Abstract:
To prevent a crack in a joint part of flattened tubes and a header, and smoothly distribute a fluid into the flattened tubes. In the joint part to the header, a reinforcement member having a curved reinforcement portion of U-shape is integrally brazed and fixed to outer peripheries of curved surfaces of the flattened tubes.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a heat exchanger for cooling a heated fluid by external air like an automobile radiator, particularly to a reinforcement structure for preventing a crack generated in a joint part of flattened tubes and a header by thermal stress. 
         [0003]    2. Description of the Related Art 
         [0004]    Like an automobile radiator, there is a heat exchanger in which a core is formed by disposing a large number of flattened tubes side by side and arranging fins between the flattened tubes, and headers are provided in both ends of the flattened tubes. High-temperature engine cooling water is distributed into the flattened tubes, and the air is blown to the outer surface side of the tubes, so that heat is exchanged between the both. Thickness of the flattened tubes is about 0.3 mm as one example, and thickness of the headers is about 2 mm. 
         [0005]    In such a heat exchanger, thermal stress is applied during heat exchange. Then, a crack is sometimes generated in joint parts of the headers and the flattened tubes. In particular, in the flattened tubes at four corners of the core, more thermal loads are generated. Thus, a crack is easily generated on front surfaces of the joint parts of the flattened tubes. 
         [0006]    Therefore, a heat exchanger described in Unexamined Japanese Patent Publication No. 2007-163124 proposes that reinforcement members are inserted in front ends and rear ends of opening portions of flattened tubes in a header. A similar heat exchanger is proposed in Unexamined Japanese Patent Publication No. 2005-221127. 
         [0007]    In any of reinforcement structures described in the above prior art, the reinforcement members are inserted into openings of the flattened tubes at corners of the core. Thus, inlets of the flattened tubes are narrowed by an occupied area of insertion parts of the reinforcement members. Then, a flow rate of the flattened tubes at the corners of the core is decreased more than the other flattened tubes, so that a heat exchanging performance is lowered. Further, heat exchange amounts of the parts are varied, and further larger thermal stress is partially generated, so as to cause a crack of the flattened tubes. 
       SUMMARY OF THE INVENTION 
       [0008]    Therefore, an object of the present invention is to provide a structure capable of reinforcing a joint part of flattened tubes without decreasing a section area of inlets of the flattened tubes. 
         [0009]    The present invention according to a first aspect thereof is a reinforcement structure of a heat exchanger, wherein each of a large number of flattened tubes ( 3 ) includes a pair of parallel flat surfaces ( 1 ) and curved surfaces ( 2 ) connecting between both ends of the flat surfaces, the flattened tubes ( 3 ) are disposed side by side so that the flat surfaces thereof are parallel to each other, a large number of fins ( 4 ) are fixed to outer surfaces of the flattened tubes ( 3 ) so as to form a core ( 5 ), in a state that both ends of the flattened tubes ( 3 ) are inserted into tube insertion holes ( 6   c ) of a header ( 6 ), the inserted parts are integrally brazed, and in at least part of the flattened tubes ( 3 ), on the outer surface side of the inserted parts, on outer peripheries of the curved surfaces ( 2 ) in a joint part to the header ( 6 ), a reinforcement member ( 7 ) having a curved reinforcement portion ( 7   a ) of U-groove shape to be matched with the outer peripheries is integrally brazed and fixed. 
         [0010]    With the present invention according to a second aspect thereof, in the reinforcement structure of the heat exchanger according to the first aspect, in the reinforcement member ( 7 ), a plurality of curved reinforcement portions ( 7   a ) is integrally formed via a coupling portion ( 8 ), and the curved reinforcement portions ( 7   a ) are brazed to the adjacent flattened tubes ( 3 ). 
         [0011]    With the present invention according to a third aspect thereof, in the reinforcement structure of the heat exchanger according to the second aspect, the coupling portion ( 8 ) is brazed and fixed to an outer surface of the header ( 6 ). 
         [0012]    With the present invention according to a fourth aspect thereof, in the reinforcement structure of the heat exchanger according to the third aspect thereof, an inspection hole ( 9 ) for seeing a brazing state is provided to project from part of the coupling portion ( 8 ). 
         [0013]    With the present invention according to a fifth aspect thereof, in the reinforcement structure of the heat exchanger according to any of the first to fourth aspects, an inspection hole ( 10 ) for seeing a brazing state is provided to project from part of the curved reinforcement portion ( 7   a ). 
         [0014]    With the present invention according to a sixth aspect thereof, in the reinforcement structure of the heat exchanger according to any of the first to fifth aspects, the reinforcement members ( 7 ) are respectively provided in the joint parts of the flattened tubes ( 3 ) at four corners of a plane of the core ( 5 ). 
         [0015]    With the present invention according to a seventh aspect thereof, in the reinforcement structure of the heat exchanger according to any of the first to sixth aspects, space portions ( 12 ) in which the fins ( 4 ) do not exist are provided at the both ends of the flattened tubes ( 3 ), and the curved reinforcement portions ( 7   a ) of the reinforcement members ( 7 ) are provided in the space portions ( 12 ). 
         [0016]    In the first aspect of the invention, in the joint part of the flattened tubes  3  and the header  6 , on the outer peripheries of the curved surfaces  2  of the flattened tubes  3 , the curved reinforcement portion  7   a  of U-groove shape is integrally brazed and fixed. 
         [0017]    Therefore, there is an effect of preventing a crack which is easily generated in the joint part by increasing thickness of the joint part. Since the reinforcement is performed from the outer side of the tubes, an internal fluid of the flattened tubes is smoothly distributed, so that heat exchange can be facilitated. That is, inlets of the flattened tubes are not narrowed unlike the reinforcement structures of the conventional examples. 
         [0018]    In the second aspect of the invention, the plurality of curved reinforcement portions  7   a  of the reinforcement member  7  is integrally formed via the coupling portion  8 , and the curved reinforcement portions  7   a  are brazed to the adjacent flattened tubes  3 . Therefore, the plurality of adjacent flattened tubes can be integrally brazed by one part, so that the reinforcement structure can be readily manufactured. At the same time, since the coupling portion  8  couples between the adjacent flattened tubes, strength is more increased than single reinforcement. 
         [0019]    In the third aspect of the invention, the coupling portion  8  is brazed and fixed to the outer surface of the header  6 . Thus, the coupling portion and the header are entirely integrated, so that the strength is more increased. 
         [0020]    In the fourth aspect of the invention, the inspection hole ( 9 ) for seeing the brazing state is provided to project from part of the coupling portion ( 8 ). Thus, it can be confirmed that a brazing material is attached to an edge of the hole, and in that case, it can be determined at a glance that the brazing state of the coupling portion  8  and the header  6  is favorable. Conversely, when the brazing material is not attached to the edge of the hole, it can be found that brazing of the both is unfavorable. 
         [0021]    In the fifth aspect of the invention, the inspection hole  10  for seeing the brazing state is provided to project from part of the curved reinforcement portion  7   a.  Thus, as well as for the fourth aspect, it can be determined at a glance whether or not brazing of the reinforcement member  7  and the flattened tubes  3  is favorable, so that the reinforcement structure with high reliability can be provided. 
         [0022]    In the sixth aspect of the invention, the reinforcement members  7  are provided in the joint parts of the flattened tubes  3  at the four corners of the core  5 . Thus, the flattened tubes at the four corners to which larger thermal stress is easily applied can be effectively protected. 
         [0023]    In the seventh aspect of the invention, the reinforcement members  7  are provided in the space portions  12  in which the fins  4  do not exist in both the ends of the flattened tubes  3 . Thus, the outer peripheries in the joint parts of the flattened tubes which are easily damaged by contact with a foreign substance can be protected. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  is a perspective view of a reinforcement member  7  of a first embodiment of the present invention; 
           [0025]      FIG. 2  is a sectional view by an arrow II-II of  FIG. 3 , showing a state that the reinforcement member  7  is brazed to a flattened tube  3  and a header plate  6   a  of a heat exchanger; 
           [0026]      FIG. 3  is a front view of major parts of the heat exchanger; 
           [0027]      FIG. 4  is a perspective view of a reinforcement member  7  of a second embodiment of the present invention; 
           [0028]      FIG. 5  is a front view of major parts in which the reinforcement member  7  is attached to the heat exchanger; 
           [0029]      FIG. 6  is a perspective view of a reinforcement member  7  of a third embodiment of the present invention; and 
           [0030]      FIG. 7  is a perspective view in which the reinforcement member  7  is attached to the heat exchanger. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    Next, embodiments of the present invention will be described based on the drawings. 
         [0032]      FIGS. 1 to 3  show a first embodiment of the present invention, and a reinforcement member  7  thereof has a pair of curved reinforcement portions  7   a  and a coupling portion  8  coupling the curved reinforcement portions as shown in  FIG. 1 . 
         [0033]    As shown in  FIGS. 2 and 3 , this reinforcement member  7  is fitted onto outer peripheries of curved surfaces  2  in a joint part of flattened tubes  3  to a header  6 , and integrally brazed and fixed to the outer peripheries. 
         [0034]    As clear from  FIGS. 2 and 3 , each of the flattened tubes  3  is formed by a pair of parallel flat surfaces  1  and the curved surfaces  2  connecting both ends of the flat surfaces, and the flat surfaces  1  are disposed side by side in parallel to each other. Fins  4  are integrally fixed between the flattened tubes  3  so as to form a core  5  of a heat exchanger. 
         [0035]    Both upper and lower ends of the flat surfaces  1  (the lower ends are not shown in the figure) are inserted into tube insertion holes  6   c  of header plates  6   a,  and the inserted parts are consistently brazed and fixed. An opening end of a header main body  6   b  is fitted onto an opening of the header plate  6   a,  and the opening end and the opening are integrally brazed and fixed, so as to form the header  6 . As one example, high-temperature engine cooling water is supplied to the flattened tubes  3  via the header  6 , and cooling air  11  accompanying air blowing is distributed in the direction parallel to the flat surfaces  1  of the flattened tubes  3  as in  FIG. 2 , so that heat is exchanged between the high-temperature cooling water and the cooling air  11 . 
         [0036]    At this time, thermal stress is applied the most to the curved surfaces  2  of the flattened tubes  3  in the front row on the side of the cooling air  11  at four corners of the core  5 . This is because distribution of the cooling water is inferior to the other parts, heating is caused, and accordingly, thermal strain is increased. Thus, in this example, the reinforcement members  7  are brazed and fixed to the curved surfaces  2  on the front side of the flattened tubes  3  in the front row. 
         [0037]    In  FIG. 1 , an interval between the pair of curved reinforcement portions  7   a  of the reinforcement member  7  is matched with a pitch P of the pair of flattened tubes  3  as clear from  FIG. 3 . Tongue piece portions  7   b  extend in the curved reinforcement portions  7   a.  Front ends of the tongue piece portions  7   b  are slightly expanded into an inverted V shape, and have an elastic property so as to be easily fitted to the flattened tubes  3 . The curved reinforcement portions  7   a  are formed into a U shape, and inner peripheral surfaces thereof are matched with the curved surfaces  2  of the flattened tubes  3 . 
         [0038]    The coupling portion  8  coupling between the pair of curved reinforcement portions  7   a  is formed so as to be matched with an outer periphery of the header plate  6   a  of the header  6 . In this example, since the header plate  6   a  is formed into a wave shape in the longitudinal direction thereof, the coupling portion has a wave-shape inner peripheral surface to be matched. Further, an inspection hole  9  is provided in center of the coupling portion  8 , and inspection holes  10  are provided in lower parts of the curved reinforcement portions  7   a.    
         [0039]    As one example, thickness of the header plate  6   a  is 1.5 mm to 4.5 mm, and thickness of the flattened tubes  3  is 0.2 mm to 0.4 mm. Thickness of the reinforcement member  7  is 0.4 mm to 0.6 mm. Length of the curved reinforcement portions  7   a  is substantially equal to height of a space portion  12  as in  FIG. 3 . This space portion  12  is a space which is arranged between the adjacent flattened tubes  3  and in which the fins  4  do not exist. 
         [0040]    As in  FIG. 3 , the reinforcement members  7  are fitted to the joint parts of the flattened tubes  3  and the header plates  6   a  at the four corners of the core  5  (the other three corners are not shown in the figure). The pair of curved reinforcement portions  7   a  is fitted to outer surfaces of the curved surfaces  2  of the flattened tubes  3 , and the coupling portion  8  is in contact with an outer surface of the header plate  6   a.  A brazing material is coated over or arranged in any one of the contact parts, and brazing is integrally performed in a furnace in a state that the parts are assembled. It can be confirmed that the reinforcement member  7  is attached to the flattened tubes  3  in an assembled state from an outer surface of an assembled body before brazing. 
         [0041]    Meanwhile, in a case where the reinforcement members are attached to openings of the tubes as in the conventional examples, the reinforcement members cannot be confirmed from an exterior after assembling. 
         [0042]    When brazing is finished, the brazing material thereof is exposed at openings of the inspection hole  9  of the reinforcement member  7  and the inspection holes  10  of the curved reinforcement portions  7   a.  Thereby, it is found that the brazing material is hardened in a state of sufficiently penetrating into the curved reinforcement portions  7   a.  That is, by seeing edges of the inspection hole  9  and the inspection holes  10 , it can be determined whether or not brazing is favorable. 
         [0043]    Next,  FIGS. 4 and 5  show a second embodiment of the present invention. In this example, a large number of curved reinforcement portions  7   a  are continued, and coupling portions  8  are formed on the both sides and between ends thereof. As in  FIG. 5 , the reinforcement members  7  are integrally brazed and fixed to both upper and lower ends (the lower end is not shown in the figure) of the heat exchanger. 
         [0044]    Next,  FIGS. 6 and 7  show a third embodiment of the present invention. In this example, the coupling portion  8  is formed so as to have a U shape section, and facing wall surfaces thereof are integrally brazed and fixed to the flattened tubes  3  and the header plate  6   a.    
         [0045]    It should be noted that the present invention is not limited to the above embodiments as a matter of course but the number of the curved reinforcement portions  7   a  of the reinforcement member  7  may be one or more. 
         [0046]    The reinforcement structure of the present invention is not limited to a radiator but can also be utilized for a heat exchanger such as an intercooler, an EGR cooler, and an oil cooler.