30, and an outer diameter of a rear end of the tapered portion 11a of the copper pipe 10 is equal to or larger than an outer diameter of the tip end of the diameter-enlarged portion 21 of the aluminum pipe 20. An air conditioner includes a refrigerant circuit, and the refrigerant circuit includes the joint body 1 in which the copper pipe 10 and the aluminum pipe 20 are joined.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a joint in which a copper pipe and an aluminum pipe are joined together, and to an air conditioner including the joint. [Background technology]

[0002] Copper pipes have traditionally been used as refrigerant piping in refrigeration and air conditioning equipment. However, in recent years, aluminum pipes have been increasingly used as refrigerant piping due to their low material cost, 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, joining the copper and aluminum pipes is required.

[0003] Copper pipes and aluminum pipes are mainly 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 generated at the contact surface. When heated under pressure and then rapidly cooled, a bonded body is obtained in which the copper and aluminum are diffusion bonded via the Cu-Al eutectic phase.

[0004] Patent Document 1 discloses a joint of a copper pipe and an aluminum pipe made using a 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 over the entire circumference. A sealed 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. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-072820 Summary of the Invention [Problem to be solved by the invention]

[0006] When forming a joint between a copper pipe and an aluminum pipe by the eutectic bonding method, it is necessary to generate a sufficient amount of eutectic melt to reduce bonding defects. It is also necessary to ensure the strength of the joint between the copper pipe and the aluminum pipe. Therefore, it is important to ensure a sufficient contact area between the copper pipe and the aluminum pipe. It is desirable to form a joint with a large contact area between the copper pipe and the aluminum pipe, in which many atoms at the interface are diffused into each other.

[0007] However, as described in Patent Document 1, a conventional joint of a copper pipe and an aluminum pipe has a structure in which an aluminum pipe is fitted onto the tip of a reduced diameter copper pipe. Simply forming such a structure poses a problem in that a sufficient contact area between the copper pipe and the aluminum pipe is not ensured. 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.

[0008] Furthermore, as described in Patent Document 1, a conventional joint of a copper pipe and an aluminum pipe has 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 causes a problem of increased refrigerant noise when the refrigerant flows through. A joint that can ensure a large contact area between the copper pipe and the aluminum pipe while suppressing abnormal refrigerant noise is desired.

[0009] Therefore, the present invention aims to provide a joint in which a copper pipe and an aluminum pipe are joined together, which makes it easier to ensure a sufficient contact area between the copper pipe and the aluminum pipe, reduces poor joining between the copper pipe and the aluminum pipe, suppresses abnormal noise caused by the flow of fluid, and provides high joining strength, and an air conditioner equipped with the joint. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, the joined body of the present invention is a joined body in which a copper tube and an aluminum tube are joined, wherein the copper tube and the aluminum tube each have an enlarged diameter portion at their tip, the enlarged diameter portion of the copper tube has a tapered portion whose diameter decreases toward the tip, the tapered portion of the copper tube and the tip side 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.

[0011] 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 pipe and an aluminum pipe, and the copper pipe and the aluminum pipe each have an enlarged diameter portion at their tip, the enlarged diameter portion of the copper pipe has a tapered portion whose diameter decreases toward the tip, the tapered portion of the copper pipe and the tip of the enlarged diameter portion of the aluminum pipe are joined to each other via a eutectic phase, and the outer diameter of the rear end of the tapered portion of the copper pipe is equal to or greater than the outer diameter of the tip of the enlarged diameter portion of the aluminum pipe. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a joint in which a copper pipe and an aluminum pipe are joined together, which makes it easier to ensure a sufficient contact area between the copper pipe and the aluminum pipe, reduces poor joining between the copper pipe and the aluminum pipe, suppresses abnormal noise caused by the flow of fluid, and provides high joining strength, and an air conditioner equipped with the joint. [Brief explanation of the drawings]

[0013] [Figure 1] 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 2] 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. [Figure 3] 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. [Figure 4] 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. [Figure 5] FIG. 2 is a diagram illustrating an example of a heat exchanger. [Figure 6] 1 is a cross-sectional view illustrating a primary tube expansion process performed on a heat transfer tube of a heat exchanger. [Figure 7] 1 is a cross-sectional view illustrating a secondary tube expansion process performed on a heat transfer tube of a heat exchanger. [Figure 8] 1 is a diagram showing an example of the configuration of an air conditioner according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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 drawings will be assigned the same reference numerals, and duplicated explanations will be omitted.

[0015] In this specification, the term "front end" refers to the end or part of a tube that is located on the side where the tubes are joined, and the term "rear end" refers to the end or part of a tube that is located on the opposite side from the side where the tubes are joined.

[0016] Fig. 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. Fig. 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 Fig. 1, a 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 expanded together via a Cu-Al eutectic phase 30.

[0017] The copper tube 10 is a tubular body such as a circular tube, and is made of phosphorus-deoxidized copper, oxygen-free copper, or the like. The copper tube 10 has an expanded diameter portion 11 at its tip where it is joined to the aluminum tube 20, where the inner and outer diameters are larger than those of the mother tube used as the raw material. Further, the copper tube 10 has a reduced diameter portion 12, where the inner and outer diameters are reduced from the expanded diameter portion 11, rearward of the expanded diameter portion 11. Further, the copper tube 10 has a non-expanded diameter portion 13, where the inner and outer diameters are not expanded from those of the mother tube used as the raw material, rearward of the reduced diameter portion 12.

[0018] The expanded diameter portion 11 is formed by expanding the base pipe of the copper pipe 10. The expanded diameter portion 11 has an inner diameter larger than that of the non-expanded diameter portion 13 and an outer diameter larger than that of 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, and is a portion where the inner diameter and outer diameter 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 pipe 10 that has not been expanded.

[0019] The expanded diameter portion 11 of the copper tube 10 has a tapered portion 11a with a tapered outer shape at the tip end side where it is joined to the aluminum tube 20. The tapered portion 11a is formed so that 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 side of the expanded diameter portion 11. The tapered portion 11a has an inner diameter larger than that of the non-expanded diameter portion 13 from the tip to the rear end, and an outer diameter larger than that of the non-expanded diameter portion 13.

[0020] The diameter expansion portion 11 of the copper tube 10 has a straight portion 11b with a straight outer shape at the rear end side where it connects to the non-diameter expansion portion 13. The straight portion 11b is provided in a straight shape in which the outer diameter does not substantially change along the longitudinal direction of the copper tube 10. The straight portion 11b has an inner diameter larger than the non-diameter expansion portion 13 and the tapered portion 11a, and an outer diameter larger than the non-diameter expansion portion 13 and the tapered portion 11a.

[0021] 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-based or Al-Mg-Si-based alloy. The aluminum tube 20 has an expanded diameter portion 21 at its tip where it is joined to the copper tube 10, where the inner and outer diameters are larger than those of the mother tube used as the raw material. Furthermore, the aluminum tube 20 has a reduced diameter portion 22, where the inner and outer diameters are reduced from the expanded diameter portion 21, located rearward of the expanded diameter portion 21. Furthermore, the aluminum tube 20 has a non-expanded diameter portion 23, where the inner and outer diameters are not expanded from those of the mother tube used as the raw material, located rearward of the reduced diameter portion 22.

[0022] The expanded diameter portion 21 is formed by subjecting the base tube of the aluminum tube 20 to a pipe expansion process. The expanded diameter portion 21 has an inner diameter larger than that of the non-expanded diameter portion 23, and an outer diameter larger than that of 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 subjected to a pipe expansion process.

[0023] 2 is a cross-sectional view showing a copper tube and an aluminum tube that form a joined assembly formed by joining a copper tube and an aluminum tube according to an embodiment of the present invention. As shown in FIG. 2, when joining a copper tube 10 and an aluminum tube 20 together, the copper tube 10 and the aluminum tube 20 are arranged 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 onto the tip end of the copper tube 10.

[0024] The copper tube 10 and the aluminum tube 20 are joined using a eutectic bonding method that utilizes the eutectic reaction between Cu and Al. When the tip end of the aluminum tube 20 is fitted onto the tip end 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 end 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 the aluminum tube 20 are pressurized in a compressive direction parallel to their longitudinal directions, while the contact surfaces between the copper tube 10 and the aluminum tube 20 are heated.

[0025] In the eutectic bonding method, the contact surfaces of the copper pipe 10 and the aluminum pipe 20 are pressed together at a lower pressure than in general pressure welding, allowing for bonding at a low temperature. The contact surfaces of the copper pipe 10 and the aluminum pipe 20 are heated to a temperature equal to or higher than 548°C, which is the eutectic temperature of Cu-Al, but lower than the melting points of Cu and Al. To prevent thermal deformation, it is preferable to restrain at least the outer surface of the aluminum pipe 20 with a mold.

[0026] Heating methods that can be used include resistance heating, which directly applies current to the copper tube 10 and the 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 the outer surfaces of the tubes, or clamp-type electrodes that can grip the tubes. Resistance heating, which directly applies 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 bonded body 1.

[0027] When the contact surface between the copper tube 10 and the aluminum tube 20 is heated to a temperature above the eutectic temperature, stable phases such as AlCu and AlCu are generated, which then 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.

[0028] The joined body 1, in which the copper tube 10 and the aluminum tube 20 are joined, is formed by the eutectic bonding method, so that, as shown in Fig. 1, the outer surface of the tapered portion 11a of the copper tube 10 and the inner surface of the leading end of the expanded diameter portion 21 of the aluminum tube 20 are joined to each other via a Cu-Al eutectic phase 30. By diffusion bonding via the eutectic phase 30, the outer surface of the tapered portion 11a and the inner surface of the leading end of the expanded diameter portion 21 are joined together over the entire circumference without any gaps.

[0029] 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 side 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 joined body 1 that has 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 short joining times and increased productivity.

[0030] FIG. 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 FIG. 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 diameter 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 diameter portion 11 of the copper tube 10. The symbol D2 indicates the inner diameter of the non-expanded diameter portion 13 of the copper tube 10. The symbol D3 indicates the inner diameter of the expanded diameter portion 21 of the aluminum tube 20. The symbol D4 indicates the inner diameter of the non-expanded diameter portion 23 of the aluminum tube 20. The symbol Da indicates the outer diameter of the expanded diameter 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.

[0031] As shown in Figure 3, when the copper pipe 10 and the aluminum pipe 20 are joined, the outer surface of the tapered portion 11a of the copper pipe 10 is in oblique contact with the inner surface of the leading end of the expanded diameter portion 21 of the aluminum pipe 20. When this state is formed, high pressure can be applied to the contact surface between the copper pipe 10 and the aluminum pipe 20 in a direction parallel to the longitudinal direction of the copper pipe 10 and the aluminum pipe 20. Furthermore, when the copper pipe 10 is compressed in the compression direction, a component force is generated in the tapered portion 11a of the copper pipe 10 toward the center of the pipe, which reduces shape abnormalities such as eccentricity between the pipes.

[0032] 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.

[0033] Therefore, during bonding by the eutectic bonding method, sufficient eutectic melt is generated, reducing bonding defects between the copper pipe 10 and the aluminum pipe 20. Furthermore, high bonding strength can be achieved when bonding 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 taper angle or thickness of the tapered portion 11a. Since the flow path resistance of the bonded body 1 is reduced, abnormal noises caused by the flow of fluid, such as refrigerant noise caused by the flow of a refrigerant, can be suppressed. Furthermore, because of the relationship between the outer diameters, the bonding condition can be easily estimated by visual inspection from the outside.

[0034] The inner diameter D3 of the expanded diameter portion 21 of the aluminum tube 20 is preferably set 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 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 any Lt.

[0035] 3, when joining a copper pipe 10 and an aluminum pipe 20, the expanded diameter portion 11 of the copper pipe 10 is inserted into the expanded diameter portion 21 of the aluminum pipe 20 up to a midpoint in the longitudinal direction of the aluminum pipe 20. It is preferable that the expanded diameter portion 11 of the copper pipe 10 is 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 pipe 20. By inserting in this manner, the outer surface of the tapered portion 11a can ensure a large contact area between the copper pipe 10 and the aluminum pipe 20.

[0036] The portion of the expanded diameter portion 21 of the aluminum pipe 20 near the tip becomes a joining portion 21a that is joined to the copper pipe 10. The portion of the expanded diameter portion 21 of the aluminum pipe 20 excluding the joining portion 21a becomes a non-joining portion 21b that is not joined to the copper pipe 10. The inner diameter of the section of the expanded diameter portion 21 of the aluminum pipe 20 that includes the non-joining portion 21b is larger than that of the base pipe used as the material. With this structure, the flow resistance of the joined body 1 is reduced, thereby suppressing abnormal noise caused by the flow of a fluid, for example, refrigerant noise caused by the flow of a refrigerant.

[0037] It is preferable that the portion of the enlarged diameter portion 11 of the copper tube 10, excluding the tapered portion 11a, has a straight shape in which the outer diameter does not change substantially along the longitudinal direction of the copper tube 10. In other words, it is preferable that the enlarged diameter portion 11 is composed only of the tapered portion 11a and the straight portion 11b. With such a shape, the heating electrode can easily 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.

[0038] The expanded diameter portion 21 of the aluminum pipe 20 preferably has a straight shape with an outer diameter that does not change substantially along the longitudinal direction of the aluminum pipe 20. With such a shape, the heating electrode can easily come into contact with the outer surface of the expanded diameter portion 21 when joining the copper pipe 10 and the aluminum pipe 20. This facilitates a uniform flow of current between the electrode and the aluminum pipe 20, improving the efficiency of heating the contact surface and the uniformity of heating at the contact surface. In addition, gaps are less likely to form between the heating electrode or a fixing jig such as a clamp and the aluminum pipe 20. Because heat is less likely to penetrate around the aluminum pipe 20, melting of the aluminum pipe 20 can be prevented even when the copper pipe 10 is sufficiently heated.

[0039] 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.

[0040] The length 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 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 pipe 20, the straight portion 11b of the copper pipe 10 is adjacent to the 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 pipe 20 side, so that the heat dissipation path on the copper pipe 10 side can suppress excessive temperature rise at the contact surface, etc. Furthermore, the heat dissipation path on the copper pipe 10 side can efficiently dissipate heat from the joined body 1 after the eutectic reaction.

[0041] 4 is a cross-sectional view showing an embodiment of a joined body in which a copper pipe and an aluminum pipe are joined together, covered with a heat-shrinkable tube, according to the present invention. As shown in FIG. 4, a 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.

[0042] The heat-shrinkable tube 40 is made of resin and is formed into a cylindrical shape. The heat-shrinkable tube 40 is a covering material that shrinks when heated, thereby 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. Since the copper pipe 10 or aluminum pipe 20 is prevented from coming into contact with the outside air, corrosion due to moisture contained in the outside air, condensation, etc. can be suppressed.

[0043] Examples of materials for the heat shrink tube 40 include polyvinyl chloride, silicone rubber, polyolefin, polystyrene, polyester, polycarbonate, polyamide, polyimide, polyamideimide, polyether ketone, fluororesin, acrylic resin, etc. The shrinkage ratio of the heat shrink tube 40 is not particularly limited, but is preferably 2:1 (50%) or more.

[0044] Examples of polyolefins include polyethylene and polypropylene. Examples of fluororesins include polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene / ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, etc. Examples of acrylic resins include ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, etc.

[0045] The heat shrink tubing 40 may or may not contain additives. Examples of additives include antioxidants, heat stabilizers, metal deactivators, flame retardants, UV absorbers, antistatic agents, colorants, etc. The heat shrink tubing 40 may or may not have an adhesive applied to its surface.

[0046] The copper tube 10 and the aluminum tube 20 constituting the joined assembly 1 are preferably covered with a heat-shrinkable tube 40 in a heat-shrunk state 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 least a portion of 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 the 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 sections prevents contact between the pressure marks and the outside air, effectively suppressing corrosion due to moisture in the outside air, condensation, and the like.

[0047] FIG. 5 is a diagram showing an example of a heat exchanger. The structure of a joined body 1 in which a copper tube 10 and an aluminum tube 20 are joined can be applied to joining to heat transfer tubes of a heat exchanger. FIG. 5 shows a plate-fin heat exchanger as an example of a heat exchanger. As shown in FIG. 5, the heat exchanger 100 includes a plurality of fins 101 that dissipate heat from a working medium, side plates 102 that are arranged to sandwich the plurality of fins 101, and heat transfer tubes 103 that are arranged to penetrate the plurality of fins 101 and the side plates 102 and through which the working medium flows.

[0048] 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 fins 101. The heat exchanger 100 can be provided as, for example, a condenser that condenses the refrigerant of an air conditioner or an evaporator that evaporates the refrigerant.

[0049] 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, thereby promoting heat exchange between the working medium and the air. The multiple fins 101 are stacked in parallel at predetermined intervals. The fins 101 are formed with through holes that penetrate the thickness direction to allow the heat transfer tubes 103 to pass through. The through holes can be formed as burring holes with protruding collars by burring. The through holes are formed in positions that are concentric with each other on the multiple fins 101. The fins 101 are formed of aluminum, an aluminum alloy, or the like.

[0050] The side plates 102 are fixed to both ends of the stacked fins 101. Through holes for inserting the heat transfer tubes 103 are formed in the side plates 102 so as to penetrate the side plates 102 in the thickness direction. The through holes in the side plates 102 are formed in positions concentric with the through holes in the fins 101. The side plates 102 are made of aluminum, an aluminum alloy, stainless steel, or the like.

[0051] 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, a copper alloy, aluminum, an aluminum alloy, or the like.

[0052] In the heat exchanger 100, the working fluid flows into the heat transfer tubes 103 from one side of the stacked fins 101 and flows to the other side, passing through the stacked fins 101. The working fluid then turns around at a bend tube on the other side and flows 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.

[0053] The fins 101, the side plates 102, and the heat transfer tubes 103 are preferably made of aluminum or an aluminum alloy. Aluminum is lightweight and has high corrosion resistance and workability, which is advantageous for reducing the weight of the heat exchanger 100, improving durability, and production. Furthermore, aluminum has lower material costs and is more readily available than copper and other materials, which is advantageous for improving the productivity of the heat exchanger 100.

[0054] 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 tube may be divided into multiple pipe passages by partition walls formed along the short side direction. The fins 101 may be corrugated. The fins 101 and the heat transfer tubes 103 may be joined by crimping or brazing.

[0055] The heat exchanger 100 may also be of a parallel flow type. In the parallel flow type, tank-like headers are arranged on both ends of the stacked fins 101. The working fluid is distributed to a plurality of heat transfer tubes arranged parallel to each other or to a plurality of pipes partitioned inside the heat transfer tubes. Heat exchange is performed by the working fluid being divided into multiple flows that 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.

[0056] Fig. 6 is a cross-sectional view illustrating a primary tube expansion process performed on a heat transfer tube of a heat exchanger. Fig. 7 is a cross-sectional view illustrating a secondary tube expansion process performed on a heat transfer tube of a heat exchanger. Figs. 6 and 7 show cross-sectional views of the fins 101, side plates 102, and heat transfer tubes 103 provided in the heat exchanger 100 shown in Fig. 5, as well as processing tools (110, 120, 130) provided in the tube expansion device, in order to explain the types of tube expansion processes performed on heat transfer tubes.

[0057] 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 of the fin 101. Reference numeral 102a denotes a through hole of the side plate 102. Reference numeral d1 denotes the outer diameter of the heat transfer tube before the primary tube expansion. Reference numeral d2 denotes the outer diameter of the heat transfer tube after the primary tube expansion and before the secondary tube expansion. Reference numeral d3 denotes the inner diameter of the heat transfer tube after the primary tube expansion and before the secondary tube expansion. Reference numeral d4 denotes the inner diameter of the heat transfer tube after the secondary tube expansion.

[0058] 6, when manufacturing the heat exchanger 100, a primary tube expansion process is performed on 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. The heat transfer tubes 103 are fixed to the fins 101 by the primary tube expansion process.

[0059] The fins 101 are made by pressing a plate material that has been subjected to a surface treatment for hydrophilicity. 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 a tube material. The heat transfer tubes 103 are bent into a U shape by bending.

[0060] 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 so as to sandwich the multiple fins 101. The stack of fins 101 is fixed onto a receiver plate of a tube expanding device capable of supporting the U-shaped bent side by side clamps that support the side surface, 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 face the same direction.

[0061] 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 a plurality of mandrels 110 arranged in parallel so that they can be inserted from the ends of a plurality of heat transfer tubes 103 that are arranged in parallel so that they face 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.

[0062] 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 provided with an outer diameter that is larger than the inner diameter of the base tube of the heat transfer tube 103 and is equal to the target inner diameter of the heat transfer tube 103 by 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 the outer diameter and inner diameter are expanded. As a result, the outer surface of the heat transfer tube 103 comes 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.

[0063] The primary pipe 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 pipe expansion is calculated by the following formula (1). (Expansion rate of primary expansion) [%] = [(outer diameter after primary expansion d2) - (outer diameter before primary expansion d1)] / (outer diameter before primary expansion d1) × 100 (1)

[0064] 7, after the primary expansion of the heat transfer tube 103, a secondary expansion process is performed on the end of the heat transfer tube 103 inserted into the through-hole 101a of the fin 101 or the through-hole 102a of the side plate 102. The secondary expansion process makes it possible to connect other tubes to the heat transfer tube 103 having a smaller diameter.

[0065] After the primary expansion of the heat transfer tubes 103, a secondary expansion head 130 fixed to the middle part of the mandrel 110 is inserted into the end of the heat transfer tube 103. The secondary expansion head 130 is inserted into the open 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 face the same direction.

[0066] The secondary tube expansion head 130 has a tapered tip surface. The secondary tube expansion head 130 is provided with an outer diameter larger than the inner diameter of the heat transfer tube 103 after the primary tube expansion process and equal to the target inner diameter of the heat transfer tube 103 after the secondary tube expansion process. The heat transfer tube 103 is plastically deformed by the pressure generated by inserting the secondary tube expansion head 130, and its outer and inner diameters are expanded. 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 in contact with multiple fins 101, which are heat transfer plates that perform heat exchange, on its outer periphery, and a joint section 103b located at the end of the heat exchange section 103a, with an inner diameter larger than the inner diameter of the heat exchange section 103a, to which other pipes are joined.

[0067] The secondary tube expansion process 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 of joint after secondary expansion d4) - (inner diameter of heat exchange section before secondary expansion d3)] / (inner diameter of heat exchange section before secondary expansion d3) × 100 (2)

[0068] Next, the mandrel 110 is pulled out from 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, bent tubes are brazed to the ends of the heat transfer tubes 103 to connect the heat transfer tubes 103 together.

[0069] The joined body 1 in which the copper pipe 10 and the aluminum pipe 20 are joined can be applied to joining the heat transfer tube 103 of such a heat exchanger 100. The joined body 1 in which the copper pipe 10 and the aluminum pipe 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 applied to joining the copper pipe 10 to the aluminum pipe 20 that is the heat transfer tube 103 of the heat exchanger 100, or to joining the copper pipe 10 to the aluminum pipe 20 that is the refrigerant pipe connected to the heat transfer tube 103 of the heat exchanger 100.

[0070] The difference between the maximum and minimum outer diameters of the enlarged diameter portion 11 of the copper tube 10 and the difference between the maximum and minimum outer diameters of the enlarged diameter portion 21 of the aluminum tube 20 are preferably smaller than the difference between the maximum and minimum outer diameters of the heat transfer tube of the heat exchanger connected to the rear end of the aluminum tube 20. Generally, the inner diameter of the heat transfer tube of the heat exchanger is primarily controlled for heat transfer calculation purposes. On the other hand, it is desirable to control the outer diameters of the copper tube 10 and the aluminum tube 20 constituting the assembly 1 in order to ensure the contact area between the copper tube 10 and the aluminum tube 20. With such a relationship between the outer diameter differences, the effect of limiting the outer diameter of the rear end of the tapered portion 11a of the copper tube 10 can be more reliably achieved.

[0071] The expansion ratio of the expanded diameter portion 11 of the copper tube 10 and the expansion ratio of the expanded diameter portion 21 of the aluminum tube 20 are preferably greater than the expansion ratio of the secondary expansion applied to the end of the heat transfer tube of a heat exchanger connected to the rear end of the aluminum tube 20. Internally grooved tubes are generally 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 groove bottom is generally thinner than that of an ungrooved tube. Therefore, when comparing tubes with the same outer and inner diameters, the expansion ratio of the secondary expansion 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 the 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 a fluid, such as refrigerant noise.

[0072] 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)

[0073] The expansion ratio of the expanded diameter portion 21 of the aluminum pipe 20 is calculated by the following formula (4). (Expansion ratio of the expanded portion of the aluminum pipe) [%] = [(inner diameter D3 of the expanded portion of the aluminum pipe) - (inner diameter D4 of the non-expanded portion of the aluminum pipe)] / (inner diameter D4 of the non-expanded portion of the aluminum pipe) × 100 (4)

[0074] Fig. 8 is a diagram showing an example of the configuration of an air conditioner according to an embodiment of the present invention. A joined body 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 Fig. 8, the air conditioner 200 includes 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.

[0075] 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. A 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, and then blows the air out into the room to adjust the temperature and humidity inside the room.

[0076] The air conditioner 200 includes 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 devices 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.

[0077] 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 in 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.

[0078] 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, the four-way valve 203, the outdoor heat exchanger 204, the expansion valve 205, the accumulator 207, and the outdoor blower fan 208 are housed in an outdoor unit 210. The indoor heat exchanger 206 and the indoor blower fan 209 are housed in an indoor unit 220.

[0079] The compressor 202 is a device that compresses a refrigerant, sucking in a low-pressure gas refrigerant, compressing it adiabatically, and discharging it as a high-pressure gas refrigerant. The compressor 202 variably controls the amount of refrigerant circulated by inverter control. The compressor 202 can be of any suitable type, such as a scroll type, piston type, rotary type, screw type, or centrifugal type.

[0080] The four-way valve 203 has four ports and changes the flow path between the ports depending on the operating mode, such as cooling operation or heating operation, of the air conditioner 200. The four-way valve 203 switches the circulation direction in the refrigerant circuit 201 of the refrigerant discharged from the compressor 202.

[0081] 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 to 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 whose opening degree can be adjusted, and functions as a pressure reducer during heating operation.

[0082] 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 to 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.

[0083] Accumulator 207 is a tank-shaped device that separates refrigerant gas from liquid refrigerant, and separates and stores the liquid refrigerant contained in the refrigerant gas. By removing the liquid refrigerant that has not completely evaporated from the refrigerant gas on the suction side of compressor 202, liquid compression by compressor 202, which can lead to abnormal noise and breakdowns, is prevented.

[0084] Cooling operation of the air conditioner 200 is performed as follows. High-temperature, high-pressure gas refrigerant adiabatically compressed by the compressor 202 is 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 by heat exchange with outside air in the outdoor heat exchanger 204, which functions as a condenser. The liquid refrigerant is decompressed and expanded by the expansion valve 205, becoming a low-temperature, low-pressure two-phase gas-liquid refrigerant containing a small amount of gas refrigerant.

[0085] 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 a 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 loses heat 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.

[0086] Heating operation of the air conditioner 200 is performed in a cycle reverse to that of 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 a liquid refrigerant. The liquid refrigerant is decompressed by the expansion valve 205 and becomes a low-temperature, low-pressure liquid refrigerant.

[0087] 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 a 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.

[0088] 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, an aluminum alloy, or the like. The side plates of the outdoor heat exchanger 204 and the indoor heat exchanger 206 are made of aluminum, an aluminum alloy, stainless steel, or the like. The heat transfer tubes of the outdoor heat exchanger 204 and the indoor heat exchanger 206 are made of copper, a copper alloy, aluminum, an aluminum alloy, or the like.

[0089] At least one of the outdoor heat exchanger 204 and the indoor heat exchanger 206 preferably has a heat transfer tube made of aluminum or an aluminum alloy, and more preferably has the fins, heat transfer tubes, etc., entirely made of aluminum or an aluminum alloy. From the viewpoint of weight reduction, size, and other requirements, it is preferable that at least the indoor heat exchanger 206 be made entirely of aluminum.

[0090] The structure of the joined body 1 in which the copper pipe 10 and the aluminum pipe 20 are joined can be applied to joining to the heat transfer tube of the outdoor heat exchanger 204 or to joining to the heat transfer tube of the indoor heat exchanger 206. The rear end of the aluminum pipe 20 constituting the joined body 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 tube 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 tube of the outdoor heat exchanger 204 or the indoor heat exchanger 206.

[0091] When the rear ends of the aluminum tubes 20 constituting the assembled body 1 are 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 portions 11 of the copper tubes 10 constituting the assembled body 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 ends of the aluminum tubes 20 and the difference between the maximum and minimum outer diameters of the heat transfer tubes of the indoor heat exchanger 206 connected to the rear ends of the aluminum tubes 20. Furthermore, the difference between the maximum and minimum outer diameters of the expanded diameter portions 21 of the aluminum tubes 20 constituting the assembled body 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 ends of the aluminum tubes 20 and the difference between the maximum and minimum outer diameters of the heat transfer tubes of the indoor heat exchanger 206 connected to the rear ends of the aluminum tubes 20. This relationship in the outer diameter difference more reliably achieves the effect of limiting the outer diameter of the rear ends of the tapered portions 11a of the copper tubes 10.

[0092] When the rear end of the aluminum pipe 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 to the inner diameter of the non-expanded portion 13 of the copper pipe 10, expressed by equation (3), is 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 pipe 103 of the outdoor heat exchanger 204 connected to the rear end side of the aluminum pipe 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 pipe 103 of the indoor heat exchanger 206 connected to the rear end side of the aluminum pipe 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 formula (4), is preferably larger 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 a tube expansion ratio relationship, the flow resistance of the copper tube 10 or the aluminum tube 20 is smaller than the flow resistance of the inner grooved tube that constitutes the heat transfer tube, thereby more reliably suppressing abnormal noise associated with the flow of a fluid, for example, refrigerant noise associated with the flow of a refrigerant.

[0093] 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 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.

[0094] 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. Bonding using the eutectic bonding method can be more time-consuming and costly than general brazing. By limiting the location where the bonded body 1 is formed to the periphery of the indoor heat exchanger 206, it is possible to facilitate installation of the air conditioner 200 while ensuring bonding strength and airtightness around the indoor heat exchanger 206 and suppressing refrigerant noise.

[0095] 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 preferable that the joined body 1 is formed at least in a section of the refrigerant circuit connecting the indoor heat exchanger 206 and the four-way valve 203. The joined body 1 is preferably formed in the refrigerant piping located downstream of the indoor heat exchanger 206 during cooling operation, at least in 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 a 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 in the refrigerant piping located upstream of the indoor heat exchanger 206 during cooling operation, not in the upstream refrigerant piping connected to the indoor heat exchanger 206.

[0096] 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, and 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, and low-temperature, low-pressure gas-liquid two-phase 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. By limiting the location where the joined body 1 is formed to the four-way valve 203 side of the indoor heat exchanger 206, refrigerant noise can be effectively suppressed while facilitating installation around the indoor heat exchanger 206.

[0097] The joined body 1, in which the copper pipe 10 and the aluminum pipe 20 are joined, is preferably formed at all the locations where the copper pipe and the aluminum pipe are joined in the indoor heat exchanger 206. Since the indoor heat exchanger 206 is installed indoors, it is required to ensure the sealing of the refrigerant circuit and suppress refrigerant noise. If the joined body 1 is formed at all the locations of the indoor heat exchanger 206, it is possible to more reliably ensure the joining strength and sealing of the indoor heat exchanger 206 and suppress refrigerant noise.

[0098] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and includes various modifications without departing from the technical scope. For example, the above-described embodiments are not necessarily limited to those including all of the configurations described above. 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. Furthermore, it is also possible to add other configurations to, delete configurations from, or replace part of the configuration of an embodiment.

[0099] For example, the copper pipe 10 and the aluminum pipe 20 constituting the joined body 1 have non-expanded portions 13, 23 that are not expanded relative to the base pipes, but the non-expanded portions 13, 23 may be subjected to other processes such as expansion, except for the expansion process for joining the copper pipe 10 and the aluminum pipe 20. The non-expanded portions 13, 23 are not limited to a linear shape, and may be formed into a curved, bent, or other bent shape.

[0100] The air conditioner 200 may also be equipped with devices that constitute a refrigerant circuit (not shown), such as a receiver, an oil separator, a dryer, etc., and sensors such as temperature sensors that measure the temperature of 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 evaporator from the condenser.

[0101] 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. [Explanation of symbols]

[0102] 1 zygote 10 copper tube 11 Expanded diameter part 11a Tapered section 11b straight section 12 Reduced diameter part 13 Non-expanded section 20 Aluminum tubes 21 Expanded diameter part 22 Reduced diameter part 23 Non-expanded section 30 Eutectic phase 40 Heat shrink tubing 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 ventilation fan 209 Indoor ventilation fan 210 Outdoor unit 220 Indoor unit

Claims

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

Images