Abstract:
A battery housing for a traction motor battery of a vehicle is disclosed that includes a plurality of elongated impact absorbing carbon fiber reinforced polymer members attached to the walls of the enclosure. The impact absorbing members may be corrugated members that have ridges and furrows connected by ramp surfaces that define trapezoidal spaces relative to the sides of the enclosure. The ridges are designed to be deformed into the trapezoidal space in the event of an impact to absorb impact forces and protect the battery. The impact absorbing members may be retained by T-shaped guides on the outer surface of the walls of the enclosure or may be adhesively attached to the sides 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, an enclosure for a battery is disclosed that includes a plurality of aluminum alloy enclosure walls disposed about the battery and a plurality of corrugated impact absorbing members made of carbon fiber reinforced polymer (CFRP) attached to the enclosure walls. The impact absorbing members have at least one ridge and a plurality of furrows that define a plurality of trapezoidal spaces between the impact absorbing members and the enclosure walls. 
         [0008]    According to other aspects of the method, each of the impact absorbing members may include at least one ridge that is disposed parallel to the enclosure wall. A first ramp surface and a second ramp surface extend from the ridge to the furrows on opposite sides of the ridge and toward the enclosure wall at an angle. The enclosure may further comprise an attachment flange provided on a first side and a second side of the impact absorbing members that extend parallel to the enclosure walls. The attachment flange on the first side is connected to one of the first ramp surfaces and the attachment flange on the second side is connected to one of the second ramp surfaces. 
         [0009]    The enclosure may further comprise a plurality of T-shaped guides attached to the enclosure walls that define receptacles for the impact absorbing members between two T-shaped guides. The T-shaped guides extend parallel to each other so that each of the attachment flanges of the impact absorbing members are disposed between one of the T-shaped guides and one of the enclosure walls. The impact absorbing members absorb an impact applied to the enclosure by collapsing into the trapezoidal spaces and towards the enclosure wall. 
         [0010]    According to another aspect of this disclosure, an enclosure for a battery is disclosed that comprises a plurality of planar aluminum enclosure walls disposed about the battery and a plurality of planar impact absorbing members attached in a face-to-face orientation to substantially cover the enclosure walls. 
         [0011]    The enclosure may further comprise a plurality of T-shaped guides attached to the enclosure walls that define receptacles for the impact absorbing members between two T-shaped guides that extend parallel to each other. The planar impact absorbing members include a first attachment flange and a second attachment flange that are disposed between one of the T-shaped guides and one of the enclosure walls. The planar impact absorbing members may be adhesively attached to the enclosure walls. 
         [0012]    According to another aspect of this disclosure, a method is disclosed for providing an impact absorbing battery enclosure for a battery of a vehicle having a battery powered fraction motor. The method comprises the steps of: providing a plurality of sides and a top side and a bottom side; assembling all of the sides together about the battery; and assembling a plurality of impact absorbing carbon fiber reinforced polymer members to the sides to form an impact absorbing assembly that encloses the battery enclosure. 
         [0013]    According to other aspects of this disclosure as it relates to the method, the impact absorbing carbon fiber reinforced polymer members may be corrugated and have at least one ridge and a plurality of furrows that define a plurality of trapezoidal spaces between the impact absorbing members and the sides of the enclosure. Each of the impact absorbing carbon fiber reinforced polymer members may include the at least one ridge that is disposed parallel to the side of the enclosure and a first ramp surface and a second ramp surface that each extend from the at least one ridge to the furrows on opposite sides of the at least one ridge. The ramp surfaces extend toward the side of the enclosure at an angle to define a trapezoidal space with the side that the impact absorbing member is attached. The impact absorbing carbon fiber reinforced polymer members absorb an impact applied to the enclosure by collapsing into the trapezoidal spaces and towards the side of the enclosure. 
         [0014]    According to other aspects of the method, the method may further comprise the steps of providing an attachment flange on a first side and a second side of the impact absorbing carbon fiber reinforced polymer members that extend parallel to the side of the enclosure and connecting the attachment flange on the first side and on the second side to one of the sides of the enclosure. 
         [0015]    The method may further comprise providing a plurality of T-shaped guides on the side of the enclosure that define receptacles for the impact absorbing carbon fiber reinforced polymer members between two T-shaped guides that extend parallel to each other. Each of the attachment flanges of the impact absorbing carbon fiber reinforced polymer members may be inserted between one of the T-shaped guides and one of the sides of the enclosure. 
         [0016]    The above aspects of this disclosure and other aspects are described below with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a diagrammatic bottom plan view of a vehicle illustrating a battery enclosure disposed on the vehicle frame beneath the passenger compartment. 
           [0018]      FIG. 2  is a perspective view of a first embodiment of a battery enclosure including corrugated carbon fiber reinforced polymer (CFRP) impact absorbing members provided on the sides and top of the enclosure. 
           [0019]      FIG. 3  is a fragmentary enlarged perspective view of a portion of the battery enclosure illustrated in  FIG. 2 . 
           [0020]      FIG. 4  is a fragmentary cross-sectional view of a portion of the battery enclosure illustrated in  FIG. 2 . 
           [0021]      FIG. 5  is a perspective view of a second embodiment of a battery enclosure including planar carbon fiber reinforced polymer (CFRP) impact absorbing members provided on the sides and top of the enclosure. 
           [0022]      FIG. 6  is a fragmentary enlarged perspective view of a portion of the battery enclosure illustrated in  FIG. 5 . 
           [0023]      FIG. 7  is a fragmentary cross-sectional view of a portion of the battery enclosure illustrated in  FIG. 5 . 
           [0024]      FIG. 8  is a graph of battery case deformation comparing the two different embodiments of the battery case having impact absorbing members made according to  FIGS. 2 and 5 , respectively. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    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. 
         [0026]    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 . 
         [0027]    Referring to  FIGS. 2-4 , 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 . 
         [0028]    Impact absorbing members, generally indicated by reference numeral  46 , are ribbed or corrugated carbon fiber reinforced polymer (CFRP) attachments  46  to the battery enclosure  28 . The corrugated CFRP attachments  46  have alternating furrows  48  and ridges  50 . The furrows  48  are planar areas that are adjacent to one the enclosure walls ( 38  in  FIG. 4 ). The ridges  48  are planar areas that are spaced from one the enclosure walls. The ridges  50  and furrows  48  are connected by ramp surfaces  52  and  54  on a first and a second side of each ridge  50 . The ridges  50  and furrows  48  define trapezoidal spaces  55  between the impact absorbing members and the enclosure walls. 
         [0029]    The corrugated CFRP attachments  46  include carbon fiber reinforcing fibers that are oriented to extend substantially in the direction corresponding to the length of the corrugated CFRP attachments  46 . The carbon fibers are oriented to extend parallel to the ridges  50  and furrows  48 . The CFRP attachments substantially cover (understood to be at least 90% coverage) the sides of the enclosure. The carbon fibers are encapsulated in a polymer resin to form the corrugated CFRP attachments  46 . In one example, the corrugated CFRP attachment may have a thickness of 2.0 mm. 
         [0030]    T-shaped guides  56  are either assembled to the walls of the enclosure  28  or integrally molded with the walls of the enclosure  28 . The T-shaped guides  56  are disposed to be parallel to the next adjacent T-shaped guides  56 . The furrows  48  may be partially received between the enclosure wall and T-shaped guides, as shown in  FIG. 4 , to retain the impact absorbing members  46  on the enclosure  28 . The portions of the furrows  48  that are received by the T-shaped guides may be referred to as attachment flanges  58 . In one example that was tested in a simulation, the enclosure and T-shaped guides may be 1.0 mm thick aluminum alloy, such as AL6061-T6 and had a mass of 27 kg. 
         [0031]    Referring to  FIGS. 5-7 , a second embodiment of the battery enclosure, generally indicated by reference numeral  60 , is shown to include a bottom wall  30  (shown in  FIG. 1 ) and a top wall  62 . A front wall  66  faces the front bumper  24  (shown in  FIG. 1 ) and a rear wall  68  faces the rear bumper  26  (shown in  FIG. 1 ). The battery enclosure  60  includes a right side wall  70  and a left side wall  72 . The side walls are joined at corners  74 . 
         [0032]    Impact absorbing members, generally indicated by reference numeral  76 , are planar carbon fiber reinforced polymer (CFRP) attachments  76  to the battery enclosure  60 . CFRP attachments  76  include carbon fiber reinforcing fibers that are oriented to extend substantially in the direction corresponding to the length of the corrugated CRFP attachments  76 . The carbon fibers are encapsulated in a polymer resin to form the corrugated CRFP attachments  76 . In one example, the corrugated CFRP attachments  46  may have a thickness of 2.0 mm. The CFRP attachments  46  substantially cover (understood to be 90% coverage) of the sides of the enclosure. 
         [0033]    T-shaped guides  78  are either assembled to the walls of the enclosure  60  or integrally molded with the walls of the enclosure  60 . The T-shaped guides  78  are disposed to be parallel to the next adjacent T-shaped guides  78 . In one example, the enclosure and T-shaped guides may be 1.0 mm thick aluminum alloy, such as AL6061-T6 and had a mass of 27 kg. as tested. 
         [0034]    The impact absorbing members  76  may be partially received between the enclosure wall and T-shaped guides, as shown in  FIG. 7 , to retain the impact absorbing members  46  on the enclosure  28 . In one example, the enclosure and T-shaped guides may be 1.0 mm thick and formed of an aluminum alloy. Alternatively, the planar impact absorbing members may be adhesively attached to the enclosure walls. 
         [0035]    Referring to  FIG. 8 , a graph illustrates the battery case deformation in millimeters over time. A simulated test result for a base steel battery enclosure made of 1.5 mm HSLA 450 steel having a mass of 52 kg as tested and was compared to each of the two embodiments described above. The test results for the embodiment illustrated in  FIG. 2-4  with corrugated CFRP, of the battery enclosure  28  and shows that battery case deformation resulted in a maximum simulated battery deformation of slightly less than 75 mm over a period of 15 ms. The simulated test results for the embodiment illustrated in  FIG. 5-7  of the battery enclosure  60  resulted in a maximum deformation of approximately 85 mm over a period of about 15 ms. Both of the battery enclosures  28  or  60  resulted in a marked reduction of battery case deformation compared to the base steel battery enclosure without the impact absorbing members  46  (or  76 ) that projected about 440 mm of crush over a period of 80 milliseconds. 
         [0036]    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.