JP2001091178A - Flat tube for aluminum heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flat tube for aluminum heat exchanger having substantially B-shaped cross-section and coated with a solder material and a sacrifice anode material, respectively, on the outer and inner surfaces thereof in which the inner surface side of the tube is protected against corrosion due to the solder material flowing out from an abutting part. SOLUTION: Opposite edge parts are bent inward to abut against each other and the forward ends thereof are bent to depart from each other thus making an enlarged part 5. The enlarged part 5 abuts against the top of a part having protruding cross-section 4 formed on the inner surface of a tube and the abutting part is secured by soldering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a flat tube for a heat exchanger by bending an aluminum brazing sheet, and more particularly, to a flat tube having a sacrificial anode material coated on an inner surface thereof and a solder tube on an outer surface of the tube. The present invention relates to a material which is covered with a material and has a substantially B-shaped cross section.

[0002]

2. Description of the Related Art In an aluminum heat exchanger,
A brazing sheet is often used as a material for the flat tube. The material is A300 as core material
An aluminum alloy such as A3203 or A3203 is coated with an aluminum alloy such as A4343 as a brazing material on one surface, and an aluminum alloy such as A7072 is coated as a sacrificial anode material on the other side. Such a brazing sheet is bent in the width direction by a forming roller to be formed into a flat tubular shape as shown in FIGS. 3 and 4, and both ends of the strip-shaped aluminum plate are each formed into an inverted L-shaped cross section on the inner surface side of the tube. A flat tube 10 has been proposed in which the flat tube 10 is formed in the shape of a tube, butted against the opposite flat surfaces of the inverted L-shape to form a butted portion 9a, and the tip of the butted portion is brought into contact with the center of the inner surface of the tube. ing. Such a flat tube 10 comes into contact with the fins 7 on the outer surface side, is heated in a high-temperature furnace as a whole, melts the brazing material, and integrally brazes the components as shown in FIG. In addition, the gap between the tubes is brazed to form a liquid-tight structure.

[0003]

As shown in FIG. 4, when the tip of the butted portion 9a of the flat tube 10 is joined to the center of the inner surface of the tube, the brazing material 8a flows out to the joined portion, and the sacrificial anode on the inner surface of the tube at that portion. There is a problem that the effect is impaired, and the corrosion of that portion is apt to proceed. In other words, when the surface of the sacrificial anode material 2 is coated with the brazing material 8a, a potential difference occurs at the end thereof, and erosion such as erosion is concerned. Then, this invention makes it a subject to solve such a problem.

[0004]

According to the present invention, a strip-shaped metal plate in which a sacrificial anode material 2 is coated on the inner surface of a core material 1 and a brazing material 3 is coated on the outer surface is bent in the width direction to flatten the flat metal plate. In a flat tube for an aluminum heat exchanger, which is formed in a tubular shape and whose joint portion is bent and protruded toward the inner surface and has a substantially B-shaped cross section, both edges of the joint portion are in contact with each other. As shown in the figure, the inner surface is bent so that the leading edges thereof are separated from each other, and has an expanded portion 5 expanded in a C-shaped cross section, and the inner surface facing the joint portion. Is a flattened tube for an aluminum heat exchanger in which a cross-section convex portion 4 is formed by folding back, and the expanding portion 5 is located at the top of the convex portion 4 so as to be joined to each other. .

[0005]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a main part of a flat tube for a heat exchanger of the present invention, showing a state before brazing. FIG. 2 is a cross-sectional view showing the state after brazing. In this flat tube for heat exchanger, the band-shaped metal plate is made of aluminum brazing sheet,
The core material 1 has an outer surface coated with a brazing material 3 and an inner surface coated with a sacrificial anode material 2. The brazing sheet having an appropriate width thus formed is bent in the width direction by a forming roll or the like to form a flat tube, and both edges thereof are bent in reverse L-shaped sections on the inner surface side of the pipe, respectively. The inverted L-shaped portions are brought into contact with each other, and are bent in a C-shaped cross section so that the respective tips are separated from each other, thereby forming the expanded portion 5 there. Then, the inner surface side of the opposing surface of the expanding portion 5 is folded back and bent to form a convex section 4, and the expanding section 5 is located at the top of the convex section 4, and they contact each other.

[0006] Thus, the flat tube 6 is formed,
The fins 7 are arranged on the outer surface side, and the whole is inserted into a high-temperature furnace in a state where both ends in the axial direction of the flat tubes 6 are inserted into tube insertion holes of a tube plate (not shown) to melt the brazing material 3. Then, it is cooled and solidified to form an inverted L-shaped bent contact portion 9 between the fin 7 and the outer surface of the flat tube 6, a convex portion 4 in cross section, and an expanded portion 5 as shown in FIG. And are integrally brazed and fixed. At this time, the brazing material slightly flows out from the tip of the bending contact portion 9, and the brazing material 4
Is held at the top. However, the top is double-formed with an aluminum plate, which is reinforced against corrosion and the like. When the flat tube 6 and the fin 7 are assembled and the whole is held as shown in FIG.
, The shape is maintained and brazing is performed accurately.

[0007]

In the flat tube for an aluminum heat exchanger of the present invention, a convex section 4 is formed in a bent shape on the inner surface of the tube, and the tip of a bent contact section 9 is formed on the top of the convex section 4. Is formed so that the C-shaped expansion portion 5 is located and the two are brazed to each other. Therefore, alignment between the expanded portion 5 and the top of the cross-section convex portion 4 can be easily performed, and a reliable fillet of the brazing material 3 can be formed there. Since the top of the cross-section convex portion 4 and the bending contact portion 9 are joined by brazing, the brazing material 3 is held between the double bent portions on the inner surface side of the tube, and Even if erosion occurs at the top, the flat tube 6 does not leak. In other words, when the brazing material 3 is coated on the protruding section 4, a potential difference is generated between the sacrificial anode material 2 and erosion is feared. However, the present invention can sufficiently withstand the erosion because the thickness of the top portion to be brazed is doubled.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing a state before brazing of a flat tube for an aluminum heat exchanger of the present invention before brazing.

FIG. 2 is a cross-sectional view of a main part showing a state of the flat tube for an aluminum heat exchanger after brazing.

FIG. 3 is a schematic cross-sectional view of a conventional flat tube for a heat exchanger.

FIG. 4 is a cross-sectional view of a main part of a conventional flat tube for a heat exchanger.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core material 2 Sacrificial anode material 3 Brazing material 4 Cross section convex part 5 Expanding part 6 Flat tube 7 Fin 8 Brazing part 8a Brazing material 9 Bend contact part 9a Butt part 10 Flat tube

Claims (1)

[Claims] A sacrificial anode material 2 is coated on an inner surface of a core material 1 and a band-shaped metal plate coated with a brazing material 3 on an outer surface is bent in the width direction to form a flat tube. In a flat tube for an aluminum heat exchanger having a joint portion bent and projected to the inner surface side and having a generally B-shaped cross section, the joint portion is bent inward so that both edges of the joint portion abut against each other. At the same time, the distal end edges are bent so as to be separated from each other, and have an expanded portion 5 expanded in a C-shaped cross section, and a cross-sectional convex portion 4 is folded back on the inner surface facing the joint portion. A flat tube for an aluminum heat exchanger, which is formed in a bent shape, wherein the enlarged portion 5 is located at the top of the convex portion 4 and is joined to each other.