JP2000234890A - Air conditioner heat exchanger and method of manufacturing the same - Google Patents

Abstract

An object of the present invention is to provide an air-conditioning heat exchanger that is small and lightweight, has excellent heat exchange properties, and can significantly reduce manufacturing costs, and a method for manufacturing the same. is there. The gist of the present invention lies in the following two points. (1) In an air-conditioning heat exchanger using a gas such as air as a heat-exchange outer medium and using a liquid refrigerant as a heat-exchange inner medium, the air-conditioner heat exchanger has a plurality of pipes serving as flow paths for the liquid refrigerant. Part, an intermediate fin part provided between the plurality of tubular parts, and an outer edge fin installed on the outer peripheral surface of the tubular part located on the outermost side of the plurality of tubular parts. Heat exchanger for air conditioning. (2) Two metal plates having grooves formed on one surface are set in a pressing device such that the grooved surfaces face each other, and then the plurality of tubular portions and the plurality of metal plates are formed by the pressing device. An intermediate fin portion between the tubular portions, and a heat exchanger for air conditioning characterized in that press forming is performed so that outer edge fins are formed on the outer peripheral surface of the outermost tubular portion among the plurality of tubular portions. Manufacturing method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat exchanger for air conditioning and a method for manufacturing the same.

[0002]

2. Description of the Related Art Air conditioning equipment has become an indispensable facility in recent buildings.

[0003] On the other hand, this type of air conditioner has been strongly demanded for energy saving and efficiency from the viewpoint of protection of ozone holes and prevention of global warming. For this reason,
There is also a strong demand for heat exchangers used in air conditioners to have an increased heat transfer area, more efficient heat exchange airflow, more compact size, and the like.

FIG. 15 is an explanatory perspective view showing a main part of a conventional fin tube type heat exchanger used for an air conditioner.

[0005] In Fig. 15, reference numeral 20 denotes a conventional fin tube type heat exchanger, 21 denotes a conventional welded heat transfer tube with an inner groove,
Reference numeral 22 denotes a conventional plate fin, and 23 denotes an insertion hole.

As can be seen from FIG. 15, the conventional fin tube type heat exchanger 20 has a plurality of conventional heat transfer tubes 21 piped at predetermined intervals, and the plurality of conventional heat transfer tubes with internal grooves are provided. A plurality of plate fins 22 are attached to the outer periphery of the heat transfer tube 21 at predetermined intervals along the longitudinal direction.

FIG. 16 is a sectional view of the conventional welded heat transfer tube 21 with an inner groove used in FIG.

In FIG. 16, reference numeral 6 denotes an inner groove, 21 denotes a conventional heat transfer tube with an inner groove, and 24 denotes a tubular weld.

More specifically, the conventional welded heat transfer tube 21 with an inner groove is used.
Is a tube type internal grooved welded heat transfer tube with advanced internal groove processing.

This is because it is difficult to perform advanced internal grooving with a seamless heat transfer tube with internal grooves, while the internal grooved welded heat transfer tube 21 performs advanced grooving when flat.
Thereafter, the flat plate subjected to the advanced grooving process is formed into a tube to form the welded heat transfer tube 21 with the internal grooving, so that the advanced internal grooving process is easy. Here, the tubular welding portion 24 is performed by high frequency welding.

The surface of the conventional plate fin 22 used in FIG. 15 has been subjected to advanced groove processing and roughening processing.

The welding of the inner grooved heat transfer tube 21 and the plate fin 22 is performed by first inserting the inner grooved welded heat transfer tube 21 into the insertion hole 23 of the plate fin 22, and then inserting the plate fin 22. The diameter of the portion of the welded heat transfer tube 21 with an inner groove inserted into the hole 23 is increased, so that the outer peripheral surface of the welded heat transfer tube 21 with an inner groove is
The second through hole 23 is completely brought into contact with the inner peripheral surface.

[0013]

As described above, the conventional fin tube type heat exchanger is provided with an inner grooved welded heat transfer tube 21 having a high degree of inner groove processing and a high degree of groove processing and roughening. The use of the processed plate fins 22 is disadvantageous in that the manufacturing cost is high and the weight is large because a large number of plate fins 22 are used in order to measure high performance. Was.

Further, the joining between the outer peripheral surface of the inner grooved welded heat transfer tube 21 and the inner peripheral surface in the insertion hole 23 of the plate fin 22 is performed by expanding the inner grooved welded heat transfer tube 21.
In the manufacturing process, a diameter expanding operation is required, and furthermore, the obtained expanded diameter portion has a disadvantage that the thermal resistance is large and the heat exchange property is low.

The present invention has been made in view of such a point, and aims at solving the above-mentioned disadvantages of the prior art, being small and lightweight, having excellent heat exchange properties, and significantly increasing the manufacturing cost. An object of the present invention is to provide a heat exchanger for air conditioning and a method for manufacturing the same, which can be reduced to a minimum.

[0016]

The gist of the present invention lies in the following two points.

(1) In an air conditioning heat exchanger using a gas such as air as a heat exchange outside medium and using a liquid refrigerant as a heat exchange inside medium, the air conditioning heat exchanger serves as a flow passage for the liquid refrigerant. A plurality of tubular portions, an intermediate fin portion provided between the plurality of tubular portions, and an outer edge fin provided on an outer peripheral surface of a tubular portion located on the outermost side of the plurality of tubular portions. A heat exchanger for air conditioning characterized by the following.

(2) Two metal plates having grooves formed on one surface are set in a pressing device such that the grooved surfaces face each other, and then a plurality of tubular portions are formed by the pressing device. An intermediate fin portion between the plurality of tubular portions, and press forming such that outer edge fins are formed on the outer peripheral surface of the outermost tubular portion of the plurality of tubular portions, respectively. Manufacturing method of heat exchanger.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of an air conditioner heat exchanger and a method for manufacturing the same according to the present invention will be described with reference to the drawings.

(First Embodiment of the Air-Conditioning Heat Exchanger of the Present Invention)
FIG. 1 is a perspective view showing a first embodiment of an air conditioner heat exchanger according to the present invention.

In FIG. 1, reference numeral 1 denotes an air-conditioning heat exchanger according to the first embodiment of the present invention;
1 is an intermediate fin portion, 4-1 and 4-2 are outer edge fin junction portions, 5 is an intermediate fin junction portion, 6 is an inner surface groove, 7-1 and 7-
2 is a tubular part.

That is, the air conditioner heat exchanger 1 according to the first embodiment of the present invention is provided with an intermediate fin portion 3-1 at the intermediate portion thereof, and secondly, at the intermediate fin portion 3-1. Thirdly, tubular portions 7-1 and 7-2 are provided on both sides, respectively.
1, 2-2 are attached.

Here, the tubular portions 7-1 and 7-2 serve as refrigerant passages. The outer edge fins 2-1 and 2-2 and the intermediate fin 3-1 exchange heat with the air-conditioning heat exchanger 1 of the first embodiment of the present invention and air.

In the method for manufacturing the air conditioner heat exchanger 1 according to the first embodiment of the present invention, first, two metal flat plates having the same dimensions are prepared.

Next, a groove is formed on one surface of each of the two metal flat plates.

Next, the two metal flat plates whose grooves are formed on the surface are mounted on a half-tubular press, and then pressed to form a half-tubular body for a refrigerant flow path.

Next, the two intermediate products thus formed are mounted on a tubular press in a state where they face each other so that the tubular portions 7-1 and 7-2 can be formed, and then the press is operated. Outer fin portion 2-1, tubular portion 7
1, the intermediate fin portion 3-1, the tubular portion 7-2, and the outer edge fin portion 2-2 are formed.

Next, the obtained integrated air conditioning heat exchanger 2
The welded part of the two processed metal flat plates is locally welded.

Next, the joining portion of the intermediate fin portion 3-1 is spot-welded by a spot welding device.

(Second embodiment of the air-conditioning heat exchanger of the present invention)
FIG. 2 is a sectional explanatory view showing a second embodiment of the air conditioner heat exchanger of the present invention.

In FIG. 2, 2-1 and 2-2 are outer edge fins, 3-1 is an intermediate fin, 4-1 and 4-2 are outer edge fins, 5 is an intermediate fin and 7-1. , 7-2 are tubular parts, 10, 11, 12, 13 are open outer fins, 1
9 is a protruding fin.

That is, the feature of the second embodiment of the air conditioner heat exchanger of the present invention is that the outer edge fin portions 2-1, 2-2 are opened to provide outer edge fins 10, 11, 12, 13; Further, a plurality of protruding fins 19 are provided on the outer periphery of the tubular portions 7-1 and 7-2.

(Third Embodiment of Air-Conditioning Heat Exchanger of the Present Invention)
FIG. 3 is an explanatory sectional view showing a third embodiment of the air conditioner heat exchanger of the present invention.

In FIG. 3, reference numerals 2-1 and 2-2 denote outer edge fin portions, 3-1 and 3-2 and 3-3 and 3-4 denote intermediate fin portions, and 7-1, 7-2 and 7-3. , 7-4 and 7-5 are tubular portions.

That is, the feature of the third embodiment of the air-conditioning heat exchanger of the present invention is that the intermediate fin portions 3-1, 3-2, 3-3, 3
-4, and tubular portions 7-1, 7-2, 7-3, 7-4, 7-
5 are alternately arranged in series.

(Fourth Embodiment of the Air-Conditioning Heat Exchanger of the Present Invention)
FIG. 4 is an explanatory sectional view showing a fourth embodiment of the air conditioner heat exchanger of the present invention.

In FIG. 4, 2-1 and 2-2 are outer edge fin portions, 3-1 is an intermediate fin portion, and 8-1 and 8-2 are elliptical portions.

That is, a feature of the fourth embodiment of the air conditioner heat exchanger of the present invention is that elliptical portions 8-1 and 8-2 are provided.

(Fifth Embodiment of Air-Conditioning Heat Exchanger of the Present Invention)
FIG. 5 is an explanatory sectional view showing a fifth embodiment of the air conditioner heat exchanger of the present invention.

In FIG. 5, 2-1 and 2-2 are outer edge fin portions, 3-1 is an intermediate fin portion, and 9-1 and 9-2 are triangular portions.

That is, a feature of the fifth embodiment of the air conditioning heat exchanger of the present invention is that triangular portions 9-1 and 9-2 are provided.

FIG. 6 shows a modification of the fifth embodiment of the air conditioner heat exchanger of the present invention, in which these two sets are overlapped in the opposite direction.

(Sixth Embodiment of the Air-Conditioning Heat Exchanger of the Present Invention)
FIG. 7 is an explanatory sectional view showing a sixth embodiment of the air conditioner heat exchanger of the present invention.

In FIG. 7, 2-1 and 2-2 are outer fin portions, 3-1 and 3-2 are intermediate fin portions, and 7-1 and 7-2.
Is a tubular portion, and 18 is an intermediate tubular portion.

That is, a feature of the sixth embodiment of the air conditioner heat exchanger of the present invention is that an intermediate tubular portion 18 is provided. The intermediate tubular portion 18 can be used as an auxiliary tube for heat exchange. (Seventh Embodiment of Air-Conditioning Heat Exchanger of the Present Invention) FIG. 8 is a sectional explanatory view showing a seventh embodiment of the air-conditioning heat exchanger of the present invention.

In FIG. 8, 2-1 2-2, 2-3 are outer fin portions, 3-1 -3-2, 3-3 are intermediate fin portions, 7-1, 7-2, 7-3. Is a tubular part.

That is, the feature of the seventh embodiment of the air conditioner heat exchanger of the present invention resides in that the tubular portions 7-1, 7-2, 7-3 are branched not in series but in three directions. By doing so, the size is reduced.

(Eighth Embodiment of the Air-Conditioning Heat Exchanger of the Present Invention)
FIG. 9 is an explanatory sectional view showing an eighth embodiment of the air conditioner heat exchanger of the present invention.

In FIG. 9, 2-1 2-2, 2-3 are outer edge fin portions, 3-1 -3-2, 3-3 are intermediate fin portions, 7-1, 7-2, 7-3. Is a tubular portion, and 18 is an intermediate tubular portion.

That is, the eighth embodiment of the air-conditioning heat exchanger according to the present invention is characterized in that the tubular portions 7-1, 7-2, and 7-3 are branched not in series but in three directions, and the intermediate tubular portion 18 That is, By branching in three directions, compactness is achieved, and the intermediate tubular portion 18 can be used as an auxiliary tube for heat exchange.

(First Embodiment of Manufacturing Method of Air-Conditioning Heat Exchanger of the Present Invention) The air-conditioning heat exchanger of the first embodiment of the present invention shown in FIG. 1 is manufactured as follows.

(1) Preparation of Two Metal Flat Plates First, two metal flat plates having the same dimensions are prepared.

(2) Surface Processing of Two Metal Flat Plates Next, these two metal flat plates are formed by forming a groove on the whole surface on one side thereof, respectively, or forming tubular portions 7-1, 7
-2 is grooved only on the inner side, and the outer edge fin portion 2-1, the intermediate fin portion 3-1, and the outer edge fin portion 2-2 can be fitted when pressed after overlapping. As described above, a concave portion or a convex portion is formed on one metal plate, and a convex portion or a concave portion is formed on the other metal plate.

Here, the torsion angle of the inner surface groove 6 engraved in the tubular portion is desirably 0 degree from the point of fitting.

(3) Half-tubular pressing of a metal flat plate Next, the two flat metal plates thus processed are mounted on a half-tubular pressing machine and then pressed.

By this pressing, one metal flat plate on one side is divided into one side of the outer edge fin portion 2-1, one half side of the tubular portion 7-1, one side of the intermediate fin portion 3-1, and the tubular portion 7. -2, and one side of the outer edge fin portion 2-2 is molded.

The other metal flat plate is provided on the other side of the outer edge fin portion 2-1, the other half of the tubular portion 7-1, the other side of the intermediate fin portion 3-1 and the tubular portion 7-. 2 and the other side of the outer edge fin portion 2-2 are formed.

(4) Integrated press of two processed metal flat plates Next, two intermediate products formed in this way are put into a tubular part 7-
1, 2 are mounted on a tubular press in a state where they face each other so that they can be molded.

FIG. 10 is an explanatory sectional view showing a state in which two processed metal flat plates are mounted on a tubular press.

In FIG. 10, 2-1 and 2-2 are outer edge fin portions, 3-1 is an intermediate fin portion, 7-1 and 7-2 are tubular portions, and 14 is a press device.

Next, the press device 14 is operated to form the outer edge fin portion 2-1, the tubular portion 7-1, the intermediate fin portion 3-1, the tubular portion 7-2, and the outer edge fin portion 2-2. At this time, the outer edge fin portion 2-1, the intermediate fin 3-1, and the outer edge fin portion 2-2 of two processed metal flat plates whose one side is formed into a concave portion and the other side is formed into a convex portion are fitted by pressing.

FIG. 11 is a partially enlarged sectional explanatory view showing a fitting state of the intermediate fin portion.

In FIG. 11, 3-1 is an intermediate fin portion,
6 is an inner surface groove, 7-1 and 7-2 are tubular parts, and 5 is an intermediate fin joint part.

By this press, the two processed metal flat plates are integrated into an air conditioner heat exchanger.

(5) Local Welding of Integrated Air-Conditioning Heat Exchanger Next, the joint of the two processed metal flat plates of the obtained integrated air-conditioning heat exchanger is locally welded as shown in FIG. An air-conditioning heat exchanger 1 according to a first embodiment of the present invention is obtained.

FIG. 12 is an explanatory sectional view showing the welding state.

In FIG. 12, 2-2 is an outer edge fin portion,
3-1 is an intermediate fin portion, 7-2 is a tubular portion, 16 is a spot welding device, and 17 is a high-frequency welding device.

That is, the intermediate fin portion 3-1 is spot-welded by the spot welding device 16.

On the other hand, the outer edge fin portion 2-2 is entirely welded by the high frequency welding device 17. Of course, although not shown, the outer edge fin portion 2-1 is also entirely welded by the high frequency welding device 17.

Although not shown, the second to eighth embodiments of the air conditioner heat exchanger of the present invention are basically the same as the first embodiment of the method of manufacturing the air conditioner heat exchanger of the present invention. It can be manufactured by overlapping two processed metal flat plates.

For example, in the fifth embodiment of the air conditioner heat exchanger of the present invention shown in FIG. 5, one of two metal flat plates is subjected to surface processing, and the other one is subjected to surface processing and triangular portions. 9-1, 9-2
And then these two sheets are integrated.

In a modification of the fifth embodiment of the air conditioner heat exchanger of the present invention shown in FIG. 6, both of the two metal flat plates are subjected to surface processing and triangular portions 9-1 and 9-2. It is processed to make it, and then the processed two sheets are superimposed on each other in the opposite direction to obtain a double triangular tube type air conditioning heat exchanger.

(Evaporation and Cooling Operation of Conventional Air-Conditioning Heat Exchanger) First, referring to FIG.
The operation principle of cooling will be described.

FIG. 13 shows the evaporation of a conventional air conditioning heat exchanger.
It is sectional explanatory drawing which showed the operation | movement principle of cooling.

In FIG. 13, reference numeral 21 denotes a welded heat transfer tube with an inner groove, 22 denotes a plate fin, 25 denotes a refrigerant, 26 denotes air, 27 denotes a temperature drop straight line, and 28 denotes a flow direction of the refrigerant.

That is, in the conventional air-conditioning heat exchanger, the air 26 is cooled by the convective heat transfer of the plate fins 22, thereby lowering the temperature of the air 26. Next, the air 26 is supplied to the plate fins 22 and the welded heat transfer tubes 2 with inner grooves.
1, the temperature further decreases due to the thermal resistance of the material of the plate fin 22, and after reaching the inner surface of the inner grooved heat transfer tube 21, the temperature further decreases due to the evaporation of the refrigerant. That is, the temperature of the air 26 decreases as indicated by the temperature decrease line 27.

(Evaporation and Cooling Operation of Air-Conditioning Heat Exchanger of the Present Invention) Next, the principle of evaporation and cooling of the air-conditioning heat exchanger of the present invention will be described with reference to FIG.

FIG. 14 is an explanatory sectional view showing the principle of operation of evaporation and cooling of the heat exchanger for air conditioning according to the present invention.

In FIG. 14, 7-1 is a tubular portion, 25 is a refrigerant, 26 is air, 27 is a temperature drop straight line, and 28 is a flow direction of the refrigerant.

That is, in the air-conditioning heat exchanger of the present invention, there is no plate fin 22 as in the conventional air-conditioning heat exchanger, so that the material of the plate fin 22 has no thermal resistance. As described above, when the thermal resistance of the material of the plate fins 22 disappears, the required temperature difference between the air 26 and the refrigerant 25 becomes smaller, thereby improving the performance of the heat exchanger. That is, an increase in the amount of heat exchange at the same temperature difference can be measured.

In the embodiment of the present invention, the tubular portion 7-1, the elliptical portion 8-1, and the triangular portion 9-
1 and the like, but among these, the elliptical portion 8
-1 is most desirable in terms of heat exchange properties and the like. The shapes of these flow paths are appropriately determined depending on the amount of pressure loss on the refrigerant side and the like.

In the present invention, it is desirable to provide spot welding at a plurality of locations at an appropriate pitch in consideration of strength and the like.

In the present invention, the protruding plate fins 19
The size and number are appropriately determined so as to improve the heat transfer performance.

[0084]

The heat exchanger for air conditioning of the present invention and the method for producing the same have the following excellent effects and are industrially useful.

(1) The heat exchanger for air-conditioning and the method of manufacturing the same according to the present invention can omit the manufacturing process of the pipe, resulting in a remarkable improvement in productivity, a significant reduction in weight and a significant increase in manufacturing cost. A significant reduction can be achieved.

(2) In the method for manufacturing an air-conditioning heat exchanger of the present invention, the shape of the groove can be arbitrarily processed and the groove is manufactured by press fitting and welding. Therefore, the heat exchange property of the air-conditioning heat exchanger is designed. Can be made on the street.

(3) The air-conditioning heat exchanger of the present invention has low heat resistance and excellent heat exchange properties because there is no joint between the fin and the pipe.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of an air conditioner heat exchanger according to the present invention.

FIG. 2 is an explanatory sectional view showing a second embodiment of the air conditioner heat exchanger of the present invention.

FIG. 3 is an explanatory sectional view showing a third embodiment of the air conditioner heat exchanger of the present invention.

FIG. 4 is an explanatory sectional view showing a fourth embodiment of the air conditioner heat exchanger of the present invention.

FIG. 5 is an explanatory sectional view showing a fifth embodiment of the air conditioner heat exchanger of the present invention.

FIG. 6 shows a modification of the fifth embodiment of the air conditioner heat exchanger of the present invention.

FIG. 7 is an explanatory sectional view showing a sixth embodiment of the air conditioner heat exchanger of the present invention.

FIG. 8 is an explanatory sectional view showing a seventh embodiment of the air conditioner heat exchanger of the present invention.

FIG. 9 is an explanatory sectional view showing an eighth embodiment of the air conditioner heat exchanger of the present invention.

FIG. 10 is an explanatory cross-sectional view showing a state in which two processed metal flat plates are mounted on a tubular press device in the method for manufacturing an air conditioner heat exchanger of the present invention.

FIG. 11 is a partially enlarged cross-sectional explanatory view showing a fitting state of an intermediate fin portion in the method for manufacturing an air conditioner heat exchanger of the present invention.

FIG. 12 is an explanatory cross-sectional view showing a welding situation in the method for manufacturing an air-conditioning heat exchanger of the present invention.

FIG. 13 is an explanatory cross-sectional view showing the operation principle of evaporation and cooling of a conventional air conditioning heat exchanger.

FIG. 14 is an explanatory sectional view showing an operation principle of evaporation and cooling of the air-conditioning heat exchanger of the present invention.

FIG. 15 is a perspective explanatory view showing a main part of a conventional fin tube type heat exchanger.

FIG. 16 is a cross-sectional view of a conventional welded heat transfer tube with internal grooves.

[Explanation of symbols]

 1. Heat Exchanger for Air Conditioning 2-1 of First Embodiment 2-1 2-2, 2-3 Outer edge fin portion 3-1, 3-2, 3-3, 3-4 Intermediate fin portion 4-1, 4-2 Outer edge fin joint part 5 Intermediate fin joint part 6 Inner surface groove 7-1, 7-2, 7-3, 7-4, 7-5 Tubular part 8-1, 8-2 Oval part 9-1, 9-2 Triangular portion 10, 11, 12, 13 Open outer fin 14 Pressing device 16 Spot welding device 17 High frequency welding device 18 Intermediate tubular portion 19 Protruding fin 20 Fin tube type heat exchanger 21 Welded heat transfer tube with inner groove 22 Plate fin 23 Insertion hole 24 Tubular welded part 25 Refrigerant 26 Air 27 Temperature drop straight line 28 Refrigerant flow direction

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) F28D 1/053 F24F 1/00 391B 1/02 401B

Claims (8)

[Claims] 1. An air conditioner heat exchanger using a gas such as air as a heat exchange outer medium and a liquid refrigerant as a heat exchange inner medium, wherein the air conditioner heat exchanger serves as a flow path for the liquid refrigerant. A tubular portion, an intermediate fin portion provided between the plurality of tubular portions, and an outer edge fin provided on an outer peripheral surface of the tubular portion located on the outermost side of the plurality of tubular portions. Characteristic heat exchanger for air conditioning. 2. The air-conditioning heat exchanger according to claim 1, wherein a plurality of tubular portions are installed in parallel. 3. The air-conditioning heat exchanger according to claim 1, wherein the plurality of tubular portions are installed in three directions shifted by 120 ° in angle. 4. The air-conditioning heat exchanger according to claim 1, wherein the tubular portion is one selected from a circular tubular portion, an elliptical tubular portion, and a triangular tubular portion. 5. The air-conditioning heat exchanger according to claim 1, wherein projecting fins are attached to an outer peripheral surface of the tubular portion. 6. A metal plate having a groove formed on one surface thereof is set in a pressing device such that the grooved surface is on the inside, and then a plurality of tubular portions are formed by the pressing device. An intermediate fin portion between the plurality of tubular portions, and press forming so that outer edge fins are formed on the outer peripheral surface of the outermost tubular portion among the plurality of tubular portions, respectively. Exchanger manufacturing method. 7. The method according to claim 6, wherein the fitting portion of the intermediate fin portion is spot-welded by a spot welding device. 8. The method for manufacturing an air-conditioning heat exchanger according to claim 6, wherein the entire surface of the fitting portion of the outer edge fin is welded by a high frequency welding device.