JPWO2017141943A1 - Heat exchanger - Google Patents

Abstract

Provided is a heat exchanger (1) which is low in cost and can suppress corrosion of a heat transfer tube over a long period of time. The heat exchanger (1) has an aluminum tube (2), an aluminum fin (3), a conduction part (11), and an adhesive layer (4). The aluminum fin (3) has an assembly hole (31) into which the aluminum tube (2) is inserted. The aluminum pipe (2) is in contact with the aluminum fin (3) at the conduction portion (11). The adhesive layer (4) is formed between the aluminum tube (2) and the aluminum fin (3). The length of the conductive portion (11) when the sum of the length of the adhesive layer (4) and the length of the conductive portion (11) is 100% in a plan view as viewed from the thickness direction of the aluminum fin (3). Is 5-40%. The natural potential on the surface of the aluminum tube (2) is more noble than the natural potential on the surface of the aluminum fin (3), and the potential difference between them is 30 to 200 mV.

Description

  The present invention relates to a fin-and-tube heat exchanger.

  The fin-and-tube heat exchanger has a heat transfer tube through which a refrigerant flows and a large number of fin plates joined to the heat transfer tube. This type of heat exchanger is often incorporated into, for example, a home air conditioner or a commercial air conditioner.

  The fin plate of the fin-and-tube heat exchanger is fixed to the heat transfer tube by a method such as metal bonding by brazing or fixing by tube expansion. Thereby, the fin plate and the heat transfer tube are electrically connected. Further, the fin plate is configured so that the natural potential is lower than the natural potential of the heat transfer tube. In the conventional heat exchanger configured as described above, the fin plate serves as a sacrificial anode, whereby corrosion of the heat transfer tube can be suppressed over a long period of time.

  However, when brazing the fin plate and the heat transfer tube, it is necessary to heat the fin plate and the heat transfer tube at a relatively high temperature in a nitrogen atmosphere, and thus it is difficult to reduce the manufacturing cost. Moreover, it is difficult to apply the tube expansion process to a heat transfer tube having a columnar structure inside, for example, a flat multi-hole tube.

  Thus, in order to solve these problems, a technique for joining a heat transfer tube to a fin plate using an adhesive has been proposed (Patent Document 1).

JP 2014-152955 A

  However, since the adhesive does not have electrical conductivity, it is difficult to electrically connect the heat transfer tube and the fin plate when the heat transfer tube is joined to the fin plate using the adhesive. Therefore, it is difficult for the heat exchanger in which the heat transfer tube and the fin plate are joined by the adhesive to cause the fin plate to act as a sacrificial anode. For example, when a defect such as a pinhole is present in the adhesive, the heat transfer tube is likely to corrode starting from the defect.

  In order to make the fin plate act as a sacrificial anode, for example, a method of adding conductivity to the adhesive by adding a conductive filler such as silver or carbon to the adhesive can be considered. However, since the adhesive to which the conductive filler is added is relatively expensive, there is a problem that the manufacturing cost of the heat exchanger is increased.

  The present invention has been made in view of such a background, and is intended to provide a heat exchanger that is low in cost and can suppress corrosion of a heat transfer tube over a long period of time.

One aspect of the present invention is an aluminum tube;
An aluminum fin having an assembly hole into which the aluminum tube is inserted;
A conducting portion where the aluminum tube and the aluminum fin are in contact;
Having an adhesive layer formed between the aluminum tube and the aluminum fin,
In a plan view as viewed from the thickness direction of the aluminum fin, the length of the conductive portion is 5 to 40% when the sum of the length of the adhesive layer and the length of the conductive portion is 100%,
The natural potential on the surface of the aluminum tube is higher than the natural potential on the surface of the aluminum fin, and the potential difference between the two is 30 to 200 mV.

  The heat exchanger includes the aluminum tube and the aluminum fin. The aluminum tube is electrically connected to the aluminum fin through the conduction portion. The natural potential on the surface of the aluminum tube is nobler than the natural potential on the surface of the aluminum fin, and the potential difference between them is 30 to 200 mV. Therefore, the aluminum fin serves as a sacrificial anode, and corrosion of the aluminum tube can be suppressed over a long period of time.

  The adhesive layer is formed between the aluminum tube and the aluminum fin. Therefore, in the operation | work which adhere | attaches the said aluminum pipe | tube to the said aluminum fin, while being able to make heating temperature low compared with brazing, it can heat in an atmospheric condition. Furthermore, since the aluminum tube and the aluminum fin are electrically connected at the conduction portion, it is not necessary to add a conductive filler to the adhesive layer to impart conductivity. As a result, the heat exchanger can be manufactured at a lower cost than conventional heat exchangers.

  As mentioned above, the said heat exchanger is low-cost, and can suppress corrosion of an aluminum pipe over a long period of time.

It is a perspective view of the principal part of the heat exchanger in Example 1. FIG. FIG. 2 is a partially enlarged cross-sectional view in the vicinity of a conduction part in FIG. 1. FIG. 3 is a partial cross-sectional view taken along line III-III in FIG. 1. It is a perspective view of the test piece used for adhesive evaluation in Experimental example 1. FIG.

  In the heat exchanger, the conduction portion is formed in a portion where the adhesive layer is not present between the aluminum tube and the aluminum fin. That is, the aluminum tube has, on its outer surface, a region that is in contact with the aluminum fin and a region that is covered with the adhesive layer.

  The length of the conductive portion is 5 to 40% when the sum of the length of the adhesive layer and the length of the conductive portion is 100% in a plan view as viewed from the thickness direction of the aluminum fin. By setting the length of the conductive portion to 5% or more, the area where the aluminum fin and the aluminum tube are in metal contact can be sufficiently widened. Thereby, an aluminum fin and an aluminum pipe can be reliably electrically connected, and corrosion of the aluminum pipe can be suppressed over a long period of time.

  Moreover, the adhesion area of an aluminum fin and an aluminum tube can be fully enlarged by making the length of a conduction | electrical_connection part 40% or less. As a result, the adhesive force between the aluminum fin and the aluminum tube can be further increased.

  Therefore, by setting the length of the conducting portion to 5 to 40%, it is possible to increase the adhesive force between the aluminum fin and the aluminum tube while obtaining the effect of suppressing the corrosion of the aluminum tube. From the same viewpoint, it is preferable that the length of the conductive portion is 10 to 30%.

  The natural potential on the surface of the aluminum tube is more noble than the natural potential on the surface of the aluminum fin, and the potential difference between them is 30 to 200 mV. By setting the potential difference between the two in the specific range, the aluminum fin can act as a sacrificial anode. As a result, corrosion of the aluminum tube can be suppressed over a long period of time.

  When the natural potential of the aluminum tube is lower than the natural potential of the aluminum fin, the aluminum tube corrodes before the aluminum fin, so that the corrosion of the aluminum tube is accelerated.

  If the potential difference between the two is less than 30 mV, the effect of suppressing corrosion of the aluminum tube may be insufficient. From the viewpoint of avoiding such a problem, the potential difference between the natural potential on the surface of the aluminum tube and the natural potential on the surface of the aluminum fin is set to 30 mV or more. From the same viewpoint, it is preferable that the potential difference between them is 60 mV or more.

  On the other hand, when the potential difference between the two is greater than 200 mV, the corrosion rate of the aluminum fins is excessively increased, and the action of the sacrificial anode by the aluminum fins may be impaired early. As a result, the effect of suppressing corrosion of the aluminum tube may be insufficient. From the viewpoint of avoiding such a problem, the potential difference between the natural potential on the surface of the aluminum tube and the natural potential on the surface of the aluminum fin is set to 200 mV or less. From the same viewpoint, it is preferable that the potential difference between the two is 150 mV or less.

  As the aluminum tube, pipe materials having various shapes such as a round tube, an elliptical tube, and a flat tube can be employed. The aluminum tube may be an extruded shape formed by extrusion, or may be a formed plate formed by joining aluminum plates formed into a tubular shape by brazing or the like. The flat tube described above includes a so-called flat multi-hole tube having a plurality of flow paths inside the tube.

  When the aluminum tube is a flat tube, it is preferable that the end portion in the width direction of the flat tube is in contact with the aluminum fin. That is, it is preferable that a conducting portion is formed at the end in the width direction of the flat tube. When the aluminum tube is a flat tube, the flat tube and the aluminum fin can be brought into contact with each other with a relatively small pressing force by pressing the flat tube inserted into the assembly hole in the width direction. Therefore, in this case, in the operation of bonding the flat tube to the aluminum fin, the deformation of the flat tube and the aluminum fin accompanying pressing can be more effectively suppressed.

  The adhesive layer is preferably formed between the flat surface of the flat tube and the aluminum fin. An adhesive can be easily applied to the flat surface of the flat tube using, for example, a roll coater. And an adhesive layer can be more easily formed between an aluminum fin and a flat surface by inserting the flat tube which apply | coated the adhesive agent to the flat surface previously in an assembly hole. Therefore, in this case, the workability of the work of bonding the flat tube to the aluminum fin can be further improved.

A zinc thermal spray coating may be formed on the surface of the aluminum tube. In this case, corrosion of the aluminum tube can be suppressed for a longer period. In the case of forming a zinc spray coating, the amount of zinc attached to the surface of the aluminum tube is preferably 3 to 12 g / m ² .

  The aluminum tube may be made of aluminum or aluminum alloy. As an aluminum alloy, for example, an alloy containing Mn (manganese), Si (silicon), Fe (iron) and Cu (copper), with the remainder having chemical components composed of Al (aluminum) and inevitable impurities should be adopted. Can do.

  The Mn content is preferably 0.10 to 1.50 mass%. By setting the Mn content to 0.10% by mass or more, the amount of the Al—Mn intermetallic compound can be increased. As a result, the strength of the aluminum tube can be further improved. In the case where Mn and Fe coexist, Fe is taken into the Al-Mn intermetallic compound, so that a decrease in corrosion resistance due to Fe can be avoided.

  Further, Mn can make the natural potential of the aluminum tube noble. Therefore, the potential difference between the aluminum tube and the aluminum fin can be easily increased by setting the Mn content to 0.10% by mass or more. As a result, the corrosion resistance of the aluminum tube can be further improved.

  On the other hand, if the amount of the Al—Mn intermetallic compound is excessively increased, the extrudability may be deteriorated. Therefore, from the viewpoint of avoiding a decrease in extrudability, the Mn content is preferably 1.50% by mass or less.

  The Si content is preferably 0.10 to 0.60 mass%. Coexistence of Si and Mn produces an Al—Mn—Si intermetallic compound. Thereby, the production amount of the Al—Mn intermetallic compound can be reduced. Therefore, by setting the Si content to 0.10% by mass or more, excessive generation of Al-Mn intermetallic compounds can be easily avoided, and the extrudability of the aluminum tube can be easily reduced. It can be avoided.

  On the other hand, when the content of Si is excessively large, there is a possibility that the life of the extrusion die or the extrudability is deteriorated. Therefore, from the viewpoint of avoiding these problems, the Si content is preferably 0.60% by mass or less.

  The Fe content is preferably 0.10 to 0.80 mass%. Coexistence of Fe with Mn or Si produces an Al—Mn—Fe intermetallic compound or an Al—Mn—Fe—Si intermetallic compound. Thereby, the production amount of the Al—Mn intermetallic compound can be reduced. Therefore, by setting the Fe content to 0.10% by mass or more, excessive generation of Al—Mn intermetallic compounds can be easily avoided, and hence the extrudability of the aluminum tube can be easily reduced. It can be avoided.

  On the other hand, if the Fe content is excessively large, an intermetallic compound containing Fe crystallizes on the surface of the aluminum tube, which may lead to a decrease in corrosion resistance. In this case, the extrudability of the aluminum tube may be reduced. Therefore, from the viewpoint of avoiding these problems, the Fe content is preferably 0.80% by mass or less.

  The Cu content is preferably 0.050 to 0.70 mass%. Cu can make the natural potential of the aluminum tube noble. Therefore, the potential difference between the aluminum tube and the aluminum fin can be easily increased by setting the Cu content to 0.050 mass% or more. As a result, the corrosion resistance of the aluminum tube can be further improved.

  On the other hand, when the content of Cu is excessively large, an intermetallic compound containing Cu may be precipitated. Since this intermetallic compound promotes the cathode reaction, it may increase the corrosion rate. Therefore, from the viewpoint of avoiding an increase in the corrosion rate, the Cu content is preferably 0.70% by mass or less.

  The aluminum fins assembled to the aluminum tube usually have a plate thickness of 0.07 to 0.15 mm. The aluminum fin has an assembly hole for inserting an aluminum tube. The assembly hole is formed in a shape corresponding to the outer shape of the aluminum tube, such as a circle, an ellipse, or an oval.

  The assembly hole may be a notch provided in the aluminum fin. In this case, the heat exchanger can be manufactured by a so-called knuckling method in which an aluminum tube is press-fitted from the opening of the notch. In this case, the aluminum fin and the aluminum tube can be easily brought into contact with each other after the aluminum tube is press-fitted into the notch. As a result, the conduction part can be easily formed.

  The cutout is preferably formed in a shape corresponding to the outer shape of the aluminum tube, such as a semicircular shape, a semielliptical shape, or a U shape. In this case, the electrical connection between the aluminum fin and the aluminum tube can be performed more easily, and the adhesive force between the two can be further increased.

  The aluminum fin may have a collar portion protruding from the periphery of the assembly hole. In this case, the aluminum tube inserted into the assembly hole can be easily brought into contact with the collar portion. As a result, the conduction part can be easily formed.

  When the aluminum tube is a flat tube, the height of the collar portion is 200 μm or more and ½ or less of the thickness of the flat tube, and the collar portion and the adhesive layer in the height direction of the collar portion The contact length is preferably not less than 200 μm and not more than the height of the collar portion.

  By setting the height of the collar portion to 200 μm or more, the area of the contact portion between the flat tube and the collar portion can be further increased. As a result, the conduction part can be easily formed. On the other hand, when the height of the collar portion is excessively high, it is necessary to increase the pitch of the aluminum fins, so that the number of aluminum fins attached to the flat tube is reduced. As a result, the cooling performance of the heat exchanger may be deteriorated. From the viewpoint of avoiding such a problem, it is preferable that the height of the collar portion is ½ or less of the thickness of the flat tube.

  Moreover, the adhesive force of a flat tube and an aluminum fin can be made higher by making the contact length of a collar part and an adhesive bond layer 200 micrometers or more. The contact length between the collar portion and the adhesive layer is structurally less than the height of the collar portion.

  The aluminum fin may be made of aluminum or may be made of an aluminum alloy. Examples of the aluminum alloy include additive elements such as Zn (zinc), Fe, Mn, Si, Cu, Mg (magnesium), Cr (chromium), Ti (titanium), V (vanadium), and Sn (tin). 1 type or more is contained and what consists of Al and an inevitable impurity can be employ | adopted for the remainder.

  The Zn content is preferably 6.0% by mass or less. Zn can lower the natural potential of the aluminum fin surface. By setting the Zn content in the specific range, the potential difference between the natural potential on the surface of the aluminum fin and the natural potential on the surface of the aluminum tube can be easily adjusted. As a result, the potential difference in the specific range can be easily realized.

  On the other hand, if the Zn content is excessively large, the self-corrosion resistance of the aluminum fins may be lowered. From the viewpoint of avoiding such a problem, the Zn content is preferably 6.0% by mass or less.

  The Fe content is preferably 0.10 to 0.80 mass%. Fe dissolves in the Al matrix, and the strength of the aluminum fins can be improved by solid solution strengthening. Further, Fe can be dispersed in the base material as an Fe-based crystallized product, and the strength of the aluminum fin can be improved by dispersion strengthening. By setting the content of Fe to 0.10% by mass or more, the strength of the aluminum fin can be further increased by solid solution strengthening and dispersion strengthening.

  When the Fe content is excessively large, an intermetallic compound containing Fe is crystallized on the surface of the aluminum fin, which may cause a decrease in corrosion resistance. Therefore, from the viewpoint of avoiding a decrease in corrosion resistance, the Fe content is preferably 0.80% by mass or less.

  The Mn content is preferably 0.10 to 2.0 mass%. By setting the Mn content to 0.10% by mass or more, the amount of the Al—Mn intermetallic compound can be increased. As a result, the strength of the aluminum tube can be further improved. In the case where Mn and Fe coexist, Fe is taken into the Al-Mn intermetallic compound, so that a decrease in corrosion resistance due to Fe can be avoided.

  On the other hand, when the content of Mn is excessively large, a coarse intermetallic compound is formed, which may cause a deterioration in manufacturability. Therefore, from the viewpoint of avoiding deterioration in manufacturability, the Mn content is preferably set to 2.0% by mass or less.

  The content of Si is preferably 0.10 to 1.50% by mass. Si has a function of being dissolved in the aluminum matrix and improving the strength of the aluminum fin in accordance with the amount of addition. In addition, Si coexists with Mn to precipitate a fine Al—Mn—Si intermetallic compound, thereby improving the strength and workability. These effects can be obtained by setting the Si content to 0.10% by mass or more.

  On the other hand, when the Si content is excessively large, the corrosion resistance of the aluminum fins may be reduced. Therefore, from the viewpoint of avoiding a decrease in corrosion resistance, the Si content is preferably 1.50% by mass or less.

  The Cu content is preferably 0.10% by mass or less. If the Cu content is excessively large, the corrosion rate of the aluminum fins may be increased and the natural potential of the surface may become noble. By restricting the Cu content to 0.10% by mass or less, these problems can be easily avoided.

  Further, in order to further improve the strength and corrosion resistance of the aluminum fin, Mg, Cr, Ti, V, Sn and the like may be added as appropriate.

  An adhesive layer is formed between the aluminum tube and the aluminum fin. As the adhesive layer, for example, an adhesive such as a hot melt adhesive such as a thermoplastic resin and a hot melt adhesive; a reactive adhesive such as a thermosetting resin and a thermosetting adhesive can be used. . Specific examples of the heat curable adhesive include known adhesives such as epoxy adhesives, polyurethane adhesives, and phenol adhesives. These adhesives may be used independently and may use multiple types together.

  It is preferable that the adhesive layer covers the entire outer surface of the aluminum tube excluding the conductive portion. In this case, the presence of the adhesive layer can further improve the corrosion resistance of the aluminum tube.

  Moreover, it is preferable that the aluminum pipe and the aluminum fin have a chemical conversion film on the surface. By forming the chemical conversion film on the surfaces of the aluminum tube and the aluminum fin, the adhesiveness of the adhesive layer can be further increased. As a result, the adhesive force between the aluminum tube and the aluminum fin can be further increased.

  Examples of the chemical conversion film include reactive chemical conversion treatment such as phosphate chromate treatment, chromate chromate treatment, zirconium phosphate treatment, and titanium phosphate treatment; coating chemical conversion treatment such as coating chromate treatment and coating zirconium treatment; boehmite Films formed by various treatments such as an oxide film-based chemical conversion treatment such as treatment can be employed.

Example 1
An embodiment of the heat exchanger will be described with reference to the drawings. As shown in FIG. 1, the heat exchanger 1 has an aluminum tube 2, an aluminum fin 3, a conduction part 11, and an adhesive layer 4. As shown in FIGS. 1 and 3, the aluminum fin 3 has an assembly hole 31 into which the aluminum tube 2 is inserted. As shown in FIGS. 1 and 2, the aluminum tube 2 is in contact with the aluminum fin 3 at the conduction portion 11. As shown in FIGS. 1 to 3, the adhesive layer 4 is formed between the aluminum tube 2 and the aluminum fin 3.

  The aluminum tube 2 is electrically connected to the aluminum fin 3 via the conduction portion 11. The natural potential on the surface of the aluminum tube 2 is noble than the natural potential on the surface of the aluminum fin 3, and the potential difference between them is 30 to 200 mV.

  As shown in FIG. 1, the heat exchanger 1 of this example includes a number of aluminum fins 3 arranged at intervals in the plate thickness direction, and a plurality of aluminum tubes 2 extending in the plate thickness direction of the aluminum fins 3. And have. The aluminum fin 3 has a substantially rectangular shape in plan view as viewed from the thickness direction.

  As shown in FIG. 1, the assembly hole 31 in the aluminum fin 3 of this example is a notch 311 provided at the outer peripheral edge of the aluminum fin 3. The notch 311 extends in the plate width direction from the outer peripheral edge of the aluminum fin 3 and has a U shape in plan view. The notch 311 is configured so that the aluminum tube 2 can be press-fitted from an open portion 312 provided at the outer peripheral edge of the aluminum fin 3.

  As shown in FIGS. 1 and 3, the aluminum fin 3 of this example has a collar portion 32 protruding from the periphery of the assembly hole 31. Although the height of the color part 32 is not specifically limited, For example, it can be 200 micrometers or more.

  As shown in FIG. 1, the aluminum tube 2 of the present example is a flat multi-hole tube 21 having a cross section in the longitudinal direction that is oval and having a plurality of channels 211 formed therein. The flat multi-hole tube 21 is disposed so that the width direction thereof is parallel to the plate width direction of the fin plate. As shown in FIGS. 1 and 2, the flat multi-hole tube 21 is in contact with the collar portion 32 at one end portion 212 in the width direction, that is, a portion having a curved surface. The one end portion 212 of the flat multi-hole tube 21 and the tip portion 321 of the U-shape of the collar portion 32 constitute the conducting portion 11.

  As shown in FIG. 1, the flat surface 213 and the other end 214 of the flat multi-hole tube 21 are covered with the adhesive layer 4. As shown in FIGS. 2 and 3, the adhesive layer 4 is formed between the flat surface 213 of the flat multi-hole tube 21 and the collar portion 32.

  The heat exchanger 1 of this example can be manufactured as follows, for example. First, the aluminum fins 3 prepared by a conventional method are arranged at intervals in the plate thickness direction. Next, an adhesive is applied to the flat surface 213 and the other end 214 of the flat multi-hole tube 21 prepared by a conventional method using a roll coater or the like. At this time, one end 212 of the flat multi-hole tube 21 may be covered with a masking material. In this case, adhesion of the adhesive to one end 212 can be reliably prevented.

  After applying the adhesive, the flat multi-hole tube 21 is press-fitted into the assembly hole 31 of the aluminum fin 3, and one end 212 of the flat multi-hole tube 21 and the tip 321 of the collar portion 32 are brought into contact with each other. Thereby, the conduction | electrical_connection part 11 is formed. Thereafter, the adhesive is heated and cured, thereby forming the adhesive layer 4 and bonding the aluminum fin 3 and the flat multi-hole tube 21 together. As described above, the heat exchanger 1 can be manufactured.

  Next, the effect of the heat exchanger 1 of this example is demonstrated. The heat exchanger 1 has a flat multi-hole tube 21 as an aluminum tube 2 and aluminum fins 3. The flat multi-hole tube 21 is electrically connected to the aluminum fin 3 through the conduction portion 11. Moreover, the natural potential on the surface of the flat multi-hole tube 21 is more noble than the natural potential on the surface of the aluminum fin 3, and the potential difference between them is 30 to 200 mV. Therefore, the aluminum fin 3 becomes a sacrificial anode, and corrosion of the flat multi-hole tube 21 can be suppressed over a long period of time.

  Further, as shown in FIGS. 2 and 3, an adhesive layer 4 is formed between the flat multi-hole tube 21 and the aluminum fin 3. Therefore, in the operation | work which adhere | attaches the flat multi-hole tube 21 to the aluminum fin 3, while being able to make heating temperature low compared with brazing, it can heat in an atmospheric condition. Furthermore, since the flat multi-hole tube 21 and the aluminum fin 3 are electrically connected in the conducting portion 11, it is not necessary to add a conductive filler to the adhesive layer 4 to impart conductivity. As a result, the heat exchanger 1 can be manufactured at a lower cost than the conventional heat exchanger 1.

  As described above, the heat exchanger 1 is low in cost and can suppress the corrosion of the flat multi-hole tube 21 over a long period of time.

  As shown in FIGS. 1 and 2, in this example, the shape of one end 212 in the width direction of the flat multi-hole tube 21 corresponds to the shape of the collar portion 32 of the aluminum fin 3. Therefore, the conduction part 11 can be formed more easily.

  In addition, since the collar portion 32 is formed, the aluminum fin 3 has higher rigidity than an aluminum fin that does not have the collar portion 32. Thereby, in the operation | work etc. which press-fit the flat multi-hole pipe 21 in the assembly hole 31, the deformation | transformation of the aluminum fin 3 accompanying a press can be suppressed more effectively.

  As shown in FIGS. 2 and 3, the adhesive layer 4 is formed between the flat surface 213 of the flat multi-hole tube 21 and the aluminum fin 3. Therefore, the adhesive layer 4 can be more easily formed between the aluminum fin 3 and the flat surface 213 by inserting the flat multi-hole tube 21 in which the adhesive is previously applied to the flat surface 213 into the assembly hole 31. it can. Therefore, in this case, the workability of the work of bonding the flat multi-hole tube 21 to the aluminum fin 3 can be further improved.

  As shown in FIG. 1, the assembly hole 31 of this example is a U-shaped notch 311 provided in the aluminum fin 3. Therefore, the heat exchanger 1 can be easily manufactured by press-fitting the flat multi-hole tube 21 from the opening 312 of the notch 311. Furthermore, after the flat multi-hole tube 21 is press-fitted into the notch 311, the aluminum fin 3 and the flat multi-hole tube 21 can be easily brought into contact with each other. As a result, the conduction part 11 can be easily formed.

  The aluminum fin 3 has a collar portion 32 that protrudes from the peripheral edge of the assembly hole 31. In this case, the flat multi-hole tube 21 inserted into the assembly hole 31 can be easily brought into contact with the collar portion 32. As a result, the conduction part 11 can be easily formed.

(Experimental example 1)
In this example, the performance of the heat exchanger 1 is evaluated. The specimen used for evaluation was produced as follows. Of the reference numerals used below, the same reference numerals as those used in the examples indicate the same components as in the first example unless otherwise specified.

<Preparation of aluminum fin 3>
An ingot of an aluminum alloy (alloys A1 to A7) having chemical components shown in Table 1 was successively subjected to hot rolling, cold rolling, annealing and cold rolling to produce an aluminum plate having a thickness of 0.1 mm. The obtained aluminum plate was pressed to produce aluminum fins 3 having the same shape as in Example 1. The length of the aluminum fin 3 in this example is 40 mm, the plate width is 20 mm, and the height of the collar portion 32 is 150 μm. The aluminum fin 3 was formed with three notches 311 at equal intervals. Moreover, the symbol “Bal.” In Table 1 is a symbol indicating the remainder.

<Preparation of flat multi-hole tube 21>
Casting of an aluminum alloy containing Si: 0.15% by mass, Mn: 0.12% by mass, Cu: 0.43% by mass and Fe: 0.20% by mass with the balance being a chemical component consisting of Al and impurities The lump was extruded to produce a flat multi-hole tube 21 having an oval cross-sectional shape. The flat multi-hole tube 21 of this example has a length of 60 mm, a width of 14 mm, a thickness of 1.5 mm, and a wall thickness of 0.35 mm. Further, the flat multi-hole tube 21 includes 16 channels 211 having a square shape of 0.5 mm square.

<Assembly of specimen>
One end 212 in the width direction of the flat multi-hole tube 21 and the vicinity thereof were covered with a masking material so that the length of the conductive portion 11 was a value shown in Table 2. Next, an epoxy adhesive was applied to the flat surface 213 and the other end 214 of the flat multi-hole tube 21, and the adhesive was dried by heating at 100 ° C. for 10 minutes. Thereafter, the masking material was peeled from the flat multi-hole tube 21 to expose the aluminum alloy.

  Next, 20 aluminum fins 3 were arranged at a pitch of 1.5 mm. The flat multi-hole tube 21 was press-fitted into the assembly holes 31 of these aluminum fins 3 from one end 212, and the end 212 and the tip 321 of the collar 32 were brought into contact with each other. Then, these were heated at 175 degreeC for 15 minutes, maintaining the state which the flat multi-hole tube 21 and the collar part 32 contact | abutted. As a result, the adhesive was cured to form an adhesive layer 4 having a thickness of 15 to 25 μm. Thus, test specimens shown in Table 2 were produced.

  Using the specimen obtained as described above, the following items were evaluated.

<Electric contact between flat multi-hole tube 21 and aluminum fin 3>
A terminal of a conductivity meter (“Sigma Test 2.069” manufactured by Nihon Felster Co., Ltd.) was brought into contact with each of the aluminum fin 3 and the flat multi-hole tube 21 to measure electric resistance. As a result, “A” is described in the column of “Metal contact” in Table 2 for the test piece having an electrical resistance value of 0Ω, and “A” is shown in the same column for the test piece having a value larger than 0Ω. B ".

<Spontaneous potential>
A 5% NaCl aqueous solution adjusted to pH 3 with acetic acid was prepared. Using this aqueous solution, the natural potential on the surface of the aluminum fin 3 and the natural potential on the surface of the flat multi-hole tube 21 were measured at room temperature. The results are shown in Table 2. Further, the potential difference obtained by subtracting the natural potential of the surface of the aluminum fin 3 from the natural potential of the surface of the flat multi-hole tube 21 is shown in the “potential difference” column of Table 2.

<Length of the conductive portion 11>
Each test body was cut at the center in the height direction of the collar portion 32 to expose the cross section. And the optical microscope image of this cross section was acquired. Based on the obtained optical microscope image, the length L _A [mm] of the portion where the collar portion 32 and the adhesive layer 4 are in contact and the length of the portion where the collar portion 32 and the flat multi-hole tube 21 are in contact with each other. L _B [mm] was calculated. The length Satoshi adhesive layer 4 to L _A, as the length of the conductive portion 11 of the L _B, and calculate the value of _{L B / (L A + L} B) × 100. The results are shown in Table 2.

<Adhesiveness>
Separately from the test body used for the corrosion resistance evaluation etc., as shown in FIG. 4, a test piece in which one flat multi-hole tube 21 was bonded to the aluminum fin 3 was prepared. This test piece has a through hole 33 for connecting the aluminum fins 3 with the connecting pin 5 provided in the aluminum fin 3 and the number of the flat multi-hole tubes 21 is one. It has the same configuration as the test specimen used for corrosion resistance evaluation. In FIG. 4, the flat multi-hole tube 21 is simplified by reducing the number of the flow paths 211.

  As shown in FIG. 4, the connecting pins 5 were inserted into the through holes 33 to connect the aluminum fins 3 to each other. Then, the connecting pin 5 was pulled with the flat multi-hole tube 21 fixed, and the maximum load until the flat multi-hole tube 21 was completely pulled out from the aluminum fin 3 was measured. Then, the value obtained by dividing the obtained maximum load by the number of aluminum fins 3 was defined as the adhesive force between the flat multi-hole tube 21 and the aluminum fins 3. When this adhesive force is 400 N or more, “A +” is described in the “adhesive” column of Table 2, and when it is 300 N or more and less than 400 N, “A” is described in the same column. When it is less than 300 N, “B” is described in the same column.

<Corrosion resistance>
The SWAAT test was carried out for 3000 hours by a method according to ASTM G85. After the test was completed, the cross section of the flat multi-hole tube 21 was observed, and the maximum corrosion depth was measured. As a result of cross-sectional observation, when the maximum corrosion depth is 100 μm or less, “A +”, and when the maximum corrosion depth is more than 100 μm and less than 350 μm, “A”, the flat multi-hole tube 21 penetrates due to corrosion. In this case, the symbol “B” is shown in the column of “Corrosion resistance” in Table 2.

  As shown in Table 1 and Table 2, the test bodies 1 to 21 have the conduction part 11, and the potential difference between the natural potential on the surface of the flat multi-hole tube 21 and the natural potential on the surface of the aluminum fin 3 is the above. It was a specific range. Therefore, it was excellent in both adhesiveness and corrosion resistance.

  Moreover, the test bodies 2-3, 6-7, 10-12, 15-16, and 19-20 in which the electric potential difference of both exists in the range of 60-150 mV showed the especially excellent corrosion resistance.

  On the other hand, the specimens 22, 24, and 26 had a small potential difference, so that the anticorrosion effect by the aluminum fins 3 was insufficient. Moreover, since the test bodies 23, 25, and 27 had a large potential difference, the corrosion rate of the aluminum fin 3 was excessively increased. As a result, the action of the sacrificial anode by the aluminum fin 3 was impaired early.

Since the length of the conduction | electrical_connection part 11 was smaller than the said specific range as for the test bodies 28-31, the electrical connection of the flat multi-hole pipe 21 and the aluminum fin 3 was not formed. As a result, the aluminum fin 3 was not a sacrificial anode.
Since the length of the conduction | electrical_connection part 11 was larger than the said specific range, the test bodies 32-35 had the low adhesiveness of the flat multi-hole pipe 21 and the aluminum fin 3. FIG.

(Experimental example 2)
In this example, the adhesiveness between the aluminum fin 3 and the aluminum tube 2 is evaluated when the height of the collar portion 32 is variously changed. In this example, a test specimen was prepared in the same manner as in Experimental Example 1 except that the height of the collar portion 32 was changed as shown in Table 3. And evaluation of the adhesiveness of the obtained test body was performed by the same method as Example 2.

  In this example, the contact length between the collar portion 32 and the adhesive layer 4 in the obtained specimen was measured by the following method.

<Contact length between collar portion 32 and adhesive layer 4>
Each specimen was cut at the center in the plate width direction of the aluminum fin 3 to expose the cross section shown in FIG. And the optical microscope image of this cross section was acquired. Based on the obtained optical microscope image, the length of the portion where the color portion 32 and the adhesive layer 4 are in contact with each other was measured. The results are shown in the column of “Contact length between collar portion 32 and adhesive layer 4” in Table 3.

  As shown in Table 3, in the test bodies 36 and 37, the height of the collar portion 32 was 200 μm or more and 1/2 or less of the thickness of the flat multi-hole tube 21. Further, the contact length between the collar portion 32 and the adhesive layer 4 was 200 μm or more and not more than the height of the collar portion 32. Therefore, the adhesiveness was better than that of the test body 38 in which the height of the collar portion 32 and the contact length between the collar portion 32 and the adhesive layer 4 were outside the specific range.

(Experimental example 3)
In this example, the adhesion between the aluminum fin 3 and the aluminum tube 2 when the chemical conversion film is formed is evaluated using a test piece. In this example, a test piece was produced as follows and a tensile shear test defined in JIS K6850 was performed.

<Base material and adherend>
A plurality of plate materials made of JIS A1050 aluminum having a thickness of 3.0 mm, a width of 25 mm, and a length of 100 mm were prepared and subjected to a degreasing treatment. Then, the phosphoric acid chromate process was performed to some board | plate materials, and the chemical conversion film was formed in the surface. The amount of Cr deposited in the phosphoric acid chromate treatment was 20 mg / m ² .

<Production of test piece>
Using the plate material obtained as described above as a base material and an adherend, a test piece was prepared according to the following procedure. First, an epoxy adhesive was applied to the surface of the substrate, and the adhesive was dried by heating at 100 ° C. for 10 minutes. The thickness of the adhesive was 15 to 25 μm. Subsequently, the base material and the adherend were overlapped in the combinations shown in Table 4, and heated at 170 ° C. for 15 minutes. The overlapping length of the base material and the adherend was 12.5 mm ± 0.25 mm. The base material and the adherend were bonded as described above to produce a test piece.

  Using the obtained test piece, a tensile shear adhesion test was performed, and the fracture mode of the adhesive was observed. The results are shown in Table 4.

  As shown in Table 4, the fracture form of the test piece B1 in which the chemical conversion film was formed on both the substrate and the adherend was cohesive failure of the adhesive. On the other hand, the fracture forms of the test bodies B2 to B4 were all interfacial peeling at the interface between the base material not having a chemical conversion film and the adhesive or the interface between the adherend and the adhesive not having the chemical conversion film. From these results, it can be understood that the adhesiveness between the adhesive layer 4 and the chemical conversion film is higher than the adhesiveness between the adhesive layer 4 and aluminum. Therefore, it can be understood that the adhesiveness between the aluminum tube 2 and the aluminum fin 3 can be increased by forming the chemical conversion film on both the aluminum tube 2 and the aluminum fin 3.

  In addition, the heat exchanger 1 of this invention is not limited to the aspect of the Example and experiment example which were mentioned above, A structure can be changed suitably in the range which does not impair the meaning. For example, in the first embodiment, the example in which the entire surface of the outer surface of the aluminum tube 2 other than the conductive portion 11 is covered with the adhesive layer 4 has been described, but the other end 214 of the aluminum tube 2 is the adhesive layer 4. The aluminum may be exposed without being covered.

  In the examples and experimental examples, the flat multi-hole tube 21 is used as the aluminum tube 2, but a round tube or an elliptic tube can be used instead of the flat multi-hole tube 21. Further, in the examples and experimental examples, the example in which the assembly hole 31 is the notch 311 has been shown. Good. In this case, the heat exchanger 1 can be assembled by inserting the aluminum tube 2 whose surface is previously coated with an adhesive into the assembly hole 31 from the thickness direction of the aluminum fin 3.

  Moreover, the flow path 211 formed inside the aluminum tube 2 can be changed as appropriate according to the required cooling performance. For example, in the examples and the experimental examples, the example of the flat multi-hole tube 21 having the square channel 211 is shown, but the shape of the channel 211 may be triangular. Further, it is possible to provide a protrusion or the like for disturbing the flow of the refrigerant in the flow path 211.

Claims (5)

An aluminum tube,
An aluminum fin having an assembly hole into which the aluminum tube is inserted;
A conducting portion where the aluminum tube and the aluminum fin are in contact;
Having an adhesive layer formed between the aluminum tube and the aluminum fin,
In a plan view as viewed from the thickness direction of the aluminum fin, the length of the conductive portion is 5 to 40% when the sum of the length of the adhesive layer and the length of the conductive portion is 100%,
The heat exchanger in which the natural potential on the surface of the aluminum tube is nobler than the natural potential on the surface of the aluminum fin, and the potential difference between the two is 30 to 200 mV.   The heat exchanger according to claim 1, wherein the aluminum tube is a flat tube, and an end portion of the flat tube in a width direction is in contact with the aluminum fin.   The heat exchanger according to claim 2, wherein the adhesive layer is formed between a flat surface of the flat tube and the aluminum fin.   The aluminum fin has a collar portion protruding from a peripheral edge of the assembly hole, and the height of the collar portion is 200 μm or more and ½ or less of the thickness of the flat tube. 4. The heat exchanger according to claim 2, wherein a contact length between the collar portion and the adhesive layer in a height direction is 200 μm or more and not more than a height of the collar portion.   The heat exchanger according to any one of claims 1 to 4, wherein the aluminum pipe and the aluminum fin have a chemical conversion film on a surface thereof.

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