JP6964497B2 - Manufacturing method of heat transfer tube, heat exchanger and heat transfer tube - Google Patents

Description

The present invention relates to a heat transfer tube having excellent moldability, and a method for manufacturing a heat exchanger and a heat transfer tube using the same.

Heat transfer tubes made of copper-based materials such as copper and copper alloys are used in general fin-and-tube type heat exchangers used in air conditioners, etc., but the price of copper metal has risen in recent years. As a result, material replacement with aluminum alloys, which are cheaper, lighter, and more recyclable, is progressing. Examples of the heat transfer tube made of an aluminum alloy include the heat transfer tube shown in Patent Document 1 manufactured by extrusion processing having a straight groove on the inner surface, and the tube by extrusion is used.

Japanese Unexamined Patent Publication No. 2016-28219

As a method for manufacturing a heat transfer tube by extrusion using an aluminum alloy, there is a port hole extrusion method as a method for manufacturing a heat transfer tube having a straight groove. The port hole extrusion method is a method in which a mandrel and a die are connected by a bridge, and an aluminum alloy material is extruded through a plurality of port holes formed between them to form a raw tube. Since the aluminum alloy material is separated at the port hole, merged, welded again, and integrated, a plurality of welded portions called weld lines are formed linearly along the length direction of the heat transfer tube.

Generally, in fin-and-tube type heat exchangers of air conditioners and refrigerators, a heat transfer tube with a pre-bent hairpin is inserted into the holes of aluminum heat sinks arranged at equal pitches, and a tube expansion plug with a diameter larger than the inner diameter is inserted. By inserting and expanding the tube, the heat transfer tube and the heat sink are joined. Then, the end of the hairpin-bent heat transfer tube is expanded by flaring to increase the diameter, and a U-bend tube that has been bent in advance is fitted and brazed to the tube end, which is assembled and manufactured. If there is an unwelded part in the weld line, cracks will occur at the end of the pipe that has been expanded during flaring, which will cause poor brazing.

There is no problem in strength of the weld line as long as sufficient diffusion is obtained at the bonding interface, but if it is insufficient and unwelded, the bonding strength is low. In the latter case, when the heat transfer tube is processed, cracks or breaks are likely to occur starting from those unwelded parts, which tends to cause molding defects. If the welding is insufficient, the tube is expanded during the flare processing described above. The end of the pipe is prone to cracking.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an aluminum heat transfer tube having excellent moldability, particularly excellent tube expandability for inserting a U-bend in a heat exchanger assembly.

The heat transfer tube of the present invention is a heat transfer tube made of a twisted tube made of aluminum, has a plurality of spirally formed fins on the inner peripheral surface, and has a spiral weld line on the outer peripheral surface in the length of the tube. The weld line is formed intermittently along the direction, and the weld line is a portion including 30 or more pits having a diameter of 10 μm or more in the observation in the observation field of 180 μm × 250 μm, and the lead angle of the weld line is 9. ° or more and 15 ° or less, and the length of the weld line is 5 mm or less.

Further, in the above-mentioned heat transfer tube, a configuration in which the length of the weld line is 1.5 mm or more and 2 mm or less may be adopted.

Further, in the above-mentioned heat transfer tube, if the lead angle of the fin is θ1, the lead angle of the weld line is θ2, the inner peripheral length of the tube is α, and the wall thickness of the tube is β, tan θ2 = { A configuration having a relationship of (α + 2πβ) tan θ1} / α may be adopted.

Further, the heat exchanger according to one aspect of the present invention is a heat exchanger including the above heat transfer tube and a heat sink coupled to the heat transfer tube.

Then, in the above-mentioned method for manufacturing a heat transfer tube, a first twisting method is performed in which a raw tube having a plurality of straight grooves formed along the length direction on the inner peripheral surface is reduced in diameter and twisted to form an intermediate twisted tube. It has a pulling step, a second twist pulling step of reducing the diameter of the intermediate twisted pipe and applying a twist, and an empty pulling step of reducing the diameter by pulling after the pulling step, and reducing the total of each step. The diameter ratio is 30% or more, the diameter reduction ratio of each step is 25% or less, and the heat treatment step of 4 hours or more is performed at a high temperature of 400 ° C. or higher after the dry drawing step.

According to the present invention, the heat transfer tube is spiral and has weld lines with a lead angle of 9 ° or more and 15 ° or less and a length of 5 mm or less intermittently along the length direction of the tube, and cracks occur when the tube is expanded. A difficult heat transfer tube can be provided.
According to the present invention, the extruded raw pipe in which the weld line is generated is subjected to strong drawing and twisting, and then heat-treated at a high temperature to promote the diffusion of the weld line and further enhance the bonding of the portion. Thereby, in the processing when assembling the heat transfer tube to the heat exchanger, it is possible to provide an aluminum heat transfer tube having excellent moldability, a heat exchanger using the heat transfer tube, and a method for manufacturing the same.

It is a front view of the heat exchanger of an embodiment. It is a partial perspective view of the heat exchanger of an embodiment. It is a cross-sectional view of the heat transfer tube of an embodiment. It is a vertical sectional view of the heat transfer tube of an embodiment. It is a side view of the heat transfer tube of an embodiment. It is a vertical sectional view of the raw pipe (straight grooved pipe) in the manufacturing method of embodiment. It is a perspective view of the raw pipe (straight grooved pipe) in the manufacturing method of embodiment. It is a front view which shows the manufacturing apparatus which performs the twisting process in the manufacturing method of embodiment. It is a top view of the floating frame seen from the arrow IX direction in FIG. It is an image taken by a laser microscope of the outer peripheral part of a heat transfer tube, (a) is a part where a weld line remains, and (b) is a part where a weld line disappears.

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 characteristic parts, the characteristic parts may be enlarged for convenience, and the dimensional ratios of the respective components may not be the same as the actual ones. No. Further, for the same purpose, a part that is not a feature may be omitted in the figure.

[Heat exchanger]
1 and 2 are schematic views of the heat exchanger 80 of the embodiment.
The heat exchanger 80 has a structure in which a heat transfer tube 81 is provided in a meandering manner as a tube through which a refrigerant passes, and a plurality of aluminum heat sinks 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 plates 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 adjacent main pipes 81A with a U-shaped elbow pipe 81B. It becomes. Further, the refrigerant inlet portion 87a is formed on one end side of the heat transfer tube 81 penetrating the heat radiation plate 82, and the refrigerant outlet portion 87b is formed on the other end side of the heat transfer tube 81. The heat exchanger 80 is configured.

[Heat transfer tube]
Next, the heat transfer tube 10 before expansion of the heat exchanger 80 used for manufacturing the above-mentioned heat exchanger 80 will be specifically described.
FIG. 3 is a cross-sectional view of the heat transfer tube 10 of the embodiment, and FIG. 4 is a vertical cross-sectional view. Further, 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 for an extruded raw tube. As the heat transfer tube 10, one made of aluminum or an aluminum alloy can be used. When an aluminum alloy is used for the heat transfer tube 10, the aluminum alloy is not particularly limited, and is a pure aluminum system such as 1050, 1100, 1200 specified by JIS, or 3000 represented by 3003 to which Mn is added. A system aluminum alloy or the like can be applied. In addition to these, the heat transfer tube 10 may be configured by using any of the 5000 series to 7000 series aluminum alloys specified in JIS. In addition, in this specification, "aluminum" is a concept including an aluminum alloy and pure aluminum.

The heat transfer tube 10 is a tube material having a circular outer shape in cross section. The diameter of the outer peripheral surface (tube surface layer) 10a of the heat transfer tube 10 is, for example, 4 mm or more and 20 mm or less. A plurality of fins 3 formed spirally along the length direction are provided on the inner peripheral surface 10b of the heat transfer tube 10. A spiral groove 4 having an inner diameter larger than that of the tip of the fin 3 is formed between the fins 3.

In this embodiment, 30 to 60 fins 3 are provided. The height of the fin 3 (that is, the dimension in the radial direction) is 0.1 mm or more and 0.3 mm or less. The bottom wall thickness β of the heat transfer tube 10 (that is, 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 (the angle formed by the side surfaces of the fin 3) is 10 ° to 30 °.

As shown in FIG. 3, four weld lines WLs arranged at equal intervals along the circumferential direction are provided on the outer peripheral surface 10a of the heat transfer tube 10. Further, as shown in FIG. 5, the weld line WL is spirally formed on the outer peripheral surface 10a of the heat transfer tube 10. The weld line WL is a portion where the materials are merged and welded during extrusion processing. The weld line WL extends in the depth direction from the outer peripheral surface 10a toward the inner peripheral surface 10b side.
The number of weld lines WL is not limited to four. The weld line WL is formed in a portion where billets housed in the apparatus are divided into a plurality of flow paths and pumped and merged in extrusion processing. Therefore, the number of weld lines WL is determined according to the number of flow paths in the extruder.

In the present embodiment, the lead angle θ2 of the weld line WL spirally formed on the outer surface of the heat transfer tube is 8 ° or more. As will be described later, the heat transfer tube 10 of the present embodiment is formed by applying a twisting process to a raw tube 10B (see FIG. 6) having a linear fin 3 and a linear weld line WL. There is.

In a conventional heat transfer tube, since the weld line is formed linearly along the longitudinal direction of the heat transfer tube, if a crack occurs at the tube end during flaring, the crack grows along the longitudinal direction. It was easy and the entire heat transfer tube could not be used. According to the heat transfer tube 10 of the present embodiment, since the weld line WL is formed in a spiral shape, even if a crack occurs at the end of the pipe during flaring, the crack is difficult to propagate and is defective. It is possible to suppress the occurrence of large cracks. Such an effect can be remarkably exhibited by setting the lead angle θ2 of the weld line WL to 8 ° or more.

In this embodiment, the spiral weld line WL is formed intermittently along the length direction. In other words, the weld line WL is formed discontinuously, and the weld line WL is provided with a partially interrupted portion. As described above, the weld line WL is formed along the welded portion between the materials when the extrusion process is performed. Therefore, in the heat transfer tube 10, the structure of the weld line WL is different from that of other parts. As will be described later, the heat transfer tube 10 of the present embodiment is manufactured by repeatedly drawing and twisting a raw tube formed by extrusion processing, and is eliminated by heat treatment. The weld line WL is mixed with the surrounding structure by being subjected to the processing a plurality of times, and the boundary becomes ambiguous. As a result, the weld line WL partially disappears and becomes intermittent.

According to this embodiment, the weld line WL is formed intermittently. In addition, the portion where the weld line WL has disappeared is mixed with the surrounding tissue and homogenized. Therefore, the strength of the heat transfer tube 10 along the weld line WL can be increased. As a result, it is possible to provide a heat transfer tube 10 having excellent workability, which is less likely to crack during flaring.

The length of each intermittently formed weld line WL (that is, the length of the weld line WL in the continuous portion) is preferably 5 mm or less. By setting the length of each weld line WL to 5 mm or less, the occurrence and propagation of cracks due to the weld line WL can be effectively suppressed. The length of the weld line WL is a three-dimensional length on the cylindrical outer peripheral surface 10a of the heat transfer tube 10.

When the heat transfer tube 10 is immersed in an 8% caustic soda aqueous solution for 20 seconds and etched, the weld line WL rises like a white streak on the surface. Further, since the white streak-shaped portion is a welded portion, there is a difference in the etching method as compared with other portions, and fine pits are generated. In this state, in the weld line WL, light is scattered and can be identified as a streak-like portion.

10A and 10B are images taken by a laser microscope on the outer peripheral portion of the heat transfer tube 10. FIG. 10A is a portion where the weld line remains, and FIG. 10B is a weld line disappearance portion. As shown in FIG. 10, by etching, fine pits on the outer peripheral portion of the heat transfer tube become apparent. As shown in FIG. 10A, when the outer peripheral surface is observed with a laser microscope, pits having a diameter of 10 μm or more are formed on the weld line. On the other hand, as shown in FIG. 10B, only a few pits having a diameter of 10 μm or more are formed in the weld line disappearance portion.

In the present specification, in the observation in the range of the observation field of view of 180 μm × 250 μm with a laser microscope, the portion including 30 or more pits having a diameter of 10 μm or more is defined as a weld line WL. Therefore, it is considered that the weld line WL has disappeared in the portion where the number of pits having a diameter of 10 μm or more is less than 30.

Further, according to the present embodiment, a plurality of fins 3 formed spirally along the length direction are provided on the inner peripheral surface 10b of the heat transfer tube 10. By forming the spiral fins 3 on the inner peripheral surface 10b, the heat exchange efficiency between the heat transfer tube 10 and the refrigerant liquid flowing inside the heat transfer tube 10 can be improved. The heat transfer tube 10 provided with the spiral fins 3 can be formed by applying a twist to the raw tube 10B having fins extending linearly in the length direction by extrusion processing. Further, by applying a twist, the weld line WL can be formed in a spiral shape, and the heat transfer tube 10 which is less likely to be cracked by flaring can be provided.

As shown in FIG. 4, the fins 3 are formed in a spiral shape with a lead angle θ1. On the other hand, as shown in FIG. 5, the weld line WL is formed in a spiral shape with a lead angle θ2. When α is the inner peripheral length and β is the bottom wall thickness, the lead angle θ1 of the fin 3 and the lead angle θ2 of the weld line WL satisfy the following relationship.

According to the above equation, the lead angle θ2 of the weld line WL is larger than the lead angle θ1 of the fin 3 from the above equation. This is because the surface that serves as a reference for the lead angle θ1 of the fin 3 and the lead angle θ2 of the weld line WL is different between the outer peripheral surface and the inner peripheral surface due to the difference in wall thickness.

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

<Extrusion molding 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 step, 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, a raw pipe 10B in which a plurality of straight grooves 4B along the length direction are formed on the inner surface at intervals in the circumferential direction is manufactured (straight groove). Attached pipe extrusion process). In the raw tube 10B formed by the extrusion molding step, four weld lines WL extending linearly in the length direction of the raw tube 10B are formed. The four weld lines WL are located at equal intervals (90 ° intervals) along the circumferential direction of the raw tube 10B.

<Twisting process>
Next, the twisting process will be described.
The twisting step is a step of spiraling the weld line WL, the fins 3B, and the straight groove 4B by applying a twist to the above-mentioned raw pipe 10B while drawing out.

In this specification, the pipe material before twisting (that is, the above-mentioned raw pipe 10B) is referred to as a "straight grooved pipe". Further, the tube material after twisting (that is, the heat transfer tube 10 described above) is referred to as an "inner surface spiral grooved tube". Further, in the process from the straight grooved pipe to the inner spiral grooved pipe, an intermediate formed product to which about half the twist is given as compared with the inner spiral grooved pipe is called an "intermediate twisted pipe". Further, the “tube material” in the present specification is a superordinate concept of a straight grooved pipe, an intermediate twisted pipe and an inner spiral grooved pipe, and means a pipe to be processed regardless of the stage of the manufacturing process.
In the present specification, the "pre-stage" and "rear stage" mean the front-back 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 for the inner spiral grooved pipe. The portion arranged in the front stage is not always arranged in the front, and the portion arranged in the rear stage is not always arranged in the rear.

<Manufacturing equipment that performs drawing and twisting processes and empty drawing processes>
FIG. 8 is a front view showing a manufacturing apparatus A for manufacturing an inner spiral grooved tube (heat transfer tube) 10 by applying two twists to a straight grooved tube (bare tube) 10B. First, the manufacturing apparatus A will be described, and then the twisting step and the empty pulling step using the manufacturing apparatus A will be described.

The manufacturing apparatus A includes a revolution 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 revolution capstan. It includes 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, the details of each part will be described in detail.

(Revolution mechanism)
The revolution mechanism 30 has 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 rotating shaft 35, and the first revolution capstan 21, the second revolution capstan 22, and the revolution flyer 23 fixed to the rotating shaft 35.
Further, the revolution mechanism 30 maintains a stationary state of the floating frame 34 located coaxially with the rotating shaft 35 and supported by the rotating 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 maintained in a stationary state.

Both the front shaft 35A and the rear shaft 35B have a cylindrical shape with a hollow inside. Both the front shaft 35A and the rear shaft 35B are arranged coaxially with the revolution center axis C (pass line of the first drawing die) as the center axis. The front shaft 35A is rotatably supported by the front stand 37A via a bearing 36, and extends from the front stand 37A toward the rear (rear stand 37B side). Similarly, the rear shaft 35B is rotatably supported by the rear stand 37B via a bearing, and extends from the rear stand 37B toward 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 portion 35Ab of the front shaft 35A at a tip penetrating 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 penetrating the rear stand 37B and interlocks with the linear motion shaft 39f via the belt 39d. As a result, the front shaft 35A and the rear shaft 35B rotate synchronously around the revolution center axis C.

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

(Floating frame)
The floating frame 34 is supported by bearings 34a at the ends 35Aa and 35Ba of the front shaft 35A and the rear shaft 35B of the rotating shaft 35 facing each other. The floating frame 34 also 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 viewed from the direction of arrow IX in FIG. As shown in FIGS. 8 and 9, the floating frame 34 has a box shape that opens vertically. The floating frame 34 has a front wall 34b and a rear wall 34c that face each other in the front-rear direction, and a pair of support walls 34d that face each other in the left-right direction and extend in the front-rear direction.

Through holes are provided in the front wall 34b and the rear wall 34c, and the ends 35Aa and 35Ba of the front shaft 35A and the rear shaft 35B are inserted, respectively. A bearing 34a is interposed between the ends 35Aa and 35Ba and the through holes of the front wall 34b and the rear wall 34c. As a result, it is difficult for the rotation of the rotating shaft 35 (front shaft 35A and rear shaft 35B) to be transmitted to the floating frame 34. The floating frame 34 keeps a stationary state with respect to the ground G even when the rotating shaft 35 is in a rotating state. A weight that biases the center of gravity of the floating frame 34 with respect to the revolution 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 34d has the unwinding bobbin 11, the first guide capstan 18, and the first drawing die 1 arranged on both sides in the left-right direction (vertical direction in FIG. 9). There is. The pair of support walls 34d rotatably support the bobbin support shaft 12 that holds the unwinding bobbin 11 and the rotation shaft J18 of the first guide capstan 18. Further, the support wall 34d supports the first drawing die 1 via a die support (not shown).

(Unwinding bobbin)
A straight grooved pipe 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 pipe 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 rotating shaft 35. Further, the bobbin support shaft 12 is supported by a floating frame 34 so as to rotate and rotate. Here, the rotation rotation means rotation around the central axis of the bobbin support shaft 12 itself. The bobbin support shaft 12 holds the unwinding bobbin 11 and rotates on its axis in the supply direction of the unwinding bobbin 11 to assist the feeding of the pipe material 5 of the unwinding bobbin 11.

The unwinding bobbin 11 is removed when all the wound straight grooved pipes 10B are supplied, and is replaced with another unwinding bobbin. The removed empty unwinding bobbin 11 is attached to an extruder forming the straight grooved pipe 10B, and the straight grooved pipe 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 randomly wound on the unwinding bobbin 11, the supply can be performed without any problem, and the unwinding bobbin 11 can be used without rewinding. Further, the weight of the unwinding bobbin 11 does not limit the number of revolutions of the revolution rotation for imparting a twist to the pipe material 5 in the manufacturing apparatus A. Therefore, the long pipe material 5 can be wound around the unwinding bobbin 11. As a result, the long pipe material 5 can be twisted, and the manufacturing efficiency can be improved.

The bobbin support shaft 12 is provided with a brake portion 15. 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 regulates the rotation of the unwinding bobbin 11 in the unwinding direction. A rear 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 torque as a braking force can be adopted.

(1st guide capstan)
The first guide capstan 18 has a disk shape. The pipe material 5 unwound from the unwinding bobbin 11 is wound around the first guide capstan 18 once. The tangential direction of the outer circumference of the first guide capstan 18 coincides with the revolution center axis C. The first guide capstan 18 guides the pipe member 5 along the first direction D1 on the revolution center axis C.
The first guide capstan 18 is supported by a floating frame 34 so as to rotate and rotate. Further, on the outer circumference of the first guide capstan 18, the guide rollers 18b that can rotate and rotate are arranged side by side. The first guide capstan 18 of the present embodiment rotates on its own axis and the guide roller 18b rotates, but if either one rotates, the pipe material 5 can be smoothly conveyed. In FIG. 9, the guide roller 18b is not shown.

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

(1st pull-out die)
The first drawing die 1 reduces the diameter of the pipe material 5 (straight grooved pipe 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 center axis C of the rotating shaft 35. Further, the first direction D1 is parallel to the revolution center axis C.
Lubricating oil is supplied to the first drawing die 1 by the lubricating oil supply device 9A fixed to the floating frame 34. As a result, the pulling force of the first pulling die 1 can be reduced.
The pipe material 5 that has passed through the first drawing die 1 is introduced into the front shaft 35A through a through hole provided in the front wall 34b of the floating frame 34.

(1st revolution capstan)
The first revolution capstan 21 has a disk shape. The first revolution capstan 21 is arranged in a lateral hole 35Ac that radially penetrates the inside and outside of the hollow front shaft 35A. The first revolving capstan 21 is supported by a support 21a fixed to the outer peripheral portion of the rotating shaft 35 (front shaft 35A) with the center of the disk as the rotating shaft J21 in a state where the rotation can be freely rotated.

In the first revolution capstan 21, one of the tangents on the outer circumference substantially coincides with the revolution center axis C.
A pipe material 5 conveyed in the first direction D1 on the revolution center axis C is wound around the first revolution capstan 21 for one or more turns. The first revolution capstan 21 winds the pipe material 5 and pulls it out from the inside of the front shaft 35A to guide it to the revolution flyer 23.

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

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

The first revolution capstan 21 and the drive motor 20 are preferably arranged at positions symmetrical with respect to the revolution center axis C so that the center of gravity is located on the revolution center axis C of the front shaft 35A. Thereby, the balance of rotation of the front shaft 35A can be stabilized. If the weight difference between the first revolution 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 reverses the pipe line of the pipe material 5 between the first drawing die 1 and the second drawing die 2. The revolving flyer 23 reverses the pipe material 5 conveyed in the first direction D1 which is the drawing direction of the first drawing die 1, and sets the conveying direction to 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 the 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 simply a plate-like structure for the pipe to pass through and a shape to which a ring for passing the pipe is attached. This ring may be provided on a plate-shaped member. A part of this ring may be composed of a part of this plate-shaped member. The plate-shaped member may be supported by the rotating shaft 35 in the same manner as the guide roller support.
The guide rollers 23a are arranged in a bow shape that curves outward with respect to the revolution center axis C. The guide roller 23a itself rolls and smoothly conveys the pipe material 5. The revolution flyer 23 rotates around the floating frame 34, the first drawing die 1 supported in the floating frame 34, and the unwinding bobbin 11 around the revolution rotation center axis C.

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

The revolution flyer 23 of the present embodiment has been described as being for transporting the pipe material 5 by the guide roller 23a. However, the revolution flyer 23 may be formed from a strip formed in an arch shape, and the pipe material 5 may be transported by sliding one surface of the strip.
Further, in FIG. 8, a case where the pipe material 5 passes outside the guide roller 23a is illustrated.
However, when the rotation speed of the revolution flyer 23 is high, the pipe material 5 may derail from the revolution flyer due to centrifugal force. In such a case, it is preferable to further provide a guide roller 23a on the outside of the pipe material 5.
A plurality of dummy flyers having the same weight as the revolution flyer 23 and extending from the front shaft 35A to the rear shaft 35B and rotating synchronously with the revolution flyer 23 may be provided. Thereby, the rotation of the rotating shaft 35 can be stabilized.

(Second revolution 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 in a state where it can rotate freely. Further, on the outer circumference of the second revolving capstan 22, guide rollers 22c that can rotate and rotate are arranged side by side. The second revolving capstan 22 of the present embodiment rotates on its own axis and the guide roller 22c rotates, but if either one rotates, the pipe material 5 can be smoothly conveyed.

In the second revolution capstan 22, one of the tangents on the outer circumference substantially coincides with the revolution center axis C.
A pipe material 5 conveyed in the second direction D2 on the revolution center axis C is wound around the second revolution capstan 22 for one or more turns. The second revolution capstan 22 feeds the wound pipe material in the second direction D2 on the revolution center axis C.

The second revolution capstan 22 revolves around the revolution center axis C together with the rear shaft 35B. The revolution center axis C extends in a direction orthogonal to the rotation axis J22 of the rotation rotation of the second revolution capstan 22. The pipe material 5 unwound from the second revolution capstan 22 is reduced in diameter in 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. As a result, the pipe material 5 changes from the intermediate twisted pipe 10C to the inner spiral grooved pipe 10.

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

(Second pull-out die)
The second drawing die 2 is arranged after the second revolution capstan 22. The second drawing die 2 has the 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 center axis C of the rotating shaft 35.

The second drawing die 2 is supported by the gantry 62, for example, via a die support (not shown). Further, lubricating oil is supplied to the second drawing die 2 by the lubricating oil supply device 9B attached to the gantry 62. As a result, the pulling force of the second pulling die 2 can be reduced.
Due to the diameter reduction and twisting of the second drawing die 2, the pipe material 5 changes from the intermediate twisted pipe 10C to the inner spiral grooved pipe 10.

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

The second guide capstan 61 is rotatably supported by the gantry 62 around the rotation shaft J61. Further, the rotating shaft 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 and rotated by the drive motor 63 in the winding direction (conveying direction) of the pipe material 5. As the drive motor 63, it is preferable to use a torque motor capable of torque control.

A forward tension is applied to the pipe material 5 by driving the second guide capstan 61. As a result, the pipe material 5 is conveyed forward by applying the drawing stress required for processing in the second drawing die 2.

<Finishing 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 step (finishing drawing step) using the finish drawing die 7, the change in the cross section due to the drawing is small, the surface and dimensions are finished and shaped, and the roundness of the pipe material 5 is restored. Further, in the dry drawing step, the non-uniformity 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 take-up bobbin 71.

(Take-up bobbin)
The take-up bobbin 71 is provided at the end of the pipeline of the pipe material 5, and collects the pipe material 5. An induction portion 72 is provided in front of the take-up bobbin 71. The guide portion 72 has a traverse function, and winds up the pipe material 5 and winds it around the bobbin 71 in an aligned manner.

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 pipe material 5 without loosening it. The take-up bobbin 71 is removed when the pipe material 5 is sufficiently wound and replaced with another take-up bobbin 71.

<Twisting process>
A method of manufacturing the inner spiral grooved tube 10 by using the above-mentioned inner surface spiral grooved tube manufacturing apparatus A will be described.
First, as a preliminary step, the straight grooved tube 10B is unwound and wound around the bobbin 11 in a coil shape. Further, the unwinding bobbin 11 is set in the floating frame 34 of the manufacturing apparatus A. Further, the pipe material 5 (straight grooved pipe 10B) is unwound from the unwinding bobbin 11 and the pipeline of the straight grooved pipe 10B is set in advance. Specifically, the pipe material 5 is divided into 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 in this order and set.

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

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

In the first torsional pull-out step, a forward tension is applied to the pipe material 5 by the drive motor 20 that drives the first revolution capstan 21. At the same time, a rear tension is applied to the pipe material 5 by the brake portion 15 of the unwinding bobbin 11. Therefore, it is possible to apply an appropriate tension to the pipe material 5, and it is possible to impart a stable twist angle to the pipe material 5 without causing buckling or breakage.

The pipe material 5 is passed through the first drawing die 1 and then wound around the first revolving capstan 21 that revolves. The pipe material 5 is reduced in diameter by the first drawing die 1 and twisted by the first revolution capstan 21. As a result, the straight groove 4B (see FIG. 6) on the inner surface of the pipe material 5 (straight grooved pipe 10B) is twisted to form the spiral groove 4 on the inner surface. By the first twisting and pulling step, the straight grooved pipe 10B becomes an intermediate twisted pipe 10C. The intermediate twisted pipe 10C is a pipe material in an intermediate stage in the manufacturing process of the inner surface spiral grooved pipe 10, and is in a state in which a spiral groove having a twist angle shallower than that of the spiral groove 4 of the inner surface spiral grooved pipe 10 is formed.

In the first torsional drawing step, the pipe material 5 is twisted and at the same time the diameter is reduced by the drawing die. That is, the pipe material 5 is subjected to a composite stress due to simultaneous machining of twisting and diameter reduction. Under the combined stress, the yield stress of the pipe material 5 becomes smaller than that in the case where only the twisting process is performed, and a large twist can be applied to the pipe material 5 before the buckling stress of the pipe material 5 is reached. As a result, it is possible to impart a large twist while suppressing the occurrence of buckling of the pipe material 5.

A first guide capstan 18 is provided in front of the first drawing die 1 to regulate the rotation of the pipe material 5. That is, the pipe material 5 is restrained from being deformed in the twisting direction in the front stage of the first drawing die 1. The pipe material 5 is twisted between the first drawing die 1 and the first revolving capstan 21. That is, in the first torsional drawing step, the region (machining area) where the pipe material 5 is twisted is limited between the first drawing die 1 and the first revolution capstan 21.
There is a correlation between the length of the machining area and the limit twist angle (the maximum twist angle that can be twisted without buckling), and even if a large twist angle is given by shortening the machining area. Buckling is unlikely to occur. By providing the first guide capstan 18, the machining area can be set short without twisting in the front stage of the first drawing die 1. Further, by reducing the distance between the first drawing die 1 and the first revolution capstan 21, the machining area can be set short, and a large twist can be applied to the pipe material 5 without causing buckling.

The diameter reduction ratio of the pipe material 5 by the first drawing die 1 is preferably 2% or more. A correlation is observed between the limit twist angle and the diameter reduction ratio, and the limit twist angle tends to increase as the diameter reduction ratio at the time of drawing increases. That is, if the diameter reduction ratio is too small, the effect of pulling out is poor and it is difficult to obtain a large twist angle. Therefore, it is preferably 2% or more. For the same reason, it is more preferable that the diameter reduction ratio is 5% or more.
On the other hand, if the diameter reduction ratio becomes too large, fracture is likely to occur at the processing limit, so it is preferably 25% or less.

Next, the pipe material 5 is wound around the revolution flyer 23, and the transport direction of the pipe material 5 is directed to the second direction D2 on the revolution center 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). As a result, the transport 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 around the floating frame 34 about the revolution center axis C. The first revolution capstan 21, the revolution flyer 23, and the second revolution capstan 22 rotate synchronously about the revolution center axis C. Therefore, between the first revolution capstan 21 and the second revolution capstan 22, the pipe material 5 does not rotate relatively and is not twisted.

Next, the pipe material 5 that rotates together with the second revolution capstan 22 is passed through the second drawing die 2. As a result, the diameter of the pipe material 5 is reduced and a twist is applied to further increase the twist angle of the spiral groove 4 (second twisting and pulling step). The intermediate torsion tube 10C becomes the inner spiral grooved tube 10 by the second torsional drawing step.

In the second torsional pull-out step, forward tension is applied to the pipe material 5 by the drive motor 63 that drives the second guide capstan 61. When a torque controllable torque motor is used as the drive motor 63, the second guide capstan 61 can adjust the forward tension applied to the pipe material 5. By adjusting the forward tension with the second guide capstan 61, it is possible to apply an appropriate tension to the pipe material 5 in the second torsional pull-out step. As a result, a stable twist angle can be imparted to the pipe material 5 without causing buckling or breakage.

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 diameter of the pipe material 5 is reduced by the second drawing die 2, and the pipe material 5 is twisted by the second revolution capstan 22. As a result, a larger twist is applied to the spiral groove 4 on the inner surface of the pipe material 5, and the twist angle of the spiral groove 4 becomes larger. The intermediate torsion tube 10C becomes the inner spiral grooved tube 10 by the second torsional drawing step.

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 regulate the rotation of the pipe material 5. That is, the pipe material 5 is restrained from being deformed in the twisting direction before and after the second drawing die 2, and the pipe material 5 is twisted between the second revolution capstan 22 and the second guide capstan 61. Granted. That is, in the second twist-drawing step, the region (machining area) where the pipe material 5 is twisted is limited between the second revolution capstan 22 and the second drawing die 2. As described above, by shortening the processing area, buckling is less likely to occur even if a large twist angle is applied. By providing the second guide capstan 61, the machining area can be set short without twisting in the subsequent stage of the second drawing die 2.

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

In the second torsional pull-out step, as in the first torsional pull-out step, twisting and diameter reduction are performed to apply a composite stress to the pipe material 5. As a result, before the buckling stress of the pipe material 5 is reached, a large twist can be applied to the pipe material while suppressing the occurrence of buckling.

The diameter reduction ratio of the pipe material 5 by the second drawing die 2 is preferably 2% or more (more preferably 5% or more) and 25% or less, as in the first torsional drawing step.
If the first drawing die 1 is subjected to a large diameter reduction (for example, a diameter reduction of 30% or more), the pipe material 5 is work-hardened, so that the second drawing die 2 is subjected to a large diameter reduction. It becomes difficult. Therefore, the total of the diameter reduction ratio of the first drawing die 1 and the diameter reduction ratio of the second drawing die 2 is preferably 4% or more and 50% or less.

<Sky pulling process>
Next, the pipe material 5 is passed through the finish drawing die 7 (finish drawing step). By passing the pipe material 5 through the finish drawing die 7, the surface is shaped and the uneven thickness of the bottom wall thickness is reduced. Further, even if the pipe material 5 is slightly crushed or otherwise deformed, the deformation can be corrected by undergoing this finish drawing step to obtain a pipe 5R with an inner spiral groove having a predetermined roundness. can. The force for transporting the pipe material 5 with respect to the pulling load of the finishing pulling die 7 is applied by the drive motor 74 provided on the take-up bobbin 71.

Further, a heat transfer tube having a stable surface texture and shape can be manufactured by performing an air-pulling step after the twist-pulling step (the first twist-pulling step and the second twist-pulling step). The diameter reduction ratio of the pipe material 5 in the dry drawing step is preferably 25% or less. Further, the total diameter reduction ratio of the first drawing step, the second pulling step and the empty pulling step is preferably 30% or more.

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

<Heat treatment process>
Next, the heat treatment step will be described.
The heat treatment step is performed after the above-mentioned twisting step (strong processing). The heat treatment step is performed at a high temperature of 400 ° C. or higher for 4 hours or longer, and the bonding strength of the weld line is increased by diffusion by the heat treatment.

According to the twisting step of the present embodiment, the linear weld line WL formed in the extrusion molding step becomes spiral. As a result, it is possible to form a weld line WL in which cracks are unlikely to occur with an increase in internal pressure.
Further, according to the twisting step of the present embodiment, the twisting is repeated a plurality of times. As a result, the weld line WL formed in the extrusion molding process mixes with the surrounding structure and the boundary becomes ambiguous. As a result, the weld line WL can be partially eliminated and formed intermittently, and as a result, the heat transfer tube 10 having high pressure resistance can be manufactured.

According to the manufacturing method of the present embodiment, by directly applying a twist to the linear grooved pipe 10B, the weld line WL and the fin 3 can be spirally and intermittently formed at the same time. As a result, the inner spiral grooved tube that simultaneously achieves the effect of improving the pressure resistance by forming the weld line WL spirally and intermittently and the effect of improving the heat exchange rate by the spiral fin 3. 10 can be manufactured.

According to the manufacturing method of the present embodiment, the weld line generated in the raw pipe 5 by extrusion is performed by performing heat treatment (O material formation step) after twisting and drawing the raw pipe 5 formed by extrusion processing. The diffusion bonding of WL can be strengthened and the bonding strength can be increased.

According to the manufacturing method of the present embodiment, the total diameter reduction ratio of each step (first pulling step, second pulling step and empty pulling step) is 30% or more. By setting the diameter reduction ratio to 30% or more, a large twist can be imparted. Further, according to the manufacturing method of the present embodiment, the diameter reduction ratio of each step is 25% or less. When the diameter reduction ratio in each process is 25% or less, work hardening can be suppressed and the diameter reduction in the subsequent process can be smoothly performed.

According to the twisting step of the present embodiment, since the diameter is reduced at the same time as the twisting, the outer diameter and the cross-sectional area of the starting material and the final product are different. Further, since the combined stress of torsion and diameter reduction is applied to the pipe material, it is possible to reduce the shear stress required for the twisting process, and a large twist is applied to the pipe material 5 before the buckling stress of the pipe material 5 is reached. can. Therefore, a heat transfer tube having a large fin 3 with a lead angle θ1 and a thin bottom wall thickness can be manufactured without causing buckling. The heat exchange efficiency of the inner spiral grooved tube 10 can be improved by increasing the lead angle θ1. Further, the inner surface spiral grooved pipe 10 can be made lighter and less expensive by reducing the bottom wall thickness. That is, according to the present embodiment, it is possible to manufacture the inner spiral grooved tube 10 which is lightweight, inexpensive, and has high heat exchange efficiency.

According to the twisting step of the present embodiment, since the straight grooved pipe 10B is twisted and the diameter is reduced, a large twisting angle can be imparted while suppressing the occurrence of buckling. In the present embodiment, the outer diameter of the straight grooved pipe 10B, which is a material, is 1.1 times or more the outer diameter of the final product, the inner spiral grooved pipe 10.

According to the twisting step of the present embodiment, the pipe material 5 is twisted by the first revolution capstan 21 between the first drawing die 1 and the second drawing die 2. Further, the drawing directions of the first drawing die 1 and the second drawing die 2 are reversed. As a result, the pipe material 5 can be twisted by matching the twisting directions in the first twisting and pulling step and the second twisting and pulling step. Further, it is not necessary to revolve the unwinding bobbin 11 which is the start end of the pipeline of the pipe material 5 and the take-up bobbin 71 which is the end of the pipeline. Since the speed of the line depends on the rotation speed, the rotation speed can be easily increased in the twisting step 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.
Further, in the present embodiment, since the unwinding bobbin 11 is not revolved, a long straight grooved pipe 10B (tube material 5) can be wound around the unwinding bobbin 11. Therefore, according to the twisting step of the present embodiment, the unwinding bobbin 11 can be twisted in a single stroke without replacing the unwinding bobbin 11. That is, according to the present embodiment, mass production of the inner spiral grooved tube 10 becomes easy.

In the twisting step of the present embodiment, the pipe material 5 is twisted through at least two twisting and pulling steps. Therefore, it is possible to give a large twist angle by accumulating the twist angles given in the twist pulling step of each stage.

According to the twisting step of the present embodiment, the front tension and the rear tension are applied to the pipe material 5 in the first twisting and pulling step and the second twisting and pulling step. The forward 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. As a result, 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 pipe material 5 and the straight grooved pipe 10B enters the drawing die without misalignment, a stable twist angle can be imparted to the pipe 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 holes are located on the revolution center axis C. As a result, the pipe material 5 passing through the die hole can be arranged linearly with respect to the die hole, so that the diameter of the pipe material 5 can be uniformly reduced and buckling at the time of twisting can be suppressed. In the first drawing die 1 and the second drawing die 2, the position of the die hole with respect to the revolution center axis C is allowed as long as the diameter of the pipe material 5 can be reduced normally.

In the present embodiment, it is assumed that 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 interchanged and arranged. In this case, the transport path of the pipe material 5 is reversed. Further, the first drawing die 1 and the second drawing die 2 are arranged interchangeably, and the drawing directions of the respective drawing dies 1 and 2 are reversed and arranged along the conveying direction. Further, in the capstans located before and after the drawing dies 1 and 2, the capstan located at the rear stage of the drawing dies is driven in the winding direction (conveying direction) of the pipe material to apply a forward tension against the pulling force of the drawing dies. give.

(Evaluation of tube expandability)
As a test for confirming the soundness of the weld line, a pipe expansion test is performed by pushing a cone with an apex angle of 60 degrees (material SS400) into the pipe. The length of the pipe is 40 mm, the outer diameter is 6.35 mm, the bottom wall thickness is 0.55 mm, the number of rows is 45, the fin height is 0.24 mm, the fin bottom width is 0.23 mm, the fin top angle is 25 °, and the lead angle is 0. Samples varied from 1 to 15 ° were used. The end face was smoothed using a lathe. During the tube expansion test, beef tallow was applied to the surface in contact with the conical pipe with a brush to suppress variations in the results due to seizure.
Under the above conditions, the tube expansion load (force applied to the cone along the length direction of the heat transfer tube) and the pushing amount at the time when the heat transfer tube was cracked were measured.

As shown in Table 1, when the weld line was spiral, the tube expansion load and the pushing amount were larger than those of the linear shape. More specifically, when the weld line was spiral, the pushing amount could be 3 mm or more.

Although various embodiments of the present invention have been described above, the configurations and combinations thereof in each embodiment are examples, and the configurations are added, omitted, replaced, etc. within the range not deviating from the gist of the present invention. And other changes are possible. Further, the present invention is not limited to the embodiments.

1 ... 1st drawing die, 2 ... 2nd drawing die, 3, 3B ... Fins, 4 ... Spiral groove, 4B ... Straight groove, 5 ... Tube material, 10 ... Inner surface spiral grooved tube (heat transfer tube), 81 ... Expansion tube (heat transfer tube), 10a ... outer peripheral surface (tube surface layer), 10b ... inner peripheral surface, 10B ... straight grooved tube (bare tube), 10C ... intermediate spiral tube, 23 ... revolving flyer, 80 ... heat exchanger, 82 ... heat dissipation plate, 82a ... insertion hole, WL ... weld line, D1 ... first direction, D2 ... second direction

Claims (5)

A heat transfer tube made of aluminum twisted tube
It has a plurality of spirally formed fins on the inner peripheral surface, and has a plurality of fins.
Spiral weld lines are intermittently formed on the outer peripheral surface along the length direction of the pipe.
The weld line is a portion including 30 or more pits having a diameter of 10 μm or more in an observation in an observation field of view of 180 μm × 250 μm.
The lead angle of the weld line is 9 ° or more and 15 ° or less.
The length of the weld line is 5 mm or less.
Heat transfer tube. The length of the weld line is 1.5 mm or more and 2 mm or less.
The heat transfer tube according to claim 1. Assuming that the lead angle of the fin is θ1, the lead angle of the weld line is θ2, the inner circumference of the tube is α, and the wall thickness of the tube is β, then tan θ2 = {(α + 2πβ) tan θ1} / α. The heat transfer tube according to claim 1 or 2, wherein the heat transfer tube has a relationship. The heat transfer tube according to any one of claims 1 to 3 and a heat sink coupled to the heat transfer tube are provided.
Heat exchanger. The method for manufacturing a heat transfer tube according to any one of claims 1 to 3.
The first twist-pulling step of reducing the diameter of a raw tube having a plurality of straight grooves formed along the length direction on the inner peripheral surface and applying a twist to form an intermediate twisted tube.
A second torsional pull-out step of reducing the diameter of the intermediate torsion tube and imparting a twist,
After the drawing step, there is an empty drawing step in which the diameter is reduced by drawing.
The total diameter reduction ratio of each process is 30% or more, and the diameter reduction ratio of each process is 25% or less.
After the blanking step, a heat treatment step of 4 hours or more is performed at a high temperature of 400 ° C. or higher.
Manufacturing method of heat transfer tube.

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