Abstract:
A side impact door trim buckle initiator design is provided in a vehicle armrest and grab handle region. The disclosed support structure design induces buckling in the door handle supports while continuing to provide acceptable durability and strength. Two modifications to the door armrest and grab handle structures are made. First, an angled section is added to the material flow strap of the armrest supporting structure to promote buckling. This approach overcomes the difficulty of known material flow straps which tend to be horizontal, thus introducing a strong compressive load path. By adding an angle to the flow straps the vertical motion is forced upon a lateral impact. Second, vertical components of the door handle support structure are removed while a buckle initiator in the door handle support is added.

Description:
TECHNICAL FIELD 
   The present invention relates generally to collapsible door structures for use with vehicle doors. More particularly, the present invention relates to collapsible door trim buckle initiator design in the armrest and grab handle region of the vehicle door. The collapsible door structures are strong and durable under normal use but demonstrate compromised lateral stiffness in the event of a side impact. 
   BACKGROUND OF THE INVENTION 
   Side impact events in vehicles have been identified as one of the top priorities for both research and regulation with government requirements continuing to become more stringent. These additional requirements make designs for door trim systems more challenging because they may impact the door trim at the door armrest supports and at the grab handle. It is known in vehicles to provide an armrest in a door typically having an integrated grab handle to allow the occupant to pull the door shut. According to known arrangements, the door armrest and grab handle are generally anchored to the vehicle door inner panel by a variety of structures. In addition to being anchored to the vehicle door inner panel, the grab handle is also solidly connected to the armrest substrate. This makes the area surrounding the grab handle quite stiff, which may negatively affect occupant injury results. 
   The known approaches to anchoring the armrest and door grab handle provide a good degree of lateral door function to the vehicle occupant while opening and, particularly, closing the door. Accordingly, a reduction in stiffness of the door trim panel in this area may improve side impact performance. But until now no solution has been available to this problem without compromising armrest and grab handle tensile and vertical strength. 
   Accordingly, as in so many areas of vehicle technology, there is room in the art of vehicle door design for an alternative configuration to known door armrest and door grab handle and adjacent support structures. The alternate configurations should allow the translation of horizontal force impacting the vehicle door in the event of an impact to vertical movement which deforms or buckles a portion of the armrest substrate to thereby prevent or minimize the movement of the armrest and its associated structure vehicle inward into the passenger area. 
   SUMMARY OF THE INVENTION 
   The present invention provides alternative arrangements to known vehicle door armrest and grab handle support structure designs. According to the present invention, a support structure design is provided which induces buckling in the door handle supports while continuing to provide acceptable durability and strength. To accomplish this two modifications to the door armrest and grab handle structures are made. First, an angled or curved section is added to the material flow strap of the armrest supporting structure to promote buckling. This approach overcomes the difficulty of known material flow straps which tend to be horizontal, thus introducing a strong compressive load path. By adding an angle to the flow straps the vertical motion is forced upon a lateral impact. Second, vertical components of the door handle support structure are removed while a buckle initiator in the door handle support is added. 
   This vertical motion contacts a buckle-line designed into the armrest substrate. This arrangement effectively provides the use of a secondary load path to pre-buckle the primary load path, insuring that the buckle will start a location defined by the buckle initiator, thus controlling the buckle and its development. By designing the armrest to buckle a reduction in the compressive strength is realized, while providing a load path for tensile forces. 
   Other advantages and features of the invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention wherein: 
       FIG. 1  illustrates a perspective view of a door assembly viewed from the inside of the vehicle having a trim buckle initiator configuration according to the present invention; 
       FIG. 2  illustrates a perspective exploded view of the door frame, the grab handle back side plate, the armrest substrate, the energy-absorbing foam backing, and the armrest cover; 
       FIG. 3  illustrates a plan exploded view of the elements of  FIG. 2 ; 
       FIG. 4  illustrates a sectional view of a conventional material flow strap assembly; 
       FIG. 5  illustrates a sectional view of a material flow strap assembly according to the disclosed invention shown in its pre-impact state; 
       FIG. 6  illustrates a sectional view of the material flow strap assembly of  FIG. 5  illustrated in its post-impact state; 
       FIG. 7  illustrates a top sectional view of a portion of an armrest substrate according to an alternate embodiment of the disclosed invention prior to impact; 
       FIG. 8  illustrates the same view as shown in  FIG. 7  but after a side impact; 
       FIG. 9  illustrates a perspective view of the grab handle back side plate of the disclosed invention; 
       FIG. 10  illustrates a lateral view of the grab handle back side plate of the disclosed invention; and 
       FIG. 11  illustrates a perspective view of a portion of the armrest substrate. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In the figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for different constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting. 
   With reference to  FIG. 1 , a perspective view of a door assembly of the present invention, generally illustrated as  10 , is shown. The door assembly  10  includes a frame  12 , an interior panel  14 , and an armrest and grab handle assembly  16 . It is to be understood that the configuration of the door assembly  10  shown in  FIG. 1  is for illustrative purposes only and is not intended as being limiting. Particularly, the armrest and grab handle assembly  16  could be configured differently in terms of shape, size and overall configuration as well as in terms of placement of the grab handle itself. 
   With reference to  FIGS. 2 and 3 , exploded views of the door assembly  10  are illustrated. The door assembly  10  includes the door frame  12 , a grab handle back side plate  18 , an armrest substrate  20 , an energy-absorbing foam backing  22 , and an armrest cover  24 . The energy-absorbing foam backing  22  is of known construction, as is the armrest cover  24  which may be of vinyl or another polymerized material as preferred and as is known in the art. 
   The door frame  12  includes a plurality of material flow straps  26 ,  26 ′,  26 ″ and  26 ′″ to which the armrest substrate  20  is attached. The number and placement of the flow straps  26 ,  26 ′,  26 ″,  26 ′″ . . . can be modified and adapted as required. However, according to the disclosed invention, the construction of the material flow straps  26 ,  26 ′,  26 ″, and  26 ′″ is modified to allow them to buckle under compressive load. 
   A known material flow strap and associated elements are illustrated in  FIG. 4 . With reference to that figure, a conventional material flow strap  30 , having an horizontal arm, is shown. The material flow strap  30  is continuous with a door trim substrate  32 . The door trim substrate  32  is adjacent a door inner sheet metal  34 . 
   A door handle support  36  is filled over the material flow strap  30  in a known manner and is fastened thereto by a first heat stake  38  and a second heat stake  40 . In the event of an impact situation the substantially horizontal portion of the material flow strap  30  may force the associated elements vehicle inward. 
   To improve on the situation possibly posed by the prior art, the material flow strap has been modified so that it buckles under compressive load. This structure is shown in  FIGS. 5 and 6 . In  FIG. 5  a sectional view of a supporting structure, generally illustrated as  40 , is shown. The supporting structure  40  includes a material flow strap  42  having a substantially horizontal portion  44 , an angled portion  46 , and a substantially vertical portion  48 . The substantially horizontal portion  44  is continuous with a door trim substrate  50 . Adjacent the door trim substrate  50  is a door inner sheet metal  52 . 
   Fitted to the material flow strap  42  is a door handle support  54  having a buckling initiator  56  formed therein. The buckling initiator  56  may be formed from a variety of methods, such as notching or slotting. The door handle support  54  is attached to the material flow strap  42  by a number of methods, such as by heat staking. As illustrated, attachment has been made by a heat stake  58  and by a heat stake  60 . 
   The supporting structure  40  is illustrated in  FIG. 5  as the arrangement would appear prior to an impact event. In  FIG. 6 , the arrangement is illustrated after the impact event. As is shown, the material flow strap  42  has buckled between the substantially horizontal portion  44  and the angled portion  46 . The buckling initiator  56  allows the substantially vertical movement of the material flow strap  42  and begins buckling in a specific, controlled location. By effecting upward, buckled movement of the material flow strap  42  and the door handle support  54 , the movement of the supporting structure and the lateral compressive stiffness is reduced. 
   An alternative arrangement for material flow straps is illustrated in  FIGS. 7 and 8 . With reference first to  FIG. 7 , an angled material flow strap  62  formed as set forth above in  FIGS. 5 and 6  is provided and is shown prior to an impact event. Adjacent the angled material flow strap  62  is another angled material flow strap  64  which is provided at an angle which is generally perpendicular to the angled material flow strap  62 . Both the angled material flow strap  62  and the angled material flow strap  64  are fixed between a first portion of a door trim substrate  65  and a second portion of a door trim substrate  66 . A door inner sheet metal  67  is adjacent the first portion of the door trim substrate  65 . A handle closeout  68  is formed adjacent the angled material flow strap  64 . A switch area  69  is formed beside the handle closeout  68 . 
   The arrangement of  FIG. 7  is shown after an impact event in  FIG. 8 . As illustrated, both the angled material flow strap  62  and the angled material flow strap  64  are shown as having partially collapsed as has the handle closeout  68 . The impact energy is distributed away from the vehicle occupant and along the longitudinal axis of the vehicle through the armrest substrate and associated areas. 
   The invention disclosed herein also provides a modification to the grab handle back side plate  18 . This modification is illustrated in  FIG. 9  in which the grab handle back side plate  18  is shown in perspective view. The grab handle back side plate  18  includes a pair of spaced apart side arms  70  and  72  which are joined by a curved bridge piece  74 . At the end of the side arm  70  is provided an attachment flange  76  having a door handle closeout attachment point  78 . At the end of the side arm  72  is provided an attachment flange  80  having a door handle closeout attachment point  82 . 
   In the event of a side impact event the rigid grab handle back side plate, as is known in the art, may be driven vehicle inward. To provide a potentially improved response, a plurality of buckling initiators are provided along each of the side arms  70  and  72 . Buckling initiators  84 ,  84 ′, and  84 ″ are formed perpendicular to the long axis of the side arm  70 . Buckling initiators  86 ,  86 ′ and  86 ″ are formed perpendicular to the long axis of the side arm  72 . Each of the buckling initiators  84 ,  84 ′,  84 ″,  86 ,  86 ′, and  86 ″ may be formed by notching, slitting or by any other known technique. An additional buckling initiator  88  may be formed at the corner of the side arm  70  and the attachment flange  76 . An additional buckling initiator  89  may also be formed at the corner of the side arm  72  and the attachment flange  80 . Furthermore, a buckling initiator  90  may be formed at the corner of the side arm  70  and the curved bridge piece  74 . An additional buckling initiator  92  may be formed at the corner of the side arm  72  and the curved bridge piece  74 . 
     FIG. 10  is a lateral view of the grab handle back plate  18  looking inward towards the center of the vehicle. This view illustrates the change in the thicknesses of the walls  70  and  72  over their respective vertical heights. The walls  70  and  72  are shown in broken lines at their attachment points to the attachment flanges  76  and  80  respectively. The thickness varies in order to accept tensile loads between the curved bridge piece  74  and the door handle closeout attachment points  78  and  82  during closing, while insuring that non-load bearing portions of the side walls  70  and  72  are effectively non-structural. 
   In addition to modifications being made to the material flow straps and to the grab handle back side plate as discussed above and shown in the related figures, further controlled buckling of the vehicle armrest can be established by making appropriate changes to the configuration of the armrest substrate. Such modifications are shown in  FIG. 11 . 
   With reference to  FIG. 11 , a perspective view of a portion of the armrest substrate  20  is illustrated. The armrest substrate  20  includes a grab handle cut out area  100  and a rearward armrest portion  102 . The rearward armrest portion  102  includes a top side  104 , a back end  106 , a front side  108 , and a front lip  110 . In general, slots, holes and apertures of a variety of shapes and sizes may be formed through the armrest substrate  20  according to the desired buckling path. The illustrated slots, holes and apertures are suggestive only and are not intended as being limiting, as other shapes and configurations may be formed in different places on the armrest substrate  20 . 
   By way of illustration, a plurality of elongated slots  112  and  112 ′ are formed along the top side  104  of the armrest substrate  20 . Ordinarily this area would be ribbed to provide structural integrity. The elongated slots  112  and  112 ′ are provided in lieu of the ribs without sacrificing structural integrity while providing an area for buckling initiation. In addition, a slot  114  may be provided along the front lip  110 . A plurality of vertical slots, for example, slots  116  and  116 ′, may be formed on the front side  108  of the armrest substrate  20 . To provide further or alternative buckling initiation a corner slot  118  may be formed as well. 
   The grab handle cut out area  100  may be strategically modified by removing the hard edge, by thinning the edge, or by forming an incline along the edge. Modifications may also include the formation of a buckling initiator slot  120  along the grab handle cut out area  100 . An upstanding vertical flange  122  is provided. The upstanding vertical flange  122  may be slotted, cut, or removed entirely, based upon the desired buckle kinematics. This embodiment shows the elongated slot  112 ′ to be approximately in-line with an upstanding vertical flange buckle initiator  124 . Each of these approaches would enable focused buckling initiation in the event of a side impact. 
   The foregoing discussion discloses and describes exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.