Abstract:
A method of manufacturing a heat exchanger and the heat exchanger made according to the method. The heat exchanger includes a pair of headers that define a plurality of slots. Each of the slots has a pair of nose ends that are disposed within the planar surface. Each of the slots have a first flange and second flange formed on opposite sides of the slots that extend between the pair of nose ends and are recessed into the header relative to the planar surface. One end of each of the tubes is assembled into one of the slots and is connected by a braze weld to the first flange, the second flange, and the nose ends.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to heat exchangers, and in particular header plates of heat exchangers and related manufacturing methods. 
       BACKGROUND 
       [0002]    Heat exchangers are used to remove heat from mechanical systems. For instance, radiators are used in automobiles to remove heat from the engines. Other types of heat exchangers include heater cores, condensers, evaporators and the like. A radiator consists of two opposing radiator tanks separated by a tube bundle and fins surrounding the tube bundle. As coolant is passed through an engine block, the coolant absorbs the heat from the engine. The hot coolant is then fed into a radiator tank and is circulated through the tube bundle. The heat from the coolant is transferred to the fins and transferred to ambient air. The coolant transfers heat as it travels to the opposite radiator tank, which is then fed back to the engine. 
         [0003]    Each radiator tank may include a header plate that receives one end of the tubes in the tube bundle. The header plate defines openings for receiving the tubes. Header plates vary depending on how the tube receiving openings are created. One type of header plate type is a punched style header plate. The openings in a punched style header plate type are punched into the header plate with a punch that removes a slug from the header plate. The openings may have circular, oval or rectangular shapes. A problem with punched style header plates is that the tube walls have only limited contact with the punched edges of the header plates. This problem is magnified when the tubes are folded tubes. The folded tubes have a delta region that does not provide a surface that sits flush with the punched style header plate. This delta region can be difficult to seal with braze clad during the manufacturing process. 
         [0004]    Another type of header plate type is a pierced style header plate. The openings in a pierced style header plate type are formed by piercing through the header plate to form an opening by cutting a slit in the material and forming the edges of slit apart. Unlike the punched style header plate, no slug is removed when piercing the header plate. A problem with pierce style header plates is that they have collars that may crack around the nose area. Cracked collars may be difficult to seal with braze clad during the manufacturing process. 
         [0005]    The above problems and other problems are addressed by this disclosure as summarized below. 
       SUMMARY 
       [0006]    One aspect of the present disclosure relates to a method of making a heat exchanger by punching a pair of spaced nose openings in a header and piercing a portion of the header between the nose openings. A first and a second flange are formed and are recessed into the header that extends between the pair of nose openings. A tube is attached to the header and brazed to the flanges. 
         [0007]    Other aspects of the above method may also include cladding the header with a layer of brazing material before punching and piercing the header. The tube may be folded longitudinally to form a plurality of fluid channels in the tube. A delta region where the tube ends are folded may be filled with cladding material. The tube may be clad before folding the tube. The tube may be brazed to the second flange and the nose openings of the header. 
         [0008]    Another aspect of the present disclosure relates to a method of making a heat exchanger that includes punching a pair of spaced nose openings in the header and piercing a portion of the header between the nose openings to form a first flange and a second flange that are recessed into the header and that extend between the pair of nose openings. The tube is cladded and folded to form a plurality of fluid channels in the tube. The tube is then assembled into the header and brazed to the header at the first flange, the second flange, and the nose openings of the header. 
         [0009]    Yet another aspect of the present disclosure relates to a heat exchanger. The heat exchanger includes a plurality of tubes and a header having a planar surface and defining a plurality of slots. Each of the slots preferably has a pair of nose ends that lie within the planar surface. Each of the slots further has a first and a second flange formed on opposing sides of the slots that extend between the pair of nose ends. The slots are recessed into the header relative to the planar surface. One end of each of the tubes is assembled into one of the slots and is connected by a braze weld to the first flange, the second flange, and the ends. 
         [0010]    The other aspects of the heat exchanger above include tubes that are folded longitudinally and a clad fill in a delta region where two sides of a tube are folded towards. The heat exchanger includes a layer of clad material covering the header, a first a second flange formed by piercing the header, or a pair of nose ends formed by punching nose ends through the header. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an exploded perspective view of a heat exchanger showing the tanks and the header plates. 
           [0012]      FIG. 2  is a flowchart of an exemplary method of making a heat exchanger. 
           [0013]      FIG. 3  is a fragmentary perspective view of a header plate with spaced nose openings separated by bridge portions. 
           [0014]      FIG. 4  is a fragmentary perspective view of a header plate with spaced nose openings and pierced bridge portions. 
           [0015]      FIG. 5  is a fragmentary perspective view of an exemplary folded tube for use with the heat exchanger of the present disclosure. 
           [0016]      FIG. 6  is a fragmentary perspective view of the header plate attached to a tube bundle. 
           [0017]      FIG. 7  is a top plan view of a folded tube attached to one of the header plate slots of  FIG. 6 . 
           [0018]      FIG. 8  is a cross-section view taken along the line  8 - 8  in  FIG. 7 . 
           [0019]      FIG. 9  is a cross-section view taken along the line  9 - 9  in  FIG. 7 . 
           [0020]      FIG. 10  is a cross-section view taken along the line  10 - 10  in  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The illustrated embodiments are disclosed with reference to the drawings. However, it is to be understood that the disclosed embodiments are intended to be merely examples that may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed are not to be interpreted as limiting, but as a representative basis for teaching one skilled in the art how to practice the disclosed concepts. 
         [0022]    Referring to  FIG. 1 , a heat exchanger  20  is illustrated as a radiator. The present disclosure is not limited to vehicles and is applicable to many forms of heat exchangers, such as air conditioners, oil coolers, and intercoolers. The heat exchanger  20  includes a top tank  22  and a bottom tank  24  that are separated by tubes  26  and fins  28 . The top tank  22  includes a top header plate  30 . Tubes  26  attach to the top header plate  30 . The top tank  22  includes a fill port  32  and an inlet  34  to be connected to a liquid cooled mechanical system, such as an engine. The other ends of the tubes  26  are attached to a bottom header plate  36  that forms a part of the bottom tank  24 . A cooling medium, such as a coolant, water, or air, is preferably circulated through the liquid cooled mechanical system, the tanks, and the tubes to cool the mechanical system. 
         [0023]      FIG. 2  shows an example of a method of making a header plate, such as the top header plate  30  or the bottom header plate  36 . The method  38  begins by providing a header plate at step  40 . The header plate  30 ,  36  is covered by cladding material, such as brazing compounds including aluminum, copper, zinc, nickel, and combinations thereof at step  41 . At step  42 , header plate slots are made by punching spaced nose openings through the header plate leaving a bridge of material between the spaced nose openings. The bridge of material is pierced to provide a full length slot that extends between the two nose openings at step  44 . Steps  42  and  44  are preferably repeated until the desired number of header plate slots are formed at step  46 . 
         [0024]    The tubes  26  are folded longitudinally in step  50 . The folded tubes are arranged with the fins  28  to facilitate heat transfer. Both ends of the folded tubes are attached to the header plates at step  52 . The folded tubes  26  are brazed to the header plates in step  53  such as by heating a filler metal above melting point and applying the filler material between the tubes and the header plates by capillary action. 
         [0025]    Referring to  FIG. 3 , the step of creating nose openings is shown in detail. A header plate  54  is provided that has a planar surface. A first nose opening  56  is formed on the header plate  54  by punching a D-shaped hole through the planar surface. A second nose opening  58  is formed on the header plate  54  by punching a second D-shaped hole through the planar surface. The first nose opening  56  and the second nose opening  58  are separated by a first bridge of the header plate material  60 . Nose openings  62  and  64  are also formed and separated by bridge of header plate material  66 . Nose openings  68  and  70  are further formed and separated by bridge of header plate material  72 . The nose openings may also be shaped as a circle or an oval. The pairs of punched nose openings are formed in the header plate preferably in a single punching operation. 
         [0026]    Referring to  FIG. 4 , the header plate  54  is pierced to form flanges from the bridge of header plate materials  60 ,  66 , and  72 . The planar surfaces of the header plate portions surrounding the punched openings are raised as a result of piercing. Bridge of header plate material  60  is pierced to form first flange  74  and second flange  76 . Bridge of header plate material  66  is pierced to form third flange  78  and fourth flange  80 . Bridge of header plate material  72  is pierced to form fifth flange  82  and sixth flange  84 . 
         [0027]    The illustrated portion of a header plate  54  has three header plate slots. The first header plate slot  86  includes the first nose opening  56 , the second nose opening  58 , and the pierced opening surrounded by first flange  74  and second flange  76 . The second header plate slot  88  includes the nose openings  62  and  64  and the pierced opening defined by the third flange  78  and the fourth flange  80 . The third header plate slot  90  includes the nose openings  68  and  70  and the pierced opening defined by the fifth flange  82  and the sixth flange  84 . After the desired number of header plate slots is formed on the header plate, the header plate may be covered with one or more layers of clad materials. Header plate  54  includes a combination of punched and pierced header plate slots. 
         [0028]    Referring to  FIG. 5 , a folded tube  92  is illustrated that is adapted for use with the heat exchanger of the present disclosure. The folded tube  92  may be made of a stamped sheet of metal having sides preferably folded towards its center  98  to create two symmetrical fluid flow paths or channels  94  and  96 . In other embodiments, multiple folds may be made in the tubes to define multiple fluid flow paths. The folded tube  92  includes nose portions  93  and  95  on both sides of the folded tube  92 . The nose portions  93  and  95  are separated by a belly portion  97  at the periphery of the folded tube  92  that is opposite the center  98  where the folded sides meet. The symmetrical fluid flow paths allow a fluid medium, such as liquid or air, to flow for efficient heat exchange. The folded tube  92  may alternatively be made as an extrusion having a longitudinal fold in the center. One or more layers of clad materials may be added to the folded tube  92  either before folding the tube or after folding the tube  92 . 
         [0029]    Referring to  FIG. 6 , several folded tubes  92  may be arranged in a pattern with several fins  28 . The folded tubes  92  may alternatively have fins embedded with them. The previously described header plate  54  may then be assembled with the tubes  92  such that the ends of the tubes  92  are inserted into their respective slots  86 ,  88 , or  90 . As shown in  FIG. 7 , brazing material  100  is added between the surfaces of the header plate in contact with the folded tubes  92 . The brazing material  100  fills a delta region  102  that is the area formed between the header plate and the crease at the center  98  of the folded tube  92 . Referring to  FIGS. 3 ,  4 , and  7 , the nose portions  93  and  95  occupy the punched nose openings  56  and  58  or  62  and  64  or  68  and  70 . The belly portion  97  of the folded tube  92  is adjacent to the flange formed from piercing, such as flange  76 ,  80 , or  84 . The belly portion  97  directly contacts the braze material  100  that attaches the belly portion  97  to the flange  76 ,  80 , or  84 . The brazing material may be the same as the clad material in certain embodiments. 
         [0030]    Referring to  FIGS. 8-10 , nose portions  93  and  95  of tube  92  occupy the punched nose openings formed from punching the header plate and are directly contacting the braze material  100  that attach the tube to the header plate. The center  98  of the tube  92  is in direct contact with the braze material  100  between the flange  76  and the tube  92 . The delta region is filled with braze material  100  as previously shown in  FIG. 7 . The belly portion  97  directly contacts the braze material  100  that attaches the belly portion  97  to the flange  76  ( FIG. 9 ). In  FIG. 10 , the center portion  98  and the belly portion  97  of the tube  92  are surrounded by and contact the braze material  100  that is sandwiched in between flange  76  and  74 . Flange  76  and  74  may also be covered by braze material  100 . In certain embodiments, the braze material and the clad material are made of a different materials. The tubes and the header plates may be covered by clad material where the braze materials and the clad materials are different. Braze material may be applied between the nose portions of the tubes and the nose openings and between the flanges and belly portion or the center portion of the tubes. 
         [0031]    Punched style header plates that have header plate slots formed by punching holes on the header plates do not ensure direct contact between the tubes and either the header material or the clad material. The problem is magnified when the tubes being used are folded tubes. Tubes may detach from the header plates causing the heater exchange tanks including the header plate to leak. The folded tubes have a delta region that does not provide a surface that sits flush with the header plate. Pierced style header plates have been proposed to solve this problem. However, existing pierced style header plates that have header plate slots formed by piercing the header plates may have collars that crack, especially around the nose area. Cracked collars may be difficult to seal with braze clad during the manufacturing process. 
         [0032]    The heat exchanger of the present disclosure includes header plates that ensure that the tubes have sufficient contact with the braze materials covering the header plates, regardless of whether the tubes are folded or not. The header plates have slots that are both punched and pierced. Thus, the header plates combine the beneficial aspects of punched and pierced header plates. The header plates have punched spaced nose openings and are less susceptible to cracking The nose openings are spaced apart by bridge material that is pierced so that the delta regions of the folded tubes can be filled with braze or clad materials when the tubes are attached to the header plate. 
         [0033]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the disclosed apparatus and method. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure as claimed. The features of various implementing embodiments may be combined to form further embodiments of the disclosed concepts.