Heat exchanger

Abstract

Disclosed is a heat exchanger comprising pipes and at least one receptacle (20). Said receptacle encompasses at least one pipe bottom (30) that is provided with passages (70), said passages (70) being surrounded by flanks (91-94).

Description

The present invention relates to a heat exchanger, in particular a charge-air cooler for a motor vehicle.

In order to increase the power of an internal combustion engine, it is possible for the air which is to be fed for combustion to be compressed, for example using a turbocharger, before it is fed to the combustion chambers of the internal combustion engine. However, compressing the air at the same time also heats it, which is disadvantageous for an optimum sequence of the combustion process. By way of example, this can cause premature ignition or increased emissions of nitrogen oxide. To avoid the disadvantageous consequences of combustion of superheated air supplied, a heat exchanger designed as a charge-air cooler, which can be used to cool the compressed air to an acceptable temperature before its combustion, is connected downstream of a turbocharger.

A charge-air cooler is described, for example, in DE 197 57 034 A1. In the heat exchanger disclosed therein, the hot air is introduced into a first header passage of the heat exchanger, where it is distributed and flows into flat tubes which open out into the header passage. The flat tubes are arranged next to one another and with the side faces which include the long sides of their cross section parallel to one another, forming a flow path through which cooling air is routed. Cooling fins, which are responsible for effective heat exchange between the flat tubes and the cooling air stream, are arranged between the flat tubes in the flow path. After the cooling air stream has passed through, the flat tubes open out into a second header passage, which feeds the cooled, compressed charge air flowing into it for combustion in the engine.

In heat exchangers, such as in particular charge-air coolers of this type, the tubes are usually fitted into openings in a tube plate and are soldered in place in a fluid-tight manner. Each time that compressed air is applied, this soldered join is subject to high mechanical loads on account of rapid pressure changes. In particular the narrow sides of flat tubes do not satisfy the increasing demands on strength, which can result in leaks in particular in regions of tube-plate joins of this type which face the sides of the tube plate.

A simple way of increasing the strength of tube-plate joins is to use tubes and/or tube plates with a greater wall thickness or external and/or internal fins with a greater material thickness. The increased mechanical stability is useful in both cases, but the increased outlay that is required on material costs and weight is very high.

Other proposed solutions deal with a reduction in the mechanical loading on the tube-plate joins by the use of tie rods in the charge-air boxes. These tie rods stabilize the charge-air boxes and thereby relieve the load on the tube-plate joins, but also increase the outlay on material and the pressure loss caused by the charge-air cooler.

The object of the invention is to provide a heat exchanger, in particular a charge-air cooler, in which mechanical loads on tube-plate joins are reduced without an increased outlay on material.

This object is achieved by a heat exchanger having the features of claim 1.

According to claim 1, a heat exchanger has tubes which are suitable to have a first medium flowing through them and a second medium flowing around them, so that heat can be transferred from the first medium to the second medium or vice versa. At least one header box which is in communication with the tubes comprises at least one tube plate, the tube plate being of essentially flat design and having rims into which the tubes can be fitted in order to form the communicating connection to the header box.

The basic concept of the invention is to geometrically configure those regions of the tube plate which surround the rims in the form of depressions or elevations in such a manner that the rims are in each case arranged on the “base” of a depression or on the “summit” of an elevation. As a result of this, the rims are enclosed peripherally by flanks, namely the flanks of the depressions or elevations. A geometrical configuration of this type, particularly the peripheral configuration of the flanks, increases the flexural rigidity of the tube plate in a plurality of directions in comparison to a flat tube plate, thus reducing deformations that occur due to a compressive load on the header box, as a result of which joins of tubes to the tube plate are mechanically relieved of load. The depressions or elevations are preferably of such a width that the flanks of in each case two adjacent rims border each other with a reinforcing bead being formed.

The configuration of the heat exchanger according to the invention increases its mechanical strength and therefore also its service life without requiring an increased outlay on material or number of parts.

Advantageous embodiments of the invention are the subject matter of the subclaims.

According to a preferred embodiment, the flanks each have an essentially constant width over the circumference of a rim. This essentially uniformly increases the flexural rigidity of the tube plate in all directions.

According to an advantageous embodiment, the tubes are designed as flat tubes and are arranged in one or more rows. The rims and the beads which are situated in between and are formed by the flanks are then of elongate design corresponding to the tube cross sections.

The flanks preferably each have a rounded portion with an approximately constant radius of curvature or a plurality of rounded portions with different radii of curvature. This achieves a particularly good approximation to a semicircular cross section of the beads situated between the rims, thus resulting in particularly high flexural rigidity.

According to another embodiment, the flanks each comprise one or more planar regions, so that the flanks or the beads have a faceted form between the rims. This allows reliable production with low manufacturing tolerances.

The at least one planar region particularly preferably forms an obtuse angle with the respective rim. This means that the rim itself brings about an additional increase in the flexural rigidity of the tube plate, since the rim faces in the same direction as the depression or elevation on the “base” of which or on the “summit” of which the rim is situated.

The angle between the planar region of the flank and the rim is preferably between 300 and 600, particularly preferably approximately 45°. In this case, a width of the flank is, under some circumstances, approximately equal to a height of the flank, thus resulting in particularly high stability of the tube plate to deformations.

According to an advantageous configuration, the rims face out of the at least one header box. This has, if appropriate, the advantage that in each case one region of the flanks, which region is adjacent to an edge of the tube plate, merges into an edge of the tube plate, which edge is raised under some circumstances, thus resulting in a further increase in strength of the tube plate.

According to a preferred development, the heat exchanger according to the invention is designed as a charge-air cooler which can particularly preferably be used in motor vehicles. In particular, the charge-air cooler has two header boxes, a first of which is provided to distribute charge air and a second of which is provided to collect charge air. It is advantageous for each of the header boxes to have precisely one tube plate, which is provided with a row of tube openings. It is also advantageous to use a row of flat tubes with in particular soldered corrugated fins between them, since this increases the heat-transfer surface area. The cooling medium used is preferably air, although other cooling media, such as water or coolant, are also conceivable.

According to an advantageous embodiment of the invention, a tube plate is produced by one or more edge regions of a planar metal sheet being raised by means of a forming process and depressions, which border one another, being placed into the metal sheet. In this case, the depressions each have an essentially planar base surface and a flank enclosing and encircling the base surface. Subsequently, the base surfaces of the depressions are pierced with the aid of a draw-through process with rims being formed. If tubes are to be fitted into the tube plate from the side of the depressions, it is particularly preferable for introductory slopes to be impressed therein in order to facilitate a fitting of tubes in this way into the rims.

An embodiment of a tube plate with one or more rows of identical flanks and/or rims is advantageous in terms of manufacturing.

The invention is explained below on the basis of exemplary embodiments and with reference to the drawings, in which

FIG. 1 shows an oblique view of a tube plate,

FIG. 2 shows a side view of a tube plate with a tube inserted,

FIG. 3 shows a longitudinal section through a tube plate with tubes inserted,

FIG. 4 shows a longitudinal section through an excerpt of a tube plate with a tube inserted, and

FIG. 5 shows a longitudinal section through an excerpt of a tube plate with a tube inserted.

FIG. 1 shows an excerpt from a heat exchanger 10 in the form of a perspective illustration. A header box 20 for distributing a first medium comprises a tube plate 30 and a box cover (not shown), which are welded to each other at a common contact surface 50. In this case, the box cover is fitted into the tube plate 30. However, it is also conceivable for the box cover to be fitted onto the tube plate 30 or attached to the tube plate 30 in some other way. In other exemplary embodiments (not shown), a tube plate and a box cover are joined to one another by soldering, adhesive bonding or a positive lock or are formed as a single part or integrally with one another, i.e., for example from a deformed plate.

The tube plate 30 has a tube opening 60, the edge 70 of which is deformed out of the header box as what is described as a rim. An essentially rectangular flat tube can be fitted into the tube opening 60 and can be soldered or welded to the tube plate 30. Corrugated fins which adjoin the flat tube (not shown) on both sides and are soldered to said flat tube, so that heat transfer from a medium flowing through the tube to a medium flowing around the tube and the fins or vice versa is increased, are not shown. In total, the heat exchanger 10 comprises an entire row of alternating flat tubes and corrugated fins, which form what is known as a tube-fin block.

If the header box 20 is acted upon by a medium under pressure, the header box 20 is under certain circumstances deformed in such a manner that its cross-sectional shape approximates a circular shape. To oppose a deformation of this type, the rim 70 is enclosed by an encircling flank 90 which adjoins the rim at an obtuse angle. The flank has a width which is essentially constant all the way around the rim 70. This results in a uniform stiffening of the tube plate 30 both in the longitudinal direction of the tube plate, by means of the flank regions 91, 92 on the end sides of the rim 70, and also in the transverse direction of the tube plate, by means of the flank regions 93, 94 on the longitudinal sides of the rim 70.

This results in reduced deformation of the tube plate 30 when the header box 20 is under compressive load. This reduced deformation of the tube plate 30 involves a reduction in the mechanical load on the tube or on the tube-plate join. In particular, the end sides of the flat tube, which in mechanical terms are under the highest loads in the event of such pressure-induced deformations, are relieved of load as a result.

As can be seen in the side view of the heat exchanger 110 in FIG. 2, the tube 120 is fitted into the tube opening 160 sufficiently far for an upper edge region 121 of the tube 120 to project beyond the tube plate 130. This ensures good utilization of an inner surface (not visible), which faces the tube 120, of the rim 170 as a bearing surface for a tube-plate join. This serves, for example, to ensure sealed soldering. To avoid an unnecessarily high pressure drop of the first medium across the heat exchanger, the extent to which the tube 120 projects above the tube plate 130 is to be minimized. For this reason, the tube opening 160 is situated in an essentially planar central region 131 of the tube plate 130. The rim 170 is enclosed by a flank 190, the end sides 191, 192 of which, firstly, merge into the rim 170 at an obtuse angle and, secondly, likewise at an obtuse angle, merge into a raised edge region 132 of the tube plate 130. An additional reduction in load on the tube 120 and/or the tube-plate join is brought about on account of the associated S-shaped cross section of the tube plate 130 in the region of the cover connection surface 150—edge region 132—flank region 191/192—rim 170.

FIG. 3 shows a further exemplary embodiment of part of a heat exchanger 210 in a longitudinal section. Tubes 220, 221, 222 are fitted in rims 270, 271, 272 of a tube plate 230. In order to reduce a drop in pressure across the heat exchanger 210 of a medium flowing through the heat exchanger 210 and, inter alia, through the tubes 220, 221, 222, the rims 270, 271, 272 face out of the header box (otherwise not shown) and the tubes 220, 221, 222 do not protrude over the tube plate 230 or the rims 270, 271, 272 thereof.

The rims 270, 271, 272 are enclosed here by flanks 290 which each have a planar subregion 295. The planar subregion 295 encloses an obtuse angle with the rim 270, as a result of which the reinforcing effect of the depression, which is formed by the flank 290, in the tube plate 230 is additionally increased. The flanks 290 are directly adjacent to one another here, so that beads 299 are formed, which can be seen in cross section in FIG. 3. As is clearly shown in this cross section, the beads 299 do not have any horizontal regions situated between the flanks 290.

The width b is advantageously similar to the height h of the flanks 290, particularly preferably is approximately the same. For this reason, the angle between the planar subregion 295 of the flank 290 and the rim 270 is approximately 45°. For the beads 299, this results in a bead angle α of approximately 90°, which is associated with a particularly high stiffening effect of the beads 299.

FIG. 4 shows the excerpt of a modified configuration of the heat exchanger from FIG. 3. The tube 320 protrudes here over the rim 370, but ends below a surface 335 of the tube plate 330. This results in increased manufacturing reliability with regard to a fluid-tight connection between the tube plate 330 and the tube 320. For example, a soldered join is improved by a soldering gap 376 to be additionally added to the soldering gap 375. The soldering gap serves here at the same time as an introductory slope for facilitating the fitting of the tube 320 into the tube plate 330.

In contrast thereto, in the exemplary embodiment illustrated in FIG. 5, the tube 420 protrudes beyond the rim 470 and beyond a surface 435 of the tube plate 430. Owing to the associated, relatively large tolerances with respect to the length of the tube 420, a further increase in the manufacturing reliability results.

Claims

1. A heat exchanger having tubes and at least one header box, the header box comprising at least one tube plate, the tube plate having rims into which the tubes can be fitted, wherein the rims are enclosed by a respective peripheral flank, the flanks of two adjacent rims bordering each other with a bead being formed.

2. The heat exchanger as claimed in claim 1, wherein the flanks each have an essentially constant width over the circumference of a rim.

3. The heat exchanger as claimed in claim 1, wherein the tubes are flat tubes arranged in at least one row, in that the rims are of elongate design corresponding to the tube cross sections, and in that the flanks of the rims border one another with elongate beads being formed.

4. The heat exchanger as claimed in claim 1, wherein the flanks each have a rounded portion with an approximately constant radius of curvature.

5. The heat exchanger as claimed in claim 4, wherein the flanks each have a plurality of rounded portions with different radii of curvature.

6. The heat exchanger as claimed in claim 1, wherein the flanks each have at least one planar region.

7. The heat exchanger as claimed in claim 6, the at least one planar region forms an obtuse angle, in particular an angle of between 30° and 60°, with the respective rim.

8. The heat exchanger as claimed in claim 1, wherein the rims face out of the at least one header box.

9. A charge-air cooler, in particular for a motor vehicle, characterized by the features of claim 1.

10. A method for producing a tube plate, comprising: a) providing a planar metal sheet, b) raising one or more edge regions of the planar metal sheet by means of a forming process, c) placing depressions, which border one another, into the metal sheet by means of a forming process, the depressions each having an essentially planar base surface and a flank enclosing and encircling the base surface, d) piercing the base surfaces by means of a draw-through process and, in particular, and e) impressing introductory slopes therein in order to facilitate an introduction of tubes into the rims produced in step d).