Abstract:
A tube having a multi-channel tube and branch tubes, a connection structure thereof and a connection method therefor are disclosed. The tube is provided with: a multi-channel tube including a partition wall to partition an interior of the multi-channel tube into plural channels and an expanded end portion ; branch tubes inserted into the expanded end portion and respectively communicating with the channels; and clearances for being filled with brazing metal, which are respectively kept between the multi-channel tube and each of the branch tubes.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a tube having a multi-channel tube and branch tubes branching therefrom, a connection structure therefor and a method for forming and connection thereof.  
         [0003]     2. Description of the Related Art  
         [0004]     Many machines are equipped with tubes for supply and/or circulation of fluid and, in certain cases, the tubes are required to branch into two or more branch tubes. Such a branching tube is formed in accordance with the following procedure. First, a multi-channel tube which has a partition wall to partition the interior thereof into plural channels is provided. Second, branch tubes are respectively inserted into the channels of the multi-channel tube. Finally, brazing among the multi-channel tube and the branch tubes are carried out.  
         [0005]     In this procedure, a gap between the branch tubes is in general too narrow to carry out brazing since the gap is regulated only by a thickness of the partition wall provided in the interior of the multi-channel tube. Therefore failure of brazing among the multi-channel tube and the branch tubes, in particular, between the partition wall and each of the branch tubes is likely to happen. Moreover, since the branch tubes having relatively narrow inner flow channels as compared with the multi-channel tube are inserted in the channels, steps are formed in the channels and cross sectional areas thereof are reduced. They may cause turbulent or not smooth flow of the fluid and increase flow resistance.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention has been achieved in view of the above problem.  
         [0007]     In accordance with a first aspect of the present invention, a tube is provided with: a multi-channel tube including a partition wall to partition an interior of the multi-channel tube into plural channels and an expanded end portion; branch tubes inserted into the expanded end portion and respectively communicating with the channels; and clearances for being filled with brazing metal, the clearances being respectively kept between the multi-channel tube and each of the branch tubes.  
         [0008]     Preferably, the branch tubes respectively include broadened end portions to be inserted into the expanded end portion of the multi-channel tube.  
         [0009]     Preferably, the expanded end portion of the multi-channel tube has greater diameters in any radial directions except a direction along the partition wall than a diameter of a main portion of the multi-channel tube.  
         [0010]     More preferably, the expanded end portion of the multi-channel tube is expanded only in a direction perpendicular to the direction along the partition wall.  
         [0011]     More preferably, the multi-channel tube includes a reducer portion having larger diameters at a first end linking with the expanded end portion and reducing diameters toward a second end linking with the main portion of the multi-channel tube.  
         [0012]     Still preferably, each of end portions of the branch tubes, the end portions being inserted into the expanded end portion of the multi-channel tube, is inclined with respect to a direction in which the end portion is inserted into the expanded end portion.  
         [0013]     Still preferably, the branch tubes are treated with presswork to have offsets with respect to the multi-channel tube.  
         [0014]     Still preferably, cylindrical portions of the respective branch tubes, the cylindrical portions being apart from end portions of the branch tubes, are separated from each other in a state where the branch tubes are inserted into the expanded end portion.  
         [0015]     Still preferably, the branch tubes have offsets with respect to the multi-channel tube in a state where the branch tubes are inserted into the expanded end portion, wherein first end portions of the branch tubes, the first end portions being inserted into the expanded end portion, are parallel with second end portions of the branch tubes, and wherein the branch tubes have different lengths.  
         [0016]     In accordance with a second aspect of the present invention, a method for connection of a multi-channel tube with plural branch tubes is provided with steps of: expanding an end portion of the multi-channel tube; inserting the branch tubes into the expanded end portion, respectively; and brazing each of the branch tubes with the expanded end portion.  
         [0017]     Preferably, the method is further provided with steps of: broadening an end portion of each branch tube; clamping a cylindrical portion of the branch tube, the cylindrical portion being apart from the broadened end portion of the branch tube; press-working the broadened end portion of the branch tube to have an offset with respect to the cylindrical portion of the branch tube; and forming the broadened end portion of the branch tube to have a D-letter cross sectional shape.  
         [0018]     More preferably, the step of broadening includes shaping the end portion of the branch tube to have an elliptic cross sectional shape.  
         [0019]     More preferably, the step of clamping includes steps of inserting a mandrel into the broadened end portion of the branch tube, and bringing down an upper die to clamp the cylindrical portion of the branch tube between an upper clamp and a lower clamp and fix the branch tube by means of repulsive force of an elastic body of the upper die, and wherein the steps of press-working and forming are simultaneously carried out by forcing down the upper die to press down an upper mold onto the broadened end portion of the branch tube and press down a mandrel presser onto the mandrel so that the broadened end portion of the branch tube is formed to have the D-letter cross sectional shape and the branch tube is bent.  
         [0020]     Still preferably, the method is further provided with steps of: clamping a cylindrical portion of each branch tube, the cylindrical portion being apart from an end portion of the branch tube; press-working the end portion of the branch tube to have an offset with respect to the cylindrical portion of the branch tube; and forming the end portion of the branch tube to have a D-letter cross sectional shape.  
         [0021]     Further preferably, the method is further provided with a step of: broadening an end portion of each branch tube before the steps of clamping, press-working and forming.  
         [0022]     Further preferably, the method is further provided with a step of: broadening an end portion of each branch tube to have an elliptic cross sectional shape before the steps of clamping, press-working and forming. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  shows a vertical section of a connection structure among a multi-channel tube and branch tubes in accordance with a first embodiment of the present invention;  
         [0024]      FIG. 2  shows an enlargement taken from a circle II of  FIG. 1 ;  
         [0025]      FIG. 3  shows a cross section of an expanded end portion of the multi-channel tube;  
         [0026]      FIG. 4  shows a vertical section of the expanded end portion of the multi-channel tube taken from the line IV-IV of  FIG. 3 ;  
         [0027]      FIG. 5  shows a vertical section of the expanded end portion of the multi-channel tube taken from the line V-V of  FIG. 3 ;  
         [0028]      FIGS. 6A, 6B  and  6 C are respectively a plan view, a side view and a vertical sectional view of the branch tube, where  FIG. 6C  is taken from the line VIC-VIC of  FIG. 6A ;  
         [0029]      FIG. 7  is a flow chart of a method for forming the branch tube in accordance with the first embodiment of the present invention;  
         [0030]      FIG. 8  is a schematic drawing illustrating a step of setting the branch tube in a forming machine;  
         [0031]      FIG. 9  is a schematic drawing illustrating a step of clamping the branch tube;  
         [0032]      FIG. 10  is a schematic drawing illustrating a step of shaping an end portion of the branch tube and a step of bending;  
         [0033]      FIG. 11  shows a cross section taken from the line XI-XI of  FIG. 10 ;  
         [0034]      FIG. 12  is a flow chart of a method for forming the branch tube in accordance with a second embodiment of the present invention;  
         [0035]      FIG. 13  is a schematic drawing illustrating a step of setting the branch tube in a forming machine;  
         [0036]      FIG. 14  is a schematic drawing illustrating a step of shaping an end portion of the branch tube;  
         [0037]      FIG. 15  is a schematic drawing illustrating a step of bending the branch tube;  
         [0038]      FIG. 16  shows a cross section taken from the line XVI-XVI of  FIG. 15 ;  
         [0039]      FIG. 17  shows a cross section of the branch tube before and after shaping; and  
         [0040]      FIG. 18  shows a side view of an upper mold and a lower mold for shaping the end portion of the branch tube.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0041]     Certain embodiments of the present invention will be described hereinafter with reference to the appended drawings.  
         [0042]     In accordance with a first embodiment of the present invention, a multi-channel tube  1  is brazed with two branch tubes  10  to form a branching tube  9  as shown in  FIG. 1 .  
         [0043]     The multi-channel tube  1  is provided with an outer tubular portion  2  formed in a cylindrical shape and a partition wall  3 , which partitions the interior of the multi-channel tube  1  into a pair of channels  4 . The channels  4  are formed to be symmetrical and also have substantially the same cross sectional shape of a D-letter shape as shown in  FIGS. 3 through 5 . The outer tubular portion  2  is opened at both longitudinal ends.  
         [0044]     One end portion of the multi-channel tube  1  is expanded in radial directions to have an expanded end portion  6  and a reducer portion  5  smoothly linking the expanded portion  6  with a main portion (un-expanded proximal portion) of the multi-channel tube  1 . The reducer portion  5  has a tapered shape becoming thinner from one end linking with the expanded portion  6  toward the other end linking with the main portion. More specifically, the reducer portion  5  gradually reduces diameters from a diameter of the expanded portion  6  to a diameter of the main portion so as to smoothly linking therewith. A tip end of the expanded portion  6  is further expanded to be a flaring portion  7 , which is used for supporting brazing metal before and during brazing.  
         [0045]     The partition wall  3 , except for a portion around an end thereof, is tightly fixed with inner peripheries of the outer tubular portion  2  so as to keep air-tightness between both sides of the partition wall  3 . The flaring portion  7  is separated from the partition wall  3  at the end thereof so as to have spaces  8  therebetween to allow fused brazing metal to pass therethrough.  
         [0046]     The branch tubes  10  have substantially the same shape and the same dimension except for end portions thereof as shown in  FIGS. 6A through 6C . The end portion of each branch tube  10  has a D-letter broadened portion  12  and a transitional portion  11 . The D-letter broadened portion  12  is composed of a flat portion  12   a  for being contact with the partition wall  3  and an arc portion  12   b  for being contact with the outer tubular portion  2  and hence has a D-letter cross sectional shape. Exterior dimensions of the D-letter broadened portion  12  are greater than standard dimensions of each channel  4  and smaller than interior dimensions of the expanded portion  6 . Each of the end portions of the branch tubes  10 , which is inserted into the expanded end portion  6  of the multi-channel tube  1 , is inclined with respect to an insertion direction in which the end portion is inserted into the expanded end portion  6 .  
         [0047]     The flat portion  12   a  stepwise bulges outward from a straight portion of the branch tube  10  so as to form a step portion  13  where a boundary between the D-letter broadened portion  12  and the transitional portion  11  substantially exists as shown in  FIG. 6C . The step portion  13  is to recede from an end surface  3   a  of the partition wall  3  in a length d in a state that the branch tube  10  is inserted into the multi-channel tube  1  as shown in  FIG. 2 .  
         [0048]     A method for forming the branch tube  10  will be described hereinafter with reference to  FIGS. 7 through 11 . The method for forming utilizes a lower die  21  and an upper die  22  as shown in  FIGS. 8 through 11 . On the lower die  21 , a support member  23 , a mandrel  24 , a lower mold  25  and a lower clamp  26  are provided. Beneath the upper die  22 , a mandrel presser  27 , an upper mold  28  and an upper clamp  29  are provided.  
         [0049]     The support member  23  is vertically movably attached to the lower die  21  with a spring  30  intervening therebetween. The mandrel presser  27  is so dimensioned as to press down the support member  23  when the upper die  22  goes down. The mandrel  24  has a D-letter cross section which is smaller than the cross section of the interior of the end portion of the branch tube  10  and projects sideward from the support member  23  to be inserted into an end portion  31   a  of a raw pipe  31 . The raw pipe  31  is a raw material to form the branch tube  10 . The end portion  31   a  of the raw pipe  31  is expanded in advance and another portion thereof, which is apart from the end portion  31   a  to a certain extent, is a cylindrical portion  31   b  left cylindrical as is produced.  
         [0050]     As shown in  FIG. 11 , the lower mold  25  has a flat upper surface to shape a lower side of the end portion  31   a  of the raw pipe  31  into a flat portion by presswork. A lower side of the upper mold  28  has a half cylindrical recess portion  32  to shape an upper side of the end portion  31   a  of the raw pipe into a complementary shape.  
         [0051]     The upper clamp  29  is attached to the upper die  22  with an elastic body  33  of, for example, urethane rubber intervening therebetween and is vertically movable with respect to the upper die  22 . The upper clamp  29  and the lower clamp  26  in combination are configured to support the cylindrical portion  31   b  of the raw pipe  31 .  
         [0052]     Steps of the method can be illustrated as the flowchart of  FIG. 7 . First, as a step S 1  of  FIG. 7 , the raw pipe  31  for forming the branch tube  10  as a workpiece is disposed between the lower die  22  and the upper die  21  as shown in  FIG. 8 . Then, the cylindrical portion  31   b  of the raw pipe  31  is disposed on the lower clamp  26  and the mandrel  24  is inserted into the end portion  31   a  of the raw pipe  31 . Next, as a step S 2 , the upper die  22  is brought down so as to clamp the cylindrical  31   b  of the pipe  31  between the upper clamp  29  and the lower clamp  26  and fix the raw pipe  31  by means of repulsive force of the elastic body  33  of the upper die  22  as shown in  FIG. 9 .  
         [0053]     As a step S 3 , the upper die  22  is further brought down so as to force down the upper mold  28  onto the end portion  31   a  of the raw pipe  31  and press down the mandrel presser  27  onto the mandrel  24  as shown in  FIG. 10 . Thereby, the end portion  31   a  of the raw pipe  31  is formed to have a D-letter cross sectional shape and the raw pipe  31  is bent. Meanwhile, since, as is already described, the mandrel  24  has the D-letter cross section smaller than the end portion of the branch tube  10 , in the course of pressing the branch tube  10  from both sides by the lower mold  25  and the upper mold  28 , the mandrel  24  supports the branch tube  10  from the interior thereof so that the end portion of the branch tube  10  is formed to have the D-letter cross section.  
         [0054]     After shaping the branch tube  10 , as a step S 4 , the branch tube  10  as the workpiece after shaping is detached therefrom.  
         [0055]     Next, steps of connection of the multi-channel tube  1  with the branch tubes  10  will be described hereinafter. The branch tubes  10  are respectively inserted into the channels  4  through the end portion  6  of the multi-channel tube  1  so that tip ends of the branch tubes  10  abut on and are stopped by an inner periphery of the reducer portion  5 . Next, brazing metal  14  is disposed on the end surfaces of the multi-channel tube  1  and around peripheries of the branch tubes  10  as indicated by a double-dotted line in  FIG. 2 . The brazing metal  14  is also disposed on the end surface  3   a  of the partition wall  3  with facility since the branch tubes  2  are separated from each other. The branch tubes  10  may not necessarily abut on the inner periphery of the reducer portion  5  despite the above description.  
         [0056]     Next, the multi-channel tube  1  in combination with the branch tubes  10  is inserted in any heating chamber in a state that the multi-channel tube  1  is oriented downward and the branch tubes  10  are oriented upward. Then they are heated. By heating, the brazing metal  14  is fused and flows downward by gravity force. The flowing brazing metal  14  flows into clearances respectively kept between the multi-channel tube  1  and each of the branch tubes  10 . When they are cooled, the fused brazing metal  14  solidifies to form a fillet  15 . In this occasion, string-like brazing metal  14  may be adhered to and along the outer periphery of the branch tube  10  so as to be a D-letter shape and fused by heating by means of a burner so that fused brazing metal  14  flows into where is between the inner periphery of the multi-channel tube  1  and the outer periphery of each branch tube  10 . Thereby the respective branch tubes  10  are brazed with the multi-channel tube  1  with sufficient unitization ranging total circumferences thereof.  
         [0057]     In accordance with the present first embodiment, fusion and flow of the brazing metal  14  take place constantly at positions receding from the ends of the multi-channel tube  1 . Therefore the fused brazing metal  14  is promoted to flow into clearances kept between the multi-channel tube  1  and each of the branch tubes  10  and further prevented from spilling outward.  
         [0058]     Since the end portions of the branch tubes  10  are inclined with respect to the insertion directions thereof, the end portions generate smaller resistance to the flow of the fluid therein as compared with a case where the end portions are perpendicular to the insertion directions.  
         [0059]     The branch tubes  10  have offsets with respect to the multi-channel tube  1  and the cylindrical portions of the branch tubes  10  are separated from each other in a state where the branch tubes are inserted into the expanded end portion. Such a structure provides easiness and therefore reliability in placing the brazing metal  14  around the total circumferences of the branch tubes  10  and connection of the multi-channel tube  1  with the branch tubes  10 .  
         [0060]     Since the outer periphery of the end portion of the outer tubular portion  2  is provided with the flaring portion  7  for supporting the brazing metal  14 , relatively large clearances between the inner periphery of the outer tubular portion  2  and the outer peripheries of the branch tubes  10  are kept. The relatively large clearances promote the fused brazing metal  14  to flow therein and keep the brazing metal  14  therein, thereby the fillet  15  is uniformly formed to range the total circumferences of the branch tubes  10 .  
         [0061]     Since the reducer portion  5  receives the inserted branch tubes  10 , nothing but pushing the branch tubes  10  to abut on the reducer portion  5  is required to position the branch tubes  10  to predetermined positions. It leads to easiness and reliability in working of production of the branching tube  9 .  
         [0062]     The reducer portion  5  and the expanded end portion  6  having the same diameter as the reducer portion  5  in combination hold the branch tubes  10  in the regular positions and hence provide stability in positioning the branch tubes  10 . It leads to further easiness and reliability in working of production of the branching tube  9 .  
         [0063]     Since the spaces  8  held between the flaring portion  7  and the partition wall  3  at the end thereof allow the fused brazing metal  14  to pass therethrough, the fused brazing metal  14  around one of the branch tubes  10  may easily flow toward another of the branch tubes  10  via the spaces  8 . Therefore the unitization ranging total circumferences of the branch tubes  10  is further assured and hence reliability of the connection is further assured.  
         [0064]     Forming the broadened end portions of the branch tubes  10  and bending the branch tubes  10  are simultaneously carried out by the step S 3  of  FIG. 7 , namely forcing down the upper die  22  to press down an upper mold  28  onto the broadened end portions of the branch tubes  10  and press down a mandrel presser  27  onto the mandrel  24 . Therefore reduced number of steps for production of the branching tube  9  is realized.  
         [0065]     Formation of the D-letter cross section of the broadened end portion of the branch tube  10  is carried out in a state that the mandrel  24  having the D-letter cross section is inserted in the end portion  31   a  of the raw pipe  31 , any irregular and localized deformation can be prevented. It leads to precise production.  
         [0066]     Since the branch tubes  10  are inserted in the broadened end portion of the multi-channel tube  1 , thicknesses of the outer walls of the branch tubes  10  do not severely reduce the cross sectional area of the flow paths in the branching tube  9 . Therefore smooth flow of the fluid therein can be assured. It also leads to a smaller resistance to the flow of the fluid therein. Smooth flow of the fluid can be realized.  
         [0067]     A second embodiment of the present invention will be described hereinafter with reference to  FIGS. 12 through 18 .  
         [0068]     As compared with the above first embodiment, the second embodiment differs only in a method of shaping the branch tubes  10  and is substantially the same as the first embodiment in the other respects.  
         [0069]     In accordance with the present second embodiment, on the lower die  21 , a support member  41 , a mandrel  42 , a lower mold  43  and a lower clamp  44  are provided, and, on the upper die  22 , an upper mold  45  and an upper clamp  46  are provided.  
         [0070]     The support member  41  is fixed on the lower die  21 . The mandrel  42  has a D-letter cross section which is smaller than the cross section of the interior of the end portion of the branch tube  10 . A pivot  47  of the support member  41  swingably supports the mandrel  42 .  
         [0071]     As shown in  FIG. 18 , the lower mold  43  has a half cylindrical recess portion  48  to shape a lower side of the end portion  31   a  of the raw pipe into a complementary shape. The upper mold  45  has a flat lower surface to shape a lower side of the end portion  31   a  of the raw pipe  31  into a flat portion by presswork.  
         [0072]     The-upper clamp  46  is attached to the upper die  22  with an elastic body  49  of, for example, urethane rubber interveneing therebetween and is vertically movable with respect to the upper die  22 . The upper clamp  46  and the lower clamp  44  in combination are configured to support the cylindrical portion  31   b  of the raw pipe  31 .  
         [0073]     In accordance with the present second embodiment, as a step S 11  of  FIG. 12 , the raw pipe  31  as a workpiece is disposed between the lower die  22  and the upper die  21  as shown in  FIG. 13 . Then, the end portion  31   a  of the raw pipe  31  is disposed over the lower mold  43  and the mandrel  42  is inserted into the end portion  31   a  of the raw pipe  31 . Next, as a step S 12 , the upper die  22  is brought down so as to clamp the end portion  31   a  of the raw pipe  31  between the upper mold  45  and the lower mold  43  as shown in  FIG. 14 . Simultaneously, the upper mold  45  and the lower mold  43  squeeze the end portion  31   a  to have a D-letter cross sectional shape. Then, the mandrel  42  swings around the pivot  47  and presses the inner periphery of the end portion  31   a  of the raw pipe  31 . Next, as a step S 13 , the upper die  22  is further brought down with clamping the end portion  31   a  of the raw pipe  31  by means of repulsive force of the elastic body  49  so as to force down the upper clamp  46  onto the cylindrical portion  31   b  of the raw pipe  31  as shown in  FIG. 15 . Thereby the raw pipe  31  is bent and shaping of the branch tube  10  is completed. After shaping the branch tube  10 , as a step S 14 , the branch tube  10  as the workpiece after shaping is detached therefrom.  
         [0074]     In accordance with the present second embodiment, forming the broadened end portions of the branch tubes  10  and bending the branch tubes  10  are simultaneously carried out by the step S 12  of  FIG. 12 . Therefore reduced number of steps for production of the branching tube  9  is realized.  
         [0075]     The above embodiments may be modified. For example, though broadening and shaping of the end portion  31   a  into the D-letter cross sectional shape are simultaneously carried out in the above description, shaping the end portion  31   a  to have an elliptic cross sectional shape may be carried out before the steps of clamping, press-working and forming. It may leads to better shaping of the end portion  31   a  into the D-letter cross sectional shape.  
         [0076]     Moreover, the flaring portion  7  may not be required to support the brazing metal. A minimum requirement is to keep certain clearances respectively between the multi-channel tube  1  and each of the branch tubes  10 . Further, though the end portion  6  of the multi-channel tube  1  is expanded to have greater diameters in any radial directions except a direction along the partition wall  3  than a diameter of a main portion of the multi-channel tube  1  in accordance with the above description, the expanded end portion  6  of the multi-channel tube  1  may be expanded only in a direction perpendicular to the direction along the partition wall  3 .  
         [0077]     Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings.