BRPI1103196A2 - aluminum alloy cladding element, and, heat exchanger - Google Patents

Abstract

ELEMENT OF ALUMINUM ALLOY COATING, AND, HEAT EXCHANGER. In a heat exchanger 10 made of an aluminum alloy in which collecting tanks 4 are joined at the ends of a plurality of tubes 2 in their longitudinal direction by brazing, and corrosion resistance is given to tubes 2 by the sacrificial corrosion action of the fins 3 arranged among the plurality of tubes 2, an aluminum alloy coating element is used to form the collecting tanks 4, in which the aluminum alloy coating element has a brazing material containing Si in an amount not less than 3.5% by weight, but not more than 5.0% by weight. This makes it possible to establish the distances L1 from the collecting tank 4 to the fins 3 not less than 0 mm, but not more than 4 mm, which is less than in the conventional heat exchanger. As a result, the sacrificial corrosion action of the fins 3 can be used for all tubes, and the corrosion resistance of the tubes can be further improved compared to the prior art.

Description

"ALUMINUM ALLOY COATING ELEMENT, AND, HEAT EXCHANGER" TECHNICAL FIELD

This invention relates to an aluminum alloy coating element and a heat exchanger using it. TECHNICAL BACKGROUNDS

A heat exchanger with tubes and fins that are rolled into a plurality of units and both ends of the tubes are inserted into the collecting tanks that were produced by assembling the pipes and the collecting tanks together and then joining them together by brazing.

In order to form the pipes and manifolds, an aluminum alloy casing element is used in the heat exchanger, which comprises an aluminum alloy core element coated with an Al-Si brazing material (see, for example, Japanese unexamined patent publication H7-305994). SUMMARY OF THE INVENTION

The tubes can be roughly grouped into two types, depending on their forming methods. One is of the extrusion type which is formed by an extrusion forming method, and the other is of the plate type which is formed by bending a plate element such as a coating element.

In the heat exchanger in which extrusion type tubes are used, zinc is thermally bonded to the outer surfaces of the tubes to maintain the corrosion resistance of the tubes.

On the other hand, in the heat exchanger in which plate type tubes are used, zinc is added to the fin elements to make the corrosion potential of the fins smaller than that of the tubes, to give corrosion resistance to the tubes based on sacrificial corrosion action of the fins. However, in the conventional heat exchanger using plate type pipes, no fin was arranged in the pipe portions near the collecting tanks. In the portions of the pipes where there was no fin from the collecting tanks to the fins, therefore, there was the problem that no sacrificial corrosion action obtained by the fins was obtained.

No fins were arranged in the pipe portions near the collecting tanks, because if the fins were arranged close to the collecting tanks, or in a manner in contact with the collecting tanks, the brazing material of the coating element used to forming the collecting tanks was fluidized to contact the fins at the time of brazing, and the fins would fuse because of the Si component in the brazing material. In other words, the melting point of the fin element itself is greater than the heating temperature at the time of brazing. However, if the Si component in the brazing material of the collecting tanks diffuses into the fin element, the melting point of the fin element decreases and the fins fuse at the heating temperature at the time of brazing.

Therefore, in the conventional heat exchanger in which corrosion resistance was imparted to the tubes by the sacrificial corrosion action of the fins, the fins were arranged keeping a certain distance (5 mm or more) from the collecting tank. Thus, the sacrificial corrosion action of the fins cannot be used for all tubes, and the heat exchanger as a whole had low corrosion resistance.

In view of the above-mentioned points, an object of the present invention is to provide an aluminum alloy liner element for collector tanks that prevents the fins from melting at the time of brazing, reducing fin clearance for the collector tank to be smaller than the conventionally employed clearances in order to utilize the sacrificial corrosion action of the fins for all tubes. With regard to the heat exchanger using tubes in which corrosion resistance is imparted by the sacrificial corrosion action of the fins, another object of the present invention is to further improve the corrosion resistance of the heat exchanger than conventional ones using sacrificial corrosion action of the fins of all tubes. MEANS OF SOLVING PROBLEMS

In order to achieve the stated objectives, the invention described in claim 1 is an aluminum alloy coating element for collecting tanks used to form collecting tanks (4) of a heat exchanger (10) made of an aluminum alloy, wherein the collecting tanks (4) are joined at the ends of a plurality of pipes (2) in their longitudinal direction by brazing, and corrosion resistance by a sacrificial corrosion action of the fins (3) arranged between the plurality of pipes (2) ) is imparted to the tubes (2), and a brazing material is coated on a core element made of an aluminum alloy, wherein the brazing material comprises a Si-containing aluminum alloy in an amount of not less than 3.5 % by weight but not exceeding 5,0% by weight.

By using the aluminum alloy coating element with a Si content of not less than 3,5% but not exceeding 5,0% in its brazing material to form the collecting tanks, it is possible to prevent the fins from melting at the time of brazing, even when the gaps between the fins and the collecting tank are reduced to be smaller than those of the previous technology.

As a result, by using the aluminum alloy liner of the present invention to form the heat exchanger collecting tanks, the gaps between the fins and the collecting tank may be reduced to be smaller than those of the prior art, and the Sacrificial fin corrosion action can be used for all pipes to further improve the heat exchanger's corrosion resistance than prior technology.

In the invention described in claim 1, it is desirable that the Si content in the brazing material is not less than 4.0%, but not greater than 4.5%, as in the invention described in claim 2. This makes it possible to improve adhesion between the collecting tank and the pipes, and improve the effect of preventing fin fusion at the time of brazing.

The invention described in claim 3 is directed to a heat exchanger made of an aluminum alloy comprising:

a plurality of tubes (2), having been formed by bending a plate member, and having therein a passage of the thermal medium into which the thermal medium flows;

collecting tanks (4) having been joined at the ends of the plurality of pipes (2) in their longitudinal direction by brazing, and having their interiors in communication with the passages of the thermal medium; and corrugated fins (3) having been arranged between the plurality

pipe (2), and consisting of a material with a corrosion potential that is less than that of the pipe material;

wherein the collecting tanks (4) are formed using the aluminum alloy liner element to form the collecting tanks described in claim 1 or 2; and

The distances (ll) from the collecting tank (4) to the fins (3) in the longitudinal direction of the pipes (2) are not less than 0 mm, but not greater than 4 mm.

As previously described, since the collecting tanks are formed using the aluminum alloy liner element for the collecting tanks described in claim 1 or 2, the distance from the collecting tank to the fins may be no less than 0 mm but not larger than 4 mm, which is smaller than previous technology. As a result, the sacrificial corrosion action of the fins can be used for all tubes in the heat exchanger where the fins are constituted using a material with a corrosion potential that is lower than that of the material constituting the tubes. Therefore, the corrosion resistance of the heat exchanger can be further improved over previous technology.

It is desirable that the distances (ll) from the collecting tank (4) to the fins (3) are not greater than 2 mm as described in the claim. As will be learned from the evaluation results in the following modalities, the heat exchanger corrosion resistance can be further improved over the prior art.

Reference numbers; in parentheses denoting the above-described devices and in the claims correspond to the reference numerals set forth in the concrete devices described in the following embodiments.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 shows a front view of a capacitor according to a first embodiment of the invention.

Figure 2 shows an enlarged view of an Al region in the

figure 1.

Figure 3 shows a metallographic microphotograph of a fin 3 near a collecting tank 4 in a heat exchanger when the brazing material has a Si content of 4.0% by weight and the distance L1 is 0 mm in the embodiment of the invention. .

Figure 4 shows a metallographic microphotograph of fin 3 near the collector tank 4 in the heat exchanger when the brazing material has a Si content of 5.0 wt% and the distance L1 is 0 mm in the embodiment of the invention.

Figure 5 shows a metallographic microphotograph of fin 3 near the collector tank 4 in the heat exchanger when the brazing material has a Si content of 6.0 wt% and the distance Ll is 0 mm in a reference embodiment of the invention. . DETAILED DESCRIPTION OF THE INVENTION First Mode

In this embodiment, a heat exchanger according to the present invention is applied to a condenser to cool a refrigerant by heat exchange between air and refrigerant circulating in a refrigeration cycle (air conditioning equipment) for non-vehicle. is shown.

Figure 1 is a front view of a capacitor according to this embodiment. As shown in Figure 1, the capacitor 10 is provided with a substantially rectangular parallelepiped core portion 1, the core portion 1 being comprised of a plurality of tubes 2 and a plurality of fins 3 which are alternately laminated to one another. another in the up and down direction. Tube 2 has a refrigerant passage through which a

A refrigerant which is a thermal medium flows, and is of the plate-type formed by folding a coating element made of an aluminum alloy, which is a plate element which will be described below in a predetermined form. In pipe 2 of this embodiment, the longitudinal direction (hereinafter referred to as the longitudinal direction of the pipe) is in accordance with the horizontal direction and the pipe 2 has a flat shape in its cross section, so that the direction of its largest diameter is according to the direction in which the cooling air flows.

The fins 3 are joined to the outer surfaces of the pipes 2 by brazing, and function to promote heat exchange between the refrigerant flowing through the pipes 2 and the cooling air. The fins 3 are made of an aluminum alloy, and are corrugated, i.e. have a corrugated (corrugated) shape in the cross section.

Collector tanks 4 are arranged at both ends of the tubes 2 in their longitudinal direction, which extend in a direction substantially at right angles to the longitudinal direction of the tubes, and form spaces in them. The ends of the pipes 2 in their longitudinal direction are joined to the collecting tanks 4 by brazing, and the passages of many pipes 2 are in communication with the spaces in the collecting tanks 4.

The collecting tank 4 includes a core plate 4a made of an aluminum alloy which will be described below, and in which the pipes 2 are brazed together; and a tank body 4b made of an aluminum alloy that is joined to the core plate 4a by brazing, and constitutes a space in the collecting tank 4 together with the core plate 4a.

Figure 2 is an enlarged view of a region A1 near a portion where the pipes 2 are joined to the collecting tank 4 in figure 1. In this embodiment, as shown in figure 2, the fins are arranged closer to the collecting tanks 4 than in the previous technology. Specifically, the distance L1 from collecting tank 4 to fin 3 in the longitudinal direction of the pipe is not less than 0 mm, but not greater than 4 mm and preferably not greater than 2 mm. For example, the distance L1 of 0 mm refers to a state where fin 3 is in contact with collecting tank 4.

Referring further to Figure 1, side plates 5 are arranged at both ends of the core portion 1 in a direction in which the tubes 2 are laminated in order to reinforce the core portion 1. Side plates 5 are made of a aluminum alloy, extend in a direction parallel to the longitudinal direction of the pipes, and are joined in the collector tanks 4 at their ends on both sides by brazing.

The condenser 10 constituted as referred to is produced by assembling the pipes 2, fins 3, core plates 4a, tank bodies 4b and side plates 5 together and then heating them to a predetermined brazing temperature in an oven to Bind them together as a unitary structure. At the time of brazing them as a unitary structure, the pipes 2 are formed by brazing of cladding elements. However, brazing of tubes 2 may be performed prior to brazing of the unitary structure.

At this time, as the pipe forming material 2, the cladding element, on which the brazing material has been coated on a surface of the core element (surface on the outer side of the pipe), is used. In the casing member 2, the core member comprises an Al-Mn-Cu type alloy (e.g., A3003 alloy specified in JIS) and the brazing material comprises an Al-Si alloy (e.g. alloy) A4045 specified in JIS) or an Al-Si-Zn type alloy. In this embodiment, the Si content in the brazing material in the liner to form the pipes 2 is higher than the Si content in the brazing material in the liner to form the core sheets 4a, which will be described below.

Additionally, the fins 3 are made of an Al-Mn-Cu-Zn type alloy (for example, A3N03 alloy specified in JIS). Thus, since Zn is added to the fin forming material 3, the fin forming material 3 has a corrosion potential that is lower than that of the forming material 2 (i.e. the core element of the finning element). coating). Therefore, the corrosion resistance attributed to the sacrificial corrosion action of the fins 3 can be conferred to the tubes 2.

Tank bodies 4b and side plates 5 are made of an Al-Mn-Cu type alloy (for example, A3003 alloy specified in JIS).

In addition, as the core sheet forming material 4a, the cladding element, in which the brazing material has been coated on a core element surface (i.e., the surface on the outer side of the collecting tank) is used. The sheathing element for the core sheets 4a comprises the Al-Mn-Cu-type alloy core element (for example, A3003 alloy specified in JIS) and the Al-Si-type brazing material, and the content of Si is not less than 3.5 wt% but not greater than 5.0 wt% and preferably not less than 4.0 wt% but not greater than 4.5 wt% based on in all brazing material, and the remainder is Al and impurities.

In this embodiment, as described above, as the coating element for forming the core sheets 4a, brazing material having a Si content of no more than 5.0% by weight is used. Therefore, fluidization of brazing material at the time of brazing can be eliminated. As a result, as will be learned from the evaluation results in the examples described below, fin 3 may be prevented from melting at the time of brazing, even when the gaps between fin 3 and collector tank 4 are decreased to become smaller. than previous technology.

In addition, if the Si content in the brazing material in the liner to form the core sheets 4a is not less than 3.5% by weight, a favorable joint is obtained between the collecting tanks 4 and the pipes 2, as will be the case. learned from the results of the evaluation in the examples described below.

In capacitor 10 of this embodiment, distances L1 from collecting tank 4 to fins 3 are not less than 0 mm, but no greater than 4 mm, which is less than distances from the prior art. Therefore, the sacrificial corrosion action by the fins 3 can be used for all pipes, and the corrosion resistance of condenser 10 can be further improved than conventional condensers. Specifically, when the distances L1 from collecting tank 4 to fins 3 are set no less than 0 mm but no greater than 2 mm, the corrosion resistance of condenser 10 as a whole can be further improved, as will be learned from the results of the study. evaluation shown in the following examples.

Here, even if the fin 3 is separated from the collecting tank 4, the sacrificial corrosion action of the fins 3 can be obtained, provided that the distances Ll from the collecting tank 4 to the fins 3 are not greater than 4 mm, as will be learned by the evaluation results shown in the following examples. This is because when the distances L1 are small as previously described, a predetermined potential difference between the tubes 2 and the fins 3 is considered to occur.

(1) In the embodiment shown, the brazing material in the cladding element to form the core sheets 4a was Al-Si type alloy having a Si content of not less than 3.5% by weight but not greater than 5, 0% by weight, and the residues were Al and impurities. However, any other elements such as Zn, Cu and the like may be contained, provided that the Si content in all brazing material is the same as above.

(2) In the above embodiment, the heat exchanger according to the invention was applied to the condenser. However, the invention may also be applied to automotive heat exchangers such as radiators, heater cores, etc., as well as to other heat exchangers.

(3) The above embodiment employed the cladding element to form the core sheets 4a, the core element being comprised of the Al-Mn-Cu type alloy. However, without being limited to this alone, the core element may be comprised of an Al-Mn-type alloy containing components other than Cu, or may be comprised of any other aluminum alloy.

(4) In the above embodiment, the brazing material was coated on a surface of the coating element to form the core sheets 4a. However, the coating element may be coated with brazing material on both its surfaces.

(5) The previous embodiment had the constitution in which the collecting tanks have both the core plate and the tank body. However, collecting tanks can be constituted in other ways. The aluminum alloy liner for forming the collecting tanks of the invention may be effectively applied to the portions of the collecting tanks, where the collecting tanks are joined to the pipes. EXAMPLES

Examples of the invention will now be described.

Tubes 2, fins 3, and collector tanks 4 were formed using the following materials, assembled together, and were completely brazed to produce a heat exchanger. The heating temperature for brazing was 600 ° C.

As the lining element for forming the pipes 2, the core element with the components of Al-1.2 Mn-0.5 Cu (the numbers represent percentages by weight, the remainder being Al and impurities), and the material brazing with Si components: 10 wt% and the remainder being Al and impurities (Al-IOSi) were used. Additionally, the lining member for forming the pipes 2 had the sheet thickness of 0.2 as a whole, while the brazing material had a thickness of 28 µηι.

Fins 3 were corrugated fins consisting of Al-1.2 Mn-0.1 Cu-1.5 Zn (numbers represent percentages by weight, and the remainder is Al and impurities).

As the cladding element to form the core sheets 4a, the core element with the Al-1 components, 2Mn-0.5Cu (the numbers represent percentages by weight, the remainder being Al and impurities) and the brazing material with Si components: 3.5-5.0% by weight for all brazing material, and the remainder being Al and impurities, as shown in table 1 below. Moreover, in a reference example, the core element with the same components, and the brazing material with the Si components: 3.0 wt% or 6.0 wt% and the remainder being Al and impurities were used as the cladding element to form the core plate 4a. Additionally, the cladding element for forming the core sheets 4a had a sheet thickness of 1.2 mm as a whole, while the brazing material had a thickness of 140 μιη.

The elements constituting the bodies of the tank 4b of the collecting tanks 4, and the side plates 5 had the components Al-1.2 Mn-0.5 Cu (the numbers represent% by weight and the remainder is Al and impurities).

The heat exchanger that was produced had the sizes described below.

In the heat exchanger, the width W (core portion 1 + collector tanks 4 on both sides) was 500 mm, and the height H (core portion 1) was 360 mm. Additionally, the tubes had a width of 16 mm in the direction in which the air flows (in the direction perpendicular to the paper surface in Figure 2) and a thickness of 1.8 mm in the direction in which the tubes 2 were rolled (in the direction up and down in figure 2). Fins 3 had a Fp fin pitch of 2.8 mm and an Fh fin height of 8 mm.

The distances L1 from the collecting tank 4 to the fins 3 in the longitudinal direction of the pipes were set at 0 mm, 2 mm and 4 mm. As a reference example, a heat exchanger was produced by setting the distances L1 from the collecting tank 4 to the fins 3 by 5 mm.

Previously produced heat exchangers were evaluated as described below for (1) adhesion between collecting tanks and pipes, (2) fin fusion prevention, and (3) corrosion resistance.

(1) Adhesion assessment between collecting tanks and pipes

Each heat exchanger was inspected for leakage (helium leakage test). A He gas was introduced into the heat exchanger in a vacuum chamber, and the He gas leak from the heat exchanger was inspected using a mass analyzer.

The heat exchangers, which were inspected not to leak, were further inspected to verify that the size of the fillet formed at the junction portion between the collector tank 4 core plate 4 and the pipe 2 was larger than a reference size. The reference size refers to the size of the fillet required to maintain a predetermined strength in the static pressure burst test and the repetitive pressure test, and was empirically determined by the applicant.

Based on the results of leakage inspection and fillet size, adhesion after brazing of collecting tanks 4 and pipes 4 was determined to be "excellent", "good" or "bad" as described below.

"Excellent": Leak inspection found no leak, and fillet was larger than reference size.

"Good": The leak inspection did not find a leak, but the fillet was smaller than the reference size.

"Bad": Leak inspection found leak.

(2) Evaluation of the prevention of fin fusion

The fins 3 near the heat exchanger collecting tanks were observed using a metallographic microscope to inspect whether the fins 3 fused because of the brazing material of the casing element to form the core plates 4a at the time of brazing. Depending on the results of the observation, the fin fusion impedance was determined to be "excellent", "good" or "bad" as described below.

"Excellent": There were no melting traces of the fins (base material "(see figure 3)." Good ": There was no melting trace of the fins (base material), but the fins are in an imminent melting state (see figure 4).

"Bad": there was a trace of melting of the fins (base material) (see

figure 5).

(3) Corrosion resistance rating

By the use of a test apparatus (salt and wet dry composite cycle test machine: CYP-90, manufactured by Suga Shikenki Co.) the wet and dry cycle test (sprinkling -> drying -> wetting) was conducted. using an acid solution (pH = 3) containing chlorine ions and the corrosion resistance of tubes 2 was determined to be "excellent", "good" or "bad" as described below based on the drilling time at which tubes 2 were drilled after the start of the test.

"Excellent": drilling time was greater than a first reference value (2,000 hours).

"Good": drilling time was greater than a second reference value (750 hours).

"Bad": drilling time was less than the second reference value (750 hours).

Here, the first reference value was set at 2,000 hours, since the drilling time was 2,000 hours when the distances Ll from sink 4 to fins 3 was 0 mm. In addition, the second reference value was set at 750 hours since the minimum time was 750 hours when the same test was conducted using a conventional heat exchanger using extrusion type tubes.

Table 1 shows the results of the evaluation of the heat exchangers produced. The general determinations in table 1 were based on the results of having fully evaluated the above mentioned items (1) to (3).

"Excellent": All items reviewed were completely

satisfactory. "Good": The items evaluated were all satisfactory. "Bad": At least one of the evaluated results was not

satisfactory.

Table 1

Si Content in Adhesion Between Distances between Prevention Resistance Material determination of the pipes of the melt collector tank the general corrosion brazing (% in catalyst and the fins (mm) of the fins weight) the pipes 3.0 poor 0 excellent excellent 2 excellent excellent bad 4 excellent good bad 5 excellent bad bad 3.5 good 0 excellent excellent good 2 excellent excellent good 4 excellent good good 5 excellent bad kidney 4.0 excellent 0 excellent (figure 3) excellent excellent 2 excellent excellent excellent 4 excellent good good 5 excellent bad bad 4.5 excellent 0 excellent excellent excellent 2 excellent excellent excellent 4 excellent good good 5 excellent bad bad 5.0 excellent 0 good (figure 4) excellent good 2 good excellent good 4 good good good 5 good bad bad 6.0 excellent 0 X (figure 5) excellent bad 2 bad excellent bad 4 bad good bad 5 good bad bad

From the evaluated adhesion results of collecting tanks 4 and pipes 2, the Si content of the brazing material in the liner to form the core sheets 4a should not be less than 3.5% by weight and preferably should not be less than 4.0%.

As for fin fusion prevention assessment results, if the Si content in the brazing material was not less than 4.5%, there were no fusion traces of the fins 3, as shown in figure 3, even when the distances Ll between the collecting tank 4 and the fins 3 were set at 0 to 4 mm, which were smaller than the conventional distance. If the Si content in the brazing material was 5.0%, the outer shapes of the fins 3 were retained and there were no melting traces of the fins 3, even when the distances Ll between the collecting tank 4 and the fins 3 were set in. 0 to 4 mm. However, in this case, shown in figure 4, there were fusion traces because of the brazing material in the crystalline grain outlines of the base material of the fins 3. On the other hand, if the Si content in the brazing material was 6.0% , fins 3 ruptured, as shown in figure 5, and there were traces of fusion of fins 3 when the distances L1 between collecting tank 4 and fins 3 were set at 0 to 4 mm. Therefore, it can be said that the Si content of the brazing material in the coating element to form the core sheets 4a must be no more than 5.0% by weight, preferably no more than 4.5%.

As for the corrosion resistance assessment results of the pipes 2, the drilling time was about 2,000 hours when the distances Ll between the collecting tank 4 and the fins 3 were 0 mm, regardless of the Si content in the brazing material. In this case, holes occurred (corrosion occurred) not in pipes 2, but in collecting tanks 4. When distances Ll were 2 mm, additionally, results were obtained as when distances Ll were 0 mm. When the distances Ll were 4 mm, the drilling time was slightly longer than 750 hours. Therefore, it can be said that the distances L1 between the collecting tank 4 and the fins 3 cannot be less than 0 mm, but not more than 4 mm, and preferably no more than 2 mm.

Claims (4)

1. Aluminum alloy casing element, characterized in that it is used to form collecting tanks (4) of a heat exchanger (10) made of an aluminum alloy, the collecting tanks (4) are joined at the ends of a plurality of tubes (2) in their longitudinal direction by brazing, and the corrosion resistance by a sacrificial corrosion action of the fins (3) arranged between said plurality of tubes (2) is imparted to said tubes (2), and a brazing material is coated on a core element made of an aluminum alloy, wherein said brazing material comprises an Si-containing aluminum alloy in an amount not less than 3.5% by weight, but not greater than 5, 0% by weight. Aluminum alloy coating element for forming the collecting tanks according to claim 1, characterized in that the Si content in said brazing material is not less than 4.0% but not greater than 4.5%. Heat exchanger made from an aluminum alloy, characterized in that it comprises: a plurality of tubes (2), having been formed by bending a plate member and having in them a passage of the thermal medium in which a thermal medium flows; collecting tanks (4), having been joined at the ends of said plurality of tubes (2) in their longitudinal direction by brazing, and having the interiors in communication with said passages of thermal medium; and corrugated fins (3) having been arranged between said plurality of tubes (2) and being made of a material with a lower corrosion potential than the material constituting said tubes; wherein said collecting tanks (4) are formed using the aluminum alloy liner element to form the collecting tanks described in claim 1 or 2; and the distances (ll) of said collecting tank (4) to said fins (3) in the longitudinal direction of said pipes (2) are not less than 0 mm, but not greater than 4 mm. Heat exchanger according to claim 3, characterized in that said distances (L1) are not greater than 2 mm.