AU615787B2

AU615787B2 - A process for producing brazeable pipes and a process for producing heat exchangers using the brazeable pipes

Info

Publication number: AU615787B2
Application number: AU40291/89A
Authority: AU
Inventors: Ryoichi Hoshino; Hideyuki Kobayashi; Noboru Kodachi; Tutomu Motohashi; Mitsuru Nobusue; Hironaka Sasaki
Original assignee: Showa Aluminum Corp
Current assignee: Resonac Holdings Corp
Priority date: 1988-07-14
Filing date: 1989-08-25
Publication date: 1991-10-10
Anticipated expiration: 2009-08-25
Also published as: AU4029189A

Description

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6 1578 FORM 10 F 7f: 105618 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int Class So Complete Specification Lodged: Accepted: Published: Priority: Related Art: Name and Address of Applicant: o a a B 4 C' Showa Aluminum Kabushiki Kaisha 224-banchi Kaizancho 6-cho Sakaishi Osaka

JAPAN

Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Males, 2000, Australia Address for Service: S Complete Specification for the invention entitled: 0 0 A Process for Producing Brazeable Pipes and a Process for Producing Heat Exchangers using the Brazeable Pipes The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/3

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ABSTRACT

A process for producing brazeable pipes particularly for use in heat exchangers, the process comprising preparing a brazing sheet which comprises a core sheet coated with a brazing substance at least on one surface, forming a bulged portion of a semicircular cross-section in the central section of the brazing sheet, providing apertures in the bulged portion for insertion of the ends of the tubes, and ;S rolling the brazing sheet into a cylinder with its opposite ends being butt jointed to each other.

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C IEl(fC1-_--*~i A process for producing brazeable pipes and a process of producing heat exchangers using the brazeable pipes The present invention relates to the production of brazeable pipes particularly for use as headers in heat exchangers such as condensers, evaporators, and radiators in automobile air conditioning systems.

A heat exchanger includes cylindrical headers which introduce a cooling medium into the tubes and 0 discharge it after it has circulated throughout the tubes. The cylindrical headers, hereinafter referred to as header pipes, are made by rolling a brazing sheet into a cylinder. The brazing sheet is made of a core sheet coated with a brazing substance on one or both surfaces. The headers, the tubes and other components such as fins are brazed to one another at o *vacuum or with the use of flux.

The header pipes are produced in the following manner: The brazing sheet is prepared and rolled until its both ends are butted. The butted ends are electrically welded to form a seamed pipe as a whole.

Then a given number of holes are made in the header pipe for allowing the connection of tubes therein.

To make the holes a punching pressure is applied to the header pipes, but under the pressure the pipes are in danger of crushing or deforming because of the 1A- L i r relatively weak welded seams. To avoid such problems, the holes are made by a milling. The milling unavoidably produces flashes, so that the trimming of flashes is required. This is a time- and laborconsuming work. In order to keep the header pipes tough the holes must be off the welded seam. It is required in each milling operation to ascertain whether or not the spot to be holed is off the welded seam.

Accordingly an object of the present invention is to provide a process for producing brazeable pipes particularly for use as header pipes without the possibility of crush and deformation.

Another object of the present invention is to provide a process for producing brazeable pipes which enables easy removal of flashes possibly caused in milling the holes.

A further object of the present invention is to provide a process for producing brazeable pipes having holes produced off the seam.

Other objects and advantages of the present e invention will become more apparent from the following detailed description, when taken in conjunction with the accompanying drawings which show, for the purpose of illustration only, one embodiment in accordance with the present invention.

These objects of the present invention is achieved by providing a process for producing -2- i- _I brazeable pipes particularly for use in heat exchangers, the process comprising preparing a brazing sheet which comprises a core sheet coated with a brazing substance at least on one surface, forming a bulged portion of a semi-circular cross-section in the 1 central section of the brazing sheet, providing apertures in the bulged portion for insertion of the ends of the tubes, and rolling the brazing sheet into a cylinder with its opposite ends being butt jointed to each other.

A specific embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 is a perspective view showing a header pipe produced according to the present invention; Fig. 2 is a front view showing the header pipe; Fig. 3 is a front view showing a heat exchanger assembled by using the header pipes of Fig. 1; Fig. 4 is a plan view of the heat exchanger of SFig. 3; Fig. 5 is a cross-sectional view on an enlarged i n o scale taken along the line V-V in Fig. 3; Fig. 6 is an exploded perspective view showing the header pipe, tubes and corrugated fins; Fig. 7 is a cross-sectional view on an enlarged scale taken along the line I-W of Fig. 3; Fig. 8 is a cross-sectional view showing on an enlarged scale showing the butt joint between the -3- 3_gtL L i header walls; Fig. 9 is a cross-sectional view showing on an enlarged scale showing a deformation occurring in the seam; Fig. 10 is an exploded perspective view of a header and a cap; Fig. 11 is a partly cross-sectional front view showing the header and the cap jointed together; Fig. 12 is a perspective view showing a brazing sheet shown in Fig. 1; Fig. 13 is a cross-sectional view on an enlarged scale taken along the line Xm-Xm in Fig. 12; c: Fig. 14 is a perspective view showing the brazing sheet having slits at opposite sides for insertion of partitions; Fig. 15 is a cross-sectional view on an enlarged scale showing the brazing sheet whose ends become slanted; Fig. 16 is a perspective cross-sectional view on an enlarged scale showing the brazing sheet having a bulged portion; Fig. 17 is a perspective cross-sectional view on s o" an enlarged scale showing the brazing sheet whose bulged portion has slits for insertion of the tubes; Fig. 18 is a side view on an enlarged scale showing chamfered edges of the slits shown in Fig. 17; Fig. 19 is a perspective view showing the brazing sheet of Fig. 17 which is bent in U-shape; -4- ~ib i_ i i Fig. 20 is a perspective view showing a heat exchanger incorporating a modified header pipe; Fig. 21 is a perspective view showing the heat exchanger of Fig. 20 in which the header and the tubes are separated; Fig. 22 is a perspective view on an enlarge scale showing the header pipe of Fig. 21; and Fig. 23 is a cross-sectional perspective view on an enlarged scale showing the brazing sheet in process of making the header pipe of Fig. 21.

Fig. 24 is a cross-sectional view on an enlarged scale showing a modified example of the brazing sheet, particularly to show the butt joint between the pipe walls; Fig. 25 is a cross-sectional view showing the brazing sheet of Fig. 24; Fig. 26 is a perspective view showing a modified n example of the header pipe; and Fig. 27 is a cross-sectional plan view on an enlarged scale showing the brazing sheet of Fig. 26, particularly to show the butt joint between the pipe walls.

As shown in Figs. 3 to 7 the illustrated embodiment is applicable to an aluminum heat exchangers as condensers for automobile air conditioning systems. Herein the aluminum includes aluminum-base alloy, and the "circular" includes elliptic.

1 1- Referring to Figs. 3 to 7, the heat exchanger has a plurality of flat tubes 1 stacked one above another, corrugated fins 2 sandwiched between the tubes 1, and header pipes 3, 4 connected to the ends of the tubes 1 such that cooling medium paths are formed in zigzag patterns through the header pipes 3, 4 and the tubes 1.

The tubes 1 are made of aluminum extrusion.

Alternatively they can be made of multi-bored pipes, commonly called "harmonica" tubes. The bores provide coolant medium paths. Or else, they can be made of electrically seamed pipes. The corrugated fins 2 have the same width as that of the tubes 1 and are brazed thereto. The corrugated fins are also made of aluminum, anct preferably provided with louvers on their surfaces.

The headers 3, 4 are cylindrical having apertures 13 for allowing the insertion of the tubes 1. As shown in Fig. 7, the tubes 1 are insertedly brazed in the apertures 13. The reference numeral 15 denotes fillets. As shown in Fig. 3, the left-hand header 3 is connected to an inlet 5 through which a cooling medium is taken in, and the right-hand header 4 is connected to an outlet 6 through which the used 4 cooling medium is discharged outside. The headers 3, 4 are covered with caps 7, and 8, respectively. The inner space of the header 3 is equally divided into two sections by a partition 9. The inner space of the header 4 is unequally divided into two sections by a -6- 6 partition 10 disposed below the center of the header 4. A cooling medium is introduced into the header 3 through the inlet 5, and is discharged through the outlet 6. While the cooling medium flows from the inlet 5 to the outlet 6, heat exchanges between the cooling medium and air passing through the corrugated fins 2. The air is introduced through the corrugated fins 2 in the direction in Fig. 5. In this way the air condenses. The used cooling medium is j discharged through the outlet 6. The reference numerals 11 and 12 denote side plates fixed to the 4 outermost fins 2.

The header pipes 3, 4 are made in the following manner: Referring to Figs. 3 to 7, a brazing sheet 30 is prepared by coating an aluminum core sheet 30a with a brazing substance to form a layer 30b. The brazing substance is aluminum-silicone alloy containing about 6.0% to 13% Si. In this specification the percentage is represented in terms of weight unless specified to o the contrary.

SAs shown in Fig. 14, the brazing sheet 30 is provided with a desired number of slits 34 at opposite sides, wherein the pair of slits 34 are symmetrical with respect to the lengthwise axis. Each pair of opposite slits 34 constitute a slit 14 for receiving the partitions 9 and 10 when the brazing sheet 30 is I rolled into the header pipe 3, 4.

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i 1 i Referring Fig. 15, each end of the brazing sheet is slanted at 35a', 35b' which are also covered with the brazing layer 30b. As shown in Figs. 7 and 8, the opposite slanted ends 35a' and 35b' are butted and brazed, thereby forming a seam 31 therebetween.

The advantage of the slanted ends 35a' and 35b' is that their contact area becomes larger than when both ends have straight faces, thereby securing the liquidtight joint.

After the slits 34 are made in the brazing sheet the central portion thereof is lengthwise pressed so as to give a bulged portion 36 and two horizontal portions 38 shaped like wings, hereinafter referred to as wing portions. The bulged portion 36 has a semicircular cross-section.

Then the brazing sheet 30 is provided with apertures 13 produced by means of a punching die and mold. The apertures 13 receive the tubes 1. By being backed up by the mold the bulged portion 36 is prevented from becoming crushed or deformed, thereby producing the apertures 13 at required places to a precise dimension. Instead of the press a milling can be used. Flashes, if any, can be trimmed from the inner side of the bulged portion 36.

Preferably, each aperture 13 is chamfered so as to allow the smooth insertion of the tube 1. In Fig.

18 the reference numeral 37 denotes chamfered edges.

When necessary, the surface of the brazing sheet -8- L_ i i L U I is flattened. Then the wing portions 38 are straightened as shown in Fig. 19 until the whole configuration has a U-shape cross-section. Finally the U-shape brazing sheet 30 is rolled into a cylinder in which the slanted ends 35a', 35b' are butted complementarily to the thickness of the brazing sheet shown in Fig. 7. The butted ends 35a', 35b' of the brazing sheet 30 are brazed to each other in a brazing furnace at the same time when the headers, the tubes and the fins are brazed together.

In constructing a heat exchanger the ends of the tubes 1 are inserted into the apertures 13 of the header pipes 3, 4 as shown in Fig. 7. The corrugated fins 2 are sandwiched between the tubes 1, and the partitions 9, 10 are inserted into the slits 14 of the header pipes 3, 4. The outermost fins are respectively provided with the side plates 11, 12.

The tubes 1, the fins 2, the header pipes 3, 4, the partitions 9, 10, the side plates 11, 12 and the the inlet pipe 5, and the outlet pipe 6 are provisionally assembled, and placed in a brazing furnace. In this way the mass brazing is effected. Preferably, the fins 2 are also made of brazing sheets, that is, a f core sheet coated with a brazing substance, so that the fins 2 can be jointed to the tubes 1. As shown in Fig. 7, the tube 1 is liquidtightly jointed to the header pipe 3, 4 with fillets 15. The ends 35a', of the brazing sheet 30 are butted complementarily to 9 the thickness of the brazing sheet 30, wherein the seams 31 are flush with the wall surfaces of the header pipes 3, 4.

The open ends of the headers 3, 4 are covered with the caps 7, 8. As shown in Figs. 10 and 11, each cap 7, 8 has a relatively thick bottom and a tapered side wall. The tapered side wall becomes progressively thin so that the terminating edge of the cap keeps contact with the wall surface of the header pipe without steps therebetween. The cap 7, 8 is also C 0 ,effective to prevnt the header pipe 3, 4 from expanding or deforming by heat involved in the brazing operation. When the heat exchanger is used as a condenser, the caps 7, 8 are effective to prevent the header pipes 3, 4 from exploding owing to the build-up of internal pressure.

Figs. 20 and 21 show a heat exchanger used as a heat exchanger for automobile air conditioning system.

The heat exchanger incorporates header pipes 3, 4 produced under the present invention. The heat exchanger comprises a multi-bored tube corrugated fins 2 sandwiched between the walls of the tube an inlet header pipe 3' and an outlet header pipe 1 As shown in Fig. 23, the header pipes 4' are respectively provided with bulged portions 36' in which a slit 13' is made for receiving the single tube i The other parts of the heat exchanger are made I and assembled in the same manner with the first 10 1 i .ik I example described above. Throughout Figs. 20 to 23 like reference numerals refer to like and corresponding parts. Brazing is effected in the same manner. A cooling medium is introduced into the tube 1 through the inlet pipe 5' and discharged through the outlet pipe The header pipes 3' and 4' are respectively closed by caps 7' and respectively.

The caps 7' and 8' are also effective to prevent the seams of the header pipes 4' from becoming separated owing to heat involved in the brazing operation.

Figs. 23 and 24 show a further modification of the brazing sheet which have step ends 35a" and The stepped ends 35a" and 35b" of the sheet 30' are butted to each other so as to be complementary to the thickness of the brazing sheet 30'. The stepped ends and 35b" can be formed in the known manner such as by a press or a hammer. In Figs. 24 and 25 the reference numerals 30a', 30b' and 31' denote a core sheet such as aluminum sheet, a brazing substance layer, and a seam, respectively.

Figs. 26 and 27 show a further modification of the brazing sheet, characterized in that one end 43 of the brazing sheet is bent in the form of a hook and the other end is bent in the form of letter L, which consists of a first leg 40 and a second leg 41. The first leg 40 and the second leg 41 form a step 42, which allows the other end 43 to rest on. The two 11t^.

bent ends are butted and joined in a complementary manner as shown in Fig. 27. The advantage of these end configurations is that if the header 3, 4 softens and elongates owing to heat involved in brazing as shown by chain lines in Fig. 27, the first leg 40 and the portion 43 elongate together with maintaining the seam 31. In Figs. 26 and 27 the reference numerals 30b", 13", and 14" denote a core sheet, brazing substance layer, slits for insertion of the tubes, and the partitions 9 and In the illustrated embodiment the headers 3, 4 are coated with a brazing substance on both surfaces, but they can be coated on one surface.

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Claims

2. A process for producing brazeable pipes, the process uo' comprising: preparing a brazing sheet which comprises a core sheet coated with a brazing substance at least on one surface, forming a bulged portion of a semi-circular cross-section in the brazing sheet, providing apertures in the bulged portion for insertion of tube ends, and rolling 0om the brazing sheet into a cylinder with its opposite ends being butt jointed to each other.
3. A process as defined in claim 2, wherein the apertures are oo provided in the direction of circumference of the bulged portion.
4. A process as defined in claim 2, wherein the apertures are o provided in the direction of the length of the brazing sheet. oo A process as defined in claim 2, wherein the apertures are produced by means of a press against an external chill placed in contact with the surface of the bulged portion.
6. A process as defined in claim 2, wherein the apertures are produced by means of milling. S7. A process as defined in claim 2, wherein the brazing sheet has its ends slanted so that when the brazing sheet is rolled into a cylinder, the slanted ends coated with a brazing substance are butt Sjointed complementary to the thickness of the brazing sheet so as to form seams flush with the walls of the rolled cylinder. S8. A process for producing brazeable pipes, the process comprising: preparing a brazing sheet which comprises a core sheet 13 Y P STA/1601N coated with a brazing substance at least on one surface, forming a bulged portion of a semi-circular cross-section in the brazing sheet, providing apertures in the bulged portion for insertion of tube ends, rolling the brazing sheet into a cylinder with its opposite ends being butt jointed to each other, and covering at least one of the open ends of the rolled cylinder with a cap. DATED this TENTH day of JULY 1991 Showa Aluminum Kabushiki Kaisha t00000o 00, 00 0 o tt Patent Attorneys for the Applicant SPRUSON FERGUSON Sa 0 0 o0 14 STA/1601W A