EP2294350B1 - Heat exchanger - Google Patents

Description

The invention relates to a heat exchanger according to the preamble of claim 1 and a method for producing a heat exchanger according to the preamble of claim 3. Furthermore, one embodiment of the invention relates to a motor vehicle air conditioning system.

Heat exchangers are used to transfer heat from one fluid to another fluid. For example, a heat exchanger transfers heat from a cooling liquid to the ambient air. This is used in particular in motor vehicles in which the heat exchanger is used to transfer the waste heat released by the internal combustion engine to the ambient air. The heat exchanger generally consists of two header tubes, between which a large number of tubes are arranged. Openings into which the pipes open are made in the header pipes. The tubes are connected in a fluid-tight manner to the openings in the header tubes.

The openings in the headers are made by punching or piercing. When punching through a wall of the collecting tube, the opening is punched through, so that that part of the wall which forms the subsequent opening is removed. The bearing surface of the tubes in the openings of the header tubes thus corresponds to the thickness of the wall of the header tube in the area of the opening. When the openings are pierced through the wall of the collecting tube, an annular passage is formed at the openings, which corresponds to the deformed wall of the collecting tube in the partial area. The sub-area is that area of the wall of the collecting pipe which corresponds to the opening after the production. The passage, which the wall of the collecting pipe corresponds in the area of the openings, is essentially not stretched during the piercing, but only bent. This corresponds to a cross-section z. B. circular opening the length of the passage the radius of the opening.

The length of the passage or the contact surface of the pipe at the opening has a significant influence on the mechanical stress on the connection between the pipe and the collecting pipe. A mechanical stress on this connection results, for example, from thermal stresses due to large compressive and / or tensile forces or expansions in the pipes or the manifold, as well as superimposed bends and bends or deformations of the pipes or the manifold. This can cause damage, in particular leaks, to the connection between the pipe and the header pipe, which leads to a failure of the heat exchanger. This is generally associated with high costs because it is not possible to repair the heat exchanger and it therefore has to be replaced. In particular, in motor vehicles the leakage of the heat exchanger leads to a loss of cooling liquid, so that the journey with the motor vehicle has to be interrupted.

The EP 0 990 868 B1 shows a generic heat exchanger. The thickness of the passages in which the pipes are introduced corresponds to the thickness of the wall of the collecting pipe outside the openings for inserting the pipes. In addition, there is only a partial area of the passage in the direction of an axis of the openings in contact between the passages and the pipes. As a result, there is only a small contact surface of the pipe on the passage, so that there is only a low mechanical strength in this important connection area between the pipe and the collecting pipe.

From the DE 33 16 960 A1 a generic heat exchanger is known. The openings are pierced by a punch. After the wall of the collecting tube has been pierced with the punch, some of the passages are cut off. As a result, the passages have a short length in the direction of the axis of the opening, so that a small contact area is formed between the pipe and the passage. Disadvantageously, this results in a low mechanical strength between the pipe and the collecting pipe in the area of the passage.

The DE 696 17 598 T2 shows a generic heat exchanger. A header plate has openings into which the ends of flat tubes are inserted which are connected to the wall of the header plate by means of soldering. To facilitate this connection, each hole is surrounded by a collar.

document DE4129573 shows a heat exchanger with the features of the preamble of claim 1.

The object of the present invention is therefore to improve the mechanical strength between the pipes and the header pipe in a heat exchanger, a motor vehicle air conditioning system and a method for producing a heat exchanger. The heat exchanger and the motor vehicle air conditioning system should work inexpensively to manufacture and reliable and safe in operation. Furthermore, the method for producing a heat exchanger should be able to be carried out simply and inexpensively.

The object is achieved with a heat exchanger according to claim 1. The object is also achieved with a method according to claim 3. Furthermore, the object is achieved with a motor vehicle air conditioning system according to claim 6.

According to the invention, the thickness of the passages increases from the beginning of the passages on the wall of the collecting pipe to one end of the passages, preferably steadily, from. The end of the passage can either end in the flow space of the collecting pipe, ie end in the same way as the end of the pipe which is arranged in the collecting pipe or end outside the collecting pipe, ie the end of the passage ends in the opposite direction than the end of the pipe , which is arranged in the manifold.

In one embodiment according to the invention, the thickness of the passages from the beginning at the bottom to a tip of the passages is at least 10% of the thickness of the wall, in particular in the area of the openings, of the collecting pipe, the length of the tip of the passage being at least 10% of the thickness the wall, in particular in the area of the openings, of the collecting pipes.

In a further embodiment according to the invention, the thickness of the passages from the beginning at the bottom to 0.8 times the total length of the passage in front of a tip is less than 0.9 times the thickness of the wall, in particular in the area of the openings Manifold.

The maximum length of the passages is preferably greater than half, in particular greater than 1.1 to 3 times half the minimum diameter of the openings. The wall of the collecting pipe in the partial area of the later opening is reshaped or bent to form the passage, and the passage is also stretched. As a result, the maximum length of the passage is greater than half the minimum diameter of the opening. In the case of a tube or opening with a rectangular cross section, the minimum diameter of the opening corresponds to the width of the opening. The length of the passage is greater than half the width of the opening, because the wall of the collecting tube during the production of the passage is stretched. In the case of a pipe or opening with a circular cross-section, half of the minimum diameter thus corresponds to the radius of the opening.

The pipes are expediently connected to the passages in a fluid-tight, in particular liquid-tight manner, with a material fit, preferably by soldering.

In a further embodiment, the tubes and / or the at least one collecting tube consist at least partially of aluminum and / or aluminum alloys and / or of plastic.

The manifold can also be constructed in several parts. For example, the collecting tube can consist of a base made of metal, in particular aluminum, and a box made of plastic. The box is, for example, U-shaped in cross section and fastened in grooves in the floor. The fluid-tight connection between the box and the floor is made by means of a seal in the channel. This creates a flow space between the floor and the box. In a further embodiment, the collecting tube can consist, for example, of a base with an approximately U-shaped cross section and a cover. Both the base and the cover are made of metal, in particular aluminum. A channel is formed on the cover, by means of which the cover is connected to the floor in a fluid-tight manner. The seal between the channel in the cover and the base is generally made without a separate seal.

In a method according to the invention for producing a heat exchanger with the steps of creating tubes, at least partially creating at least one header tube with a wall, piercing a partial area of the wall of the at least one header tube to form openings with passages, introducing the tubes into the openings and making them fluid-tight When the pipes are connected to the passages, the wall of the at least one header pipe is stretched to form impressions in the subregions before being pierced, so that the thickness of the passages is less than the thickness of the wall of the collector pipe in the subregions before the extension.

According to the invention, the passages are stretched in such a way that the thickness of the passages from a start at the bottom to a tip of the passages is at least 10% of the thickness of the wall, in particular in the area of the openings, of the collecting pipe, the length of the tip being the Passages at least 10% of the thickness of the wall, in particular in the area of the openings, of the collecting pipe.

In a supplementary variant, the wall of the at least one collecting pipe is stretched in the partial areas in a separate operation before the piercing. The expansion of the wall of the at least one collecting pipe is thus carried out in time before the piercing. The stretching can be carried out both in a partial area of the wall of the at least one collecting pipe in which the subsequent opening is created, and beyond this area. If the wall is stretched beyond this partial area, the thickness of the wall of the collecting pipe is considered to be that part which is not stretched. When the wall is stretched, an expression is created in the sub-area.

Appropriately, no material such. B. by means of punching, removed, that is, the opening is made exclusively by deforming, in particular bending, the wall of the manifold.

In a supplementary variant, the wall of the at least one collecting pipe is stretched in the partial areas with a tool other than the piercing.

The section of the collecting tube on which the openings are embossed and pierced can have different shapes. For example, the collecting tube can be flat or curved in this area.

A heat exchanger according to the invention, in particular a heat exchanger for a motor vehicle, comprises a plurality of pipes, at least one manifold with openings on which the pipes are partially arranged in the region of one end of the pipes and are connected to the openings in a fluid-tight manner, the manifold being composed of a base and a Box consists and the openings are formed in the floor and one end of the box is received by a channel formed in the floor for connecting the box to the floor, at least one inlet opening for introducing a fluid and at least one outlet opening for discharging the fluid, with between an outside of the channel and the outside of the tubes, in particular between the seal and a tube axis of the tube, there is a material connection. The material connection is preferably made indirectly between the two outer sides by means of a material, for. B. soldering material to produce the integral connection.

In particular, the material connection is a soldered connection and / or an adhesive connection. To produce a soldered connection between the outside of the channel and the outside of the pipe, in particular a narrow side of the pipe, in the case of a pipe with a rectangular cross-section, there is a small distance between the outside of the channel and the outside of the pipe, for example between 0 and 2 mm . This can When soldering, the soldering material rises capillary or is inserted in the area between the outside of the channel and the outside of the pipe.

In a further embodiment, the outside of the channel in the area of the material connection is formed essentially parallel to the outside of the at least one pipe.

In an additional embodiment, preferably ring-shaped passages are formed in the axial direction of the openings, the pipes being arranged on the passages in the region of one end of the pipes and a fluid-tight connection between the passages and the pipes.

A motor vehicle air conditioning system or a motor vehicle comprises the heat exchanger described in this application.

Fig. 1

eine Ansicht eines Wärmetauschers,

Fig. 2

einen Querschnitt A-A eines Sammelrohres mit einem Rohr des Wärmetauschers gemäß Fig. 1 in einer ersten Ausführungsform,

Fig. 3

einen Querschnitt A-A des Sammelrohres mit dem Rohr des Wärmetauschers gemäß Fig. 1 in einer zweiten Ausführungsform,

Fig. 4

einen Teillängsschnitt eines Bodens des Sammelrohres gemäß Fig. 2 vor dem Einbringen von Öffnungen für die Rohre,

Fig. 5

den Teillängsschnitt des Bodens gemäß Fig. 4 nach dem Einbringen der Öffnungen und

Fig. 6

eine Ansicht der Öffnungen in Richtung einer Achse der Öffnungen.

In the following, three exemplary embodiments of the invention are described in more detail with reference to the accompanying drawings. It shows:

Fig. 1

a view of a heat exchanger,

Fig. 2

a cross section AA of a manifold with a tube of the heat exchanger according to Fig. 1 in a first embodiment,

Fig. 3

a cross section AA of the header with the tube of the heat exchanger according to Fig. 1 in a second embodiment,

Fig. 4

a partial longitudinal section of a bottom of the manifold according to Fig. 2 before making openings for the pipes,

Fig. 5

the partial longitudinal section of the floor according to Fig. 4 after introduction the openings and

Fig. 6

a view of the openings in the direction of an axis of the openings.

In Fig. 1 a view of a heat exchanger 1 is shown. A plurality of tubes 2 are arranged between two header tubes 3. The two header pipes 3 are connected to one another at the top and bottom with a connecting flange 26. Corrugated fins 4, which connect the tubes 2 both mechanically and thermally, are formed between the tubes 2. The corrugated fins 4 serve to enlarge the surface area of the heat exchanger 1 and thereby increase the heat transfer. At the in Fig. 1 The manifold 3 shown on the right has an inlet opening 5 and an outlet opening 6. The heat exchanger 1 is used in a motor vehicle to give off the heat of the cooling liquid to the environment. Cooling liquid thus flows through the inlet opening 5 into the heat exchanger 1 and it flows out again in a cooled state through the outlet opening 6. The two collecting pipes 3 each consist of a base 9 made of aluminum and each a box 10 made of plastic, in which the inlet opening 5 and the outlet opening 6 are also formed. The tubes 2, which are rectangular in cross-section, open into the bottom 9 of the collecting tube 3. As a result, there is a hydraulic connection between the two collecting tubes 3 and the tubes 2. One end of the tube 2 ends in the flow space 25.

The bottom 9 and the box 10 enclose a flow space 25 for the cooling liquid ( Fig. 2 and 3 ). The box 10 is essentially U-shaped in cross section. The bottom 9 is provided with a channel 21 at each end in cross section. A seal 12 is arranged in the channel 21. The seal 12, an elastic part, serves to connect the bottom 9 to the box 10 in a liquid-tight manner. There are openings 13 in the bottom 9 formed, in which the tubes 2 with tube axles 31 are arranged. An opening wall 14 of the collecting pipe 3 or of the bottom 9 has been shaped into a passage 7. The end of the passage 7 ends in the flow space 25 of the collecting pipe 3. The passage 7 thus represents the former opening wall 14 of the base 9 ( Fig. 5 ), which has been formed into the passage 7.

During the production of the openings 13 of the base 9 (not shown), an impression 27 is first applied in a partial area 20 of the wall 8 of the base 9, ie the opening wall 14, by means of a stamp. The sub-area 20 ( Fig. 4 ) corresponds to a section of the wall 8 that is reshaped to form the passage 7. The sub-area 20 is in Fig. 4 that portion of the wall 8 which is formed within the dashed line. The values 27 are in Fig. 4 also shown in dashed lines. Due to this formation of the embossments 27, the wall 8 is stretched in the partial area 20, which corresponds to the later passage 7, so that the thickness 16 of the passage 7 is less than the thickness 17 of the wall 8 of the base 7 in the non-deformed area, ie outside the sub-area 20 or the thickness 17 of the opening walls 14. After the formation, the opening 13 is produced by means of a piercing tool. In this case, the wall 8 of the base 9 is bent over within the sub-area 20, so that the in Fig. 2 and 5 Shown shape of the passage 7 results. The thickness 17 of the wall 8 of the base 9 is thus greater than the thickness 16 of the passage 9. A point 15 is formed at the end of the passage 7 due to the piercing process. The tip 15 is essentially triangular in cross section. The thickness of the passage 7 in front of the tip 15 is, for example, 20 to 30% of the thickness 17 of the wall 8 of the base 9 before the deformation.

Between the passage 7 and the pipe 2 there is an integral connection 22 designed as a soldered connection 23 ( Fig. 2 ). In Fig. 2 the plane of the drawing is parallel to a plane of a broad side wall of the tube 2 and perpendicular to a plane of a narrow side wall 28 of the tube 2. The length 18 of the passage 7 is greater than half the minimum diameter 29 of the opening 13, because the wall 8 of the bottom 9 has been stretched in the sub-area 20 during the formation of the passage 7. The opening 13 is also rectangular in shape corresponding to the rectangular cross-section of the tube 2. The length 18 of the passage 7 is greater than half the width of the opening 13. A diameter 19 of the opening 13 is slightly smaller than a corresponding outer diameter (not shown) of the pipe 2. This is necessary so that in the entire area between the outside of the The distance between the passage 7 and the pipe 2 is, for example, in the range between 0.2 and 1 mm, so that the brazing material can penetrate into this gap by capillary action. If the tubes 2 and the base 9 are plated with a solder and the soldered connection is made in a soldering furnace, no spacing is required.

The thickness of the passage 7 decreases steadily from the beginning of the passage 7 on the wall 8 of the base 9 or of the collecting pipe 3 to the end of the passage 7 at the tip 15 of the passage 7. This results from the production of the passage 7. When the expression 27 of the wall 8 is created in the sub-area 20, the middle area is stretched more than the edge area of the sub-area 20 near the non-deformed or stretched wall 8 of the base 9 the passage 7 is also stretched when it is pierced and this stretching is also greater here in the region of the end of the passage 7 than at the beginning of the passage 7.

In Fig. 5 a partial longitudinal section of the bottom 9 after the penetration of the sub-area 20 is shown. The passages 7 are formed parallel to an axis 24 of the opening 13.

In Fig. 6 is a view of the openings 13 shown in the direction of an axis of the openings. The openings 13 are rectangular and have a minimum diameter 29 and a maximum diameter 30.

In Fig. 3 a second embodiment of the manifold 3 of the heat exchanger 1 is shown. In the following, only the differences from the first embodiment according to FIG Fig. 2 described. The bottom 9 is designed in such a way that there is a small distance in the range between 0 and 2 mm between an outside of the channel 21 and the pipe 2. In this gap with a thickness between 0 and 2 mm there is a material connection 22 designed as a soldered connection 23. The thickness of this gap between the outside of the channel 21 and the outside of the pipe 2 is preferably 0.2 to 0.8 mm, so that the soldering material for the soldered connection 23 can expand capillary in the gap and rise. The pipe 2 is thus advantageously also connected to the base 9 and thereby the strength of the mechanical connection between the pipe 2 and the base 9 or the collecting pipe 3 is increased. Mechanical stress, which results in particular from thermal deformations of the heat exchanger 1, can thereby be better absorbed. Damage to the heat exchanger 1 resulting from damage to the connection between the pipe 2 and the header pipe 3 can thereby be reduced.

Viewed overall, the heat exchanger 1 according to the invention is associated with considerable advantages. During the production of the passage 7 is the passage 7 is stretched in such a way that the length 18 of the passage 7 is stretched in the direction of the axis 24 of the opening 13. This increases the contact surface between the pipe 2 and the passage 7, formed as a soldered connection 23. The mechanical stresses on the connection between the pipe 2 and the passage 7, which result in particular from thermal deformations of the heat exchanger 1, can thereby be absorbed more easily. Damage to the heat exchanger 1 resulting therefrom, for example leaks at the connection between the tube 2 and the passage 7, can thereby be significantly reduced. The larger contact surface thus leads to a larger contact surface and support surface of the pipe 2 on the passage 7. This can significantly increase the reliability of a heat exchanger 1 according to the invention and a motor vehicle air conditioning system according to the invention.

List of reference symbols

1

Heat exchanger

2

pipe

3

Manifold

4th

Corrugated ribs

5

Inlet opening

6th

Outlet opening

7th

Draft

8th

Wall of the collecting pipe

9

Bottom of the collecting tube made of aluminum

10

Plastic header box

11

End of the pipe

12th

poetry

13th

opening

14th

Opening wall of the collecting pipe in the area of the openings

15th

Tip of the draft

16

Thickness of the passage

17th

Thickness of the wall of the manifold

18th

Length of the passage

19th

Diameter of the opening

20th

Sub-area

21

Gutter

22nd

Cohesive connection

23

Solder connection

24

Axis of opening

25th

Flow space

26th

Connecting flange

27

Expression

28

Narrow side wall

29

Minimum diameter

30th

Maximum diameter

31

Pipe axis

Claims (6)

1. A heat exchanger (1), in particular a heat exchanger (1) for a motor vehicle, comprising

   - a plurality of tubes (2),

   - at least one collecting tube (3) with a base (9) which has a wall (8), wherein openings (13) are provided in the wall (8), wherein passages (7) are formed which protrude from the wall (8) in the axial direction of the openings (13), wherein the tubes (2) are disposed partially at the passages (7) in the area of one end (11) of the tubes (2) and a fluid-tight connection exists between the passages (7) and the tubes (2),

   - at least one inlet opening (5) for introducing a fluid, and

   - at least one outlet opening (6) for discharging the fluid, wherein the thickness (16) of the passages (7) is less than the thickness (17) of the wall (8) of the collecting tube (3), in particular in the area of the openings (13), and the thickness (16) of the passages (7) decreases, preferably in a steady manner, from the beginning of the passages (7) at the wall (8) of the collecting tube (3) to an end of the passages (7), characterised in that the thickness (16) of the passages (7) from a beginning at the base (9) to a tip (15) of the passages (7) is at least 10% of the thickness (17) of the wall (8) of the collecting tube (3), in particular in the area of the openings (13), wherein the length of the tip (15) of the passages (7) is at least 10% of the thickness of the wall (8) of the collecting tube (3), in particular in the area of the openings (13), and wherein the thickness (16) of the passages (7) from a beginning at the base (9) to 0.8 times the total length of the passage (7) upstream of the tip (15) is less than 0.9 times the thickness of the wall (8) of the collecting tube (3), in particular in the area of the openings (13).
2. The heat exchanger according to claim 1, characterised in that the maximum length of the passages (7) is greater than half, in particular greater than 1.1 to 3 times half the minimum diameter (29) of the openings (13).
3. A method for manufacturing a heat exchanger (1) according to one or more of the preceding claims, with the steps

   - producing tubes (2),

   - at least partially producing at least one collecting tube (3) with a wall (8),

   - puncturing a sub-area (20) of the wall (8) of the at least one collecting tube (3) to openings (13) with passages (7),

   - introducing the tubes (2) into the openings (13), and

   - connecting the tubes (2) to the passages (7) in a fluid-tight manner,

   characterised in that
   the wall (8) of the at least one collecting tube (3) is expanded in the sub-areas (20) to raised regions (27) prior to puncturing, so that the thickness (16) of the passages (7) is less than the thickness (17) of the wall (8) of the collecting tube (3) in the sub-areas (20) prior to expansion.
4. The method according to claim 3, characterised in that the expansion of the wall (8) of the at least one collecting tube (3) in the sub-areas (20) is carried out in a separate operation prior to puncturing.
5. The method according to one or more of claims 3 or 4, characterised in that the expansion of the wall (8) of the at least one collecting tube (3) in the sub-areas (20) is carried out using a tool other than the puncturing and/or no material is removed from the wall (8), e.g. by punching.
6. A motor vehicle air conditioning system, characterised in that the motor vehicle air conditioning system comprises a heat exchanger according to one or more of claims 1 or 2.

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