JP6986942B2 - Manufacturing method of heat transfer tube, heat exchanger and heat transfer tube - Google Patents

Description

The present invention relates to an excellent heat transfer tube having excellent thermal characteristics and tube expandability, a heat exchanger provided with such a heat transfer tube, and a method for manufacturing the heat transfer tube.

Conventionally, copper alloys have been used for the heat transfer tubes of fin-and-tube type heat exchangers, but due to the depletion of copper resources, soaring copper metal prices, and recyclability, they are lightweight and inexpensive to recycle. Aluminum heat transfer tubes with excellent properties are beginning to be used.
In a heat transfer tube using a copper alloy and an aluminum alloy, a heat transfer tube having a spiral groove on the inner surface has been proposed in order to enhance its thermal characteristics. The area of the inner circumference of the pipe can be increased by spiraling the groove on the inner surface. In addition, by spiraling the grooves on the inner surface, when the refrigerant changes from liquid to gas inside the heat transfer tube, the refrigerant is pushed up along the protrusions between the grooves by the flow velocity. As a result, the refrigerant easily enters the gaps between the protrusions and evaporates, so that the heat transfer property is improved. Further, when the refrigerant changes from gas to liquid, the refrigerant tends to condense at the protrusions. Furthermore, by spiraling the groove on the inner surface, the movement of the refrigerant due to gravity becomes remarkable. As a result, the dry surface on the inner peripheral surface of the heat transfer tube is easily exposed, and the heat transfer performance is improved.
In general, in fin-and-tube type heat exchangers of air conditioners and refrigerators, heat transfer tubes with hairpins bent are inserted into the holes of heat dissipation plates arranged at equal pitches, and the heat transfer tubes are expanded with a tube expansion plug. Join the heat dissipation plate and the heat transfer tube. Then, it is assembled and manufactured by fitting and brazing a U-bend tube which has been previously bent to the tube end of an adjacent hairpin tube.

Japanese Unexamined Patent Publication No. 2008-267779

However, if the groove shape on the inner surface used in the heat transfer tube made of copper material is used as it is for the heat transfer tube made of aluminum material, the strength of the aluminum alloy is inferior to that of copper, so the pressure resistance due to the refrigerant is maintained. Therefore, the bottom wall thickness of the heat transfer tube is increased, which makes it difficult to process by the conventional manufacturing method, and there is a problem that the degree of freedom of the obtained inner groove shape is low.
In addition, there is a problem of surface scratches, for example, cracks are likely to occur starting from the hairpin bending process.

An object of the present invention is to provide a heat transfer tube having sufficient heat transferability and workability.

The heat transfer tube according to one aspect of the present invention is an aluminum heat transfer tube which is a twisted material of an extruded raw tube, and is formed on the inner peripheral surface along the circumferential direction and spirally along the length direction. a plurality of fins, said fins, Ri magnitude der tip width than the bottom width, wet edge length (E) and the outer peripheral is the surface length along the circumferential direction of the inner circumference of the heat transfer tube The ratio [E / D] of the length (D) is 1.9 or more and 2.3 or less, and the length (F) occupied by the bottom of the groove located between the fins and the wet edge length (the wet edge length). The ratio [F / E] of E) is 0.20 or more and 0.31 or less, the arc length of the bottom of the fin is 0.13 mm or more, and the lead angle of the fin is 15 ° or more and 45. Less than °.

Further, in the above-mentioned heat transfer tube, it is preferable that the lead angle of the fin is 15 ° or more and 25 ° or less.
Further, in the above-mentioned heat transfer tube, the arc length of the fin bottom is preferably 0.15 mm or less.

Further, in the above-mentioned heat transfer tube, the fins have a pair of side wall portions that approach each other from the tip side to the bottom side, and the angle between the pair of side wall portions is larger than 0 ° and 35 ° or less. There may be a configuration in which the lead angle of the fin is 15 ° or more and less than 45 °.

Further, in the above-mentioned heat transfer tube, a spiral die mark may be formed on the outer peripheral surface, and the maximum depth of the die mark may be 35 μm or less.
Further, in the above-mentioned heat transfer tube, it is preferable that the outer diameter is 4 mm or more and 15 mm or less.

The heat exchanger according to one aspect of the present invention includes the above heat transfer tube and a heat radiation plate coupled to the heat transfer tube.

The method for manufacturing a heat transfer tube, which is one aspect 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 molding step of molding by extrusion an aluminum blank tube having a twisting withdrawal step of twisting angle imparts twist more than 15 ° with the withdrawal to the base tube, radial contraction rate after the drawing process is 10% Including the above-mentioned pulling-out step, the inner peripheral surface has a plurality of fins arranged along the circumferential direction and spirally formed along the length direction, and the fins have a bottom width at the tip. The ratio [E / D] of the wet edge length (E) and the outer peripheral length (D), which is larger than the width and is the surface length along the circumferential direction in the inner circumference of the heat transfer tube, is 1.9 or more. The ratio [F / E] of the length (F) occupied by the bottom of the groove located between the fins to the wet edge length (E) is 0.20 or more and 0. This includes obtaining a heat transfer tube having a fin bottom arc length of 0.13 mm or more and a fin lead angle of 15 ° or more and less than 45 °.
In the method for manufacturing a heat transfer tube according to one aspect of the present invention, the fins have a pair of side wall portions that approach each other from the tip side toward the bottom side, and the angle between the pair of side wall portions is 0 °. It is more preferably 35 ° or less.

According to the present invention, it is possible to provide a heat transfer tube having excellent thermal characteristics and tube expandability.

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 partially enlarged view of FIG. 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, and is the figure which shows typically the die mark. It is a vertical sectional view of the raw pipe (the pipe with a straight groove) in the manufacturing method of an embodiment. It is a perspective view of the raw pipe (straight grooved pipe) in the manufacturing method of an embodiment. It is a front view which shows the manufacturing apparatus which performs the twisting process in the manufacturing method of embodiment. 9 is a plan view of a floating frame seen from the direction of arrow X in FIG. 9. (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. The side view which shows the tube expansion jig used in an Example. The holding jig used in the embodiment and the procedure of the tube expansion test using the holding jig are shown, (a) is a perspective view showing the support base and the first holding member fixed to the support base, and (b) is the first. A perspective view showing a state in which the holding member and the second holding member are overlapped and fixed, (c) is a perspective view showing a state in which a heat transfer tube with an inner spiral groove is inserted into a hole, and (d) is a heat transfer tube with an inner spiral groove. It is a perspective view which shows the state which the tube expansion tool was inserted in. A heat transfer characterization device for performing the condensation test used in the examples. A heat transfer characterization device for performing the evaporation test used in the examples.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In addition, 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 each component may not be the same as the actual ones. No. In addition, for the same purpose, there are cases where non-characteristic parts are omitted.

[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 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 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. The U-shaped main pipe 81A and the elbow pipe 81B are formed by bending the heat transfer tube 10 described later into a U-shape. 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 an enlarged view of a part of FIG. FIG. 5 is a vertical sectional view of the heat transfer tube 10. FIG. 6 is a side view of the heat transfer tube 10 and is a diagram schematically showing the dice mark DM on the outer peripheral surface 10a.

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 represented by a pure aluminum system such as 1050, 1100, 1200, etc. 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 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 10a of the heat transfer tube 10 is 4 mm or more and 15 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 is formed between the fins 3.

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.

In this embodiment, for example, 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. Further, 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.

As shown in FIG. 4, the fin 3 has a tip portion 3a located on the inner peripheral side, a bottom portion 3b located on the outer peripheral side, and a pair of side wall portions 3c located between the tip portion 3a and the bottom portion 3b. The bottom portion 3b is located on the inner peripheral surface of the heat transfer tube 10 and is continuous with the inner peripheral surface. The side wall portion 3c extends linearly along the radial direction.

The width of the tip portion 3a of the fin 3, that is, the tip width d2 is the width of the bottom portion 3b, that is, the size of the bottom width d1 or more. Therefore, in the spiral groove 4 located between the fins 3, the opening 4b facing inward in the radial direction is narrower than that on the bottom side, or the groove width is uniform from the opening 4b to the bottom side. By setting the tip width d2 of the fin 3 to a size equal to or larger than the bottom width d1, the surface area on the inner peripheral surface of the heat transfer tube 10 can be increased, and the thermal characteristics of the heat transfer tube 10 can be improved. Further, according to the shape of the fin 3 of the present embodiment, it can be expected that a high evaporation heat transfer coefficient and a high condensation heat transfer coefficient can be obtained by promoting the turbulent flow effect, suppressing the film thickness of the refrigerant, and the like.

In the present embodiment, the arc length of the bottom 3b of the fin 3 is preferably 0.13 mm or more. If the arc length of the bottom 3b of the fin 3 is less than 0.13 mm, the stability of the fin 3 is lowered, and as a result, a tube expansion plug (tube expansion jig) is inserted inside the heat transfer tube 10 to expand the heat transfer tube 10. In the process, the fin 3 is likely to fall down. By setting the arc length of the bottom portion 3b of the fin 3 to 0.13 mm or more, the fall of the fin 3 can be sufficiently suppressed.

In the present embodiment, the pair of side wall portions 3d approach each other from the tip side to the bottom side. Therefore, in the present embodiment, the angle between the pair of side wall portions 3d, that is, the fin apex angle γ is a negative angle inclined to the opposite side as compared with the fin apex angle of the conventional tapered fin.

The fin apex angle γ is preferably 0 ° or more and 35 ° or less. Further, it is more preferable that the fin apex angle γ is larger than 0 ° and 35 ° or less.
By setting the fin apex angle γ to 0 ° or more, the effect of increasing the surface area of the heat transfer tube 10 can be obtained. Further, by making the fin apex angle γ larger than 0 °, the effect of increasing the surface area of the heat transfer tube 10 can be further enhanced.
Further, when the fin apex angle γ exceeds 35 °, the fin 3 is likely to fall down in the step of inserting the expansion plug into the heat transfer tube 10 to expand the heat transfer tube 10. By setting the fin apex angle γ to 35 ° or less, the fin 3 can be sufficiently suppressed from collapsing. Further, when the fin apex angle γ becomes larger than 35 °, the opening 4b on the radial inner side of the groove 4 becomes too narrow, making it difficult for the refrigerant to enter the groove 4, and there is a possibility that the heat transfer property deteriorates. be. In addition, there is a problem that the pressure loss of the refrigerant becomes large. By setting the fin apex angle γ to 35 ° or less, the opening 4b of the groove 4 can be sufficiently made to improve the heat transfer to the refrigerant and to make the flow of the refrigerant smooth.

As described above, the heat transfer tube 10 of the present embodiment has a large inner peripheral surface area because the tip width d2 of the fin 3 is strange to have a bottom width d1 or more. The surface length along the circumferential direction of the inner circumference of the heat transfer tube 10 is called the wet edge length (E). The product of the wet edge length (E) and the length in the longitudinal direction of the heat transfer tube 10 is the surface area of the inner circumference of the heat transfer tube 10.

Conventionally, spiral grooves have been formed for both copper-based and aluminum alloy-based heat transfer tubes by a manufacturing method called a groove rolling method. The groove rolling method is a manufacturing method in which a grooved plug on the inner surface of a pipe is pressed from the outer circumference of the pipe with a rolling ball to form a groove in a valley portion of the grooved plug by plastic flow. Therefore, in the groove portion, the frontage on the apex side (tube center side) of the fin was larger than that on the bottom side. On the other hand, in the present embodiment, as described in the latter stage, the extruded raw pipe is twisted to form the spiral fin 3 and the spiral groove 4, so that the fin 3 and the fin 3 and the spiral groove 4 cannot be formed by the groove rolling method. The shape of the spiral groove 4 can now be formed. As a result, it has become possible to increase the ratio of the wet edge length, which has a great influence on the heat transfer property, as compared with the conventional heat transfer tube.

In the present embodiment, the ratio [E / D] of the wet edge length (E) to the outer peripheral length (D) is preferably 1.3 or more and 3.0 or less. By setting the ratio [E / D] of the wet edge length (E) to the outer peripheral length (D) to 1.3 or more, the heat exchange efficiency with the refrigerant passing through the inside of the heat transfer tube 10 can be improved. On the other hand, by setting the ratio [E / D] of the wet edge length (E) to the outer peripheral length (D) to 3.0 or less, the pressure loss of the refrigerant due to the complicated inner peripheral shape of the heat transfer tube 10 becomes excessive. Can be suppressed.

Further, in the present embodiment, the ratio [F / E] of the length (F) occupied by the bottom portion 4a of the groove 4 located between the fins 3 to the wet edge length (E) is determined. It is preferably 0.15 or more and 0.65 or less.
If the ratio [F / E] of the length (F) occupied by the bottom 4a to the wet edge length (E) is less than 0.15, the effect on the thermal characteristics is small. On the other hand, when the ratio [F / E] of the length (F) occupied by the bottom 4a to the wet edge length (E) exceeds 0.65, the bottom 3b of the fin 3 is too short, so that the fin 3 is stable. The properties are reduced, and the fins 3 tend to fall down significantly in the tube expansion process. That is, by setting the ratio [F / E] of the length (F) occupied by the bottom 4a to the wet edge length (E) to 0.15 or more and 0.65 or less, the thermal characteristics are improved and the pipe expansion step is performed. The fall of the fin 3 can be sufficiently suppressed.

In the present embodiment, the lead angle θ1 (twist angle) of the spirally formed fin 3 is 5 ° or more and less than 45 °. By setting the lead angle θ1 to 5 ° or more, the effect of improving the thermal characteristics by making the fins 3 spiral can be sufficiently exhibited. Further, by setting the lead angle θ1 of the fin 3 to less than 45 °, the fin 3 can be sufficiently suppressed from collapsing in the manufacturing process. Further, if the lead angle θ1 of the fin 3 is 45 ° or more, the pressure loss of the refrigerant may become excessive. By setting the lead angle θ1 to less than 45 °, the flow of the refrigerant can be made smooth.

As shown in FIG. 6, a spiral die mark DM is formed on the outer peripheral surface 10a 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 processing. The die mark DM is formed due to the influence of scratches on the extrusion die and the bearing surface. The heat transfer tube 10 of the present embodiment is manufactured by twisting the extruded raw tube while drawing it out. Therefore, the die mark DM formed linearly by extrusion processing becomes spiral with the addition of twist.
The dice mark DM of FIG. 6 is shown so that one dice mark DM is continuously formed for the sake of clarity. The actual dice marks are formed intermittently along the length direction as shown as photographs in FIGS. 11 (a) and 12 (a). Further, a plurality of dice mark DMs extend spirally and in parallel along the circumferential direction of the outer peripheral surface of the heat transfer tube 10.
In addition, in this specification, the term "dice mark" is used not only for the recess formed by the extrusion process but also for the recess of the heat transfer tube after twisting the raw tube having the recess. Strictly speaking, the concave portion of the pipe material after being twisted is a concave portion due to the die mark. However, for the sake of clarity in the present specification, the concept including these is referred to as a die mark.

The maximum depth of the dice mark DM after the twist is applied is 35 μm or less. As described above, the heat transfer tube 10 is bent into a hairpin shape when used as a heat exchanger 80 (see FIGS. 1 and 2). In such a bending process, the die mark DM tends to be a starting point of damage to the heat transfer tube 10. According to the present 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 which is not easily damaged by additional processing such as bending.

The method of measuring the depth of the die mark will be described.
For the die mark depth measurement, for example, the surface shape can be measured using a scanning laser scanning microscope (VK-X100 / X200) manufactured by KEYENCE CORPORATION. Further, in the measurement analysis, the die mark depth can be measured by using an analysis application (VK-H1XA).
First, the sample is placed on the stage of a scanning laser microscope (VK-X100 / X200), and after focusing at an observation magnification of 50 times, the observation height upper and lower limit range is 100 μm, and the surface shape is 0.5 μm pitch. Make a measurement.
Next, the dice mark depth on the image obtained by using the analysis application (VK-H1XA) is measured. As a pretreatment before measurement, tilt correction was performed to flatten the arc on the surface of the pipe. From the surface shape that was pretreated, three straight lines were drawn so as to be parallel to the circumferential direction of the tube, and the maximum valley depth (Rv) and maximum height (Rz) were obtained from the obtained roughness curve. In the measurement of the die mark depth, the measurement is performed as the maximum cross-sectional height (Rt).
In the analysis application, the surface roughness analysis was performed with the roughness parameters defined in JISB0601-2001 and JIS0601-1994 based on "Definition of Surface Roughness" (JISB0601: 2001).
11 (b) shows the depth measurement result of the dice mark DM of FIG. 11 (a). Similarly, FIG. 12 (b) shows the depth measurement result of the dice mark DM of FIG. 12 (a). The heat transfer tube having the die mark DM exemplified in FIGS. 11 and 12 is an example of the heat transfer tube 10 of the present embodiment.

[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. 7 is a vertical sectional view of a raw pipe (straight grooved pipe) 10B formed by an extrusion molding step, and FIG. 8 is a perspective view of the raw pipe 10B.
By extruding a billet made of an aluminum material, as shown in FIG. 8, a raw tube 10B in which a plurality of straight grooves 4B along the length direction are formed at intervals in the circumferential direction is manufactured (straight groove). Attached pipe 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 step.

<Pulling out and twisting process, empty pulling process>
Next, the drawing and twisting process and the empty drawing process will be described.
The drawing and twisting step is a step of forming the die mark DM, the fins 3B, and the straight groove 4B into a spiral shape by applying a twist to the above-mentioned raw tube 10B while drawing out.
Further, the empty pulling step is a step of pulling out the pipe material without applying twist to adjust the outer diameter of the pipe material.

In addition, in this specification, a pipe material before applying a twist (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 "pipe 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 "post-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 for drawing and twisting process and emptying process>
FIG. 9 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 drawing and twisting process and the empty pulling process 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 pull-out 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 rotary 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 revolution shaft 35.
Further, the revolution mechanism 30 maintains a stationary state of the floating frame 34 located coaxially with the rotary shaft 35 and supported by the rotary 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 has 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 the 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 with respect to the revolution center axis C.

A first revolution capstan 21, a second revolution capstan 22, and a revolution flyer 23 are fixed to the rotary 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 revolution center axis C.

(Floating frame)
The floating frame 34 is supported by bearings 34a at the 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. 10 is a plan view of the floating frame 34 seen from the arrow X direction in FIG. As shown in FIGS. 9 and 10, 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 facing each other in the front-rear direction, and a pair of support walls 34d facing each other in the left-right direction and extending 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. 10, 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. 10). 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 tube 10B (see FIG. 7) 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. 10, the bobbin support shaft 12 extends in a direction orthogonal to the rotary shaft 35. Further, the bobbin support shaft 12 is supported by the floating frame 34 so as to be rotatable and rotatable. 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 tubes 10B are supplied, and is replaced with another unwinding bobbin. The removed empty unwinding bobbin 11 is attached to an extruder forming the linear grooved tube 10B, and the linear 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 irregularly wound around 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 tube 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. 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 material 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 be rotatable and rotatable. Further, on the outer periphery of the first guide capstan 18, rotation-rotating guide rollers 18b 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. 10, the guide roller 18b is not shown.

As shown in FIG. 10, a pipeline guide portion 18a is provided between the first guide capstan 18 and the unwinding bobbin 11. The pipe 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.
The 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 (transport 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 at the revolution rotation center axis C of the front shaft 35A. As a result, 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 revolution flyer 23 reverses the pipe material 5 conveyed in the first direction D1 which is the extraction direction of the first extraction die 1, and sets the transfer direction to the second direction D2 which is the extraction direction of the second extraction 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 drawn out 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 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 conveyed by sliding one surface of the strip.
Further, in FIG. 9, a case where the pipe material 5 passes outside the guide roller 23a is illustrated.
However, if 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 in synchronization with the revolution flyer 23 may be provided. As a result, 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 revolution 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 periphery of the second revolving capstan 22, guide rollers 22c that can rotate and rotate are arranged side by side. The second revolution 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.
The 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 revolution 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 surface 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 surface 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. The 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 rotary 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 in the winding direction (conveying direction) of the pipe material 5 by the drive motor 63. As the drive motor 63, it is preferable to use a torque motor capable of torque control.

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 finishing drawing die 7, the change in the cross section due to the drawing is small, the surface and the dimensions are finished and shaped, and the roundness of the pipe material 5 is restored. Further, in the blanking 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 the pipe material 5 is wound up and wound 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 the tube material 5 is taken up without loosening. The take-up bobbin 71 is removed when the pipe material 5 is sufficiently wound and replaced with another take-up bobbin 71.

<Pulling out and twisting process>
A method of manufacturing the inner surface spiral grooved tube 10 will be described using the above-mentioned inner surface spiral grooved tube manufacturing apparatus A.
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 provided with 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 surface spiral grooved pipe 10, it will be described 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 and pulling step).

In the first torsional pull-out step, 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. 7) 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 torsion drawing step, the straight grooved pipe 10B becomes an intermediate torsion 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 where a spiral groove having a shallower twist angle than 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 the combined stress due to the simultaneous processing of the torsion and the reduced diameter. Under the combined stress, the yield stress of the pipe material 5 becomes smaller as compared with 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 revolution 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 processing 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, so it is preferably 2% or more. For the same reason, it is more preferable to set the diameter reduction ratio to 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). By the second torsional drawing step, the intermediate torsion tube 10C becomes the inner surface spiral grooved tube 10.

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 drawing 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. 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. By the second torsional drawing step, the intermediate torsion tube 10C becomes the inner surface spiral grooved tube 10.

In the front stage of the second drawing die 2, the pipe material 5 is wound around the second revolution capstan 22. In the rear 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 torsional 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, twisting and diameter reduction are performed in the same manner as in the first torsional pulling-out step, and a composite stress is applied 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. Will be 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.

In the first and second twist pulling steps, a total twist of 5 ° or more is applied. In the twisting and pulling step, the die mark DM is sufficiently stretched by applying a twist of 5 ° or more together with the pulling out. As a result, the depth of the die mark can be set to 35 μm or less, and the heat transfer tube 10 capable of bending the hairpin without cracking or wrinkling can be manufactured.

<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 deformed such as crushed, the deformation can be corrected by going through this finish drawing step to obtain a pipe 10 with an inner spiral groove having a predetermined roundness. can. The force for transporting the pipe material 5 with respect to the drawing load of the finishing drawing die 7 is applied by the drive motor 74 provided on the take-up bobbin 71.

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

<O material conversion process>
Next, the O-material conversion process will be described.
The O materialization step is performed after the twisting step. The O-material conversion step is a heat treatment step of subjecting the pipe material 5 to an annealing treatment. By performing the O materialization process, the strain of the aluminum material can be removed and the internal stress can be removed.

<Summary of manufacturing method>
The raw tube 10B manufactured by extrusion has a concave die mark extending in the longitudinal direction, and the depth is 40 μm or less, but there is also a mark locally close to 50 μm, which is empirically deep. The dice is 50 μm or less. By performing the twisting and pulling step and the empty pulling step on the raw pipe 10B, the diameter of the pipe is reduced and expanded, and the concave die mark DM on the outer peripheral surface becomes shallow. Furthermore, since twisting is applied by compound processing, the degree of elongation increases with the spiral angle, and the concave dice mark can be made shallower more effectively. By processing under appropriate conditions, the depth of the concave on the outer circumference of the pipe Can be controlled to 35 μm or less. That is, according to the pull-out twisting step of the present embodiment, twisting and pulling are repeated a plurality of times. As a result, the die mark DM formed in the extrusion molding step can be stretched a plurality of times to make it shallow, and as a result, a heat transfer tube 10 having high strength can be manufactured.

According to the manufacturing method of the present embodiment, the total diameter reduction ratio of each step (first drawing step, second drawing step and empty drawing 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.

In the drawing and twisting step of the present embodiment, the first twisting and pulling step and the second twisting and pulling step are performed again on the inner spiral grooved tube 10 formed through the above steps, and a larger twist angle is imparted. You may. In this case, the inner spiral grooved tube 10 that has undergone the above steps is heat-treated (annealed) to form an O material. Further, the unwinding bobbin 11 is wound around the unwinding bobbin 11 and attached to the manufacturing apparatus A having the first drawing die and the second drawing die having an appropriate diameter reduction ratio. Further, the manufacturing apparatus A can manufacture a tube with an inner spiral groove having a larger twist angle by going through the same steps (first twist-pulling step and second twist-pulling step) as described above.

According to the drawing and 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 twisting, 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, by reducing the bottom wall thickness of the inner spiral grooved tube 10, the weight can be reduced and the material cost can be reduced to reduce the cost. 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 pull-out twisting step of the present embodiment, since the straight grooved tube 10B is twisted and the diameter is reduced, a large twist 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 the material, is 1.1 times or more the outer diameter of the final product, the inner spiral grooved pipe 10.

According to the drawing and 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 pipe line of the pipe material 5 and the take-up bobbin 71 which is the end point of the pipe line. Since the speed of the line depends on the rotation speed, the rotation speed can be easily increased in the drawing and 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 tube 10B (tube material 5) can be wound around the unwinding bobbin 11. Therefore, according to the pull-out and twisting step of the present embodiment, the unwinding bobbin 11 can be twisted in one go without replacing the unwinding bobbin 11. That is, according to this embodiment, mass production of the inner spiral grooved tube 10 becomes easy.

In the pull-out and 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 twisting angle by accumulating the twisting angles given in the twisting and pulling steps of each stage.

According to the pull-out / twisting step of the present embodiment, forward tension and backward tension are applied to the pipe material 5 in the first twisting / pulling step and the second twisting / 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 for braking 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 this embodiment, it is assumed that the unwinding bobbin 11 is supported by the floating frame 34 and the unwinding 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. 9, 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, and the forward tension against the pulling force in the drawing dies is applied. give.

((Heat transfer tube of the example))
An extruded raw tube made of a JIS A3003 series aluminum alloy is extruded to manufacture an extruded raw tube having a straight groove on the inner surface. Next, the raw tube was subjected to compound processing (pulling + twisting) to manufacture an inner spiral grooved tube. The heat transfer tube has an outer diameter D of 6.00 mm and 7.00 mm, a fin bottom width arc length W of 0.13 mm and 0.15 mm, a groove lead angle β of 15 °, a fin number of 45, and a fin. The height H is 0.25 mm, the fin apex angle α is variously varied in the range of −5 to −25 °, and the bottom wall thickness t is 0.50 mm. As shown in FIG. 4, the shape of the fin of the heat transfer tube of the embodiment has a tip width equal to or larger than the bottom width.

((Heat transfer tube of comparative example))
As a comparative example, a heat transfer tube having a conventional fin shape having a bottom width larger than the tip width was prepared. In the heat transfer tube of the comparative example, the fins are formed in a spiral shape as in the heat transfer tube of the embodiment. Moreover, each dimension of the heat transfer tube of the comparative example was made the same as each dimension of the heat transfer tube of the said Example.
Further, in order to confirm the influence of the lead angle, in some comparative examples, the lead angle of the heat transfer tube having the same shape as that of the example was varied to 0 °, 5 ° and 10 °, and the same investigation was performed.

((measurement))
Regarding the obtained heat transfer tubes of Examples and Comparative Examples, the shapes of grooves and fins on the inner surface of the tubes, heat transfer characteristics, hairpin bending workability, and the presence or absence of seizure of the plug after the tube expansion were investigated. The groove shape was examined by vertically dividing the heat transfer tube (length 300 mm) into two and measuring the height of the fins on the inner surface of the tube, the bottom wall thickness, the arc length of the bottom width, and the like.

(Heat transfer characteristics)
The heat transfer characteristics were examined by measuring the heat transfer coefficient in the tube (condensation in the tube and evaporation in the tube) using the conventionally known heat transfer performance evaluation devices shown in FIGS. 15 and 16. FIG. 15 is a heat transfer characteristic evaluation device for performing a condensation test, and FIG. 16 is a heat transfer characteristic evaluation device for performing an evaporation test. In each test device, the refrigerant mass velocity was 250 kg / m ² · s. Other test conditions are as follows: for the condensed side in the pipe, the average saturation temperature of the refrigerant is 45 ° C, the refrigerant inlet superheat degree is 20 ° C, the refrigerant outlet supercooling degree is 5 ° C, the pipe inlet pressure is 2.63 MPa, and the evaporation side in the pipe. The average saturation temperature of the refrigerant was 5 ° C, the dryness of the refrigerant inlet was 0.2, the superheat degree of the refrigerant outlet was 7 ° C, the pipe outlet pressure was 0.86 MPa, the heat transfer tube length used for the measurement was 4 m, and the evaluation was made with the refrigerant R32. Was done. The standard is with a conventional copper inner groove with an outer diameter of 7.00 mm and 6.00 mm, a bottom wall thickness of 0.25 mm, a fin height of 0.17 mm, a fin apex angle of 25 °, a number of threads of 55, and a lead angle of 10 °. For the heat transfer tube, the heat transfer coefficient in the tube was measured by the same method as above. The heat transfer coefficient in the tube was measured for each of the three heat transfer tubes, and the average value was taken as the heat transfer coefficient in the tube of the heat transfer tube.

(Expansion test)
FIG. 13 shows a tube expansion tool 114 provided with a tube expansion plug 113A and a rod 113 used in the tube expansion test. Further, FIG. 14 shows the tube holder 130 used in the tube expansion test.
The tube expander 114 has a rod 113 on the tip end side of the handle H, and a tube expander plug 113A is formed at the tip thereof. The tube holder 130 includes a disk-shaped support base 134 having a slide groove 134a on the upper surface side, and a block-shaped first holding portion 131 and a second holding portion 132 mounted on the slide groove 134a of the support base 134. Have. The first holding portion 131 and the second holding portion 132 are configured to be integrated so as to be aligned with each other by a fixing bolt 132a screwed into a screw hole formed on the side surface thereof. Further, round grooves 131A and 132A are formed on the side center side of the first holding portion 131 and the second holding portion 132, respectively.

First, as shown in FIGS. 14A and 14B, the first holding portion 131 and the second holding portion 132 are erected, overlapped, and fixed on the slide groove 134a. As a result, the holes 133 are formed by superimposing the round grooves 131A and 132A on the boundary between the first holding portion 131 and the second holding portion 132.
Next, as shown in FIG. 14 (c), the heat transfer tube J of the sample is inserted into the hole 133. The inner diameter of the hole 133 is formed to be sufficiently larger than the outer diameter of the heat transfer tube J, and can be easily inserted from above, and the length of the heat transfer tube J to be inserted is 125 mm.
Next, as shown in FIG. 14 (d), the heat transfer tube J is expanded by inserting the rod 113 to which the tube expansion plug 113A of FIG. 13 is attached. Finally, by removing the fixing bolt 132a and opening the first holding portion 131 and the second holding portion 132, the expanded heat transfer tube J can be taken out. This was carried out 200 times in a row, and it was confirmed whether or not the expansion plug was seized after that. Those with burn-in were marked with x, and those without burn-in were marked with ○.

The diameter of the outermost diameter of the tube expansion plug 113A used in this tube expansion test is 5.9 mm for the outer diameter D7.00 mm and 5.4 mm for the outer diameter D6.00 mm, and one made of cemented carbide is used. board. The insertion speed of the tube expansion plug 113A was set to 285 mm / min.

(Measurement of strength against hairpin bending)
The heat transfer tube of each sample was bent by 180 ° in a hairpin shape with an outer diameter of 7.0 mm having a radius of curvature (R = 15) and an outer diameter of 6.0 mm at R = 10. Evaluation was made under each condition n = 20, and those in which cracks were observed on the outer peripheral surface of the heat transfer tube were evaluated as x, and those in which no cracks were observed were evaluated as 〇.

Tables 1 and 2 show the dimensions and test results of Examples and Comparative Examples.
In Tables 1 and 2, the “lead angle” means the lead angle θ1 of the fin 3. In Tables 1 and 2, the apex angle means the fin apex angle γ. In Tables 1 and 2, the "bottom wall thickness circumference / wet edge length" means the ratio [F / E] of the length (F) occupied by the bottom 4a to the wet edge length (E). In Tables 1 and 2, "wet edge length / outer circumference" means the ratio [E / D] of the wet edge length (E) and the outer circumference length (D). Further, the item of "heat transfer characteristics" in Tables 1 and 2 is displayed at a ratio when the value of Example 1 measured under the conditions of the above-mentioned evaluation test of heat transfer characteristics is set to 100.

From Tables 1 and 2, it can be seen that the heat transfer tubes of each example are superior in heat transfer property and seizure property at the time of expansion as compared with the heat transfer tubes of each comparative example.

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

1 ... 1st drawing die, 2 ... 2nd drawing die, 3, 3B ... Fins, 3a ... Tip, 3b ... Bottom, 3c ... Side wall, 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 surface, 10b ... Inner peripheral surface, 10B ... Straight grooved tube (bare tube), 10C ... Intermediate twisted tube, 23 ... revolving flyer, 80 ... heat exchanger, 82 ... radiator plate, 82a ... insertion hole, DM ... die mark, D1 ... first direction, D2 ... second direction, d1 ... bottom width, d2 ... tip width

Claims (9)

A heat transfer tube made of aluminum, which is a twisted material of an extruded raw tube, and has a plurality of fins arranged along the circumferential direction on the inner peripheral surface and spirally formed along the length direction. , the tip width is more than the bottom width Ri magnitude der,
The ratio [E / D] of the wet edge length (E) and the outer peripheral length (D), which is the surface length along the circumferential direction in the inner circumference of the heat transfer tube, is 1.9 or more and 2.3 or less.
The ratio [F / E] of the length (F) occupied by the bottom of the groove located between the fins and the wet edge length (E) is 0.20 or more and 0.31 or less.
A heat transfer tube having an arc length of the bottom of the fin of 0.13 mm or more and a lead angle of the fin of 15 ° or more and less than 45 °. The lead angle of the fin is 15 ° or more and 25 ° or less.
The heat transfer tube according to claim 1. The arc length of the bottom of the fin is 0.15 mm or less.
The heat transfer tube according to claim 1 or 2. The fins have a pair of side wall portions that approach each other from the tip side to the bottom side.
The angle between the pair of side walls is greater than 0 ° and less than or equal to 35 °.
The heat transfer tube according to any one of claims 1 to 3. A spiral dice mark is formed on the outer peripheral surface, and the maximum depth of the dice mark is 35 μm or less.
The heat transfer tube according to any one of claims 1 to 4. The heat transfer tube according to any one of claims 1 to 5, wherein the outer diameter is 4 mm or more and 15 mm or less. The heat transfer tube according to any one of claims 1 to 6 and a heat radiation plate coupled to the heat transfer tube are provided.
Heat exchanger. Extrusion molding to extrude an aluminum raw 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 and
A twisting and pulling process that applies a twist of 15 ° or more to the raw pipe together with pulling out.
A blank drawing step of pulling out with a diameter reduction ratio of 10% or more after the drawing step is included.
The inner peripheral surface has a plurality of fins arranged along the circumferential direction and spirally formed along the length direction, and the fins have a tip width equal to or larger than the bottom width.
The ratio [E / D] of the wet edge length (E) and the outer peripheral length (D), which is the surface length along the circumferential direction in the inner circumference of the heat transfer tube, is 1.9 or more and 2.3 or less.
The ratio [F / E] of the length (F) occupied by the bottom of the groove located between the fins and the wet edge length (E) is 0.20 or more and 0.31 or less.
It is characterized in that a heat transfer tube having an arc length of the bottom of the fin of 0.13 mm or more and a lead angle of the fin of 15 ° or more and less than 45 ° is obtained.
Manufacturing method of heat transfer tube. The fins have a pair of side wall portions that approach each other from the tip side to the bottom side.
The angle between the pair of side walls is greater than 0 ° and less than or equal to 35 °.
The method for manufacturing a heat transfer tube according to claim 8.

Images