Abstract:
A battery housing for a traction motor battery of a vehicle is disclosed that includes a plurality of elongated impact absorbing members attached to the walls of the enclosure. The impact absorbing members may be integrally formed with the walls of the enclosure. The impact absorbing members include an arcuate wall that is designed to be deformed in the event of an impact to absorb impact forces and protect the battery. The impact absorbing members may be oriented to extend either in a horizontal orientation or vertical orientation. The impact absorbing members may be retained by T-shaped guide on the outer surface of the walls of the enclosure or may be integrally formed in one piece on the outer surface of each of the walls of the enclosure.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to protective structures for battery enclosures for electric vehicle batteries. 
       BACKGROUND 
       [0002]    Electric vehicles use batteries that are enclosed in an enclosure or housing that is assembled to the vehicle body. The battery may be assembled to the vehicle body at a location that is spaced from the front, rear and sides of the vehicle. For example, the battery may be assembled below the passenger compartment, in the trunk, in front of the passenger compartment or in a longitudinally extending tunnel. 
         [0003]    The battery must be protected from damage in a collision. The battery housing may be tightly packed with lithium ion battery packs or other types of battery cells. Deformation of the battery housing is to be avoided to prevent intrusion of the housing into the area housing the battery cells. Intrusions into the battery housing may rupture of battery cells and spill the contents of the battery cells. 
         [0004]    When the battery housing is assembled in a central location in the vehicle, e.g. beneath the passenger compartment, limited crush space is available between the side of the vehicle body and the battery enclosure. More crush space is available between the battery enclosure and the front or rear ends of the vehicle. In either situation, there is a long felt and unfulfilled need for an efficient and effective lightweight structure for absorbing energy from a collision that minimizes battery enclosure deformation. The structure must have limited package space requirements while providing added stiffness to the battery enclosure assembly including the impact absorbing structure. 
         [0005]    Some approaches to protecting the battery enclosure have proposed adding beams and cross members on the battery enclosure or extending outboard of the battery enclosure. These approaches add weight to the vehicle and require additional space to package the beams and cross members. Added weight is to be avoided because added weight adversely affects fuel economy. Increasing packaging space requirements adversely affects vehicle design freedom. 
         [0006]    The above problems and other problems are addressed by this disclosure as summarized below. 
       SUMMARY 
       [0007]    According to one aspect of this disclosure, a housing is disclosed for a traction motor battery of a vehicle that comprises a plurality of vertical walls, a top wall and a bottom wall. A plurality of elongated impact absorbing members are attached to each wall with the length of the impact absorbing members on the top wall and the bottom wall extending horizontally and the length of the impact absorbing members on some of the vertical walls extending vertically. 
         [0008]    According to other aspects of this disclosure, the impact absorbing members on the top and bottom walls may extend in the horizontally in the fore-and-aft direction. The impact absorbing members may be arc-shaped and may be generated as an arc about an axis of curvature that is parallel to the length of the impact absorbing members. The impact absorbing members on the vertical walls may include front and rear walls that extend in the vertical direction above and below the impact absorbing members on the top and bottom walls. 
         [0009]    The impact absorbing members may be retained by T-shaped guides on the outer surface of each of the walls. Alternatively, the impact absorbing members may be integrally formed in one piece on the outer surface of each of the walls. 
         [0010]    According to another aspect of this disclosure as it relates to a housing for a fraction motor battery of a vehicle, the housing comprises a plurality of vertical walls including a front wall, a rear wall, a right wall and a left wall. A plurality of elongated impact absorbing members are disposed on outer surfaces of each of the walls. Impact absorbing members on the right wall and the left wall extend horizontally fore-and-aft beyond the front wall and the rear wall. 
         [0011]    According to other aspects of this disclosure, the housing may include a top wall and a bottom wall. The impact absorbing members each have a lengthwise dimension and the length of the impact absorbing members on the front wall and rear wall may extend in the vertical direction. The length of the impact absorbing members on the top wall and bottom wall may extend horizontally in the fore-and-aft direction beyond the front wall and the rear wall. 
         [0012]    The impact absorbing members each have a length and the impact absorbing members on the front wall and rear wall extend lengthwise in the vertical direction. The impact absorbing members on the right wall and left wall extend lengthwise in the horizontal direction. The impact absorbing members on the top and bottom walls have a length extending in the horizontal direction and are coextensive with the front wall and rear wall. 
         [0013]    According to another aspect of this disclosure, a method is disclosed for providing a battery enclosure for a vehicle having a battery powered traction motor. According to the method, a plurality of vertically extending sides and at least one horizontally extending side are provided with each of the sides having a planar wall and a plurality of impact absorbing walls spaced from the planar walls that each define a pocket. The sides are assembled together about the battery to form an impact absorbing assembly outside the battery. 
         [0014]    According to other aspects of the method, the impact absorbing walls may be assembled to the planar walls. The planar walls may have T-shaped guides to which the impact absorbing walls are attached. Alternatively, the impact absorbing walls and the planar walls of each of the vertically extending sides and the at least one horizontally extending side may be extruded together in a single piece for each of the walls. 
         [0015]    The above aspects of this disclosure and other aspects are described below with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a diagrammatic bottom plan view of a vehicle illustrating a battery enclosure disposed on the vehicle frame beneath the passenger compartment. 
           [0017]      FIG. 2  is a perspective view of a first embodiment of a battery enclosure including semi-cylindrical impact absorbing members provided on the sides and top of the enclosure. 
           [0018]      FIG. 3  is a fragmentary enlarged perspective view of a portion of the battery enclosure illustrated in  FIG. 2 . 
           [0019]      FIG. 4  is a perspective view of a second embodiment of a battery enclosure including semi-cylindrical impact absorbing members provided on the sides and top of the enclosure. 
           [0020]      FIG. 5  is a fragmentary enlarged perspective view of a portion of the battery enclosure illustrated in  FIG. 4 . 
           [0021]      FIG. 6  is a perspective view of a third embodiment of a battery enclosure including semi-cylindrical impact absorbing members provided on the sides and top of the enclosure. 
           [0022]      FIG. 7  is a fragmentary enlarged perspective view of a portion of the battery enclosure illustrated in  FIG. 6 . 
           [0023]      FIG. 8  is an end view of a first embodiment of a semi-cylindrical impact absorbing member. 
           [0024]      FIG. 9  is an end view of a second embodiment of a semi-cylindrical impact absorbing member. 
           [0025]      FIG. 10  is a fragmentary diagrammatic cross-section view of impact absorbing members retained on one of the walls of the battery enclosure by a T-shaped guide attached to the wall. 
           [0026]      FIG. 11  is a fragmentary enlarged cross-section view of a T-shaped guide extruded as part of a wall that retains two impact absorbing members on one of the walls of the battery enclosure. 
           [0027]      FIG. 12  is a graph of battery case deformation comparing the three different embodiments of the battery case having impact absorbing members made according to  FIGS. 2, 4 and 6 , respectively. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    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. 
         [0029]    Referring to  FIG. 1 , a vehicle  10  is diagrammatically illustrated with a battery  12  for a battery-powered traction motor. The vehicle  10  includes a body  14  that is supported on a frame  16 . A traction motor  18  is also assembled to the frame  16 . The traction motor  18  is a battery-powered traction motor that is powered by the battery  12  to drive the wheels  20 . The body  14  includes a side body  22 , a front bumper  24  and a rear bumper  26 . The battery  12  is shown to be centrally located underneath the passenger compartment of the vehicle  10 . It should be noted that there is a substantially greater amount of space between the battery and the front and rear bumper  24  and  26  compared to the relatively closer spacing of the side body  22  to the battery  12 . Side impact collisions that result in driving the side body  22  toward the battery  12  present a greater challenge when designing impact absorbing elements for the battery  12  due to the reduced amount of crush space available between the side body  22  and the battery  12 . 
         [0030]    Referring to  FIGS. 2 and 3 , a first embodiment of the battery enclosure, generally indicated by reference numeral  28 , is shown to include a bottom wall  30  (shown in  FIG. 1 ) and a top wall  32 . A front wall  36  faces the front bumper  24  (shown in  FIG. 1 ) and a rear wall  38  faces the rear bumper  26  (shown in  FIG. 1 ). The battery enclosure  28  includes a right side wall  40  and a left side wall  42 . The side walls are joined at corners  44 . 
         [0031]    Impact absorbing members, generally indicated by reference numeral  46 , include an impact absorbing wall  48  and a planar wall  50 . It should be understood that the impact absorbing members may be formed integrally with the walls  30 - 42  or may be attachments to the walls. The impact absorbing wall  48  in the embodiment illustrated in  FIGS. 2 and 3  is an arcuate, or semi-cylindrical, wall that forms a pocket  52  with the planar wall  50 . The impact absorbing wall  48  is an arcuate shaped elongated member with the arc of the wall being generated about a horizontal axis X when the impact absorbing member  46  is mounted in a horizontal orientation or a vertical axis Y when the impact absorbing member  46  is formed on the battery enclosure  28  integrally. 
         [0032]    In  FIGS. 2 and 3 , the top wall  32  is shown spanning the top surface of the battery  12  (shown in  FIG. 1 ) and extends from the front wall  36  to the rear wall  38  and between the right side wall  40  and the left side wall  42 . The impact absorbing wall  48  of the impact absorbing members  46  shown on the top wall  32  are recessed below the upper ends of the walls  36 - 42 . In the embodiment shown in  FIGS. 2 and 3 , impacts to the sides or front and rear wall are absorbed by the impact absorbing members  46  on the front wall  36  and rear wall  38 . The impact absorbing members or wall  48  on the bottom wall  30  and top wall  32  are not involved until the battery enclosure  28  is deformed. 
         [0033]    Referring to  FIGS. 4 and 5 , a battery enclosure  58  is illustrated that is made according to a second embodiment of the present disclosure. Battery enclosure  58  is similar to battery enclosure  28  and the same reference numerals will be used to describe similar parts of the various embodiments disclosed herein. Battery enclosure  58  includes side walls  40 ,  42  that extend beyond the planar wall  50  of the front wall  36  and rear wall  38 . The impact absorbing members  46  include an impact absorbing wall  48  that is in an arcuate shape and a planar wall  50  that is either attached to or formed integrally with the front wall  36  and rear wall  38 . 
         [0034]    Loads applied to the impact absorbing members  46  on the rear wall  38  are also resisted by the impact absorbing members  46  that are disposed on the side walls  40  and  42 . A portion of any impact force applied to the rear wall  38  is absorbed by collapsing the impact absorbing walls  48  toward the planar wall  50 . In addition, the impact absorbing member  46  on the side walls  40 ,  42  result in an axial load being applied to the ends of the impact absorbing members  46  on the side walls  40  and  42 . 
         [0035]    Referring to  FIGS. 6 and 7 , a third embodiment of the battery enclosure is generally indicated by reference numeral  60 . The third embodiment  60  also includes horizontally extending impact absorbing members  46  on both the right and left side and also on the top and bottom walls  30 ,  32 . The impact absorbing members  46  on the right and left side walls  40  and  42  extend beyond the front wall  36  and rear wall  38  and are coextensive with the impact absorbing wall  48  of the impact absorbing members  46  on the front wall  36  and rear wall  38 . The horizontally extending impact absorbing members  46  on the top and bottom walls also overhang the impact absorbing members  46  on the front wall  36  and rear wall  38  and are coextensive with the impact absorbing wall  38  on the front wall  36  and rear wall  38 . 
         [0036]    In this embodiment, the third embodiment  60  loads applied to the front and rear walls of the enclosure  60  are absorbed by the impact absorbing members  46  on the respective walls and are also absorbed by the axially directed loads applied to the impact absorbing members on the side walls  40 ,  42  and the top and bottom walls  30 ,  32 . 
         [0037]    Referring to  FIG. 8 , an impact absorbing member  46  is illustrated that includes an arcuate portion  64  that is disposed between two side flanges  66 . The arcuate portion  64  is the portion of the impact absorbing member  46  that absorbs impacts as it is deformed toward the wall to which it is attached. The side flanges  66  are used to secure the impact absorbing member  46  to the enclosure. 
         [0038]    Referring to  FIG. 9 , another embodiment of an impact absorbing member  46  is shown that includes an arcuate portion  68  that is integrally formed with a planar portion  70 . The planar portion  70  includes two outwardly extending side flanges  72  that extend outboard of the arcuate portion  68 . Again, the arcuate portion  68  absorbs the impact as it collapses toward the planar portion  70 . The side flanges  72  are used to secure the impact absorbing member to an enclosure. It should be noted that the embodiment shown in  FIG. 9  may also be formed as an integral part of the battery enclosure wherein the planar portion  70  may be part of the respective wall of the battery enclosure  28 ,  58 , and  60 . Each of the walls  30 - 42  may be separately extruded and assembled together to form the battery enclosure. 
         [0039]    Referring to  FIG. 10 , an impact absorbing member  46  is shown to be attached to an enclosure wall  76  by a T-shaped guide  74 . The T-shaped guide  74  is attached to the enclosure wall  76 . The impact absorbing member  46  slides into the T-shaped guide  74  with the side flanges  76  being retained by the T-shaped guide  74 . The arcuate portion  64  collapses toward the enclosure wall  76  in an impact. 
         [0040]    Referring to  FIG. 11 , another embodiment is shown wherein a T-shaped guide  78  is extruded, or integrally formed, with the enclosure wall  80 . In this embodiment, it is not necessary to attach the T-shaped guide  78  to the enclosure wall  80 , but they may be formed as an extrusion. The side flanges  66  are retained by the T-shaped guide  78  with the arcuate portion  64  of the impact absorbing member  46  being disposed between the two adjacent T-shaped guides  78 . 
         [0041]    Referring to  FIG. 11 , a graph showing a simulated test result for each of the three embodiments described above. The graph illustrates the battery case deformation in millimeters over time and illustrates the test results for embodiment one, concept one, of the battery enclosure  28  and shows that battery case deformation in embodiment one of the battery enclosure  28  results in a maximum battery deformation of slightly less than 120 mm. 
         [0042]    Concept two corresponds to the simulated test results for the second embodiment of the battery enclosure  58 . The battery enclosure  58  resulted in a maximum deformation of approximately 105 mm. 
         [0043]    Concept three corresponds to the simulated test results for the third embodiment, battery enclosure  60 . In the third embodiment, the side walls and top and bottom walls overhang or extend to the impact absorbing wall on the front and rear walls  36  and  38 . The deformation is limited to a deformation of slightly more than 50 mm. 
         [0044]    In conclusion, the battery enclosure  60  results in a mark reduction of battery case deformation compared to either battery enclosure  58  or battery enclosure  28  that correspond to concepts one and two in the graph shown in  FIG. 11 . The first and second embodiments  28  and  58  both show marked improvements compared to an enclosure without the impact absorbing members  46  that showed about 440 mm of crush over a period of 80 milliseconds. 
         [0045]    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.