Abstract:
An elongated beam, or rocker assembly, is disclosed that includes a first panel and a second panel attached to the first panel to define a cavity. A reinforcement is disposed in the cavity that includes a first tubular member adhesively connected to the first panel inside the cavity and a pair of tubular members are connected with an adhesive to the second panel, to each other, and the first tubular member. The tubular members are arranged in a triangular array within the cavity and extend along the length of the elongated beam. The wall thickness and bending strength of the tubular members are selected to provide an insert that collapses preferentially with the outer tubular member of the insert collapsing before the inner tubular members.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to a rocker assembly for a vehicle including an insert having a plurality of connected tubular members and that reduces the extent of intrusion toward a battery pack and reduces acceleration of the battery pack in a side pole impact. 
       BACKGROUND 
       [0002]    Rocker assemblies are provided between the front and rear wheel wells and below the doors of a vehicle to provide resistance to intrusion into the passenger compartment in side impact collisions. Rocker assemblies may include an outer rocker panel that is joined to a side sill. Various reinforcements have been proposed to strengthen rocker assemblies. 
         [0003]    Electric vehicles may be provided with an underfloor mounted battery that powers an electric traction motor. Batteries for a hybrid electric vehicle may be attached between a central tunnel and the rocker assembly on both sides of the vehicle. Space is provided around the underfloor battery pack to reduce the potential for plastic deformation of the battery pack. If the rocker assembly is too soft it may provide inadequate protection from intrusion in side impact collisions. 
         [0004]    Batteries for hybrid electric vehicles may be damaged internally by an impact. The battery pack may be damaged in a collision if the impact causes an acceleration spike, in particular, if the acceleration spike is of longer duration. If the rocker assembly is too rigid, acceleration of the battery caused by a side impact may create a longer spike of substantial duration and may cause damage to internal battery connections. 
         [0005]    This disclosure is directed to solving the above problems and other problems as summarized below. 
       SUMMARY 
       [0006]    According to one aspect of this disclosure, a rocker assembly is provided for a vehicle that comprises an outer panel, a side sill defining a cavity with the outer panel and an insert disposed in the cavity. The insert includes a plurality of longitudinally extending pipes connected with an adhesive to each other, the outer panel and the side sill. The wall thickness of one of the plurality of pipes is different than the wall thickness of another of the plurality of pipes. 
         [0007]    According to another aspect of this disclosure, a rocker assembly is provided for a vehicle that comprises an outer panel, a side sill defining a cavity with the outer panel, and a plurality of tubular members. A first tubular member is adhesively connected to the outer panel inside the cavity. A second tubular member and a third tubular member extend in a longitudinal vehicle direction and are adhesively connected to the side sill and the first tubular member. 
         [0008]    According a further aspect of this disclosure, an elongated beam is provided that comprises a first panel, a second panel attached to the first panel to define a cavity, and a reinforcement disposed in the cavity. The reinforcement includes a first tubular member adhesively connected to the first panel inside the cavity and a pair of tubular members adhesively connected to the second panel, to each other, and the first tubular member. The tubular members are arranged within the cavity to extend along the length of the elongated beam. 
         [0009]    The above rocker assembly or beam may have pipes or tubular members that a cylindrical in shape. The pipes or tubular members may be connected in a triangular array with two of the pipes or tubular members being connected to the side sill and one of the pipes or tubular members being connected to the outer panel. 
         [0010]    The above rocker assembly or elongated beam may be constructed so that the sum of the wall thickness of the two pipes connected to the side sill is greater than the wall thickness of the one pipe connected to the outer panel. The wall thickness of each of the two pipes connected to the side sill may be less than the wall thickness of the one pipe connected to the outer panel. The relative thickness of the pipes or tubular members are selected to collapse preferentially with the first pipe collapsing prior to the pair of pipes. 
         [0011]    The above aspects and other aspects of this disclosure are described below with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a diagrammatic bottom plan view of a prior art vehicle including a battery pack attached to the vehicle between the rocker assemblies and below the floor of the passenger compartment. 
           [0013]      FIG. 2  is a fragmentary transverse cross-section view taken along the line  2 - 2  in  FIG. 1  of a prior art vehicle having a conventional rocker assembly. 
           [0014]      FIG. 3  is a fragmentary transverse cross-section view of a vehicle having a rocker assembly with an insert including a plurality of pipes or tubular members interconnected in a triangular array that is disposed in the rocker assembly. 
           [0015]      FIGS. 4A-4C  illustrate a computer simulation of a side impact prior to impact (0 ms), at an intermediate point during the impact event (30 ms) and at the maximum intrusion of the impact event (50 ms). 
           [0016]      FIG. 5  is a graph comparing the extent of intrusion (mm) over time (ms) for a simulated impact applied to a rocker assembly without an insert to a rocker assembly with an insert. 
           [0017]      FIG. 6  is a graph comparing battery acceleration (g) over time (ms) for a simulated impact applied to a rocker assembly without an insert to a rocker assembly with an insert. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The illustrated embodiments are disclosed with reference to the drawings. However, it is to be understood that the disclosed embodiments are intended to be merely examples that may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed are not to be interpreted as limiting, but as a representative basis for teaching one skilled in the art how to practice the disclosed concepts. 
         [0019]    Referring to  FIG. 1 , the underbody of a vehicle  10  is illustrated. A rocker assembly  12 , also referred to as an elongated beam, is provided on right and left sides of the vehicle  10 . A central tunnel  14  extends longitudinally between the rocker assemblies  12  and forms part of the floor pan  16  of the vehicle  10 . The floor pan  16  underlies the passenger compartment of the vehicle  10  and is illustrated with an underfloor battery  18  attached below the floor pan  16  with brackets of the underbody structure (not shown). A protected area box  20  is labelled with the letter “A” and an impact absorbing area box  22  is labelled with the letter “B”. The vehicle  10  has a pair of front wheels  26  and a pair of rear wheels  28 . The rocker assembly  12  extends between the wheel wells of the front wheels  26  and rear wheels  28 .  FIG. 1  is identified as a prior art, but it should be understood that the vehicle depicted in  FIG. 1  may include the rocker insert formed by connected tubular members that are not visible because they are disposed within the rocker assembly  12 . 
         [0020]    Referring to  FIG. 2 , a prior art vehicle structure is shown to include a rocker assembly  12  on one side of the floor pan  16  and central tunnel  14 . The rocker assembly  12  includes a rocker outer  30  and a side sill  32  that are assembled together to define the cavity  34 . The under-floor battery  18  is shown secured below the floor pan  16  inboard of a sled runner beam  36  and the rocker assembly  12 . 
         [0021]    Referring to  FIG. 3 , the rocker assembly  12  is shown secured to the sled runner beam  36  and a cross member  38  that extends from the rocker assembly  12  inboard towards the central tunnel  14  (shown in  FIGS. 1 and 2 ). The rocker assembly  12  is reinforced with an insert that is disposed in the cavity  34  defined by the rocker outer  30  and side sill  32 . The insert includes an outer reinforcement pipe  40  (or tubular member), an inner/lower reinforcement pipe  42 , and an inner/upper reinforcement pipe  44 . The reinforcement pipes  40 ,  42  and  44  are secured together by a structural adhesive  46  and, in combination, comprise the insert. The structural adhesive  46  is also used to secure the outer reinforcement pipe  40  to the rocker outer  30 . The inner/lower reinforcement pipe  42  and inner/upper reinforcement pipe  44  are secured by the structural adhesive  46  to the side sill  32 . 
         [0022]    Referring to  FIGS. 4A-4C , a computer simulation of a side impact is shown progressively at 0 ms, 30 ms and 50 ms during the course of a side impact collision. 
         [0023]    Referring to  FIG. 4A  at 0 mm, the rocker assembly  12  is shown with the three reinforcement pipes,  40 ,  42  and  44  connected together and inside the rocker assembly  12  by the structural adhesive  46 . The three reinforcement pipes are connected together in a triangular array and are also connected to the rocker outer  30  and side sill  32  as previously described. The rocker assembly is shown connected to the sled runner beam  36  and cross member  38 . The cross member  38  is disposed above the floor pan  16  that extends to the central tunnel  14 . It should be understood that the underfloor battery  18  (shown in  FIGS. 1 and 2 ) is attached below the floor pan  16  between the sled runner beam  36  and the central tunnel  14 . 
         [0024]    Referring to  FIG. 4B , the structure shown at 30 ms into a side collision event. At this point, the outer rocker panel is deformed and the pipes start to compress to absorb energy from the collision. At the 30 mm point, the outer single pipe deforms completely and the second layer of inner pipes begins to deform. 
         [0025]    Referring to  FIG. 4C , the side impact event is shown at 50 mm. At this point, the inner rocker panel and sled runner are partially deformed, but there is no cross member buckling. At 50 mm, the outer single pipe deforms completely and the gap between the pipes is diminished. Also at the 50 mm point, the inner pipes  42  and  44  are partially deformed. The outer pipe  40  deforms first with the second layer of inner pipes  42  and  44  deforming partially thereafter to facilitate progressive deformation of the rocker assembly insert. 
         [0026]    Referring to  FIG. 5 , intrusion caused by a side impact collision with the baseline structure shown in  FIG. 2  is shown to experience intrusion of a maximum of approximately 30 mm, while in the disclosed embodiment of the rocker assembly including the pipe inserts intrusion as shown by line  52  indicates that the maximum intrusion is reduced to approximately 22 mm. Maximum intrusion indicated by the baseline intrusion line  50  occurs at approximately 70 ms. The maximum intrusion for the disclosed embodiment as shown by line  52  occurs at approximately 55 ms. 
         [0027]    Referring to  FIG. 6 , a baseline battery acceleration line  54  is shown compared to a disclosed embodiment of the rocker assembly including the pipe inserts battery acceleration that is shown by line  56 . A battery acceleration limit line  58  corresponds to a limit of acceleration that, if exceeded, may result in internal damage to battery connections. Battery acceleration is important for the protection of internal battery connections within the battery pack. Acceleration having excessive duration and high peaks may be detrimental to battery internal connections. Referring to the baseline battery acceleration line  54 , it is shown that the maximum acceleration peak is approximately 69 g. The maximum battery acceleration for the disclosed embodiment as shown by line  56 , is approximately 56 g. The duration of the maximum peak is less than 10 mm for the disclosed embodiment battery acceleration line  56 . While the disclosed embodiment battery acceleration line  56  exceeds the battery acceleration limit line  58 , the extent to which it exceeds the limit and short duration of the peak represents a significant improvement compared to the baseline battery acceleration in line  54  that has a peak that is 18% higher than the disclosed embodiment and that approaches 10 mm in duration. Resultant peak acceleration is decreased by 18% using the pipe inserts. It should also be noted that in the case of the disclosed embodiment, the acceleration peak is at an early stage in the graph of  FIG. 6 . 
         [0028]    The reinforcement pipes  40 ,  24 ,  44  are provided with different wall thicknesses to provide a controlled degree of impact absorption and also reduce battery acceleration resulting from a side impact collision impacting the rocker assembly  12 . For example, the outer reinforcement pipe  40  may have a wall thickness of 7 mm, the inner/lower reinforcement pipe  42  may have a wall thickness of 4 mm, and the inner/upper reinforcement pipe  44  may have a wall thickness of 5 mm. The reinforcement pipes,  40 ,  42 ,  44  are connected in a triangular array with two pipes being connected to the side sill and one of the pipes being connected to the outer panel. In at least one embodiment, the sum of the wall thicknesses of the two inner reinforcement pipes connected to the side sill is greater than the sum of the wall thickness of the reinforcement pipe connected to the outer panel. While the sum of the wall thicknesses of the inner pipes is greater than the wall thickness of the pipe connected to the outer panel, the wall thickness of each of the two pipes connected to the side sill may be less than the wall thickness of the pipe connected to the outer panel. The outer reinforcement pipe connected to the outer panel is intended to collapse preferentially relative to the two pipes connected to the side sill. 
         [0029]    The tubular members are preferably cylindrical tubular members and may be aluminum pipes having the desired wall thicknesses. Alternatively, the tubular members may be selected based upon bending strength instead of wall thickness. If so, the bending strength of the outer reinforcement pipe would be selected to be less than the combined strength of the two inner pipes  42 ,  44 . The bending strength of the pipes may be related to wall thickness or may be related to the material or heat treatment of the pipes. 
         [0030]    The embodiments described above are specific examples that do not describe all possible forms of the disclosure. The features of the illustrated embodiments may be combined to form further embodiments of the disclosed concepts. The words used in the specification are words of description rather than limitation. The scope of the following claims is broader than the specifically disclosed embodiments and also includes modifications of the illustrated embodiments.