JP2006281311A - Device and method for manufacturing internally grooved tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for manufacturing an internally grooved tube which is excellent in grooving workability. <P>SOLUTION: The invented device is equipped with a wiper 9, a drawing machine 8 and an intermediate reshaping die 11 which are located between a floating plug 4 and a grooved plug 5 in the drawing direction of an mother tube 1a and are mounted on the head of the floating plug 4. A load F is given onto a floating die 2 when the mother tube 1a is drawn. In the invented method, the difference between the maximum and minimum values of the load F is 500 N or less. The load F given onto the floating die 2 is detected by a load cell 21 mounted on the floating die 2. The secular changes of the load F are converted into electronic signals while the mother tube 1a is drawn and are input to a control section. The control section transmits the signals to the drawing machine 8 so as to restrain the secular changes of the load F, and according to the signals the drawing machine 8 transmits power to pulleys 81 while controlling rotary torque. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an internally grooved tube used in a heat transfer tube for a heat exchanger such as a refrigerator or an air conditioner, and a manufacturing apparatus therefor.

  Conventionally, for example, a rolling process has been adopted in order to process a small-diameter inner surface grooved pipe having a large number of spiral grooves on the inner surface. That is, a floating plug and a grooved plug rotatably connected to the floating plug via a rod are inserted into a metal pipe, and the grooved plug is disposed downstream of the floating plug. The tube is continuously drawn along the tube axis direction, and the diameter of the tube is reduced by the floating plug and the floating die, and the periphery of the tube is revolved at a high speed at the position of the grooved plug. However, a plurality of processing balls that idle and rotate to press the element tube against the grooved plug process in parallel a plurality of grooves having a predetermined twist angle with respect to the tube axis on the inner peripheral surface of the element tube. Is.

  In recent years, in order to meet the demands for miniaturization and higher efficiency of heat exchangers, the inner grooved tube thickness has been reduced, or the inner groove has been deepened, and the torsion angle of the groove has been increased to improve performance. Yes. However, in the manufacturing method described above, the pipe may break due to plastic deformation resistance and friction resistance when the pipe is pulled out.

  There is an example in which the plastic deformation resistance and the frictional resistance are reduced by arranging an auxiliary drawing device when the pipe is drawn (for example, Patent Document 1).

Japanese Patent Laid-Open No. 11-711

  However, since the number of contact portions that come into contact with the metal tube changes periodically due to the movement of the belt when the metal tube is pulled out, the pulling force generated by the auxiliary pulling device changes periodically. When the pulling force changes periodically and the amount of change increases, the inner fin size of the inner grooved tube varies in the longitudinal direction, resulting in insufficient adhesion with the aluminum fin during pipe expansion, resulting in a decrease in heat exchange performance. End up.

  In the modification of the invention of Patent Document 1, a cleaning device for removing the oil film on the surface of the metal tube is provided on the entrance side of the auxiliary drawing device. The cleaning device contains a cleaning solution, and the cleaning solution removes the lubricating oil used in the drawing die attached to the surface of the metal tube. Thereby, the frictional force between the belt and the metal tube is increased, and the pulling force of the metal tube can be reduced. However, if the cleaning liquid attached to the surface of the metal tube comes into contact with the auxiliary drawing device before it dries, the cleaning liquid reduces the frictional force between the belt and the metal tube, causing slippage, and does not play the role of the auxiliary drawing device. (When the slip occurs, the pulling force changes, and the inner fin size of the inner grooved tube changes). In addition, since the foreign matter adhering to the surface of the metal tube cannot be removed by the cleaning liquid, the surface of the metal tube is damaged in the auxiliary drawing and the grooving process in the next process. This causes cracks in the tube expansion process when fixing the aluminum heat dissipating fins.

  In addition, since the pressure is applied to the metal tube by the auxiliary drawing device and the cross section becomes flat, there is a problem that the groove is not uniform in the groove processing in the next process.

  An object of the present invention is to solve the above-mentioned problems, and is an inner grooved tube that facilitates the removal of lubricating oil and foreign matter on the surface of the metal tube and prevents the metal tube cross-section from being flattened. A manufacturing apparatus and a manufacturing method thereof are provided.

The object of the present invention is realized by the following means.
[1] A processing head 3 is installed in order along the drawing direction of the raw tube 1a, and a raw tube 1a into which a floating plug 4 and a grooved plug 5 rotatably connected to the floating plug 4 are inserted. Is passed through the floating die 2 and the machining head 3, the raw tube 1a is moved without using a winding drive device, the diameter is reduced by the floating die 2 and the floating plug 4, and the grooved plug 5 is removed. Is arranged so as to come into contact with the outer periphery of the raw tube 1d into the processing head 3 at the position of FIG. 5, and the raw tube 1d is pressed against the grooved plug 5 by a plurality of balls 6 that rotate and revolve as the processing head 3 rotates. Thus, a device for forming a large number of fine grooves 10 on the inner surface of the element tube 1d is provided between the floating plug 4 and the grooved plug 5 at the end of the floating plug 4. Wiper 9 along the drawing direction of the 1a, withdrawal device 8, characterized in that the intermediate shaping die 11 is provided, apparatus for producing an internally grooved tube.
[2] A method for manufacturing an internally grooved tube using the apparatus according to [1], wherein a difference between a maximum value and a minimum value of the load F applied to the floating die 2 when the raw tube 1a is drawn is 500 N or less. A method for producing an internally grooved tube, characterized in that
[3] A method of manufacturing an internally grooved tube using the apparatus according to [1] or [2], wherein a load cell 21 attached to the floating die 2 detects a load F applied to the floating die 2. The time-dependent change of the load F is converted into an electric signal while the raw tube 1a is pulled out, and is input to the control unit. The control unit transmits a signal to the drawing device 8 so as to suppress the time-dependent change of the load F. Then, the pulling device 8 transmits power to the pulley 81 while controlling the rotational torque by the signal, and the manufacturing method of the internally grooved tube.
[4] A method of manufacturing an internally grooved tube using the apparatus according to [1] or [2], wherein a load cell 21 attached to the floating die 2 detects a load F applied to the floating die 2. The time-dependent change of the load F is converted into an electric signal while the raw tube 1a is pulled out, and is input to the control unit. The control unit transmits a signal to the drawing device 8 so as to suppress the time-dependent change of the load F. Then, the pulling device 8 transmits a pressing force to the pulleys 81 and 82 by the signal, and a method for manufacturing an internally grooved tube.
[5] The ratio K1 between the radius of curvature R of the pad groove 84 of the pad 83 of the drawing device 8 and the outer diameter Db of the raw tube 1b is 0.5 to 0.5025, and the tightening ratio K2 is 0.98 to 1.0. The method for producing an internally grooved tube according to any one of [1] to [4], which is 1.0.
[6] The inner grooved pipe according to any one of [1] to [5], wherein an outer diameter reduction ratio K3 of the intermediate shaping die 11 is 0.001 to 0.1. Production method.

  The present invention specifies the shape of the contact portion between the drawing device and the metal tube and reduces the amount of change in drawing force in the drawing device, so that the inner fin size of the inner grooved tube can be reduced without using a winding device. Variation can be suppressed, and slippage at the contact portion between the drawing device and the metal tube and flattening of the metal tube cross-sectional shape can be suppressed. Further, by installing the wiping device, it is possible to prevent slippage and foreign object damage at the contact portion between the drawing device and the metal tube. Furthermore, by installing an intermediate shaping die after the drawing device, the cross-sectional shape of the metal tube can be restored to a state close to a perfect circle. Therefore, there is a significant industrial effect.

  With reference to FIG. 1 and FIG. 2, a preferred embodiment of an apparatus for producing an internally grooved tube according to the present invention will be described. FIG. 1 is a cross-sectional view showing an embodiment of an apparatus for producing an internally grooved tube 1 according to the present invention, and FIG. 2 is a cross-sectional view showing an embodiment of a pad 83 used in FIG.

  A floating die 2 and a machining head 3 independent of the floating die 2 are sequentially installed along the drawing direction of the raw tube 1a so as to be rotated by different driving means (not shown). In the machining head 3, a plurality of balls 6 are arranged at regular intervals around the raw pipe 1d that rolls in contact with the inner peripheral surface and passes through the inside. These balls 6 are pressed toward the upstream side in the drawing direction by a flange-like stopper 31 attached to another member via a bearing 32 on the downstream side. A shaping die 7 is installed further downstream of the machining head 3 in the drawing direction.

  A metal tube having good thermal conductivity such as copper, an alloy thereof, aluminum or an alloy thereof is used for the elementary tube 1a. The floating tube 4 and the floating plug 4 can be freely rotated through a plug rod 51 in the elementary tube 1a. Insert the grooved plug 5 connected to. The processing head 3 is rotated while the raw tube 1 a is pulled out through the floating die 2 and the processing head 3. The raw tube 1a is reduced in diameter by the floating die 2 and the floating plug 4 along with the drawing. Next, the outer peripheral surface of the tube 1d is pressed against the surface of the grooved plug 5 by a plurality of balls 6 that rotate around the tube 1d as the machining head 3 rotates at the position of the grooved plug 5. Then, a large number of fine grooves 10 are formed on the inner surface by transferring the grooves 50 on the peripheral surface of the grooved plug 5 to the inner surface of the element tube 1d. Thereafter, it is shaped by the shaping die 7 on the downstream side and reduced in diameter to produce the inner grooved tube 1.

  In the manufacturing apparatus of this embodiment, since a large number of fine grooves 50 are formed in parallel on the peripheral surface of the grooved plug 5, the groove 10 is formed on the inner surface of the internally grooved tube 1 manufactured as described above. Is formed.

  In the manufacturing apparatus of the present invention, a drawing device 8 capable of adjusting the drawing force and the drawing speed is provided at the front part of the grooved part after the floating die 2 to adjust the load applied to the raw tube 1c at the front part of the grooved part. Thus, a wiper 9 is provided at the front of the drawing device 8 and an intermediate shaping die 11 is provided at the rear.

The drawing device 8 pulls out the raw tube 1 b by a pair of belts 80. The belt 80 is arranged vertically or horizontally. The belt 80 is supported by pulleys 81 and 82, is in contact with the raw tube 1b, and is moved by the rotation of the pulleys 81 and 82. The belt 80 is formed in a loop shape.
A pad 83 is attached to the outer peripheral surface of the belt 80. The pad 83 is pressed against and sandwiched from the raw tube 1c from both sides, and the raw tube 1c is pulled out by rotating the belt 80.

  A load cell 21 is attached to the floating die 2 and a load F applied to the floating die 2 can be detected. When the raw tube 1a is pulled out, the load F changes periodically. This is because the number of pads 83 that come into contact with the raw tube 1b periodically changes due to the movement of the belt 80. The load F increases when there are many pads 83 in contact with the raw tube 1b, and conversely the load F decreases when there are few pads 83 in contact with the raw tube 1b.

  When the amount of change in the periodic change of the load F is increased, the inner fin size of the inner grooved tube 1 varies in the longitudinal direction, so that poor adhesion with the aluminum fin occurs during the pipe expansion. If the amount of change of the load F is 500 N or less, variations in the fins on the inner surface can be suppressed, and cracking during tube expansion and insufficient adhesion with the aluminum fins can be prevented. The smaller the amount of change in the load F, the better.

  As a method of preventing the periodic change of the load F, there are a method of limiting the shape of the pad 83 and a method of controlling the rotational torque of the pulley 81 or the pressing force of the pad 83 in the drawing device 9.

  The rotational torque control of the pulley 81 is performed as follows. That is, in FIG. 1, the load cell 21 attached to the floating die 2 detects the load F applied to the floating die 2, and converts the change over time of the load F into an electrical signal while pulling out the raw tube 1a. The control unit transmits a signal to the pulling device 8 so as to suppress the change with time of the load F, and the pulling device 8 controls the rotational torque by the signal to power the pulley 81. To communicate.

  The pressing force control of the pad 83 is performed as follows. That is, in FIG. 1, the load cell 21 attached to the floating die 2 detects the load F applied to the floating die 2, and converts the change over time of the load F into an electrical signal while pulling out the raw tube 1a. The control unit transmits a signal to the drawing device 8 so as to suppress the change with time of the load F, and the drawing device 8 transmits a pressing force to the pulleys 81 and 82 by the signal. .

  It should be noted that controlling the rotational torque of the pulley 81 or the pressing force of the pad 83 in the drawing device 8 may be performed independently or both at the same time.

  The pad 83 has an arc-shaped pad groove 84 that is brought into contact with the raw tube 1 b in accordance with the outer diameter of the raw tube 1 b after the diameter reduction processing by the floating die 2. The pad groove 84 has a curved surface with a radius of curvature R.

  A ratio K1 = R / Db of the radius of curvature R to the outer diameter Db of the raw tube 1b is set to K1 = 0.5 to 0.5025. This is to prevent the occurrence of slipping at the pad portion and stabilize the load F, thereby suppressing the change in the inner fin size of the inner grooved tube 1 and preventing deformation of the raw tube 1b. If it is less than 0.5, the raw tube 1b does not enter the pad groove 84, or even if it is pushed hard and enters the pad groove 84, the surface of the raw tube 1b is damaged, and then passes through the drawing device 8. Since a load is applied to pull the base tube 1c away from the pad, the load F is not stable, and there arises a problem that the change of the inner fin size of the inner grooved tube 1 increases. If it exceeds 0.5025, there arises a problem that flatness at the pad portion becomes large. Preferably it is 0.5005-0.5015.

  A tightening ratio K2 when the element tube 1b is tightened by the pad 83 is K2 = {2πR−4 (R−H)} ÷ (πDb). That is, the tightening ratio K2 is a ratio between the outer circumference of the raw tube 1b and twice the length of the arc portion of the pad 83. Here, H is the pad depth. The tightening ratio K2 is set to 0.98 to 1.0. As the tightening ratio K2 is decreased, a larger pulling force can be obtained. However, if the tightening ratio K2 is less than 0.98, the deformation of the raw tube 1c increases (the dent remains at the portion pinched by the pad), and the grooved plug 5 is uniform. The problem arises in that it cannot be grooved. If it exceeds 1.0, the required pulling force cannot be obtained. If a pad with a tightening ratio K2 set to 1.0 is used, it may not be pulled out stably due to the machining tolerance of the tool. Preferably it is 0.990-0.999.

  The pad 83 is made of a material harder than the metal base tube 1a such as metal or resin. Preferably it is made of tool steel.

  The wiper 9 has an effect of removing an oil film and foreign matter adhering to the outer surface of the raw tube 1b. When the wiper 9 is not provided, slipping occurs in the drawing device 8 due to an oil film or foreign matter, the drawing of the raw tube 1c is not stable, and the cross-sectional shape is not stable, resulting in a problem that the dimension of the groove 50 varies. End up. The wiper 9 has a hole having a diameter smaller than the outer diameter Db of the raw tube 1b, and allows the raw tube 1b to pass through the hole. The wiper 9 is preferably made of rubber from the viewpoint of the oil film and foreign matter removal effect.

  The intermediate shaping die 11 has the effect of returning the cross-sectional shape of the flat tube 1c flattened by the drawing device 8 to a shape close to a perfect circle. The diameter of the intermediate shaping die 11 is the same as or smaller than the diameter of the floating die 2 according to the shape of the raw tube 1c. The outer diameter reduction ratio K3 in the intermediate shaping die 11 is K3 = (Db−Dd) / Db. The outer diameter reduction ratio K3 is preferably 0.001 to 0.1. If it is less than 0.001, if the flatness of the raw tube 1c is large, the shape does not recover and remains flat, and the dimensions of the groove 50 are not stable (the inner fin dimensions on the circumference also vary, and even after pipe expansion) The problem of insufficient adhesion to the aluminum fins remains in the flat shape. On the contrary, if it exceeds 0.1, the processing load by the intermediate shaping die 11 increases, and the inner grooved tube 1 processed in front of the winding device may break. Further, the inner surface of the raw tube 1d is in a rough state with fine irregularities, and if the grooving is performed as it is, a large number of fine whisker-like cracks remain on the inner surface of the processed inner grooved tube. Therefore, since it is difficult to remove the inner surface processing oil that has entered the portion, an inner grooved tube with a large amount of residual oil in the tube is formed. If the amount of residual oil in the pipe increases, brazing defects may occur or the performance may deteriorate due to reaction with the operating oil (compressor oil) of the air conditioner. . The outer diameter reduction ratio K3 in the intermediate shaping die 11 is preferably 0.001 to 0.05. The intermediate shaping die 11 is made of a material harder than the material of the metal tube 1a such as metal or ceramic. Preferably, it is made of cemented carbide.

  The inner grooved tube of the present invention can be processed by moving the raw tube 1a by the driving force of the drawing device 8 without using a winding device.

  The present invention is not limited to the embodiment described above, and can be implemented in various modes without departing from the gist of the present invention.

  Examples of the present invention and effects thereof will be described in detail below.

Example 1
Table 1 shows the experimental results of the internally grooved tube 1 processed by the manufacturing apparatus of the present invention. In the experiment, the inner grooved tube 1 was processed 3000 m, and was further brought into close contact with the aluminum fin by expanding the tube. The grooved plug 5 used in the experiment has an outer diameter of 10.0 mm, a groove number of 50, a groove depth of 0.25 mm, a groove apex angle of 15 degrees, and a twist angle of 50 degrees. The outer diameter of the raw tube 1a was 14.0 mm, the wall thickness was 0.40 mm, and the outer diameter of the floating die 2 was 10.9 mm. The load adjustment of the drawing device 8 was adjusted by setting the pressing force of the pad 83.

  In the conventional example 1, the drawing device 8 is not arranged between the floating die 2 and the machining head 3 which is a groove machining part, and the winding drive device for the inner surface grooved tube arranged after the shaping die 7 ( The case where it draws by (not shown) is shown. Conventional examples 2 to 4 are used in the present invention between the floating die 2 and the machining head 3 which is a groove machining portion while being pulled out by a winding drive device for an internally grooved tube disposed after the shaping die 7. In the case where the drawing device 8 assists the drawing, and when the load of the winding drive device (not shown) for the inner grooved tube 1 is reduced, the drawing speed of the drawing device 8 is set to the winding drive for the inner grooved tube 1. When the load of the winding drive device (not shown) of the inner surface grooved tube 1 is increased in synchronism faster than the drawing speed of the device (not shown) and conversely, the drawing speed of the drawing device 8 is increased. This was carried out by setting a lower speed than the pulling speed of the winding drive device (not shown) of 1 and synchronizing it. The winding drive device is arranged after the shaping die 7.

  Subsequently, it was made to contact | adhere to the aluminum fin (radiation fin) by pipe expansion. Variations in the total thickness (height from the outside of the tube to the top of the inner fin) of the inner grooved tube 1 in these processing experiments and the state of the processing experiment were evaluated. The processing speed ratio was a value of (drawing speed of the drawing device 8) / (drawing speed of the winding device) × 100. The results are shown in Table 1.

  As is clear from Table 1, the example of the present invention obtained a good inner grooved tube. On the other hand, since the conventional example 1 does not have a drawing device, the tube is broken. Since the conventional example 2 does not have a wiping device and an intermediate shaping die, the change in the load F and the flatness of the raw tube become large, and the variation in the total thickness becomes large. In Comparative Example 1, since there was no wiping device, the change in the load F became large, and the total thickness varied in the longitudinal direction. In Comparative Example 2, since there was no intermediate shaping die, the raw tube remained flat and the total thickness varied in a circumferential shape. In Comparative Example 3, the load F was intentionally changed greatly by load control, but the variation in the total thickness in the longitudinal direction increased. In Conventional Example 2 and Comparative Examples 1, 2, and 3, poor adhesion to the aluminum fin occurred.

(Example 2)
With respect to the shape of the pad 83, experiments on the sliding load Fb at the time of pulling out and grooving workability were performed. In the experiment, as shown in FIG. 3, the pad 83 having the pad groove 84 shown in Table 2 is paired, and the element tube 1b is sandwiched with a sandwiching load Fa of 1000N to 10000N. Drawing out in the direction of Fb, the sliding load Fb when the raw tube 1b started to slide was measured. Comparison notation was made assuming that the sliding load Fb of Example 1 of the present invention was 100. Here, the sliding load Fb is a limit pulling force of the pad to be used, and the higher this value, the more stable the pulling out without slipping. Evaluation of grooving workability was performed by sequentially replacing the pads 83 attached to the drawing device 8 of FIG. Those with no problems are marked with a circle. Table 2 shows the experimental results.

  As is clear from Table 2, the sliding load ratio increases as the tightening ratio decreases, and the example of the present invention has a high sliding load ratio and good grooving workability. On the other hand, the comparative examples 1 and 2 have a large tightening ratio, so that the sliding load is low, and when the grooving process is performed, only a slight pulling force is obtained by the pulling device, so that the pipe is broken. In Comparative Example 2, since the tightening ratio K2 is small, a large amount of dent marks remain when sandwiched by the pad on the outer surface of the raw tube 1b, and the intermediate shaping die cannot be corrected, and the dimensions of the inner fin vary on the circumference. In Comparative Example 3, since K1 was small, a load was applied to pull the base tube away from the pad, and the load was not stable, and the inner fin dimensions varied in the longitudinal direction. In Comparative Examples 5 and 6, since K1 is large, the pad depth H must be reduced in order to reduce the tightening ratio K2, in which case the flatness of the element tube 1b becomes very large. In the case of a large flat tube, the tube was buckled at the intermediate shaping die part, and grooving could not be performed.

(Example 3)
The outer diameter reduction ratio K3 of the intermediate shaping die 11 was changed to confirm the grooving workability and the amount of residual oil in the pipe. Other conditions were the same as in Example 1. As for the grooving workability, ◎ indicates good, ○ indicates no problem, and × indicates defective (pipe breakage). As for the amount of residual oil in the pipe, “good” is indicated by “◎”, and poor is indicated by “x”. Table 3 shows the results.

  As is apparent from Table 3, the inventive examples had excellent grooving workability, and the amount of residual oil in the pipe was small. On the other hand, in Comparative Examples 1 and 2, since the outer diameter reduction ratio K3 in the intermediate shaping die 11 is large, the amount of residual oil in the pipe has increased. In Comparative Example 3, the outer diameter reduction ratio K3 in the intermediate shaping die 11 was large, so that the grooved workability was inferior and the amount of residual oil in the pipe was increased.

It is sectional drawing which shows one Embodiment of the manufacturing apparatus of the inner surface grooved pipe | tube 1 which concerns on this invention. FIG. 2 is a cross-sectional view showing an embodiment of a pad 83 used in FIG. 1. It is the schematic of the measuring method of the load concerning the Example of this invention.

Explanation of symbols

1 Internal grooved tube 1a Raw tube 1b Raw tube 1c Raw tube 1d Raw tube 10 Groove 2 Floating die 21 Load cell 3 Processing head 31 Stopper 32 Bearing 4 Floating plug 5 Grooved plug 50 Groove 51 Plug rod 6 Ball 7 Shaping die 8 Drawing Device 80 Belt 81 Pulley 82 Pulley 83 Pad 84 Pad groove 9 Wiper 95 Load cell 96 Chuck 11 Intermediate shaping die L1 Pulling direction L2 Direction of rotation R Curvature radius H Pad depth Db Outer diameter Dd of raw pipe 1b Outer diameter of intermediate shaping die 11 Fa sandwiching load Fb sliding load

Claims (6)

The processing head 3 is installed in order along the drawing direction of the raw tube 1a, and the raw tube 1a into which the floating plug 4 and the grooved plug 5 rotatably connected to the floating plug 4 are inserted is described above. The raw tube 1a is moved through the floating die 2 and the machining head 3 without using a winding drive device, and the diameter is reduced by the floating die 2 and the floating plug 4, and at the position of the grooved plug 5. The processing tube 3 is arranged in contact with the outer periphery of the tube 1d, and the tube 1d is pressed against the grooved plug 5 by a plurality of balls 6 that rotate and revolve as the processing head 3 rotates. A device for forming a large number of fine grooves 10 on the inner surface of a raw tube 1d, between the floating plug 4 and the grooved plug 5, and at the end of the floating plug 4 Wiper 9 along the drawing direction, drawing device 8, the manufacturing apparatus of the inner grooved tube, characterized in that the intermediate shaping die 11 is provided. It is a manufacturing method of an internally grooved pipe using the device according to claim 1, wherein the difference between the maximum value and the minimum value of the load F applied to the floating die 2 when the raw pipe 1a is drawn is 500N or less. A method for producing an internally grooved tube. A method of manufacturing an internally grooved tube using the apparatus according to claim 1 or 2, wherein a load cell 21 attached to the floating die 2 detects a load F applied to the floating die 2 and While pulling, the change over time of the load F is converted into an electric signal and input to the control unit, and the control unit sends a signal to the drawing device 8 so as to suppress the change over time of the load F, and the drawing device 8. A method of manufacturing an internally grooved tube, wherein 8 transmits power to a pulley 81 while controlling rotational torque by the signal. A method of manufacturing an internally grooved tube using the apparatus according to claim 1 or 2, wherein a load cell 21 attached to the floating die 2 detects a load F applied to the floating die 2 and While pulling, the change over time of the load F is converted into an electric signal and input to the control unit, and the control unit sends a signal to the drawing device 8 so as to suppress the change over time of the load F, and the drawing device 8 is a method of manufacturing an internally grooved tube, characterized in that a pressing force is transmitted to the pulleys 81 and 82 by the signal. The ratio K1 between the radius of curvature R of the pad groove 84 of the pad 83 of the drawing device 8 and the outer diameter Db of the raw tube 1b is 0.5 to 0.5025, and the tightening ratio K2 is 0.98 to 1.0. The method for producing an internally grooved tube according to any one of claims 1 to 4, wherein: 6. The method for manufacturing an internally grooved tube according to claim 1, wherein an outer diameter reduction ratio K3 of the intermediate shaping die 11 is 0.001 to 0.1.

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