EP1623176A4

EP1623176A4 - Evaporator and process for fabricating same

Info

Publication number: EP1623176A4
Application number: EP04729495A
Authority: EP
Inventors: Shintaro Nakagawa
Original assignee: Showa Denko KK
Current assignee: Resonac Holdings Corp
Priority date: 2003-04-28
Filing date: 2004-04-26
Publication date: 2007-12-26
Also published as: EP1623176A1; WO2004097322A1; KR20060005400A; AU2004234672A1; US20060236538A1

Abstract

An evaporator 1 comprises a flat tube 2 bent zigzag, and a corrugated fin 3 disposed between each adjacent pair of straight tube portions 2a of the flat tube 2 and brazed thereto by the flux brazing method. The flux remains on the surface of the portion of the corrugated fin 3 not brazed to the straight tube portions 2a in an amount of 0.03 to 1 g/m2. &commat;The evaporator 1 is fabricated by a process including applying the flux in an amount of 0.05 to 2.8 g/m2 to the outer surface of a zigzag flat tube 2, disposing a corrugated fin 3 between each adjacent pair of straight tube portions 2a of the flat tube 2 and brazing the fin 3 to the flat tube 2. The evaporator 1 can be effectively inhibited from emanating odor.

Description

DESCRIPTION

EVAPORATOR AND PROCESS FOR FABRICATING SAME

CROSS REFERENCE TO RELATED APPLICATIONS

This application is an application filed under 35 U.S.C. §111 (a) claiming the benefit pursuant to 35 U.S.C. §119 (e) (1) of the filing date of Provisional Application No. 60/477,746 filed JUNE 12, 2003 pursuant to 35 U.S.C. §111 (b) .

TECHNICAL FIELD

The present invention relates to evaporators and a process for fabricating the same, and more particularly to evaporators, for example, for use in motor vehicle air conditioners wherein a chloroflurocarbon refrigerant or C0₂ refrigerant is used, and a process for fabricating the evaporator.

BACKGROUND ART

Evaporators of the 'type mentioned are in wide use which comprise refrigerant passing hollow bodies and corrugated fins brazed to the outer surfaces of adjacent hollow bodies.

Such evaporators are fabricated by making a combination of refrigerant passing hollow bodies and corrugated fins, spraying a flux suspension prepared by suspending a noncorrosive fluoride flux in water onto the combination in its entirety and brazing the fins to adjacent hollow bodies by heating the combination in a nitrogen gas atmosphere.

However, the evaporator fabricated in this way inevitably permits the flux to remain on the portions of the corrugated fins which are not brazed to the hollow bodies. We have found that if the evaporator has an increased amount of flux residue remaining therein, the evaporator gives off a relatively strong odor when incorporated into a motor vehicle air conditioner, and is likely to make the passenger in the vehicle compartment feel discomfort.

The amount of flux residue can be reduced by decreasing the quantity of the flux in the suspension, but this entails the likelihood that faults will occur in the brazed joints.

The evaporators described above include those of the stackedplate type wherein the refrigerant passing hollowbodies each comprise two plates provided by a brazing sheet having a brazing material layer on opposite sides thereof and brazed to each other at their peripheral edge portions, the two plates defining therebetween a bulging refrigerant channel and a bulging header-forming portion communicating with each of opposite ends of the channel, the hollow bodies being stacked so that the outer surfaces of the header-forming portions of each adjacent pair of hollow bodies are in contact with each other, the corrugated fins being arranged between the portions of adjacent hollow bodies corresponding to the respective refrigerant channels thereof and brazed to the hollow bodies. In order to simplify or eliminate the step of washing away the flux residue after brazing, it is known to apply a reduced amount of flux, for example 3 to 7 g/m² of flux, to the outer surfaces of the plates making the refrigerant passing hollow bodies in fabricating evaporators of the staked type described (see the publication of JP-A No. 2000-202620) .

However, the evaporator fabricated by the method disclosed in the above publication still remains to be improved in fully reducing the emanation of odor due to the flux residue . An object of the present invention is to overcome the above problem and to provide an evaporator which is adapted to effectively suppress the emanation of odor and a process for fabricating the same.

DISCLOSURE OF THE INVENTION

To fulfill the above obj ect, thepresent invention comprises the following modes.

1) An evaporator comprising a refrigerant passing hollow body, and a fin brazed to an outer surface of the hollow body by the flux brazing method, the portion of the fin not brazed to the hollow body having a flux remaining on a surface thereof in an amount of 0.03 to 1 g/m².

2) An evaporator set forth in the above para. 1) wherein the flux remains on the surface of the portion of the fin not brazed to the hollow body in an amount of 0.05 to 0.5 g/m².

3) An evaporator set forth in the above para. 1) wherein the flux is a noncorrosive fluoride flux.

4) An evaporator set forth in the above para. 1) wherein the refrigerant passing hollow body comprises a flat tube bent zigzag, and the fin comprises a corrugated fin made of a brazing sheet having a brazing material layer on opposite sides thereof, the corrugated fin being disposed between and brazed to each adjacent pair of straight tube portions of the zigzag flat tube.

5) An evaporator set forth in the above para. 1) which comprises a plurality of straight flat tubes each constituting the refrigerant passing hollow body and wherein the fin comprises a corrugated fin made of a brazing sheet having a brazing material layer on opposite sides thereof, the plurality of flat tubes being arranged in parallel as spaced from one another, the corrugated fin being disposedbetween andbrazed to each adj acent pair of flat tubes. 6) An evaporator set forth in the above para. 1) which comprises a plurality of refrigerant passing hollow bodies each comprising two plates made of a brazing sheet having a brazing material layer on opposite sides thereof and brazed to each other at peripheral edge portions thereof, the two plates defining therebetween a bulging refrigerant channel and a bulging header-forming portion communicating with each of opposite ends of the refrigerant channel, the fin comprising a corrugated fin, the plurality of hollow bodies being stacked so that outer surfaces of the header-forming portions of each adjacent pair of hollow bodies are in contact with each other, the corrugated fin being arranged between the portions of each adjacent pair of hollow bodies corresponding to the respective refrigerant channels thereof and brazed to the hollow bodies.

7) An evaporator set forth in the above para. 1) which has been subjected to a treatment for imparting hydrophilic properties thereto.

8) A refrigeration cycle which comprises a compressor, a condenser and an evaporator and wherein a chlorofluorocarbon refrigerant is used, the evaporatorbeing an evaporator according to any one of claims 1 to 7.

9) A vehicle having installed therein a refrigeration cycle set forth in the above para. 8) as a motor vehicle air conditioner.

10) A process for fabricating an evaporator comprising preparing a flat tube bent zigzag and having a refrigerant passing channel inside thereof and a fin made of a brazing sheet having a brazing material layer on opposite sides thereof, applying a flux to an outer surface of the zigzag flat tube in an amount of 0.05 to 2.8 g/m², disposing the fin between each adjacent pair of straight tube portions of the zigzag flat tube, and brazing the fin to the zigzag flat tube.

11) A process for fabricating an evaporator set forth in the above para. 10) wherein the flux is applied to the flat tube in an amount of 1 to 2 g/m².

12) A process for fabricating an evaporator comprising preparing a plurality of straight flat tubes each having a refrigerant passing channel inside thereof and a fin made of a brazing sheet having a brazing material layer on opposite sides thereof, applying a flux to an outer surface of each of the flat tubes in an amount of 0.05 to 2.8 g/m², arranging the plurality of flat tubes in parallel as spaced from one another, disposing the fin between each adjacent pair of flat tubes, and brazing the fin to the flat tubes.

13) A process for fabricating an evaporator set forth in the above para. 12) wherein the flux is applied to the flat tube in an amount of 1 to 2 g/m². 14) A process for fabricating an evaporator comprising preparing plates each having a channel-forming bulging portion and a header-forming bulging portion bulging to a greater extent than the channel-forming portion and extending from each of opposite ends of the channel-forming portion and fins f om a brazing sheet having a brazing material layer on opposite sides thereof; applying a flux is to opposite surfaces of each of the plates, with the amount of the flux applied to the outer surfaces of both the bulging portions of each plate adjusted to 0.05 to 2.8 g/m²; arranging the plates in stacked pairs each comprising the combination of two plates with openings of the bulging portions of each type opposed to each other in corresponding relation so that the outer surfaces of bottom walls of the header-forming bulging portions of adjacent pairs of plates are in contact with each other, and arranging the fins between the portions of respective adjacent pairs of plates corresponding to the channel-forming bulging portions thereof; brazing the two plates in each pair to each other along peripheral edge portions thereof to form a refrigerant passing hollow body and brazing the fins to respective adjacent pairs of hollow bodies .

15) A process for fabricating an evaporator set forth in the above para. 14) wherein the flux is applied to the outer surfaces of both the bulging portions of each plate in an amount of 1 to 2 g/m².

16) A process for fabricating an evaporator set forth in any one of the above para. 10) to 15) wherein the flux is applied as suspended in water containing a binder. 17) A process for fabricating an evaporator set forth in any one of the above para. 10) to 15) wherein a corrugated fin is used as the fin.

18) A process for fabricating an evaporator set forth in any one of the above para. 10) to 15) wherein the brazed assembly is finally subjected to a treatment for imparting hydrophilic properties thereto.

With the evaporators described in the above para. 1) and 4) to 6) , the amount of flux remaining on the surface of the portion of the fin not brazed to the refrigerant passing hollow body is 0.03 to 1 g/m², so that the emanation of odor is effectively inhibited. Moreover, the invention obviates occurrence of faulty brazed joints between the hollow body and the fin in fabricating the evaporator. The evaporator described in the above para.2) is inhibited from emanating odor more effectively.

With the processes described in para. 10), 12) and 14) for fabricating an evaporator, the flux remains on the surface of the portion of the fin not brazed to the refrigerant passing flat hollow body in an amount of 0.03 to 1 g/m², so that the emanation of odor is effectively suppressed. Moreover, the invention obviates occurrence of faulty brazed joints between the hollow body and the fin in fabricating the evaporator. With the processes described in para. 11), 13) and 15) for fabricating an evaporator, the evaporator fabricated is inhibited from releasing odor more effectively.

With the process described in para. 16) for fabricating an evaporator, the binder acts to prevent the flux frombecoming released or removed during the assembling procedure following the application of the flux and included in the process set forth in the para. 10), 12 or 14) .

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an evaporator as a first embodiment of the invention. FIG. 2 is a fragmentary perspective view showing an evaporator as a second embodiment of the invention. FIG. 3 is a perspective view partly exploded and showing an evaporator as a third embodiment of the invention.

BEST MODE OF CARRYING OUT THE INVENTION

Embodiments of the invention will be described below with reference to the drawings. In the following description, the term "aluminum" includes aluminum alloys in addition to pure aluminum.

FIG.1 shows a first embodiment of evaporator of the present invention.

With reference to FIG. 1, the evaporator 1 comprises a flat tube (refrigerant passing hollow body) 2 made of an aluminum extrudate and bent zigzag, wavy louvered corrugated fins 3 made of an aluminum brazing sheet having a brazing material layer on opposite sides, and two aluminum headers 4 brazed respectively to opposite ends of the zigzag flat tube 2. The zigzag flat tube 2 is disposed with straight tube portions 2a thereof positioned vertically, and the corrugated fin 3 is interposed between and brazed to each adjacent pair of straight tube portions 2a. The straight tube portion 2a positioned at each of opposite ends of the zigzag flat tube 2 is provided externally thereof with a wavy louvered corrugated fin 3A made of an aluminum brazing sheet having a brazing material layer on opposite sides, and with an aluminum side plate 5 positioned externally of the fin 3A. The corrugated fin 3A is brazed to the straight tube portion 2a and the side plate 5. Although not shown, the zigzag flat tube 2 has a plurality of parallel refrigerant channels inside thereof. The corrugated fins 3, 3A comprise parallel flat portions and a bent portion interconnecting each adjacent pair of flat portions. The fin is brazed to the straight portion 2a or to the side plate 5 at the outer ends of the bent portions.

The straight tube portions 2a of the zigzag tube 2 or the side plate 5 are brazed to the corrugated fin 3 or 3A with a noncorrosive fluoride flux.

The amount of flux remaining (hereinafter referred to as the "amount of flux residue") on the surfaces of the portions of the corrugated fins 3, 3A which portions are not brazed to the straight tube 2a or the side plate 5 is 0.03 to 1 g/m². The amount of flux residue is so limited because if the amount is less than 0.03 g/m², the amount of flux for brazing is insufficient and likely to result in faulty brazed joints, and further because if the amount is in excess of 1 g/m², the evaporator 1 will emanate a strong odor. The amount of flux re-sidue on the surfaces of the portions of the corrugated fins 3, 3A which portions are not brazed to the straight tube

2a or the side plate 5 is preferably 0.05 to 0.5 g/m². The

_^portions of the corrugated fins 3, 3A which are not brazed to the straight tube 2a or the side plate 5 are each the above-mentioned flat portion in its entirety and may include part of the above-mentioned bent portion.

The evaporator 1 is fabricated by the process to be described below.

Preparedfirst are a flat tube 2made of analuminumextrudate and bent zigzag, louvered corrugated fins 3, 3A made of a brazing sheet having a brazingmaterial layer on opposite sides, aluminum side plates 5, and two aluminum headers 4. A flux is then applied to the outer surfaces of the zigzag flat tube 2 in an amount of 0.05 to 2.8 g/m² by a suitable method. The flux is used as suspended in water containing a binder, and the amount of flux to be applied is the amount of flux itself as contained in the suspension. The amount of flux to be applied to the outer surfaces of the zigzag flat tube 2 is limited to 0.05 to 2.8 g/m² because if the amount is less than 0.05 g/m², the amount of flux for brazing is insufficient and likely to result in faulty brazed joints, and further because if the amount is in excess of 2.8 g/m², the evaporator 1 will emanate a strong odor. The amount of flux to be applied to the outer surfaces of the zigzag flat tube 2 is preferably 1 to 2 g/m².

Subsequently, corrugated fins 3 are disposed between the respective adjacent pairs of straight tube portions 2a of the zigzag tube 2, and the remaining corrugated fins 3 are placed externally of the straight portions 2a positioned respectively at opposite ends of the tube. The headers 4 are attached respectively to opposite ends of the tube 2. The resulting assembly is tacked by a suitable jig. The tacked assembly is thereafter heated at a predetermined temperature in a heating furnace having a nitrogen gas atmosphere to braze the straight tube portions 2a of the l_^ zag flat tube 2 to the side plates or to the corrugated fins 3, 3A, and the tube 2 to the two headers 4. In this way, the evaporator 1 is fabricated.

After the brazing operation, the evaporator 1 is subjected, for example, to a cleaning treatment, chemical conversion treatment and a treatment for making the assembly hydrophilic. The cleaning treatment is conducted by bringing the evaporator 1 into contact with an acid cleaning agent containing at least one acid selected from the group consisting of nitric acid, sulfuric acid and hydrofluoric acid. The acid cleaning agent to be used is, for example, one containing 0.01 to 5 mass % of an iron salt. Examples of useful iron salts are an iron sulfate, iron nitrate, iron acetate and iron hydrochloride. Preferably, the evaporator 1 is brought into contact with the acid cleaning agent at 10 to 85° C for 30 seconds to 5 minutes for cleaning. The chemical conversion treatment is conducted by forming a chemical conversion coating using a chromic acid or phosphoric acid chromating treating agent, or by forming a chemical conversion coating with a nonchromium agent, e.g., zirconium treating agent. In forming a chemical conversion coating using the zirconium treating agent, it is essential to conduct the cleaning treatment with an acid cleaning agent containing an iron salt.

The treatment for rendering the evaporator hydrophilic is conducted using an agent for giving hydrophilic properties which contains finely divided silica and a vinyl alcohol polymer in a mass ratio of 30:70 to 70:30 and in a combined amount of 0.2 to 25 mass % and wherein the finely divided silica is dispersed in an aqueous medium in the form of fine particles coated with the vinyl alcohol polymer, the coated particles having a mean particle size of 5 to 1000 nm. The agent may contain an odor inhibitor comprising an organic compound having an amido group and/or a phenolic group. The agent may further contain an antibacterial or fungicidal agent.

In this way, corrosion resistance or hydrophilic properties are imparted to the evaporator 1.

FIG. 2 shows a second embodiment of evaporator of the present invention. With reference to the second embodiment, the upper and lower sides, and the left- and right-hand sides of FIG. 2 will be referred to as "upper," "lower," "left" and "right," respectively, and the direction toward which an air stream flows (i.e., the direction indicated by the arrow A in FIG. 2) will be referred to as the "front," and the opposite direction as the "rear."

With reference to FIG. 2, the evaporator 10 comprises a pair of upper and lower aluminum headers 11, 12 spaced apart from each other, flat tube groups 14, 15 in the form of front and rear two rows of refrigerant passing flat tubes (refrigerant passing hollow bodies) 13 made of an aluminum extrudate and arranged in parallel leftward or rearward, i.e., laterally, at a spacing, and wavy louvered corrugated fins 16 made of an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof. Each refrigerant passing flat tube 13 has a plurality of parallel refrigerant channels inside thereof.

The interior of the upper header 11 is divided into front and rear two header chambers 11a, lib by a partition wall 17 extending laterally. In the flat tube groups 14, 15, the flat tubes 13 are arranged with their widthwise direction positioned forward or rearward, i.e., transversely of the evaporator 10. All the flat tubes 13 of the front group 14 have their upper ends brazed to the upper header 11 so as to communicate with the front header chamber 11a and have their lower ends brazed to the front portion of the lower header 12 in communication with the interior thereof. All the flat tubes 13 of the rear group 15 have their upper ends brazed to the upper header 11 so as to communicate with the rear header chamber lib and have their lower ends brazed to the rear portion of the lower header 12 in communication with the interior thereof. The corrugated fin 16 is disposed between and brazed to each adjacent pair of flat tubes 13. The refrigerant passing flat tubes 13 are brazed to the corrugated fins 16 and to the two headers 11, 12 with use of a noncorrosive fluoride flux.

The amount of flux residue on the surfaces of the portions of the corrugated fin 16 which portions are not brazed to the flat tube 13 is 0.03 to 1 g/m², preferably 0.05 to 0.5 g/m². The amount of flux residue is thus limited for the same reason as in the case of the first embodiment described. Each of the portions of the corrugated fin 16 which are not brazed to the flat tube 13 is also the same portion as described in the case of the first embodiment.

The evaporator 10 is fabricated by the process to be described below. Prepared first are refrigerant passing flat tubes 13 made of an aluminum extrudate, louvered corrugated fins 16 made of a brazing sheet having a brazing material layer on opposite sides, and upper and lower headers 11, 12. A flux is then applied to the outer surfaces of the flat tubes 13 in an amount of 0.05 to 2.8 g/m², preferably 1 to 2 g/m², by a suitable method. The flux is used as suspended in water containing a binder, and the amount of flux to be applied is the amount of flux itself as contained in the suspension. The amount of flux to be applied to the outer surfaces of the flat tubes 13 is limited as above for the same reason as in the case of the first embodiment .

Next, the flat tubes 13 are arranged in front and rear two rows to form flat tube groups 14, 15, and the corrugated fin 16 is disposed between each adjacent pair of flat tubes 13.' Opposite ends of the flat tubes 13 are then placed into corresponding insertion holes (not shown) formed in the upper and lower headers 11, 12, and the assembly is tacked by a suitable jig-

The tacked assembly is thereafter heated at a predetermined temperature in a heating furnace having a nitrogen gas atmosphere, and the flat tubes 13 are brazed to the headers 11, 12 and to the dorrugated fins 16. In this way, the evaporator 10 is fabricated. FIG.3 shows a third embodiment of evaporator of the present invention.

With reference to FIG. 3, the evaporator 20 comprises a plurality of flat hollow bodies (refrigerant passing hollow bodies) 21 arranged in parallel and brazed to one another at their upper ends in communication, and louvered corrugated fins 22 made of an aluminum bare material and arranged between and brazed to respective adjacent pairs of flat hollow bodies 21. A refrigerant flowing into the evaporator through a fluid inlet 23 flows through all the flat hollow bodies 21 and flows out via a fluid outlet 24.

Each flat hollow body 21 is formed from two plates 25 made of a brazing aluminum sheet having a brazing material layer on opposite sides thereof, by brazing the two plates 25 to each other at their peripheral edge portions. The two plates 25 define therebetween a generally U-shaped bulging refrigerant channel 26, and a header-forming portion 27 bulging to a greater height than the channel 26 and communicating with each of opposite ends of the channel 26. The hollow bodies 21 are stacked and brazed to one another so that the outer

1 surfaces of the header-forming portions 27 of each adjacent pair of hollow bodies 21 are in contact with each other. The corrugated fins 22 are arranged between the portions of adjacent hollow bodies 21 corresponding to the respective refrigerant channels 26 thereof and brazed to the hollow bodies 21.

The above-mentioned plates 25 are brazed to each other, and the flat hollow bodies 21 are brazed to the corrugated fins 22, using a noncorrosive fluoride flux. The amount of flux residue on the surfaces of the portions of the corrugated fin 22 which portions are not brazed to the flat hollow body 21 is 0.03 to 1 g/m², preferably 0.05 to 0.5 g/m². The amount of flux residue is thus limited for the same reason as in the case of the first embodiment described. Each of the portions of the corrugated fin 22 which are not brazed to the flat hollow body 21 is also the same portion as described in the case of the first embodiment.

The evaporator 20 is fabricated by the process to be described below.

First, a brazing sheet having a brazing material layer on opposite sides thereof is used to prepare plates 25 each having a generally U-shaped channel-forming bulging portion 25a and a header-forming bulging portion 25b bulging to a greater extent than the portion 25a and extending from each of opposite ends of the portion 25a and corrugated fins 22.

A flux is then applied to opposite surfaces of each plate 25 by a suitable method. At this time, 0.05 to 2.8 g/m², preferably 1 to 2 g/m², of flux is applied to the outer surfaces of both the bulging portions 25a, 25b of the plate 25. The flux is used as suspended in water containing a binder, and the amount of flux to be applied is the amount of flux itself as contained in the suspension. The amount of flux to be applied to the outer surfaces of both the bulging portions 25a, 25b is limited as above for the same reason as in the case of the first embodiment .

The plates 25 are then arranged in stacked pairs each comprising the combination of two plates with the openings of the bulging portions of each type 25a (25b) opposed to each other in corresponding relation so that the outer surfaces of bottom walls of the header-forming bulging portions 25b of the adjacent pairs of plates 25 are in contact with each other, and the corrugated fins 22 are arranged between the portions of respective adj cent pairs of plates 25 corresponding to the channel-forming bulging portions 25a thereof. The resulting assembly is tacked by a suitable jig.

The tacked assembly is thereafter heated at a predetermined temperature within a heating furnace having a nitrogen gas atmosphere to braze the two plates in each pair to each other along the peripheral edge portions thereof to form a flat hollow body and braze the fins to respective adjacent pairs of flat hollow bodies. In this way, the evaporator 20 is fabricated.

According to the second and third embodiments, the evaporator fabricated is subjected to a cleaning treatment, chemical conversion treatment and treatment for imparting hydrophilic properties in the same manner as is the case with the first embodiment .

Along with a compressor, condenser and expansion valve, each of the evaporators 1, 10, 20 of the first to third embodiments

•provides a refrigeration cycle wherein a chlorofluorocarbon refrigerant is used and which is installed in a vehicle, for •example, in a motor vehicle, for use as a motor vehicle air conditioner.

Further along with a compressor, gas cooler, intermediate heat exchanger and expansion valve, each of the evaporators 1, 10, 20 of the first to third embodiments provides a refrigeration cycle wherein a C0₂ refrigerant is used and which is installed in a vehicle, for example, in a motor vehicle, for use as a motor vehicle air conditioner. Specific examples of the invention will be described below together with a comparative example. Evaporators so shaped as shown in FIG. 1 were used in these examples and comparative example. Examples 1-4 A flux suspension was prepared which comprised a flux (FL-7, product of Morita Kagaku Co., Ltd.) suspended in water containing a binder (SURFBEST 1100, product of NIPPON PAINT Co., Ltd.). Also prepared were zigzag flat tubes made of an aluminum extrudate, corrugated fins made of an aluminum brazing sheet having a brazing material layer on opposite sides thereof, aluminum side plates and two kinds of aluminum headers.

The flux suspension was applied by brushing to the zigzag flat tubes over the entire outer surfaces thereof in varying amounts (calculated as the flux itself) . Corrugated fins were then arranged between respective adjacent pairs of straight tube portions of each zigzag tube, two corrugated fins were arranged externally of the respective straight tube portions at opposite ends of the tube, two side plates were arranged externally of these respective end corrugated fins, two headers were attached to opposite ends of the zigzag tube, and the resulting arrangement was tacked by a suitable jig.

Each tacked assembly was thereafter heated at a predetermined temperature within a heating furnace having a nitrogen gas atmosphere to braze the straight tube portions of the zigzag tube and the side plates to the corrugated fins, and the zigzag flat tube to the two headers to fabricate an evaporator. Comparative Example

A flux suspension was prepared which comprised a flux (FL-7, product of Morita Kagaku Co., Ltd.) suspended in water. Alsopreparedwere a zigzag flat tubemade of an aluminumextrudate, corrugated fins made of an aluminum brazing sheet having a brazing material layer on opposite sides thereof, aluminum side plates and two aluminum headers.

Corrugated fins were then arranged between respective adjacent pairs of straight tube portions of the zigzag tube, the remaining corrugated fins were arranged externally of the respective straight tube portions at opposite ends of the tube, the side plates were arranged externally of these respective end corrugated fins, the two headers were attached to opposite ends of the zigzag tube, and the resulting arrangement was tacked by a suitable jig. The flux suspension was then sprayed onto the tacked assembly.

The assembly was thereafter heated at a predetermined temperature within a heating furnace having a nitrogen gas atmosphere to braze the straight tube portions of the zigzag tube and the side plates to the corrugated fins, and the zigzag flat tube to the two headers to fabricate an evaporator. Evaluation Test

The surfaces of the portions of the corrugated fin of each of the evaporators of Examples 1 to 4 and Comparative Example which portions were not brazed to the zigzag flat tube were checked for the amount of residual flux. Table 1 shows the results.

The amount of residual flux was measured by the method to be described below. Test pieces of J1S A1000 aluminum were degreased, a solution of polyvinyl alcohol in KCl was applied to the test pieces, the test pieces were then dried at 170° C for 3 minutes and K_α rays of the K were thereafter determined by X-ray fluorometry (diameter 30 mm) . This procedure was repeated by coating test pieces with varying amounts of KCl to determine the correlation between the intensity of X-rays and the amount of K. The correlation between the intensity of X-rays and KA1F₄ was then determined from this correlation. Fluorescent X-rays were projected onto the surfaces of the portions of the corrugated fin of each of the evaporators of Examples 1 to 4 and Comparative Example which portions were not brazed to the zigzag flat tube to measure the intensity of the rays. The amount of residual flux was determined from the intensity of X-rays based on the correlation between the intensity of X-rays and KA1F₄.

Furthermore the evaporators of Examples 1 to 4 and Comparative Examples were checked for the intensity of odor in an environment having a relative humidity of 90% and temperature of 20° C. The intensity of odor was measured by the following method.

The evaporator was checked for odor by at least five panelists suitable for the determination of odor, and the odor was rated on a scale of 1 to 5. The stronger the odor, the greater the value of rating. The average of the ratings given by all the panelists is taken as the intensity of odor.

Table 1 shows the results along with the amounts of flux applied. Table 1

The results given in Table 1 reveal that the evaporators of Examples 1 to 4 are smaller in the amount of flux residue and lower in the intensity of odor than the evaporator of Comparative Example. Furthermore, the results achieved by Examples 1 to 4 indicate that the process of the present invention has no correlation between the amount of flux applied and the amount of flux residue.

INDUSTRIAL APPLICABILITY

The evaporator of the invention is suitable for use in motor vehicle air conditioners wherein a chlorofluorocarbon refrigerant is used, or in those wherein a C0₂ refrigerant is used.

Claims

1. An evaporator comprising a refrigerant passing hollow body, and a fin brazed to an outer surface of the hollow body by the flux brazing method, the portion of the fin not brazed to the hollow body having a flux remaining on a surface thereof in an amount of 0.03 to 1 g/m².

2. An evaporator according to claim 1 wherein the flux remains on the surface of the portion of the fin not brazed to the hollow body in an amount of 0.05 to 0.5 g/m². 3. An evaporator according to claim 1 wherein the flux is a noncorrosive fluoride flux.

4. An evaporator according to claim 1 wherein the refrigerant passing hollow body comprises a flat tube bent zigzag, and the fin comprises a corrugated fin made of a brazing sheet having a brazing material layer on opposite sides thereof, the corrugated fin being disposed between and brazed to each adjacent pair of straight tube portions of the zigzag flat tube.

5. An evaporator according to claim 1 which comprises a plurality of straight flat tubes each constituting the refrigerant passing hollow body and wherein the fin comprises a corrugated finmade of a brazing sheet having a brazingmaterial layer on opposite sides thereof, the plurality of flat tubes being arranged in parallel as spaced from one another, the corrugated finbeing disposedbetween andbrazed to each adjacent pair of flat tubes.

6. An evaporator according to claim 1 which comprises a plurality of refrigerant passing hollow bodies each comprising two plates made of a brazing sheet having a brazing material layer on opposite sides thereof and brazed to each other at peripheral edge portions thereof, the two plates defining therebetween a bulging refrigerant channel and a bulging header-forming portion communicating with each of opposite ends of the refrigerant channel, the fin comprising a corrugated fin, the plurality of hollow bodies being stacked so that outer surfaces of the header-forming portions of each adjacent pair of hollow bodies are in contact with each other, the corrugated fin being arranged between the portions of each adjacent pair of hollow bodies corresponding to the respective refrigerant channels thereof and brazed to the hollow bodies.

7. An evaporator according to claim 1 which has been subjected to a treatment for imparting hydrophilic properties thereto.

8. A refrigeration cycle which comprises a compressor, a condenser and an evaporator and wherein a chlorofluorocarbon refrigerant is used, the evaporatorbeingan evaporator according to any one of claims 1 to 7. 9. A vehicle having installed therein a refrigeration cycle according to claim 8 as a motor vehicle air conditioner.

10. A process for fabricating an evaporator comprising preparing a flat tube bent zigzag and having a refrigerant passing channel inside thereof and a fin made of a brazing sheet having a brazing material layer on opposite sides thereof, applying a flux to an outer surface of the zigzag flat tube in an amount of 0.05 to 2.8 g/m², disposing the fin between each adjacent pair of straight tube portions of the zigzag flat tube, and brazing the fin to the zigzag flat tube.

11. A process for fabricating an evaporator according to claim 10 wherein the flux is applied to the flat tube in an amount of 1 to 2 g/m². 12. A process for fabricating an evaporator comprising preparing a plurality of straight flat tubes each having a refrigerant passing channel inside thereof and a fin made of a brazing sheet having a brazing material layer on opposite sides thereof, applying a flux to an outer surface of each of the flat tubes in an amount of 0.05 to 2.8 g/m², arranging the plurality of flat tubes in parallel as spaced from one another, disposing the fin between each adjacent pair of flat tubes, and brazing the fin to the flat tubes.

13. A process for fabricating an evaporator according to claim 12 wherein the flux is applied to the flat tube in an amount of 1 to 2 g/m².

14. A process for fabricating an evaporator comprising preparing plates each having a channel-forming bulging portion and a header-forming bulging portion bulging to a greater extent than the channel-forming portion and extending from each of opposite ends of the channel-forming portion and fins from a brazing sheet having a brazing material layer on opposite sides thereof; applying a flux is to opposite surfaces of each of the plates, with the amount of the flux applied to the outer surfaces of both the bulging portions of each plate adjusted to 0.05 to 2.8 g/m²; arranging the plates in stacked pairs each comprising the combination of two plates with openings of the bulging portions of each type opposed to each other in corresponding relation so that the outer surfaces of bottom walls of the header-forming bulging portions of adjacent pairs of plates are in contact with each other, and arranging the fins between the portions of respective adjacent pairs of plates corresponding to the channel-forming bulging portions thereof; brazing the twoplates in eachpairto each other alongperipheral edge portions thereof to form a refrigerant passing hollow body and brazing the fins to respective adjacent pairs of hollow bodies. 15. A process for fabricating an evaporator according to claim 14 wherein the flux is applied to the outer surfaces of both the bulging portions of each plate in an amount of

1 to 2 g/m².

16. A process for fabricating an evaporator according to any one of claims 10 to 15 wherein the flux is applied as suspended in water containing a binder.

17. A process for fabricating an evaporator according to any one of claims 10 to 15 wherein a corrugated fin is used as the fin. 18. -A process for fabricating an evaporator according to any one of claims 10 to 15 wherein the brazed assembly is finally subjected to a treatment for imparting hydrophilic properties thereto.