EP1952904A2 - Forming process and forming device for the production of a fold in a heat exchanger tube - Google Patents

Abstract

The method involves bending and compressing corner seams (4) of a metal strip (1) in three bending stages and two compression stages by using upper and lower rollers. A chamfer is impressed at a free end of the corner seams in the compression stages. A ring groove of the rollers is provided for deforming the corner seams, and the rollers are emanating from groove flanks. A wedge-shaped opening is provided between the corner seams and the groove flanks. An intermediate space is provided at an inner side of the corner seams. An independent claim is also included for a deformation device for manufacturing corner seams for a heat exchanger pipe.

Description

The invention relates to a forming method for producing a Eckfalzes for heat exchanger tubes with at least two Rohrkammem, wherein the Eckfalz is bent and compressed by means of rollers. The invention further relates to a forming device with an upper or lower roller, which has an annular groove with a groove bottom for forming the Eckfalzes, emanating from the two groove edges. The invention further relates to a heat exchanger tube with a Eckfalz.

From the European patent application EP 0 829 316 A2 For example, a roll forming method is known for forming a flat tube having a corner fold which is reshaped and compressed in two stages.

The object of the invention is to optimize the geometry of heat exchanger tubes in the region of the Eckfalzes, in particular with regard to the solderability.

The object is in a forming process for producing a Eckfalzes for heat exchanger tubes with at least two Rohrkammem, wherein the Eckfalz is bent and compressed by means of rollers, achieved in that the Eckfalz is bent and compressed in at least three, especially five, stages. In the forming process according to the invention are Contrary to the trend to reduce tooling costs, consciously accepting higher tooling costs. As a result, the forming result can be unexpectedly improved significantly. In addition, the tool wear can be reduced because the abrasion is reduced by the at least three forming stages. In addition, the Schmierrnitteleinsatz can be limited, whereby the effort in post-processing, for example, when degreasing the surfaces to be soldered, is reduced.

A preferred embodiment of the forming process is characterized in that the Eckfalz is bent in at least two, in particular three, pure bending steps and compressed in at least one, in particular two, pure compression stages. In the pure bending stages, the seam height is kept constant. In the pure compression stages, the bending angle of the Eckfalzes is not changed.

A further preferred embodiment of the forming process is characterized in that the corner fold is in each case both bent and compressed in several bending and compression stages. In the combined bending and compression stages, the rebate height during bending is reduced.

A further preferred embodiment of the forming process is characterized in that in at least one forming stage, in particular a pure upsetting step, a bevel is impressed on the free end of the Eckfalzes. By embossing the bevel, the removal of the Eckfalzes is simplified.

In a forming device for producing a Eckfalzes for heat exchanger tubes with at least two Rohrkammem, wherein the Eckfalz is bent and compressed by means of rollers, with an upper or lower roller, which has an annular groove with a groove bottom for forming the Eckfalzes, emanating from the two groove flanks, the above-stated object is achieved in that between the Eckfalz and one of the groove flanks, viewed in cross section through the Eckfalz, a substantially wedge-shaped gap is provided, which widens, based on the upper roller to the outside. The intermediate space facilitates the removal of the Eckfalzes.

A further preferred embodiment of the forming device is characterized in that the intermediate space is provided on the inside of the Eckfalzes. This allows a good support of Eckfalzes on the outside.

Another preferred embodiment of the forming device is characterized in that the groove bottom is inclined to the intermediate space. Thereby, an undesired buckling of the Eckfalzes be prevented in the gap.

The invention also relates to a heat exchanger tube having one with a Eckfalz, which has been prepared by a previously described forming process and in particular with a previously described forming device.

Figur 1

einen Blechstreifen mit einem Eckfalz, der in fünf Umformstufen gebogen und gestaucht wird;

Figur 2

einen Ausschnitt eines erfindungsgemäßen Wärmetauscherrohrs mit zwei Eckfalzen vor dem Verlöten;

Figur 3

einen ähnlichen Ausschnitt wie in Figur 2 mit einer durchgängigen Plattierschicht;

Figur 4

einen ähnlichen Ausschnitt wie in Figur 2 mit angeschrägten Falzenden nach dem Verlöten;

Figur 5

den gleichen Ausschnitt wie in Figur 4, wobei die Falzenden in einer anderen Richtung angeschrägt sind;

Figur 6

einen ähnlichen Ausschnitt wie in Figur 4;

Figur 7

ein Wärmetauscherrohr mit zwei Rohrkammem im Querschnitt;

Figur 8

ein ähnliches Wärmetauscherrohr wie in Figur 7 mit vier Rohrkammern;

Figur 9

ein Werkzeug mit einer Oberrolle und einer Unterrolle einer ersten Umformstufe;

Figur 10

ein Werkzeug mit einer Oberrolle und einer Unterrolle einer zweiten Umformstufe;

Figur 11

ein Werkzeug mit einer Oberrolle und einer Unterrolle einer dritten Umformstufe;

Figur 12

ein Werkzeug mit einer Oberrolle und einer Unterrolle einer vierten Umformstufe;

Figur 13

eine ähnliche Darstellung wie in Figur 12 und

Figur 14

ein Werkzeug mit einer Oberrolle und einer Unterrolle einer vierten Umformstufe gemäß einem weiteren Ausführungsbeispiel.

Further advantages, features and details of the invention will become apparent from the following description in which, with reference to the drawings, various embodiments are described in detail. Show it:

FIG. 1

a sheet metal strip with a corner fold, which is bent and compressed in five forming steps;

FIG. 2

a detail of a heat exchanger tube according to the invention with two Eckfalzen before soldering;

FIG. 3

a similar section as in FIG. 2 with a continuous plating layer;

FIG. 4

a similar section as in FIG. 2 with beveled fold ends after soldering;

FIG. 5

the same section as in FIG. 4 wherein the fold ends are chamfered in a different direction;

FIG. 6

a similar section as in FIG. 4 ;

FIG. 7

a heat exchanger tube with two Rohrkammem in cross section;

FIG. 8

a similar heat exchanger tube as in FIG. 7 with four tube chambers;

FIG. 9

a tool with an upper roller and a lower roller of a first forming stage;

FIG. 10

a tool with an upper roller and a lower roller of a second forming stage;

FIG. 11

a tool with an upper roller and a lower roller of a third forming stage;

FIG. 12

a tool with an upper roller and a lower roller of a fourth forming stage;

FIG. 13

a similar representation as in FIG. 12 and

FIG. 14

a tool with an upper roller and a lower roller of a fourth forming stage according to another embodiment.

In FIG. 1 are five forming steps or steps 1 to 5 for producing a sharp Eckfalzes shown below each other. A sheet metal strip 1 has the shape of a rectangular plate 2, from which a Eckfalz 4 is bent at right angles. The sheet metal strip 1 has a thickness S. In the first forming step, the corner fold 4 is bent by an angle of about 30 degrees. The length of Eckfalzes 4 is designated x1. In the second forming step, the corner fold 4 is bent over approximately 40 degrees. The length of Eckfalzes 4 is designated x2. In the third forming step, the corner fold 4 is bent over by a further 20 degrees. The length of Eckfalzes 4 is denoted by x3.

After the third forming step, the corner fold 4 is arranged at an angle of 90 degrees to the rectangular plate 2. The width of the rectangular plate 2 is denoted by L3. In the fourth forming step, the corner fold 4 is compressed and, if necessary, the width of the rectangular plate 2 is reduced. In addition, the free end of Eckfalzes 4 is bevelled α at an angle. The length of Eckfalzes 4 is denoted by x4. The width of the rectangular plate 2 is denoted by L4. In the fifth forming step, the corner fold 4 and optionally the width of the rectangular plate 2 are further reduced. The length of Eckfalzes 4 is designated x5. The width of the rectangular plate 2 is indicated by L5. In addition, the free end of Eckfalzes 4 is further bevelled, as indicated by an angle β.

In the three forming stages 1 to 3 of the corner fold 4 is bent. The leg height x1 to x3 of the Eckfalzes 4 is preferably kept constant in order to form a sharp corner Falzecke. However, the leg height can also already be reduced in the forming stages 1 to 3 as a function of the ratio of the finished seam height x5 to the pipe wall thickness S from stage to stage. In the forming steps 4 and 5, the fold is calibrated at least once. During the calibration either the width L3 to L5 is reduced and the seam height is kept constant, or the width L3 to L5 is kept constant and the seam height x3 to x5 is reduced. It is also possible to reduce the folding height x and the width L together. The optimum geometry depends on the processing properties of the pipe strip 1 and the ratio of the pipe wall thickness to the finished seam height.

In the calibration stages 4 and 5, a bevel is impressed on the strip edge at the free end of the corner fold 4. The embossing of the slope allows a top roller contour, in which the rebate width are recessed and therefore can be better demolded. The slope is inclined at an angle α, β so that it presses the fold on the vertical roller wall, on which the fold 4 can be supported. As a result, an undesired buckling of the Eckfalzes 4 can be prevented on the free, not supported folded side. This in turn means that the corner fold 4 can be compressed more strongly and thus can be formed with a sharp-edged shape, without any demolding problems between the roll and the fold.

In FIG. 2 is a section of a tube 10 shown in cross section. The tube 10 is a flat tube of a heat exchanger. The tube 10 comprises a tube wall piece 11 which has substantially the shape of a rectangular plate. In addition, the tube 10 comprises two further tube wall pieces 12 and 13, which are arranged parallel to the tube wall piece 11. Of the pipe wall pieces 12 and 13, a Eckfalz 14, 15 is bent at right angles. The free ends of the Eckfalze 14 and 15 are soldered to the pipe wall piece 11. As a result of this design of the corner folds 14 and 15, two tube chambers 16 and 17 are formed in the tube 10. The pipe wall thickness is denoted by S. The pipe wall thickness in the region of the bend of the Eckfalze is designated by x. The outer radius in the region of the bend of the Eckfalzes 14, 15 is denoted by R. The finished leg height of Eckfalzes 14, 15 is designated by xF. According to one aspect of the invention, the thickness x in the region of the bend is greater than or equal to the pipe wall thickness S. In addition, the radius R according to a further aspect of the invention is smaller than the pipe wall thickness S.

In FIG. 3 is indicated that the tube wall pieces 12 and 13 are internally provided with a continuous cladding layer 18, 19. The tube wall piece 11 is also provided with a plating layer 20. The plating layers 18 to 20 are integrally connected to each other. Thus, the Rohrwandkammem 16, 17 are provided inside with a complete Schutzplattierung. This increases the corrosion resistance. To improve the soldering, in particular solder plating is provided instead of or in addition to protective plating.

In FIG. 4 it can be seen that the free ends 24 and 25 of the Eckfalze 14 and 15 are each beveled at an angle β. Characterized a wedge-shaped gap is formed between the free ends 24 and 25 and the pipe wall piece 11, which widens to the associated pipe wall chamber 16, 17 out. The Eckfalze 14 and 15 are soldered together on their outer side. Furthermore, the free ends 24 and 25 of the Eckfalze 14 and 15 are soldered to the pipe wall piece 11.

In FIG. 5 is indicated that the free ends 28 and 29 of the Eckfalze 14 and 15 may be chamfered in the opposite direction, as indicated by an angle γ. At the in FIG. 5 illustrated embodiment results from the bevels of the free ends 28 and 29 is a substantially triangular space between the pipe wall piece 11 and the free ends 28, 29 of the corner seams 14, 15. This gap is filled with solder. Due to the beveled or bevelled fold ends, as in the FIGS. 4 and 5 is shown, the wettability of the Falzverbindung with solder improved.

In FIG. 6 is a similar representation as in FIG. 4 shown. The folding ends are bevelled by an angle γ. At 32 it is indicated that at the Falzkalibrierung a burr may arise. However, this burr does not adversely affect the quality of the heat exchanger tube 10.

In FIG. 7 the heat exchanger tube 10 is shown completely in cross section. In FIG. 7 it can be seen that the pipe wall pieces 12 and 13 are integrally connected to the pipe wall piece 11.

In FIG. 8 a heat exchanger tube 40 is shown in cross section having four Rohrkammem.

In FIG. 9 a section of an upper roller 41 is shown in section, which is rotatable about a rotation axis 42. Furthermore, a lower roller 43 is shown in section, which is rotatable about a rotation axis 44. Between the upper roller 41 and the lower roller 43, a sheet metal strip 1 is arranged, which has the shape of a rectangular plate 2, from which a Eckfalz 4 is bent. The length of Eckfalzes 4 is designated x1. FIG. 9 corresponds to the forming stage 1 in FIG. 1 ,

FIG. 10 corresponds to the forming stage 2 in FIG. 1 , The metal strip 1 is arranged between an upper roller 45 and a lower roller 46.

FIG. 11 corresponds to the forming step 3 in FIG FIG. 1 , The metal strip 1 is arranged between a further upper roller 47 and a further lower roller 48.

In FIG. 12 a calibration step is indicated. The metal strip 1 is arranged between an upper roller 51, which is rotatable about a rotation axis 52, and a lower roller 53, which is rotatable about a rotation axis 54. The upper roller 51 is provided with an annular groove in which the Eckfalz 4 is arranged. The corner fold 4 rests with its outer side against the upper roller 51. Between the inside of Eckfalzes 4 and the upper roller 51, a wedge-shaped gap 57 is provided which widens to the rectangular plate 2 out.

In FIG. 13 is the metal strip 1 between an upper roller 61 which is rotatable about a rotation axis 62, and a lower roller 63 which is rotatable about a rotation axis 64. At the in FIG. 13 illustrated embodiment, the annular groove in which the Eckfalz 4 is arranged, wider than in the previous embodiment. This creates between the inside of Eckfalzes 4 and the upper roller 61, a gap 67 which is larger than in the previous embodiment. This has the consequence that at the free end of Eckfalzes 4 burr fi8 can arise. However, this ridge 68 does not affect the solder joint between the corner fold 4 and the associated pipe wall piece (11 in FIG. 2 ).

In FIG. 14 is the 131echstreifen 1 between an upper roller 71 which is rotatable about a rotation axis 72, and a lower roller 73 which is rotatable about a rotation axis 74. The free end of Eckfalzes 4 is angled in the opposite direction by an angle γ as in the previous embodiments. In addition, the annular groove, in which the Eckfalz 4 is arranged, formed so that the Eckfalz 4 rests with its inner side on the upper roller 71. Between the outside of Eckfalzes 4 and the upper roller 71, a wedge-shaped gap 77 is formed, which widens to the lower roller 73 out.

Claims (8)

Forming method for producing a corner fold (4, 14, 15) for heat exchanger tubes (10, 40) having at least two tube chambers (16, 17), wherein the corner fold is formed by means of rollers (41, 43, 45, 46, 47, 48, 51 , 53, 61, 63, 71, 73) are bent and compressed, characterized in that the corner fold (4, 14, 15) is bent and compressed in at least three, in particular five, steps. Forming method according to claim 1, characterized in that the Eckfalz (4; 14,15) is bent in at least two, in particular three, pure bending steps and in at least one, in particular two, pure compression step (s) is compressed. Forming method according to one of the preceding claims, characterized in that the Eckfalz (4; 14,15) in both bending and compression stages each both bent and compressed. Forming method according to one of the preceding claims, characterized in that in at least one forming step, in particular a pure upsetting step, a bevel is impressed on the free end (24, 25; 28, 29) of the corner fold (14, 15). Forming device for producing a Eckfalzes for heat exchanger tubes (10; 40) with at least two Rohrkammem (16,17), wherein the Eckfalz (4; 14,15) by means of rollers (41,43; 45,46; 47,48; 51 , 53, 61, 83, 71, 73) are bent over and compressed, in particular by a method according to one of claims 1 to 4, with an upper and / or lower roller (47, 51, 61, 71), which is used to reshape the Eckfalzes an annular groove having a groove base, emanating from the two groove flanks, characterized in that between the Eckfalz (4) and one of the groove flanks, viewed in cross section through the Eckfalz, a substantially wedge-shaped gap (57; 67; 77) is provided , which expands outward, in relation to the upper or lower role. Forming device according to claim 5, characterized in that the intermediate space (57,57) is provided on the inside of the Eckfalzes. Forming device according to claim 5 or 6, characterized in that the groove base is inclined towards the intermediate space (57; 67; 77). Heat exchanger tube with a corner fold (4, 14, 15) which has been produced by a forming method according to one of claims 1 to 4 and in particular with a forming device according to one of claims 5 to 7.

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