JP2021063612A - Heat exchanger and air conditioning device provided with same - Google Patents

Abstract

To effectively suppress or prevent the preferential corrosion of a fillet formed adjacent to a joined section of brazing sheets even if the fillet contains zinc, and improve the corrosion resistance of a heat exchanger.SOLUTION: Brazing sheets 10: are each provided with an aluminum alloy core material 11, a brazing material layer 12, and a sacrificial anode material layer 13 that contains zinc; and have bonding surfaces 10a that constitute a joined section 21 and non-bonding adjacent surfaces 10b that are adjacent to the bonding surfaces 10a. At the bonding surface 10a the sacrificial anode material layers 13 are bonded. A fillet 22 is formed at a site that is between the non-bonding adjacent surfaces 10b and adjacent to the bonding surfaces 10a, and an epoxy-based coating film 14, 10-50 μm in thickness, is disposed on the bonding surfaces 10a and the fillet 22.SELECTED DRAWING: Figure 1

Description

The present invention relates to a brazing sheet used for a member constituting a heat exchanger, a joining structure for joining the brazing sheets to each other, and a heat exchanger having the joining structure.

A general heat exchanger usually includes a pipe and fins, and has a configuration in which a plurality of fins are attached to the outer circumference of the pipe. As the material of the tube, copper (Cu) or an alloy thereof (referred to as "copper material" for convenience) has been used, but in recent years, aluminum (Al) or an alloy thereof (aluminum material) has also been used. As a fin material, an aluminum material is generally used.

In the manufacture of heat exchangers, brazing filler metal joints are generally used to attach fins to pipes. If both the pipe and the fin are made of an aluminum material, for example, a brazing sheet in which a brazing material layer is clad (coated) on at least one surface of a core material made of an aluminum alloy is used. Considering the corrosion resistance of the pipe and fins, a brazing sheet in which a brazing material is clad on one surface of the core material and a sacrificial anode material layer is clad on the other surface is used.

As the brazing material, an aluminum-silicon (Si) -based alloy used for brazing an aluminum alloy is generally used, and as a sacrificial anode material, aluminum is generally used in order to make its potential low. An alloy in which zinc (Zn) is added is used. As a typical sacrificial anode material, a brazing material of a general aluminum-silicon alloy with zinc added can be mentioned. As a result, the sacrificial anode material also functions as a brazing material.

As an example of the brazing sheet in which the sacrificial anode material layer is clad, for example, the one disclosed in Patent Document 1 is known. Patent Document 1 discloses an aluminum alloy brazing sheet used for a heat exchanger for an automobile, particularly a passage component of a fluid (cooling water, a refrigerant, etc.), and has good brazing property and excellent after brazing. The components of the core material and the sacrificial anode material are adjusted to achieve the strength and corrosion resistance.

In this brazing sheet, the content of silicon, iron (Fe) and manganese (Mn) in the sacrificial anode material is regulated to 0.15% by mass or less. This is because the formation of Al-Mn-Si-based or Al-Fe-Mn-Si-based compounds is suppressed, and the decrease in strength after brazing is suppressed. Further, in this brazing sheet, the silicon content of the core material is regulated to 0.15% by mass or less, and copper is added to the core material in the range of 0.40 to 1.2% by weight. The reason for adding copper is to improve the strength of the core material, increase the potential difference between the core material and the sacrificial anode layer, and improve the anticorrosion effect due to the sacrificial anode action.

Further, as another example of the brazing sheet in which the sacrificial anode material layer is clad, for example, the one disclosed in Patent Document 2 is known. Patent Document 2 also discloses an aluminum alloy brazing sheet used for an automobile heat exchanger, particularly a fluid passage component, has a sacrificial anticorrosive effect on both sides, and has a brazing function on one side thereof. Furthermore, in order to prevent preferential corrosion of the joint, not only the core material and the sacrificial anode material but also the components of the brazing material are adjusted.

In this brazing sheet, zinc (Zn) is added not only to the sacrificial anode material but also to the brazing material, and copper is further added to the brazing material in the range of 0.1 to 0.6 mass%. Copper is also added to the core material in the range of 0.05 to 1.2 mass%. The purpose of adding copper to each material is different, for the brazing material, to make the potential of the brazing material noble, and for the core material, to improve the strength of the core material.

Japanese Unexamined Patent Publication No. 2010-163674 Japanese Unexamined Patent Publication No. 2013-155404

In the brazing sheet disclosed in Patent Document 1, the strength is improved by adding copper to the core material, and the anticorrosion effect is improved by the sacrificial anode action. However, in this brazing sheet, the silicon content of both the sacrificial anode material and the core material is limited to 0.15% by mass or less, and the core material also contains various metal elements other than copper. It is specified in detail. Therefore, the range of material choices that can be used as the core material and the sacrificial anode material is reduced. Moreover, in this brazing sheet, the silicon content of the sacrificial anode material is regulated to a very small amount. Therefore, it is considered that this sacrificial anode material layer does not have a function as a general brazing material.

In the brazing sheet disclosed in Patent Document 2, by adding copper together with zinc to the brazing material, not only zinc is concentrated at the brazing joint but also copper is concentrated in the same manner. Therefore, by concentrating (containing) this copper, it is possible to prevent the potential of the joint portion from being overly based by zinc. However, when copper and zinc are used in combination, the preferential corrosive action of the sacrificial anode material layer is reduced, resulting in a decrease in corrosion resistance.

For example, depending on the type of heat exchanger, a structure is included such that when the brazing sheets are joined to each other, the angle formed by the respective joining surfaces becomes an acute angle. For convenience, if such a structure is referred to as an "acute-angled joint structure" and a surface that is not joined adjacent to the joint surface of the brazing sheet is referred to as a "non-joint adjacent surface", in such a sharp-angle joint structure, non-joins that form an acute angle with each other Fillets are formed between the adjacent surfaces. This fillet is defined herein as a solidified wax or sacrificial anode material that has flowed out of the joint surface during joining.

When copper and zinc are used in combination as in Patent Document 2, zinc having a low potential and copper having a noble potential coexist in the fillet as described above. If the sacrificial anode material layer is configured to contain copper in advance, the potential of the fillet may be too noble due to copper, the sacrificial anode action of zinc may be reduced, and the corrosion resistance of the fillet may be lowered. In this case, corrosion may proceed from the fillet to the joint portion, resulting in a decrease in the joint strength of the joint portion.

The present invention has been made to solve such a problem, and even if the fillet generated adjacent to the joint between the brazing sheets contains only zinc or copper and zinc, the fillet is concerned. The purpose is to effectively suppress or prevent the preferential corrosion of the heat exchanger and improve the corrosion resistance of the heat exchanger.

In the heat exchanger according to the present invention, in order to solve the above-mentioned problems, in order to protect the joint portion between the brazing sheets, the joint portion is concentrated on the header portion, and the metal particles having a lower potential than the joint portion. This is a configuration in which an epoxy-based paint containing the above is overcoated only on the relevant portion and its surroundings. Furthermore, as an air conditioner equipped with the heat exchanger, in order to protect the coating film of the heat exchanger, a heat exchanger is installed inside the box to prevent ultraviolet rays from entering, and inside the box to promote heat exchange. Is equipped with a blower fan, and a heat exchanger is placed so that the painted part is a non-ventilated part so that the peeled coating film and corrosion products due to aging deterioration are not discharged to the space intended for air conditioning by the blower, and directly under it. It has a structure with a drainage receiver.

According to the above configuration, the joint between the brazing sheets having a relatively low potential is protected by the sacrificial anodic action of the metal particles having a relatively low potential. In addition, an epoxy-based paint that has good adhesion to the aluminum material is used for the painted portion, and deterioration and peeling of the coating film are suppressed by structurally protecting the weather resistance, which is a drawback thereof. As a result, it is possible to effectively suppress or prevent the possibility that corrosion progresses from the fillet to the joint and causes a decrease in the joint strength of the joint, so that the corrosion resistance at the joint of the heat exchanger is further improved. can do. Further, by washing away the peeled matter of the coating film and the corrosion product derived from the metal particles with the dew condensation water generated during the operation of the heat exchanger, it is possible to suppress the pollution of the surrounding environment due to their scattering.

In the present invention, even when the potential of the fillet generated adjacent to the joint between the brazing sheets is lower than that of the surroundings, the preferential corrosion of the fillet is easily and effectively suppressed or prevented by the above configuration. , The effect is that the corrosion resistance of the heat exchanger can be improved.

(A) is a schematic cross-sectional view showing a schematic structure of a brazing sheet according to a typical embodiment of the present invention, and (B) is a joining of a brazing sheet according to a typical embodiment of the present invention. It is a schematic cross-sectional view which shows the schematic structure of the structure. (A) is a schematic cross-sectional view which shows an example of the header of the plate fin laminated type heat exchanger constructed by using the brazing sheet shown in FIG. 1, and (B) is the brazing which the header shown in (A) has. It is a schematic partial cross-sectional view which enlarged the joint structure of a sheet. (A) is a schematic partial cross-sectional view showing an example of a parallel flow capacitor (PFC) configured using the brazing sheet shown in FIG. 1, and (B) is a brazing sheet included in the PFC shown in (A). It is a schematic partial cross-sectional view which enlarged the joint structure of. It is a schematic cross-sectional view which shows the schematic structure which installed the plate fin laminated type heat exchanger which applied dipping coating on the header shown in FIG. 2 in an air conditioner. It is a molecular structure of epichlorohydrin / bisphenol A type resin. (A) to (D) are diagrams showing the results of a corrosion resistance test of a coating film installed on a brazing sheet or a heat exchanger according to an example or a comparative example. (A) to (C) are diagrams showing the adhesion test results after the corrosion resistance test of the coating film placed on the brazing sheet according to the example or the comparative example. (A) to (C) are diagrams showing the adhesion test results after the moisture resistance test of the coating film placed on the brazing sheet according to the example or the comparative example. It is a graph which shows the relationship between the thickness and adhesion of the coating film which concerns on this invention.

In the heat exchanger according to the present invention, in order to solve the above-mentioned problems, in order to protect the joint portion between the brazing sheets, the joint portion is concentrated on the header portion, and the metal particles having a lower potential than the joint portion. This is a configuration in which an epoxy-based paint containing the above is overcoated only on the relevant portion and its surroundings.

Here, the method for evaluating the potential is not particularly limited, and a known method can be preferably used. Typically, a potential measurement sample (for example, a brazing sheet 10 or a core material 11, a brazing material, a sacrificial anode material, a fillet 22 or a joint portion 21, or a composition simulating these) is used on a potato stat / galvanostat. (Alloy, etc.), the counter electrode, and the reference electrode (for example, silver / silver chloride (Ag / AgCl) electrode) are connected and immersed in an electrolytic solution (for example, 5% by weight & sodium chloride (NaCl) solution) to refer to the sample. A method of measuring the potential difference from the electrode can be mentioned.

As an anticorrosion coating, generally, an epoxy-based paint that can obtain suitable adhesion strength to an aluminum material is used as the undercoat, and a urethane-based paint is used as the topcoat for the purpose of protecting the undercoat coating film from ultraviolet rays. Although it is used, it is not desirable from the viewpoint of cost control and environmental protection after the second coat. As a result of the studies by the inventors, it has been clarified that a structure that sufficiently suppresses the invasion of ultraviolet rays into the painted portion can sufficiently improve the corrosion resistance life as a heat exchanger. In addition, by concentrating the joints that need to be painted on the header part, for example, even complicated shapes can be painted at once by dip painting, heat exchangers can be produced more easily, and the burden on the environment can be reduced. Is possible. Further, in the case of the header portion, the heat exchange efficiency is not as good as that of the fin portion and the heat transfer tube portion, so that the efficiency decrease can be minimized by making the header portion a relative non-ventilation portion.

Further, in the configuration in which the heat exchanger is installed so that the header portion is located at the vertically lowermost part of the heat exchanger, the dew condensation water generated during the operation can more reliably wash away the peeled coating film and the corrosion products. As a result, it is possible to effectively suppress or prevent the release coating film and the scattering of corrosion products.

Hereinafter, typical embodiments of the present invention will be described with reference to the drawings. In the following, the same or corresponding elements will be designated by the same reference numerals throughout all the figures, and duplicate description thereof will be omitted.

(Embodiment 1)
[Blazing sheet]
The brazing sheet according to the present disclosure is made of an aluminum alloy used for a heat exchanger. Specifically, for example, as shown in FIG. 1A, the brazing sheet 10 according to the present disclosure includes a core material 11, a brazing material layer 12, and a sacrificial anode material layer 13. The brazing material layer 12 is coated (clad) on one surface of the core material 11, and the sacrificial anode material layer 13 is coated on the other surface of the core material 11, that is, the surface opposite to the surface on which the brazing material layer 12 is coated. Has been done. The core material 11, the brazing material forming the brazing material layer 12, and the sacrificial anode material forming the sacrificial anode material layer 13 are all aluminum alloys.

Alternatively, although not shown, the brazing sheet 10 according to the present disclosure may include a core material 11 and a sacrificial anode material layer 13, and may not include a brazing material layer 12. In such a brazing sheet 10, a sacrificial anode material layer 13 is formed on both surfaces of the core material 11.

The brazing sheet 10 according to the present disclosure has a joint surface at least on the side of the sacrificial anode material layer 13, and a joint portion is formed by joining the joint surfaces to each other. The structure in which the brazing sheets 10 are joined to each other at the joining surface is the joining structure of the brazing sheets 10 according to the present disclosure. The brazing sheet 10 according to the present disclosure has a non-joint adjacent surface adjacent to the joint surface. When the brazing sheets 10 are joined together to form a joined structure, the angle formed by the respective non-joined adjacent surfaces is an acute angle.

In the joining structure 20 according to the present disclosure, when the brazing sheets 10 are joined together to form the joining portion 21, a fillet 22 is formed between the non-joining adjacent surfaces 10b as shown in FIG. 1 (B). To. The heat exchanger includes a member or structure on which such a fillet 22 is formed, and in such a member or structure, the non-joined adjacent surfaces 10b often form an acute angle. .. In the present embodiment, the fillet 22 is defined as a solidified brazing material (or sacrificial anode material) that has flowed out from the joint surface 10a at the time of joining.

In the present disclosure, in a heat exchanger using the brazing sheet 10, it is intended to effectively suppress or prevent the fillet 22 from being preferentially corroded.

In the brazing sheet 10 according to the present disclosure, the joint surface 10a may be set at least on the sacrificial anode material layer 13. Therefore, as will be described later, the sacrificial anode material also serves as a brazing material. That is, the sacrificial anode material layer 13 contributes to joining the brazing sheets 10 as a brazing material at the time of joining, and contributes to the anticorrosion effect of the brazing sheet 10 as a sacrificial anode material after joining.

In the brazing sheet 10 according to the present disclosure, a non-joint adjacent surface 10b is set adjacent to the joint surface 10a. Therefore, the non-bonded adjacent surface 10b is also the sacrificial anode material layer 13 like the bonded surface 10a.

In the bonding structure 20 of the brazing sheet 10 according to the present disclosure, corrosion may proceed in the directions shown by the block arrows C1 and C2 in FIG. 1 (B). The direction of the block arrow C1 is a corrosion direction that progresses from the non-joint adjacent surface 10b (and the non-joint surface that is not adjacent to the joint surface 10a) with respect to the direction of the core material 11, and the direction of the block arrow C2 includes the fillet 22. In the joint portion 21, it is a corrosion direction that progresses along the direction of the joint surface 10a.

Of these, the corrosion that progresses in the corrosion direction C1 is suppressed (avoided or prevented) by the sacrificial anode action of the sacrificial anode material layer 13, but the corrosion that progresses in the corrosion direction C2 is that zinc is concentrated in the fillet 22. Therefore, there is a possibility that the potential of the joint portion 21 including the fillet 22 is too low and progresses. In the brazing sheet 10 according to the present disclosure, by installing the epoxy-based coating film 14 on the surfaces of the joint surface 10a and the fillet 22, corrosion in the corrosion direction C2 can be effectively suppressed (avoided or prevented).

[Blazing sheet joint structure and heat exchanger]
The brazing sheet 10 according to the present disclosure can be particularly suitably used for manufacturing a heat exchanger as described above. As described above, the bonding structure 20 formed when the brazing sheet 10 according to the present disclosure is applied to the heat exchanger has a structure as illustrated in FIG. 1 (B), but more specifically, it has a structure as illustrated in FIG. 1 (B). Examples include a plate fin laminated heat exchanger having a structure as shown in FIGS. 2 (A) and 2 (B) and a parallel flow capacitor (PFC) having a structure as shown in FIGS. 3 (A) and 3 (B). it can.

Although not shown, the plate fin laminated heat exchanger is a plate fin laminated body having a flow path through which a refrigerant, which is a first fluid, flows, and air, which is a second fluid, is flowed between each plate fin laminated body to flow the first fluid. It exchanges heat between the fluid and the second fluid. The plate fin included in this heat exchanger has a flow path region having a plurality of first fluid flow paths through which the first fluid flows in parallel, and a header flow path communicating with each first fluid flow path in this flow path region. It has a header area and.

In the plate fin laminated heat exchanger, end plates having substantially the same shape as the plate fins in a plan view are provided on both sides of the plate fin laminated body in the laminating direction, and are interposed between these pair of end plates. The plurality of plate fins to be formed are joined and integrated by brazing in a laminated state. FIG. 2A shows a schematic structure of a header portion in the plate fin laminated body 30 as a partial cross section, and a plurality of plate fins 32 are laminated with respect to an end plate 31 located at the uppermost part in the drawing. ..

An opening is provided in each of the end plate 31 and the plate fin 32, and the header opening 33 is formed by laminating these plates to form the plate fin laminated body 30. In the configuration shown in FIG. 2A, the refrigerant as the first fluid flows in from the outside of the header opening 33 in the direction indicated by the block arrow in the drawing, and further flows in between the plate fins 32. As described above, each plate fin 32 is provided with the first fluid flow path, so that the refrigerant flowing between the plate fins 32 flows through the first fluid flow path. Further, the air, which is the second fluid, flows in the space formed between the plate fins 32 so as to intersect the direction in which the refrigerant flows (the direction of the first fluid flow path). As a result, the air is cooled by the refrigerant.

FIG. 2B is a partially enlarged view of the plate fin laminate 30 shown in FIG. 2A, and schematically shows an example of the joining structure 20 of the brazing sheet 10 according to the present disclosure. In the examples shown in FIGS. 2A and 2B, the plate fin 32 is the brazing sheet 10 according to the present disclosure, and the joint structure 20 according to the present disclosure is the joint portion 21 located on the header opening 33 side. In FIG. 2B, the plate fin 32, which is the brazing sheet 10, is shown by emphasizing the sacrificial anode material layer 13 with hatching, and also highlighting the fillet 22 with hatching.

At the joint portion 21 on the header opening 33 side, the joint surfaces 10a of the plate fins 32 are joined to each other, and a fillet 22 is formed between the non-joint adjacent surfaces 10b adjacent to the joint surface 10a. In the present disclosure, the epoxy coating film 14 is installed on the surfaces of the joint surface 10a and the fillet 22. As a result, the preferential corrosion of the joint portion 21 is satisfactorily suppressed (avoided or prevented), so that the corrosion resistance life of the plate fin laminated heat exchanger can be improved.

Specific configuration examples of such a plate fin laminated heat exchanger include, for example, JP-A-2017-180856, JP-A-2018-066531, JP-A-2018-066532, and JP-A-2018-066533. It is described in Japanese Patent Application Laid-Open No. 2018-066534, Japanese Patent Application Laid-Open No. 2018-066535, Japanese Patent Application Laid-Open No. 2018-066536, etc. It shall be a part of the description of the specification.

A parallel flow condenser (PFC) is a heat exchanger widely used for car air conditioners (air conditioners for automobiles). A plurality of flat tubes are arranged between a pair of header tubes, and heat is dissipated between these flat tubes. Corrugated fins are arranged. These header pipes, flat pipes, corrugated fins and the like are joined by brazing. FIG. 3A shows a schematic structure of a connecting portion between the header pipe 41 and the flat pipe 42 in the PFC 40 as a partial cross section. Corrugated fins 43 are provided between the flat pipes 42, and these are also joined by brazing. However, the joining structure 20 according to the present disclosure is the header pipe 41 and as shown in an enlarged view in FIG. 3 (B). It is a connecting portion with the flat tube 42.

In the example shown in FIG. 3B, the header tube 41 and the flat tube 42 are both brazing sheets 10, and the header tube 41 and the flat tube 42 are shown by emphasizing the sacrificial anode material layer 13 with hatching. There is. The fillet 22 is also highlighted by hatching. Since the sacrificial anode material layer 13 of the flat tube 42 is flat, the joint surface 10a and the non-joint adjacent surface 10b are set as different regions on a continuous single surface (the surface of the sacrificial anode material layer 13). Therefore, the flat tube 42 has a flat shape such that the brazing sheet 10 does not have a bent portion.

The header pipe 41 has an opening for penetrating and inserting the flat pipe 42, and the joint surface 10a and the non-joint adjacent surface 10b are provided in the opening. In FIG. 3B, the joint surface 10a of the header pipe 41 is shown as a surface parallel to the joint surface 10a (outer surface) of the flat pipe 42, but the present invention is not limited to this, and the flat pipe 42 It may be a surface that is not parallel to the outer surface. The opening of the header tube 41 has a shape having a one-step bent portion as the brazing sheet 10.

In the joint structure 20 shown in FIG. 3B, a fillet is formed between the non-joint adjacent surface 10b adjacent to the joint surface 10a of the header pipe 41 and the non-joint adjacent surface 10b adjacent to the joint surface 10a of the flat pipe 42. 22 is formed. In the present disclosure, the epoxy coating film 14 is installed on the surface of the fillet 22. As a result, the preferential corrosion of the joint portion 21 is satisfactorily suppressed (avoided or prevented), so that the corrosion resistance life of the PFC can be improved.

The method for producing the bonded structure 20 of the brazing sheet 10 is not particularly limited, and a known brazing method or the like can be preferably used. For example, a method in which a known flux is applied to the joint surface 10a of the brazing sheet 10 and then heated in a nitrogen atmosphere furnace at a temperature of, for example, about 600 ° C. can be mentioned.

[Installation form of heat exchanger]
An example of the mode in which the above-mentioned plate fin laminated heat exchanger or PFC is installed in the air conditioner is shown in FIG. A heat exchanger 51 and a blower fan 53 are installed in the box body 56, and the above-mentioned epoxy-based coating film installation portion 52 exists in a part of the heat exchanger 51. This portion corresponds to the header portion of the heat exchanger 51. Further, the condensed water generated from the heat exchanger 51 during operation is received by the drainage receiver 55 and discharged to the outside of the box body 56. The air passage of air, which is the second fluid described above, is indicated by a block arrow in the figure, and the fluid sucked by the blower fan 53 passes through the air filter 54 and is heat exchanged by the heat exchanger 51, and the box body 56 It is discharged to the outside. At this time, the epoxy-based coating film installation portion 52 constitutes a part of the air passage, but since the air passage is partially blocked by the drainage receiver 55, the air volume is the non-installation of the coating film in the heat exchanger 51. It is smaller than the part. For convenience, the portion where the air passage is relatively blocked is called a non-ventilation portion.

In such a structure, when the epoxy-based coating film installation portion 52 is focused on, the ultraviolet rays from the outside of the box body 56 are blocked by the box body 56, so that the ultraviolet rays are substantially unaffected. Therefore, the deterioration of the coating film due to ultraviolet rays is suppressed, and the life of the coating film is extended. Further, the peeled coating film and the corrosion product due to the deterioration of the coating film are almost certainly washed away by the dew condensation water generated from the heat exchanger 51 because the epoxy-based coating film installation portion 52 is a non-ventilated portion, and drained. It is received by the receiver 55 and discharged to the outside of the box together with the condensed water. Therefore, heat exchange can be performed without scattering the product in an environment for air conditioning.

[Epoxy paint]
The epoxy-based epoxy-based coating material according to the present disclosure has an epoxy group at the terminal and is produced by a ring-opening reaction, and is any of epichlorohydrin and phenol, alcohol, aldehyde, ester, amine, fatty acid, and isocyanate. Refers to the reaction product with or (s). The molecular weight is not specified.

FIG. 5 shows the molecular structure of epichlorohydrin / bisphenol A type resin, which is a typical epoxy resin. Epichlorohydrin / bisphenol A type resin has highly reactive epoxy groups at both ends, has a rigid bisphenol nucleus as a skeleton, is connected by a flexible ether group, and has hydroxyl groups that contribute to adhesion at appropriate intervals. It has a structure that is arranged in. Therefore, it exhibits good adhesion, chemical resistance, water resistance, and electrical insulation by utilizing various cross-linking reactions. The base of aluminum to be painted is covered with a dense and smooth oxide film, and generally, suitable adhesion cannot be obtained without base treatment such as chromate treatment or blast treatment, but even epoxy-based paints can be used. For example, for the above reason, it has adhesion that can withstand the rust prevention purpose of this heat exchanger without surface treatment. Therefore, the painting process can be simplified.

Further, it is desirable that the epoxy-based paint contains a metal powder such as zinc oxide or zinc powder, which has a lower potential than aluminum in a pure water environment or a salt water environment, for the purpose of improving corrosion resistance. Other than zinc, lead, indium, etc. can be substituted, but zinc and its alloy (for example, an alloy of aluminum and zinc) are desirable from the viewpoint of environmental protection and cost control. The amount to be added is not specified, but it is set so that the sacrificial anodic action can be sufficiently obtained. The particle size of the powder is not particularly specified, but it is desirable to make the order of several μm or less so that the powder is uniformly dispersed as a paint.

As the diluting solvent, one having high compatibility with the epoxy-based paint component is selected. Typical examples include, but are not limited to, ethylbenzene, xylene, toluene, methyl ethyl ketone and the like. Since the viscosity of the coating material changes depending on the dilution ratio, and as a result, the thickness of the coating film after coating changes, the amount of the diluting solvent is adjusted so as to obtain the desired coating film thickness.

Other components that improve the durability of the epoxy-based paint, for example, various weather-resistant agents may be added to compensate for the fragile weather resistance (ultraviolet ray resistance) that is a drawback of the epoxy-based paint, but in the present invention, it is structural. It is not necessary to add it to implement countermeasures.

[Thickness of coating film]
When the coating film is thick, the sacrificial anodic action acts for a long period of time due to the large amount of metal particles present in the coating film, and the ability to shield from the surrounding environment by effectively suppressing the permeation of oxygen and water in the coating film. However, due to thermal expansion caused by the operation of the heat exchanger, a stress load is applied to the inside of the coating film and the contact surface with the aluminum material, and the coating film is easily peeled off. The effect of improving the corrosion resistance is significantly impaired. Further, when a minute space for heat insulation between fluids having different temperatures is provided in the header portion, the performance as a heat exchanger may be significantly deteriorated by filling the space with a coating film. Furthermore, the cost increases due to the increase in the amount of paint used.

When the coating film is thin, the above-mentioned drawbacks are eliminated, but since the abundance of metal particles in the coating film is small, the sacrificial anodic action acts only for a short period of time, and oxygen and water in the coating film are effectively permeated. It cannot be suppressed and peeling occurs due to corrosion under the coating film, and the effect of improving the corrosion resistance of the heat exchanger cannot be sufficiently obtained.

As will be described later, as a result of the studies by the inventors, if the coating film thickness is 10 μm to 50 μm, sufficient environmental blocking and sacrificial anode action can be exhibited, and early coating film peeling can be suppressed, resulting in heat exchange. It was clarified that the corrosion resistance of the vessel can be effectively improved.

The corrosion resistance test, moisture resistance test and adhesion test in the following Examples and Comparative Examples were carried out as follows.

[Corrosion resistance test]
The corrosion resistance of the coating film of the heat exchanger was evaluated based on the SWAAT test (Sea Water Certified Test) defined by ASTM G85-A3.

[Moisture resistance test]
The moisture resistance of the coating film of the heat exchanger was evaluated by holding the sample in a constant temperature and humidity layer set at an ambient temperature of 40 ° C. and a relative humidity of 98%.

[Adhesion test]
The adhesion of the coating film after the durability test was evaluated based on the 100-square grid test defined by JIS K5400.

(Comparative Example 1)
As the coating film according to Comparative Example 1, an epichlorohydrin / bisphenol A type coating film containing zinc powder was placed on a brazing sheet with a film thickness of 80 μm.

The above-mentioned corrosion resistance test and subsequent adhesion test were carried out on the coating film. As a result, as shown in the cross-sectional photograph of FIG. 6 (A), there was almost no progress of corrosion on the brazing sheet in terms of corrosion resistance, and a sacrificial anticorrosion function by zinc powder was observed, but in terms of adhesion, it is shown in FIG. 7 (A). As shown above, remarkable peeling of the coating film was confirmed.

The above-mentioned moisture resistance test and subsequent adhesion test were carried out on the coating film. As a result, as shown in FIG. 8A, remarkable peeling of the coating film was confirmed.

(Comparative Example 2)
As the coating film according to Comparative Example 2, an epichlorohydrin / bisphenol A type coating film containing zinc powder was placed on a brazing sheet with a film thickness of 5 μm.

The above-mentioned corrosion resistance test and subsequent adhesion test were carried out on the coating film. As a result, as shown in the cross-sectional photograph of FIG. 6B, the progress of corrosion on the brazing sheet under the coating film was observed in terms of corrosion resistance. In the subsequent adhesion, remarkable peeling was confirmed as shown in FIG. 7 (B).

The above-mentioned moisture resistance test and subsequent adhesion test were carried out on the coating film. As a result, peeling of the coating film was not confirmed as shown in FIG. 8 (B).

(Example 1)
As the coating film according to Example 1, an epichlorohydrin / bisphenol A type coating film containing zinc powder was placed on a brazing sheet with a film thickness of 40 μm.

The above-mentioned corrosion resistance test and subsequent adhesion test were carried out on the coating film. As a result, as shown in the cross-sectional photograph of FIG. 6C, no progress of corrosion to the brazing sheet was observed in the corrosion resistance, and the sacrificial anticorrosion function by the zinc powder was observed. No peeling was confirmed in the subsequent adhesion as shown in FIG. 7 (C).

The above-mentioned moisture resistance test and subsequent adhesion test were carried out on the coating film. As a result, peeling of the coating film was not confirmed as shown in FIG. 8C.

(Example 2)
As the coating film according to Example 2, an epichlorohydrin / bisphenol A type coating film containing zinc powder was installed in a fillet portion of a heat exchanger composed of a brazing sheet with a film thickness of 40 μm.

The above-mentioned corrosion resistance test was carried out on the coating film. As a result, as shown in the cross-sectional photograph of FIG. 6D, it was confirmed that the preferential corrosion of the header portion was effectively suppressed in the corrosion resistance.

(Comparison between Examples and Comparative Examples)
As is clear from the comparison of (A), (B), and (C) of FIGS. 6 and 7, if the coating film thickness is sufficiently thick (Example and Comparative Example 1), the sacrificial anticorrosion function effectively and the coating film Corrosion does not occur under the coating film, but if the coating film thickness is sufficiently thin (Comparative Example 2), corrosion under the coating film occurs due to insufficient blocking of water and oxygen.

Further, as is clear from the comparison of (A), (B), and (C) in FIG. 8, if the coating film thickness is sufficiently thick (Comparative Example 1), the coating film is applied due to stress generation inside the coating film and at the interface with the substrate. The film is easily peeled off, but if the coating film thickness is sufficiently thin (Examples and Comparative Examples 2), the adhesion of the coating film is ensured.

Further, as shown in FIG. 9, the horizontal axis is defined as the coating film thickness, the vertical axis is defined as the adhesiveness remaining in the 100-square grid test, and the adhesiveness of Example 1 and Comparative Example is plotted. It can be seen that 10 to 50 μm is the most suitable condition for ensuring corrosion resistance.

The present invention is not limited to the description of the above-described embodiment, and various modifications can be made within the scope of the claims, and the present invention is disclosed in different embodiments and a plurality of modifications. Embodiments obtained by appropriately combining the above technical means are also included in the technical scope of the present invention.

The present invention can be widely and suitably used in the field of aluminum heat exchangers for air conditioners.

10: Brazing sheet 10a: Bonded surface 10b: Non-joined adjacent surface 11: Core material 12: Brazing material layer 13: Sacrificial anode material layer 14: Epoxy coating film 20: Bonding structure of brazing sheet 21: Joint portion 22: Fillet 30: Plate fin laminate 31: End plate 32: Plate fin 33: Header opening 34: Plate fin laminate 35: Plate fin 40: Parallel flow capacitor (PFC)
41: Header pipe 42: Flat pipe 43: Corrugated fin 51: Heat exchanger 52: Epoxy coating film installation part 53: Blower fan 54: Air filter 55: Drainage receiver

Claims (10)

A heat exchanger made of aluminum, which has a layer of epoxy-based coating film on a part of the surface of the heat exchanger, and the thickness of the coating film is in the range of 10 to 50 μm. A heat exchanger that is installed inside the box so that it is not directly irradiated with ultraviolet rays. The heat exchanger according to claim 1, wherein the epoxy coating film contains a metal powder having a lower potential than aluminum. The heat exchanger according to claim 1, wherein the epoxy-based coating film contains zinc powder. The heat exchanger according to any one of claims 1 to 3, wherein the coating film is installed in a non-ventilated portion. The heat exchanger according to any one of claims 1 to 4, wherein the product associated with the deterioration of the coating film is removed by the condensed water generated during the operation of the heat exchanger. The heat exchanger is composed of a brazing sheet, which is coated on an aluminum alloy core material and one or both sides of the core material, and is sacrificed by an aluminum alloy containing zinc (Zn) and silicon (Si). The heat exchanger according to any one of claims 1 to 5, further comprising a sacrificial anode material layer made of an anode material. The heat exchanger according to claim 6, wherein the coating film is applied to the joint including the sacrificial anode layer. The heat exchanger is made of an aluminum tube or a brazing sheet, the aluminum tube is made of an aluminum alloy, and the surface of the aluminum tube contains zinc (Zn) or zinc (Zn) and silicon (Si). A sacrificial anode material layer made of a sacrificial anode material of an aluminum alloy is provided, and the brazing sheet is coated on a core material made of an aluminum alloy and one or both sides of the core material, and zinc (Zn) or zinc (Zn) and silicon (Zn) and silicon (Zn). The heat exchanger according to any one of claims 1 to 5, further comprising a sacrificial anode material layer made of a sacrificial anode material of an aluminum alloy containing Si). The heat exchanger according to claim 8, wherein the coating film is applied to the joint including the sacrificial anode layer. An air conditioner including the heat exchanger according to any one of claims 1 to 9, wherein the air conditioner is provided with a drainage receiver for receiving dew condensation water generated from the heat exchanger, and the coating is applied vertically above the drainage receiver. An air conditioner provided with a film part.

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