JP6762719B2 - How to make a heat exchanger - Google Patents

Description

The present invention relates to a method of manufacturing a cross fin tube type heat exchanger.

In recent years, aluminum heat transfer tubes and connecting tubes have begun to be used in order to reduce the material cost of heat exchangers. Therefore, Al-Cu-Si-based and Al-Cu-Si-Zn-based low melting point brazing materials for preventing buckling deformation of thin-walled materials such as fins and lowering the brazing temperature are described in Patent Document 1, for example. Proposed.

Japanese Unexamined Patent Publication No. 2001-62587

Here, the inventors have described a cross-fin tube type in which the above-mentioned Al-Cu-Si-based or Al-Cu-Si-Zn-based low melting point brazing material includes a heat transfer tube, a connecting tube, and fins. I thought that it could be an effective means for partial brazing of the heat exchanger. Therefore, the inventors have proceeded with a study on the application of a low melting point brazing material to a heat exchanger that has been changed from the conventional copper to aluminum. However, it was discovered that there are the following problems peculiar to low melting point brazing materials.

First, Al-Cu-Si-based and Al-Cu-Si-Zn-based low-melting point brazing materials have a heavier specific gravity of 1.5 to 1.6 times that of Al-Si-based brazing materials. It is characterized by the fact that the low melting point brazing material easily flows downward in the direction of gravity due to the influence of gravity during partial brazing. Therefore, when the molten low melting point brazing material flows into the brazing material filling portion, the component containing silicon invades the aluminum base material and makes a part of the base material into a brazing material. That is, the low melting point brazing material erodes a part of the base material, and the base material is likely to be significantly thinned.

The present invention has been made in view of the above point, the purpose is to provide a manufacturing method that can improve the yield of manufacturing the aluminum cross fin tube type heat exchanger.

In order to achieve the above object, in the invention according to claim 1, the connecting pipe (40) made of aluminum and the fin (20) made of aluminum are joined, and the inner diameter of the tip portion (13) is the connecting pipe. Prepare an aluminum heat transfer tube (10) larger than the outer diameter, and attach the connection tube to the tip of the heat transfer tube so that the connection tube is located on the upper side in the gravity direction and the heat transfer tube is located on the lower side in the gravity direction. It includes a joining step of inserting into a portion to form a fitting portion (42) and partially brazing the fitting portion.

Then, in the joining step, partial brazing is performed using an Al-Cu-Si-based or Al-Cu-Si-Zn-based brazing material (60), and a connection tube thicker than the heat transfer tube is used. used Rutotomoni, a brazing method thinning the connection tube when the flow braze the fitting portion to the brazing material is a brazing material of eroding a portion of the connection by melting tube occurs, in the bonding step, as the brazing material, Ru using specific gravity is large compared with the Al-Si based brazing material. In the joining step, the brazing material is supplied to the outer wall surface of the connecting pipe so that at least a part of the brazing material is located above the end surface (16) of the tip end portion of the heat transfer tube before the partial brazing.

According to this, even if the aluminum connecting pipe is eroded by the brazing material during partial brazing and the wall thickness is reduced, the thick connecting pipe is only thinned, so the thickness of the connecting pipe is maintained above a certain level. can do. Therefore, the manufacturing yield of the heat exchanger can be improved.

In addition, the reference numerals in parentheses of each means described in this column and the scope of claims indicate the correspondence with the specific means described in the embodiment described later.

It is a perspective view of the heat exchanger which concerns on one Embodiment of this invention. It is sectional drawing of the heat transfer tube shown in FIG. It is a partial cross-sectional view of the vicinity of the fitting portion of a heat transfer tube and a connection tube. FIG. 3 is an enlarged cross-sectional view of part A in FIG. It is a figure for demonstrating the tube expansion process in the manufacturing process of a heat exchanger. It is a figure for demonstrating the joining process in the manufacturing process of a heat exchanger. It is a partial cross-sectional view of the vicinity of the fitting portion which showed one of the comparative examples. It is a partial cross-sectional view of the vicinity of the fitting portion which showed the comparative example different from FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The heat exchanger according to the present embodiment is applied to, for example, a cross fin tube type heat exchanger that exchanges heat between the refrigerant and air in the refrigeration cycle.

As shown in FIG. 1, the cross fin tube type heat exchanger 1 includes a heat transfer tube 10, fins 20, side plates 30, 31, connecting tubes 40, and headers 50, 51. The heat transfer tubes 10, fins 20, side plates 30, 31, connecting tubes 40, and headers 50, 51 are made of aluminum. Made of aluminum means that it is made of aluminum or an aluminum alloy.

The heat transfer tube 10 is a tube component through which a refrigerant flows. The heat transfer tube 10 is formed by being bent into a hairpin shape, that is, a substantially U shape. A plurality of heat transfer tubes 10 are provided in the heat exchanger 1 so that the longitudinal portions are arranged in parallel. The U-shaped portion of each heat transfer tube 10 is arranged in one direction of the longitudinal portion. Each heat transfer tube 10 is joined to the fin 20.

As shown in FIG. 2, a plurality of grooves 11 are spirally formed on the inner surface of the heat transfer tube 10. That is, the heat transfer tube 10 is a tube with an inner groove. The groove 11 extends in a direction inclined with the tube axis of the heat transfer tube 10. On the inner surface of the heat transfer tube 10, fins 12 extending spirally as protrusions between the spiral grooves 11 are formed. Since the grooves 11 and fins 12 are formed on the inner surface of the heat transfer tube 10, the contact area between the inner surface of the heat transfer tube 10 and the refrigerant is increased, so that the heat transfer performance of the heat transfer tube 10 is improved.

The fin 20 is a heat transfer promoting member that increases the heat transfer area between the air and the heat transfer tube 10 and promotes heat exchange between the air and the refrigerant. The fin 20 is a plate fin formed in a plate shape. A plurality of fins 20 are provided in the heat exchanger 1. The side plates 30 and 31 are plate parts provided in the uppermost layer and the lowermost layer of the plurality of fins 20.

The connection tube 40 is a tube component that connects the tip portions 13 of the plurality of heat transfer tubes 10 to each other. The connecting pipe 40 is formed in a U shape. The connecting tube 40 is thicker than the heat transfer tube 10. For example, as the connecting pipe 40, a smooth pipe having a wall thickness of 1.5 times or more the bottom wall thickness of the heat transfer pipe 10 is used. The bottom wall thickness is the thickness from the bottom surface of the groove 11 of the heat transfer tube 10 to the outer wall surface. The headers 50 and 51 are parts that distribute or assemble the refrigerant to the heat transfer tube 10.

Next, the connection structure between the heat transfer tube 10 and the connection tube 40 will be described. As shown in FIG. 3, the tip portion 13 of the heat transfer tube 10 has a mouth expanding portion 14 and a flared portion 15. The mouth expansion portion 14 is a portion whose inner diameter is larger than the outer diameter of the connecting pipe 40. The flared portion 15 is a portion in which the tip portion of the mouth expanding portion 14 is expanded in a conical shape.

The fitting portion 42 is formed by inserting the tip portion 41 of the connecting pipe 40 into the tip portion 13 of the heat transfer tube 10. As shown in FIG. 4, the length of the heat transfer tube 10 in the fitting portion 42 in the longitudinal direction, that is, the length of the portion where the heat transfer tube 10 and the connecting tube 40 overlap in the radial direction of the heat transfer tube 10 is It is 1 mm or more.

Further, in the fitting portion 42, the gap between the inner surface of the mouth expanding portion 14 and the outer surface of the connecting pipe 40 is 0.05 mm or more in terms of pipe diameter difference. The gap is filled with the brazing filler metal 60. The brazing material 60 is a part of the end face 43 of the tip 41 of the connection tube 40 from the position on the tip 41 side of the connection tube 40 with respect to the end face 16 of the tip 13 of the heat transfer tube 10 in the longitudinal direction of the heat transfer tube 10. It is filled to the position where it covers. Note that the brazing material 60 is omitted in FIG.

The brazing material 60 is a fixing material for fixing the heat transfer tube 10 and the connecting tube 40 at the fitting portion 42. As the brazing material 60, a material having a three-element eutectic composition of Al—Cu—Si coated with a cesium fluoride-based non-corrosive flux, or a material having Zn added to the component thereof is used. That is, the brazing material 60 is an Al-Cu-Si type or an Al-Cu-Si-Zn type.

The components of the Al—Cu—Si based brazing material 60 are adjusted so that the solidus temperature is 510 ° C. and the liquidus temperature is about 540 ° C. As a result, the brazing material 60 is significantly lowered in temperature with respect to the conventional Al—Si-based solid phase temperature of 577 ° C. That is, the brazing material 60 according to the present embodiment is a low melting point brazing material. The flux is active from a low temperature of 420 ° C. for brazing in this temperature range.

Here, the connecting pipe 40 has a recess 44. The recess 44 is a portion formed by erosion of a part of the connecting pipe 40 by the brazing material 60 at the time of brazing. On the other hand, the recess 44 may not be formed in the connecting pipe 40 due to brazing. However, the Si component of the brazing filler metal 60 penetrates into the connecting pipe 40 regardless of whether the recess 44 is formed or not formed in the connecting pipe 40. Therefore, the Si component is always left in the portion corresponding to the recess 44. The above is the overall configuration of the heat exchanger 1.

Next, a method of manufacturing the heat exchanger 1 will be described. First, a tube made of aluminum or an aluminum alloy is formed by drawing. Further, by rolling the inner surface of the pipe, a heat transfer tube 10 having a groove 11 is formed on the inner surface.

Subsequently, a plurality of fins 20 and side plates 30 and 31 are prepared, and through holes (not shown) through which the heat transfer tube 10 is inserted are formed in the fins 20 and the side plates 30 and 31. Then, after arranging the plurality of fins 20 at equal intervals, the heat transfer tube 10 is inserted into the through hole.

After that, a tube expansion step of expanding the heat transfer tube 10 is performed. As shown in FIG. 5, a tube expander 100 having a diameter larger than the inner diameter of the heat transfer tube 10 is inserted into the heat transfer tube 10, and the heat transfer tube 10 is mechanically expanded by the tube expander 100. By expanding the heat transfer tube 10, the plurality of fins 20, the side plates 30 and 31, and the heat transfer tube 10 are brought into close contact with each other and joined. Further, the mouth expansion portion 14 and the flare processing portion 15 are formed at the tip portion 13 of the heat transfer tube 10 by the same construction method. In FIG. 5, the groove 11 on the inner surface of the heat transfer tube 10 is omitted.

Next, a joining step of joining the connecting tube 40 to the heat transfer tube 10 is performed. Therefore, the heat transfer tube 10 and the connection tube 40 acquired in the tube expansion step are prepared. As the connecting tube 40, one having a thickness thicker than that of the heat transfer tube 10 is used. Further, the connecting tube 40 is inserted into the tip portion 13 of the heat transfer tube 10 so that the connecting tube 40 is located on the upper side in the gravity direction and the heat transfer tube 10 is located on the lower side in the gravity direction to form the fitting portion 42.

Then, before the partial brazing of the fitting portion 42, as shown in FIG. 6, the connecting pipe is provided so that at least a part of the brazing material 60 is located above the end surface 16 of the tip portion 13 of the heat transfer tube 10. The brazing material 60 is supplied to the outer wall surface 45 of the 40. For example, the brazing filler metal 60 is continuously arranged once in the circumferential direction of the connecting pipe 40, or partially arranged intermittently in the circumferential direction. As described above, the brazing material 60 used is Al-Cu-Si type or Al-Cu-Si-Zn type.

By supplying the brazing filler metal 60 to the connecting pipe 40 in this way, the melted brazing filler metal 60 can be drawn into the gap of the fitting portion 42. Further, it is possible to prevent the brazing material 60 from being drawn into the fitting portion 42 in a state where the voids are contained. It should be noted that such an effect can be further enhanced by locating the entire brazing material 60 above the end surface 16 of the tip portion 13.

Subsequently, the fitting portion 42 is partially brazed. Therefore, first, the connection pipe 40 is heated with priority over the heat transfer pipe 10. Specifically, the portion of the connecting pipe 40 where the brazing filler metal 60 is arranged is locally heated to about 550 ° C. to melt the brazing filler metal 60. Further, the temperature of the heat transfer tube 10 is heated lower than the temperature of the connection tube 40. For example, the temperature of the lower part of the fitting portion 42, that is, the lower part of the opening portion 14 of the heat transfer tube 10 is adjusted to be equal to or lower than the solidus temperature of the brazing material 60 (for example, 410 ° C.).

By heating the fitting portion 42 in this way, the molten brazing material 60 flows from the thick connecting pipe 40 side into the gap of the fitting portion 42 via the flared portion 15 on the thin heat transfer tube 10 side. As described above, since a plurality of grooves 11 are formed on the inner surface of the heat transfer tube 10, the brazing material 60 is drawn into the gap by the capillary phenomenon.

Here, when the brazing material 60 applied to the connecting pipe 40 reaches the melting temperature, the brazing material 60 flows into the gap between the mouth expanding portion 14 of the heat transfer tube 10 and the tip portion 41 of the connecting pipe 40, but the brazing material 60 Since the specific gravity is high, the connecting pipe 40 is not a little eroded by the base metal, and the wall thickness is reduced. However, since the thick connecting pipe 40 is only thinned, the thickness of the connecting pipe 40 can be maintained above a certain level. Of course, there is no problem with the pressure resistance of the connecting pipe 40.

Further, since the temperature of the lower part of the mouth expansion portion 14 of the heat transfer tube 10 is adjusted to be equal to or lower than the solidus temperature of the brazing material 60, the brazing material 60 is likely to solidify at the lower part of the mouth expansion portion 14. Therefore, even if the inner grooved tube is used as the heat transfer tube 10, the brazing material 60 does not flow further downward in the gravity direction than the fitting portion 42. Further, since the brazing material 60 is less likely to flow below the fitting portion 42 in the direction of gravity, there is no possibility that the fitting portion 42 will be poorly brazed. Since the heat transfer tube 10 has a lower temperature than the connecting tube 40, the heat transfer tube 10 is hardly eroded by the brazing material 60.

Further, the headers 50 and 51 are brazed and joined to the heat transfer tube 10. In addition, the finishing process is performed. In this way, the heat exchanger 1 is completed.

Here, a comparative example of partial brazing will be described. In the comparative example shown in FIG. 7, the temperature of the connecting tube 110 is higher than that of the heat transfer tube 120, but the thickness of the connecting tube 110 is substantially the same as that of the heat transfer tube 120. In this configuration, significant wall thinning occurred on the connecting pipe 110 side due to erosion of the brazing filler metal 60. In this case, the wall thickness of the connecting pipe 110 required for pressure resistance cannot be secured. Further, the brazing length of the fitting portion 130 in the longitudinal direction of the heat transfer tube 120 is also shorter than that of the above configuration.

In another comparative example shown in FIG. 8, the temperature of the heat transfer tube 120 is higher than that of the connection tube 110, and the thickness of the connection tube 110 is substantially the same as that of the heat transfer tube 120. In this case, the brazing material 60 did not stay in the gap of the fitting portion 130, but flowed to the lower part of the fitting portion 130. Therefore, the brazing length in the longitudinal direction of the heat transfer tube 120 becomes extremely short, and the brazing length required for pressure resistance cannot be secured. In addition, the heat transfer tube 120 was eroded by the brazing material 60, resulting in wall thinning.

In contrast to the above comparative example, in the present embodiment, since the connecting pipe 40 is thicker than the heat transfer pipe 10, the manufacturing yield of the heat exchanger 1 can be improved. Further, since the temperature of the connecting tube 40 is higher than that of the heat transfer tube 10, the brazing material 60 can easily stay in the fitting portion 42, and the brazing length of the brazing material 60 can be secured.

The heat transfer tube 10 is expanded by the tube expander 100. However, in the aluminum heat transfer tube 10, the higher the tube expansion load, the more the tube expander 100 adheres to the tube and the tube cannot be expanded. However, since erosion of the brazing material 60 is unlikely to occur in the heat transfer tube 10, the heat transfer tube 10 can be made thin. Since the heat transfer tube 10 can be thinned, the heat transfer tube 10 can be expanded with a low tube expansion load, and the heat transfer tube 10 does not fail to expand. In addition, the pressure loss of the heat transfer tube 10 can be reduced.

Further, by using the brazing material 60 having a low melting point, the difference in melting point between the base material and the brazing material 60 becomes large. Therefore, since the temperature range in which brazing is possible is widened, the heat exchanger 1 can be manufactured with good yield even if temperature variations occur in many brazed parts due to heating using equipment such as a line burner.

(Other embodiments)
The configuration of the heat exchanger 1 shown in each of the above embodiments is an example, and the configuration is not limited to the configuration shown above, and other configurations capable of realizing the present invention can be used. For example, in the joining step, it is not necessary to heat the connecting pipe 40 more preferentially than the heat transfer pipe 10.

Further, from the viewpoint that the quality of the connecting pipe 40 can be maintained even if the connecting pipe 40 is eroded, it is not necessary to lower the temperature of the heat transfer pipe 10 to be lower than the temperature of the connecting pipe 40 in the joining step. Specifically, the temperature below the opening portion 14 of the heat transfer tube 10, that is, below the fitting portion 42 in the direction of gravity does not necessarily have to be lower than the solidus temperature of the brazing filler metal 60.

As a method of supplying the brazing material 60 to the connecting pipe 40 in the joining step, a ring-shaped brazing material casting, a molded product of a resin binder, a molded product of a rubber binder, or the like may be used.

In the above, an example in which an inner grooved tube is used as the heat transfer tube 10 has been described, but a smooth tube may be used as the heat transfer tube 10.

10 Heat transfer tube 13 Tip part 20 Fin 40 Connection tube 42 Fitting part 60 Wax material

Claims (3)

An aluminum heat transfer tube (10) to which an aluminum connecting pipe (40) and an aluminum fin (20) are joined and the inner diameter of the tip portion (13) is larger than the outer diameter of the connecting pipe. The connecting tube is inserted into the tip of the heat transfer tube so that the connecting tube is located on the upper side in the gravity direction and the heat transfer tube is located on the lower side in the gravity direction. ), Which is a method for manufacturing a cross-fin tube type heat exchanger including a joining step of partially brazing the fitting portion.
In the joining step, the partial brazing is performed using an Al-Cu-Si-based or Al-Cu-Si-Zn-based brazing material (60), and further, the connecting pipe is thicker than the heat transfer pipe. Rutotomoni with things, thinning to the connection tube when said brazing material to flow into the fitting portion to the brazing material is a brazing material of eroding a portion of said connection tube by melting occurs It is a brazing method, and in the joining step, a brazing material having a larger specific gravity than an Al—Si-based brazing material is used .
In the joining step, the brazing is applied to the outer wall surface of the connecting pipe so that at least a part of the brazing material is located above the end surface (16) of the tip end portion of the heat transfer tube before the partial brazing. A method of manufacturing a heat exchanger that supplies materials. The method for manufacturing a heat exchanger according to claim 1, wherein in the joining step, a connection tube having a thickness 1.5 times or more thicker than that of the heat transfer tube is used . The manufacture of the heat exchanger according to claim 1 or 2, wherein in the joining step, the connecting pipe is heated preferentially over the heat transfer pipe, and the temperature of the heat transfer pipe is made lower than the temperature of the connecting pipe. Method.

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