Abstract:
A device is provided for fastening a battery module ( 2 ) to a bodyshell ( 1 ) of a motor vehicle. The battery module has a battery ( 15 ) and a support ( 16 ) connected fixedly to the battery. The support ( 16 ) has an undercut ( 22 ) that interacts with an undercut ( 11 ) on the bodyshell. Such a connection can be produced in a simple manner and, moreover, is reliably secure in the event of a crash, in particular a rear crash of the motor vehicle.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 USC 119 to German Patent Appl. No. 10 2012 105 140.2 filed on Jun. 14, 2012, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a device for fastening a battery module to a bodyshell of a motor vehicle. 
     2. Description of the Related Art 
     High voltage batteries are used in motor vehicles in conjunction with a hybrid drive of a motor vehicle or a purely electrically drivable motor vehicle. 
     It is the object of the invention to provide a device for fastening a battery module to the bodyshell of the motor vehicle, and particularly a device that can be made in a simple manner and that ensures a reliably secure connection in the event of a crash, such as a rear crash of the motor vehicle. 
     SUMMARY OF THE INVENTION 
     The invention relates to a device for fastening a battery module to the bodyshell of a motor vehicle. The battery module has a battery, a support connected fixedly to the battery, and means for screwing the support and the bodyshell together. The support has an undercut that interacts with an undercut on the bodyshell. 
     The battery is relatively heavy component and is subject to high acceleration forces in the event of a crash. However, the undercuts of the support and the bodyshell interact to absorb forces acting between the support of the battery module so that the screw connection between the support and bodyshell is not damaged. Accordingly, the form-fitting connection between the undercuts brings about a significant reduction of the forces acting on the screwing points in the event of a crash. 
     The undercuts of the support and the bodyshell also define a stop that simplifies the alignment of the battery module during assembly of the motor vehicle. 
     The large mass of the battery module causes high forces to act on the screwing points of the support and the bodyshell in the event of a rear crash of the motor vehicle. The interacting undercuts on the support and the bodyshell ensure that these high forces will not cause the battery module to be torn off in a crash and penetrate from the rear region of the motor vehicle into the passenger compartment where the battery module could cause serious safety problems. 
     The battery preferably is a high voltage battery. 
     The undercuts of the support and the bodyshell preferably are positioned so that the undercut of the support contacts the undercut of the body part when the support is fastened to the bodyshell. Thus, the contact connection already exists prior to a crash, and therefore, the battery module cannot be displaced with respect to the bodyshell in the event of a crash. This arrangement also is of particular advantage for positioning the battery module with respect to the bodyshell during assembly. 
     Accordingly, the undercuts of the support and the bodyshell are supported on each other immediately at the onset of an impact on the rear of the motor vehicle. 
     The bodyshell preferably has a battery box in the rear region of the motor vehicle has for insertion of the battery. The battery is supported on the base of the battery box and is screwed to the bodyshell by the support connected fixedly to the battery. 
     The battery preferably is arranged in the transverse direction of the vehicle. 
     The bodyshell preferably has rear longitudinal members of the motor vehicle on both sides and brackets are fixedly connected to the longitudinal members. The brackets function to mount the support on both sides of the battery. The support protrudes beyond the battery at remote ends so that the connection to the rear longitudinal members can take place in a simple manner. 
     The support preferably has at least two undercuts, and the bodyshell has a corresponding number of undercuts that interact with the undercuts of the support. The support preferably has an undercut in the region of each bracket for interacting with an undercut of the bracket on the bodyshell. 
     Each bracket preferably is a forged or cast part. 
     The support preferably is arranged on an upper side of the battery and rests on an upper side of the brackets. In this arrangement, the battery preferably rests on a base of the battery box. 
     The support may be a crossmember with screwing points to the bodyshell on both sides of the battery to ensure a secure screw connection between the support and the bodyshell. Specifically, the support preferably has bores for receiving screws to define means for screwing the support and the bodyshell together. The bodyshell or the brackets also may have bores or threaded bores for the screws. Threaded bores enable each screw to be screwed directly therein, while unthreaded bores are used with nuts. 
     Each bracket preferably is oriented in the longitudinal extent of the motor vehicle and has front and rear rests for the support. The rear of the front rest may have the undercut the interacts with the undercut of the support. 
     Further features of the invention emerge from the dependent claims, the attached drawing and the description of the preferred exemplary embodiment, which is reproduced in the drawing, without being restricted to said exemplary embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a three-dimensional illustration of a rear region of a motor vehicle, with a battery module connected to the bodyshell, as seen obliquely from above. 
         FIG. 2  shows the bodyshell of  FIG. 1 . 
         FIG. 3  shows the battery module of  FIG. 1 . 
         FIG. 4  is a cross section taken along line A-A of  FIG. 1  and shows the arrangement of the bodyshell and the support of the battery module. 
         FIG. 5  is a three-dimensional illustration of the arrangement of a bracket of the bodyshell and of the support interacting with the bracket. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows the rear region of a bodyshell  1  and a battery module  2  fastened to the bodyshell  1 . The bodyshell  1  is illustrated by itself in  FIG. 2 . A battery box  3  is provided in a region of the bodyshell  1  near the rear of the motor vehicle and a battery can be inserted into the battery box  3 . The battery box  3  extends in the transverse direction of the motor vehicle and is illustrated as a substantially cuboidal cavity. A base  4  of the battery box  3  supports the battery. The battery box  3  has end walls  5  that run in the longitudinal direction of the motor vehicle, and the bodyshell  1  has two screwing points  6  in the region of each end wall  5  next to the battery box  3 . The battery module  2  is connectable to the bodyshell  1  in the region of the screwing points  6 . Two front brackets  7  and two rear brackets  8  are provided on the body shell  1  in the region of the screwing points  6  and are welded or otherwise connected to rear longitudinal members  9  that form part of the bodyshell  1 . Therefore, a front bracket  7  and a rear bracket  8  are connected to each longitudinal member  9 . Each bracket  7 ,  8  has a through hole  10  that can be a threaded bore and forms a screwing point to the battery module  2 . The rear-facing side of each front bracket  7  has an undercut  11  formed by a substantially vertically oriented wall  12  of the front bracket  7 . The brackets  7  and  8  have upper receiving surfaces  13  through which the holes  10  pass. The receiving surfaces  13  are arranged in a plane and function to support the battery module  2 . The front and rear brackets  7  and  8  assigned to each longitudinal member  9  form a constructional unit  14 . 
       FIG. 3  shows the battery module  2 . The battery module  2  has a high voltage battery  15  that defines part of a hybrid drive for the motor vehicle. The battery  15  has a plurality of individual batteries that are interconnected to define a substantially cuboidal body unit. The battery module  2  also has a support  16  that is made, for example, of steel and that is connected fixedly to the battery  15  The support  16  is placed onto the upper surface of the battery  15  and is connected fixedly thereto, for example by screws. A battery manager  17  is connected to an end of the battery  15 . The support  16  is a crossmember arranged in the transverse direction of the bodyshell  1  and in the longitudinal direction of the battery box  3 . The support  16  has remote ends  18  that protrude beyond the battery  15  and the battery manager  17 . The support  16  also has an upper, substantially rectangular frame part  19 . The frame part  19  has holes  21  in regions of the frame limbs  20  and facing the ends  18 . The holes  21  constitute the screwing points for screwing the support  16  and the entire battery module  2  to the brackets  7 ,  8  and hence to the bodyshell  1 . 
     The lower side of the support  16  has an undercut  22  in the region of the two frame limbs  20  of the support  16  and adjacent to the front hole  21  of each frame limb  20 , as shown in  FIGS. 4 and 5 . The undercut  22  is formed by a projection  23  on the frame limb  20 . The projection  23  has a front surface  24  which, in the installed position of the support  16  and the bodyshell  1 , makes contact with the wall  12  of the front bracket  7  so that a form-fitting connection is provided between the support  16  and the bodyshell  1  in the direction of the arrow x in  FIG. 4 . 
     During installation, the battery module  2  is grasped in the region of the frame limbs  20  and the battery  15  inserted into the battery box  3  from above. The dimensions are selected so that the two frame limbs  20  of the support  16  rest in a planar manner on the two front brackets  7  and the two rear brackets  8  as shown in  FIGS. 4 and 5  with the battery  15  resting on the base  4  of the battery box  3 . During this installation, the two projections  23  of the support  16  are inserted directly behind the two front brackets  7  and bear against the walls  12  thereof, as shown in  FIGS. 4 and 5 . The holes  10  and  21  are aligned with each other and four fastening screws  25  are inserted through or threaded into the holes  10 . Thus, the support  16  and the entire battery module  2  are fixed to the brackets  7  and  8 , and therefore to the bodyshell  1 . 
     This fastening of the battery module  2  to the bodyshell  1  meets safety requirements in the event of a rear crash by preventing the screws  25  arranged in the region of the screwing points  6  and the holes  10  and  21  from being torn off. The interaction of the support  16  and the bodyshell  1  with regard to the undercuts  11  and  22  enduringly reduces the forces acting on the screws  25  in the event of a crash. Additionally, the undercuts  11 ,  22  define a stop to ensure a simple alignment of the battery module  2  in the bodyshell  1  during assembly of the vehicle.