Heat Exchanger Tube, Heat Exchanger, and Manufacturing Method Thereof

- SHOWA DENKO K.K

This invention relates to a method of manufacturing an aluminum heat exchanger tube. In forming a thermally sprayed layer 21 on a surface of an aluminum flat tube by thermally spraying Al—Si alloy thermal-spraying particles, quenching the thermally sprayed thermal-spraying particles in a molten state to make them adhere to the tube core 2a. The surface of the thermally sprayed layer 21 is smoothed with, e.g., reduction rolls to form a brazing layer 20. With this method, brazing defects due to fin detachment, erosion to the tube of the brazing material, etc., can be prevented, resulting in good brazing performance.

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Description

This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2004-113784 filed on Apr. 8, 2004 and U.S. Provisional Application No. 60/561,903 filed on Apr. 14, 2004, the entire disclosures of which are incorporated herein by reference in their entireties.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is an application filed under 35 U.S.C. §111(a) claiming the benefit pursuant to 35 U.S.C. §119(e)(1) of the filing date of U.S. Provisional Application No. 60/561,903 filed on Apr. 14, 2004, pursuant to 35 U.S.C. §111(b).

TECHNICAL FIELD

The present invention relates to an aluminum heat exchanger used for, for example, a refrigeration cycle for car air-conditioners, a tube for such heat exchangers, and a method of manufacturing the same.

In this disclosure including claims, the wording of “aluminum” denotes aluminum and its alloy.

BACKGROUND ART

The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.

As an aluminum heat exchanger for use in a refrigeration cycle for car air-conditioners, the so-called multi-flow type or parallel flow type heat exchanger 51 as shown in FIG. 5 is well-known. In this heat exchanger, a plurality of flat tubes 52 are arranged in the thickness direction with a corrugated fin 53 interposed therebetween, and hollow headers 54 are connected to the ends of the tubes 52 in fluid communication.

In manufacturing such a heat exchanger 51, commonly, heat exchanger components are fabricated into a provisional assembly, and then the assembly is integrally brazed in a furnace. As a method of forming a brazing layer, as disclosed by Patent Document 1 (Japanese Unexamined Laid-open Patent Publication No. S59-10467) for example, it is well-known that brazing alloy is thermally sprayed onto a surface of an aluminum heat exchanger tube.

In cases where a brazing alloy is thermally sprayed onto a surface of a heat exchanger tube 52 to form a brazing material layer, however, unevenness of the brazing material layer is large, and therefore a brazing layer contracts after the brazing. As a result, as exaggeratingly shown in FIG. 5, some joining scheduled portions between the heat exchanger tube 52 and the fin 53 may become un-joined continuously along the longitudinal direction of the tube 52, which may cause a poor brazed portion such as the so-called fin detachment.

To solve the problem, conventionally, various technique have been proposed. For example, Patent document 2 (JP, H11-33709,A) discloses a technique in which a brazing alloy is thermally sprayed onto a streaked surface of a heat exchanger tube (tube core) to thereby form a brazing layer. Patent document 3 (JP, H06-200344,A) discloses a technique in which at the time of thermally spraying brazing alloy powder the brazing powder is thermally sprayed on a surface of a heat exchanger tube in a state in which non-fused structure remains partially without completely fusing the alloy powder.

In the technique in which streaked irregularities are formed on the surface of the tube core, however, capillary force will be generated along the streaked irregularity portions causing an easy flow of the fused brazing material on the tube surface during the brazing. This in turn generates erosion of the tube by the brazing material, resulting in poor brazing.

In the technique in which the brazing alloy powder is thermally sprayed in a state in which non-fused structure remains partially, in cases where, for example, the thermally spraying particle size is large, a cavity will be formed between particles thermally sprayed on the tube surface. This causes deteriorated volume rate (filling rate) of the substantial brazing material (net thermally sprayed layer) in the entire thermally sprayed layer (apparent thermally sprayed layer) including the cavity. As a result, the actual amount of brazing material tends to decrease. Thus, there is a room to be improved.

The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. Indeed, certain features of the invention may be capable of overcoming certain disadvantages, while still retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.

Other objects and advantages of the present invention will be apparent from the following preferred embodiments.

DISCLOSURE OF INVENTION

The preferred embodiments of the present invention have been developed in view of the above-mentioned and/or other problems in the related art. The preferred embodiments of the present invention can significantly improve upon existing methods and/or apparatuses.

The present invention was made in view of the aforementioned conventional technology, and aims to provide a heat exchanger tube capable of preventing occurrence of poor brazing due to fin detachment or erosion of a tube by brazing material and attaining good brazing, a heat exchanger and a method of manufacturing them.

To attain the aforementioned objects, the structure of the present invention can be summarized as follows.

[1] A method of manufacturing an aluminum heat exchanger tube, the method comprising the steps of:

in forming a thermally sprayed layer on a surface of an aluminum flat tube by thermally spraying Al—Si alloy thermal-spraying particles, quenching the thermally sprayed thermal-spraying particles in a molten state to make them adhere to the tube core; and

smoothing a surface of the thermally sprayed layer to form a brazing layer.

The aluminum heat exchanger tube obtained by the manufacturing method of this invention will be combined with and brazed to, for example, an aluminum fin. At this time, good brazing performance can be secured.

That is, in the heat exchanger tube obtained by the manufacturing method of this invention, the surface of the thermally sprayed layer formed by thermally spraying alloy is smoothed to obtain a brazing layer. Therefore, a fin can be joined in a balanced manner over the entire surface of the brazing layer, which assuredly prevents poor joining such as fin detachment.

Furthermore, in this invention, since the thermally sprayed layer is smoothed to form the brazing layer, the smoothing enhances the brazing material filling rate of the brazing layer, resulting in a sufficient amount of the brazing material as the brazing layer, which can assuredly prevent poor brazing due to shortage of brazing material.

Furthermore, in this invention, since the molten thermal-spraying particles are quenched, moderate brittleness can be given to the thermally sprayed layer as compared with the case where thermal spraying is performed in a state in which the thermal-spraying particles are partially in a non-molten state and where the thermal-spraying particles are not quenched but gradually cooled. For this reason, when the thermally sprayed layer is formed into the brazing layer by smoothing the thermally sprayed layer, only the thermally sprayed layer can be assuredly formed into a desired state. Thus, for example, the deformation of the tube core can be prevented effectively, resulting in high quality.

In this invention, “melting” of the thermal-spraying particles can be performed by adjusting the thermal-spraying temperature to 3,000° C. or above, preferably 3,500° C. or above, more preferably 4,000° C. or above, still more preferably 4,500° C. or above. In cases where an arc spraying method is employed, “melting” of the thermal spraying particles can be performed more assuredly. In this invention, especially in cases where the thermal-spraying temperature is set to a high temperature, it is considered that smoothing of the thermally sprayed layer can be executed effectively. That is, in the case of high temperature thermal spraying, it is considered that the thermal-spraying particles decrease in size, the cooling rate increases, the quickly cooled small sized thermal-spraying particles accumulate on the tube surface to form a desired brittle structure as the thermally sprayed layer, which enables effective smoothing of the thermally sprayed layer.

Moreover, in this invention, by adjusting the temperature difference between the thermal-spraying particles in a molten state and the thermal-spraying particles reached the tube core in a cooled state to 2,500° C. or more, preferably 3,000° C. or more, more preferably 3,500° C. or more, and/or by performing the thermal spraying at the thermal-spraying distance of 30 to 150 mm by an arc thermal spraying method, “quenching” of the thermal-spraying particles can be performed.

[2] The method of manufacturing an aluminum heat exchanger tube as recited in the aforementioned Item 1, wherein surface roughness (Ry) of the tube core is adjusted to less than 10 μm.

In this invention, since the surface of the tube core is formed into a smooth surface, the brazing layer can be stably secured to a wide surface area of the tube core. Thus, it is possible to effectively prevent unexpected flow of the molten brazing material on the surface of the tube core during the brazing, which can assuredly prevent defects, such as erosion to the tube core of the brazing material.

[3] The method of manufacturing an aluminum heat exchanger tube as recited in the aforementioned Item 1 or 2, wherein surface roughness (Ry) of the brazing layer is adjusted to less than 50 μm.

In this invention, since the surface of the brazing layer is smoothed, a fin can be brazed to the brazing layer assuredly, which more assuredly prevents occurrence of brazing defects such as fin detachment.

[4] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 3, wherein a thermal-spraying temperature of the thermal-spraying particles is adjusted to 3,000° C. or above.

In this invention, melting of the thermal-spraying particles can be assuredly attained in the thermal spraying processing.

[5] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 4, wherein the thermal-spraying particles are cooled to 800° C. or below after reaching the tube core.

In this invention, quenching of the thermal-spraying particles can be smoothly performed at the time of the thermal spraying.

[6] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 5, wherein in thermally spraying the thermal-spraying particles, a temperature difference between the thermal-spraying particles in a molten state and the thermal-spraying particles reached the tube core in a cooled state is adjusted to 2500° C. or more.

In this invention, quenching of the thermal-spraying particles can be assuredly performed at the time of the thermal spraying.

[7] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 6, wherein in thermally spraying the thermal-spraying particles, the thermal-spraying particles reached the tube core is cooled by releasing the heat to the tube core.

In this invention, quenching of the thermal-spraying particles can be more smoothly performed at the time of the thermal spraying.

[8] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 7, wherein an average equivalent diameter of Si crystallization particles in the thermally sprayed layer is adjusted to 1 μm or less.

In this invention, melting and quenching of the thermal-spraying particles are assuredly performed at the time of the thermal spraying.

[9] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 8, wherein an apparent volume rate (filling rate) of the brazing material in the brazing layer is adjusted to 40% or more.

In this invention, a sufficient amount of the brazing material can be secured in the brazing layer, which in turn can assuredly prevent occurrence of brazing defects due to shortage of brazing material.

[10] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 9, wherein in thermally spraying the thermal-spraying particles, a thermal-spraying distance from a spraying position of the thermal-spraying particles to an adhering position on the tube core is adjusted to 30 to 150 mm.

In this invention, quenching, etc., of thermal-spraying particles can be performed more assuredly.

[11] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 10, wherein thermal spraying of the thermal-spraying particles is performed by an arc spraying method.

In this invention, melting, etc., of the thermal-spraying particles can be performed more assuredly.

[12] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 11, wherein a Si content in the thermally sprayed layer is adjusted to 6 to 15 mass %.

In this invention, a brazing layer further improved in brazing performance can be formed.

[13] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 12, wherein an average thickness of the brazing layer is adjusted to 3 to 50 μm.

In this invention, a stable brazing layer can be formed.

[14] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 13, wherein the surface of the thermally sprayed layer is pressed with reduction rolls to smooth the surface.

In this invention, smoothing of the thermally sprayed layer can be performed continuously, improving the working efficiency.

[15] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 14, wherein Zn is contained to the thermally sprayed layer.

In this invention, a sacrificial protection layer can be formed on the tube surface.

[16] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 15, wherein Zn and Cu are contained to the thermally sprayed layer.

In this invention, a sacrificial protection layer can be formed on the tube surface, and the potential of the tube surface can also be adjusted.

[17] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 16, wherein the tube core is formed by extrusion, and the thermal-spraying particles are thermally sprayed to the tube core immediately after the extrusion.

In this invention, a desired thermally sprayed layer can be formed assuredly in an efficient manner, which in turn can form a desired brazing layer assuredly and efficiently.

[18] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 17, wherein each thermal-spraying particle adheres to the surface of the tube core in a flat state.

In this invention, quenching of the thermal-spraying particles can be performed efficiently.

[19] The method of manufacturing an aluminum heat exchanger tube as recited in any one of the aforementioned Items 1 to 18, wherein the thermal-spraying particles are thermally sprayed under a non-oxidizing atmosphere.

In this invention, forming of an oxide film on the thermal-spraying particles can be prevented, which enables formation of a stable thermally sprayed layer.

[20] A method of manufacturing an aluminum heat exchanger tube, the method comprising the steps of:

in forming a thermally sprayed layer on a surface of an aluminum flat tube by thermally spraying Al—Si alloy thermal-spraying particles, thermally spraying the thermal-spraying particles to a tube core by an arc spraying method, and quenching the thermally sprayed thermal-spraying particles to 800° C. or below; and

smoothing a surface of the thermally sprayed layer to form a brazing layer.

In the heat exchanger tube obtained by the manufacturing method of this invention, in the same manner as mentioned above, the brazing layer is obtained by smoothing the surface of the thermally sprayed layer obtained by the thermal spraying of brazing alloy. A fin can be brazed to the brazing layer assuredly, which more assuredly prevents occurrence of brazing defects such as fin detachment.

Furthermore, in this invention, since the brazing layer is formed by smoothing the thermally sprayed layer, the smoothing can increase the brazing material filling rate of the brazing layer, a sufficient amount of brazing material in the brazing layer can be secured, which assuredly can prevent brazing defects due to shortage of brazing material.

Furthermore, in this invention, molten thermal-spraying particles are thermally sprayed on the tube core by an arc spraying method and the sprayed thermal-spraying particles are quenched to a predetermined temperature or below. Therefore, moderate brittleness can be given to the thermally sprayed layer as compared with the case where thermal spraying is performed in a state in which the thermal-spraying particles are partially in a non-molten state and where the thermal-spraying particles are not quenched but gradually cooled. For this reason, when the thermally sprayed layer is formed into the brazing layer by smoothing the thermally sprayed layer, only the thermally sprayed layer can be assuredly formed in a desired state. Thus, for example, the deformation of the tube core can be prevented effectively, resulting in high quality.

[21] A method of manufacturing an aluminum heat exchanger tube, the method comprising the steps of:

in forming a thermally sprayed layer on a surface of an aluminum flat tube by thermally spraying Al—Si alloy thermal-spraying particles, performing the thermal spraying by an arc spraying method in which a thermal-spraying distance from a spraying position of the thermal-spraying particles to an adhering position on the tube core is adjusted to 30 to 150 mm; and

smoothing a surface of the thermally sprayed layer to form a brazing layer.

In the heat exchanger tube obtained by the manufacturing method of this invention, good brazing performance can be secured in the same manner as mentioned above.

Furthermore, in this invention, molten thermal-spraying particles are thermally sprayed to the tube core by an arc spraying method, and the thermal-spraying particles are sprayed to tube core with high kinetic energy to thereby be deformed into a flat shape and quenched. Therefore, in the same manner as in the above-mentioned case, a heat exchanger tube of high quality can be secured.

[22] A method of manufacturing an aluminum heat exchanger tube, the method comprising the steps of:

in forming a thermally sprayed layer on a surface of an aluminum flat tube by thermally spraying Al—Si alloy thermal-spraying particles, thermally spraying the thermal-spraying particles with a thermal-spraying temperature of 3,000° C. or above and cooling them to 800° C. or below to make them adhere to a tube core; and

smoothing a surface of the thermally sprayed layer to form a brazing layer.

In the heat exchanger tube obtained by the manufacturing method of this invention, in the same manner as mentioned above, good brazing performance can be secured.

Furthermore, in this invention, molten thermal-spraying particles are sprayed to the tube core at a high temperature, and the sprayed thermal-spraying particles are quenched at a temperature below a predetermined temperature. Therefore, in the same manner as mentioned above, high quality heat exchanger tube can be provided.

[23] A method of manufacturing an aluminum heat exchanger tube, the method comprising the steps of:

in forming a thermally sprayed layer on a surf ace of an aluminum flat tube by thermally spraying Al—Si alloy thermal-spraying particles, thermally spraying the thermal-spraying particles in a molten state and cooling to make them adhere to a tube core, and adjusting a temperature difference between the thermal-spraying particles in a molten state and the thermal-spraying particles after the cooling is adjusted to 2,500° C. or more; and

smoothing a surface of the thermally sprayed layer to form a brazing layer.

In the heat exchanger tube obtained by the manufacturing method of this invention, in the same manner as mentioned above, good brazing performance can be secured.

Furthermore, in this invention, since molten thermal-spraying particles are sprayed to the tube core and the sprayed thermal-spraying particles are quenched, in the same manner as mentioned above, high quality heat exchanger tube can be provided.

[24] An aluminum heat exchanger tube manufactured by the method as recited in any one of the aforementioned Items 1 to 23.

The heat exchanger tube of this invention is obtained by the aforementioned manufacturing method of this invention, and therefore in the same manner as mentioned above, good brazing performance and high quality can be secured.

[25] An aluminum heat exchanger tube, comprising:

an aluminum flat tube core; and

a thermally sprayed layer formed on a surface of the tube core by thermally spraying thermal-spraying particles of molten Al—Si alloy,

wherein a surface of the thermally sprayed layer is smoothed to form a brazing layer, and

wherein an average equivalent diameter of Si crystallization particles in the thermally sprayed layer is adjusted to 1 μm or less.

In the heat exchanger tube of this invention, since the brazing layer is formed by smoothing the thermally sprayed layer, in the same manner as mentioned above, good brazing performance can be secured.

Moreover, since the Si crystallization in the thermally sprayed layer is small, it is possible to confirm the melting and quenching of the thermal-spraying particles at the time of the thermal spraying, and therefore a heat exchanger tube of high quality can be obtained.

[26] The aluminum heat exchanger tube as recited in the aforementioned Item 25, wherein an apparent volume rate (filling rate) of the brazing material in the brazing layer is adjusted to 40% or more.

In the heat exchanger tube of this invention, since the filling rate of the brazing material in the brazing layer is high, a sufficient amount of brazing material can be secured, and further improved brazing performance can be secured.

[27] An aluminum heat exchanger including aluminum heat exchanger tubes and aluminum fins brazed to the tubes in an assembled state, wherein the heat exchanger tubes are manufactured by the method as recited in any one of the aforementioned Items 1 to 23.

Since this specifies a heat exchanger equipped with a heat exchanger tube as a main component obtained by the aforementioned method of the invention, in the same manner as mentioned above, the same functions and results can be secured.

[28] An aluminum heat exchanger including a pair of aluminum headers and a plurality of heat exchanger tubes arranged in a longitudinal direction of the header with a fin interposed therebetween, end portions of the heat exchanger tubes being communicated with the headers,

wherein the heat exchanger tubes are manufactured by the method as recited in any one of the aforementioned Items 1 to 23.

This invention specifies the so-called parallel-flow type or multi-flow type heat exchanger equipped with the heat exchanger tubes obtained by the aforementioned manufacturing method of the invention as main components. Therefore, in the same manner as mentioned above, the same functions and results can be secured.

[29] A method of manufacturing an aluminum heat exchanger, the method comprising:

a step of preparing an aluminum heat exchanger tube manufactured by the method as recited in any one of the aforementioned Items 1 to 23;

a step of preparing an aluminum fin; and

a step of brazing the heat exchanger tube and the fin in an assembled state.

In this invention, since the heat exchanger is manufactured using the heat exchanger tube obtained by the aforementioned manufacturing method of the invention, in the same manner as mentioned above, the same functions and results can be secured.

[30] A method of manufacturing an aluminum heat exchanger, the method comprising:

a step of preparing a plurality of aluminum heat exchanger tubes manufactured by the method as recited in any one of the aforementioned Items 1 to 23;

a step of preparing a plurality of aluminum fins;

a step of preparing a pair of headers;

a step of obtaining a provisional assembly in which the plurality of heat exchanger tubes arranged in a longitudinal direction of the header with the fin interposed therebetween are assembled with the headers with end portions of each heat exchanging tube communicated with the headers;

a step of integrally brazing adjacent heat exchanger tubes and the fins by simultaneously brazing the provisional assembly.

In this invention, the so-called parallel-f low type or multi-flow type heat exchanger is manufactured by using the heat exchanger tubes obtained by the aforementioned manufacturing method of the invention. Therefore, in the same manner as mentioned above, the same functions and results can be secured.

[31] A refrigeration cycle in which refrigerant compressed by a compressor is condensed with a condenser, and the condensed refrigerant is decompressed by passing through a decompressor, and the decompressed refrigerant is evaporated with an evaporator and returned to the compressor,

wherein the condenser is constituted by the aluminum heat exchanger as recited in the aforementioned Item 28.

In the refrigeration cycle of this invention, the same effects can be demonstrated.

EFFECTS OF THE INVENTION

As mentioned above, according to the present invention, brazing defects due to fin detachment, erosion to the tube of brazing material, etc., can be prevented, and therefore good brazing performance can be secured.

The above and/or other aspects, features and/or advantages of various embodiments will be further appreciated in view of the following description in conjunction with the accompanying figures. Various embodiments can include and/or exclude different aspects, features and/or advantages where applicable. In addition, various embodiments can combine one or more aspect or feature of other embodiments where applicable. The descriptions of aspects, features and/or advantages of particular embodiments should not be construed as limiting other embodiments or the claims.

BRIEF DESCRIPTION OF DRAWINGS

The preferred embodiments of the present invention are shown by way of example, and not limitation, in the accompanying figures, in which:

FIG. 1 is a front view showing an aluminum heat exchanger according to an embodiment of this intention;

FIG. 2 is an enlarged perspective view showing joined portions of the tubes and fins in the heat exchanger of the aforementioned embodiment;

FIG. 3A is an enlarged cross-sectional view showing a tube core immediately after thermal spraying during a manufacturing process of the heat exchanger tube according to the embodiment, and FIG. 3B is an enlarged cross-sectional view showing the tube core immediately after smoothing of the thermally sprayed brazing material;

FIG. 4A is an enlarged cross-sectional view showing a tube core immediately after thermal spraying in a manufacturing process of the heat exchanger tube, which is an example outside the scope of the invention, and FIG. 4B is an enlarged cross-sectional view showing the tube core immediately after smoothing of the tube core; and

FIG. 5 is a front view showing a conventional heat exchanger in which fin detachment occurred due to brazing.

 BEST MODE FOR CARRYING OUT THE INVENTION

In the following paragraphs, some preferred embodiments of the invention will be described by way of example and not limitation. It should be understood based on this disclosure that various other modifications can be made by those in the art based on these illustrated embodiments.

FIG. 1 is a front view showing an aluminum heat exchanger 1 which is an embodiment of this invention. As shown in this figure, this heat exchanger 1 is used as a condenser for use in a refrigeration cycle of a car air-conditioner, and constitutes a multi-flow type heat exchanger.

In this heat exchanger 1, a plurality of flat heat exchanging tubes 2 arranged horizontally are disposed between a pair of vertical hollow headers 4 and 4 arranged in parallel with each other with the ends of the tubes communicated with the hollow headers 4 and 4. Between the adjacent tubes 2 and outside the outermost tubes, a corrugated fin 3 is disposed, and a side plate 10 is disposed outside the outermost corrugated fin 3.

In this heat exchanger 1, as the tube 2, a tube made of aluminum (including its alloy, hereinafter simply referred to as “aluminum”) is used, and brazing material is covered on predetermined portions of each component. The tubes 2, fins 3, headers 4 and side plates 10 are provisionally assembled into a provisional heat exchanger assembly, and the assembly is integrally brazed in a furnace, whereby the entire assembly is integrally brazed.

As shown in FIG. 2, the tube 2 includes a tube core 2a which is an aluminum extruded member and a brazing layer 20 of an Al—Si alloy as brazing alloy formed on at least one surface of the tube core.

As the core 2a of the tube 2, an Al—Mn alloy with high pressure resistance (high strength) and high heat resistance, such as a JIS3003 alloy, can be preferably used.

In this embodiment, by extruding this alloy, the tube core 2a is formed.

It is preferable that the surface roughness Ry of the tube core 2a is adjusted to less than 10 μm. That is, if the surface roughness Ry exceeds 10 μm, capillary attraction occurs on the surface of the tube core 2a, resulting in easy flow of brazing material, which in turn causes erosion to the tube by the brazing material. Thus, there is a possibility that brazing defects occur.

In this embodiment, the brazing layer 20 on the tube core 2a is formed by forming a thermally sprayed layer 21 by making Al—Si alloy adhere to the tube core by a thermal spraying method as shown in FIG. 3A, and then smoothing the surface of the thermally sprayed layer 21 by compressing the surface as shown in FIG. 3B.

In this embodiment, although a method of carrying out thermal spraying of the Al—Si alloy as a brazing alloy to the surface of the tube core 2a is not limited to a specific one, in performing the thermal spraying, the thermal-spraying particles are sprayed to the tube core 2a and quenched. In other words, the thermal spraying method of this invention is not specifically limited so long as the aforementioned quenching can be performed.

In this embodiment, in order to melt the thermal-spraying particles, the thermal-spraying temperature can be set to 3,000° C. or above, or any known means including a means using arc spraying can be adopted.

As a means for quenching the thermal-spraying particles, for example, it is preferable to employ a method in which the thermal-spraying temperature of the brazing alloy at the time of thermal spraying is adjusted to high, the hot thermal-spraying particles are sprayed on the tube core 2a, and the heat of the thermal-spraying particles is made to emit to the tube core 2a immediately after the reaching of the thermal-spraying particles to the core member 2a to thereby quickly cool the thermal-spraying particles to a temperature of the tube core member 2a. For example, a means for cooling the thermal-spraying particles whose thermal-spraying temperature is 3,000° C. or above to 800° C. or below by making them adhere the tube core 2a can be employed.

Concretely, in this embodiment, it is preferable to employ a means for quenching the thermally sprayed particles whose thermal-spraying temperature is high (4,500 to 5,500° C.) to the tube core temperature (400 to 500° C.) immediately after the extrusion by using an arc spraying method. In cases of flame spraying or high velocity flame spraying, since the thermal-spraying temperature is low (2,000 to 3,000° C.) as compared with arc spraying, there are possibilities that melting of the thermal-spraying particles cannot fully be performed, or increasing of the cooling rate is difficult and therefore quenching cannot fully be performed. Furthermore, since they use brazing alloy powder, there is a possibility that the filling rate may deteriorate and therefore it is not always suitable.

In this invention, however, if quenching can be performed irrespective of the thermal-spraying temperature and/or the tube core temperature, any kind of thermal spraying method can be employed. For example, the quenching of the thermal-spraying particles can be performed by controlling the thermal-spraying distance which will be explained below.

In this embodiment, in performing thermal-spraying, it is preferable to adjust the thermal-spraying distance from the spraying portion (spraying position) of the thermal spraying gun to the tube core surface (adhering position) to 30 to 150 mm. That is, in cases where the thermal-spraying distance is within the aforementioned specified range, the speed of thermal-spraying particles is high, and therefore the kinetic energy of the thermal-spraying particles is high. For this reason, since the thermal spraying particles change into a flat shape and adhere to the tube core surface when the thermal spraying particles are sprayed on the tube core surface, the filling rate becomes high and the heat release performance of the thermal spraying particles to the tube core 2a is also improved, which enables sufficient quenching. Furthermore, the thermal-spraying distance is relatively short, i.e., 30 to 150 mm, resulting in a shorter arriving time of the thermal-spraying particles to the tube core 2a, or a shorter time from the thermal-spraying of the thermal-spraying particles to the cooling initiation, which in turn can perform the quenching more assuredly. In other words, in cases where the thermal-spraying distance is less than 30 mm or exceeds 150 mm, the speed of the thermal-spraying particles becomes slower and therefore sufficient kinetic energy cannot be secured, causing a smaller amount of deformation of the thermal-spraying particles when the thermal-spraying particles adhere to the tube core, resulting in low filling rate. Furthermore, the heat releasing performance of the thermal-spraying particles to the tube core deteriorates, resulting in a failure of quenching. Especially in cases where the thermal-spraying distance exceeds 150 mm, during the flying of the thermal-spraying particles, the thermal-spraying particles different in flying speed may aggregate. For example, large particles and small particles will aggregate to become large particles to be deposited. As a result, the thermally sprayed layer 21 becomes hard and moderate brittleness cannot be secured. Thus, as will be detailed below, there is a possibility that smoothing of the thermally sprayed layer 21 cannot be attained effectively, and therefore it is not preferable.

In cases where a brazing alloy is sprayed by an arc spraying method, for example, a method of scanning a thermal spraying gun of an arc spraying machine with respect to the tube core 2a or a method of carrying out thermal spraying while rewinding the core member 2a rolled into a coiled form can be adopted. Furthermore, in cases where the tube core 2a is an extruded member, a method in which extrusion and thermal spraying are performed continuously while placing a thermal spraying gun arranged immediately after an extrusion die can be employed. Especially in cases where extrusion and thermal spraying are performed continuously, productive efficiency can be improved.

Furthermore, if an oxide film is formed on thermal-spraying particles at the time of thermal spraying processing, the surface of the thermal-spraying particle hardens, resulting in decreased deformation of the thermal-spraying particle to be caused by colliding against the tube core 2a, which may cause deterioration of the filling rate. For this reason, in order to prevent the formation of an oxide film on thermal-spraying particles, it is preferable to perform the thermal spraying processing in a non-oxidizing atmosphere, such as a nitrogen atmosphere or an argon atmosphere. From the economical view point, it is preferable to perform the thermal spraying in a nitrogen atmosphere.

The thermally sprayed layer 21 can be formed only on one surface of the tube core 2a, and also can be formed on both surfaces. Needless to say, in cases where the thermally sprayed layer 21 is formed on both surfaces of the tube core, it is preferable to arrange thermal spraying guns at upper and lower sides of the tube core 2a.

In this embodiment, although the content of Si in the thermally sprayed layer 21 is not specifically limited, in order to secure good brazing performance, it is preferable to adjust the Si content to 6 to 15 mass %.

It is preferable that the thermally sprayed layer 21 contains Zn in order to form a sacrificial protection layer on the surface of the tube. The Zn content in the thermally sprayed layer 21 is preferably adjusted to 1 to 30 mass %.

Furthermore, it is preferable that the thermally sprayed layer 21 contains Cu within the range of 0.1 to 1 mass % for the purpose of potential adjustment, etc.

Furthermore, in this embodiment, the thermally sprayed layer 21 may contain other elements, such as Fe, Mn, In, Sn, Ni, Ti, and Cr, as long as it is within the range that affects neither brazing performance nor corrosion resistance.

In this embodiment, after forming a thermally sprayed layer 21 on the tube core 2a as shown in FIG. 3A, the surface of the thermally sprayed layer 21 is smoothed to form a brazing layer 20 as shown in FIG. 3B. Thus, a heat exchanger tube 2 is obtained.

Although the method of smoothing the surface of the thermally sprayed layer 2 is not specifically limited, a pressing method using reduction rolls and a cutting method such as scalping (trimming) can be exemplified. Among other things, a method of smoothing using reduction rolls is preferably employed since the method can improve the productivity by consecutive operation.

This smoothing processing is preferably performed at the tube correcting step. That is, as described above, in cases where the extrusion step of extruding the tube core 2a and the thermal spraying step of thermally spraying the brazing material to the extruded tube member (tube core) are performed continuously, it is usually performed that the extruded tube member after the brazing material thermal spraying is rolled into a coiled form and thereafter the thermally sprayed tube is cut into a predetermined size while being unwinding in the following tube correcting step to thereby manufacture heat exchanger tubes 2. At the tube correcting step, by performing the smoothing processing using reduction rolls, smoothing processing can be performed simultaneously with the tube correcting processing.

In this embodiment, the surface roughness Ry of the smoothed brazing layer 20 is preferably adjusted to 50 μm or less, more preferably to 40 μm or less. That is, in cases where the surface roughness falls within the specified range, the fin 3 can be brazed to the brazing layer 20 in a balanced manner, which can prevent occurrence of brazing defects such as fin detachment.

In this embodiment, since the thermal-spraying particles are sprayed in a molten state and then quenched at the aforementioned thermal spraying processing, moderate brittleness can be given to the thermally sprayed layer 21. Therefore, as shown in FIG. 3B, the crushing of the brittle peak portions of the thermally sprayed layer 21 can be evenly performed over the entire region with rollers, etc. Thus, the surface of the thermally sprayed layer 21 (surface of the brazing layer) can be assuredly formed to have a desired smooth surface. Furthermore, since compressive deformation of only the thermally sprayed layer 21 can be performed appropriately, the volume rate (filling rate) of the brazing material in the entire brazing layer (apparent brazing layer) containing voids can be improved, resulting in a sufficient amount of brazing material on the tube required to perform brazing.

In this embodiment, the filling rate of the brazing material in the brazing layer 20 is preferably adjusted to 40% or more, more preferably 60% or more. Securing the filling rate within the aforementioned range secures a sufficient amount of the brazing material, which effectively prevents occurrence of brazing defects such as fin detachment.

In cases where quenching of the thermal-spraying particles is inadequate or a part of the thermal-spraying particles (thermal-spraying powder) is in a non-molten state at the time of thermal spraying processing, the rigidity of the thermally sprayed layer 121 becomes high excessively as shown in FIG. 4A. As a result, even if the tube core 2a having the thermally sprayed layer 121 of high rigidity is rolled with reduction rollers, as shown in this FIG. 4B, the tube core 2a is deformed without causing any deformation of the thermally sprayed layer 121, which may cause deteriorated quality. Furthermore, since the thermally sprayed layer 121 is not compressed, the filling rate of the brazing material in the thermally sprayed layer 121 cannot be improved, which may make it difficult to secure the necessary amount of brazing material required for brazing.

In this embodiment, it is preferable to adjust the average equivalent diameter of the Si crystallization in the brazing layer 20 to 1 μm or less. That is, in cases where the dispersibility of Si in the brazing layer 20 is good and the brazing performance is good, Si crystallization becomes small. Also in cases where the brazing alloy is fully molten at the thermal spraying step and quenching is fully made and therefore the thermal-spraying particles has moderate brittleness, the crystallization of Si becomes small. Accordingly, in this embodiment, the particle diameter of Si crystallization is preferable small. Concretely, it is preferable to adjust the average equivalent diameter of Si crystallization to 1 μm or less.

Although the thickness (average thickness) of the brazing layer 20 is not specifically limited, it is preferable to adjust the thickness to 3 to 50 μm. More preferably, the lower limit is adjusted to 5 μm or more and the upper limit to 30 μm or less. That is, in cases where the thickness of the brazing layer 20 is adjusted within the aforementioned range, the joining of the tube 2 and the fin 3 can be performed assuredly, and fin detachment, etc., can be prevented effectively.

The heat exchanger tube 2 of this embodiment is used together with other heat exchanger components, such as hollow headers 4 and 4, corrugated fins 3 and side plates 10, and is assembled into a provisional heat exchanger assembly. Thereafter, flux is applied to this assembly and dried. Then, the assembly is heated in a furnace of a nitrogen gas atmosphere to thereby integrally braze the components. Thus, a heat exchanger 1 is manufactured.

The obtained heat exchanger 1 is free from brazing defects such as fin detachment, and is excellent in joined strength.

That is, in the heat exchanger tube 2 of this embodiment, since the brazing layer 20 is obtained by smoothing the surface of the thermally sprayed layer 21 formed by the thermal spraying of brazing alloy, the fin 3 can be joined to the entire surface of the brazing layer 20 in a balanced manner, which in turn can assuredly prevent brazing defects such as fin detachment.

Especially in this embodiment, if the surface roughness Ry of the tube core 2a is adjusted to less than 10 μm, the brazing layer 20 is secured to the entire surface of the tube core 2a in a stable manner. Therefore, unexpected flowing of the molten brazing material during the brazing can be effectively prevented, which can assuredly prevent occurrence of defects such as erosion to the tube of the brazing material.

Moreover, in this embodiment, since the brazing layer 20 is formed by compressing the thermally sprayed layer 21, the brazing material filling rate of the brazing layer 20 can be improved. Therefore, sufficient amount of brazing material for the brazing layer 20 can be secured, which can assuredly prevent occurrence of brazing defects due to shortage of brazing material.

Furthermore, in this embodiment, since fully molten thermal spraying particles are quenched, moderate brittleness can be given to the thermally sprayed layer 21. Therefore, at the time of smoothing the thermally sprayed layer 21 with reduction rollers, etc., only the thermally sprayed layer 21 can be compressed into a desired compressed shape. Thus, crush deformation of the tube core 2a can be prevented effectively, resulting in high quality.

In addition, in this embodiment, in cases where the surface roughness Ry of the brazing layer 20 is adjusted to below the specific value, the fin 3 can be brazed to the brazing layer 20 in a balanced manner, which can more assuredly prevent occurrence of brazing defects such a fin detachment.

EXAMPLE

Hereafter, examples related to the present invention and comparative examples for verifying the effects of the invention will be explained.

TABLE 1 Surface Thermal spraying processing roughness Thermal Thermal-spraying Smoothing of Filling Average of core Thermal spraying Thermal Thermal particles brazing layer rate of equivalent member spraying tempera- spraying spraying Molten Cooling (surface brazing diameter of Si (Ry) method ture distance environment state*1 rate*2 roughness Ry) material crystallization Example 1 10 μm  Arc thermal 5,000° C. 120 mm Air Molten Quenching Smoothed 50% 0.7 μm spraying (40 μm) Example 2 8 μm Arc thermal 5,500° C.  60 mm Nitrogen Molten Quenching Smoothed 50% 0.1 μm spraying (37 μm) Example 3 7 μm Arc thermal 4,800° C.  60 mm Nitrogen Molten Quenching Smoothed 60% 0.5 μm spraying (35 μm) Example 4 8 μm Arc thermal 5,000° C.  80 mm Air Molten Quenching Smoothed 50% 0.4 μm spraying (40 μm) Example 5 8 μm Arc thermal 4,800° C. 120 mm Nitrogen Molten Quenching Smoothed 40% 0.8 μm spraying (40 μm) Example 6 8 μm Arc thermal 5000° C. 100 mm Nitrogen Molten Quenching Smoothed 50% 0.6 μm spraying (42 μm) Com. Ex. 1 8 μm Arc thermal 5,000° C. 150 mm Air Molten Quenching Non-smoothed 30% 0.9 μm spraying (60 μm) Com. Ex. 2 15 μm  Flame thermal 2,800° C. 150 mm Air Partially Non- Smoothed 30% 1.5 μm spraying not molten quenching (40 μm) Com. Ex. 3 10 μm  Flame thermal 2,500° C. 200 mm Air Partially Non- Non-smoothed 20%   2 μm spraying not molten quenching (60 μm) Com. Ex. 4 40 μm  Arc thermal 5,000° C. 120 mm Air Molten Quenching Non-smoothed 20% 0.7 μm spraying (60 μm) Com. Ex. 5 30 μm  Flame thermal 3,000° C. 250 mm Air Molten Non- Smoothed 40% 1.8 μm spraying quenching (60 μm) Com. Ex. 6 8 μm HVOF thermal 2,600° C. 100 mm Air Partially Quenching Smoothed 50%   2 μm spraying not molten (65 μm) *1“Molten”: the thermal spraying temperature is 3,000° C. or above; “Partially not molten”: below 3,000° C. *2“Quenching”: the temperature difference between the thermal-spraying particles and the extruded tube material is 2,500° C. or above; “Non-quenching”: below 2,500° C.

Example 1

As shown in Table 1, a flat multi-bored extruded tube (tube core) 16 mm width, 3 mm height and 0.5 mm wall thickness was extruded with an extruder using extrusion material of an Al alloy (Cu: 0.4 mass %, Mn: 0.21 mass %; Al: balance). The surface roughness Ry of the obtained tube core was 10 μm.

An Al—Si alloy was thermally sprayed to the upper and lower surfaces of the extruded tube through thermal spraying guns of an arc spraying machine arranged at the upper and lower sides of the outlet of the extruder, to thereby form a thermally sprayed layer. In this thermal spraying processing, the thermal-spraying distance was adjusted to 120 mm in the atmosphere.

The molten thermal-spraying particles to be sprayed against the tube core adhered to the tube core by being cooled from the thermal-spraying temperature to a temperature of the tube core by being absorbed in heat by the tube core when they reached the tube core.

In Table 1, as for the cooling degree of the thermal-spraying particles, in cases where the difference between the thermal-spraying temperature of the thermal-spraying particles and the temperature of the tube core was 2,500° C. or more, it was denoted as “quenching”, and in cases where it was less than 2,500° C., it was denoted as “non-quenching.” In the case of Example 1, the thermal-spraying temperature of the thermal-spraying particles was 5,000° C., the temperature of the tube core was 400° C., and those temperature difference was 4,600° C. Accordingly, the cooling degree in Example was quenching.

After performing the thermal spraying, the aforementioned extruded tube with a thermally sprayed layer was immersed in a cooling bath to be cooled, and then continuously rolled into a coil form.

Thereafter, while recoiling, the coil foamed tube was pressed with reduction rollers to compress the thermally sprayed layer to smooth the surface, thereby forming a brazing layer 50% in net filling rate of the brazing material (apparent filling rate of the brazing material to the brazing layer), 20 μm in thickness, and 40 μm in surface roughness (Ry), and then cut into a predetermined length to obtain heat exchanger tubes. In these tubes, the average equivalent diameter of Si crystallization was 0.7 μm.

Then, using the aforementioned heat exchanger tubes, the so-called multi-flow type aluminum heat exchanger (see FIG. 1) was provisionally assembled. Slurry in which non-corrosive flux was suspended in water was sprayed to the heat exchanger provisional assembly and then dried. Then, the assembly was heated at 600° C. for 10 minutes in a nitrogen gas atmosphere furnace to integrally braze the components to thereby obtain the heat exchanger in Example 1.

Example 2

As shown in table 1, against the extruded tube 8 μm in surface roughness Ry, thermal spraying was performed by an arc spraying method at the thermal-spraying temperature of 5,500° C. and the thermal-spraying distance of 60 mm in a nitrogen atmosphere. The tube member with the thermally sprayed layer was pressed with reduction rollers to form a brazing layer 50% in brazing material filling rate, 15 μm in thickness, 37 μm in surface roughness Ry. Thus, the heat exchanger tube was manufactured in the same manner as mentioned above. In this tube, the average equivalent diameter of Si crystallization was 0.1 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubes in the same manner as in the aforementioned Example.

Example 3

As shown in table 1, against the extruded tube 7 μm in surface roughness Ry, thermal spraying was performed by an arc spraying method at the thermal-spraying temperature of 4,800° C. and the thermal-spraying distance of 60 mm in a nitrogen atmosphere. The tube member with the thermally sprayed layer was pressed with reduction rollers to form a brazing layer 60% in brazing material filling rate, 20 μm in thickness, 35 μm in surface roughness Ry. Thus, the heat exchanger tube was manufactured in the same manner as mentioned above. In this tube, the average equivalent diameter of Si crystallization was 0.5 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubes in the same manner as in the aforementioned Example.

Example 4

As shown in table 1, against the extruded tube 8 μm in surface roughness Ry, thermal spraying was performed by an arc spraying method at the thermal-spraying temperature of 5,000° C. and the thermal-spraying distance of 80 mm in an atmosphere. The tube member with the thermally sprayed layer was pressed with reduction rollers to form a brazing layer 50% in brazing material filling rate, 30 μm in thickness, 40 μm in surface roughness Ry. Thus, the heat exchanger tube was manufactured in the same manner as mentioned above. In this tube, the average equivalent diameter of Si crystallization was 0.4 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubes in the same manner as in the aforementioned Example.

Example 5

As shown in table 1, against the extruded tube 8 μm in surface roughness Ry, thermal spraying was performed by an arc spraying method at the thermal-spraying temperature of 4,800° C. and the thermal-spraying distance of 120 mm in a nitrogen atmosphere. The tube member with the thermally sprayed layer was pressed with reduction rollers to form a brazing layer 40% in brazing material filling rate, 20 μm in thickness, 40 μm in surface roughness Ry. Thus, the heat exchanger tube was manufactured in the same manner as mentioned above. In this tube, the average equivalent diameter of Si crystallization was 0.8 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubes in the same manner as in the aforementioned Example.

Example 6

As shown in table 1, against the extruded tube 8 μm in surface roughness Ry, thermal spraying was performed by an arc spraying method at the thermal-spraying temperature of 5,000° C. and the thermal-spraying distance of 100 mm in a nitrogen atmosphere. The tube member with the thermally sprayed layer was pressed with reduction rollers to form a brazing layer 50% in brazing material filling rate, 25 μm in thickness, 42 μm in surface roughness Ry. Thus, the heat exchanger tube was manufactured in the same manner as mentioned above. In this tube, the average equivalent diameter of Si crystallization was 0.6 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubes in the same manner as in the aforementioned Example.

Comparative Example 1

As shown in table 1, against the extruded tube 8 μm in surface roughness Ry, thermal spraying was performed by an arc spraying method at the thermal-spraying temperature of 5,000° C. and the thermal-spraying distance of 150 mm in an atmosphere. Without performing the smoothing of the thermally sprayed layer, the brazing layer 30% in brazing material filling rate, 60 μm in thickness, 60 μm in surface roughness Ry was formed. Thus, the heat exchanger tube was manufactured in the same manner as mentioned above. In this tube, the average equivalent diameter of Si crystallization was 0.9 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubes in the same manner as in the aforementioned Example.

Comparative Example 2

As shown in table 1, against the extruded tube 15 μm in surface roughness Ry, thermal spraying was performed by a flame spraying method at the thermal-spraying temperature of 2,800° C. and the thermal-spraying distance of 150 mm in an atmosphere. The tube member with the thermally sprayed layer was pressed with reduction rollers to form a brazing layer 30% in brazing material filling rate, 40 μm in thickness, 40 μm in surface roughness Ry. Thus, the heat exchanger tube was manufactured in the same manner as mentioned above. In this tube, the average equivalent diameter of Si crystallization was 1.5 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubes in the same manner as in the aforementioned Example.

Comparative Example 3

As shown in table 1, against the extruded tube 10 μm in surface roughness Ry, thermal spraying was performed by a flame spraying method at the thermal-spraying temperature of 2,500° C. and the thermal-spraying distance of 200 mm in an atmosphere. Without performing the smoothing of the thermally sprayed layer, the brazing layer 20% in brazing material filling rate, 40 μm in thickness, 60 μm in surface roughness Ry was formed. Thus, the heat exchanger tube was manufactured in the same manner as mentioned above. In this tube, the average equivalent diameter of Si crystallization was 2 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubes in the same manner as in the aforementioned Example.

Comparative Example 4

As shown in table 1, against the extruded tube 40 μm in surface roughness Ry, thermal spraying was performed by an arc spraying method at the thermal-spraying temperature of 5,000° C. and the thermal-spraying distance of 120 mm in an atmosphere. Without performing the smoothing of the thermally sprayed layer, the brazing layer 20% in brazing material filling rate, 40 μm in thickness, 60 μm in surface roughness Ry was formed. Thus, the heat exchanger tube was manufactured in the same manner as mentioned above. In this tube, the average equivalent diameter of Si crystallization was 0.7 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubes in the same manner as in the aforementioned Example.

Comparative Example 5

As shown in table 1, against the extruded tube 30 μm in surface roughness Ry, thermal spraying was performed by a flame spraying method at the thermal-spraying temperature of 3,000° C. and the thermal-spraying distance of 250 mm in an atmosphere. Without performing the smoothing of the thermally sprayed layer, the brazing layer 40% in brazing material filling rate, 80 μm in thickness, 60 μm in surface roughness Ry was formed. Thus, the heat exchanger tube was manufactured in the same manner as mentioned above. In this tube, the average equivalent diameter of Si crystallization was 1.8 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubes in the same manner as in the aforementioned Example.

Comparative Example 6

As shown in table 1, against the extruded tube 8 μm in surface roughness Ry, thermal spraying was performed by a HVOF (high-speed flame) splaying method at the thermal-spraying temperature of 2,600° C. and the thermal-spraying distance of 100 mm in an atmosphere. Without performing the smoothing of the thermally sprayed layer, the brazing layer 50% in brazing material filling rate, 80 μm in thickness, 65 μm in surface roughness Ry was formed. Thus, the heat exchanger tube was manufactured in the same manner as mentioned above. In this tube, the average equivalent diameter of Si crystallization was 2 μm.

Then, a heat exchanger was manufactured using the heat exchanger tubes in the same manner as in the aforementioned Example.

<Evaluation>

As for each heat exchanger of the aforementioned Examples and Comparative Examples, the joining rate between the fin and the tube was measured. In the evaluation, “⊚” denotes that the joining rate between the fin and the tube was 95% or more; “∘” denotes that the joining rate between the fin and the tube was 90% or more but less than 95%; “Δ” denotes that the joining rate between the fin and the tube was 60% or more but less than 90%; “X” denotes that the joining rate between the fin and the tube was less than 60% or fin detachment was occurred. The evaluation results are collectively shown in the following Table 2.

TABLE 2 Evaluation Fin/tube joining rate Remarks Example 1 ⊚ — Example 2 ⊚ — Example 3 ⊚ — Example 4 ⊚ — Example 5 ◯ — Example 6 ⊚ — Com. Example 1 X — (fin detachment) Com. Example 2 ◯ Deformed in cross-section of tube core Com. Example 3 X — (fin detachment) Com. Example 4 X Erosion of tube core by (fin detachment) brazing material Com. Example 5 ◯ Deformed in cross-section of tube core Com. Example 6 ◯ Deformed in cross-section of tube core

As will be clear from Table 2, in Examples 1 to 6 satisfying the requirements of this invention, brazing defects such as fin detachment was prevented, and good brazing performance was secured. Furthermore, in Examples 1 to 6, tube deformation due to the smoothing was assuredly prevented, resulting in high quality.

To the contrary, in Comparative Examples deviating from the requirements of this invention, good performance was not secured. For example, like in Comparative Examples 1, 3 or 4 in which smoothing of the thermally sprayed layer was not performed and the brazing material filling rate was low, fin detachment occurred and good brazing performance was not secured. Furthermore, in cases where melting of the thermal-spraying particles at the time of thermal spraying was inadequate like in Comparative Examples 2, 5 and 6, or in cases where quenching was inadequate, the tube itself was crushed at the time of smoothing the thermally sprayed layer, causing deterioration of quality.

INDUSTRIAL APPLICABILITY

This invention can be applied to an aluminum heat exchanger for use in a car air-conditioning refrigeration cycle, a heat exchanger tube used for such a heat exchanger, and a manufacturing method thereof.

While the present invention may be embodied in many different forms, a number of illustrative embodiments are described herein with the understanding that the present disclosure as to be considered as providing examples of the principles of the invention and such examples are not intended to limit the invention to preferred embodiments described herein and/or illustrated herein.

While illustrative embodiments of the intention have been described herein, the present invention is not limited to the various preferred embodiments described herein, but includes any and all embodiments having equivalent elements, modifications, omissions, combinations (e.g., of aspects across various embodiments), adaptations and/or alterations as would be appreciated by those in the art based on the present disclosure. The limitations in the claims are to be interpreted broadly based on the language employed in the claims and not limited to examples described in the present specification or during the prosecution of the application, which examples are to be construed as non-exclusive. For example, in the present disclosure, the term “preferably” is non-exclusive and means “preferably, but not limited to.” In this disclosure and during the prosecution of this application, means-plus-function or step-plus-function limitations will only be employed where for a specific claim limitation all of the following conditions are present in that limitation: a) “means for” or “step for” is expressly recited; b) a corresponding function is expressly recited; and c) structure, material or acts that support that structure are not recited. In this disclosure and during the prosecution of this application, the terminology “present invention” or “invention” may be used as a reference to one or more aspect within the present disclosure. The language present invention or invention should not be improperly interpreted as an identification of criticality, should not be improperly interpreted as applying across all aspects or embodiments (i.e., it should be understood that the present invention has a number of aspects and embodiments), and should not be improperly interpreted as limiting the scope of the application or claims. In this disclosure and during the prosecution of this application, the terminology “embodiment” can be used to describe any aspect, feature, process or step, any combination thereof, and/or any portion thereof, etc. In some examples, various embodiments may include overlapping features. In this disclosure and during the prosecution of this case, the following abbreviated terminology may be employed: “e.g.” which means “for example;” and “NB” which means “note well.”

Claims

1. A method of manufacturing an aluminum heat exchanger tube, the method comprising the steps of:

in forming a thermally sprayed layer on a surface of an aluminum flat tube by thermally spraying Al—Si alloy thermal-spraying particles, quenching the thermally sprayed thermal-spraying particles in a molten state to make them adhere to a tube core; and
smoothing a surface of the thermally sprayed layer to form a brazing layer.

2. The method of manufacturing an aluminum heat exchanger tube as recited in claim 1, wherein surface roughness (Ry) of the tube core is adjusted to less than 10 μm.

3. The method of manufacturing an aluminum heat exchanger tube as recited in claim 1 or 2, wherein surface roughness (Ry) of the brazing layer is adjusted to less than 50 μm.

4. The method of manufacturing an aluminum heat exchanger tube as recited in any one of claims 1 to 3, wherein a thermal-spraying temperature of the thermal-spraying particles is adjusted to 3,000° C. or above.

5. The method of manufacturing an aluminum heat exchanger tube as recited in any one of claims 1 to 4, wherein the thermal-spraying particles are cooled to 800° C. or below after reaching the tube core.

6. The method of manufacturing an aluminum heat exchanger tube as recited in any one of claims 1 to 5, wherein in thermally spraying the thermal-spraying particles, a temperature difference between the thermal-spraying particles in a molten state and the thermal-spraying particles reached the tube core in a cooled state is adjusted to 2500° C. or more.

7. The method of manufacturing an aluminum heat exchanger tube as recited in any one of claims 1 to 6, wherein in thermally spraying the thermal-spraying particles, the thermal-spraying particles reached the tube core are cooled by releasing the heat to the tube core.

8. The method of manufacturing an aluminum heat exchanger tube as recited in any one of claims 1 to 7, wherein an average equivalent diameter of Si crystallization particles in the thermally sprayed layer is adjusted to 1 μm or less.

9. The method of manufacturing an aluminum heat exchanger tube as recited in any one of claims 1 to 8, wherein an apparent volume rate (filling rate) of the brazing material in the brazing layer is adjusted to 40% or more.

10. The method of manufacturing an aluminum heart exchanger tube as recited in any one of claims 1 to 9, wherein in thermally spraying the thermal-spraying particles, a thermal-spraying distance from a spraying position of the thermal-spraying particles to an adhering position on the tube core is adjusted to 30 to 150 mm.

11. The method of manufacturing an aluminum heart exchanger tube as recited in any one of claims 1 to 10, wherein thermal spraying of the thermal-spraying particles is performed by an arc spraying method.

12. The method of manufacturing an aluminum heat exchanger tube as recited in any one of claims 1 to 11, wherein a Si content in the thermally sprayed layer is adjusted to 6 to 15 mass %.

13. The method of manufacturing an aluminum heart exchanger tube as recited in any one of claims 1 to 12, wherein an average thickness of the brazing layer is adjusted to 3 to 50 μm.

14. The method of manufacturing an aluminum heart exchanger tube as recited in any one of claims 1 to 13, wherein the surface of the thermally sprayed layer is pressed with reduction rolls to smooth the surface.

15. The method of manufacturing an aluminum heat exchanger tube as recited in any one of claims 1 to 14, wherein Zn is contained to the thermally sprayed layer.

16. The method of manufacturing an aluminum heat exchanger tube as recited in any one of claims 1 to 15, wherein Zn and Cu are contained to the thermally sprayed layer.

17. The method of manufacturing an aluminum heat exchanger tube as recited in any one of claims 1 to 16, wherein the tube core is formed by extrusion, and the thermal-spraying particles are thermally sprayed to the tube core immediately after the extrusion.

18. The method of manufacturing an aluminum heat exchanger tube as recited in any one of claims 1 to 17, wherein each thermal-spraying particle adheres to the surface of the tube core in a flat state.

19. The method of manufacturing an aluminum heat exchanger tube as recited in any one of claims 1 to 18, wherein the thermal-spraying particles are thermally sprayed under a non-oxidizing atmosphere.

20. A method of manufacturing an aluminum heat exchanger tube, the method comprising the steps of:

in forming a thermally sprayed layer on a surface of an aluminum flat tube by thermally spraying Al—Si alloy thermal-spraying particles, thermally spraying the thermal-spraying particles to a tube core by an arc spraying method, and quenching the thermally sprayed thermal-spraying particles to 800° C. or below; and
smoothing a surface of the thermally sprayed layer to form a brazing layer.

21. A method of manufacturing an aluminum heat exchanger tube, the method comprising the steps of:

in forming a thermally sprayed layer on a surf ace of an aluminum flat tube by thermally spraying Al—Si alloy thermal-spraying particles, performing the thermal spraying by arc spraying in which a thermal-spraying distance from a spraying position of the thermal-spraying particles to an adhering position of the tube core is adjusted to 30 to 150 mm; and
smoothing a surface of the thermally sprayed layer to form a brazing layer.

22. A method of manufacturing an aluminum ha at exchanger tube, the method comprising the steps of:

in forming a thermally sprayed layer on a surface of an aluminum flat tube by thermally spraying Al—Si alloy thermal-spraying particles, thermally spraying the thermal-spraying particles with a thermal-spraying temperature of 3,000° C. or above and cooling them to 800° C. or below to make them adhere to a tube core; and
smoothing a surface of the thermally sprayed layer to form a brazing layer.

23. A method of manufacturing an aluminum heat exchanger tube, the method comprising the steps of:

in forming a thermally sprayed layer on a surf ace of an aluminum flat tube by thermally spraying Al—Si alloy thermal-spraying particles, thermally spraying the thermal-spraying particles in a molten state and cooling to make them adhere to a tube core, and adjusting a temperature difference between the thermal-spraying particles in a molten state and the thermal-spraying particles after the cooling is adjusted to 2,500° C. or more; and
smoothing a surface of the thermally sprayed layer to form a brazing layer.

24. An aluminum heat exchanger tube manufactured by the method as recited in any one of the claims 1 to 23.

25. An aluminum heat exchanger tube, comprising:

an aluminum flat tube core; and
a thermally sprayed layer formed on a surface of the tube core by thermally spraying thermal-spraying particles of molten Al—Si alloy,
wherein a surface of the thermally sprayed layer is smoothed to form a brazing layer, and
wherein an average equivalent diameter of Si crystallization particles in the thermally sprayed layer is adjusted to 1 μm or less.

26. The aluminum heat exchanger tube as recited in claim 25, wherein an apparent volume rate (filling rate) of the brazing material in the brazing layer is adjusted to 40% or more.

27. An aluminum heat exchanger including aluminum heat exchanger tubes and aluminum fins brazed to the tubes in an assembled state, wherein the heat exchanger tubes are manufactured by the method as recited in any one of claims 1 to 23.

28. An aluminum heat exchanger including a pair of aluminum headers and a plurality of heat exchanger tubes arranged in a longitudinal direction of the header with a fin interposed therebetween, end portions of the heat exchanger tubes being communicated with the headers,

wherein the heat exchanger tubes are manufactured by the method as recited in any one of claims 1 to 23.

29. A method of manufacturing an aluminum heat exchanger, the method comprising:

a step of preparing an aluminum heat exchanger tube manufactured by the method as recited in any one of claims 1 to 23;
a step of preparing an aluminum fin; and
a step of brazing the heat exchanger tube and the fin in an assembled state.

30. A method of manufacturing an aluminum heat exchanger, the method comprising:

a step of preparing a plurality of aluminum heat exchanger tubes manufactured by the method as recited in any one of claims 1 to 23;
a step of preparing a plurality of aluminum fins;
a step of preparing a pair of headers;
a step of obtaining a provisional assembly in which the plurality of heat exchanger tubes arranged in a longitudinal direction of the header with the fin interposed therebetween are assembled with the headers with end portions of each heat exchanging tube communicated with the headers;
a step of integrally brazing adjacent heat exchanger tubes and the fins by simultaneously brazing the provisional assembly.

31. A refrigeration cycle in which refrigerant compressed by a compressor is condensed with a condensed, and the condensed refrigerant is decompressed by passing through a decompressor, and the decompressed refrigerant is evaporated with an evaporator and returned to the compressor,

wherein the condenser is constituted by the aluminum heat exchanger as recited in claim 28.
Patent History
Publication number: 20090008068
Type: Application
Filed: Apr 8, 2005
Publication Date: Jan 8, 2009
Applicant: SHOWA DENKO K.K (Tokyo)
Inventors: Kazuhiko Minami (Tochigi), Tomoaki Yamanoi (Tochigi), Takenori Hashimoto (Tochigi)
Application Number: 11/547,796
Classifications
Current U.S. Class: With Coated, Roughened Or Polished Surface (165/133); Silicon Containing Coating (427/452)
International Classification: F28F 19/06 (20060101);