JPS598461B2 - How to connect aluminum tubes with fins for heat exchangers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for connecting finned aluminum tubes constituting a heat exchanger used as an evaporator or as a condenser, for example in refrigerators, low-temperature showcases, room coolers, etc.

For example, in the evaporator of a refrigerator, it is necessary to connect a finned aluminum tube and a copper tube, and conventionally this connection has been made by flash welding or pad welding.

However, the cross-sectional shape of conventional finned aluminum tubes is generally rectangular, as shown in FIG. 3, while the cross-sectional shape of copper tubes is circular. Therefore, when connecting these two by the method described in L, the connecting blue,
A copper-aluminum joint pipe with a predetermined cross-sectional shape is interposed between the aluminum pipe and the joint pipe, and the joint pipe and the copper pipe are each heated with argon.
The connections were made using arc welding. However, according to this conventional method, even though two pipes, a finned aluminum pipe and a copper pipe, are connected, there are two welding points, which increases the number of leakage points, and Since an extra joint pipe is used to connect both pipes, there is a problem that it is wasteful and uneconomical. The method of connecting finned aluminum tubes for heat exchangers according to the present invention has been made in order to solve the above problems, and has a large number of tongue-like fins formed by cutting on both the upper and lower surfaces, and has a connecting end. A process of preparing an aluminum pipe with a circular cross-sectional joint surface, and immersing the joint end of a copper pipe with a circular cross-section in a plating layer made of zinc or molten zinc-based alloy, and during the immersion, a plating bath or A process of applying ultrasonic vibration to a copper pipe to form a plating layer of zinc or zinc-based alloy on the joint surface of the joint end, and heating the plating layer of the copper pipe to bring it into at least a semi-molten state. This method is characterized by the step of fitting the joint end of the copper pipe and the joint end of the aluminum pipe to join their joint surfaces to each other.

In the above, the cross-sectional shape of the joint surface of the joint end of the finned aluminum pipe is circular, similar to the cross-sectional shape of the joint surface of the joint end of the copper pipe, and both joint ends are fitted into each other. For example, there are the following two types.

First, as shown in Figure 1, we cut both the top and bottom of an extruded aluminum tube material so that the cross-sectional shape of the inner peripheral surface is a perfect circle, and the cross-sectional shape of the outer peripheral surface is approximately rectangular. A large number of tongue-like fins 2 are formed in a row in the axial direction of the aluminum tube 1 by cutting the tube material in the transverse direction using a cutting tool. The cross-sectional shape of the inner circumferential surface of the refrigerant passage 3 of the aluminum tube 1 manufactured in this manner is a perfect circle, and the outer circumferential surface of the tube 1 is rectangular in cross-section. On the other hand, the outer peripheral surface of the joint end 4a of the copper tube 4 is drawn and tapered so that it can be smoothly inserted into the joint end 1a of the aluminum tube 1. Secondly, as shown in Figure 3,
In the conventional aluminum tube 11 having a large number of tongue-like fins 12 on the upper and lower surfaces, both the inner and outer surfaces of the refrigerant passage 13 are square in cross section, but in the present invention, the joint end 11a of this tube is expanded. The joint end portion 21a is deformed into a cylindrical shape as shown in FIG.
An aluminum tube 21 is made in which only the cross-sectional shape is circular and the other portions are square in cross-sectional shape. This tube 2
The cross-sectional shape of the inner peripheral surface of the first refrigerant passage 23 is circular at the joint end 21a, and rectangular at other parts. Also, a large number of tongue-like fins 2 are provided on both the upper and lower surfaces of the tube 21.
2 is provided in the same manner as in the case of S shown in Fig. 3 above. On the other hand, the outer peripheral surface of the joint end 24a of the copper tube 24 is drawn in the same way as in the above case, and is tapered so that it can be inserted into the joint end 21a of the aluminum tube 21. In this case, conversely, the joint end 24 of the copper pipe 24
The inner diameter of a is larger than the outer diameter of the joint end 21a of the aluminum 5 aluminum tube 21, and the joint end 24a of the copper tube 24 is
It is also possible to externally fit the joint end portion 21a of the aluminum tube 21. In addition, the above finned aluminum tubes 1 and 2
1 and the copper tubes 4 and 24 are preferably fitted as tightly as possible for reasons described later. The composition of the zinc or zinc-based alloy molten metal is pure Zn or AtlO%, Cu5%.
, balance Zn, and particularly those consisting of 5% At, balance Zn, or 8% At, 4% Cu, balance Zn.
Preferably something with more than 4 dimensions.

It is not so preferable to use pure Zn, and it is preferable to use a molten alloy having a eutectic composition of aluminum and zinc, that is, an aluminum content higher than 5%. Further, the addition of copper makes it easier to detect aging of the copper pipe when it is immersed in a molten zinc-based alloy. In addition, At 10%, C
If u is added in excess of 5%, the melting point will rise, resulting in poor melt flow. Further, as a method of applying the above-mentioned ultrasonic vibration, it is particularly preferable to apply high vibration of about 24 to 27K1Iz to the plating bath.

Further, the heating during the above-mentioned fitting is performed by a burner, and the temperature thereof is approximately 350 to 420°C.

The aluminum tube and the copper tube are then fitted together while being heated, and if the clearance is kept as small as possible at this time, the semi-molten or molten plating layer will be squeezed and built up on the end of the tube inserted inside. This makes it possible to completely eliminate the problem of leakage defects. Next, embodiments of the invention will be described with reference to the drawings.

This example relates to a finned aluminum tube and a copper tube in a refrigerator evaporator. First, a case will be described in which the finned aluminum tube 1 and the copper tube 4 shown in FIG. 1 are connected.

A finned aluminum tube 1 having an inner circumferential surface having a perfect circular cross-sectional shape and an outer circumferential surface having a rectangular cross-sectional shape is prepared.
On the other hand, the outer peripheral surface of the joint end 4a of the copper tube 4 is drawn and tapered so as to fit inside the joint end 1a of the aluminum tube 1. Next, At7%, Cul%,
A plating bath consisting of the remainder Zn is prepared in a stainless steel crucible, and after preheating the copper tube 4 whose end is drawn, the part to be fitted is immersed in the plating bath. 26 in this plating bath
Apply ultrasonic vibrations of about KHz. This removes dirt and oxide film adhering to the surface of the copper tube, and forms a uniform plating layer. Furthermore, since the surface tension of the bath is reduced by ultrasonic waves, the fluidity of the bath is improved, promoting wetting and improving plating properties. Next, as shown in FIG. 2, the joint end 4a of the copper pipe 4 having the zinc-based alloy plating layer 5 on the outer peripheral surface is connected to the joint end 1a of the aluminum pipe 1 as described above.
Insert inside. At this time, heat it to 400℃ with a burner,
The plating layer 5 at the end of the copper tube 4 is melted and fitted. After this fitting, an ultrasonic soldering gun is applied to the outer surface of the joint end 1a of the aluminum tube 1, and ultrasonic waves having a frequency of about 20 KHz are applied for about 2 seconds. When the molten plating layer solidifies after fitting in this manner, the space between the overlapping portions of the two tubes 1 and 4 is completely filled with the plating layer 5, thus completing the pipe connection. Note that the connection between the finned aluminum tube 21 and the copper tube 24, whose joint end 21a has a circular cross-sectional joint surface formed by tube expansion, as shown in FIG. be able to.

According to the present invention, as described above, the joint end of the finned aluminum tube has a joint surface having a circular cross section, and the joint end of the copper pipe having the joint surface having a circular cross section is directly fitted to this joint end. Because they are connected together, there is no need to use a copper-aluminum joint pipe as in the conventional method, and the number of parts for connecting both pipes can be reduced, reducing material costs to the minimum necessary. It is economical to do so.

Furthermore, since dirt and oxide film on the surface of the copper tube are removed during plating by ultrasonic vibration, the bond with the aluminum tube becomes tighter. Furthermore, since the plating layer of copper pipes is heated to melt or semi-molten it, fitting is easy, and the plating layer is squeezed to form a thickening at the end of the inner tube. Since the plating layer is densely present at the seam between the two tubes, leakage defects will not occur. Moreover, since the finned aluminum tube is directly connected to the copper tube, there is only one joint, and the number of joints is reduced compared to the conventional method, which has the effect that liquid leakage is less likely to occur.

[Brief explanation of drawings]

Fig. 1 is a partial perspective view showing the process of fitting a finned aluminum tube and a copper tube in the first embodiment of the present invention, Fig. 2 is an enlarged sectional view of the main part after fitting, and Fig. 3 is a conventional finned aluminum tube and a copper tube. FIG. 4 is a partial perspective view showing the aluminum tube with
FIG. 2 is a partial perspective view showing the finned aluminum tube and the copper tube in the process of being fitted together in the example. 1, 21... Aluminum tube, 1a, 21a.
...its joint end, 2,22...tongue-like fin,
3, 23... Refrigerant passage, 4, 24...
Copper tubes, 4a, 24a... Their joint ends, 5...
...Plating layer.

Claims (1)

[Claims] 1. A process of preparing an aluminum tube having a large number of tongue-like fins formed by cutting on both the upper and lower surfaces and having a circular cross-sectional joint surface at the joint end, and a joint end of a copper pipe with a circular cross-section. is immersed in a plating bath made of molten zinc or zinc-based alloy, and during the immersion, ultrasonic vibration is applied to the plating bath or the copper tube to form a plating layer of zinc or zinc-based alloy on the joint surface of the joint end. The process involves heating the plating layer of this copper pipe to bring it to at least a semi-molten state, and then fitting the joint end of the copper pipe and the joint end of the aluminum pipe together so that their joining surfaces are mutually connected. A method for connecting finned aluminum tubes for heat exchangers, which involves a joining process.