Patent Publication Number: US-2023159108-A1

Title: Vehicle strengthening member

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a U.S. National Phase entry of, and claims priority to, PCT Application PCT/JP2021/015697, filed Apr. 16, 2021, which claims priority to Japanese Patent Application No. 2020-073269, filed Apr. 16, 2020, both of which are incorporated herein by reference in their entireties for all purposes. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a vehicle strengthening member for a roof center reinforcement, front bumper, or other component of a vehicle body. 
     BACKGROUND 
     The roof of a vehicle includes a strengthening member known as a roof center reinforcement, which is located at a position between the right and left center pillars. The roof center reinforcement has a generally hat-shaped cross section perpendicular to its longitudinal direction, and extends between the left and right center pillars. The roof center reinforcement has a plurality of bend portions along the longitudinal direction, and is formed in a curved shape so that the height from the vehicle floor is larger at the central portion in its longitudinal direction. 
     SUMMARY 
     The above-mentioned roof center reinforcement is formed by pressing sheet steel. However, a problem may arise in that the product cannot be manufactured with high accuracy because of spring back which occurs during the press forming process. It is thus desirable to reduce the amount of spring back when a strengthening member is press formed. 
     One aspect is a vehicle strengthening member, comprising a top wall and a pair of lateral walls, so that the vehicle strengthening member has a hat-shaped cross section. The vehicle strengthening member further includes a plurality of bend portions bent along a fold line extending in a transverse direction so that the vehicle strengthening member is curved as a whole. The top wall includes a recess extending in a longitudinal direction and along a center of the top wall. The top wall also includes a pair of ridges extending in the longitudinal direction and along lateral sides of the recess. The top wall includes at least one raised bead in the recess. Each raised bead is at a position corresponding to each of the bend portions, each raised bead extending in the transverse direction. Each raised bead comprises ends, each of which is joined to a side of the ridge. 
     In some embodiments, each ridge comprises a recessed bead extending along the longitudinal direction and is at a position corresponding to each of the bend portions. 
     In some embodiments, the at least one raised bead corresponding to the associated bend portion comprises one raised bead positioned across the fold line. 
     In some embodiments, the fold line of each of the bend portions is interrupted by the corresponding raised bead, and a top of the raised bead comprises a flat surface. 
     In some embodiments, the at least one raised bead corresponding to the associated bend portion comprises two raised beads positioned between the two recessed beads associated with the same bend portion. The two raised beads are disposed on opposite sides of the corresponding fold line. 
     In some embodiments, the vehicle strengthening member is a roof center reinforcement. The top wall of the vehicle strengthening member is positioned on an inner side of the curvature of the roof center reinforcement due to being bent at the bend portions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a roof center reinforcement according to one embodiment. 
         FIG.  2    is an enlarged perspective view of the roof center reinforcement of  FIG.  1   . 
         FIG.  3    is an enlarged perspective view of a bend portion of the roof center reinforcement of  FIG.  1   . 
         FIG.  4    is a view of the roof center reinforcement of  FIG.  2    as seen along arrow IV of  FIG.  2   . 
         FIG.  5    is a cross-sectional view of the roof center reinforcement of  FIG.  2    taken along line V-V of  FIG.  2   . 
         FIG.  6    is a sectional view of the bend portion of  FIG.  3    taken along line VI-VI of  FIG.  3   . 
         FIG.  7    is an enlarged perspective view of a bend portion of a roof center reinforcement as another embodiment, as compared to  FIG.  3   . 
         FIG.  8    is a cross-sectional view of the bend portion of  FIG.  7    taken along line of  FIG.  7   . 
         FIG.  9    is a plan view of a roof center reinforcement as another embodiment. 
         FIG.  10    is an enlarged perspective view of a bend portion of a roof center reinforcement as another embodiment, as compared to  FIG.  3   . 
         FIG.  11    is an illustrative view of the amount of reduced spring back of the roof center reinforcement of  FIG.  1    in comparison with a comparative example. 
         FIG.  12    is an illustrative view of the amount of reduced spring back of the roof center reinforcement of  FIG.  1    in comparison with another comparative example. 
         FIG.  13    is an illustrative view of the amount of reduced spring back of the roof center reinforcement of  FIG.  7    in comparison with a comparative example. 
         FIG.  14    is an illustrative view of the amount of reduced spring back of the roof center reinforcement of  FIG.  9    in comparison with a comparative example. 
     
    
    
     DETAILED DISCLOSURE 
     Roof Center Reinforcement 
       FIG.  1    shows a roof center reinforcement as an embodiment of the present disclosure. While the roof center reinforcement will be hereinafter described as an example, various features described below can be applied to various strengthening members or reinforcement members of a vehicle body, such as a strengthening member of a front bumper.  FIG.  1    shows a framework structure of an upper portion of a vehicle body. As shown in  FIG.  1   , roof side rails  2  are provided on both the left and right sides of the vehicle  1 . The left and right roof side rails  2  are supported from below by respective left and right front pillars (not shown), left and right center pillars  6 , and left and right rear pillars  7 . Between the left and right roof side rails  2 , a transverse member known as a roof center reinforcement  3  is fixed between the left and right center pillars  6 . Other transverse members, known as a front header  4  and a rear header  5 , are fixed between the left and right roof side rails  2  behind and in front of the roof center reinforcement  3 . Between the left and right roof side rails  2 , a roof panel  8  is fixed, covering the front header  4 , the roof center reinforcement  3 , and the rear header  5 . 
       FIGS.  2  to  6    show the roof center reinforcement  3  in isolation. For convenience in explanation, the roof center reinforcement  3  is shown in  FIGS.  2  to  6    upside down with respect to that shown in  FIG.  1   . As shown in  FIG.  1   , the roof center reinforcement  3  is arranged with its longitudinal side facing the left and right direction of the vehicle. As shown in  FIGS.  2  and  5   , the roof center reinforcement  3  has a generally hat-shaped cross section. Specifically, the roof center reinforcement  3  includes a top wall  10 , a pair of lateral walls  13  extending from the lateral edges of the top wall  10 , and a pair of flanges  14  extending from the edges of the lateral walls  13 . The top wall  10  includes a recess  11  extending in the longitudinal direction and formed at the transverse center of the top wall  10 . The top wall  10  thus includes ridges  12  extending in the longitudinal direction on both sides of the recess  11  of the top wall  10 . The roof center reinforcement  3  may be formed, for example, by press forming a long sheet of high tensile strength steel (for example, with a tensile strength of about 1,180 MPa). The thickness of the high tensile strength steel sheet may be, for example, about 1.2 to 1.6 mm. 
     Bend Portions 
     As shown in  FIG.  2    and  FIG.  4   , the roof center reinforcement  3  is curved as a whole by being bent at a plurality of bend portions  15 , each of which is spaced apart along the longitudinal direction. The intervals between the bend portions may be constant; however, in other embodiments, the intervals may not be constant. The direction of curvature of the roof center reinforcement  3  is such that the top wall  10  is situated on the inner side of the curvature. The roof center reinforcement  3  is fixed to the left and right roof side rails  2  with the top wall  10  facing downward. As a result, the roof center reinforcement  3 , when assembled to the vehicle body as shown in  FIG.  1   , is highest from the vehicle floor at its longitudinal center. 
     As shown in  FIGS.  4  and  6   , the roof center reinforcement  3  is bent by an angle θ across the fold line  18  in each bend portion  15 . The bending angle of each bend portion  15  may be determined so that the roof center reinforcement  3  has the desired curved shape as a whole. The bend portions  15  may be rounded so that the fold line  18  does not appear as a clear single line (the triple lines shown in the drawings represent the result of applying a fillet process with CAD software). 
     Recessed Beads 
     As shown in  FIG.  3   , the ridges  12  may include recessed beads  16 , with their length extending in the longitudinal direction, positioned so as to correspond to associated bend portions  15 . Each recessed bead  16  may be a depression in the ridge  12  such that the ridge  12  has a reduced height of protrusion at the transverse center of the ridge  12 . The recessed beads  16  help increase the flexural rigidity of the roof center reinforcement  3  in the areas around the bend portions  15 . 
     Raised Beads 
     The recessed portion  11  includes raised beads  17  protruding in the same direction as the ridges  12 , each recessed portion  11  being positioned to correspond to an associated bend portion  15 . Each raised bead  17  extends in the transverse direction of the roof center reinforcement  3 . The raised beads  17  extend to supplement the fold line  18  of the bend portions  15 . The two ends of the raised bead  17  are joined to a side of the associated ridge  12 . Therefore, the raised beads  17  are situated between the two opposing recessed beads  16 . The raised beads  17  thus formed increase the flexural rigidity of the roof center reinforcement  3  in the areas around the bend portion  15 . As shown in  FIG.  2   , the longitudinal ends of the roof center reinforcement  3 , where no bend portion  15  is provided, may each include a raised bead  17  similar to the raised bead  17  formed at the bend portion  15 . This increases the flexural rigidity of the longitudinal ends of the roof center reinforcement  3 . As shown in  FIG.  3   , the fold line  18  of each bend portion  15  is interrupted by the raised bead  17  whose top has a flat surface. The suppression of the fold line in the raised bead  17  may slightly increase the flexural rigidity of the roof center reinforcement  3  in the areas around the bend portions  15 , as compared with the case where the fold line is formed in the raised bead  17 . 
     Test on the Amount of Spring Back 
     Press forming of roof center reinforcements of several forms was simulated by a CAE (computer aided engineering) analysis, and the amount of spring back at their ends was compared. Each roof center reinforcement was press formed from a high tensile strength steel sheet with a tensile strength of 1,180 MPa, and having a length (in the longitudinal direction) of 1,000 mm, a width (in the transverse direction) of 17 mm, and a thickness of 1.4 mm.  FIG.  11    depicts two roof center reinforcements prepared for comparison, drawn in combination for the sake of convenience, with the right side of the center line (shown by a dot-chain line) being the roof center reinforcement  3  of the embodiment configured as described above, and the left side of the center line being a roof center reinforcement of a comparative example. The comparative example does not include the above-described recessed beads  16  or raised beads  17 . The numerical values indicated at two points in the right end of  FIG.  11    represent the differences in the amount of spring back at those points between the two roof center reinforcements  3  after having been press formed. The press forming of each roof center reinforcement  3  was performed while the roof center reinforcement  3  was fixed at its center. Since the left and right of each roof center reinforcement  3  are generally symmetrical, it should be understood that, while not shown, the numerical values at the right end of each of the roof center reinforcements  3  of  FIG.  11    similarly applies to the left end of each of the roof center reinforcements  3  of  FIG.  11    as well. From these values, it was found that the amount of spring back in the roof center reinforcement  3  of the present embodiment (right side roof center reinforcement  3  of  FIG.  11   ) was about 2.8 mm less than that of the comparative example (left side roof center reinforcement of  FIG.  11   ). Therefore, the roof center reinforcement  3  of the present embodiment can be more accurately manufactured than the comparative example. 
       FIG.  12    depicts another combination of roof center reinforcements, with the right side of the center line being the same as that of  FIG.  11   , but the left side of the center line showing a comparative roof center reinforcement in which the fold line  18  crosses the raised bead  17 . From the numerical values indicated at the right end of  FIG.  12   , it was found that the amount of spring back in the roof center reinforcement  3  of the present embodiment (right side roof center reinforcement  3  of  FIG.  12   ) was about 0.35 mm less on each side than the comparative example (left side roof center reinforcement  3  of  FIG.  12   ). Therefore, in the present embodiment in which a fold line is not formed across the raised bead  17 , the roof center reinforcement  3  can be manufactured with higher accuracy than the case where a fold line  18  is formed across the raised bead  17 . 
     Double Raised Beads 
     As shown in  FIGS.  7  and  8   , each raised bead  17  may be replaced with a pair of raised beads  17   a ,  17   b . Specifically, the two raised beads  17   a ,  17   b  are positioned across the bend portion  15  in the longitudinal direction of the roof center reinforcement  3 . Each end of the two raised beads  17   a ,  17   b  is joined to a side of the associated ridge  12 . As a result, the longitudinal dimension L 1  of the area over which the two raised beads  17   a ,  17   b  are in the recess  11  is approximately the same as the longitudinal dimension L 2  of the recessed beads  16 . 
       FIG.  13    shows a roof center reinforcement  3  including the two raised beads (on the right side), drawn in combination with a comparative roof center reinforcement with neither recessed beads  16  nor raised beads  17  (on the left side). From the numerical values indicated at the right end of  FIG.  13   , the roof center reinforcement  3  of the present embodiment shows that the amount of spring back is about 2.3 mm less on each side than that of the comparative example. Therefore, the roof center reinforcement  3  of the present embodiment can be more accurately manufactured than the comparative example. 
     Omission of the Recessed Beads 
     As shown in  FIG.  9   , the recessed bead  16  may be omitted. In this case, raised beads  17  similar to those in the above-described embodiment of  FIG.  2    may still be included in each of the corresponding bend portions  15 . 
       FIG.  14    shows a roof center reinforcement  3  with no recessed beads  16  (on the right side of the center line), drawn in combination with a comparative roof center reinforcement with neither recessed beads  16  nor raised beads  17  (on the left side of the center line). From the numerical values indicated at the right end of  FIG.  14   , it was found that the amount of spring back of the roof center reinforcement  3  of the present embodiment is about 0.8 mm less on each side as compared to the comparative example. Therefore, in the present embodiment, the roof center reinforcement  3  can be more accurately manufactured than the comparative example. 
     Cross-Shaped Raised Beads 
     As shown in  FIG.  10   , each raised bead  17  may be replaced with a cross-shaped raised bead  17   c  with its intersection at the bend portion  15  of the recess  11 . Specifically, the cross-shaped raised bead  17   c  has the shape of a cross with its intersection at the bend portion  15  of the recess  11 , and with each end joined to a side of the associated ridge  12 . As a result, the longitudinal dimension L 3  of the area over which the raised bead  17   c  extends in the recessed portion  11  is slightly larger than, but nearly equal to, the longitudinal dimension L 4  of the recessed bead  16 . 
     While not shown, the amount of spring back when the roof center reinforcement  3  of  FIG.  9    was press formed was approximately the same as that of the embodiment of  FIG.  7   . Therefore, the roof center reinforcement  3  of the present embodiment can be more accurately manufactured than a comparative example. 
     Advantages of the Embodiments 
     The embodiments described above have at least the following advantages. 
     In the above-described embodiments, the raised bead  17  is included in an area corresponding to the bend portion  15 , thereby leading to an increased flexural rigidity in the areas around the bend portions  15 . This reduces the amount of spring back when the vehicle strengthening member (e.g., a roof center reinforcement  3 ) is press formed, as compared with the case where no raised beads  17  are formed. The raised bead  17  also reduces the variation of the amount of spring back. As a result, the vehicle strengthening member can be manufactured with higher accuracy. 
     In some embodiments, a recessed bead  16  is further included in the ridge  12  in an area corresponding to the bend portion  15 . This increases the flexural rigidity in the areas around the bend portions  15 . This reduces the amount of spring back when the vehicle strengthening member (e.g., the roof center reinforcement  3 ) is press formed, as compared with the case where no recessed beads  16  are formed. The recessed beads  16  also reduce the variation in the amount of spring back. As a result, the vehicle strengthening member can be manufactured more accurately. 
     In some embodiments, one raised bead  17  is positioned to supplement the fold line  18  of the bend portion  15  between the recessed beads  16 . The raised bead  17  therefore reliably functions to ensure an increased flexural rigidity in the areas around the bend portions  15 . This reduces the amount of spring back when the vehicle strengthening member (e.g., the roof center reinforcement  3 ) is press formed, leading to a higher accuracy with which the vehicle strengthening member can be manufactured. 
     In some embodiments, the top of the raised bead  17  has a flat surface. This increases the flexural rigidity in the areas around the bend portions  15 , as compared with the case where the fold line of the bend portion  15  passes through the top of the raised bead  17 . This reduces the amount of spring back when the vehicle strengthening member (e.g., the roof center reinforcement  3 ) is press formed, as compared with the case where the fold line passes through the top of the raised bead  17 . This also reduces the variation in the amount of spring back. As a result, the vehicle strengthening member can be manufactured more accurately. 
     In some embodiments, even when the fold line of the bend portion  15  extends across the recessed portion  11 , two raised beads  17   a ,  17   b  are formed on either side the fold line. This leads to an increased flexural rigidity in the areas around the bend portion  15 . This also reduces the amount of spring back when the vehicle strengthening member (e.g., the roof center reinforcement  3 ) is press formed, as compared with the case where no raised beads  17   a ,  17   b  are formed. The raised beads  17   a ,  17   b  also reduce the variation in the amount of spring back. As a result, the vehicle strengthening member can be manufactured with higher accuracy. 
     In some embodiments, the raised beads  17 ,  17 A,  17 B,  17 C are formed in areas corresponding to the bend portion  15  of the roof center reinforcement  3 . This reduces the amount of spring back when the roof center reinforcement  3  is press formed, thereby leading to a higher accuracy with which the roof center reinforcement  3  can be manufactured. 
     While the specific embodiments have been described above, the present disclosure is not limited to these embodiments, and various modifications, substitutions, additions, and/or omissions can be made by those skilled in the art.