Abstract:
A heat exchanger is provided that includes a housing and an exchanger region which is arranged in the housing and has tubes and at least one base, wherein the tubes are connected to the at least one base, wherein the housing is manufactured from a plastic and has a housing inner surface, wherein the housing inner surface is covered at least in regions or in sections by at least one metallic element for protecting the housing from a thermal load. The invention further relates to a method for producing a heat exchanger.

Description:
[0001]    This nonprovisional application is a continuation of International Application No. PCT/EP2014/073157, which was filed on Oct. 28, 2014, and which claims priority to German Patent Application No. 10 2013 221 932.6, which was filed in Germany on Oct. 29, 2013, and which are both herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a heat exchanger, in particular for a motor vehicle and a motor vehicle with a heat exchanger. The invention also relates to a method for producing a heat exchanger. 
         [0004]    2. Description of the Background Art 
         [0005]    In a heat exchanger, which can also be referred to as a heat transfer unit, thermal energy can be transferred from one material flow to another. In a motor vehicle, different embodiments of heat exchangers are used, in particular i-flow heat exchangers and u-flow heat exchangers. The heat exchangers should be as light as possible in order to reduce the total weight in the vehicle. Preferably, the heat exchangers are at least in part or in places manufactured from a lightweight material, in particular from a plastic. Currently, only u-flow heat exchangers with a plastic housing are on the market and in use in motor vehicles. For manufacturing reasons, the i-flow heat exchangers are currently manufactured from metallic materials, in particular steel or cast aluminum. 
         [0006]    DE 10 2009 050 884 A1, which corresponds to US 2012/0305220 and which is incorporated herein by reference, disclose an exhaust gas heat exchanger in particular for a motor vehicle, comprising at least a diffuser for supplying and/or discharging an exhaust gas stream, a transfer portion with axially extending exchanger tubes, the exchanger tubes being connected at one end with a base. Further, the exhaust gas heat exchanger comprises a housing than can be flowed through by a refrigerant, which is formed of a non high-temperature resistant material, in particular plastic or aluminum, wherein a connecting element is partially embedded in the housing to secure the connecting element to the housing. The connecting element is connected in a first adhesive bond area cohesively with the base, which is connected to a second adhesive bond area cohesively with the diffuser. 
       SUMMARY OF THE INVENTION 
       [0007]    It is therefore an object of the invention to provide an improved heat exchanger which has a low weight. 
         [0008]    In an exemplary embodiment, a heat exchanger comprises a housing and an exchange region having tubes and at least one base disposed in the housing, the tubes being connected at one end of the tube with the at least one base, wherein the housing can be made of a plastic and has a housing inner surface, the inner surface of the housing being at least in parts or sections covered with at least one metallic element to protect the housing from a thermal load. The thermal load can hereby be caused by a joining process, in particular by laser welding. As a result, the metallic element, which at least partially covers the inner surface of the housing, can protect the housing from being damaged by the thermal load. 
         [0009]    The metallic element can be disposed in the housing, starting from an edge area of the inner surface of said housing, which at least partially covers the inner surface of the housing. 
         [0010]    The heat exchanger can have two bases, the tube end being a first tube end and the tube having a second tube end, which is connected to a second base. Thus, the tubes of the exchanger region are connected to the first base and the second base, form a tube/base package and are arranged in an assembled state within the housing. 
         [0011]    The tubes can be arranged in the axial direction in the exchanger region. On the first or the second base, a diffuser may be arranged to supply an exhaust gas stream. Through the tubes arranged in the housing, a first fluid can flow during operation of the heat exchanger, preferably a coolant. 
         [0012]    Outside of the tubes, a second fluid, for example, an exhaust gas flow to be cooled, can flow through the housing. 
         [0013]    The tubes and the base can be cast from a thermally stable, particularly high temperature resistant material, for example, made of a metal. Due to the arrangement of the metallic element in areas of the housing inner surface, it is possible that at least a connection between one of the bases and one of the tube ends can be made, after tubes at least partially inserted in the base are arranged in the housing. 
         [0014]    The connection between tubes and base can be made by means of a joining technique, in particular by means of laser welding. For example, in each case a tube end can be arranged in the first base, for example inserted, thereby creating a tube/base package, the tube/base package can be inserted in the housing, the remaining tube ends are inserted in the second base and the tube ends are welded to the respective bases. 
         [0015]    In the inventive method for producing a heat exchanger with an exchanger region with tubes, which are flowed through by a fluid, comprising a housing in which the exchanger region is arranged, and bases, in a first method step at least one tube end of the tubes is inserted into at least one of the bases, and in a second method step, a non-releasable, in particular solid tube-base connection, is produced with a connection technique. 
         [0016]    The non-releasable connection cannot be easily separated by a reversal of the connection or joining process. The non-releasable connection may be a solid compound which is separable only by destruction. Preferably, the connection is a cohesive connection. For example, the connection technique can be a joining method, preferably a laser welding process or a brazing process. The tube-base connection can be made at one end of the tube/base package when the latter is disposed in the housing, or on both sides of the tube/base package. Thus, a heat exchanger having a plastic housing can be easily and inexpensively manufactured, in particular an i-flow heat exchanger. In particular, the tube/base connection can be made without the need for costly intermediate elements as in the prior art. For example, the metallic element can be disposed respectively at the points at which scattered light could occur during laser welding of the tubes into the base. The metallic elements can be arranged at the open ends of the housing into which the tube/base unit is inserted. Thus, the area of the housing which is arranged in the immediate vicinity of the tube/base junction is protected from scattered laser light. 
         [0017]    A singular or a plurality of metallic elements can be arranged on at least one housing inner surface in which the metallic element/s is/are poured into the plastic of the housing. The heat exchanger can have an area for receiving a base or an area of the housing directly adjacent to a base, wherein at least the at least one metallic element can be disposed on one of the housing inner surfaces. The at least one metallic element may have an annular cross section and the outer surfaces of the metallic element may simulate the inner surface of the housing. Here, in particular, a closed form of the metallic element is ensured due to the annular cross section. The annular cross section may in this case be circular. The metallic element may have straight sections as well as rounded corners, and may have a more rectangular shape with rounded corners, and with this geometric configuration may ensure a closed cover of the housing inner surface. 
         [0018]    In an embodiment, the at least one metallic element may have an at least partially encircling angled edge region. For example, the at least partially encircling angled edge region can form a stop against the housing. 
         [0019]    The at least one metallic element can be formed in two parts, wherein the division can be produced by separating cuts on two opposite surfaces of the metallic element. The inlay hereby can have an inlay element at least partially enveloping, for example, a top and one or two lateral housing inner surfaces, and a second inlay element at least partially enveloping, for example, a lower housing inner surface. Between the first inlay element and the second element, a dividing line can be formed on the lateral housing inner surfaces. However, the dividing line can also be arranged on the upper and/or lower housing inner surface. This more easily allows for the inner surface of an asymmetrical housing to be enveloped by the metallic element, in particular, by the inlay. 
         [0020]    The at least one metallic element can be an inlay. The inlay can be at least in parts made of metal. The inlay may be co-injected in the plastic housing. This is advantageous if the plastic housing is an injection molded part. However, the inlay can also be manufactured as a separate component and be subsequently arranged in the housing. 
         [0021]    In an embodiment of the heat exchanger, the inlay is integrally formed. At one or both ends of the housing, the inlay can be inserted in the latter or formed thereon. 
         [0022]    The at least one metallic element can be formed as a metallic coating of the housing, for example, the inner surface of the housing. Coatings, especially metallic coatings, can be designed thin. They can also be easily applied to the inner surface of the housing by means of generally known coating processes. The metallic coating is particularly suitable for complicated shapes of the housing inner surface. 
         [0023]    In an embodiment of the heat exchanger, the at least one metallic element can completely cover the inner surface of the housing. The metallic element in this case can extend inside from a first housing end to a second housing end. For example, the coating can be implemented throughout. Alternatively, the metallic element can completely cover the dimensions of the housing inner surface in the longitudinal direction. However, this way the metallic element can cover the periphery of the housing inner surface only in some areas. 
         [0024]    The housing of the heat exchanger can be a 2-component plastic part. 
         [0025]    The object is also achieved by a motor vehicle with at least one heat exchanger, wherein the exchanger region with tubes is welded on both sides, in each case with a base, after said region has already been arranged in the plastic housing. Here, no intermediate elements are necessary to facilitate the weld. By doing without intermediate elements according to the method of the invention, weight can be reduced. In addition, a weight-reduced i-flow heat exchanger with two bases (one base per housing side) and made of lightweight plastic can be used. 
         [0026]    The heat exchanger can be an exhaust gas heat exchanger. 
         [0027]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes, combinations and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein: 
           [0029]      FIG. 1  is a housing of an i-flow heat exchanger according to an exemplary embodiment; 
           [0030]      FIG. 2  shows the housing with associated inlays; and 
           [0031]      FIG. 3  is the housing with the assembled tube/base package. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]      FIG. 1  shows an exemplary embodiment of a housing  10  of a heat exchanger in a perspective side view looking into the housing interior  12 . The housing  10  is made of a plastic material and preferably produced by injection molding. The housing  10  is constructed as i-flow housing  10  and has an elongated case body  14 , which is formed by a housing jacket  11  made of plastic and on the front side has a first opening  16  and a second opening  18 . 
         [0033]    The interior of the housing  12  has four substantially planar housing inner surfaces  20 ,  22 ,  24  and  26 . The housing inner surfaces  20  and  24  and the housing inner surfaces  22  and  26  are situated opposite one another. 
         [0034]    On the housing inner surface  22 , a recess  28  is shown to which a connector can be connected for supplying a fluid. 
         [0035]    On the housing inner surfaces  20 ,  22 ,  24  and  26 , an inlay  30  is arranged, having a first inlay element  32  and a second inlay element  34 . The inlay  30  is constructed of two parts. The inlay  30  may in this case be a two-part design (as shown in  FIG. 1 ) or a 3-part or generally multi-part design and have the appropriate number of inlay elements. The inlay  30  or inlay elements  32 ,  34  are formed by a metallic element  30  or by a plurality of metallic elements  32 ,  34 . The term inlay  30  or inlay element  32 ,  34  is hereinafter referred to as equivalent to the term metallic element  30 ,  32 ,  34 . 
         [0036]    Preferably, the inlay element  30  which forms the metallic element  30  is designed as an annular body. The curve of the outer surfaces of the annular body is modeled after the shape of the housing inner surfaces  20 ,  22 ,  24 ,  26 . The annular body can thus be applied in full surface contact at the housing inner surfaces  20 ,  22 ,  24 ,  26 . The annular body may in this case either be inserted through one of the openings  16 ,  18 , or encapsulated by the material forming the housing  10  during the manufacturing process of the housing  10 . For this purpose, the inlay  30  or the inlay elements  32 ,  34  can be advantageously inserted into the mold of the housing  10  and then be encapsulated with the material forming the housing  10 . 
         [0037]    The inlay  30  or the inlay elements  32 ,  34  preferably have an at least partially encircling edge region, which is angled relative to the region forming the annular body. The angled edge portion forms a stop against the housing  10  and in particular against the respective flange regions  36 ,  38  at the openings  16 ,  18  of the housing  10 . Due to the angled edge region, the depth of insertion of the inlay  30  and inlay elements  32 ,  34  is limited. 
         [0038]    The inlay  30 ,  32 ,  34  lines the housing inner surfaces  20 ,  22 ,  24 ,  26  in the embodiment in the region of the openings  16  and  18 . The dimensions of the inlay  30 ,  32 ,  34  can, however, also correspond to the dimension in the longitudinal extension of the housing body  11  and extend from the opening  16  to the opening  18 . The inlay  30 ,  32 ,  34  may be a separate metallic element or be designed as a coating of the housing inner surfaces  20 ,  22 ,  24  and  26 . Here, at least in the region of the openings  16  and  18 , the housing inner surfaces  20 ,  22 ,  24  and  26  are covered by a metallic material. Preferably, the metallic element  30 ,  32 ,  34  extends a few centimeters from the respective opening  16  and  18  into the housing interior  12 . 
         [0039]    The housing  10  on both sides has a flange each, these are connecting flanges  36  and  38 . The flanges  36  and  38  have recesses  40 . Further, the housing  10  has a sealing groove  44  at its front end  42 . 
         [0040]      FIG. 2  shows the housing  10  in an exploded view. The metallic element  30 ,  32  and  34 , designed here exemplified as a one-piece inlay  30  as two inlay elements  32  and  34 , is respectively disposed outside the housing body  14  and may be inserted in the interior of the housing  12  along the housing inner surfaces  20 ,  22 ,  24  and  26 . 
         [0041]    The separation of the metallic element  30  into two or more elements  32 ,  34  is advantageously realized by separating cuts, which extend at substantially opposing surfaces of the metallic element  30 ,  32 ,  34 . The cuts may in this case run parallel to each other or, as shown in  FIG. 2 , be inclined in opposite directions to each other. This opposite orientation of the cuts prevents a shifting of the individual elements  32 ,  34  against each other. 
         [0042]      FIG. 3  shows a heat exchanger  45  with the housing  10  in the assembled state. On the housing  10 , a first base  46  and a second base  48  are mounted at the respective connecting flange  36  and  38 . In the first base  46  and the second base  48 , tubes  49  are arranged, particularly plugged in and integrally connected to the respective base, in particular welded or soldered, preferably connected by a laser welding method, in particular non-releasably connected. At the opening  28 , a connector  50  is mounted through which a fluid, in particular gaseous fluid, can enter the interior of the housing  12  and can flow between the tubes  49 , through which a cooling fluid can flow. 
         [0043]    The method for producing the heat exchanger thus can have the steps of: Producing a housing body  11  made of a plastic material, preferably by means of an injection molding process; Producing a metallic element  30 ,  32 ,  34  at least in the region of the two end openings  42  at the housing inner surfaces  20 ,  22 ,  24  and  26 ; Arranging the tube-base package, in which in each case at least one tube end of the tubes  49  is inserted in each case in openings  52  of the at least one base  46  or  48 ; Optional: arranging the second base  46  or  48  when the tube/base package is disposed in the housing body  14 ; and Welding, in particular by means of laser welding, of the respective tube ends of the tubes  49  to the respective base  46 ,  48 . 
         [0044]    After the core of the heat exchanger  45  composed of the housing  10  and the tube/base package is mounted, the heat exchanger  45  can be installed in a motor vehicle (not shown), and connecting elements can be connected to the connectors  50  for a gaseous fluid, and tubes  49  can be connected to the cooling fluid circuit. 
         [0045]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.