JPH11713A - Manufacturing method of heat transfer tube with inner groove - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a heat transfer tube with which a heat exchanger having excellent heat transfer characteristics is obtained because deep grooves are uniformly formed, the tube is excellent in heat transfer characteristics and its expansion is excellently executed. SOLUTION: In a manufacturing method of the heat transfer tube having grooved inside surface including the stage where many grooves are formed on the surface of a metallic band plate which is delivered in a fixed direction with a combined grooving roll 30 which is composed by mounting plural grooving rolls 32, 33, 34 on the peripheral surfaces of which many grooves are formed in the coaxial direction, stage where the band plate is formed into a tubular body by making the grooved surface of the metallic band plate inside and successively rounding the band plate in the width direction and stage where the butt end-faces of the tubular body are welded, the ratio M/L of the width M of the metallic band plate, which is rolled with the grooving rolls 32, 34 which are situated in the end parts of the combined grooving roll 30, to the entire width L of the grooved part is taken as <1/7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a heat transfer tube with an inner groove used in a heat exchanger of a refrigerating air conditioner such as an air conditioner.

[0002]

2. Description of the Related Art A heat transfer tube for a heat exchanger used in an air conditioner or the like has conventionally used a heat transfer tube having a smooth inner surface. Has become widely used. Since the flow of the refrigerant flowing through the inner surface groove is disturbed by the groove, the heat transfer characteristics of the inner surface grooved heat transfer tube are greatly improved as compared with the heat transfer tube having a smooth inner surface. Conventionally, this heat transfer tube with an inner groove is manufactured by pulling out the outer periphery of the smooth tube while pressing the outer periphery of the smooth tube with a rolling tool while holding the plug with the groove in the smooth tube, and forming the groove of the grooved plug on the inner surface of the smooth tube. Has been carried out by a drawing method of transferring

However, in this drawing method, grooves are formed only in one direction, so that the flow of the refrigerant becomes monotonous, and there is a limit in improving the heat transfer characteristics. Therefore, a groove is formed on one side of the metal strip by groove roll rolling, and the metal strip is rolled into a tubular body with the groove forming surface inside, and the butted end faces of the tubular body are welded and reduced in diameter through a die. (Japanese Patent Application Laid-Open No. 4-158193). In this rolling welding method, as shown in FIGS. 6 (a) and 6 (b), four or six grooved rolls 22 each having the same width are rolled by grooved rolls 20, each of which is a metal strip. A plurality of grooves having different directions are formed in the plate, and in the obtained heat transfer tube, the flow of the refrigerant in the tube is complicatedly disturbed, and the heat transfer characteristics are improved. Further, it is required to form a groove deeper for higher heat transfer characteristics. Incidentally, flat portions are formed at both ends of the metal strip after the formation of the groove, and the flat portions are formed at the bottom thickness of the groove forming portion so that welding of the butted end faces of the tubular body is performed stably. (See Japanese Patent Application Laid-Open Nos. Hei 6-137778 and Hei 4-157636). For this reason, the flat portion has a small amount of reduction, and the material easily escapes from the groove forming portion to the flat portion during the groove roll rolling. As shown in FIG. 7, the groove depth (fin height) near the flat portion is reduced. Fluctuation (variation) is likely to occur. This tendency is intensified as the depth of the groove is increased. As a result, there is a problem that the heat transfer characteristic of the heat transfer tube is reduced and the effect of the deep groove cannot be sufficiently obtained.
In addition, heat transfer tubes with such large fluctuations in groove depth cannot be uniformly expanded in the heat exchanger assembly process in which the heat transfer tubes are inserted into the holes in the aluminum fins and expanded and joined. A gap is generated between the heat transfer tubes and the adhesion between the heat transfer tubes and the aluminum fins is reduced (poor bonding occurs). As a result, the heat transfer characteristics of the heat exchanger deteriorate. Therefore, the present inventors have conducted intensive studies to solve the above-mentioned problems, and found that the escape of the material to the flat portion can be suppressed by reducing the width of the grooved rolls at both ends of the grooved combination roll. And further advanced the research to complete the present invention.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat transfer tube with an inner groove which has a deep groove, a small variation in groove depth (fin height), excellent heat transfer characteristics, and good expansion. It is to provide a manufacturing method.

[0005]

According to the first aspect of the present invention,
Forming a plurality of grooves by a grooved combination roll formed by attaching a plurality of grooved rolls having a large number of grooves formed on a peripheral surface thereof to a surface of a metal strip which is unreeled in a fixed direction; A step of forming a strip into a tubular body by successively rolling the strip in the width direction with the groove forming surface inside, and a step of welding a butt end face of the tubular body, wherein the grooved heat transfer tube includes: An inner groove having a ratio M / L of a width M of a metal strip rolled by a grooved roll positioned at an end of a combination roll to a total width L of a groove forming portion is less than 1/7. This is a method for manufacturing a heat transfer tube.

The invention according to claim 2 is characterized in that a projection, a groove, or a projection and a groove are formed between a plurality of grooved rolls constituting the grooved combination roll.
It is a manufacturing method of the heat transfer tube with an inner surface groove as described in the above.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method for determining a ratio M / L of a width M of a metal strip rolled by grooved rolls located at both ends of a grooved combination roll and a total width L of a groove forming portion. By reducing the size, the escape of the material to the flat part during groove rolling is suppressed,
Thus, it is possible to manufacture a heat transfer tube with an inner groove having a deep groove and a uniform groove depth (fin height). The ratio M
The reason why the material is prevented from escaping to the flat part by reducing / L is that the width of the grooved roll at the end becomes narrow,
It is considered that the pressure generated during rolling to move the material to the flat end is reduced. In the present invention, the ratio M / L
Has been limited to less than 1/7 based on many experiments.

According to the present invention, by forming projections, grooves, or projections and grooves between a plurality of grooved rolls constituting the grooved combination roll, the flow of material across the grooved rolls is more effectively suppressed. In addition, the fluctuation of the groove depth is further reduced.

[0009]

The present invention will be described below in detail with reference to examples. (Embodiment 1) As shown in FIG. 1, a copper strip (width 30 mm, thickness 0.5 mm) 10 fed out in a certain direction is replaced with an outer diameter 10.
Rolled by a two-stage rolling mill consisting of a combination roll 30 having a groove of 0 mm and a flat roll 31 having an outer diameter of 120 mm,
A groove 11 is formed on the surface of the tube 10, and the copper strip 10 after the formation of the groove is formed by the forming device 40 so that the grooved surface is on the inside and the tubular body 12 is formed.
The butt end face of this tubular body 12 is
Base tube (outer diameter 9.55mm) continuously welded with 50
The tube 13 was passed through a finishing die 60 to produce a heat transfer tube 14 with an inner groove (outer diameter: 9.53 mm).

[0010] The grooved combination roll 30 has a structure shown in FIG.
(B) A plurality of grooved rolls having spiral grooves formed in the circumferential direction shown in (A), (B), and a plurality of grooved rolls mounted in the coaxial direction were used. The grooved combination roll shown in FIG. 2A is composed of three grooved rolls 32, 33, and 34, and each grooved roll is mounted so that the direction of the spiral groove is opposite between adjacent rolls. ing. The width (M) of the grooved rolls 32, 34 at both ends is set so that the ratio M / L of the obtained metal strip becomes 1/8. (L) is the total width of the grooved roll portion of the grooved combination roll. The grooved combination roll shown in FIG. 2B is composed of six grooved rolls, and the grooved rolls at both ends are provided.
The width (M) of 32,34 is such that the ratio M / L of the obtained metal strip is 1
/ 10. In addition, a smooth surface disk (width 0.5 mm) between each grooved roll except the center
36 is sandwiched. The grooved combination roll shown in FIG. 2C is composed of eight grooved rolls having the same width (M), and the width (M) of the grooved rolls 32, 34 at both ends is determined by the ratio of the obtained metal strip. M / L is set to be 1/8. FIG.
In (a), (b), and (c), the grooved rolls 32, 34 on both the left and right sides are used.
Have the same width (M), but this is to facilitate the forming process, and does not necessarily have to be the same.

(Conventional Example 1) An inner grooved heat transfer tube (9.53 mm in outer diameter) was manufactured in the same manner as in Example 1 except that the grooved combination roll shown in FIGS. Manufactured.

FIG. 3 is an enlarged sectional view of each of the heat transfer tubes. This has 50 grooves 11 and a depth H of the grooves 11.
Is 0.28 mm and the thickness t of the bottom portion 15 of the groove 11 is 0.30 m
m, a high-performance shape in which the apex angle α of the fin 16 is 10 degrees.

The depth of the groove of each of the obtained heat transfer tubes was measured, and the distribution diagram is shown in FIG. Fig. 2 (a) (b)
The groove depths of the rolls produced by the grooved combination roll (c) are almost equal at the center and at the end. In particular, since the disc is sandwiched between the rolls, the flow of material is more reliably suppressed, and the difference between the groove depth at the center and the end is 0.02.
mm, which is extremely small. On the other hand, in each of the conventional products, the difference in groove depth between the center and the end was as large as 0.2 mm.

Embodiment 2 FIGS. 2 (a) and 2 (b) show a copper strip in the same manner as in Embodiment 1 except that the width M of the grooved roll at the end of the grooved combination roll is variously changed. A groove was formed in the groove. With respect to the obtained grooved copper strip, the variation width of the groove depth with respect to the ratio M / L was examined. The fluctuation width was indicated by the difference between the maximum groove depth and the minimum groove depth. FIG. 5 shows the results.

As is clear from FIG. 5, the ratio M / L is 1 /
If it is less than 7, the fluctuation width ΔH of the groove depth becomes small. In particular, by sandwiching a disk (width 0.5 mm) between the grooved rolls, the effect is further exhibited.

(Example 3) Using the groove-formed copper strip obtained in Example 2, a heat transfer tube was manufactured by the same method as in Example 1, and this heat transfer tube was expanded and joined to aluminum fins. Was examined. Table 1 shows the results. When the joint between the heat transfer tube and the aluminum fin did not form a gap with the aluminum fin, the joint was good, and when the gap was formed and the joint was insufficient, the mark was x.

[0017]

[Table 1]

As is clear from Table 1, all of the products of the present invention were successfully joined to aluminum fins. This is because the variation width ΔH of the groove depth was small. On the other hand, in the conventional product, a gap was formed between the heat transfer tube and the aluminum fin.

[0019]

As described above, the heat transfer tube manufactured according to the present invention has a deep groove formed at a uniform depth on the inner surface, and has excellent heat transfer characteristics of the tube itself and good expansion. And no gaps are formed between the fins and the aluminum fins, and the heat transfer characteristics after assembly in the heat exchanger are good. Therefore, an industrially remarkable effect is achieved.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a method for manufacturing a heat transfer tube with an inner groove according to the present invention.

FIG. 2A is a partial front view showing a first example of a grooved combination roll used in the manufacturing method of the present invention, FIG. 2B is a partial front view showing a second example, and FIG. It is a partial front view showing the example of No. 3.

FIG. 3 is an enlarged sectional view of a high-performance internal grooved pipe.

FIG. 4 is a distribution diagram of a groove depth of a copper strip having a groove formed therein.

FIG. 5 shows a variation width of a groove depth of a copper strip having a groove and a ratio M /
FIG. 6 is a diagram illustrating a relationship with L.

FIGS. 6A and 6B are partial front views of a conventional grooved combination roll.

FIG. 7 is a cross-sectional view of a conventional metal strip after grooves are formed.

[Explanation of symbols]

 10 ... Copper strip 11 ... Groove 12 ... Tubular body 13 ... Element tube 14 ... Heat transfer tube with inner groove 15 ... Bottom wall of groove 16 ... Fin 22 ... Roll with groove at end 30 ... Combination roll with groove 31 ... Flat Roll 32 ... Groove roll at end 34 ... Groove roll at end 33 ... Groove roll 36 ... Smooth disk 40 ... Forming device 50 ... High frequency welding machine 60 ... Dies

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiaki Hashizume 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd.

Claims (2)

[Claims] 1. A large number of grooves are formed by a grooved combination roll formed by mounting a plurality of grooved rolls having a large number of grooves formed on a peripheral surface thereof in a coaxial direction on a surface of a metal strip which is fed in a predetermined direction. A step of forming the metal strip plate into a tubular body by sequentially rolling in a width direction with the groove forming surface inside, and a step of welding a butt end face of the tubular body. Wherein the ratio M / L of the width M of the metal strip rolled by the grooved roll positioned at the end of the grooved combination roll to the total width L of the groove forming portion is less than 1/7. Method for manufacturing a heat transfer tube with an inner groove. 2. The heat transfer tube with an inner groove according to claim 1, wherein a protrusion, a groove, or a protrusion and a groove are formed between a plurality of grooved rolls constituting the grooved combination roll. Production method.