Priority is hereby claimed to German Patent Application No. DE 10 2008 035 358.2, filed Jul. 29, 2008, the entire contents of which is incorporated herein by reference.
The present invention relates to a heat exchanger, in particular a condenser or gas cooler, having the further features of the preamble of claim 1. The invention also relates to a collecting tube for the above-specified heat exchanger and to a method for producing the same.
WO 02/079708 A2 discloses a conventional heat exchanger. Here, the profile of the collecting tube is advantageously produced by deformation of a single-piece metal strip, as illustrated for example in
The tank for high-pressure refrigerant heat exchangers presented in German patent application DE 10 2007 039 756 A1 is also produced in one piece from a metal strip, with internal stiffening structures of the tank, such that the tank must be produced in a plurality of successive embossing and deep-drawing steps.
German patent application DE 103 02 412 A1 likewise presents a collecting tube: the profile of said collecting tube is produced in one piece, as shown for example in
One independent object of the invention is to provide a heat exchanger which is improved with regard to internal pressure resistance and costs for production and material expenditure.
One or more objects are achieved according to the invention with regard to the heat exchanger by means of the use of the features of claim 1. Other claims contain refining features of the heat exchanger.
According to some embodiments of the invention, the base of the collecting tube is reinforced between the heat exchanger tubes, in order to increase the internal pressure resistance, by virtue of the longitudinal edge strips of the metal strip nestling at the inside against the contour of the base over at least ⅓ of the surface area of the base, preferably at least over 50% to 70% of the total surface area, and thereby providing reinforcement, by forming at least a doubled wall thickness, in the region weakened by the openings for the heat exchanger tubes. Within the context of the invention, the base is to be understood approximately to mean that strip-shaped region, which runs in the longitudinal direction, on the collecting tube which is assigned to the openings for the heat exchanger tubes and which extends approximately from the one narrow side to the other narrow side of the heat exchanger tubes or of the openings. Here, said type of reinforcement increases not only the internal pressure resistance but rather also the dimensional stability required for the soldering, welding or brazing process. The above-specified 50% to 70% of the base over which the longitudinal edge strips nestle is a preferred range. In the case of an approximately rectangular design of the cross section of the chambers of the collecting tube, it is also possible for a range of approximately 70% to 90% to be provided.
A collecting tube according to the invention is characterized in that the reinforcement which is formed from the longitudinal edge strips extends at least over ⅓ of the surface area of the base.
A method according to the invention for producing the collecting tube is characterized in that the two longitudinal edge strips are rolled in and thereby bear against the inner side of the base in such a way as to reinforce at least ⅓ of the surface area of the base, but preferably considerably more than ⅓.
The profile of the collecting tube is produced in one piece from a metallic strip, preferably from an aluminum strip, wherein the strip may be solder-plated on one side or both sides. To ensure the best resistance to the high internal pressures in particular in operation as a gas cooler for CO2 motor vehicle air-conditioning systems, the two chambers of the collecting tube profile have approximately a circular shape: the ideal circular shape is sought for the internal pressure loading, which circular shape is divided here, to reduce the structural height, into two individual circular shapes which are however adjacent and connected to one another.
Here, the two longitudinal edge strips of the endless metal strip are deformed inwardly in such a way as to form two overlapping regions of the inwardly rolled longitudinal-side ends of the metal strip with two sections situated in the edge region of the heat exchanger tubes. Here, the inwardly rolled longitudinal edge strips of the metal strip nestle against the base or against the wall. The profile of the collecting tube is thus composed of two shapes which virtually correspond to the ideal circular shape and which are connected to one another approximately along the central longitudinal axis of the collecting tube and to the base of the collecting tube approximately in the edge region of the heat exchanger tubes. In contrast to known designs, the reinforcements according to the invention formed from the longitudinal edge strips significantly improve the internal pressure resistance, since said reinforcements extend over the greater part of the base. In this way, the best possible internal pressure resistance is obtained with a reduced material thickness. This advantage is not provided for example in the published document WO 02/079708 A2, since here, the longitudinal edge strips of the metal strip nestle against the base region, and are connected to the latter, in each case only over approximately three times the material thickness of the metal strip.
The medium to be cooled is conducted through heat exchanger tubes, wherein said heat exchanger tubes may for example be formed, as multi-chamber tubes with two narrow sides and two wide sides, from extruded aluminum profiles with a plurality of inner ducts. The multi-chamber tubes are plugged into the openings in the base of the collecting tube, with the ends of the multi-chamber tubes extending approximately up to the inner surface of the inwardly deformed longitudinal edges. The multi-chamber tubes may also be formed from two halves joined together.
To ensure the best possible soldering of the overlapping regions in order to obtain the greatest possible internal pressure resistance, the corresponding surfaces of the overlapping regions are pre-treated in a particular way: it has been found that, by mechanically roughening the surfaces, a particularly uniform and reliable flow of solder is obtained in the region of the overlapping portions. Said locally limited surface treatment is carried out before the deformation of the metal strip to form the profile of the collecting tube. Rotationally symmetrical rotating deformation tools are used for the deformation of the endless metal strip, and the endless metal strip is additionally perforated and punched out before said deformation process.
The collecting tube is of course completed at both end sides with closure covers.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
The invention is described below on the basis of the appended figures, in two exemplary embodiments. The description contains further features and their advantages. In the figures, in partially schematic form:
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
The longitudinal edge strips 5 of the metal strip are deformed inwards in such a way that additional reinforcements 15 are formed between the heat exchanger tubes 2 in the base region 11 of the collecting tube 1, which additional reinforcements 15 extend over the greater region of the base 11. Here, a narrow region 14 along the central longitudinal axis 23 is formed without reinforcement. Said reinforcements 15 in the form of at least a doubled wall thickness also contribute to increased dimensional stability during the soldering, welding and/or brazing process.
A second exemplary embodiment of the collecting tube 1 having a wall 10 and two chambers 13 is illustrated in simplified form in
The metal strip for producing the collecting tube 1 which can be seen in
The deformation stages of the metal strip from the planar strip to the profile of the collecting tube 1 are illustrated in
A heat exchanger tube 2 which is used for the heat exchanger is illustrated in
Various features and advantages of the invention are set forth in the following claims.
Number | Date | Country | Kind |
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102008035358.2 | Jul 2008 | DE | national |