JP3780432B2 - Internal grooved tube processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for processing an internally grooved tube used in air-cooled heat exchangers such as domestic and commercial air conditioners, and more particularly to an internally grooved tube that can efficiently and easily form a groove on the tube inner surface. It relates to a processing method.
[0002]
[Prior art]
The condenser of the air-cooled heat exchanger uses an internally grooved tube in which a spiral groove is formed on the tube inner surface to improve heat transfer efficiency. FIG. 3 is a sectional view in the tube axis direction showing a processing device for an internally grooved tube (Japanese Patent Laid-Open No. 63-309321). As shown in FIG. 3, a floating plug 4 is inserted into the raw tube 3. The floating plug 4 has a substantially truncated cone shape in which the outer diameter on the tube supply side is slightly smaller than the inner diameter of the raw tube 3 and the outer diameter on the tube drawing side is smaller than that on the tube supply side. A holding die 5 for reducing the diameter of the pipe 3 together with the floating plug 4 is disposed on the outer surface of the pipe 3 at a position aligned with the floating plug 4. Further, a substantially cylindrical grooved plug 2 is connected to the floating plug 4 via a connecting shaft 6. The grooved plug 2 is formed with a groove having a shape to be formed on the inner peripheral surface of the raw tube 3 on the peripheral surface. Furthermore, the grooved plug 2 can freely rotate about the connecting shaft 8. A plurality of rolling balls 1 are arranged on the outer surface of the raw tube 3 at a position aligned with the grooved plug 2 so as to be rotatable in the tube circumferential direction about the tube axis. Further, on the downstream side of the rolling ball 1 in the tube drawing direction, a finishing die 7 for reducing the outer diameter of the raw tube 3 having fins formed on the inner surface to a predetermined size is provided in contact with the raw tube 1. Yes. FIG. 4 is a cross-sectional view perpendicular to the tube axis direction showing a grooved plug and a rolling ball in a conventional processing method. As shown in FIG. 4, the rotation direction 9 b of the rolling ball 1 disposed on the outer surface of the tube is opposite to the rotation direction 8 of the grooved plug 2 provided on the inner surface of the tube.
[0003]
A conventional processing method using the processing device for an internally grooved tube configured as described above is as follows. First, the tube 3 is reduced by the floating plug 4 and the holding die 5. The tube 3 that has been subjected to the tube contraction is contracted by the rolling ball 1 and is pressed against the grooved plug 2 disposed inside the tube 3 by receiving the rolling force of the rolling ball 1. Is done. The grooved plug 2 is connected to the floating plug 4 through the connecting shaft 6, and the floating plug 4 is aligned with the holding die 5 by the frictional force generated by pulling out the raw tube 3 and the drag from the holding die 5. Therefore, the grooved plug 2 is also stopped at a position where it is aligned with the rolling ball 1. Therefore, when the rolling ball 1 is brought into rolling contact with the outer peripheral surface of the raw tube 3 and rotationally driven in the circumferential direction, fins are formed on the inner peripheral surface of the raw tube 3 by the cooperative action with the grooved plug 2. Further, the base tube 3 having fins formed on the inner surface is subjected to contraction processing by a finishing die 7 to produce an inner grooved tube having a desired outer diameter.
[0004]
In this internally grooved tube, in order to improve the heat transfer efficiency, a deep groove that deepens the groove on the inner surface is desired.
[0005]
[Problems to be solved by the invention]
However, when trying to process a high fin on a long material having a length of, for example, 4000 m or more using a conventional processing method, the groove of the grooved plug is likely to be chipped. For this reason, it is difficult to manufacture an internally grooved tube with high heat transfer efficiency that has been finned by a conventional method.
[0006]
The present invention has been made in view of such a problem, and provides a method for processing an internally grooved tube capable of stably forming a high fin in a raw tube without chipping the groove of the grooved plug. It is in.
[0007]
[Means for Solving the Problems]
The inner grooved tube is processed by sequentially reducing the diameter of the element pipe with a holding die and a plurality of rolling balls, and a floating plug in the element pipe and the floating plug can be relatively rotated via a rod. A grooved plug connected thereto, the floating plug is engaged with the holding die, the grooved plug is positioned at the rolling ball placement position, and the rolling tube is used to insert the element tube into the grooved portion. In the processing method of the inner surface grooved tube in which the groove shape of the grooved plug is transferred to the inner surface of the raw tube by pressing against the plug, the rolling ball and the grooved plug rotate in the same direction with respect to the raw tube. It is characterized by making it.
[0008]
In the present invention, since the rolling ball disposed on the outer surface of the tube and the grooved plug provided on the inner surface of the tube rotate in the same direction, it takes a long time for the rolling ball to pass through the groove of the grooved plug. Is possible. For this reason, the groove of the grooved plug can be made difficult to chip, and a high fin can be formed on the inner surface of the tube.
[0009]
Moreover, in the processing method of the said inner surface grooved pipe | tube, the process of diameter-reducing the outer surface of the said elementary pipe to a predetermined dimension with a finishing die can be provided.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The internal grooved tube processing apparatus used in the method of this embodiment is the same as that shown in FIG. 3, and the floating plug, connecting shaft, grooved plug, holding die, rolling roll, and finishing die are conventional processing. It is provided with the same positional relationship as the apparatus. In other words, a substantially frustoconical floating plug is inserted inside the raw tube, and a holding die for reducing the diameter of the raw tube together with the floating plug is disposed on the outer surface of the raw tube at a position aligned with the floating plug. ing. Further, the floating plug is connected with a grooved plug in which a groove is formed in a substantially cylindrical peripheral surface via a connecting shaft. Further, the grooved plug can freely rotate about the connecting shaft. A plurality of rolling balls are arranged on the outer surface of the raw tube at a position aligned with the grooved plug so as to be rotatable in the tube circumferential direction about the tube axis. Further, a finishing die for reducing the outer diameter of the raw tube to a predetermined dimension is provided in contact with the raw tube on the tube drawing side separated from the rolling ball by a predetermined length.
[0011]
As shown in FIG. 1, the method of the present embodiment is different from the conventional method in that a plurality of rolling balls 1 disposed on the outer surface of the tube and a grooved plug 2 provided on the inner surface of the tube are provided in the raw tube 3. It is to rotate in the same direction.
[0012]
[Means for Solving the Problems]
According to the method of processing an internally grooved pipe according to the present invention, the base pipe is sequentially reduced in diameter by a holding die and a plurality of rolling balls, and a floating plug is placed in the base pipe and a relative to the floating plug via a rod. A grooved plug that is rotatably connected to the holding die, and the grooved plug is positioned at the position where the rolling ball is disposed. In the method of processing an inner surface grooved tube by transferring the groove shape of the grooved plug to the inner surface of the raw tube by pressing the grooved plug against the grooved plug, the rolling ball and the grooved plug are is rotated in the same direction, the processing unit drawing speed Va (m / min), when the relative velocity with respect to the compaction ball of the grooved plug was Vb (m / min), Vb / Va It characterized in that 32 to a 38.
[0013]
If the rotation direction 9b of the rolling ball 1 and the rotation direction 8 of the grooved plug 2 are opposite to each other as in the prior art, the time required for the rolling ball 1 to pass through the groove of the grooved plug 2 is short. For this reason, the raw tube 3 is hard to be pressed against the grooved plug 2 and is strongly processed, so that the groove of the grooved plug 2 is likely to be chipped, and the fin height of the inner surface grooved tube is not desired. .
[0014]
However, in this embodiment, when the base tube 3 is pressed against the grooved plug 2 by the rolling ball 1, the rotation direction 9 a of the rolling ball 1 and the rotation direction 8 of the grooved plug 2 are matched. Therefore, the time for the rolling ball 1 to pass through the groove of the grooved plug 2 can be lengthened. For this reason, the raw tube 3 is sufficiently pressed against the grooved plug 2, and the groove of the grooved plug 2 is not easily chipped, and a high fin can be easily formed on the inner surface of the raw tube 3.
[0015]
【Example】
Next, an example of the present invention will be described in comparison with a comparative example in which the conditions before processing deviate from the scope of the claims.
[0016]
First, as Example 1, while changing the speed ratio Vb / Va (= K) between the processed part drawing speed Va (m / min) and the relative speed Vb (m / min) of the grooved plug to the rolling ball, An internally grooved tube was manufactured by making the rotation direction of the rolling ball coincide with the rotation direction of the grooved plug. As Comparative Example 2, an internally grooved tube was manufactured while changing the speed ratio K and rotating the rolling ball in the opposite direction to the rotating direction of the grooved plug. And the groove filling rate (%) of the inner surface grooved tube of Example 1 and Comparative Example 2 was measured. The groove filling rate is a forming rate of the fin height formed on the inner surface of the tube with respect to the groove depth of the groove plug. The result is shown in FIG. FIG. 2 is a graph showing the relationship between the speed ratio K on the horizontal axis and the groove filling rate on the vertical axis. In FIG. 2, □ indicates Example 1 and ■ indicates Comparative Example 2. As shown in FIG. 2, since Example 1 manufactures the internally grooved tube by the processing method according to the present invention, the groove filling is performed at a lower speed ratio as compared with Comparative Example 2 manufactured by the conventional method. The rate is high and the groove filling rate is excellent over a wide range.
[0017]
【The invention's effect】
As described above in detail, according to the present invention, when a raw tube is pressed against a grooved plug provided on the inner surface of a tube by a rolling ball disposed on the outer surface of the tube, a fin is formed on the inner surface of the tube. Since the rotation direction of the pressure ball and the rotation direction of the grooved plug coincide with each other, a high fin can be formed on the inner surface of the tube, and the chipping of the grooved plug can be prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view perpendicular to a tube axis direction showing a grooved plug and a rolling ball according to an embodiment of the present invention.
FIG. 2 is a graph showing a relationship of a groove filling rate to a speed ratio K.
FIG. 3 is a sectional view in the tube axis direction showing a processing device for an internally grooved tube.
FIG. 4 is a cross-sectional view perpendicular to the tube axis direction showing a conventional grooved plug and a rolling ball.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1; Rolling ball 2; Grooved plug 3; Base pipe 4; Floating plug 5; Holding die 6; Connecting shaft 7; Finishing dies 8, 9a, 9b;

Claims (2)

The base tube is successively reduced in diameter by a holding die and a plurality of rolling balls, and a floating plug and a grooved plug connected to the floating plug through a rod so as to be relatively rotatable are arranged in the base tube. Then, the floating plug is engaged with the holding die, the grooved plug is positioned at the rolling ball placement position, and the raw tube is pressed against the grooved plug by the rolling ball. In the method of processing an inner surface grooved tube in which the groove shape of the grooved plug is transferred to the inner surface of the inner surface, the rolling ball and the grooved plug are rotated in the same direction with respect to the raw tube , and the processing portion drawing speed is set to Va (m / min), when the relative velocity with respect to the compaction ball of the grooved plug was Vb (m / min), and wherein the Vb / Va is 32 to 38 Processing method of imposition grooved tube. 2. The method for processing an internally grooved tube according to claim 1, wherein after forming the groove, the outer surface of the raw tube is subjected to diameter reduction processing by a finishing die.

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