JPH0796125B2 - Method and device for forming inner groove on metal pipe - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to the manufacture of a metal tube with an inner groove, and particularly to an inner groove of a metal tube suitable for a heat transfer tube of a heat exchanger such as a refrigerator after air conditioning. Processing method and device.

(Prior Art) Copper used for heat transfer tubes of heat exchangers such as air conditioners and refrigerators,
As a metal tube made of aluminum or the like, a tube having inner grooves of various shapes is required.

As a method for manufacturing such an inner grooved tube, there has been hitherto been disclosed in JP-A-54
-37059, as disclosed in JP-A-55-103215, etc., forming a groove on the inner surface while reducing the diameter of the processed metal pipe,
There is a rolling drawing method as one of the so-called reduced tube type grooved processing methods.

In this rolling drawing method, as shown in FIG. 3, the metal tube 1 is pressed from the outside by the hole die 2 and the floating plug 3 while holding the tip of the metal tube 1 with a chuck and drawing it out to reduce the diameter. Then, the inner surface of the metal tube 1 is pressed against the grooved plug 5 which is mounted in the tube in advance and rotatably connected by the die rod 8 by the rolling rolls or rolling balls 4 arranged on the outer periphery of the metal tube 1. The groove 6 is formed on the inner surface of the pipe, and then the diameter of the metal pipe is adjusted by the diameter adjusting die 7.

However, with such a method, when the inner surface grooving of a small diameter thick metal pipe such as a copper pipe with an outer diameter of 9.52 mm and a wall thickness of 0.50 mm is performed at high speed, a large amount of pipe meat is drawn in the metal pipe drawing direction It was difficult to move and get regular dimensions. Therefore, in order to solve this problem, a method has been proposed in which the relationship between the outer diameters of the working sphere and the metal tube in contact with the working sphere is regulated (Japanese Patent Laid-Open No. 62-292215).
issue).

(Problems to be Solved by the Invention) Generally, in the case of the inner surface grooved working apparatus using the working sphere as described above, there are the following phenomena.

That is, the metal tube whose diameter has been reduced by the first die (hole die) is pressed by a plurality of processing balls on the upper portion of the rotatable grooved plug to form the inner surface groove. In this case, the surface of the grooved metal pipe is rippled by the processing sphere, but the ripple is flattened by the second die (diameter adjusting die).

However, if the diameter of the processed sphere is smaller than the diameter of the metal pipe of the groove forming portion, the material tends to flow in the drawing direction rather than in the fin forming direction when the peak angle is small and the groove is deep. Therefore, in order to sufficiently form the fins, the work becomes a strong work, the hardening is great, and the second die cannot sufficiently flatten the work. If the outer surface of the pipe has irregularities, when the metal pipe is inserted into the fin and expanded, the friction between the fin and the metal pipe causes
The fins are displaced with each other, the fin interval is not constant, and the heat exchanging ability is reduced.

However, in the proposal of Japanese Patent Laid-Open No. 62-292215, the relationship between the outer diameter of the working sphere and the metal tube in contact with the working sphere is regulated, and the diameter (d) of the working sphere with respect to the outer diameter (D) of the metal tube. The ratio d / D value of 1.74 to 1.406 is set, but in the case of the processing method under such conditions, there are the following problems.

There is a large ripple due to the processed sphere, and it is necessary to reduce the drawing speed or to increase the processing rate with the diameter adjusting die in order to make the surface smooth. In the former case, the productivity is impaired, and in the latter case, the total processing rate is high, and it is difficult to form a fin having a peak height of 0.15 mm or more and a crest angle of 45 ° or less.

It is difficult to form fins with a large thickness reduction ratio of material and product and a peak height of 0.15 mm or more and a crest angle of 45 ° or less, but if this is forcibly formed, the second die (former The effect of adjusting the diameter with a diameter die and the effect of smoothing the surface are diminished.

The present invention has been made to solve the above-mentioned problems of the prior art, without reducing the productivity, there is little unevenness on the outer surface of the pipe, the peak height is 0.15 mm or more, and the peak angle is 45 ° or less. It is an object of the present invention to provide a metal pipe inner surface grooved processing method capable of processing at a low processing rate even with such a small difficult-to-machine inner surface groove shape.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present inventor machined a difficult-to-machine inner surface groove shape having a large peak height and a small peak angle in such an inner surface grooved machining method. Therefore, as a result of comprehensively researching various processing conditions in consideration of the condition of the outer surface of the pipe, a new processing condition could be found here.

That is, according to the present invention, in short, the diameter of the metal tube is reduced by means of working in cooperation with the floating plug, and then the plurality of spheres supported by the retaining ring and the tie rod behind the floating plug are rotated. The inner surface of the metal pipe is grooved by a grooved plug that is connected as much as possible, and further the inner diameter of the metal pipe is adjusted by a diameter adjusting die. It is characterized in that the diameter (d) of the sphere is within a range satisfying the ratio d / D value: 1.451 to 2.076 with respect to the outer diameter (D) of the metal tube.

Further, in the method, the feed length L of the metal tube per revolution of the sphere is in the range of 0.5 to 1.5 mm, or the outer diameter reduction rate of the sizing die is 65 to 85%. It is characterized by.

The present invention will be described in more detail below.

(Operation) First, in the inner surface grooved processing method of the present invention, it is basically based on the restriction of the diameter of the processed sphere from the relationship between the processing of the inner surface groove having a difficult-to-machine shape and the external surface condition of the pipe. is there.

That is, in the method according to the above-mentioned proposal (Japanese Patent Laid-Open No. 62-292215), the relationship between the outer diameters of the working sphere and the metal tube in contact with the working sphere is
Ratio of diameter (d) of processed sphere to outer diameter (D) of metal tube
By restricting the d / D value to be 1.174 to 1.406, it is intended to enable the inner surface grooving of thin and thick metal pipes. However, under these conditions, even if simple groove shape processing is possible, in the case of difficult-to-process inner surface groove shape with large peak height and small peak angle,
Unevenness occurs on the outer surface of the tube, making it difficult to obtain a high-quality product. Therefore, in the present invention, in order to enable the processing of the inner surface groove shape, which is difficult to process, while obtaining a good outer surface quality of the tube, the spherical diameter is regulated in relation to the outer surface state of the tube. Of.

It has been found that the following problems are encountered in the case of such difficult-to-work inner groove processing.

That is, if the number of processing balls and other processing conditions are the same, the larger the spherical diameter is, and the smaller the feed length per revolution of the processing ball is, the more the surface irregularities are geometrically apparent. Be improved. However, there is a restriction that neither can be infinite.

In the former case, as the sphere diameter is increased, the number of machined spheres decreases, and the feed rate per revolution of the machined sphere increases. Therefore, the merit of increasing the spherical diameter cannot be obtained, and the unevenness of the surface becomes large. Therefore, in order to reduce the feed length per revolution of the machined ball and increase the drawing speed, it is sufficient to increase the number of rotations of the retaining ring that orbits the machined ball. The entire tool is large and heavy, making it unsuitable for high speed rotation.

Therefore, the inventor of the present invention, in order to find a condition that can reduce the unevenness of the outer surface of the tube even when the diameter of the processing sphere is increased,
First, the relationship between the sphere diameter (diameter d) of the processed sphere and the amount of metal thinning was examined using the ratio d / D value to the metal pipe outer diameter (D) as an index. As a result, as shown in FIG. 1, it can be seen that the larger the d / D value, the smaller the amount of thinning. In a shape with a small peak angle and a high fin height, a processing rate for forming a groove becomes large, and thus a large d / D value is preferable. Further, by utilizing the fact that the amount of wall thickness reduction changes depending on the d / D value, it is possible to unify materials whose material dimensions were different for each shape.

Therefore, in the present invention, the diameter (d) of the sphere is compared with the outer diameter (D) of the metal tube reduced by the floating plug.
Are within the range satisfying the ratio d / D value: 1.451 to 2.076.

Next, when the size of the processed sphere is regulated as described above, there may occur a case where the grooved plug may not rotate properly or the condition of the outer surface of the tube may be unfavorable. It is preferable to control the feed length of the metal tube or the diameter reduction ratio of the diameter adjusting die.

That is, the grooved plug rotates by the reaction force when the material to be drawn fills the groove of the grooved plug. Therefore,
The greater the drawing speed, the greater the force to rotate the grooved plug. On the contrary, if the feed length per revolution of the processed sphere is too small, the grooved plug may be defectively rotated. Therefore, when the conditions for keeping the condition of the outer surface of the tube in good condition without causing the rotation failure of the grooved plug were investigated, the results shown in FIG. 2 were obtained.

FIG. 2 is a view showing the relationship between the feed length (L) per revolution of the processed ball and the roughness (μmRa) of the outer surface, and the feed length (L) per revolution of the processed ball is small. The larger the ratio d / D, and the larger the diameter reduction ratio (α) in the diameter adjusting die, the smaller the surface roughness. Therefore, the feed length (L) per revolution of the processed sphere is preferably in the range of 0.5 to 1.5 mm.

It should be noted that the larger the diameter reduction ratio (α) with the diameter adjusting die, the smoother the surface irregularities, but the higher the total processing rate,
It is difficult to form a deep groove with a small peak angle. Further, the twist angle before and after the diameter adjusting die changes.
The twist angle becomes smaller after the sizing die. On the other hand, the twist angle of the grooved plug is restricted in terms of processing, and a large twist angle cannot be obtained. Further, the larger the twist angle, the more difficult the grooved plug is to rotate in the groove forming portion. Therefore, the diameter reduction ratio (α) in the diameter adjusting die is preferably in the range of 65 to 85%, more preferably about 75%.

By the above method, it is possible to process a difficult-to-machine inner surface groove shape with less unevenness on the outer surface of the pipe, but it is needless to say that even in the case of inner surface grooves of other shapes and dimensions, it can be processed in the same good outer surface condition. . Further, the inner surface grooved processing device is not limited to the so-called contracted tube rolling type shown in FIG. 3, but a so-called expanded tube rolling type (eg, JP-A-61-266121) can also be used. It is also possible to use various modifications.

Next, examples of the present invention will be described.

(Example) Using the apparatus shown in FIG. 3, a copper tube having an inner groove having the following shape and dimensions was manufactured under the conditions shown in Table 1. A rolling ball was used as the processing ball.

Groove shape dimensions Outer diameter: 9.52 mm Bottom wall thickness: 0.30 mm Groove angle: 50 ° Groove number: 60 Groove depth: 0.2 mm When the outer surface roughness of the obtained inner grooved pipe was examined, the results are shown in the same table. As shown, there were few irregularities and the surface condition was good.

(Effect of the Invention) As described in detail above, according to the present invention, the peak height is 0.15 mm.
As described above, even in the case of the inner surface groove processing having a difficult-to-process shape such that the crest angle is 45 ° or less, it is possible to reduce the unevenness on the outer surface of the pipe without reducing the productivity. Further, by changing the diameter of the processed sphere relatively, it is possible to unify the specifications of the material without changing the material size for the inner surface grooves of various shapes.

[Brief description of drawings]

Fig. 1 shows the relationship between the d / D value and the amount of wall thinning, and Fig. 2 shows the relationship between the feed length (L) per revolution of the processed ball (rolled ball) and the outer surface roughness (μmRa). FIG. 3 and FIG. 3 are views showing an example of the inner surface grooved processing apparatus. DESCRIPTION OF SYMBOLS 1 ... Metal tube, 2 ... Hole die, 3 ... Floating plug, 4 ... Processing ball (rolling roll or rolling ball), 5 ... Groove plug, 6 ... Inner surface groove, 7 ... Diameter adjusting die, 8 ... Tie rod.

Claims (6)

[Claims] Claim: What is claimed is: 1. A metal tube is reduced in diameter by means of working in cooperation with a floating plug, and is then rotatably connected to a plurality of spheres supported by a retaining ring by a tie rod behind the floating plug. A grooved plug formed on the inner surface of the metal pipe, and a metal pipe inner surface groove forming apparatus for adjusting the diameter of the metal pipe with a diameter adjusting die. An inner surface grooving device for a metal pipe, wherein the diameter (d) of the sphere is within a range satisfying the ratio d / D value: 1.451 to 2.076 with respect to the diameter (D). 2. The apparatus according to claim 1, wherein the metal pipe feed length per revolution of the ball is in the range of 0.5 to 1.5 mm. 3. The outer diameter reduction rate of the diameter adjusting die is 65 to 85%.
The device according to claim 1 or 2. 4. A metal tube is reduced in diameter by means of working in cooperation with a floating plug, and is then rotatably connected to a plurality of spheres supported by a retaining ring by a tie rod behind the floating plug. In the groove forming method for a metal pipe, wherein the inner surface of the metal pipe is grooved by the grooved plug and the metal pipe is further grooved by a diameter adjusting die. Ratio of diameter (d) of the sphere to diameter (D) d /
A method for forming a groove on an inner surface of a metal pipe, characterized in that a D value satisfies 1.451 to 2.076. 5. The method according to claim 4, wherein the metal pipe feed length per revolution of the sphere is in the range of 0.5 to 1.5 mm. 6. The method according to claim 4, wherein the outer diameter reduction rate of the diameter adjusting die is 65 to 85%.