The invention relates to a heat exchanger, especially a charge-air cooler for motor vehicles, according to the preamble of-patent claim 1.
Known heat exchangers for motor vehicles, such as, for example, charge-air coolers and coolant radiators, are produced from aluminum (aluminum alloys) and soldered, this applying either only to the heat exchanger block or the entire heat exchanger, including header boxes. The heat exchanger block, especially where charge-air coolers are concerned, is constructed from a series of flat tubes, between which corrugated ribs are arranged. The tube ends of the flat tubes are received in orifices, what are known as rim holes, of the tube bottom and are soldered to the rim holes. This gives rise to a firm and leaktight tube/bottom connection. The header boxes are soldered or welded to the tube bottoms. For the connection between header box and tube bottom, the tube bottom has a peripheral edge strip which engages over or under the header box and thus forms a soldering surface. The rim holes in the tube bottom extend over the entire depth of the latter, that is to say from longitudinal side to longitudinal side, there being between the narrow sides of the rim holes and the edge strips a transitional region which has a channel-like, for example approximately U-shaped design. The tube bottom thus has an approximately rectangularly designed, if appropriate continuous channel which is composed of two parallel longitudinal sides and two parallel narrow sides. The longitudinal sides of the tube bottom are located opposite the narrow sides of the rim holes. During operation, the header boxes are loaded by the internal pressure of the heat exchange medium, for example compressed charge air. This gives rise, in the transitional region between the longitudinal sides of the tube bottom and the narrow sides of the rim holes, to deformations as a result of bending stresses which lead to stress peaks in the region of the narrow sides of the rim holes. The tube/bottom connection, in particular, is subjected to these stresses and deformations on its narrow side and in the tube corner regions in such a way that leaks of the heat exchanger may occur.
The object of the present invention is, in a heat exchanger of the type initially mentioned, to improve the tube/bottom connection and to avoid adverse stresses.
This object is achieved by means of the features of patent claim 1. According to the invention, a reinforcement is provided in the transitional region of the tube bottom. This affords the advantage that an inadmissible deformation or flexion of the tube bottom in the transitional region is avoided and the harmful stress peaks are reduced. The tube bottom, which, by being produced from a sheet steel billet, has approximately the same wall thickness in the remaining region, thus becomes deformable to a lesser extent on the longitudinal sides in the region of the tube narrow sides. The tube/bottom connection is consequently subjected to less or virtually no bending stress, but essentially to shearing stress, which constitutes an appreciably more favorable load.
The reinforcement of the transitional region may be implemented by means of various structural solutions which arise as advantageous refinements from the subclaims. For example, the reinforcement may be configured as a material thickening, thus leading to an increased bending resistance for the transitional region. This could take place, in production terms, by means of the compression of the material. Another advantageous possibility for reinforcement is to reinforce the tube bottom in the transitional region, for example, by one or more beads. Thus, by stability being increased, with the wall thickness of the tube bottom remaining the same, an increased deformation resistance would be achieved. The beads are preferably to be arranged in the region of the narrow sides of the rim holes, in order to achieve an increased bending resistance there.
According to a further advantageous refinement of the invention, the reinforcement is designed as a profile strip which fills the channel-like transitional region and is soldered to the tube bottom. This profile strip likewise achieves a reinforcement, that is to say by means of an additional part which is connected to the tube bottom to form a bend-resistant region. Between the outer edge strip of the tube bottom and the narrow side of the rim hole, therefore, a connection, that is to say a firm bridge, is produced, which prevents a flexion or deformation of the transitional region. The harmful bending stresses are consequently “kept away” from the tube/bottom connection.
According to an advantageous development of the invention, the profile strip is produced or integrated in one piece with the header box, that is to say it forms a prolongation of the longitudinal edges of the header box downward, that is to say in the direction of the tube bottom. This does not entail any additional outlay in terms of manufacture or assembly, since the header box is placed onto the bottom and soldered to the latter, as hitherto.
According to a further refinement of the invention, the profile strip is designed as a (separate) insert strip, that is to say an additional part which is inserted into the channel-like transitional region and is soldered to the tube bottom. The advantage of this solution is that modifications do not have to be made either to the tube bottom or to the header box. For example, such insert strips may be used for heat exchangers, especially charge-air coolers, which are to be employed for higher charge-air pressures. Thus, by means of this simple purposeful measure, the same cooler can be adapted to the higher operating stresses.
In a further advantageous refinement of the invention, the profile or insert strips have toward the inside of the tube bottom, in the region of the tube narrow sides, recesses which partially surround the rim holes, that is to say bear against the narrow sides and corner regions and are supported with respect to these. Consequently, in particular, the corner regions of the tubes are also protected from harmful stress peaks.
Exemplary embodiments of the invention are illustrated in the drawing and are described in more detail below. In the drawing:
a shows a cross section through the tube bottom, and
The bottom plate 7 is planar on the longitudinal sides of the tube bottom 4, that is to say outside the rim holes 8, but has a channel-like design within the edge strips 5, 6, this channel merging, on the one hand, into the bottom plate 7 and, on the other hand, into the edge strips 5, 6, that is to say forming the transitional regions 12, 13. These transitional regions 12, 13 thus form longitudinal beads for increasing the stability of the tube bottom 4. By the box 1 being loaded by the internal pressure caused by the compressed charge air, this gives rise in the longitudinal sides 2, 3 of the box 1 to compressive and/or tensile forces which are transmitted to the edge strips 5, 6 of the bottom and bring about bending stresses and deformations in the transitional regions 12, 13. This is where the invention comes in with the arrangement of the insert strips 10, 11 which are designed as profile strips and have a profile which corresponds to that of the transitional regions 12, 13. The insert strips 10, 11 thus bear on the outside against the edge strips 5, 6, at the bottom against the channel-like transitional regions 12, 13 and on the inside against the narrow sides of the rim holes 8. Air gaps 14, 15 are left above the edge strips 10, 11. As already mentioned, the insert strips 10, 11, which preferably likewise consist of an aluminum alloy, are soldered to the bottom 4, that is to say in one operation with the entire heat exchanger.
a shows the tube bottom 4 in cross section, with the rim holes 8 which have an outer conical region 8c and an inner cylindrical region 8d (adapted to the cross section of the flat tubes 9). The conical region 8c also serves as an introduction slope for the tube ends 9a. The rim holes 8 are produced from the tube bottom plate 7 by hole-punch pressing (cf.
Further solutions, not illustrated here, for reinforcing the transitional regions are possible, for example reinforcement by means of beads, that is to say an increase in the bending resistance by an appropriate shaping for increasing the moment of resistance. The beads may be formed in the region of the narrow sides of the rim holes at the same time as the production of the bottom. Furthermore, there is the possibility of designing the transitional region with a greater wall thickness, which may be carried out, for example, by compressing the bottom in the transitional region. These solutions, too, have the result that the harmful stress peaks in the region of the tube/bottom connection, that is to say in the region of the narrow sides and of the tube corner regions, are reduced.
1 Charge-air box
Number | Date | Country | Kind |
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103 16 756.0 | Apr 2003 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP04/02967 | 3/22/2004 | WO | 10/11/2005 |