JP5128515B2 - Manufacturing apparatus and manufacturing method for internally grooved tube - Google Patents

Description

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

A heat transfer tube used for a heat exchanger of an air conditioner or a water heater is often a copper tube with a groove on the inner surface because of the requirement for heat exchange performance.
In recent years, in particular, thinner inner-surface grooved tubes for heat transfer tubes have been demanded in order to reduce the weight of heat exchangers and save metal resources.

  Patent Documents 1 and 2 disclose a manufacturing apparatus and a manufacturing method of an internally grooved tube for manufacturing such an internally grooved tube.

  The apparatus for manufacturing an internally grooved tube of Patent Document 1 includes a diameter reducing die and a floating plug for reducing the diameter of the element tube, and forms a large number of grooves on the inner surface of the element tube on the downstream side in the drawing direction of the element tube. A grooved plug and a pressing tool are provided. Further, a wiper, a drawing device (intermediate drawing portion), and an intermediate shaping die are provided between the reduced diameter die and the machining head along the drawing direction of the blank tube in order to prevent breakage of the blank tube during the machining. This is a configuration provided.

  Similarly, the manufacturing apparatus of the inner surface grooved pipe of Patent Document 2 also reduces the diameter of the element pipe, and the groove processing part forms a large number of grooves on the inner surface of the element pipe on the downstream side in the drawing direction of the element pipe. And a drawing means that also serves as a take-up drum for winding up the processed inner grooved tube. Furthermore, it is a structure provided with the auxiliary | assistant extraction apparatus (intermediate extraction part) which assists the said extraction means, and the control means which controls the extraction force of the said extraction means and an auxiliary extraction apparatus so that it may be settled in a target range.

  According to the inner grooved pipe manufacturing apparatus disclosed in Patent Documents 1 and 2, the intermediate pulling portion can reduce the drawing load during processing and suppress breakage of the pipe during processing.

  However, even if the entire tensile load can be reduced, if the tensile load fluctuates, it has not been possible to perform processing sufficiently corresponding to such a load fluctuation.

  For example, in the manufacturing apparatus disclosed in Patent Document 1, a wiper is provided to prevent the pad that comes into contact with the element pipe from sliding against the element pipe, or the groove shape of the pad is defined in the intermediate extraction unit. Although measures have been taken, load fluctuations can still occur.

  On the other hand, in the manufacturing apparatus disclosed in Patent Document 2, control is performed so that the pulling force of the pulling means and the auxiliary pulling apparatus falls within the target range. However, instantaneous load fluctuations that cannot be controlled can occur.

  Thus, when the load fluctuates during processing, there is a problem that the shape of the groove formed on the inner surface of the tube changes, or the raw tube breaks during processing.

JP 2008-36640 A JP 2008-87004 A

  Therefore, in the present invention, by reducing and stabilizing the tensile load, it is possible to realize processing with a stable inner surface shape over the entire length of the tube without breaking even a long tube, and an internally grooved tube having excellent heat transfer performance. It is an object of the present invention to provide a manufacturing apparatus and a manufacturing method for an internally grooved tube.

The present invention includes a diameter reducing portion that reduces the diameter of the raw tube along the drawing direction of the raw tube, and a groove processing portion that forms a large number of grooves on the inner surface of the raw tube, and the diameter reducing portion and the groove An intermediate drawing portion for drawing the raw pipe reduced in diameter by the reduced diameter processed portion is provided between the processed portion, and the reduced diameter processed portion is disposed in the reduced diameter die and the raw pipe, and the raw diameter together with the reduced diameter die And a grooved plug having a plurality of grooves formed on the outer periphery thereof, and a grooved plug formed by a floating plug for reducing a diameter of the tube, the groove processing portion being rotatably connected to the floating plug in the element tube, and an outer side of the element tube And a pressing tool arranged to revolve around the pipe axis while pressing the element pipe toward the grooved plug side, and an outer diameter D of the element pipe the _o (mm), the diameter _D 2 (mm) of the diameter _die, R D = {( _o -D ₂₎ / _{D o}} radial contraction rate of mother tube represented by × 100 (%) _R D (percent), is set to _{R D} ≦ 30 in the diametral reduction part, the outer diameter of the floating plug D ₁ (mm) and the diameter D ₂ (mm) of the reduced diameter die are set to satisfy D ₁ −D ₂ ≧ 0.1.

Further, the present invention performs a diameter reducing process for reducing the diameter of the element pipe and a groove forming process for forming a plurality of grooves on the inner surface of the element pipe in the process of moving the element pipe in the drawing direction, While performing the grooving step, an intermediate drawing step of pulling out the raw pipe reduced in the diameter reduction processing step is performed, and the diameter reduction processing step is arranged in the diameter reducing die and the raw pipe, and the diameter reduction is performed. A grooved plug having a plurality of grooves formed on the outer periphery thereof, wherein the groove processing step is pivotally connected to the floating plug in the element pipe, and the element pipe And a pressing tool arranged to revolve around the tube axis while pressing the raw tube toward the grooved plug side, the inner grooved tube manufacturing method, D _o (mm), the diameter D ₂ (mm) of the reduced diameter die Therefore, the diameter reduction ratio R _D (%) of the raw tube expressed by R _D = {(D _o −D ₂ ) / D _o } × 100 (%) is set to R _D ≦ 30, and the floating plug The outer diameter D ₁ (mm) and the diameter D ₂ (mm) of the reduced diameter die are set to satisfy D ₁ −D ₂ ≧ 0.1.

As in the manufacturing apparatus and the manufacturing method of the inner surface grooved pipe, by setting the diameter reduction rate of the raw pipe to 30% or less in the diameter reduction processing section, the base pipe is reduced in diameter after the diameter reduction processing section. The so-called chatter phenomenon that slightly vibrates is suppressed, and the load assist that assists the pull-out load at the intermediate pull-out portion can be stabilized.
Specifically, if the diameter reduction ratio of the blank pipe is greater than 30%, the contact area between the blank pipe and the diameter reduction die increases, and the frictional resistance increases, so the processing load on the diameter reduction die increases, The thinning of the outer diameter of the tube is smaller than the diameter of the outlet of the reduced diameter die.

  Further, due to the thinning, the contact between the raw tube and the reduced diameter die is not stable, the chatter phenomenon is likely to occur, and the thickness is reduced. Vibration due to chattering phenomenon is transmitted to the intermediate pull-out part, and the outer diameter of the pipe becomes thin by pulling, so the pressing force against the base pipe of the pad provided to hold the pipe in the intermediate pull-out part becomes unstable. As a result, load assistance at the intermediate drawing portion becomes unstable.

  Therefore, in the present invention, the diameter reduction rate of the raw pipe is set to 30% or less in the diameter reduction processed portion so that such a problem does not occur during processing.

Furthermore, the chatter phenomenon is more effectively achieved by setting the outer diameter D ₁ (mm) of the floating plug and the diameter D ₂ (mm) of the reduced diameter die so that D ₁ −D ₂ ≧ 0.1. Can be suppressed.
More specifically, when the difference in diameter (D ₁ -D ₂ ) between the floating plug and the reduced diameter die is 0.1 mm or less, the area where the floating plug and the reduced diameter die overlap is reduced.

  Thus, the area where the floating plug and the reduced diameter die overlap is reduced, so that when the blank tube is pulled in between, the corner of the floating plug, more specifically, the outer peripheral surface of the floating plug Since the inner surface of the pipe strongly hits the boundary between the upstream non-tapered surface and the downstream tapered surface, the load on the floating plug becomes excessive. Reduction, load assist instability in the intermediate drawing machine is likely to occur.

Therefore, in the present invention, D ₁ −D ₂ ≧ 0.1 is set so that such a problem does not occur during processing.

  As an aspect of the present invention, the revolution direction of the pressing tool is set to be opposite to the rotation direction of the grooved plug (hereinafter referred to as “reverse direction”), and the processing pitch P of the pressing tool ( mm) can be set in a range of 0.2 ≦ P ≦ 0.7.

With this configuration, it is possible to stably manufacture an internally grooved tube having a groove with high processing accuracy.
This is because, when P is smaller than 0.2 mm, it has been confirmed from experience that it is difficult to form a groove on the inner surface of the raw tube even if the load assistance by the intermediate drawing portion is increased. On the other hand, if it is larger than 0.7 mm, the tensile load is not stable and the fluctuation becomes large.

In addition, in order to further stabilize the load assistance by the intermediate drawing portion and increase the groove machining accuracy, the revolution direction of the pressing tool is set in the reverse direction, and the machining pitch P is set to P ≧ 0.2. It is better to set it as small as possible.
In detail, when giving priority to the processing in which the processing accuracy of the groove is higher than the productivity of the internally grooved tube, the processing pitch P is within the range of 0.2 ≦ P ≦ 0.7, for example, 0 .2 ≦ P ≦ 0.4 is preferable.

On the other hand, in order to increase the productivity of the internally grooved tube, it is better to set the revolution direction of the pressing tool in the reverse direction and to set the machining pitch P large in a range satisfying P ≦ 0.7. .
Specifically, in the case where the productivity of the internally grooved tube is given priority over the processing with higher groove processing accuracy, the processing pitch P is set within the range of 0.2 ≦ P ≦ 0.7, for example, 0 It is better to set 4 ≦ P ≦ 0.7.

  As an aspect of the present invention, the revolution direction of the pressing tool is set to the same direction as the rotation direction of the grooved plug (hereinafter referred to as “positive direction”), and the processing pitch P of the pressing tool ( mm) can be set in a range of 0.2 ≦ P ≦ 0.4.

  Even if the revolving direction of the pressing tool is the positive direction as in the above configuration, the inner surface fin is set by setting the machining pitch P (mm) to be in the range of 0.2 ≦ P ≦ 0.4. In this case, the hems of the slabs do not have any glazing, and the groove depth is deep and the machining accuracy is high.

  Specifically, in order to manufacture an internally grooved tube having a deep groove on the tube inner surface, it is desirable that the revolving direction of the pressing tool is a positive direction. An unfilled portion of a material called “egre” is likely to occur at the bottom of the fin formed between the two. Further, the greater the processing pitch P is, the easier it is to generate the egress.

  For this reason, in order to prevent aggression while forming a deep groove, it is desirable that the revolution direction of the pressing tool is a positive direction and 0.2 ≦ P ≦ 0.4.

  In general, the thinner the pipe, the harder it is to form the fins, and the easier it is to break. However, the present invention can be applied regardless of the thickness of the pipe, including thin pipes. Therefore, the thinner the pipe is, the more effective the production conditions of the present invention.

  In addition, according to the present invention, the shape of the inner surface is stable over the entire length of the long tube and can be processed without breaking, so that it can be applied regardless of the length of the raw tube, and the yield and productivity can be improved. it can.

  In the present invention, by reducing and stabilizing the tensile load, it is possible to process a stable inner surface shape over the entire length of the tube without breaking even a long tube, and an internally grooved tube having excellent heat transfer performance can be obtained. An apparatus and a method for manufacturing an internally grooved tube that can be configured can be provided.

Sectional drawing which shows the manufacturing apparatus of the inner surface grooved pipe | tube of this embodiment. The structure explanatory view of the diameter-reduction processing part which showed the diameter-reduction processing part of this embodiment in the partial cross section. Action | operation explanatory drawing which shows a mode that an element pipe is diameter-reduced by the diameter-reduction process part of this embodiment. Explanatory drawing explaining the processing pitch of the processing ball of this embodiment. Sectional drawing which shows a part of pipe inner surface which has the fin which the egle has generate | occur | produced. Explanatory drawing which shows a mode that an element pipe is diameter-reduced by the conventional diameter reduction process part.

An embodiment of the present invention will be described below with reference to the drawings.
In addition, FIG. 1 is explanatory drawing of the manufacturing apparatus 12 of the inner surface grooved pipe | tube in this embodiment.

  As shown in FIG. 1, the inner grooved tube manufacturing apparatus 12 in this embodiment includes a diameter reducing portion 13 for reducing the diameter of the element tube 11 a along the drawing direction X of the element tube 11 a, and the inner surface of the element tube 11 a. And an intermediate drawing portion for drawing the element tube 11a having a diameter reduced by the diameter reducing portion 13 between the diameter reducing portion 13 and the groove processing portion 14. 17 is provided.

  The reduced diameter processing portion 13 includes a reduced diameter die 22 and a floating plug 23 that is disposed in the raw tube 11 a and reduces the diameter of the raw tube 11 a together with the reduced diameter die 22.

  The grooved portion 14 is rotatably connected to the floating plug 23 via a connecting rod 25 in the raw tube 11a, and a grooved plug 24 having a plurality of grooves formed on the outer periphery, and the outer side of the raw tube 11a. In FIG. 3, the base tube 11a is composed of a plurality of processed balls 26 arranged to revolve around the tube axis while pressing the grooved plug 24 side.

In the manufacturing apparatus 12 and the manufacturing method of the inner surface grooved tube 11 using the manufacturing apparatus 12, as shown in FIG. 2, the outer diameter D _o (mm) of the raw tube 11 a and the reduced diameter die 22 The diameter reduction ratio R _D of the raw tube 11a represented by R _D = {(D _o −D ₂ ) / D _o } × 100 (%) by the diameter D ₂ (mm) is 30 in the diameter reduction processing portion 13. % Or less is set.

Furthermore, the outer diameter D ₁ (mm) of the floating plug 23 and the diameter D ₂ (mm) of the reduced diameter die 22 are set to satisfy D ₁ −D ₂ ≧ 0.1.

  Furthermore, the revolution direction of the processed ball 26 is set in the reverse direction, and the processed pitch P (mm) of the processed ball 26 is set in a range of 0.2 ≦ P ≦ 0.7.

  Alternatively, when the revolution direction of the processed ball 26 is set to the positive direction, the processing pitch P (mm) is set to be in a range of 0.2 ≦ P ≦ 0.4.

Hereinafter, the manufacturing apparatus 12 for an internally grooved tube in the present embodiment will be described in detail.
The manufacturing apparatus 12 constitutes a diameter reducing portion 13, an intermediate drawing portion 17, a groove processing portion 14, a shaping die 15, and a drawing portion 16 along the drawing direction X from the upstream side to the downstream side.

  Further, the manufacturing apparatus 12 is movable in the drawing direction with respect to the fixed base 50, a movable base 33 that supports the reduced diameter portion 13, the intermediate drawing device 17, and the groove processing portion 14, and the movable base 33. A load cell 28 for detecting a load F acting in accordance with the movement with respect to the fixed base 50, and a control device 45 for controlling the intermediate pulling portion 17 and the pulling portion 16 based on the load F detected by the load cell 28; It consists of.

As described above, the diameter reducing portion 13 includes the diameter reducing die 22 and the floating plug 23.
The diameter-reducing die 22 is formed in a cylindrical shape having a communication hole 22a communicating with the drawing direction X, and the communication hole 22a has an upstream portion (inlet side) in the drawing direction X as a downstream portion (outlet side). On the other hand, it is configured in a shape that opens toward the upstream side.

  The floating plug 23 is formed in a cylindrical shape, and the outer periphery of the downstream portion is formed in a tapered shape.

As shown in FIG. 2, the outer diameter of the floating plug 23 is set to D ₁ (mm), and the inner diameter on the outlet side of the reduced diameter die 22 is set to D ₂ (mm).

  The groove processing portion 14 includes a grooved plug 24, a plurality of processing balls 26, and a processing head 27 that holds the processing balls 26 from the outer peripheral side.

The processing head 27 is formed with a processing ball holding groove 27a having a semicircular cross section.
The plurality of processed balls 26 are held so as to revolve freely while pressing the surface of the raw tube 11a by the processed ball holding grooves 27a. The plurality of processed balls 26 are held by the processed ball holding grooves 27a so that the revolution speed can be changed while pressing the surface of the raw tube 11a in either the forward direction or the reverse direction.

  The shaping die 15 performs a process of smoothly shaping, for example, distortion of the pipe surface caused by pressing of the machining ball 26 in the grooving part 14 when the inner grooved pipe 11 passes.

The drawing portion 16 also has a winding drum 36 for winding the processed inner surface grooved tube 11, and includes a motor M ₁ that drives the winding drum 36, and the inner surface grooved tube 11 is driven by rotation of the motor M _1. Is wound around the winding drum 36.

  The intermediate drawing portion 17 assists drawing by the drawing device 16 by drawing the base tube 11 a in the drawing direction X between the reduced diameter portion 13 and the groove processing portion 14. That is, the grooving by the grooving portion 14 becomes resistance when the raw tube 11a is pulled out, and the drawing load during the grooving increases, but the drawing load applied to the raw tube 11a by the intermediate drawing portion 17 is increased. Can be dispersed.

The intermediate extraction portion 17 includes a pair of belts 42a and 42a disposed on the upper and lower sides or the left and right sides of the raw tube 11a. Each belt 42a, 42a are formed in a loop shape (endless) and is tensioned by a rotatable pulley 43 by the rotation of the motor M _2. The belts 42a, 42a are provided with a plurality of pads 44 on the outer peripheral surface thereof along the length direction.

  Although not shown, the pad 44 is formed with a pad groove in which the cut surface with respect to the connecting direction of the plurality of pads 44 has an arc shape at the contact portion with the outer surface of the base tube 11a after being reduced in diameter by the reduced diameter portion 13. doing.

The intermediate withdrawal unit 17 is a pad 44 configured to be pressed against the base pipe 11a surface by driving of the motor M _3.
A wiper 51 for removing an oil film and foreign matter adhering to the outer surface of the raw tube 11a is provided on the upstream side of the intermediate drawing portion 17, and an intermediate shaping die 52 is provided on the downstream side.

The wiper 51 is provided to remove an oil film and foreign matter adhering to the outer surface of the raw tube 11a, and a through hole having a diameter slightly smaller than the outer diameter of the raw tube 11a is passed through the raw tube 11a. For example, a rubber cylindrical body formed in the central portion.
In addition, when the wiper 51 is not installed, slipping occurs in the intermediate extraction portion 17 due to an oil film or foreign matter, and the drawing of the raw tube 1c is not stable, and the cross-sectional shape is not stable, so that the dimension of the groove varies. Will occur.

The intermediate shaping die 52 is provided to return the cross-sectional shape of the element tube 11a flattened by the intermediate extraction portion 17 to a shape close to a perfect circle, and has the same diameter as the floating die 22 according to the shape of the element tube 11a. It is configured with a small die diameter.
The intermediate shaping die 52 is made of a material harder than the material of the metal tube 11a such as metal or ceramic. Preferably, it is made of cemented carbide.

  The movable table 33 is installed on the fixed table 50 via a plurality of wheels 33a so as to be movable in the drawing direction or the opposite direction with respect to the fixed table 50. The part 14, the finishing part 15, the intermediate drawing device 17, the wiper 51, and the intermediate shaping die 52 are installed in a state where they are accommodated in the box 32.

  The load cell 28 is provided at the downstream end portion of the movable table 33 in the pulling direction on the fixed table 50 so that the load F received from the movable table 33 according to the pulling force of the raw tube 11a can be detected.

The control unit 45 receives a load detection signal S _{in obtained} by converting the load F detected by the load cell 28 into an electrical signal, and the motors M ₁ , M ₂ , and M of the extraction unit 16 and the intermediate extraction unit 17 according to a control program. A control signal S _out for controlling the driving of M ₃ is output.

Further, although not shown, the control unit 45 temporarily stores a computing unit (CPU) for executing signal analysis processing and arithmetic processing, a hard disk for storing necessary control programs, and the load detection signal S _in . In addition to the memory for storing, input means such as a keyboard for inputting control parameters and display means such as a monitor can be appropriately provided.

The control unit 45, by controlling the driving of the motor M ₃ of the intermediate withdrawal unit 17 controls the pressing force by the pad 44 of the intermediate pullout portion 17 against base pipe 11a.
By pressing the pad 44 against the base tube 11a with an appropriate pressing force, the slip between the pad 44 and the base tube 11a is reduced, and the variation in the load F is reduced.

  When the fluctuation of the load F becomes large, the shape of the groove in the longitudinal direction varies, and if the depth of the groove in the longitudinal direction varies, a certain heat transfer performance cannot be secured, and the aluminum fin of the heat exchanger This is because there is a variation in the degree of tube expansion when the tube is installed, and therefore the tube expansion is partially insufficient, resulting in a decrease in heat exchanger performance due to insufficient adhesion with the aluminum fins.

  In order to reduce the fluctuation of the load F, the rotation of the belts 42a and 42a at the intermediate extraction portion 17 may be controlled. At this time, the controller 45 is not limited to the rotational torque of the pulley 43, and may be configured to control other control parameters such as the rotational speed and acceleration.

  Then, the manufacturing method of the inner surface grooved tube 11 using the inner surface grooved tube manufacturing apparatus 12 described above includes a diameter reduction processing step of reducing the diameter of the raw tube 11a in the process in which the raw tube 11a advances in the drawing direction X. An intermediate drawing is performed in which a groove forming step for forming a large number of grooves on the inner surface of the element tube 11a is performed, and the element tube 11a reduced in the diameter reducing step is extracted during the diameter reducing step and the groove forming step. Perform the process.

The diameter reduction process is performed by a diameter reducing die 22 and a floating plug 23 that is disposed in the element tube 11 a and reduces the diameter of the element tube 11 a together with the diameter reducing die 22.
In the groove machining step, a grooved plug 24 that is rotatably connected to the floating plug 23 via a connecting rod 25 in the raw tube 11a and has a plurality of grooves formed on the outer periphery, and on the outer side of the raw tube 11a. This is performed with a plurality of processing balls 26 arranged to revolve around the tube axis while pressing the base tube 11a toward the grooved plug 24 side.

The said manufacturing apparatus 12 and a manufacturing method can have the following effects.
As described above, the manufacturing apparatus 12 and the manufacturing method are configured such that R _D = {(D, based on the outer diameter D _o (mm) of the raw tube 11 a and the diameter D ₂ (mm) of the reduced diameter die 22. _o -D ₂₎ / _{D o}} the radial contraction rate _{R D} of the mother tube 11a represented by × 100 (%), is set to 30% or less in the diameter reduction portion 13.

  For this reason, the so-called chatter phenomenon in which the tube 11a slightly vibrates after the diameter reduction at the diameter reduction processing portion 13 is suppressed, and the load assist for assisting the extraction load at the intermediate extraction portion 17 can be stabilized.

As described above, in the manufacturing apparatus 12 and the manufacturing method, the outer diameter D ₁ (mm) of the floating plug 23 and the diameter D ₂ (mm) of the reduced diameter die 22 are set such that D ₁ −D ₂ ≧ It is set to be 0.1.

  For this reason, generation | occurrence | production of a chatter phenomenon can be suppressed more effectively and it can be thinned in the diameter reduction process and can prevent thickness reduction.

  As described above, in the manufacturing apparatus 12 and the manufacturing method, when the revolution direction of the processing ball 26 is set in the reverse direction, the processing pitch P (mm) is set to 0.2 ≦ P ≦ 0.7. The range is set.

  For this reason, it is possible to stably manufacture a grooved tube with high groove processing accuracy.

  Alternatively, as described above, in the manufacturing apparatus 12 and the manufacturing method, when the revolution direction of the processed ball 26 is set to the positive direction, the processing pitch P (mm) of the processed ball 26 is set to 0.2 ≦ It is set to be in the range of P ≦ 0.4.

  As a result, there is no aggression at the skirt portion of the inner fin, and a groove having a deep groove depth and high processing accuracy can be obtained.

Subsequently, in order to verify the effectiveness of the manufacturing apparatus 12 and the manufacturing method, a processing experiment for processing the raw tube 11a into the inner grooved tube 11 was performed.
In Example 1, the diameter reduction rate R _D of the raw tube 11a in the diameter reducing portion 13 is engaged, in Example 2, the engagement of the floating plug 23 and the diameter reducing die 22 (D ₁ -D ₂ ), and in Example 3, The processing pitch P of the processing ball 26, the groove depth and the twist angle of the grooved plug 24 in Example 4, the revolution speed of the processing ball 26 in Example 5, and the number of processing balls 26 in Example 6, respectively. It was changed as a parameter and the processing quality was evaluated.

  Hereinafter, each of Examples 1 to 6 will be described in detail.

Example 1
In Example 1, it was subjected to grooving experiment to investigate the effect on the processing by changing the radial contraction rate R _D of the base pipe 11a in the diameter reduction portion 13.

  In this machining experiment, machining conditions were set for each of Invention Examples 1 to 3 and Comparative Examples 1 and 2 to machine the raw tube 11a, thereby creating an internally grooved tube 11.

In Invention Examples 1 to 3 and Comparative Examples 1 and 2, the wall thickness (T _o ) of the raw tube 11a, the diameter (D ₂ ) of the reduced diameter die 22, the outer diameter (D ₁ ) of the floating plug 23, and the grooved plug The outer diameter, the number of grooves, the twist angle, the groove depth, the groove apex angle, the number of processed balls 26, the revolution speed, and the processing pitch of 24 were processed under common conditions as shown in Table 1.

さらに加工実験では、本発明例１〜３、比較例１，２のそれぞれについて表２に示すように、縮径ダイス２２のダイス径Ｄ_２を一定とし、素管１１ａの外径Ｄ_ｏのみを変化させることで、縮径率Ｒ_Ｄを変化させた。

The further processing experiments, Examples 1 to 3, each of Comparative Examples 1 and 2 As shown in Table 2, the die diameter D ₂ of the diameter reduction dies 22 is constant, only the outer diameter D _o of the blank pipe 11a The diameter reduction ratio _RD was changed by changing.

As shown in Table 2, in Examples 1 to 3 of the present invention, in each of Comparative Examples 1 and 2, the diameter reduction ratio _RD is larger than 30% under the setting that the diameter reduction ratio _RD is 30% or less. Processing was performed under the following settings.

The processing result was evaluated by the variation in the groove depth in the longitudinal direction of the groove formed on the inner surface of the raw tube 11a after the grooving.
Further, the variation in the groove depth in the longitudinal direction and the degree of stability of the load F detected during the diameter reduction processing by the load cell 28 installed in the diameter reduction processing portion 13 are closely related. For this reason, when a load variation occurs, it affects the groove shape (particularly the groove depth) formed on the inner surface of the raw tube 11a, and the magnitude of the load variation is the same as the variation of the groove depth in the longitudinal direction of the groove. Appears in size.

  For this reason, the degree of stability of the load F detected at the time of diameter reduction can be evaluated by evaluating the variation in the groove depth in the longitudinal direction of the groove formed on the inner surface of the element tube 11a.

  The processing result is “◎” when the variation in the groove depth in the longitudinal direction indicating the stability of the load is 0 to 0.020 mm, and “◯” when 0.021 to 0.050 mm. The case of 0.051 mm or more was evaluated as “x”.

  Table 2 shows the results of processing performed under the conditions of Invention Examples 1 to 3 and Comparative Examples 1 and 2.

表２のとおり、本発明例１は「○」、本発明例２，３は「◎」となり、本発明例１〜３は、所望の内面溝付管１１が得られたのに対して、比較例１、２は、いずれも「×」となり、所望の内面溝付管１１が得られなかった。

As shown in Table 2, Example 1 of the present invention is “◯”, Examples 2 and 3 of the present invention are “◎”, and Examples 1 to 3 of the present invention obtained the desired internally grooved tube 11, In Comparative Examples 1 and 2, both were “x”, and the desired internally grooved tube 11 was not obtained.

Specifically, when the diameter reduction ratio _RD is greater than 30%, as in Comparative Examples 1 and 2, the variation in groove depth in the longitudinal direction of the groove increases.

When radial contraction rate _{R D} of the base pipe 11a is greater than 30%, as shown in FIG. 6 (a), the frictional resistance increases the contact area A of the base pipe 11a and the reduced diameter die 22A is increased. Then, the processing load at diameter die 22A is increased, pulling the outer diameter D _f of the mother tube 11a is thinner than the diameter D ₂ of the outlet of the reduced diameter die 22A thinning occurs (FIG. 6 ( (See an enlarged view of the area Z1 in a)).

  Further, due to the thinning, the contact between the element tube 11a and the reduced diameter die 22A is not stable, the chatter phenomenon is likely to occur, and the thickness is reduced.

Thus, the degree of outer diameter D _f of the base pipe 11a after diameter reduction portion 13 passes is smaller than the diameter D ₂ of the diameter reduction dies 22A "pull thinning" and "thickness reduction" is increased, the intermediate The load assistance at the drawing portion 17 became unstable. In addition, chatter phenomenon in which the pipe vibrates slightly occurred, and the instantaneous fluctuation of the load increased accordingly.
For this reason, it is thought that it appeared in the result of the variation of the groove depth in the longitudinal direction of the groove increased in Comparative Examples 1 and 2.

  In the inner surface grooved tube 11 in which the groove depth varies in the longitudinal direction as in Comparative Examples 1 and 2, the heat transfer performance decreases. In addition, since the degree of expansion of pipes varies when the heat exchanger is expanded and incorporated into the aluminum fins, the expansion of the pipes is partially insufficient and the heat exchanger performance is deteriorated due to insufficient adhesion with the aluminum fins.

  Furthermore, if the load fluctuation is large, it may break during processing, so it is desirable that the load fluctuation be small.

In contrast, as the results in Table 2, if radial contraction rate R _D is less than 30% at the diameter reduction portion 13, variation of the groove depth in the longitudinal direction as in the present invention Examples 1-3 Became smaller. Thereby, it was proved that the stability of the load F was good, and in particular, the stability of the load F was improved as the diameter reduction ratio _RD was small.

Specifically, in Invention Examples 1 to 3, as shown in FIG. 3, when the diameter reduction ratio _RD is 30% or less and D ₁ −D ₂ ≧ 0.1, the raw tube 11 a after the diameter reduction processing is performed. since the outer diameter _{D f,} becomes substantially the same as the diameter _{D 2} of the diameter reduction dies 22, the thickness _{T f} of the base pipe 11a after diameter reduction is increased equal to or slightly thicker _{T o} of the base pipe 11a Processing was realized.

(Example 2)
In Example 2, a grooving experiment was conducted to examine the influence on the machining by changing the meshing (D ₁ -D ₂ ) of the floating plug 23 and the reduced diameter die 22 in the reduced diameter processing portion 13.
In this processing experiment, the raw tube 11a was processed for each of the conditions of Invention Examples 4 to 8 and Comparative Example 3, and the inner grooved tube 11 was created.

In this machining experiment, the outer diameter D _{1 of the} floating plug 23 with respect to the die diameter D ₂ of the constant diameter-reduced die 22 as shown in Table 3 under the machining conditions of Invention Examples 4 to 8 and Comparative Example 3. And the degree of engagement (D ₁ -D ₂ ) between the floating plug 23 and the reduced diameter die 22 was changed.

In Examples 4 to 8 of the invention, (D ₁ -D ₂ ) is all set under 0.1 or more, and in Comparative Example 3, (D ₁ -D ₂ ) is set under 0.1. Was processed.

Table 3 shows the results of machining performed under the machining conditions of Invention Examples 4 to 8 and Comparative Example 3.
The present invention examples 4-8, Comparative Example 3, 9.53 mm outer diameter _{D o} of the blank pipe 11a, with a common size of base pipe 11a of 8.93mm internal diameter, for the other conditions, As shown in Table 1, processing was performed under common conditions. In addition, the processing results were evaluated as “評 価”, “◯”, and “×” based on the variation in the groove depth in the longitudinal direction of the grooves formed after the grooving process, as in Example 1. .

表３から明らかなように、本発明例４〜８は、加工結果が「◎」か「○」となり所望の内面溝付管１１が得られたのに対して、比較例３では、加工結果が「×」となり所望の内面溝付管１１が得られなかった。

As is clear from Table 3, the inventive examples 4 to 8 have a processing result of “◎” or “◯” and a desired inner grooved tube 11 is obtained, whereas in the comparative example 3, the processing result is obtained. Was “x”, and the desired internally grooved tube 11 could not be obtained.

Thus, when (D ₁ -D ₂ ) is smaller than 0.1, the load at the reduced diameter processed portion 13A becomes unstable as in Comparative Example 1.

  Specifically, when the engagement (D1-D2) of the floating plug 23A and the reduced diameter die 22A is smaller than 0.10 mm, as shown in the enlarged view of the region Z3 in FIG. 6B, the corner portion C of the floating plug 23A. Only the vicinity contacts the inner surface of the raw tube 11a, and the load applied in the drawing direction X is received only in the vicinity of the corner C.

Normally, when the diameter is, the thickness of the mother tube 11a is without thinning, for some of be thickened within 0.01mm _Conversely, the _(D 1 -D ₂₎ 0.1 If it is smaller, the diameter of the tube 11a will be reduced while reducing the thickness, and the load will be excessively increased, as shown in the enlarged view of the region Z2 in FIG. Thinning occurs.

The smaller the engagement (D ₁ -D ₂ ) between the floating plug 23A and the reduced diameter die 22A is, the larger the instantaneous fluctuation of the load becomes. In particular, when (D ₁ -D ₂ ) is smaller than 0.10 mm, the tube becomes finer. The vibration chatter phenomenon also occurs, and the instantaneous fluctuation of the load further increases, and the degree of thinning also changes.
As a result, the raw tube 11a may break at the reduced diameter processed portion 13A.

  When the intermediate extraction portion 17 is provided in this state, the contact area between the pad 44 and the raw tube 11a in the intermediate extraction portion 17 is fluctuated, so that a sufficient contact area cannot be secured, and load assistance at the intermediate extraction portion 17 is prevented. It becomes unstable. In addition, when the intermediate drawing portion 17 is provided, the number of contacts of the pads 44 changes, or vibration due to repeated contact and opening of the pads 44 with the base tube 11a is affected, so that conventional processing without the intermediate drawing portion 17 is provided. Compared with the method, the instantaneous fluctuation of the load becomes larger.

On the other hand, if (D ₁ -D ₂ ) is 0.1 or more, the stability of the load at the diameter-reduced portion 13 is good as in Examples 4-8 of the present invention. As shown in FIG. 3, it was proved that machining under a stable load can be performed as (D ₁ -D ₂ ) is larger than the machining results of 4-6.

(Example 3)
In Example 3, a grooving experiment was conducted to examine the effect on machining by changing the machining pitch P.
In this machining experiment, as in the conditions of Invention Examples 9 to 32 shown in Table 4, the inner groove is formed under the machining conditions in which the machining pitch P is changed in each of the case where the revolution direction of the machining ball 26 is the forward direction and the reverse direction. The tube 11 was processed.

Inventive Examples 9 to 32 were all processed on the internally grooved tube 11 under the processing conditions that satisfy the conditions of the present invention in which the reduction ratio _RD was 30% or less. Invention Examples 11 to 18 and Invention Examples 23 to 25 surrounded by a thick frame are obtained by processing the internally grooved tube 11 under particularly preferable processing conditions.

  Specifically, in Invention Examples 11 to 18, the revolution direction of the processed ball 26 is set in the reverse direction, and the processing is performed under the setting where the processing pitch P (mm) is 0.2 mm or more and 0.7 mm or less. In Invention Examples 23 to 25, the revolving direction of the processed ball 26 was set to the positive direction, and the processing was performed under a setting in which the processing pitch P (mm) was 0.2 mm or more and 0.4 mm or less.

  On the other hand, in Examples 9, 10, 19, and 20 of the present invention, the revolution direction of the processed ball 26 is set to the reverse direction, and the processing pitch P (mm) is set to be smaller than 0.2 mm or larger than 0.7 mm. Was processed. In each of Examples 21, 22, 26 to 32 of the present invention, the revolution direction of the processed ball 26 is set to the positive direction, and the processing pitch P (mm) is set to be smaller than 0.2 mm or larger than 0.4 mm. Was processed.

  Further, in Examples 9 to 32 of the present invention, a common element tube 11a having an outer diameter of 9.53 mm and an inner diameter of 8.93 mm is used, and other conditions are the same as shown in Table 1. Was processed.

Here, the processing pitch P (mm) means that the processing ball 26 revolves around the base tube 11a by an angle equally distributed on the outer periphery of the base tube 11a by the number of processing balls 26 arranged on the outer periphery. The distance that the tube 11a travels in the drawing direction X is shown.
Specifically, in the third embodiment, since four processed balls 26 are arranged on the outer periphery of the raw tube 11a, as shown in FIG. 4, the processed tube 26 rotates while the outer periphery of the raw tube 11a rotates 90 degrees. The moving distance P that 11a travels in the drawing direction X is defined as a processing pitch P.

  FIG. 4 is an explanatory diagram for explaining the processing pitch P schematically shown by omitting part of the vicinity of the groove processing portion 14. In addition, La, Ld, and Lb indicated by phantom lines in FIG. 4 are the three processed balls 26a and 4b shown in FIG. 4 among the four processed balls 26 arranged on the outer periphery of the raw tube 11a. 26d and 26b show the locus | trajectory which pressed the raw tube 11a. Furthermore, FIG. 4 shows a case where the revolution direction of the processed ball 26 is the reverse direction (the reverse direction to the rotational direction of the grooved plug 24). Note that when the processed ball 26 is in the positive direction, the trajectories La, Lb, and Ld of the processed ball 26 are lowered to the right in FIG.

  The processing results were evaluated by “groove formation” (whether or not filled with tube flesh) formed on the inner surface of the raw tube 11a after grooving and “groove processing accuracy” (occurrence of aggression).

  Here, as shown in FIG. 5, the “egre” indicates an unfilled portion 101 of a material having a shape in which the fin 100 is notched in the thickness direction at the skirt portion of the inner surface fin 100 in the groove processing portion 14. .

“Groove formation” is defined as “◯” when the whole groove of the grooved plug 24 is filled with meat (having a groove with a predetermined depth) and without filling (having a predetermined depth). (Where no groove was formed) was evaluated as “Δ” or “×”. “Δ” is unfilled, but is in a practically usable range. Furthermore, "the processing accuracy of Groove" gouge is missing or gouges depth H _e is what is within 10% of the fin Hem and "◎" gouges depth H _e is within 30% of the fin Hem Those with a value of “◯” were evaluated, and those with 30% or more were evaluated as “Δ” or “×”. "△" is gouge depth H _e is equal to or more than 30% of the fin Hem, practically, is within the range that can be used.

  Table 4 shows the results of processing performed for each of the conditions of Invention Examples 9 to 32.

表４から明らかなように、本発明例９〜３２は、いずれも「◎」、「○」、「△」のいずれかとなり、「×」のものはなかった。殊に、本発明例１１〜１８，２３〜２５では、いずれも「◎」か「○」となった。

As is clear from Table 4, Examples 9 to 32 of the present invention were any one of “、”, “◯”, and “Δ”, and there was no “×”. In particular, in Examples 11 to 18 and 23 to 25 of the present invention, all were “◎” or “○”.

  Specifically, as shown in Table 4, “groove formation” is “Δ” in Invention Examples 9, 10, 21, and 22, whereas “O” in Invention Examples 11 to 20, 23 to 32. " From this result, it was proved that the groove on the inner surface can be formed to a predetermined depth when the processing pitch P is 0.20 mm or more regardless of the revolution direction of the processing ball 26.

  In addition, “groove processing accuracy” was “Δ” in Invention Example 20, but “」 ”or“ ◯ ”in Invention Examples 9-18. From this result, it was proved that, when the revolving direction of the processed ball 26 is the reverse direction and the processing pitch P is 0.70 mm or less, it is particularly difficult for the hems of the inner fins to be prone to the occurrence of an egress.

  Furthermore, regarding the “groove processing accuracy”, in Examples 26 to 32 of the present invention, “△”, whereas in Examples 21 to 25 of the present invention, “◯” or “◎”. From this result, In the case where the revolution direction of the processed ball 26 is the positive direction, if the processing pitch P is 0.40 mm or less, it has been proved that it is particularly difficult for the hem portions of the inner fins to be prone to the occurrence of an egg.

  Thus, if the depth of the angle is within 30% of the fin hem width, it is preferable that there is no possibility that the inner fin will collapse when the heat exchanger is assembled into the aluminum fin of the heat exchanger to be post-processed.

  As described above, the inventive examples 11 to 18 and the inventive examples 23 to 25 are those of the inner grooved tube 11 under the processing conditions that are particularly preferable among the inventive examples from the viewpoints of “groove formation” and “groove machining accuracy”. We were able to demonstrate that processing was possible.

  Specifically, when the revolution direction of the processed ball 26 is set to the reverse direction and the processing pitch P (mm) is set to be in the range of 0.2 ≦ P ≦ 0.7, or the revolution of the processed ball 26 is set. The effectiveness of the present invention characterized by setting the direction to the positive direction and setting the machining pitch P (mm) to be in the range of 0.2 ≦ P ≦ 0.4 could be verified.

Example 4
In Example 4, a grooving experiment was conducted to examine the effect of changing the groove depth and twist angle of the fluted plug 24 in the grooving process.
In this machining experiment, the machining pitch P of the machining balls 26 is changed to 0.20 mm, 0.40 mm, and 0.60 mm in each case where the revolution direction of the machining balls 26 is the forward direction and the reverse direction. I did it.
Further, in the processing performed in this processing experiment, using a base tube 11a of the common dimensions outer diameter _{D o} is φ9.53mm raw tube 11a, diameter die diameter _{D 2,} the floating plug outside diameter _{D 1,} a grooved The outer diameter of the plug 24, the number of grooves, the groove apex angle, the number of processed balls 26, and the revolution speed were the same as in Example 1 under the common conditions shown in Table 1.

The processing results are as shown in Tables 5-7.
Tables 6 and 7 show the results of experiments conducted by changing the groove depth and twist angle of the grooved plug 24 and the processing pitch P of the processed ball 26 when the revolution direction of the processed ball 26 is the forward direction and the reverse direction, respectively. Indicates.

  Further, Table 5 shows the processing conditions in Tables 6 and 7 and the experimental results obtained by extracting a part of the processing results.

  As in Example 3, the machining results were verified for “groove formation” and “groove machining accuracy”, and all of these elements were “O” or “◎”. Was evaluated as “x”, and “x” was not included in any of them, and “Δ” was included in one of them.

As shown in Tables 5 to 7, also in the processing experiment in Example 4, the inner surface grooved tube under the processing conditions satisfying the conditions of the present invention in which the diameter reduction ratio _RD is 30% or less. There was no "x" because it was processed 11.

一般に、溝が深く、ねじれ角が大きい加工が困難とされる加工条件の場合、例えば、溝深さが０．２０ｍｍよりも大きく、且つねじれ角が５５度よりも大きな加工条件の場合、加工時に大きな引抜き力を要する。

Generally, in the case of a machining condition in which machining with a deep groove and a large helix angle is difficult, for example, in a machining condition where the groove depth is greater than 0.20 mm and the helix angle is greater than 55 degrees, Requires a large pulling force.

  As shown in Table 5, even when the groove depth of the grooved plug 24 is deeper than 0.20 mm, which is 0.22 mm, and the twist angle is larger than 55 degrees, which is 60 degrees, the revolution direction of the processed ball 26 is If it was in the positive direction and the processing pitch was in the range of 0.20 mm to 0.40 mm, the processing result was “◯” and processing was possible (see the column of * 1 in Table 5).

  From this result, even when the groove of the grooved plug 24 is deep and machining with a large helix angle is difficult, the revolution direction of the machining ball 26 is the positive direction and the machining pitch P is not too large. If it was 0.4 mm, it was proved that processing was possible.

  On the other hand, as shown in Table 5, even when the groove depth of the grooved plug 24 is smaller than 0.20 mm such as 0.18 mm or 0.15 mm and the twist angle is smaller than 55 degrees such as 50 degrees, If the revolution direction of the processed ball 26 is the reverse direction, the processing results were all “◯” regardless of the setting of the processing pitch P, and the processing was possible (see the column * 2 in Table 5).

  From this result, when the groove depth of the grooved plug 24 is small and the helix angle is small, at the same processing pitch P, the direction of revolution of the processed ball 26 is reverse as compared to the case of the positive direction. Since it is difficult to generate the egress on the inner surface of the fin and is small even if generated, it was proved that the processing pitch P can be set as large as 0.6 mm, for example.

  In general, the larger the processing pitch P, the higher the processing speed and the productivity. Therefore, when the revolving direction of the processed ball 26 can be processed in the reverse direction, the revolving direction of the processed ball 26 is processed in the reverse direction. preferable.

(Example 5)
In Example 5, a grooving experiment was conducted to examine the influence of the revolution speed R (rpm) of the machining ball 26 on the machining.
Here, generally, the drawing speed at the time of machining the inner grooved tube 11 is V (m / min), the revolution speed of the machining ball 26 is R (rpm), the machining pitch of the machining ball 26 is P (mm), When the arrangement number of the balls 26 is C (pieces), the drawing speed V (m / min) can be expressed by V = R × P × C / 1000 (1). From this equation (1), it can be seen that even if the revolution speed is changed by R (rpm), the machining pitch P (mm) can be kept constant by changing the drawing speed by V (m / min) accordingly. .

  Therefore, in this machining experiment, the drawing speed V is set so that the machining pitch of the machining ball 26 is constant based on the formula (1) for each revolution speed of the machining ball 26 of 10000 rpm, 30000 rpm, and 40000 rpm. Processing experiments similar to those in Example 3 and Example 4 were performed.

  As a result, even if the revolution speed of the processed ball 26 was changed, if the processing pitch P was the same, the result was the same as in the third and fourth embodiments.

  After all, if the processing pitch P can be maintained within a predetermined range, it can be demonstrated that the same evaluation result can be obtained regardless of the difference in the revolution speed of the processing ball 26. The revolution speed of the processing ball 26 may be appropriately selected in consideration of the life of the processing tool such as the processing ball 26.

(Example 6)
In Example 6, a grooving experiment was conducted to examine the influence of the number C (pieces) of processing balls 26 arranged.
Here, from the relationship of the formula (1), even if the arrangement number C (pieces) of the processed balls 26 is changed, the drawing speed is changed by changing V (m / min) and the revolution speed R (rpm) accordingly. The processing pitch P (mm) can be kept constant.

  Therefore, in Example 6, in each of the cases where the number C of the processed balls 26 is 3 and 5, the drawing speed is set to V so as to keep the processing pitch P (mm) constant based on the relationship of the expression (1). (M / min) and revolution speed were set to R (rpm), respectively, and processing experiments similar to those in Example 3, Example 4, and Example 5 were performed.

  As a result, even if the revolution speed of the processed ball 26 was changed, the results were the same as those of Example 3, Example 4, and Example 5 as long as the processing pitch P was the same.

  Eventually, if the processing pitch P can be kept within a predetermined range, it has been proved that the same evaluation result can be obtained regardless of the difference in the number C (number) of processing balls 26. What is necessary is just to select the arrangement | positioning number of the process ball | bowl 26 suitably with the inner surface grooved pipe | tube 11 to process.

In the correspondence between the embodiment described above and the configuration of the present invention,
The processing ball 26 corresponds to a pressing tool,
The present invention is not limited only to the configuration of the above-described embodiment, and many embodiments can be obtained.

For example, the pressing tool is not limited to the processed ball 26, and other tools such as a roller may be used as long as they can press the raw tube 11a.
Furthermore, the elementary tube 11a can be formed of a material having excellent thermal conductivity such as copper, aluminum, or an alloy thereof.

DESCRIPTION OF SYMBOLS 11 ... Internal grooved pipe 11a ... Elementary pipe 12 ... Internal grooved pipe manufacturing apparatus 13 ... Diameter reduction processing part 14 ... Groove processing part 17 ... Intermediate drawing part 22 ... Diameter reduction die 23 ... Floating plug 24 ... Grooved plug 26 ... Processed balls

Claims (6)

A diameter reducing portion for reducing the diameter of the raw tube along a drawing direction of the raw tube, and a groove processing portion for forming a plurality of grooves on the inner surface of the raw tube, and the diameter reducing portion and the groove processing portion are provided. In the middle, provided with an intermediate extraction part for extracting the raw pipe reduced in diameter at the reduced diameter processing part,
The diameter-reduced portion is composed of a diameter-reduced die and a floating plug that is arranged in the element pipe and that reduces the diameter of the element pipe together with the diameter-reduced die,
The grooved portion is rotatably connected to the floating plug in the raw tube, and a grooved plug having a plurality of grooves formed on the outer periphery thereof, and the raw tube is disposed on the outer side of the raw tube toward the grooved plug. An inner grooved pipe manufacturing apparatus configured with a pressing tool arranged to revolve around a pipe axis while pressing,
By the outer diameter D _o (mm) of the raw tube and the diameter D ₂ (mm) of the reduced diameter die,
R _D = {(D _o −D ₂ ) / D _o } × 100 (%)
The diameter reduction ratio R _D (%) of the element pipe expressed by the following formula is obtained: R _D ≦ 30 in the diameter reduction processed portion
Set to
The outer diameter D ₁ (mm) of the floating plug and the diameter D ₂ (mm) of the reduced diameter die are as follows:
D ₁ -D ₂ ≧ 0.1
Manufacturing equipment for internally grooved tubes set to be The revolution direction of the pressing tool is set to be opposite to the rotation direction of the grooved plug,
The processing pitch P (mm) of the pressing tool is
0.2 ≦ P ≦ 0.7
The apparatus for manufacturing an internally grooved tube according to claim 1, which is set so as to fall within the range. The revolution direction of the pressing tool is set to the same direction as the rotation direction of the grooved plug,
The processing pitch P (mm) of the pressing tool is
0.2 ≦ P ≦ 0.4
The apparatus for manufacturing an internally grooved tube according to claim 1, which is set so as to fall within the range. In the process of moving the pipe in the drawing direction, a diameter reducing process for reducing the diameter of the pipe, and a groove forming process for forming a plurality of grooves on the inner surface of the pipe, the diameter reducing process and the groove processing process are performed. While performing, an intermediate drawing process is performed to pull out the raw pipe reduced in diameter in the diameter reducing process,
The diameter reduction processing step is performed with a diameter reduction die and a floating plug that is arranged in the element pipe and reduces the diameter of the element pipe together with the diameter reduction die,
In the groove processing step, a grooved plug that is rotatably connected to the floating plug in the raw tube and has a plurality of grooves formed on the outer periphery thereof, and the raw tube on the outer side of the raw tube toward the grooved plug. A method for manufacturing an internally grooved tube with a pressing tool arranged to revolve around a tube axis while pressing,
By the outer diameter D _o (mm) of the raw tube and the diameter D ₂ (mm) of the reduced diameter die,
R _D = {(D _o −D ₂ ) / D _o } × 100 (%)
The diameter reduction ratio R _D (%) of the elemental tube expressed by
Set R _D ≦ 30,
The outer diameter D ₁ (mm) of the floating plug and the diameter D ₂ (mm) of the reduced diameter die are as follows:
D ₁ -D ₂ ≧ 0.1
The manufacturing method of an internally grooved tube set to be The revolution direction of the pressing tool is set to be opposite to the rotation direction of the grooved plug,
The processing pitch P (mm) of the pressing tool is
0.2 ≦ P ≦ 0.7
The method for manufacturing an internally grooved tube according to claim 4, wherein the inner grooved tube is set so as to fall within the range. The revolution direction of the pressing tool is set to the same direction as the rotation direction of the grooved plug,
The processing pitch P (mm) of the pressing tool is
0.2 ≦ P ≦ 0.4
The method for manufacturing an internally grooved tube according to claim 4, wherein the inner grooved tube is set so as to fall within the range.

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