Patent Publication Number: US-11639091-B2

Title: Motor vehicle

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates to a motor vehicle having a floor structure with a housing for energy-storage devices fastened to an underside of the floor structure. 
     From U.S. Pat. No. 9,045,030 B2, a motor vehicle is already known in which a housing with a cover is arranged on an underside of a floor of a body shell. Energy-storage devices—such as batteries, for instance—are arranged in the housing. 
     The object of the invention is to provide a motor vehicle in which a housing for energy-storage devices is arranged on an underside of a floor assembly of the motor vehicle in such a way that the vibrations of the floor assembly are reduced. 
     A motor vehicle according to the invention exhibits a body shell with a passenger cell which includes a floor structure. A housing structure for energy-storage devices has been fastened to an underside of the floor structure. The housing structure is a closed container which has a trough-shaped component and a cover which is spaced from the trough-shaped component. The trough-shaped component exhibits, for instance, circumferential side walls and a floor arranged on the side walls. 
     In an interspace between the underside of the floor and an external surface of the cover of the housing structure at least one damping component is arranged which has been installed under initial tension in the interspace between the cover of the housing structure and the floor. 
     In an advantageous embodiment, the damping component is a purposefully designed elastomer spring, the material property of which under dynamic loading displays a dynamic hardening, so that under dynamic loading starting from a frequency of greater than 0.1 Hz the stiffness is greater, by a dynamic hardening factor that is greater than 2, than the static stiffness that is present under quasi-static loading, such as in the mounting case. 
     The property of a dynamic hardening of the elastomer spring has the effect that the stiffness under dynamic loading is higher than under quasi-static loading. By this means, in the quasi-static loading case as in the quasi-static mounting case, the result is that a lower force is required for compressing the damping component. Under dynamic loading, in the case of exposure to a frequency greater than 0.1 Hz, a dynamic hardening occurs which, by reason of the increased stiffness, brings about a reduction in vibration. 
     In an advantageous embodiment, within the frequency range from 0.1 Hz to 100 Hz the dynamic hardening displays a dynamic hardening factor that lies within a range from 2 to 30. 
     In an advantageous embodiment, the damping component is an elastomer component, the material properties of which displays a damping factor of at least 0.2 within the frequency range from 0.1 Hz to 800 Hz. 
     In another advantageous embodiment, the damping component is an elastomer component, the material property of which displays a damping factor of at least 0.7 within the frequency range from 0.1 Hz to 100 Hz. 
     The damping component has advantageously been compressed to a predetermined height by the fastening of the housing structure onto the floor of the body shell. The component height is dependent on various parameters. These parameters include the tolerance situation between the underside of the floor and the external surface of the cover of the housing structure. The existing tolerances are partially conditioned by production. Furthermore, tolerances for mounting are required. 
     The component height is additionally dependent on an oscillation amplitude that arises at the place of attachment of the damping component below the floor in the course of travel of the motor vehicle and in the course of the excitation, associated therewith, of the floor. 
     In an advantageous embodiment, the damping component has been adhesion-bonded to the external surface of the cover of the housing structure of the energy-storage device and/or to the underside of the floor. 
     The damping component advantageously covers at least 0.1 percent to 90 percent of the external surface on the underside of the floor. 
     Embodiments of the invention will be described below by way of example with reference to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a floor of a body shell, which has been fastened to the side skirts at its two side edges. 
         FIG.  2    shows a natural-oscillation mode arising in the course of a corresponding excitation of the floor of the body shell, which moves up in the form of a bulge and down in the form of a bulge from a neutral center line between the two fastened side ends. 
         FIG.  3    is a cross-sectional view of a damping component in the neutral state, which displays an upwardly pointing concave shape corresponding to the upwardly pointing oscillation mode in  FIG.  2   . 
         FIG.  4    is a cross-sectional view of the floor shown in  FIG.  1   , of a damping component which is located on the underside of the floor in a compressed state and which is shown in  FIG.  3   , and of a housing structure which has been arranged below the damping component and fastened to longitudinal members of the floor. 
         FIG.  5    is a top view of an upper side of the housing structure on which large-area damping components have been arranged at points relevant to vibration. 
         FIG.  6    is a cross-sectional view, from the front, of the housing structure shown in  FIG.  5   , with the damping components arranged thereon. 
         FIG.  7    is a view from above of the upper side of the housing structure on which a single large-area damping component with a cross-section corresponding to  FIG.  3    has been arranged. 
         FIG.  8    is a cross-sectional view of the embodiment shown in  FIG.  7   , in which the damping component has a cross-section that is composed of a rectangular cross-section and a circular-segment-shaped cross-section. 
         FIG.  9    is a diagram wherein the dynamic stiffening factor has been plotted on the left ordinate axis, the damping factor has been plotted on the right ordinate axis, and the frequency has been plotted on the abscissa axis. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG.  1    shows a schematic diagram of a floor  3  of a body shell  2 , not represented in any detail, of a motor vehicle  1 . The floor  3  has, in principle, been firmly clamped at its two sides edges  1   a  and  1   b  via side skirts or longitudinal members  18 ,  19 , represented in  FIG.  4   , and side frames, located above them, of a passenger cell of the body shell  2 . 
     The floor  3  of the motor vehicle  1  is a system capable of oscillation which, for instance, has the natural-oscillation mode  4  shown in  FIG.  2   . The natural-oscillation mode  4  displays an upwardly oscillating bulge-shaped or convex portion  5  and a downwardly oscillating, bulge-shaped concave portion  6 . The convex portion  5  and the concave portion  6  have the same maximum oscillation amplitude a 5,6 . In  FIG.  2   , the neutral, non-oscillating state of the floor  3  has been represented in a dashed line  3   a.    
     In  FIG.  3    a cross-section of a damping component  7  consisting of an elastomer spring has been represented in a neutral—that is to say, not initially tensioned—state  25 . In the static, not initially tensioned state  25  without exposure to vibration, the elastomer spring displays a linear spring characteristic. 
     The elastomer spring is a three-dimensional body which may be, for instance, a hollow body or a solid body or a combination of the two. 
     The elastomer spring may consist of the vulcanizates of natural rubber or synthetic rubbers. 
     The damping component  7  is composed of a lower rectangular portion  8  and an upper circular-segment-shaped portion  9 . The damping component  7  has an overall height z 7 . A continuous separation line  10  marks the transition between the two portions  8  and  9 . 
     The circular-segment-shaped portion  9  has been supplemented at its two ends  11   a  and  11   b  in  FIG.  3    with a dotted contour line. The circular-segment-shaped portion  9  which has been enlarged by the dotted contour line corresponds to the circular-segment-shaped convex portion  5  of  FIG.  2    with a segment height z 5,6  corresponding to the maximum oscillation amplitude a 5,6 . 
     The circular-segment-shaped portion  9  has a segment height z 9  that is less than the maximum oscillation amplitude a 5,6  of the convex portion  5  of  FIG.  2   . The rectangular portion  8  has a height z 8 . 
       FIG.  4    shows a floor or a floor structure  3  of a motor vehicle  1 . The motor vehicle  1  exhibits a body shell  2  with a passenger cell which is not represented. The passenger cell is delimited on opposing sides by side frames which each exhibit at their respective lower end a side skirt with an integrated or separate longitudinal member. 
     A housing structure  13  for an energy-storage device  14  has been fastened to an external surface  12   a  of an underside  12  of the floor structure  3 . The housing structure  13  is a closed container consisting of a trough-shaped component  22  and a cover  16 . The trough-shaped component  22  exhibits circumferential side walls and a floor arranged on the side walls. 
     The cover  16  is spaced apart from the floor  22   a  of the trough-shaped component  22 , forming a cavity. Energy-storage devices  14  in the form of batteries and, where appropriate, in the form of a fuel tank have been arranged in the cavity of the housing structure  13 . 
     A damping component  7  has been arranged in an interspace  28  between the underside  12  of the floor  3  of the body shell  2  of the motor vehicle  1  and an external surface  15  of the cover  16  of the housing structure  13 . 
     The mounting of the damping component  7  and of the housing structure  13  is undertaken in one embodiment in such a way that the damping component  7  is firstly arranged on the floor  3  and subsequently the housing structure  13  is positioned on the damping component  7 . In another embodiment, the damping component  7  is firstly arranged on the housing structure  13  and subsequently the housing structure  13  with the damping component  7  is positioned on the floor  3 . 
     After this, the fastening of the housing structure  13  to a respective lateral longitudinal member or to a side skirt  18 ,  19 , which has been formed on the respective outer edge  20 ,  21  of the floor  3 , is undertaken, for instance via a threaded joint  23 . 
     In the course of the fastening of the housing structure  13  to the floor  3 , the damping component  7  is compressed by an amount z which, in the embodiment shown, amounts to z 5,6 —that is to say, the maximum oscillation amplitude a 5,6  shown in  FIG.  2   . The damping component  7  has a height z 7,17  in the initially tensioned state  17  shown in  FIG.  4   . 
     The damping component  7  has been more intensely compacted in the central region than at the marginal regions. In the course of an oscillation of the floor  3  upward, the compacted region of the damping component  7  follows the region of the floor  3  situated opposite it, so the floor  3  is braked by the damping component  7  when the floor  3  is oscillating back. 
     By virtue of the initial tension of the damping component  7 ,  24   a  to  24   d ,  26 , a compensation of the tolerances that are present by reason of mounting processes and production processes also takes place. 
     The degree of initial tension of the damping component  7  is dependent on several parameters. For the purpose of carrying out the mounting of the housing structure  13  and of the damping component  7  onto the floor  3  and the fastening  23  of the housing structure  13  to the floor  13 , a mounting clearance of s 13  is required. For instance, the mounting clearance amounts to 2 mm≤s 13 ≤6 mm. 
     In addition, there is a component tolerance t 3,13  of the floor  3  and/or of the housing structure  13 , which amounts to, for instance, −3 mm≤t 3,13 ≤3 mm. 
     A possible maximum oscillation amplitude a of the floor  3  amounts to, for instance, −1 mm≤a 3 ≤1 mm. By the mounting clearance s 13 , the manufacturing tolerance t 3,13  and the maximum oscillation amplitude a max  being taken into consideration, the minimum and maximum extensions of the initially tensioned damping component  7  result. 
     The flux of force between the external surface  15  of the housing structure  13  and the external surface  12   a  on the underside  12  of the floor  3  and the initially tensioned damping component  7  arranged in between is consequently ensured via the material property and geometrical design in any tolerance situation. 
     In one embodiment, the damping component  7  is an elastomer spring. The material of the damping component  7  has high damping properties, is geometrically adaptable to the shape to be damped of the floor  3  and of the housing structure  13  of the energy-storage device  14 , and can be initially tensioned or compressed up to 70%. 
     The bracing of the damping component is undertaken by the fastening  23  of the housing structure  13 —for instance, via a screw coupling—to the respective side skirts or longitudinal members  18  or  19 . 
     In one embodiment, the damping component  7  has been adhesion-bonded to the external surface  12   a  of the underside  12  of the floor  3  and/or to the external surface  15  of the cover  16  of the housing structure  13 . 
       FIGS.  5  and  6    show an embodiment in which individual damping components  24   a ,  24   b ,  24   c  and  24   d  have been partially arranged on the upper side  16  of the housing structure  13  at points at which the floor  3  has a higher oscillation amplitude a. 
     In the view from the front in  FIG.  6   , damping components  24   a  to  24   d  are in the relaxed state  25 . By virtue of the varying heights of damping components  24   a  to  24   d  shown in  FIG.  6   , a varying vibration damping is possible. 
     In  FIGS.  7  and  8    a second embodiment is shown, in which a large-area damping component  26  has been arranged on the upper side  16  of the housing structure  13 . Damping component  26  is in the relaxed state  25  in  FIGS.  7  and  8   . 
       FIG.  9    shows a diagram wherein the dynamic stiffening factor has been plotted on the left ordinate axis, the damping factor has been plotted on the right ordinate axis, and the frequency has been plotted on the abscissa axis. 
     The characteristic values of a material with a lower dynamic stiffening have been plotted over the frequency on a lower curve V unten  composed of small squares, and the characteristic values of a material with a dynamic high stiffening have been plotted over the frequency on an upper curve V oben  composed of small squares. 
     In the case of the lower curve V unten , the dynamic stiffening factor rises from a value “1” at a low frequency of about 0.1 Hz to a value of about “1.2” at a frequency of about 35 Hz. 
     In the case of the upper curve V oben , the dynamic stiffening factor rises from a value “1” at a low frequency of about 0.1 Hz to a value of about “8.5” at a frequency of about 35 Hz. 
     The damping component  7 ,  24 ,  26  is an elastomer component, the material properties of which displays a dynamic hardening, so that the stiffness under dynamic loading is higher than under quasi-static loading. By this means, in the quasi-static mounting case a lower force arises for compressing the damping component, whereas in the dynamic design case an increased stiffness is acting for the purpose of reducing vibration. 
     In  FIG.  9    a lower curve D unten  has further been represented in a continuous line for a damping component, the material properties of which displays a damping factor between 0.1 and 0.2 within the frequency range from 0.1 Hz to 50 Hz. 
     Furthermore, in  FIG.  9    an upper curve D oben  has been represented in a continuous line for a damping component, the material properties of which displays a damping factor of at least 0.7 within the frequency range from 0.1 Hz to 50 Hz. 
     The damping components are adhesion-bonded, for instance onto the transverse structure of the housing of the energy-storage device and/or to the underside of the floor. The energy-storage device is, for instance, a high-voltage storage device. 
     Through the use of the aforementioned damping components for the stated purpose, the acoustics and the vibration comfort in a battery-driven vehicle (or BEV—that is to say, battery electric vehicle) are heightened, without disadvantages arising during the mounting process. 
     The damping component takes the form of an elastomer component and serves for bracing between the energy-storage device—a high-voltage storage device—and the body shell, the damping component which takes the form of an elastomer component displaying the property of a dynamic hardening. 
     This material property describes the effect of a stiffening of material in the case of dynamic loading (for example, at 40 Hz) in comparison with a quasi-static stiffness. This material property is advantageous in this application. 
     The effectiveness of the initially tensioned elastomer spring according to the invention with regard to vibration damping and structural dynamics of the composite constituted by energy-storage device and body shell can be distinctly heightened by a purposeful design of the dynamic hardening of the elastomer spring according to the invention, without disadvantages arising for the composite constituted by energy-storage device and body shell by reason of a strain in the quasi-static mounting.