JP2010230242A - Connecting structure of aluminum tube and heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connecting structure of an aluminum tube used for a refrigerator, capable of considerably improving coating adhesiveness and exhibiting an excellent anticorrosive effect relative to the coating of the connecting structure, even under a severe high corrosive environment. <P>SOLUTION: In a welding structure for joining the aluminum tube 1a and the aluminum tube 1b by a Nocolok flux brazing material 5, a coating part 6 is arranged so as to completely coat the flux 2 that occurs after brazing, and then, a boehmite coating 3 is formed on the surface of the aluminum tube 1. Moreover, on the surface of the coating part 6 and the boehmite coating 3, a coating film 4 made of a special urethane modified epoxy resin is applied, thereby enhancing the adhesiveness between the aluminum tubes 1a, 1b, and the coating part 6 and the coating film 4, and suppressing the infiltration of a corrosive material such as a sulfur system or carboxylic acid into the coating film 4, and moreover, obtaining the anticorrosive effect highly reliable over a long period. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a connection structure of aluminum tubes (tube bodies) through which fluid flows, and a heat exchanger including an aluminum tube used in a refrigerator or the like.

  As a method of interconnecting aluminum tubes (hereinafter referred to as aluminum tubes), brazing using a brazing material of aluminum-silica (Al-Si) is generally used. In order to braze, it is necessary to remove the oxide film of aluminum, and flux is used as the means.

  As the flux, a mixture of inorganic chlorides that are water-soluble compounds (for example, alkali metal chlorides and alkaline earth metal compounds) has been often used.

  However, since these water-soluble compounds are corrosive to aluminum in the presence of moisture, they had to be de-fluxed to remove the flux after brazing.

  In recent years, nocoloc flux has been proposed and used in place of such inorganic chloride fluxes. This Nocolok flux is non-hygroscopic before brazing and substantially water-insoluble after brazing, and becomes reactive at temperatures below the melting point of the brazing material and becomes aluminum oxide. Although it acts as a fluxing agent, it has the property of being non-reactive with aluminum at room temperature.

  Therefore, when brazing is performed using a Nocolok flux, the point of corrosion of aluminum due to the residual flux observed in the case of conventional inorganic chloride fluxes is substantially eliminated.

  Now, in an aluminum tube brazed using such a Nocolok flux, it is common to paint for rust prevention after brazing. And since the flux which remains after brazing is non-corrosive, it coats, without removing a flux after brazing (for example, refer patent document 1).

In general, the anti-corrosion coating uses a paint whose main component is a polyester resin, an alkyd resin, an acrylic resin, an epoxy resin, or the like, which is a thermosetting resin.
Japanese Patent Publication No. 6-47190

  However, in this case, where the corrosive environment is relatively low, the influence of the flux residue on the coating is small, and the rust prevention effect can be sufficiently exhibited. However, in a harsh corrosive environment, the binding molecules of the paint were easily destroyed.

For example, the environment of commercial refrigerators is often an environment in which highly corrosive gas is likely to be generated because a large amount of food that generates highly corrosive gas is stored without wrapping. . For example, sulfur-based gas is generated from eggs, mayonnaise, cheese, seafood, and the like, and carboxylic acids (organic acids such as acetic acid and formic acid) are generated from mayonnaise, sauce, baker's yeast, and the like. In addition, when food rots, organic substances such as protein and fat, which are food components, undergo oxidative decomposition and hydrolysis, and sulfur-based gas, carboxylic acid, ammonia gas, and ethylene gas are generated.

  Recently, bleach, bactericides, or alcohol for disinfection have been used more frequently due to measures to strengthen pathogens. Sodium hypochlorite or the like is used as a bleaching agent and disinfectant, and chlorine gas is generated. In addition, the sterilizing alcohol generates carboxylic acid along with oxidative decomposition.

  Therefore, when the disinfection countermeasures are performed outside the warehouse, the corrosive gas enters the interior from the outside by opening and closing the refrigerator door.

  As described above, when an aluminum tube structure that has been brazed and rust-proofed is placed in a place where the corrosive environment is severe, the aluminum tube is cooled and the condensed water adheres to it. Sulfur, formic acid, acetic acid and other carboxylic acids, chlorine, etc., dissolve in the condensed water and begin to erode the coating film. As this progresses further, the binding molecules of the coating film are destroyed, making it easier for moisture to enter. .

  When moisture permeates into the under-painted flack as the moisture permeates, the adhesion of the coating film to the aluminum tube extremely decreases. As a result, the swelling of the coating film is promoted and the peeling progresses entirely.

  When this happens, the corrosion protection effect of the paint film disappears and the aluminum tube begins to corrode. Further, the surface of the aluminum tube is pitted due to the action of the corrosive battery, eventually there is a hole, and the fluid (refrigerant) in the aluminum tube leaks. There was a problem that led to a fatal flaw.

  In addition, alkyd resin, acrylic resin, and polyester resin paints are used for the above-mentioned coating film, but painting using these paints has an anticorrosive effect in a general environment (where the corrosive environment is relatively low). However, in highly corrosive environments such as sulfur-based and carboxylic acids, the cross-linked parts of the cross-linked resin monomers are hydrolyzed and destroyed, and the condensed water containing corrosive substances is absorbed and the anti-corrosion effect is remarkable. There is a problem of lowering.

  On the other hand, coating with epoxy resin paint has higher water permeability than coating with alkyd resin, acrylic resin, and polyester resin, so it crosslinks even in highly corrosive environments such as sulfur and carboxylic acids. The cross-linked portion between the resin monomers is difficult to hydrolyze and the anticorrosion effect is relatively maintained, but on the other hand, there is a problem that the adhesion with the aluminum substrate decreases with the passage of time, and the anticorrosion effect decreases.

  In general, when viewed from the painted surface, rust preventive paints such as polyester resins, alkyd resins, acrylic resins, and epoxy resins have a major problem that a sufficient anticorrosion effect cannot be obtained in a severe corrosive environment.

  In other words, when anticorrosive paints such as polyester resin, alkyd resin, acrylic resin, and epoxy resin are used in places where the corrosive environment is severe, the adhesion of the paint due to the residue of the flux is reduced, and the aluminum substrate due to hydrolysis of the anticorrosive paint. There was a problem that the coating film peeled off in a short period of time due to the lowering of the adhesiveness.

  The present invention solves the above-described conventional problems. Even when a structure in which aluminum tubes are brazed to each other is arranged in a severe and highly corrosive environment, the connecting portion of the tubes (brazing) The present invention has an object to provide an aluminum tube connection structure that can remarkably improve the adhesion of the coated aluminum substrate to the aluminum substrate and exhibit an excellent anticorrosive effect.

  In order to solve the above-described conventional problems, the present invention provides a structure in which a flux generated when a brazing material is welded to a connecting portion of the tube in a configuration in which aluminum tubes are brazed and connected to each other. A boehmite film is formed on the surface of each tube including the covering member, and a coating film mainly composed of a urethane-modified epoxy resin is applied to the surface.

  That is, since the coating film is not deposited on the flux by covering the coating member so that the coating film is not deposited on the flux, the coating on the flux is performed even in a severe and highly corrosive environment. The film can be prevented from peeling off, and thus the pitting corrosion of the aluminum tube can be prevented.

  Moreover, the said coating | coated member is excellent in waterproofing and anticorrosion, and the anticorrosion performance excellent in applying the coating film | membrane which has a urethane-modified epoxy resin as a main component on the coating | coated member can be exhibited.

  Further, the boehmite film is formed on a portion not covered with the covering member. Since the surface of the boehmite film is in a state where fine irregularities are formed, the surface area of the aluminum tube is increased, and the aluminum tube surface is made OH group (hydroxyl group). As a result, adhesion with the urethane-modified epoxy resin coating film is improved.

  Furthermore, by applying a urethane-modified epoxy resin in which a molecular structure of a dibasic acid is compounded on the surface of the boehmite film, OH groups (hydroxyl groups) in the coating film are propagated by urethane bonds, and the base (aluminum) In addition to improving adhesion, the dibasic acid enhances the reaction acceleration during baking and drying of urethane-modified epoxy resins, and the cross-linking in the molecular structure of the coating film is improved, resulting in a coating film of a polymer structure with a three-dimensional network structure. This can increase the anticorrosion effect.

  Therefore, even when a structure in which aluminum tubes are brazed together is placed in a severe and highly corrosive environment and corrosive substances such as sulfur and carboxylic acid gradually infiltrate into the coating film layer, As described above, the coating member provided at the connection portion of the aluminum tube can enhance the corrosion resistance of the connection portion, and further exhibits an excellent anticorrosion effect even when placed in a severe and highly corrosive environment by coating. be able to. Therefore, it is not necessary to consider the deterioration of the corrosion resistance of the coating film due to the influence of the flux residue.

  In addition to the covering member, the boehmite film significantly improves the adhesion between the tube surface and the coating, so that the corrosive substance can be prevented from reaching the substrate (aluminum) and is excellent. An anticorrosive effect can be exhibited. Furthermore, the boehmite film treatment and the urethane-modified epoxy resin having a dibasic acid in the molecular structure have good binding properties, so that the adhesion is remarkably increased, and the adhesion can be maintained over a long period of time. The anticorrosion effect can be made extremely high.

The connection structure of the aluminum tube of the present invention is a structure in which aluminum tubes are brazed (welded) to each other with a Nocolok flux brazing material, and a coating material provided at the connection portion of the tube and a boehmite film formed on the material By applying a special urethane-modified epoxy resin film on the surface, sufficient corrosion resistance against corrosive substances such as sulfur and carboxylic acid can be obtained. Especially, the special urethane-modified epoxy resin is dibasic in its molecular structure. By having a structure containing an acid molecule, the anti-corrosion effect of the coating film is remarkably exhibited by the polymer reaction promoting effect of the dibasic acid, and the pitting corrosion resistance of the connection structure portion of the aluminum tube is improved. it can. As a result, generation of pitting corrosion at the brazed portion can be suppressed and long-term reliability can be ensured.

  Further, before the boehmite film treatment is performed, the portion where the flux is generated is covered with a covering member without removing the flux residue caused by the brazing, thereby improving the corrosion resistance of the connection portion. Can do. Furthermore, by applying the coating, an excellent anticorrosive effect can be exhibited even if it is placed in a severe and highly corrosive environment.

  Furthermore, even when the heat exchanger of the present invention is placed in a highly corrosive environment, corrosion is suppressed due to its excellent anticorrosive effect, and it can be used over a long period of time. An exchanger can be obtained.

  The invention according to claim 1 is the first tube made of aluminum processed into a diameter of a predetermined dimension, and the second tube made of aluminum having an insertion diameter portion into which one end of the first tube is inserted, A welded structure that brazes and joins the end portion of the insertion diameter portion with a Noclock flux brazing material, and covers the connection portion of the first and second tubes where the flux generated during the brazing joining is generated. An aluminum tube provided with a covering member, formed with a boehmite film on the surfaces of the first and second tubes including the covering member, and further provided with a coating film of a special urethane-modified epoxy resin on the surface of the boehmite film This is a connection structure.

  By adopting such a configuration, the coating member prevents adhesion between the flux and the coating film, so that the coating film does not react with the flux even in a severe and highly corrosive environment. Tube pitting corrosion can be prevented.

  Moreover, since the covering member is excellent in waterproofing and anticorrosion, a further excellent anticorrosion performance can be exhibited by applying a coating film mainly composed of a urethane-modified epoxy resin on the covering portion.

  In addition, the adhesion between the boehmite film and the coating applied to the surface of the boehmite film can be significantly improved for parts other than the covering member, and the penetration of corrosive gas into the coating film can be suppressed, resulting in an excellent anticorrosive effect. Can be obtained.

  In addition, the increase in surface area by boehmite coating treatment, the OH group (hydroxyl group) effect, and the effect of OH group (hydroxyl group) in the coating film due to urethane bonds are synergistic, and the adhesion to the aluminum tube is remarkably improved. Accordingly, the anticorrosion effect can be further enhanced.

  According to a second aspect of the present invention, in the first aspect of the present invention, a heat-shrinkable tube that shrinks by heat is used as the covering member.

  As a result, it is possible to cover the place where the flux is easily generated by the heating action, and the flux removal process is unnecessary or extremely simple, so that the aluminum tube and the heat-shrinkable tube are in close contact with each other. Work can be done quickly and easily. Moreover, the adhesiveness with an aluminum tube increases by heating, and the pitting corrosion prevention of an aluminum tube can be made more reliable. What is necessary is just to select a well-known waterproof and anticorrosion thing as a heat shrinkable tube, and also it is not necessary to consider the adhesiveness with a coating film by the influence of a flux residue, and the fall of corrosion resistance.

  The invention according to claim 3 is the invention according to claim 1, wherein a self-bonding tape is used for the covering portion.

  As a result, the self-bonding tape is self-welded by being wound around the tube and strengthens the adhesion to the aluminum tube. As a result, pitting corrosion of the aluminum tube can be prevented. What is necessary is just to select a well-known waterproof property and a high anti-corrosion thing as a self-fusing tape, and also it is not necessary to consider the adhesiveness with a coating film by the influence of a flux residue, and the fall of corrosion resistance.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the special urethane-modified epoxy resin has a structure in which a dibasic acid is added to the molecular structure of the urethane-modified epoxy resin. It is what you have.

  As a result, the polymer reaction promoting effect of the dibasic acid acts, the cross-linking of the molecular structure in the coating film of the boehmite film and the special urethane-modified epoxy resin film is increased, and the adhesion between the two is enhanced, and the anticorrosive effect of the coating film Can be remarkably exhibited, and the corrosion resistance can be improved.

  The invention according to claim 5 is a heat exchanger having a refrigerant flow path through which a refrigerant flows, and that promotes heat exchange with surrounding gas or liquid. It is a heat exchanger which made the flow path the refrigerant flow path which comprised the connection structure as described in any one of Claims 1 thru | or 4.

  As a result, a heat exchanger having high corrosion resistance can be obtained. Therefore, even when the heat exchanger is placed in a highly corrosive environment, the corrosion resistance of the heat exchanger is suppressed due to the excellent anticorrosive effect, and the heat exchanger can be used for a long time. An exchanger can be obtained.

  Embodiments of an aluminum tube connection structure and a heat exchanger according to the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a cross-sectional view from the tube axis direction of a connecting portion of an aluminum tube according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1 at the connection portion of the aluminum tube.

  As shown in FIG. 1, the connection structure of an aluminum tube (hereinafter referred to as an aluminum tube) 1 includes a first aluminum tube 1a and a connection portion formed by a well-known tube expansion process (in the insertion diameter portion of the present invention). Equivalent) It is comprised by the 2nd aluminum tube 1b which equips one end with 1c.

  The first and second aluminum tubes 1a and 1b are brazed and connected by fitting and connecting one end of the first aluminum tube 1a to the connecting portion 1c of the second aluminum tube 1b. The aluminum tube 1 is brazed (welded) by melting a Noclock flux brazing material (hereinafter referred to as a brazing material) 5 at the fitting connection portion while heating the fitting connection portion (not shown). ) Connection is complete.

Here, when welding is performed using the brazing filler metal 5 described above, the flux 2 is generated over the first and second aluminum tubes 1a and 1b mainly on the surface of the connecting portion 1c. Since this flux 2 is a non-corrosive substance, the second aluminum tube 1b is not corroded by the flux 2, but it adheres to the surface of the second aluminum tube 1b and remains. If coating is performed in a state in which the flux 2 remains, an adverse effect on the coating occurs, so it is desirable to remove the residue of the flux 2.

  For removal, it is necessary to use a jig or the like and perform polishing work. However, it takes time to process and there are many problems in terms of work.

  Therefore, the covering member 6 is provided on the first and second aluminum tubes 1a and 1b, and the connecting portion 1c where the flux 2 is generated by the covering material 6 is removed without removing the flux 2 generated in the vicinity of the connecting portion 1c. It was set as the structure which coat | covers a sufficient range.

  The covering member 6 uses a known heat shrinkable tube that shrinks by heat. The material is a polyolefin resin mainly composed of polyethylene.

  Thus, by using a heat-shrinkable tube for the covering member 6, it is possible to easily perform contact work with the first and second aluminum tubes 1 a and 1 b by heating. Moreover, the adhesiveness with the 1st, 2nd aluminum tubes 1a and 1b and the connection part 1c increases by heating, and the pitting corrosion of the aluminum tube 1 can be prevented. The heat-shrinkable tube is preferably excellent in waterproofness and anticorrosion properties in view of the subsequent processing steps.

  After covering the residual portion of the flux 2 with the covering member 6 as described above, the step of generating the boehmite film 3 is performed.

  By the step of generating the boehmite film 3, the boehmite film 3 is formed on a portion of the aluminum tube 1 excluding the covering member 6. The boehmite film 3 has a fine uneven surface, increases the surface area of the aluminum tube 1, and makes the surface of the aluminum tube 1 an OH group (hydroxyl group). As a result, the adhesion with the urethane-modified epoxy resin coating film 4 described later is improved.

  This boehmite film treatment is performed by immersing the aluminum tube 1 in hot water at a temperature of 95 ° C. or higher for a predetermined time (for example, about 1 hour) using ion-exchanged water (electric conductivity 2 μs / cm or less). A stable and uniform boehmite film 3 can be formed on the surface of the aluminum tube 1. In this case, the boehmite film 3 is not formed on the surface of the covering member 6 and the portion covered with the covering member 6 even if the boehmite treatment step is performed.

  After the boehmite film treatment, the surface of the boehmite film 3 is coated with a special urethane-modified epoxy resin that contains a dibasic acid as a paint, and the surface of the boehmite film 3 is coated with a special urethane-modified epoxy resin. (Hereinafter referred to as a resin coating film) 4 is formed.

  The coating of the special urethane-modified epoxy resin can be performed by, for example, immersing the entire aluminum tube 1 having the above-described connection structure in a paint and applying the paint, and then performing a high-temperature baking and drying process. Do. This coating and drying are performed in order to form a three-dimensional network structure polymer film with a close cross-link constituting the molecular structure of the resin coating film 4, and a polymerization reaction between blocked isocyanate and dibasic acid. The polymer coating resin coating film 4 is formed.

  Specifically, the paint is used by dissolving a special urethane-modified epoxy resin with a volatile solvent containing additives and the like in a liquid state.

This resin coating film 4 has a high average molecular weight of the epoxy resin, further increases the glass transition point, and hardens the coating film. This makes it difficult for water containing corrosive substances to enter.

  The formation of the resin coating film 4 can be a so-called overlap coating in which the resin coating film 4 is formed on the surface of the formed resin coating film 4 in accordance with the environment in which the aluminum tube 1 is disposed. In Embodiment 1, the special urethane-modified epoxy resin coating is repeated twice. This multiple coating method is not limited to the same coating method. For example, a combination of different coating methods may be used, for example, the first time is a dip coating method and the second time is a spray coating method. it can.

  Therefore, as shown in FIG. 2, the surface of the aluminum tube 1 that has undergone the above-described process is in a state in which a plurality of treatment layers composed of the covering member 6, the boehmite film 4 and the resin coating film 4 coated with the flux 2 are formed.

  That is, in the connecting portion 1c, the brazing material 5 is slightly interposed between the first aluminum tube 1a and the second aluminum tube 1b, and is generated on the surfaces of the first and second aluminum tubes 1a and 1b during brazing. The covering member 6 is formed so as to completely cover the flux 2, and the resin coating film 4 is formed on the surface of the covering portion 6. Further, the portion other than the covering member 6 has a structure of a treatment layer in which the boehmite film 3 is formed on the surface of the aluminum tube 1 and the resin coating film 4 is formed on the surface of the boehmite film 3.

  In particular, the resin coating film 4 is excellent in adhesion to the boehmite film 3 and is a coating film of a polymer structure having a three-dimensional network structure in which crosslinks constituting the molecular structure of the coating film are densely formed by a high temperature baking coating method. In addition to the above, blocked isocyanate and dibasic acid are polymerized to form a coating film of a polymer structure, so that the surface is firmly adhered to the surfaces of the first and second aluminum tubes 1a and 1b. Yes.

  As described above, in the first embodiment, by providing the covering member 6 so as to cover the flux 2 generated around the surface of the connecting portion 1c which is the brazing surface of the aluminum tube 1, the flux 2 Since the resin coating film 4 is not attached to the top, peeling of the coating film on the flux 2 can be prevented even in a severe and highly corrosive environment, and as a result, pitting corrosion of the aluminum tube 1 can be prevented.

  Further, excellent anticorrosion performance can be obtained by applying the resin coating film 4 mainly composed of urethane-modified epoxy resin on the covering member 6. Further, a boehmite film 3 is formed on the portion other than the covering member 6 to greatly improve the adhesion with the coating after the boehmite film 3. In addition, it is not necessary to consider a decrease in the corrosion resistance of the resin coating film 4 due to the influence of the residue of the flux 2.

  Further, a resin coating film in which a dibasic acid molecule is further blended in a portion other than the covering member 6 subjected to the treatment of the connecting portion 1c of the first and second aluminum tubes 1a and 1b provided with the covering member 6 and the boehmite film 3. By repeating step 4 twice, even if a corrosive substance such as sulfur or carboxylic acid gradually enters (penetrates) inside the coating film layer, it covers a sufficient range centering on the connecting portion 1c. Since the member 6 is provided, the adhesiveness with the first and second aluminum tubes 1a and 1b including the connecting portion 1c can be greatly improved. As a result, the corrosive substance on the surface of the aluminum tube 1 can be improved. Reaching can be prevented and the anticorrosive effect can be exhibited.

Further, the portion other than the covering member 6 greatly improves the adhesion with the coating after the boehmite film 3, and further increases the surface area and the OH group (hydroxyl group) effect accompanying the generation process of the boehmite film 3. Has a synergistic effect of the OH group (hydroxyl group) in the resin coating film 4 due to the urethane bond and remarkably improves the adhesion to the substrate (aluminum), so that the corrosive substance reaches the surface of the aluminum tube 1. Can be strongly inhibited and an excellent anticorrosive effect can be exhibited.

  Furthermore, since the anti-corrosion effect of the resin coating film 4 is remarkably exhibited by the effect of promoting the polymer reaction of the dibasic acid, the pitting corrosion resistance of the connection structure portion of the first and second aluminum tubes 1a and 1b is increased, and pitting corrosion Generation | occurrence | production can be prevented, and deterioration of the aluminum tube 1 can be suppressed over a long period of time.

  In particular, the resin-coated film (special urethane-modified epoxy resin film) 4 has a three-dimensional network that increases the acceleration of reaction during baking and drying, and has a dense cross-link of the coating film, by molecularly blending dibasic acid into the molecular structure. It can be set as the coating film of the polymer structure of a structure, and can improve the anticorrosion effect more. Further, the coating film becomes a polymer structure due to the polymerization reaction of the blocked isocyanate and the dibasic acid, and an extremely excellent anticorrosion effect is obtained.

  In addition, excellent corrosion resistance can be realized while simplifying the process of removing the flux 2 residue, and in addition, the adhesion with the coating film 4 due to the influence of the residue of the flux 2 and the corrosion resistance decrease. You don't have to think about

  In the first embodiment, the heat-shrinkable tube is used as the covering member 6, but the cover member 6 is tightly fixed by itself as it is wound around the aluminum tube 1 instead of the heat-shrinkable tube. The same operation can be performed using a well-known self-bonding tape. This self-bonding tape is made of butyl rubber or the like, and unlike a heat-shrinkable tube, it has a winding specification so that it can be easily operated.

  Further, since the self-bonding tape is fused and fixed to the aluminum tube 1 around the connecting portion 1c, the adhesiveness with the aluminum tube 1 is enhanced and the pitting corrosion of the aluminum tube 1 can be prevented. . In addition, the self-bonding tape is highly waterproof and anticorrosive, and can be coated over a wide range including the flux 2, thereby reducing adhesion and corrosion resistance with the coating film due to the influence of the flux 2 residue. There is no need to think about it, and the corrosion resistance of the first and second aluminum tubes 1a and 1b and the connecting portion 1c can be improved without removing the flux 2 as in the case of using a heat-shrinkable tube.

(Embodiment 2)
FIG. 3 is a front view in which a connection structure is formed in the inlet piping portion and the outlet piping portion of the heat exchanger according to Embodiment 2 of the present invention. FIG. 4 is a front view in which a connection structure is formed in the intermediate piping portion of the heat exchanger. The same constituent elements as those of the first embodiment will be described with the same reference numerals, and the portions that cannot be illustrated in FIGS. 3 and 4 will be described with reference to FIGS. .

  A heat exchanger 7 shown in FIG. 3 is a fin tube type heat exchanger having a well-known configuration, and a plurality of aluminum tubes 1 curved in a meandering manner penetrate through aluminum fins 7a arranged in parallel. Yes. The both ends of the aluminum tube 1 form an inlet pipe portion 8a and an outlet pipe portion 8b, respectively.

Connection pipes 8c are brazed and connected to the inlet pipe portion 8a and the outlet pipe portion 8b, respectively. The connecting pipe 8c is made of an aluminum metal similar to the aluminum tube 1, and the connecting portion indicated by the symbol C is brazed using the Nocolok flux brazing material 5 described in the first embodiment. In this case, the inlet pipe portion 8a and the outlet pipe portion 8b correspond to the second aluminum tube 1a of the first embodiment, and the connection pipe 8c corresponds to the first aluminum tube 1b of the first embodiment.

  After the connecting pipe 8c is brazed, the surface of the heat exchanger 7 is provided with a covering member 6 that covers the flux 2 generated during brazing, as described in the first embodiment, and is subjected to heat shrink processing. Next, the boehmite film 3 is formed on the entire heat exchanger 7 by appropriate means, and then the resin coating film (special urethane-modified epoxy resin film) 4 is formed on the entire heat exchanger 7. It becomes the composition.

  Further, in the heat exchanger 9 shown in FIG. 4, a plurality of aluminum tubes 1 bent into a U-shape pass through a large number of aluminum fins 7 a arranged side by side, and both ends of adjacent aluminum tubes 1. The meandering flow path is formed by sequentially brazing and connecting the opening (intermediate part of the flow path) with an aluminum return bend pipe 8d formed in a U-shape.

  In this case as well, the connection portions of the aluminum tubes 1 and the return bend pipes 8d indicated by the reference symbol C are brazed using a Noclock flux brazing material 5. The aluminum tube 1 corresponds to the first aluminum tube 1a of the first embodiment, and the return bend pipe 8d corresponds to the second aluminum tube 1b of the first embodiment.

  The surface of the heat exchanger 9 is also provided with a covering member 6 that covers the flux 2 generated during brazing as described in the first embodiment after the return bend pipe 8d is brazed. Shrinking is performed, and then the boehmite film 3 is formed on the entire heat exchanger 9 by appropriate means, and then the resin coating film (special urethane-modified epoxy resin film) 4 is formed on the entire heat exchanger 9. It has become the configuration that has been done.

  Therefore, since the heat exchangers 7 and 9 in the second embodiment are subjected to surface treatment processing that provides the highly reliable anticorrosion effect described in the first embodiment, heat exchange with high corrosion resistance is performed. 7 and 9 can be used.

  As a result, even when these heat exchangers 7 and 9 are mounted on equipment used in highly corrosive environmental conditions, corrosion is suppressed by an excellent anticorrosive effect, and it can be used for a long period of time. It can be set as the heat exchangers 7 and 9 with high reliability.

  Since the connection structure of the present invention provides high corrosion resistance, it can be applied to piping circuits used in severe and highly corrosive environments, or heat exchangers installed in equipment, so it can be used in refrigerators or showcases. It can be widely applied as a connection structure for aluminum tubes used in refrigeration equipment such as automobiles and the like.

Sectional drawing from the pipe-axis direction of the connection part of the aluminum tube in Embodiment 1 of this invention Sectional drawing by the AA line of FIG. 1 in the connection part of the tube made from the same aluminum The front view which formed the connection structure in the inlet piping part and outlet piping part of the heat exchanger in Embodiment 2 of this invention Front view of the connection structure formed in the intermediate pipe of the heat exchanger

1 Aluminum tube (Aluminum tube)
DESCRIPTION OF SYMBOLS 1a 1st aluminum tube 1b 2nd aluminum tube 1c Connection part 2 Flux 3 Boehmite film 4 Resin coating film (coating film of special urethane modified epoxy resin)
5 Noclock flux brazing material 6 Cover member 7 Heat exchanger 8a Inlet pipe 8b Outlet pipe 8c Connection pipe 8d Return bend 9 Heat exchanger

Claims (5)

An aluminum first tube having a diameter of a predetermined dimension and an aluminum second tube having an insertion diameter portion into which one end of the first tube is inserted are sawlocked at the end of the insertion diameter portion. A welding structure for brazing and joining with a flux brazing material, wherein a covering member is provided at a connection portion of the first and second tubes to cover a portion where a flux generated during the brazing joining is generated, and the covering member is provided An aluminum tube connection structure in which a boehmite film is formed on the surfaces of the first and second tubes, and a special urethane-modified epoxy resin coating film is applied on the surface of the boehmite film. The aluminum tube connection structure according to claim 1, wherein a heat-shrinkable tube that shrinks by heat is used as the covering member. The aluminum tube connection structure according to claim 1, wherein a self-bonding tape is used for the covering member. The connection structure for an aluminum tube according to any one of claims 1 to 3, wherein the special urethane-modified epoxy resin has a structure in which a dibasic acid is mixed with a molecular structure of the urethane-modified epoxy resin. 5. A heat exchanger comprising a connection structure of a plurality of refrigerant tubes and having a refrigerant flow path through which a refrigerant flows, and promoting heat exchange with surrounding gas or liquid, wherein the refrigerant flow path is defined in claim 1. A heat exchanger as a refrigerant flow path comprising the connection structure according to any one of the above.