JP2002292419A - Contracting method for pipe diameter and contracting device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contracting method for a pipe diameter and contracting device therefor suppressing the increase in the wall thickness of the pipe, and contracting the pipe diameter with a large contraction rate and a low cost. SOLUTION: In a manufacturing device for a seamless heat transfer pipe provided with a groove on the inner face, a pair of shoes 17 is provided between rolling balls 6 and a die 8 so as to clamp a raw pipe 1 from the upper side and lower side. And the upper and lower faces of the pair of the shoes 17 are connected to a U-shaped clamp 18. The contracting device is composed of the shoes 17, the clamp 18, the die 8, and a drawing device for the raw pipe 1. By pressing of the shoes 17, a friction force is produced between the shoes 17 and the raw pipe 1 so that a backward tension is impressed to the raw pipe in the direction reverse to the reduction drawing direction. The strength of the backward tension is made to be 10-70% of the strength of the reduction drawing force. In this way, the increase of the wall thickness of the raw pipe 1 accompanying the contraction of the diameter of the raw pipe by the die 8 can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe diameter reducing method and a pipe diameter reducing apparatus for suppressing an increase in the pipe wall thickness due to the pipe diameter reduction.

[0002]

2. Description of the Related Art Internally grooved tubes are used as heat transfer tubes for air-cooled heat exchangers incorporated in household and commercial air conditioners. There are two types of inner grooved pipes: a seamless inner grooved pipe manufactured by rolling and a welded inner grooved pipe manufactured by high frequency induction welding or the like, depending on the processing method.

[0003] A method of manufacturing a seamless inner grooved pipe will be described below. FIG. 7 is a cross-sectional view showing a configuration of a conventional apparatus for manufacturing a heat transfer tube with a seamless inner surface groove. As shown in FIG. 7, a straight plug 2 is inserted into a raw tube 1 made of a metal or an alloy as a workpiece. The straight plug 2 has a substantially cylindrical shape, and is provided on the pipe supply side (upstream side).
Is slightly smaller than the inner diameter of the raw tube 1, and the outer diameter on the tube drawing side (downstream side) is smaller than the outer diameter on the tube supply side. The outer surface of the straight plug 2 is smooth. On the outside of the raw tube 1 at a position where the straight plug 2 is aligned,
A straight die 3 for reducing the diameter of the raw tube 1 together with the straight plug 2 is arranged. In addition, a hole is formed in the straight plug 2 so as to include the central axis thereof.
One end of the connection shaft 4 is fitted into this hole. The other end of the connecting shaft 4 is rotatably connected to a hole formed to include the central axis of the grooved plug 5. That is, the grooved plug 5 is rotatably connected to the straight plug 2 by the connecting shaft 4. On the outer peripheral surface of the grooved plug 5, a groove having a shape to be formed on the inner peripheral surface of the raw tube 1 is machined.

[0004] A plurality of rolled balls 6 are arranged on the outer side of the tube 1 at positions matching the grooved plugs 5 so as to be able to revolve around the tube axis of the tube 1 in the circumferential direction of the tube. Have been. Further, each rolled ball 6 can rotate on its own axis, and each rolled ball 6 can rotate on a planet while rolling on the outer surface of the raw tube 1. The grooved plug 5 and the rolled ball 6 constitute a rolled portion 7. A die 8 is provided on the tube drawing side (downstream side) of the rolled part 7. The die 8 is for reducing the diameter of the raw tube 1 having a groove formed on its inner surface to a predetermined size. On the downstream side of the die 8, a drawing device (not shown) for applying a drawing / drawing force to the seamless inner surface grooved tube 9 is provided.

A method for manufacturing a heat transfer tube with a seamless inner surface groove using this conventional manufacturing apparatus will be described. The raw pipe 1 is supplied to the straight die 3 from the pipe supply side (upstream side), and the raw pipe 1 is reduced in diameter by the straight plug 2 and the straight die 3. Next, the diameter-reduced raw tube 1 is reduced by pressing the outside of the raw tube 1 with a rolling ball 6 that rotates in a planetary manner.
Press Thereby, the grooved plug 5 is formed on the inner surface of the raw tube 1.
The groove on the outer peripheral surface is transferred. At this time, the grooved plug 5
Rotates along a groove formed by itself on the inner surface of the raw tube 1.

At this time, the grooved plug 5 is connected to the connecting shaft 4.
The straight plug 2 is stationary at a position where it is aligned with the straight die 3 due to the frictional force caused by pulling out the raw tube 1 and the drag force from the straight die 3. 5 also stops at a position matching the rolled ball 6. Next, the raw tube 1 having a groove formed on the inner surface passing through the rolled portion 7 is
Is inserted into the inside and the diameter is reduced. Thus, the seamless inner grooved pipe 9 is manufactured. Seamless internal grooved pipe 9
Has a spiral groove with a lead angle of one direction formed on its inner surface. Seamless inner grooved pipes have higher productivity than welded inner grooved pipes.

Next, a method of manufacturing a grooved tube with a welded inner surface will be described below. First, a band-shaped rolled strip of a certain width made of a metal or an alloy is prepared. Next, the rolled strip is sandwiched and rolled between a grooved roll having a groove on the surface and a smooth roll having a smooth surface to form a rolled strip having a groove on one side.
Next, the rolled material is curved in the width direction with the groove forming surface inside, and both ends in the width direction are abutted. Next, this butt portion is welded by high-frequency induction welding using a heating coil or the like, thereby producing a tube with a welded inner surface groove. The grooved ring constituting the grooved roll is made of a hard metal material such as a cemented carbide, and the outer peripheral surface end of the grooved ring is chamfered to prevent the grooved ring from being chipped. . In addition to the spiral groove, grooves having various patterns such as a pine needle shape and a cross groove shape having different lead angles can be formed in the welded grooved tube. In addition, a groove having a high lead angle and a high fin shape can be formed.

In recent years, as the performance of air conditioners has become higher, it has been required to improve the heat transfer performance of heat transfer tubes.
Further, in order to reduce the cost of the air conditioner, it is required to reduce the material cost, and it is required to reduce the weight of the heat transfer tube. In order to improve the heat transfer performance of the heat transfer tube, it is effective to reduce the diameter of the heat transfer tube in addition to increasing the lead and the fin of the groove shape. To reduce the weight of the heat transfer tube, it is effective to make the heat transfer tube thinner and to make the bottom wall thinner.

The method of reducing the diameter of the seamless inner grooved pipe includes a method of reducing the inner diameter of a die for reducing the diameter of the rolled pipe online, and the method of drawing and drawing the rolled pipe offline. There is a method and a method in which a raw tube having a small outer diameter is manufactured in advance, and the raw tube is rolled to form a groove.

The method of reducing the diameter of the grooved pipe on the inner surface of the weld includes a method of continuously reducing the diameter of the welded pipe online.
There are a method of reducing the diameter of the pipe after welding off-line, and a method of manufacturing a rolled strip having a narrow width in advance and groove-rolling the rolled strip to weld.

[0011]

However, the above-mentioned prior art has the following problems. In a method of reducing the inner diameter of a die for reducing the diameter of a rolled tube on-line by reducing the inner diameter of the die, the outer diameter reduction ratio that does not cause material fracture is limited to about 25.
%, There is a problem that when the outer diameter of the rolled tube is, for example, 9.5 mm, the outer diameter of the reduced tube can be reduced to only about 7 mm. Further, in this method, there is a problem that the wall thickness of the tube increases as the diameter decreases. For this reason, although the diameter of the pipe can be reduced, the weight of the pipe cannot be reduced. If the wall thickness of the tube is forcibly reduced in the rolling process, the tube is likely to break during rolling. Further, even if rolling can be performed, problems such as flattening are likely to occur.

[0012] In addition, the method of performing off-line drawing and drawing of a rolled pipe also has a problem that the wall thickness of the pipe increases as the diameter is reduced. Further, when the wall thickness of the pipe is forcibly reduced in the rolling process, problems such as breakage and flattening of the pipe during rolling are likely to occur.

Further, a method of reducing the diameter of a seamless inner grooved pipe by previously manufacturing a raw pipe having a small outer diameter includes a tool inserted into a pipe such as a grooved plug, a straight plug, a connecting shaft, and a rolled ball. It is necessary to newly arrange a set of tools to be set outside the tube, such as a retainer for holding the workpiece and a processing ring. In addition, since these tools need to be smaller than before, processing costs for precisely processing the tools are required, and equipment costs are increased. In addition, by reducing the outer diameter of the grooved plug, the strength of the grooved plug is reduced, and the grooved plug is likely to be broken during rolling. When the grooved plug is lost, the raw tube being rolled is discarded, the yield of the heat transfer tube is reduced, and the productivity is reduced by replacing the grooved plug. For this reason, the forming limit of the small-diameter grooved plug is that the outer diameter is about 7 mm. As described above, the limit of the outer diameter reduction ratio that does not cause material fracture is about 25.
%, The critical outer diameter of a tube that can be formed without causing breakage by a reduced-diameter die is about 5.5 mm, and a tube smaller than this cannot be manufactured.

On the other hand, in the method of continuously reducing the diameter of a pipe after welding, it is necessary to introduce a sizing device such as a roll or a die into existing welding pipe manufacturing equipment. However, when the pipe is reduced in diameter by such a sizing device, the wall thickness of the pipe increases with the reduction in diameter.
For this reason, there is a problem that even if the pipe can be reduced in diameter, the pipe cannot be reduced in weight. In the case of a roll-type sizing device, the equipment becomes large-scale, and a large space and a large capital investment are required to introduce this equipment. In the case of a die-type sizing device, equipment for giving a large drawing / pulling force to the pipe is required, which also requires a large capital investment.

Also, in the method of reducing the diameter of the pipe after welding off-line, there is a problem that the pipe is emptied without inserting a plug into the pipe, and the wall thickness of the pipe increases similarly to the case of a pipe with a seamless inner surface groove. is there. In addition, the number of manufacturing processes increases by one, resulting in an increase in cost.

Further, a method of manufacturing a rolled strip having a small width in advance, groove-rolling the rolled strip and welding the pipe to reduce the inner diameter of the grooved pipe on the inner surface of the welded pipe includes forming rolls, seam guides, sizing rolls and the like. Almost a complete set of equipment is needed. In addition, since these tools need to be finer than before, processing costs for precisely processing the tools are required, and equipment costs are significantly increased. Further, since the width of the welded portion does not change even if the width of the rolled strip is reduced, the ratio of the welded portion in the pipe circumferential direction on the inner surface of the pipe increases, and the heat transfer performance is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a method of reducing the diameter of a pipe, which suppresses an increase in the wall thickness of the pipe, reduces the diameter of the pipe at a large reduction rate, and at low cost. It is an object of the present invention to provide a tube diameter reducing device.

[0018]

According to the present invention, there is provided a method for reducing the diameter of a pipe, wherein the outer diameter of the pipe is reduced by applying a drawing / drawing force to the pipe to pass through a die. On the upstream side of the die, a tension in a direction opposite to the drawing / pulling force is applied to the tube, and the magnitude of the tension in the opposite direction is 10 to 7 times the magnitude of the drawing / pulling force.
0%.

In the present invention, by applying a tension in a direction opposite to the traveling direction of the pipe to the pipe, stress in the pipe axis direction acting on the pipe at the time of diameter reduction is increased, and an increase in the wall thickness of the pipe is suppressed. can do. The upstream side refers to a side to which the pipe is supplied. Further, the pipe may be a bare pipe having a smooth inner surface, or may be a pipe having an inner groove. The inner grooved tube may be a seamless inner grooved tube or a welded inner grooved tube.

[0020] A pipe diameter reducing apparatus according to the present invention is provided with a drawing means for applying a drawing / drawing force to a pipe, a die for passing the pipe to reduce the outer diameter of the pipe, and a die provided upstream of the die. And a tension applying means for applying a tension in a direction opposite to the drawing / pulling force to the tube. Hereinafter, the tension in the direction opposite to the drawing / pulling force applied to the tube is simply referred to as the backward tension.

Further, the tension applying means may be a shoe provided on the upstream side of the die and pressing the tube to apply a frictional force. Note that the shoe refers to a pressing member having a plate-like shape. Thereby, a backward tension can be applied to the tube by the frictional force.

Further, the good intentional tension applying means may be a rotating body formed of a rotatable roll or a caterpillar which is in rolling contact with the outer peripheral surface of the pipe at an upstream side of the die. Thereby, a rearward tension can be applied without damaging the outer peripheral surface of the tube. Still further, the tension applying means includes:
A powder brake for applying a rotation resistance to the rotating body can be provided. Alternatively, a motor that applies a rotational driving force to the rotating body in a direction that hinders movement of the tube can be provided.

Further, it is preferable that the shoe is made of a resin, and the surface of the rotating body is preferably coated with a resin such as urethane. This can reliably prevent the outer peripheral surface of the tube from being damaged.

Furthermore, it is preferable that a concave portion curved so as to contact a part of the outer surface of the tube in the circumferential direction of the tube is formed on a surface of the shoe, caterpillar or roll that contacts the tube. Thereby, lateral displacement of the tube can be prevented. Further, it is preferable that irregularities extending in the direction perpendicular to the tube axis are formed on the contact surface of the concave portion. Thereby, the holding property to the pipe can be improved.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. First, a first embodiment of the present invention will be described. FIG. 1 is a side view showing the configuration of the pipe diameter reducing device according to the present embodiment. As shown in FIG. 1, in the diameter reducing device 10, a pair of shoes 12 for pressing the tube 11 from above and below is provided, and a load cell 13 is provided on the upper shoe 12. Load cell 13
Are connected to a U-shaped clamp 14, and the load cell 13 and the pair of shoes 12 are connected to each other.
The tube 11 is clamped by a clamp 14. The load cell 13 measures the force with which the clamp 14 presses the shoe 12. The clamp 14 is connected to a clamp control device (not shown). A die 16 is provided downstream of the shoe 12 in the traveling direction of the tube 11, and a load cell 15 is provided between the shoe 12 and the die 16.
Is provided. The load cell 15 measures the force of the shoe 12 toward the die 16, and the load cell 1
The output terminal 5 is connected to the input terminal of the clamp control device. A drawing device (not shown) that applies a drawing / drawing force to the tube 11 is provided downstream of the die 16.

FIG. 2A shows the shoe 12 in this embodiment.
FIG. 3B is a perspective view showing the configuration of FIG.
It is sectional drawing which shows A 'cross section. The shoe 12 is made of resin. The surface of the shoe 12 is provided with a concave portion 23 that extends in the pipe axis direction of the pipe 11 and is curved so as to contact a part of the outer surface of the pipe 11 in the pipe circumferential direction. In addition, irregularities 24 extending in a direction orthogonal to the tube axis of the tube 11 are provided on a contact surface of the concave portion 23 with the tube 11. Shoe 1
2 may be replaced by a caterpillar or a roll which is in contact with the tube 11.

The material of the tube 11 is copper deoxidized copper, Cu-Fe-P alloy, Cu-Ni-Si alloy, Cu-S
A copper alloy such as an n-P alloy or an aluminum alloy may be used. The shape of the pipe 11 may be a smooth pipe (bare pipe) or an inner grooved pipe. The inner grooved pipe may be a seamless inner grooved pipe or a welded inner grooved pipe. Is also good.

In the diameter reducing device 10, the clamp 14 is
The pair of shoes 12 is pressed in a direction sandwiching the tube 11. Thereby, the pair of shoes 12 presses the tube 11 from above and below.
Further, a drawing device (not shown) applies a drawing / drawing force to the tube 11, the tube 11 is drawn in the direction of the arrow shown in FIG. 1, and the tube 11 is reduced in diameter by passing through the die 16. At this time, a frictional force is generated between the shoe 12 and the tube 11, and a tension (backward tension) acting on the tube 11 in a direction opposite to the drawing / pulling force is applied to the tube 11. The load cell 15 measures the tension applied to the tube 11. The load cell 13 measures a pressing force applied to the tube 11 by the clamp 14. The tension measured by the load cell 15 is fed back to a clamp controller (not shown), and the clamp controller automatically controls the pressing force applied to the tube 11 by the clamp 14. At this time, the rear tension is 10 to 70% of the drawing / pulling force.

For example, as described in "The Japan Society for Technology of Plasticity, 197th Symposium on Plasticity, page 7", at the time of drawing a pipe, the stress acting in the circumferential direction of the pipe is increased in the pipe axial direction. Above the working stress, the wall thickness of the tube increases. On the other hand, at the time of drawing the pipe, if the stress acting in the pipe axis direction of the pipe is made larger than the stress acting in the pipe circumferential direction, the wall thickness of the pipe can be reduced. In this embodiment, by applying a rearward tension to the tube 11 by the frictional force between the shoe 12 and the tube 11,
It is possible to increase the stress in the pipe axis direction at the time of drawing the pipe 11 and suppress an increase in the wall thickness of the pipe accompanying the diameter reduction processing. Thus, a tube having a small outer diameter and a small wall thickness can be formed.

The reasons for limiting the numerical values in the constituent elements of the present invention will be described below.

The magnitude of the back tension: the magnitude of the drawing / pulling force
When the magnitude of the rear tension of 10 to 70% is less than 10% of the magnitude of the drawing / pulling force, the effect of suppressing the increase in the wall thickness of the tube due to the diameter reduction is insufficient. On the other hand, if it exceeds 70%, the above effect is saturated, and most of the drawing / drawing force is offset by the back tension, so that the pipe cannot be smoothly reduced in diameter. Therefore, the magnitude of the backward tension is set to 10 to 70% of the magnitude of the drawing / pulling force. Preferably it is 20 to 50%.

Next, a second embodiment of the present invention will be described. FIG. 3 is a cross-sectional view showing a configuration of a manufacturing apparatus of a seamless inner grooved pipe in which the diameter reducing device according to the present embodiment is incorporated. Of the components of the apparatus for manufacturing a seamless inner grooved pipe shown in FIG. 3, the same elements as those of the conventional apparatus for manufacturing a seamless inner grooved pipe shown in FIG. Is omitted. In the manufacturing apparatus shown in FIG. 3, a pair of shoes 17 is provided between the rolled ball 6 and the die 8 so as to sandwich the raw tube 1 from above and below. The upper and lower surfaces of the pair of shoes 17 are connected to a U-shaped clamp 18. Shoe 17, clamp 1
The diameter reducing device of the present embodiment is constituted by a drawing device (not shown) for the die 8, the die 8 and the raw tube 1. Note that a rolling roll may be used instead of the rolling ball 6. The configuration other than the above in the apparatus for manufacturing a seamless inner grooved pipe of this embodiment is the same as the configuration of the apparatus for manufacturing a seamless inner grooved pipe shown in FIG.

In the apparatus for manufacturing a tube with a seamless inner groove according to the present embodiment, the clamp 17 clamps the shoe 17 from above and below, so that the shoe 17 presses the rolled tube 1. As a result, a frictional force is generated between the shoe 17 and the tube 1, and the frictional force acts as a rearward tension on the tube 1. The back tension is 10 to 70% of the drawing / pulling force. Thereby, when the diameter of the raw tube 1 is reduced by the die 8, the stress acting in the tube axis direction of the raw tube 1 increases, and an increase in the wall thickness of the raw tube 1 can be suppressed. Further, since the manufacturing apparatus of the seamless inner grooved pipe of the present embodiment has a simple configuration in which a shoe and a clamp are added to the conventional manufacturing apparatus, the equipment cost required for realizing this manufacturing apparatus is very small. It is slight. The other operations and functions of the apparatus for manufacturing a seamless inner grooved pipe of this embodiment are the same as those of the apparatus for manufacturing a seamless inner grooved pipe shown in FIG.

In order to simply increase the stress acting on the raw tube 1 in the tube axis direction, a method of increasing the drawing / pulling force applied from a drawing device (not shown) may be considered. However, when the drawing / drawing force is increased, the stress applied to the raw tube 1 in the rolled portion 7 becomes too large,
In the rolled portion 7, the raw tube 1 is broken. On the other hand, according to the present embodiment, the stress in the tube axis direction applied to the raw tube 1 in the die 8 can be increased without increasing the stress applied to the raw tube 1 in the rolled portion 7. Therefore, breakage of the raw tube 1 in the rolled portion 7 does not occur.

Next, a third embodiment of the present invention will be described. FIG. 4 is a cross-sectional view showing a configuration of a manufacturing apparatus of a seamless inner grooved pipe in which the diameter reducing device according to the present embodiment is incorporated. Among the components of the apparatus for manufacturing a seamless inner grooved pipe shown in FIG. 4, the same elements as those of the conventional apparatus for manufacturing a seamless inner grooved pipe shown in FIG. Is omitted. In the apparatus for manufacturing a tube with a seamless inner surface groove according to the present embodiment, as shown in FIG. 4, a pair of caterpillars 19 are provided between the rolled ball 6 and the die 8 so as to sandwich the raw tube 1 from above and below. And is in rolling contact with the upper and lower surfaces of the raw tube 1. The tracks 19 are each connected to a powder brake 22. The caterpillar 19 is rotatable, but a constant rotation resistance is applied by the powder brake 22. The surface of the caterpillar 19 is covered with a resin (not shown) such as urethane. The outer peripheral surface of the caterpillar 19 extends in the tube axis direction of the raw tube 1 to prevent lateral displacement of the raw tube 1, and is curved so as to be in contact with a part of the outer surface of the raw tube 1 in the pipe circumferential direction. A recess (not shown) is formed. Further, on the contact surface of the concave portion with the raw tube 1, irregularities (not shown) extending in the direction perpendicular to the tube axis of the raw tube 1 are provided in order to improve the holding ability of the raw tube 1. The caterpillar 19, the powder brake 22, the die 8, and the drawing device (not shown) of the raw tube 1 constitute a diameter reducing device of the present embodiment. The configuration other than the above in the apparatus for manufacturing a seamless inner grooved pipe of this embodiment is the same as the configuration of the apparatus for manufacturing a seamless inner grooved pipe shown in FIG.

In the apparatus for manufacturing a tube with a seamless inner surface groove according to the present embodiment, the drawing device applies a drawing / pulling force to the raw tube 1 and the raw tube 1 moves in the direction of the drawing / pulling force. And
The caterpillar 19 rotates as the raw tube 1 moves. However, since the caterpillar 19 is provided with a rotational resistance by the powder brake 22, the caterpillar 19 applies a force to the base tube 1 so as to prevent the movement of the base tube 1. Thereby, a tension opposite to the drawing force, that is, a backward tension, can be applied to the raw tube 1. At this time, the rear tension is 10 to 70% of the drawing / pulling force. In the present embodiment, the caterpillar 19 rolls into the base tube 1 without slipping compared to the second embodiment described above.
The outer surface of the raw tube 1 is not damaged. In addition, since the manufacturing apparatus of the seamless inner grooved pipe of the present embodiment has a simple configuration in which the caterpillar and the powder brake are added to the conventional manufacturing apparatus, the manufacturing apparatus can be realized at low cost. In the present embodiment, the pipe 1
Although an example in which the caterpillar 19 is used as a means for applying tension to the motor is described above, in the present invention, a roll may be used instead of the caterpillar. Further, in the present embodiment, the example in which the powder brake 22 is used has been described. However, the powder brake 22 may be omitted, and the rotational resistance of the caterpillar 19 itself may be used.

Next, a fourth embodiment of the present invention will be described. FIG. 5 is a cross-sectional view illustrating a configuration of a manufacturing apparatus of a seamless inner grooved pipe in which the diameter reducing device according to the present embodiment is incorporated. Of the components of the apparatus for manufacturing a seamless inner grooved pipe shown in FIG. 5, the same elements as those of the conventional apparatus for manufacturing a seamless inner grooved pipe shown in FIG. Is omitted. In the apparatus for manufacturing a tube with a seamless inner groove according to the present embodiment, as shown in FIG. 5, a pair of caterpillars 20 is provided between a rolled ball 6 and a die 8 so as to sandwich the raw tube 1 from above and below. And is in rolling contact with the upper and lower surfaces of the raw tube 1. The caterpillar 20 is connected to a motor 21. Caterpillar 20, motor 2
The diameter reducing device of the present embodiment is constituted by a device 1, a die 8, and a device (not shown) for extracting the raw tube 1. The other configuration of the apparatus for manufacturing a seamless inner grooved pipe of the present embodiment is the same as that of the apparatus for manufacturing a seamless inner grooved pipe according to the third embodiment described above.

In the apparatus for manufacturing a seamless inner grooved pipe according to the present embodiment, by driving the motor 21, a rotational driving force can be applied to the caterpillar 20 in a direction in which the movement of the raw pipe 1 is hindered. The caterpillar 20 is in rolling contact with the raw tube 1, and the caterpillar 20 rotates with the movement of the raw tube 1 in the drawing / pulling-out direction. Raw pipe 1
Backward tension can be applied. The apparatus for manufacturing a seamless inner grooved pipe of the present embodiment is different from the apparatus for manufacturing a seamless inner grooved pipe according to the third embodiment described above,
By controlling the driving force of the motor 21, the magnitude of the tension applied to the raw tube 1 can be arbitrarily controlled.

[0039]

The effects of the embodiment of the present invention will be specifically described below in comparison with a comparative example outside the scope of the claims. Using the diameter reducing device shown in FIG.
m, a tube having a bottom thickness of 0.255 mm was subjected to diameter reduction processing so that the diameter reduction rate was 13%. At this time, the drawing speed is 10m
/ Min, and the back tension was changed in the range of 0 to 1000N. Table 1 shows the ratio between the applied rear tension and the drawing / pulling force and the rate of change in the bottom wall thickness after diameter reduction. FIG. 6 shows the effect of the rear tension on the bottom wall thickness of the pipe by plotting the ratio between the rear tension and the drawing / pulling force on the horizontal axis and the rate of change of the bottom wall thickness after diameter reduction on the vertical axis. FIG.

[0040]

[Table 1]

No. 1 shown in Table 1. 2 to 9 are embodiments of the present invention. Example No. In Nos. 2 to 9, the backward tension was applied when the diameter of the tube was reduced. The bottom wall thickness of the tube after diameter reduction was smaller than that of the case of No. 1. Also, in Example No. Among 2 to 9, as the ratio of (backward tension / drawing / pulling force) increases, the rate of change of the bottom wall thickness decreases, and the increase in the bottom wall thickness due to the diameter reduction is suppressed.

On the other hand, No. 1 shown in Table 1 1 is a comparative example. Comparative Example No. In No. 1, since the pipe was reduced in diameter without applying a rearward tension, the increase in the bottom wall thickness accompanying the reduction in diameter was large.

[0043]

As described in detail above, according to the present invention,
A pipe diameter reducing method and a pipe diameter reducing apparatus that reduce the diameter of a pipe at a low cost with a large diameter reduction rate while suppressing an increase in the wall thickness of the pipe can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view showing a configuration of a pipe diameter reducing apparatus according to a first embodiment of the present invention.

FIG. 2A is a perspective view illustrating a configuration of a shoe according to the present embodiment, and FIG. 2B is a cross-sectional view illustrating an AA ′ cross-section illustrated in FIG.

FIG. 3 is a cross-sectional view showing a configuration of a manufacturing apparatus of a seamless inner grooved pipe in which a diameter reducing device according to a second embodiment of the present invention is incorporated.

FIG. 4 is a cross-sectional view showing a configuration of a manufacturing apparatus for a seamless inner grooved pipe in which a diameter reducing device according to a third embodiment of the present invention is incorporated.

FIG. 5 is a cross-sectional view illustrating a configuration of a manufacturing apparatus of a seamless inner grooved pipe in which a diameter reducing device according to a fourth embodiment of the present invention is incorporated.

FIG. 6 is a graph showing the effect of the rear tension on the bottom wall thickness of a pipe, with the horizontal axis representing the ratio between the rear tension and the drawing / pulling force, and the vertical axis representing the rate of change of the bottom wall thickness after diameter reduction. FIG.

FIG. 7 is a cross-sectional view illustrating a configuration of a conventional apparatus for manufacturing a heat transfer tube with a seamless inner surface groove.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1; Base tube 2; Straight plug 3; Straight die 4; Connecting shaft 5; Slotted plug 6; Rolled ball 7; Rolled portion 8; Die 9; Seamless inner surface grooved tube 10; Shoe 13; Load cell 14; Clamp 15; Load cell 16; Die 17; Shoe 18; Clamp 19, 20; Caterpillar 21; Motor 22; Powder brake 23;

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Taku Nagata 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo F-term in Kobe Steel Research Institute Kobe Research Institute (reference) 4E096 EA17 HA13 KA08

Claims (17)

[Claims] 1. A method for reducing the outer diameter of a tube by applying a drawing / drawing force to a tube and passing the drawing through a die, wherein the drawing / drawing force is applied to the tube upstream of the die. A tension in the opposite direction is applied thereto, and the magnitude of the tension in the opposite direction is equal to the magnitude of the drawing / pulling force.
A method for reducing the diameter of a pipe, wherein 2. The device according to claim 1, wherein the tension in the opposite direction is provided by a frictional force between a shoe provided on the upstream side of the die and pressing the tube and pressing the tube. How to reduce the diameter of the tube. 3. The method according to claim 1, wherein the tension in the opposite direction is provided by a rotational resistance of a rotating body formed of a roll or a caterpillar rotatably provided so as to be in rolling contact with the outer peripheral surface of the pipe at an upstream side of the die. The method for reducing the diameter of a pipe according to claim 1, wherein: 4. The reverse tension is used to rotationally drive a rotating body composed of a roll or a caterpillar provided so as to be in rolling contact with the outer peripheral surface of the tube on the upstream side of the die in a direction that hinders movement of the tube. 2. A method as claimed in claim 1, characterized in that the method is provided by: 5. A drawing means for applying a drawing / pulling force to a tube, a die passing through the tube to reduce the outer diameter of the tube, and a drawing / pulling force provided to the tube provided upstream of the die. A tube diameter reducing device, comprising: tension applying means for applying a tension in an opposite direction to the tube. 6. The pipe diameter reducing device according to claim 5, wherein the tension applying means is a shoe provided on an upstream side of the die to apply a frictional force by pressing the pipe. 7. The shoe has a concave portion curved so as to be in contact with a part of the outer surface of the tube in the circumferential direction of the tube, and irregularities extending in a direction perpendicular to the tube axis on a contact surface of the concave portion. The apparatus for reducing the diameter of a pipe according to claim 6, wherein: 8. The apparatus for reducing the diameter of a pipe according to claim 6, wherein the shoe is made of a resin. 9. The tension applying means includes: measuring means for measuring a tension applied to the tube in a direction opposite to the drawing / pulling force; and a pressing force of the shoe on the tube based on the measurement result. Control means for controlling to be constant;
9. The method according to claim 6, wherein:
Item 8. A tube diameter reducing device according to Item 1. 10. The tube according to claim 5, wherein the tension applying means is a rotating body formed of a rotatable roll or a caterpillar which is in rolling contact with an outer peripheral surface of the tube at an upstream side of the die. Diameter reducing device. 11. The apparatus according to claim 10, wherein the tension applying means includes a powder brake for applying a rotational resistance to the rotating body. 12. The tube diameter reducing apparatus according to claim 10, wherein the tension applying unit includes a motor that applies a rotational driving force to the rotating body in a direction that hinders movement of the tube. 13. The rotating body is provided in one or more pairs,
The pipe diameter reducing apparatus according to any one of claims 10 to 12, wherein each pair presses the pipe with the pipe interposed therebetween. 14. The tube diameter reducing apparatus according to claim 10, wherein the rotating body has a surface coated with a resin. 15. The rotating body has a concave portion curved so as to contact a part of the outer surface of the tube in the circumferential direction of the tube, and irregularities extending in a direction perpendicular to the tube axis on a contact surface of the concave portion. The apparatus for reducing the diameter of a pipe according to any one of claims 10 to 14, wherein: 16. The tension applying means includes: measuring means for measuring a tension applied to the tube in a direction opposite to the drawing / pulling force; and applying the powder brake to the rotating body based on the measurement result. The apparatus for reducing the diameter of a pipe according to claim 11, further comprising control means for controlling the rotating resistance force to be constant. 17. The tension applying means for measuring a tension applied to the tube in a direction opposite to the drawing / pulling force, and the motor applying the tension to the rotating body based on the measurement result. The apparatus according to claim 12, further comprising control means for controlling the rotational driving force to be constant.