JP2018089641A - Heat transfer pipe, heat exchanger and method for manufacturing heat transfer pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat transfer pipe that is capable of stable production free from cracks and wrinkles at the time of hairpin processing of assembling a heat exchanger with a heat transfer pipe.SOLUTION: An aluminum heat transfer pipe 10 that is a twisted material of an extruded material pipe includes a plurality of fins helically formed inside the inner peripheral surface thereof and is formed with a helical die mark DM at the outer peripheral surface thereof. In the heat transfer pipe 10, the die mark DM has a maximum depth of 35 μm or less.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a heat transfer tube excellent in tube expandability and hairpin processability, a heat exchanger equipped with such a heat transfer tube, and a method of manufacturing the heat transfer tube.

  In general, fin-and-tube type heat exchangers used in air conditioners and the like use copper or copper alloy heat transfer tubes, and a plurality of spiral grooves are formed on the inner surface in order to increase heat transfer. Yes. In recent years, aluminum alloys that are inexpensive, lightweight, and excellent in recyclability have started to be used by these heat transfer tubes, and the groove rolling method is used in the same manner as copper and copper alloy heat transfer tubes. The inner surface spiral grooved tube made of aluminum alloy using the groove rolling method is rolled into a hollow cylindrical element tube formed by extrusion after repeated drawing and shrinking to an appropriate tube diameter. It is manufactured by transferring the groove on the inner surface of the tube by the method (for example, Patent Document 1).

Republished WO2012 / 008463

  In the groove rolling method, a grooved plug is inserted into the inner surface of the tube, and the rolled ball is planetarily rotated from the outer periphery of the tube in the direction perpendicular to the longitudinal direction of the tube, and the tube is pressed against the grooved plug on the inner peripheral side from the outer periphery In this method, the groove is formed by plastic flow of the material in the valley of the grooved plug. Depending on the pipe diameter and bottom wall thickness to be manufactured, the groove shape of the inner surface and the line speed, it is a strong process that rotates a plurality of rolling balls at a speed of several tens of thousands of revolutions per minute. Rolling scratches are formed by the trajectories of a plurality of rolling balls substantially perpendicular to the longitudinal direction of the pipe. At that time, a scratch having a deep rolling flaw is likely to be formed.

The fin-and-tube type heat exchanger inserts a heat transfer tube bent into a hairpin into the holes of aluminum heat sinks stacked and arranged at an equal pitch, and expands the heat transfer tube with a tube expansion plug. Are joined. Then, it is assembled and manufactured by fitting and brazing a U-bend tube that has been previously bent to the tube end of the adjacent hairpin tube. When the hairpin is bent, if there are scratches as described above on the outer periphery or inner periphery of the tube bending portion, cracks and wrinkles are generated starting from the scratch. Also, if there are multiple rolling flaws that are almost perpendicular to the longitudinal direction of the pipe as described above, when the hairpin bent pipe is inserted through the hole in the aluminum heat sink, the heat sink touches and gets caught in the damaged valley. There is a problem that the tube cannot be inserted successfully.
Therefore, there is a demand for a heat transfer tube having a surface property that suppresses the generation of scratches that affect the processing when assembled in the heat exchanger as described above, and enables stable production.

  This invention is made | formed in view of such a situation, and it aims at provision of the heat exchanger tube which can produce stably without generation | occurrence | production of a crack and a wrinkle at the time of the hairpin process which assembles a heat exchanger tube to a heat exchanger.

  A heat transfer tube according to one embodiment of the present invention is an aluminum heat transfer tube that is a twisted material of an extruded element tube, and includes a plurality of fins formed in a spiral shape on an inner peripheral surface, and a spiral on an outer peripheral surface. A die mark having a shape is formed, and the maximum depth of the die mark is 35 μm or less.

  In the above heat transfer tube, the lead angle of the spiral die mark on the outer peripheral surface may be 1.0 ° or more larger than the lead angle of the spiral fin.

  The heat exchanger which is 1 aspect of this invention is a heat exchanger provided with said heat exchanger tube and a heat sink connected with the said heat exchanger tube.

  The manufacturing method of the heat exchanger tube which is one mode of the present invention has a plurality of fins extending linearly along the length direction on the inner peripheral surface, and a die mark extending linearly along the length direction on the outer peripheral surface. An extrusion process for forming an aluminum element tube having an extrusion by extrusion, a torsion extraction process for imparting a twist with a twist angle of 5 ° or more to the element tube, and a diameter reduction ratio of 10% after the extraction process The empty drawing process which performs the above drawing, The manufacturing method of a heat exchanger tube.

  Moreover, the manufacturing method of the above-mentioned heat exchanger tube is good also as a manufacturing method by which the die mark after the said emptying process is extended | stretched 1.02 times or more with respect to the die mark after the said extrusion molding process.

  According to the present invention, it is possible to provide a heat transfer tube that is free from cracks and wrinkles during bending of a hairpin and that is easy to insert when assembled with a heat sink fin and has excellent tube expandability.

It is a front view of the heat exchanger of an embodiment. It is a fragmentary perspective view of the heat exchanger of an embodiment. It is a cross-sectional view of the heat transfer tube of the embodiment. It is a longitudinal cross-sectional view of the heat exchanger tube of embodiment. It is a side view of the heat exchanger tube of an embodiment. It is a longitudinal cross-sectional view of the raw tube (straight grooved tube) in the manufacturing method of embodiment. It is a perspective view of an element pipe (straight grooved pipe) in a manufacturing method of an embodiment. It is a front view which shows the manufacturing apparatus which performs a twist process in the manufacturing method of embodiment. It is a top view of the floating frame seen from the arrow IX direction in FIG. (A) is an image of an example of a dice mark, and (b) is a measurement graph of the depth of the dice mark. (A) is an image of an example of a dice mark, and (b) is a measurement graph of the depth of the dice mark.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the drawings used in the following description, for the purpose of emphasizing the feature portion, the feature portion may be shown in an enlarged manner for convenience, and the dimensional ratios of the respective constituent elements are not always the same as in practice. Absent. In addition, for the same purpose, portions that are not characteristic may be omitted from illustration.

[Heat exchanger]
1 and 2 are schematic views of a heat exchanger 80 of the embodiment.
The heat exchanger 80 has a structure in which a heat transfer tube 81 is provided meandering as a tube through which a refrigerant passes, and a plurality of aluminum heat radiation plates 82 are arranged in parallel around the heat transfer tube 81. The heat transfer tube 81 is provided so as to pass through a plurality of insertion holes provided so as to penetrate the heat radiating plate 82 arranged in parallel.

  In the heat exchanger 80, the heat transfer tube 81 connects a plurality of U-shaped main pipes 81A that linearly penetrate the heat radiating plate 82 and adjacent end openings of the adjacent main pipes 81A with U-shaped elbow pipes 81B. It becomes. The U-shaped main tube 81A and the elbow tube 81B are formed by bending the heat transfer tube 10 described later in a U shape. Further, the refrigerant inlet portion 87 a is formed on one end side of the heat transfer tube 81 penetrating the heat radiating plate 82, and the refrigerant outlet portion 87 b is formed on the other end side of the heat transfer tube 81. A heat exchanger 80 is configured.

[Heat transfer tube]
Next, the heat transfer tube 10 before the tube expansion used for manufacturing the heat exchanger 80 will be specifically described.
FIG. 3 is a transverse sectional view of the heat transfer tube 10 of the embodiment, and FIG. 4 is a longitudinal sectional view. FIG. 5 is a side view of the heat transfer tube 10.

  The heat transfer tube 10 of the present embodiment is a twisted material of an extruded element tube. The heat transfer tube 10 can be made of aluminum or an aluminum alloy. When an aluminum alloy is used for the heat transfer tube 10, the aluminum alloy is not particularly limited, and is typically pure aluminum such as 1050, 1100, 1200, etc. defined by JIS, or 3000 represented by 3003 with Mn added thereto. A series aluminum alloy or the like can be applied. Moreover, you may comprise the heat exchanger tube 10 using either the 5000 series-7000 series aluminum alloy prescribed | regulated to JIS. In this specification, “aluminum” is a concept including an aluminum alloy and pure aluminum.

  The heat transfer tube 10 is a tube having a circular outer cross-section. The diameter of the outer peripheral surface 10a of the heat transfer tube 10 is 4 mm or more and 15 mm or less. A plurality of fins 3 formed in a spiral shape along the length direction are provided on the inner peripheral surface 10 b of the heat transfer tube 10. A spiral groove 4 is formed between the fins 3.

  In the present embodiment, for example, 30 to 60 fins 3 are provided. The height (that is, the dimension in the radial direction) of the fin 3 is 0.1 mm or more and 0.3 mm or less. The average bottom wall thickness β of the heat transfer tube 10 (that is, the average value of the thickness of the heat transfer tube 10 corresponding to the bottom of the spiral groove 4) is 0.2 mm or more and 0.8 mm or less. The apex angle of the fin 3 (angle formed between the side surfaces of the fin 3) is 10 ° to 30 °. The lead angle θ1 (twist angle) of the fin 3 formed in a spiral shape is 5 ° or more and 45 ° or less.

As shown in FIG. 5, a spiral dice mark DM is formed on the outer peripheral surface 10 a of the heat transfer tube 10. The die mark DM is a linear recess formed along the extrusion direction on the peripheral surface of a member formed by extrusion. The die mark DM is formed due to the influence of a scratch on the extrusion mold or the bearing surface. The heat transfer tube 10 of the present embodiment is manufactured by twisting while pulling out the extruded raw tube. For this reason, the die mark DM formed in a linear shape by extrusion processing becomes a spiral shape with the application of twist.
Note that the dice mark DM of FIG. 5 is illustrated as one dice mark DM formed continuously for easy understanding. Actual dice marks are formed intermittently along the length direction. A plurality of dice marks DM extend spirally and in parallel along the circumferential direction of the outer peripheral surface of the heat transfer tube 10.
In the present specification, the term “die dice” is used not only for a straight line-shaped recess formed by an extrusion process but also for a bare line-shaped recess after a twist is applied to an elemental tube having such a recess. Strictly speaking, the spiral streak-shaped recess after the twist is applied is a recess due to the die mark. However, for easy understanding in this specification, a concept including these is called a dice mark.

  The maximum depth of the die mark DM after the twist is applied is 35 μm or less. As described above, when the heat transfer tube 10 is used as the heat exchanger 80 (see FIGS. 1 and 2), the heat transfer tube 10 is bent to be bent into a hairpin shape. In such a bending process, the die mark DM is likely to be a starting point for damage to the heat transfer tube 10. According to this embodiment, by setting the maximum depth of the die mark DM to 35 μm or less, it is possible to increase the strength of the heat transfer tube 10 and provide the heat transfer tube 10 that is not easily damaged by additional processing such as bending.

A dice mark depth measurement method will be described.
The die mark depth measurement can be performed by measuring the surface shape using, for example, a scanning laser microscope (VK-X100 / X200) manufactured by Keyence Corporation. In the measurement analysis, the die mark depth can be measured using an analysis application (VK-H1XA).
First, a sample is placed on the stage of a scanning laser microscope (VK-X100 / X200), and after focusing on an observation magnification of 50 times, the upper and lower limit range of observation height is 100 μm, and the surface shape is 0.5 μm pitch. Measure.
Next, the die mark depth on the image obtained using the analysis application (VK-H1XA) is measured. As pre-processing before measurement, inclination correction for flattening the arc on the tube surface was performed. From the surface shape subjected to pretreatment, three straight lines are drawn so as to be parallel to the pipe circumferential direction, and the maximum valley depth (Rv) and maximum height (Rz) are obtained from the obtained roughness curve, In the measurement of the die mark depth, the maximum cross-sectional height (Rt) is measured.
In the analysis application, surface roughness analysis was performed with the roughness parameters defined in JISB0601-2001 and JIS0601-1994 based on "Definition of surface roughness" (JISB0601: 2001).
FIG. 10B shows the depth measurement result of the dice mark DM shown in FIG. Similarly, FIG. 11B shows the depth measurement result of the dice mark DM in FIG. Note that the heat transfer tube having the die mark DM illustrated in FIGS. 10 and 11 is an example of the heat transfer tube 10 of the present embodiment.

  As shown in FIG. 4, the fin 3 is formed in a spiral shape with a lead angle θ1. On the other hand, as shown in FIG. 5, the dice mark DM is formed in a spiral shape with a lead angle θ2. When α is the inner circumferential length and β is the bottom wall thickness, the lead angle θ1 of the fin 3 and the lead angle θ2 of the die mark DM satisfy the following relationship.

  According to the above equation, the lead angle θ2 of the die mark DM is larger than the lead angle θ1 of the fin 3 from the above equation. This is due to the fact that the reference surface of the lead angle θ1 of the fin 3 and the lead angle θ2 of the die mark DM is different between the outer peripheral surface and the inner peripheral surface due to the thickness difference. The lead angle θ2 of the spiral die mark DM on the outer peripheral surface 10a of the heat transfer tube 10 is 1.0 ° or more larger than the lead angle θ1 of the spiral fin 3. In addition, the outer diameter of the heat exchanger tube 10 obtained by this embodiment is 4 mm or more and 15 mm or less. Furthermore, the outer diameter of the heat transfer tube 10 is 70% or less compared to the extruded raw tube diameter that is the starting material.

  Further, according to the present embodiment, the plurality of fins 3 formed in a spiral shape along the length direction are provided on the inner peripheral surface 10 b of the heat transfer tube 10. By forming the helical fin 3 on the inner peripheral surface 10b, the heat exchange efficiency between the heat transfer tube 10 and the refrigerant liquid flowing through the heat transfer tube 10 can be increased. The heat transfer tube 10 provided with the spiral fin 3 can be formed by applying a twist while being drawn out to the raw tube 10B in which a fin extending linearly in the length direction is formed by extrusion. Thereby, the heat transfer tube 10 excellent in strength can be provided by extending the dice mark DM and making it sufficiently shallow.

[Production method]
Hereinafter, an embodiment of a method for manufacturing a heat transfer tube 10 according to the present invention will be described with reference to the drawings. The manufacturing method of the heat exchanger tube 10 includes an extrusion molding process and a twisting process in this order.

<Extrusion process>
First, the extrusion molding process will be described.
FIG. 6 is a vertical cross-sectional view of a raw pipe (straight grooved pipe) 10B formed by an extrusion molding process, and FIG. 7 is a perspective view of the raw pipe 10B.
By extruding a billet made of an aluminum material, as shown in FIG. 7, an element tube 10 </ b> B in which a plurality of linear grooves 4 </ b> B along the length direction are formed at intervals in the circumferential direction as shown in FIG. A tube extrusion process). A die mark DM extending linearly along the length direction is formed on the outer peripheral surface of the raw tube 10B formed by the extrusion molding process.

<Drawing twisting process, empty drawing process>
Next, the drawing twisting process and the empty drawing process will be described.
The drawing twisting process is a process in which the die mark DM, the fin 3B, and the straight groove 4B are spiraled by applying twist to the above-described raw tube 10B while performing the drawing.
In addition, the emptying step is a step of drawing the tube material without imparting a twist to adjust the outer shape of the tube material.

In addition, in this specification, the pipe material (that is, the above-described raw pipe 10B) before being twisted is referred to as a “straight grooved pipe”. Moreover, the pipe material (that is, the above-described heat transfer tube 10) after being twisted is referred to as an “inner surface spiral groove tube”. Further, in the process from the straight grooved tube to the inner surface spiral grooved tube, an intermediate formed product to which about half of the twist is applied as compared with the inner surface spiral grooved tube is called an “intermediate twisted tube”. Further, the “tube material” in the present specification is a superordinate concept of a straight grooved tube, an intermediate twisted tube, and an inner spiral grooved tube, and means a tube to be processed regardless of the stage of the manufacturing process.
In the present specification, the “front stage” and the “rear stage” mean the front-rear relationship (that is, upstream and downstream) along the processing order of the pipe material, and do not mean the arrangement of each part in the apparatus.
The pipe material is conveyed from the front stage (upstream) side to the rear stage (downstream) side in the manufacturing apparatus of the inner surface spiral grooved pipe. The part arranged in the front stage is not necessarily arranged in the front, and the part arranged in the rear stage is not necessarily arranged in the rear.

<Manufacturing apparatus that performs a drawing twist process and an empty drawing process>
FIG. 8 is a front view showing a manufacturing apparatus A that manufactures the inner surface spiral grooved tube (heat transfer tube) 10 by applying two twists to the straight grooved tube (element tube) 10B. First, after explaining the manufacturing apparatus A, a drawing twisting process and an empty drawing process using the manufacturing apparatus A will be described.

The manufacturing apparatus A includes a revolving mechanism 30, a floating frame 34, an unwinding bobbin (first bobbin) 11, a first guide capstan 18, a first drawing die 1, and a first revolving capstan. 21, a revolution flyer 23, a second revolution capstan 22, a second drawing die 2, a second guide capstan 61, and a take-up bobbin (second bobbin) 71.
Hereinafter, details of each unit will be described in detail.

(Revolution mechanism)
The revolution mechanism 30 includes a rotating shaft 35 including a front shaft 35A and a rear shaft 35B, a drive unit 39, a front stand 37A, and a rear stand 37B.
The revolution mechanism 30 rotates the rotation shaft 35, the first revolution capstan 21, the second revolution capstan 22, and the revolution flyer 23 fixed to the rotation shaft 35.
In addition, the revolution mechanism 30 maintains the stationary state of the floating frame 34 that is positioned coaxially with the rotation shaft 35 and supported by the rotation shaft 35. As a result, the unwinding bobbin 11, the first guide capstan 18 and the first drawing die 1 supported by the floating frame 34 are kept stationary.

  Both the front shaft 35A and the rear shaft 35B have a hollow cylindrical shape. Both the front shaft 35 </ b> A and the rear shaft 35 </ b> B are arranged coaxially with the revolution rotation central axis C (pass line of the first drawing die) as the central axis. The front shaft 35A is rotatably supported by the front stand 37A via a bearing 36, and extends rearward (from the rear stand 37B side) from the front stand 37A. Similarly, the rear shaft 35B is rotatably supported by the rear stand 37B via a bearing, and extends from the rear stand 37B to the front (front stand 37A side). A floating frame 34 is bridged between the front shaft 35A and the rear shaft 35B.

The drive unit 39 includes a drive motor 39c, a linear motion shaft 39f, belts 39a and 39d, and pulleys 39b and 39e. The drive unit 39 rotates the front shaft 35A and the rear shaft 35B.
The drive motor 39c rotates the linear motion shaft 39f. The linear motion shaft 39f extends in the front-rear direction at the lower part of the front stand 37A and the rear stand 37B.
A pulley 39b is attached to the front end 35Ab of the front shaft 35A at the tip that penetrates the front stand 37A. The pulley 39b is interlocked with the linear motion shaft 39f via the belt 39a. Similarly, the rear end portion 35Bb of the rear shaft 35B has a pulley 39e attached to the tip that penetrates the rear stand 37B, and interlocks with the linear motion shaft 39f via a belt 39d. Thereby, the front shaft 35A and the rear shaft 35B rotate synchronously around the revolution rotation center axis C.

  A first revolving capstan 21, a second revolving capstan 22, and a revolving flyer 23 are fixed to the rotating shaft 35 (the front shaft 35A and the rear shaft 35B). As the rotary shaft 35 rotates, these members fixed to the rotary shaft 35 revolve around the revolution rotation center axis C.

(Floating frame)
The floating frame 34 is supported via bearings 34a on end portions 35Aa and 35Ba of the front shaft 35A and the rear shaft 35B of the rotary shaft 35 facing each other. Further, the floating frame 34 supports the unwinding bobbin 11, the first guide capstan 18, and the first drawing die 1.

  FIG. 9 is a plan view of the floating frame 34 as seen from the direction of the arrow IX in FIG. As shown in FIGS. 8 and 9, the floating frame 34 has a box shape that opens up and down. The floating frame 34 includes a front wall 34b and a rear wall 34c that are opposed to each other in the front-rear direction, and a pair of support walls 34d that are opposed to the left-right and extend in the front-rear direction.

  A through hole is provided in the front wall 34b and the rear wall 34c, and ends 35Aa and 35Ba of the front shaft 35A and the rear shaft 35B are inserted, respectively. A bearing 34a is interposed between the end portions 35Aa and 35Ba and the through holes of the front wall 34b and the rear wall 34c. Thereby, the rotation of the rotation shaft 35 (the front shaft 35A and the rear shaft 35B) is not easily transmitted to the floating frame 34. The floating frame 34 remains stationary with respect to the ground G even when the rotating shaft 35 is in a rotating state. Note that a weight that biases the center of gravity of the floating frame 34 with respect to the revolution rotation center axis C may be provided to stabilize the stationary state of the floating frame 34.

  As shown in FIG. 9, the pair of support walls 34 d are arranged so that the unwinding bobbin 11, the first guide capstan 18 and the first drawing die 1 are arranged on both sides in the left-right direction (vertical direction in FIG. 9). Yes. The pair of support walls 34d rotatably support the bobbin support shaft 12 that holds the unwinding bobbin 11 and the rotation axis J18 of the first guide capstan 18. The support wall 34d supports the first drawing die 1 via a die support (not shown).

(Unwinding bobbin)
A straight grooved tube 10B (see FIG. 6) in which a straight groove 4B is formed is wound around the unwinding bobbin 11. The unwinding bobbin 11 unwinds the straight grooved tube 10B and supplies it to the subsequent stage.
The unwinding bobbin 11 is detachably attached to the bobbin support shaft 12.

  As shown in FIG. 9, the bobbin support shaft 12 extends in a direction orthogonal to the rotation shaft 35. The bobbin support shaft 12 is supported by the floating frame 34 so as to be able to rotate and rotate. In addition, autorotation means rotating around the central axis of the bobbin support shaft 12 itself here. The bobbin support shaft 12 holds the unwinding bobbin 11 and rotates in the supply direction of the unwinding bobbin 11 to assist the unwinding of the tube material 5 of the unwinding bobbin 11.

  The unwinding bobbin 11 is removed when all the wound straight grooved tubes 10B are supplied, and is replaced with another unwinding bobbin. The removed empty unwinding bobbin 11 is attached to an extrusion apparatus that forms a straight grooved tube 10B, and the straight grooved tube 10B is wound again. The unwinding bobbin 11 is supported by the floating frame 34 and does not revolve. Therefore, even if the straight grooved tube 10B is turbulently wound around the unwinding bobbin 11, the supply can be performed without hindrance, and it can be used without rewinding. Further, the number of revolutions for imparting twist to the pipe 5 in the manufacturing apparatus A is not limited by the weight of the unwinding bobbin 11. Therefore, the long tube material 5 can be wound around the unwinding bobbin 11. Thereby, a twist can be provided with respect to the elongate pipe material 5, and manufacturing efficiency can be improved.

  A brake unit 15 is provided on the bobbin support shaft 12. The brake unit 15 applies a braking force to the rotation of the bobbin support shaft 12 with respect to the floating frame 34. That is, the brake unit 15 restricts the rotation of the unwinding bobbin 11 in the unwinding direction. Backward tension is applied to the pipe material 5 conveyed in the unwinding direction by the braking force of the brake unit 15. As the brake unit 15, for example, a powder brake or a band brake capable of adjusting a torque as a braking force can be adopted.

(First guide capstan)
The first guide capstan 18 has a disk shape. The tube material 5 fed out from the unwinding bobbin 11 is wound around the first guide capstan 18 once. The tangential direction of the outer periphery of the first guide capstan 18 coincides with the revolution rotation center axis C. The first guide capstan 18 guides the tube material 5 onto the revolution rotation center axis C along the first direction D1.
The first guide capstan 18 is supported by the floating frame 34 so as to rotate and rotate. In addition, on the outer periphery of the first guide capstan 18, a guide roller 18b capable of rotating and rotating is arranged side by side. The first guide capstan 18 of the present embodiment rotates by itself and the guide roller 18b rolls. However, if any one of them rotates, the tube material 5 can be smoothly conveyed. In FIG. 9, the guide roller 18b is not shown.

  As shown in FIG. 9, a pipe guide 18 a is provided between the first guide capstan 18 and the unwinding bobbin 11. The pipe guide part 18a is a plurality of guide rollers arranged so as to surround the pipe material 5, for example. The pipe guide part 18 a guides the pipe material 5 supplied from the unwinding bobbin 11 to the first guide capstan 18.

  Instead of the first guide capstan 18, a guide tube having a traverse function may be provided between the unwinding bobbin 11 and the first drawing die 1. When the guide tube is provided, the distance between the unwinding bobbin 11 and the first drawing die 1 can be shortened, and the space in the factory can be effectively used.

(First drawing die)
The first drawing die 1 reduces the diameter of the tube material 5 (straight grooved tube 10B). The first drawing die 1 is fixed to the floating frame 34. The first drawing die 1 has the first direction D1 as the drawing direction. The center of the first drawing die 1 coincides with the revolution rotation center axis C of the rotation shaft 35. The first direction D1 is parallel to the revolution rotation center axis C.
Lubricating oil is supplied to the first drawing die 1 by a lubricating oil supply device 9 </ b> A fixed to the floating frame 34. Thereby, the drawing force in the first drawing die 1 can be reduced.
The pipe material 5 that has passed through the first drawing die 1 is introduced into the front shaft 35 </ b> A through a through hole provided in the front wall 34 b of the floating frame 34.

(First Recap Capstan)
The first revolution capstan 21 has a disk shape. The first revolving capstan 21 is disposed in a lateral hole 35Ac that penetrates the inside and outside of the hollow front shaft 35A in the radial direction. The first revolving capstan 21 is supported in a freely rotatable manner on a support 21a fixed to the outer peripheral portion of the rotary shaft 35 (front shaft 35A) with the center of the disk as the rotation axis J21.

One of the outer tangents of the first revolution capstan 21 substantially coincides with the revolution rotation center axis C.
The tube material 5 conveyed in the first direction D1 on the revolution rotation center axis C is wound around the first revolution capstan 21 by one or more rounds. The first revolving capstan 21 winds the pipe material 5, draws it from the inside of the front shaft 35 </ b> A to the outside, and guides it to the revolving flyer 23.

  The first revolving capstan 21 revolves around the revolving rotation center axis C together with the front shaft 35A. The revolution rotation center axis C extends in a direction orthogonal to the rotation axis J21 of the rotation of the first revolution capstan 21. The pipe 5 is twisted between the first revolving capstan 21 and the first drawing die 1. Thereby, the pipe material 5 changes from the straight grooved tube 10B to the intermediate twisted tube 10C.

  Along with the first revolving capstan 21, a drive motor 20 is provided on the front shaft 35A. The drive motor 20 drives and rotates the first revolving capstan 21 in the winding direction (conveying direction) of the tube material 5. As a result, the first revolving capstan 21 imparts a forward tension for passing the first drawing die 1 to the tube material 5.

  It is preferable that the first revolving capstan 21 and the drive motor 20 are arranged symmetrically with respect to the revolution rotation center axis C so that the center of gravity is located at the revolution rotation center axis C of the front shaft 35A. Thereby, the balance of rotation of the front shaft 35A can be stabilized. When the difference in weight between the first revolving capstan 21 and the drive motor 20 is large, a weight may be provided to stabilize the center of gravity.

(Revolution flyer)
The revolution flyer 23 inverts the pipe line of the pipe material 5 between the first drawing die 1 and the second drawing die 2. The revolution flyer 23 reverses the tube material 5 conveyed in the first direction D1 which is the drawing direction of the first drawing die 1, and the conveying direction is the second direction D2 which is the drawing direction of the second drawing die 2. Turn to. More specifically, the revolution flyer 23 guides the pipe material 5 from the first revolution capstan 21 to the second revolution capstan 22.

The revolution flyer 23 has a plurality of guide rollers 23a and a guide roller support (not shown) that supports the guide rollers 23a. Here, the guide roller support is not shown in order to eliminate complexity, but the guide roller support is supported by the rotating shaft 35. However, the guide roller is not indispensable for the structure of the flyer, and it may be a plate-like structure for allowing the tube to pass therethrough and having a shape attached with a ring for passing it. This ring may be provided on a plate-shaped member. A part of this ring may be constituted by a part of this plate-shaped member. The plate-shaped member may be supported on the rotating shaft 35 in the same manner as the guide roller support.
The guide rollers 23 a are arranged in a bow shape that curves outward with respect to the revolution rotation center axis C. The guide roller 23a itself rolls to convey the tube material 5 smoothly. The revolution flyer 23 rotates around the revolution rotation center axis C around the floating frame 34 and the first drawing die 1 and the unwinding bobbin 11 supported in the floating frame 34.

  One end of the revolution flyer 23 is located outside the first revolution capstan 21 with respect to the revolution rotation center axis C. The other end of the revolution flyer 23 passes through a lateral hole 35Bc that penetrates the inside and outside of the hollow rear shaft 35B in the radial direction and extends into the rear shaft 35B. The revolution flyer 23 guides the pipe member 5 wound around the first revolution capstan 21 and fed outward to the rear shaft 35B side. Further, the revolution flyer 23 feeds the pipe material 5 on the revolution rotation center axis C along the second direction D2 inside the rear shaft 35B.

In addition, the revolution flyer 23 of this embodiment was demonstrated as what conveys the pipe material 5 with the guide roller 23a. However, the revolution flyer 23 may be formed from a strip formed in an arcuate shape, and the tube material 5 may be transported by sliding on one surface of the strip.
Moreover, in FIG. 8, the case where the pipe material 5 passes the outer side of the guide roller 23a was illustrated.
However, when the rotational speed of the revolution flyer 23 is high, the pipe material 5 may be derailed from the revolution flyer by centrifugal force. In such a case, it is preferable to further provide a guide roller 23a outside the tube material 5.
A plurality of dummy fryer having the same weight as the revolution flyer 23 and extending from the front shaft 35 </ b> A to the rear shaft 35 </ b> B and rotating synchronously with the revolution flyer 23 may be provided. Thereby, rotation of the rotating shaft 35 can be stabilized.

(Second Revolving Capstan)
The second revolution capstan 22 has a disk shape, like the first revolution capstan 21. The second revolving capstan 22 is supported by a support 22a provided at the tip of the end portion 35Bb of the rear shaft 35B so as to be freely rotatable. In addition, on the outer periphery of the second revolving capstan 22, guide rollers 22c that are capable of rotating and rotating are arranged side by side. The second revolving capstan 22 of the present embodiment rotates itself and the guide roller 22c rolls. If either one rotates, the tube material 5 can be smoothly conveyed.

One of the outer tangents of the second revolution capstan 22 substantially coincides with the revolution rotation center axis C.
The tube material 5 conveyed in the second direction D2 on the revolution rotation center axis C is wound around the second revolution capstan 22 by one turn or more. The second revolution capstan 22 feeds the wound pipe material in the second direction D2 on the revolution rotation center axis C.

  The second revolution capstan 22 revolves around the revolution rotation center axis C together with the rear shaft 35B. The revolution rotation center axis C extends in a direction perpendicular to the rotation axis J22 of the rotation of the second revolution capstan 22. The pipe material 5 drawn out from the second revolution capstan 22 is reduced in diameter at the second drawing die 2. Since the second drawing die 2 is stationary with respect to the ground G, the pipe material 5 can be twisted between the second revolving capstan 22 and the second drawing die 2. Thereby, the pipe material 5 becomes the internal spiral grooved tube 10 from the intermediate twisted tube 10C.

  The support 22 a that supports the second revolution capstan 22 supports the weight 22 b at a position symmetrical to the second revolution capstan 22 with respect to the revolution center axis C. The weight 22b stabilizes the balance of rotation of the rear shaft 35B.

(Second drawing die)
The second drawing die 2 is disposed at the rear stage of the second revolving capstan 22. The second drawing die 2 has an opposite second direction D2 as the drawing direction. The second direction D2 is a direction parallel to the revolution center axis C. The second direction D2 is opposite to the first direction D1, which is the drawing direction of the first drawing die 1. The pipe material 5 passes through the second drawing die 2 along the second direction D2. The second drawing die 2 is stationary with respect to the ground G. The center of the second drawing die 2 coincides with the revolution rotation center axis C of the rotation shaft 35.

The second drawing die 2 is supported by the gantry 62 via a die support body (not shown), for example. The second drawing die 2 is supplied with lubricating oil by a lubricating oil supply device 9B attached to the gantry 62. Thereby, the drawing force in the second drawing die 2 can be reduced.
By reducing the diameter and applying the twist in the second drawing die 2, the tube material 5 changes from the intermediate twisted tube 10 </ b> C to the inner spiral grooved tube 10.

(Second guide capstan)
The second guide capstan 61 has a disk shape. The tangential direction of the outer periphery of the second guide capstan 61 coincides with the revolution rotation center axis C. The pipe material 5 conveyed in the second direction D2 on the revolution rotation center axis C is wound around the second guide capstan 61 by one turn or more.

  The second guide capstan 61 is rotatably supported by the gantry 62 around the rotation axis J61. The rotation axis J61 of the second guide capstan 61 is connected to the drive motor 63 via a drive belt or the like. The second guide capstan 61 is driven to rotate in the winding direction (conveying direction) of the tube material 5 by the drive motor 63. The drive motor 63 is preferably a torque motor capable of torque control.

  When the second guide capstan 61 is driven, a forward tension is applied to the pipe material 5. As a result, the pipe 5 is conveyed forward with a drawing stress necessary for processing in the second drawing die 2.

<Finished drawing die>
The finish drawing die 7 is located between the second guide capstan 61 and the take-up bobbin 71. The finish drawing die 7 finishes and shapes the pipe material 5. The finish drawing die 7 is provided for the skin pass of the pipe material 5 that has passed through the first and second drawing dies 1 and 2. In the empty drawing process (finish drawing process) by the finishing drawing die 7, the change in the cross section due to drawing is small, the surface and dimensions are finished and the roundness of the pipe material 5 is restored. Further, in the emptying step, nonuniformity of the bottom wall thickness of the pipe material 5 is reduced.
The finish drawing die 7 may be provided at any position as long as it is between the second drawing die 2 and the winding bobbin 71.

(Winding bobbin)
The winding bobbin 71 is provided at the end of the pipe line of the pipe material 5 and collects the pipe material 5. A guiding portion 72 is provided in the front stage of the winding bobbin 71. The guide part 72 has a traverse function and winds the tube material 5 around the winding bobbin 71.

  The take-up bobbin 71 is detachably attached to the bobbin support shaft 73. The bobbin support shaft 73 is supported by the gantry 75 and is connected to the drive motor 74 via a drive belt or the like. The take-up bobbin 71 is driven and rotated by the drive motor 74 and takes up the tube material 5 without slackening it. The winding bobbin 71 is removed when the pipe material 5 is sufficiently wound, and is replaced with another winding bobbin 71.

<Drawing twisting process>
A method of manufacturing the inner spiral grooved tube 10 using the above-described inner spiral grooved tube manufacturing apparatus A will be described.
First, as a preliminary process, the straight grooved tube 10B is wound around the unwinding bobbin 11 in a coil shape. Further, the unwind bobbin 11 is set on the floating frame 34 of the manufacturing apparatus A. Moreover, the pipe material 5 (straight grooved pipe 10B) is drawn out from the unwinding bobbin 11, and the pipe line of the straight grooved pipe 10B is set in advance. Specifically, the pipe material 5 is made up of a first guide capstan 18, a first drawing die 1, a first revolution capstan 21, a revolution flyer 23, a second revolution capstan 22, and a second drawing die 2. The second guide capstan 61 and the take-up bobbin 71 are passed through and set in this order.

In the manufacturing process of the inner spiral grooved tube 10, a description will be given along the pipe material conveyance path.
First, the pipe material 5 is sequentially unwound from the unwinding bobbin 11.
Next, the pipe material 5 fed out from the unwinding bobbin 11 is wound around the first guide capstan 18. The first guide capstan 18 guides the pipe member 5 to the die hole of the first drawing die 1 located on the revolution rotation center axis C (first guiding step).

Next, the pipe material 5 is passed through the first drawing die 1. Further, the tube material 5 is wound around the first revolving capstan 21 at the subsequent stage of the first drawing die 1 and rotated around the rotation axis.
As a result, the diameter of the tube material 5 is reduced and twist is applied (first twist extraction step).

  In the first twist drawing process, a forward tension is applied to the pipe member 5 by the drive motor 20 that drives the first revolving capstan 21. At the same time, rear tension is applied to the pipe member 5 by the brake portion 15 of the unwinding bobbin 11. For this reason, it is possible to apply an appropriate tension to the tube material 5, and it is possible to provide a stable twist angle without causing the tube material 5 to buckle and break.

  After passing through the first drawing die 1, the pipe material 5 is wound around a first revolving capstan 21 that revolves and rotates. The pipe 5 is reduced in diameter by the first drawing die 1 and is twisted by the first revolving capstan 21. Thereby, a twist is given to the linear groove 4B (refer FIG. 6) of the inner surface of the pipe material 5 (tube 10B with a linear groove), and the spiral groove 4 is formed in an inner surface. The straight grooved tube 10B becomes an intermediate twisted tube 10C by the first twist drawing process. The intermediate twisted tube 10 </ b> C is a tube material in an intermediate stage in the manufacturing process of the inner surface spiral grooved tube 10, and a state in which a spiral groove having a shallower twist angle than the spiral groove 4 of the inner surface spiral grooved tube 10 is formed.

  In the first twist drawing process, the pipe 5 is subjected to twisting and simultaneously contracted by a drawing die. That is, the pipe material 5 is given a composite stress by simultaneous processing of twisting and diameter reduction. Under the combined stress, the yield stress of the tube material 5 becomes smaller than when only twisting is performed, and a large twist can be imparted to the tube material 5 before reaching the buckling stress of the tube material 5. Thereby, a big twist can be provided, suppressing generation | occurrence | production of the buckling of the pipe material 5. FIG.

A first guide capstan 18 is provided in the preceding stage of the first drawing die 1 to restrict the rotation of the tube material 5. That is, the pipe 5 is constrained from being deformed in the twisting direction before the first drawing die 1. The tube material 5 is twisted between the first drawing die 1 and the first revolving capstan 21. That is, in the first twist drawing process, a region (working region) where the tube material 5 is twisted is limited between the first drawing die 1 and the first revolving capstan 21.
There is a correlation between the length of the machining area and the limit torsion angle (the maximum torsion angle that can be twisted without buckling), and even if a large torsion angle is applied by shortening the machining area Buckling is unlikely to occur. By providing the first guide capstan 18, the processing area can be set short without being twisted before the first drawing die 1. Further, by shortening the distance between the first drawing die 1 and the first revolving capstan 21, the machining area can be set short, and a large twist can be imparted to the tube material 5 without causing buckling.

It is preferable that the diameter reduction ratio of the pipe material 5 by the first drawing die 1 is 2% or more. There is a correlation between the limit torsion angle and the diameter reduction rate, and a tendency for the limit torsion angle to increase as the diameter reduction rate at the time of drawing increases is observed. That is, when the diameter reduction rate is too small, the effect of drawing is poor and it is difficult to obtain a large twist angle, so it is preferable to set it to 2% or more. For the same reason, it is more preferable to reduce the diameter reduction ratio to 5% or more.
On the other hand, if the diameter reduction rate is too large, breakage tends to occur at the processing limit, so 40% or less is preferable.

  Next, the pipe material 5 is wound around the revolution flyer 23 and the conveyance direction of the pipe material 5 is directed to the second direction D2 on the revolution rotation central axis C. Further, the pipe material 5 is wound around the second revolution capstan 22 and the pipe material 5 is introduced into the second drawing die 2 (second induction step). Thereby, the conveyance direction of the pipe material 5 is reversed from the first direction D1 to the second direction D2, and is aligned with the center of the second drawing die 2. The revolution flyer 23 rotates about the revolution rotation center axis C around the floating frame 34. The first revolution capstan 21, the revolution flyer 23, and the second revolution capstan 22 rotate synchronously around the revolution rotation center axis C. Therefore, the tube material 5 does not rotate relatively between the first revolving capstan 21 and the second revolving capstan 22, so that no twist is applied.

  Next, the tube material 5 that rotates together with the second revolving capstan 22 is passed through the second drawing die 2. As a result, the tube material 5 is reduced in diameter and twisted, and the twist angle of the spiral groove 4 is further increased (second twist-drawing step). The intermediate twisted tube 10C becomes the inner spiral grooved tube 10 by the second twist pulling process.

  In the second torsion drawing process, a forward tension is applied to the pipe member 5 by the drive motor 63 that drives the second guide capstan 61. When a torque motor capable of torque control is used as the drive motor 63, the second guide capstan 61 can adjust the front tension applied to the tube material 5. By adjusting the front tension by the second guide capstan 61, it is possible to apply an appropriate tension to the tube material 5 in the second twist drawing process. Thereby, a stable twist angle can be imparted to the tube material 5 without causing buckling and fracture.

  The pipe material 5 passes through the second drawing die 2 after being wound around the second revolving capstan 22 that revolves and rotates. The tube material 5 is reduced in diameter by the second drawing die 2 and is twisted by the second revolving capstan 22. As a result, a larger twist is imparted to the spiral groove 4 on the inner surface of the tube material 5 and the twist angle of the spiral groove 4 is increased. The intermediate twisted tube 10C becomes the inner spiral grooved tube 10 by the second twist pulling process.

  In the front stage of the second drawing die 2, the pipe material 5 is wound around the second revolution capstan 22. In the subsequent stage of the second drawing die 2, a second guide capstan 61 is provided to restrict the rotation of the tube material 5. That is, the pipe 5 is constrained from being deformed in the twisting direction before and after the second drawing die 2, and the pipe 5 is twisted between the second revolving capstan 22 and the second guide capstan 61. Is granted. That is, in the second twist drawing process, the region (working region) where the tube material 5 is twisted is limited between the second revolution capstan 22 and the second drawing die 2. As described above, by shortening the machining area, buckling is unlikely to occur even when a large twist angle is applied. By providing the second guide capstan 61, twisting is not applied in the subsequent stage of the second drawing die 2, and the processing area can be set short.

  In the present embodiment, the second revolution capstan 22 is provided behind the rear stand 37B (on the second drawing die 2 side), but the second revolution capstan 22 is connected to the front stand 37A. You may be located between back stand 37B. However, by arranging the second revolving capstan 22 rearward with respect to the rear stand 37B and bringing it closer to the second drawing die 2, the processing area in the second twist drawing step can be shortened. Thereby, generation | occurrence | production of buckling can be suppressed more effectively.

  In the second twist extraction step, twisting and diameter reduction are performed in the same manner as in the first twist extraction step, and a composite stress is applied to the tube material 5. Thereby, before reaching the buckling stress of the pipe material 5, a big twist can be provided to the pipe material while suppressing the occurrence of buckling.

The diameter reduction rate of the tube material 5 by the second drawing die 2 is preferably 2% or more (more preferably 5% or more) and 40% or less, as in the first twist drawing process.
In addition, in the 1st drawing die 1, when a big diameter reduction (for example, diameter reduction of 30% or more of diameter reduction) is performed, since the pipe material 5 will work harden | cure, the large diameter reduction in the 2nd drawing die 2 is performed. It becomes difficult. Therefore, the total of the diameter reduction rate of the first drawing die 1 and the diameter reduction rate of the second drawing die 2 is preferably 4% or more and 50% or less.

  In the first and second twist pulling steps, a total of 5 ° or more is applied. In the twist drawing process, the die mark DM is sufficiently stretched by applying a twist of 5 ° or more together with the drawing. Thereby, it becomes possible to make the depth of a dice mark 35 micrometers or less, and the heat exchanger tube 10 which can bend a hairpin without generation | occurrence | production of a crack and a wrinkle can be manufactured.

<Empty drawing process>
Next, the pipe material 5 is passed through the finish drawing die 7 (finish drawing step). The pipe material 5 passes through the finish drawing die 7 so that the surface is shaped and the uneven thickness of the bottom wall thickness is reduced. Further, even if the pipe material 5 is slightly deformed or deformed, the finishing pulling process is performed to correct the deformation so that the inner spiral grooved pipe 5R having a predetermined roundness can be obtained. it can. A force for conveying the pipe material 5 with respect to the drawing load of the finish drawing die 7 is applied by a drive motor 74 provided on the winding bobbin 71.

  Moreover, a heat transfer tube having a stable surface property and shape can be manufactured by performing an empty drawing step after the twist drawing step (the first twist drawing step and the second twist drawing step).

<Recovery process>
Next, the pipe material 5 is wound around the winding bobbin 71 and collected. The take-up bobbin 71 is able to take up the tube material 5 without slack by rotating in synchronization with the conveying speed of the tube material 5 by the drive motor 74.
Through the above steps, the inner spiral grooved tube 10 can be manufactured using the manufacturing apparatus A.

<O materialization process>
Next, the O materializing step will be described.
The O materializing process is performed after the twisting process. The O materializing process is a heat treatment process in which the pipe material 5 is subjected to an annealing process. By performing the O material forming step, the distortion of the aluminum material can be removed and the internal stress can be removed.

<Summary of manufacturing method>
In the raw tube 10B manufactured by extrusion, a concave die mark extending in the longitudinal direction is generated, and the depth thereof is 40 μm or less, but there is also a mark locally having a depth close to 50 μm. The thickness is 50 μm or less. By performing the twisting and drawing process and the emptying process on the raw tube 10B, the tube is reduced in diameter and elongated, and the concave die mark DM on the outer peripheral surface becomes shallow. In addition, since twisting is applied in composite processing, the degree of elongation increases with the helix angle, and the concave die mark can be shallowed more effectively. By processing under appropriate conditions, the depth of the concave on the outer periphery of the tube Can be controlled to 35 μm or less. That is, according to the drawing and twisting process of this embodiment, the twisting and drawing are repeated a plurality of times. Thereby, the dice mark DM formed in the extrusion molding process can be extended and shallowed several times, and as a result, the heat transfer tube 10 having high strength can be manufactured.

  In the pulling and twisting process of the present embodiment, the first spiral pulling process and the second twisting and pulling process are performed again on the inner surface spiral grooved tube 10 formed through the above-described process, thereby providing a larger twist angle. May be. In this case, heat treatment (annealing) is performed on the inner surface spiral grooved tube 10 that has been subjected to the above-described steps, and the O material is formed. Furthermore, it winds around the unwinding bobbin 11, and this unwinding bobbin 11 is attached to the manufacturing apparatus A which has the 1st drawing die which has a suitable diameter reduction rate, and a 2nd drawing die. Furthermore, an internal spiral grooved tube having a larger twist angle can be manufactured by performing the same steps (first twist drawing step and second twist drawing step) as those described above by the manufacturing apparatus A.

  According to the drawing twisting process of this embodiment, since the diameter is reduced simultaneously with the twisting, the outer diameter and the cross-sectional area of the starting material and the final product are different. In addition, since a combined stress of twisting and reducing diameter is applied to the pipe material, it becomes possible to reduce the shear stress necessary for the twisting process, and before the buckling stress of the pipe material 5 is reached, a large twist is applied to the pipe material 5. it can. Therefore, the heat transfer tube having the fin 3 having a large lead angle θ1 and a thin bottom wall thickness can be manufactured without causing buckling. The inner surface spiral grooved tube 10 can increase the heat exchange efficiency by increasing the lead angle θ1. Moreover, the inner surface spiral grooved tube 10 can be made inexpensive by reducing the bottom wall thickness and reducing the material cost. That is, according to the present embodiment, it is possible to manufacture the inner spiral grooved tube 10 that is lightweight, inexpensive, and has high heat exchange efficiency.

  According to the drawing torsion process of the present embodiment, a twist is imparted to the straight grooved tube 10B and a diameter is reduced, so that a large twist angle can be imparted while suppressing the occurrence of buckling. In addition, in this embodiment, the outer diameter of the straight grooved tube 10B used as a raw material is 1.1 times or more with respect to the outer diameter of the inner surface spiral grooved tube 10 which is a final product.

According to the drawing twisting process of the present embodiment, the tube material 5 is twisted by the first revolving capstan 21 between the first drawing die 1 and the second drawing die 2. Furthermore, the drawing directions of the first drawing die 1 and the second drawing die 2 are reversed. Thereby, the twist can be imparted to the tube material 5 by matching the twist directions in the first twist pulling process and the second twist pulling process. Further, it is not necessary to revolve the unwinding bobbin 11 that is the starting end of the pipe line of the pipe material 5 and the winding bobbin 71 that is the terminal end of the pipe line. Since the speed of the line depends on the rotational speed, the rotational speed can be easily increased in the drawing and twisting process of the present embodiment in which the unwinding bobbin 11 or the winding bobbin 71 which is a heavy object is not rotated. That is, according to this embodiment, the line speed can be easily increased.
Furthermore, in this embodiment, since the unwinding bobbin 11 is not revolved, a long straight grooved tube 10B (tube material 5) can be wound around the unwinding bobbin 11. For this reason, according to the drawing twist process of this embodiment, without twisting out the unwinding bobbin 11, a twist can be imparted to the long tubular material 5 at once. That is, according to this embodiment, mass production of the inner spiral grooved tube 10 is facilitated.

  The drawing and twisting process of the present embodiment imparts twist to the tube material 5 through at least two twisting and drawing processes. For this reason, the twist angle provided by the twist extraction process of each step can be piled up and a big twist angle can be provided.

  According to the drawing torsion process of the present embodiment, a front tension and a rear tension are applied to the tube material 5 in the first twist drawing process and the second twist drawing process. The front tension is applied to the pipe material 5 by the second guide capstan 61, and the rear tension is applied to the pipe material 5 by the brake portion 15 that brakes the unwinding bobbin 11. Thereby, an appropriate tension can be stably applied to the pipe material 5 to be processed. Since there is no slack in the pipe line of the tube material 5 and the straight grooved tube 10B enters the drawing die without being misaligned, a stable twist angle can be imparted to the tube material 5 without causing buckling or breakage.

  In the present embodiment, the centers of the first drawing die 1 and the second drawing die 2 die hole are located on the revolution rotation center axis C. Thereby, since the pipe material 5 passing through the die hole can be arranged linearly with respect to the die hole, the pipe material 5 can be uniformly reduced in diameter, and buckling at the time of applying a twist can be suppressed. In the first drawing die 1 and the second drawing die 2, the die hole is allowed to be misaligned with respect to the revolution rotation center axis C as long as the tube material 5 can be normally reduced in diameter.

  In the present embodiment, the unwinding bobbin 11 is supported by the floating frame 34 and the winding bobbin 71 is installed on the ground G. However, either the unwinding bobbin 11 or the winding bobbin 71 may be supported by the floating frame 34. That is, in FIG. 8, the unwinding bobbin 11 and the winding bobbin 71 may be replaced with each other. In this case, the conveyance path of the pipe material 5 is reversed. In addition, the first drawing die 1 and the second drawing die 2 are replaced and arranged, and the drawing directions of the respective drawing dies 1 and 2 are reversed along the conveying direction. Further, in the capstans positioned before and after the drawing dies 1 and 2, the capstan located after the drawing dies is driven in the winding direction (conveying direction) of the pipe material, and the front tension against the pulling force in the drawing dies is obtained. give.

  A sample of a heat transfer tube manufactured according to the manufacturing method described in the above-described embodiment and having a spiral fin formed on the inner surface and a spiral die mark DM formed on the outer peripheral surface was prepared. Each sample has an outer shape, a difference between the maximum bottom wall thickness and the minimum bottom wall thickness, a torsion angle on the outer peripheral surface, a torsion angle ratio ρ, a ratio of the length of one round to the helical pitch with respect to the die mark DM, and the depth of the die mark DM. The flatness is different. The parameters of each sample are summarized in Table 1 below.

(Measurement of strength against hairpin bending)
The heat transfer tube of each sample was bent by a 180 ° bend into a hairpin shape with a radius of curvature (R = 15). Evaluation was made under each condition n = 20, and at least one crack was observed on the outer peripheral surface of the heat transfer tube, and x was not observed.
The evaluation results are summarized in Table 1.

  From the results shown in Table 1, it was confirmed that in a heat transfer tube provided with a twist with a sufficient lead angle, it is difficult to cause breakage by hairpin bending.

  Although various embodiments of the present invention have been described above, each configuration in each embodiment and combinations thereof are examples, and additions, omissions, and substitutions of configurations are within the scope not departing from the gist of the present invention. And other changes are possible. Further, the present invention is not limited by the embodiment.

DESCRIPTION OF SYMBOLS 1 ... Drawing die, 1 ... 1st drawing die, 2 ... 2nd drawing die, 3, 3B ... Fin, 4 ... Spiral groove, 4B ... Linear groove, 5 ... Pipe material, 10 ... Internal spiral grooved pipe (Transmission) Heat pipe), 81 ... expansion pipe (heat transfer pipe), 10a ... outer peripheral surface, 10b ... inner peripheral face, 10B ... straight grooved pipe (elementary pipe), 10C ... intermediate twisted pipe, 23 ... revolution flyer, 80 ... heat exchanger , 82 ... heat sink, 82a ... insertion hole, DM ... dice mark, D1 ... first direction, D2 ... second direction

Claims (5)

A heat transfer tube made of aluminum that is a twisted material of an extruded element tube,
Having a plurality of fins spirally formed on the inner peripheral surface,
A spiral die mark is formed on the outer peripheral surface,
A heat transfer tube in which the maximum depth of the die mark is 35 μm or less. The lead angle of the spiral die mark on the outer peripheral surface is 1.0 ° or more larger than the lead angle of the spiral fin.
The heat transfer tube according to claim 1.   A heat exchanger comprising the heat transfer tube according to claim 1 and a heat radiating plate coupled to the heat transfer tube. Extrusion molding by extrusion forming an aluminum tube having a plurality of fins extending linearly along the length direction on the inner peripheral surface and a die mark extending linearly along the length direction on the outer peripheral surface Process,
A torsion drawing process for imparting a torsion angle of 5 ° or more together with drawing to the raw tube;
An empty drawing step of drawing after the drawing step that the diameter reduction rate is 10% or more,
Manufacturing method of heat transfer tube.   The manufacturing method of the heat exchanger tube of Claim 4 with which the die mark after the said emptying process is extended | stretched 1.02 times or more with respect to the die mark after the said extrusion molding process.