JP3451544B2 - Prevention method of frost pinch in torch brazing part of evaporator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing frost pinch in a torch brazing part of an evaporator such as a roll bond panel.

[0002]

For example, in the manufacture of a roll bond panel, two component panels are stacked, rolled, expanded, and cut into a predetermined shape, and a refrigerant inlet pipe and an outlet pipe are ringed. When torch brazing is performed using a brazing material, blow holes are likely to occur in the fillet. When the manufactured roll bond panel is used in the refrigeration cycle, dew condensation water accumulates in the blow holes and is frozen, and the volume thereof is about 2
The blowhole becomes large because the number of blowholes increases. Further, as a result of repeated operation and stoppage by the thermostat in the refrigeration cycle, freezing and defrosting of the condensed water in the blowhole are repeated,
Each time, the blow hole gradually expanded, and finally a crack was generated in the torch brazing portion (so-called frost pinch), and there was a risk of refrigerant leakage.

An object of the present invention is to provide a method for preventing frost pinch in the torch brazing part as described above.

[0004]

A method for preventing frost pinch in a torch brazing part of an evaporator according to the present invention is a method in which a silicone rubber liquid is applied to a fillet of a torch brazing part in a coated evaporator and the fillet is applied to the fillet. It is characterized in that a silicone rubber coating film is formed on the fillet by drying.

Specific examples of the evaporator include roll bond panels used in refrigerators and the like, and laminated evaporators used in automobile air conditioners.

The silicone rubber liquid has a coating film of 10 μm.
If it is less than 100 μm, the torch brazing part is transparent and a sufficient waterproof effect cannot be obtained. On the other hand, if the coating film exceeds 70 μm, dripping of the silicone rubber liquid may occur and workability may be deteriorated and the coating film may not be even 10-7 because it becomes difficult to secure
It is preferable that the coating is carried out in the range of 0 μm. The method for applying the silicone rubber liquid is not particularly limited, but brush application is preferable in order to apply the silicone rubber liquid to the fillet of the torch brazing part in the evaporator accurately and efficiently.

The above-mentioned evaporator is usually powder-coated or solvent-coated, but when the thickness of the coating film is less than 20 μm, the aluminum base material constituting the evaporator is transparent,
If the thickness of the coating exceeds 120 μm, it is difficult to secure sufficient resistance of the coating when bending the coated flat roll bond panel or when some impact is applied from the outside. It is preferably in the range of 20 to 120 μm.

According to the method of the present invention, since the silicone rubber coating film is formed on the fillet of the torch brazing portion in the evaporator, even if the blowhole is generated in the fillet of the torch brazing portion, the blowhole is formed. It is covered with the above silicone rubber coating film, so that dew condensation water does not enter into the blow hole during operation of the evaporator.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment in which the present invention is applied to a torch brazing part of a roll bond panel constituting an evaporator for a refrigerator will be described with reference to the drawings.

As shown in FIGS. 1 and 2, the pipes (3A) and (3B) for the inlet and the outlet of the refrigerant are inserted between the upper and lower roll bond panels (1) and (2), and the pipes are made of a ring brazing material. (3
When A) and (3B) are torch brazed, the flux on the fillet (4) surface (4a) of the torch brazing part is brushed and removed, and then pre-treatment (degreasing → water washing → chemical conversion coating → water washing → pure → Washing with water → drying with water) and then powder coating according to the following procedure to obtain a roll bond panel
The coating film (5) was formed on the surface (4a) of the fillet (4) of the (1), (2), the pipes (3A), (3B) and the torch brazing part so that a film thickness of about 70 μm was obtained.

That is, as the powder coating, an epoxy-polyester resin coating (baking temperature 175 ° C. × 20
Min) was used for electrostatic powder coating.

Then, the surface (4a) of the fillet (4) in the brazing part of the torch and its periphery are brushed with a silicone rubber liquid, Hermesyl SS-66CTS manufactured by Nippon Hermetics Co., Ltd., and dried. Thus, the silicone rubber coating film (6) was formed on the powder coating film (5) in the relevant portion so as to have a film thickness of about 40 μm.

In the case of this embodiment, the torch brazing part (4)
Even if there is a blow hole in the blow hole, since it is covered with the silicone rubber coating film (6), the condensed water during the operation of the evaporator does not enter the blow hole.

In the present embodiment, the epoxy-polyester resin paint is used, but instead of this, a polyester resin paint (baking temperature 180 ° C. × 20 minutes) is used, and instead of electrostatic powder coating, friction charging is used. You may paint.

Next, the heat cycle test of the silicone rubber coating film in the roll bond panel and the effect test of the silicone rubber coating film on the heat-shrinkable polyvinyl chloride tube (7) (influence of "Hermeseal" solvent vapor) The cold shock test will be described.

First, a powder-coated roll-bonded panel was brush-coated with the above silicone rubber liquid (“Hermeseal”) and allowed to stand at room temperature for 2 hours, and a solvent-coated roll-bonded panel was coated with the above. For each of the above tests, three test pieces prepared by brushing the silicone rubber liquid and leaving it at room temperature for 2 hours were prepared. The structure of each test body is similar to that of the above embodiment.

[Heat Cycle Test] Each of the three powder-coated test specimens and the solvent-coated three test specimens was placed in an atmosphere of 80 ° C. for 30 minutes, and then kept at room temperature for 3 minutes.
It is left for 0 minute, then placed in an atmosphere of −20 ° C. for 30 minutes, and then left at room temperature for 30 minutes.
Went cycle. And after the end of the last cycle, 1 /
A 2φ x 300g weight is placed on the roll bond panel above the 3
The roll-bonded panel was dropped 5 times from a height of 0 cm and the presence or absence of peeling or cracking of the silicone rubber coating film on the roll bond panel was visually observed. As a result, no peeling or cracking of the silicone rubber coating film was observed in any of the test bodies. Further, the adhesiveness of the coating film was confirmed in a cross-cut test (100 × 100).

[Effect test on heat-shrinkable polyvinyl chloride tube] Three powder-coated test bodies and solvent-coated three
A heat-shrinkable polyvinyl chloride tube was attached to each of the three test pieces, and they were placed in a heating furnace set at 130 ° C for 2 minutes to heat them, and the state of each test piece taken out from the heating furnace was changed. It was visually observed. As a result, there was no change in the heat-shrinkable polyvinyl chloride tube, and no abnormality such as peeling or cracking was observed in the silicone rubber coating film on the roll bond panel.

[Cold Impact Test] Each of the three powder-coated test bodies and the three solvent-coated test bodies was placed in an environmental test chamber set at −20 ° C. for 2 hours to cool and then removed from the test chamber. For each test body, 1 / 2φ x 500g
The weight was dropped 5 times from a height of 10 cm, and the presence or absence of peeling or cracking of the silicone rubber coating film on the roll bond panel was visually observed. As a result, no peeling or cracking of the silicone rubber coating film was observed in any of the test bodies.

In the above embodiment, the heat-shrinkable polyvinyl chloride tube (7) is attached to the pipe (3), but this may not be used.

[0021]

According to the method of the present invention, since the silicone rubber liquid is applied to the fillet of the torch brazing part in the evaporator, even if a blowhole is generated in the fillet of the torch brazing part, the blowhole is not covered with the above silicone. It is covered with a coating film of rubber liquid, so that dew condensation water does not enter the blowhole during the refrigeration cycle operation. Therefore, unlike the prior art, freezing and defrosting of the condensed water are not repeated in the blowhole, and therefore, there is no possibility that the refrigerant leaks due to the frost pinch in the torch brazing.

[Brief description of drawings]

FIG. 1 is a horizontal sectional view of an end portion of a roll bond panel showing an embodiment of a method of the present invention.

FIG. 2 is a perspective view of an evaporator using a roll bond panel.

[Explanation of symbols]

(1) (2): Roll bond panel (4): Fillet of torch brazing part (6): Silicone rubber coating

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B23K 1/00 F25D 19/00

Claims (2)

(57) [Claims] 1. A torch for an evaporator, characterized in that a silicone rubber liquid is applied to a fillet of a torch brazing part of the evaporator and the silicone rubber coating film is formed on the fillet by drying the silicone rubber liquid. Frost pinch prevention method in brazing part. 2. The coating film of silicone rubber liquid is 10 to 70.
The method for preventing frost pinch in a torch brazing part of an evaporator according to claim 1, wherein the method is applied so as to have a thickness of μm.