DE202015005696U1 - Heat exchanger flat tube and heat exchanger - Google Patents

Abstract

Heat exchanger flat tube (1) with a corrugated sheet metal insert (2), the running in the longitudinal direction of the tube (1) running channels (3) for example with exhaust gas or charge air and extends over approximately a length of the flat tube (1) with two edges (20) of the sheet metal insert (2), which have a distance to narrow sides (10) of the flat tube (1), characterized in that at least one of the ends (21, 22) of the corrugated sheet metal insert (2) at its two edges (20) and a piece (23) far enough in the longitudinal direction such that the deformed edges (20) have a firm metallic connection on an inner side (11) of the flat tube (1) or permit, wherein on one over a Length of the piece (23) out reaching length of the sheet metal insert (2) substantially no or at least a less durable metallic connection of the edges (20) with the inside (11) of the flat tube (1) is present.

Description

The invention relates to a heat exchanger flat tube with a corrugated sheet metal insert, which provides in the longitudinal direction of the tube running channels for the flow with, for example, exhaust gas or charge air and a heat exchanger equipped therewith.

Heat exchanger flat tubes with a corrugated sheet metal insert often suffer from the problem that the ends of the sheet metal insert can be released from the inside of the tube and even break under extreme dynamic and thermal loads. Such mostly relatively small fragments can get into a combustion engine by means of a recirculated exhaust gas flow and cause serious damage.

The dynamic and thermal loads are particularly extreme at the inlet end of an exhaust gas heat exchanger, if there is also a valve disposed there, with the aid of which the exhaust gas flow is controlled as needed.

If heat exchanger flat tubes are provided with a corrugated sheet metal insert, such as in 10 of the US 2003/0010479 A1 are shown, the problem can be at least reduced. Namely, these flat tubes consist of two sheet metal shells, which are pressed in the course of their soldering in a brazing furnace by means of a force and therefore lead to proper solder joints of the corrugated sheet metal insert on the inside of the tube.

This is not the case to a sufficient extent if, on the other hand, one-piece flat tubes are to be used, for example those which have a welded longitudinal seam. These flat tubes are easier, cheaper and faster to produce. An example of this comes from the DE 3 743 293 C2 out. However, such flat tubes are less yielding when they are loaded with the mentioned pressing force, with the result that the solder joints with the corrugated sheet metal insert may not be as good quality. It is inadmissible to increase the pressing force beyond all measure, because of course a lasting deformation of the flat tube must be avoided.

Particular importance is attached to the problem addressed when the corrugated sheet metal insert should have approximately vertical sides of the flat tube standing wave flanks, as shown in the aforementioned US-US Scripture, because even such vertical flanks have a great resistance to the force acting on the broad sides of the flat tube pressing force ,

The object of the invention is to make it difficult for heat exchanger flat tubes, the breaking off of fragments from the corrugated sheet metal insert at least, also to reduce manufacturing costs and to achieve other advantages.

This object is achieved with a heat exchanger flat tube having the features of claim 1. The claim 14 includes a equipped with the flat tubes heat exchanger, which serves the solution of the task.

An essential aspect of the invention relating to the flat tube is that at least one of the ends of the sheet metal insert and the flat tube is deformed at the two edges of the sheet metal insert and somewhat longitudinally such that the deformed edges form a firm metallic connection on an inner side have or allow the flat tube, wherein on the remaining, preferably on the predominant length of the flat tube, substantially no or at least only a less durable metallic connection of the edges with the inside of the flat tube is present. The addressed edges are preferably the longitudinal edges of the sheet metal insert.

The inventors have analyzed errors that have occurred and found that in the prior art, the solder joints that must be formed near the two narrow sides of the flat tube, are particularly poor because the narrow sides are quite stiff and counteract the above-mentioned pressing force. There occur the also mentioned fragments. The proposal has improved the quality of the solder joint of the entire piece with the inside of the flat tube, so not only the quality of the solder joint to the mentioned formed longitudinal edges in the region of the piece.

The corrugated sheet metal insert may be a single or even several, for example, three in the flat tube successively arranged sheet inserts, which, however, for the purpose of description and understanding of the claims should be considered and understood as a single sheet metal insert. This is not contrary to the idea according to the invention. It is also possible to provide the several sheet-metal inserts at their ends with the proposed edge forming, because then it is not necessary to ensure compliance with a specific sequence of insertion. But you can also refrain from making a marginal deformation at a middle sheet metal insert.

The above-mentioned at least one end of the sheet metal insert with the edge deformation is very particularly preferably the inlet-side end of the sheet metal insert or of the flat tube. A second end may be the exit end, which may be formed with or without edge deformation.

Because the quality of the metallic connection of the longitudinal edges of the corrugated sheet metal insert has been significantly improved with the inside of the flat tube in the area of the piece, it will not happen so quickly in the future that break off parts of the sheet metal insert and cause damage. The metallic connection is preferably - as mentioned - a solder joint which is formed in the course of the soldering of the heat exchanger in a soldering oven.

The addressed piece of reshaped edges in one embodiment is no longer than about 25% of the length of the flat tube.

In another embodiment, the piece is no longer or even significantly shorter than about 10% of the flat tube length. The inventors state at a heat exchanger length or at a tube length of about one meter that already about 50 mm may be sufficient as the length of the piece.

As a result of the implementation of the features of claim 1, the edges of the sheet metal insert at its at least one end to a geometry that differs from the geometry of the edges of the remaining length of the sheet metal insert.

According to a further feature, one of the channels is an edge-side channel which runs between the edge and the narrow side, wherein the cross-section of the edge channel in the region of the piece is slightly larger than in the area outside the piece, which is the predominant length region of the flat tube or sheet metal insert is.

The mentioned shaping of the edges comprises the formation of a connecting flange on the corrugated sheet metal insert for metallic connection on the inside of the flat tube. The connecting flange allows a full, flat system of the same on the mentioned inside. He is therefore with a corresponding angle of a wave edge projecting and lying on the level of wave crests or troughs, which are known to characterize a corrugated sheet metal insert formed.

Further, the reshaping of the edges of the corrugated sheet metal insert comprises the at least partial removal, that is the cutting, at least one outer wave flank.

A manufacturing method for a heat exchanger flat tube, in which a corrugated sheet metal insert is produced with two edges and inserted from an open end of the flat tube in the same, is characterized in that before inserting the sheet metal insert at least one of its ends, at both edges and reaching over a piece of its length, a forming step is carried out.

For the purposes of the proposal, "before insertion" means as much as before complete insertion. That is to say that there may be embodiments in which the sheet metal insert is initially partially inserted into the flat tube, wherein the piece of sheet metal insert is still on the flat tube end. Then, the forming step is performed on the piece, and then the complete inserting operation is completed.

In a preferred embodiment, a sheet of solder is placed on the sheet metal insert before inserting the sheet metal insert into the flat tube and pushed together with the sheet metal insert in the flat tube.

The flat tube length is, for example, identical to the length of the sheet metal insert, wherein ends of the tube coincide with ends of the sheet metal insert approximately. However, the mentioned lengths may also be slightly different, wherein either the sheet metal insert or preferably the tube wall at least one end has a corresponding projection in the single-digit mm - range.

A heat exchanger with at least one stack of flat tubes and ribs, which is located in a housing on which at least one collecting box is arranged, is characterized according to the invention in that the flat tubes are equipped with a corrugated sheet metal insert as described above. Incidentally, attention is drawn to the dependent claims.

The invention will now be described in an embodiment with reference to the accompanying drawings.

This description below contains further features that may optionally serve to further distinguish the invention from the prior art.

The 1a shows a small part of a sheet metal insert in a plan view and in a view of the end face and the 1b shows a plan view with a slightly modified piece 23 of the sheet metal insert 2 ,

The 2 shows a side view of the sheet metal insert 2 ,

The 3 shows a sketch of a flat tube, in which three sheet metal inserts 2a , b, c are located.

The 4 shows a belonging to a heat exchanger stack of flat tubes 1 in a perspective view.

The 5 shows a perspective view of a part of the sheet metal insert 2 ,

The 6 shows a section 5 ,

The 7 contains several illustrations and sections of a flat tube end.

The 8th shows a heat exchanger in a perspective view.

The 9 shows an enlarged piece 8th ,

The flat tubes 1 The embodiments are made of a single sheet metal strips flat tubes 1 in a narrow side 10 one in 4 and 7 indicated longitudinal weld 12 exhibit. Such flat tubes 1 can be made continuously with a very high speed in a known manner of an "endless" sheet metal strip. They are therefore very inexpensive.

The corrugated metal inserts 2 are similarly inexpensive, running from another "endless" sheet metal strip, produced in a known manner (also not shown). The production of sheet metal inserts 2 is made so that the width of the sheet metal strip about the (later) length of the sheet metal inserts 2 represents. Thus, therefore, the waves with associated wave edges 25 of the sheet metal insert 2 formed transversely to the longitudinal direction of the sheet metal strip. In the representations of the embodiments are approximately 20 wave edges 25 per sheet metal insert 2 available. Are the approx. 20 ripples 25 has been formed by means of a roller-like or a punch-like forming process, a finished sheet metal insert 2 Cut from the sheet metal strip, after which the manufacturing process of other sheet inserts 2 runs continuously. In the 1a On the left, an arrow indicates the direction in which the corrugated sheet inserts 2 run through a preferably punch-like forming tool, which must extend over an entire sheet metal strip width. Such a tool is known to have a rising and falling upper part, which intermittently engages in a correspondingly designed lower part, wherein the sheet metal strip runs between upper part and lower part and is correspondingly shaped.

Depending on the length of the flat tubes required for the respective heat exchanger application 1 with the corrugated sheet metal insert 2 It may be that in the flat tube 1 either only a single sheet metal insert 2 with one of the flat tube length is about corresponding length or even several successively arranged sheet inserts 2 , a, b, c, which in sum correspond approximately to the flat tube length, as already mentioned above.

The background for arranging multiple sheet metal inserts 2 consists in the mentioned production of the same. One would like to keep tooling costs as low as possible, which is why one does not need an extra forming tool for producing the corrugated sheet metal inserts for each flat tube length required - for example, if it is in the range of slightly more or less than one meter (1.0 m) 2 provides. It would also not be necessary to provide a sheet metal strip with the appropriate width for each flat tube length (see above). Better to take three sheet inserts 2a , b, c, for example, 330 mm in length, which are needed anyway for other flat tube lengths and arranges these lying one behind the other in the flat tube 1 at. In 3 For example, there are three sheet metal inserts 2a , b, c in the flat tube 1 ,

This arranging also does the formation of in the longitudinal direction of the flat tube 1 running channels 3 no demolition, because the adjacent sheet metal inserts 2a , b, c are at least approximately identical with regard to the channel formation or with regard to their wave formation. The mentioned channels 3 are preferably discrete channels 3 that is, adjacent channels 3 not in fluid communication. However, in contrast, you can also openings in the corrugation flanks 25 provide that allow the mentioned hydraulic connection.

The corrugated sheet metal insert 2 of the embodiment provides longitudinally serpentine channels 3 to disposal ( 1 or 6 ).

Taking into account economic aspects, the process of inserting the sheet metal inserts can be 2 in the flat tubes 1 largely mechanize / automate. So-called tube stuffing machines are available, which are not discussed in the present context. In the course of this mechanized process is also a solder foil on or around the sheet metal insert 2 then placed together with the same in the flat tube 1 is inserted. The solder foil can also be replaced by solder paste or solder powder. The separate provision of solder material already indicates to the person skilled in the art that in the exemplary embodiment a base material is a stainless steel for the flat tube 1 and for the sheet metal insert 2 is used.

Before the process of insertion is completed, must be at the sheet metal inserts 2 connecting flanges 24 be formed. At least one end 21 of the sheet metal insert 2 or of the flat tube 1 which is the later inflow end 21 of the flat tube 1 is to flow into the example, extremely hot exhaust gases, a forming step is performed, which is used to form the connecting flanges 24 leads. According to the embodiment shown, the forming step comprises the cutting of a single wave flank 25 on both edges 20 of the piece 23 , The furthest outboard flank 25 will be removed ( 1a ). According to 1b In contrast, several wave flanks were 25 away. The forming step is only on a short piece 23 the length of the sheet metal insert 2 executed. This causes the initially mentioned, applied in the course of a soldering pressing force the connecting flange 24 tighter to the inside 11 the pipe wall presses, which is why the quality of the solder joint is improved. In contrast, the quality of the solder joint at the edges 20 outside the play 23 to be worse. In 7 Two striking arrows indicate the direction of the mentioned pressing force. This is on the broad sides of the flat tubes 1 directed. As the inventors have found, for some applications it is also acceptable that there is no solder joint at the edges 20 outside the play 23 is available.

The forming step can either separately, that is, at the individual sheet metal insert 2 , or even in the course of producing the corrugated sheet inserts 2 More precisely, in the course of cutting off individual corrugated metal inserts 2 as described in the introduction.

In other embodiments, not shown, a larger connection flange 24 designed as the one shown here. This will be a wave flank 25 only about half cut off and to a larger area connecting flange 24 reshaped.

In 7 you can see that the geometry of edge channels 30a in the area of the piece 23 is different from the one outside the play 23 , The cross-sectional size is also in the edge channel 30a larger than in the edge channel 30b that's outside the play 23 is available.

One has noticed that one in the inlet collection box 5 arranged valve 6 , with control element 7 as in the 8th and 9 it can be seen, in particular the thermal loads on heat exchangers without this valve 6 significantly increases in this place. It can lead to the formation of adverse hotspots. Therefore, the solution proposed described and shown particularly in connection with such a design is of particular importance. In 8th Block arrows indicate an exhaust gas and a dashed arrow indicates a coolant (inlet 8th ).

The in the 4 and 9 partially shown stack of such flat tubes 1 has small distances between the flat tubes 1 , the flow channels 9 provide for the coolant. There are a plurality of spaced in the longitudinal direction of the stack or the heat exchanger grid-like structures 13 intended. The flat tubes 1 extend through matching openings in the grid structures 13 therethrough. The grid structures 13 force a meandering flow path of the coolant and they provide a stable and also acting against vibration mount for the stack in the housing 4 ready. In 9 is because of the partially broken representation only a single grid construction 13 partially recognizable.

An alternative embodiment not shown has in the flow channels 9 arranged ribs or similar structures to further improve the heat transfer.

The corrugated sheet inserts shown 2 show in a short entrance area 27 in their ripples 25 longitudinally extending kinks 26 on ( 5 and 7 ), which in the present context make a helping contribution because they provide more resilience under the effect of the press force mentioned several times. In the exemplary embodiment, each wave edge has 25 three such kinks 26 , As you can see, the short entry area is with the creases 26 much shorter than the length of the piece 23 ( 1 and 7 ). You can also say the short entrance area 27 is a part of the piece 23 ,

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2003/0010479 A1 [0004]
• DE 3743293 C2 [0005]

Claims (15)

Heat exchanger flat tube ( 1 ) with a corrugated sheet metal insert ( 2 ), which in the longitudinal direction of the tube ( 1 ) running channels ( 3 ) provides for the flow with, for example, exhaust gas or charge air and which extends approximately over a length of the flat tube ( 1 ), with two edges ( 20 ) of the sheet metal insert ( 2 ), which are at a distance to narrow sides ( 10 ) of the flat tube ( 1 ), characterized in that at least one of the ends ( 21 . 22 ) of the corrugated sheet metal insert ( 2 ) at its two edges ( 20 ) and a piece ( 23 ) is shaped far enough in the longitudinal direction such that the reshaped edges ( 20 ) a solid metallic compound on an inner side ( 11 ) of the flat tube ( 1 ), wherein on one over a length of the piece ( 23 ) beyond reaching length of the sheet metal insert ( 2 ) substantially no or at least a less durable metallic compound of the edges ( 20 ) with the inside ( 11 ) of the flat tube ( 1 ) is available. Heat exchanger flat tube according to claim 1, characterized in that the piece ( 23 ) with the reshaped edges ( 20 ) no longer than about 25% of the length of the flat tube ( 1 ). Heat exchanger flat tube according to claim 1, characterized in that the piece ( 23 ) is no longer than about 15% of the flat tube length. Heat exchanger flat tube according to claim 1, characterized in that the piece ( 23 ) is no longer than about 10% of the flat tube length. Heat exchanger flat tube according to one of claims 1-4, characterized in that the edges ( 20 ) of the sheet metal insert ( 2 ) at its at least one end ( 21 . 22 ) and the length of the piece ( 23 ) have a geometry that differs from the geometry of the edges ( 20 ) at the predominant length of the sheet metal insert ( 2 ) or outside of the piece ( 23 ) is different. Heat exchanger flat tube according to one of claims 1-5, characterized in that one of the channels ( 3 ) a marginal channel ( 30a . 30b ), which is between the edge ( 20 ) and one of the narrow sides ( 10 ), wherein the cross section of the edge channel ( 30a ) in the area of the piece ( 23 ) is slightly larger than in the majority of the length of the flat tube ( 1 ) or outside of the piece ( 23 ). Heat exchanger flat tube according to one of the preceding claims, characterized in that the forming of the edges ( 20 ) the formation of a connecting flange ( 24 ) on the corrugated sheet metal insert ( 2 ) to the metallic compound on the inside ( 11 ) of the flat tube ( 1 ). Heat exchanger flat tube according to one of the preceding claims, characterized in that the forming of the edges ( 20 ) of the corrugated sheet metal insert ( 2 ) the at least partially removing at least one outer wave edge ( 25 ). Heat exchanger flat tubes according to one of the preceding claims, characterized in that the corrugated sheet metal insert ( 2 ) is a single part whose length corresponds approximately to the flat blank length. Heat exchanger flat tube according to one of the preceding claims 1-8, characterized in that the corrugated sheet metal insert ( 2 ) consists of several parts (a, b, c), which in the longitudinal direction of the flat tube ( 1 ) are arranged one behind the other, wherein the sum of the lengths of the parts (a, b, c) corresponds approximately to the flat tube length. Heat exchanger flat tube according to one of the preceding claims, characterized in that the sheet metal inserts ( 2 ) over a short entrance area ( 27 ) in their wavefronts ( 25 ) longitudinally extending kinks ( 26 ) exhibit. Heat exchanger flat tube according to one of the preceding claims, characterized in that a length of the inlet region ( 27 ) with the creases ( 26 ) is much shorter than the length of the piece ( 23 ). Heat exchanger flat tube according to all preceding claims, characterized in that the flat tube ( 1 ) is made of a single sheet metal strip and in a narrow side ( 10 ) a weld ( 12 ) having. Heat exchanger with at least one stack of flat tubes ( 1 ) or flat tubes and interposed ribs, which are housed in a housing ( 4 ) at which at least one collection box ( 5 ), characterized in that the flat tubes ( 1 ) with a corrugated sheet metal insert ( 2 ) are formed according to one of the preceding claims. Heat exchanger according to claim 14, characterized in that in the collecting box ( 5 ) a valve ( 6 ) is arranged, which the flow through the flat tubes ( 1 ) regulates.

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