JPH11142078A - Aluminum heat exchanger and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow an assurance of a corrosion resistance of a porous flat tube and a lightening of the tube to be compatible in a heat exchanger using the tube. SOLUTION: Recesses are formed at sites of an outer periphery of a porous flat tube 14 having many fluid passage holes 141 between the holes 141, and sacrificial corrosion materials are filled in the recesses to partly form a sacrificial corrosion layer 144 on an outer periphery of a tube body 140. Thus, a minimum thickness t3 of a non-sacrificial corrosion layer 143 formed between the outer periphery of the body 140 and an edge of the hole 141 can be ensured at a maximum limit in a range of an original outer peripheral thickness H of the body 140.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum heat exchanger having a multi-hole flat tube and a method for manufacturing the same, and more particularly, to achieving both corrosion resistance and weight reduction of the multi-hole flat tube. It is suitable for use in a condenser of a vehicle air conditioner.

[0002]

2. Description of the Related Art Conventionally, in an aluminum heat exchanger in a condenser or the like of a vehicle air conditioner, a multi-hole flat plate having a large number of fluid passage holes formed in parallel in a flat cross section direction as a tube through which a heat exchange fluid such as a refrigerant flows. A tube is used. According to this multi-hole flat tube, there is an advantage that the pressure resistance can be improved because a large number of inner pillars (passage partitioning portions) having an extruded multi-hole structure are integrally formed with the tube.

In this type of multi-hole flat tube, a sacrificial corrosion layer is generally formed on the outer peripheral surface of the multi-hole flat tube in order to improve corrosion resistance. This sacrificial corrosion layer is usually formed of a Zn diffusion layer whose electrode potential becomes lower than that of the aluminum material forming the tube main body. This sacrificial corrosion layer corrodes preferentially over the tube body in a corrosive environment of aluminum (sacrificial corrosion)
By doing so, pitting corrosion of the tube main body can be prevented.

FIG. 2 (b) shows a multi-hole flat tube 14 in a conventional heat exchanger. In the drawing, reference numeral 140 denotes a tube body made of aluminum having a flat cross section, and a sacrificial corrosion layer 144 is provided on the outer peripheral surface thereof. It is formed with a uniform thickness t ₁ .
A large number of fluid passage holes 14 are provided inside the tube body 140.
The fluid passage holes 141 are separated from each other by an inner pillar 142.

In recent years, there has been a tendency to increase the radius R of the circular arc shape at the root of the inner pillar 142 in order to improve the pressure resistance. With the increase of the radius R of the base arc shape,
The shape of the fluid passage hole 141 is circular as shown in FIG. Incidentally, when the radius R of the circular arc shape at the root of the inner column 142 is close to zero, the shape of the fluid passage hole 141 is substantially rectangular as shown by a broken line.

[0006]

As described above, when the shape of the fluid passage hole 141 is circular, the tube main body portion 14 is formed.
The thickness of the non-sacrificial corrosion layer 143 formed between the edge of the fluid passage hole 141 and the sacrificial corrosion layer 144 is the same as that of the fluid passage hole 1.
41 will change along the circular shape. The lifetime leakage by pitting of the tube body portion 140, when it is determined by the minimum thickness t ₂ of the non-sacrificial corrosion layer 143 is set to a dimension for the required service life ensure the minimum thickness t _2, minimum thickness t portion other than ₂ parts, inevitably thickness is increased to a large size more than necessary life.

For this reason, the weight of the multi-hole flat tube 14 is increased.
And increase the weight of the heat exchanger. Also tube
The increase in material increases the cost of the heat exchanger. Reverse
In order to reduce the weight of the heat exchanger, the minimum thickness t_TwoTo
If it is small, this minimum thickness t _TwoIs governed by
It leads to shortened life time. In view of the above, the present invention has a multi-hole flat
In a heat exchanger using tubes, multi-hole flat tubes
Of corrosion resistance and weight reduction of multi-hole flat tube
The purpose is to let them.

[0008]

The sacrificial corrosion layer is not uniformly formed on the entire outer peripheral surface of the tube, but is effective in a small area of about several mm even if there is no sacrificial corrosion layer. In view of the fact that acts effectively, the present invention aims to achieve the above object by devising a method of forming a sacrificial corrosion layer.

That is, in the inventions according to claims 1 to 4,
Of the outer peripheral surface of the multi-hole flat tube (14) having a large number of fluid passage holes (141), a large number of fluid passage holes (141)
A concave portion (140a) is formed in a portion between them, and the concave portion (140a) is filled with a sacrificial corrosion material (144a, 144b) to form a sacrificial corrosion layer (144) on the outer peripheral surface of the tube body (140). It is characterized by doing.

According to this, a large number of fluid passage holes (14)
1) A sacrificial corrosion layer (144) is partially formed in the vicinity of the concave portion (140a) located at an intermediate portion between each other. Therefore,
No sacrificial corrosion layer (144) is formed around the portion (X) of the outer peripheral surface of the tube body (140) where a straight line passing through the center of the fluid passage hole (141) is orthogonal.

Therefore, the minimum thickness (t ₃ ) of the non-sacrificial corrosion layer (143) formed between the outer peripheral surface of the tube body (140) and the edge of the fluid passage hole (141) is reduced by sacrificial corrosion. Without being reduced by the layer (144), it is possible to secure the maximum within the range of the original outer peripheral thickness (H) of the tube main body (140), and to prolong the leak life time of the multi-hole flat tube (14).

Further, since a method is employed in which a sacrificial corrosion layer (144) is partially formed in the vicinity of the concave portion (140a) located at an intermediate portion between the plurality of fluid passage holes (141), a conventional structure is employed. There is no increase in the weight of the multi-hole flat tube (14). The invention according to claims 5 and 6 relates to a method for manufacturing an aluminum heat exchanger, and can satisfactorily manufacture the aluminum heat exchanger according to claims 1 to 4.

The reference numerals in parentheses of the above means indicate the correspondence with the concrete means described in the embodiments described later.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First Embodiment First, a condenser of a vehicle air conditioner will be described with reference to FIG. 1 as an aluminum heat exchanger to which the present invention is applied. A condenser 10 is provided in a refrigeration cycle of a vehicle air conditioner (not shown). ) To cool and condense the high-temperature and high-pressure superheated gaseous refrigerant discharged from the above. Also, as is well known, the condenser 10 is disposed at the forefront (in front of the engine cooling radiator) in the vehicle engine room, and cooling air (outside air) blown by a cooling fan common to the engine cooling radiator. Cooling.

The condenser 10 has a pair of header tanks, that is, first and second header tanks 11 and 12 arranged at a predetermined interval.
Reference numerals 1 and 12 each have a shape extending in a substantially cylindrical shape in the vertical direction. A core 13 for heat exchange is arranged between the first and second header tanks 11 and 12. Condenser 10 of this example
Is generally referred to as a multi-flow type, and the core portion 13 includes first and second header tanks 11 and 12.
A plurality of flat tubes 14 through which the refrigerant flows in the horizontal direction are arranged in parallel in the vertical direction.
And a corrugated fin 15 is interposed therebetween.
One end of the flat tube 14 communicates with the first header tank 11, and the other end communicates with the second header tank 12.

The flat tube 14 is a multi-hole flat tube in which a number of refrigerant passage holes are formed in parallel in a cross section flat direction (longitudinal direction in cross section), and is made of an aluminum material (for example, A105).
It is formed by the extrusion process of 0). The corrugated fin 15 is made of a brazing material (for example, A434).
3) A corrugated aluminum clad sheet material obtained by cladding both sides of a core material (for example, A3923).

A refrigerant inlet piping joint (refrigerant inlet) 16 is arranged and joined above the second header tank 12. A refrigerant outlet-side piping joint (refrigerant outlet) 17 is arranged and joined below the second header tank 12. Further, in the present example, one separator 18 is arranged in an intermediate portion between the inlet-side piping joint 16 and the outlet-side piping joint 17 in the second header tank 12, so that the second header tank 12 The inside is vertically divided into two spaces 12a and 12b. Also, the first and second header tanks 11, 12
The openings at both ends in the axial direction (longitudinal direction) are sealed by cap members 19 to 22, respectively.

The first and second header tanks 11, 12
Are made of a double-sided clad material in which a brazing material is clad on both sides in the same manner as the fin 15. Also, the cap member 19
22 are made of a single-sided clad material in which only one side surface to be joined to the first and second header tanks 11 and 12 is clad with a brazing material. The inlet-side pipe joint 16 and the outlet-side pipe joint 17 are made of an aluminum bare material in which a brazing material is not clad.

With the above configuration, the refrigerant from the inlet side pipe joint 16 is supplied to the upper space 12 of the second header tank 12.
a, the refrigerant flows into the upper half flat tube 14 of the core portion 13, and then the refrigerant is U-turned in the first header tank 11 to flow into the lower half flat tube 14 of the core portion 13. The refrigerant flows to the outlet-side piping joint 17 through the lower space 12b of the two header tanks 12. During this time, the refrigerant exchanges heat with cooling air (outside air) passing through the core portion 13 through the flat tubes 14 and the corrugated fins 15 to be cooled and condensed.

Next, the multi-hole flat tube 14 which is an essential part of the present invention will be described in detail. FIG. 2 (a) shows an end face shape of the multi-hole flat tube 14, and a tube main body portion 140 thereof. In FIG. 2, a large number of refrigerant (fluid) passage holes 141 are extruded in parallel in a cross-section flat direction (in the cross-section longitudinal direction, the left-right direction in FIG. 2A). An inner pillar 142 forming a passage partition is formed between the plurality of refrigerant passage holes 141. FIG. 2B shows a comparison of the end face shape of the conventional flat tube 14 described above.

Here, the shape of the refrigerant passage hole 141 is a circular shape without a corner at the root in order to improve the pressure resistance. In the outer peripheral surface of the tube main body 140, a portion between the plurality of refrigerant passage holes 141 (in other words, a portion where the inner pillar 142 is formed) and shoulder portions at both ends of the tube main body 140 in the cross-sectional flat direction are shown in FIG. As shown in FIG.
Is formed. The recess 140a is formed over the entire length of the tube in the longitudinal direction (the left-right direction in FIG. 1).

The shape of the recess 140a is, for example,
The concave portion 140a is filled with a sacrificial corrosion material, and a sacrificial corrosion layer 144 is partially formed near the concave portion 140a on the outer peripheral surface of the tube main body 140. Therefore, the sacrificial corrosion layer 144 is not formed around the portion X where the straight line passing through the center of the refrigerant passage hole 141 is orthogonal to the outer peripheral surface of the tube main body 140.

Therefore, the minimum thickness t ₃ of the non-sacrificial corrosion layer 143 formed between the outer peripheral surface of the tube main body 140 and the edge of the circular refrigerant passage hole 141 is smaller than that of the sacrificial corrosion layer 14.
4, it is possible to ensure the maximum within the range of the original outer peripheral thickness H of the tube main body 140. And
The thickness of the sacrificial corrosion layer 144 formed on the outer peripheral surface of the tube main body 140 is not uniform, but non-uniform along the shape of the concave portion 140a.

Next, a method of manufacturing the aluminum heat exchanger having the extruded multi-hole flat tube 14 will be described. First, the tube body 140 of the multi-hole flat tube 14 is extruded. FIG. 3 shows a state after the extrusion process. The tube main body 140 of the flat tube 14 is formed by extruding an aluminum material such as A1050 into the shape shown in FIG.

In this extrusion process, a circular fluid passage hole 141 is formed inside the tube main body 140 having a flat cross section, and at the same time, a concave portion 140a is formed on the outer peripheral surface. The recess 140a is formed over the entire length of the tube in the longitudinal direction. In the example of FIG.
1 Not only the part between each other (the formation part of the inner pillar 142),
It is also formed at the shoulders at both ends in the longitudinal direction of the tube body 140 having a flat cross section.

Next, a material for forming the sacrificial corrosion layer 144 is filled in the concave portion 140a on the outer peripheral surface of the tube main body 140. As a specific method of filling the sacrificial corrosion material, for example, the wire 144a is made of a material (for example, an Al—Zn-based material) whose electrode potential becomes lower than the aluminum material (for example, A1050) of the tube main body 140. The wire 144a is formed as shown in FIG.
Fit into 40a.

As another method, a solution in which a powder of a sacrificial corrosion material made of the same material is mixed with a resin binder is applied to the concave portion 140a, or the sacrificial corrosion material made of the same material is coated Thermal spraying may be performed in the recess 140a. FIG. 5 shows the sacrificial corrosion material 144b applied or sprayed in the recess 140a. Thereafter, the flat tube 14 is assembled with other components such as the header tanks 11 and 12 and the corrugated fins 15 in the heat exchanger structure shown in FIG. Then, the assembled state of the assembled body is held by an appropriate jig, and the assembled body is carried into a heating furnace for brazing to a brazing temperature (the brazing temperature of aluminum is around 600 ° C.). Heat. Thereby, the brazing material of each component of the assembled body is melted, and the entire heat exchanger is integrally brazed, thereby completing the assembly of the heat exchanger.

In the above brazing heating step, Zn is added to the aluminum material of the tube body 140 by about 100 μm.
m, the Al—Zn layer (Z
n high concentration layer), Al-Zn layer (Zn low concentration layer), A
The three layers of the l layer are sequentially distributed in the depth direction.

The electrode potential gradually increases in the order of the Al-Zn high-concentration layer → the Al-Zn low-concentration layer → the Al layer. Therefore, in the use state of the heat exchanger, corrosion on the surface of the flat tube 14 proceeds in the order of →→. That is, the layers constitute the sacrificial corrosion layer 144, which layer is preferentially sacrificed, and after the sacrificial corrosion is completed, finally, the tube body 140
Is started.

Here, as shown in comparison with FIGS. 2A and 2B, when the outer peripheral wall thickness H of the flat tube 14 is the same, in the case of FIG. , The minimum thickness t of the non-sacrificial corrosion layer 143 of the tube body 140
₃ is replaced with the non-sacrifice corrosion layer 143 of FIG.
Can be longer than the minimum thickness t _{2 of} the tube main body 140, so that the leakage life of the tube body 140 (the time until leakage due to pitting corrosion) can be extended.

FIG. 7 shows a tube body 1 according to this embodiment.
It is a conceptual diagram which graphs the effect of extending the leak life of 40, and shows the corrosion depth of the flat tube 14 on the vertical axis and the heat exchanger usage time on the horizontal axis. In FIG. 7, only the sacrificial corrosion layer 144 is preferentially corroded until the use time reaches T ₁ , so that the corrosion depth is a predetermined amount D determined by the thickness of the sacrificial corrosion layer 144. stay in _1.

Then, when the corrosion of the sacrificial corrosion layer 144 is completed, the corrosion of the tube body 140 is started. However, according to the conventional structure of FIG. the minimum thickness t ₂ of the sacrificial corrosion layer 143 is small, the use time T ₂ the total thickness of the non-sacrificial corrosion layer 143 corrosion penetrates, since leakage by pitting occurs, leakage life and time T ₂ Become.

On the other hand, according to the present embodiment, the minimum thickness t ₃ of the non-sacrificial corrosion layer 143 of the tube main body 140 is larger than the minimum thickness t _{2 of the} conventional structure, so that the leakage life is longer than the time T ₂ . long time T _3, and the possible extension of the leakage life. In the conventional structure of FIG. 2B, if the non-sacrificial corrosion layer 143 of the tube body 140 has the minimum thickness t _2.
Is increased to the same level as the minimum thickness t ₃ according to the present embodiment, the weight of the tube body 140 increases as described in the section of the related art, and the weight of the heat exchanger increases.
This leads to higher costs.

According to the present embodiment, the sacrificial corrosion layer 144 is not formed around the portion X where the straight line passing through the center of the refrigerant passage hole 141 is orthogonal on the outer peripheral surface of the tube main body 140, but is about several mm. It is confirmed that the sacrificial corrosion effect of the adjacent sacrificial corrosion layer 144 is exerted even if the sacrificial corrosion layer 144 is not formed in the minute range. In the condenser 10, the diameter of the fluid passage hole 141 is usually 1.
Since it is about 0 mm and not more than 2.0 mm at the maximum, the sacrificial corrosion action can be sufficiently exerted on the portion X, and the leakage life can be extended.

(Second Embodiment) FIG. 8 shows a second embodiment, in which the outer peripheral surface of the non-sacrificial corrosion layer 143 of the tube main body 140 has a combination of circumferential shapes along the circle of the fluid passage hole 141. In addition, a concave portion 140a is formed in the lower portion, whereby the thickness t of the non-sacrifice corrosion layer 143 of the tube main body portion 140 is made substantially the same in almost the entire region. Other points are the same as the first embodiment.

(Other Embodiments) In the first embodiment, the case where the present invention is applied to the multi-flow type condenser 10 shown in FIG. 1 has been described. However, a serpent type condenser as shown in FIG. The present invention can of course be applied to 10 '. In this serpent type condenser 10 ', the multi-hole flat tube 14 is bent in a meandering shape, and corrugated fins 15 bent in a wave shape are arranged between the meandering tubes 14 and joined. ing. In the example of FIG. 9, the refrigerant flow from the refrigerant inlet joint 16 is branched into three multi-hole flat tubes 14, and after the refrigerant flows in parallel into the three multi-hole flat tubes 14, the refrigerant is merged. Then, the refrigerant flows out from the refrigerant outlet joint 17 to the outside.

In the first embodiment, the case where the concave portion 140a is formed simultaneously with the extrusion of the multi-hole flat tube 14 has been described. However, after the multi-hole flat tube 14 is extruded and formed, the formation of the concave portion 140a is performed independently. It may be performed. As a method of filling the concave portion 140a with the sacrificial corrosion material, Zn or the like may be sprayed on the concave portion 140a.

The present invention can of course be applied to a heat exchanger other than the condenser as long as it is an aluminum heat exchanger using the multi-hole flat tube 14.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a heat exchanger to which the present invention is applied.

2A is a cross-sectional view of a multi-hole flat tube according to a first embodiment of the present invention, and FIG. 2B is a cross-sectional view of a conventional multi-hole flat tube.

FIG. 3 is a perspective view showing a state after extrusion molding of the multi-hole flat tube according to the first embodiment of the present invention.

FIG. 4 is a perspective view showing a state after a sacrificial corrosion material has been filled into a concave portion of the multi-hole flat tube in the first embodiment.

FIG. 5 is a perspective view showing a state after a sacrificial corrosion material is filled in a concave portion of the multi-hole flat tube by another method in the first embodiment.

FIG. 6 is a perspective view showing a distribution state of a sacrificial corrosion layer on the outer peripheral surface of the multi-hole flat tube in the first embodiment.

FIG. 7 is a conceptual diagram showing the relationship between the corrosion depth of a multi-hole flat tube and the use time of a heat exchanger.

FIG. 8 is a sectional view of a multi-hole flat tube according to a second embodiment of the present invention.

FIG. 9 is a perspective view showing another example of the heat exchanger to which the present invention is applied.

[Explanation of symbols]

11, 12: header tank, 14: multi-hole flat tube, 140: tube body, 140a: recess, 141
... refrigerant (fluid) passage hole, 142 ... inner column, 143 ... non-sacrificial corrosion layer, 144 ... sacrificial corrosion layer.

Claims (6)

[Claims] 1. A multi-hole flat tube (140) having an aluminum tube main body (140) having a flat cross section and a plurality of fluid passage holes (141) provided in the cross section direction of the tube main body (140). 14) In the aluminum heat exchanger provided with (14), a concave portion (140) is formed in the outer peripheral surface of the tube main body portion (140) between the plurality of fluid passage holes (141).
a) is formed, and the sacrificial corrosion material (144a, 14a) is formed in the concave portion (140a).
4b), wherein a sacrificial corrosion layer (144) is formed on the outer peripheral surface of the tube body (140). 2. The aluminum heat exchanger according to claim 1, wherein the fluid passage hole has a circular shape. 3. The concave portion (140a) is formed so that an outer peripheral surface of the tube body (140) has a combination of a circumferential shape along a circular shape of the fluid passage hole (141). The aluminum heat exchanger according to claim 2, wherein 4. The sacrificial corrosion material (144a, 144)
The aluminum heat exchanger according to claim 1 or 2, wherein b) contains at least Zn. 5. A multi-hole flat tube (140) having a tube main body (140) made of aluminum having a flat cross section and a plurality of fluid passage holes (141) provided in a direction of cross section of the tube main body (140). 14) The method for manufacturing an aluminum heat exchanger according to (14), wherein a concave portion (140) is formed in an outer peripheral surface of the tube body (140) between the plurality of fluid passage holes (141).
a) forming a sacrificial corrosion material (144a, 14) in the recess (140a);
4b) filling step, assembling the multi-hole flat tube (14) together with other heat exchanger parts into an assembly having a predetermined structure, and heating the assembly to a brazing temperature. Then, the assembled body is integrally brazed and the sacrificial corrosion material (144)
a, 144b) in the aluminum material of the tube body (140) to form a sacrificial corrosion layer (144). 6. The tube body (140) is extruded from an aluminum material and simultaneously with the recess (1).
40. The method according to claim 5, wherein (a) is formed.