JP2008089257A - Manufacturing method of heat exchanger for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a residual flux amount by suppressing intrusion of flux into tube interiors. <P>SOLUTION: An attaching process S1 is provided for assembling a core part 19 by attaching a tie plate 17 to a lamination part wherein tubes 11 and corrugated fins 12 are mutually laminated, a tie plate face masking process S2 is provided for masking an end face 17a of the tie plate 17 such that flux does not intrude into the interiors of the tubes 11, a powder flux shaking process S3 is provided for shaking flux powder on the core part 19 after the tie plate face masking process, and a brazing process S4 is provided for carrying out heat treatment and brazing of the core part 19 after the powder flux shaking process S3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a heat exchanger for a fuel cell, and more particularly to a technique for preventing flux from entering a tube.

  For example, a polymer electrolyte membrane fuel cell system has been developed as a fuel cell for an FCEV vehicle (fuel cell electric vehicle) that is a fuel cell vehicle equipped with a fuel cell as a drive source. This system is configured so that hydrogen fuel in the fuel cell stack is protonated by the action of a proton catalyst supported on a polymer electrolyte membrane, and potential is generated by cooperation with oxygen existing across the polymer electrolyte membrane. Has been.

  In such a system, since there are many conductive members such as electrodes in the fuel cell stack, it is necessary to make the conductivity of the refrigerant low to prevent electric shock. For this reason, pure water having extremely low conductivity is used as circulating water (cooling water), and cooling of the circulating water with a heat exchanger is performed because of the necessity for reaction control. In such a system, since the cooling water circulating through the heat exchanger is in direct contact with the proton catalyst, it is desired to suppress the mixing of ions such as metals into the cooling water from the viewpoint of catalyst poisoning. ing.

  Here, the core of a heat exchanger such as a radiator or an evaporator is composed of a plurality of corrugated fins made of aluminum material formed into a wave shape and a plurality of tubes made of aluminum material (clad material) formed into a flat shape. And are alternately stacked. Then, the core of the heat exchanger is manufactured by applying a liquid flux to the surface of the core, brazing, and then cleaning to remove the flux residue that has entered the inside of the tube.

  By the way, the flux is usually washed away at the time of the cleaning process after the brazing process, but when a nocolok flux is used as the flux, a residue is likely to remain after the brazing. In addition, since the residue dissolves in water and generates ions, in heat exchangers for fuel cells that use low-conductivity aqueous solutions or pure water, the flux should be removed carefully, especially considering adverse effects on polymer electrolyte membranes. There is a need.

  Therefore, conventionally, an aqueous nocollock flux solution is poured or showered only on the outer surface of the core so that the flux does not adhere as much as possible inside the tube. However, when an aqueous solution is used for the flux, even if the flux is applied only to the outer surface of the core, the penetration of the flux into the tube cannot be effectively suppressed.

  For example, as indicated by an arrow in FIG. 11, the flux 101 ejected from the nozzle 100 enters the tube from the portion where the end of the tube 102 is inserted into the tube insertion hole 104 formed in the seat plate 103, and the flux 101 Enters the surface of the seat plate 103 from the core surface and enters the inside of the tube.

As a method of removing the flux that has entered the inside of the tube, for example, a method of cleaning by immersing the core in pure water heated to 100 ° C. after brazing for 24 hours, or a cleaning method using a strong alkaline degreasing agent for aluminum is used. Adopted (see, for example, Patent Document 1).
JP 2001-167782 A

  However, even in this case, the flux that has entered the details cannot be removed, and the cleaning time of the residual flux is very long (it takes 24 hours or more), so that the residual flux treatment is a bottleneck in manufacturing the heat exchanger.

  Therefore, the present invention has been made in view of the above-described conventional problems, and in particular, suppresses the flux intrusion into the tube, reduces the amount of residual flux, and shortens the residual flux removal process. An object of the present invention is to provide a method of manufacturing a heat exchanger for a fuel cell that can be used.

  The method of manufacturing a heat exchanger for a fuel cell according to the present invention includes an assembling step of assembling a core portion by assembling a seat plate to a laminated portion in which tubes and corrugated fins are alternately laminated, and flux does not enter the inside of the tube. After the seat plate surface masking step for masking the end surface of the seat plate, after the seat plate surface masking step, after the powder flux distribution step of sprinkling powder flux on the core portion, after the powder flux distribution step, And a brazing step of brazing the core portion by heat treatment.

  In the seat plate surface masking step, the tube end portion is covered with a cloth, tape, or cover on the seat plate surface from which the tube end portion projects, thereby preventing flux from entering the inside of the tube.

  According to the method for manufacturing a heat exchanger for a fuel cell of the present invention, before the flux is applied, the end face of the seat plate is masked so that the flux does not enter the inside of the tube. Can be prevented from entering. At this time, by using a powder instead of an aqueous solution as the flux, it is possible to further prevent the flux from entering the tube.

  Therefore, according to the method of the present invention, the amount of residual flux adhering to the inside of the tube, which is difficult to remove mechanically, is eliminated or extremely small, so that the cleaning time for the subsequent residual flux removal step can be greatly shortened. Can do.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  First, before explaining the manufacturing method of the heat exchanger for a fuel cell according to the present embodiment, the FCEV cooling system using the heat exchanger of the present invention will be briefly explained.

"Schematic configuration of FCEV cooling system"
FIG. 1 is a cooling system diagram of an electric vehicle equipped with a fuel cell. A so-called fuel cell vehicle using a fuel cell as a driving source generates the electricity most efficiently by maintaining the temperature of the fuel cell at about 80 ° C. to generate electricity most efficiently. The fuel cell is cooled by circulating a refrigerant so that it does not pass.

  In this cooling system 1, when the refrigerant that cools the heated fuel cell flows through the flow path formed in the fuel cell main body 2, the refrigerant is sent to the heat exchanger 4 by the pump 3 and warmed by power generation. Is cooled by the heat exchanger 4. Then, the cooled refrigerant is sent again to the fuel cell main body 2 and is cooled so as to keep the heated fuel cell at a predetermined temperature. As the refrigerant circulating in such a path, for example, pure water with low conductivity or a mixture of pure water and ethylene glycol as an antifreezing agent is used. This is because an electrode made of a conductive material is provided inside the fuel cell main body 2, and if the refrigerant circulating in the inside has conductivity, it adversely affects the reaction between hydrogen and oxygen. It is.

"Schematic configuration of heat exchanger for fuel cell"
Next, the configuration of the fuel cell heat exchanger manufactured by the manufacturing method of the present invention will be briefly described.

  FIG. 2 is a diagram showing an example of a heat exchanger for a fuel cell manufactured in the present embodiment. A fuel cell heat exchanger (hereinafter simply referred to as a heat exchanger) 4 includes aluminum tubes 11 and corrugated fins 12 that are alternately stacked, and a pair of header tank portions (tank portions) 13 at both ends of a core portion 19. , 14 are disposed, and an inlet pipe 15 and an outlet pipe 16 are provided in communication with these header tank portions 13, 14.

  Each of the header tank portions 13 and 14 includes a seat plate 17 and a tank cover 18 attached to the seat plate 17, and a tank chamber (not shown) is formed therein. Further, the seat plate 17 has a fitting hole corresponding to the end of each tube 11, and the end of each tube 11 is inserted into the fitting hole and coupled in a state of protruding into the tank chamber. Has been.

  In the heat exchanger 4 configured as described above, circulating water (pure water in the present embodiment) flowing from the inlet pipe 15 is distributed and distributed to each tube 11 in the header tank section 13 on the inlet side, and is positioned below. To the outlet-side header tank 14. The pure water is cooled through the tube 11 cooled by the corrugated fins 12 in the process of circulating the tube 11.

"Production method of heat exchanger for fuel cell"
Next, a method for manufacturing the heat exchanger 4 will be described. FIG. 3 is a process diagram showing a heat exchanger manufacturing process, FIG. 4 is a heat exchanger manufacturing process, showing an assembly process for assembling a core, and FIG. 5 is a heat exchanger manufacturing process. FIG. 6 is an enlarged cross-sectional view of the main part of FIG. 5, FIG. 7 is a view showing a heat exchanger manufacturing process, a powder flux distribution step, and FIG. 9 is a characteristic diagram showing the amount of ion elution when sprayed with powder, FIG. 9 is a characteristic diagram showing the cleaning time when the flux is showered and applied, and when sprayed with powder, FIG. 10 is a diagram of the heat exchanger It is a figure which shows a manufacturing process and shows the cover mounting state in a seat board surface masking process.

  In order to manufacture the heat exchanger 4 of the present embodiment, first, the assembly process S1 in the process diagram of FIG. 3 is performed. In the assembling step S1, the tubes 11 and the corrugated fins 12 are alternately stacked as shown in FIG. Next, a seat plate 17 made of stainless steel, aluminum or the like is assembled to the laminated portion made of the tube 11 and the corrugated fin 12. Thus, the core portion 19 is formed.

  The seat plate 17 is formed with a fitting hole which is a slit for inserting the end of each tube 11. The end portion 11 a of the tube 11 inserted into the fitting hole is a position retracted from the end surface 17 a of the seat plate 17.

  Next, a seat plate surface masking step S2 is performed. In the seat plate surface masking step S2, as shown in FIG. 5, a masking material 20 such as cloth or tape is attached to the end surface 17a of the seat plate 17. By affixing the masking material 20 to the end surface 17a of the seat plate 17, the opening side of the seat plate 17 is closed and the end portion 11a of the tube 11 is covered with the masking member 20 as shown in FIG. . In order to attach the masking member 20 to the end surface 17a of the seat plate 17, an adhesive or the like is used.

  Next, a powder flux distribution step S3 is performed. In the powder flux distribution step S3, a powder flux is used instead of a conventional aqueous solution flux. As the powder flux, a fluoride flux is preferable instead of a chloride flux that hardly causes residual residue after brazing.

A typical example of the fluoride-based flux powder is a nocolok flux developed by ALCAN. As a compound form of Nocolok flux, there is a mixture of KAIF ₄ and K ₂ AIF ₅ .H ₂ O, for example, FL7 manufactured by Furukawa Aluminum Co., Ltd. can be used. Table 1 shows the chemical composition and compound form of the Nocolok flux.

  In the powder flux distribution process, as shown in FIG. 7, the powder flux 22 is sprinkled on the outer surface of the core portion 19 from the tip of the nozzle 21. When the powder flux 22 is sprinkled on the outer surface of the core portion 19, since the masking member 20 is attached to the end surface 17a of the seat plate 17, the penetration of the powder flux 22 into the tube is prevented. In particular, when an aqueous solution is used as the flux, the flux enters from the insertion portion of the tube 11 and the seat plate 17, but the use of powder flux can suppress the penetration of the flux from the insertion portion. it can.

  Next, brazing process S4 is performed. In the brazing step S4, after the masking member 20 is removed, the brazed core portion 19 is placed in a furnace and subjected to heat treatment to perform brazing, thereby joining the tube 11 and the corrugated fin 12 and the tube 11 and the seat. The plate 17 is joined.

  Next, after the core portion 19 is taken out of the furnace and cooled, a tank is attached to the seat plate 17. Next, a cleaning step S5 is performed. In the cleaning step S <b> 5, the core part 19 is cleaned to remove residual flux from the inner surface of the core part 19. Next, coating process S6 is performed. The coating step S6 includes a coating step S7, a drying step S8, and a baking step S11 for forming a resin coating layer on the inner surface through which circulating water from the fuel cell of the brazed core portion 19 circulates.

  In the coating step S <b> 7, the coating liquid is discharged from the core part 19 and applied to the inner surface of the core part 19. The drying step S8 is a step of drying the coating agent applied to the inner surface of the core portion 19, and includes an upright drying step S9 and a horizontal drying step S10. In the upright drying step S <b> 9, the tube 11 is dried in a state where the tube 11 is positioned in the vertical direction. In the horizontal drying step S10, the tube 11 is dried with the tube 11 positioned in the horizontal direction. In the baking step S <b> 11, the coating liquid is baked on the inner surface of the core portion 19.

  Thus, the heat exchanger 4 shown in FIG. 2 is completed. In the heat exchanger 4 manufactured in this way, as shown in FIG. 8, the amount of ion elution can be reduced by the powder distribution method of the present invention compared to the conventional shower coating method. I understand. In addition, as shown in FIG. 9, it can be seen that the cleaning time can be greatly shortened by the method of the present invention. That is, according to the method of the present invention, since the amount of residual flux can be extremely reduced, the cleaning time which has conventionally taken 24 hours or more can be shortened to only about 1 hour. Therefore, the amount of residual flux adhering to the inside of the tube, which is difficult to remove mechanically, is eliminated or extremely small, and mass production of the heat exchanger 4 is facilitated.

  In the above embodiment, the masking member 20 such as cloth or tape is attached to the end surface 17a of the seat plate 17 in the seat plate surface masking step S2, but the temporary tank 23 is attached to the seat plate 17 as shown in FIG. The temporary tank 23 may cover the opening of the seat plate 17. By attaching the temporary tank 23, flux can be prevented from entering the inside of the tube 11.

It is a schematic block diagram of the cooling system in a fuel cell vehicle. It is a figure which shows an example of the heat exchanger for fuel cells manufactured by this Embodiment. It is process drawing which shows the manufacturing process of a heat exchanger. It is a figure which shows the manufacturing process of a heat exchanger, and shows the assembly | attachment process of assembling a core part. It is a figure which shows the manufacturing process of a heat exchanger, and shows a seat board surface masking process. It is a principal part expanded sectional view of FIG. It is a figure which shows the manufacturing process of a heat exchanger, and shows a powder flux distribution process. It is a characteristic view which shows the amount of ion elution when a flux is applied by showering and when it is distributed with powder. It is a characteristic view which shows the washing | cleaning time when a flux is showered and apply | coated and it distributes with powder. It is a figure which shows the manufacturing process of a heat exchanger, and shows the cover mounting state in a seat board surface masking process. FIG. 11A is a view showing a state in which the flux enters the inside of the tube when the aqueous solution flux is applied, and FIG. 11B is a plan view of the main part of the seat plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cooling system 2 ... Fuel cell main body 3 ... Pump 4 ... Heat exchanger 11 ... Tube 12 ... Corrugated fin 13, 14 ... Tank part 17 ... Seat plate 17a ... End surface of seat plate 20 ... Masking member 22 ... Powder flux

Claims (1)

An assembling step (S1) for assembling the core portion (19) by assembling the seat plate (17) to the laminated portion where the tubes (11) and the corrugated fins (12) are alternately laminated;
A seat plate surface masking step (S2) for masking the end surface (17a) of the seat plate (17) so that flux does not enter the inside of the tube (11);
After the said seat board surface masking process (S2), the powder flux distribution process (S3) which sprinkles the powder flux on the said core part (19),
After the said powder flux distribution process (S3), it has the brazing process (S4) which heat-processes the said core part (19), The manufacturing method of the heat exchanger for fuel cells characterized by the above-mentioned.

Images