Patent Publication Number: US-2016244102-A1

Title: Coupling member

Description:
CROSSREFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2015-034743, filed on Feb. 25, 2015, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a coupling member which couples members for use in frames of vehicles. 
     BACKGROUND 
     Conventionally, a technique has been disclosed in which a cowl side and a front side member are coupled as a frame structure of a vehicle front section of an automobile (Patent 
     Document 1: Japanese Unexamined Patent Application Publication No. 2010-64638). In the frame structure disclosed in Patent Document 1, a sheet metal joining body is provided which couples a front side member which extends in the front-back direction at the lower section of the vehicle body front section to a cowl side which protrudes frontward from a front pillar. In this type of frame structure for automobile, for example, a structure is adopted in which, when the vehicle front section collides with an object and the impact therefrom is applied to the front side member, a plurality of members branched variously propagates the applied impact to other frame members (a cowl side, etc.). 
     For example, as shown in  FIG. 11 , a cowl side  101  is joined by welding to upper surfaces  203  and  205  of a front side member  201 . The upper surface  205  is bent at a predetermined angle to the upper surface  203 . In addition, a mark “X” in the figure indicates a welding portion by spot welding as an example. A tip end portion of the cowl side  101  is provided with flange sections  103  and  105 , and the flange sections  103  and  105  are joined by spot welding to the upper surfaces  203  and  205  of the front side member  201 , respectively. The cowl side  101  is formed of, for example, a metal plate material bent in a substantially U-shape. The flange section  103  is formed at a tip end of a first side plate  107 , and the flange portion  105  is formed at a tip end of a second side plate  109  orthogonal to the first side plate  107 . A notch  111  is formed between the flange portion  103  and the flange portion  105 . 
     The notch  111  is, for example, a notch portion which is formed in the light of formability in order to prevent the section between the flange portions  103  and  105  from being deformed or cracking at the time of bending and forming the cowl side  101  so as to bend the second side plate  109  with respect to the first side plate  107 , followed by bending the tip end concerned to form the flange sections  103  and  105 . 
     SUMMARY OF THE INVENTION 
     For example, as indicated by an arrow  301  in the figure, when a load is applied from the front side of the vehicle to the rear side so that the impact propagates from the front side member  201  to the cowl side  101 , a force is applied concentrically on the periphery of the notch  111 , particularly on a base portion  111 A of the notch  111  where the flange portions  103  and  105  intersect. As a result, cracks and deformation may occur in the notch  111 , thereby decoupling the cowl side  101  from the front side member  201 . 
     In view of foregoing, the technique disclosed in the present application is offered. The object thereof is to provide a coupling member capable of fixing a branching section more firmly which couples frame members of a vehicle to each other. 
     A coupling member of according to an aspect of the present invention is the coupling member of vehicle frame for coupling a first member extending in the first direction to a second member extending in the second direction different from the first direction, comprising: a first cover section covering the first member; a second cover section covering the second member; and a concave portion connecting two side edge portions, that is, a first side edge portion and a second side edge portion, in a branching section coupling the first member to the second member, wherein the concave portion inserted in an inner portion of a branch sandwiched between the first and second members, the first side edge portion provided in the first cover section and provided at the position as being an inner side portion of the branch in the width direction of the first member, the second side edge portion provided in the second cover section and provided at the position as being an inner side portion of the branch in the width direction of the second member. 
     In the coupling member, the first and second members are coupled while the first member is covered with the first cover section and the second member is covered with the second cover section. The first and second cover sections are connected to each other at the branching section by the concave portion inserted into the inner side portion of the branch. The concave portion connects the first side edge portion as being the inner side portion of the branch in the first cover section to the second side edge portion as being the inner side portion of the branch in the second cover section. In such a structure, since the first member and the second member are coupled by the coupling member, it becomes unnecessary to provide a flange portion which is any of first or second member (such as a cowl side) with a notched portion that is conventionally used. Furthermore, in the coupling member concerned, it is possible to close the portion corresponding to the notched portion in the conventional structure by the concave portion which connects the first and second cover sections at the inner side portion of the branch. Therefore, even if a load by an impact or the like in the direction away from the second cover section is applied to the first cover section, for example, the impact applied from the first side edge portion of the first cover section toward the second side edge portion of the second cover section is transmitted via the concave portion, so that the load to be applied is not applied concentrically to the point at which the first cover section and the second cover sections intersect with each other. Therefore, it is possible to prevent the branching section from being deformed or cracking, resulting in separation of the first member and the second member. Consequently, it is possible to fix the first member and the second member more firmly by the coupling member. 
     The coupling member according to another aspect of the present invention is the coupling member according to claim  1 , wherein the concave portion is formed in a flat plate shape, and has a bottom section to be joined to at least one of the first and second members. 
     In the coupling member concerned, the concave portion is joined to at least one of the first and second members by the bottom section. For example, if the fixing plate portion corresponding to a flat-shaped bottom section is provided in the first member, the fixing plate portion of first member and the bottom section of the concave portion can be joined by spot welding while overlapping each other. This makes it easier to join the concave portion to the first and second members. In other words, the coupling member makes it possible to easily and firmly fix the first member and the second member. 
     The coupling member according to another aspect of the present invention is the coupling member according to claim  1 , wherein the concave portion has an inclining section gradually inclining toward the depth direction in the inner portion of the branch as it is closer from a basal portion side of the branch to a ramification side. 
     The coupling member concerned makes it easily to forming by press working. For example, the metal plate material put on the lower die is press worked using the upper die corresponding to the shape of the inclining section, so that it becomes possible to easily form the concave portion which is formed continuously to the first cover section and the second cover section. Thereby, it becomes possible to reduce cost for manufacturing the coupling member capable of coupling the first member and the second member more firmly. 
     The coupling member according to another aspect of the present invention is the coupling member according to claims  1 , comprising: a first outer wall section connected to the first cover section, and covering the outer periphery of the first member in the outer section of the branch; and a second outer wall section connected to the second cover section, and covering the outer periphery of the second member in the outer section of the branch. 
     The coupling member concerned is provided with the first and second outer wall sections which cover the outer periphery of each of the first and second member. Therefore, for example, the first and second outer wall sections are joined by welding or the like to the outer periphery respestively, so that it becomes possible to fix the coupling member to the first and second members more firmly. In other words, the first and second members are coupled more firmly by the first and second outer wall sections. 
     The coupling member according to another aspect of the present invention is the coupling member according to claims  1 , wherein the concave portion for connecting the first cover section and the second cover section is formed from a fan-shaped metal plate material by press working without fixing an arc-shaped portion of the fan-shaped metal plate material. 
     In the section where the frame members of a vehicle, such as a cowl side or a front side member, the branching section makes a variety of angles, some of which are often sharp, for example. In such a case, in the coupling member which couples the first member having an sharp angle to the second member, if it is intended to provide the concave portion to be inserted into the branching section deeper, the angle of the concave portion becomes acute. At the time of forming the coupling member by press working, for example, it is necessary to stretch a part of the metal plate material while fixing the metal plate material to the lower die or the like so as to form an acute concave portion by drawing or the like. This is, however, not an easy way to form. Then, in the press working of the coupling member concerned, a fan-shaped metal plate material is depressed by press working without fixing an arc-shaped portion. In this method for forming, the metal plate material is moved so as to be pulled toward the portion to be depressed, and the section to be depressed by press working is stretched so that the concave portion having a desired depth is formed. This makes it possible to manufacture the concave portion having an sharp angle with high accuracy, and, for example, the first and second members making the branching section of the sharp angle can be fixed firmly by the coupling member. Here, it can be considered that the concave portion is joined to the first and second cover sections by welding or the like, for example, however, such as structure is intended to provide the weaker strength at the section joined by welding or the like. In contrast, in the coupling member concerned, it is possible to form the first cover section, the second cover section, and the concave portion integrally by a metal plate material, thereby joining the first and second cover sections and the concave portion more firmly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a part of a frame structure of a vehicle front section of a vehicle in which frame members are coupled by a coupling member of Embodiment 1. 
         FIG. 2  is an enlarged view of a portion where the coupling member is provided in  FIG. 1 . 
         FIG. 3  is a cross sectional view showing a cross section taking a line A-A in  FIG. 2  seeing from the direction of an arrow. 
         FIG. 4  is a cross sectional view corresponding to  FIG. 3  for explaining joining state in another example of Embodiment 1. 
         FIG. 5  is an enlarged view of a portion where a coupling member is provided in Embodiment 2. 
         FIG. 6  is a cross sectional view showing a cross section taking a line B-B in  FIG. 5  seeing from the direction of an arrow. 
         FIG. 7  is a plan view of a metal plate material for explaining a method for manufacturing a coupling member. 
         FIG. 8  is a perspective view showing a state of press working for explaining a method for manufacturing a coupling member. 
         FIG. 9  is a perspective view showing a state of press working for explaining a method for manufacturing a coupling member. 
         FIG. 10  is a perspective view for explaining a method for manufacturing a coupling member. 
         FIG. 11  is a perspective view for explaining a state of joining frame members of a vehicle of a comparative embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 1 
     Description will be given below as an example of a frame structure for a vehicle in a case where a coupling member according to the present invention is applied to a structure of a vehicle front section.  FIG. 1  shows a part of a frame in a front section of a vehicle  10  according to Embodiment 1. The front-back (F means the forward direction and B means the backward direction in  FIG. 1 ) direction shown in the figure indicates the traveling direction of the vehicle. Furthermore, the right-left (R means the rightward direction and Le means the leftward direction in  FIG. 1 ) direction indicates the vehicle width direction of the vehicle  10  which travels forward and/or backward. Therefore,  FIG. 1  shows a part of a frame on the left side of the vehicle width direction in the vehicle front section. 
     As shown in  FIG. 1 , the vehicle  10  is provided with a cowl side  11 , a front side member  12 , etc. The cowl side  11  is provided so as to extend in the front-back direction on the upper side of the front section of the vehicle  10 . A front end section  11 A of the cowl side  11  is bent toward the vehicle width direction (rightward (R) in the figure), and joined to an upper frame  13  at a bent portion thereof. The upper frame  13  is provided so as to extend in the vehicle width direction on the upper portion of the front section of the vehicle  10 . An end section  13 A in the vehicle width direction of the upper frame  13  is joined to the front end section  11 A of the cowl side  11 . 
     A rear end section  11 B of the cowl side  11  is joined to a front pillar  15 . The front pillar  15  is provided with a front pillar upper  15 A which extends downward toward the front direction from a roof, and a front pillar lower  15 B which extends downward from the front end of the front pillar upper  15 A to continue to front end section  17 A of a side sill  17 . The rear end section  11 B of the cowl side  11  is joined to a front end of the front pillar upper  15 A, and is joined to a portion to be an upper end of the front pillar lower  15 B. Consequently, the cowl side  11  is provided so as to protrude forward from the intermediate portion in the upper-lower (U means the upperward direction and Lo means the lowerward direction in  FIG. 1 ) direction of the front pillar  15 . 
     Furthermore, the front side member  12  is provided so as to extend in front-back direction on the lower side of the front section of the vehicle  10 . A front end section  12 A of the front side member  12  is joined to a lower member  19 . The lower member  19  is a member for coupling the cowl side  11  to the front side member  12 . The lower member  19  is provided on the outside of the front side member  12  in the vehicle width direction, and extends in the upper-lower direction of the vehicle  10 . The front end section  12 A of the front side member  12  is joined to a lower end section  19 A of the lower member  19  which is located on the outside of the vehicle width direction. 
     Furthermore, the rear end section  12 B of the front side member  12  is joined to an outrigger  21 . The outrigger  21  is provided so as to extend in the vehicle width direction on the vehicle lower section, and each of the ends in the vehicle width direction is joined to the inner side portion of a side sill  17   
     An upper end section  19 B of the lower member  19  is joined to an intermediate portion  11 C of the cowl side  11  extending in the front-back direction of the vehicle  10 . The upper end section  19 B is coupled to the lower side portion of the intermediate portion  11 C. An coupled section where the cowl side  11  and the lower member  19  are coupled to each other is provided with a coupling member  51 . A section where the cowl side  11  and the lower member  19  are coupled by the coupling member  51  is substantially Y-shaped when viewed from the outside of the vehicle width direction of the vehicle  10 . 
     The frame members, such as the cowl side  11 , etc., of the vehicle  10  described above are formed, for example, by press-working a metal plate material in the shape of bottomed box in which is opened by removing one of the inner or outer side walls of the vehicle width direction (see  FIG. 3 ). In addition, the cowl side  11  or the like may have the shape of bottomed box which is opened by removing an upper wall or a lower wall located in the upper-lower direction of the vehicle  10 , or may have the shape in which a rear wall on the rear side of the vehicle  10  is omitted. Furthermore, the cowl side  11  or the like may be, for example, in the shape of a rectangular parallelepiped box. Furthermore, the cowl side  11  or the like may not have a hollow structure, and may be a member inside of which is formed to be dense. Furthermore, the cowl side  11  or the like may be in the polygonal cylindrical shape, or may be in the circular cylindrical shape such as circle, ellipse, etc. 
     Here, for example, when an impact by an collision or the like is applied from the front of the vehicle as shown by an arrow  24  in  FIG. 1 , the frame structure of the vehicle  10  having the structure described above dispersedly transmits the applied impact to the cowl side  11 , the front side member  12 , or the like, so as to absorb the impact, as shown by an arrow  25  in  FIG. 1 . The vehicle  10  is structured to disperse the impact to the front pillar  15  or the side sill  17  depending on the magnitude of the applied impact so as to absorb the impact with high efficiency. For this reason, in order to transmit and disperse the applied impact with certainty, a member for fixing the coupled section, such as the coupling member  51 , becomes more important. 
     Next, a detailed structure of the coupling member  51  will be explained with reference to  FIG. 2 ,  FIG. 2  shows an enlarged view of the section where the coupling member  51  is provided in  FIG. 1 , In addition, a mark “X” in  FIG. 2  indicates a welding portion by spot welding as an example. In addition, the cowl side  11 , the lower member  19 , and the coupling member  51  may be joined not only by welding, but by swaging or the like. 
     The cowl side  11  is opened by removing the inner side wall in the vehicle width direction, and is in the shape of a bottomed box which has an upper wall  31  and a lower wall  33  facing each other in the upper-lower direction, and a side wall  35  provided on the outside of the vehicle width direction. Likewise, the lower member  19  is opened by removing the inner side wall in the vehicle width direction, and is in the shape of a bottomed box which has an upper wall  41  and a lower wall  43  facing each other in the upper-lower direction, and a side wall  45  provided on the outside of the upper wall  41  front side member  12  externally in the vehicle width direction. 
     In the inner side portion of the substantially Y-shaped branch which is sandwiched between the cowl side  11  and the lower member  19 , a groove section  23  is configured so that the distance in theupper-lower direction between the lower wall  33  of the cowl side  11  and the upper wall  41  of the lower member  19  gradually decreases from the front side section where the branch is expanded toward an intersection point  60  of the branch on the rear side. The upper end section  19 B of the lower member  19  is opened at the rear wall on the rear side of the vehicle  10 , and an the end section  47  having a substantially U-shaped cross section when taken in the width direction is fixed coming into contact with the lower wall  33  of the cowl side  11 . In addition, the lower member  19  may be configured not to bring the end section  47  of the upper end section  19 B into contact with the lower wall  33  of the cowl side  11 , but to be fixed with a predetermined space from the lower wall  33 . The lower wall  33  is shaped to be inclined downward along the shape of the end section  47  of the upper end section  19 B from the intersection point  60  toward the rear. Furthermore, the lower wall  33  is formed toward the rear side of the vehicle so as to be approximately parallel with the upper wall  31  in the section further behind the coupling section to the end section  47 . Consequently, the cowl side  11  has an extended width in theupper-lower direction from the intersection point  60  to the section where the end section  47  comes into contact with the lower wall  33 , i.e., the width thereof is partially widened. 
     The coupling member  51  is shaped so that it covers the section where the cowl side  11  and the lower member  19  are branched in substantially Y-shape, and the branching section is provided with a first cover section  53  which covers the side wall  35  of the cowl side  11 , and second cover section  55  which covers the side wall  45  of the lower member  19 . The first cover section  53  and the second cover section  55  are connected to each other by a concave portion  56  at the groove section  23  that is the inner side portion of the branch. The concave portion  56  is formed along the shape of the groove section  23 . The coupling member  51  is formed, for example, by press working a metal plate material, and the first cover section  53 , the second cover section  55 , and the concave portion  56  are integrally formed. The second cover section  55  continues to the first cover section  53  at the section where the end section  47  of the lower member  19  comes into contact with the lower wall  33  of the cowl side  11 . The first cover section  53  is joined by spot welding to the side wall  35  at the end section in the front-back direction. Furthermore, the second cover section  55  is joined by spot welding to the side wall  45  at the end section on the front side in the front-back direction. 
     The concave portion  56  is provided with a first inner wall section  57 , a second inner wall section  59 , and a the bottom section  61 . The first inner wall section  57  is formed continuously from the lower end section of the first cover section  53 , that is, a side edge portion  53 A of the first cover section  53  provided at the position as being the inner side portion of the branch in the width direction (the thickness direction) of the cowl side  11 , and is formed toward the right side in the vehicle width direction. The side edge portion  53 A is formed along a corner in the cowl side  11  formed by the side wall  35  and the lower wall  33 . The first inner wall section  57  is formed along the lower wall  33  so as to entirely cover the lower wall  33  of the cowl side  11  in the groove section  23 . 
     Likewise, the second inner wall section  59  is formed continuously from the upper end section of the second cover section  55 , that is, a side edge portion  55 A of the second cover section  55  provided at the position as being the inner side portion of the branch in the width direction (the thickness direction) of the lower member  19 , and is formed toward the right side in the vehicle width direction. The side edge portion  55 A is formed along a corner in the lower member  19  formed by the side wall  45  and the upper wall  41 . The second inner wall section  59  is formed along the upper wall  41  so as to entirely cover the upper wall  41  of the lower member  19  in the groove section  23 . 
     The bottom section  61  is provided so as to close the opening on the right side of the groove section  23  in the vehicle width direction. In other words, the bottom section  61  is provided at the depth side of the groove section  23  (the deepest position in the groove) in FIG.  2  to connect the first inner wall section  57  to the second inner wall section  59 . The bottom section  61  is formed continuously from end section of each of the first inner wall section  57  and the second inner wall section  59 , and is in the shape of substantially triangle when viewing from the vehicle width direction. In this manner, the concave portion  56  inserted into the groove section  23  is formed to connect the side edge portion  55 A of the second cover section  55  to the side edge portion  53 A of the first cover section  53  by the first inner wall section  57 , the second inner wall section  59 , and the bottom section  61 . 
     A fixing plate portion  33 A corresponding to the shape of the bottom section  61  is formed on the lower wall  33  of the cowl side  11 . The fixing plate portion  33 A is formed to be bent downward from the end section on the right side in the vehicle width direction of the lower wall  33 . Furthermore, a fixing plate portion  41 A corresponding to the shape of the bottom section  61  is formed on the upper wall  41  of the lower member  19 . The fixing plate portion  41 A is formed to be bent upward from the end section on the right side in the vehicle width direction of the upper wall  41 . The fixing plate portion  33 A and the fixing plate portion  41 A are provided to overlap the bottom section  61 , and are joined by spot welding to the bottom section  61 . 
     Furthermore, the coupling member  51  has a first outer wall section  63  which covers the upper wall  31  of the cowl side  11 , and a second outer wall section  65  which covers the lower wall  43  of the lower member  19  (see  FIG. 3 ).  FIG. 3  shows a cross section taking a line A-A in  FIG. 2  seeing from the direction of an arrow. As shown in  FIGS. 2 and 3 , the first outer wall section  63  is formed continuously from a side edge portion  53 B as being the upper end side of the first cover section  53 , and is formed toward the right side in the vehicle width direction. The side edge portion  53 B is formed along a corner in the cowl side  11  formed by the side wall  35  and the upper wall  31 . The first outer wall section  63  is formed along the upper wall  31  so as to entirely cover the upper wall  31  of the cowl side  11 . 
     The upper wall  31  has a flange portion  31 A formed to be bent upward on the right side in the vehicle width direction. The flange portion  31 A is formed toward the front-back direction with a predetermined width. Furthermore, the first outer wall section  63  is provided with a flange portion  63 A in accordance with the shape of the flange portion  31 A of the upper wall  31 . As shown in  FIG. 2 , the flange portion  31 A of the upper wall  31  and the flange portion  63 A of the first outer wall section  63  are joined by spot welding. 
     Furthermore, the second outer wall section  65  is formed continuously from a side edge portion  55 B as being the lower end side of the second cover section  55 , and is formed toward the right side in the vehicle width direction. The side edge portion  55 B is formed along a corner in the lower member  19  formed by the side wall  45  and the lower wall  43 . The second outer wall section  65  is formed along the lower wall  43  so as to entirely cover the lower wall  43  of the lower member  19 . 
     Furthermore, the lower wall  43  has a flange portion  43 A formed to be bent downward on the right side in the vehicle width direction. The flange portion  43 A is formed toward the front-back direction with a predetermined width. Furthermore, the second outer wall section  65  is provided with a flange portion  65 A in accordance with the shape of the flange portion  43 A of the lower wall  43 . The flange portion  43 A of the lower wall  43  and the flange portion  65 A of the second outer wall section  65  are joined by spot welding. 
     As shown in  FIG. 3 , the coupling member  51  in Embodiment 1 is formed in the branching section in accordance with the shapes of the cowl side  11  and the lower member  19 , and each of the members such as the first cover section  53 , the flange portion  63 A, the bottom section  61 , etc., is joined to the cowl side  11  and the lower member  19 . The joined coupling member  51  is fixed in close contact with the outer peripheral surface of the cowl side  11  and the lower member  19  (the side wall  35 , etc.). 
     In addition, the cowl side  11  is an example of the first member. The lower member  19  is an example of the second member. The side edge portion  53 A is an example of the first side edge portion. The side edge portion  55 A is an example of the second side edge portion. 
     The effect described below will be provided by Embodiment 1 described above. 
     The first and second cover sections  53  and  55  are connected to each other at the branching section where the cowl side  11  and the lower member  19  are joined, by the concave portion  56  inserted into the groove section  23  which is the inner side portion of the branch. The concave portion  56  connects the side edge portion  53 A on the side of the groove section  23  of the first cover section  53  to the side edge portion  55 A on the side of the groove section  23  of the second cover section  55 . The coupling member  51  closes the opening of the groove section  23  by the concave portion  56  which connects the first and second cover sections  53  and  55 . Therefore, even if a load by an impact or the like in the direction away from the second cover section  55  (such as in the upper direction of the vehicle) is applied to the first cover section  53 , for example, the impact applied from the side edge portion  53 A of the first cover section  53  toward the side edge portion  55 A of the second cover section  55  is transmitted via the concave portion  56 , so that the load to be applied is not applied concentrically to the intersection point  60  at which the first and second cover sections  53  and  55  intersect with each other. Therefore, it is possible to prevent the branching section from being deformed or cracking, resulting in separation of the cowl side  11  and the lower member  19 . 
     Furthermore, the bottom section  61  of the concave portion  56  is formed in the shape of a flat plate that closes the opening of the groove section  23 , and connects the first inner wall section  57  to the second inner wall section  59 . The fixing plate portion  33 A corresponding to the shape of the bottom section  61  is formed on the lower wall  33  of the cowl side  11 . 
     Furthermore, the fixing plate portion  41 A corresponding to the shape of the bottom section  61  is formed on the upper wall  41  of the lower member  19 . Then, the fixing plate portion  33 A and the fixing plate portion  41 A are joined by spot welding so as to overlap the bottom section  61 . In such a structure, the bottom section  61  in the flat-plate manner makes it possible to easily and firmly fix the cowl side  11  and the lower member  19 . 
     Furthermore, the coupling member  51  has the first outer wall section  63  which covers the upper wall  31  of the cowl side  11 , and the second outer wall section  65  which covers the lower wall  43  of the lower member  19 . The flange portion  31 A of the upper wall  31  and the flange portion  63 A of the first outer wall section  63  are joined by spot welding. Furthermore, the flange portion  43 A of the lower wall  43  and the flange portion  65 A of the second outer wall section  65  are joined by spot welding. Consequently, the coupling member  51  can fix the cowl side  11  and the lower member  19  more firmly by the first and second outer wall sections  63  and  65 . 
     While the present invention has been explained above based on Embodiment 1, the present invention is not limited to Embodiment 1 described above, but a variety of improvements and modifications can be made without departing the spirit of the present invention. 
     For example, as shown in  FIG. 3 , Embodiment 1 described above includes the fixing plate portion  33 A of the lower wall  33  and the fixing plate portion  41 A of the upper wall  41  which are provided to be overlapped each other. However, the structure is not limited to this, but, as shown in  FIG. 4 , for example, the bottom section  61  may be configured so that the fixing plate portion  33 A and the fixing plate portion  41 A are joined at different positions. In the structure shown in  FIG. 4 , the fixing plate portion  33 A has the width protruding toward the side of the lower member  19  that is smaller than that in Embodiment 1. Likewise, the fixing plate portion  41 A has the width protruding toward the side of the cowl side  11  that is smaller than that in Embodiment 1. A gap is provided between the fixing plate portion  33 A and the fixing plate portion  41 A. Even in such a structure, it is possible to fix the cowl side  11  and the lower member  19  more firmly, similar to Embodiment 1. 
     Embodiment 2 
     Next, Embodiment 2 will be explained which has the different structure from Embodiment 1. In Embodiment 1, the concave portion  56  is configured so that the first inner wall section  57  is formed along the lower wall  33 , and the second inner wall section  59  is formed along the upper wall  41 , however, the structure is not limited to this. For example, as shown in  FIG. 5 , a concave portion  71  may be in the curved shape.  FIG. 5  is an enlarged view of a portion where a coupling member  70  is provided in Embodiment 2.  FIG. 6  is a cross sectional view showing a cross section taking a line B-B in  FIG. 5  seeing from the direction of an arrow. In addition, in the explanation below, like reference numerals refers to like components in Embodiment 1, and the explanations thereof will be omitted if not necessary. 
     As shown in  FIGS. 5 and 6 , in the concave portion  71 , an inclining section  73  is formed which gradually inclines toward the depth direction of the groove section  23  which is the inner side portion of the branch, from the intersection point  60  which is a basal portion of the branch toward the front side of the vehicle which is a ramification side. The term “depth direction” used herein refers to the direction toward the right side in the vehicle width direction in the case shown in  FIG. 5 , whereas being the direction toward the lower side in the figure in the case shown in  FIG. 6 . The first and second inner wall sections  57  and  59  of the concave portion  71  are formed integrally across the inclining section  73 . The concave portion  71  has the substantially U-shaped cross section when taken along the line B-B (see  FIG. 6 ). The first inner wall section  57  is inclined from the side edge portion  53 A of the first cover section  53  toward the inclining section  73 . Different from Embodiment 1, there is provided a section spaced from the lower wall  33  of the cowl side  11 . Likewise, the second inner wall section  59  is inclined from the side edge portion  55 A of the second cover section  55  toward the inclining section  73 , and there is provided a section spaced from the upper wall  41  of the lower member  19 . While the detailed description will be made later, the coupling member  70  makes it easier to conduct press working compared to the coupling member  51  in Embodiment 1. 
     Next, the explanation will be made regarding an example of a method of manufacturing the coupling member  51  in Embodiment 1 and the coupling member  70  in Embodiment 2 shown in  FIG. 5  with reference to  FIGS. 7 to 10 . The explanation will be made regarding the manufacturing steps of forming the coupling member  70  by press working a fan-shaped metal plate material  81  shown in  FIG. 7 , for example. As shown in  FIG. 7 , the metal plate material  81  has a fan-shaped section  83  having the shape of a fan in a plan view, and a rectangular section  85  which is formed integrally on the inner periphery of the fan-shaped section  83 . 
     As shown in  FIG. 8 , the metal plate material  81  is put on a lower die (not shown) so that an arc-shaped part of the fan-shaped section  83  is press worked by an upper die  87 . In the example shown in  FIG. 8 , the upper die  87  is pressed against the center area of the circumference of the fan-shaped section  83 . The upper die  87  has the convex shape corresponding to the shape of the concave portion  71  of the coupling member  70  in Embodiment 2 shown in  FIG. 5 . Here, at the time of press working the metal plate material  81  by the upper die  87 , it may be preferable that the metal plate material  81  is not fixed. For example, the groove section  23  that is the branching section between the cowl side  11  and the lower member  19  in Embodiment 1 takes the form of an sharp angle. If it is intended to form the concave portion  71  to be inserted into the groove section  23  deeper, the angle of the concave portion  71  becomes acute. Therefore, it is difficult at the time of press working to form the acute concave portion  71  by stretching only a part to be the concave portion  71  by the upper die  87  while fixing the metal plate material  81  to the lower die. Then, in the method for manufacturing concerned, a part of the fan-shaped section  83  is press worked by the upper die  87  without fixing the fan-shaped section  83  of the metal plate material  81 . In the present method for forming, the fan-shaped section  83  of the metal plate material  81  is moved so as to be pulled toward the central area of the circumference depressed by the upper die  87 , as indicated by an arrow  88  in  FIG. 8 . Therefore, in the metal plate material  81 , the portion depressed by the upper die  87  is stretched, while the fan-shaped section  83  is moved so as to be pulled by upper die  87 . This reduces the load to be applied to the metal plate material  81 , compared to the case of stretching only a part of the material while being fixed to the lower die. This makes it possible to manufacture the concave portion  71  having an acute angle with high accuracy. 
     As shown in  FIG. 8 , press working of the concave portion  71  of the coupling member  70  in Embodiment 2 shown in  FIG. 5  becomes feasible by a method in which the fan-shaped section  83  is not fixed. However, in the concave portion  56  of the coupling member  51  in Embodiment 1, the first inner wall section  57  is formed along the lower wall  33 , and the second inner wall section  59  is formed along the upper wall  41 , so that it becomes necessary to form the first and second inner wall sections  57  and  59  which are acuter than the concave portion  71  of the coupling member  70  shown in  FIG. 5 . Therefore, if it is difficult to manufacture the acute concave portion  56  like the groove section  23  having a sharp angle it can be considered that once the concave portion  71  having the inclining section  73  is formed on the metal plate material  81 , and then the metal plate material  81  is again press worked, thereby forming the concave portion  56  in Embodiment 1, as shown in  FIG. 9 . In the manufacturing method concerned, one more step of press working is necessary to form the concave portion  56  in Embodiment 1 compared to the case of forming the concave portion  71  show in  FIG. 5 . In other words, it can be said that the manufacturing of the coupling member  70  shown in  FIG. 5  can reduce the step of press working compared to manufacturing of the coupling member  51 , thereby achieving facilitation. In addition, it of course may be possible to form the coupling member  51  having the concave portion  56  by press working one time to the metal plate material  81  if it is formable. Furthermore, the concave portion  56  and the concave portion  71  may be formed by drawing in which the metal plate material  81  is fixed to the lower die. 
     As shown in  FIG. 9 , the metal plate material  81  is put on a lower die (not shown) so that the section of the fan-shaped section  83  where the concave portion  71  is formed is press worked by an upper die  89 . The upper die  89  has the convex shape corresponding to the shape of the concave portion  56  of the coupling member  51  in Embodiment 1. The press working concerned may not require fixing the fan-shaped section  83  of the metal plate material  81  fixed to the lower die. Thereby, the concave portion  56  having the bottom section  61  is formed in the metal plate material  81 . Then, the metal plate material  81  after press worked shown in  FIG. 9  is subjected to press working corresponding to the first outer wall section  63  and the flange portion  63 A, and thus it is possible to form the coupling member  51  shown in  FIG. 10 . In addition, press working of the first outer wall section  63  and the flange portion  63 A is conducted by bending, for example. In this manner, it becomes possible to manufacture the coupling member  51  in Embodiment 1. Likewise, the metal plate material  81  on which the concave portion  71  is formed as shown in  FIG. 8  is subjected to press working corresponding to the first outer wall section  63  and the flange portion  63 A, and thus it becomes possible to form the coupling member  70 . 
     Furthermore, while Embodiment 1 described above explains taking the cowl side  11  and the lower member  19  as the example of the first and second member coupled by the coupling member  51 , the coupling member of the present application can be applied to any other coupling portions. More specifically, irrespective of the structure of the vehicle front section, it is possible to apply the coupling member  51  for coupling a variety of branching sections of frames of the vehicle, such as the rear structure. 
     Furthermore, in Embodiment 1 described above, the coupling member  51  is structured to have the concave portion  56  inserting into the groove section  23  of the branching section, however, the structure is not limited to this. For example, the coupling member of the present application may be in the shape for only entirely covering the branching section between the cowl side  11  and the lower member  19 . More specifically, the coupling member  51  may be structured so that the first and second cover sections  53  and  55  are formed in the shape of a single plate, without providing the concave portion  56 , the first outer wall section  63 , and the second outer wall section  65 . Then, the first and second cover sections  53  and  55  are joined by welding or the like to the side wall  35  of the cowl side  11  or the side wall  45  of the lower member  19 . Even in such a structure, it is possible to join two members without the necessity of flange portions  103  and  105  having a notch  111  provided therebetween as shown in  FIG. 11 . 
     Furthermore, in Embodiment 1 described above, two members (the cowl side  11  and the lower member  19 , etc.) may be joined using the flange portions  103  and  105  having the notch  111  provided therebetween as shown in  FIG. 11 , as well as joined by means of the coupling member  51 . Thereby, it is possible to fix the cowl side  11  and the lower member  19  more firmly while suppressing cracking or the like in the notch  111  by the coupling member  51 . 
     Furthermore, in each of the embodiments described above, the first and second cover sections  53  and  55  may be structured to be connected only by the concave portion  56 . More specifically, in each of the embodiments, while the second cover section  55  is formed continuously to the first cover section  53  at the section where the end section  47  of the lower member  19  comes into contact with the lower wall  33  of the cowl side  11 , the section concerned may be structured to be discontinued. In this case, for example, each of the first and second cover sections  53  and  55  is arranged in the vehicle upper-lower direction, and is coupled by the concave portion  56  provided between the upper-lower direction so as to be integrally formed. 
     According to the technique disclosed in the present application, it is possible to provide a coupling member capable of fixing a branching section more firmly which couples frame members of a vehicle to each other.