EP1027942A1

EP1027942A1 - Tube for heat exchanger and method of manufacturing same

Info

Publication number: EP1027942A1
Application number: EP98931008A
Authority: EP
Inventors: Soichi Zexel Corporation Kohnan Plant KATO; Muneo Zexel Corporation Kohnan Plant SAKURADA; Shin Zexel Corporation Kohnan Plant KURIHARA; Sadao Zexel Corporation Kohnan Plant HAIYA; Takashi Zexel Corporation Kohnan Plant SUGITA; Shoji Zexel Corporation Kohnan Plant AKIYAMA; Takahumi Zexel Corporation Kohnan Plant UMEHARA
Original assignee: Zexel Corp
Current assignee: Valeo Thermal Systems Japan Corp
Priority date: 1997-07-09
Filing date: 1998-07-08
Publication date: 2000-08-16
Also published as: WO1999002283A1; JPH1130493A; EP1027942A4

Abstract

To provide a tube for a heat exchanger, which is formed by folding a metal strip plate (P) into two and brazing joint portions (22), (22) formed at either end of the plate (P) in its breadth direction, and a groove (21a) is formed along a portion-to-be-folded (21') of the plate (P) in a longitudinal direction of the plate (P). Thus, the plate for the tube can be folded accurately and easily. As a result, brazing property is improved.

Description

FIELD OF THE INVENTION

The present invention relates to a tube for use in a heat exchanger and a method for producing it.

BACKGROUND OF THE INVENTION

A conventionally known heat exchanger has a plurality of tubes laminated with fins interposed between tubes and both ends of the tubes connected to communicate with header pipes, in which a medium is flowed to meander a plurality of times between inlet and outlet joints disposed on the header pipes.
It is known that the tubes used for the aforesaid type of heat exchanger are formed by roll forming, pressing or the like of a strip plate of metal such as an aluminum alloy and brazing its required portions.
Generally, the plate being used is a brazing sheet which has a brazing material clad on its entire surface, brazing of the required portions of the tubes and other required portions of the heat exchanger is performed by assembling the tubes, fins and header pipes into one body by means of a jig and the like and heating the assembled body by one operation.
For example, a tube 20 shown in Fig. 6 is formed by folding a strip plate into two and mutually brazing flat joint portions 22, 22 which are formed at both ends of the plate in its breadth direction. The plate is folded along a folding portion 21 at a predetermined curvature corresponding to a thickness of the tube 20, and the joint portions 22, 22 are formed to have a predetermined height corresponding to the thickness of the tube 20.
And, this tube 20 has beads 23 formed at appropriate intervals between the folding portion 21 and the joint portions 22, 22 of the plate by bending the plate to form recesses in order to improve pressure resistance and heat exchange efficiency of the tube 20. Namely, these beads 23, 23 have their tops brazed to opposed portions in the tube 20 to form a plurality of passages 24, 24 which are separated by the beads 23, 23 in the tube 20.
As described above, when a metal strip plate is folded to mutually braze the joint portions which are formed at either end of the plate in its breadth direction, it is necessary to securely braze the joint portions, and when the beads are formed, it is necessary to securely braze the bead tops with the opposed portions.
Specifically, since a failure of brazing of the joint portions and the beads causes a defect in fluid-tightness and pressure resistance of the tube, the function of the heat exchanger is heavily degraded. Therefore, it is important that the joint portions as well as the bead tops and their opposed portions are adjacent to each other so that they are securely brazed.
In practice, however, when the plate is folded, the folding portion of the plate may be displaced somewhat from a predetermined position or the resilience of the folding portion of the plate acts, for example, as shown in Fig. 7, so that displacement A between the joint portions 22, 22, gap B between the joint portions or gaps C between the tops of the beads 23 and their opposed portions are formed to typically cause a failure in brazing.
In view of the aforesaid drawbacks, it is an object of the present invention to provide a tube for a heat exchanger with brazing property improved by accurately folding a plate for forming the tube with ease and a method for producing it.

SUMMARY OF THE INVENTION

The invention recited in claim 1 is a tube for a heat exchanger which is formed by folding a metal strip plate into two and mutually brazing joint portions which are formed at either end of the plate in its breadth direction, wherein a groove is formed along a portion-to-be-folded of the plate in its longitudinal direction.
Thus, when the groove is formed at the portion-to-be-folded of the plate along its longitudinal direction, the plate can be folded more accurately and easily than before, so that brazing property at the joint portions can be improved, and a non-defective unit rate of the tube and the heat exchangers configured by using this tube can be improved.
Specifically, when the plate is folded, any displacement of the folding portion of the plate from a predetermined position displaces the joint portions, causing a failure of brazing of the joint portions. But, the present invention can control the position of the folding portion of the plate by means of the groove, so that the plate can be folded accurately. As a result, the joint portions can be prevented from being displaced, and a defect of brazing can be decreased.
This is because when the plate is folded, it is deformed starting from the position where the groove is formed, and accurate forming can be obtained.
When the plate is folded, a gap is formed between the joint portions due to the action of resiliency of the folding portion of the plate, causing a defect in brazing. But, since the plate of the present invention has the groove to decrease the thickness of the folding portion, the resiliency is decreased. Therefore, the plate can be folded easily, the joint portions can be prevented from separating from each other, thereby preventing a gap, which may cause a brazing failure, from being formed, and a brazing failure can be decreased.
Besides, when the bead tops are brazed with the opposed inside portions between the folding portion and the joint portions of the plate, the plate can be folded accurately and easily. Therefore, the brazing property at the joint portions can be improved, and the brazing property at the beads can also be improved.
The invention recited in claim 2 is the tube for a heat exchanger according to claim 1, wherein the vicinity of the folding portion of the plate is compressed before brazing the joint portions to decrease a radius of curvature of the folding portion of the plate.
Thus, when the vicinity of the folding portion of the plate is compressed before brazing the joint portions so to decrease a radius of curvature of the folding portion of the plate, the resiliency of the folding portion of the plate can be further decreased. As a result, the brazing property at the joint portions and the beads can be improved further.
According to this invention, where a heat exchanger is produced particularly by laminating a plurality of tubes, the heat exchanger can be prevented from being deformed in shape owing to the accumulation of imbalanced strength in the breadth direction of the respective tubes.
Specifically, where required portions of the assembled body of the plurality of tubes laminated were conventionally brazed, a pressing force applied from a jig or the like to the layer of tubes was not distributed properly because a strength of the tubes in their thickness direction was especially strong in the vicinity of the folding portion of the plate, and there was a problem of making it difficult to secure a balanced shape of the assembled body. But, the present invention can remedy such a problem and improve assembling property by compressing the vicinity of the folding portion of the plate to decrease a radius of curvature of the folding portion of the plate.
The invention recited in claim 3 is a method for producing a tube for a heat exchanger by folding a metal strip plate and mutually brazing joint portions which are formed at either end of the plate in its breadth direction, wherein a groove is formed at a portion-to-be-folded of the plate in its longitudinal direction.
Thus, when the groove is formed at the portion-to-be-folded of the plate along the longitudinal direction of the plate, the plate can be folded more accurately and easily, so that brazing property at the joint portions can be improved, and a non-defective unit rate of the tube and the heat exchangers configured by using this tube can be improved.
Specifically, when the plate is folded, any displacement of the folded portion of the plate from a predetermined position displaces the joint portions, causing a failure of brazing. But, the present invention can control the position of the folding portion of the plate by means of the groove, so that the plate can be folded accurately. As a result, the joint portions can be prevented from being displaced, and a defect of brazing can be decreased.
This is because when the plate is folded, it is deformed starting from the position where the groove is formed, and accurate forming can be obtained.
When the plate is folded, a gap is formed between the joint portions due to the action of resiliency of the folding portion of the plate, causing a defect in brazing, but the present invention has the groove to decrease the thickness of the folding portion so to decrease the resiliency. Therefore, the plate can be folded easily, and the joint portions can be prevented from being separated from each other, thereby preventing a gap, which may cause a brazing failure, from being formed, and a brazing failure can be decreased.
Besides, when the bead tops are brazed with the opposite inside portions between the folding portion and the joint portions of the plate, the plate can be folded accurately and easily. Therefore, the brazing property at the joint portions can be improved, and the brazing property at the beads can also be improved.
The invention recited in claim 4 is the method for producing a tube for a heat exchanger according to claim 3, wherein the vicinity of the folding portion of the plate is compressed before brazing the joint portions to decrease a radius of curvature of the folding portion of the plate.
Thus, when the vicinity of the folding portion of the plate is compressed before brazing the joint portions so to decrease a radius of curvature of the folding portion of the plate, the resiliency of the folding portion of the plate can be further decreased. As a result, the brazing property at the joint portions and the beads can be improved further.
According to this invention, where a heat exchanger is produced particularly by laminating a plurality of tubes, the heat exchanger can be prevented from being deformed in shape owing to the accumulation of imbalanced strength in the breadth direction of the respective tubes.
Specifically, where required portions of the assembled body of the plurality of tubes laminated were conventionally brazed, a pressing force applied from a jig or the like to the layer of tubes was not distributed properly because a strength of the tubes in their thickness direction was especially strong in the vicinity of the folding portion of the plate, and there was a problem of making it difficult to secure the assembled body in a balanced shape. But, the present invention can remedy such a problem and improve assembling property by compressing the vicinity of the folding portion of the plate to decrease a radius of curvature of the folding portion of the plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a front view to show a heat exchanger according to an embodiment of the invention;
Fig. 2 is an exterior view to show a tube for the heat exchanger according to the embodiment of the invention;
Fig. 3 is an exterior view to show folding of a plate according to the embodiment of the invention;
Fig. 4 is an exterior view to show a plate according to the embodiment of the invention;
Fig. 5 is an exterior view to show a tube for a heat exchanger according to another embodiment of the invention;
Fig. 6 is an exterior view to show a tube for a heat exchanger according to a conventional embodiment; and
Fig. 7 is an exterior view to show joint portions and beads with a plate folded according to the conventional embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the invention will be described in detail with reference to the drawings.
As shown in Fig. 1, a heat exchanger 1 of this embodiment has a plurality of tubes 2, 2, which are laminated with fins 5, 5 interposed between tubes connected to communicate with header pipes 3, 4 which are disposed at both ends of the tubes 2,2.
The header pipes 3, 4 are cylindrical pipes which have their top and bottom openings closed with blind caps 6, 6, their interiors being divided by partition plates 7, 7 which are disposed at predetermined positions, and provided with an inlet joint 3a to intake in a medium or an outlet joint 4a to externally discharge the medium. Tube insertion holes 9, 9 are formed at predetermined intervals along a longitudinal direction of each of the header pipes 3, 4. The tubes 2, 2 have their both ends inserted into and brazed to the tube insertion holes 9, 9. A side plate 8 is placed on the top and bottom of the stacked tubes 2, 2. The side plate 8 has its ends fixed to the header pipes 3, 4 to reinforce the structural strength of the heat exchanger.
By configuring as described above, the medium taken in through the inlet joint 3a is meandered a plurality of times to flow between the header pipes 3, 4 in a predetermined group unit of tubes 2 while heat exchanging, and discharged from the outlet joint 4a. And the heat exchange by the medium is promoted by an effect of heat radiation of the fins 5 interposed between the tubes 2 and also between the side plates 8.
Fig. 2 is an exterior view to show the tube 2, and Figs. 3, 4 are exterior views to show a plate P used to form the tube 2. As shown in these drawings, the tube 2 of this embodiment is formed by folding the strip plate P into two and mutuallyy brazing the joint portions 22, 22 formed at the ends of the plate P in its breadth direction. And, the outside form of a transverse cross section of the tube 2 is slightly smaller than the tube insertion holes 9, 9 of the header pipes 3, 4.
A portion-to-be-folded 21' of the plate P is formed a groove 21a in a longitudinal direction of the plate P, and the plate P is folded along the groove 21a at a predetermined curvature corresponding to a thickness of the tube 2. And, the portion-to-be-folded 21' of the plate P is determined as a folding portion 21 of the plate P.
A plurality of beads 23, 23 are formed at predetermined intervals between the folding portion 21 and the joint portions 22, 22 of the plate 9, and a plurality of passages 24, 24 divided by the beads 23, 23 are formed within the tube 2.
As a material for the plate P of this embodiment, an aluminum light alloy excelling in formability is used and its front and back surfaces are clad with a brazing material.
The joint portions 22, 22 and the beads 23, 23 are formed by bending the plate P by roll forming. The roll forming is performed by passing the plate P between rotary rolls with a predetermined shape disposed to oppose mutually.
The groove 21a is formed by forming the joint portions 22, 22 and the beads 23, 23 and thereafter pressing the surface of the plate P at its center in the breadth direction which is to be the inside of the tube 2 by a roll having a periphery in the shape of the groove 21a along the longitudinal direction of the plate P.
In this embodiment, the groove 21a has a transverse cross section in a V-shape and a depth of one half or below of a thickness of the tube 2. Namely, by appropriately determining the shape and depth of the groove 21a, weakening of the tube 2 involved in thinning the thickness of the plate P is suppressed to secure its strength.
And, the tube 2 is formed by further bending the plate P provided with the joint portions 22, 22, the beads 23, 23 and the groove 21a, by roll forming. Specifically, the tube 2 is formed by folding the plate P along the groove 21a, putting the joint portions 22, 22 together and also contacting the tops of the beads 23, 23 to the opposed positions. Since the groove 21a is formed, the plate P can be folded accurately and easily.
The tubes 2 formed as described above are integrally fitted to the header pipes 3, 4 and the fins 5, 5, and the assembled body is sent into a furnace and brazed by heat treatment. Specifically, the mutual joint portions 22, 22, and the tops of the beads 23, 23 and their opposed portions are brazed together with the tube insertion holes 9, 9 of the header pipes 3, 4 and respective required portions in contact with the fins 5, 5 by one operation.
And, since the groove 21a is filled with the flowed brazing material, pressure resistance to the medium at the folding portion 21 where the groove 21a is formed can be kept at a satisfactory level.
In this embodiment, the groove 21a is formed on the inside of the tube 2 but may be formed as a starting point for bending the plate P so to be formed on the outside surface of the tube 2. And, its transverse cross section is not limited to the V-shape, but may have a U-shape.
Thus, by forming the groove along the portion-to-be-folded of the plate in its longitudinal direction, the plate can be folded more accurately and easily. Therefore, the brazing property at the joint portions can be improved, and a non-defective unit rate of the tubes and the heat exchanger configured by using these tubes can be improved.
Specifically, when the plate is folded, any displacement of the folded portion of the plate from a predetermined position displaces the joint portions, causing a failure of brazing. But, the present invention can control the position of the folding portion of the plate by means of the groove, so that the plate can be folded accurately. Consequently, the joint portions can be prevented from being displaced, and a defect of brazing can be decreased.
This is because when the plate is folded, it is deformed starting from the position where the groove is formed, and accurate forming can be obtained.
Especially, the tube of this embodiment has the beads alternately formed from its top and bottom inner walls, and the plate before forming is formed into a horizontally asymmetrical shape with the folding portion at the center, so that a defective forming at the folding portion due to the asymmetrical shape can be prevented by the groove formed.
When the plate is folded, a gap is formed between the joint portions due to the action of resiliency of the folding portion of the plate, causing a defect in brazing them, but the present invention has the groove to decrease the thickness of the folding portion of the plate so to decrease the resiliency. Therefore, the plate can be folded easily, the joint portions can be prevented from separating from each other, thereby preventing a gap, which may cause a brazing failure, from being formed, and a brazing failure can be decreased.
Besides, when the bead tops are brazed with the opposed inside portions between the folding portion and the joint portions of the plate, the plate can be folded accurately and easily. Therefore, the brazing property at the joint portions can be improved, and the brazing property at the beads can also be improved.
Now, another embodiment of the invention shown in Fig. 5 will be described.
The tube 2 of this embodiment is formed after the vicinity of the folding portion of the plate is compressed before brazing the joint portions 22, 22 so to decrease a radius of curvature of the folding portion 21 of the plate. Specifically, compressed portions 25, 25 which have a tapered transverse cross section are formed in the vicinity of the folding portion 21 of the plate. These compressed portions 25, 25 are formed by roll forming. And other portions of the tube are configured in the same way as in the previous embodiment, so that their description is omitted.
Thus, when the vicinity of the folding portion of the plate is compressed before brazing the joint portions so to decrease a radius of curvature of the folding portion of the plate, the resiliency of the folding portion of the plate can be further decreased. As a result, the brazing property at the joint portions and the beads can be improved further.
According to this embodiment, where a heat exchanger is produced particularly by laminating a plurality of tubes, the heat exchanger can be prevented from being deformed in shape owing to the accumulation of imbalanced strength in the breadth direction of the respective tubes.
Specifically, where required portions of the assembled body of the plurality of tubes laminated were conventionally brazed, a pressing force applied from a jig or the like to the layer of tubes was not distributed properly because a strength of the tubes in their thickness direction was especially strong in the vicinity of the folding portion of the plate, and there was a problem of making it difficult to secure the assembled body in a balanced shape. But, this embodiment can remedy such a problem by compressing the vicinity of the folding portion of the plate to decrease a radius of curvature of the folding portion of the plate and improve assembling property.

INDUSTRIAL APPLICABILITY

The present invention provides a tube with its brazing property improved by bending a plate for the tube accurately and easily and a method for producing it. The invention is applied to a general radiator and evaporator and also to a condenser required to have a pressure resistance.

Claims

A tube for a heat exchanger which is formed by folding a metal strip plate into two by roll forming and mutually brazing joint portions which are formed at either end of the plate in its breadth direction, wherein:

a groove is formed at a portion-to-be-folded of the plate in a longitudinal direction of the plate by roll forming, and the plate is folded along the groove by roll forming.
A tube for a heat exchanger according to claim 1, wherein the vicinity of the folding portion of the plate is compressed by roll forming before brazing the joint portions to decrease a radius of curvature of the folding portion of the plate.
A method for producing a tube for a heat exchanger by bending a metal strip plate by roll forming and mutually brazing joint portions which are formed at either end of the plate in its breadth direction, comprising the steps of:

forming a groove at a portion-to-be-folded of the plate in a longitudinal direction of the plate by roll forming.
A method for producing a tube for a heat exchanger according to claim 3, further comprising the steps of compressing the vicinity of the folding portion of the plate by roll forming before brazing the joint portions to decrease a radius of curvature of the folding portion of the plate.