US20060102328A1

US20060102328A1 - Aluminum heat exchanger and manufacturing method thereof

Info

Publication number: US20060102328A1
Application number: US11/280,632
Authority: US
Inventors: Taketoshi Toyama; Yoshiharu Hasegawa; Naohiro Ohya; Yasunaga Itoh; Yuji Hisatomi; Hirokazu Tanaka
Original assignee: Denso Corp; Sumitomo Light Metal Industries Ltd
Current assignee: Denso Corp; Sumitomo Light Metal Industries Ltd
Priority date: 2004-11-16
Filing date: 2005-11-16
Publication date: 2006-05-18

Abstract

A sheet material for the tube 10 includes: a core material 10 b; and a sacrifical corrosion material 10 c clad on one face of the core material 10 b which becomes an outside of the tube 10. A sheet material for the fin is a bare aluminum material on which a brazing filler metal is not clad. A mixture composition 10 e, in which powder of a brazing filler metal and flux are mixed with each other, is coated on the outside of the tube 10. The tube 10 and the fin are brazed to each other with this mixture composition 10e. Even after the completion of brazing, the sacrifical corrosion material 10 c remains on the outside of the tube 10.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to an aluminum heat exchanger in which tubes composed of sheet members are protected from pitting corrosion and fins composed of sheet members and brazed to the outside of the tubes are protected from intergranular corrosion. The present invention also elates to a method of manufacturing the heat exchanger. The heat exchanger of the present invention is preferably applied to a condenser and evaporator incorporated into an air conditioner for vehicle use.
2. Description of the Related Art
Conventionally, it is well known that aluminum heat exchangers used for condensers and evaporators of air conditioners for vehicle use are composed of extruded perforated tubes. Concerning this technique, for example, refer to the official gazette of Japanese Patent No. 3337416.
According to this prior art, as the tubes are composed of extruded perforated tubes, it is impossible to clad a brazing filler metal onto the tubes. Therefore, when a mixture composition composed of Si powder, which acts as a brazing filler metal by forming an eutectic alloy together with Al, and also composed of flux is coated on the surface of the extruded perforated tubes, Si powder in the mixture composition exhibits an action of the brazing filler metal, so that the tubes and the fins can be brazed to each other. In this connection, corrugated fins, which are composed of corrugated sheet members, are representative of the fins brazed to the tubes.
In this connection, various aluminum heat exchangers, in which the tubes are composed of sheet members, are well known. In this case, as shown in FIG. 8 described later, the brazing filler metal is clad on the core material of the plate member composing the tube and also the brazing filler metal is clad on the core material of the plate member composing the fin, so that the tube and the fin can be brazed.
In this connection, in order to decrease the weight and material expense of the aluminum heat exchanger for vehicle use, there is a demand for reducing the thickness of the member composing the aluminum heat exchanger. For the object of reducing the thickness, it is effective to use a high strength aluminum material. Specifically, it is effective to apply an alloy of Al—Mn—Mg containing Mg of a relatively high concentration.
However, concerning this high strength aluminum material, the deforming resistance is increased as the material strength is increased. Accordingly, the extruding formability is lowered. Accordingly, when the high strength aluminum material is used as a tube material, the productivity of extruded perforated tubes is deteriorated.
As a result, in the case where the high strength aluminum material is used as a tube material, from the viewpoint of ensuring the productivity, the tube composed of a sheet member is more advantageous than the extruded perforated tube.
FIG. 8 is a table showing Examples 1 to 4 of the combination of specific materials of the sheet member for a tube and the sheet member for a fin in the aluminum heat exchanger of the prior art in which the tube is composed of a sheet member. In this connection, the tube materials of Examples 1 to 3 are double clad materials, on one face of the core material of which the outside brazing filler metal is clad and on the other face of the core material of which the inside brazing filler metal is clad.
This outside brazing filler metal is used for joining the tube to the fin. On the other hand, the inside brazing filler metal is used for joining the sheet member for the tube itself. Therefore, in Examples 1 to 3, a bare aluminum material, on which the brazing filler metal is not clad, is used as the fin material.
In Example 1, only the brazing filler metal is clad on the core material made of aluminum alloy. Therefore, it is impossible to exhibit a sacrifical corrosion action with respect to the core material, and the corrosion resistance (the pitting corrosion preventing action) of the tube material is not practically sufficient.
Therefore, in Example 2, a sacrifical corrosion material made of aluminum alloy to which Zn is added is provided between the core member of the tube material and the outside brazing filler metal, so that the corrosion resistance (the pitting corrosion preventing action) of the tube material can be increased. In this case, the sacrifical corrosion material is an aluminum alloy, to which Zn is added, the electric potential of which is poorer than that of aluminum so that the sacrifical corrosion action can be exhibited.
In Example 3, Zn capable of exhibiting a sacrifical corrosion action with respect to aluminum is added to the brazing filler metal, so that the corrosion resistance (the pitting corrosion preventing action) of the tube material can be increased.
Further, in Example 4, a double clad material, in which the brazing filler metal is clad on both faces of the core material, is used for the fin material, and the tube and fin are brazed to each other by the brazing filler metal provided on the fin side. Due to the foregoing, only the sacrifical corrosion material is clad on the outside of the core material of the tube material, so that the corrosion resistance (the pitting corrosion preventing action) of the tube material can be increased. On the other hand, on the inside of the core material of the tube material, the inside brazing filler metal for joining the sheet member of the tube is clad.
In the structure of Example 2, for the reasons of manufacturing the tube material, the clad ratio with respect to one side of the tube core material of Example 2, in which both the outside brazing filler metal and the sacrifical corrosion material are clad, is the same as the clad ratio with respect to one side of the tube core material of Example 1, in which only the outside brazing filler metal is clad. The clad thickness of the outside brazing filler metal is set preferentially to the clad thickness of the sacrifical corrosion material so as to ensure the brazing property.
As a result, it becomes difficult to ensure a necessary clad thickness of the sacrifical corrosion material, and it impossible to provide a sufficiently high sacrifical corrosion action, which deteriorates the corrosion resistance of the tube material. As the tube thickness has been recently reduced, when the structure of Example 2 is adopted, it becomes difficult to ensure the clad thickness of the sacrifical corrosion material, that is, it becomes more difficult to ensure the corrosion resistance of the tube material.
In the structure of Example 3, as Zn used for sacrifical corrosion is added to the brazing filler metal itself, the brazing filler metal is selectively corroded while the heat exchanger is being used. Therefore, the corrosion resistance of the brazed portion is deteriorated. As a result, a phenomenon, in which the fins are disconnected from the tubes, occurs relatively early.
In the structure of Example 4, the corrosion resistance of the tube material can be increased by the sacrifical corrosion material which is clad on the outside of the core material of the tube material. On the other hand, in the fin material on which the brazing filler metal is clad, Si contained in the brazing filler metal is diffused into the core material of the fin, and the intergranular corrosion is caused in the core material of the fin.
That is, when the material is heated at the time of brazing, Si contained in the brazing filler metal is preferentially diffused along the boundary portion (the grain boundary) of crystal grains in the core material. As the wall thickness of the fin material is so small, that is, as the wall thickness of the fin material is approximately 0.05 mm, when Si is diffused, it penetrates the wall thickness of the fin material.
As a portion (a grain boundary portion) in the core material, into which Si has been diffused, forms a portion in which the electric potential is electro-chemically noble as compared with the crystal grain portion of Al alloy in the neighborhood, a periphery of Si diffusing portion (the grain boundary portion) forms a portion in which the electric potential becomes relatively poor. As a result, the periphery of Si diffusing portion (the grain boundary portion) is selectively corroded. This is the intergranular corrosion of the fin material, which is a cause of deteriorating the corrosion resistance of the core material of the fin.
In the patent documents described above, the tube is composed of an extruded perforated tube. Therefore, in the same manner as that of the brazing filler metal, the sacrifical corrosion material cannot be clad on the tube. Therefore, it is possible to consider a method in which the thermal spraying layer of Zn used for sacrifical corrosion is formed on the surface of the extruded perforated tube so as to increase the corrosion resistance of the tube. However, according to this countermeasure, it is necessary to add a special process of forming the thermal spraying layer. Therefore, this countermeasure is disadvantageous in that the manufacturing cost is raised.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of the above points. It is an object of the present invention to increase a corrosion resistance of both the tube composed of a sheet member and the fin composed of a sheet member which are incorporated into an aluminum heat exchanger in which the tube and the fin are brazed to each other.
It is another object of the present invention to provide an aluminum heat exchanger advantageous in the reduction of the manufacturing cost.
In general, the heat exchanger such as a condenser or an evaporator includes: tubes which are arranged at predetermined intervals; and fins interposed between the tubes which are adjacent to each other. The tubes divide a plurality of refrigerant passages. By the tubes, heat is exchanged between the refrigerant and the air around the tubes when the refrigerant flows in the refrigerant passages. When consideration is given to the mechanical strength, the weight and formability, the tubes and fins are made of aluminum in many cases.
It is possible to manufacture aluminum tubes by means of extrusion. Concerning this technique, refer to the official gazette of JP-A-2001-153571. However, in the case where an aluminum alloy is selected when importance is attached to the mechanical strength, the aluminum alloy is inferior in the extrusion property. Therefore, a case is provided in which a plurality of protrusions are formed at predetermined intervals on two sheet members (core materials), and these sheet members are joined to each other to form a tube. Concerning this technique, refer to the official gazette of JP-A-2003-240378. In the heat exchanger described in the latter patent document, the inside of the joining portion between the protruded portions of the first core member made of aluminum and the inside of the joining portion between the protruded portions of the second core member are brazed to each other.
The inside of the joining portion of the first and the second core material composing the tube is not exposed to the outside air. Accordingly, there is no possibility of the occurrence of corrosion. However, the outside exposed to the outside air tends to be corroded. In order to protect the core material from corrosion, a sacrifical corrosion layer is formed on the outside of the core material. Concerning this technique, refer to the official gazette of JP-A-2000-205785. The sacrifical corrosion layer is made of material which is easily corroded. Therefore, the sacrifical corrosion layer is corroded by itself so that the core material (the base material) can be protected from corrosion.
However, in the above example of the prior art, the following problems may be encountered. First, in the case where the brazing filler metal layer is clad, the clad ratio (the ratio of the clad wall thickness to the entire wall thickness) is limited for the reasons of manufacture. Further, in the case where the powder brazing filler metal is coated, the powder brazing filler material melts the sacrifical corrosion layer at the time of brazing and the brazing filler metal layer is formed. Therefore, it becomes difficult to ensure the thickness of the sacrifical corrosion layer of the tube, the wall thickness of which is reduced. Secondly, as the brazing filler metal layer is electro-chemically noble as compared with the sacrifical corrosion layer and facilitates the corrosion of the sacrifical corrosion layer. Accordingly, the corrosion resistance is inferior.
The present invention has been accomplished to solve the above problems. An object of the present invention is to provide an improved heat exchanger and a method of manufacturing the heat exchanger. Another object of the present invention is to provide a heat exchanger in which an influence of the brazing filler metal, which is given to the outside of the tube, on the sacrifical corrosion layer is suppressed and also to provide a method of manufacturing the heat exchanger.
It is still another object of the present invention to provide a heat exchanger in which the brazing strength of brazing the fin can be maintained when the sacrifical corrosion layer and the outside brazing filler metal layer are formed on the outside for ensuring the corrosion resistance and for brazing the fin and further the deterioration of the corrosion resistance by the brazing filler metal layer is suppressed. Further, the present invention is to provide a method of manufacturing the heat exchanger.
In order to accomplish the above object, according to a first aspect of the present invention, there is provided an aluminum heat exchanger in which a tube (10) composed of a sheet material is brazed to a fin (12) composed of a sheet material, the sheet material for the tube (10) includes a core material (10 b) and also includes a sacrifical corrosion material (10 c) clad on one face of the core material (10 b) which becomes an outside of the tube (10), wherein the sheet material for the fin (12) is a bare aluminum material on which a brazing filler metal is not clad, the tube (10) and the fin (12) are brazed to each other with powder of brazing filler metal, and the sacrifical corrosion material (10 c) remains on the outside of the tube (10) even after the completion of brazing.
Due to the foregoing, as the tube (10) and the fin (12) are brazed to each other by using the brazing filler metal powder. Therefore, it is unnecessary that the brazing filler metal is clad either on the sheet member for the tube (10) or on the sheet member of the fin (12).
Therefore, only the sacrifical corrosion material (10 c) may be clad on the outside of the sheet member for the tube (10). Therefore, even when the thickness of the sheet member for the tube (10) is reduced, it is possible to ensure a necessary thickness of the sacrifical corrosion material (10 c) and it is also possible to ensure the corrosion resistance (the tube pitting corrosion preventing effect) of the tube (10). As a result, the corrosion resistance of the tube (10), the reduction of the tube (10) weight and the reduction of the material expense can be compatible with each other.
As the fin (12) is composed of an aluminum bare material on which the brazing filler metal is not clad, as compared with the fin (12) composed of a clad material on which the brazing filler metal is clad, it is possible to remarkably suppress the diffusion of Si, which is a component of the brazing filler metal, into the fin material. Therefore, the intergranular corrosion of the fin (12) can be prevented.
As the tube (10) is composed of a sheet member, even when the core material (10 b) of the sheet member for the tube (10) is made of an alloy of Al—Mn—Mg of high strength containing Mg of a relatively high concentration, such a problem that the extrusion formability is lowered is not caused, which is unlike in the case of an extruded perforated tube. Accordingly, the mechanical strength of the tube (10) can be increased. At the same time, the tube (10) can be effectively formed by a high productivity.
According to a second aspect of the present invention, concretely, the tube (10) and the fin (12) are brazed to each other when a mixture composite (10 e), in which the powder of brazing filler metal and fluoride flux are mixed with each other, is coated on a surface of the sacrifical corrosion material (10 c) on the sheet material for the tube (10).
Due to the foregoing, as compared with the case in which the mixed composition (10 e) is coated on the sheet member for the fin (12), the diffusion of the brazing filler metal into the fin material can be suppressed, and a non-corrosion property with respect to Al alloy can be exhibited by using the fluoride flux. Accordingly, disposal of the flux residue can be abolished or simplified.
According to a third aspect of the present invention, the brazing filler metal powder may be, concretely, Si powder.
According to a fourth aspect of the present invention, the brazing filler metal powder may be concretely mixture powder in which Si powder and Al powder are mixed with each other.
When the mixed powder, in which Si powder and Al powder are mixed with each other, is used as the brazing filler metal powder, Si powder reacts with Al powder at the time of brazing and an alloy of Al—Si (a brazing filler metal) is generated. Therefore, it is possible to decrease a melting depth of the sacrifical corrosion material layer (10 c) melted by Si powder. Accordingly, it becomes easy to ensure the residual thickness of the sacrifical corrosion material (10 c) after the completion of brazing.
According to a fifth aspect of the present invention, a brazing filler metal (10 d) of Al—Si may be clad on the other face of the core material (10 b) of the sheet material for the tube (10) which becomes an inside of the tube (10), and a joining face (10 a) of the sheet material for the tube (10) may be brazed by the brazing filler metal (10 d) of Al—Si.
According to a sixth aspect of the present invention, a joining face (10 a) of the sheet material for the tube (10) is brazed when a mixture composite, in which the brazing filler metal powder and flux of fluoride are mixed with each other, is coated on the other side of the core material (10 b) of the sheet material of the tube (10) which becomes an inside of the tube (10).
According to a seventh aspect of the present invention, the aluminum heat exchanger has an inner fin (13) arranged in the tube (10), wherein the inner fin (13) is composed of a sheet material having a core material (10 b) and a brazing filler metal (13 b, 13 c) clad on the core material (10 b), a joining face (10 a) of the tube (10) is brazed by the brazing filler metal (13 b, 13 c) of the inner fin (13).
Due to the foregoing, when the brazing filler metal (13 b, 13 c) on the inner fin (13) side is used as it is, the joining face (10 a) of the tube can be brazed. Therefore, it becomes unnecessary to supply the brazing filler metal to the inside of the sheet member for the tube (10).
As described in the eighth aspect of the present invention, when the thickness of the residual layer after the completion of brazing the sacrifical corrosion material (10 c) is not less than 0.015 mm, the tube pitting corrosion preventing effect by the sacrifical corrosion material (10 c) can be positively exhibited.
According to a heat exchanger of a ninth aspect of the present invention, a heat exchanger comprises: a plurality of tubes having an inner passage in which a heat exchange medium is circulated; and members to be joined which are attached to outsides of the tubes, each tube includes: a first core material portion in which a plurality of protruded and recessed portions are formed; and a second core material portion which composes an inner passage together with the first core material portion in which a plurality of protruded and recessed portions are formed. The first core material portion and the second core material portion are brazed to each other with an inside brazing filler metal layer which is interposed between an inside protruded portion of the first core material portion and an inside protruded portion of the second core material portion. A sacrifical corrosion layer is clad on the outside of the first core material portion, an outside brazing filler metal layer is clad and coated on the sacrifical corrosion layer of an outside protruded portion, a sacrifical corrosion layer is clad on an outside of the second core material portion, and an outside brazing filler metal layer is coated on the sacrifical corrosion layer of the outside protruded portion. The members to be joined are respectively brazed to the outside protruded portion of the first core material portion and the outside protruded portion of the second core material portion with the outside brazing filler metal layer.
According to a heat exchanger of a tenth aspect of the present invention, the inside brazing filler metal layer is coated on an inside of the inside protruded portion of the first core material portion and/or an inside of the inside protruded portion of the second core material portion. According to a heat exchanger of an eleventh aspect of the present invention, the inside brazing filler metal layer is clad on the entire inside of the first core material portion and/or the entire inside of the second core material portion. According to a heat exchanger of a twelfth aspect of the present invention, the inside brazing filler metal layer and the outside brazing filler metal layer respectively contain brazing filler metal powder and flux.
According to a heat exchanger of a thirteenth aspect of the present invention, a plurality of protruded and recessed portions of the first core material portion and a plurality of protruded and recessed portions of the second core material portion are respectively composed of a plurality of protruded portions and a plurality of recessed grooves, and the protruded portions are opposed to each other to form the inside passage. According to a heat exchanger of a fourteenth aspect of the present invention, a plurality of protruded and recessed portions of the first core material portion and a plurality of protruded and recessed portions of the second core material portion are respectively composed of a plurality of protrusions and hollows, and a portion of the protrusion of the first core material portion and a portion of the protrusion of the second core material portion are communicated with each other so that the inside passage can be formed.
According to a heat exchanger of a fifteenth aspect of the present invention, the first core material portion and the second core material portion are respectively formed into different bodies and put on each other. According to a heat exchanger of a sixteenth aspect of the present invention, the first core material portion and the second core material portion are formed when one core material is bent, and the first core material portion and the second core material portion are integrated with each other into one body. According to a heat exchanger of a seventeenth aspect of the present invention, the member to be joined is a corrugated fin. According to a heat exchanger of an eighteenth aspect of the present invention, the wall thickness of the first core material portion and the second core material portion is 0.1 to 0.2 mm, and the wall thickness of the member to be joined is 0.03 to 0.07 mm.
According to a method of manufacturing a heat exchanger of a nineteenth aspect of the present invention, the heat exchanger including: a plurality of tubes having an inner passage in which a heat exchange medium is circulated; and members to be joined which are brazed to the outsides of the tubes, the method of manufacturing the heat exchanger comprising: a protruded and recessed portion forming step of forming a large number of protruded and recessed portions in the first core material portion, on the outside of which a sacrifical corrosion layer is clad, and in the second core material portion, on the outside of which a sacrifical corrosion layer is clad; a coating step of coating an outside brazing filler metal layer on a sacrifical corrosion layer of the outside protruded portion of the first core material portion and on a sacrifical corrosion layer of the outside protruded portion of the second core material portion; and a brazing step in which the first core material portion and the second core material portion are brazed to each other with an inside brazing filler metal layer which is interposed between an inside protruded portion of the first core material portion and an inside protruded portion of the second core material portion, and members to be joined are brazed to an outside protruded portion of the first core material portion and an outside protruded portion of the second core material portion with the outside brazing filler metal layer.
According to a method of manufacturing a heat exchanger of a twentieth aspect of the present invention, the inside brazing filler metal layer is clad on the inside of the first core material portion and the inside of the second core material portion before the protruded and recessed portion forming step. According to a method of manufacturing a heat exchanger of a twenty-first aspect of the present invention, the inside brazing filler metal layer is coated on the inside of the inside protruded portion of the first core material portion and the inside of the inside protruded portion of the second core material portion in the coating step. According to a method of manufacturing a heat exchanger of a twenty-second aspect of the present invention, the outside brazing filler metal layer is coated with a rotating roller in the coating step. According to a method of manufacturing a heat exchanger of a twenty-third aspect of the present invention, the brazing filler metal layer is not provided on the fin which is a member to be joined.
According to a heat exchanger of a twenty-fourth aspect of the present invention, the heat exchanger comprises: a tube, in the inner passage of which a heat exchange medium is circulated; and a member to be joined which is joined to the outside of the tube by means of brazing, wherein a wall of the tube is composed of a metallic sheet on which a plurality of protruded and recessed portions are formed, the inner passage of the tube is formed when top portions of the inside protruded portions of the metallic sheet, which are opposed to each other, are joined to each other by means of brazing and edge portions of the metallic sheet are joined to each other by means of brazing, the metallic sheet including: a core material; a sacrifical corrosion layer which is clad on the core material so that the sacrifical corrosion layer can be located outside the tube; an inside brazing filler metal provided at the top of the inside protruded portion of the metallic sheet; and an outside brazing filler metal coated only on the top portion of the outside protruded portion of the metallic sheet, wherein the tube and the member to be joined are brazed to each other by the outside brazing filler metal.
According to a heat exchanger of a twenty-fifth aspect of the present invention, the member to be joined is a corrugated fin formed out of a sheet material. According to a heat exchanger of a twenty-sixth aspect of the present invention, the tube is composed in such a manner that two metallic sheets are put on each other and edge portions of two pairs of the two metallic sheets are joined to each other by means of brazing. According to a heat exchanger of a twenty-seventh aspect of the present invention, the tube is composed in such a manner that one metallic sheet is bent and both edges portions of the metallic sheet are joined to each other by means of brazing. According to a heat exchanger of a twenty-eighth aspect of the present invention, the inside brazing filler metal is an inside brazing filler metal layer which is clad on the core material so that the inside brazing filler metal layer can cover the entire inside including the top portion of the inside protruded portion of the metallic sheet. According to a heat exchanger of a twenty-ninth aspect of the present invention, the inside brazing filler metal is an inside brazing filler metal layer which is coated only in the top portion of the inside protruded portion of the metallic sheet.
According to the ninth aspect of the present invention, the inside protruded portion of the first core material portion and the inside protruded portion of the second core material portion are brazed by the inside brazing filler metal layer, and the member to be joined is brazed to the outside protruded portions of the first core material portion and the second core material portion by the outside brazing filler metal layer via the sacrifical corrosion layer. As the sacrifical corrosion layer is clad on the entire outside of the first core material portion and the second core material portion, the corrosion resistance is excellent. As the outside brazing filler metal is coated only on the outside (the top face) of the outside protruded portion, a reduction of the thickness of the sacrifical corrosion layer and a facilitation of corrosion conducted by the outside brazing filler metal layer can be minimized.
According to the heat exchanger of the tenth aspect, the inside brazing filler metal is coated only on the insides (the top faces) of the inside protruded portions of the first and the second core material portion. Therefore, the amount of the inside brazing filler metal used can be reduced. According to the heat exchanger of the eleventh aspect, the inside brazing filler metal layer can be previously clad on the entire inside of the clad material. Therefore, the inside brazing filler metal layer can be easily formed. According to the heat exchanger of the twelfth aspect, the inside brazing filler metal layer and the outside brazing filler metal layer contain not only the brazing filler metal powder but also flux. Therefore, oxide films can be removed from the first core material portion and the second core material portion. Accordingly, the brazing work can be easily performed.
According to the heat exchanger of the thirteenth aspect, the outside protruded portion of the first core material portion and the outside protruded portion of the second core material portion can divide a linear inner passage. Therefore, the inner passage can be easily divided. According to the heat exchanger of the fourteenth aspect, the outside protruded portion of the first core material portion and the outside protruded portion of the second core material portion can divide a labyrinth-shaped inner passage. Therefore, the thermal efficiency is high. According to the heat exchanger of the fifteenth aspect, the first core material portion and the second core material portion are formed into bodies different from each other. Therefore, the protruded portion and the recessed portion can be easily formed. According to the heat exchanger of the sixteenth aspect, the first core material portion and the second core material portion are integrated with each other into one body. Therefore, the number of parts can be decreased. According to the heat exchanger of the seventeenth aspect, the fin arranged between the tubes, which are adjacent to each other, can make it possible to conduct heat exchange effectively.
According to the method of manufacturing a heat exchanger of the nineteenth aspect, the sacrifical corrosion layer is clad before the protruded portions and the recessed portions are formed on the outsides of the first core material portion and the second core material portion. Therefore, the corrosion resistance of the entire outside can be increased. As the outside brazing filler metal is coated only on the outside protruded portions, the sacrifical corrosion layer of the recessed portion (a portion at the rear of the inside protruded portion) between the outside protruded portion, which are adjacent to each other, does not melt, and the thickness of the sacrifical corrosion layer can be maintained in a wide range.
According to the manufacturing method of the twentieth aspect of the present invention, before the process of forming the recessed and the protruded portions, the inside brazing filler metal layer has already been clad on the insides of the first core material portion and the second core material portion. Accordingly, the inside brazing filler metal layer can be easily formed on the inside protruded portions. According to the manufacturing method of the twenty-first aspect, in the coating process, the inside brazing filler metal is coated only on the inside protruded portions of the first core material portion and the second core material portion. Therefore, the amount of the inside brazing filler metal used can be reduced. According to the manufacturing method of the twenty-second aspect, the outside brazing filler metal layer can be uniformly coated on the sacrifical corrosion layer of the outside protruded portion by a rotating roller. According to the manufacturing method of the twenty-third aspect, as the brazing filler metal layer is not clad on the fins, the thickness of which is small, it is possible to prevent the generation of intergranular corrosion of the fins.
According to the heat exchanger of the twenty-fourth aspect of the present invention, an influence of the outside brazing filler metal given to the sacrifical corrosion layer can be suppressed. According to the heat exchanger of the twenty-fifth aspect of the present invention, even when the outside brazing filler metal is used for brazing the fins, while the fins are being positively joined, an influence of the brazing filler metal given to the sacrifical corrosion layer can be suppressed. According to the heat exchanger of the twenty-sixth aspect of the present invention, two metallic sheets are put on each other, and the inner passage can be composed between them. According to the heat exchanger of the twenty-seventh aspect of the present invention, the tube can be composed of one metallic sheet. According to the heat exchanger of the twenty-eighth aspect of the present invention, the inside brazing filler metal can be positively provided. According to the heat exchanger of the twenty-ninth aspect of the present invention, the amount of the brazing filler metal of the inside brazing filler metal layer can be suppressed.
Incidentally, the reference numerals in parentheses, to denote the above means, are intended to show the relationship of the specific means which will be described later in an embodiment of the invention.
The present invention may be more fully understood from the description of preferred embodiments of the invention set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:
FIG. 1 is a perspective view showing an evaporator used for air conditioning in a vehicle to which the first embodiment of the present invention is applied;
FIG. 2 is a partially cutaway schematic perspective view showing an outline of a portion of FIG. 1;
FIG. 3A is a cutaway perspective view showing a tube in the first embodiment;
FIG. 3B is a sectional view of a tube material;
FIG. 4 is a table showing specific compositions of the tube material and the fin material in the first embodiment;
FIG. 5 is a schematic illustration showing a result of the evaluation of the melting depth made by Si powder in the first embodiment;
FIG. 6 is a graph showing a relation between the clad thickness and the tube sheet material thickness;
FIG. 7A is a cutaway perspective view of the tube in the second embodiment;
FIG. 7B is a sectional view showing an inner fin material;
FIG. 8 is a table showing an example of the combination of the tube material with the fin material in the prior art;
FIG. 9 is a schematic illustration of the entire air conditioner including the fourth embodiment of the present invention;
FIG. 10 is a perspective view showing a condenser of the fourth embodiment of the present invention;
FIG. 11 is a cutaway perspective view of a primary portion of the above condenser;
FIG. 12 is a partially enlarged sectional view of the tube of the above heat exchanger;
FIG. 13 is a perspective view showing an end portion of the tube;
FIGS. 14A to 14E are schematic illustrations showing a manufacturing process of manufacturing a condenser;
FIG. 15 is a graph showing a result of the experiment of the fourth embodiment and the comparative example;
FIG. 16 is a sectional view showing the first variation of the fourth embodiment, wherein FIG. 16 corresponds to FIG. 12;
FIG. 17 is a perspective view showing the second variation of the fourth embodiment;
FIG. 18A is a plan view showing a primary portion of the second variation of the fourth embodiment; and
FIG. 18B is a front view showing the primary portion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First of all, the first embodiment will be explained below. The first embodiment is an example in which the present invention is applied to an evaporator of an air conditioner for vehicle use. First, by referring to FIGS. 1 to 3, explanations will be made into an outline of the evaporator of the air conditioner for vehicle use. The evaporator is composed as follows. Tubes 10 and header tanks 11 are joined by being brazed to each other under the condition that both end portions in the longitudinal direction of a large number of tubes 10, in which the refrigerant flows, are communicated with the inside of the header tanks 11.
In this embodiment, as shown in FIG. 3A, each tube 10 is composed in such a manner that one aluminum sheet is bent so as to form a passage, the cross section of which is flat. The joining face 10 a composing a connecting portion of the passage is provided at one end portion of the flat cross section of the tube 10.
Each header tank 11 is formed into a long, slender tank-shape extending in the laminating direction (the lateral direction in FIGS. 1 and 2) of the tubes 10. Inside of this tank-shape, a communicating space is formed with which one end portion in the longitudinal direction of the tube 10 is communicated, that is, both end portions in the longitudinal direction of the tube 10 are communicated the communicating spaces formed in the header tanks 11. As shown in FIG. 2, in the header tanks 11, the flat through-holes 11 a are formed into which both end portions in the longitudinal direction of the tubes are inserted.
Both end portions in the longitudinal direction of the tubes 10 are inserted into these through-holes 11 a. The header tanks 11 and the tubes 10 are brazed to each other in the portions of the through-holes 11 a.
Between a large number of tubes 10, the fins 12 composing outer fins are arranged to be extended in the longitudinal direction of the tube. These fins 12 are corrugated fins which are formed by bending an aluminum sheet into a wave-shape. Top portions of the wave-shape are in contact with and brazed to the outsides of the tubes 10 which are arranged adjacent to the fins 12.
In the evaporator, a flow of air is blown in the gap portions of the heat exchange core section, which is composed of the tubes 10 and the fins 12, in the direction of arrow A shown in FIG. 1. Heat exchange is conducted between the flow of air and the refrigerant flowing in the tubes 10 via the tubes 10 and the fins 12. In this way, the flow of air absorbs latent heat of vaporization from the refrigerant so that the air can be cooled.
Next, referring to FIGS. 3B and 4, specific material compositions of the tube 10 and the fin 12 will be explained below. As shown in FIG. 3B, the tube 10 is composed of a sheet material (double side clad material). The sheet material includes: a core material 10 b; a sacrifical corrosion material 10 c which is clad onto one face of the core material 19 b; and a brazing filler metal 10 d which is clad on the other face of the core material 10 b.
In this structure, the sacrifical corrosion material 10 c is clad onto one face of the core material 10 b which becomes the outside (the face on the air side) of the tube 10, and the brazing filler metal 10 d is clad on the other side of the core material 10 b which becomes the inside (the face on the refrigerant side) of the tube 10.
FIG. 4 is a table on which specific compositions of the materials of the tube 10 and the fin 12 are expressed by mass %. Concerning the compositions of the core material 10 b of the tube 10, two examples of items (1) and (2) are shown. Both the core materials 10 b shown in items (1) and (2) are made of a high strength aluminum alloy of Al—Mn—Mg containing Mg of a relatively high concentration. In this connection, mark (−) in FIG. 4 shows that the amount of addition is 0.0 mass % or the amount of addition is an inevitably small amount.
In this case, a preferable addition range of Mg is 0.1 to 1.0 mass %, and a preferable addition range of Mn is 1.0 to 1.8 mass %. In this connection, in the example shown in the drawing, the amount of addition of Mg is 0.4 mass %, and the amount of addition of Mn is 1.65 mass %.
In the composition of the core material 10 b of item (1), Cu is added to the composition of the core material 10 b of item (2) by 0.5 mass %. Cu is added in this way for the object of enhancing the mechanical strength of the tube core material 10 b.
The sacrifical corrosion material 10 c composing the outside clad layer is specifically an aluminum alloy to which Zn is added by 4.0 mass %. In this case, when Zn is added to the sacrifical corrosion material 10 c, the electric potential of the sacrifical corrosion material 10 c becomes poor with respect to the core material 10 b. Therefore, the sacrifical corrosion material 10 c exhibits a sacrifical corrosion action with respect to the core material 10 b.
The brazing filler metal composing the inside clad layer is an alloy of Al—Si commonly used. When Si forms an eutectic alloy together with Al, the melting point of the brazing filler metal 10 d is lower than the melting point of the core material 10 b by a predetermined temperature.
On the other hand, the sheet material composing the fin 12 is a bare aluminum material on which the brazing filler metal is not clad. This bare aluminum material for fins is an aluminum alloy of Al—Mn to which Mg is not added. Zn is added to this bare aluminum material for fins by 1.4 mass % for the object of exhibiting the sacrifical corrosion effect with respect to the tube 10 by the fin 12 itself.
On the outside of the sheet material for the tube 10, that is, on the surface of the clad layer of the sacrifical corrosion material 10 c, a mixture composition 10 e for brazing the tube 10 to the fin 12, in which the brazing filler metal powder and flux are mixed with each other, is coated. In this case, the brazing filler metal powder is specifically Si powder. Only Si powder may be used as the brazing filler metal powder. However, a mixed powder, in which Si powder and Al powder are mixed with each other, may be used as the brazing filler metal powder.
The flux is made of fluoride, that is, the flux is a non-corrosion type flux. To be specific, the flux is one of KAlF₄, K₃AlF₆, K₂AlF₅, AlF₃and KZnF₃. Alternatively, the flux is a mixture in which a plurality of the above chemical compounds are mixed with each other.
On the inside of the sheet material for the tube 10, that is, on the clad layer surface of the brazing filler metal 10 d, the flux 10 f is coated. This flux 10 f is the same as the flux of the above mixture composition 10 e (the flux of fluoride).
In this connection, in this embodiment, the wall thickness t of the sheet material for the tube 10, that is, the total wall thickness t including the thickness of the clad layers 10 c, 10 d on both faces is 0.20 mm. The clad ratio of the sacrifical corrosion material 10 c, which is the outside clad layer, is 20% and the clad ratio of the brazing filler metal 10 d, which is the inside clad layer, is 15%. Accordingly, the thickness of the sacrifical corrosion material 10 c is 0.04 mm, and the thickness of the brazing filler metal 10 d is 0.03 mm.
The wall thickness of the fin 12, that is, the wall thickness of the bare aluminum material for fins is 0.05 mm. As the header tank 11 is a strength member for supporting the tubes 10 and others, the wall thickness of the header tank 11 is sufficiently larger than the wall thickness of the fin 12. For example, the wall thickness of the header tank 11 is 0.6 mm. The header tank 11 is composed of double clad material in which the brazing filler metal is clad on both faces of the core material.
Next, a method of manufacturing an aluminum heat exchanger of this embodiment will be explained below. The manufacturing method of this embodiment includes the steps of: (1) a step in which the mixture composition 10 e and the flux 10 f are coated on parts composing the heat exchanger and a step in which each part is formed; (2) a step in which the parts composing the heat exchanger are assembled; and (3) a brazing step.
First, explanations will be made into a coating step in which flux is coated on each part and a forming step in which each part is formed. The sheet material for the tube 10 is a double clad material. This double clad material includes: a core material 10 b; a sacrifical corrosion material 10 c which is an outside clad layer; and a brazing filler metal 10 d which is an inside clad layer. When this double clad material is flat, the mixture composition 10 e, in which Si powder for the brazing filler metal and the flux of fluoride are mixed with each other, is coated on the outside (the surface of the sacrifical corrosion material 10 c).
In this case, at the time of coating the mixture composition 10 e, a solution having an appropriate viscosity is made in which Si powder and flux powder are dissolved in a solvent containing a binder made of resin, and this solution of the mixture composition 10 e is coated on the outside of the sheet material for the tube 10 by a well known coating method such as a roller coating method or a spraying method. In this case, the meaning of the solution includes a paste-like solution.
The flux 10 f is coated on the inside (the surface of the brazing filler metal 10 d) of the sheet material for the tube 10. At the time of coating this flux 10 f, to be specific, a solution having an appropriate viscosity is made in which the flux powder is dissolved into a solvent containing a binder made of resin, and the thus made solution may be coated on the inside of the sheet material for the tube 10 by a well known coating method.
After the mixture composition 10 e and the flux 10 f have been coated in this way, the sheet material for the tube 10 is bent into a passage, the cross section of which is flat as shown in FIG. 3A, and further the joining face 10 a is formed at the bent end portion.
The sheet material for fins 12 is formed into corrugated fins when the above bare aluminum material is bent into a wave-shape as it is.
The sheet material for the header tank 11 is formed into a tank shape shown in FIG. 2 when the above clad material is formed. The flux, to be specific, the flux of fluoride is coated on the sheet material for the header tank 11 by the well known coating method described before.
Next, the assembling step will be explained as follows. Parts such as tubes 10 for the heat exchanger, header tanks 11 and fins 12 are assembled so as to form a predetermined structure shown in FIGS. 1 and 2, and the this assembled body, which is in a provisionally assembled state, is fastened and held with a jig such as a wire.
Next, the brazing step will be explained as follows. The above assembled body is held by the jig and carried into a furnace for brazing. When the assembled body is heated to a brazing temperature, the parts of the heat exchanger are brazed and integrated to each other.
In this case, Si powder of the mixture composition 10 e, which is coated on the outside of the tube 10 (the surface of the sacrifical corrosion material 10 c), reacts with Al of the sacrifical corrosion material 10 c and forms an eutectic alloy and melts at the brazing temperature. In this way, Si powder of the mixture composition 10 e fulfills a function of the brazing filler metal. That is, the tube 10 and the fin 12 can be brazed to each other with Si powder of the mixture composition 10 e.
The joining faces of the tube 10 can be brazed to each other by the brazing filler metal 10 f which is clad on the inside of the tube 10.
The header tank 11 and both end portions of the tube 10 can be brazed to each other with the brazing filler metal, which is clad to the header tank 11, and Si powder of the mixed composition 10 e provided on the tube 10 side.
In this brazing step, the flux powder of the mixture composition 10 e coated on the outside of the tube 10 (the surface of the sacrifical corrosion material 10 c), the flux 10 f coated on the inside of the tube 10, and the flux coated on the header tank 11 are melted at the brazing temperature and uniformly spread onto the joining faces between the parts.
By this melted flux component, the oxide film on the surface of the aluminum material of each part is reduced so that the wettability between the melted brazing filler metal and the aluminum base material can be improved. The atmosphere in the furnace for brazing is maintained by inert gas such as N₂gas. Therefore, the re-oxidization of the aluminum material can be prevented. Due to the foregoing, each part can be brazed in a good condition.
Any flux coated on each portion is the flux of fluoride. This flux of fluoride does not corrode the aluminum material. Therefore, it is possible to abolish the washing step for removing the flux residue after the completion of brazing. Alternatively, it is possible to simplify the washing step for removing the flux residue.
In this connection, as described above, according to this embodiment, Si powder of the mixture composition 10 e reacts with Al of the sacrifical corrosion material 10 c and forms an eutectic alloy and melts at the brazing temperature. In this way, Si powder of the mixture composition 10 e fulfills a function of the brazing filler metal. Accordingly, a melted hole is generated in the sacrifical corrosion material 10 c by the brazing filler metal of Si powder, and the wall thickness of the sacrifical corrosion material 10 c is decreased.
FIG. 5 is a view showing the melting depth (unit: mm) made by the brazing filler metal of Si powder. The material compositions of the tube 10 and the fin 12 to be evaluated are shown in FIG. 4. In this connection, concerning the core material 10 b of the tube 10, the same melting depth is obtained when either item (1) or item (2) in FIG. 4 is used.
In FIG. 5, the total number of the heat exchangers to be evaluated (the total of N) is 22, and a distribution of the melting depths (mm) is shown at the interval of 0.001 mm. The average melting depth to be evaluated was 0.015 mm.
In this case, the wall thickness t of the sheet material for the tube 10 is 0.20 mm as described above, and the clad ratio of the sacrifical corrosion material 10 c is 20%. Therefore, the thickness of the sacrifical corrosion material 10 c before brazing (the clad thickness) is 0.04 mm. Accordingly, the average thickness of the sacrifical corrosion material 10 c after brazing is determined by the expression 0.04-0.015=0.025 mm.
According to the investigations made by the present inventors, the following was found. In order to ensure the corrosion resistance of the tube 10, the thickness of the sacrifical corrosion material 10 c must be not less than 0.015 mm. According to the present embodiment, it is possible to obtain the thickness of the sacrifical corrosion material 10 c, which greatly exceeds the above minimum necessary thickness, after the completion of brazing. Therefore, the corrosion resistance of the tube 10 can be excellently accomplished by the sacrifical corrosion material 10 c.
Next, FIG. 6 is a graph showing a condition by which the minimum necessary thickness=0.015 mm of the sacrifical corrosion material 10 c can be ensured. The axis of abscissas represents the wall thickness t of the sheet material for the tube 10, and the axis of ordinate represents the clad thickness on the outside of the sheet material of the tube 10. Straight line A shows a relation between the wall thickness t and the clad thickness under the condition of the clad ratio of the outside=20%.
As described above, the average melting depth=0.015 mm, and the minimum necessary thickness of the sacrifical corrosion material 10 c=0.015 mm. Therefore, the sacrifical corrosion clad thickness may be 0.015 mm+0.015 mm=0.03 mm. Accordingly, it is sufficient that the wall thickness t is not less than 0.15 mm.
However, when both the sacrifical corrosion material and the brazing filler metal are clad on the outside of the sheet material for the tube 10 in the manner of the multiple layer clad, the necessary thickness of the brazing filler metal is 0.035 mm at the minimum. When the necessary minimum thickness=0.015 mm of the sacrifical corrosion material 10 c is added to this, the total necessary clad thickness=0.05 mm. Therefore, the wall thickness t must be not less than 0.25 mm. For the above reasons, it is necessary that the wall thickness of the sheet material for the tube 10 is increased as compared with the present embodiment.
In other words, according to the present embodiment, as compared with Example 2 of the prior art shown in FIG. 8, it is possible to ensure the corrosion resistance of the tube 10 and it is also possible to decrease the wall thickness of the tube 10. Therefore, the weight of the aluminum heat exchanger can be reduced and, further, the material expense can be decreased.
In this connection, in the first embodiment, only Si powder is used for the brazing filler metal powder of the mixture composition 10 e. However, the mixed powder, in which Si powder and Al powder are mixed with each other, may be used for the brazing filler metal powder of the mixture composition 10 e.
When the mixed powder, in which Si powder and Al powder are mixed with each other, is used for the brazing filler metal powder as described above, Si powder reacts with Al powder at the time of brazing, and an alloy of Al—Si (a brazing filler metal) is generated. Accordingly, it is possible to decrease the melting depth of the sacrifical corrosion material 10 c made by Si powder. Therefore, the residual thickness of the sacrifical corrosion material 10 c after the completion of brazing can be easily ensured.
Next, the second embodiment will be explained below.
In the first embodiment, the joining face 10 a of the tube 10 is brazed with the brazing filler metal 10 d which is clad on the inside of the sheet material for the tube 10. However, in the second embodiment, as shown in FIG. 7, the joining face 10 a of the tube 10 is brazed with the brazing filler metals 13 b, 13 c which are clad on the inner fin 13 side arranged inside the tube 10.
The second embodiment will be more specifically explained below. The inner fin 13 is a corrugated fin which is bent into the wave-shape as shown in FIG. 7A. This inner fin 13 is arranged inside the tube 10 so as to extend a heat transfer area on the inner fluid (refrigerant) side. The inner fin is arranged all over the length in the longitudinal direction (the vertical direction in FIGS. 1 and 2). The top portions of the wave-shape of the inner fin 13 are in contact with and brazed to the inside of the tube 10.
As shown in FIG. 7B, the sheet material of the inner fin 13 is composed of double clad material in which the brazing filler metals 13 b, 13 c are clad on both faces of the core material 13 a. The wall thickness ti of the sheet material for the inner fin 13 is 0.050 mm in the same manner as that of the fin (outer fin) 12 brazed to the outside of the tube 10.
The inner fin 13 is provided with an end portion 13 d which is interposed to be sandwiched between the joining faces 10 a of the tube 10. Due to this structure, the brazing filler metals 13 b, 13 c on the inner fin 13 side can be supplied to the joining faces 10 a. Therefore, the joining faces 10 a can be brazed to each other.
Accordingly, in the second embodiment of the present invention, it is unnecessary to clad the brazing filler metal 10 d of the first embodiment on the inside of the core material 10 b of the sheet material for the tube 10. Therefore, the flux 10 f in the first embodiment may be directly coated on the inside of the core material 10 b of the sheet material for the tube 10. In this case, the flux 10 f may not be coated on the inside of the core material 10 b of the sheet material for the tube 10 but the flux 10 f may be coated on the surfaces of the brazing filler metals 13 b, 13 c of the sheet material for the inner fin 13.
In this connection, in the first embodiment, only when both end portions of the sheet material for the tube 10 are put on each other, the joining face 10 a of the tube 10 is formed. However, in the second embodiment, one end portion of the sheet material for the tube 10 is curled so that the one end portion can be curled around the other end portion of the sheet material for the tube 10. In this way, the joining face 10 a of the tube 10 is formed.
Next, the third embodiment will be explained below. In the first embodiment, the joining face 10 a of the tube 10 is brazed with the brazing filler metal 10 d which is clad on the inside of the sheet material for the tube 10. However, in the third embodiment, the brazing filler metal 10 d of the first embodiment is not clad on the inside of the core material 10 b of the sheet material for the tube 10. Instead of that, the same mixture composition as the mixture composition 10 e of the first embodiment, in which the brazing filler metal and the flux powder are mixed with each other, is directly coated on the inside of the core material 10 b of the sheet material for the tube 10. With the brazing filler metal powder of this mixture composition, the joining faces 10 a of the tube 10 are brazed to each other.
Even when the joining faces 10 a of the tube are brazed to each other as described in the second and the third embodiment, concerning the brazing structure for brazing the tube 10 to the fin 12, the same structure as that of the first embodiment is employed in these embodiments. Therefore, these embodiments can exhibit the same action and effect as those of the first embodiment.
Next, another embodiment will be explained below. In this connection, in the embodiments described above, in the case of composing the tube 10 out of the sheet material, one sheet material is bent so as to compose a passage, the cross section of which is flat. However, the passage of the tube 10, the cross section of which is flat, may be composed when two sheet materials are stuck to each other.
The present invention can be applied to not only the aluminum heat exchanger of an air conditioner for vehicle use but also the aluminum heat exchanger used for various purposes.
Next, the fourth embodiment will be explained below. In this embodiment of the present invention, the following manufacturing method and structure are employed. A sacrifical corrosion layer is clad on the outsides of the first core material portion and the second core material portion. After that, a plurality of protruded and recessed portions are formed. Then, an outside brazing filler metal layer is coated on an outside protruded portions of both the core portions.
The heat exchanger includes: a plurality of tubes having an inner passage in which the heat exchange medium is circulated; and members to be joined attached to the outsides of the tubes. The tube includes: a first core material portion in which a plurality of protruded and recessed portions are formed; and a second core material portion which composes an inner passage together with the first core material portion in which the plurality of protruded and recessed portions are formed. The first core material portion and the second core material portion are brazed to each other with the inside brazing filler metal layer which is interposed between the inside protruded portion of the first core material portion and the inside protruded portion of the second core material portion. A sacrifical corrosion layer is clad on the outside of the first core material portion, an outside brazing filler metal layer is clad on the sacrifical corrosion layer of the outside protruded portion, a sacrifical corrosion layer is clad on the outside of the second core material portion, and an outside brazing filler metal layer is coated on the sacrifical corrosion layer of the outside protruded portion. Members to be joined are respectively brazed to the outside protruded portion of the first core material portion and the outside protruded portion of the second core material portion with the outside brazing filler metal layer.
Next, various forms of the components of the heat exchanger will be explained as follows. Concerning the heat exchanger, there are provided a condenser and evaporator used for an air conditioner for vehicle use. The condenser is a heat exchanger for exchanging heat between the gas refrigerant of high temperature and pressure, which is sent from a compressor, and the outside air, which is supplied from a blower, so that the refrigerant can be cooled, condensed and liquidized. The evaporator is a heat exchanger for depriving the air, which flows in the periphery of the evaporator, of heat when the air is turned into cold air by liquidizing the refrigerant in the condenser and the temperature and pressure are reduced by an expansion valve. However, the heat exchanger is not limited to the vehicle use. It is possible to apply the heat exchanger to an air conditioner for domestic use. The heat exchanger may include: a plurality of tubes having an inner passage in which a heat exchange medium is circulated; and members to be joined which are attached onto the outsides of the tubes.
The tube may include: a first core material portion in which a plurality of protruded and recessed portions are formed; and a second core portion in which an inner passage is formed together with the first core material portion in which the plurality of protruded and recessed portions are formed. The first core material portion is made of light aluminum or aluminum alloy, and the wall thickness of the first core material portion can be selected from the range of 0.1 to 0.3 mm. The plurality of protruded and recessed portions can be formed as follows. Concerning the protruded portions, for example, a plurality of outside protruded portions are protruded onto the outside of the first core material portion. Concerning the recessed portions, a plurality of inside protrusions (recessed grooves when they are viewed from the outside) are protruded from the inside side. The plurality of outside protruded portions and inside protruded portions can be alternately formed.
A plurality of outside protrusions protruding from the outside of the first core material portion can be formed as the protruded portions. A plurality of inside protrusions (hollow portions when they are viewed from the outside) can be formed at positions shifted from the outside protruded portions as the recessed portions. On the outside (the outside protruded portions and portions except for them) of the first core material portion, a sacrifical corrosion layer described later is clad, and an outside brazing filler metal layer described later is coated on the sacrifical corrosion layer on the outside protruded portions.
The second core material portion is made of the essentially same material as that of the first core material, and the wall thickness of the second core material portion is the same as that of the first core material. The structure of the second core material portion is symmetrical to the structure of the first core material portion with respect to the brazing face. A sacrifical corrosion layer is clad on the entire outside (the outside protruded portions and portions except for them) of the second core material, and an outside brazing filler metal layer is coated on the sacrifical corrosion layer of the outside protruded portion.
The outside protruded portions of the first core material portion and the outside protruded portions of the second core material portion are opposed to each other and capable of dividing the linear inner passage. When the outside protrusions of the first core material portion and the outside protrusions of the second core material portion are partially put on each other in a plan view and communicated with each other, it is possible to divide a bent labyrinth-shaped inner passage. The first core material portion and the second core material portion are formed into bodies different from each other. Therefore, the first core material portion and the second core material portion may be put on each other. Alternatively, the first core material portion and the second core material portion may be formed into one body by bending one core material. In any case, the inside protruded portions of the first core material portion and the inside protruded portions of the second core material portion are brazed to each other by the inside brazing filler metal layer.
The sacrifical corrosion layer protects the outsides of the first core material portion and the second core material portion from corrosion. Therefore, the sacrifical corrosion layer is made of aluminum alloy, the electric potential of which is poor compared with the electric potentials of the first core material portion and the second core material portion, and the aluminum alloy exhibits a sacrifical corrosion action with respect to both the core material portions. The outside brazing filler metal layer is used for brazing the portions to be joined to the outside protruded portions of the first core material portion and the outside protruded portions of the second core material portion via the sacrifical corrosion layer.
The inside brazing filler metal layer is used for brazing the inside protrusions of the first core material portion to the inside protrusions of the second core material portion. The inside brazing filler metal layer is coated on the inside (the top face) of at least one inner face protrusion. In this connection, the inside brazing filler metal may be clad onto the entire insides (the inside protrusions and portions except for them) of the first core material portion and the second core material portion.
The outside brazing filler metal layer and the inside brazing filler metal layer may be made of only brazing filler metal powder. However, it is desirable that the outside brazing filler metal layer and the inside brazing filler metal layer contain flux in addition to the brazing filler metal powder. Examples of the brazing filler metal powder are: Si powder, Al—Si powder alloy, Al—Si—Cu powder alloy, Al—Si—Zn powder alloy, and Al—Si—Cu—Zn powder alloy. Concerning the flux, it is suitable to use flux of fluoride. Examples of the flux of fluoride are: KAlF4, K3AlF4, K3AAlF6, AlF3, K2AAlF5, and KZnF3.
The members to be joined are brazed to the outside protruded portions of the first core material portion and the second core material portion with the outside brazing filler metal layer. A corrugated fin is representative of the member to be joined. However, it is possible to use a tube. In the case of fins, it is preferable that the fins are composed of core material and that the brazing filler metal is not clad on the fins. The wall thickness of the fin is smaller than the wall thickness of the first core material and the second core material. Specifically, the wall thickness of the fin is selected from the range of 0.03 to 0.07 mm.
The present invention provides a method of manufacturing a heat exchanger. The heat exchanger includes: a plurality of tubes having an inner passage in which a heat exchange medium is circulated; and members to be joined which are brazed to the outsides of the tubes. The method of manufacturing a heat exchanger comprises: a protruded and recessed portion forming step of forming a large number of protruded and recessed portions in the first core material portion, on the outside of which a sacrifical corrosion layer is clad, and in the second core material portion, on the outside of which a sacrifical corrosion layer is clad; a coating step of coating an outside brazing filler metal layer on a sacrifical corrosion layer of the outside protruded portion of the first core material portion and on a sacrifical corrosion layer of the outside protruded portion of the second core material portion; and a brazing step in which the first core material portion and the second core material portion are brazed to each other with an inside brazing filler metal layer which is interposed between an inside protruded portion of the first core material portion and an inside protruded portion of the second core material portion, and members to be joined are brazed to an outside protruded portion of the first core material portion and an outside protruded portion of the second core material portion with the outside brazing filler metal layer.
Each step of the method of manufacturing a heat exchanger will be explained as follows. In the protruded and recessed portion forming step, a plurality of the protruded and recessed portions are formed by means of press forming in the first core material portion, on the outside of which the sacrifical corrosion layer is clad and in the second core material portion, on the outside of which the sacrifical corrosion layer is clad. In this connection, before this protruded and recessed portion forming step, the inside brazing filler metal layer may be clad on the insides of the first core material portion and the second core material portion. In this case, when the protruded and recessed portions are formed, the inside brazing filler metal layer is formed on the entire inside. In this connection, the inside brazing filler metal may be coated in the coating step described later.
In the coating step, the outside brazing filler metal layer is coated on the sacrifical corrosion layer on the outside protruded portion in the first core material portion and on the sacrifical corrosion layer on the outside protruded portion in the second core material portion. In this connection, while keeping pace with coating of the outside brazing filler metal layer, before or after that, the inside brazing filler metal layer may be coated on the inside (the top face) of the inside protruded portion of the first core material portion and on the inside (the top face) of the inside protruded portion of the second core material portion. In the case where the member to be joined is a fin, it is desirable that the brazing filler metal is not clad on the fin in the coating step and other steps.
In the brazing step, the first core material portion and the second core material portion are brazed to each other with the inside clad layer which is interposed between the inside protruded portion of the first core material portion and the inside protruded portion of the second core material portion. The members to be joined are brazed to the outside protruded portion of the first core material portion and the outside protruded portion of the second core material portion with the outside brazing filler metal layer. The order of brazing the first core material portion to the second core material portion and brazing the members to be joined to the first core material portion and the second core material portion is not particularly limited. Either brazing work may be conducted first. Alternatively, both brazing works may be simultaneously conducted.
Next, the constitution will be explained below. FIG. 9 is a view showing a refrigerating cycle composing an air conditioner. FIG. 10 is a view showing a condenser used for the air conditioner. The refrigerating cycle includes: a compressor 18, condenser 20, expansion valve 14 and evaporator 16. The condenser 20 includes: a core portion 21 and a pair of header tanks 23, 25 which are arranged at both end portions of the core portion 21. The core portion 21 is composed of a plurality of tubes 30 so that the refrigerant can make U-turn. In the header tank 23, the inlet portion 24 a and the outlet portion 24 b of the refrigerant are formed. In the other header tank 25, the receiver 27 is integrated into one body.
In more detail, the core portion 21 includes: a plurality of tubes 30 for communicating the header tank 23 with the header tank 25; and a plurality of corrugated fins interposed between the tubes 30. The header tanks 23, 25 are cylindrical bodies, both ends of which are closed. The inside of each header tank is divided into several chambers by the separator plates. On the wall of each header tank facing the core portion 21, a plurality of slits are formed. Into these slits, end portions of the tubes 30 are inserted and brazed. These header tanks provide a refrigerant distributing portion for distributing the refrigerant to the plurality of tubes 30 and also provide a refrigerant collecting portion for collecting the refrigerant from the plurality of tubes 30. The receiver 27 is provided in the middle of the passage of the refrigerant formed by the condenser 30. The receiver 27 stores a surplus refrigerant and has a function of separating gas and liquid from each other.
FIGS. 11 and 12 are views showing the tube 30 and the fin 65 in detail. However, FIG. 11 is a schematic illustration showing a model of the tube 30 and the fin 65. Therefore, in order to make the understanding easy, some members and parts are omitted in the drawing. The tube 30 is composed in such a manner that the first core material 35 and the second core material 45 are brazed to each other. The first core material 35 has a predetermined width w and length l. In the first core material 35, a plurality of outside protruded portions 37 and inside protruded portions 41, which extend in the longitudinal direction, are formed alternately in the width direction. The outside protruded portions 37 are protruded onto the outside (the upper side in FIGS. 11 and 12) and open on the inside. Each outside protruded portion 37 includes: an outer wall portion 38; and a pair of side wall portions 39, wherein the cross section of the outside protruded portion 37 is a C-shape. Each inside protruded portion 41 includes: a pair of side wall portions 39; and an inner wall portion 42.
With respect to the brazing face, the shape of the second core material 45 is substantially symmetrical to the shape of the first core material 35. In the second core material 45, a plurality of outside protruded portions 47 and inside protruded portions 51, which extend in the longitudinal direction, are formed alternately in the width direction. The outside protruded portions 47 are protruded onto the outside (the lower side in FIGS. 11 and 12) and open on the inside. Each outside protruded portion 47 includes: an outer wall portion 48; and a pair of side wall portions 49, and the cross section of the outside protruded portion 47 is a C-shape. Each inside protruded portion 51 includes: a pair of side wall portions 49; and an inner wall portion 52.
The outside protruded portions 37 and 47, which are opposed to each other, respectively have the same width and divide a refrigerant communicating passage 33, the lateral cross section of which is rectangular. The inside protruded portions 41 and 51, which are opposed to each other, respectively have the same width and are brazed to each other with the inside brazing filler metal layers 43, 53 made of the brazing filler metal. The inside brazing filler metal layer 43 is clad onto the inside of the outer wall portion 38, the inner side of the side wall portion 39 and the inner wall portion 42. The clad ratio, which is a ratio of the wall thickness of the first core material 35 to the layer thickness of the inside brazing filler metal layer 43, is 20%. Concerning the second core material 45, in the same manner, the inside brazing filler metal layer 53 is clad onto the inside of the outer wall portion 48, the inner side face of the side wall portion 49 and the inside of the inner wall portion 52. The inside of the inside protruded portion 41 and the inside of the inside protruded portion 51 are brazed to each other with the inside brazing filler metal layers 43 and 53.
The corrugated fin 65 is brazed to the outer wall portion 38 of the outside protruded portion 37 of the first core material 35 via the sacrifical corrosion layer 55 by the outside brazing filler metal layer 57 in which the flux is mixed with the brazing filler metal powder. In more detail, the sacrifical corrosion layer 45 is clad to the outside of the outer wall portion 38 of the first core material 35, the outside of the side wall portion 39 and the outside of the inner wall portion 42. By the outside brazing filler metal 57 coated on the sacrifical corrosion layer 55 a on the outside of the outer wall portion 38, the top portion 67 of the fin 65 is brazed. The clad ratio of the outside brazing filler metal layer 57 is 15%.
In the same manner, the sacrifical corrosion layer 61 is clad to the outside of the outer wall portion 48 of the second core material 45, the outside of the side wall portion 49 and the outside of the inner wall portion 52. By the outside brazing filler metal 63 coated on the sacrifical corrosion layer 61 a on the outside of the outer wall portion 48, the top portion 67 of the fin 65 is brazed.
As shown in FIG. 11, the flat side portions 31 a on both sides in the width direction of the tube 30 are brazed. As can be seen in FIG. 13, at one end portion 32 in the longitudinal direction of the tube 30, the outside protruded portions 37, 47 are not formed. The reason why the outside protruded portions 37, 47 are not formed is that one end portion 32 is inserted into the slit of the header tank 23. These circumstances are the same in the other end portions in the longitudinal direction of the tube 30.
Referring to FIG. 14, the method of manufacturing a condenser will be explained below, wherein an example is employed in this explanation in which a set of the first core material 35, the second core material 45 and the fin 65 are used. First of all, as shown in FIG. 14A, a clad material is prepared. In this clad material, the sacrifical corrosion material 55 (shown in FIG. 12) is clad onto the entire outside 35 a of the first core material 15 of 0.20 mm wall thickness, the shape of which is flat and rectangular, and the inside brazing filler metal layer, which is made of only powder brazing filler metal, is clad on the entire inside 35 b of the clad material. In this case, the clad ratio of the inside brazing filler metal layer 42 to the inside 35 b is about 20%. These circumstances are the same in the second core material 45 not shown in FIG. 14.
Next, when the first core material 35 is protruded outside by means of press forming as shown in FIG. 14B, a plurality of outside protruded portions 37 are formed at predetermined intervals. Then, a plurality of inside protrusions 41 are formed between the adjoining outside protrusions 37. The outside protrusions 37 are protruded outside (on the upper face side of FIG. 14) and open inside, and the plurality of outside protrusions 37 are parallel to each other. On one side in the width direction of the first core material 35, the inclined portion 31 b is formed. Also on the other side in the width direction of the first core material 35, the inclined portion 31 b is formed.
Next, as shown in FIG. 14C, on the sacrifical corrosion layer 55 of the outside protrusions 37 of the first core material 35, the outside brazing filler metal layer (the powder brazing filler metal and flux) is coated with the roller coating device 70. The roller coating device 70 includes a pickup roller 71, transfer roller 72, application roller 73, which are in contact with each other, and also includes a backup roller 75 which is arranged to be opposed to the application roller 53. The pickup roller 71 picks up the outside brazing filler metal layer 57 accommodated in the storage case 77, and the transfer roller 72 transfers the outside brazing filler metal layer 57 which has been picked up in the above way. The application roller 73 applies the outside brazing filler metal layer 57, which has been transferred, to the first core material 35. At this time, the flux is coated on the inside brazing filler metal layer 43 made of the brazing filler metal of the first core material 35.
As shown in FIG. 14D, one end portion and the other end portion in the axial direction of the first core material 35 is pressed in the thickness direction (the perpendicular direction) with a press not shown in the drawing. As a result, the outside protruded portion 37 and the inside protruded portion 41, which are arranged at both end portions, are crushed, and a flat portion is formed in the middle in the width direction of the first core material 35 of both end portions. With respect to the second core material 45, the circumstances are the same. Successively, as shown in FIG. 14E, onto the outside of the outside protruded portion 37 of the first core material 35, the fin 65 is brazed with the outside brazing filler metal layer 57 which has been coated before. The thickness of the fin 65 is 0.05 mm, and the fin 65 is composed of only the core material. Therefore, the brazing filler metal layer is clad neither on the surface side nor on the reverse side. While keeping pace with brazing of the fins 65, the inside protruded portion 41 of the first core material 35 and the inside protruded portion 51 of the second core material 45 are brazed to each other with the inside brazing filler metal layers 43, 53.
Next, the operation will be explained below. In FIGS. 9 and 10, the refrigerant of high temperature and pressure, which has been compressed by the compressor 8, flows into one header tank 23 from the inlet portion 24 a. Then, the refrigerant further flows into a plurality of tubes 30 a on one side (the upper side) of the core portion 21. At this time, the refrigerant flows in the tubes 30 a while heat is being exchanged between the refrigerant and the outside air flowing in the perpendicular direction to the tubes 30 a. Then, the refrigerant flows into the other header tank 25. Gas and liquid in the refrigerant are separated from each other in the receiver 27. Only the liquid refrigerant flows into the tubes 30 b on the other side (the lower side) and discharges from the outlet portion 24 b. That is, the tubes 30 b on the other side compose a supercooling portion. The liquid refrigerant, which has flowed out from the outlet portion 24 b, is decompressed and expanded by the expansion valve 14 and evaporated by the evaporator 16.
Next, the corrosion test (the wet and dry repetition corrosion test) will be explained as follows. The corrosion test was conducted not only on the condenser 20 of the above embodiment but also on the condensers of Comparative Examples 1, 2 and 3. In Comparative Example 1, the inside brazing filler metal layer 43 is clad on the inside of the inside protruded portion 41 of the first core material 35, and only the outside brazing filler metal layer 57 is clad on the outside of the outside protruded portion 37. Concerning the second core material 45, the circumstances are the same. The brazing filler metal layer is not clad onto the fin 65.
In Comparative Example 2, the inside brazing filler metal layer 43 is clad on the inside of the inside protruded portion 41 of the third core material 35, and only the sacrifical corrosion layer 55 is clad on the outside of the outside protruded portion 37. Concerning the second core material 45, the circumstances are the same. In the fin 65, the brazing filler metal is clad onto the core material for the object of brazing. In Comparative Example 3, the inside brazing filler metal layer 43 is clad on the inside of the inside protruded portion 41 of the first core material 35, and the sacrifical corrosion layer 55 and the outside brazing filler metal layer 57 are clad on the outside of the outside protruded portion 37. Concerning the second core material 45, the circumstances are the same. The brazing filler metal layer is not clad on the fin 65.

Table 1 shows compositions of the

core materials

35, 45 of the tube 30 of the present embodiment and Comparative Examples 1 to 3. Table 1 also shows compositions of the

clad layers

43, 53, 57, 63 and the core material and the brazing filler metal layer (only Comparative Example) of the fin 65.

	TABLE 1


	Composition

						Residue
						(containing
Fe	Si	Cu	Mu	Mg	Zn	impurities)

Tube	Core material	.2	1.0	—	1.65	.4	—	Al
	Clad layer	.2	11.5	—	—	—	—	Al
	Sacrifical	.2	0.5	—	0.8	—	4.0	Al
	corrosion layer
Fin	Core material	.2	0.4	.15	1.2	—	2.5	Al
material	Clad layer	.2	11.5	—	—	—	—	Al

Weight %

The condition of the corrosion test is described as follows. A corroding solution was sprayed to a test piece for 2 hours, the test piece was wetted for 6 hours, and then the test piece was dried for 4 hours. This cycle was repeated. In this test, the temperature was maintained at 50° C. In the first 5 cycles, the corroding solution was maintained as follows. Cl ion was 6000 ppm, SO₄ion was 200 ppm, and Cu ion was 10 ppm. In the cycles after that, the corroding solution was maintained as follows. Cl ion was 6000 ppm, SO₄ion was 200 ppm.
The result of the test is shown in FIG. 15. In the graph of FIG. 15, the axis of abscissas represents the test time, and the axis of ordinate represents the maximum corrosion depth. In the embodiment, as can be understood from the curve “a”, even when the time passes, the tube 30 is not corroded. On the other hand, as can be understood from the curve “b”, in Comparative Example 1, in which only the outside brazing filler metal layer 47 is clad on the outside of the first core material 35, the tube 30 is very quickly corroded. As can be understood from the curve “c”, in Comparative Example 3, in which the sacrifical corrosion layer 55 and the outside brazing filler metal layer 57 are clad on the outside of the first core material 35, the tube 30 is corroded at a corrosion rate lower than that of Comparative Example 1, however, the corrosion rate of Comparative Example 3 is higher than that of the embodiment, that is, Comparative Example 3 is not sufficiently satisfactory.
The reason why the corrosion rate of the comparative example is high is described as follows. There are two reasons. The first reason is that the thickness of the sacrifical corrosion layer 55 is not sufficiently large. In the case where the inside brazing filler metal layer 43 is clad on the inside of the first core material 35 and in the case where the sacrifical corrosion layer 55 and the clad layer 57 are clad on the outside of the first core material 35 as in Comparative Example 3, it is necessary to suppress the wall thickness of the clad material to be not more than a predetermined value for the reasons of manufacturing. When the wall thickness of the clad material is too large, a pushing force cannot be sufficiently transferred. Accordingly, there is a possibility that the layer cannot be sufficiently clad. Further, the smaller the wall thickness of the first core material 35, the smaller the required predetermined thickness. When the sacrifical corrosion layer 55 and the outside brazing filler metal layer 57 are clad on the outside before the protruded and recessed portions are formed in the first core material 35, this phenomenon occurs.
The second reason is described as follows. As the electric potential of the outside brazing filler metal layer 57 is nobler than that of the sacrifical corrosion layer 55, the corrosion of the sacrifical corrosion layer 55 a is facilitated.
The advance of corrosion in the embodiment is substantially the same as that of Comparative Example 2, in which only the sacrifical corrosion material 55 is clad on the outside of the first core material 35, shown by the curve “d”. In Comparative Example 2, no problems of corrosion are caused in the first core material 35. However, in the fin 65 onto which the brazing filler metal layer is clad, the pitting corrosion is likely to occur by the diffusion of Si. In this case, “the pitting corrosion” is defined as a phenomenon in which the electric potential of crystal grains, the concentration of Si of which is high, electro-chemically becomes noble and the peripheral portion is selectively corroded. The generation of the pitting corrosion is confirmed on a photograph. The reason why the pitting corrosion is generated is that the wall thickness of the fin 65 is small and the brazing filler metal layer is clad (the clad ratio: 10%).
Next, the effects will be explained below. According to the condenser of the embodiment, the following effects can be provided. First, the tube 30 is composed in such a manner that the first core material 35 and the second core material 45 are brazed to each other, no restrictions are given, which is unlike in the case in which the tube 30 is manufactured by means of extrusion. As the tube 30 is made of aluminum alloy, the weight is light, and the composition can be determined so that the mechanical strength of the tube 30 can be increased. Secondly, except for the portion to which the fin is brazed, the outsides of the first core material 35 and the second core material 45 are covered with the sacrifical corrosion layers 55, 61. Accordingly, the corrosion resistance is excellent. Especially, onto the inner wall face of the recessed groove (the rear portions of the inside protruded portions 41 and 51) between the outside protruded portions 37 and 38, which are adjacent to each other, the sacrifical corrosion layers 55 b and 61 b are clad, so that the corrosion can be prevented. The fin 65 is brazed by the outside brazing filler metal layers 57 and 63 coated on the outside protruded portions 37 and 47, and the brazing filler metal layer is not clad on the fin 65. Therefore, the pitting corrosion is hardly generated.
According to the method of manufacturing the condenser of the embodiment, first, after the protruded and recessed portion forming step shown in FIGS. 14A and 14B has been executed, the coating step shown in FIG. 14C is executed. Therefore, the outside brazing filler metal layers 57, 63 can be coated only on the outside protruded portion of the tube which becomes a joining portion to be joined to the fin. In the recessed groove between the outside protruded portions 37 and 47 in which the outside brazing filler metal layer is not widely coated, the wall thickness of the sacrifical corrosion layers 55 b and 61 b is not reduced by the outside brazing filler metal layers 57 and 63. Therefore, the corrosion resistance can be increased. In the coating step shown in FIG. 14C, it is possible to coat the outside brazing filler metal layers 57 and 63 of sufficient layer thickness. Accordingly, there is no possibility of lack of the brazing force for brazing the fin 65 to the first core material 35 and the second core material 45.
Secondly, as the inside brazing filler metal layer 43 is previously clad on the clad material in which the recessed and protruded portion is formed, the inside brazing filler metal layers 43 and 53 can be easily formed on the inside of the inside protruded portion 41 of the first core material 35 and on the inside of the inside protruded portion 51 of the second core material 45. Thirdly, the outside brazing filler metal layers 57 and 63 can be effectively coated by the roller coating device 70. Further, the outside brazing filler metal layers 57 and 63 can be uniformly coated by the roller coating device 70.
Next, variations of the fourth embodiment will be explained as follows.
(1) First Variation
FIG. 16 is a view showing a variation of the embodiment described above. This variation is different from the above embodiment in the constitution (composition) of the inside brazing filler metal layers 80 and 82 and in the way of forming the inside brazing filler metal layers 80 and 82 on the first core material 35 and the second core material 45. Other points of the variation are essentially the same as those of the embodiment. The different points will be mainly explained below.
As can be seen in FIG. 16, the inside brazing filler metal 80 is coated only on the inside of the inside protruded portion 41 of the first core material 35. This inside brazing filler metal layer 80 is made of a mixture in which the flux is mixed with the brazing filler metal powder. This inside brazing filler metal layer 80 was coated in the coating step shown in FIG. 14C. Accordingly, the inside brazing filler metal layer 80 is not clad on the clad material shown in FIG. 14A. In the same manner, on the inside protruded portion 51 of the second core material 45, the inside brazing filler metal layer 82, in which the flux is mixed with the brazing filler metal powder, is coated. According to this variation, as the clad material does not contain the inside brazing filler metal, its thickness can be reduced. Further, the amount of the inside brazing filler metal layers 80 and 82 used can be reduced.
(2) Second Variation
In the second variation shown in FIGS. 17 to 18B, a plurality of outside protrusions 90 of a predetermined length are formed in the longitudinal direction at predetermined intervals. In the outside protrusion 90, the first core material 35 is protruded on the outside. As a result, between the protrusions 90, which are adjacent to each other in the width and the length direction, a plurality of inside protrusions (hollows when they are seen from the outside) 92 are formed. In the same manner, a plurality of outside protrusions 94 and inside protrusions 96 are formed in the second core material 45.
In the width direction, the outside protrusion 94 is located at the same position as that of the outside protrusion 90. However, in the longitudinal direction, the outside protrusion 94 is located at a position shifted from the position of the outside protrusion 90. In the plan view (shown in FIG. 18A), an end portion in the longitudinal direction of the protrusion 90 of the first core material 35 and an end portion in the longitudinal direction of the protrusion 94 of the second core material 45 are a little overlapped with each other, and the overlapped portions are communicated with each other in the communicating portion 98 in the vertical direction. The inside brazing filler metal layers 80, 82 (shown in FIG. 16), in which the flux is mixed with the brazing filler metal powder, are coated on the inside protrusion 92 of the first core material 35 and the inside protrusion 96 of the second core material 45. In this connection, the inside brazing filler metal layers 43 and 53 (shown in FIG. 12) may be coated on the entire inner faces of the first core material 35 and the second core material 45.
According to this variation, the outside protrusion 90 of the first core material 35, the outside protrusion 94 of the second core material 45, the outside protrusion 90 of the first core material 35, . . . , the end portions of which are communicated with each other, divide the bent inner passage. As a result, the surface area of the inner passage can be extended and the efficiency of exchanging heat between the refrigerant and the outside air can be increased.
While the invention has been described by reference to specific embodiments chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.

Claims

1. An aluminum heat exchanger in which a tube (10) composed of a sheet material is brazed to a fin (12) composed of a sheet material,

the sheet material for the tube (10) including a core material (10 b) and also including a sacrifical corrosion material (10 c) clad on one face of the core material (10 b) which becomes an outside of the tube (10), wherein

the sheet material for the fin (12) is a bare aluminum material on which a brazing filler metal is not clad,

the tube (10) and the fin (12) are brazed to each other with powder of brazing filler metal, and

the sacrifical corrosion material (10 c) remains on the outside of the tube (10) even after the completion of brazing.

2. An aluminum heat exchanger according to claim 1, wherein the tube (10) and the fin (12) are brazed to each other when a mixture composite (10 e), in which the powder of brazing filler metal and fluoride flux are mixed with each other, is coated on a surface of the sacrifical corrosion material (10 c) on the sheet material for the tube (10).

3. An aluminum heat exchanger according to claim 1, wherein the brazing filler metal powder is Si powder.

4. An aluminum heat exchanger according to claim 1, wherein the brazing filler metal powder is mixture powder in which Si powder and Al powder are mixed with each other.

5. An aluminum heat exchanger according to claim 1, wherein a brazing filler metal (10 d) of Al—Si is clad on the other face of the core material (10 b) of the sheet material for the tube (10) which becomes an inside of the tube (10), and

a joining face (10 a) of the sheet material for the tube (10) is brazed by the brazing filler metal (10 d) of Al—Si.

6. An aluminum heat exchanger according to claim 1, wherein a joining face (10 a) of the sheet material for the tube (10) is brazed when a mixture composite, in which the brazing filler metal powder and flux of fluoride are mixed with each other, is coated on the other side of the core material (10 b) of the sheet material of the tube (10) which becomes an inside of the tube (10).

7. An aluminum heat exchanger according to claim 1 having an inner fin (13) arranged in the tube (10), wherein

the inner fin (13) is composed of a sheet material having a core material (10 b) and a brazing filler metal (13 b, 13 c) clad on the core material (10 b),

a joining face (10 a) of the tube (10) is brazed by the brazing filler metal (13 b, 13 c) of the inner fin (13).

8. An aluminum heat exchanger according to claim 1, wherein thickness of a residual layer of the sacrifical corrosion material (10 c) after the completion of brazing is not less than 0.015 mm.

9. A heat exchanger comprising: a plurality of tubes (30) having an inner passage in which a heat exchange medium is circulated; and members (65) to be joined which are attached to outsides of the tubes,

each tube including: a first core material portion (35) in which a plurality of protruded and recessed portions (37, 41) are formed; and a second core material portion (45) which composes an inner passage (33) together with the first core material portion in which a plurality of protruded and recessed portions (47, 51) are formed, wherein

the first core material portion and the second core material portion are brazed to each other with an inside brazing filler metal layer (43, 53) which is interposed between an inside protruded portion (41) of the first core material portion and an inside protruded portion (51) of the second core material portion,

a sacrifical corrosion layer (55) is clad on the outside of the first core material portion, an outside brazing filler metal layer (57) is clad and coated on the sacrifical corrosion layer (55 a) of an outside protruded portion (37), a sacrifical corrosion layer (61) is clad on an outside of the second core material portion, and an outside brazing filler metal layer (63) is coated on the sacrifical corrosion layer (61 a) of the outside protruded portion (47), and

the members (65) to be joined are respectively brazed to the outside protruded portion of the first core material portion and the outside protruded portion of the second core material portion with the outside brazing filler metal layer.

10. A heat exchanger according to claim 9, wherein the inside brazing filler metal layer is coated on an inside of the inside protruded portion of the first core material portion and/or an inside of the inside protruded portion of the second core material portion.

11. A heat exchanger according to claim 9, wherein the inside brazing filler metal layer is clad on the entire inside of the first core material portion and/or the entire inside of the second core material portion.

12. A heat exchanger according to claim 11, wherein the inside brazing filler metal layer and the outside brazing filler metal layer respectively contain brazing filler metal powder and flux.

13. A heat exchanger according to claim 9, wherein a plurality of protruded and recessed portions of the first core material portion and a plurality of protruded and recessed portions of the second core material portion are respectively composed of a plurality of protruded portions and a plurality of recessed grooves, and the protruded portions are opposed to each other to form the inside passage.

14. A heat exchanger according to claim 9, wherein a plurality of protruded and recessed portions of the first core material portion and a plurality of protruded and recessed portions of the second core material portion are respectively composed of a plurality of protrusions and hollows, and a portion of the protrusion of the first core material portion and a portion of the protrusion of the second core material portion are communicated with each other so that the inside passage can be formed.

15. A heat exchanger according to claim 9, wherein the first core material portion and the second core material portion are respectively formed into different bodies and put on each other.

16. A heat exchanger according to claim 9, wherein the first core material portion and the second core material portion are formed when one core material is bent, and the first core material portion and the second core material portion are integrated with each other into one body.

17. A heat exchanger according to claim 9, wherein the member to be joined is a corrugated fin.

18. A heat exchanger according to claim 9, wherein the wall thickness of the first core material portion and the second core material portion is 0.1 to 0.2 mm, and the wall thickness of the member to be joined is 0.03 to 0.07 mm.

19. A method of manufacturing a heat exchanger,

the heat exchanger including: a plurality of tubes (30) having an inner passage in which a heat exchange medium is circulated; and members (65) to be joined which are brazed to the outsides of the tubes,

the method of manufacturing the heat exchanger comprising:

a protruded and recessed portion forming step of forming a large number of protruded and recessed portions (37, 41, 47, 51) in the first core material portion (35), on the outside of which a sacrifical corrosion layer (55) is clad and, in the second core material portion (45), on the outside of which a sacrifical corrosion layer (61) is clad;

a coating step of coating an outside brazing filler metal layer (57, 63) on a sacrifical corrosion layer (55 a) of the outside protruded portion (37) of the first core material portion and on a sacrifical corrosion layer (61 a) of the outside protruded portion (47) of the second core material portion; and

a brazing step in which the first core material portion and the second core material portion are brazed to each other with an inside brazing filler metal layer (43, 53) which is interposed between an inside protruded portion (41) of the first core material portion and an inside protruded portion (51) of the second core material portion, and members (65) to be joined are brazed to an outside protruded portion (41) of the first core material portion and an outside protruded portion (51) of the second core material portion with the outside brazing filler metal layer.

20. A method of manufacturing a heat exchanger according to claim 19, wherein the inside brazing filler metal layer is clad on the inside of the first core material portion and the inside of the second core material portion before the protruded and recessed portion forming step.

21. A method of manufacturing a heat exchanger according to claim 19, wherein the inside brazing filler metal layer is coated on the inside of the inside protruded portion of the first core material portion and the inside of the inside protruded portion of the second core material portion in the coating step.

22. A method of manufacturing a heat exchanger according to claim 19, wherein the outside brazing filler metal layer is coated with a rotating roller in the coating step.

23. A method of manufacturing a heat exchanger according to claim 19, wherein the brazing filler metal layer is not provided on the fin which is a member to be joined.

24. A heat exchanger comprising: a tube, in the inner passage of which a heat exchange medium is circulated; and a member to be joined which is joined to the outside of the tube by means of brazing, wherein

a wall of the tube is composed of a metallic sheet on which a plurality of protruded and recessed portions are formed,

the inner passage of the tube is formed when top portions of the inside protruded portions of the metallic sheet, which are opposed to each other, are joined to each other by means of brazing and edge portions of the metallic sheet are joined to each other by means of brazing,

the metallic sheet including:

a core material;

a sacrifical corrosion layer which is clad on the core material so that the sacrifical corrosion layer can be located outside the tube;

an inside brazing filler metal provided at the top of the inside protruded portion of the metallic sheet; and

an outside brazing filler metal coated only on the top portion of the outside protruded portion of the metallic sheet, wherein

the tube and the member to be joined are brazed to each other by the outside brazing filler metal.

25. A heat exchanger according to claim 24, wherein the member to be joined is a corrugated fin formed out of a sheet material.

26. A heat exchanger according to claim 24, wherein the tube is composed in such a manner that two metallic sheets are put on each other and edge portions of two pairs of the two metallic sheets are joined to each other by means of brazing.

27. A heat exchanger according to claim 24, wherein the tube is composed in such a manner that one metallic sheet is bent and both edges portions of the metallic sheet are joined to each other by means of brazing.

28. A heat exchanger according to claim 24, wherein the inside brazing filler metal is an inside brazing filler metal layer which is clad on the core material so that the inside brazing filler metal layer can cover the entire inside including the top portion of the inside protruded portion of the metallic sheet.

29. A heat exchanger according to claim 24, wherein the inside brazing filler metal is an inside brazing filler metal layer which is coated only in the top portion of the inside protruded portion of the metallic sheet.