JP6391139B2 - Manufacturing method of internally spiral grooved tube - Google Patents

Description

The present invention relates to a manufacturing method of the inner surface helical grooved tube for use in heat exchangers of the heat transfer tube or the like.

In general, heat transfer tubes for flowing refrigerant are used in fin tube heat exchangers of air conditioners and refrigerators. The structure is such that a heat transfer tube hairpin bent into a U-shape is inserted into aluminum fins laminated after pressing, and the heat transfer tube is expanded and joined to the fin through a tube expansion process. As the refrigerant flowing through the heat transfer tube, a chlorofluorocarbon refrigerant or an alternative refrigerant or the like is used, and heat exchange is performed using a phase change of the refrigerant.
Heat exchangers are required to be highly efficient for energy saving, and heat transfer tubes have fins with triangular or trapezoidal cross-sections formed between the grooves to improve heat transfer characteristics. ing. Recently, in order to further improve thermal characteristics, a heat transfer tube having a groove formed in a spiral shape (spiral grooved tube) has been used. In addition, with the widespread use of heat-pump air conditioners with air conditioning and heating functions, heat transfer tubes with both evaporative performance and condensing performance enhanced with the same heat transfer tubes are required. To meet these requirements, fin height, Heat transfer tubes that define the groove lead angle, fin shape, fin apex angle, and the like have been proposed.

Further, as a method of manufacturing a spiral grooved tube, a groove rolling method (Patent Document 1) is known in which a twisted groove is rolled on the inner surface of the tube.
Copper heat transfer tubes for heat exchangers that are widely used at present are generally manufactured by the groove rolling method described above. In the groove rolling method, a grooved plug is held in a pipe to be processed by a holding plug, and a rolling ball provided on the outer periphery of the pipe rotates and planetarily rotates at a high speed while pressing the pipe against the grooved plug. This is a method for manufacturing a spiral grooved tube while transferring the shape of the plug to the inner surface of the tube.

JP-A-6-190476

Until now, copper-based materials such as copper and copper alloys have been mainly used for heat transfer tubes, but due to the recent rise in copper bullion, the price of copper heat transfer tubes has increased, putting pressure on product prices. Therefore, there is a demand for a heat transfer tube using aluminum and aluminum alloy which are cheaper and more stable. With aluminum, in addition to its specific gravity price stability since lighter compared to 2.7 g / cm ³ and copper 8.9 g / cm ^3, it is possible to reduce the weight of the heat exchanger. In addition, there is no need to disassemble and separate the heat exchanger into copper alloy heat transfer tubes and aluminum alloy fins during recycling, and the heat exchanger is made of all aluminum to facilitate recycling. .

However, it is difficult to manufacture aluminum and aluminum alloy heat transfer tubes by the conventional groove rolling method. In the first place, since the strength of aluminum alloy is lower than that of copper alloy, the heat transfer tube manufactured from aluminum alloy needs to have a thicker bottom wall than copper heat transfer tube in order to obtain pressure resistance. In that case, in the groove rolling method in which the tube is pressed from the outer periphery of the tube to the grooved plug on the inner periphery of the tube, and the groove is transferred to the inner periphery by plastic flow of the tube bottom thick part, the predetermined height It is difficult to form a groove having a defect, and defects due to defective plastic flow such as a groove chip are likely to occur. Recently, the groove shape of heat transfer tubes tends to be highly accurate to improve heat transfer properties, but when these groove shapes are manufactured by the groove rolling method, the predetermined shape cannot be obtained, and if forcibly processed, the tube is disconnected. Or cause seizure due to adhesion between the grooved plug and the tube. Further, in a heat transfer tube made of an aluminum alloy, aluminum flaws are generated during groove rolling, and it is difficult to remove them, resulting in clogging. For the above reasons, it is difficult to manufacture an aluminum alloy heat transfer tube by the groove rolling method, and there is a limit to the groove shape that can be manufactured.
Further, in the groove rolling method, since a floating plug is inserted into the inner surface of the tube to roll the groove, it has been difficult to apply to a heat transfer tube having an outer diameter of φ5 mm or less. After forming the groove by the groove rolling method, it is possible to reduce the diameter to 5 mm or less by drawing, but the entire tube is stretched in the longitudinal direction by drawing, and the added twist angle becomes shallow accordingly. End up. Therefore, there is a problem that a thin tube and a high twist angle cannot be compatible.

  For this reason, in order to manufacture a heat transfer tube made of aluminum alloy having a small diameter and a large twist angle, a manufacturing method other than the groove rolling method is necessary. A method using an electric resistance welded tube that is processed into a round tubular shape by roll forming and welds the joint surface has been proposed, but in that case, the bead of the inner surface welded part hinders the expansion of the tube and not only deteriorates the expandability. This causes problems such as refrigerant leakage due to poor bonding of the weld surfaces.

  As a result of studying various production methods, the present inventor believes that a method of directly twisting a raw tube having a straight groove in advance is suitable for manufacturing a heat transfer tube made of aluminum and an aluminum alloy. . Extrusion is suitable for the production of a raw pipe having a straight groove, and a high slim fin type groove shape with a narrow fin apex angle and a high fin height is also easy. Moreover, it is possible to manufacture an internally spiral grooved tube having a high twist angle while the outer diameter is 5 mm or less. By reducing the outer diameter of the heat transfer tube, the amount of refrigerant used in the heat exchanger can be reduced. Thereby, the heat exchanger which performs heat exchange efficiently with a small amount of refrigerant can be realized.

However, if the crystal grain size of the raw tube is above a certain range, the crystal grain size of the manufactured inner spiral grooved tube becomes coarse, and when the tube is expanded, an orange peel with rough skin like an orange peel is applied to the outer peripheral surface. And unevenness occurs on the surface.
When the heat transfer tube is assembled in a heat exchanger, a heat expansion tube having a diameter larger than that of the heat transfer tube is inserted into the heat transfer tube to expand the diameter of the heat transfer tube and mechanically joined to the aluminum alloy radiating fin. Since the joint surface between the heat radiating fin and the heat transfer tube is reduced due to unevenness caused by rough skin on the outer periphery of the tube and the joining rate is lowered, the thermal characteristics deteriorate.

  Another problem is due to rough skin on the inner circumference side of the pipe, and when viewed in a vertical cross section in the longitudinal direction of the heat transfer pipe, the fins that are originally formed in the bottom thick part in the center direction of the circle are It is a problem that the fin collapse is amplified when the tube is expanded by the tube expansion plug due to the unevenness of the surface. In that case, the force acting in the outer peripheral direction from the tube expansion plug is absorbed by the fin collapse and is difficult to be transmitted to the bottom wall thickness part, so that the predetermined tube expansion rate cannot be obtained, and the heat radiation fin and the heat transfer tube Sufficient bonding cannot be obtained, leading to deterioration of thermal characteristics. Further, when the degree is severe, fin collapse becomes large and the refrigerant flow path is blocked, and the thermal characteristics are greatly deteriorated. Note that such fin collapse tends to become more prominent when the bottom wall thickness of the heat transfer tube increases.

  These orange peels are not only generated on the surface of the heat transfer tube when the tube is expanded, but also when the crystal grain size of the raw tube used for manufacturing the heat transfer tube is large, it is generated during the manufacture of the heat transfer tube, and irregularities are formed on the outer and inner peripheral surfaces. Therefore, it is necessary to limit not only the crystal grain size in the crystal grain structure of the manufactured internally spiral grooved tube but also the crystal grain size of the raw pipe used. Furthermore, the manufactured inner surface spiral grooved tube is work-hardened as it is, and as it is, only the groove is easily crushed by expanding the tube, so annealing for making O material is necessary. Since it grows, regarding the heat transfer tube, it is necessary to set a limit on the crystal grain size after the final heat treatment.

The present invention relates to a method of manufacturing a heat transfer tube with a spiral groove obtained by directly twisting an aluminum or aluminum alloy extruded element tube having a straight groove on its inner surface, and has a small outer diameter and a large twist angle. It is another object of the present invention to provide a spiral grooved tube that has excellent heat expandability and has no orange peel during heat transfer tube processing and tube expansion.

The method of manufacturing an internally spiral grooved tube according to the present invention includes an aluminum or aluminum alloy in which a plurality of straight grooves along the length direction are formed on the inner surface at intervals in the circumferential direction, and fins are formed between the straight grooves. A feeding device for supplying the raw pipe in a straight line toward the die hole is installed on the introduction side of the die hole of the drawing die, and the winding device for the raw pipe is provided on the outlet side of the drawing die The feed device is provided so as to rotate about the extension line of the center line passing through the center of the die hole as a central axis, and from the feed device to the die hole of the drawing die A straight tension is applied to the pipe from the die hole of the drawing die to the take-up device, and the pipe passing through the die hole is applied to the pipe. Drawing and twisting By applying processing, a plurality of spiral grooves along the length direction are formed on the inner surface at an interval, the outer diameter is 5 mm or less, the twist angle of the spiral groove is 20 ° or more and 40 ° or less, An internal spiral grooved tube having an average grain size of 120 μm or less in the structure is manufactured.

In the manufacturing method of the inner surface spiral groove tube according to the present invention, when manufacturing the inner surface spiral groove tube, all the metal structures are fibrous structures along the length direction of the tube or only the surface layer has a thickness of 5 on the outer and inner peripheries. It is preferable to use an extruded element tube in which the% or less is a recrystallized structure and all other parts are fibrous structures, or the average crystal grain size of the metal structure is 80 μm or less.
In the method for manufacturing an internally spiral grooved tube according to the present invention, the average crystal grain size of 120 μm or less is preferably an average crystal grain size achieved after annealing.
In the manufacturing method of the inner surface spiral groove tube according to the present invention, it is preferable to manufacture the inner surface spiral groove tube having a fin tilt angle of 1 ° or less of the fin formed along the inner surface spiral groove.

In the manufacturing method of the inner surface helical grooved tubes according to the present invention, have preferably be produced surface roughness (Rmax) orange peel is not an inner surface helical grooved tube is defined as a step in excess of 15μm on the outer surface.

According to the present invention, since it can be manufactured by directly twisting the extruded element tube, it is possible to provide an internally spiral grooved tube having an outer diameter of 5 mm or less and a groove twist angle of 20 ° or more. . When this inner surface spiral grooved tube is used as a heat exchanger tube of a heat exchanger, by setting the twist angle of the groove to 20 ° or more, the internal surface area through which the refrigerant flows can be increased, and the thermal characteristics are improved. . Moreover, by setting it as (phi) 5 mm or less, while the freedom degree in the design of a heat exchanger increases, it can contribute to size reduction, and it becomes possible to arrange | position a small-diameter heat exchanger tube at high density.
Moreover, since the average crystal grain size of the metal structure is 120 μm or less , even if it is a small diameter such as a heat transfer tube for a heat exchanger, it does not cause rough skin like an orange peel, has excellent surface properties, and is on the inner surface side. Thus, it is possible to provide an internally spiral grooved tube that can be formed into a desired shape.
Moreover, since it is excellent in surface property, when it assembles | assembles to a heat exchanger with a fin, it can provide an internal spiral grooved tube which cannot produce the joining defect of a fin, a fin fall, etc. easily.

The schematic diagram which shows 1st Embodiment of the apparatus which manufactures the internal spiral grooved pipe | tube which concerns on this invention. It is a figure which shows the extrusion element | tube with which several straight groove | channels were formed in the inner surface, FIG. 2 (a) is a front view, FIG.2 (b) is a longitudinal cross-sectional view. The longitudinal cross-sectional view which shows an example of an internal spiral grooved tube. The schematic diagram which shows an example of the manufacturing apparatus of an internal spiral grooved pipe. The flowchart explaining an example of the manufacturing process of an internal spiral grooved pipe. The figure explaining the flatness of a pipe | tube. The 2nd Embodiment of the apparatus which manufactures the inner surface spiral grooved tube which concerns on this invention is shown, FIG. 7 (a) is a side view, FIG.7 (b) is a principal part top view. The figure explaining the twist cycle of a pipe | tube. The figure explaining the calculation method of the twist angle of a pipe | tube. The graph which shows the relationship between a winding roll diameter and a twist angle. FIG. 11A shows a metal structure photograph of a partial cross section of the inner surface spiral groove tube obtained in Example 1, and FIG. 11B shows an inner surface spiral groove tube. Fig. 11 (c) is a photograph showing a state in which the inner spiral grooved tube is cut obliquely, and Fig. 11 (d) is a partial cross section of the inner spiral grooved tube. A photograph showing the groove shape. FIG. 12A shows a metal structure photograph of a partial cross section of the inner surface spiral grooved tube obtained in the comparative example, and FIG. 12B shows a part of the inner surface spiral grooved tube. Fig. 12 (c) is a photograph showing the groove shape of the partial cross section of the inner surface spiral grooved tube. FIG. 13 (a) shows the state of the presence or absence of orange peel in the inner spiral grooved tube of the example and the comparative example, and FIG. 13 (a) is a photograph showing the surface state of the inner spiral grooved tube of the example in which no orange peel occurs. FIG. 13B is a photograph showing the surface state of the inner surface spiral grooved tube of the comparative example in which the orange peel is generated. Explanatory drawing which shows the fin fall angle in an internal spiral grooved pipe. The metal structure photograph which shows an example of the cross section of the inner surface spiral grooved tube obtained in Example 2. FIG. The photograph which shows the external appearance of the internal spiral grooved pipe | tube without an orange peel obtained in Example 2. FIG. The photograph which shows the external appearance of the internal spiral grooved tube with the orange peel obtained by the comparative example. FIG. 18A is a side view and FIG. 18B is a perspective view illustrating an embodiment of a heat exchanger according to the present invention.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of an internally spiral grooved tube and a manufacturing method thereof according to the present invention will be described with reference to the drawings.
The manufacturing apparatus 100 of the inner surface spiral grooved tube of the first embodiment includes an extruded element tube 11 (see FIG. 2) in which a plurality of straight grooves 11a along the length direction are formed on the inner surface at intervals in the circumferential direction. This is an apparatus for producing an inner spiral grooved tube 11R (see FIG. 3) having a certain twist and having an inner spiral groove 11d.

The inner spiral grooved tube 11R is made of, for example, the international aluminum alloy standard 3000 series and is not particularly limited in the present invention, and may be made of any aluminum alloy or pure aluminum. In the present embodiment, the term “made of aluminum alloy” includes any aluminum alloy or pure aluminum.
Regarding the shape of the inner spiral grooved tube 11R, the outer diameter is 1.5 mm or more and 5 mm or less, preferably less than 5 mm. In addition, the inner spiral grooved tube 11R has a plurality of, for example, 30 to 60 convex spiral fins 11c and a plurality of, for example, 30 to 60, concave spiral grooves 11d on its inner peripheral surface. In this inner surface spiral grooved tube 11R, the height t0.1 to 0.4 mm of the spiral fin 11c, the fin apex angle θ ₁ 10 to 30 °, the bottom thickness d (the thickness of the tube at the position of the bottom of the spiral groove) 0 .3 to 0.6 mm, groove twist angle θ 20 ° to 40 °, groove inner corner corner R of spiral groove 11d is 0.15 mm or less, more preferably R is 0.08 mm or less. Yes. As shown in FIG. 3, the twist angle θ of the groove refers to the portion of the spiral groove or spiral fin displayed on the inside of the tube when the longitudinal cross section of the inner spiral grooved tube 11R is drawn. The angle between the extension line S and the outer surface of the tube is shown.

  As described above, it is preferable that the outer diameter of the inner spiral grooved tube 11R be φ1.5 mm or more. When the outer diameter is less than φ1.5 mm, it is difficult to maintain a bottom wall thickness d of 0.3 mm or more, and the pressure resistance is reduced. Further, if the outer diameter is less than φ1.5 mm, the flow path through which the refrigerant flows becomes narrow and the pressure loss increases, which is not preferable.

  As will be described later, the extruded element tube 11 is subjected to a drawing process in addition to a twisting process to be processed into an inner spiral grooved tube 11R, and thus a pipe having a larger outer diameter by about 5 to 50% than the inner spiral grooved tube 11R. It is preferable to use a body. The extruded element tube 11 has substantially the same cross-sectional shape as the inner spiral grooved tube 11R. Further, the extruded element tube 11 is a fibrous structure in which the metal structure is all along the length direction of the tube, or 5% or less of the thickness of the surface layer is a recrystallized structure in the outer periphery and the inner periphery, respectively. Other than that, all are made into a fibrous structure or a crystal grain having a whole surface average crystal grain size of 80 μm or less.

A manufacturing apparatus 100 for processing the extruded element tube 11 into the inner spiral grooved tube 11R has a configuration shown in FIGS. 1 and 4. The manufacturing apparatus 100 includes a winding means 20 for winding an extruded element tube 11 having an inner surface fin 11b formed by straight grooves 11a on an inner surface in a coil shape on a winding roll 21, and a coiled tube material 11C formed in a coil shape. Is stretched along the coil axis 26 to form a straight tube, a pulling means 40 for correcting the cross-sectional shape of the tube after pulling, and a heat treatment for heating the internally spiral grooved tube 11E after correction. Means 49.
1 mainly shows the configuration of one winding means 20 and pulling means 30 of the manufacturing apparatus 100. In detail, the manufacturing apparatus 100 has a plurality of winding means 20 and multiple pulling means 30 as shown in FIG. The drawing means 40 and the heat treatment means 49 are arranged in series (three in series in the example of FIG. 4).

The winding means 20 sandwiches the extruded tube 11 between the winding roll 21 and the winding roll 21 that winds the extruded tube 11 in a coil shape, and the extruded tubular material 11 extends along the surface of the winding roll 21. A groove with a constant pitch that sandwiches the extruded tube material 11 that is fed out and the take-up roll 21 and guides the take-up is provided on the outer periphery of the take-up roll 21. And a pair of guide plates 23 formed so as to constitute part of a spiral along the surface. Further, on the opposite side of the outer peripheral portion of the take-up roll 21 from the side on which the feed roll 22 is provided, a pressing roll 24 that is rotatably supported so as to sandwich the extruded tube material 11 with the take-up roll 21. Is provided. A motor 25 as a drive source is connected to the central axis of the feed roll 22.
The pair of guide plates 23 are formed in a circular arc shape facing the outer peripheral surface of the take-up roll 21, and grooves 23 a along the outer peripheral surface of the take-up roll 21 are formed at regular intervals on the inner surface thereof. It is preferable that at least two 23 are arranged on both sides of the take-up roll 21. By passing the extruded tube material 11 between the surface of the take-up roll 21 and the groove 23 a of the guide plate 23, the extruded tube material 11 is wound in a coil shape along the outer periphery of the take-up roll 21, and is wound up. The coiled tubular material 11 </ b> C can be sent out from the end of the take-up roll 21 in the spiral extension direction.

  On the surface layer of the winding roll 21 and the pressing roll 24, a sheathed heater is disposed perpendicular to the circumferential direction of the rolls. While the roll surface temperature is kept high, the extruded element tube 11 can be heated to a high temperature while the extruded element tube 11 is wound on the surface of the take-up roll 21 and fed out. The surface temperature of these rolls 21 and 24 is preferably RT (room temperature) to 300 ° C.

  The pulling means 30 chucks the coiled tubular material 11C for a plurality of turns sent from the winding roll 21 along the extension of the axis of the winding roll 21 (coil axis 26 of the coiled tubular material 11C). A stretcher 31 that extends along the extension of the coil axis 26 is provided. In addition, two pairs of pinch rolls 32 arranged at intervals along the extension line of the coil axis 26 are provided on the rear side of the stretcher 31. The coiled tube material 11C stretched to some extent by the stretcher 31 can be sandwiched between these pinch rolls 32 and formed into a straight tube while applying a constant tension. Further, the pulling means 30 is provided with a high-frequency heating furnace capable of high-speed heating or a heating furnace 33 using radiant heat, and can be stretched while heating the coiled tube material 11C.

Note that the phrase “along the extension line of the axis 26 of the coiled tube material 11 </ b> C does not only mean that the extension line of the coil axis line 26 coincides, but a slight deviation is allowed. However, the stretching of the coiled tube material 11C is preferably performed so as to coincide with the extension line of the coil axis 26.
The drawing means 40 is configured to correct the cross-sectional shape of the pipe material by drawing the pipe material through a drawing die having a hollow hole. The heat treatment means 50 performs the intermediate annealing of the pipe material after correcting the roundness. In addition, as a heating means of this embodiment, the sheathed heater which heats the surface of the winding roll 21 and the press roll 24, and the heating furnace 33 which heats the pipe material in the middle of extending correspond.

  In the manufacturing apparatus 100 of the first embodiment, as shown in detail in FIG. 4, three sets of winding means 20 and pulling means 30 are provided in series, and drawing means 40 and heat treatment means 49 are provided on the subsequent stage side. Yes. Hereinafter, in the manufacturing apparatus 100 of the first embodiment, for convenience, the first set of winding rolls 21 will be referred to as a winding roll 21a, and the second set of winding rolls 21 will be referred to as a winding roll 21b. The winding roll 21 in the set may be referred to as a winding roll 21c.

Next, a method for manufacturing the inner spiral grooved tube 11R using the manufacturing apparatus 100 configured as described above will be described.
In order to manufacture the inner surface spiral grooved tube using the manufacturing apparatus 100, the extruded element tube 11 in which the straight groove is formed on the inner surface by the extrusion molding method is manufactured.
The extruded element tube 11 used in the present embodiment has a plurality of straight grooves 11a formed along the length direction thereof. Further, the extruded element tube 11 is a fibrous structure in which the metal structure is all along the length direction of the tube, or 5% or less of the thickness of the surface layer is a recrystallized structure in the outer periphery and the inner periphery, respectively. Other than that, all are made into a fibrous structure or a crystal grain having a whole surface average crystal grain size of 80 μm or less.
The extruded element tube 11 having the metal structure and the groove shape can be manufactured by controlling the extrusion speed and the temperature in the billet of the extrusion apparatus. The extrusion speed is controlled by controlling the temperature at which the aluminum material is charged into the extrusion apparatus to 540 to 560 ° C. under the production conditions in which the extrusion speed is controlled to about 40 m / min. It means heating at about 595 ° C. for several hours to 10 hours.
By extruding under the above-mentioned conditions, the metal structure of the aluminum alloy constituting the extruded tube 11 is a fibrous structure in which the metal structure is all along the length direction of the tube, or only the surface layer is 5% of the thickness of the outer and inner peripheries. The following is the recrystallized structure, and all other than that can be controlled to a fibrous structure or a crystal grain having an overall average crystal grain size of 80 μm or less. Increasing the material input temperature or increasing the extrusion rate to increase the heat generated by processing increases the crystal grain size, which is not desirable.

  Using the extruded element tube 11 having the above-mentioned average crystal grain size, the extruded element tube 11 in which straight grooves are formed on the inner surface is fed by a feed roll 22 that rotates at a constant speed, and on the surface of the take-up roll 21a, The extruded element tube 11 is wound so as to have a coil shape with the same diameter. At this time, the extruding tube 11 is guided between the surface of the take-up roll 21a and the drive feed roll 22, the guide plate 23, and the pressing roll 24, and the take-up roll along the surface of the take-up roll 21a. Winding is performed along the axis (coil axis 26) of the winding roll 21a from one end side to the other end side of 21a. At this time, the tube material released from the other end side (upper side in FIG. 1) of the winding roll 21a is a coiled tube material 11C.

Next, a part of a plurality of turns of the coiled tube material 11C released from the other end side of the winding roll 21a is chucked by the stretcher 31, and along the extension line of the coil axis 26 of the coiled tube material 11C. Add preliminary correction. The pipe material corrected to a state close to a straight tube passes between the two pairs of pinch rolls 32, and is formed into a straight tube while a tension of 0.3 kN or more is applied between these pinch rolls 32.
The stretcher 31 performs preliminary correction on the coiled tube material 11C, and then moves to the original position as shown by a two-dot chain line in FIG. 1 to chuck the end portions of the coiled tube material 11C that are sequentially fed. Repeat preliminary correction. The tube material 11L that has been straightened by the pinch roll 32 is wound around the winding roll 21b in a coil shape.

  The tubular material 11L wound up in this way is formed with a spiral groove having a twist angle θ determined by the diameter of the winding roll 21a and the winding pitch of the tubular material wound up by the winding roll 21a. The twist angle θ increases as the diameter of the winding roll (winding diameter) decreases, and increases as the winding pitch decreases. Since the twist angle depends on the diameter of the take-up roll, it is possible to generate a large twist angle at once by winding it on a take-up roll with a small diameter. It is difficult to wind up.

  In this case, it is possible to obtain a tubular material having a large twist angle θ by winding up on a winding roll having a large diameter and adding the twist to the tubular material by repeating the winding process and the pulling process a plurality of times. However, depending on the material of the tube material, the tube material is hardly twisted due to work hardening by repeating the winding process and the pulling process in order to increase the twist angle θ. Therefore, like the heating furnace 33 and the take-up roll 21 of the present embodiment, a means for in-line heating is provided, and the heated tube material is twisted or heat-treated in the middle of each step. It is preferable to remove the strain. In addition, the heat processing performed in the middle of a process performs the intermediate annealing for 0.5 to 4 hours at 200-350 degreeC, for example to a pipe material.

Further, when manufacturing an internally spiral grooved tube having a larger twist angle θ, for example, as shown in the flowchart of FIG. 5, the drawing process and the heat treatment process are performed each time the winding process and the pulling process are repeated a certain number of times. Preferably it is done.
In the flowchart of FIG. 5, as shown in S101 to S103, after repeating the process consisting of the combination of the winding process and the pulling process three times, the drawing process (S104) and the heat treatment process (S105) are sandwiched for a total of 8 times. The winding process and the tensioning process are performed (S101 to S112). And whenever a winding process and a tension | pulling process are repeated, a fixed twist is added to the pipe material 11, and the twist angle | corner (theta) can be enlarged gradually.

  When the winding process and the pulling process are repeated a plurality of times, when the tube material is wound around the winding roll 21a, it is pressed against the surface of the winding roll 21, so that as shown in FIG. The shape is gradually crushed flat. Tubing with increased cross-sectional flatness may be buckled during winding, and when the buckled tube is subjected to a pulling process, it is locally bent at the buckled part (necking). ), A tube material in which a uniform twist angle is formed on the entire tube material cannot be obtained. Therefore, it is preferable to perform at least one drawing process and a heat treatment process for heating the straightened tube material while repeating the winding process and the pulling process.

The drawing process is performed by drawing the pipe material through the hollow hole of the drawing die by the drawing means 40, and one drawing process is performed with respect to the diameter of the original pipe material within 120% of the flatness of the pipe material. It is performed so that reduction of 5% or more can be achieved. And the pipe material after roundness correction is heated by a heat treatment process, and distortion is removed. In the heat treatment step, for example, the same heat treatment as described above is performed, and the straightened pipe material is subjected to intermediate annealing at 200 to 350 ° C. for 0.5 to 4 hours.
As described above, when the flattening ratio of the tube material is increased by repeating the winding process and the pulling process, the roundness can be recovered by the drawing process, and buckling can be prevented. By providing at least one drawing process to correct the cross-sectional shape of the tube material after the pulling process, it is possible to suppress the collapse of the tube material and to repeat the winding process and the pulling process multiple times, and to twist the tube material. The corner can be increased.
In addition, flatness means the ratio of the maximum diameter X with respect to the minimum diameter Y of the pipe material 11 shown in FIG.

From the above description, the manufactured inner spiral grooved tube 11 </ b> R is manufactured using the extruded element tube 11. The extruded element tube 11 is a fibrous structure in which the metal structure is all along the length direction of the tube, or 5% or less of the thickness of the surface layer is the recrystallized structure on the outer periphery and the inner periphery, respectively. Are all made of fibrous structure or crystal grains having an average average crystal grain size of 80 μm or less. Since it is manufactured using such an extruded element tube 11, there is no generation of orange peel after manufacture, and the average crystal grain size of the internally spiral grooved tube after annealing for forming O material is 120 μm or less. Even if the pipe is expanded, an orange peel is not generated, and it is possible to provide a pipe with an inner surface spiral groove that has excellent pipe expandability that is unlikely to cause fin collapse and that has a high joining ratio with the radiation fin.
In addition, the inner surface spiral grooved tube 11R obtained after the processing is work-hardened, and as it is, the hardness is high, and the tube expansion by the tube expansion plug is hindered. Easy to expand. O-materialization by annealing means a process of heating the inner spiral grooved tube 11R in a temperature range of 300 to 420 ° C. for 0.5 hours or more and within 4 hours and then gradually cooling.
If the heating temperature at the time of forming the O material is less than 300 ° C., the tube after processing cannot be completely distorted, and if the heat treatment is longer than 4 hours, crystal grains may grow too much, leading to the generation of orange peel. is there.

  Further, by causing the extruded element tube 11 to have a constant twist, the inner spiral grooved tube 11R having a small diameter and a large twist angle θ can be formed. By increasing the twist angle of the groove, the internal surface area through which the refrigerant flows can be increased, and the thermal characteristics are improved. Further, by making the diameter small, the degree of freedom in designing the heat exchanger can be increased, contributing to downsizing, and it becomes possible to arrange the small-diameter heat transfer tubes at a high density.

Hereinafter, a second embodiment of the method of manufacturing the inner surface spiral groove tube according to the second embodiment of the inner surface spiral groove tube according to the present invention will be described with reference to the drawings.
FIG. 7 shows an apparatus 50 for manufacturing an internally spiral grooved tube according to the second embodiment. This manufacturing apparatus 50 is similar to the manufacturing apparatus 100 of the first embodiment, in the extruded element tube 11 (see FIG. 2) in which a plurality of straight grooves 11a along the length direction are formed on the inner surface at intervals in the circumferential direction. This is an apparatus for producing an inner surface spiral grooved tube 11R (see FIG. 3) having a certain twist and having an inner surface having a spiral groove 11d.

The inner spiral grooved tube 11R manufacturing apparatus 50 includes an unwinding drum (feeding device) 51 that unwinds an extruded element tube 11 having a straight groove on the inner surface, and an extruded element tube 11 from the unwinding drum 51. Rotating means 52 for rotating and twisting the extruded tube 11 is provided. Further, a drawing die 53 for pulling out the extruded element tube 11 to which the twist is applied, and a winding drum (winding device) 55 for winding the inner spiral grooved tube 11 </ b> R drawn from the drawing die 53 are provided. Yes. The extrusion element tube 11 can be attached to the unwinding drum 51 by previously winding the extrusion element tube 11 around the bobbin 56 and attaching the extrusion element tube 11 together with the bobbin 56 to the unwinding drum 51.
In addition, a brake device 54 such as a drum brake or a disc brake is built inside the unwind drum 51 so that a constant braking force can be applied to the rotation of the unwind drum 51. By adjusting the braking force generated by the brake device 54, a predetermined rear tension (back tension) can be applied to the extruded element tube 11 that is unwound from the unwinding drum 51 and tries to pass through the drawing die 53. .

  The unwinding drum 51 is supported so as to be rotatable about an axis by supporting a rotating shaft 51 a at the center thereof on a rectangular support frame (supporting body) 57. Support shafts 58 and 59 are formed on both end sides of the support frame 57 so as to be coaxial with each other, and leg portions 60 and 60 for supporting both end sides of the support frame 57 installed horizontally. Thus, the support frame 57 is rotatably supported around the support shafts 58 and 59.

The leg portions 60, 60 are erected on a base (base) 61 on which the manufacturing apparatus 50 is installed so as to be separated from each other, and bearing portions are formed on the upper end portions thereof, and the support frame is formed by these bearing portions. 57 support shafts 58 and 59 are supported horizontally. The support shaft 59 on one side (right side in FIG. 7) of the support frame 57 has a hollow structure, and a drawing die 53 is built in the support shaft 59.
A passage hole 57 a through which the extruded tube 11 passes is formed at the end of the support frame 57 on the side where the support shaft 59 is provided so as to communicate with the die hole of the die 53, and is unwound from the unwind drum 51. The extruded element tube 11 is configured to be led out to the drawing die 53 side through the passage hole 57 a and to be taken up to the winding drum 55 side through the drawing die 53. With the configuration described above, the unwinding drum 51 can rotate in the circumferential direction of the extruded extrusion tube 11, and the extrusion tube 11 about to pass through the die 53 can be twisted around the circumference.

The take-up drum 55 is provided with a rotary drive device with a take-up force adjusting function such as a servo motor, and is installed horizontally on the base 61 so as to be rotatable about its central axis. The rotational force of the rotating shaft 55 a of the winding drum 55 is controlled by a servo motor 48 built in the driving device 47.
The servo motor 48 of the winding drum 55 is configured so that the winding force can be adjusted by adjusting the rotational driving force. Accordingly, an arbitrary forward tension can be applied to the extruded element tube 11 that attempts to pass through the drawing die 53 by adjusting the force with which the inner spiral grooved tube 11R that has passed through the drawing die 53 is drawn.
An extension shaft portion 62 is formed at the end of the support frame 57 on the side where the support shaft 58 is provided. The extension shaft portion 62 extends to the outside of the leg portion 60, and the extension shaft portion 62 is a base below the extension shaft portion 62. The drive device 63 installed at 61 is rotationally driven via a conduction device 64.
In the manufacturing apparatus 50 according to the second embodiment, the driving device 63, the transmission device 64, the legs 60 and 60, and the support frame 57 constitute the rotating means 52 of the unwinding drum 51.

Next, a method for manufacturing the inner spiral grooved tube 11R by the manufacturing apparatus 50 of the second embodiment will be described.
First, the extruding element tube 11 with the inner surface straight groove wound around the bobbin 56 is attached to the unwinding drum 51 together with the bobbin 56, and the extruding element tube 11 and the bobbin 56 are rotated together with the unwinding drum 51, Torsion. Since the rotation of the unwinding drum 51 can be controlled by the rotation state of the support frame 57 via the conduction device 64 by the driving device 63, the necessary twisting force can be applied to the extruded element tube 11.
Simultaneously with the application of the twist, the extruded element tube 11 passes through the drawing die 53, is reduced in diameter simultaneously with the application of the twist, is formed into the inner spiral grooved tube 11 </ b> R, and is wound around the winding drum 55.

  At this time, as shown in FIG. 7A, the extruded tube 11 is twisted while the front side thereof is twisted with the drawing die 53 as a fulcrum and the diameter is reduced in the drawing die 53. At this time, the unwinding drum 51 side measures the number of windings of the extruded element tube of the installed bobbin 56 and its winding diameter, and applies it to the extruded element tube 11 where a predetermined rear tension is always unwound by brake control by the brake device 54. In this state, on the winding drum 55 side, a constant forward tension is applied to the inner spiral grooved tube 11R by servo motor control. If the front tension and the rear tension are inappropriate, sagging occurs in the extruded tube 11 during processing, buckling occurs during twisting, and conversely, if the forward tension is too strong, the extruded tube 11 breaks.

  According to the manufacturing apparatus 50 of the second embodiment, by adjusting the front tension and the rear tension to balance the twisting force and the diameter reducing force that are applied to the extruded element tube 11, it is easy to buckle and break. Even the extruded element tube 11 can be helically processed and reduced in diameter without hindrance, so that the inner spiral grooved tube 11R can be manufactured from the extruded element tube 11. In other words, twisting and diameter reduction processing can be performed while suppressing breakage and buckling of the extruded element tube 11 by releasing and balancing the stress during twisting with the stress during diameter reduction processing. Further, by adjusting the front tension and the rear tension according to the drawing speed of the extruded element tube 11, smooth twisting and drawing processes can be performed while preventing the extruded element tube 11 from being broken or buckled.

It is to be noted that the effects as described above can be achieved so that the diameter can be reduced by directly supplying to the drawing die 53 while twisting the extruded element tube 11 drawn from the unwinding drum 51 rotated together with the support frame 57. It is characterized in that it is configured. In this respect, when a guide member such as a roller or a fulcrum member is disposed between the unwinding drum 51 and the drawing die 53, the diameter of the extruded member 11 supported by the guide member or the fulcrum member is reduced by a twisting force. Since no force acts, the extruded tube breaks or buckles at these support portions.
For example, in the manufacturing apparatus described in Japanese Patent No. 3489359 (Japanese Patent Laid-Open No. 10-166606), the pass line of the original pipe is regulated between the feeding drum and the die, and the original pipe is horizontally placed in the die hole of the die. Since a fulcrum for guiding is inevitably present, the manufacturing apparatus described in this patent tends to cause breakage or buckling of the original pipe at the fulcrum portion.
On the other hand, in the apparatus of this embodiment, the position where the twisting force is applied to the extruded element tube 11 and the position where the reduced diameter force is applied to the extruded element tube 11 are set in the same region inside the drawing die 53, and the front tension and Since the back tension is balanced, the manufacturing apparatus 50 that does not buckle and break the extruded element tube 11 can be obtained. For this reason, even if it is the extrusion element | tube 11 of the small diameter as mentioned above, it can shape | mold to the inner surface spiral grooved pipe | tube 11R without trouble.

  Further, if the speed at which the extruded element tube 11 is pulled out is changed, the position where the twisting force is applied to the extruded element tube 11 and the position where the reduced diameter force is applied to the extruded element tube 11 are slightly changed, so that buckling and fracture occur. There is a fear. On the other hand, even if the drawing speed is changed by adjusting the above-described rear tension and front tension, it is possible to make it difficult for the extruded tube 11 to buckle and break. For this reason, even if the drawing speed is improved in order to improve productivity, the inner spiral grooved tube 11R can be manufactured without causing breakage or buckling by adjusting the rear tension and the front tension. This has the effect of improving productivity.

Example 1
An internally spiral grooved tube was manufactured using a 3003 aluminum alloy extruded element tube having an outer diameter of 10 mm, an inner diameter of 8.86 mm, and a straight groove formed on the inner surface. The inner diameter means the diameter of a circle on the inner surface drawn by connecting the bottoms of the grooves (straight grooves or spiral grooves).
The extrusion element tube was manufactured by carrying out billet homo-treatment for 5 hours at an extrusion speed of 40 m / min, an extrusion apparatus billet temperature of 550 ° C., and a billet homo-treatment temperature of 580 ° C. for 5 hours. It is a tube.
The number of straight grooves on the inner surface is 36 (36), the height of fins formed by these straight grooves is 0.26 mm, and the fin apex angle is 10 °. It consists of crystal grains with a diameter of 80 μm.
Moreover, although the fin shape etc. were equivalent, the extrusion element pipe | tube which has a crystal grain structure | tissue whose average grain size is 140 micrometers was used as an extrusion element tube of a comparative example. The extrusion element tube of this comparative example is an extrusion element tube manufactured under the conditions that the extrusion speed is 40 m / min, the extrusion device billet temperature is 520 ° C. when the aluminum material is charged, and the billet homo treatment is held at 610 ° C. for 8 hours.

  The coil formed into the coil shape after varying the diameter of the take-up roll in the range of 20 to 760 mm in diameter using these extruded element tubes, and taking up at a take-up pitch of 15 mm with each take-up roll. It was stretched along the coil axis of the tube-shaped pipe (tensile process). Further, in the pulling process, the lower end of the coiled tube material fed from the take-up roll by three turns is straightened by a stretcher in a heating furnace heated to 250 ° C., and then stretched to a straight tube to some extent. After that, the tube material that had been cooled to room temperature was straightened into a straight tube while applying a tension of 1 to 2 kN between two pairs of pinch rolls. Further, on the outer peripheral surface of the pipe material, linear marking is performed in advance along the longitudinal direction, and the length in the longitudinal direction (twisting cycle) when the marking line L is twisted by one turn as shown in FIG. B) was measured. The twist angle θ was calculated from the length A of the diameter of the tube material and the twist cycle B as shown in FIG. In FIG. 10, the relationship between the winding roll diameter (winding diameter) obtained by implementing as mentioned above and a twist angle is shown.

  As shown in FIG. 10, for example, with a winding diameter of φ100 mm, a twist angle of about 5 ° can be generated at one time. As the winding diameter decreases, the twist angle increases, and it is possible to manufacture an internally spiral grooved tube having a twist angle corresponding to the winding diameter. Further, for each manufactured inner surface spiral grooved tube, when the period of the spiral groove formed on the inner surface by cutting it in the longitudinal direction of the tube was confirmed, the period of the inner surface spiral groove and the twisting period B of the marking line are It was consistent.

Next, the inner spiral grooved tube was manufactured by repeating the winding process and the pulling process seven times using the tube material and a winding roll of φ100 mm.
First, after winding on a winding roll at a winding pitch of 15 mm, the coiled tube material is stretched, and after repeating the winding process and the pulling process three times, a hollow hole of φ7.5 mm is provided. The tube material, which was drawn with a drawing die and crushed to a flat rate of 118%, was restored again to a perfect circle with a flat rate of 103% (drawing step).
Thereafter, intermediate annealing was performed at 350 ° C. for 4 hours (heat treatment step), and winding was performed again with a winding roll of φ100 mm at a winding pitch of 12 mm. After performing the winding process and the pulling process three times each, the drawing process was performed with a drawing die having a φ7.5 mm hollow hole, and a heat treatment was performed at 350 ° C. for 4 hours.
Next, winding was performed with a winding roll of φ100 mm at a winding pitch of 11.25 mm, and the winding process and the pulling process were performed once. Finally perform withdrawal in the drawing die of the hollow hole of Fai4.3Mm, the inner surface helical grooved tube finally twist angle 20 ° were produced.
The winding speed and the drawing speed were 30 m / min. In addition, in the tensioning process, the lower end of the coiled tube material for three turns sent out from the take-up roll is corrected with a stretcher and stretched to a certain extent to a straight tube, and then between two pairs of pinch rolls. The straight tube was corrected while applying a tension of 1 to 2 kN.

Each time the winding process and the pulling process are repeated three times, the roundness of the flat tube material is restored by performing the drawing process, and the straightened pipe material is strained by heating the straightened pipe material. Can be removed. As a result, the winding step and the pulling step can be further repeated, and finally the outer diameter φ4 mm, the inner diameter φ3.3 mm, the twist angle 20 °, the fin apex angle 10 °, the fin height 0.2 mm, An internally spiral grooved tube having a bottom wall thickness of 0.35 mm could be manufactured.
The inner surface spiral grooved tube obtained by the above process was heat-treated at 350 ° C. for 4 hours for tube expansion. FIG. 11 (a) shows an enlargement of the metal structure of a partial cross section of the internally spiral grooved tube obtained using an extruded element tube having a crystal grain structure with an average grain size of 80 μm. FIG. 11 (b) shows a state where the portion is cut open, FIG. 11 (c) shows a state where the inner surface spiral grooved tube is cut obliquely, and FIG. 11 shows the groove shape of the transverse section of the inner surface spiral groove tube. Shown in (d). Further, FIG. 12 (a) shows an enlargement of the metal structure of a partial cross section of the internally spiral grooved tube obtained using the extruded element tube having a crystal grain structure with an average crystal grain size of 140 μm. FIG. 12B shows a state in which a part of the tube is cut open, and FIG. 12C shows the groove shape of the cross section of the inner surface spiral grooved tube.

In the inner spiral grooved tube of the example shown in FIG. 11, the shape of fins formed between the obtained spiral grooves and the grooves was uniform, and the fins and spiral grooves of the desired shape could be formed. Moreover, rough skin such as orange peel could not be observed on the surface of the inner spiral grooved tube.
On the other hand, the inner spiral grooved tube exceeding 80 μm in the comparative example shown in FIG. 12 has irregular fin shapes, such as a part of the fins being bent, and so on. Further, as shown in the structure photograph shown in FIG. 12 (a), the crystal grains are large, and the crystal grains form part of the grooves and the fins. Therefore, some of the crystal grains fall off and some of the fins are missing. I was able to confirm multiple locations. Moreover, rough skin expressed as orange peel on the surface was confirmed.

FIG. 13 is a diagram showing a comparison of the surface states of the inner surface spiral grooved tube of the example and the inner surface spiral grooved tube of the comparative example, and the inner surface obtained in the example as shown in FIG. The spiral grooved tube shows no smooth surface condition with no orange peel. On the other hand, as shown in FIG.13 (b), the internal spiral grooved tube of the comparative example generate | occur | produced an orange peel and the rough surface was seen on the surface.
From the above comparison, it is clear that the inner spiral grooved tube obtained by using the extruded element tube having a crystal grain structure with an average crystal grain size of 80 μm has a better fin shape and excellent surface properties. It is clear that there is.

  Separately, an inner spiral grooved tube having an outer diameter of 5 mm (inner diameter of 4 mm), an outer diameter of 4 mm (inner diameter of 3 mm) and an outer diameter of 2.5 mm (inner diameter of 1.5 mm), each having a twist angle of 20 °, is described above. It was confirmed that it could be produced through the same steps as in FIG.

Table 1 below shows the relationship between the size of the crystal grain size of the 3003 aluminum alloy used in the test, the homoprocessing conditions, and the extrusion conditions for the presence or absence of orange peel generation.
The presence or absence of orange peel occurred when the outer surface of the obtained spiral grooved tube with a length of 30 cm was observed with a microscope and no orange peel could be observed. I decided.

  As is apparent from Table 1, it is understood that the generation of orange peel is suppressed in the extruded element tube having an average crystal grain size of 80 μm or less or the spiral grooved tube using the extruded element tube in which the crystal structure is a fiber structure. .

Next, an inner spiral grooved tube was prepared by the same manufacturing method as described above using the extruded element tube shown in Table 2 below, and the average crystal grain size (μm) of each sample in the extruded element tube state, The average crystal grain size (μm) of the inner spiral grooved tube, the presence or absence of orange peel generation, the average groove tilt angle (°) of the inner peripheral surface after processing, and the surface roughness (μm) were measured and evaluated.
When expanding the inner spiral grooved tube, the inner spiral grooved tube obtained in the example was subjected to heat treatment (annealing) at 350 ° C. for 4 hours.
Moreover, the cross section of the sample cut perpendicularly to the longitudinal direction of the inner spiral grooved tube was observed with a CCD camera, and the tilt angle of the fin was measured. The tilt angle θ ₂ of the fin draws a straight line L1 across the fin base as shown in FIG. 14, and draws a perpendicular line from the central part b of the straight line L1 in the circular center direction (inner spiral grooved tube center direction) The point where it intersects the top of the fin is c, and the angle abc is measured from the central part a of the top. For measuring the inclination of the fin, eight points were appropriately measured from each of the three fields of view of the inner spiral grooved tube cut out arbitrarily, and the average value of a total of 24 points was obtained.
In the four fins 11c shown in FIG. 14, the three fins 11c described on the left side are not deformed, and the one fin 11c described on the right side is illustrated as a deformed fin. Since the right side of the fins 11c of FIG. 14 is deformed, but the inclination angle theta ₂ can be measured from the corner abc, since the left fin 11c is not deformed and formed into a circular central direction from the center b of the straight line L1 Since the apex center part a is located on the vertical line, the fin collapse angle θ _{2 in} this case is 0 °. In addition, FIG. 14 is drawn in order to illustrate the fin apex angle, and fin collapse usually occurs in the plurality of fins 11c.
Table 2 below shows the average crystal grain size of the extruded raw tube used in the test and the inner surface spiral grooved tube after the heat treatment for the presence or absence of orange peel.

About each produced inner surface spiral grooved tube, it was observed visually whether the orange peel had generate | occur | produced on the outer peripheral side. The presence or absence of orange peel occurred when the outer surface of the obtained spiral grooved tube with a length of 30 cm was observed with a microscope and no orange peel could be observed. I decided. Details of the evaluation method are as described above. The test results for each sample are shown in Table 2 below.
Moreover, about the outer periphery of the obtained internal spiral grooved pipe, the surface roughness (Rmax) was measured with a two-dimensional roughness meter (Surfcom 1400D: Tokyo Seimitsu Co., Ltd.). For parameter calculation, the JIS '94 standard was selected, the least square straight line correction was added, the sample inclination was canceled, the measurement length was 4 mm, the measurement speed was 0.3 mm / s, and the measurement range was ± 400.0 μm.

From the results shown in Table 2, the extruded fiber tubes (Sample Nos. 1, 2 and 3) of the entire surface fiber structure, double-sided surface layer 3% recrystallized (remaining fiber structure), double-sided surface layer 5% recrystallized structure (remaining fiber structure) If used, it was possible to reduce the average crystal grain size to 80 μm or less for the internally spiral grooved tube after processing. In these samples, no orange peel was observed, and the fin collapse angle could be controlled to 0.3 ° or less.
For these samples, no. Samples 4, 5, and 6 were samples with an average crystal grain size exceeding 80 μm or samples with a double-sided surface layer of 8% recrystallized structure. Orange peel was observed, and the fin collapse angle increased beyond 1 °. It was.
When the fin collapse angle is large, when the heat exchanger is assembled by expanding the inner spiral grooved tube with a tube expansion plug, the inner surface fin that the tube expansion force exerted by the tube expansion plug collapses is more easily acted. If it will be in this state, as a result of deform | transforming so that an inner surface fin may fall down further, the expansion of an inner surface spiral grooved tube will become insufficient, and manufacture of a heat exchanger will be hindered. For example, when the heat exchanger is composed of an inner spiral grooved tube and an external fin, the inner spiral grooved tube is inserted into a through-hole formed in the outer fin, and the inner spiral grooved tube is expanded. Although the exchanger is assembled, if the tube expansion is insufficient, the adhesion between the external fin and the inner spiral grooved tube is inferior, and the heat exchange performance is deteriorated.

(Example 2)
Next, the inner spiral grooved tube was manufactured using the manufacturing apparatus 50 having the structure shown in FIG. A 3003 aluminum alloy extruded element tube having an outer diameter of 7 mm and an inner diameter of 6.2 mm and 36 straight grooves formed on the inner surface at regular intervals in the circumferential direction was evacuated and reduced to an outer diameter of 6 mm and an inner diameter of 5.2 mm. A spiral grooved tube was manufactured using a raw tube. The inner surface groove shape of the extruded element tube has a groove height of 0.2 mm and a fin apex angle of 10 °, and the average crystal grain size of the extruded element tube is 30 to 170 μm.

These extruded element tubes were wound around an unwinding drum, unwound at a line speed of 5 m / min, and the support body was rotated together with the unwinding drum at a rotation speed of 77 rpm to give a twist angle of 15 ° to the element tube. . The drawing die had a hole diameter of 7.0 mm and was drawn by 18%. The inner spiral grooved tube having an outer diameter of φ7.0 mm that was twisted and pulled out was wound around a winding drum. The front and rear tensions were 20 kgf (196 N). A heat treatment of 410 ° C. × 4 h was performed on each of the produced inner spiral grooved tubes for the purpose of annealing for forming an O material (processing for forming an O material).

  About each obtained inner surface spiral grooved tube, the presence or absence of orange peel generation | occurrence | production was confirmed similarly to the case of Example 1, and the outer periphery of the obtained inner surface spiral grooved tube was surfaced similarly to the case of Example 1. The roughness (Rmax) was measured with a two-dimensional roughness meter (Surfcom 1400D: Tokyo Seimitsu Co., Ltd.).

From the results shown in Table 3, the extruded fiber tubes (Sample Nos. 7, 8, and 9) of the entire surface fiber structure, double-sided surface layer 3% recrystallized (remaining fiber structure), double-sided surface layer 5% recrystallized structure (remaining fiber structure). If used, the inner spiral grooved tube after processing could have an average crystal grain size of 80 μm or less (for example, 50 μm or less). In these samples, no orange peel was observed, and the fin collapse angle could be controlled to 1 ° or less, for example 0.2 ° or less.
For these samples, no. Samples 10, 11, and 12 were samples with an average crystal grain size exceeding 120 μm and samples with double-sided surface layer 8% recrystallization. Orange peel was observed, and the fin collapse angle was significantly increased.
When the fin collapse angle is large, when the heat exchanger is assembled by expanding the inner spiral grooved tube with a tube expansion plug, the inner surface fin that the tube expansion force exerted by the tube expansion plug collapses is more easily acted. If it will be in this state, as a result of deform | transforming so that an inner surface fin may fall down further, the expansion of an inner surface spiral grooved tube will become insufficient, and manufacture of a heat exchanger will be hindered. For example, when the heat exchanger is composed of an inner spiral grooved tube and an external fin, the inner spiral grooved tube is inserted into a through-hole formed in the outer fin, and the inner spiral grooved tube is expanded. Although the exchanger is assembled, if the tube expansion is insufficient, the adhesion between the external fin and the inner spiral grooved tube is inferior, and the heat exchange performance is deteriorated.

  Sample No. shown in Table 3 A metallographic photograph of the cross section of the inner spiral grooved tube of No. 9 is shown in FIG. FIG. 16 shows the appearance of the inner spiral grooved tube 9 and no orange peel. In FIG. The external appearance of the internal spiral grooved tube with the orange peel obtained in 12 comparative examples is shown.

In the inner spiral grooved tube of the example shown in FIG. 15, the shape of fins formed between the obtained spiral grooves and the grooves was uniform, and the fins and spiral grooves of the desired shape could be formed. Further, as shown in FIG. 16, rough skin such as orange peel could not be observed on the surface of the inner spiral grooved tube.
It was also found that when the inner spiral grooved tube having a fibrous structure is annealed (heat treatment) for forming an O material, a metal structure composed of crystal grains having an average crystal grain size of 80 μm or less shown in FIG.
In contrast, the comparative example No. 1 shown in FIG. No. 12 double-sided surface layer 8% recrystallized inner surface spiral grooved tube was able to confirm rough skin expressed as orange peel on the surface.

FIG. 18 is a schematic view showing an example of a heat exchanger 80 provided with an inner surface spiral grooved tube according to the present invention, and an inner surface spiral grooved tube 81 is provided meandering as a tube through which a refrigerant passes. A plurality of aluminum alloy fin members 82 are arranged around the grooved tube 81 in parallel. The inner surface spiral grooved tube 81 is provided so as to pass through a plurality of through holes provided so as to penetrate the fin material 82 disposed in parallel.
In the structure of the heat exchanger shown in FIG. 18, the inner spiral grooved tube 81 includes a plurality of U-shaped main tubes 81 </ b> A that linearly penetrate the fin material 82, and adjacent end openings of the adjacent main tubes 81 </ b> A. As shown in FIG. 18, it is connected by a letter-shaped elbow pipe 81B. Also, a refrigerant inlet 86 is formed on one end side of the inner spiral grooved tube 81 penetrating the fin material 82, and a refrigerant outlet 87 is formed on the other end of the inner spiral grooved tube 81. As a result, a heat exchanger 80 shown in FIG. 18 is configured.

A heat exchanger 80 shown in FIG. 18 is provided with an inner surface spiral grooved tube 81 so as to penetrate through holes formed in the fin material 82, and after being inserted into the through hole of the fin material 82, an inner surface spiral groove is formed by a tube expansion plug. The outer diameter of the attached tube 81 is expanded and assembled by mechanically integrating the inner spiral grooved tube 81 and the fin material 82.
By applying the inner surface spiral grooved tube 81 to the heat exchanger 80 shown in FIG. 18, it is possible to provide the heat exchanger 80 with good heat exchange efficiency.

DESCRIPTION OF SYMBOLS 100 ... Manufacturing apparatus of an inner surface spiral grooved tube, 11, 11C, 11L ... Extrusion element tube, 11a ... Straight groove, 11b ... Fin, 11c ... Fin (spiral fin), 11d ... Spiral groove, 11E ... Inner surface spiral after correction Grooved tube, 11R ... Inner spiral grooved tube, 20: Winding means, 21, 21a, 21b, 21c ... Winding roll, 22 ... Feed roll, 23 ... Guide plate, 24 ... Presser roll, 25 ... Motor, 26 ... Axis, 30 ... Tensioning means, 31 ... Stretcher, 32 ... Pinch roll, 33 ... Heating furnace (heating means), 40 ... Pulling means, 49 ... Heat treatment means, 50 ... Production equipment, 51 ... Unwinding drum, 51a ... Unwinding drum rotating shaft 52 ... Rotating means 53 ... Drawing die 54 ... Brake device 55 ... Winding drum (winding device) 56 ... Bobbin 57 ... Support frame (support) 58,59 DESCRIPTION OF SYMBOLS ... Support shaft, 60 ... Leg part, 61 ... Base, 62 ... Extension shaft part, 63 ... Driving device, 64 ... Conduction device, 80 ... Heat exchanger, d ... Bottom wall thickness, t ... Height, θ ... Twist Angle, θ ₁ ... fin apex angle, θ ₂ ... tilt angle

Claims (5)

A plurality of straight grooves along the length direction are formed on the inner surface at intervals in the circumferential direction, and using an elementary tube made of aluminum or aluminum alloy in which fins are formed between the straight grooves,
A feeding device for supplying the raw pipe in a straight line toward the die hole is installed on the introduction side of the die hole of the drawing die, and a winding device for the raw pipe is installed on the outlet side of the drawing die. The feeding device is provided so as to rotate in the direction around the axis with an extension line of the center line passing through the center of the center, and while maintaining the straight tube from the feeding device to the die hole of the drawing die in a straight line A backward tension and a rotational force are applied to the raw pipe, a forward tension is applied to the pipe extending from the die hole of the drawing die to the winding device, and a drawing process and a twisting process are applied to the raw pipe passing through the die hole. By
A plurality of spiral grooves along the length direction are formed on the inner surface at intervals, the outer diameter is 5 mm or less, the twist angle of the spiral groove is 20 ° or more and 40 ° or less, and the average grain size in the grain structure A method for producing an inner surface spiral grooved tube made of aluminum or aluminum alloy, characterized in that an inner surface spiral grooved tube having a diameter of 120 μm or less is manufactured.  When manufacturing the inner surface spiral grooved tube, all metal structures are fibrous structures along the length direction of the tube, or only the surface layer has a recrystallized structure with 5% or less of the outer and inner circumferences, and all other than that are fibers. 2. The method for producing an internally spiral grooved tube according to claim 1, wherein an extruded element tube having a grain structure or an average crystal grain size of a metal structure of 80 μm or less is used.  The method for producing an internally spiral grooved tube according to claim 1 or 2, wherein the average crystal grain size of 120 µm or less is an average crystal grain size achieved after annealing.  The inner surface according to any one of claims 1 to 3, wherein an inner surface spiral grooved tube having a fin tilt angle of 1 ° or less is formed along the inner surface spiral groove. A method of manufacturing a spiral grooved tube.  5. An inner surface spiral according to claim 1, wherein an inner surface spiral grooved tube having no orange peel defined as a step having a surface roughness (Rmax) exceeding 15 μm on the outer surface is manufactured. A method of manufacturing a grooved tube.