Abstract:
Provided is a seat belt pretensioner device for a seat belt having a plurality of anchor points attached to different parts of a vehicle body which includes a G control vehicle body member which deforms in a different pattern from a remaining part of the vehicle body at the time of a vehicle crash. One of the anchor points, which typically consists of a seat belt buckle, is attached to the G control vehicle body member via a force transmitting member such as a cable member which is adapted to move the anchor point in a direction to increase a tension of the seat belt at the time of a vehicle crash. A seat belt pretensioner device can be thus achieved in a simple manner without requiring any special power actuator.

Description:
TECHNICAL FIELD 
     The present invention generally relates to an automotive vehicle body structure for improving the vehicle crash safety, and in particular to a seat belt pretensioner device which is powered by a relative displacement between two parts of the vehicle body at the time of a vehicle crash. 
     BACKGROUND OF THE INVENTION 
     In recent years, with the aim of improving the safety of vehicle occupants at the time of a vehicle crash, various vehicle body structures have been proposed in which the deformation mode of the part of a vehicle body other than the passenger compartment is appropriately controlled in such a manner that the deceleration of the passenger compartment of the vehicle is reduced, and the deformation would not reach the passenger compartment (Japanese patent laid-open publication No. 07-101354 and others). 
     At the time of a vehicle crash, the deceleration of a vehicle occupant who is restrained to a vehicle seat by an occupant restraint system such as a seat belt rises sharply only when the forward inertia force acting on the occupant is received by the seat belt. As it is not possible to eliminate the tendency of the seat belt to act as a spring, the vehicle occupant moves forward under the inertia force, and the deceleration of the vehicle occupant reaches the peak value when the elongation of the seat belt reaches the maximum value. The greater the displacement of the vehicle occupant under the inertia force, the higher the peak value of the vehicle occupant becomes, and the peak value of the vehicle occupant acceleration is said to exceed the average deceleration of the vehicle body. 
     In view of minimizing the injury to the vehicle occupant at the time of a vehicle crash, the maximum acceleration (deceleration) of the vehicle occupant should be reduced. The vehicle occupant deceleration is dictated by the waveform (time history) of the vehicle body deceleration when the vehicle occupant is held integrally with the vehicle body by the seat belt. As shown in FIG. 9, to minimize the vehicle occupant deceleration (G 1 ), a preferred waveform (G 2 ) of the deceleration of the vehicle body (seat) should consist of an initial interval (a) characterized by a high deceleration, an intermediate interval (b) characterized by an opposite deceleration, and a final interval (c) characterized by an average deceleration. 
     To achieve such a waveform, proposals have been made in copending U.S. patent application Ser. No. 09/377,366 now U.S. Pat. No. 6,186,574 and Ser. No. 09/376,888 now U.S. Pat. No. 6,193,296 both filed on Aug. 18, 1999, to impart a relative deceleration and acceleration to the vehicle seat or the member carrying the vehicle seat with respect to the main part of the vehicle body so that the vehicle occupant may experience a deceleration from an early stage of a vehicle crash, and the maximum vehicle occupant deceleration may be reduced by distributing the inertia force acting on the vehicle occupant over a longer period of time. Similar proposals have been made in additional copending patent applications. This can be accomplished either by using a power actuator or solely through the controlled deformation of the various members of the vehicle body including that of the G-control member. The contents of these applications are hereby incorporated in this application by reference. 
     In such an arrangement, if there is any excessive slack in the seat belt, even though the seat may undergo a relatively controlled time history of deceleration itself, the failure to properly restrain the occupant causes a delay in the time history of deceleration for the occupant, resulting in a relatively sharp rise in the occupant&#39;s deceleration level as the seat belt finally becomes effective in restraining the occupant. In other words, for such an arrangement to be effective, it is essential to provide a suitable seat belt pretensioner system so that the occupant may be effectively restrained to the occupant seat from an early phase of a crash. 
     When a G-control member is used in a vehicle body, the vehicle body not only deforms in a controlled manner but also a controlled relative displacement occurs, in particular, between the G-control member and the rest of the vehicle body. Such a displacement can be conveniently used as a power source for a seat belt pretensioner device. This can be accomplished by providing at least one of the anchor points of the seat belt in a part of the vehicle body which is not part of the) G-control member. 
     This however may create an inconvenience because the position of the anchor point may significantly change as the position of the occupant seat is adjusted in the fore-and-aft direction to accommodate for the difference in the build of the occupant and ensure the comfort of the occupant. For instance, if the anchor point is provided in the rear end of the seat slide so as to ensure the function of the restraint system over the entire range of the seat slide movement, some problems arise when the seat is placed at the front most position because the anchor point is so far away from the vehicle occupant that the vehicle occupant experiences some difficulty in reaching the anchor point which may consist of a buckle provided with a latch device that needs to be manually operated. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of such a recognition by the inventors, a primary object of the present invention is to provide a seat pretensioner device which does not require any power source. 
     A second object of the present invention is to provide a seat pretensioner device which enhances the performance of a G-control vehicle body which minimizes the peak value of the deceleration for the vehicle occupant at the time of a vehicle crash. 
     A third object of the present invention is to provide a seat pretensioner device which makes use of a relative displacement between two parts of the vehicle body, but allows the fore-and-aft adjustment of the seat without causing any inconvenience. 
     According to the present invention, such objects can be accomplished by providing a seat belt pretensioner device for a seat belt having a plurality of anchor points attached to different parts of a vehicle body, the vehicle body including a G control vehicle body member which deforms in a different pattern from a remaining part of the vehicle body at the time of a vehicle crash; wherein: at least one of the anchor points, which typically consists of a seat belt buckle, is attached to the G control vehicle body member via a force transmitting member which is adapted to move the one anchor point in a direction to increase a tension of the seat belt at the time of a vehicle crash. 
     Thus, a seat belt pretensioner device can be achieved in a simple manner without requiring any special power actuator. According to a preferred embodiment, the power transmitting member comprises a flexible member such as a cable member having one end attached to the G control member, and an anchor point guide member supporting the anchor point and having another end of the cable member attached thereto, the anchor point guide member being adapted to move in a direction to increase a tension of the seat belt. Thus, it is possible to use a relative displacement of vehicle body parts which may be significantly remote from the anchor point in question. 
     The anchor point is required to be guided to move along a prescribed path, and it can be readily accomplished if the anchor point guide member comprises an arm member pivotally supported by a seat and having the anchor point attached to a free end thereof. The arm member may also consist of a pulley member. In this case, the cable member may be passed around an arcuate section of the pulley member for a desired motion of the anchor point. 
     A vehicle seat is normally required to be adapted to fore-and-aft adjustment, and this should not interfere with the pretensioner device of the present invention even when the anchor point is integral with the vehicle seat. If the anchor point guide member comprises a pulley member, the movement of the anchor point that is caused by the fore-and-aft adjustment of the vehicle seat can be minimized by controlling the way the cable member is paid out from the arcuate section of the pulley member. 
     The G control member may take a number of different forms without departing from the principle of the present invention. For instance, the G control member may be disposed under a floor panel while the cable member is attached to the G control member at one end thereof, and is passed through an opening formed in the floor panel to be attached to the anchor point guide member. 
     According to a preferred embodiment of the present invention, the seat is connected to the G control member, and the cable member is connected between the anchor point guide member and the G control vehicle body member, a cable guide member being provided in the opening of the floor panel and adapted to push an intermediate part of the cable member at the time of a vehicle crash. In this case, a seat adjustment arrangement may be provided between the seat and the G control member. 
     Alternatively, the seat may be attached to the floor panel while the cable member is connected between the anchor point guide member and the G control vehicle body member, a cable guide member being provided in the opening of the floor panel and adapted to push an intermediate part of the cable member at the time of a vehicle crash. In this case, a seat adjustment arrangement may be provided between the seat and the floor panel member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Now the present invention is described in the following with reference to the appended drawings, in which: 
     FIG. 1 is a simplified side view of a vehicle body embodying the present invention; 
     FIG. 2 is a view taken along line II—II of FIG. 1; 
     FIG. 3 is an exploded perspective view of the floor panel and the G control frame of the vehicle body; 
     FIG. 4 is an enlarged side view of the vehicle body; 
     FIG. 5 is a view similar to FIG. 2 showing the second embodiment of the present invention; 
     FIG. 6 is a view similar to FIG. 3 showing the second embodiment of the present invention; 
     FIG. 7 is a view similar to FIG. 4 showing the second embodiment of the present invention; 
     FIG. 8 is a view similar to FIG. 4 showing the third embodiment of the present invention; and 
     FIG. 9 is a graph showing a desired pattern of deceleration of the seat and the vehicle occupant at the time of a vehicle crash. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates the general structure of a vehicle embodying the present invention. To restrain a vehicle occupant  2  with respect to a seat  1 , the seat  1  is fitted with a seat belt  3 . The seat  1  is fixedly supported on a seat frame  1   a , and the seat frame  1   a  is in turn mounted on a seat base frame  6  via a seat slide arrangement  5  as shown in the sectional view of FIG. 2 taken along line II—II of FIG. 1 so that the seat  1  may be moveable in the fore-and aft direction with respect to the seat base frame  6 . The seat base frame  6  is in turn placed on a floor panel  4 , forming an integral part of the vehicle body, so as to be moveable with respect to the floor panel  4  as described hereinafter. In the illustrated embodiment, the seat belt anchors including a seat belt buckle  15  are all provided in the seat  1  or the seat frame  1   a  which is integral with the seat  1 . However, at least one of the anchor points, such as the shoulder anchor point, may be connected to a fixed part of the vehicle body such as an upper part of the center pillar without departing from the spirit of the present invention. 
     A side sill  7  having a rectangular cross section is fixedly attached to each side of the floor panel  4 , and a floor frame  8  having a U-shaped cross section is fixedly attached to the lower surface of the floor panel  4  so as to extend in the fore-and-aft direction under each seat  1 . These members reinforce the floor panel  4  which has a generally planar configuration. 
     A G control frame  9  formed as a ladder frame is provided under the middle part of the floor panel  4 . Referring to FIG. 3, the G control frame  9  comprises a pair of longitudinal frame members  9   a  extending in the fore-and-aft direction of the vehicle body on either side thereof, and a front cross bar  9   b , a middle cross frame  9   c  and a rear cross bar  9   d  extend across the longitudinal frame members  9   a.    
     The front end of the floor panel  4  is integrally connected to a bulkhead panel  11  which obliquely rises toward the front end of the vehicle body, and a pair of side frames  12  extend in the forward direction, one next to the other, from the floor frame  8  beyond the bulkhead panel  11 . 
     As shown in FIGS. 2 and 3, the G control frame  9  is integrally provided with a pair of coupling members  10  projecting upward from the upper surface thereof, and are each passed through an opening  4   b  provided in the floor panel  4  to engage the corresponding seat base frame  6 . Thus, the seat base frame  6 , along with the seat  1  and the seat frame  1   a , is integrally attached to the G control frame  9  while the fore-and-aft position of the seat  1  can be adjusted with respect to the seat base frame  6  via the seat slide arrangement  5 . 
     In this vehicle having the above described structure, at the time of a frontal crash, following the deformation of the front bumper, the body front portion starts collapsing, and the impact load is applied to both the side frames  12  and the G control frame  9 . Due to the difference in rigidity against the impact load, the side frames  12  first undergo a compressive deformation, and the G control frame  9  undergoes a compressive deformation thereafter. Thus, the impact of the crash is immediately applied to the vehicle seat  1  via the G control frame  9 , and the G control frame  9  is thereafter subjected to a forward acceleration to avoid any excessive rise in the deceleration level by using a power source or a control deformation of the vehicle body although it is not shown in the drawings. FIG. 9 shows the time history of a typical frontal crash which can be achieved by the use of G control member. For more detailed description of the vehicle body structure including a G control member, reference should be made to copending U.S. patent applications Ser. Nos. 09/377,366 and 09/376,888 both filed on Aug. 18, 1999, and additional copending applications of later dates. 
     Referring to FIGS. 2 and 4, a fan-shaped pulley member  14  is pivotally mounted on a side of the seat base frame  6  by a pivot pin  13  so as to be rotatable in the vertical direction. A seat belt buckle  15  is attached to a part of the pulley member  14 . A torsion coil spring  18  urges the pulley member  14  in the upward direction or in counter clockwise direction as seen in FIG.  4 . Thus, one of the anchor points of the seat belt, which consists of the seat belt buckle  15  in this embodiment, is guided by the pulley member  14  along an arcuate path rearward and downward. 
     An end of a cable  16  is attached to the pulley member  14 , and is passed around the arcuate section  14   a  of the pulley member  14 . The other end of the cable  16  extends downward through an opening  4   a  provided in the floor panel  4 , and is attached to the rear cross bar  9   d  of the G control frame  9 . A cable guide  17  is attached to the floor panel  4  to allow the cable  16  to be guided along a curved path without causing any undesired wear or stress to the cable  16 . In the illustrated embodiment, the cable  16  extends vertically downward from the pulley member  14 , and is bent rearward around the cable guide  17  to be attached to the rear cross bar  9   d  of the G control frame  9 . Under normal condition, the cable  16  is kept taut under the spring force of the torsion coil spring  18 . 
     In the vehicle structure described above, in an initial phase of a frontal crash, because the side frame  12  (floor panel  4 ) undergoes a compressive deformation before the G control frame  9  does, as mentioned earlier, the longitudinal frame members  9   a  and the seat base frame  6  move rearward with respect to the floor panel  4  as indicated by arrow A in FIG.  4 . As a result, the cable  16  connected to the longitudinal frame member  9   a  (rear cross bar  9   d ) is sharply bent by the cable guide  17 , which, along with the floor panel  4 , moves forward with respect to the seat base frame  6  and the G control frame  9 . As a result, the pulley member  14  is turned in a clockwise direction, and this causes a downward and rearward movement of the seat belt buckle  15  as indicated by arrow B so that an addition tension is applied to the seat belt  3  which is connected to the buckle  15 . This causes the vehicle occupant  2  to be restrained to the seat  1  more securely, thereby preventing the vehicle occupant  2  from being thrown forward. This is advantageous in controlling the deceleration of the vehicle occupant, and helps achieve the desired purpose of the G control frame. 
     Normally, a vehicle seat is required to be provided with an arrangement for adjusting the fore-and-aft position of the seat so as to suit the build of the seat occupant. However, if any one of the anchor points of the seat belt is attached to a stationary part of the vehicle body near the seat, the fore-and-aft adjustment of the seat would cause the anchor point, such as a seat belt buckle, to change in position so that the occupant may experience some difficulty in accessing the anchor point such as a seat belt buckle. The anchor point may also consist of the one which is adjacent to the shoulder of the vehicle occupant which may be adapted for a vertical adjustment. The illustrated embodiment is designed to address such a problem. 
     In the illustrated embodiment, the pulley member  14  is attached to the seat frame  1   a  which is integral with the seat  1  so that the buckle  15  attached to the pulley member  14  maintains a fixed position relative to the seat  1  without regard to the fore-and-aft movement of the seat  1 . In FIG. 4, the positions of the buckle  15  when the seat is adjusted to the front most and rear most positions are indicated by imaginary lines and letters F and R, respectively. It is desired that the position or elevation of the buckle  15  relative to the floor panel  4  is desired to be fixed without regard to the fore-and-aft position of the seat  1 . 
     When the seat  1  is at the front most position as indicated by arrow F in FIG. 4, the cable  16  is partly unwound from the arcuate section  14   a  of the pivotally mounted pulley member  14  as indicated by the corresponding imaginary lines. When the seat is at the rear most position as indicated by arrow R in FIG. 4, the pulley member  14  may tilt slightly, but the elevation of the buckle would not change to any significant extent. Because the elevation of the anchor point  15  would not substantially change without regard to the position of the seat (seat frame  1   a ), there is no problem in latching the seat belt  3  to the buckle  15 , and the fastening and unfastening of the seat belt  3  can be accomplished without any inconvenience. 
     When the vehicle crashes onto an object, the main part of the vehicle body including the floor panel  4  collapses before the G control frame  9  does so that the floor panel  4  moves forward ahead of the G control frame  9  and the seat  1  in an early phase of a vehicle crash. In other words, the cable guide  17  which is attached to the floor panel  4  advances relative to the G control frame  9  and the seat  1 , and pushes the part of the cable  16  extending between the pulley member  14  and the G control frame  9  with the result that the pulley member  14  is turned in a clockwise direction, and the buckle  15  is pulled downward. Thus, the relative displacement between the G control frame  9  and the floor panel  4  increases the tension of the seat belt  3 . In other words, this arrangement provides the function of a seat belt pretensioner which is powered by a relative displacement between two parts of the vehicle body such as the floor panel  4  and the G control frame  9 . 
     As can be readily appreciated by a person skilled in the art from the foregoing description, this arrangement can be applied to any vehicle body which involves a certain relative displacement between two parts of the vehicle body at the time of a vehicle crash. FIGS. 5 to  7  show a second embodiment of the present invention, and the parts corresponding to those of the previous embodiment are denoted with like numerals. In this embodiment, the seat  1  and the seat frame  1   a  are supported by the floor panel  4  via a seat slide arrangement  5 . A lower frame  9  is provided under the floor panel  4 , and is adapted to follow a somewhat different collapsing pattern from that of the rest of the vehicle body. 
     As best shown in FIG. 7, the fore-and-aft position of the seat frame  1   a  can be adjusted relative to the floor panel  4  without substantially changing the elevation of the seat buckle  15 . When the vehicle crashes onto an object, the lower frame  9  which is relatively rigid remains relatively intact in an early phase of the crash while the remaining part of the vehicle body, in particular the floor panel  4 , collapses to a more significant extent. Because the seat frame  1   a  is fixedly attached to the floor panel  4  via the lock mechanism of the seat slide arrangement not shown in the drawings, at the time of the vehicle crash, the seat  1  stays substantially fast with the floor panel  4 . Therefore, in the early phase of the vehicle crash, the lower frame  9  moves rearward relative to the floor panel  4  as indicated by arrow D, and the cable guide  17  attached to the floor panel  4  pushes an intermediate part of the cable  16  sideways, causing the pulley member  14  to rotate in clockwise direction and the buckle  15  to be pulled downward. 
     Depending on the vehicle body structure, the lower frame  9  may be adapted to collapse before the remaining part of the vehicle body does. FIG. 8 shows such an arrangement, and the parts corresponding to the previous embodiment are denoted with like numerals. This embodiment is similar to the previous embodiment, and the only difference is that the lower frame  9  moves forward relative to the remaining part of the vehicle body at the time of a vehicle crash as indicated by arrow E. 
     As can be appreciated from the foregoing description, according to the present invention, at the time of a vehicle crash, because the anchor point guide member is moved owing to the relative displacement between two parts of the vehicle body, this motion causes a displacement of the seat belt anchor point, such as a seat belt buckle, in the direction to tension the seat belt so that the restraint of the vehicle occupant at the time of a vehicle crash can be improved. If the cable is passed around an arcuate section of a pivotally mounted pulley member, and can be paid out from the arcuate section of the pivotally mounted member as the seat is moved for slide positional adjustment of the seat, the pivotally mounted pulley member is prevented from rotating to any substantial extent. Thus, the anchor point can be moved with the seat, and the handling of the seat belt at the anchor point is not inconvenienced in any way. 
     Although the present invention has been described in terms of preferred embodiments thereof, it is obvious to a person skilled in the art that various alterations and modifications are possible without departing from the scope of the present invention which is set forth in the appended claims.