JPS61273227A - Method and device for producing flat tube for heat exchanger - Google Patents

Abstract

PURPOSE:To enable the forming of the flat tube having high straightness and accuracy by forming with compression the straight pipe part of a circular pipe by the upper and lower opposing dies providing the groove with smaller width than the diameter of the circular pipe. CONSTITUTION:The U-shaped pipe 2' with circular cross section is subjected to a compression work with pressing the outer diameter of the circular pipe with both shoulder parts of the groove by using a pair of tools 4 and 4', or 7 and 7' having the linear groove with uniform groove width. The hairpin-shaped flat pipe with the necessary good accuracy is thus formed with the work of the shoulder part of the groove so as to set he center of the circular pipe and the center of the groove and by flattening the circular pipe with its amending in linear shape even in case of its bending slightly.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a manufacturing method and manufacturing device for flat tubes for heat exchangers, and particularly to a manufacturing method and manufacturing device suitable for cross-fin tube heat exchangers. be.

[Background of the invention]

The cross fin tube heat exchanger is as shown in Figure 5.
It consists of a large number of plate-shaped fins 1 and a conduit 2 that passes through the plate-shaped fins and conducts a heat medium inside.

The fluid to be cooled or heated passes between the fins in a direction 3 perpendicular to the tube axis. In the past, the cross-sectional shape of pipes was generally circular, but recently it has been attempted to reduce the flow resistance of fluid passing between the pipes by using pipes with flat cross-sections, as shown in Figure 6. It's coming.

To manufacture a conduit as shown in Figure 5, it is common practice to alternately connect U-shaped pipes 2' with long straight pipe parts and elbows 2 with almost no straight pipe parts, as shown in Figure 7. It is. In the U-shaped tube 2', the mutual spacing between the two straight tube sections must be highly accurate in order to facilitate insertion into the fin group.

Also, the straight pipe section is required to have high straightness.

Furthermore, as is clear from Fig. 6, the precision of the angle θ between the long axis of the flat shape of the cross section and the U-shaped surface is required, so machining of a U-shaped tube with a flat cross section is not suitable for machining a circular cross section tube. It is much more difficult than machining.

There are several possible methods for manufacturing a U-shaped tube with a flat cross section, but each method has the following problems. 1st
In order to bend a straight pipe that has been flattened in advance into a U-shape, as mentioned earlier, the direction of the long axis of the flattened pipe is parallel and twisted from the plane of the U-shape, so when processing a double-bend pipe, it is necessary to Buckling and wrinkles occur, making it impossible to perform highly accurate machining. Second, replacing a U-shaped pipe with a combination of a flat straight pipe and an elbow increases the number of joints in the pipe, which increases the probability of pipe leakage and increases manufacturing costs. .

Therefore, in the conventional method of manufacturing flat tubes, a pair of tools having grooves of the same shape as the outer contour of the flat tube are used to form the tube, but when forming with a tool of such a shape, the positioning of the circular tube during forming is difficult. It became unstable and it was difficult to maintain the accuracy of the flat tube.

[Purpose of the invention]

The present invention provides a method and apparatus for manufacturing a flat tube with high straightness and high precision.

[Summary of the invention]

The present invention manufactures flat tubes with high straightness and precision by compression molding the straight portion of a circular tube using opposing upper and lower molds having grooves with a uniform groove width smaller than the diameter of a circular tube. This made it possible.

[Embodiments of the invention]

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

Here, we will take steel pipes used in heat exchangers for air conditioners as an example.
A method for manufacturing a U-shaped tube with a flat cross section will be explained step by step.

The material steel pipe has a circular cross section, and the wall thickness is approximately 3 to 3 times the outer diameter.
．． It is 5%. The length of the straight pipe portion of the U-shaped pipe to be manufactured is at least 50 times the outer diameter of the pipe. The processing process consists of the following two steps.

In the first step, the bending angle is 1 while keeping the cross section of the tube circular.
Process the pipe to bend at 80°. In order to precisely machine the distance between the axes of the straight pipe portions of the U-shaped tube, it is desirable to employ a precise bending method such as the rotary routing method. In the second step, the two straight pipe portions of the U-shaped tube obtained in the above step are simultaneously processed into flat parts.

The processing process of the cross section of the U-shaped tube in the second step is shown in FIGS. 1 to 4. A U-shaped tube 2 with a circular cross section is made by holding the outer diameter of a circular tube with both shoulders of the groove using a pair of tools 4 and 4' or 7 and 7' that have a straight groove with a uniform groove width. Since the groove is compressed while being compressed, the shoulder part of the groove works to align the center of the circular tube with the center of the groove, and even if the circular tube is slightly bent, it is straightened and flattened while being flattened, so it is possible to produce a hairpin with the desired precision. A shaped flat tube is obtained.

1 and 3 show before processing, and FIGS. 2 and 4 show after processing, respectively.

In addition, in the heat exchanger, it is only necessary to flatten the straight pipe part of the U-shaped tube, so the curved pipe part is not processed in this process, and the angle between the direction of flattening and the U-shaped surface is It is determined by the horizontal position in FIGS. 1 and 2, or the positional relationship between the left and right grooves of the tool in FIGS. 3 and 4. The axis of the workpiece tube sinks as the machining progresses, but since the upper and lower or left and right tubes are machined by the same amount at the same time, the distance between the tube axes remains constant during machining. If it is left free, it is possible to avoid adding new strain to the curved pipe section that has already been formed with high precision.

As described above, according to the present invention, the force that causes the core of the groove to coincide with the core of the circular tube acts, so the formed tube has high straightness, and the spacing between the tubes accurately matches the spacing between the grooves. The angle formed by the position of the long axis of the flat tube and the bend of the U-shaped tube can also be processed accurately by accurately stopping the fixed groove interval position and the vertical stroke of the mold.

As shown in Figures 2 and 4, the molded tube hits the shoulder of the groove, creating a bead-shaped contact on the inside, which has the effect of increasing the rigidity of the tube when assembling the fins and pipe. When expanding the pipe to fix the fins, the inward deformation is easily corrected by the expansion pressure, and the shape becomes the same as the fin's conduit.

Furthermore, it is possible to use a rotary bending machine in the first process and a press machine in the second process, making it possible to perform processing with high mass productivity.
The industrial value of the present invention is extremely large.

〔Effect of the invention〕

According to the present invention, since a circular tube is compressed while being constantly held by a pair of tools having grooves, a stable flat tube with high straightness can be obtained. Furthermore, since the shoulder portion of the groove positions the circular tube, a flat tube with excellent accuracy and straightness can be obtained.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of a tool used in the present invention for horizontally flattening a U-shaped tube, showing the start and end of the process, respectively, and Figures 3 and 4 are views of the tool used in the present invention. Figure 5 is a cross-sectional view of a tool used to process a flat tube at an angle to a U-shaped tube, showing the start and end of the process, respectively.
The figure is a side view showing the cross-fin tube heat exchanger structure.
6 is a sectional view taken along the line AA in FIG. 1, and FIG. 7 is a diagram of the U-shaped pipe and elbow that constitute the conduit shown in FIG. 5. 1...Fin, 2...Pipe line, 2...U-shaped pipe, 2...
... Elbow, 3... Direction of flow of fluid passing through the heat exchanger. 4... flat processing tool, 4... flat processing tool, 5...
・Holder, 5...Holder, 7...Flat processing tool with steps, 7'...Flat processing tool with steps, 8.
...Holder, 8'...Holder, θ...Angle between the flat long axis of the tube and the U-shaped surface, P...Distance between the axes of a pair of straight pipe parts of the U-shaped tube. ＼Hisashi

Claims (3)

[Claims] 1. A mold with a groove with a width smaller than the diameter of the circular tube,
A method for manufacturing a flat tube for a heat exchanger, characterized in that the grooves are arranged so as to face each other, and after the circular tube is positioned in the groove, the circular tube is compressed. 2. The method for manufacturing a flat tube for a heat exchanger according to claim 1, wherein the opposing molds simultaneously compress two straight pipe portions of a circular tube bent into a hairpin shape. 3. 1. An apparatus for manufacturing a flat tube for a heat exchanger, comprising a plurality of molds in which grooves each having a width smaller than the diameter of the circular tube are formed, and the molds are arranged so that the grooves are positioned opposite each other.