Abstract:
A panel joining structure for a vehicle includes a first plate, a second plate, a braze and a surface area enlargement portion. The first plate is formed of a metal and a first joining portion is formed thereat. The second plate is formed of a different metal from the first plate and a second joining portion that is to be joined with the first joining portion is formed thereat. The braze is interposed between the first joining portion and the second joining portion. The braze joins the first joining portion with the second joining portion. The surface area enlargement portion is formed in a range that makes contact with the braze at, of the first joining portion and the second joining portion, a side at which the braze and a heterogenous metal are disposed. At least one of protrusions and recesses are formed at the surface area enlargement portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 USC 119 from Japanese Patent Application No. 2014-152115 filed Jul. 25, 2014, the disclosure of which is incorporated by reference herein. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a panel joining structure for a vehicle, and particularly relates to a panel joining structure for a vehicle in which the joining is implemented by brazing. 
         [0004]    2. Related Art 
         [0005]    Heretofore, a roof structure for a vehicle has been proposed in which a mohican portion is not provided at a region of joining between a roof panel of the vehicle and a roof side rail of the vehicle. For example, Japanese Patent Application Laid-Open (JP-A) No. 2004-131062 discloses a structure in which a joining surface of a roof panel and a joining surface of a body panel (a roof rail) are joined by an adhesive material and the adhesive material is covered with a sealant material. Further, in JP-A No. 2005-161909, a roof panel and a roof side rail are joined by laser brazing (brazing). 
         [0006]    However, with the joining disclosed in JP-A No. 2004-131062, because the join is based on adhesive, it is difficult to assure joining strength. In a case of brazing joining as in JP-A No. 2005-161909, if the roof panel and the roof side rail are formed of different metallic materials, then at least one of the roof panel and the roof side rail is a metallic material that is heterogenous from the braze. In this case, intermetallic compounds may be produced at the welding interface. As a result, the joining strength between the braze and the heterogenous material may be weak and it may be difficult to assure joining strength between the roof panel and the roof side rail. 
       SUMMARY 
       [0007]    In consideration of the situation described above, the present invention provides a panel joining structure for a vehicle that may assure joining strength when two vehicle panels formed of different metallic materials are joined by brazing. 
         [0008]    A panel joining structure for a vehicle according to a first aspect of the present invention includes: a first plate that is formed of a metal, at which a first joining portion is formed; a second plate that is formed of a different metal from the first plate, a second joining portion that is to be joined with the first joining portion being formed at the second plate; a braze that is interposed between the first joining portion and the second joining portion, the braze joining the first joining portion with the second joining portion; and a surface area enlargement portion in a range that makes contact with the braze at, of the first joining portion and the second joining portion, a side at which the braze and a heterogenous metal are disposed, at least one of protrusions and recesses being formed at the surface area enlargement portion. 
         [0009]    In the first aspect of the present invention, the first joining portion of the first plate and the second joining portion of the second plate are joined via the braze. At least one of the first plate and the second plate is formed of a metal of a kind that is different from the braze (the heterogenous metal). However, the surface area enlargement portion at which one or both of protrusions and recesses are formed is provided in the range that makes contact with the braze at, of the first joining portion and the second joining portion, each side at which the braze and a heterogenous metal are disposed (the first plate, the second plate, or both the first plate and the second plate). 
         [0010]    According to the first aspect of the present invention, a mutual joining area between the plate of the heterogenous metal and the braze is enlarged by the surface area enlargement portion being formed in the range that makes contact with the braze at, of the first joining portion and the second joining portion, the side at which the braze and the heterogenous metal are disposed. That is, because the surface area enlargement portion is formed, the joining area with the braze is enlarged, as a result of which a joining strength between the first plate and the second plate may be assured. 
         [0011]    In a panel joining structure for a vehicle according to a second aspect of the present invention, unevenness is formed at the surface area enlargement portion by a shelf portion that is formed in a step shape. 
         [0012]    According to the second aspect of the present invention, the unevenness is formed by the shelf portion that is formed in the step shape, and the mutual joining area between the plate of the heterogenous metal and the braze may be enlarged with ease. 
         [0013]    In a panel joining structure for a vehicle according to a third aspect of the present invention, second unevennesses are formed at a surface of the shelf portion that makes contact with the braze. 
         [0014]    According to the third aspect of the present invention, because the second unevennesses are additionally formed at the shelf portion, the surface area of the surface area enlargement portion is further enlarged, and the mutual joining area between the plate of the heterogenous metal and the braze may be enlarged. 
         [0015]    In a panel joining structure for a vehicle according to a fourth aspect of the present invention, the first plate is a steel plate and the second plate is an aluminium plate. 
         [0016]    According to the fourth aspect of the present invention, in a case in which an aluminium plate is employed in order to reduce weight and used together with a steel plate in order to assure strength, the joining strength of the two plates in joining by brazing may be assured. That is, a joining strength per unit of area of the second joining portion, of the steel plate or the aluminium plate, with the braze may be increased. Thus, the joining strength of the first plate with the second plate may be assured. 
         [0017]    A panel joining structure for a vehicle according to a fifth aspect of the present invention further includes: a seal shelf portion structured by a portion of one of the first plate or the second plate, the seal shelf portion extending from the first joining portion or the second joining portion in line with an outer surface of the braze; and a sealing material layer that is layered onto the braze and an outer side of the seal shelf portion, the sealing material layer being layered between the first joining portion and the second joining portion. 
         [0018]    According to the fifth aspect of the present invention, because the seal shelf portion is formed in line with the outer surface of the braze, the sealing material layer that is layered onto the braze may also be formed at the outer side of the seal shelf portion. Although irregularities tend to occur at the outer surface of a braze, because the seal shelf portion is employed, thickness of the sealing material layer may be easily controlled, and the sealing material layer at the outer surface may easily be formed with a suitable thickness. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    Exemplary Embodiments of the present invention will be described in detail based on the following figures, wherein: 
           [0020]      FIG. 1  is a perspective view showing an upper portion of a vehicle roof in accordance with a first exemplary embodiment of the present invention. 
           [0021]      FIG. 2  is a vertical sectional diagram of the vehicle roof taken along line A-A of  FIG. 1 . 
           [0022]      FIG. 3  is a partial magnified view of  FIG. 2 . 
           [0023]      FIG. 4  is a partial magnified view of a vertical section of a vehicle roof in accordance with a variant example of the first exemplary embodiment. 
           [0024]      FIG. 5  is a partial magnified view of a vertical section of a vehicle roof in accordance with an alternative variant example of the first exemplary embodiment. 
           [0025]      FIG. 6  is a partial magnified view of a vertical section of a vehicle roof in accordance with a second exemplary embodiment. 
           [0026]      FIG. 7  is a partial magnified view of a vertical section of a vehicle roof in accordance with a third exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
     First Exemplary Embodiment  
       [0027]    Herebelow, a first exemplary embodiment of a panel joining structure for a vehicle according to the present invention is described using the attached drawings. In the present exemplary embodiment, the panel joining structure for a vehicle is described using an example in which the panel joining structure for a vehicle is applied to a vehicle roof  10 . 
         [0028]    In  FIG. 1 , an upper portion of the vehicle roof  10  according to the first exemplary embodiment is shown in a perspective view.  FIG. 2  shows a sectional diagram taken along line A-A of  FIG. 1 . An arrow UP that is shown in the drawings indicates a vehicle upward side, an arrow OUT indicates a vehicle width direction outer side, and an arrow FR indicates a vehicle forward side. 
         [0029]    As shown in  FIG. 1 , the vehicle roof  10  includes a roof panel  30  and roof side rail portions  12 . The roof panel  30  serves as a second plate and covers a cabin. The roof side rail portions  12  are provided at each of two vehicle width direction sides. An outer shell of the vehicle is structured with the roof panel  30 . The roof side rail portions  12  are arranged along the vehicle front and rear direction as a pair at left and right. 
         [0030]    As shown in  FIG. 2 , each roof side rail portion  12  is structured with three panels: a rail inner panel  14 , a rail outer reinforcement  16  and a side outer panel  18  that serves as a first plate. The rail inner panel  14  is disposed at a vehicle cabin inner side and the rail outer reinforcement  16  is disposed at the vehicle cabin outer side relative to the rail inner panel  14 . A closed cross section is formed by the rail inner panel  14  and the rail outer reinforcement  16 . The side outer panel  18  is disposed at the vehicle cabin outer side of the rail outer reinforcement  16 . The rail inner panel  14 , the rail outer reinforcement  16  and the side outer panel  18  are all fabricated of steel plate. 
         [0031]    The rail inner panel  14  is structured by a main body portion  14 A, an inner side flange portion  14 B and an outer side flange portion  14 C. The main body portion  14 A forms a closed cross section with the rail outer reinforcement  16 . The inner side flange portion  14 B is inflected substantially horizontally to the vehicle width direction inner side from an inner end portion of the main body portion  14 A. The outer side flange portion  14 C is inflected diagonally downward and outward from an outer end portion of the main body portion  14 A. 
         [0032]    The rail outer reinforcement  16  is formed with a hat-shaped cross section that is somewhat opened out. The rail outer reinforcement  16  is structured by a main body portion  16 A, an inner side flange portion  16 B and an outer side flange portion  16 C. The main body portion  16 A is disposed so as to oppose the main body portion  14 A. The inner side flange portion  16 B is inflected substantially horizontally to the vehicle width direction inner side from an inner end portion of the main body portion  16 A. The outer side flange portion  16 C is inflected diagonally downward and outward from an outer end portion of the main body portion  16 A. 
         [0033]    The side outer panel  18  is structured by a main body portion  18 A, an inner side flange portion  18 B and an outer side flange portion  18 C. The main body portion  18 A is in a protruding shape capable of covering the main body portion  16 A of the rail outer reinforcement  16  from the vehicle cabin outer side thereof. The inner side flange portion  18 B is inflected substantially horizontally to the vehicle width direction inner side from an inner end portion of the main body portion  18 A. The outer side flange portion  18 C is inflected diagonally downward and outward from an outer end portion of the main body portion  18 A. 
         [0034]    As shown in  FIG. 3 , a diagonal wall  20  is formed at the vehicle width direction inner side of the main body portion  18 A. The diagonal wall  20  is inflected and rises diagonally upward to the vehicle outer side from an outer side end portion of the inner side flange portion  18 B. The diagonal wall  20  is structured with an inner side portion  22 , a first joining portion  24  and an outer side portion  26 . The inner side portion  22  refers to a region from an end portion of the diagonal wall  20  at the side at which the inner side flange portion  18 B is disposed to a contact point T at which the diagonal wall  20  makes contact with an inflected end portion  34  of the roof panel  30 , which is described below. The first joining portion  24  refers to a region that is brazed with a braze  50 , which is described below, from the contact point T to a region corresponding with an upper end of the braze  50 . The outer side portion  26  refers to a region from the region corresponding with the upper end of the braze  50  to the upper end of the diagonal wall  20 . 
         [0035]    A first protrusion portion  24 A and a first recess portion  24 B are formed at the first joining portion  24 . The first protrusion portion  24 A is curved to the vehicle outer side so as to form a protrusion, and the first recess portion  24 B is curved such that the vehicle outer side is recessed. A first shelf portion  24 C is formed between a ridge line A of a peak portion of the first protrusion portion  24 A and a trough line B of a floor portion of the first recess portion  24 B. The outer side portion  26  is formed to continue from the first joining portion  24 . 
         [0036]    The above-described inner side flange portion  14 B of the rail inner panel  14 , inner side flange portion  16 B of the rail outer reinforcement  16  and inner side flange portion  18 B of the side outer panel  18 —the three plates—are superposed and joined by spot welding. Similarly, the outer side flange portion  14 C of the rail inner panel  14 , outer side flange portion  16 C of the rail outer reinforcement  16  and outer side flange portion  18 C of the side outer panel  18 —the three plates—are superposed and joined by spot welding. Thus, a vehicle framework member along the vehicle front and rear direction is formed at the roof side rail portion  12 . 
         [0037]    The roof panel  30  is provided with a roof main body portion  32  that is formed in a gently curved shape that protrudes to the vehicle upward side. The roof main body portion  32  covers the cabin from the vehicle upward side thereof. The inflected end portion  34  is formed at each of two vehicle width direction end portions of the roof panel  30 . Each inflected end portion  34  is inflected to the vehicle downward side. The inflected end portion  34  is arranged so as to oppose the diagonal wall  20  of the side outer panel  18 . The roof panel  30  is fabricated of aluminium. 
         [0038]    As shown in  FIG. 3 , a seal wall portion  44 , a seal shelf portion  42 , a second joining portion  40 , a foldback portion  38  and a distal end portion  36  are formed at the inflected end portion  34  in this order from the side thereof at which the roof main body portion  32  is disposed. The seal wall portion  44  is inflected to the vehicle cabin inner side from a vehicle width direction outer side end portion of the roof main body portion  32 . The seal shelf portion  42  is inflected to the vehicle width direction outer side from a lower end of the seal wall portion  44 . The seal shelf portion  42  is formed to be co-planar with an outer surface of the braze  50  that is described below. The meaning of the term “co-planar” as used herein does not necessarily require that an upper face of the seal shelf portion  42  and the outer surface of the braze  50  are completely in the same plane but encompasses structures that include steps of some size but that can be judged as being substantially co-planar. 
         [0039]    The second joining portion  40  refers to a region that is brazed with the braze  50  that is described below, from the contact point T to a region corresponding with the upper end of the braze  50 . The foldback portion  38  is an inflected portion that is folded back to the inner side (the vehicle cabin side) in the vehicle width direction from the contact point T. The distal end portion  36  refers to a portion from the foldback portion  38  to a distal end of the inflected end portion  34 . 
         [0040]    A recess portion  48  is formed between the first joining portion  24  and the second joining portion  40 . The braze  50  is filled into the recess portion  48 . In the present exemplary embodiment, the braze  50  is an aluminium braze whose principal component is aluminium. Therefore, the braze  50  is a metal that is homogenous with the roof panel  30  but heterogenous from the side outer panel  18 . The braze  50  flows in between the first joining portion  24  and the second joining portion  40  in a molten state caused by laser brazing, and adheres to the first joining portion  24  formed with the first shelf portion  24 C and the second joining portion  40 . Thus, the first joining portion  24  and second joining portion  40  are joined via the braze  50 . An outer face of the braze  50  is formed to be substantially co-planar with the seal shelf portion  42 . 
         [0041]    The sealing material layer  52  is layered onto an outer side of the braze  50 . The sealing material layer  52  covers an outer surface of the braze  50  and is also layered onto the upper portion of the seal shelf portion  42 . The outer face of the sealing material layer  52  is substantially co-planar with an upper face of the roof main body portion  32 , forming a flat surface from the vehicle width direction end portion of the roof main body portion  32  to the outer side portion  26 . 
         [0042]    Now, operation and effects of the present exemplary embodiment are described. When the roof panel  30  and the roof side rail portion  12  are to be joined, the roof panel  30  is disposed at the upper portion of a body that includes the roof side rail portion  12 . At this time, the roof panel  30  gains access to the body from the upper side and is disposed such that each inflected end portion  34  opposes the diagonal wall  20 . The braze  50  is heated and melted by laser brazing. The braze  50  flows in between the first joining portion  24  and the second joining portion  40 , filling the recess portion  48 , and hardens. The outer face of the braze  50  is formed to be substantially co-planar with the seal shelf portion  42 . The braze  50  adheres to the first joining portion  24  and the second joining portion  40 . Thus, the first joining portion  24  and second joining portion  40  are joined via the braze  50 . 
         [0043]    Subsequently, the sealing material layer  52  is formed on the braze  50  and the upper side of the seal shelf portion  42 . The sealing material layer  52  is formed to be substantially co-planar with the upper face of the roof main body portion  32 . The sealing material layer  52  is leveled to be uniform from the vehicle width direction end portion of the roof main body portion  32  to the outer side portion  26 , forming a flat surface. 
         [0044]    The side outer panel  18  of the present exemplary embodiment is fabricated of steel plate, and intermetallic compounds are produced between the steel plate and the aluminium braze. However, the first protrusion portion  24 A and the first recess portion  24 B are formed at the first joining portion  24 , and the first shelf portion  24 C is formed between the first protrusion portion  24 A and the first recess portion  24 B. Therefore, a contact area between the first joining portion  24  and the braze  50  is expanded, and even though the brazing is implemented with the braze  50  that is an aluminium braze, joining strength with the steel plate may be assured. 
         [0045]    In the present exemplary embodiment, the seal shelf portion  42  is formed in line with the outer surface of the braze  50 . Therefore, the sealing material layer  52  layered on the braze  50  may also be formed at the outer side of the seal shelf portion  42 . Although irregularities tend to occur at the outer surface of the braze  50 , irregularities of the braze  50  may be covered over by the braze  50  being covered with the sealing material layer  52 . Here, because the seal shelf portion  42  is employed, the thickness of the sealing material layer  52  is easily controlled, and the sealing material layer  52  at the outer surface may easily be formed with a suitable thickness. 
         [0046]    In the present exemplary embodiment, one set of unevenness shapes (the first protrusion portion  24 A and first recess portion  24 B) is formed at the first joining portion  24 , and a single shelf portion (the first shelf portion  24 C) is formed between the unevenness shapes. However, as illustrated in  FIG. 4 , two sets of unevenness shapes (two sets of the first protrusion portion  24 A and first recess portion  24 B) may be formed at the first joining portion  24  and two of the first shelf portion  24 C may be formed. 
         [0047]    Further, in the present exemplary embodiment, the first shelf portion  24 C is formed at the first joining portion  24 . However, as illustrated in  FIG. 5 , a trough portion  24 D and a ridge portion  24 E in which a height difference of the unevenness is larger may be formed instead of the first shelf portion  24 C. 
       Second Exemplary Embodiment  
       [0048]    Now, a second exemplary embodiment of the panel joining structure for a vehicle according to the present invention is described. In the present exemplary embodiment, the panel joining structure for a vehicle according to the present invention is described using an example in which the panel joining structure for a vehicle is applied to a vehicle roof  60 . Portions that are similar to the first exemplary embodiment are illustrated with the same reference numerals applied and detailed descriptions thereof are not given. 
         [0049]    In the vehicle roof  60  according to the present exemplary embodiment, the shape of the first joining portion  24  is different from the first exemplary embodiment. Other structures are the same as in the first exemplary embodiment. As shown in  FIG. 6 , tiny unevennesses  25  are formed at the first shelf portion  24 C of the first joining portion  24 . The unevennesses  25  may be formed by a roughening treatment of the surface of the first shelf portion  24 C, or edging or the like. 
         [0050]    In the present exemplary embodiment, the braze  50  and the sealing material layer  52  may be formed in the recess portion  48  by the same procedure as in the first exemplary embodiment. 
         [0051]    In the present exemplary embodiment, because the unevennesses  25  are formed at the first shelf portion  24 C of the first joining portion  24 , the contact area between the braze  50  and the first joining portion  24  is further enlarged, and joining strength of the braze  50  and the first joining portion  24  may be assured. 
         [0052]    In the present exemplary embodiment, the unevennesses  25  are formed at the first shelf portion  24 C. However, the unevennesses  25  may be formed at other locations of the first joining portion  24 . For example, the unevennesses  25  may be formed at the side at which the inner side portion  22  is disposed relative to the first shelf portion  24 C, or may be formed at the side at which the outer side portion  26  is disposed relative to the first shelf portion  24 C. Furthermore, the unevennesses  25  that may assure joining strength may be formed over the whole of the first joining portion  24 . 
         [0053]    The unevennesses  25  of the present exemplary embodiment may be formed at the first joining portions  24  according to the variant examples of the first exemplary embodiment that are illustrated in  FIG. 4  and  FIG. 5 . 
       Third Exemplary Embodiment  
       [0054]    Now, a third exemplary embodiment of the panel joining structure for a vehicle according to the present invention is described. In the present exemplary embodiment, the panel joining structure for a vehicle according to the present invention is described using an example in which the panel joining structure for a vehicle is applied to a vehicle roof  62 . Portions that are similar to the first and second exemplary embodiments are illustrated with the same reference numerals applied and detailed descriptions thereof are not given. 
         [0055]    In the vehicle roof  62  according to the present exemplary embodiment, the shape of the second joining portion  40  is different from the first exemplary embodiment. The present exemplary embodiment also differs from the first exemplary embodiment in that the braze is a metal that is heterogenous from the roof panel  30  and the side outer panel  18 . Other structures are the same as in the first exemplary embodiment. 
         [0056]    A second protrusion portion  40 A and a second recess portion  40 B are formed at the second joining portion  40 . The second protrusion portion  40 A is curved so as to protrude to the vehicle outer side, and the second recess portion  40 B is curved to the vehicle outer side so as to form a recess. A second shelf portion  40 C is formed between a ridge line C of a peak portion of the second protrusion portion  40 A and a trough line D of a floor portion of the second recess portion  40 B. 
         [0057]    A recess portion  49  is formed between the first joining portion  24  and the second joining portion  40 . The recess portion  49  is filled with a braze  70 . In the present exemplary embodiment, the braze  70  is a zinc braze whose principal component is zinc. The braze  70  flows in between the first joining portion  24  and the second joining portion  40  in a molten state caused by laser brazing, and adheres to the first joining portion  24  at which the first shelf portion  24 C is formed and the second joining portion  40  at which the second shelf portion  40 C is formed. Thus, the first joining portion  24  and second joining portion  40  are joined via the braze  70 . An outer face of the braze  70  is formed to be substantially co-planar with the seal shelf portion  42 . 
         [0058]    The sealing material layer  52  is layered onto an outer side of the braze  70 . The sealing material layer  52  covers an outer surface of the braze  70  and is also layered onto the upper portion of the seal shelf portion  42 . The outer face of the sealing material layer  52  is substantially co-planar with the upper face of the roof main body portion  32 , forming a flat surface from the vehicle width direction end portion of the roof main body portion  32  to the outer side portion  26 . 
         [0059]    In the present exemplary embodiment too, the braze  70  and the sealing material layer  52  may be formed in the recess portion  49  by the same procedure as in the first exemplary embodiment. 
         [0060]    In the present exemplary embodiment, the first shelf portion  24 C and the second shelf portion  40 C are formed at the first joining portion  24  and the second joining portion  40 , respectively, expanding contact areas between the braze  70  and the first joining portion  24  and second joining portion  40 . Therefore, even though the join between the roof panel  30  and the side outer panel  18  is implemented with the braze  70  that is heterogenous from both the roof panel  30  and the side outer panel  18 , joining strengths of the braze  70  with the first joining portion  24  and the second joining portion  40  may be assured. 
         [0061]    The second joining portion  40  according to the present exemplary embodiment may be combined with the first joining portions  24  according to the variant examples of the first exemplary embodiment that are illustrated in  FIG. 4  and  FIG. 5 . Furthermore, the unevennesses  25  according to the second exemplary embodiment may be formed at the first joining portion  24  and the second joining portion  40  according to the present exemplary embodiment. 
         [0062]    In the present exemplary embodiment, an example is described in which a zinc braze is used. However, brazes whose principal components are alternative materials may be used, such as, for example, a copper braze whose principal component is copper. 
         [0063]    In the first to third exemplary embodiments described above, the panel joining structure for a vehicle relating to the present invention is applied to a vehicle roof. However, the panel joining structure for a vehicle relating to the present invention may be applied to alternative portions. For example, the panel joining structure for a vehicle may be applied to portions at which heterogenous metal panels are joined together at side panels, trunk lids and hoods of vehicles.