JPS59150632A - Manufacturing method of flat tube - Google Patents

Abstract

PURPOSE:To produce a flat tube having excellent accuracy in the straightness in both straight pipe parts and the distance between said parts by grasping a copper U-shaped tube having a circular section between tools each having a desired flat shaped groove and compressing said tube with a pressing member having wedge surfaces. CONSTITUTION:A copper tube having a circular section is bent 180 deg. while the circular shape of the section is maintained, thereby forming a U-shaped tube 2'. The straight pipe parts of such tube 2' are grasped in the grooves of tools 4, 4' each having a groove of a desired flat section. A wedge-shaped pressing tool 5 having the same slope is forced onto the sloped outside surface of the tools 4, 4' and is pressed from above to bring both tools 4, 4' into press contact with each other thus flattening the section in the straight pipe parts of the U-shaped tube grasped thereon. The flat tube for a heat exchanger having excellent accuracy in the straightness in both straight pipe parts of the U-shaped tube and the distance between the same is produced.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for manufacturing flat tubes used in heat exchangers for air conditioners, etc. Regarding the method.

[Prior art]

As shown in Fig. 1, a plate-fin heat exchanger used in air conditioners, etc. consists of a large number of plate-shaped fins 1 and a pipe line 2 through which a heat medium passes through the fins. or the fluid to be heated (air in air conditioners)
passes between the fins in a direction perpendicular to the tube axis. In the past, the cross-sectional shape of pipes was generally circular, but recently, designs have been developed to reduce the flow resistance of fluid passing between the pipes by using pipes with flat cross-sections, as shown in Figure 2. It's starting to change.

In order to manufacture a conduit as shown in Fig. 1, it is best to alternately connect U-shaped pipes 2' with long straight pipe parts and elbows 2'' with almost no straight pipe parts, as shown in Fig. 3. Common.U-shaped tube 2
From the viewpoint of insertability into the fin group, it is required that the mutual spacing between the two straight pipe portions be highly accurate and that the straight pipe portions have high straightness. Furthermore, as is clear from Fig. 2, the precision of the angle θ between the main axis of the flat cross-section and the U-shaped surface is also required, so machining of a U-shaped tube with a flat cross section is similar to machining of a circular cross-section tube. is much more difficult than.

The present inventors have previously proposed a manufacturing method for a tube in which the angle θ between the flat main axis and the U-shaped surface shown in FIG. 2 is larger than a certain angle. However, especially in small air conditioners where the volume of the heat exchanger needs to be reduced, θ=00U
Tubes may be required. In the above invention, after bending a circular tube into a U-shape, the straight tube portions at both ends are simultaneously compressed using a pair of dies, thereby producing a flat U-shaped tube with high precision in the axis distance of the blood vessel portion. can do. However, if the value of θ is small, the tool will interfere and
Simultaneous molding of the inner straight pipe section becomes impossible. Individually flattening the inner straight pipe portions results in a decrease in the accuracy of the distance between the shafts. To avoid this, a method is required that simultaneously processes the double-sided tube while keeping the distance between both axes constant during flattening.

Furthermore, as a manufacturing means for air conditioners and the like, high mass production processability is also required.

[Purpose of the invention]

It is an object of the present invention to target a flat U-shaped tube in which the helix angle θ is 00 as shown in FIG. An object of the present invention is to provide a method for manufacturing a flat tube.

[Summary of the invention]

In the present invention, in order to improve the accuracy of the distance between the axes of the straight pipe parts, a straight pipe with a circular cross-sectional shape is precisely bent, and then the straight pipe part is straightened and flattened. Compression molding is done using a special tool that was invented. This tool consists of a pair of compression tools each corresponding to the inner straight pipe section, and the movement of the compression tools is all synchronized by the movement of the suppression member having multiple wedge surfaces, so that even during machining, the axis of the double-sided pipe is The above objective was achieved by flattening the straight pipe portion while keeping the distance constant.

[Embodiments of the invention]

The present invention will be explained in detail below using examples.

Here, we will explain step by step how to manufacture U-shaped tubes with a flat cross section, using steel tubes used in heat exchangers for air conditioners as an example.

The material steel pipe has a circular cross section and the thickness of the ram is approximately 3 to 3 times the outside diameter.
．． It is 5%. The length of the straight pipe portion of the U-shaped pipe to be manufactured is 50 times or more the outer diameter of the pipe.

The processing process consists of the following two steps. In the first step,
The pipe is bent at a bending angle of 180° while keeping its cross section circular. It is desirable to adopt a precise bending method such as the mutual axis P21) of the straight pipe parts of a U-shaped pipe.

In the second step, the two straight pipe portions of the U-shaped tube obtained in the above step are flattened simultaneously. The structure and function of the special tool used here will be explained with reference to FIGS. 4 and 5.

FIG. 4 is a processed cross-sectional view showing the positional relationship of each member at the time of starting the process, and FIG. 5 is the positional relationship of each member at the end of the process. First, a U-tube 2' of circular cross section is inserted between a pair of tools 4 and 4' having grooves of the same shape as the profile of the desired flat tube. Since there are two straight pipe parts in one U-shaped pipe, two pairs of flattening tools are also required. The distance between each tool is 4th
As shown in the figure, it is set equal to the distance P between the axes of the blood vessel parts of the U-shaped tube. The flattening tools 4 and 4' have sloped outer surfaces, and are fitted into a wedge-shaped suppression tool 5 having the same slope as the sloped surface. Flattening is performed by pushing the suppression tool 5 into the holder 6. The positional relationship of the tools after machining is as shown in Figure 5.

The four wedge surfaces of the suppression tool each move the four flattening tools synchronously, so that the two pairs of flattening tools slide on the holder 6 without changing the distance P between their centers. , block the machined surface. By this movement, the UU-shaped tube 2' is flattened without changing the distance between the axes of the straight pipe portions, and a highly accurate flat U-shaped tube can be obtained.

The present invention is excellent in mass productivity in that not only a single U-shaped tube but also a plurality of U-shaped tubes can be flattened at the same time. FIG. 6 is an overview of machining when three U-shaped tubes are machined at the same time. The tools are in the form of the single U-tube machining tools shown in FIGS. 4 and 5 that are laterally connected. One stroke of the ram of the press presses the wedge-shaped suppression tool 5 in the direction shown in FIG. 7, making it possible to form three U-shaped tubes at the same time.

〔Effect of the invention〕

According to the present invention, the following effects can be obtained.

Since the U-shaped tube is flattened while maintaining a constant distance between the axes of the two straight tubes, a flat U-shaped tube with high dimensional accuracy can be formed. Furthermore, since it is easy to mold a plurality of U-shaped tubes at the same time, it is also excellent in mass productivity.

As a result, it is required for compact heat exchangers, such as those used in small air conditioners. Flat '[J
It became possible to manufacture double-shaped tubes.

[Brief explanation of the drawing]

Figure 1 is a side view showing the structure of the plate-fin heat exchanger, Figure 2 is a cross-sectional view taken along line A-A in Figure 1, and Figure 3 is a cross-sectional view showing the structure of the plate-fin heat exchanger.
Figures 4 and 5 are cross-sectional views of the processing tool used in the present invention, respectively showing the start and end of processing, and Figure 6 is a diagram of the U-shaped pipe and elbow that make up the pipe line in the figure. FIG. 4 is an overview diagram of processing when flattening a plurality of U-shaped tubes at the same time. 1...Fin, 2...Pipeline, 2'...U-shaped tube, 2
"... Elbow, 3... Direction of fluid flow passing through the heat exchanger, 4... Flat processing tool, 4'... Flat processing tool, 5... Wedge-shaped suppression tool, 6... ·holder,
7... Suppressing direction of the wedge-shaped pressing tool, θ... Angle between the flat main axis of the tube and the U-shaped surface, P... Mutual flatness of a pair of straight pipe parts of the U-shaped tube 4 Figure 5 Figure 1: Akane Okishi JP-A-59-150632 (4) Figure 2

Claims (1)

[Claims] ■ A suppression tool having a plurality of wedge surfaces is simultaneously pushed between a plurality of rows of forming tools to maintain a constant distance between the axes of the straight pipe portion of the U-shaped pipe that is the workpiece. A method for manufacturing a flat tube, which is characterized by flattening a circular tube while maintaining the same shape. 2. The method for manufacturing a flat tube according to item 1, characterized in that the plurality of U-shaped pipes are processed at the same time.