WO2019013202A1

WO2019013202A1 - Pipe with spirally grooved inner surface, and method for manufacturing same

Info

Publication number: WO2019013202A1
Application number: PCT/JP2018/026021
Authority: WO
Inventors: 聖健澤; 永尾　誠一
Original assignee: 株式会社Uacj; 株式会社Ｕａｃｊ押出加工
Priority date: 2017-07-14
Filing date: 2018-07-10
Publication date: 2019-01-17
Also published as: JP2019018224A; JP6966884B2

Abstract

Provided is a method for manufacturing a pipe (1) with a spirally grooved inner surface, the method enabling an increase in the helix angle of grooves through a simple process. When a pipe (1) with a spirally grooved inner surface is manufactured, first, a pipe blank (2) which is provided with a number of fins (21) protruding from an inner surface and extending in a direction parallel with a pipe axis (20), and with grooves (22) formed between the fins (21) is prepared. Then, the pipe blank (2) is subjected to a bending process for bending in a direction perpendicular to the pipe axis (20), while providing the pipe blank (2) with a torsional moment centered about the pipe axis (20), thereby plastically deforming the fins (21) and the grooves (22) in a helical shape revolving around the pipe axis (20). In this way, it is possible to obtain a pipe (1) with spirally grooved inner surface, the pipe (1) having the helical-shaped fins (11) and grooves (12) revolving around the pipe axis (10).

Description

Inner surface spiral grooved tube and method of manufacturing the same

The present invention relates to an internally helical grooved tube and a method of manufacturing the same.

A heat exchanger such as an evaporator or a condenser, which is incorporated in a refrigeration unit or an air conditioner, has a heat transfer pipe through which a refrigerant flows. As a heat transfer tube of this type, there is an internally grooved tube provided with a large number of fins projecting from the inner surface of the tube and a groove formed between the fins. The grooves provided on the inner surface of the tube have effects such as increasing the surface area inside the tube, stirring the refrigerant, and facilitating holding the liquid film on the inner surface of the tube by capillary action. The inner grooved tube can efficiently evaporate or condense the refrigerant inside the tube due to these effects.

Conventionally, as the inner grooved tube, an inner surface spiral grooved tube made of a copper material and provided with spiral fins and grooves on the inner surface by rolling is widely used. However, in recent years, the demand for internal spiral grooved tubes consisting of aluminum materials (including aluminum and aluminum alloys; the same applies hereinafter), which is low in material cost compared to copper and easy to recycle, in place of copper tubes It is getting worse.

It is difficult to form a spiral groove and a fin on the inner surface of the tube by rolling because the tube made of aluminum material has lower rolling formability than a copper tube. Therefore, a base pipe having straight grooves and fins extending in a direction parallel to the pipe axis is prepared, and the base pipe is subjected to a twisting process centering on the pipe axis to form grooves in the inner surface of the pipe and Techniques have been proposed to deform the fins in a spiral.

For example, Patent Document 1 describes a method of manufacturing an internally helical grooved tube in which a tube having a straight groove on its inner surface is used as a base tube, and the tube is drawn on the front side of a drawing die by twisting. The aluminum material which comprises an element pipe flows plastically, when the pipe reduction process which reduces an outer diameter in drawing die is given. Therefore, the groove and the fin on the inner surface of the tube can be deformed in a spiral shape by utilizing the above-described plastic flow by performing the tube contraction process while rotating around the tube axis.

However, in the case of subjecting an element pipe to a contraction process, the hardness of the internally spiral grooved pipe is higher than that of the element pipe due to work hardening. Patent Literature 2 and Patent Literature 3 describe a technique for eliminating work hardening at the time of tube contraction processing by annealing the inner surface spiral grooved tube.

Japanese Patent Application Laid-Open No. 10-166086 JP, 2014-140896, A JP, 2014-140897, A

In the manufacturing methods of Patent Documents 1 to 3, as described above, the plastic flow of the aluminum material in the drawing die is utilized, and the grooves and fins on the inner surface of the blank are helically deformed at the inlet side of the drawing die. There is. In these methods, the inner surface helical grooved tube which has passed through the drawing die is stretched in the axial direction of the tube compared to the blank tube by the reduction of the outer diameter compared to the blank tube. Therefore, the twist angle of the groove in the internally helical grooved tube is smaller than the twist angle of the groove on the inlet side of the drawing die. As described above, the twisting process accompanied with the tube reduction process as in Patent Documents 1 to 3 has a problem that the process efficiency is essentially low because the twist angle of the groove is reduced during the tube reduction process.

Further, Patent Documents 2 to 3 also describe a technique for increasing the twist angle of the groove by repeatedly applying the rotation to the raw pipe and the contraction process. When the contraction process is performed, the width of the groove is narrowed according to the reduction of the outer diameter, and the height of the fin interposed between the grooves is reduced. On the other hand, the wall thickness at the bottom of the groove does not decrease in response to the reduction of the outer diameter, but rather increases by contraction.

As described above, in the contraction process, the overall size of the raw pipe is not uniformly reduced, and the shape of the dimensional change differs depending on the position of the raw pipe, so the cross-sectional shape of the inner spiral grooved pipe is raw pipe It changes from the cross-sectional shape. Therefore, when the application of rotation to the base tube and the contraction process are repeated, the cross-sectional shape of the finally obtained internal spiral grooved tube becomes different from the desired shape, and the heat transfer performance is deteriorated. There is a risk of

In addition, for example, in the case of an inner surface spiral grooved tube, in order to reduce the thickness of the bottom portion of the groove, it is necessary to make the thickness of the bottom portion of the groove in the base tube thinner than that of the inner surface spiral grooved tube. In this case, the cross section of the raw pipe tends to be a flat shape such as an oval shape or an oval shape, which may cause an increase in manufacturing cost and an increase in the variation in quality of the internally spiral grooved tube.

Furthermore, in the case of repeatedly applying the rotation to the raw pipe and the contraction process, it is necessary to perform annealing at every completion of the contraction process to eliminate work hardening, so the number of processes increases and manufacturing equipment Could lead to the complexity of In addition, with the complication of manufacturing facilities, problems such as increases in facility costs and running costs may occur.

The present invention has been made in view of the above background, and an object of the present invention is to provide a method of manufacturing an inner surface spiral grooved tube capable of increasing the twist angle of the groove by a simple process.

One aspect of the present invention is a raw tube made of an aluminum material, comprising a plurality of fins projecting from the inner surface and extending in a direction parallel to the tube axis, and grooves formed between the fins. Prepare
The base tube is subjected to a bending process in which it is bent in a direction perpendicular to the tube axis while applying a twisting moment around the tube axis, whereby the fin and the groove are spirally wound around the tube axis Plastically deform,
A method of manufacturing an inner surface spiral grooved tube.

In the method of manufacturing the inner surface spiral grooved tube, a blank having a plurality of fins extending in a direction parallel to the tube axis and a groove formed between the fins is prepared, and Bending is performed in a direction perpendicular to the tube axis while applying a twisting moment around the tube axis. As described above, by simultaneously applying a twisting moment and a bending moment to the blank in bending, the blank can be plastically deformed with a smaller twisting moment than when no bending moment is applied. As a result, it is possible to plastically deform the straight fins and the grooves provided on the inner surface of the blank into a spiral that turns around the tube axis, to obtain an internally spiral grooved tube.

According to the manufacturing method, the fins and the grooves can be plastically deformed in a spiral shape regardless of the pipe forming process. Therefore, various problems in the conventional manufacturing method involving the tube forming process such as reduction of the twist angle of the groove, change of the cross-sectional shape from the raw pipe, complication of the manufacturing process and increase of manufacturing cost are avoided and simple. According to the process, it is possible to produce an inner surface helical grooved tube having a large twist angle of the groove.

FIG. 7 is an explanatory view of a method of manufacturing an inner surface spiral grooved tube in the first embodiment. It is an enlarged view of the 1st roll vendor in FIG. FIG. 10 is a cross-sectional view of a cross section perpendicular to the tube axis of the blank tube in the second embodiment. FIG. 16 is a cross-sectional view of a blank at the time of pipe contraction processing in Comparative Example 2.

In the above-mentioned manufacturing method, a base pipe which is a material of the inner surface spiral grooved pipe has a large number of fins projecting from the inner surface and a groove formed between the fins. Further, the fins and grooves in the raw tube have a linear shape extending in a direction parallel to the tube axis. The outer diameter of the base tube, the thickness of the bottom of the groove, the number of fins, the height and the apex angle can be set as appropriate according to the outer diameter of the internally spiral grooved tube to be obtained.

Specifically, the outer diameter of the raw pipe can be appropriately set, for example, in the range of 5 to 10 mm. Further, the thickness of the bottom of the groove can be appropriately set from the range of 0.30 to 0.70 mm.

Further, when the base pipe subjected to the bending process is used as the inner surface spiral grooved pipe as it is, the cross sectional shape of the inner surface spiral grooved pipe is almost the same as the cross sectional shape of the base pipe. Therefore, in this case, the outer diameter of the blank, the thickness of the bottom of the groove, the number of fins, the height and the apex angle may be set to desired values in the internally spiral grooved tube.

The raw pipe may be an extruded material produced by extrusion processing. Moreover, the chemical composition of the aluminum material which comprises an element pipe | tube can be selected from well-known aluminum and aluminum alloy according to the use and the desired characteristic of an inner surface grooved pipe. For example, as an aluminum material, 3000 series aluminum alloys, such as a JIS A 3003 alloy, and 1000 series aluminum can be used. From the viewpoint of strength and processability, it is preferable to use a 3000 series aluminum alloy as the aluminum material.

In order to plastically deform the fins and grooves of the base tube in a helical manner, as described above, the base tube is bent in a direction perpendicular to the axis while applying a twisting moment about the axis. A twisting moment centering on the tube axis and a bending moment to bend the blank in a direction perpendicular to the tube axis are simultaneously applied to the blank during bending. As a result, the raw pipe can be plastically deformed with a lower twisting moment than in the case where no bending moment is applied. The reason can be described, for example, as follows.

In the case of applying plastic deformation by applying a twisting moment to the blank, it is necessary to apply a shear stress larger than the yield point of the blank. According to the maximum shear stress theory, the shear stress τ [N · m] is Z for the section coefficient of the raw tube, T [N · m] for the magnitude of the twisting moment, and M [N · m] for the bending moment ], It is represented by the following formula.
τ = (T ² + M ² ) ^0.5 / 2Z

The inner helical grooved tube used in the heat exchanger has a relatively small outer diameter, so it is difficult to increase the twisting moment T. Also, if it is attempted to increase only the twisting moment T, the raw pipe may be locally deformed, and furthermore, the raw pipe may be buckled starting from this deformation point. On the other hand, increasing the bending moment M is easier than the twisting moment T. Therefore, by simultaneously applying the twisting moment T and the bending moment M to the blank, the stress τ can be increased while suppressing the buckling of the blank. As a result, it is possible to easily plastically deform the fins and grooves of the raw tube in a helical manner, and obtain an internally helical grooved tube.

In the above-mentioned bending process, as a method of applying a twisting moment to the raw pipe, for example, rotation of the raw pipe about the pipe axis is given to either the upstream side or the downstream side of the bending machine. There is a method of regulating the rotation of the raw pipe on the other side. In addition, the bending direction of the hollow tube in bending may be any direction as long as it is a direction orthogonal to the tube axis. For example, in the case where the tube axis direction of the raw tube is the front-rear direction, the bending direction may be the left-right direction or the up-down direction. In addition, it is also possible to bend the raw tube in a direction inclined to the left-right direction or the up-down direction.

Moreover, the number of times of bending the raw pipe may be one, or may be two or more. In the case where the number of times the element tube is bent is two or more, for example, the element tube may be repeatedly bent in the same direction, or the element tube is bent in the vertical direction and then bent in the left and right direction. You can also change the direction.

In the bending process, it is preferable to elastically deform the raw tube in a direction perpendicular to the tube axis. When a bending load equal to or higher than the elastic limit of the hollow shell is applied to the hollow shell during bending, the hollow shell may be plastically deformed in the bending direction. In this case, the bending moment is rather reduced, which may lead to a reduction in shear stress applied to the blank. By making the magnitude of the bending load smaller than the elastic limit of the blank and elastically deforming the blank in the direction perpendicular to the tube axis in bending, such problems can be avoided and the fins and grooves can be efficiently spiraled. It can be plastically deformed.

Before and after the bending process, the outer diameter of the blank is OD ₀ [mm], the thickness of the bottom of the groove in the blank is TF ₀ [mm], and the outer diameter of the internally spiral grooved tube is OD ₁ [mm] When the thickness of the bottom of the groove in the internally helical grooved tube is TF ₁ [mm], the following formulas (1) to (2) may be satisfied.
0 <(OD ₁ −OD ₀ ) / OD ₀ <0.03 (1)
0 ≦ (TF ₁ −TF ₀ ) / TF ₀ <0.04 (2)

As described above, in the conventional manufacturing method involving the tube contraction process, the cross-sectional shape of the inner surface helical grooved tube changes from the cross-sectional shape of the base tube by the tube contraction process, which may cause deterioration of the heat transfer performance. was there. On the other hand, according to the said manufacturing method, the element pipe in which the bending process was given can be used as an inner surface spiral grooved pipe as it is. Therefore, it is possible to suppress an unintended change in the cross-sectional shape at the time of the contraction process, which has occurred in the conventional manufacturing method, and to be substantially similar to the cross-sectional shape of the raw pipe as in the above formulas (1) to An internally helical grooved tube with a cross-sectional shape can be obtained. As a result, it is possible to easily avoid the deterioration of the heat transfer performance of the internally spiral grooved tube.

In the above manufacturing method, when the tensile strength of the raw pipe is σ _B0 [MPa] and the tensile strength of the inner surface spiral grooved pipe is σ _B1 [MPa], the following formula (3) is satisfied. It is also good.
0.02 <(σ _B1 -σ _B0 ) / σ _B0 <0.10 (3)

As described above, in the conventional manufacturing method that involves tube contraction, annealing is usually performed to eliminate work hardening during tube reduction. However, when annealing is performed, the aluminum material of the inner surface spiral grooved tube is recrystallized, and there is a possibility that the tensile strength and the fatigue strength may be reduced as compared with the raw pipe.

On the other hand, in the above-mentioned manufacturing method, as described above, since the raw pipe subjected to the bending process can be used as the inner surface spiral grooved pipe as it is, as in the above-mentioned formula (3) The tensile strength of the pipe can be made equal to or higher than that of the raw pipe. As described above, according to the manufacturing method, it is possible to obtain an inner surface spiral grooved tube having high strength characteristics as compared with the inner surface spiral grooved tube according to the conventional manufacturing method while avoiding a decrease in tensile strength and the like due to annealing. Can.

In the production method, if necessary, heat treatment such as stress relief annealing may be added after bending, or processing such as pipe expansion may be additionally performed.

The inner surface spiral grooved tube obtained by the above manufacturing method has a large number of fins and grooves formed between the fins on the inner surface. Also, the fins and grooves in the internally helical grooved tube are in the form of a spiral that pivots around the tube axis. The twist angle of the groove in the internally helical grooved tube, that is, the angle between the axial direction of the groove and the extending direction of the groove can be, for example, more than 0 degrees and not more than 30 degrees.

From the viewpoint of further enhancing the heat transfer performance of the inner surface helical grooved tube, it is preferable to increase the twist angle of the groove. However, if the twist angle of the groove is large, the manufacturing cost of the internally spiral grooved tube may be increased. Therefore, it is preferable to set the twist angle of the groove to 5 degrees or more and 20 degrees or less from the viewpoint of enhancing the heat transfer performance while suppressing the increase in the manufacturing cost.

In the above manufacturing method, when the base pipe subjected to the bending process is used as the inner surface spiral grooved pipe as it is, it is possible to obtain an inner surface spiral grooved pipe provided with almost the same metal structure as the metal structure of the base pipe. For example, in the case of using an element tube made of a 3000 series aluminum alloy such as an A3003 alloy, the structure of the inner surface spiral grooved tube obtained can be a recrystallized structure having an average crystal grain size of 80 μm or less. Moreover, in this case, the tensile strength of the internally spiral grooved tube can be made 115 MPa or more, the proof stress can be made 95 MPa or more, and the elongation can be made 20% or more.

Since the internally spiral grooved tube having such characteristics is excellent in workability in machine expansion processing, for example, a cross fin type heat exchanger in which the internally spiral grooved pipe and the fins are joined by mechanical expansion processing. It can be used suitably. Further, the inner surface spiral grooved tube can be applied to uses other than the cross fin type heat exchanger. The average grain size of the internally spiral grooved tube can be calculated, for example, according to the cutting method defined in JIS G0551 (ASTM E 112-96, ASTM E 1382-97).

Example 1
An embodiment of the inner surface spiral grooved tube and a method of manufacturing the same will be described with reference to FIGS. 1 and 2. In the method of manufacturing the internally spiral grooved tube according to the present embodiment, first, the raw pipe 2 (see FIG. 2) made of an aluminum material is prepared. As shown in FIG. 2, the raw tube 2 has a large number of fins 21 projecting from the inner surface and extending in a direction parallel to the tube axis 20 and a groove 22 formed between the fins 21. doing.

As shown in FIG. 2, the fins 21 and the grooves 22 are formed by bending the raw pipe 2 in a direction (arrow m) orthogonal to the pipe axis 20 while applying a twisting moment centering on the pipe axis 20. Are plastically deformed in a spiral shape which turns around the tube axis 20. By the above, it is possible to obtain the inner surface spiral grooved tube 1 provided with the spiral fin 11 and the groove 12 which are turned around the tube axis 10.

Hereinafter, the said manufacturing method is demonstrated more concretely, demonstrating the structure of the manufacturing apparatus 3 of the inner surface spiral grooved pipe 1 used in this example. As shown in FIG. 1, the manufacturing apparatus 3 of this example includes a raw tube delivery unit 4, a bender unit 5, a rotation restricting unit 6, and a winding unit 7. The raw pipe 2 drawn out from the raw pipe delivery section 4 is subjected to bending processing in a state where a twisting moment is applied in the bender section 5, and becomes the inner surface spiral grooved pipe 1. The internally spiral grooved tube 1 having passed the bender portion 5 is conveyed toward the winding portion 7 by the rotation restricting portion 6 and is wound by the winding portion 7.

The raw pipe delivery unit 4 extends in the conveying direction 200 of the raw pipe 2 and the feed drum 41 around which the raw pipe 2 is wound, and is a drum holding portion that holds the central shaft 411 of the raw drum 41 rotatably. 42 and a frame 43 for supporting the drum holding portion 42. The raw pipe 2 is pulled out of the feed drum 41 according to the rotation of a conveyance belt 61 (described later) in the rotation restricting unit 6 and is guided to the bender unit 5 along the conveyance direction 200.

In addition, the raw tube delivery unit 4 transmits the driving force of the motor 44 to the drum holding unit 42. The motor 44 rotates the feeding drum 41 together with the drum holding unit 42 around the conveying direction 200 of the raw tube 2. And a belt 45. When the motor 44 is driven in the raw tube delivery unit 4, the driving force of the motor 44 is transmitted to the drum holding unit 42 via the transmission belt 45. As a result, the feed-out drum 41 and the drum holding portion 42 rotate about the conveying direction 200 of the raw pipe 2 (FIG. 1, arrow 412). As a result, as shown in FIG. 2, the raw pipe 2 drawn from the feed drum 41 can be rotated about the pipe axis 20 (FIG. 2, arrow t).

The raw pipe 2 delivered from the raw pipe delivery unit 4 is transported along the transport direction 200 while being rotated about the tube axis 20 and is guided to the bender unit 5.

The bender unit 5 has a first roll bender 51 located on the upstream side in the transport direction 200, that is, the raw pipe delivery unit 4 side, and a second roll bender 52 located on the downstream side, that is, the winding unit 7 side. doing. The first roll bender 51 includes two lower rolls 511 spaced apart in the transport direction 200 and an upper roll 512 disposed between the two lower rolls 511 in the transport direction 200. Have. The upper roll 512 is disposed so that the lower end thereof is located below the upper end of the lower roll 511.

The raw pipe 2 guided to the bender unit 5 enters between the lower roll 511 and the upper roll 512 in the first roll bender 51. As shown in FIG. 2, at the inlet of the first roll bender 51, the fins 21 and the grooves 22 of the raw tube 2 have a linear shape extending in a direction parallel to the tube axis 20. In addition, at the inlet of the first roll bender 51, the raw pipe 2 rotates in the direction of the arrow t about the pipe axis 20. The rotation of the raw pipe 2 is restricted by the rotation restricting portion 6 as described later. Therefore, when passing between the lower roll 511 and the upper roll 512, the blank tube 2 is twisted in the direction of the arrow t around the tube axis 20.

A bending load to the lower side (arrow m) is applied to the raw tube 2 that has entered between the lower roll 511 and the upper roll 512. Further, as described above, the raw pipe 2 is twisted in the direction of the arrow t around the pipe axis 20 between the lower roll 511 and the upper roll 512.

As a result, when passing between the lower roll 511 and the upper roll 512, the raw pipe 2 is subjected to a bending process in which it is bent downward in a state in which a twisting moment about the pipe axis 20 is applied. Ru. The fins 21 and the grooves 22 of the raw tube 2 are plastically deformed in a spiral shape gradually while being moved along the transport direction 200 between the lower roll 511 and the upper roll 512 by bending. As a result, at the outlet of the first roll bender 51, an inner surface spiral grooved tube provided on the inner surface with a spiral fin 11 that pivots about the tube axis 10 and a groove 12 formed between the fins 11 You can get one.

The internally spiral grooved tube 1 having passed through the first roll bender 51 is guided to the second roll bender 52. The second roll bender 52 has two upper rolls 522 spaced apart in the transport direction 200 and a lower roll 521 disposed between the two upper rolls 522 in the transport direction 200. doing. Further, the lower roll 521 is disposed such that the upper end thereof is positioned above the lower end of the upper roll 522.

Although not shown in the figure, the inner spiral grooved tube 1 in the second roll bender 52 is twisted in the direction of the arrow t about the pipe axis 10 in the same manner as the raw tube 2 in the first roll bender 51 There is. The inner spiral grooved tube 1 is bent upward by the upper roll 522 and the lower roll 521 in a state in which a twisting moment about the pipe axis 10 is applied. (Refer to FIG. 2) of the groove 12 at the outlet of the second roll bender 52, that is, the angle formed by the extending direction of the groove 12 with respect to the direction parallel to the tube axis 10 It can be greater than the twist angle α of the groove 12 at the outlet.

As described above, the bender portion 5 of this example can perform bending on the base pipe 2 by bending in the vertical direction. Then, in the bender section 5, the base pipe 2 is subjected to bending while giving a twisting moment centering on the pipe axis 20, thereby obtaining the inner surface spiral grooved pipe 1 having a desired twist angle α of the groove 12. be able to. The internally spiral grooved tube 1 which has passed the bender portion 5 is transported along the transport direction 200 and guided to the rotation restricting portion 6.

As shown in FIG. 1, the rotation restricting portion 6 has a pair of conveying belts 61 which sandwich the inner surface spiral grooved tube 1 in the vertical direction. The conveyance belt 61 can press the inner surface spiral grooved tube 1 in the up and down direction, and can restrict rotation in the direction of the arrow t (see FIG. 2) about the tube axis 10. Further, the transport belt 61 pulls the raw pipe 2 out of the feeding drum 41 by its own rotation and transports it along the transport direction 200 and transports the inner surface spiral grooved tube 1 toward the winding portion 7. it can.

The internally spiral grooved tube 1 delivered in the transport direction 200 by the rotation restricting portion 6 is wound by the winding portion 7.

Next, the operation and effect of the method of manufacturing the internally spiral grooved tube 1 of the present embodiment will be described. As shown in FIGS. 1 and 2, in the manufacturing method of this embodiment, a raw material having a large number of fins 21 extending in a direction parallel to the tube axis 20 and grooves 22 formed between the fins. The pipe 2 is prepared, and the base pipe 2 is bent in the vertical direction orthogonal to the pipe axis 20 while applying a twisting moment centering on the pipe axis 20. As described above, by simultaneously applying the twisting moment and the bending moment to the element tube 2, the element tube 2 can be plastically deformed with a smaller twisting moment as compared with the case where the bending moment is not applied. As a result, it is possible to plastically deform the straight fins 21 and the grooves 22 provided on the inner surface of the raw pipe 2 in a helical manner, and obtain the internally spiral grooved pipe 1.

According to the manufacturing method of this example, the fins 21 and the grooves 22 can be plastically deformed in a spiral shape regardless of the pipe contraction process. Therefore, various problems in the conventional manufacturing method involving tube contraction processing, such as reduction of the twist angle α of the groove 22, change of sectional shape from the raw pipe 2, complication of manufacturing process and increase of manufacturing cost, are avoided. The spiral grooved tube 1 having a large twist angle α of the groove 12 can be manufactured by a simple process.

The specific configuration for bending the raw pipe 2 is not limited to the configuration of the manufacturing apparatus 3 of this example. For example, in the manufacturing apparatus 3 of this example, the bending process is performed on the raw pipe 2 by the two roll vendors of the first roll bender 51 and the second roll bender 52 in the bender unit 5. It may be a group, or may be three or more. Further, the direction in which the raw tube 2 is bent can also be a direction other than the vertical direction such as the horizontal direction. Furthermore, it is also possible to bend the raw pipe 2 using a bending machine or the like other than the roll bender.

In the manufacturing method of this embodiment, the rotational speed of the feed drum 41 and the transport speed of the raw pipe 2 can be appropriately set according to the desired magnitude of the twist angle α of the groove 12. For example, the amount of twist of the raw pipe 2 in the bender portion 5 can be increased by increasing the rotational speed of the feed drum 41 or decreasing the transfer speed of the raw pipe 2. As a result, the internally spiral grooved tube 1 having a large twist angle α of the groove 12 can be manufactured.

(Example 2)
This example is an example of the inner surface spiral grooved tube 1 manufactured by the above-mentioned manufacturing method. Of the reference numerals used in the present and subsequent embodiments, the same reference numerals as those used in the previously described embodiments and comparative examples indicate the same constituent elements as those in the previously described embodiments and the like unless otherwise specified. Indicates

In this example, as the raw tube 2, an extruded shaped material having a recrystallized structure with an average crystal grain size of 30 μm and made of A3003-H112 material was prepared. As shown in FIG. 3, the raw tube 2 of this example is formed on its inner surface between a large number of fins 21 extending in a direction parallel to the tube axis 20 (not shown) and the fins 21. And a groove 22. The number of fins 21 and the number of grooves 22 can be appropriately set, for example, in the range of 30 to 70. In this example, the number of fins 21 and the number of grooves 22 are 50.

The outer diameter OD ₀ of the raw pipe 2 can be appropriately set, for example, in the range of 5 to 10 mm. When the raw pipe 2 of this example was pulled out from the feed drum 41 and the outer diameter of the raw pipe 2 at various positions was measured, the outer diameter was slightly changed depending on the measurement position. In the present example, the average value of the maximum value and the minimum value of the outer diameter obtained based on these measurement results was taken as the outer diameter OD _{0 of the} raw pipe. Specifically, the outer diameter OD _{0 of the} raw pipe was 7.00 mm. Moreover, based on the measurement result of the outer diameter, the difference between the maximum value of the outer diameter and the minimum value of the outer diameter was calculated, and this value is described in Table 1 as an outer diameter deviation ΔD. Specifically, the value of the outer diameter deviation ΔD was 0.25 mm.

The fins 21 project from the inner surface of the blank 2 as shown in FIG. In addition, the fin 21 has a trapezoidal shape in which the width becomes narrower as it approaches the tube axis 20 in a cross section perpendicular to the tube axis 20. The height HF ₀ of the radial fins 21 based on the bottom 221 of the groove 22 can be set as appropriate, for example, from the range of 0.10 to 0.40 mm. In addition, the apex angle γ ₀ of the fins 21, that is, the angle between the extension lines L of the side surfaces 211 of the fins 21 in a cross section perpendicular to the tube axis 20 is appropriately set from, for example, a range of more than 0 degrees and less than 20 degrees. be able to. In this example, the height HF ₀ of the fins 21 is 0.28 mm, and the apex angle γ ₀ of the fins 21 is 10 degrees.

The thickness TF ₀ (see FIG. 3) at the bottom 221 of the groove 22 can be appropriately set, for example, from the range of 0.30 to 0.70 mm. In this example, the thickness TF _{0 at} the bottom 221 of the groove 22 is 0.40 mm.

With respect to the raw pipe 2 having such a configuration, a tensile test was carried out by a method according to the definition of JIS Z2241, and values of tensile strength σ _B0 , proof stress and elongation were measured. These results were as shown in Table 1.

In addition, the base pipe 2 was subjected to bending processing by the same method as the method shown in the first embodiment, to produce the inner surface spiral grooved pipe 1 in which the twist angle α of the groove 12 is 10 degrees. The cross section perpendicular to the tube axis 10 is observed for the obtained internally spiral grooved tube 1, and the outer diameter OD ₁ , the thickness TF _{1 at} the bottom of the groove 12, and the height HF of the fins 11 are the same as the raw tube 2. ₁ was measured vertical angle gamma ₁ fin 11 (not shown). Furthermore, the tensile test of the internally grooved grooved tube 1 was carried out by the method according to the definition of JIS Z2241, and the values of tensile strength σ _B1 , proof stress and elongation were measured. These results were as shown in Table 1. Further, the inner surface spiral grooved tube 1 of the present example had a recrystallized structure with an average crystal grain size of 30 μm, similarly to the raw tube 2.

When a hairpin bending process with a bending pitch of 21 mm was performed on the inner surface spiral grooved tube 1 of this example, no cracking or buckling occurred after the process.

(Example 3)
In the present example, an inner surface spiral grooved tube 1 was produced in the same manner as in Example 2 except that the twist angle α of the groove 12 was 15 degrees. Then, the value of such an outer diameter OD ₁ of the obtained inner surface helical grooved tube 1 was measured in the same manner as in Example 2. These results were as shown in Table 1. Further, the inner surface spiral grooved tube 1 of the present example had a recrystallized structure with an average crystal grain size of 30 μm, similarly to the raw tube 2.

(Comparative example 1)
This example is an example of a manufacturing method which applies only a twisting moment to the raw pipe 2 and does not apply a bending moment. In this example, the raw pipe 2 drawn out from the raw pipe delivery unit 4 is directly led to the rotation restricting unit 6 without the bender unit 5. Moreover, in this example, the amount of twist was enlarged to the limit in the range which the raw pipe 2 does not buckle. An inner surface spiral grooved tube 1 was produced in the same manner as in Example 2 except for the above. Evaluation similar to Example 2 was performed about the cross-sectional shape etc. of the obtained inner surface spiral grooved tube 1. As shown in FIG. The cross-sectional shape etc. of the inner surface spiral grooved tube 1 of this example were as shown in Table 1.

As shown in Table 1, in the internally helical grooved tube of this example, the twist angle α of the groove was 1.5 degrees. Moreover, when the twisting moment was made larger than this, the base pipe 2 was buckled, and the internal spiral grooved pipe 1 could not be manufactured.

(Comparative example 2)
This example is an example of the manufacturing method of the conventional inner surface spiral grooved tube 8 with diameter reduction processing. In this example, the outer diameter OD ₀ is 8 mm, and the thickness TF _{0 at} the bottom portion 221 of the groove 22 is 0.38 mm, in consideration of the reduction of the outer diameter by diameter reduction processing and the increase of the thickness at the bottom of the groove 12. The raw pipe 2 was used. As shown in FIG. 4, the base tube 2 is introduced into the drawing die 9 while being rotated in the direction of the arrow u about the pipe axis 20, and diameter reducing processing is performed to reduce the outer diameter at the diameter reducing portion 91 of the drawing die 9. went. The magnitude | size of the twisting moment given to the element pipe | tube 2 in diameter reduction process was 2.32 N * m.

The same evaluation as in Example 2 was performed on the internally spiral grooved tube 8 after diameter reduction processing. As a result, as shown in Table 1, the cross-sectional shape of the inner surface spiral grooved tube 8 of this example was substantially the same as the inner surface spiral grooved tube 1 of Example 2.

However, in the case of the internally spiral grooved tube 8 of this example, the metal structure becomes a processed structure during diameter reduction processing. Further, as a result of work hardening, the tensile strength σ _B1 and the proof stress become higher as compared with the inner surface helical grooved tube 1 of Example 2, and the elongation is lowered. Therefore, when the hairpin bending process of bending pitch 21mm was given to the inner surface spiral grooved tube 8 of this example, a crack, buckling, etc. of the inner surface spiral grooved tube 8 occurred after processing.

(Comparative example 3)
In this example, in order to improve the processability of the inner surface helical grooved tube 8 of Comparative Example 2, annealing is performed after diameter reduction processing. In this example, after producing the inner surface spiral grooved tube 8 by the same method as Comparative Example 2, the inner surface spiral grooved tube 8 was annealed by heating at 420 ° C. for 1 hour. And evaluation similar to Example 2 was performed about the obtained inner surface spiral grooved tube 8. FIG.

As shown in Table 1, the inner surface spiral grooved tube 8 of this example was stretched more than the inner surface spiral grooved tube 8 of Comparative Example 2 by annealing. Therefore, the inner surface spiral grooved tube 8 of this example can suppress the occurrence of cracking, buckling, and the like after the hairpin bending with a bending pitch of 21 mm.

However, in the inner surface spiral grooved tube 8 of this example, recrystallization proceeds by annealing, so that the metallographic structure becomes a recrystallized structure with an average crystal grain size of 120 μm. Further, since the work hardening was eliminated by the annealing, the tensile strength σ _B1 and the proof stress were reduced as compared with the inner surface spiral grooved tube 1 of the second embodiment.

(Comparative example 4)
This example is an example in which a thicker base pipe 2 having an outer diameter OD ₀ is used in the conventional manufacturing method. In this example, using the raw tube 2 having an outer diameter OD ₀ of 9.52 mm and a thickness TF _{0 at} the bottom 221 of the groove 22 of 0.36 mm, the inner surface spiral groove is formed by the same method as in Comparative Example 2. An attempt was made to manufacture the attached tube 8.

However, in this embodiment, since the thin wall thickness TF ₀ at the bottom 221 of the groove 22, the outer radially polarized difference ΔD raw tube 2 fed from Feeding drum 41 is larger than that in Example 2. As a result, buckling occurred in the raw pipe 2 at the inlet of the drawing die 9. Therefore, in the present example, the inner surface spiral grooved tube 8 could not be manufactured.

Table 1 summarizes the results of these Examples and Comparative Examples. As can be understood from Table 1, by subjecting the raw tube 2 to a bending process in which it is bent in a direction orthogonal to the tube axis while applying a twisting moment centering on the tube axis, an internal spiral with a large twist angle α of the groove 12 The grooved tube 1 can be easily manufactured. Moreover, according to such a method, it is possible to suppress an unintended change in the cross-sectional shape of the inner surface spiral grooved tube 1 and to avoid the deterioration of the heat transfer performance. Furthermore, according to the manufacturing method, the deterioration of the mechanical properties of the inner surface spiral grooved tube 1 can be avoided, so the inner surface spiral grooved tube 1 excellent in various workability such as hairpin bending is manufactured. be able to.

Thus, the internally spiral grooved tube 1 produced by the above-mentioned manufacturing method is suitable for use in a cross fin type heat exchanger.

On the other hand, as shown in Comparative Example 1, when it is intended to plastically deform the fins 21 and the grooves 22 of the raw pipe 2 in a helical manner by applying only a twisting moment, the twist angle α of the grooves 12 is increased. It is difficult.

Moreover, as shown to the comparative example 2, if it does not anneal after the tube reduction process in the conventional manufacturing method with a tube reduction process, it is difficult to improve the processability of the internally spiral grooved tube 8.
As shown in Comparative Example 3, when annealing is performed after the tube contraction process, the mechanical properties of the raw pipe 2 are lost. Further, the inner surface spiral grooved tube 8 shown in Comparative Example 3 has a larger average crystal grain size and smaller tensile strength σ _B1 and yield strength than the inner surface spiral grooved tube 1 of Example 2, so There is a risk that the pressure resistance and fatigue strength when the refrigerant flows will be reduced.

Further, as shown in Comparative Example 4, the conventional manufacturing method has a limitation in the shape of the raw pipe 2 that can be used.

Claims

Preparing a raw tube made of an aluminum material, comprising: a plurality of fins projecting from the inner surface and extending in a direction parallel to the tube axis; and a groove formed between the fins;
The base tube is subjected to a bending process in which it is bent in a direction perpendicular to the tube axis while applying a twisting moment around the tube axis, whereby the fin and the groove are spirally wound around the tube axis Plastically deform,
The manufacturing method of the inner surface spiral grooved tube.
The outer diameter of the raw tube is OD 0 [mm], the thickness of the bottom of the groove in the raw tube is TF 0 [mm], the outer diameter of the inner spiral grooved tube is OD 1 [mm], the inner spiral The method for producing an internally helical grooved tube according to claim 1, wherein the following formulas (1) to (2) are satisfied, where the thickness of the bottom of the groove in the grooved tube is TF 1 [mm].
0 <(OD 1 −OD 0 ) / OD 0 <0.03 (1)
0 ≦ (TF 1 −TF 0 ) / TF 0 <0.04 (2)
When the tensile strength of the raw pipe is σ B0 [MPa] and the tensile strength of the inner surface helical grooved pipe is σ B1 [MPa], the following formula (3) is satisfied: Of the inner surface spiral grooved tube.
0.02 <(σ B1 -σ B0 ) / σ B0 <0.10 (3)
An internally helical grooved tube made of a 3000 series aluminum alloy, wherein
It consists of a recrystallized structure with an average grain size of 80 μm or less,
A number of fins projecting from the inner surface and presenting a spiral that pivots around the tube axis;
And a groove formed between the fins.
Internal spiral grooved tube.
The internally spiral grooved tube according to claim 4, wherein the tensile strength is 115 MPa or more, the proof stress is 95 MPa or more, and the elongation is 20% or more.