JP2001347311A - Manufacturing method of internally grooved tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method capable of manufacturing an internally grooved tube by the form rolling at a high speed. SOLUTION: In a step of pressing a circumferential surface of a stock tube 1 against a grooved plug 5 by making use of a drawing force of the stock tube 1 by a plurality of balls 6 disposed at predetermined intervals in the radial direction so that the grooved plug 5 is revolved while it is rotated around the axis of the stock tube 1 at the position of the grooved plug 5 while drawing the rotatably inserted metal stock tube 1, the machining force in the axial direction of the stock tube 1 is applied to each ball 6 outside the revolution track for the center of each ball and from different positions in two directions before and behind the drawing direction with the revolution track as a reference, and the position of application of the machining force applied from different positions in the two directions with respect to the balls 6 is different in distance from the axis of the stock tube 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an inner grooved tube used as a heat exchanger tube for a heat exchanger in an air conditioner, a refrigerator, and the like. The present invention relates to a method for manufacturing a seamless inner grooved tube suitable for processing a sharp groove at a higher speed.

[0002]

2. Description of the Related Art With reference to FIG. 3, a conventional apparatus for manufacturing a grooved tube having an inner surface (described in Japanese Patent Application Laid-Open No. 62-263820) and a manufacturing method using the apparatus will be described. A floating die 2 and a processing head 4 (outer race) are sequentially installed from the upstream side along the drawing direction of the metal tube 1. The processing head 4 has a conical inner peripheral surface 40 that gradually diverges toward the downstream side in the drawing direction, and the inner peripheral surface 40 is provided with a certain distance in the radial direction by a ball retainer (not shown). The ball 6 arranged to hold is in rolling contact. These balls 6 are regulated by a flange-like (annular) stopper 8 attached to a member holding the processing head 4 via a bearing 81 on the downstream side so as not to move downstream in the drawing direction. I have. The stopper surface 80 of the stopper 8 that contacts the ball 6 is formed in a conical surface shape that tapers at an acute angle toward the upstream side in the drawing direction. The taper of the inner peripheral surface 40 of the processing head 4 is 2 to 3 degrees with respect to the axis, and the taper of the stopper surface 70 is 75 to 85 degrees with respect to the axis.

[0003] In order to form a groove in the raw tube 1, a rotatable grooved plug 5 having a number of grooves 50 parallel to each other and spirally formed around the axis on a peripheral surface, and a plug into the grooved plug 5 is provided. The floating plug 3 connected via the rod 51 is inserted into the raw tube 1 in order along the drawing direction. The raw tube 1 is passed through the floating die 2 and the processing head 4 so that the grooved plug 5 is located inside the ball 6 and the floating plug 3 is located in the floating die 2, and the raw tube 1 is moved through an arrow a. The processing head 4 is rotated at a high speed while being pulled out in the direction of. By pulling out the raw tube 1,
The diameter of the raw tube 1 is reduced by the floating die 2 and the floating plug 3, and then reduced by the ball 6 and the grooved plug 5 that revolve around the outer circumference of the raw tube 1 by the rotation of the processing head 4. At the same time, grooving is performed on the inner surface.

In the machining head 4, the thrust force applied to each ball 6 by pulling out the raw tube 1 is received by the stopper surface 80 of the stopper 8, and the direction is changed to the outer peripheral direction by the taper of the stopper surface 80. (In the radial direction) and further directed by the inner peripheral surface 40 of the processing head 4 in the axial direction of the raw tube 1. Accordingly, the tube wall of the raw tube 1 is pressed against the surface of the grooved plug 5 by each of the revolving and rotating balls 6, so that the diameter of the raw tube 1 is reduced and the groove 50 of the grooved plug 5 is formed on the inner surface thereof. Transferred, the inner grooved pipe 1a is manufactured. Inner grooved pipe 1a
Is shaped and reduced in diameter by drawing with a shaping die installed downstream of the processing head 4.

[0005]

SUMMARY OF THE INVENTION In this kind of method for manufacturing an inner grooved tube, the number of balls = x and the number of revolutions of the ball =
Assuming that N (rpm) and the processing pitch (the pressing width along the drawing direction per ball, shown in FIG. 3) = P, the processing speed (production speed) V (m / min) of the inner grooved tube is V =
It is obtained by the formula of (x · N · P) / 1000. In order to improve the heat transfer performance of the inner grooved tube, it is necessary to form a groove having a deeper and sharper cross-sectional shape. But,
If the groove is designed to be deeper and the shape is sharper, the same processing speed as when the groove is designed to be relatively shallow and the shape of the groove is not sharp, as described above. When the grooving is performed, as shown in FIG. 4, a defect such as a scouring 12 may occur near the root of the fin 11 in the inner grooved tube 1a. This undercut 12 increases in proportion to the size of the processing pitch P. Therefore,
In order to suppress the increase of the gouging 12 without lowering the processing speed, the number of revolutions of the ball, that is, the number of revolutions of the processing head 4 (however, the number of revolutions of the ball Increases in proportion to the number of revolutions, but they do not match, and the former is less than the latter.)
Need to be raised. However, when the number of revolutions of the ball is increased by a certain amount or more, the pipe is torsionally deformed at the grooved portion (portion of the grooved plug 5), and the pipe may be broken. This torsional deformation of the tube occurs when the processing pitch P is smaller and the number of ball revolutions is smaller.

When observing the state of the outer surface of the tube when the tube is torsionally deformed, turbulence and meandering of each processing pitch P, which is the contact trajectory of the ball, are observed. Considering this, according to the above-described conventional manufacturing method, when each ball 6 attempts to fluctuate in the radial direction due to centrifugal force when revolving at a high speed, the processing force on the raw tube 1 with respect to each ball 6 is reduced at the ball center. Acts only in one direction outside the orbit to be formed (outside the orbit formed by the center of the ball, each ball 6 is held only at one point of contact with the inner peripheral surface 40 of the processing head 4). Therefore, it is considered that the fluctuation (fluctuation) of the ball 6 is increased by the influence of the centrifugal force, and the orbit of the ball becomes more unstable than at the time of low-speed revolution. If the number of balls is the same, the smaller the processing pitch P, the smaller the force in the thrust direction of the ball against the stopper surface 80, so that the ball (revolution orbit) tends to be unstable. When the processing pitch is smaller than when P is large, torsional deformation occurs even if the number of ball revolutions is relatively small.

[0007] The present invention is proposed from the above-mentioned study on the conventional manufacturing method, and its object is to increase the number of revolutions of the ball (the number of rotations of the processing head) in order to perform groove processing at a higher speed. However, it is an object of the present invention to provide a manufacturing method which does not cause torsional deformation of a pipe and therefore can manufacture an internally grooved pipe at a higher speed.

[0008]

A method of manufacturing an inner grooved tube according to the present invention is configured as follows to solve the above-mentioned problems. In other words, the method for manufacturing an inner grooved tube according to claim 1 provides a grooved plug 5 having a plurality of grooves 50 parallel to the axis or spiral in the peripheral surface.
Are drawn at predetermined intervals in the radial direction so as to revolve around the tube axis of the tube 1 at the position of the grooved plug 5 while pulling out the metal tube 1 rotatably inserted. In the process of pressing the peripheral surface of the base tube 1 against the grooved plug 5 using the pulling force of the base tube 1 by the plurality of balls 6, the center of the balls is formed for each ball 6. A processing force in the tube axis direction of the raw tube 1 is applied from different positions in two directions before and after the drawing direction with respect to the orbit outside the orbit, and the processing force is applied from the different positions in the two directions. Are characterized in that the position of action on the ball 6 is different from the distance from the tube axis of the raw tube 1.

According to a second aspect of the present invention, there is provided a method of manufacturing an inner grooved tube according to the first aspect, wherein an outer peripheral portion of each ball 6 with respect to a revolving orbit formed by the center of each ball is:
A conical inner peripheral surface 40 formed in the processing head 4 and diverging at a gentle angle toward the downstream side in the drawing direction.
And a stopper surface of an annular stopper 7 having a stopper surface 70 which is set in the processing head 4 so as not to rotate integrally with the processing head 4 and has a stopper surface 70 against which each ball 6 abuts when the base tube 1 is pulled out. 70 and held,
The stopper surface 70 is characterized in that it is formed in a conical surface shape that widens at an acute angle toward the upstream side in the drawing direction.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of a method for manufacturing an inner grooved pipe according to the present invention will be described with reference to FIGS. 1 and 2A. FIG. 1 is a partial cross-sectional view of a manufacturing apparatus for explaining an embodiment of a manufacturing method, and FIG.
FIG. 2 is a partially enlarged sectional view of a grooved portion of the apparatus of FIG. 1, and FIG. 2B is a partially enlarged sectional view of an apparatus used in a conventional method for comparison with the operation of the apparatus in FIG. .

In FIG. 1, reference numeral 2 denotes a floating die, and reference numeral 4 denotes a processing head which is rotated at a high speed by driving means (not shown). The processing head 4 has a conical inner peripheral surface 40 that gradually expands toward the downstream side in the drawing direction of the metal raw tube 1, and the inner peripheral surface 40 is provided with a ball retainer 60. The ball 6 held so as to keep a constant interval in the radial direction is configured to roll.
On the downstream side in the pulling-out direction, these balls 6 are regulated by an annular stopper 7 attached to a member holding the processing head 4 via a bearing 71 so as not to move to the downstream side in the pulling-out direction. I have. The stopper 7 does not rotate integrally with the processing head 4 due to the interposition of the bearing 71 described above. The stopper surface 70 of the stopper 7 that contacts the ball 6 is formed in a conical surface shape that widens at an acute angle toward the upstream side in the drawing direction.

Next, an embodiment of the manufacturing method will be described together with the operation of the manufacturing apparatus shown in FIG. The raw tube 1 is provided with a floating plug 3 and a grooved plug 5 rotatably connected to the floating plug 3 via a plug rod 51 such that the grooved plug 5 is located on the downstream side in the pulling-out direction. Insert On the outer peripheral surface of the grooved plug 5, a large number of parallel grooves 50 are formed spirally with respect to the axis. With the grooved plug 5 located inside the plurality of balls 6 and the floating plug 3 located inside the floating die 2, the raw tube 1 is passed through the processing head 4 and the floating die 2, and the raw tube 1 is marked with an arrow. The processing head 4 is rotated at a high speed in the clockwise direction toward the drawing direction while being pulled out in the direction a.

By the rotation of the processing head 4, each ball 6 revolves around the raw tube 1 while revolving along the rotation direction. Each of the balls 6 during the drawing of the raw tube 1 is held by the inner peripheral surface 40 of the processing head and the stopper surface 70 outside the orbit formed by the center of the ball. That is, by pulling out the raw tube 1, the pulling force is reduced by the ball 6
Acts on the stopper surface 70 of the stopper 7 in the thrust direction. The force in the thrust direction is applied to the ball 6 via the contact portion (point) between the stopper surface 70 and the ball 6.
At the same time as a working force in the tube axis direction of the raw tube 1, and at the same time as a working force in the tube axis direction on the ball 6 via a contact portion (point) between the inner peripheral surface of the working head 4 and the ball 6. Works.

As shown in FIG. 2A in an enlarged manner, FIG.
(B), the angle of the taper of the stopper surface 70 with respect to the pipe axis is opposite to and larger than the angle of the taper of the inner peripheral surface 40 of the processing head with respect to the pipe axis. Therefore, the contact portion between each ball 6 and the stopper surface 70 is located outside the orbit around the center of the ball and on the downstream side in the drawing direction with respect to the orbit. Is located outside the orbit and upstream of the orbit in the drawing direction. The distance between the contact portion between each ball 6 and the stopper surface 70 and the tube axis of the raw tube 1 is larger than the distance between the contact portion between each ball 6 and the inner peripheral surface 40 of the processing head and the tube axis of the raw tube 1. Is also small. Accordingly, a processing force is applied to each ball 6 in the axial direction of the raw tube 1 from two different positions outside the orbit around the ball center and in two directions before and after the drawing direction with reference to the orbit. The working position of the processing force acting from these two different positions on the ball 6 is
At different distances from the tube axis. That is, FIG.
In the embodiment shown in the drawings, a processing force in the axial direction acts on the processing head inner peripheral surface 40 and the stopper surface 70 at two locations, whereas in the conventional example (B), the processing head inner peripheral surface is shown in FIG. 40
A machining force is acting from only one location in the axial direction.

According to the manufacturing method of this embodiment, the pipe 1
In the process of pressing the peripheral surface of the base tube 1 against the grooved plug 5 using the pulling force of the above, the pulling direction of each ball 6 with respect to the outer side of the revolving orbit of the ball center and the revolving orbit as a reference. The working force in the tube axis direction of the raw tube 1 is applied from different positions in the two directions before and after, and the working position of the working force applied from the different positions in the two directions on the ball 6 is changed from the tube axis of the raw tube 1. Since the distance is different, the orbit of the ball 6 is more stable, and as a result, even if the number of revolutions of the ball (the number of rotations of the processing head) is increased, the tube is less likely to be twisted. . Therefore, the inner grooved pipe can be manufactured at a higher speed.

Manufacturing Experiment Under the following manufacturing conditions, an inner grooved tube was manufactured by the manufacturing method according to the present invention and the manufacturing method according to the comparative example. In the example of the present invention, the grooved portion uses an apparatus having a form as shown in FIG. 2A, and the taper angle θ1 of the stopper surface 70 with respect to the radial direction is changed as shown in Table 1, so that the inner grooved pipe is formed. In the comparative example, the grooved portion has an apparatus as shown in FIG. 2B (the ball retainer is not shown).
The inner grooved pipe was manufactured by changing the taper angle θ2 of the stopper surface 80 with respect to the radial direction as shown in Table 1. Manufacturing conditions Raw tube: outer diameter = 12.7 mm, wall thickness = 0.40 mm, material = copper tube Grooved plug: outer diameter = 10 mm, number of grooves = 60, torsion angle of groove center axis = 25 °, groove depth Length = 0.26mm, groove bottom angle = 2
0 ° Ball: Outer diameter = 12mm, Number of arrangement = 4 at equal angle Processing head rotation direction: Rotate clockwise toward pull-out direction Taper angle of processing head inner peripheral surface to pipe axis: 2 °

In each of the examples, the machining pitch is set to 0.3 mm, 0.4 mm, and 0.5 mm, respectively, and the number of revolutions of the machining head is increased. The ratio is shown in Table 1 with the case of Comparative Example 1 as 1. In each comparative example, when the processing pitch is 0.5 mm, the processing head rotation speed at the time of occurrence of torsional deformation of the tube is set to 1, and when the processing pitch is equal to or less than the above, the processing head rotation speed at the time of occurrence of torsional deformation. The ratios are shown in parentheses in Table 1, respectively.

[0018]

[Table 1] (Ratio of rotational speed of processing head when torsion deformation of tube occurs)

As shown in Table 1, in each of the present invention examples, the number of revolutions of the processing head (the number of ball revolutions) at the time of occurrence of torsional deformation of the tube is larger than in each of the comparative examples. The machining speed has been improved.

[0020]

According to the method for manufacturing an inner grooved tube according to the present invention, in the process of pressing the peripheral surface of the raw tube 1 against the grooved plug 5 using the pulling force of the raw tube 1, Ball 6
On the other hand, a processing force in the tube axis direction of the raw tube 1 is applied from two different positions in two directions before and after the drawing direction on the basis of the orbit outside the orbit of the center of the ball. Since the working position of the machining force acting from the position on the ball 6 is configured so that the distance from the tube axis of the raw tube 1 is different, the orbit of the ball 6 is more stable, and as a result, the orbit of the ball 6 Number (number of rotations of processing head)
Even if is made larger, twist deformation of the tube is unlikely to occur.
Therefore, the inner grooved pipe can be manufactured at a higher speed.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a manufacturing apparatus for explaining an embodiment of a manufacturing method according to the present invention.

2A is a partially enlarged sectional view of a grooved portion of the apparatus of FIG. 1, and FIG. 2B is a partially enlarged view of an apparatus used in a conventional method for comparison with the operation of the apparatus in FIG. It is sectional drawing.

FIG. 3 is a partial sectional view of a manufacturing apparatus for explaining a conventional manufacturing method.

FIG. 4 is a partially enlarged cross-sectional view showing a state in which scouring has occurred at the root of a fin of the inner surface grooved tube.

[Explanation of symbols]

a Pulling direction P Working pitch θ1, θ2 Taper angle of stopper surface with respect to radial direction 1 Base tube 10 Inner surface groove 1a Inner surface grooved tube 2 Floating die 3 Floating plug 4 Processing head 40 Inner peripheral surface 5 Groove plug 50 Groove 51 plug Rod 6 Ball 60 Ball retainer 7, 8 Stopper 70, 80 Stopper surface 71, 81 Bearing

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Sumitomo Tetsuya 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. F-term (reference) 4E028 HA02 4E096 EA17 FA04

Claims (2)

[Claims] 1. A metal tube 1 into which a grooved plug 5 having a large number of grooves 50 parallel or spiral to an axis on a peripheral surface is rotatably inserted, while pulling out the metal tube 1. The plurality of balls 6 arranged at predetermined intervals in the radial direction so as to revolve around the tube axis of the tube 1 at the position of the attached plug 5 and revolve around the tube axis using the pulling force of the tube 1. In the process of pressing the peripheral surface of the raw tube 1 against the grooved plug 5, each ball 6 is positioned outside the revolving orbit formed by the center of the ball and before and after in the drawing direction with respect to the revolving orbit. The working force in the tube axis direction of the raw tube 1 is applied from different positions in the direction, and the working position of the working force acting from the two different positions on the ball 6 varies the distance of the raw tube 1 from the tube axis. Of internally grooved pipes Construction method. 2. A conical surface formed in the processing head 4 and diverging at a gentle angle toward the downstream side in the drawing direction, wherein an outer peripheral portion of each ball 6 from a revolving orbit formed by the center of the ball is formed. An annular stopper having an inner peripheral surface 40 and a stopper surface 70 which is installed in the processing head 4 so as not to rotate integrally with the processing head 4 and against which each ball 6 abuts when the raw tube 1 is pulled out. 7 and the stopper surface 70.
The method for manufacturing an inner grooved pipe according to claim 1, wherein the groove is formed in a conical shape that widens at an acute angle toward the upstream side in the drawing direction.